Argininosuccinate synthase 1 and argininosuccinate lyase polypeptides and polynucleotides and uses thereof

Abstract

This disclosure relates to mRNA therapy for the treatment of citrullinemia type 1 (CTLN1) and related diseases, disorders or conditions. mRNAs for use in the invention, when administered in vivo, encode the argininosuccinate synthase 1 (ASS1) polypeptide. Also provided are related polypeptides for use in the invention. Polypeptide and mRNA therapies of the disclosure increase and / or restore deficient levels of ASS1 expression and / or activity in subjects. Polypeptides and mRNA therapies of the disclosure may be used in combination with argininosuccinate lyase polypeptides or mRNAs encoding the same.

Description

[0001] Attorney Docket No.45817-0022WO1 / MTX977.20 ARGININOSUCCINATE SYNTHASE 1 AND ARGININOSUCCINATE LYASE POLYPEPTIDES AND POLYNUCLEOTIDES AND USES THEREOF CROSS-REFERENCE TO RELATED APPLICATION This application claims the priority benefit of U.S. Provisional Application No.63 / 656,231, filed June 5, 2024, the content of which is incorporated by reference in its entirety herein. SEQUENCE LISTING The instant application contains a Sequence Listing which has been submitted electronically in XML format and is hereby incorporated by reference in its entirety. Said XML copy, created on June 3, 2025, is named 45817-0022WO1_SL.xml and is 2,147,712 bytes in size. BACKGROUND The urea cycle is a vital metabolic pathway involved in the removal of nitrogenous waste, e.g., ammonia, produced from breakdown of protein and other nitrogen containing compounds. Ammonia is converted to urea through 4 intermediates including carbamoyl phosphate, citrulline, argininosuccinate, and arginine. The urea cycle consists of a series of enzymatic reactions that occur in the mitochondria and cytosol of liver cells. Urea cycle disorders (UCD) arise due to defects in enzymes and transporters involved in the metabolism of ammonia to urea. Argininosuccinate synthetase 1 (ASS1) and argininosuccinate lyase (ASL) are two enzymes playing critical roles in the urea cycle. ASS1 catalyzes the conversion of citrulline and aspartate into argininosuccinate, which is further processed by ASL to generate arginine. ASS1 is a homotetrameric enzyme consisting of four identical subunits. The functional domains of ASS1 includes an N-terminal domain responsible for binding aspartate, a central domain responsible for binding citrulline, and a C- terminal domain responsible for binding ATP. ASL consists of four identical subunits, and the functional domains include an N-terminal domain responsible for binding argininosuccinate and a C-terminal domain responsible for catalytic activity. Attorney Docket No.45817-0022WO1 / MTX977.20 Mutations of ASS1 gene that result in reduced or absent ASS1 enzyme activity cause type I citrullinemia (CLTN1), one of the autosomal recessive UCDs. CLTN1 usually becomes evident in the first few days of life as ammonia accumulates, resulting in hyperammonemia. The onset of symptoms can occur in infancy or later in childhood, depending on the severity of the enzyme deficiency and the individual's metabolic tolerance. CLTN1 is challenging to diagnose due to its rarity and variable presentation. Diagnosis typically involves measuring ammonia levels in the blood, as well as specific amino acids and metabolites in urine and blood samples. Genetic testing can confirm the presence of mutations in the ASS1 gene. CLTN1 treatment may involve a low-protein diet, supplementation with essential amino acids, and medications such as ammonia scavengers or nitrogen-binding agents. In severe cases, liver transplantation may be considered as a curative option. Despite advancements in the understanding and management, there remain unmet medical needs in CLTN1, particularly in improving diagnostic methods and developing targeted therapies. Mutations of ASL gene cause adenylosuccinate lyase deficiency (ASLD), also known as argininosuccinic aciduria, another autosomal recessive UCD. ASLD may become evident in the first few days of life because of high blood ammonia, or later in life presenting with "sparse" or "brittle" hair, developmental delay, mental retardation and tremors. Diagnosis is based mainly on clinical findings and laboratory test results including elevated concentrations of ammonia, citrulline, and argininosuccinic acid in the plasma or urine. Molecular genetic testing can confirm the presence of mutations in the ASL gene. Management of ASLD focuses on reducing ammonia levels in the blood through dietary interventions and medications. However, individuals with ASLD are at risk of experiencing long-term complications, including neurodevelopmental delays, intellectual disability, and liver damage. Monitoring for these complications and providing appropriate interventions can be challenging. Targeting ASLD activity or expression may hold therapeutic potential for the treatment of metabolic disorders associated with urea cycle dysfunction, such as ASLD, as well as for other conditions where ASLD dysregulation may be implicated. There remains an unmet need for improved treatment for CTLN1, ASS1- associated disorders, ASLD, and ASL-associated disorders. Attorney Docket No.45817-0022WO1 / MTX977.20 SUMMARY The present disclosure provides polypeptide and messenger RNA (mRNA) therapeutics for the treatment of CTLN1 and other ASS1-associted disorders. In some instances, CTLN1 or the ASS1-associated disorder may be improved through expression or administration of exogenous ASS1. In some instances, CTLN1 or the ASS1-associated disorder may be improved through expression or administration of exogenous ASS1 and ASL. The present disclosure also provides polypeptide and mRNA therapeutics for the treatment of ASLD and other ASL-associated disorders. In some instances, ASLD or the ASL-associated disorder may be improved through expression or administration of exogenous ASS1 and ASL. The mRNA therapeutics of the invention are particularly well-suited for the treatment of CTLN1 and other disorders associated with ASS1-deficiency, as the technology provides for the intracellular delivery of mRNA encoding an ASS1 polypeptide, optionally in combination with an mRNA encoding an ASL polypeptide, followed by de novo synthesis of functional ASS1 polypeptide and optionally functional ASL polypeptide within target cells. The mRNA therapeutics of the invention are also particularly well-suited for the treatment of ASLD and other disorders associated with ASL-deficiency, as the technology provides for the intracellular delivery of mRNA encoding an ASS1 polypeptide and mRNA encoding an ASL polypeptide followed by de novo synthesis of functional ASS1 polypeptide and functional ASL polypeptide, respectively, within target cells. The instant invention features the incorporation of modified nucleotides within therapeutic mRNAs to (1) minimize unwanted immune activation (e.g., the innate immune response associated with the in vivo introduction of foreign nucleic acids) and (2) optimize the translation efficiency of mRNA to protein. Exemplary aspects of the disclosure feature a combination of nucleotide modification to reduce the innate immune response and sequence optimization, in particular, within the open reading frame (ORF) and untranslated regions (UTRs) of therapeutic mRNAs encoding an ASS1 or ASL polypeptide to enhance protein expression. Attorney Docket No.45817-0022WO1 / MTX977.20 In further embodiments, the mRNA therapeutic technology of the instant disclosure also features delivery of mRNA encoding an ASS1 polypeptide via a lipid nanoparticle (LNP) delivery system. For instance, in some aspects, the mRNA therapeutic technology of the instant disclosure features delivery of mRNA encoding an ASS1 polypeptide. In some instances, the delivery of mRNA encoding an ASS1 polypeptide is in combination with delivery of mRNA encoding an ASL polypeptide. The instant disclosure features ionizable amino lipid-based LNPs, which have improved properties when combined with mRNA encoding a polypeptide and administered in vivo, for example, cellular uptake, intracellular transport and / or endosomal release or endosomal escape. In certain aspects, the disclosure relates to compositions and delivery formulations comprising a polynucleotide, e.g., a ribonucleic acid (RNA), e.g., an mRNA, encoding an ASS1 polypeptide and methods for treating CTLN1 or another ASS1-associated disease in a human subject in need thereof by administering the same. In certain aspects, the methods for treating CTLN1 or another ASS1-associated disease in a human subject in need thereof by administering the compositions or delivery formulations comprising a polynucleotide, e.g., an RNA, e.g., an mRNA, encoding an ASS1 polypeptide, further comprise administering a composition or delivery formulation comprising a polynucleotide, e.g., an RNA, e.g., an mRNA, encoding an ASL polypeptide. In certain aspects, the disclosure relates to compositions and delivery formulations comprising a polynucleotide, e.g., a ribonucleic acid (RNA), e.g., an mRNA, encoding an ASL polypeptide and compositions and delivery formulations comprising a polynucleotide, e.g., an RNA, e.g., an mRNA, encoding an ASS1 polypeptide, and methods for treating ASLD or another ASL-associated disease in a human subject in need thereof by administering the same. In certain aspects, the disclosure relates to mutant ASS1 polypeptides and compositions and delivery formulations comprising said mutant ASS1 polypeptides and methods for treating CTLN1 or another ASS1-associated disease in a human subject in need thereof by administering the same. In certain aspects, the methods for treating CTLN1 or another ASS1-associated disease in a human subject in need Attorney Docket No.45817-0022WO1 / MTX977.20 thereof further comprise administering compositions or delivery formulations comprising an ASL polypeptide. In certain aspects, the disclosure relates methods for treating ASLD or another ASLD-associated disease in a human subject in need thereof by administering ASS1 polypeptides and ASL polypeptides or composition and delivery formulations comprising the same. The present disclosure provides a pharmaceutical composition comprising a lipid nanoparticle encapsulated mRNA that comprises an ORF encoding an ASS1 polypeptide, wherein the composition is suitable for administration to a human subject in need of treatment for CTLN1 or an ASS1-associated disease. In some instances, the pharmaceutical composition is administered in combination with a pharmaceutical composition comprising a lipid nanoparticle encapsulated mRNA that comprises an ORF encoding an ASL polypeptide. The present disclosure provides a pharmaceutical composition comprising a lipid nanoparticle encapsulated mRNA that comprises an ORF encoding an ASS1 polypeptide, wherein the composition is suitable for administration to a human subject in need of treatment for ASLD or an ASLD-associated disease, wherein the pharmaceutical composition is administered in combination with a pharmaceutical composition comprising a lipid nanoparticle encapsulated mRNA that comprises an ORF encoding an ASL polypeptide. The present disclosure provides a pharmaceutical composition comprising a lipid nanoparticle encapsulated mutant ASS1 polypeptide, wherein the composition is suitable for administration to a human subject in need of treatment for CTLN1 or an ASS1-associated disease. In some instances, the pharmaceutical composition is administered in combination with a pharmaceutical composition comprising a lipid nanoparticle encapsulated ASL polypeptide. The present disclosure also provides ASS1 polypeptides. In some instances, the present disclosure provides a polypeptide comprising an amino acid sequence that is at least 80% identical to the amino acid sequence of SEQ ID NO:1, wherein the amino acid sequence comprises: (a) an amino acid other than lysine (K) at the position corresponding to position 58 of SEQ ID NO:1; (b) an amino acid other than lysine (K) at the position corresponding to position 165 of SEQ ID NO:1 and an amino acid Attorney Docket No.45817-0022WO1 / MTX977.20 other than lysine (K) at the position corresponding to position 176 of SEQ ID NO:1; (c) an amino acid other than cysteine (C) at the position corresponding to position 132 of SEQ ID NO:1; or (d) an amino acid other than lysine (K) at the position corresponding to position 4 of SEQ ID NO:1; wherein the polypeptide catalyzes the conversion of citrulline to argininosuccinate. In some instances, the amino acid sequence comprises: (a) an arginine (R) at the position corresponding to position 58 of SEQ ID NO:1; (b) an arginine (R) at the position corresponding to position 165 of SEQ ID NO:1 and an arginine (R) at the position corresponding to position 176 of SEQ ID NO:1; (c) an alanine (A) at the position corresponding to position 132 of SEQ ID NO:1; or (d) an arginine (R) at the position corresponding to position 4 of SEQ ID NO:1. In some instances, the amino acid sequence comprises an arginine (R) at the position corresponding to position 58 of SEQ ID NO:1. In some instances, the polypeptide is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:1. In some instances, the polypeptide comprises the amino acid sequence of any one of SEQ ID NOs:2-5. In some instances, the polypeptide comprises the amino acid sequence of SEQ ID NO:2. The disclosure also provides an mRNA comprising an ORF encoding the polypeptide of any one of the foregoing ASS1 polypeptides. In some instances, the ORF is at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% identical to the nucleotide sequence of SEQ ID NO:11-14. In some instances, the mRNA comprises a 5' untranslated region (UTR) comprising the nucleotide sequence of SEQ ID NO:50. In some instances, the mRNA comprises a 3' UTR comprising the nucleotide sequence of SEQ ID NO:143. In some instances, the mRNA comprises a 3' UTR comprising the nucleotide sequence of SEQ ID NO:142. In some instances, the mRNA comprises a 3' UTR comprising the nucleotide sequence of SEQ ID NO:141. In some instances, the mRNA comprises the nucleotide sequence of any one of SEQ ID NOs:19-26. In some instances, the mRNA comprises a 5′ terminal cap comprising m7G(5′)ppp(5′)G-2′-O-methyl. In some instances, the mRNA comprises a poly-A region comprising A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). In some instances, the mRNA comprises: (i) a 5′ terminal cap comprising m7G(5′)ppp(5′)G-2′-O-methyl; (ii) a 5′ untranslated region (UTR) comprising the Attorney Docket No.45817-0022WO1 / MTX977.20 nucleotide sequence of SEQ ID NO:50; (iii) an open reading frame (ORF) encoding the polypeptide of SEQ ID NO: 2, wherein the ORF comprises the nucleotide sequence of SEQ ID NO:11; (iv) a 3′ UTR comprising the nucleic acid sequence of SEQ ID NO:141; and (v) a poly-A region comprising A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). The disclosure also provides an mRNA comprising an ORF encoding the ASS1 polypeptide of SEQ ID NO: 1, wherein the ORF is at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% identical to the nucleotide sequence of SEQ ID NO:8 or 9. In some instances, the mRNA comprises a 5' untranslated region (UTR) comprising the nucleotide sequence of SEQ ID NO:50. In some instances, the mRNA comprises a 3' UTR comprising the nucleotide sequence of SEQ ID NO:141. In some instances, the mRNA comprises the nucleotide sequence of SEQ ID NO:17 or 18. In some instances, the mRNA comprises a 5′ terminal cap comprising m7G(5′)ppp(5′)G-2′-O-methyl. In some instances, the mRNA comprises a poly-A region comprising A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). In some instances, the mRNA comprises: (i) a 5′ terminal cap comprising m7G(5′)ppp(5′)G-2′-O-methyl; (ii) a 5′ untranslated region (UTR) comprising the nucleotide sequence of SEQ ID NO:50; (iii) an open reading frame (ORF) encoding the argininosuccinate synthase 1 (ASS1) polypeptide of SEQ ID NO:1, wherein the ORF comprises the nucleotide sequence of SEQ ID NO:8 or 9; (iv) a 3′ UTR comprising the nucleic acid sequence of SEQ ID NO:141; and (v) a poly-A region comprising A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). In some instances, the mRNA comprises at least one chemically modified nucleobase, sugar, backbone, or any combination thereof. In some instances, all of the uracils of the mRNA are N1-methylpseudouracils. In some instances of any one of the foregoing mRNAs, the mRNA comprises a 5' UTR comprising the nucleotide sequence of SEQ ID NO:215. The disclosure also provides a pharmaceutical composition comprising any one of the foregoing polypeptides or one or more of any of the foregoing mRNAs. The disclosure also provides a lipid nanoparticle comprising any one of the foregoing polypeptides or one or more of any of the foregoing mRNAs. In some instances, the lipid nanoparticle comprises an ionizable lipid, a structural lipid, a Attorney Docket No.45817-0022WO1 / MTX977.20 phospholipid, and a polyethylene glycol (PEG)-modified lipid. In some instances, the ionizable lipid is Compound A or a salt thereof. In some instances, the ionizable lipid is Compound II or a salt thereof. In some instances, the structural lipid is cholesterol. In some instances, the phospholipid is 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). In some instances, the PEG-modified lipid is PEG-DMG or Compound I. The disclosure also provides a lipid nanoparticle comprising: a an argininosuccinate synthase 1 (ASS1) polypeptide. The disclosure also provides a method of expressing a polypeptide in a human subject in need thereof, the method comprising administering to the human subject an effective amount of any one of the foregoing mRNAs, any one of the foregoing pharmaceutical compositions, or any one of the foregoing lipid nanoparticles. The disclosure also provides a method for treating CTLN1 or another ASS1- associated disease in a human subject in need thereof, the method comprising administering to the human subject an effective amount of any one of the foregoing ASS1 polypeptides, any one of the foregoing ASS1 mRNAs, any one of the foregoing ASS1 pharmaceutical compositions, or any one of the foregoing ASS1 lipid nanoparticles. In some instances of the method for treating CTLN1 or another ASS1- associated disease, the method further comprises administering to the human subject an effective amount of an ASL polypeptide, an mRNA encoding an ASL polypeptide, or a pharmaceutical composition or lipid nanoparticle comprising the same. The disclosure also provides a method for treating ASLD or another ASL- associated disease in a human subject in need thereof, the method comprising administering to the human subject (i) an effective amount of any one of the foregoing Attorney Docket No.45817-0022WO1 / MTX977.20 ASS1 polypeptides, any one of the foregoing ASS1 mRNAs, any one of the foregoing ASS1 pharmaceutical compositions, or any one of the foregoing ASS1 lipid nanoparticles, and (ii) an effective amount of an ASL polypeptide, an mRNA encoding an ASL polypeptide, or a pharmaceutical composition or lipid nanoparticle comprising the same. In some instances, the ASL polypeptide comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of SEQ ID NO:28, wherein the amino acid sequence comprises an amino acid other than lysine (K) at the position corresponding to position 51 of SEQ ID NO:28, wherein the ASL polypeptide catalyzes the conversion of citrulline and aspartate into argininosuccinate. In some instances, the amino acid sequence comprises: (a) an arginine (R) at the position corresponding to position 51 of SEQ ID NO:28. In some instances, the polypeptide is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:28. In some instances, the ASL polypeptide comprises the amino acid sequence of SEQ ID NO:7. In some instances, the ASL mRNA comprises an ORF encoding the ASL polypeptide of SEQ ID NO:7, wherein the ORF is at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% identical to the nucleotide sequence of SEQ ID NO:15. In some instances, the mRNA comprises a 5' UTR comprising the nucleotide sequence of SEQ ID NO:50. In some instances, the mRNA comprises a 3' UTR comprising the nucleotide sequence of SEQ ID NO:135. In some instances, the mRNA comprises the nucleotide sequence of SEQ ID NO:27. In some instances, the mRNA comprises a 5′ terminal cap comprising m7G(5′)ppp(5′)G-2′-O-methyl. In some instances, the mRNA comprises a poly-A region comprising A100-UCUAG- A20-inverted deoxy-thymidine (SEQ ID NO:211). In some instances, the mRNA comprises: (i) a 5′ terminal cap comprising m7G(5′)ppp(5′)G-2′-O-methyl; (ii) a 5′ untranslated region (UTR) comprising the nucleotide sequence of SEQ ID NO:50; (iii) an open reading frame (ORF) encoding the polypeptide of SEQ ID NO:7, wherein the ORF comprises the nucleotide sequence of SEQ ID NO:15; (iv) a 3′ UTR comprising the nucleic acid sequence of SEQ ID NO:108; and (v) a poly-A region comprising A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). In Attorney Docket No.45817-0022WO1 / MTX977.20 some instances, the mRNA comprises at least one chemically modified nucleobase, sugar, backbone, or any combination thereof. In some instances, all of the uracils of the mRNA are N1-methylpseudouracils. In some instances, the ASL mRNA comprises an ORF encoding an ASL polypeptide of SEQ ID NO:28. In some instances, the mRNA comprises a 5' UTR comprising the nucleotide sequence of SEQ ID NO:50. In some instances, the mRNA comprises a 3' UTR comprising the nucleotide sequence of SEQ ID NO:135. In some instances, the mRNA comprises a 5′ terminal cap comprising m7G(5′)ppp(5′)G-2′-O- methyl. In some instances, the mRNA comprises a poly-A region comprising A100- UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). In some instances, the mRNA comprises: (i) a 5′ terminal cap comprising m7G(5′)ppp(5′)G-2′-O-methyl; (ii) a 5′ untranslated region (UTR) comprising the nucleotide sequence of SEQ ID NO:50; (iii) an open reading frame (ORF) encoding the argininosuccinate lyase (ASL) polypeptide of SEQ ID NO:28; (iv) a 3′ UTR comprising the nucleic acid sequence of SEQ ID NO:108; and (v) a poly-A region comprising A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). In some instances, the mRNA comprises at least one chemically modified nucleobase, sugar, backbone, or any combination thereof. In some instances, all of the uracils of the mRNA are N1-methylpseudouracils. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1A is a western blot depicting ASS1 protein levels in livers from mice of Group 1 (Tris), 2 (eGFP), 3 (hASS1_d2), 4 (hASS1_d4), or 5 (hASS1_d6) (see Table 10 for a description of Groups 1-5). Top image shows detection of V5 tag (top band) and GAPDH (bottom band). Bottom image shows detection of ASS1 (top band) and GAPDH (bottom band). Throughout the figures, “Tris” refers to “Tris-sucrose buffer.” FIG.1B is a graph depicting the fold change of V5 / GAPDH (arbitrary units; top graph) for the western blot of FIG.1A or fold change of ASS1 / GAPDH (arbitrary units; bottom graph) for the western blot of FIG.1A. Attorney Docket No.45817-0022WO1 / MTX977.20 FIG.2A is a graph depicting ammonia levels (uM) in plasma from mice. From left to right: Group 1, Group 2, Group 3 (7 days pre-treatment), Group 3, Group 4, and Group 5 (see Table 10 for a description of the Groups). FIG.2B is a graph depicting citrulline levels (uM) in plasma from mice. From left to right: Groups 1-5 (see Table 10 for a description of the Groups). FIG.3 is a graph depicting ASS1 activity (as determined by arginine production, pmol / min / mg) in livers harvested from mice of Groups 1-5 (see Table 10), from left to right. FIG.4A is a western blot depicting GFP (top image), ASS1 (middle image, top band), GAPDH (middle image, bottom band), ASL (bottom image, top band), and actin (bottom image, bottom band) protein levels in livers 48 hours after dosing with the indicated mRNAs. WT – GFP, KO – GFP, KO – ASS1 / GFP, KO – ASL / GFP, KO – ASS1 / ASL correspond to Groups 1-5, respectively, in Table 11. FIG.4B is a series of graphs depicting ASS1 / GAPDH (fold change over eGFP mice, Group 2 (Table 11)) and ASL / actin (fold change over eGFP mice, Group 2 (Table 11)) for the western blot of FIG.4A. For each graph, bars correspond to Groups 1-5, respectively, from left to right (Table 11). FIG.5 is a series of graphs depicting ammonia levels (ug / dL) at 24 hours (left) and 48 hours (right) post-dosing with the indicated mRNAs. Bars from left to right correspond to Groups 1-5, respectively (see Table 11). * = p value between 0.01 to 0.05, ** = **= p value between 0.001 to 0.01, **** = p <0.0001; ns = not significant. FIG.6 is a series of graphs depicting citrulline levels (uM) at 24 hours (left) and 48 hours (right) post-dosing with the indicated mRNAs. Bars from left to right correspond to Groups 1-5, respectively (see Table 11). * = p value between 0.01 to 0.05, **** = p <0.0001; ns = not significant. FIG.7 is a graph depicting ASS1 and ASL activity (as determined by arginine production, pmol / min / mg) in livers harvested from mice of Groups 1-5 (see Table 11), from left to right. ** = p value between 0.001 to 0.01 FIG.8 is a graph depicting baseline citrulline levels for the samples of FIG.7, prior to the POA assay. Attorney Docket No.45817-0022WO1 / MTX977.20 FIG.9 is a graph depicting citrulline levels (uM) at 0, 2, 6, or 9 days post- dosing with the indicated mRNAs in wild type or fold / fold (“fold”) mice. FIG.10 is a graph depicting citrulline levels (uM) at 0, 2, 6, or 9 days post- dosing with the indicated mRNAs in wild type or fold / fold (“fold”) mice. DETAILED DESCRIPTION 1. ASS1 Argininosuccinate synthetase 1 (ASS1) is an enzyme playing a critical role in the urea cycle. ASS1 catalyzes the conversion of citrulline and aspartate into argininosuccinate, which is further processed ASL to generate arginine. ASS1 is a homotetrameric enzyme consisting of four identical subunits. The functional domains of ASS1 includes an N-terminal domain responsible for binding aspartate, a central domain responsible for binding citrulline, and a C-terminal domain responsible for binding ATP. Mutations of ASS1 gene that result in reduced or absent ASS1 enzyme activity cause type I citrullinemia (CLTN1), one of the autosomal recessive UCDs. CLTN1 is the most common form of the rare disorder, affecting about one in 57,000 births worldwide. CLTN1 usually becomes evident in the first few days of life as ammonia accumulates, resulting in hyperammonemia. The onset of symptoms can occur in infancy or later in childhood, depending on the severity of the enzyme deficiency and the individual's metabolic tolerance. The coding sequence (CDS) for wild type ASS1 canonical mRNA sequence is described at the NCBI Reference Sequence database (RefSeq) under accession number NM_000050.4 (“Homo sapiens argininosuccinate synthase 1 (ASS1), transcript variant 1, mRNA”). The wild type ASS1 canonical protein sequence is described at the RefSeq database under accession number NP_000041.2" (“argininosuccinate synthase [Homo sapiens]”), SEQ ID NO:1 below. 1 msskgsvvla ysggldtsci lvwlkeqgyd viaylanigq kedfeearkk alklgakkvf 61 iedvsrefve efiwpaiqss alyedryllg tslarpciar kqveiaqreg akyvshgatg 121 kgndqvrfel scyslapqik viapwrmpef ynrfkgrndl meyakqhgip ipvtpknpws 181 mdenlmhisy eagilenpkn qappglytkt qdpakapntp dileiefkkg vpvkvtnvkd Attorney Docket No.45817-0022WO1 / MTX977.20 241 gtthqtslel fmylnevagk hgvgridive nrfigmksrg iyetpagtil yhahldieaf 301 tmdrevrkik qglglkfael vytgfwhspe cefvrhciak sqervegkvq vsvlkgqvyi 361 lgresplsly neelvsmnvq gdyeptdatg fininslrlk eyhrlqskvt ak (SEQ ID NO:1) The ASS1 protein is 412 amino acids long. It is noted that the specific nucleic acid sequences encoding the reference protein sequence in the RefSeq sequences are coding sequence (CDS) as indicated in the respective RefSeq database entry. In some instances, the ASS1 proteins of the present invention comprise a substitutional variants of a human ASS1 sequence, which can comprise one, two, three or more than three substitutions relative to human wild type ASS1. See Table 1, below, which provides the amino acid sequence of exemplary ASS1 polypeptides of the invention. Table 1 Name Sequence (substitution A Q R P N V Q K A Q R P N V Q K A Q R P N V Attorney Docket No.45817-0022WO1 / MTX977.20 RKIKQGLGLKFAELVYTGFWHSPECEFVRHCIAKSQERVEGKVQVSVLKGQ VYILGRESPLSLYNEELVSMNVQGDYEPTDATGFININSLRLKEYHRLQSK VTAK (SEQ ID NO:4) A Q R P N V Q K sequence that is at least 80% identical to the amino acid sequence of SEQ ID NO:1, wherein the amino acid sequence comprises: (a) an amino acid other than lysine (K) at the position corresponding to position 58 of SEQ ID NO:1; (b) an amino acid other than lysine (K) at the position corresponding to position 165 of SEQ ID NO:1 and an amino acid other than lysine (K) at the position corresponding to position 176 of SEQ ID NO:1; (c) an amino acid other than cysteine (C) at the position corresponding to position 132 of SEQ ID NO:1; or (d) an amino acid other than lysine (K) at the position corresponding to position 4 of SEQ ID NO:1. In some embodiments, the polypeptide comprises an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:1. In some embodiments, the polypeptide comprises an amino acid sequence that is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to any one of SEQ ID NOs:2-5, while retaining the substitution in any one of SEQ ID NOs:2-5 relative to SEQ ID NO:1. For instance, in some embodiments, the polypeptide comprises an amino acid sequence that is at least 90% identical to SEQ ID NO:2, wherein the polypeptide has the K58R substitution of SEQ ID NO:2. In some embodiments, the polypeptide comprises an amino acid sequence comprising: (a) an arginine (R) at the position corresponding to position 58 of SEQ ID NO:1; (b) an arginine (R) at the position corresponding to position 165 of SEQ ID NO:1 and an arginine (R) at the position corresponding to position 176 of SEQ ID NO:1; (c) an alanine (A) at the position corresponding to position 132 of Attorney Docket No.45817-0022WO1 / MTX977.20 SEQ ID NO:1; or (d) an arginine (R) at the position corresponding to position 4 of SEQ ID NO:1. In some embodiments, the polypeptide comprises an amino acid sequence comprising: the amino acid sequence comprises an arginine (R) at the position corresponding to position 58 of SEQ ID NO:1. In some instances, the polypeptide catalyzes the conversion of citrulline to argininosuccinate. In some embodiments, the polypeptide comprises the amino acid sequence of any one of SEQ ID NOs:2-5. In some embodiments, the polypeptide consists of the amino acid sequence of any one of SEQ ID NOs:2-5. In some embodiments, the polypeptide comprises the amino acid sequence of SEQ ID NO:2. In some embodiments, the polypeptide consists of the amino acid sequence of SEQ ID NO:2. In some embodiments, the ASS1 polypeptide has an ASS1 activity which is at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100% of the Snu13 activity of the corresponding wild-type ASS1 protein (i.e., the same ASS1 protein but without the mutation(s)). Methods for determining ASS1 activity are known in the art; see, e.g., the working examples described herein. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprising an ORF encoding an ASS1 polypeptide is sequence optimized. In certain aspects, the disclosure provides a polynucleotide (e.g., a RNA, e.g., a mRNA) comprising a nucleotide sequence (e.g., an open reading frame (ORF)) encoding an ASS1 polypeptide (e.g., an ASS1 polypeptide described herein, e.g., any one of SEQ ID NOs:1-6). In some embodiments, the ASS1 polypeptide of the invention is a wild type full length human ASS1 protein. In some embodiments, the ASS1 polypeptide of the invention is a variant, a peptide or a polypeptide containing a substitution, and insertion and / or an addition, a deletion and / or a covalent modification with respect to a wild-type ASS1 sequence (e.g., any one of SEQ ID NOs:2-5). In some embodiments, sequence tags or amino acids, can be added to the sequences encoded by the polynucleotides of the invention (e.g., at the N-terminal or C-terminal ends), e.g., for localization. In some embodiments, amino acid residues Attorney Docket No.45817-0022WO1 / MTX977.20 located at the carboxy, amino terminal, or internal regions of a polypeptide of the invention can optionally be deleted providing for fragments. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprising a nucleotide sequence (e.g., an ORF) of the invention encodes a substitutional variant of a human ASS1 sequence, which can comprise one, two, three or more than three substitutions (e.g., any one of SEQ ID NOs:2-5). In some embodiments, the substitutional variant can comprise one or more conservative amino acids substitutions. In other embodiments, the variant is an insertional variant. In other embodiments, the variant is a deletional variant. ASS1 protein fragments, functional protein domains, variants, and homologous proteins (orthologs) are also within the scope of the ASS1 polypeptides of the disclosure. A nonlimiting example of a polypeptide encoded by the ASS1 polynucleotides of the invention is shown in SEQ ID NO:1. Another nonlimiting example of a polypeptide encoded by the ASS1 polynucleotides of the invention is shown in SEQ ID NO:2. 2. ASL Argininosuccinate lyase (ASL) is an enzyme playing a critical role in the urea cycle. ASS1 catalyzes the conversion of citrulline and aspartate into argininosuccinate, which is further processed by ASL to generate arginine. ASL consists of four identical subunits, and the functional domains include an N-terminal domain responsible for binding argininosuccinate and a C-terminal domain responsible for catalytic activity. Mutations or deficiencies in the ASL gene can lead to ASLD, a rare inherited metabolic disorder characterized by a deficiency of ASL activity. The coding sequence (CDS) for wild type ASL canonical mRNA sequence is described at the NCBI Reference Sequence database (RefSeq) under accession number NM_000048.4 (“Homo sapiens argininosuccinate lyase (ASL), transcript variant 2, mRNA”). The wild type ASL canonical protein sequence is described at the RefSeq database under accession number NP_000039.2 (“argininosuccinate lyase isoform 1 [Homo sapiens]”), SEQ ID NO:28 below. 1 masesgklwg grfvgavdpi mekfnasiay drhlwevdvq gskaysrgle kaglltkaem Attorney Docket No.45817-0022WO1 / MTX977.20 61 dqilhgldkv aeewaqgtfk lnsndediht anerrlkeli gatagklhtg rsrndqvvtd 121 lrlwmrqtcs tlsgllweli rtmvdraeae rdvlfpgyth lqraqpirws hwilshaval 181 trdserllev rkrinvlplg sgaiagnplg vdrellrael nfgaitlnsm datserdfva 241 eflfwaslcm thlsrmaedl ilyctkefsf vqlsdaystg sslmpqkknp dslelirska 301 grvfgrcagl lmtlkglpst ynkdlqedke avfevsdtms avlqvatgvi stlqihqenm 361 gqalspdmla tdlayylvrk gmpfrqahea sgkavfmaet kgvalnqlsl qelqtisplf 421 sgdvicvwdy ghsveqygal ggtarssvdw qirqvrallq aqqa (SEQ ID NO:28) The ASL protein is 464 amino acids long. It is noted that the specific nucleic acid sequences encoding the reference protein sequence in the RefSeq sequences are coding sequence (CDS) as indicated in the respective RefSeq database entry. In certain aspects, the disclosure provides a polynucleotide (e.g., a RNA, e.g., a mRNA) comprising a nucleotide sequence (e.g., an open reading frame (ORF)) encoding an ASL polypeptide. In some embodiments, the ASL polypeptide of the invention is a wild type full length human ASL protein. In some embodiments, the ASL polypeptide of the invention is a variant, a peptide or a polypeptide containing a substitution, and insertion and / or an addition, a deletion and / or a covalent modification with respect to a wild-type ASL sequence. In some embodiments, sequence tags or amino acids, can be added to the sequences encoded by the polynucleotides of the invention (e.g., at the N-terminal or C-terminal ends), e.g., for localization. In some embodiments, amino acid residues located at the carboxy, amino terminal, or internal regions of a polypeptide of the invention can optionally be deleted providing for fragments. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprising a nucleotide sequence (e.g., an ORF) of the invention encodes a substitutional variant of a human ASL sequence, which can comprise one, two, three or more than three substitutions. In some embodiments, the substitutional variant can comprise one or more conservative amino acids substitutions. In other embodiments, the variant is an insertional variant. In other embodiments, the variant is a deletional variant. ASL protein fragments, functional protein domains, variants, and homologous proteins (orthologs) are also within the scope of the ASL polypeptides of the disclosure. A nonlimiting example of a polypeptide encoded by the ASL polynucleotides of the invention is shown in SEQ ID NO:7. Attorney Docket No.45817-0022WO1 / MTX977.20 3. Polynucleotides and Open Reading Frames (ORFs) The instant invention features mRNAs for use in treating or preventing CTLN1, ASLD, and other ASS1- or ASL-associated diseases or disorders. In some instances, the mRNAs featured for use in the invention are administered to subjects and encode human ASS1 protein (e.g., any one of SEQ ID NOs:1-6) in vivo. Accordingly, the invention relates, in part, to polynucleotides, e.g., mRNA, comprising an open reading frame of linked nucleosides encoding human ASS1 (e.g., any one of SEQ ID NOs:1-6), isoforms thereof, variants thereof, functional fragments thereof, and fusion proteins comprising ASS1 (e.g., any one of SEQ ID NOs:1-6). Specifically, the invention provides sequence-optimized polynucleotides comprising nucleotides encoding the polypeptide sequence of a human ASS1 (e.g., any one of SEQ ID NOs:1-6, or a variant thereof). In certain aspects, the invention provides polynucleotides (e.g., a RNA such as an mRNA) that comprise a nucleotide sequence (e.g., an ORF) encoding one or more ASS1 polypeptides (e.g., any one of SEQ ID NOs: 1-6). In some embodiments, the encoded ASS1 polypeptide of the invention can be selected from: (i) a full length ASS1 polypeptide (e.g., having the same or essentially the same length as wild-type ASS1, e.g., SEQ ID NO:1, or as any one of SEQ ID NOs:2-5); (ii) a functional fragment of ASS1 described herein (e.g., a truncated (e.g., deletion of carboxy, amino terminal, or internal regions) sequence shorter than ASS1; but still retaining ASS1 activity); (iii) a variant thereof (e.g., full length or truncated ASS1 proteins in which one or more amino acids have been replaced, e.g., variants that retain all or most of the ASS1 activity of the polypeptide with respect to a reference protein (e.g., any natural or artificial variants known in the art)); or (iv) a fusion protein comprising (i) a full length ASS1 protein (e.g., any one of SEQ ID NOs:1-6), an isoform thereof or a variant thereof or a functional fragment thereof, and (ii) a heterologous protein. Attorney Docket No.45817-0022WO1 / MTX977.20 In certain embodiments, the encoded ASS1 polypeptide is a mammalian ASS1 polypeptide, such as a human ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or a functional fragment or a variant thereof. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) encoding an ASS1 polypeptide of the invention (e.g., any one of SEQ ID NOs:1-6) increases ASS1 protein expression levels in cells when introduced in those cells, e.g., by at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100%, compared to ASS1 protein expression levels in the cells prior to the administration of the polynucleotide of the invention. ASS1 protein expression levels can be measured according to methods know in the art. In some embodiments, the polynucleotide is introduced to the cells in vitro. In some embodiments, the polynucleotide is introduced to the cells in vivo. In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence (e.g., an ORF) that encodes a wild-type human ASS1 (e.g., SEQ ID NO:1) or an isoform thereof. In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence (e.g., an ORF) that encodes a variant human ASS1 (e.g., any one of SEQ ID NOs:2-5) or an isoform thereof. In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence (e.g., an ORF) that encodes a fragment of a human ASS1 (e.g., any one of SEQ ID NOs: 1-6) or an isoform thereof. In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence (e.g., an ORF) that encodes a human ASS1 fusion protein. The polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a codon optimized nucleic acid sequence, wherein the open reading frame (ORF) of the codon optimized nucleic acid sequence is derived from an ASS1 protein sequence (e.g., any one of SEQ ID NOs:1-6). For example, for polynucleotides of the invention comprising a sequence optimized ORF encoding ASS1, the corresponding wild type sequence is the native human ASS1. Attorney Docket No.45817-0022WO1 / MTX977.20 In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence encoding ASS1 having the full length sequence of human ASS1 (i.e., including the initiator methionine; amino acids 1-412 of SEQ ID NO:1). In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence (e.g., an ORF) encoding a mutant ASS1 polypeptide. In some embodiments, the polynucleotides of the invention comprise an ORF encoding an ASS1 polypeptide that comprises at least one point mutation in the ASS1 protein sequence (e.g., any one of SEQ ID NOs:2-5) and retains ASS1 protein activity. In some embodiments, the mutant ASS1 polypeptide (e.g., any one of SEQ ID NOs:2-5) has an ASS1 activity which is at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100% of the ASS1 activity of the corresponding wild-type ASS1 protein (i.e., the same ASS1 protein but without the mutation(s)). In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprising an ORF encoding a mutant ASS1 polypeptide (e.g., any one of SEQ ID NOs:2-5) is sequence optimized. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) that encodes an ASS1 polypeptide with mutations that do not alter ASS1 protein activity. Such mutant ASS1 polypeptides can be referred to as function-neutral. In some embodiments, the polynucleotide comprises an ORF that encodes a mutant ASS1 polypeptide comprising one or more function-neutral point mutations. In some embodiments, the mutant ASS1 polypeptide has higher ASS1 protein activity than the corresponding wild-type ASS1 respectively, protein. In some embodiments, the mutant ASS1 polypeptide has an ASS1 activity that is at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100% higher than the activity of the corresponding wild-type ASS1 protein (i.e., the same ASS1 protein but without the mutation(s)). Attorney Docket No.45817-0022WO1 / MTX977.20 In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence (e.g., an ORF) encoding a functional ASS1 protein fragment, e.g., where one or more fragments correspond to a polypeptide subsequence of a wild type ASS1 polypeptide and retain ASS1 protein activity. In some embodiments, the ASS1 protein fragment has activity which is at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100% of the ASS1 protein activity of the corresponding full length ASS1 protein. In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprising an ORF encoding a functional ASS1 protein fragment is sequence optimized. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASS1 protein fragment that has higher ASS1 than the corresponding full length ASS1 protein. Thus, in some embodiments the ASS1 protein fragment has ASS1 which is at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100% higher than the ASS1 activity of the corresponding full length ASS1 protein. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASS1 protein fragment that is at least 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24% or 25% shorter than wild-type ASS1 protein. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide (e.g., the wild-type sequence (e.g., SEQ ID NO:1), functional fragment, or variant thereof (e.g., any one of SEQ ID NOs:2-5)), wherein the nucleotide sequence is at least 90%, at least 95%, at least 97%, at least 98%, or at least 99% identical to the sequence of any one of SEQ ID NOs:8-14. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide Attorney Docket No.45817-0022WO1 / MTX977.20 sequence (e.g., an ORF) encoding an ASS1 polypeptide (e.g., the wild-type sequence (e.g., SEQ ID NO:1)), wherein the nucleotide sequence is 100% identical to the sequence of any one of SEQ ID NOs:8-14. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide (e.g., the wild-type sequence (e.g., SEQ ID NO:1)), wherein the nucleotide sequence is 100% identical to the sequence of SEQ ID NO:8. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:2-5), wherein the nucleotide sequence is at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% identical to the sequence of any one of SEQ ID NOs:11-14. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide (e.g., SEQ ID NO:2), wherein the nucleotide sequence is at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% identical to the sequence of SEQ ID NO:11. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6), wherein the nucleotide sequence has at least 70%, at least 71%, at least 72%, at least 73%, at least 74%, at least 75%, at least 76%, at least 77%, at least 78%, at least 79%, at least 80%, at least 81%, at least 82%, at least 83%, at least 84%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% sequence identity to any one of SEQ ID NOs:8-14. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6), wherein the nucleotide sequence has 70% to 100%, 75% to 100%, 80% to 100%, 85% to 100%, 70% to 95%, 80% to 95%, 70% to 85%, 75% to 90%, 80% to 95%, 70% to 75%, 75% to 80%, 80% to Attorney Docket No.45817-0022WO1 / MTX977.20 85%, 85% to 90%, 90% to 95%, or 95% to 100%, sequence identity to any one of SEQ ID NOs:8-14. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6), wherein the nucleotide sequence is between 70% and 90% identical; between 75% and 85% identical; between 76% and 84% identical; between 77% and 83% identical, between 77% and 82% identical, or between 78% and 81% identical to the sequence of SEQ ID NO:8-11. In some instances, the ASS1 mRNAs featured for use in the invention are administered to subjects in combination with mRNA encoding human ASL1 protein (e.g., SEQ ID NO:7 or SEQ ID NO:28) in vivo. Accordingly, the invention relates, in part, to polynucleotides, e.g., mRNA, comprising an open reading frame of linked nucleosides encoding human ASL (e.g., SEQ ID NO:7 or SEQ ID NO:28), isoforms thereof, variants thereof, functional fragments thereof, and fusion proteins comprising ASL (e.g., SEQ ID NO:7 or SEQ ID NO:28) for use in combination with ASS1 polynucleotides described herein. Specifically, provided herein are sequence- optimized polynucleotides comprising nucleotides encoding the polypeptide sequence of a human ASL (e.g., SEQ ID NO:7 or SEQ ID NO:28, or a variant thereof). In certain aspects, provided herein are polynucleotides (e.g., a RNA such as an mRNA) that comprise a nucleotide sequence (e.g., an ORF) encoding one or more ASL polypeptides (e.g., SEQ ID NO:7 or SEQ ID NO:28). In some embodiments, the encoded ASL polypeptide of the invention can be selected from: (v) a full length ASL polypeptide (e.g., having the same or essentially the same length as wild-type ASL, e.g., SEQ ID NO:28, or as SEQ ID NO:7); (vi) a functional fragment of ASL described herein (e.g., a truncated (e.g., deletion of carboxy, amino terminal, or internal regions) sequence shorter than ASL; but still retaining ASL activity); (vii) a variant thereof (e.g., full length or truncated ASL proteins in which one or more amino acids have been replaced, e.g., variants that retain all or most of the ASL activity of the polypeptide with respect to a Attorney Docket No.45817-0022WO1 / MTX977.20 reference protein (e.g., any natural or artificial variants known in the art)); or (viii) a fusion protein comprising (i) a full length AS: protein (e.g., SEQ ID NO:7 or SEQ ID NO:28), an isoform thereof or a variant thereof or a functional fragment thereof, and (ii) a heterologous protein. In certain embodiments, the encoded ASL polypeptide is a mammalian ASL polypeptide, such as a human ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28) or a functional fragment or a variant thereof. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) encoding an ASL polypeptide of the invention (e.g., SEQ ID NO:7 or SEQ ID NO:28) increases ASL protein expression levels in cells when introduced in those cells, e.g., by at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100%, compared to ASL protein expression levels in the cells prior to the administration of the polynucleotide of the invention. ASL protein expression levels can be measured according to methods know in the art. In some embodiments, the polynucleotide is introduced to the cells in vitro. In some embodiments, the polynucleotide is introduced to the cells in vivo. In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence (e.g., an ORF) that encodes a wild-type human ASL (e.g., SEQ ID NO:28) or an isoform thereof. In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence (e.g., an ORF) that encodes a variant human ASL (e.g., SEQ ID NO:7) or an isoform thereof. In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence (e.g., an ORF) that encodes a fragment of a human ASL (e.g., SEQ ID NO:7 or SEQ ID NO:28) or an isoform thereof. In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence (e.g., an ORF) that encodes a human ASL fusion protein. Attorney Docket No.45817-0022WO1 / MTX977.20 In some instances, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a codon optimized nucleic acid sequence, wherein the open reading frame (ORF) of the codon optimized nucleic acid sequence is derived from an ASL protein sequence (e.g., SEQ ID NO:7 or SEQ ID NO:28). For example, for polynucleotides of the invention comprising a sequence optimized ORF encoding ASL, the corresponding wild type sequence is the native human ASL. In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence encoding ASL having the full length sequence of human ASL (e.g., including the initiator methionine; amino acids 1-464 of SEQ ID NO:28). In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence (e.g., an ORF) encoding a mutant ASL polypeptide. In some embodiments, the polynucleotides of the invention comprise an ORF encoding an ASL polypeptide that comprises at least one point mutation in the ASL protein sequence (e.g., SEQ ID NO:7) and retains ASL protein activity. In some embodiments, the mutant ASL polypeptide (e.g., SEQ ID NO:7) has an ASL activity which is at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100% of the ASL activity of the corresponding wild-type ASL protein (i.e., the same ASL protein but without the mutation(s)). In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprising an ORF encoding a mutant ASL polypeptide (e.g., SEQ ID NO:7) is sequence optimized. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) that encodes an ASL polypeptide with mutations that do not alter ASL protein activity. Such mutant ASL polypeptides can be referred to as function-neutral. In some embodiments, the polynucleotide comprises an ORF that encodes a mutant ASL polypeptide comprising one or more function-neutral point mutations. In some embodiments, the mutant ASL polypeptide has higher ASL protein activity than the corresponding wild-type ASL respectively, protein. In some embodiments, the mutant ASL polypeptide has an ASL activity that is at least 10%, at Attorney Docket No.45817-0022WO1 / MTX977.20 least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100% higher than the activity of the corresponding wild-type ASL protein (i.e., the same ASL protein but without the mutation(s)). In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprise a nucleotide sequence (e.g., an ORF) encoding a functional ASL protein fragment, e.g., where one or more fragments correspond to a polypeptide subsequence of a wild type ASL polypeptide and retain ASL protein activity. In some embodiments, the ASL protein fragment has activity which is at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100% of the ASL protein activity of the corresponding full length ASL protein. In some embodiments, the polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention comprising an ORF encoding a functional ASL protein fragment is sequence optimized. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASL protein fragment that has higher ASL than the corresponding full length ASL protein. Thus, in some embodiments the ASL protein fragment has ASL which is at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 100% higher than the ASL activity of the corresponding full length ASL protein. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASL protein fragment that is at least 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24% or 25% shorter than wild-type ASL protein. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASL polypeptide (e.g., the wild-type sequence (e.g., SEQ ID NO:28), functional fragment, Attorney Docket No.45817-0022WO1 / MTX977.20 or variant thereof (e.g., SEQ ID NO:7)), wherein the nucleotide sequence is at least 90%, at least 95%, at least 97%, at least 98%, or at least 99% identical to the sequence of SEQ ID NO:15. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASL polypeptide (e.g., SEQ ID NO:7), wherein the nucleotide sequence is 100% identical to the sequence of SEQ ID NO:15. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASL polypeptide (e.g., SEQ ID NO:28 or SEQ ID NO:7), wherein the nucleotide sequence has at least 70%, at least 71%, at least 72%, at least 73%, at least 74%, at least 75%, at least 76%, at least 77%, at least 78%, at least 79%, at least 80%, at least 81%, at least 82%, at least 83%, at least 84%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% sequence identity to SEQ ID NO:15. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASL polypeptide (e.g., SEQ ID NO:28 or SEQ ID NO:7), wherein the nucleotide sequence has 70% to 100%, 75% to 100%, 80% to 100%, 85% to 100%, 70% to 95%, 80% to 95%, 70% to 85%, 75% to 90%, 80% to 95%, 70% to 75%, 75% to 80%, 80% to 85%, 85% to 90%, 90% to 95%, or 95% to 100%, sequence identity to SEQ ID NO:15. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASL polypeptide (e.g., SEQ ID NO:28 or SEQ ID NO:7), wherein the nucleotide sequence is between 70% and 90% identical; between 75% and 85% identical; between 76% and 84% identical; between 77% and 83% identical, between 77% and 82% identical, or between 78% and 81% identical to SEQ ID NO:15. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises from about 900 to about 100,000 nucleotides (e.g., from 900 to 1,000, from 900 to 2,000, from 900 to 3,000, from 900 to 4,000, from 900 to 4,500, from 900 to 5,000, from 900 to 5,500, 1,000 to 2,000, from 1,000 to 3,000, from Attorney Docket No.45817-0022WO1 / MTX977.20 1,000 to 4,000, from 1,000 to 4,500, from 1,000 to 5,000, from 1,000 to 5,500, 2,000 to 3,000, from 2,000 to 4,000, from 2,000 to 4,500, from 2,000 to 5,000, from 2,000 to 5,500, from 3,000 to 4,000, from 3,000 to 4,500, from 3,000 to 5,000, from 3,000 to 5,500, from 4,000 to 4,500, from 4,000 to 5,000, from 4,000 to 5,500, 4,500 to 5,000, from 4,500 to 5,500, from 4,000 to 7,000, from 4,000 to 10,000, from 4,000 to 25,000, from 4,000 to 50,000, from 4,000 to 70,000, from 4,000 to 80,000, from 4,000 to 90,000, or from 4,000 to 100,000 nucleotides). In some embodiments, the polynucleotide of the invention (e.g., a RNA, e.g., an mRNA) comprises a nucleotide sequence (e.g., an ORF) encoding a polypeptide described herein, wherein the length of the nucleotide sequence (e.g., an ORF) is at least 500 nucleotides in length (e.g., at least or greater than about 500, 600, 700, 800, 900, 1,000, 1,100, 1,200, 1,300, 1,400, 1,500, 1,600, 1,700, 1,800, 1,900, 2,000, 2,100, 2,200, 2,300, 2,400, 2,500, 2,600, 2,700, 2,800, 2,900, 3,000, 3,100, 3,200, 3,300, 3,400, 3,500, 3,600, 3,700, 3,800, 3,900, 4,000, 4,100, 4,200, 4,300, 4,400, 4,500, 4,600, 4,700, 4,800, 4,900, 5,000, 5,100, 5,200, 5,300, 5,400, 5,500, 5,600, 5,700, 5,800, 5,900, 6,000, 7,000, 8,000, 9,000, 10,000, 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000 or up to and including 100,000 nucleotides). In some embodiments, the polynucleotide of the invention (e.g., a RNA, e.g., an mRNA) comprises a nucleotide sequence (e.g., an ORF, e.g., any one of SEQ ID NOs:8-14) encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) and further comprises at least one nucleic acid sequence that is noncoding, e.g., a microRNA binding site. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention further comprises a 5′ UTR (e.g., set forth in Table 3, e.g., SEQ ID NO:50 or SEQ ID NO:58) and a 3′ UTR (e.g., set forth in Table 4 or Table 6, e.g., SEQ ID NO:135 or any one of SEQ ID NOs:141-143). In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises the sequence of SEQ ID NO:8. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises the sequence of SEQ ID NO:11. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises the sequence of SEQ ID NO:12. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises the sequence of SEQ ID NO:13. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of Attorney Docket No.45817-0022WO1 / MTX977.20 the invention comprises the sequence of SEQ ID NO:14. In a further embodiment, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a 5′ terminal cap (e.g., m7Gp-ppGm-A, Cap0, Cap1, ARCA, inosine, N1-methyl-guanosine, 2′-fluoro- guanosine, 7-deaza-guanosine, 8-oxo-guanosine, 2-amino-guanosine, LNA- guanosine, 2-azidoguanosine, Cap2, Cap4, 5′ methylG cap, or an analog thereof) and a poly-A-tail region (e.g., about 100 nucleotides in length (SEQ ID NO:195)). In a further embodiment, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a 5′ UTR comprising a nucleic acid sequence of SEQ ID NO:50. In a further embodiment, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a 5′ UTR comprising a nucleic acid sequence of SEQ ID NO:58. In a further embodiment, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a 3′ UTR comprising a nucleic acid sequence of SEQ ID NO:135. In a further embodiment, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a 3′ UTR comprising a nucleic acid sequence of any one of SEQ ID NOs:141-143. In a further embodiment, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a 3′ UTR comprising a nucleic acid sequence of SEQ ID NO:141. In some embodiments, the mRNA comprises a polyA tail. In some instances, the poly A tail is 50-150 (SEQ ID NO:197), 75-150 (SEQ ID NO:198), 85-150 (SEQ ID NO:199), 90-120 (SEQ ID NO:193), 90-130 (SEQ ID NO:194), or 90-150 (SEQ ID NO:192) nucleotides in length. In some instances, the poly A tail is 100 nucleotides in length (SEQ ID NO:195). In some instances, the poly A tail is protected (e.g., with an inverted deoxy- thymidine). In some instances, the poly A tail comprises A100-UCUAG-A20- inverted deoxy-thymidine (SEQ ID NO:211). In some instances, the poly A tail is A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). In some embodiments, the polynucleotide of the invention (e.g., a RNA, e.g., an mRNA) comprises a nucleotide sequence (e.g., an ORF, e.g., SEQ ID NO:15) encoding an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28) and further comprises at least one nucleic acid sequence that is noncoding, e.g., a microRNA binding site. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention further comprises a 5′ UTR (e.g., set forth in Table 3, e.g., SEQ ID NO:50 or SEQ ID NO:58) and a 3′ UTR (e.g., set forth in Table 4 or Table 6, e.g., SEQ ID NO:135 or any one of SEQ ID NOs:141-143). In some embodiments, the Attorney Docket No.45817-0022WO1 / MTX977.20 polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises the sequence of SEQ ID NO:15. In a further embodiment, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a 5′ terminal cap (e.g., m7Gp-ppGm-A, Cap0, Cap1, ARCA, inosine, N1-methyl-guanosine, 2′-fluoro-guanosine, 7-deaza-guanosine, 8-oxo- guanosine, 2-amino-guanosine, LNA-guanosine, 2-azidoguanosine, Cap2, Cap4, 5′ methylG cap, or an analog thereof) and a poly-A-tail region (e.g., about 100 nucleotides in length (SEQ ID NO:195)). In a further embodiment, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a 5′ UTR comprising a nucleic acid sequence of SEQ ID NO:50. In a further embodiment, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a 5′ UTR comprising a nucleic acid sequence of SEQ ID NO:58. In a further embodiment, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a 3′ UTR comprising a nucleic acid sequence of SEQ ID NO:135. In a further embodiment, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a 3′ UTR comprising a nucleic acid sequence of any one of SEQ ID NOs:141-143. In a further embodiment, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a 3′ UTR comprising a nucleic acid sequence of SEQ ID NO:141. In some embodiments, the mRNA comprises a polyA tail. In some instances, the poly A tail is 50-150 (SEQ ID NO:197), 75-150 (SEQ ID NO:198), 85-150 (SEQ ID NO:199), 90-120 (SEQ ID NO:193), 90-130 (SEQ ID NO:194), or 90-150 (SEQ ID NO:192) nucleotides in length. In some instances, the poly A tail is 100 nucleotides in length (SEQ ID NO:195). In some instances, the poly A tail is protected (e.g., with an inverted deoxy- thymidine). In some instances, the poly A tail comprises A100-UCUAG-A20- inverted deoxy-thymidine (SEQ ID NO:211). In some instances, the poly A tail is A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). In some embodiments, the polynucleotide of the invention (e.g., a RNA, e.g., an mRNA) comprises a nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide or an ASL polypeptide is single stranded or double stranded. In some embodiments, a polynucleotide of the invention comprising a nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide or an ASL polypeptide (e.g., the wild-type sequence, functional fragment, or variant thereof) is DNA or RNA. In some embodiments, the polynucleotide of the invention is RNA. In some embodiments, the polynucleotide of the invention is, or functions as, an mRNA. Attorney Docket No.45817-0022WO1 / MTX977.20 In some embodiments, the mRNA comprises a nucleotide sequence (e.g., an ORF) that encodes at least one ASS1 polypeptide or at least one ASL polypeptide, and is capable of being translated to produce the encoded ASS1 polypeptide or ASL polypeptide, respectively, in vitro, in vivo, in situ or ex vivo. In some embodiments, the polynucleotide of the invention (e.g., a RNA, e.g., an mRNA) comprises a sequence-optimized nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide or an ASL polypeptide (e.g., the wild-type sequence, functional fragment, or variant thereof), wherein the polynucleotide comprises at least one chemically modified nucleobase, e.g., N1-methylpseudouracil or 5- methoxyuracil. In certain embodiments, all uracils in the polynucleotide are N1-methylpseudouracils. In other embodiments, all uracils in the polynucleotide are 5-methoxyuracils. In some embodiments, the polynucleotide further comprises a miRNA binding site, e.g., a miRNA binding site that binds to miR-142 and / or a miRNA binding site that binds to miR-126. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) disclosed herein is formulated with a delivery agent comprising, e.g., a compound having the Formula (I), e.g., Compound II or Compound B; a compound having the Formula (III), (IV), (V), or (VI), e.g., Compound VI or Compound I, or any combination thereof. In some embodiments, the delivery agent comprises an ionizable amino lipid (e.g., Compound II, VI, or B), a helper lipid (e.g., DSPC), a sterol (e.g., Cholesterol), and a PEG lipid (e.g., Compound I or PEG-DMG), e.g., with a mole ratio in the range of about (i) 40-50 mol% ionizable amino lipid (e.g., Compound II, VI, or B), optionally 45-50 mol% ionizable amino lipid, for example, 45-46 mol%, 46-47 mol%, 47-48 mol%, 48-49 mol%, or 49-50 mol% for example about 45 mol%, 45.5 mol%, 46 mol%, 46.5 mol%, 47 mol%, 47.5 mol%, 48 mol%, 48.5 mol%, 49 mol%, or 49.5 mol%; (ii) 30-45 mol% sterol (e.g., cholesterol), optionally 35-42 mol% sterol, for example, 30-31 mol%, 31-32 mol%, 32-33 mol%, 33-34 mol%, 35-35 mol%, 35-36 mol%, 36-37 mol%, 37-38 mol%, 38-39 mol%, or 39-40 mol%, or 40-42 mol% sterol; (iii) 5-15 mol% helper lipid (e.g., DSPC), optionally 10-15 mol% helper lipid, for example, 5-6 mol%, 6-7 mol%, 7-8 mol%, 8- 9 mol%, 9-10 mol%, 10-11 mol%, 11-12 mol%, 12-13 mol%, 13-14 mol%, or 14-15 mol% helper lipid; and (iv) 1-5% PEG lipid (e.g., Compound I or PEG-DMG), Attorney Docket No.45817-0022WO1 / MTX977.20 optionally 1-5 mol% PEG lipid, for example 1.5 to 2.5 mol%, 1-2 mol%, 2-3 mol%, 3-4 mol%, or 4-5 mol% PEG lipid. In some embodiments, the delivery agent comprises Compound II, Cholesterol, DSPC, and Compound I. In some embodiments, the polynucleotide of the disclosure is an mRNA that comprises a 5′-terminal cap (e.g., Cap1, e.g., m7Gp-ppGm-A), a 5′UTR comprising the nucleotide sequence of SEQ ID NO:50 or SEQ ID NO:58, a nucleotide sequence (e.g., an ORF, e.g., any one of SEQ ID NOs:8-14) encoding an ASS1 polypeptide (e.g., the wild-type sequence, functional fragment, or variant thereof), a 3′UTR (e.g., SEQ ID NO:135 or any one of SEQ ID NOs:141-143), and a poly A tail (e.g., about 100 nt in length, e.g., SEQ ID NO:195), wherein all uracils in the polynucleotide are N1-methylpseudouracils or 5-methoxyuracil. In some embodiments, the delivery agent is an LNP. In some embodiments, the delivery agent comprises Compound II or Compound VI as the ionizable amino lipid and PEG-DMG or Compound I as the PEG lipid. In some embodiments, the polynucleotide of the disclosure is an mRNA that comprises a 5′-terminal cap (e.g., Cap1, e.g., m7Gp-ppGm-A), a 5′UTR (e.g., SEQ ID NO:50), the ORF sequence of SEQ ID NO:8, a 3′UTR (e.g., any one of SEQ ID NOs:141-143), and a poly A tail (e.g., about 100 nt in length, e.g., SEQ ID NO:195), wherein all uracils in the polynucleotide are N1-methylpseudouracils or 5- methoxyuracil. In some embodiments, the delivery agent is an LNP. In some embodiments, the delivery agent comprises Compound II or Compound VI as the ionizable amino lipid and PEG-DMG or Compound I as the PEG lipid. In some embodiments, the polynucleotide of the disclosure is an mRNA that comprises a 5′-terminal cap (e.g., Cap1, e.g., m7Gp-ppGm-A), a 5′UTR (e.g., SEQ ID NO:50), the ORF sequence of SEQ ID NO:11, a 3′UTR (e.g., any one of SEQ ID NOs:141-143), and a poly A tail (e.g., about 100 nt in length, e.g., SEQ ID NO:195), wherein all uracils in the polynucleotide are N1-methylpseudouracils or 5- methoxyuracil. In some embodiments, the delivery agent is an LNP. In some embodiments, the delivery agent comprises Compound II or Compound VI as the ionizable amino lipid and PEG-DMG or Compound I as the PEG lipid. In some embodiments, the polynucleotide of the disclosure is an mRNA that comprises a 5′-terminal cap (e.g., Cap1, e.g., m7Gp-ppGm-A), a 5′UTR comprising Attorney Docket No.45817-0022WO1 / MTX977.20 the nucleotide sequence of SEQ ID NO:50 or SEQ ID NO:58, a nucleotide sequence (e.g., an ORF, e.g., any one of SEQ ID NOs:15) encoding an ASL polypeptide (e.g., the wild-type sequence, functional fragment, or variant thereof), a 3′UTR (e.g., SEQ ID NO:135 or any one of SEQ ID NOs:141-143), and a poly A tail (e.g., about 100 nt in length, e.g., SEQ ID NO:195), wherein all uracils in the polynucleotide are N1-methylpseudouracils or 5-methoxyuracil. In some embodiments, the delivery agent is an LNP. In some embodiments, the delivery agent comprises Compound II or Compound VI as the ionizable amino lipid and PEG-DMG or Compound I as the PEG lipid. In some embodiments, the polynucleotide of the disclosure is an mRNA that comprises a 5′-terminal cap (e.g., Cap1, e.g., m7Gp-ppGm-A), a 5′UTR (e.g., SEQ ID NO:50), the ORF sequence of SEQ ID NO:15, a 3′UTR (e.g., SEQ ID NO:135), and a poly A tail (e.g., about 100 nt in length, e.g., SEQ ID NO:195), wherein all uracils in the polynucleotide are N1-methylpseudouracils or 5-methoxyuracil. In some embodiments, the delivery agent is an LNP. In some embodiments, the delivery agent comprises Compound II or Compound VI as the ionizable amino lipid and PEG-DMG or Compound I as the PEG lipid. 4. Signal Sequences The polynucleotides (e.g., a RNA, e.g., an mRNA) of the invention can also comprise nucleotide sequences that encode additional features that facilitate trafficking of the encoded polypeptides to therapeutically relevant sites. One such feature that aids in protein trafficking is the signal sequence, or targeting sequence. The peptides encoded by these signal sequences are known by a variety of names, including targeting peptides, transit peptides, and signal peptides. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprises a nucleotide sequence (e.g., an ORF) that encodes a signal peptide operably linked to a nucleotide sequence that encodes an ASS1 polypeptide or an ASL polypeptide described herein. In some embodiments, the “signal sequence” or “signal peptide” is a polynucleotide or polypeptide, respectively, which is from about 30-210, e.g., about Attorney Docket No.45817-0022WO1 / MTX977.20 45-80 or 15-60 nucleotides (e.g., about 20, 30, 40, 50, 60, or 70 amino acids) in length that, optionally, is incorporated at the 5′ (or N-terminus) of the coding region or the polypeptide, respectively. Addition of these sequences results in trafficking the encoded polypeptide to a desired site, such as the endoplasmic reticulum or the mitochondria through one or more targeting pathways. Some signal peptides are cleaved from the protein, for example by a signal peptidase after the proteins are transported to the desired site. In some embodiments, the polynucleotide of the invention comprises a nucleotide sequence encoding an ASS1 polypeptide or an ASL polypeptide, wherein the nucleotide sequence further comprises a 5′ nucleic acid sequence encoding a heterologous signal peptide. 5. Fusion Proteins In some embodiments, the polynucleotide of the invention (e.g., a RNA, e.g., an mRNA) can comprise more than one nucleic acid sequence (e.g., an ORF) encoding a polypeptide of interest. In some embodiments, polynucleotides of the invention comprise a single ORF encoding an ASS1 polypeptide or an ASL polypeptide, a functional fragment, or a variant thereof. However, in some embodiments, the polynucleotide of the invention can comprise more than one ORF, for example, a first ORF encoding (i) an ASS1 polypeptide or an ASL polypeptide (a first polypeptide of interest), a functional fragment, or a variant thereof, and (ii) a second ORF expressing a second polypeptide of interest. In some embodiments, two or more polypeptides of interest can be genetically fused, i.e., two or more polypeptides can be encoded by the same ORF. In some embodiments, the polynucleotide can comprise a nucleic acid sequence encoding a linker (e.g., a G4S (SEQ ID NO: 200) peptide linker or another linker known in the art) between two or more polypeptides of interest. In some embodiments, a polynucleotide of the invention (e.g., a RNA, e.g., an mRNA) can comprise two, three, four, or more ORFs, each expressing a polypeptide of interest. Linkers and Cleavable Peptides Attorney Docket No.45817-0022WO1 / MTX977.20 In certain embodiments, the mRNAs of the disclosure encode more than one ASS1 or ASL domain or a heterologous domain, referred to herein as multimer constructs. In certain embodiments of the multimer constructs, the mRNA further encodes a linker located between each domain. The linker can be, for example, a cleavable linker or protease-sensitive linker. In certain embodiments, the linker is selected from the group consisting of F2A linker, P2A linker, T2A linker, E2A linker, and combinations thereof. This family of self-cleaving peptide linkers, referred to as 2A peptides, has been described in the art (see for example, Kim, J.H. et al. (2011) PLoS ONE 6:e18556). In certain embodiments, the linker is an F2A linker. In certain embodiments, the linker is a GGGS (SEQ ID NO: 201) linker. In certain embodiments, the linker is a (GGGS)n (SEQ ID NO: 202) linker, wherein n =2, 3,4, or 5. In certain embodiments, the multimer construct contains three domains with intervening linkers, having the structure: domain-linker-domain-linker-domain e.g., ASS1 domain-linker-ASS1 domain-linker-ASS1 domain or ASL domain-linker-ASL domain-linker-ASL domain. In one embodiment, the cleavable linker is an F2A linker (e.g., having the amino acid sequence GSGVKQTLNFDLLKLAGDVESNPGP (SEQ ID NO:189)). In other embodiments, the cleavable linker is a T2A linker (e.g., having the amino acid sequence GSGEGRGSLLTCGDVEENPGP (SEQ ID NO:190)), a P2A linker (e.g., having the amino acid sequence GSGATNFSLLKQAGDVEENPGP (SEQ ID NO:191)) or an E2A linker (e.g., having the amino acid sequence GSGQCTNYALLKLAGDVESNPGP (SEQ ID NO:186)). The skilled artisan will appreciate that other art-recognized linkers may be suitable for use in the constructs of the invention (e.g., encoded by the polynucleotides of the invention). The skilled artisan will likewise appreciate that other multicistronic constructs may be suitable for use in the invention. In exemplary embodiments, the construct design yields approximately equimolar amounts of intrabody and / or domain thereof encoded by the constructs of the invention. In one embodiment, the self-cleaving peptide may be, but is not limited to, a 2A peptide. A variety of 2A peptides are known and available in the art and may be used, including e.g., the foot and mouth disease virus (FMDV) 2A peptide, the equine rhinitis A virus 2A peptide, the Thosea asigna virus 2A peptide, and the porcine Attorney Docket No.45817-0022WO1 / MTX977.20 teschovirus-12A peptide. 2A peptides are used by several viruses to generate two proteins from one transcript by ribosome-skipping, such that a normal peptide bond is impaired at the 2A peptide sequence, resulting in two discontinuous proteins being produced from one translation event. As a non-limiting example, the 2A peptide may have the protein sequence of SEQ ID NO: 191, fragments or variants thereof. In one embodiment, the 2A peptide cleaves between the last glycine and last proline. As another non-limiting example, the polynucleotides of the present invention may include a polynucleotide sequence encoding the 2A peptide having the protein sequence of fragments or variants of SEQ ID NO: 191. One example of a polynucleotide sequence encoding the 2A peptide is:GGAAGCGGAGCUACUAACUUCAGCCUGCUGAAGCAGGCUGGAGACGU GGAGGAGAACCCUGGACCU (SEQ ID NO:187). In one illustrative embodiment, a 2A peptide is encoded by the following sequence: 5′- UCCGGACUCAGAUCCGGGGAUCUCAAAAUUGUCGCUCCUGUCAAACAA ACUCUUAACUUUGAUUUACUCAAACUGGCUGGGGAUGUAGAAAGCAAU CCAGGUCCACUC-3′(SEQ ID NO: 188). The polynucleotide sequence of the 2A peptide may be modified or codon optimized by the methods described herein and / or are known in the art. In one embodiment, this sequence may be used to separate the coding regions of two or more polypeptides of interest. As a non-limiting example, the sequence encoding the F2A peptide may be between a first coding region A and a second coding region B (A-F2Apep-B). The presence of the F2A peptide results in the cleavage of the one long protein between the glycine and the proline at the end of the F2A peptide sequence (NPGP (SEQ ID NO:205) is cleaved to result in NPG and P) thus creating separate protein A (with 21 amino acids of the F2A peptide attached, ending with NPG) and separate protein B (with 1 amino acid, P, of the F2A peptide attached). Likewise, for other 2A peptides (P2A, T2A and E2A), the presence of the peptide in a long protein results in cleavage between the glycine and proline at the end of the 2A peptide sequence (NPGP (SEQ ID NO:205) is cleaved to result in NPG and P). Protein A and protein B may be the same or different peptides or polypeptides of interest (e.g., an ASS1 polypeptide such as full length human ASS1). Attorney Docket No.45817-0022WO1 / MTX977.20 6. Sequence Optimization of Nucleotide Sequence Encoding an ASS1 Polypeptide or an ASL Polypeptide The polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention is sequence optimized. In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide or an ASL polypeptide, optionally, a nucleotide sequence (e.g., an ORF) encoding another polypeptide of interest, a 5′-UTR, a 3′-UTR, the 5′ UTR or 3′ UTR optionally comprising at least one microRNA binding site, optionally a nucleotide sequence encoding a linker, a polyA tail, or any combination thereof), in which the ORF(s) are sequence optimized. A sequence-optimized nucleotide sequence, e.g., a codon-optimized mRNA sequence encoding an ASS1 polypeptide or an ASL polypeptide is a sequence comprising at least one synonymous nucleobase substitution with respect to a reference sequence (e.g., a wild type nucleotide sequence encoding an ASS1 polypeptide or an ASL polypeptide, respectively). A sequence-optimized nucleotide sequence can be partially or completely different in sequence from the reference sequence. For example, a reference sequence encoding polyserine uniformly encoded by UCU codons can be sequence-optimized by having 100% of its nucleobases substituted (for each codon, U in position 1 replaced by A, C in position 2 replaced by G, and U in position 3 replaced by C) to yield a sequence encoding polyserine which would be uniformly encoded by AGC codons. The percentage of sequence identity obtained from a global pairwise alignment between the reference polyserine nucleic acid sequence and the sequence- optimized polyserine nucleic acid sequence would be 0%. However, the protein products from both sequences would be 100% identical. Some sequence optimization (also sometimes referred to codon optimization) methods are known in the art (and discussed in more detail below) and can be useful to achieve one or more desired results. These results can include, e.g., matching codon frequencies in certain tissue targets and / or host organisms to ensure proper folding; biasing G / C content to increase mRNA stability or reduce secondary structures; minimizing tandem repeat codons or base runs that can impair gene construction or expression; customizing transcriptional and translational control regions; inserting or Attorney Docket No.45817-0022WO1 / MTX977.20 removing protein trafficking sequences; removing / adding post translation modification sites in an encoded protein (e.g., glycosylation sites); adding, removing or shuffling protein domains; inserting or deleting restriction sites; modifying ribosome binding sites and mRNA degradation sites; adjusting translational rates to allow the various domains of the protein to fold properly; and / or reducing or eliminating problem secondary structures within the polynucleotide. Sequence optimization tools, algorithms and services are known in the art, non-limiting examples include services from GeneArt (Life Technologies), DNA2.0 (Menlo Park CA) and / or proprietary methods. Codon options for each amino acid are given in Table 2. Table 2. Codon Options Amino Acid Single Letter Codon Options Code of nt n some embod mens, a po ynuc eo de (e.g., a , e.g., an m ) o he invention comprises a sequence-optimized nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide or ASL polypeptide, a functional fragment, or a Attorney Docket No.45817-0022WO1 / MTX977.20 variant thereof, wherein the ASS1 polypeptide or ASL polypeptide functional fragment, or a variant thereof encoded by the sequence-optimized nucleotide sequence has improved properties (e.g., compared to an ASS1 or an ASL, respectively, polypeptide, functional fragment, or a variant thereof encoded by a reference nucleotide sequence that is not sequence optimized), e.g., improved properties related to expression efficacy after administration in vivo. Such properties include, but are not limited to, improving nucleic acid stability (e.g., mRNA stability), increasing translation efficacy in the target tissue, reducing the number of truncated proteins expressed, improving the folding or prevent misfolding of the expressed proteins, reducing toxicity of the expressed products, reducing cell death caused by the expressed products, increasing and / or decreasing protein aggregation. In some embodiments, the sequence-optimized nucleotide sequence (e.g., an ORF) is codon optimized for expression in human subjects, having structural and / or chemical features that avoid one or more of the problems in the art, for example, features which are useful for optimizing formulation and delivery of nucleic acid- based therapeutics while retaining structural and functional integrity; overcoming a threshold of expression; improving expression rates; half-life and / or protein concentrations; optimizing protein localization; and avoiding deleterious bio- responses such as the immune response and / or degradation pathways. In some embodiments, the polynucleotides of the invention comprise a nucleotide sequence (e.g., a nucleotide sequence (e.g., an ORF) encoding an ASS1 or an ASL polypeptide, a nucleotide sequence (e.g., an ORF) encoding another polypeptide of interest, a 5′-UTR, a 3′-UTR, a microRNA binding site, a nucleic acid sequence encoding a linker, or any combination thereof) that is sequence-optimized according to a method comprising: (i) substituting at least one codon in a reference nucleotide sequence (e.g., an ORF encoding an ASS1 polypeptide or an ASL polypeptide) with an alternative codon to increase or decrease uridine content to generate a uridine-modified sequence; (ii) substituting at least one codon in a reference nucleotide sequence (e.g., an ORF encoding an ASS1 polypeptide or an ASL polypeptide) with an alternative codon having a higher codon frequency in the synonymous codon set; Attorney Docket No.45817-0022WO1 / MTX977.20 (iii) substituting at least one codon in a reference nucleotide sequence (e.g., an ORF encoding an ASS1 polypeptide or an ASL polypeptide) with an alternative codon to increase G / C content; or (iv) a combination thereof. In some embodiments, the sequence-optimized nucleotide sequence (e.g., an ORF encoding an ASS1 polypeptide or an ASL polypeptide) has at least one improved property with respect to the reference nucleotide sequence. In some embodiments, the sequence optimization method is multiparametric and comprises one, two, three, four, or more methods disclosed herein and / or other optimization methods known in the art. Features, which can be considered beneficial in some embodiments of the invention, can be encoded by or within regions of the polynucleotide and such regions can be upstream (5′) to, downstream (3′) to, or within the region that encodes the ASS1 polypeptide or ASL polypeptide. These regions can be incorporated into the polynucleotide before and / or after sequence-optimization of the protein encoding region or open reading frame (ORF). Examples of such features include, but are not limited to, untranslated regions (UTRs), microRNA sequences, Kozak sequences, oligo(dT) sequences, poly-A tail, and detectable tags and can include multiple cloning sites that can have XbaI recognition. In some embodiments, the polynucleotide of the invention comprises a 5′ UTR, a 3′ UTR and / or a microRNA binding site. In some embodiments, the polynucleotide comprises two or more 5′ UTRs and / or 3′ UTRs, which can be the same or different sequences. In some embodiments, the polynucleotide comprises two or more microRNA binding sites, which can be the same or different sequences. Any portion of the 5′ UTR, 3′ UTR, and / or microRNA binding site, including none, can be sequence-optimized and can independently contain one or more different structural or chemical modifications, before and / or after sequence optimization. In some embodiments, after optimization, the polynucleotide is reconstituted and transformed into a vector such as, but not limited to, plasmids, viruses, cosmids, and artificial chromosomes. For example, the optimized polynucleotide can be reconstituted and transformed into chemically competent E. coli, yeast, neurospora, Attorney Docket No.45817-0022WO1 / MTX977.20 maize, drosophila, etc. where high copy plasmid-like or chromosome structures occur by methods described herein. 7. Sequence-Optimized Nucleotide Sequences Encoding ASS1 or ASL Polypeptides In some embodiments, the polynucleotide of the invention comprises a sequence-optimized nucleotide sequence encoding an ASS1 polypeptide disclosed herein. In some embodiments, the polynucleotide of the invention comprises an open reading frame (ORF) encoding an ASS1 polypeptide, wherein the ORF has been sequence optimized. Additional exemplary sequence-optimized nucleotide sequences encoding an ASS1 polypeptide are set forth in any one of SEQ ID NOs:8-14. In some embodiments, the sequence optimized ASS1 polypeptide, fragment, or variant thereof is used to practice the methods disclosed herein. An exemplary sequence-optimized nucleotide sequence encoding an ASS1 polypeptide is set forth as SEQ ID NO:8. In some embodiments, the sequence optimized ASS1 polypeptide, fragment, or variant thereof is used to practice the methods disclosed herein. Another exemplary sequence-optimized nucleotide sequence encoding an ASS1 polypeptide is set forth as SEQ ID NO:11. In some embodiments, the sequence optimized ASS1 polypeptide, fragment, or variant thereof is used to practice the methods disclosed herein. In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided herein, for example, m7Gp-ppGm-A; (ii) a 5′ UTR comprising a nucleotide sequence set forth in Table 3 (e.g., SEQ ID NO:50 or SEQ ID NO:58); (iii) an open reading frame encoding a polypeptide comprising an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6), e.g., a sequence optimized nucleic acid sequence encoding ASS1 set forth as any one of SEQ ID NOs:8-14; (iv) at least one stop codon (if not present at 5′ terminus of 3′UTR); Attorney Docket No.45817-0022WO1 / MTX977.20 (v) a 3′ UTR comprising a nucleotide sequence set forth in Table 4 or Table 6 (e.g., SEQ ID NO:135 or any one of SEQ ID NOs:141-143); and (vi) a poly-A tail provided above (e.g., SEQ ID NO:195). In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided herein, for example, m7Gp-ppGm-A; (ii) a 5′ UTR comprising the nucleotide sequence set forth in SEQ ID NO:50; (iii) an open reading frame encoding a polypeptide comprising an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6), e.g., a sequence optimized nucleic acid sequence encoding ASS1 set forth as any one of SEQ ID NOs:8-14; (iv) at least one stop codon (if not present at 5′ terminus of 3′UTR); (v) a 3′ UTR comprising a nucleotide sequence set forth in Table 4 or Table 6 (e.g., SEQ ID NO:135 or any one of SEQ ID NOs:141-143); and (vi) a poly-A tail provided above (e.g., SEQ ID NO:195). In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided herein, for example, m7Gp-ppGm-A; (ii) a 5′ UTR comprising a nucleotide sequence set forth in Table 3 (e.g., SEQ ID NO:50 or SEQ ID NO:58); (iii) an open reading frame encoding a polypeptide comprising an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6), e.g., a sequence optimized nucleic acid sequence encoding ASS1 set forth as any one of SEQ ID NOs:8-14; (iv) at least one stop codon (if not present at 5′ terminus of 3′UTR); (v) a 3′ UTR comprising the nucleotide sequence set forth in SEQ ID NO:141; and (vi) a poly-A tail provided above (e.g., SEQ ID NO:195). In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided herein, for example, m7Gp-ppGm-A; Attorney Docket No.45817-0022WO1 / MTX977.20 (ii) a 5′ UTR comprising the nucleotide sequence set forth in SEQ ID NO:50; (iii) an open reading frame comprising the nucleotide sequence set forth in SEQ ID NO:8; (iv) at least one stop codon (if not present at 5′ terminus of 3′UTR); (v) a 3′ UTR comprising the nucleotide sequence set forth in SEQ ID NO:141; and (vi) a poly-A tail provided above (e.g., SEQ ID NO:195). In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided herein, for example, m7Gp-ppGm-A; (ii) a 5′ UTR comprising the nucleotide sequence set forth in SEQ ID NO:50; (iii) an open reading frame comprising the nucleotide sequence set forth in SEQ ID NO:11; (iv) at least one stop codon (if not present at 5′ terminus of 3′UTR); (v) a 3′ UTR comprising the nucleotide sequence set forth in SEQ ID NO:141; and (vi) a poly-A tail provided above (e.g., SEQ ID NO:195). In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided herein, for example, m7Gp-ppGm-A; (ii) a 5′ UTR comprising the nucleotide sequence set forth in SEQ ID NO:50; (iii) an open reading frame comprising the nucleotide sequence set forth in any one of SEQ ID NOs:8-14; (iv) at least one stop codon (if not present at 5′ terminus of 3′UTR); (v) a 3′ UTR comprising the nucleotide sequence set forth in SEQ ID NO:141; and (vi) a poly-A tail provided above (e.g., SEQ ID NO:195). In certain embodiments, all uracils in the polynucleotide are N1-methylpseudouracil (G5). In certain embodiments, all uracils in the polynucleotide are 5-methoxyuracil. Attorney Docket No.45817-0022WO1 / MTX977.20 In some embodiments, the polynucleotide of the invention comprises a sequence-optimized nucleotide sequence encoding an ASL polypeptide disclosed herein. In some embodiments, the polynucleotide of the invention comprises an open reading frame (ORF) encoding an ASL polypeptide, wherein the ORF has been sequence optimized. An exemplary sequence-optimized nucleotide sequence encoding an ASL polypeptide is set forth as SEQ ID NO:15. In some embodiments, the sequence optimized ASL polypeptide, fragment, or variant thereof is used to practice the methods disclosed herein. In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASL polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided herein, for example, m7Gp-ppGm-A; (ii) a 5′ UTR comprising a nucleotide sequence set forth in Table 3 (e.g., SEQ ID NO:50); (iii) an open reading frame encoding a polypeptide comprising an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28), e.g., a sequence optimized nucleic acid sequence encoding ASL set forth as SEQ ID NO:15; (iv) at least one stop codon (if not present at 5′ terminus of 3′UTR); (v) a 3′ UTR comprising a nucleotide sequence set forth in Table 4 or Table 6 (e.g., SEQ ID NO:108); and (vi) a poly-A tail provided above (e.g., SEQ ID NO:195). In certain embodiments, all uracils in the polynucleotide are N1-methylpseudouracil (G5). In certain embodiments, all uracils in the polynucleotide are 5-methoxyuracil. The sequence-optimized nucleotide sequences disclosed herein are distinct from the corresponding wild type nucleotide acid sequences and from other known sequence-optimized nucleotide sequences, e.g., these sequence-optimized nucleic acids have unique compositional characteristics. In some embodiments, the percentage of uracil or thymine nucleobases in a sequence-optimized nucleotide sequence is modified (e.g., reduced) with respect to the percentage of uracil or thymine nucleobases in the reference wild-type nucleotide sequence. Such a sequence is referred to as a uracil-modified or thymine-modified Attorney Docket No.45817-0022WO1 / MTX977.20 sequence. The percentage of uracil or thymine content in a nucleotide sequence can be determined by dividing the number of uracils or thymines in a sequence by the total number of nucleotides and multiplying by 100. In some embodiments, the sequence- optimized nucleotide sequence has a lower uracil or thymine content than the uracil or thymine content in the reference wild-type sequence. In some embodiments, the uracil or thymine content in a sequence-optimized nucleotide sequence of the invention is greater than the uracil or thymine content in the reference wild-type sequence and still maintain beneficial effects, e.g., increased expression and / or reduced Toll-Like Receptor (TLR) response when compared to the reference wild- type sequence. Methods for optimizing codon usage are known in the art. For example, an ORF of any one or more of the sequences provided herein may be codon optimized. Codon optimization, in some embodiments, may be used to match codon frequencies in target and host organisms to ensure proper folding; bias GC content to increase mRNA stability or reduce secondary structures; minimize tandem repeat codons or base runs that may impair gene construction or expression; customize transcriptional and translational control regions; insert or remove protein trafficking sequences; remove / add post translation modification sites in encoded protein (e.g., glycosylation sites); add, remove or shuffle protein domains; insert or delete restriction sites; modify ribosome binding sites and mRNA degradation sites; adjust translational rates to allow the various domains of the protein to fold properly; or reduce or eliminate problem secondary structures within the polynucleotide. Codon optimization tools, algorithms and services are known in the art - non-limiting examples include services from GeneArt (Life Technologies), DNA2.0 (Menlo Park CA) and / or proprietary methods. In some embodiments, the open reading frame (ORF) sequence is optimized using optimization algorithms. 8. Characterization of Sequence Optimized Nucleic Acids In some embodiments of the invention, the polynucleotide (e.g., a RNA, e.g., an mRNA) comprising a sequence optimized nucleic acid disclosed herein encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., Attorney Docket No.45817-0022WO1 / MTX977.20 SEQ ID NO:7 or SEQ ID NO:28)) can be tested to determine whether at least one nucleic acid sequence property (e.g., stability when exposed to nucleases) or expression property has been improved with respect to the non-sequence optimized nucleic acid. As used herein, "expression property" refers to a property of a nucleic acid sequence either in vivo (e.g., translation efficacy of a synthetic mRNA after administration to a subject in need thereof) or in vitro (e.g., translation efficacy of a synthetic mRNA tested in an in vitro model system). Expression properties include but are not limited to the amount of protein produced by an mRNA encoding an ASS1 polypeptide or an ASL polypeptide after administration, and the amount of soluble or otherwise functional protein produced. In some embodiments, sequence optimized nucleic acids disclosed herein can be evaluated according to the viability of the cells expressing a protein encoded by a sequence optimized nucleic acid sequence (e.g., a RNA, e.g., an mRNA) encoding an ASS1 polypeptide or an ASL polypeptide disclosed herein. In a given embodiment, a plurality of sequence optimized nucleic acids disclosed herein (e.g., a RNA, e.g., an mRNA) containing codon substitutions with respect to the non-optimized reference nucleic acid sequence can be characterized functionally to measure a property of interest, for example an expression property in an in vitro model system, or in vivo in a target tissue or cell. a. Optimization of Nucleic Acid Sequence Intrinsic Properties In some embodiments of the invention, the desired property of the polynucleotide is an intrinsic property of the nucleic acid sequence. For example, the nucleotide sequence (e.g., a RNA, e.g., an mRNA) can be sequence optimized for in vivo or in vitro stability. In some embodiments, the nucleotide sequence can be sequence optimized for expression in a given target tissue or cell. In some embodiments, the nucleic acid sequence is sequence optimized to increase its plasma half-life by preventing its degradation by endo and exonucleases. In other embodiments, the nucleic acid sequence is sequence optimized to increase its resistance to hydrolysis in solution, for example, to lengthen the time that Attorney Docket No.45817-0022WO1 / MTX977.20 the sequence optimized nucleic acid or a pharmaceutical composition comprising the sequence optimized nucleic acid can be stored under aqueous conditions with minimal degradation. In other embodiments, the sequence optimized nucleic acid can be optimized to increase its resistance to hydrolysis in dry storage conditions, for example, to lengthen the time that the sequence optimized nucleic acid can be stored after lyophilization with minimal degradation. b. Nucleic Acids Sequence Optimized for Protein Expression In some embodiments of the invention, the desired property of the polynucleotide is the level of expression of an ASS1 polypeptide or an ASL polypeptide encoded by a sequence optimized sequence disclosed herein. Protein expression levels can be measured using one or more expression systems. In some embodiments, expression can be measured in cell culture systems, e.g., CHO cells or HEK293 cells. In some embodiments, expression can be measured using in vitro expression systems prepared from extracts of living cells, e.g., rabbit reticulocyte lysates, or in vitro expression systems prepared by assembly of purified individual components. In other embodiments, the protein expression is measured in an in vivo system, e.g., mouse, rabbit, monkey, etc. In some embodiments, protein expression in solution form can be desirable. Accordingly, in some embodiments, a reference sequence can be sequence optimized to yield a sequence optimized nucleic acid sequence having optimized levels of expressed proteins in soluble form. Levels of protein expression and other properties such as solubility, levels of aggregation, and the presence of truncation products (i.e., fragments due to proteolysis, hydrolysis, or defective translation) can be measured according to methods known in the art, for example, using electrophoresis (e.g., native or SDS-PAGE) or chromatographic methods (e.g., HPLC, size exclusion chromatography, etc.). c. Optimization of Target Tissue or Target Cell Viability In some embodiments, the expression of heterologous therapeutic proteins encoded by a nucleic acid sequence can have deleterious effects in the target tissue or Attorney Docket No.45817-0022WO1 / MTX977.20 cell, reducing protein yield, or reducing the quality of the expressed product (e.g., due to the presence of protein fragments or precipitation of the expressed protein in inclusion bodies), or causing toxicity. Accordingly, in some embodiments of the invention, the sequence optimization of a nucleic acid sequence disclosed herein, e.g., a nucleic acid sequence encoding an ASS1 polypeptide or an ASL polypeptide, can be used to increase the viability of target cells expressing the protein encoded by the sequence optimized nucleic acid. Heterologous protein expression can also be deleterious to cells transfected with a nucleic acid sequence for autologous or heterologous transplantation. Accordingly, in some embodiments of the present disclosure the sequence optimization of a nucleic acid sequence disclosed herein can be used to increase the viability of target cells expressing the protein encoded by the sequence optimized nucleic acid sequence. Changes in cell or tissue viability, toxicity, and other physiological reaction can be measured according to methods known in the art. d. Reduction of Immune and / or Inflammatory Response In some cases, the administration of a sequence optimized nucleic acid encoding ASS1 polypeptide or an ASL polypeptide, or a functional fragment thereof, can trigger an immune response, which could be caused by (i) the therapeutic agent (e.g., an mRNA encoding an ASS1 polypeptide or an ASL polypeptide), or (ii) the expression product of such therapeutic agent (e.g., the ASS1 polypeptide or the ASL polypeptide encoded by the mRNA), or (iv) a combination thereof. Accordingly, in some embodiments of the present disclosure the sequence optimization of nucleic acid sequence (e.g., an mRNA) disclosed herein can be used to decrease an immune or inflammatory response triggered by the administration of a nucleic acid encoding an ASS1 polypeptide or an ASL polypeptide or by the expression product of ASS1 polypeptide or ASL polypeptide encoded by such nucleic acid. In some cases, an inflammatory response can be measured by detecting increased levels of one or more inflammatory cytokines using methods known in the art, e.g., ELISA. The term "inflammatory cytokine" refers to cytokines that are elevated in an inflammatory response. Examples of inflammatory cytokines include Attorney Docket No.45817-0022WO1 / MTX977.20 interleukin-6 (IL-6), CXCL1 (chemokine (C-X-C motif) ligand 1; also known as GRO^, interferon-^ (IFN^), tumor necrosis factor ^ (TNF^), interferon ^-induced protein 10 (IP-10), or granulocyte-colony stimulating factor (G-CSF). The term inflammatory cytokines includes also other cytokines associated with inflammatory responses known in the art, e.g., interleukin-1 (IL-1), interleukin-8 (IL-8), interleukin- 12 (IL-12), interleukin-13 (Il-13), interferon α (IFN-α), etc. 9. Modified Nucleotide Sequences Encoding ASS1 or ASL Polypeptides In some embodiments, the polynucleotide (e.g., a RNA, e.g., an mRNA) of the invention comprises a chemically modified nucleobase, for example, a chemically modified uracil, e.g., pseudouracil, N1-methylpseudouracil, 5-methoxyuracil, or the like. In some embodiments, the mRNA is a uracil-modified sequence comprising an ORF encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28), wherein the mRNA comprises a chemically modified nucleobase, for example, a chemically modified uracil, e.g., pseudouracil, N1-methylpseudouracil, or 5-methoxyuracil. In some embodiments, the mRNA is a uracil-modified sequence comprising an ORF encoding an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28), wherein the mRNA comprises a chemically modified nucleobase, for example, a chemically modified uracil, e.g., pseudouracil, N1-methylpseudouracil, or 5-methoxyuracil. In certain aspects of the invention, when the modified uracil base is connected to a ribose sugar, as it is in polynucleotides, the resulting modified nucleoside or nucleotide is referred to as modified uridine. In some embodiments, uracil in the polynucleotide is at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least 90%, at least 95%, at least 99%, or about 100% modified uracil. In one embodiment, uracil in the polynucleotide is at least 95% modified uracil. In another embodiment, uracil in the polynucleotide is 100% modified uracil. In embodiments where uracil in the polynucleotide is at least 95% modified uracil overall uracil content can be adjusted such that an mRNA provides suitable protein expression levels while inducing little to no immune response. In some Attorney Docket No.45817-0022WO1 / MTX977.20 embodiments, the uracil content of the ORF is between about 100% and about 150%, between about 100% and about 110%, between about 105% and about 115%, between about 110% and about 120%, between about 115% and about 125%, between about 120% and about 130%, between about 125% and about 135%, between about 130% and about 140%, between about 135% and about 145%, between about 140% and about 150% of the theoretical minimum uracil content in the corresponding wild-type ORF (%UTM). In other embodiments, the uracil content of the ORF is between about 121% and about 136% or between 123% and 134% of the %UTM. In some embodiments, the uracil content of the ORF encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28) is about 115%, about 120%, about 125%, about 130%, about 135%, about 140%, about 145%, or about 150% of the %UTM. In this context, the term "uracil" can refer to modified uracil and / or naturally occurring uracil. In some embodiments, the uracil content in the ORF of the mRNA encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28) of the invention is less than about 30%, about 25%, about 20%, about 15%, or about 10% of the total nucleobase content in the ORF. In some embodiments, the uracil content in the ORF is between about 10% and about 20% of the total nucleobase content in the ORF. In other embodiments, the uracil content in the ORF is between about 10% and about 25% of the total nucleobase content in the ORF. In one embodiment, the uracil content in the ORF of the mRNA encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28) is less than about 20% of the total nucleobase content in the open reading frame. In this context, the term "uracil" can refer to modified uracil and / or naturally occurring uracil. In further embodiments, the ORF of the mRNA encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28) having modified uracil and adjusted uracil content has increased Cytosine (C), Guanine (G), or Guanine / Cytosine (G / C) content (absolute or relative). In some embodiments, the overall increase in C, G, or G / C content (absolute or relative) of the ORF is at least about 2%, at least about 3%, at least about 4%, at least about 5%, at least about 6%, at least about 7%, at least about 10%, at least Attorney Docket No.45817-0022WO1 / MTX977.20 about 15%, at least about 20%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, or at least about 100% relative to the G / C content (absolute or relative) of the wild-type ORF. In some embodiments, the G, the C, or the G / C content in the ORF is less than about 100%, less than about 90%, less than about 85%, or less than about 80% of the theoretical maximum G, C, or G / C content of the corresponding wild type nucleotide sequence encoding the ASS1 polypeptide or the ASL polypeptide (%GTMX; %CTMX, or %G / CTMX). In some embodiments, the increases in G and / or C content (absolute or relative) described herein can be conducted by replacing synonymous codons with low G, C, or G / C content with synonymous codons having higher G, C, or G / C content. In other embodiments, the increase in G and / or C content (absolute or relative) is conducted by replacing a codon ending with U with a synonymous codon ending with G or C. In further embodiments, the ORF of the mRNA encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28) of the invention comprises modified uracil and has an adjusted uracil content containing less uracil pairs (UU) and / or uracil triplets (UUU) and / or uracil quadruplets (UUUU) than the corresponding wild-type nucleotide sequence encoding the ASS1 polypeptide or the ASL polypeptide, respectively. In some embodiments, the ORF of the mRNA encoding an ASS1 polypeptide or an ASL polypeptide of the invention contains no uracil pairs and / or uracil triplets and / or uracil quadruplets. In some embodiments, uracil pairs and / or uracil triplets and / or uracil quadruplets are reduced below a certain threshold, e.g., no more than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 occurrences in the ORF of the mRNA encoding the ASS1 polypeptide or the ASL polypeptide. In a particular embodiment, the ORF of the mRNA encoding the ASS1 or the ASL polypeptide of the invention contains less than 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 non-phenylalanine uracil pairs and / or triplets. In another embodiment, the ORF of the mRNA encoding the ASS1 polypeptide or the ASL polypeptide contains no non- phenylalanine uracil pairs and / or triplets. In further embodiments, the ORF of the mRNA encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID Attorney Docket No.45817-0022WO1 / MTX977.20 NO:7 or SEQ ID NO:28) of the invention comprises modified uracil and has an adjusted uracil content containing less uracil-rich clusters than the corresponding wild-type nucleotide sequence encoding the ASS1 polypeptide or the ASL polypeptide. In some embodiments, the ORF of the mRNA encoding the ASS1 polypeptide or the ASL polypeptide of the invention contains uracil-rich clusters that are shorter in length than corresponding uracil-rich clusters in the corresponding wild- type nucleotide sequence encoding the ASS1 polypeptide or the ASL polypeptide. In further embodiments, alternative lower frequency codons are employed. At least about 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99%, or 100% of the codons in the ASS1 polypeptide or the ASL polypeptide-encoding ORF of the modified uracil- comprising mRNA are substituted with alternative codons, each alternative codon having a codon frequency lower than the codon frequency of the substituted codon in the synonymous codon set. The ORF also has adjusted uracil content, as described above. In some embodiments, at least one codon in the ORF of the mRNA encoding the ASS1 polypeptide or the ASL polypeptide is substituted with an alternative codon having a codon frequency lower than the codon frequency of the substituted codon in the synonymous codon set. In some embodiments, the ASS1 polypeptide- or the ASL polypeptide- encoding ORF comprising an adjusted uracil content exhibits expression levels of ASS1 or ASL, respectively, when administered to a mammalian cell that are higher than expression levels of ASS1 or ASL, respectively, from the corresponding wild- type mRNA. In some embodiments, the mammalian cell is a mouse cell, a rat cell, or a rabbit cell. In other embodiments, the mammalian cell is a monkey cell or a human cell. In some embodiments, the human cell is a HeLa cell, a BJ fibroblast cell, or a peripheral blood mononuclear cell (PBMC). In some embodiments, ASS1 or ASL is expressed at a level higher than expression levels of ASS1 or ASL, respectively, from the corresponding wild-type mRNA when the mRNA encoding ASS1 or ASL, respectively, is administered to a mammalian cell in vivo. In some embodiments, the Attorney Docket No.45817-0022WO1 / MTX977.20 mRNA is administered to mice, rabbits, rats, monkeys, or humans. In one embodiment, mice are null mice. In some embodiments, the mRNA is administered to mice in an amount of about 0.01 mg / kg, about 0.05 mg / kg, about 0.1 mg / kg, or 0.2 mg / kg or about 0.5 mg / kg. In some embodiments, the mRNA is administered intravenously or intramuscularly. In other embodiments, the ASS1 polypeptide or the ASL polypeptide is expressed when the mRNA is administered to a mammalian cell in vitro. In some embodiments, the expression is increased by at least about 2-fold, at least about 5-fold, at least about 10-fold, at least about 50-fold, at least about 500- fold, at least about 1500-fold, or at least about 3000-fold. In other embodiments, the expression is increased by at least about 10%, about 20%, about 30%, about 40%, about 50%, 60%, about 70%, about 80%, about 90%, or about 100%. In some embodiments, the ASS1 polypeptide- or ASL polypeptide-encoding ORF comprising an adjusted uracil content exhibits increased stability. In some embodiments, the mRNA exhibits increased stability in a cell relative to the stability of a corresponding wild-type mRNA under the same conditions. In some embodiments, the mRNA exhibits increased stability including resistance to nucleases, thermal stability, and / or increased stabilization of secondary structure. In some embodiments, increased stability exhibited by the mRNA is measured by determining the half-life of the mRNA (e.g., in a plasma, serum, cell, or tissue sample) and / or determining the area under the curve (AUC) of the protein expression by the mRNA over time (e.g., in vitro or in vivo). An mRNA is identified as having increased stability if the half-life and / or the AUC is greater than the half-life and / or the AUC of a corresponding wild-type mRNA under the same conditions. In some embodiments, the mRNA of the present invention induces a detectably lower immune response (e.g., innate or acquired) relative to the immune response induced by a corresponding wild-type mRNA under the same conditions. In other embodiments, the mRNA of the present disclosure induces a detectably lower immune response (e.g., innate or acquired) relative to the immune response induced by an mRNA that encodes for an ASS1 polypeptide or an ASL polypeptide but does not comprise modified uracil under the same conditions, or relative to the immune response induced by an mRNA that encodes for an ASS1 polypeptide or an ASL polypeptide and that comprises modified uracil but that does not have adjusted uracil Attorney Docket No.45817-0022WO1 / MTX977.20 content under the same conditions. The innate immune response can be manifested by increased expression of pro-inflammatory cytokines, activation of intracellular PRRs (RIG-I, MDA5, etc.), cell death, and / or termination or reduction in protein translation. In some embodiments, a reduction in the innate immune response can be measured by expression or activity level of Type 1 interferons (e.g., IFN-α, IFN-β, IFN-κ, IFN-δ, IFN-ε, IFN-τ, IFN-ω, and IFN-ζ) or the expression of interferon-regulated genes such as the toll-like receptors (e.g., TLR7 and TLR8), and / or by decreased cell death following one or more administrations of the mRNA of the invention into a cell. In some embodiments, the expression of Type-1 interferons by a mammalian cell in response to the mRNA of the present disclosure is reduced by at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99%, 99.9%, or greater than 99.9% relative to a corresponding wild-type mRNA, to an mRNA that encodes an ASS1 polypeptide or an ASL polypeptide but does not comprise modified uracil, or to an mRNA that encodes an ASS1 or an ASL, respectively, polypeptide and that comprises modified uracil but that does not have adjusted uracil content. In some embodiments, the interferon is IFN-β. In some embodiments, cell death frequency caused by administration of mRNA of the present disclosure to a mammalian cell is 10%, 25%, 50%, 75%, 85%, 90%, 95%, or over 95% less than the cell death frequency observed with a corresponding wild-type mRNA, an mRNA that encodes for an ASS1 polypeptide or an ASL polypeptide but does not comprise modified uracil, or an mRNA that encodes for an ASS1 polypeptide or an ASL polypeptide and that comprises modified uracil but that does not have adjusted uracil content. In some embodiments, the mammalian cell is a BJ fibroblast cell. In other embodiments, the mammalian cell is a splenocyte. In some embodiments, the mammalian cell is that of a mouse or a rat. In other embodiments, the mammalian cell is that of a human. In one embodiment, the mRNA of the present disclosure does not substantially induce an innate immune response of a mammalian cell into which the mRNA is introduced. 10. Methods for Modifying Polynucleotides The disclosure includes modified polynucleotides comprising a polynucleotide described herein (e.g., a polynucleotide, e.g. mRNA, comprising a nucleotide Attorney Docket No.45817-0022WO1 / MTX977.20 sequence encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28)). The modified polynucleotides can be chemically modified and / or structurally modified. When the polynucleotides of the present invention are chemically and / or structurally modified the polynucleotides can be referred to as "modified polynucleotides." The present disclosure provides for modified nucleosides and nucleotides of a polynucleotide (e.g., RNA polynucleotides, such as mRNA polynucleotides) encoding a an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28). A "nucleoside" refers to a compound containing a sugar molecule (e.g., a pentose or ribose) or a derivative thereof in combination with an organic base (e.g., a purine or pyrimidine) or a derivative thereof (also referred to herein as "nucleobase"). A “nucleotide" refers to a nucleoside including a phosphate group. Modified nucleotides can be synthesized by any useful method, such as, for example, chemically, enzymatically, or recombinantly, to include one or more modified or non-natural nucleosides. Polynucleotides can comprise a region or regions of linked nucleosides. Such regions can have variable backbone linkages. The linkages can be standard phosphodiester linkages, in which case the polynucleotides would comprise regions of nucleotides. The modified polynucleotides disclosed herein can comprise various distinct modifications. In some embodiments, the modified polynucleotides contain one, two, or more (optionally different) nucleoside or nucleotide modifications. In some embodiments, a modified polynucleotide, introduced to a cell can exhibit one or more desirable properties, e.g., improved protein expression, reduced immunogenicity, or reduced degradation in the cell, as compared to an unmodified polynucleotide. In some embodiments, a polynucleotide of the present invention (e.g., a polynucleotide comprising a nucleotide sequence encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28)) is structurally modified. As used herein, a "structural" modification is one in which two or more linked nucleosides are inserted, deleted, duplicated, inverted or randomized in a polynucleotide without significant chemical modification to the nucleotides themselves. Because chemical bonds will necessarily be broken and reformed to effect a structural modification, structural modifications are of a chemical Attorney Docket No.45817-0022WO1 / MTX977.20 nature and hence are chemical modifications. However, structural modifications will result in a different sequence of nucleotides. For example, the polynucleotide "ATCG" can be chemically modified to "AT-5meC-G". The same polynucleotide can be structurally modified from "ATCG" to "ATCCCG". Here, the dinucleotide "CC" has been inserted, resulting in a structural modification to the polynucleotide. Therapeutic compositions of the present disclosure comprise, in some embodiments, at least one nucleic acid (e.g., RNA) having an open reading frame encoding ASS1 (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28), wherein the nucleic acid comprises nucleotides and / or nucleosides that can be standard (unmodified) or modified as is known in the art. In some embodiments, nucleotides and nucleosides of the present disclosure comprise modified nucleotides or nucleosides. Such modified nucleotides and nucleosides can be naturally-occurring modified nucleotides and nucleosides or non-naturally occurring modified nucleotides and nucleosides. Such modifications can include those at the sugar, backbone, or nucleobase portion of the nucleotide and / or nucleoside as are recognized in the art. In some embodiments, a naturally-occurring modified nucleotide or nucleotide of the disclosure is one as is generally known or recognized in the art. Non-limiting examples of such naturally occurring modified nucleotides and nucleotides can be found, inter alia, in the widely recognized MODOMICS database. In some embodiments, a non-naturally occurring modified nucleotide or nucleoside of the disclosure is one as is generally known or recognized in the art. Non-limiting examples of such non-naturally occurring modified nucleotides and nucleosides can be found, inter alia, in published US application Nos. PCT / US2012 / 058519; PCT / US2013 / 075177; PCT / US2014 / 058897; PCT / US2014 / 058891; PCT / US2014 / 070413; PCT / US2015 / 36773; PCT / US2015 / 36759; PCT / US2015 / 36771; or PCT / IB2017 / 051367 all of which are incorporated by reference herein. In some embodiments, at least one RNA (e.g., mRNA) of the present disclosure is not chemically modified and comprises the standard ribonucleotides consisting of adenosine, guanosine, cytosine and uridine. In some embodiments, nucleotides and nucleosides of the present disclosure comprise standard nucleoside Attorney Docket No.45817-0022WO1 / MTX977.20 residues such as those present in transcribed RNA (e.g. A, G, C, or U). In some embodiments, nucleotides and nucleosides of the present disclosure comprise standard deoxyribonucleosides such as those present in DNA (e.g. dA, dG, dC, or dT). Hence, nucleic acids of the disclosure (e.g., DNA nucleic acids and RNA nucleic acids, such as mRNA nucleic acids) can comprise standard nucleotides and nucleosides, naturally-occurring nucleotides and nucleosides, non-naturally-occurring nucleotides and nucleosides, or any combination thereof. Nucleic acids of the disclosure (e.g., DNA nucleic acids and RNA nucleic acids, such as mRNA nucleic acids), in some embodiments, comprise various (more than one) different types of standard and / or modified nucleotides and nucleosides. In some embodiments, a particular region of a nucleic acid contains one, two or more (optionally different) types of standard and / or modified nucleotides and nucleosides. In some embodiments, a modified RNA nucleic acid (e.g., a modified mRNA nucleic acid), introduced to a cell or organism, exhibits reduced degradation in the cell or organism, respectively, relative to an unmodified nucleic acid comprising standard nucleotides and nucleosides. In some embodiments, a modified RNA nucleic acid (e.g., a modified mRNA nucleic acid), introduced into a cell or organism, may exhibit reduced immunogenicity in the cell or organism, respectively (e.g., a reduced innate response) relative to an unmodified nucleic acid comprising standard nucleotides and nucleosides. Nucleic acids (e.g., RNA nucleic acids, such as mRNA nucleic acids), in some embodiments, comprise non-natural modified nucleotides that are introduced during synthesis or post-synthesis of the nucleic acids to achieve desired functions or properties. The modifications may be present on internucleotide linkages, purine or pyrimidine bases, or sugars. The modification may be introduced with chemical synthesis or with a polymerase enzyme at the terminal of a chain or anywhere else in the chain. Any of the regions of a nucleic acid may be chemically modified. The present disclosure provides for modified nucleosides and nucleotides of a nucleic acid (e.g., RNA nucleic acids, such as mRNA nucleic acids). A “nucleoside” refers to a compound containing a sugar molecule (e.g., a pentose or ribose) or a derivative thereof in combination with an organic base (e.g., a purine or pyrimidine) Attorney Docket No.45817-0022WO1 / MTX977.20 or a derivative thereof (also referred to herein as “nucleobase”). A “nucleotide” refers to a nucleoside, including a phosphate group. Modified nucleotides may by synthesized by any useful method, such as, for example, chemically, enzymatically, or recombinantly, to include one or more modified or non-natural nucleosides. Nucleic acids can comprise a region or regions of linked nucleosides. Such regions may have variable backbone linkages. The linkages can be standard phosphodiester linkages, in which case the nucleic acids would comprise regions of nucleotides. Modified nucleotide base pairing encompasses not only the standard adenosine-thymine, adenosine-uracil, or guanosine-cytosine base pairs, but also base pairs formed between nucleotides and / or modified nucleotides comprising non- standard or modified bases, wherein the arrangement of hydrogen bond donors and hydrogen bond acceptors permits hydrogen bonding between a non-standard base and a standard base or between two complementary non-standard base structures, such as, for example, in those nucleic acids having at least one chemical modification. One example of such non-standard base pairing is the base pairing between the modified nucleotide inosine and adenine, cytosine or uracil. Any combination of base / sugar or linker may be incorporated into nucleic acids of the present disclosure. In some embodiments, modified nucleobases in nucleic acids (e.g., RNA nucleic acids, such as mRNA nucleic acids) comprise N1-methyl-pseudouridine (m1ψ), 1-ethyl-pseudouridine (e1ψ), 5-methoxy-uridine (mo5U), 5-methyl-cytidine (m5C), and / or pseudouridine (ψ). In some embodiments, modified nucleobases in nucleic acids (e.g., RNA nucleic acids, such as mRNA nucleic acids) comprise 5- methoxymethyl uridine, 5-methylthio uridine, 1-methoxymethyl pseudouridine, 5- methyl cytidine, and / or 5-methoxy cytidine. In some embodiments, the polyribonucleotide includes a combination of at least two (e.g., 2, 3, 4 or more) of any of the aforementioned modified nucleobases, including but not limited to chemical modifications. In some embodiments, a RNA nucleic acid of the disclosure comprises N1- methyl-pseudouridine (m1ψ) substitutions at one or more or all uridine positions of the nucleic acid. In some embodiments, a RNA nucleic acid of the disclosure comprises N1- methyl-pseudouridine (m1ψ) substitutions at one or more or all uridine positions of Attorney Docket No.45817-0022WO1 / MTX977.20 the nucleic acid and 5-methyl cytidine substitutions at one or more or all cytidine positions of the nucleic acid. In some embodiments, a RNA nucleic acid of the disclosure comprises pseudouridine (ψ) substitutions at one or more or all uridine positions of the nucleic acid. In some embodiments, a RNA nucleic acid of the disclosure comprises pseudouridine (ψ) substitutions at one or more or all uridine positions of the nucleic acid and 5-methyl cytidine substitutions at one or more or all cytidine positions of the nucleic acid. In some embodiments, a RNA nucleic acid of the disclosure comprises uridine at one or more or all uridine positions of the nucleic acid. In some embodiments, nucleic acids (e.g., RNA nucleic acids, such as mRNA nucleic acids) are uniformly modified (e.g., fully modified, modified throughout the entire sequence) for a particular modification. For example, a nucleic acid can be uniformly modified with N1-methyl-pseudouridine, meaning that all uridine residues in the mRNA sequence are replaced with N1-methyl-pseudouridine. Similarly, a nucleic acid can be uniformly modified for any type of nucleoside residue present in the sequence by replacement with a modified residue such as those set forth above. The nucleic acids of the present disclosure may be partially or fully modified along the entire length of the molecule. For example, one or more or all or a given type of nucleotide (e.g., purine or pyrimidine, or any one or more or all of A, G, U, C) may be uniformly modified in a nucleic acid of the disclosure, or in a predetermined sequence region thereof (e.g., in the mRNA including or excluding the polyA tail). In some embodiments, all nucleotides X in a nucleic acid of the present disclosure (or in a sequence region thereof) are modified nucleotides, wherein X may be any one of nucleotides A, G, U, C, or any one of the combinations A+G, A+U, A+C, G+U, G+C, U+C, A+G+U, A+G+C, G+U+C or A+G+C. The nucleic acid may contain from about 1% to about 100% modified nucleotides (either in relation to overall nucleotide content, or in relation to one or more types of nucleotide, i.e., any one or more of A, G, U or C) or any intervening percentage (e.g., from 1% to 20%, from 1% to 25%, from 1% to 50%, from 1% to 60%, from 1% to 70%, from 1% to 80%, from 1% to 90%, from 1% to 95%, from Attorney Docket No.45817-0022WO1 / MTX977.20 10% to 20%, from 10% to 25%, from 10% to 50%, from 10% to 60%, from 10% to 70%, from 10% to 80%, from 10% to 90%, from 10% to 95%, from 10% to 100%, from 20% to 25%, from 20% to 50%, from 20% to 60%, from 20% to 70%, from 20% to 80%, from 20% to 90%, from 20% to 95%, from 20% to 100%, from 50% to 60%, from 50% to 70%, from 50% to 80%, from 50% to 90%, from 50% to 95%, from 50% to 100%, from 70% to 80%, from 70% to 90%, from 70% to 95%, from 70% to 100%, from 80% to 90%, from 80% to 95%, from 80% to 100%, from 90% to 95%, from 90% to 100%, and from 95% to 100%). It will be understood that any remaining percentage is accounted for by the presence of unmodified A, G, U, or C. The nucleic acids may contain at a minimum 1% and at maximum 100% modified nucleotides, or any intervening percentage, such as at least 5% modified nucleotides, at least 10% modified nucleotides, at least 25% modified nucleotides, at least 50% modified nucleotides, at least 80% modified nucleotides, or at least 90% modified nucleotides. For example, the nucleic acids may contain a modified pyrimidine such as a modified uracil or cytosine. In some embodiments, at least 5%, at least 10%, at least 25%, at least 50%, at least 80%, at least 90% or 100% of the uracil in the nucleic acid is replaced with a modified uracil (e.g., a 5-substituted uracil). The modified uracil can be replaced by a compound having a single unique structure, or can be replaced by a plurality of compounds having different structures (e.g., 2, 3, 4 or more unique structures). In some embodiments, at least 5%, at least 10%, at least 25%, at least 50%, at least 80%, at least 90% or 100% of the cytosine in the nucleic acid is replaced with a modified cytosine (e.g., a 5-substituted cytosine). The modified cytosine can be replaced by a compound having a single unique structure, or can be replaced by a plurality of compounds having different structures (e.g., 2, 3, 4 or more unique structures). 11. Untranslated Regions (UTRs) Untranslated regions (UTRs) are nucleic acid sections of a polynucleotide before a start codon (5′ UTR) and after a stop codon (3′ UTR) that are not translated. In some embodiments, a polynucleotide (e.g., a ribonucleic acid (RNA), e.g., a messenger RNA (mRNA)) of the invention comprising an open reading frame (ORF) Attorney Docket No.45817-0022WO1 / MTX977.20 encoding an ASS1 polypeptide further comprises UTR (e.g., a 5′ UTR or functional fragment thereof, a 3′ UTR or functional fragment thereof, or a combination thereof). A UTR (e.g., 5′ UTR or 3′ UTR) can be homologous or heterologous to the coding region in a polynucleotide. In some embodiments, the UTR is homologous to the ORF encoding the ASS1 polypeptide. In some embodiments, the UTR is heterologous to the ORF encoding the ASS1 polypeptide. In some embodiments, the UTR is homologous to the ORF encoding the ASL polypeptide. In some embodiments, the UTR is heterologous to the ORF encoding the ASL polypeptide. In some embodiments, the polynucleotide comprises two or more 5′ UTRs or functional fragments thereof, each of which has the same or different nucleotide sequences. In some embodiments, the polynucleotide comprises two or more 3′ UTRs or functional fragments thereof, each of which has the same or different nucleotide sequences. In some embodiments, the 5′ UTR or functional fragment thereof, 3′ UTR or functional fragment thereof, or any combination thereof is sequence optimized. In some embodiments, the 5′UTR or functional fragment thereof, 3′ UTR or functional fragment thereof, or any combination thereof comprises at least one chemically modified nucleobase, e.g., N1-methylpseudouracil or 5-methoxyuracil. UTRs can have features that provide a regulatory role, e.g., increased or decreased stability, localization and / or translation efficiency. A polynucleotide comprising a UTR can be administered to a cell, tissue, or organism, and one or more regulatory features can be measured using routine methods. In some embodiments, a functional fragment of a 5′ UTR or 3′ UTR comprises one or more regulatory features of a full length 5′ or 3′ UTR, respectively. Natural 5′UTRs bear features that play roles in translation initiation. They harbor signatures like Kozak sequences that are commonly known to be involved in the process by which the ribosome initiates translation of many genes. Kozak sequences have the consensus CCR(A / G)CCAUGG, where R is a purine (adenine or guanine) three bases upstream of the start codon (AUG), which is followed by another ‘G’.5′ UTRs also have been known to form secondary structures that are involved in elongation factor binding. Attorney Docket No.45817-0022WO1 / MTX977.20 By engineering the features typically found in abundantly expressed genes of specific target organs, one can enhance the stability and protein production of a polynucleotide. For example, introduction of 5′ UTR of liver-expressed mRNA, such as albumin, serum amyloid A, Apolipoprotein A / B / E, transferrin, alpha fetoprotein, erythropoietin, or Factor VIII, can enhance expression of polynucleotides in hepatic cell lines or liver. Likewise, use of 5′UTR from other tissue-specific mRNA to improve expression in that tissue is possible for muscle (e.g., MyoD, Myosin, Myoglobin, Myogenin, Herculin), for endothelial cells (e.g., Tie-1, CD36), for myeloid cells (e.g., C / EBP, AML1, G-CSF, GM-CSF, CD11b, MSR, Fr-1, i-NOS), for leukocytes (e.g., CD45, CD18), for adipose tissue (e.g., CD36, GLUT4, ACRP30, adiponectin) and for lung epithelial cells (e.g., SP-A / B / C / D). In some embodiments, UTRs are selected from a family of transcripts whose proteins share a common function, structure, feature or property. For example, an encoded polypeptide can belong to a family of proteins (i.e., that share at least one function, structure, feature, localization, origin, or expression pattern), which are expressed in a particular cell, tissue or at some time during development. The UTRs from any of the genes or mRNA can be swapped for any other UTR of the same or different family of proteins to create a new polynucleotide. In some embodiments, the 5′ UTR and the 3′ UTR can be heterologous. In some embodiments, the 5′ UTR can be derived from a different species than the 3′ UTR. In some embodiments, the 3′ UTR can be derived from a different species than the 5′ UTR. Co-owned International Patent Application No. PCT / US2014 / 021522 (Publ. No. WO / 2014 / 164253, incorporated herein by reference in its entirety) provides a listing of exemplary UTRs that can be utilized in the polynucleotide of the present invention as flanking regions to an ORF. Additional exemplary UTRs of the application include, but are not limited to, one or more 5′UTR and / or 3′UTR derived from the nucleic acid sequence of: a globin, such as an α- or β-globin (e.g., a Xenopus, mouse, rabbit, or human globin); a strong Kozak translational initiation signal; a CYBA (e.g., human cytochrome b-245 α polypeptide); an albumin (e.g., human albumin7); a HSD17B4 (hydroxysteroid (17-β) dehydrogenase); a virus (e.g., a tobacco etch virus (TEV), a Venezuelan equine Attorney Docket No.45817-0022WO1 / MTX977.20 encephalitis virus (VEEV), a Dengue virus, a cytomegalovirus (CMV) (e.g., CMV immediate early 1 (IE1)), a hepatitis virus (e.g., hepatitis B virus), a sindbis virus, or a PAV barley yellow dwarf virus); a heat shock protein (e.g., hsp70); a translation initiation factor (e.g., elF4G); a glucose transporter (e.g., hGLUT1 (human glucose transporter 1)); an actin (e.g., human α or β actin); a GAPDH; a tubulin; a histone; a citric acid cycle enzyme; a topoisomerase (e.g., a 5′UTR of a TOP gene lacking the 5′ TOP motif (the oligopyrimidine tract)); a ribosomal protein Large 32 (L32); a ribosomal protein (e.g., human or mouse ribosomal protein, such as, for example, rps9); an ATP synthase (e.g., ATP5A1 or the β subunit of mitochondrial H+-ATP synthase); a growth hormone e (e.g., bovine (bGH) or human (hGH)); an elongation factor (e.g., elongation factor 1 α1 (EEF1A1)); a manganese superoxide dismutase (MnSOD); a myocyte enhancer factor 2A (MEF2A); a β-F1-ATPase, a creatine kinase, a myoglobin, a granulocyte-colony stimulating factor (G-CSF); a collagen (e.g., collagen type I, alpha 2 (Col1A2), collagen type I, alpha 1 (Col1A1), collagen type VI, alpha 2 (Col6A2), collagen type VI, alpha 1 (Col6A1)); a ribophorin (e.g., ribophorin I (RPNI)); a low density lipoprotein receptor-related protein (e.g., LRP1); a cardiotrophin-like cytokine factor (e.g., Nnt1); calreticulin (Calr); a procollagen- lysine, 2-oxoglutarate 5-dioxygenase 1 (Plod1); and a nucleobindin (e.g., Nucb1). In some embodiments, the 5′ UTR is selected from the group consisting of a β-globin 5′ UTR; a 5′UTR containing a strong Kozak translational initiation signal; a cytochrome b-245 α polypeptide (CYBA) 5′ UTR; a hydroxysteroid (17-β) dehydrogenase (HSD17B4) 5′ UTR; a Tobacco etch virus (TEV) 5′ UTR; a Venezuelen equine encephalitis virus (TEEV) 5′ UTR; a 5′ proximal open reading frame of rubella virus (RV) RNA encoding nonstructural proteins; a Dengue virus (DEN) 5′ UTR; a heat shock protein 70 (Hsp70) 5′ UTR; a eIF4G 5′ UTR; a GLUT1 5′ UTR; functional fragments thereof and any combination thereof. In some embodiments, the 3′ UTR is selected from the group consisting of a β-globin 3′ UTR; a CYBA 3′ UTR; an albumin 3′ UTR; a growth hormone (GH) 3′ UTR; a VEEV 3′ UTR; a hepatitis B virus (HBV) 3′ UTR; α-globin 3′UTR; a DEN 3′ UTR; a PAV barley yellow dwarf virus (BYDV-PAV) 3′ UTR; an elongation factor 1 α1 (EEF1A1) 3′ UTR; a manganese superoxide dismutase (MnSOD) 3′ UTR; a β subunit of mitochondrial H(+)-ATP synthase (β-mRNA) 3′ UTR; a GLUT13′ UTR; a Attorney Docket No.45817-0022WO1 / MTX977.20 MEF2A 3′ UTR; a β-F1-ATPase 3′ UTR; functional fragments thereof and combinations thereof. Wild-type UTRs derived from any gene or mRNA can be incorporated into the polynucleotides of the invention. In some embodiments, a UTR can be altered relative to a wild type or native UTR to produce a variant UTR, e.g., by changing the orientation or location of the UTR relative to the ORF; or by inclusion of additional nucleotides, deletion of nucleotides, swapping or transposition of nucleotides. In some embodiments, variants of 5′ or 3′ UTRs can be utilized, for example, mutants of wild type UTRs, or variants wherein one or more nucleotides are added to or removed from a terminus of the UTR. Additionally, one or more synthetic UTRs can be used in combination with one or more non-synthetic UTRs. See, e.g., Mandal and Rossi, Nat. Protoc.2013 8(3):568-82, the contents of which are incorporated herein by reference in their entirety. UTRs or portions thereof can be placed in the same orientation as in the transcript from which they were selected or can be altered in orientation or location. Hence, a 5′ and / or 3′ UTR can be inverted, shortened, lengthened, or combined with one or more other 5′ UTRs or 3′ UTRs. In some embodiments, the polynucleotide comprises multiple UTRs, e.g., a double, a triple or a quadruple 5′ UTR or 3′ UTR. For example, a double UTR comprises two copies of the same UTR either in series or substantially in series. For example, a double beta-globin 3′UTR can be used (see US2010 / 0129877, the contents of which are incorporated herein by reference in its entirety). The polynucleotides of the invention can comprise combinations of features. For example, the ORF can be flanked by a 5′UTR that comprises a strong Kozak translational initiation signal and / or a 3′UTR comprising an oligo(dT) sequence for templated addition of a poly-A tail. A 5′UTR can comprise a first polynucleotide fragment and a second polynucleotide fragment from the same and / or different UTRs (see, e.g., US2010 / 0293625, herein incorporated by reference in its entirety). Other non-UTR sequences can be used as regions or subregions within the polynucleotides of the invention. For example, introns or portions of intron sequences can be incorporated into the polynucleotides of the invention. Incorporation of Attorney Docket No.45817-0022WO1 / MTX977.20 intronic sequences can increase protein production as well as polynucleotide expression levels. In some embodiments, the polynucleotide of the invention comprises an internal ribosome entry site (IRES) instead of or in addition to a UTR (see, e.g., Yakubov et al., Biochem. Biophys. Res. Commun.2010394(1):189-193, the contents of which are incorporated herein by reference in their entirety). In some embodiments, the polynucleotide comprises an IRES instead of a 5′ UTR sequence. In some embodiments, the polynucleotide comprises an ORF and a viral capsid sequence. In some embodiments, the polynucleotide comprises a synthetic 5′ UTR in combination with a non-synthetic 3′ UTR. In some embodiments, the UTR can also include at least one translation enhancer polynucleotide, translation enhancer element, or translational enhancer elements (collectively, "TEE," which refers to nucleic acid sequences that increase the amount of polypeptide or protein produced from a polynucleotide. As a non-limiting example, the TEE can be located between the transcription promoter and the start codon. In some embodiments, the 5′ UTR comprises a TEE. In one aspect, a TEE is a conserved element in a UTR that can promote translational activity of a nucleic acid such as, but not limited to, cap-dependent or cap-independent translation. a.5′ UTR sequences 5′ UTR sequences are important for ribosome recruitment to the mRNA and have been reported to play a role in translation (Hinnebusch A, et al., (2016) Science, 352:6292: 1413-6). Disclosed herein, inter alia, is a polynucleotide, e.g., mRNA, comprising an open reading frame encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1- 6) or an open reading frame encoding an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28), which polynucleotide has a 5′ UTR that confers an increased half- life, increased expression and / or increased activity of the polypeptide encoded by said polynucleotide, or of the polynucleotide itself. In an embodiment, a polynucleotide disclosed herein comprises: (a) a 5′-UTR (e.g., as provided in Table 3 or a variant or Attorney Docket No.45817-0022WO1 / MTX977.20 fragment thereof); (b) a coding region comprising a stop element (e.g., as described herein); and (c) a 3′-UTR (e.g., as described herein), and LNP compositions comprising the same. In an embodiment, the polynucleotide comprises a 5′-UTR comprising a sequence provided in Table 3 or a variant or fragment thereof (e.g., a functional variant or fragment thereof). In an embodiment, the polynucleotide comprises a 5′-UTR comprising the sequence of SEQ ID NO:50. In an embodiment, the polynucleotide comprises a 5′-UTR comprising the sequence of SEQ ID NO:58. In an embodiment, the polynucleotide having a 5′ UTR sequence provided in Table 3 or a variant or fragment thereof, has an increase in the half-life of the polynucleotide, e.g., about 1.5-20-fold increase in half-life of the polynucleotide. In an embodiment, the increase in half-life is about 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20-fold, or more. In an embodiment, the increase in half life is about 1.5-fold or more. In an embodiment, the increase in half life is about 2- fold or more. In an embodiment, the increase in half life is about 3-fold or more. In an embodiment, the increase in half life is about 4-fold or more. In an embodiment, the increase in half life is about 5-fold or more. In an embodiment, the polynucleotide having a 5′ UTR sequence provided in Table 3 or a variant or fragment thereof, results in an increased level and / or activity, e.g., output, of the polypeptide encoded by the polynucleotide. In an embodiment, the 5′UTR results in about 1.5-20-fold increase in level and / or activity, e.g., output, of the polypeptide encoded by the polynucleotide. In an embodiment, the increase in level and / or activity is about 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20-fold, or more. In an embodiment, the increase in level and / or activity is about 1.5-fold or more. In an embodiment, the increase in level and / or activity is about 2- fold or more. In an embodiment, the increase in level and / or activity is about 3-fold or more. In an embodiment, the increase in level and / or activity is about 4-fold or more. In an embodiment, the increase in level and / or activity is about 5-fold or more. In an embodiment, the increase is compared to an otherwise similar polynucleotide which does not have a 5′ UTR, has a different 5′ UTR, or does not have a 5′ UTR described in Table 3 or a variant or fragment thereof. In an embodiment, the increase in half-life of the polynucleotide is measured according to an assay that measures the half-life of a polynucleotide. Attorney Docket No.45817-0022WO1 / MTX977.20 In an embodiment, the increase in level and / or activity, e.g., output, of the polypeptide encoded by the polynucleotide is measured according to an assay that measures the level and / or activity of a polypeptide. In an embodiment, the 5′ UTR comprises a sequence provided in Table 3 or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to a 5′ UTR sequence provided in Table 3, or a variant or a fragment thereof. In an embodiment, the 5′ UTR comprises a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 50, SEQ ID NO: 51, SEQ ID NO: 52, SEQ ID NO: 53, SEQ ID NO: 54, SEQ ID NO: 55, SEQ ID NO: 56, SEQ ID NO: 57 or SEQ ID NO: 58. In an embodiment, the 5′ UTR comprises a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 50. In an embodiment, the 5′ UTR comprises a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 51. In an embodiment, the 5′ UTR comprises a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 52. In an embodiment, the 5′ UTR comprises a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 53. In an embodiment, the 5′ UTR comprises a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 54. In an embodiment, the 5′ UTR comprises a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 55. In an embodiment, the 5′ UTR comprises a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 56. In an embodiment, the 5′ UTR comprises a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 57. In an embodiment, the 5′ UTR comprises a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 58. In an embodiment, the 5′ UTR comprises the sequence of SEQ ID NO:50. In an embodiment, the 5′ UTR consists of the sequence of SEQ ID NO:50. In an embodiment, the 5′ UTR comprises the sequence of SEQ ID NO:64. In an embodiment, the 5′ UTR consists of the sequence of SEQ ID NO:58. Attorney Docket No.45817-0022WO1 / MTX977.20 In an embodiment, a 5′ UTR sequence provided in Table 3 has a first nucleotide which is an A. In an embodiment, a 5′ UTR sequence provided in Table 3 has a first nucleotide which is a G. Table 3: 5′ UTR sequences SEQ ID Sequence Sequence NO: name AAU U A C AGC UAA A C Attorney Docket No.45817-0022WO1 / MTX977.20 A3GGAAAUCGCAAAAUUUUCUUUUCGCGUUAGAUUUCUUUUAGUUUUCUUUCAACUAGCAAGCUUUUUGUUCUCGCCGCCGC n in GGGGUGC Attorney Docket No.45817-0022WO1 / MTX977.20 67 A18GGAAACCCGCCCAAGCGACCCCAACAUAUCAGCAGUUGCCCAAUCCCAACUCCCAACACAAUCCCCAAGCAACGCCGCC GUAAGAAGAA AA a e o e , e co p ses a a a o : . a embodiment, the variant of SEQ ID NO: 50 comprises a nucleic acid sequence of Formula A: Attorney Docket No.45817-0022WO1 / MTX977.20 G G A A A U C G C A A A A (N2)X (N3)X C U (N4)X (N5)X C G C G U U A G A U U U C U U U U A G U U U U C U N6N7C A A C U A G C A A G C U U U U U G U U C U C G C C (N8 C C)x (SEQ ID NO: 59), wherein: (N2)x is a uracil and x is an integer from 0 to 5, e.g., wherein x =3 or 4; (N3)xis a guanine and x is an integer from 0 to 1; (N4)x is a cytosine and x is an integer from 0 to 1; (N5)x is a uracil and x is an integer from 0 to 5, e.g., wherein x =2 or 3; N6 is a uracil or cytosine; N7 is a uracil or guanine; N8is adenine or guanine and x is an integer from 0 to 1. In an embodiment (N2)x is a uracil and x is 0. In an embodiment (N2)x is a uracil and x is 1. In an embodiment (N2)xis a uracil and x is 2. In an embodiment (N2)x is a uracil and x is 3. In an embodiment, (N2)x is a uracil and x is 4. In an embodiment (N2)xis a uracil and x is 5. In an embodiment, (N3)x is a guanine and x is 0. In an embodiment, (N3)x is a guanine and x is 1. In an embodiment, (N4)x is a cytosine and x is 0. In an embodiment, (N4)x is a cytosine and x is 1. In an embodiment (N5)x is a uracil and x is 0. In an embodiment (N5)x is a uracil and x is 1. In an embodiment (N5)xis a uracil and x is 2. In an embodiment (N5)x is a uracil and x is 3. In an embodiment, (N5)x is a uracil and x is 4. In an embodiment (N5)xis a uracil and x is 5. In an embodiment, N6 is a uracil. In an embodiment, N6 is a cytosine. In an embodiment, N7is a uracil. In an embodiment, N7is a guanine. In an embodiment, N8 is an adenine and x is 0. In an embodiment, N8 is an adenine and x is 1. In an embodiment, N8is a guanine and x is 0. In an embodiment, N8is a guanine and x is 1. In an embodiment, the 5′ UTR comprises a variant of SEQ ID NO:50. In an embodiment, the variant of SEQ ID NO: 50 comprises a sequence with at least 50%, Attorney Docket No.45817-0022WO1 / MTX977.20 60%, 70%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, or 99% identity to SEQ ID NO: 50. In an embodiment, the variant of SEQ ID NO: 50 comprises a sequence with at least 50% identity to SEQ ID NO: 50. In an embodiment, the variant of SEQ ID NO: 50 comprises a sequence with at least 60% identity to SEQ ID NO: 50. In an embodiment, the variant of SEQ ID NO: 50 comprises a sequence with at least 70% identity to SEQ ID NO: 50. In an embodiment, the variant of SEQ ID NO: 50 comprises a sequence with at least 80% identity to SEQ ID NO: 50. In an embodiment, the variant of SEQ ID NO: 50 comprises a sequence with at least 90% identity to SEQ ID NO:50. In an embodiment, the variant of SEQ ID NO:50 comprises a sequence with at least 95% identity to SEQ ID NO:50. In an embodiment, the variant of SEQ ID NO:50 comprises a sequence with at least 96% identity to SEQ ID NO:50. In an embodiment, the variant of SEQ ID NO:50 comprises a sequence with at least 97% identity to SEQ ID NO:50. In an embodiment, the variant of SEQ ID NO:50 comprises a sequence with at least 98% identity to SEQ ID NO:50. In an embodiment, the variant of SEQ ID NO:50 comprises a sequence with at least 99% identity to SEQ ID NO:50. In an embodiment, the variant of SEQ ID NO:50 comprises a uridine content of at least 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80%. In an embodiment, the variant of SEQ ID NO:50 comprises a uridine content of at least 5%. In an embodiment, the variant of SEQ ID NO:50 comprises a uridine content of at least 10%. In an embodiment, the variant of SEQ ID NO:50 comprises a uridine content of at least 20%. In an embodiment, the variant of SEQ ID NO:50 comprises a uridine content of at least 30%. In an embodiment, the variant of SEQ ID NO:50 comprises a uridine content of at least 40%. In an embodiment, the variant of SEQ ID NO:50 comprises a uridine content of at least 50%. In an embodiment, the variant of SEQ ID NO:50 comprises a uridine content of at least 60%. In an embodiment, the variant of SEQ ID NO:50 comprises a uridine content of at least 70%. In an embodiment, the variant of SEQ ID NO:50 comprises a uridine content of at least 80%. In an embodiment, the variant of SEQ ID NO:50 comprises at least 2, 3, 4, 5, 6 or 7 consecutive uridines (e.g., a polyuridine tract). In an embodiment, the polyuridine tract in the variant of SEQ ID NO:50 comprises at least 1-7, 2-7, 3-7, 4-7, 5-7, 6-7, 1-6, 1-5, 1-4, 1-3, 1-2, 2-6, or 3-5 consecutive uridines. In an embodiment, Attorney Docket No.45817-0022WO1 / MTX977.20 the polyuridine tract in the variant of SEQ ID NO:50 comprises 4 consecutive uridines. In an embodiment, the polyuridine tract in the variant of SEQ ID NO:50 comprises 5 consecutive uridines. In an embodiment, the variant of SEQ ID NO:50 comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 polyuridine tracts. In an embodiment, the variant of SEQ ID NO:50 comprises 3 polyuridine tracts. In an embodiment, the variant of SEQ ID NO:50 comprises 4 polyuridine tracts. In an embodiment, the variant of SEQ ID NO:50 comprises 5 polyuridine tracts. In an embodiment, one or more of the polyuridine tracts are adjacent to a different polyuridine tract. In an embodiment, each of, e.g., all, the polyuridine tracts are adjacent to each other, e.g., all of the polyuridine tracts are contiguous. In an embodiment, one or more of the polyuridine tracts are separated by 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 2, 13, 14, 15, 16, 17, 18.19, 20, 30, 40, 50 or 60 nucleotides. In an embodiment, each of, e.g., all of, the polyuridine tracts are separated by 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 2, 13, 14, 15, 16, 17, 18.19, 20, 30, 40, 50 or 60 nucleotides. In an embodiment, a first polyuridine tract and a second polyuridine tract are adjacent to each other. In an embodiment, a subsequent, e.g., third, fourth, fifth, sixth or seventh, eighth, ninth, or tenth, polyuridine tract is separated by 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 2, 13, 14, 15, 16, 17, 18.19, 20, 30, 40, 50 or 60 nucleotides from the first polyuridine tract, the second polyuridine tract, or any one of the subsequent polyuridine tracts. In an embodiment, a first polyuridine tract is separated by 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 2, 13, 14, 15, 16, 17, 18.19, 20, 30, 40, 50 or 60 nucleotides from a subsequent polyuridine tract, e.g., a second, third, fourth, fifth, sixth or seventh, eighth, ninth, or tenth polyuridine tract. In an embodiment, one or more of the subsequent polyuridine tracts are adjacent to a different polyuridine tract. In an embodiment, the 5′ UTR comprises a Kozak sequence, e.g., a GCCRCC nucleotide sequence wherein R is an adenine or guanine. In an embodiment, the Kozak sequence is disposed at the 3′ end of the 5′UTR sequence. In an aspect, the polynucleotide (e.g., mRNA) comprising an open reading frame encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28) and comprising a 5′ UTR Attorney Docket No.45817-0022WO1 / MTX977.20 sequence disclosed herein is formulated as an LNP. In an embodiment, the LNP composition comprises: (i) an ionizable lipid, e.g., an amino lipid; (ii) a sterol or other structural lipid; (iii) a non-cationic helper lipid or phospholipid; and (iv) a PEG-lipid. In another aspect, the LNP compositions of the disclosure are used in a method of treating CTLN1, ASLD, or an ASS1- or ASL-associated disease or disorder in a subject. In an aspect, an LNP composition of the disclosure comprising an ASS1 polypeptide described herein or a polynucleotide disclosed herein encoding an ASS1 polypeptide, e.g., as described herein, is used in a method of treating CTLN1 or an ASS1-associated disease or disorder in a subject. In some aspects, the LNP composition is administered to the subject in combination with an LNP composition of the disclosure comprising an ASL polypeptide described herein or a polynucleotide disclosed herein encoding an ASL polypeptide, e.g., as described herein. In an aspect, (i) an LNP composition of the disclosure comprising an ASS1 polypeptide described herein or a polynucleotide disclosed herein encoding an ASS1 polypeptide, e.g., as described herein, and (ii) an LNP composition of the disclosure comprising an ASL polypeptide described herein or a polynucleotide disclosed herein encoding an ASL polypeptide, e.g., as described herein, are used in combination in a method of treating ASLD or an ASL-associated disease or disorder in a subject. In some instances, the 5′ UTR comprises the sequence of SEQ ID NO: 215. b.3′ UTR sequences 3′UTR sequences have been shown to influence translation, half-life, and subcellular localization of mRNAs (Mayr C., Cold Spring Harb Persp Biol 2019 Oct 1;11(10):a034728). Disclosed herein, inter alia, is a polynucleotide, e.g., mRNA, comprising an open reading frame encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1- 6) or an open reading frame encoding an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28) which polynucleotide has a 3′ UTR that confers an increased half- life, increased expression and / or increased activity of the polypeptide encoded by said Attorney Docket No.45817-0022WO1 / MTX977.20 polynucleotide, or of the polynucleotide itself. In an embodiment, a polynucleotide disclosed herein comprises: (a) a 5′-UTR (e.g., as described herein); (b) a coding region comprising a stop element (e.g., as described herein); and (c) a 3′-UTR (e.g., as provided in Table 4 or a variant or fragment thereof), and LNP compositions comprising the same. In an embodiment, the polynucleotide comprises a 3′-UTR comprising a sequence provided in Table 4 or a variant or fragment thereof. In some embodiments, disclosed herein is a polynucleotide, e.g., mRNA, comprising an ORF (encoding an ASS1 polypeptide or an ASL polypeptide) and a 3′ UTR comprising the nucleic acid sequence of SEQ ID NO:141. In some embodiments, disclosed herein is a polynucleotide, e.g., mRNA, comprising an ORF (encoding an ASS1 polypeptide or an ASL polypeptide) and a 3′ UTR comprising the nucleic acid sequence of SEQ ID NO:142. In some embodiments, disclosed herein is a polynucleotide, e.g., mRNA, comprising an ORF (encoding an ASS1 polypeptide or an ASL polypeptide) and a 3′ UTR comprising the nucleic acid sequence of SEQ ID NO:143. In some embodiments, the ORF encoding ASS1 is at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identical to the nucleic acid sequence of any one of SEQ ID NOs:8-14. In some embodiments, the ORF encoding ASL is at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identical to the nucleic acid sequence of SEQ ID NO:15. In some embodiments, the polynucleotide, e.g., mRNA, comprises a 5′ UTR, said 5′ UTR comprising a nucleic acid sequence at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identical to the nucleic acid sequence of SEQ ID NO:50 or SEQ ID NO:58. In some embodiments, the ORF encoding ASS1 comprises the nucleic acid sequence set forth in SEQ ID NO:8. In some embodiments, the ORF encoding ASS1 comprises the nucleic acid sequence set forth in SEQ ID NO:11. In some embodiments, the ORF encoding ASL1 comprises the nucleic acid sequence set forth in SEQ ID NO:15. Attorney Docket No.45817-0022WO1 / MTX977.20 In some embodiments, disclosed herein is a polynucleotide, e.g., mRNA, comprising an ORF encoding an ASS1 polypeptide and a 3′ UTR comprising the nucleic acid sequence of SEQ ID NO:141. In some embodiments, the ORF is at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identical to the nucleic acid sequence of SEQ ID NO:8. In some embodiments, the polynucleotide, e.g., mRNA, comprises a 5′ UTR, said 5′ UTR comprising a nucleic acid sequence at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identical to the nucleic acid sequence of SEQ ID NO:50. In some embodiments, disclosed herein is a polynucleotide, e.g., mRNA, comprising an ORF encoding an ASS1 polypeptide and a 3′ UTR comprising the nucleic acid sequence of SEQ ID NO:141. In some embodiments, the ORF is at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identical to the nucleic acid sequence of SEQ ID NO:11. In some embodiments, the polynucleotide, e.g., mRNA, comprises a 5′ UTR, said 5′ UTR comprising a nucleic acid sequence at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identical to the nucleic acid sequence of SEQ ID NO:50. In some embodiments, disclosed herein is a polynucleotide, e.g., mRNA, comprising an ORF (encoding an ASS1 polypeptide or an ASL polypeptide) and a 3′ UTR comprising the nucleic acid sequence of SEQ ID NO:135. In some embodiments, the ORF encoding ASS1 is at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identical to the nucleic acid sequence of any one of SEQ ID NOs:8-14. In some embodiments, the ORF encoding ASL is at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identical to the nucleic acid sequence of SEQ ID NO:15. In some embodiments, the polynucleotide, e.g., mRNA, comprises a 5′ UTR, said 5′ Attorney Docket No.45817-0022WO1 / MTX977.20 UTR comprising a nucleic acid sequence at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100% identical to the nucleic acid sequence of SEQ ID NO:50 or SEQ ID NO:58. In some embodiments, the ORF encoding ASS1 comprises the nucleic acid sequence set forth in SEQ ID NO:8. In some embodiments, the ORF encoding ASS1 comprises the nucleic acid sequence set forth in SEQ ID NO:11. In some embodiments, the ORF encoding ASL1 comprises the nucleic acid sequence set forth in SEQ ID NO:15. In an embodiment, the polynucleotide having a 3′ UTR sequence provided in Table 4 or a variant or fragment thereof, results in an increased half-life of the polynucleotide, e.g., about 1.5-10-fold increase in half-life of the polynucleotide. In an embodiment, the increase in half-life is about 1.5, 2, 3, 4, 5, 6, 7, 8, 9, or 10-fold, or more. In an embodiment, the increase in half-life is about 1.5-fold or more. In an embodiment, the increase in half-life is about 2-fold or more. In an embodiment, the increase in half-life is about 3-fold or more. In an embodiment, the increase in half- life is about 4-fold or more. In an embodiment, the increase in half-life is about 5-fold or more. In an embodiment, the increase in half-life is about 6-fold or more. In an embodiment, the increase in half-life is about 7-fold or more. In an embodiment, the increase in half-life is about 8-fold. In an embodiment, the increase in half-life is about 9-fold or more. In an embodiment, the increase in half-life is about 10-fold or more. In an embodiment, the polynucleotide having a 3′ UTR sequence provided in Table 4 or a variant or fragment thereof, results in a polynucleotide with a mean half- life score of greater than 10. In an embodiment, the polynucleotide having a 3′ UTR sequence provided in Table 4 or a variant or fragment thereof, results in an increased level and / or activity, e.g., output, of the polypeptide encoded by the polynucleotide. In an embodiment, the increase is compared to an otherwise similar polynucleotide which does not have a 3′ UTR, has a different 3′ UTR, or does not have a 3′ UTR of Table 4 or a variant or fragment thereof. In an embodiment, the polynucleotide comprises a 3′ UTR sequence provided in Table 4 or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to a 3′ UTR sequence provided in Table 4, or a fragment thereof. In an Attorney Docket No.45817-0022WO1 / MTX977.20 embodiment, the 3′ UTR comprises a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 100, SEQ ID NO: 101, SEQ ID NO: 102, SEQ ID NO: 103, SEQ ID NO: 104, SEQ ID NO: 105, SEQ ID NO: 106, SEQ ID NO: 107, SEQ ID NO: 108, SEQ ID NO: 109, SEQ ID NO: 110, SEQ ID NO: 111, SEQ ID NO: 112, SEQ ID NO: 113, SEQ ID NO: 114, or SEQ ID NO:115. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 100, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 100. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 101, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 101. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 102, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 102. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 103, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 103. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 104, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 104. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 105, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 105. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 106, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 106. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 107, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 107. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 108, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 108. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 109, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 109. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 110, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 110. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 111, or a sequence Attorney Docket No.45817-0022WO1 / MTX977.20 with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 111. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 112, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 112. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 113, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 113. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 114, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 114. In an embodiment, the 3′ UTR comprises the sequence of SEQ ID NO: 115, or a sequence with at least 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 115. Table 4: 3′ UTR sequences SEQ Sequence Sequence ID i f ti U C C C U C C C U C Attorney Docket No.45817-0022WO1 / MTX977.20 B7UAAUAGUAAGCUGGAGCCUCCGGAAAACUAAAAUAGAGAUAUUUCAAGAUUUUAUAAUUUUCAAAGACCUUUGAAAUAUUGUACCC G C U C U C U C C U C C U C U U C C C C U Attorney Docket No.45817-0022WO1 / MTX977.20 B16UGAUAAUAGUCCAUAAAGUAGGAAACACUACAGCUGGAGCCUCGGUGGCCUAGCUUCUUGCCCCUUGGGCCUCCAUAAAGUAGGAA A A CCC A U U U G A U U C U U G U C U U G Attorney Docket No.45817-0022WO1 / MTX977.20 133 B22UAAGUCUCCAUAAAGUAGGAAACACUACAGCUGGAGCCUCGGUGGCCUAGCUUCUUGCCCCUUGGGCCUCCAUAAAGUAGGAAACA C U G U G G C U U C G A A C A U , , e.g., as described herein, which binds to a miR present in a human cell. In an embodiment, the 3′ UTR comprises a miRNA binding site of SEQ ID NO: 212, SEQ ID NO: 174, SEQ ID NO: 152 or a combination thereof. In an embodiment, the 3′ UTR comprises a plurality of miRNA binding sites, e.g., 2, 3, 4, 5, 6, 7 or 8 miRNA binding sites. In an embodiment, the plurality of miRNA binding sites comprises the same or different miRNA binding sites. miR122 bs = CAAACACCAUUGUCACACUCCA (SEQ ID NO: 212) Attorney Docket No.45817-0022WO1 / MTX977.20 miR-142-3p bs = UCCAUAAAGUAGGAAACACUACA (SEQ ID NO: 174) miR-126 bs = CGCAUUAUUACUCACGGUACGA (SEQ ID NO: 152) In an aspect, disclosed herein is a polynucleotide encoding a polypeptide, wherein the polynucleotide comprises: (a) a 5′-UTR, e.g., as described herein; (b) a coding region comprising a stop element (e.g., as described herein); and (c) a 3′-UTR (e.g., as described herein). In an aspect, an LNP composition comprising a polynucleotide comprising an open reading frame encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1- 6) and comprising a 3′ UTR disclosed herein comprises: (i) an ionizable lipid, e.g., an amino lipid; (ii) a sterol or other structural lipid; (iii) a non-cationic helper lipid or phospholipid; and (iv) a PEG-lipid. In an aspect, an LNP composition comprising a polynucleotide comprising an open reading frame encoding an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28) and comprising a 3′ UTR disclosed herein comprises: (i) an ionizable lipid, e.g., an amino lipid; (ii) a sterol or other structural lipid; (iii) a non-cationic helper lipid or phospholipid; and (iv) a PEG-lipid. In an aspect, an LNP composition of the disclosure comprising an ASS1 polypeptide described herein or a polynucleotide disclosed herein encoding an ASS1 polypeptide, e.g., as described herein, is used in a method of treating CTLN1 or an ASS1-associated disease or disorder in a subject. In some aspects, the LNP composition is administered to the subject in combination with an LNP composition of the disclosure comprising an ASL polypeptide described herein or a polynucleotide disclosed herein encoding an ASL polypeptide, e.g., as described herein. In an aspect, (i) an LNP composition of the disclosure comprising an ASS1 polypeptide described herein or a polynucleotide disclosed herein encoding an ASS1 polypeptide, e.g., as described herein, and (ii) an LNP composition o the disclosure comprising an ASL polypeptide described herein or a polynucleotide disclosed herein encoding an ASL polypeptide, e.g., as described herein, are used in combination in a method of treating ASLD or an ASLD-associated disease or disorder in a subject. Attorney Docket No.45817-0022WO1 / MTX977.20 12. MicroRNA (miRNA) Binding Sites Polynucleotides of the invention can include regulatory elements, for example, microRNA (miRNA) binding sites, transcription factor binding sites, structured mRNA sequences and / or motifs, artificial binding sites engineered to act as pseudo- receptors for endogenous nucleic acid binding molecules, and combinations thereof. In some embodiments, polynucleotides including such regulatory elements are referred to as including “sensor sequences”. In some embodiments, a polynucleotide (e.g., a ribonucleic acid (RNA), e.g., a messenger RNA (mRNA)) of the invention comprises an open reading frame (ORF) encoding a polypeptide of interest and further comprises one or more miRNA binding site(s). Inclusion or incorporation of miRNA binding site(s) provides for regulation of polynucleotides of the invention, and in turn, of the polypeptides encoded therefrom, based on tissue-specific and / or cell-type specific expression of naturally-occurring miRNAs. The present invention also provides pharmaceutical compositions and formulations that comprise any of the polynucleotides described above. In some embodiments, the composition or formulation further comprises a delivery agent. In some embodiments, the composition or formulation can contain a polynucleotide comprising a sequence optimized nucleic acid sequence disclosed herein which encodes a polypeptide. In some embodiments, the composition or formulation can contain a polynucleotide (e.g., a RNA, e.g., an mRNA) comprising a polynucleotide (e.g., an ORF) having significant sequence identity to a sequence optimized nucleic acid sequence disclosed herein which encodes a polypeptide. In some embodiments, the polynucleotide further comprises a miRNA binding site, e.g., a miRNA binding site that binds A miRNA, e.g., a natural-occurring miRNA, is a 19-25 nucleotide long noncoding RNA that binds to a polynucleotide and down-regulates gene expression either by reducing stability or by inhibiting translation of the polynucleotide. A miRNA sequence comprises a “seed” region, i.e., a sequence in the region of positions 2-8 of the mature miRNA. A miRNA seed can comprise positions 2-8 or 2- 7 of the mature miRNA. Attorney Docket No.45817-0022WO1 / MTX977.20 microRNAs derive enzymatically from regions of RNA transcripts that fold back on themselves to form short hairpin structures often termed a pre-miRNA (precursor-miRNA). A pre-miRNA typically has a two-nucleotide overhang at its 3′ end, and has 3′ hydroxyl and 5′ phosphate groups. This precursor-mRNA is processed in the nucleus and subsequently transported to the cytoplasm where it is further processed by DICER (a RNase III enzyme), to form a mature microRNA of approximately 22 nucleotides. The mature microRNA is then incorporated into a ribonuclear particle to form the RNA-induced silencing complex, RISC, which mediates gene silencing. Art-recognized nomenclature for mature miRNAs typically designates the arm of the pre-miRNA from which the mature miRNA derives; "5p" means the microRNA is from the 5 prime arm of the pre-miRNA hairpin and "3p" means the microRNA is from the 3 prime end of the pre-miRNA hairpin. A miR referred to by number herein can refer to either of the two mature microRNAs originating from opposite arms of the same pre-miRNA (e.g., either the 3p or 5p microRNA). All miRs referred to herein are intended to include both the 3p and 5p arms / sequences, unless particularly specified by the 3p or 5p designation. As used herein, the term “microRNA (miRNA or miR) binding site” refers to a sequence within a polynucleotide, e.g., within a DNA or within an RNA transcript, including in the 5′UTR and / or 3′UTR, that has sufficient complementarity to all or a region of a miRNA to interact with, associate with or bind to the miRNA. In some embodiments, a polynucleotide of the invention comprising an ORF encoding a polypeptide of interest and further comprises one or more miRNA binding site(s). In exemplary embodiments, a 5′ UTR and / or 3′ UTR of the polynucleotide (e.g., a ribonucleic acid (RNA), e.g., a messenger RNA (mRNA)) comprises the one or more miRNA binding site(s). A miRNA binding site having sufficient complementarity to a miRNA refers to a degree of complementarity sufficient to facilitate miRNA-mediated regulation of a polynucleotide, e.g., miRNA-mediated translational repression or degradation of the polynucleotide. In exemplary aspects of the invention, a miRNA binding site having sufficient complementarity to the miRNA refers to a degree of complementarity sufficient to facilitate miRNA-mediated degradation of the polynucleotide, e.g., miRNA-guided RNA-induced silencing complex (RISC)-mediated cleavage of Attorney Docket No.45817-0022WO1 / MTX977.20 mRNA. The miRNA binding site can have complementarity to, for example, a 19-25 nucleotide long miRNA sequence, to a 19-23 nucleotide long miRNA sequence, or to a 22 nucleotide long miRNA sequence. A miRNA binding site can be complementary to only a portion of a miRNA, e.g., to a portion less than 1, 2, 3, or 4 nucleotides of the full length of a naturally-occurring miRNA sequence, or to a portion less than 1, 2, 3, or 4 nucleotides shorter than a naturally-occurring miRNA sequence. Full or complete complementarity (e.g., full complementarity or complete complementarity over all or a significant portion of the length of a naturally-occurring miRNA) is preferred when the desired regulation is mRNA degradation. In some embodiments, a miRNA binding site includes a sequence that has complementarity (e.g., partial or complete complementarity) with an miRNA seed sequence. In some embodiments, the miRNA binding site includes a sequence that has complete complementarity with a miRNA seed sequence. In some embodiments, a miRNA binding site includes a sequence that has complementarity (e.g., partial or complete complementarity) with an miRNA sequence. In some embodiments, the miRNA binding site includes a sequence that has complete complementarity with a miRNA sequence. In other embodiments, the sequence is not completely complementary. In some embodiments, a miRNA binding site has complete complementarity with a miRNA sequence but for 1, 2, or 3 nucleotide substitutions, terminal additions, and / or truncations. In some embodiments, the miRNA binding site is the same length as the corresponding miRNA. In other embodiments, the miRNA binding site is one, two, three, four, five, six, seven, eight, nine, ten, eleven or twelve nucleotide(s) shorter than the corresponding miRNA at the 5′ terminus, the 3′ terminus, or both. In still other embodiments, the microRNA binding site is two nucleotides shorter than the corresponding microRNA at the 5′ terminus, the 3′ terminus, or both. The miRNA binding sites that are shorter than the corresponding miRNAs are still capable of degrading the mRNA incorporating one or more of the miRNA binding sites or preventing the mRNA from translation. In some embodiments, the miRNA binding site binds the corresponding mature miRNA that is part of an active RISC containing Dicer. In another embodiment, binding of the miRNA binding site to the corresponding miRNA in Attorney Docket No.45817-0022WO1 / MTX977.20 RISC degrades the mRNA containing the miRNA binding site or prevents the mRNA from being translated. In some embodiments, the miRNA binding site has sufficient complementarity to miRNA so that a RISC complex comprising the miRNA cleaves the polynucleotide comprising the miRNA binding site. In other embodiments, the miRNA binding site has imperfect complementarity so that a RISC complex comprising the miRNA induces instability in the polynucleotide comprising the miRNA binding site. In another embodiment, the miRNA binding site has imperfect complementarity so that a RISC complex comprising the miRNA represses transcription of the polynucleotide comprising the miRNA binding site. In some embodiments, the miRNA binding site has one, two, three, four, five, six, seven, eight, nine, ten, eleven or twelve mismatch(es) from the corresponding miRNA. In some embodiments, the miRNA binding site has at least about ten, at least about eleven, at least about twelve, at least about thirteen, at least about fourteen, at least about fifteen, at least about sixteen, at least about seventeen, at least about eighteen, at least about nineteen, at least about twenty, or at least about twenty-one contiguous nucleotides complementary to at least about ten, at least about eleven, at least about twelve, at least about thirteen, at least about fourteen, at least about fifteen, at least about sixteen, at least about seventeen, at least about eighteen, at least about nineteen, at least about twenty, or at least about twenty-one, respectively, contiguous nucleotides of the corresponding miRNA. By engineering one or more miRNA binding sites into a polynucleotide of the invention, the polynucleotide can be targeted for degradation or reduced translation, provided the miRNA in question is available. This can reduce off-target effects upon delivery of the polynucleotide. For example, if a polynucleotide of the invention is not intended to be delivered to a tissue or cell but ends up is said tissue or cell, then a miRNA abundant in the tissue or cell can inhibit the expression of the gene of interest if one or multiple binding sites of the miRNA are engineered into the 5′ UTR and / or 3′ UTR of the polynucleotide. Thus, in some embodiments, incorporation of one or more miRNA binding sites into an mRNA of the disclosure may reduce the hazard of off-target effects upon nucleic acid molecule delivery and / or enable tissue-specific regulation of expression of a polypeptide encoded by the mRNA. In yet other Attorney Docket No.45817-0022WO1 / MTX977.20 embodiments, incorporation of one or more miRNA binding sites into an mRNA of the disclosure can modulate immune responses upon nucleic acid delivery in vivo. In further embodiments, incorporation of one or more miRNA binding sites into an mRNA of the disclosure can modulate accelerated blood clearance (ABC) of lipid- comprising compounds and compositions described herein. Conversely, miRNA binding sites can be removed from polynucleotide sequences in which they naturally occur to increase protein expression in specific tissues. For example, a binding site for a specific miRNA can be removed from a polynucleotide to improve protein expression in tissues or cells containing the miRNA. Regulation of expression in multiple tissues can be accomplished through introduction or removal of one or more miRNA binding sites, e.g., one or more distinct miRNA binding sites. The decision whether to remove or insert a miRNA binding site can be made based on miRNA expression patterns and / or their profilings in tissues and / or cells in development and / or disease. Identification of miRNAs, miRNA binding sites, and their expression patterns and role in biology have been reported (e.g., Bonauer et al., Curr Drug Targets 201011:943-949; Anand and Cheresh Curr Opin Hematol 201118:171-176; Contreras and Rao Leukemia 2012 26:404-413 (2011 Dec 20. doi: 10.1038 / leu.2011.356); Bartel Cell 2009136:215-233; Landgraf et al, Cell, 2007129:1401-1414; Gentner and Naldini, Tissue Antigens. 201280:393-403 and all references therein; each of which is incorporated herein by reference in its entirety). Examples of tissues where miRNA are known to regulate mRNA, and thereby protein expression, include, but are not limited to, liver (miR-122), muscle (miR-133, miR-206, miR-208), endothelial cells (miR-17-92, miR-126), myeloid cells (miR- 142-3p, miR-142-5p, miR-16, miR-21, miR-223, miR-24, miR-27), adipose tissue (let-7, miR-30c), heart (miR-1d, miR-149), kidney (miR-192, miR-194, miR-204), and lung epithelial cells (let-7, miR-133, miR-126). Specifically, miRNAs are known to be differentially expressed in immune cells (also called hematopoietic cells), such as antigen presenting cells (APCs) (e.g., dendritic cells and macrophages), macrophages, monocytes, B lymphocytes, T lymphocytes, granulocytes, natural killer cells, etc. Immune cell specific miRNAs are Attorney Docket No.45817-0022WO1 / MTX977.20 involved in immunogenicity, autoimmunity, the immune-response to infection, inflammation, as well as unwanted immune response after gene therapy and tissue / organ transplantation. Immune cells specific miRNAs also regulate many aspects of development, proliferation, differentiation and apoptosis of hematopoietic cells (immune cells). For example, miR-142 and miR-146 are exclusively expressed in immune cells, particularly abundant in myeloid dendritic cells. It has been demonstrated that the immune response to a polynucleotide can be shut-off by adding miR-142 binding sites to the 3′-UTR of the polynucleotide, enabling more stable gene transfer in tissues and cells. miR-142 efficiently degrades exogenous polynucleotides in antigen presenting cells and suppresses cytotoxic elimination of transduced cells (e.g., Annoni A et al., blood, 2009, 114, 5152-5161; Brown BD, et al., Nat med.2006, 12(5), 585-591; Brown BD, et al., blood, 2007, 110(13): 4144-4152, each of which is incorporated herein by reference in its entirety). An antigen-mediated immune response can refer to an immune response triggered by foreign antigens, which, when entering an organism, are processed by the antigen presenting cells and displayed on the surface of the antigen presenting cells. T cells can recognize the presented antigen and induce a cytotoxic elimination of cells that express the antigen. Introducing one or more (e.g., one, two, or three) miR-142 binding sites into the 5′ UTR and / or 3′UTR of a polynucleotide of the invention can selectively repress gene expression in antigen presenting cells through miR-142 mediated degradation, limiting antigen presentation in antigen presenting cells (e.g., dendritic cells) and thereby preventing antigen-mediated immune response after the delivery of the polynucleotide. The polynucleotide is then stably expressed in target tissues or cells without triggering cytotoxic elimination. In some embodiments, it may be beneficial to target the same cell type with multiple miRs and to incorporate binding sites to each of the 3p and 5p arm if both are abundant (e.g., both miR-142-3p and miR142-5p are abundant in hematopoietic stem cells). Thus, in certain embodiments, polynucleotides of the invention contain two or more (e.g., two, three, four or more) miR bindings sites from: (i) the group consisting of miR-142, miR-144, miR-150, miR-155 and miR-223 (which are expressed in many hematopoietic cells); or (ii) the group consisting of miR-142, miR150, miR-16 and Attorney Docket No.45817-0022WO1 / MTX977.20 miR-223 (which are expressed in B cells); or the group consisting of miR-223, miR- 451, miR-26a, miR-16 (which are expressed in progenitor hematopoietic cells). In some embodiments, it may also be beneficial to combine various miRs such that multiple cell types of interest are targeted at the same time (e.g., miR-142 and miR-126 to target many cells of the hematopoietic lineage and endothelial cells). Thus, for example, in certain embodiments, polynucleotides of the invention comprise two or more (e.g., two, three, four or more) miRNA bindings sites, wherein: (i) at least one of the miRs targets cells of the hematopoietic lineage (e.g., miR-142, miR- 144, miR-150, miR-155 or miR-223) and at least one of the miRs targets plasmacytoid dendritic cells, platelets or endothelial cells (e.g., miR-126); or (ii) at least one of the miRs targets B cells (e.g., miR-142, miR150, miR-16 or miR-223) and at least one of the miRs targets plasmacytoid dendritic cells, platelets or endothelial cells (e.g., miR-126); or (iii) at least one of the miRs targets progenitor hematopoietic cells (e.g., miR-223, miR-451, miR-26a or miR-16) and at least one of the miRs targets plasmacytoid dendritic cells, platelets or endothelial cells (e.g., miR- 126); or (iv) at least one of the miRs targets cells of the hematopoietic lineage (e.g., miR-142, miR-144, miR-150, miR-155 or miR-223), at least one of the miRs targets B cells (e.g., miR-142, miR150, miR-16 or miR-223) and at least one of the miRs targets plasmacytoid dendritic cells, platelets or endothelial cells (e.g., miR-126); or any other possible combination of the foregoing four classes of miR binding sites (i.e., those targeting the hematopoietic lineage, those targeting B cells, those targeting progenitor hematopoietic cells and / or those targeting plasmacytoid dendritic cells / platelets / endothelial cells). In one embodiment, to modulate immune responses, polynucleotides of the present invention can comprise one or more miRNA binding sequences that bind to one or more miRs that are expressed in conventional immune cells or any cell that expresses TLR7 and / or TLR8 and secrete pro-inflammatory cytokines and / or chemokines (e.g., in immune cells of peripheral lymphoid organs and / or splenocytes and / or endothelial cells). It has now been discovered that incorporation into an mRNA of one or more miRs that are expressed in conventional immune cells or any cell that expresses TLR7 and / or TLR8 and secrete pro-inflammatory cytokines and / or chemokines (e.g., in immune cells of peripheral lymphoid organs and / or splenocytes Attorney Docket No.45817-0022WO1 / MTX977.20 and / or endothelial cells) reduces or inhibits immune cell activation (e.g., B cell activation, as measured by frequency of activated B cells) and / or cytokine production (e.g., production of IL-6, IFN-^ and / or TNF^). Furthermore, it has now been discovered that incorporation into an mRNA of one or more miRs that are expressed in conventional immune cells or any cell that expresses TLR7 and / or TLR8 and secrete pro-inflammatory cytokines and / or chemokines (e.g., in immune cells of peripheral lymphoid organs and / or splenocytes and / or endothelial cells) can reduce or inhibit an anti-drug antibody (ADA) response against a protein of interest encoded by the mRNA. In another embodiment, to modulate accelerated blood clearance of a polynucleotide delivered in a lipid-comprising compound or composition, polynucleotides of the invention can comprise one or more miR binding sequences that bind to one or more miRNAs expressed in conventional immune cells or any cell that expresses TLR7 and / or TLR8 and secrete pro-inflammatory cytokines and / or chemokines (e.g., in immune cells of peripheral lymphoid organs and / or splenocytes and / or endothelial cells). It has now been discovered that incorporation into an mRNA of one or more miR binding sites reduces or inhibits accelerated blood clearance (ABC) of the lipid-comprising compound or composition for use in delivering the mRNA. Furthermore, it has now been discovered that incorporation of one or more miR binding sites into an mRNA reduces serum levels of anti-PEG anti- IgM (e.g., reduces or inhibits the acute production of IgMs that recognize polyethylene glycol (PEG) by B cells) and / or reduces or inhibits proliferation and / or activation of plasmacytoid dendritic cells following administration of a lipid- comprising compound or composition comprising the mRNA. In some embodiments, miR sequences may correspond to any known microRNA expressed in immune cells, including but not limited to those taught in US Publication US2005 / 0261218 and US Publication US2005 / 0059005, the contents of which are incorporated herein by reference in their entirety. Non-limiting examples of miRs expressed in immune cells include those expressed in spleen cells, myeloid cells, dendritic cells, plasmacytoid dendritic cells, B cells, T cells and / or macrophages. For example, miR-142-3p, miR-142-5p, miR-16, miR-21, miR-223, miR-24 and miR-27 are expressed in myeloid cells, miR-155 is expressed in dendritic Attorney Docket No.45817-0022WO1 / MTX977.20 cells, B cells and T cells, miR-146 is upregulated in macrophages upon TLR stimulation and miR-126 is expressed in plasmacytoid dendritic cells. In certain embodiments, the miR(s) is expressed abundantly or preferentially in immune cells. For example, miR-142 (miR-142-3p and / or miR-142-5p), miR-126 (miR-126-3p and / or miR-126-5p), miR-146 (miR-146-3p and / or miR-146-5p) and miR-155 (miR- 155-3p and / or miR155-5p) are expressed abundantly in immune cells. These microRNA sequences are known in the art and, thus, one of ordinary skill in the art can readily design binding sequences or target sequences to which these microRNAs will bind based upon Watson-Crick complementarity. In one embodiment, the polynucleotide of the invention comprises three copies of the same miRNA binding site. In certain embodiments, use of three copies of the same miR binding site can exhibit beneficial properties as compared to use of a single miRNA binding site. In another embodiment, the polynucleotide of the invention comprises two or more (e.g., two, three, four) copies of at least two different miR binding sites expressed in immune cells. In another embodiment, the polynucleotide of the invention comprises at least two miR binding sites for microRNAs expressed in immune cells, wherein one of the miR binding sites is for miR-142-3p. In various embodiments, the polynucleotide of the invention comprises binding sites for miR-142-3p and miR-155 (miR-155-3p or miR-155-5p), miR-142-3p and miR-146 (miR-146-3 or miR-146-5p), or miR-142-3p and miR-126 (miR-126-3p or miR-126-5p). In another embodiment, the polynucleotide of the invention comprises at least two miR binding sites for microRNAs expressed in immune cells, wherein one of the miR binding sites is for miR-126-3p. In various embodiments, the polynucleotide of the invention comprises binding sites for miR-126-3p and miR-155 (miR-155-3p or miR-155-5p), miR-126-3p and miR-146 (miR-146-3p or miR-146-5p), or miR-126-3p and miR-142 (miR-142-3p or miR-142-5p). In another embodiment, the polynucleotide of the invention comprises at least two miR binding sites for microRNAs expressed in immune cells, wherein one of the miR binding sites is for miR-142-5p. In various embodiments, the polynucleotide of the invention comprises binding sites for miR-142-5p and miR-155 (miR-155-3p or Attorney Docket No.45817-0022WO1 / MTX977.20 miR-155-5p), miR-142-5p and miR-146 (miR-146-3 or miR-146-5p), or miR-142-5p and miR-126 (miR-126-3p or miR-126-5p). In yet another embodiment, the polynucleotide of the invention comprises at least two miR binding sites for microRNAs expressed in immune cells, wherein one of the miR binding sites is for miR-155-5p. In various embodiments, the polynucleotide of the invention comprises binding sites for miR-155-5p and miR-142 (miR-142-3p or miR-142-5p), miR-155-5p and miR-146 (miR-146-3 or miR-146-5p), or miR-155-5p and miR-126 (miR-126-3p or miR-126-5p). In some embodiments, a polynucleotide of the invention comprises a miRNA binding site, wherein the miRNA binding site comprises one or more nucleotide sequences selected from Table 5, including one or more copies of any one or more of the miRNA binding site sequences. In some embodiments, a polynucleotide of the invention further comprises at least one, two, three, four, five, six, seven, eight, nine, ten, or more of the same or different miRNA binding sites selected from Table 5, including any combination thereof. In some embodiments, the miRNA binding site binds to miR-142 or is complementary to miR-142. In some embodiments, the miR-142 comprises SEQ ID NO:172. In some embodiments, the miRNA binding site binds to miR-142-3p or miR-142-5p. In some embodiments, the miR-142-3p binding site comprises SEQ ID NO:174. In some embodiments, the miR-142-5p binding site comprises SEQ ID NO:210. In some embodiments, the miRNA binding site comprises a nucleotide sequence at least 80%, at least 85%, at least 90%, at least 95%, or 100% identical to SEQ ID NO:174 or SEQ ID NO:210. In some embodiments, the miRNA binding site binds to miR-126 or is complementary to miR-126. In some embodiments, the miR-126 comprises SEQ ID NO: 150. In some embodiments, the miRNA binding site binds to miR-126-3p or miR-126-5p. In some embodiments, the miR-126-3p binding site comprises SEQ ID NO: 152. In some embodiments, the miR-126-5p binding site comprises SEQ ID NO: 154. In some embodiments, the miRNA binding site comprises a nucleotide sequence at least 80%, at least 85%, at least 90%, at least 95%, or 100% identical to SEQ ID NO: 152 or SEQ ID NO: 154. Attorney Docket No.45817-0022WO1 / MTX977.20 In one embodiment, the 3′ UTR comprises two miRNA binding sites, wherein a first miRNA binding site binds to miR-142 and a second miRNA binding site binds to miR-126. TABLE 5. miR-142, miR-126, and miR-142 and miR-126 binding sites SEQ ID NO. Description Sequence GACAGUGCAGUCACCCAUAAAGUAGAAAGCACUACUAA 172 miR-142 CAGCACUGGAGGGUGUAGUGUUUCCUACUUUAUGGAUG UGCG so e e o e s, a g s e s se e e po y uc eo e of the invention in any position of the polynucleotide (e.g., the 3′ UTR). In some embodiments, the 3′ UTR comprises a miRNA binding site. The insertion site in the polynucleotide can be anywhere in the polynucleotide as long as the insertion of the miRNA binding site in the polynucleotide does not interfere with the translation of a functional polypeptide in the absence of the corresponding miRNA; and in the presence of the miRNA, the insertion of the miRNA binding site in the polynucleotide and the binding of the miRNA binding site to the corresponding miRNA are capable of degrading the polynucleotide or preventing the translation of the polynucleotide. In some embodiments, a miRNA binding site is inserted in at least about 30 nucleotides downstream from the stop codon of an ORF in a polynucleotide of the invention comprising the ORF. In some embodiments, a miRNA binding site is inserted in at least about 10 nucleotides, at least about 15 nucleotides, at least about 20 nucleotides, at least about 25 nucleotides, at least about 30 nucleotides, at least about 35 nucleotides, at least about 40 nucleotides, at least about 45 nucleotides, at least about 50 nucleotides, at least about 55 nucleotides, at least about 60 nucleotides, Attorney Docket No.45817-0022WO1 / MTX977.20 at least about 65 nucleotides, at least about 70 nucleotides, at least about 75 nucleotides, at least about 80 nucleotides, at least about 85 nucleotides, at least about 90 nucleotides, at least about 95 nucleotides, or at least about 100 nucleotides downstream from the stop codon of an ORF in a polynucleotide of the invention. In some embodiments, a miRNA binding site is inserted in about 10 nucleotides to about 100 nucleotides, about 20 nucleotides to about 90 nucleotides, about 30 nucleotides to about 80 nucleotides, about 40 nucleotides to about 70 nucleotides, about 50 nucleotides to about 60 nucleotides, about 45 nucleotides to about 65 nucleotides downstream from the stop codon of an ORF in a polynucleotide of the invention. In some embodiments, a miRNA binding site is inserted within the 3′ UTR immediately following the stop codon of the coding region within the polynucleotide of the invention, e.g., mRNA. In some embodiments, if there are multiple copies of a stop codon in the construct, a miRNA binding site is inserted immediately following the final stop codon. In some embodiments, a miRNA binding site is inserted further downstream of the stop codon, in which case there are 3′ UTR bases between the stop codon and the miR binding site(s). In one embodiment, a codon optimized open reading frame encoding a polypeptide of interest comprises a stop codon and the at least one microRNA binding site is located within the 3′ UTR 1-100 nucleotides after the stop codon. In one embodiment, the codon optimized open reading frame encoding the polypeptide of interest comprises a stop codon and the at least one microRNA binding site for a miR expressed in immune cells is located within the 3′ UTR 30-50 nucleotides after the stop codon. In another embodiment, the codon optimized open reading frame encoding the polypeptide of interest comprises a stop codon and the at least one microRNA binding site for a miR expressed in immune cells is located within the 3′ UTR at least 50 nucleotides after the stop codon. In other embodiments, the codon optimized open reading frame encoding the polypeptide of interest comprises a stop codon and the at least one microRNA binding site for a miR expressed in immune cells is located within the 3′ UTR immediately after the stop codon, or within the 3′ UTR 15-20 nucleotides after the stop codon or within the 3′ UTR 70-80 nucleotides after the stop codon. In other embodiments, the 3′ UTR comprises more than one miRNA binding site (e.g., 2-4 miRNA binding sites), wherein there can be a spacer Attorney Docket No.45817-0022WO1 / MTX977.20 region (e.g., of 10-100, 20-70 or 30-50 nucleotides in length) between each miRNA binding site. In another embodiment, the 3′ UTR comprises a spacer region between the end of the miRNA binding site(s) and the poly A tail nucleotides. For example, a spacer region of 10-100, 20-70 or 30-50 nucleotides in length can be situated between the end of the miRNA binding site(s) and the beginning of the poly A tail. In one embodiment, the 3′ UTR comprises more than one stop codon, wherein at least one miRNA binding site is positioned downstream of the stop codons. For example, a 3′ UTR can comprise 1, 2 or 3 stop codons. Non-limiting examples of triple stop codons that can be used include: UGAUAAUAG, UGAUAGUAA, UAAUGAUAG, UGAUAAUAA, UGAUAGUAG, UAAUGAUGA, UAAUAGUAG, UGAUGAUGA, UAAUAAUAA, and UAGUAGUAG. Within a 3′ UTR, for example, 1, 2, 3 or 4 miRNA binding sites, e.g., miR-142-3p binding sites, can be positioned immediately adjacent to the stop codon(s) or at any number of nucleotides downstream of the final stop codon. When the 3′ UTR comprises multiple miRNA binding sites, these binding sites can be positioned directly next to each other in the construct (i.e., one after the other) or, alternatively, spacer nucleotides can be positioned between each binding site. In one embodiment, the 3′ UTR comprises three stop codons with a single miR-142-3p binding site located downstream of the 3rd stop codon. In one embodiment, the polynucleotide of the invention comprises a 5′ UTR comprising the nucleotide sequence of SEQ ID NO:50 or SEQ ID NO:58, a codon optimized open reading frame encoding ASS1 (e.g., any one of SEQ ID NOs:1-6), a 3′ UTR comprising the at least one miRNA binding site for a miR expressed in immune cells, and a 3′ tailing region of linked nucleosides. In various embodiments, the 3′ UTR comprises 1-4, at least two, one, two, three or four miRNA binding sites for miRs expressed in immune cells, preferably abundantly or preferentially expressed in immune cells. In one embodiment, the polynucleotide of the invention comprises a 5′ UTR comprising the nucleotide sequence of SEQ ID NO:50 or SEQ ID NO:58, a codon optimized open reading frame encoding ASL (e.g., SEQ ID NO:7 or SEQ ID NO:28), a 3′ UTR comprising the at least one miRNA binding site for a miR expressed in immune cells, and a 3′ tailing region of linked nucleosides. In various embodiments, Attorney Docket No.45817-0022WO1 / MTX977.20 the 3′ UTR comprises 1-4, at least two, one, two, three or four miRNA binding sites for miRs expressed in immune cells, preferably abundantly or preferentially expressed in immune cells. In one embodiment, the at least one miRNA expressed in immune cells is a miR-142-3p microRNA binding site. In one embodiment, the miR-142-3p microRNA binding site comprises the sequence shown in SEQ ID NO: 174. In one embodiment, the at least one miRNA expressed in immune cells is a miR-126 microRNA binding site. In one embodiment, the miR-126 binding site is a miR-126-3p binding site. In one embodiment, the miR-126-3p microRNA binding site comprises the sequence shown in SEQ ID NO: 152. Non-limiting exemplary sequences for miRs to which a microRNA binding site(s) of the disclosure can bind include the following: miR-142-3p (SEQ ID NO: 173), miR-142-5p (SEQ ID NO: 175), miR-146-3p (SEQ ID NO: 155), miR-146-5p (SEQ ID NO: 156), miR-155-3p (SEQ ID NO: 157), miR-155-5p (SEQ ID NO: 158), miR-126-3p (SEQ ID NO: 151), miR-126-5p (SEQ ID NO: 153), miR-16-3p (SEQ ID NO: 159), miR-16-5p (SEQ ID NO: 160), miR-21-3p (SEQ ID NO: 161), miR-21- 5p (SEQ ID NO: 162), miR-223-3p (SEQ ID NO: 163), miR-223-5p (SEQ ID NO: 164), miR-24-3p (SEQ ID NO: 165), miR-24-5p (SEQ ID NO: 166), miR-27-3p (SEQ ID NO: 167) and miR-27-5p (SEQ ID NO: 168). Other suitable miR sequences expressed in immune cells (e.g., abundantly or preferentially expressed in immune cells) are known and available in the art, for example at the University of Manchester’s microRNA database, miRBase. Sites that bind any of the aforementioned miRs can be designed based on Watson-Crick complementarity to the miR, typically 100% complementarity to the miR, and inserted into an mRNA construct of the disclosure as described herein. In another embodiment, a polynucleotide of the present invention (e.g., and mRNA, e.g., the 3′ UTR thereof) can comprise at least one miRNA bindingsite to thereby reduce or inhibit accelerated blood clearance, for example by reducing or inhibiting production of IgMs, e.g., against PEG, by B cells and / or reducing or inhibiting proliferation and / or activation of pDCs, and can comprise at least one miRNA bindingsite for modulating tissue expression of an encoded protein of interest. Attorney Docket No.45817-0022WO1 / MTX977.20 miRNA gene regulation can be influenced by the sequence surrounding the miRNA such as, but not limited to, the species of the surrounding sequence, the type of sequence (e.g., heterologous, homologous, exogenous, endogenous, or artificial), regulatory elements in the surrounding sequence and / or structural elements in the surrounding sequence. The miRNA can be influenced by the 5′UTR and / or 3′UTR. As a non-limiting example, a non-human 3′UTR can increase the regulatory effect of the miRNA sequence on the expression of a polypeptide of interest compared to a human 3′ UTR of the same sequence type. In one embodiment, other regulatory elements and / or structural elements of the 5′ UTR can influence miRNA mediated gene regulation. One example of a regulatory element and / or structural element is a structured IRES (Internal Ribosome Entry Site) in the 5′ UTR, which is necessary for the binding of translational elongation factors to initiate protein translation. EIF4A2 binding to this secondarily structured element in the 5′-UTR is necessary for miRNA mediated gene expression (Meijer HA et al., Science, 2013, 340, 82-85, herein incorporated by reference in its entirety). The polynucleotides of the invention can further include this structured 5′ UTR in order to enhance microRNA mediated gene regulation. At least one miRNA binding site can be engineered into the 3′ UTR of a polynucleotide of the invention. In this context, at least two, at least three, at least four, at least five, at least six, at least seven, at least eight, at least nine, at least ten, or more miRNA binding sites can be engineered into a 3′ UTR of a polynucleotide of the invention. For example, 1 to 10, 1 to 9, 1 to 8, 1 to 7, 1 to 6, 1 to 5, 1 to 4, 1 to 3, 2, or 1 miRNA binding sites can be engineered into the 3′UTR of a polynucleotide of the invention. In one embodiment, miRNA binding sites incorporated into a polynucleotide of the invention can be the same or can be different miRNA sites. A combination of different miRNA binding sites incorporated into a polynucleotide of the invention can include combinations in which more than one copy of any of the different miRNA sites are incorporated. In another embodiment, miRNA binding sites incorporated into a polynucleotide of the invention can target the same or different tissues in the body. As a non-limiting example, through the introduction of tissue-, cell-type-, or disease-specific miRNA binding sites in the 3′-UTR of a Attorney Docket No.45817-0022WO1 / MTX977.20 polynucleotide of the invention, the degree of expression in specific cell types (e.g., myeloid cells, endothelial cells, etc.) can be reduced. In one embodiment, a miRNA binding site can be engineered near the 5′ terminus of the 3′UTR, about halfway between the 5′ terminus and 3′ terminus of the 3′UTR and / or near the 3′ terminus of the 3′ UTR in a polynucleotide of the invention. As a non-limiting example, a miRNA binding site can be engineered near the 5′ terminus of the 3′UTR and about halfway between the 5′ terminus and 3′ terminus of the 3′UTR. As another non-limiting example, a miRNA binding site can be engineered near the 3′ terminus of the 3′UTR and about halfway between the 5′ terminus and 3′ terminus of the 3′ UTR. As yet another non-limiting example, a miRNA binding site can be engineered near the 5′ terminus of the 3′ UTR and near the 3′ terminus of the 3′ UTR. In another embodiment, a 3′UTR can comprise 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 miRNA binding sites. The miRNA binding sites can be complementary to a miRNA, miRNA seed sequence, and / or miRNA sequences flanking the seed sequence. In some embodiments, the expression of a polynucleotide of the invention can be controlled by incorporating at least one sensor sequence in the polynucleotide and Formulating the polynucleotide for administration. As a non-limiting example, a polynucleotide of the invention can be targeted to a tissue or cell by incorporating a miRNA binding site and Formulating the polynucleotide in a lipid nanoparticle comprising an ionizable amino lipid, including any of the lipids described herein. A polynucleotide of the invention can be engineered for more targeted expression in specific tissues, cell types, or biological conditions based on the expression patterns of miRNAs in the different tissues, cell types, or biological conditions. Through introduction of tissue-specific miRNA binding sites, a polynucleotide of the invention can be designed for optimal protein expression in a tissue or cell, or in the context of a biological condition. In some embodiments, a polynucleotide of the invention can be designed to incorporate miRNA binding sites that either have 100% identity to known miRNA seed sequences or have less than 100% identity to miRNA seed sequences. In some embodiments, a polynucleotide of the invention can be designed to incorporate miRNA binding sites that have at least: 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, Attorney Docket No.45817-0022WO1 / MTX977.20 96%, 97%, 98%, or 99% identity to known miRNA seed sequences. The miRNA seed sequence can be partially mutated to decrease miRNA binding affinity and as such result in reduced downmodulation of the polynucleotide. In essence, the degree of match or mis-match between the miRNA binding site and the miRNA seed can act as a rheostat to more finely tune the ability of the miRNA to modulate protein expression. In addition, mutation in the non-seed region of a miRNA binding site can also impact the ability of a miRNA to modulate protein expression. In one embodiment, a miRNA sequence can be incorporated into the loop of a stem loop. In another embodiment, a miRNA seed sequence can be incorporated in the loop of a stem loop and a miRNA binding site can be incorporated into the 5′ or 3′ stem of the stem loop. In some embodiments, a polynucleotide of the invention can include at least one miRNA in order to dampen the antigen presentation by antigen presenting cells. The miRNA can be the complete miRNA sequence, the miRNA seed sequence, the miRNA sequence without the seed, or a combination thereof. As a non-limiting example, a miRNA incorporated into a polynucleotide of the invention can be specific to the hematopoietic system. As another non-limiting example, a miRNA incorporated into a polynucleotide of the invention to dampen antigen presentation is miR-142-3p. In some embodiments, a polynucleotide of the invention can include at least one miRNA in order to dampen expression of the encoded polypeptide in a tissue or cell of interest. As a non-limiting example a polynucleotide of the invention can include at least one miR-142-3p binding site, miR-142-3p seed sequence, miR-142-3p binding site without the seed, miR-142-5p binding site, miR-142-5p seed sequence, miR-142-5p binding site without the seed, miR-146 binding site, miR-146 seed sequence and / or miR-146 binding site without the seed sequence. In some embodiments, a polynucleotide of the invention can comprise at least one miRNA binding site in the 3′UTR in order to selectively degrade mRNA therapeutics in the immune cells to subdue unwanted immunogenic reactions caused by therapeutic delivery. As a non-limiting example, the miRNA binding site can make a polynucleotide of the invention more unstable in antigen presenting cells. Attorney Docket No.45817-0022WO1 / MTX977.20 Non-limiting examples of these miRNAs include miR-142-5p, miR-142-3p, miR- 146a-5p, and miR-146-3p. In one embodiment, a polynucleotide of the invention comprises at least one miRNA sequence in a region of the polynucleotide that can interact with a RNA binding protein. In some embodiments, the polynucleotide of the invention (e.g., a RNA, e.g., an mRNA) comprising (i) a sequence-optimized nucleotide sequence (e.g., an ORF) encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) and (ii) a miRNA binding site (e.g., a miRNA binding site that binds to miR-142) and / or a miRNA binding site that binds to miR-126. In some embodiments, the polynucleotide of the invention (e.g., a RNA, e.g., an mRNA) comprising (i) a sequence-optimized nucleotide sequence (e.g., an ORF) encoding an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28) and (ii) a miRNA binding site (e.g., a miRNA binding site that binds to miR-142) and / or a miRNA binding site that binds to miR-126. 13. Regions having a 5′ Cap The disclosure also includes a polynucleotide that comprises both a 5′ Cap and a polynucleotide of the present invention (e.g., a polynucleotide comprising a nucleotide sequence encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1- 6) to be expressed or a polynucleotide comprising a nucleotide sequence encoding an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28) to be expressed). The 5′ cap structure of a natural mRNA is involved in nuclear export, increasing mRNA stability and binds the mRNA Cap Binding Protein (CBP), which is responsible for mRNA stability in the cell and translation competency through the association of CBP with poly(A) binding protein to form the mature cyclic mRNA species. The cap further assists the removal of 5′ proximal introns during mRNA splicing. Endogenous mRNA molecules can be 5′-end capped generating a 5′-ppp-5′- triphosphate linkage between a terminal guanosine cap residue and the 5′-terminal transcribed sense nucleotide of the mRNA molecule. This 5′-guanylate cap can then Attorney Docket No.45817-0022WO1 / MTX977.20 be methylated to generate an N7-methyl-guanylate residue. The ribose sugars of the terminal and / or anteterminal transcribed nucleotides of the 5′ end of the mRNA can optionally also be 2′-O-methylated.5′-decapping through hydrolysis and cleavage of the guanylate cap structure can target a nucleic acid molecule, such as an mRNA molecule, for degradation. In some embodiments, the polynucleotides of the present invention (e.g., a polynucleotide comprising a nucleotide sequence encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28)) incorporate a cap moiety. In some embodiments, polynucleotides of the present invention comprise a non-hydrolyzable cap structure preventing decapping and thus increasing mRNA half- life. Because cap structure hydrolysis requires cleavage of 5′-ppp-5′ phosphorodiester linkages, modified nucleotides can be used during the capping reaction. For example, a Vaccinia Capping Enzyme from New England Biolabs (Ipswich, MA) can be used with α-thio-guanosine nucleotides according to the manufacturer’s instructions to create a phosphorothioate linkage in the 5′-ppp-5′ cap. Additional modified guanosine nucleotides can be used such as α-methyl-phosphonate and seleno-phosphate nucleotides. Additional modifications include, but are not limited to, 2′-O-methylation of the ribose sugars of 5′-terminal and / or 5′-anteterminal nucleotides of the polynucleotide (as mentioned above) on the 2′-hydroxyl group of the sugar ring. Multiple distinct 5′-cap structures can be used to generate the 5′-cap of a nucleic acid molecule, such as a polynucleotide that functions as an mRNA molecule. Cap analogs, which herein are also referred to as synthetic cap analogs, chemical caps, chemical cap analogs, or structural or functional cap analogs, differ from natural (i.e., endogenous, wild-type or physiological) 5′-caps in their chemical structure, while retaining cap function. Cap analogs can be chemically (i.e., non-enzymatically) or enzymatically synthesized and / or linked to the polynucleotides of the invention. For example, the Anti-Reverse Cap Analog (ARCA) cap contains two guanines linked by a 5′-5′-triphosphate group, wherein one guanine contains an N7 methyl group as well as a 3′-O-methyl group (i.e., N7,3′-O-dimethyl-guanosine-5′- triphosphate-5′-guanosine (m7G-3′mppp-G; which can equivalently be designated 3′ Attorney Docket No.45817-0022WO1 / MTX977.20 O-Me-m7G(5′)ppp(5′)G). The 3′-O atom of the other, unmodified, guanine becomes linked to the 5′-terminal nucleotide of the capped polynucleotide. The N7- and 3′-O- methlyated guanine provides the terminal moiety of the capped polynucleotide. Another exemplary cap is mCAP, which is similar to ARCA but has a 2′-O- methyl group on guanosine (i.e., N7,2′-O-dimethyl-guanosine-5′-triphosphate-5′- guanosine, m7Gm-ppp-G). Another exemplary cap is m7G-ppp-Gm-A (i.e., N7,guanosine-5′-triphosphate- 2′-O-dimethyl-guanosine-adenosine). In some embodiments, the cap is a dinucleotide cap analog. As a non-limiting example, the dinucleotide cap analog can be modified at different phosphate positions with a boranophosphate group or a phosphoroselenoate group such as the dinucleotide cap analogs described in U.S. Patent No. US 8,519,110, the contents of which are herein incorporated by reference in its entirety. In another embodiment, the cap is a cap analog is a N7-(4- chlorophenoxyethyl) substituted dinucleotide form of a cap analog known in the art and / or described herein. Non-limiting examples of a N7-(4-chlorophenoxyethyl) substituted dinucleotide form of a cap analog include a N7-(4-chlorophenoxyethyl)- G(5′)ppp(5′)G and a N7-(4-chlorophenoxyethyl)-m3′-OG(5′)ppp(5′)G cap analog (See, e.g., the various cap analogs and the methods of synthesizing cap analogs described In Kore et al. Bioorganic & Medicinal Chemistry 201321:4570-4574; the contents of which are herein incorporated by reference in its entirety). In another embodiment, a cap analog of the present invention is a 4-chloro / bromophenoxyethyl analog. Polynucleotides of the invention can also be capped post-manufacture (whether IVT or chemical synthesis), using enzymes, in order to generate more authentic 5′-cap structures. As used herein, the phrase “more authentic” refers to a feature that closely mirrors or mimics, either structurally or functionally, an endogenous or wild type feature. That is, a “more authentic” feature is better representative of an endogenous, wild-type, natural or physiological cellular function and / or structure as compared to synthetic features or analogs, etc., of the prior art, or which outperforms the corresponding endogenous, wild-type, natural or physiological feature in one or more respects. Non-limiting examples of more authentic 5′cap structures of the present invention are those that, among other things, have enhanced Attorney Docket No.45817-0022WO1 / MTX977.20 binding of cap binding proteins, increased half-life, reduced susceptibility to 5′ endonucleases and / or reduced 5′decapping, as compared to synthetic 5′cap structures known in the art (or to a wild-type, natural or physiological 5′cap structure). For example, recombinant Vaccinia Virus Capping Enzyme and recombinant 2′-O- methyltransferase enzyme can create a canonical 5′-5′-triphosphate linkage between the 5′-terminal nucleotide of a polynucleotide and a guanine cap nucleotide wherein the cap guanine contains an N7 methylation and the 5′-terminal nucleotide of the mRNA contains a 2′-O-methyl. Such a structure is termed the Cap1 structure. This cap results in a higher translational-competency and cellular stability and a reduced activation of cellular pro-inflammatory cytokines, as compared, e.g., to other 5′cap analog structures known in the art. Cap structures include, but are not limited to, 7mG(5′)ppp(5′)N1pN2p (cap 0), 7mG(5′)ppp(5′)N1mpNp (cap 1), and 7mG(5′)- ppp(5′)N1mpN2mp (cap 2). As a non-limiting example, capping chimeric polynucleotides post- manufacture can be more efficient as nearly 100% of the chimeric polynucleotides can be capped. This is in contrast to ~80% when a cap analog is linked to a chimeric polynucleotide in the course of an in vitro transcription reaction. According to the present invention, 5′ terminal caps can include endogenous caps or cap analogs. According to the present invention, a 5′ terminal cap can comprise a guanine analog. Useful guanine analogs include, but are not limited to, inosine, N1-methyl-guanosine, 2′fluoro-guanosine, 7-deaza-guanosine, 8-oxo- guanosine, 2-amino-guanosine, LNA-guanosine, and 2-azido-guanosine. Also provided herein are exemplary caps including those that can be used in co-transcriptional capping methods for ribonucleic acid (RNA) synthesis, using RNA polymerase, e.g., wild type RNA polymerase or variants thereof, e.g., such as those variants described herein. In one embodiment, caps can be added when RNA is produced in a “one-pot” reaction, without the need for a separate capping reaction. Thus, the methods, in some embodiments, comprise reacting a polynucleotide template with an RNA polymerase variant, nucleoside triphosphates, and a cap analog under in vitro transcription reaction conditions to produce RNA transcript. As used here the term “cap” includes the inverted G nucleotide and can comprise one or more additional nucleotides 3’ of the inverted G nucleotide, e.g., 1, 2, Attorney Docket No.45817-0022WO1 / MTX977.20 3, or more nucleotides 3’ of the inverted G nucleotide and 5’ to the 5’ UTR, e.g., a 5’ UTR described herein. Exemplary caps comprise a sequence of GG, GA, or GGA, wherein the underlined, italicized G is an in inverted G nucleotide followed by a 5’-5’- triphosphate group. In one embodiment, a cap comprises a compound of formula (I) a ; ring B2 and ring B3 each independently is a nucleobase or a modified nucleobase; X2 is O, S(O)p, NR24 or CR25R26 in which p is 0, 1, or 2; Y0 is O or CR6R7; Y1 is O, S(O)n, CR6R7, or NR8, in which n is 0, 1 , or 2; each --- is a single bond or absent, wherein when each --- is a single bond, Yi is O, S(O)n, CR6R7, or NR8; and when each --- is absent, Y1is void; Attorney Docket No.45817-0022WO1 / MTX977.20 Y2 is (OP(O)R4)m in which m is 0, 1, or 2, or -O-(CR40R41)u-Q0-(CR42R43)v-, in which Q0is a bond, O, S(O)r, NR44, or CR45R46, r is 0, 1 , or 2, and each of u and v independently is 1, 2, 3 or 4; each R2and R’' independently is halo, LNA, or OR3; each R3 independently is H, C1-C6 alkyl, C2-C6 alkenyl, or C2-C6 alkynyl and R3, when being C1-C6alkyl, C2-C6alkenyl, or C2-C6alkynyl, is optionally substituted with one or more of halo, OH and C1-C6 alkoxyl that is optionally substituted with one or more OH or OC(O)-C1-C6 alkyl; each R4 and R’' independently is H, halo, C1-C6 alkyl, OH, SH,IH, or BH3-; each of R6, R7, and R8, independently, is -Q1-T1, in which Q1 is a bond or C1- C3alkyl linker optionally substituted with one or more of halo, cyano, OH and C1-C6alkoxy, and T1 is H, halo, OH, COOH, cyano, or Rs1, in which Rs1 is C1-C3 alkyl, C2- C6alkenyl, C2-C6alkynyl, C1- C6alkoxyl, C(O)O-C1-C6alkyl, C3-C8cycloalkyl, C6- C10 aryl, NR31R32, (NR31R32R33)+, 4 to 12- membered heterocycloalkyl, or 5- or 6- membered heteroaryl, and Rs1is optionally substituted with one or more substituents selected from the group consisting of halo, OH, oxo, C1-C6 alkyl, COOH, C(O)O-C1- C6alkyl, cyano, C1-C6alkoxyl, NR31R32, (NR31R32R33)+, C3-C8cycloalkyl, C6- C10 aryl, 4 to 12-membered heterocycloalkyl, and 5- or 6-membered heteroaryl; each of R10, R11, R12, R13R14, and R15, independently, is -Q2-T2, in which Q2is a bond or C1-C3 alkyl linker optionally substituted with one or more of halo, cyano, OH and C1-C6alkoxy, and T2is H, halo, OH, NH2, cyano, NO2, N3, Rs2, or ORs2, in which Rs2 is C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C3-C8 cycloalkyl, C6-C10 aryl, NHC(O)-C1-C6alkyl, NR31R32, (NR31R32R33)+, 4 to 12-membered heterocycloalkyl, or 5- or 6-membered heteroaryl, and Rs2 is optionally substituted with one or more substituents selected from the group consisting of halo, OH, oxo, C1-C6alkyl, COOH, C(O)O-C1-C6 alkyl, cyano,–C1 - C6 alkoxyl, NR31R32, (NR31R32R33)+, C3- C8cycloalkyl, C6-C10aryl, 4 to 12-membered heterocycloalkyl, and 5- or 6- membered heteroaryl; or alternatively R12 together with R14 is oxo, or R13 together with R15 is oxo, each of R20, R21, R22, and R23independently is -Q3-T3, in which Q3is a bond or C1-C3 alkyl linker optionally substituted with one or more of halo, cyano, OH and C1-C6alkoxy, and T3is H, halo, OH, NH2, cyano, NO2, N3, RS3, or ORS3, in which Attorney Docket No.45817-0022WO1 / MTX977.20 RS3 is C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C3-C8 cycloalkyl, C6-C10 aryl, NHC(O)-C1-C6alkyl, mono-C1-C6alkylamino, di-C1-C6alkylamino, 4 to 12- membered heterocycloalkyl, or 5- or 6-membered heteroaryl, and Rs3 is optionally substituted with one or more substituents selected from the group consisting of halo, OH, oxo, C1-C6 alkyl, COOH, C(O)O-C1-C6 alkyl, cyano, C1-C6 alkoxyl, amino, mono-C1-C6alkylamino, di-C1-C6alkylamino, C3-C8cycloalkyl, C6-C10aryl, 4 to 12- membered heterocycloalkyl, and 5- or 6-membered heteroaryl; each of R24, R25, and R26 independently is H or C1-C6 alkyl; each of R27 and R28 independently is H or OR29; or R27 and R28 together form O-R30-O; each R29 independently is H, C1-C6 alkyl, C2-C6 alkenyl, or C2-C6 alkynyl and R29, when being C1-C6alkyl, C2-C6alkenyl, or C2-C6alkynyl, is optionally substituted with one or more of halo, OH and C1-C6 alkoxyl that is optionally substituted with one or more OH or OC(O)-C1-C6alkyl; R30 is C1-C6 alkylene optionally substituted with one or more of halo, OH and C1-C6alkoxyl; each of R31, R32, and R33, independently is H, C1-C6 alkyl, C3-C8 cycloalkyl, C6-C10aryl, 4 to 12-membered heterocycloalkyl, or 5- or 6-membered heteroaryl; each of R40, R41, R42, and R43 independently is H, halo, OH, cyano, N3, OP(O)R47R48, or C1-C6alkyl optionally substituted with one or more OP(O)R47R48, or one R41 and one R43, together with the carbon atoms to which they are attached and Q0, form C4-C10cycloalkyl, 4- to 14-membered heterocycloalkyl, C6-C10aryl, or 5- to 14-membered heteroaryl, and each of the cycloalkyl, heterocycloalkyl, phenyl, or 5- to 6-membered heteroaryl is optionally substituted with one or more of OH, halo, cyano, N3, oxo, OP(O)R47R48, C1-C6 alkyl, C1-C6 haloalkyl, COOH, C(O)O-C1-C6 alkyl, C1-C6alkoxyl, C1-C6haloalkoxyl, amino, mono-C1-C6alkylamino, and di-C1- C6 alkylamino; R44is H, C1-C6alkyl, or an amine protecting group; each of R45 and R46 independently is H, OP(O)R47R48, or C1-C6 alkyl optionally substituted with one or more OP(O)R47R48, and each of R47and R48, independently is H, halo, C1-C6alkyl, OH, I SeH, or BH3. Attorney Docket No.45817-0022WO1 / MTX977.20 It should be understood that a cap analog, as provided herein, may include any of the cap analogs described in international publication WO 2017 / 066797, published on 20 April 2017, incorporated by reference herein in its entirety. In some embodiments, the B2middle position can be a non-ribose molecule, such as arabinose. In some embodiments R2is ethyl-based. Thus, in some embodiments, a cap comprises the following structure:

[0002] Attorney Docket No.45817-0022WO1 / MTX977.20 In yet other embodiments, a cap comprises the following structure: . R is a methyl group (e.g., C1 alkyl). In some embodiments, R is an ethyl group (e.g., C2alkyl). In some embodiments, a cap comprises a sequence selected from the following sequences: GAA, GAC, GAG, GAU, GCA, GCC, GCG, GCU, GGA , GGC, GGG, GGU, GUA, GUC, GUG, and GUU. In some embodiments, a cap comprises GAA. In some embodiments, a cap comprises GAC. In some Attorney Docket No.45817-0022WO1 / MTX977.20 embodiments, a cap comprises GAG. In some embodiments, a cap comprises GAU. In some embodiments, a cap comprises GCA. In some embodiments, a cap comprises GCC. In some embodiments, a cap comprises GCG. In some embodiments, a cap comprises GCU. In some embodiments, a cap comprises GGA. In some embodiments, a cap comprises GGC. In some embodiments, a cap comprises GGG. In some embodiments, a cap comprises GGU. In some embodiments, a cap comprises GUA. In some embodiments, a cap comprises GUC. In some embodiments, a cap comprises GUG. In some embodiments, a cap comprises GUU. In some embodiments, a cap comprises a sequence selected from the following sequences: m7GpppApA, m7GpppApC, m7GpppApG, m7GpppApU, m7GpppCpA, m7GpppCpC, m7GpppCpG, m7GpppCpU, m7GpppGpA, m7GpppGpC, m7GpppGpG, m7GpppGpU, m7GpppUpA, m7GpppUpC, m7GpppUpG, and m7GpppUpU. In some embodiments, a cap comprises m7GpppApA. In some embodiments, a cap comprises m7GpppApC. In some embodiments, a cap comprises m7GpppApG. In some embodiments, a cap comprises m7GpppApU. In some embodiments, a cap comprises m7GpppCpA. In some embodiments, a cap comprises m7GpppCpC. In some embodiments, a cap comprises m7GpppCpG. In some embodiments, a cap comprises m7GpppCpU. In some embodiments, a cap comprises m7GpppGpA. In some embodiments, a cap comprises m7GpppGpC. In some embodiments, a cap comprises m7GpppGpG. In some embodiments, a cap comprises m7GpppGpU. In some embodiments, a cap comprises m7GpppUpA. In some embodiments, a cap comprises m7GpppUpC. In some embodiments, a cap comprises m7GpppUpG. In some embodiments, a cap comprises m7GpppUpU. A cap, in some embodiments, comprises a sequence selected from the following sequences: m7G3^OMepppApA, m7G3^OMepppApC, m7G3^OMepppApG, m7G3^OMepppApU, m7G3^OMepppCpA, m7G3^OMepppCpC, m7G3^OMepppCpG, m7G3^OMepppCpU, m7G3^OMepppGpA, m7G3^OMepppGpC, m7G3^OMepppGpG, m7G3^OMepppGpU, m7G3^OMepppUpA, m7G3^OMepppUpC, m7G3^OMepppUpG, and m7G3^OMepppUpU. In some embodiments, a cap comprises m7G3^OMepppApA. In some embodiments, a cap comprises m7G3^OMepppApC. In some embodiments, a cap Attorney Docket No.45817-0022WO1 / MTX977.20 comprises m7G3^OMepppApG. In some embodiments, a cap comprises m7G3^OMepppApU. In some embodiments, a cap comprises m7G3^OMepppCpA. In some embodiments, a cap comprises m7G3^OMepppCpC. In some embodiments, a cap comprises m7G3^OMepppCpG. In some embodiments, a cap comprises m7G3^OMepppCpU. In some embodiments, a cap comprises m7G3^OMepppGpA. In some embodiments, a cap comprises m7G3^OMepppGpC. In some embodiments, a cap comprises m7G3^OMepppGpG. In some embodiments, a cap comprises m7G3^OMepppGpU. In some embodiments, a cap comprises m7G3^OMepppUpA. In some embodiments, a cap comprises m7G3^OMepppUpC. In some embodiments, a cap comprises m7G3^OMepppUpG. In some embodiments, a cap comprises m7G3^OMepppUpU. A cap, in other embodiments, comprises a sequence selected from the following sequences: m7G3^OMepppA2^OMepA, m7G3^OMepppA2^OMepC, m7G3^OMepppA2^OMepG, m7G3^OMepppA2^OMepU, m7G3^OMepppC2^OMepA, m7G3^OMepppC2^OMepC, m7G3^OMepppC2^OMepG, m7G3^OMepppC2^OMepU, m7G3^OMepppG2^OMepA, m7G3^OMepppG2^OMepC, m7G3^OMepppG2^OMepG, m7G3^OMepppG2^OMepU, m7G3^OMepppU2^OMepA, m7G3^OMepppU2^OMepC, m7G3^OMepppU2^OMepG, and m7G3^OMepppU2^OMepU. In some embodiments, a cap comprises m7G3^OMepppA2^OMepA. In some embodiments, a cap comprises m7G3^OMepppA2^OMepC. In some embodiments, a cap comprises m7G3^OMepppA2^OMepG. In some embodiments, a cap comprises m7G3^OMepppA2^OMepU. In some embodiments, a cap comprises m7G3^OMepppC2^OMepA. In some embodiments, a cap comprises m7G3^OMepppC2^OMepC. In some embodiments, a cap comprises m7G3^OMepppC2^OMepG. In some embodiments, a cap comprises m7G3^OMepppC2^OMepU. In some embodiments, a cap comprises m7G3^OMepppG2^OMepA. In some embodiments, a cap comprises m7G3^OMepppG2^OMepC. In some embodiments, a cap comprises m7G3^OMepppG2^OMepG. In some embodiments, a cap comprises m7G3^OMepppG2^OMepU. In some embodiments, a cap comprises m7G3^OMepppU2^OMepA. In some embodiments, a cap comprises Attorney Docket No.45817-0022WO1 / MTX977.20 m7G3^OMepppU2^OMepC. In some embodiments, a cap comprises m7G3^OMepppU2^OMepG. In some embodiments, a cap comprises m7G3^OMepppU2^OMepU. A cap, in still other embodiments, comprises a sequence selected from the following sequences: m7GpppA2^OMepA, m7GpppA2^OMepC, m7GpppA2^OMepG, m7GpppA2^OMepU, m7GpppC2^OMepA, m7GpppC2^OMepC, m7GpppC2^OMepG, m7GpppC2^OMepU, m7GpppG2^OMepA, m7GpppG2^OMepC, m7GpppG2^OMepG, m7GpppG2^OMepU, m7GpppU2^OMepA, m7GpppU2^OMepC, m7GpppU2^OMepG, and m7GpppU2^OMepU. In some embodiments, a cap comprises m7GpppA2^OMepA. In some embodiments, a cap comprises m7GpppA2^OMepC. In some embodiments, a cap comprises m7GpppA2^OMepG. In some embodiments, a cap comprises m7GpppA2^OMepU. In some embodiments, a cap comprises m7GpppC2^OMepA. In some embodiments, a cap comprises m7GpppC2^OMepC. In some embodiments, a cap comprises m7GpppC2^OMepG. In some embodiments, a trinucleotide cap comprises m7GpppC2^OMepU. In some embodiments, a cap comprises m7GpppG2^OMepA. In some embodiments, a cap comprises m7GpppG2^OMepC. In some embodiments, a cap comprises m7GpppG2^OMepG. In some embodiments, a cap comprises m7GpppG2^OMepU. In some embodiments, a cap comprises m7GpppU2^OMepA. In some embodiments, a cap comprises m7GpppU2^OMepC. In some embodiments, a cap comprises m7GpppU2^OMepG. In some embodiments, a cap comprises m7GpppU2^OMepU. In some embodiments, a cap comprises m7Gpppm6A2’OmepG. In some embodiments, a cap comprises m7Gpppe6A2’OmepG. In some embodiments, a cap comprises GAG. In some embodiments, a cap comprises GCG. In some embodiments, a cap comprises GUG. In some embodiments, a cap comprises GGG. In some embodiments, a cap comprises any one of the following structures: Attorney Docket No.45817-0022WO1 / MTX977.20 or . In some embodiments, the cap comprisesm7GpppN1N2N3, where N1, N2, and N3 are optional (i.e., can be absent or one or more can be present) and are independently a natural, a modified, or an unnatural nucleoside base. In some embodiments,m7G is further methylated, e.g., at the 3’ position. In some embodiments, them7G comprises an O-methyl at the 3’ position. In some embodiments N1, N2, and N3 if present, optionally, are independently an adenine, a uracil, a guanidine, a thymine, or a cytosine. In some embodiments, one or more (or all) of N1, N2, and N3, if present, are methylated, e.g., at the 2’ position. In some embodiments, one or more (or all) of N1, N2, and N3,if present have an O-methyl at the 2’ position. In some embodiments, the cap comprises the following structure: Attorney Docket No.45817-0022WO1 / MTX977.20 unnatural nucleoside based; and R1, R2, R3, and R4are independently OH or O- methyl. In some embodiments, R3 is O-methyl and R4 is OH. In some embodiments, R3and R4are O-methyl. In some embodiments, R4is O-methyl. In some embodiments, R1 is OH, R2 is OH, R3 is O-methyl, and R4 is OH. In some embodiments, R1is OH, R2is OH, R3is O-methyl, and R4is O-methyl. In some embodiments, at least one of R1 and R2 is O-methyl, R3 is O-methyl, and R4 is OH. In some embodiments, at least one of R1and R2is O-methyl, R3is O-methyl, and R4is O-methyl. In some embodiments, B1, B3, and B3are natural nucleoside bases. In some embodiments, at least one of B1, B2, and B3 is a modified or unnatural base. In some embodiments, at least one of B1, B2, and B3 is N6-methyladenine. In some embodiments, B1is adenine, cytosine, thymine, or uracil. In some embodiments, B1is adenine, B2 is uracil, and B3 is adenine. In some embodiments, R1 and R2 are OH, R3and R4are O-methyl, B1is adenine, B2is uracil, and B3is adenine. In some embodiments the cap comprises a sequence selected from the following sequences: GAAA, GACA, GAGA, GAUA, GCAA, GCCA, GCGA, GCUA, GGAA, GGCA, GGGA, GGUA, GUCA, and GUUA. In some embodiments the cap comprises a sequence selected from the following sequences: GAAG, GACG, GAGG, GAUG, GCAG, GCCG, GCGG, GCUG, GGAG, GGCG, GGGG, GGUG, GUCG, GUGG, and GUUG. In some embodiments the cap comprises a sequence selected from the following sequences: GAAU, GACU, GAGU, GAUU, GCAU, Attorney Docket No.45817-0022WO1 / MTX977.20 GCCU, GCGU, GCUU, GGAU, GGCU, GGGU, GGUU, GUAU, GUCU, GUGU, and GUUU. In some embodiments the cap comprises a sequence selected from the following sequences: GAAC, GACC, GAGC, GAUC, GCAC, GCCC, GCGC, GCUC, GGAC, GGCC, GGGC, GGUC, GUAC, GUCC, GUGC, and GUUC. A cap, in some embodiments, comprises a sequence selected from the following sequences: m7G3^OMepppApApN, m7G3^OMepppApCpN, m7G3^OMepppApGpN, m7G3^OMepppApUpN, m7G3^OMepppCpApN, m7G3^OMepppCpCpN, m7G3^OMepppCpGpN, m7G3^OMepppCpUpN, m7G3^OMepppGpApN, m7G3^OMepppGpCpN, m7G3^OMepppGpGpN, m7G3^OMepppGpUpN, m7G3^OMepppUpApN, m7G3^OMepppUpCpN, m7G3^OMepppUpGpN, and m7G3^OMepppUpUpN, where N is a natural, a modified, or an unnatural nucleoside base. A cap, in other embodiments, comprises a sequence selected from the following sequences: m7G3^OMepppA2^OMepApN, m7G3^OMepppA2^OMepCpN, m7G3^OMepppA2^OMepGpN, m7G3^OMepppA2^OMepUpN, m7G3^OMepppC2^OMepApN, m7G3^OMepppC2^OMepCpN, m7G3^OMepppC2^OMepGpN, m7G3^OMepppC2^OMepUpN, m7G3^OMepppG2^OMepApN, m7G3^OMepppG2^OMepCpN, m7G3^OMepppG2^OMepGpN, m7G3^OMepppG2^OMepUpN, m7G3^OMepppU2^OMepApN, m7G3^OMepppU2^OMepCpN, m7G3^OMepppU2^OMepGpN, and m7G3^OMepppU2^OMepUpN, where N is a natural, a modified, or an unnatural nucleoside base. A cap, in still other embodiments, comprises a sequence selected from the following sequences: m7GpppA2^OMepApN, m7GpppA2^OMepCpN, m7GpppA2^OMepGpN, m7GpppA2^OMepUpN, m7GpppC2^OMepApN, m7GpppC2^OMepCpN, m7GpppC2^OMepGpN, m7GpppC2^OMepUpN, m7GpppG2^OMepApN, m7GpppG2^OMepCpN, m7GpppG2^OMepGpN, m7GpppG2^OMepUpN, m7GpppU2^OMepApN, m7GpppU2^OMepCpN, m7GpppU2^OMepGpN, and m7GpppU2^OMepUpN, where N is a natural, a modified, or an unnatural nucleoside base. I cap, in other embodiments, comprises a sequence selected from the following sequences: m7G3^OMepppA2^oMepA2^OMepN, m7G3^OMepppA2^oMepC2^OMepN, Attorney Docket No.45817-0022WO1 / MTX977.20 m7G3^OMepppA2^oMepG2^OMepN, m7G3^OMepppA2^oMepU2^OMepN, m7G3^OMepppC2^oMepA2^OMepN, m7G3^OMepppC2^oMepC2^OMepN, m7G3^OMepppC2^oMepG2^OMepN, m7G3^OMepppC2^oMepU2^OMepN, m7G3^OMepppG2^oMepA2^OMepN, m7G3^OMepppG2^oMepC2^OMepN, m7G3^OMepppG2^oMepG2^OMepN, m7G3^OMepppG2^oMepU2^OMepN, m7G3^OMepppU2^oMepA2^OMepN, m7G3^OMepppU2^oMepC2^OMepN, m7G3^OMepppU2^oMepG2^OMepN, and m7G3^OMepppU2^oMepU2^OMepN, where N is a natural, a modified, or an unnatural nucleoside base. A cap, in still other embodiments, comprises a sequence selected from the following sequences: m7gpppA2^oMepA2^OMepN, m7gpppA2^oMepC2^OMepN, m7gpppA2^oMepG2^OMepN, m7gpppA2^oMepU2^OMepN, m7gpppC2^oMepA2^OMepN, m7gpppC2^oMepC2^OMepN, m7gpppC2^oMepG2^OMepN, m7gpppC2^oMepU2^OMepN, m7gpppG2^oMepA2^OMepN, m7gpppG2^oMepC2^OMepN, m7gpppG2^oMepG2^OMepN, m7gpppG2^oMepU2^OMepN, m7gpppU2^oMepA2^OMepN, m7gpppU2^oMepC2^OMepN, m7gpppU2^oMepG2^OMepN, and m7gpppU2^oMepU2^OMepN, where N is a natural, a modified, or an unnatural nucleoside base. In some embodiments, a cap comprises GGAG. In some embodiments, a cap comprises the following structure:

[0003] Attorney Docket No.45817-0022WO1 / MTX977.20 14. Poly-A Tails In some embodiments, the polynucleotides of the present disclosure (e.g., a polynucleotide comprising a nucleotide sequence encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28)) further comprise a poly-A tail. In further embodiments, terminal groups on the poly-A tail can be incorporated for stabilization. In other embodiments, a poly-A tail comprises des-3′ hydroxyl tails. During RNA processing, a long chain of adenine nucleotides (poly-A tail) can be added to a polynucleotide such as an mRNA molecule in order to increase stability. Immediately after transcription, the 3′ end of the transcript can be cleaved to free a 3′ hydroxyl. Then poly-A polymerase adds a chain of adenine nucleotides to the RNA. The process, called polyadenylation, adds a poly-A tail that can be between, for example, approximately 80 to approximately 250 residues long, including approximately 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240 or 250 residues long. In one embodiment, the poly-A tail is 100 nucleotides in length (SEQ ID NO:195). PolyA tails can also be added after the construct is exported from the nucleus. According to the present invention, terminal groups on the poly A tail can be incorporated for stabilization. Polynucleotides of the present invention can include des-3′ hydroxyl tails. They can also include structural moieties or 2'-Omethyl modifications as taught by Junjie Li, et al. (Current Biology, Vol.15, 1501–1507, August 23, 2005, the contents of which are incorporated herein by reference in its entirety). The polynucleotides of the present invention can be designed to encode transcripts with alternative polyA tail structures including histone mRNA. According to Norbury, "Terminal uridylation has also been detected on human replication- dependent histone mRNAs. The turnover of these mRNAs is thought to be important for the prevention of potentially toxic histone accumulation following the completion or inhibition of chromosomal DNA replication. These mRNAs are distinguished by their lack of a 3ʹ poly(A) tail, the function of which is instead assumed by a stable stem–loop structure and its cognate stem–loop binding protein (SLBP); the latter Attorney Docket No.45817-0022WO1 / MTX977.20 carries out the same functions as those of PABP on polyadenylated mRNAs" (Norbury, "Cytoplasmic RNA: a case of the tail wagging the dog," Nature Reviews Molecular Cell Biology; AOP, published online 29 August 2013; doi:10.1038 / nrm3645) the contents of which are incorporated herein by reference in its entirety. Unique poly-A tail lengths provide certain advantages to the polynucleotides of the present invention. Generally, the length of a poly-A tail, when present, is greater than 30 nucleotides in length. In another embodiment, the poly-A tail is greater than 35 nucleotides in length (e.g., at least or greater than about 35, 40, 45, 50, 55, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1,000, 1,100, 1,200, 1,300, 1,400, 1,500, 1,600, 1,700, 1,800, 1,900, 2,000, 2,500, and 3,000 nucleotides). In some embodiments, the polynucleotide or region thereof includes from about 30 to about 3,000 nucleotides (e.g., from 30 to 50, from 30 to 100, from 30 to 250, from 30 to 500, from 30 to 750, from 30 to 1,000, from 30 to 1,500, from 30 to 2,000, from 30 to 2,500, from 50 to 100, from 50 to 250, from 50 to 500, from 50 to 750, from 50 to 1,000, from 50 to 1,500, from 50 to 2,000, from 50 to 2,500, from 50 to 3,000, from 100 to 500, from 100 to 750, from 100 to 1,000, from 100 to 1,500, from 100 to 2,000, from 100 to 2,500, from 100 to 3,000, from 500 to 750, from 500 to 1,000, from 500 to 1,500, from 500 to 2,000, from 500 to 2,500, from 500 to 3,000, from 1,000 to 1,500, from 1,000 to 2,000, from 1,000 to 2,500, from 1,000 to 3,000, from 1,500 to 2,000, from 1,500 to 2,500, from 1,500 to 3,000, from 2,000 to 3,000, from 2,000 to 2,500, and from 2,500 to 3,000). In some embodiments, the poly-A tail is designed relative to the length of the overall polynucleotide or the length of a particular region of the polynucleotide. This design can be based on the length of a coding region, the length of a particular feature or region or based on the length of the ultimate product expressed from the polynucleotides. In this context, the poly-A tail can be 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100% greater in length than the polynucleotide or feature thereof. The poly-A tail can also be designed as a fraction of the polynucleotides to which it belongs. In this context, the poly-A tail can be 10, 20, 30, 40, 50, 60, 70, 80, or 90% or more of the Attorney Docket No.45817-0022WO1 / MTX977.20 total length of the construct, a construct region or the total length of the construct minus the poly-A tail. Further, engineered binding sites and conjugation of polynucleotides for Poly-A binding protein can enhance expression. Additionally, multiple distinct polynucleotides can be linked together via the PABP (Poly-A binding protein) through the 3′-end using modified nucleotides at the 3′-terminus of the poly-A tail. Transfection experiments can be conducted in relevant cell lines at and protein production can be assayed by ELISA at 12hr, 24hr, 48hr, 72hr and day 7 post-transfection. In some embodiments, the polynucleotides of the present invention are designed to include a polyA-G Quartet region. The G-quartet is a cyclic hydrogen bonded array of four guanine nucleotides that can be formed by G-rich sequences in both DNA and RNA. In this embodiment, the G-quartet is incorporated at the end of the poly-A tail. The resultant polynucleotide is assayed for stability, protein production and other parameters including half-life at various time points. It has been discovered that the polyA-G quartet results in protein production from an mRNA equivalent to at least 75% of that seen using a poly-A tail of 120 nucleotides alone (SEQ ID NO:196). In some embodiments, the polyA tail comprises an alternative nucleoside, e.g., inverted thymidine. PolyA tails comprising an alternative nucleoside, e.g., inverted thymidine, may be generated as described herein. For instance, mRNA constructs may be modified by ligation to stabilize the poly(A) tail. Ligation may be performed using 0.5-1.5 mg / mL mRNA (5′ Cap1, 3′ A100), 50 mM Tris-HCl pH 7.5, 10 mM MgCl2, 1 mM TCEP, 1000 units / mL T4 RNA Ligase 1, 1 mM ATP, 20% w / v polyethylene glycol 8000, and 5:1 molar ratio of modifying oligo to mRNA. Modifying oligo has a sequence of 5’-phosphate-AAAAAAAAAAAAAAAAAAAA- (inverted deoxythymidine (idT) (SEQ ID NO:209)) (see below). Ligation reactions are mixed and incubated at room temperature (~22°C) for, e.g., 4 hours. Stable tail mRNA are purified by, e.g., dT purification, reverse phase purification, hydroxyapatite purification, ultrafiltration into water, and sterile filtration. The resulting stable tail-containing mRNAs contain the following structure at the 3’end, starting with the polyA region: A100-UCUAGAAAAAAAAAAAAAAAAAAAA- inverted deoxythymidine (SEQ ID NO:211). Attorney Docket No.45817-0022WO1 / MTX977.20 Modifying oligo to stabilize tail (5’-phosphate- AAAAAAAAAAAAAAAAAAAA-(inverted deoxythymidine)(SEQ ID NO:209)): UCUAG-A20-inverted deoxy- . some the polyA tail consists of A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). 15. Start codon region The invention also includes a polynucleotide that comprises both a start codon region and the polynucleotide described herein (e.g., a polynucleotide comprising a nucleotide sequence encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1- 6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28)). In some embodiments, the polynucleotides of the present invention can have regions that are analogous to or function like a start codon region. In some embodiments, the translation of a polynucleotide can initiate on a codon that is not the start codon AUG. Translation of the polynucleotide can initiate on an alternative start codon such as, but not limited to, ACG, AGG, AAG, CTG / CUG, GTG / GUG, ATA / AUA, ATT / AUU, TTG / UUG (see Touriol et al. Biology of the Cell 95 (2003) 169-178 and Matsuda and Mauro PLoS ONE, 2010 5:11; the contents of each of which are herein incorporated by reference in its entirety). As a non-limiting example, the translation of a polynucleotide begins on the alternative start codon ACG. As another non-limiting example, polynucleotide Attorney Docket No.45817-0022WO1 / MTX977.20 translation begins on the alternative start codon CTG or CUG. As yet another non- limiting example, the translation of a polynucleotide begins on the alternative start codon GTG or GUG. Nucleotides flanking a codon that initiates translation such as, but not limited to, a start codon or an alternative start codon, are known to affect the translation efficiency, the length and / or the structure of the polynucleotide. (See, e.g., Matsuda and Mauro PLoS ONE, 20105:11; the contents of which are herein incorporated by reference in its entirety). Masking any of the nucleotides flanking a codon that initiates translation can be used to alter the position of translation initiation, translation efficiency, length and / or structure of a polynucleotide. In some embodiments, a masking agent can be used near the start codon or alternative start codon in order to mask or hide the codon to reduce the probability of translation initiation at the masked start codon or alternative start codon. Non-limiting examples of masking agents include antisense locked nucleic acids (LNA) polynucleotides and exon-junction complexes (EJCs) (See, e.g., Matsuda and Mauro describing masking agents LNA polynucleotides and EJCs (PLoS ONE, 20105:11); the contents of which are herein incorporated by reference in its entirety). In another embodiment, a masking agent can be used to mask a start codon of a polynucleotide in order to increase the likelihood that translation will initiate on an alternative start codon. In some embodiments, a masking agent can be used to mask a first start codon or alternative start codon in order to increase the chance that translation will initiate on a start codon or alternative start codon downstream to the masked start codon or alternative start codon. In some embodiments, a start codon or alternative start codon can be located within a perfect complement for a miRNA binding site. The perfect complement of a miRNA binding site can help control the translation, length and / or structure of the polynucleotide similar to a masking agent. As a non-limiting example, the start codon or alternative start codon can be located in the middle of a perfect complement for a miRNA binding site. The start codon or alternative start codon can be located after the first nucleotide, second nucleotide, third nucleotide, fourth nucleotide, fifth nucleotide, sixth nucleotide, seventh nucleotide, eighth nucleotide, ninth nucleotide, tenth nucleotide, eleventh nucleotide, twelfth nucleotide, thirteenth nucleotide, Attorney Docket No.45817-0022WO1 / MTX977.20 fourteenth nucleotide, fifteenth nucleotide, sixteenth nucleotide, seventeenth nucleotide, eighteenth nucleotide, nineteenth nucleotide, twentieth nucleotide or twenty-first nucleotide. In another embodiment, the start codon of a polynucleotide can be removed from the polynucleotide sequence in order to have the translation of the polynucleotide begin on a codon that is not the start codon. Translation of the polynucleotide can begin on the codon following the removed start codon or on a downstream start codon or an alternative start codon. In a non-limiting example, the start codon ATG or AUG is removed as the first 3 nucleotides of the polynucleotide sequence in order to have translation initiate on a downstream start codon or alternative start codon. The polynucleotide sequence where the start codon was removed can further comprise at least one masking agent for the downstream start codon and / or alternative start codons in order to control or attempt to control the initiation of translation, the length of the polynucleotide and / or the structure of the polynucleotide. 16. Stop Codon Region The invention also includes a polynucleotide that comprises both a stop codon region and the polynucleotide described herein (e.g., a polynucleotide comprising a nucleotide sequence encoding an ASS1 polypeptide (e.g., any one of SEQ ID NOs:1- 6) or an ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28)). In some embodiments, the polynucleotides of the present invention can include at least two stop codons before the 3′ untranslated region (UTR). The stop codon can be selected from TGA, TAA and TAG in the case of DNA, or from UGA, UAA and UAG in the case of RNA. In some embodiments, the polynucleotides of the present invention include the stop codon TGA in the case or DNA, or the stop codon UGA in the case of RNA, and one additional stop codon. In a further embodiment the addition stop codon can be TAA or UAA. In another embodiment, the polynucleotides of the present invention include three consecutive stop codons, four stop codons, or more. Attorney Docket No.45817-0022WO1 / MTX977.20 17. Combination of mRNA elements Any of the polynucleotides disclosed herein can comprise one, two, three, or all of the following elements: (a) a 5’-UTR, e.g., as described herein; (b) a coding region comprising a stop element (e.g., as described herein); (c) a 3’-UTR (e.g., as described herein) and; optionally (d) a 3’ stabilizing region, e.g., as described herein. Also disclosed herein are LNP compositions comprising the same. In an embodiment, a polynucleotide of the disclosure comprises (a) a 5’ UTR described in Table 3 or a variant or fragment thereof and (b) a coding region comprising a stop element provided herein. In an embodiment, the polynucleotide further comprises a cap structure, e.g., as described herein, or a poly A tail, e.g., as described herein. In an embodiment, the polynucleotide further comprises a 3’ stabilizing region, e.g., as described herein. In an embodiment, a polynucleotide of the disclosure comprises (a) a 5’ UTR described in Table 3 or a variant or fragment thereof and (c) a 3’ UTR described in Table 4 or a variant or fragment thereof. In an embodiment, the polynucleotide further comprises a cap structure, e.g., as described herein, or a poly A tail, e.g., as described herein. In an embodiment, the polynucleotide further comprises a 3’ stabilizing region, e.g., as described herein. In an embodiment, a polynucleotide of the disclosure comprises (c) a 3’ UTR described in Table 4 or a variant or fragment thereof and (b) a coding region comprising a stop element provided herein. In an embodiment, the polynucleotide comprises a sequence provided in Table 6. In an embodiment, the polynucleotide further comprises a cap structure, e.g., as described herein, or a poly A tail, e.g., as described herein. In an embodiment, the polynucleotide further comprises a 3’ stabilizing region, e.g., as described herein. In an embodiment, a polynucleotide of the disclosure comprises (a) a 5’ UTR described in Table 3 or a variant or fragment thereof; (b) a coding region comprising a stop element provided herein; and (c) a 3’ UTR described in Table 4 or a variant or fragment thereof. In an embodiment, the polynucleotide further comprises a cap structure, e.g., as described herein, or a poly A tail, e.g., as described herein. In an Attorney Docket No.45817-0022WO1 / MTX977.20 embodiment, the polynucleotide further comprises a 3’ stabilizing region, e.g., as described herein. Table 6: Exemplary 3’ UTR and stop element sequences SEQ ID Sequence NO information Sequence ’ C C C C C C C C C C C C C C C C C C C G A C C G U G C G U Attorney Docket No.45817-0022WO1 / MTX977.20 GCACCCGUACCCCCUCCAUAAAGUAGGAAACACUACAGUG GUCUUUGAAUAAAGUCUGAGUGGGCGGC ’ C U A C C G U G C C C U C GU C 18. Identification and Ratio Determination (IDR) Sequences  An Identification and Ratio Determination (IDR) sequence is a sequence of a biological molecule (e.g., nucleic acid or protein) that, when combined with the sequence of a target biological molecule, serves to identify the target biological molecule. Typically, an IDR sequence is a heterologous sequence that is incorporated within or appended to a sequence of a target biological molecule and can be used as a reference to identify the target molecule. Thus, in some embodiments, a nucleic acid (e.g., mRNA) comprises (i) a target sequence of interest (e.g., a coding sequence encoding a therapeutic and / or antigenic peptide or protein); and (ii) a unique IDR sequence. An RNA species (e.g., RNA having a given coding sequence) may comprise an IDR sequence that differs from the IDR sequence of other RNA species (e.g., Attorney Docket No.45817-0022WO1 / MTX977.20 RNA(s) having different coding sequence(s)). Each IDR sequence thus identifies a particular RNA species, and so the abundance of IDR sequences may be measured to determine the abundance of each RNA species in a composition. Use of distinct IDR sequences to identify RNA species allows for analysis of multivalent RNA compositions (e.g., containing multiple RNA species) containing RNA species with similar coding sequences and / or lengths, which could otherwise be difficult to distinguish using PCR- or chromatography-based analysis of full-length RNAs. Each RNA species in a multivalent RNA composition may comprise an IDR sequence that is not a sequence isomer of an IDR sequence of another RNA species in a multivalent RNA composition (e.g., the IDR sequence does not have the same number of adenosine nucleotides, the same number of cytosine nucleotides, the same number of guanine nucleotides, and the same number of uracil nucleotides, as another IDR sequence in the composition, even if those sequences have different sequences). Having identical nucleotide compositions causes sequence isomers to have the same mass, presenting a challenge to distinguishing sequence isomers using mass-based identification methods (e.g., mass spectrometry). Each RNA species in a multivalent RNA composition may comprise an IDR sequence having a mass that differs from the mass of IDR sequences of each other RNA species in a multivalent RNA composition. For example, the mass of each IDR sequence may differ from the mass of other IDR sequences by at least 9 Da, at least 25 Da, at least 25 Da, or at least 50 Da. Use of IDR sequences with distinct masses allows RNA fragments comprising different IDR sequences to be distinguished using mass-based analysis methods (e.g., mass spectrometry), which do not require reverse transcription, amplification, or sequencing of RNAs. Each RNA species in an RNA composition may comprises an IDR sequence with a different length. For example, each IDR sequence may have a length independently selected from 0 to 25 nucleotides. The length of a nucleic acid influences the rate at which the nucleic acid traverses a chromatography column, and so the use of IDR sequences of different lengths on different RNA species allows RNA fragments having different IDR sequences to be distinguished using chromatography-based methods (e.g., LC-UV). Attorney Docket No.45817-0022WO1 / MTX977.20 IDR sequences may be chosen such that no IDR sequence comprises a start codon, ‘AUG’. Lack of a start codon in an IDR sequence prevents undesired translation of nucleotide sequences within and / or downstream from the IDR sequence. IDR sequences may be chosen such that no IDR sequence comprises a recognition site for a restriction enzyme. In one example, no IDR sequence comprises a recognition site for XbaI, ‘UCUAG’. Lack of a recognition site for a restriction enzyme (e.g., XbaI recognition site ‘UCUAG’) allows the restriction enzyme to be used in generating and modifying a DNA template for in vitro transcription, without affecting the IDR sequence or sequence of the transcribed RNA. 19. Polynucleotide Comprising an mRNA Encoding an ASS1 Polypeptide or an ASL Polypeptide In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR, such as provided above; (iii) an ORF encoding a polypeptide comprising a human ASS1 polypeptide (e.g., any one of SEQ ID NOs:1-6), wherein the ORF comprises a sequence that has at least 65%, at least 70%, at least 75%, at least 80%, at least 85, at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% sequence identity to the sequence of any one of SEQ ID NOs:8-14; (iv) at least one stop codon; (v) a 3′ UTR, such as the sequences provided above; and (vi) a poly-A tail provided above. In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR comprising the sequence of SEQ ID NO:50; (iii) an ORF encoding a human ASS1 polypeptide (e.g., SEQ ID NO:1), wherein the ORF has at least 65%, at least 70%, at least 75%, at least 80%, at least 85, Attorney Docket No.45817-0022WO1 / MTX977.20 at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% sequence identity to the sequence of SEQ ID NO:8 or 9; (iv) at least one stop codon; (v) a 3′ UTR, such as the sequences provided above; and (vi) a poly-A tail provided above. In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR comprising the sequence of SEQ ID NO:50 or SEQ ID NO:58; (iii) an ORF encoding a human ASS1 polypeptide (e.g., any one of SEQ ID NOs:2-5), wherein the ORF has at least 65%, at least 70%, at least 75%, at least 80%, at least 85, at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% sequence identity to the sequence of any one of SEQ ID NOs:11-14; (iv) at least one stop codon; (v) a 3′ UTR, such as the sequences provided above; and (vi) a poly-A tail provided above. In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR such as provided above; (iii) an ORF comprising the sequence of any one of SEQ ID NOs:1-6; (iv) at least one stop codon; (v) a 3′ UTR such as provided above; and (vi) a poly-A tail provided above. In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR such as provided above; (iii) an ORF comprising the sequence of SEQ ID NO:8; Attorney Docket No.45817-0022WO1 / MTX977.20 (iv) at least one stop codon; (v) a 3′ UTR such as provided above; and (vi) a poly-A tail provided above. In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR such as provided above; (iii) an ORF comprising the sequence of SEQ ID NO:11; (iv) at least one stop codon; (v) a 3′ UTR such as provided above; and (vi) a poly-A tail provided above. In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR comprising the sequence of SEQ ID NO:50; (iii) an ORF comprising the sequence of SEQ ID NO:11; (iv) at least one stop codon; (v) a 3′ UTR comprising the sequence of SEQ ID NO:141; and (vi) a poly-A tail provided above. In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR comprising the sequence of SEQ ID NO:50; (iii) an ORF comprising the sequence of SEQ ID NO:8; (iv) at least one stop codon; (v) a 3′ UTR comprising the sequence of SEQ ID NO:141; and (vi) a poly-A tail provided above. Attorney Docket No.45817-0022WO1 / MTX977.20 In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASL polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR, such as provided above; (iii) an ORF encoding a polypeptide comprising a human ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28), wherein the ORF comprises a sequence that has at least 65%, at least 70%, at least 75%, at least 80%, at least 85, at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% sequence identity to the sequence of SEQ ID NO:15; (iv) at least one stop codon; (v) a 3′ UTR, such as the sequences provided above; and (vi) a poly-A tail provided above. In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASL polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR comprising the sequence of SEQ ID NO:50; (iii) an ORF encoding a human ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28), wherein the ORF has at least 65%, at least 70%, at least 75%, at least 80%, at least 85, at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% sequence identity to the sequence of SEQ ID NO:15; (iv) at least one stop codon; (v) a 3′ UTR, such as the sequences provided above; and (vi) a poly-A tail provided above. In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASL polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR comprising the sequence of SEQ ID NO:50; (iii) an ORF encoding a human ASL polypeptide (e.g., SEQ ID NO:7 or SEQ ID NO:28), wherein the ORF has at least 65%, at least 70%, at least 75%, at least Attorney Docket No.45817-0022WO1 / MTX977.20 80%, at least 85, at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% sequence identity to the sequence of SEQ ID NO:15; (iv) at least one stop codon; (v) a 3′ UTR, such as the sequences provided above; and (vi) a poly-A tail provided above. In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASL polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR such as provided above; (iii) an ORF comprising the sequence of SEQ ID NO:15; (iv) at least one stop codon; (v) a 3′ UTR such as provided above; and (vi) a poly-A tail provided above. In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASL polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR such as provided above; (iii) an ORF comprising the sequence of SEQ ID NO:15; (iv) at least one stop codon; (v) a 3′ UTR such as provided above; and (vi) a poly-A tail provided above. In certain embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASL polypeptide, comprises from 5′ to 3′ end: (i) a 5′ cap such as provided above; (ii) a 5′ UTR comprising the sequence of SEQ ID NO:50; (iii) an ORF comprising the sequence of SEQ ID NO:15; (iv) at least one stop codon; (v) a 3′ UTR comprising the sequence of SEQ ID NO:108; and (vi) a poly-A tail provided above. Attorney Docket No.45817-0022WO1 / MTX977.20 In some embodiments, the polynucleotide further comprises a miRNA binding site, e.g., a miRNA binding site that binds to miRNA-142. In some embodiments, the 3′ UTR comprises the miRNA binding site. In some embodiments, a polynucleotide of the present disclosure comprises a nucleotide sequence encoding a polypeptide sequence at least 65%, at least 70%, at least 80%, at least 81%, at least 82%, at least 83%, at least 84%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96% , at least 97%, at least 98%, at least 99%, or 100% identical to the protein sequence of a human ASS1 protein (e.g., any one of SEQ ID NOs:1-6) or to the protein sequence of a human ASL protein (e.g., SEQ ID NO:7 or SEQ ID NO:28). In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding a polypeptide, comprises (1) a 5′ cap such as provided above, for example, m7Gp-ppGm-A, (2) a 5′ UTR, (3) a nucleotide sequence ORF comprising the sequence of any one of SEQ ID NOs:8-14, (3) a stop codon, (4) a 3′UTR, and (5) a poly-A tail provided above, for example, a poly-A tail of SEQ ID NO:195 or A100-UCUAG-A20-inverted deoxy- thymidine (SEQ ID NO:211). In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding a polypeptide, comprises (1) a 5′ cap such as provided above, for example, m7Gp-ppGm-A, (2) a 5′ UTR, (3) a nucleotide sequence ORF comprising the sequence of SEQ ID NO:15, (3) a stop codon, (4) a 3′UTR, and (5) a poly-A tail provided above, for example, a poly- A tail of SEQ ID NO:195 or A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding a polypeptide, comprises (1) a 5′ cap such as provided above, for example, m7Gp-ppGm-A, (2) a 5′ UTR, (3) a nucleotide sequence ORF comprising the sequence of SEQ ID NO:8, (3) a stop codon, (4) a 3′UTR, and (5) a poly-A tail provided above, for example, a poly-A tail of SEQ ID NO:195 or A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). Attorney Docket No.45817-0022WO1 / MTX977.20 In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding a polypeptide, comprises (1) a 5′ cap such as provided above, for example, m7Gp-ppGm-A, (2) a 5′ UTR, (3) a nucleotide sequence ORF comprising the sequence of SEQ ID NO:11, (3) a stop codon, (4) a 3′UTR, and (5) a poly-A tail provided above, for example, a poly- A tail of SEQ ID NO:195 or A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding a polypeptide, comprises (1) a 5′ cap such as provided above, for example, m7Gp-ppGm-A, (2) a 5′ UTR, (3) a nucleotide sequence ORF comprising the sequence of SEQ ID NO:15, (3) a stop codon, (4) a 3′UTR, and (5) a poly-A tail provided above, for example, a poly- A tail of SEQ ID NO:195 or A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). Exemplary ASS1 nucleotide constructs are described below: SEQ ID NO:16 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:58, ASS1 nucleotide ORF of SEQ ID NO:10, and 3′ UTR of SEQ ID NO: 135; SEQ ID NO:17 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:58, ASS1 nucleotide ORF of SEQ ID NO:9, and 3′ UTR of SEQ ID NO: 135; SEQ ID NO:18 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:50, ASS1 nucleotide ORF of SEQ ID NO:8, and 3′ UTR of SEQ ID NO: 141; SEQ ID NO:19 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:50, ASS1 nucleotide ORF of SEQ ID NO:11, and 3′ UTR of SEQ ID NO: 141; SEQ ID NO:20 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:58, ASS1 nucleotide ORF of SEQ ID NO:11, and 3′ UTR of SEQ ID NO: 135; SEQ ID NO:21 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:50, ASS1 nucleotide ORF of SEQ ID NO:12, and 3′ UTR of SEQ ID NO: 141; SEQ ID NO:22 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:58, ASS1 nucleotide ORF of SEQ ID NO:12, and 3′ UTR of SEQ ID NO: 135; SEQ ID NO:23 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:50, ASS1 nucleotide ORF of SEQ ID NO:13, and 3′ UTR of SEQ ID NO: 141; Attorney Docket No.45817-0022WO1 / MTX977.20 SEQ ID NO:24 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:58, ASS1 nucleotide ORF of SEQ ID NO:13, and 3′ UTR of SEQ ID NO: 135; SEQ ID NO:25 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:50, ASS1 nucleotide ORF of SEQ ID NO:14, and 3′ UTR of SEQ ID NO: 141; and SEQ ID NO:26 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:58, ASS1 nucleotide ORF of SEQ ID NO:14, and 3′ UTR of SEQ ID NO: 135. Exemplary ASL nucleotide constructs are described below: SEQ ID NO:27 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:50, ASL nucleotide ORF of SEQ ID NO:15, and 3′ UTR of SEQ ID NO: 108; and SEQ ID NO:29 consists from 5′ to 3′ end: 5′ UTR of SEQ ID NO:50, ASL nucleotide ORF of SEQ ID NO:30, and 3′ UTR of SEQ ID NO: 108. In certain embodiments, in a construct with any one of SEQ ID NOs:16-27 and 29, all uracils therein are replaced by N1 methylpseudouracil. In certain embodiments, in a construct with any one of SEQ ID NOs:16-27 and 29, all uracils therein are replaced by N1 methylpseudouracil. In certain embodiments, in a construct with SEQ ID NO:19, all uracils therein are replaced by N1 methylpseudouracil. In certain embodiments, in a construct with SEQ ID NO:19, all uracils therein are replaced by N1 methylpseudouracil. In certain embodiments, in a construct with SEQ ID NO:18, all uracils therein are replaced by N1-methylpseudouracil. In certain embodiments, in a construct with SEQ ID NO:18, all uracils therein are replaced by N1-methylpseudouracil. In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASS1 polypeptide, comprises (1) a 5′ cap such as provided above, for example, m7Gp- ppGm-A, (2) a nucleotide sequence of any one of SEQ ID NOs:16-26, and (3) a poly- A tail provided above, for example, a poly A tail of ~100 residues, e.g., SEQ ID NO:195 or A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). In certain embodiments, in constructs with SEQ ID NO:18 or SEQ ID NO:19, all uracils therein are replaced by N1 methylpseudouracil. In certain embodiments, in constructs with SEQ ID NO:18 or SEQ ID NO:19, all uracils therein are replaced by 5- methoxyuracil. Attorney Docket No.45817-0022WO1 / MTX977.20 In some embodiments, a polynucleotide of the present disclosure, for example a polynucleotide comprising an mRNA nucleotide sequence encoding an ASL polypeptide, comprises (1) a 5′ cap such as provided above, for example, m7Gp- ppGm-A, (2) a nucleotide sequence of SEQ ID NO:27 or SEQ ID NO:29, and (3) a poly-A tail provided above, for example, a poly A tail of ~100 residues, e.g., SEQ ID NO:195 or A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211). In certain embodiments, in constructs with SEQ ID NO:27 or SEQ ID NO:29, all uracils therein are replaced by N1 methylpseudouracil. In certain embodiments, in constructs with SEQ ID NO:27 or SEQ ID NO:29, all uracils therein are replaced by 5- methoxyuracil. Table 7A – Modified mRNA constructs including ORFs encoding human ASS1 (constructs comprise an m7Gp-ppGm-A 5′ terminal cap and a 3′ terminal PolyA region) ASS1 mRNA 5′UTR ASS1 ORF 3′ construct SEQ ID Name SEQ ID UTR Attorney Docket No.45817-0022WO1 / MTX977.20 ASS1 mRNA 5′UTR ASS1 ORF 3′ construct SEQ ID Name SEQ ID UTR NO SE Table 7B – Modified mRNA constructs including ORFs encoding human ASL (constructs comprise an m7Gp-ppGm-A 5′ terminal cap and a 3′ terminal PolyA region) ASL mRNA 5′UTR ASL ORF 3′ UTR construct SEQ ID Name SEQ ID SEQ : In some embodiments, the polynucleotide further comprises a miRNA binding site, e.g., a miRNA binding site that binds to miRNA-142. In some embodiments, the 3′ UTR comprises the miRNA binding site. 20. Methods of Making Polynucleotides The present disclosure also provides methods for making a polynucleotide of the invention (e.g., a polynucleotide comprising a nucleotide sequence encoding an ASS1 polypeptide or an ASL polypeptide) or a complement thereof. In some aspects, a polynucleotide (e.g., a RNA, e.g., an mRNA) disclosed herein, and encoding an ASS1 polypeptide or an ASL polypeptide, can be constructed using in vitro transcription (IVT). In other aspects, a polynucleotide (e.g., a RNA, e.g., an mRNA) disclosed herein, and encoding an ASS1 polypeptide or an ASL polypeptide, can be constructed by chemical synthesis using an oligonucleotide synthesizer. In other aspects, a polynucleotide (e.g., a RNA, e.g., an mRNA) disclosed herein, and encoding an ASS1 polypeptide or an ASL polypeptide is made by using a Attorney Docket No.45817-0022WO1 / MTX977.20 host cell. In certain aspects, a polynucleotide (e.g., a RNA, e.g., an mRNA) disclosed herein, and encoding an ASS1 polypeptide or an ASL polypeptide is made by one or more combination of the IVT, chemical synthesis, host cell expression, or any other methods known in the art. Naturally occurring nucleosides, non-naturally occurring nucleosides, or combinations thereof, can totally or partially naturally replace occurring nucleosides present in the candidate nucleotide sequence and can be incorporated into a sequence- optimized nucleotide sequence (e.g., a RNA, e.g., an mRNA) encoding an ASS1 polypeptide or an ASL polypeptide. The resultant polynucleotides, e.g., mRNAs, can then be examined for their ability to produce protein and / or produce a therapeutic outcome. a. In Vitro Transcription / Enzymatic Synthesis The present disclosure also provides methods for making a polynucleotide disclosed herein or a complement thereof. In some aspects, a polynucleotide (e.g., an mRNA) disclosed herein can be constructed using in vitro transcription. In other aspects, a polynucleotide (e.g., an mRNA) disclosed herein can be constructed by chemical synthesis using an oligonucleotide synthesizer. In other aspects, a polynucleotide (e.g., an mRNA) disclosed herein is made by using a host cell. In certain aspects, a polynucleotide (e.g., an mRNA) disclosed herein is made by one or more combination of the IVT, chemical synthesis, host cell expression, or any other methods known in the art. Naturally occurring nucleosides, non-naturally occurring nucleosides, or combinations thereof, can totally or partially naturally replace occurring nucleosides present in the candidate nucleotide sequence and can be incorporated into a sequence- optimized nucleotide sequence (e.g., an mRNA) encoding an ASS1 polypeptide or an ASL polypeptide. The resultant mRNAs can then be examined for their ability to produce ASS1 or ASL and / or produce a therapeutic outcome. While RNA can be made synthetically using methods well known in the art, in one embodiment an RNA transcript (e.g., mRNA transcript) is synthesized by contacting a DNA template with a RNA polymerase (e.g., a T7 RNA polymerase or a Attorney Docket No.45817-0022WO1 / MTX977.20 T7 RNA polymerase variant) under conditions that result in the production of RNA transcript. In some aspects, the present disclosure provides methods of performing an IVT (in vitro transcription) reaction, comprising contacting a DNA template with the RNA polymerase (e.g., a T7 RNA polymerase, such as a T7 RNA polymerase variant) in the presence of nucleoside triphosphates and buffer under conditions that result in the production of RNA transcripts. Other aspects of the present disclosure provide capping methods, e.g., co- transcriptional capping methods or other methods known in the art. In one embodiment, a capping method comprises reacting a polynucleotide template with a T7 RNA polymerase variant, nucleoside triphosphates, and a cap analog under in vitro transcription reaction conditions to produce RNA transcript. IVT conditions typically require a purified linear DNA template containing a promoter, nucleoside triphosphates, a buffer system that includes dithiothreitol (DTT) and magnesium ions, and a RNA polymerase. The exact conditions used in the transcription reaction depend on the amount of RNA needed for a specific application. Typical IVT reactions are performed by incubating a DNA template with a RNA polymerase and nucleoside triphosphates, including GTP, ATP, CTP, and UTP (or nucleotide analogs) in a transcription buffer. A RNA transcript having a 5^ terminal guanosine triphosphate is produced from this reaction. A deoxyribonucleic acid (DNA) is simply a nucleic acid template for RNA polymerase. A DNA template may include a polynucleotide encoding an ASS1 polypeptide or an ASL polypeptide. A DNA template, in some embodiments, includes a RNA polymerase promoter (e.g., a T7 RNA polymerase promoter) located 5' from and operably linked to polynucleotide encoding an ASS1 polypeptide or an ASL polypeptide. A DNA template may also include a nucleotide sequence encoding a polyadenylation (polyA) tail located at the 3' end of the gene of interest. Polypeptides of interest include, but are not limited to, biologics, antibodies, antigens (vaccines), and therapeutic proteins. The term “protein” encompasses peptides. A RNA transcript, in some embodiments, is the product of an IVT reaction and, as will be understood by one of ordinary skill in the art, the DNA template for Attorney Docket No.45817-0022WO1 / MTX977.20 making an RNA molecule is known based on base complementarity. A RNA transcript, in some embodiments, is a messenger RNA (mRNA) that includes a nucleotide sequence encoding a polypeptide of interest linked to a polyA tail. In some embodiments, the mRNA is modified mRNA (mmRNA), which includes at least one modified nucleotide. A nucleotide includes a nitrogenous base, a five-carbon sugar (ribose or deoxyribose), and at least one phosphate group. Nucleotides include nucleoside monophosphates, nucleoside diphosphates, and nucleoside triphosphates. A nucleoside monophosphate (NMP) includes a nucleobase linked to a ribose and a single phosphate; a nucleoside diphosphate (NDP) includes a nucleobase linked to a ribose and two phosphates; and a nucleoside triphosphate (NTP) includes a nucleobase linked to a ribose and three phosphates. Nucleotide analogs are compounds that have the general structure of a nucleotide or are structurally similar to a nucleotide. Nucleotide analogs, for example, include an analog of the nucleobase, an analog of the sugar and / or an analog of the phosphate group(s) of a nucleotide. A nucleoside includes a nitrogenous base and a 5-carbon sugar. Thus, a nucleoside plus a phosphate group yields a nucleotide. Nucleoside analogs are compounds that have the general structure of a nucleoside or are structurally similar to a nucleoside. Nucleoside analogs, for example, include an analog of the nucleobase and / or an analog of the sugar of a nucleoside. It should be understood that the term “nucleotide” includes naturally-occurring nucleotides, synthetic nucleotides and modified nucleotides, unless indicated otherwise. Examples of naturally-occurring nucleotides used for the production of RNA, e.g., in an IVT reaction, as provided herein include adenosine triphosphate (ATP), guanosine triphosphate (GTP), cytidine triphosphate (CTP), uridine triphosphate (UTP), and 5-methyluridine triphosphate (m5UTP). In some embodiments, adenosine diphosphate (ADP), guanosine diphosphate (GDP), cytidine diphosphate (CDP), and / or uridine diphosphate (UDP) are used. Examples of nucleotide analogs include, but are not limited to, antiviral nucleotide analogs, phosphate analogs (soluble or immobilized, hydrolyzable or non- hydrolyzable), dinucleotide, trinucleotide, tetranucleotide, e.g., a cap analog, or a precursor / substrate for enzymatic capping (vaccinia or ligase), a nucleotide labeled Attorney Docket No.45817-0022WO1 / MTX977.20 with a functional group to facilitate ligation / conjugation of cap or 5^ moiety (IRES), a nucleotide labeled with a 5^ PO4to facilitate ligation of cap or 5^ moiety, or a nucleotide labeled with a functional group / protecting group that can be chemically or enzymatically cleaved. Examples of antiviral nucleotide / nucleoside analogs include, but are not limited, to Ganciclovir, Entecavir, Telbivudine, Vidarabine and Cidofovir. Modified nucleotides may include modified nucleobases. For example, a RNA transcript (e.g., mRNA transcript) of the present disclosure may include a modified nucleobase selected from pseudouridine (ψ), 1-methylpseudouridine (m1ψ), 1- ethylpseudouridine, 2-thiouridine, 4’-thiouridine, 2-thio-1-methyl-1-deaza- pseudouridine, 2-thio-1-methyl-pseudouridine, 2-thio-5-aza-uridine , 2-thio- dihydropseudouridine, 2-thio-dihydrouridine, 2-thio-pseudouridine, 4-methoxy-2- thio-pseudouridine, 4-methoxy-pseudouridine, 4-thio-1-methyl-pseudouridine, 4-thio- pseudouridine, 5-aza-uridine, dihydropseudouridine, 5-methyluridine, 5- methoxyuridine (mo5U) and 2’-O-methyl uridine. In some embodiments, a RNA transcript (e.g., mRNA transcript) includes a combination of at least two (e.g., 2, 3, 4 or more) of the foregoing modified nucleobases. The nucleoside triphosphates (NTPs) as provided herein may comprise unmodified or modified ATP, modified or unmodified UTP, modified or unmodified GTP, and / or modified or unmodified CTP. In some embodiments, NTPs of an IVT reaction comprise unmodified ATP. In some embodiments, NTPs of an IVT reaction comprise modified ATP. In some embodiments, NTPs of an IVT reaction comprise unmodified UTP. In some embodiments, NTPs of an IVT reaction comprise modified UTP. In some embodiments, NTPs of an IVT reaction comprise unmodified GTP. In some embodiments, NTPs of an IVT reaction comprise modified GTP. In some embodiments, NTPs of an IVT reaction comprise unmodified CTP. In some embodiments, NTPs of an IVT reaction comprise modified CTP. The concentration of nucleoside triphosphates and cap analog present in an IVT reaction may vary. In some embodiments, NTPs and cap analog are present in the reaction at equimolar concentrations. In some embodiments, the molar ratio of cap analog (e.g., trinucleotide cap) to nucleoside triphosphates in the reaction is greater than 1:1. For example, the molar ratio of cap analog to nucleoside triphosphates in the reaction may be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, 25:1, 50:1, or Attorney Docket No.45817-0022WO1 / MTX977.20 100:1. In some embodiments, the molar ratio of cap analog (e.g., trinucleotide cap) to nucleoside triphosphates in the reaction is less than 1:1. For example, the molar ratio of cap analog (e.g., trinucleotide cap) to nucleoside triphosphates in the reaction may be 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:15, 1:20, 1:25, 1:50, or 1:100. The composition of NTPs in an IVT reaction may also vary. For example, ATP may be used in excess of GTP, CTP and UTP. As a non-limiting example, an IVT reaction may include 7.5 millimolar GTP, 7.5 millimolar CTP, 7.5 millimolar UTP, and 3.75 millimolar ATP. The same IVT reaction may include 3.75 millimolar cap analog (e.g., trinucleotide cap). In some embodiments, the molar ratio of G:C:U:A:cap is 1:1:1:0.5:0.5. In some embodiments, the molar ratio of G:C:U:A:cap is 1:1:0.5:1:0.5. In some embodiments, the molar ratio of G:C:U:A:cap is 1:0.5:1:1:0.5. In some embodiments, the molar ratio of G:C:U:A:cap is 0.5:1:1:1:0.5. In some embodiments, a RNA transcript (e.g., mRNA transcript) includes a modified nucleobase selected from pseudouridine (ψ), 1-methylpseudouridine (m1ψ), 5-methoxyuridine (mo5U), 5-methylcytidine (m5C), α-thio-guanosine and α-thio- adenosine. In some embodiments, a RNA transcript (e.g., mRNA transcript) includes a combination of at least two (e.g., 2, 3, 4 or more) of the foregoing modified nucleobases. In some embodiments, a RNA transcript (e.g., mRNA transcript) includes pseudouridine (ψ). In some embodiments, a RNA transcript (e.g., mRNA transcript) includes 1-methylpseudouridine (m1ψ). In some embodiments, a RNA transcript (e.g., mRNA transcript) includes 5-methoxyuridine (mo5U). In some embodiments, a RNA transcript (e.g., mRNA transcript) includes 5-methylcytidine (m5C). In some embodiments, a RNA transcript (e.g., mRNA transcript) includes α-thio-guanosine. In some embodiments, a RNA transcript (e.g., mRNA transcript) includes α-thio- adenosine. In some embodiments, the polynucleotide (e.g., RNA polynucleotide, such as mRNA polynucleotide) is uniformly modified (e.g., fully modified, modified throughout the entire sequence) for a particular modification. For example, a polynucleotide can be uniformly modified with 1-methylpseudouridine (m1ψ), meaning that all uridine residues in the mRNA sequence are replaced with 1- methylpseudouridine (m1ψ). Similarly, a polynucleotide can be uniformly modified Attorney Docket No.45817-0022WO1 / MTX977.20 for any type of nucleoside residue present in the sequence by replacement with a modified residue such as any of those set forth above. Alternatively, the polynucleotide (e.g., RNA polynucleotide, such as mRNA polynucleotide) may not be uniformly modified (e.g., partially modified, part of the sequence is modified). Each possibility represents a separate embodiment of the present invention. In some embodiments, the buffer system contains tris. The concentration of tris used in an IVT reaction, for example, may be at least 10 mM, at least 20 mM, at least 30 mM, at least 40 mM, at least 50 mM, at least 60 mM, at least 70 mM, at least 80 mM, at least 90 mM, at least 100 mM or at least 110 mM phosphate. In some embodiments, the concentration of phosphate is 20-60 mM or 10-100 mM. In some embodiments, the buffer system contains dithiothreitol (DTT). The concentration of DTT used in an IVT reaction, for example, may be at least 1 mM, at least 5 mM, or at least 50 mM. In some embodiments, the concentration of DTT used in an IVT reaction is 1-50 mM or 5-50 mM. In some embodiments, the concentration of DTT used in an IVT reaction is 5 mM. In some embodiments, the buffer system contains magnesium. In some embodiments, the molar ratio of NTP to magnesium ions (Mg2+; e.g., MgCl2) present in an IVT reaction is 1:1 to 1:5. For example, the molar ratio of NTP to magnesium ions may be 1:1, 1:2, 1:3, 1:4 or 1:5. In some embodiments, the molar ratio of NTP plus cap analog (e.g., trinucleotide cap, such as GAG) to magnesium ions (Mg2+; e.g., MgCl2) present in an IVT reaction is 1:1 to 1:5. For example, the molar ratio of NTP+trinucleotide cap (e.g., GAG) to magnesium ions may be 1:1, 1:2, 1:3, 1:4 or 1:5. In some embodiments, the buffer system contains Tris-HCl, spermidine (e.g., at a concentration of 1-30 mM), TRITON®X-100 (polyethylene glycol p-(1,1,3,3- tetramethylbutyl)-phenyl ether) and / or polyethylene glycol (PEG). The addition of nucleoside triphosphates (NTPs) to the 3^ end of a growing RNA strand is catalyzed by a polymerase, such as T7 RNA polymerase, for example, any one or more of the T7 RNA polymerase variants (e.g., G47A) of the present disclosure. In some embodiments, the RNA polymerase (e.g., T7 RNA polymerase variant) is present in a reaction (e.g., an IVT reaction) at a concentration of 0.01 Attorney Docket No.45817-0022WO1 / MTX977.20 mg / ml to 1 mg / ml. For example, the RNA polymerase may be present in a reaction at a concentration of 0.01 mg / mL, 0.05 mg / ml, 0.1 mg / ml, 0.5 mg / ml or 1.0 mg / ml. In some embodiments, the polynucleotide of the present disclosure is an IVT polynucleotide. Traditionally, the basic components of an mRNA molecule include at least a coding region, a 5′UTR, a 3′UTR, a 5′ cap and a poly-A tail. The IVT polynucleotides of the present disclosure can function as mRNA but are distinguished from wild-type mRNA in their functional and / or structural design features which serve, e.g., to overcome existing problems of effective polypeptide production using nucleic-acid based therapeutics. The primary construct of an IVT polynucleotide comprises a first region of linked nucleotides that is flanked by a first flanking region and a second flaking region. This first region can include, but is not limited to, the encoded ASS1 polypeptide or ASL polypeptide. The first flanking region can include a sequence of linked nucleosides which function as a 5’ untranslated region (UTR) such as the 5’ UTR of SEQ ID NO:58. The IVT encoding an ASS1 polypeptide or an ASL polypeptide can comprise at its 5 terminus a signal sequence region encoding one or more signal sequences. The flanking region can comprise a region of linked nucleotides comprising one or more complete or incomplete 5′ UTRs sequences. The flanking region can also comprise a 5′ terminal cap...

Claims

Attorney Docket No.45817-0022WO1 / MTX977.20 WHAT IS CLAIMED IS:

1. A polypeptide comprising an amino acid sequence that is at least 80% identical to the amino acid sequence of SEQ ID NO:1, wherein the amino acid sequence comprises: (a) an amino acid other than lysine (K) at the position corresponding to position 58 of SEQ ID NO:1; (b) an amino acid other than lysine (K) at the position corresponding to position 165 of SEQ ID NO:1 and an amino acid other than lysine (K) at the position corresponding to position 176 of SEQ ID NO:1; (c) an amino acid other than cysteine (C) at the position corresponding to position 132 of SEQ ID NO:1; or (d) an amino acid other than lysine (K) at the position corresponding to position 4 of SEQ ID NO:1; wherein the polypeptide catalyzes the conversion of citrulline to argininosuccinate.

2. The polypeptide of claim 1, wherein the amino acid sequence comprises: (a) an arginine (R) at the position corresponding to position 58 of SEQ ID NO:1; (b) an arginine (R) at the position corresponding to position 165 of SEQ ID NO:1 and an arginine (R) at the position corresponding to position 176 of SEQ ID NO:1; (c) an alanine (A) at the position corresponding to position 132 of SEQ ID NO:1; or (d) an arginine (R) at the position corresponding to position 4 of SEQ ID NO:

1.

3. The polypeptide of claim 1, wherein the amino acid sequence comprises an arginine (R) at the position corresponding to position 58 of SEQ ID NO:

1.

4. The polypeptide of any one of claims 1 to 3, wherein the polypeptide is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:

1.

5. The polypeptide of claim 1, wherein the polypeptide comprises the amino acid sequence of any one of SEQ ID NOs:2-5.Attorney Docket No.45817-0022WO1 / MTX977.20 6. The polypeptide of claim 1, wherein the polypeptide comprises the amino acid sequence of SEQ ID NO:

2.

7. A messenger RNA (mRNA) comprising an open reading frame (ORF) encoding the polypeptide of any one of claims 1 to 6.

8. The mRNA of claim 7, wherein the ORF is at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% identical to the nucleotide sequence of SEQ ID NO:11-14.

9. The mRNA of claim 7 or 8, wherein the mRNA comprises a 5' untranslated region (UTR) comprising the nucleotide sequence of SEQ ID NO:

50.

10. The mRNA of any one of claims 7 to 9, wherein the mRNA comprises a 3' UTR comprising the nucleotide sequence of SEQ ID NO:

143.

11. The mRNA of claim 10, wherein the mRNA comprises a 3' UTR comprising the nucleotide sequence of SEQ ID NO:

142.

12. The mRNA of claim 10 or 11, wherein the mRNA comprises a 3' UTR comprising the nucleotide sequence of SEQ ID NO:

141.

13. The mRNA of claim 7, comprising the nucleotide sequence of any one of SEQ ID NOs:19-26.

14. The mRNA of any one of claims 7 to 13, wherein the mRNA comprises a 5′ terminal cap comprising m7G(5′)ppp(5′)G-2′-O-methyl.

15. The mRNA of any one of claims 7 to 14, wherein the mRNA comprises a poly-A region comprising A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211).Attorney Docket No.45817-0022WO1 / MTX977.20 16. The mRNA of claim 7, comprising: (i) a 5′ terminal cap comprising m7G(5′)ppp(5′)G-2′-O-methyl; (ii) a 5′ untranslated region (UTR) comprising the nucleotide sequence of SEQ ID NO:50; (iii) an open reading frame (ORF) encoding the polypeptide of SEQ ID NO:2, wherein the ORF comprises the nucleotide sequence of SEQ ID NO:11; (iv) a 3′ UTR comprising the nucleic acid sequence of SEQ ID NO:141; and (v) a poly-A region comprising A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211).

17. A messenger RNA (mRNA) comprising an open reading frame (ORF) encoding the argininosuccinate synthase 1 (ASS1) polypeptide of SEQ ID NO:1, wherein the ORF is at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% identical to the nucleotide sequence of SEQ ID NO:8 or 9.

18. The mRNA of claim 17, wherein the mRNA comprises a 5' untranslated region (UTR) comprising the nucleotide sequence of SEQ ID NO:

50.

19. The mRNA of claim 17 or 18, wherein the mRNA comprises a 3' UTR comprising the nucleotide sequence of SEQ ID NO:

141.

20. The mRNA of claim 17, comprising the nucleotide sequence of SEQ ID NO:17 or 18.

21. The mRNA of any one of claims 17 to 20, wherein the mRNA comprises a 5′ terminal cap comprising m7G(5′)ppp(5′)G-2′-O-methyl.

22. The mRNA of any one of claims 17 to 21, wherein the mRNA comprises a poly- A region comprising A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211).

23. The mRNA of claim 17, comprising:Attorney Docket No.45817-0022WO1 / MTX977.20 (i) a 5′ terminal cap comprising m7G(5′)ppp(5′)G-2′-O-methyl; (ii) a 5′ untranslated region (UTR) comprising the nucleotide sequence of SEQ ID NO:50; (iii) an open reading frame (ORF) encoding the argininosuccinate synthase 1 (ASS1) polypeptide of SEQ ID NO:1, wherein the ORF comprises the nucleotide sequence of SEQ ID NO:8 or 9; (iv) a 3′ UTR comprising the nucleic acid sequence of SEQ ID NO:141; and (v) a poly-A region comprising A100-UCUAG-A20-inverted deoxy-thymidine (SEQ ID NO:211).

24. The mRNA of any one of claims 7 to 23, wherein the mRNA comprises at least one chemically modified nucleobase, sugar, backbone, or any combination thereof.

25. The mRNA of any one of claims 7 to 23, wherein all of the uracils of the mRNA are N1-methylpseudouracils.

26. A pharmaceutical composition comprising the polypeptide of any one of claims 1 to 6 or the mRNA of any one of claims 7 to 25 and a pharmaceutically acceptable carrier.

27. A lipid nanoparticle comprising the polypeptide of any one of claims 1 to 6 or the mRNA of any one of claims 7 to 25.

28. The lipid nanoparticle of claim 27, wherein the lipid nanoparticle comprises an ionizable lipid, a structural lipid, a phospholipid, and a polyethylene glycol (PEG)- modified lipid.

29. The lipid nanoparticle of claim 28, wherein the ionizable lipid is Compound A or a salt thereof.

30. The lipid nanoparticle of claim 28, wherein the ionizable lipid is Compound II or a salt thereof.Attorney Docket No.45817-0022WO1 / MTX977.20 31. The lipid nanoparticle of any one of claims 28 to 30, wherein the structural lipid is cholesterol.

32. The lipid nanoparticle of any one of claims 28 to 31, wherein the phospholipid is 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) or 1,2-dioleoyl-sn-glycero-3- phosphoethanolamine (DOPE).

33. The lipid nanoparticle of any one of claims 28 to 32, wherein the PEG- modified lipid is PEG-DMG or Compound I.

34. A lipid nanoparticle comprising:a an argininosuccinate synthase 1 (ASS1) polypeptide.

35. A method of expressing a polypeptide in a human subject in need thereof, the method comprising administering to the human subject an effective amount of (i) the mRNA of any one of claims 7 to 25, (ii) the pharmaceutical composition of claim 26, or (iv) the lipid nanoparticle of any one of claims 27 to 34.

36. A method for treating citrullinemia type 1 (CTLN1) in a human subject in need thereof, the method comprising administering to the human subject an effective amount of (i) the polypeptide of any one of claims 1 to 6, (ii) the mRNA of any one of claims 7 to 25, (iii) the pharmaceutical composition of claim 26, or (vi) the lipid nanoparticle of any one of claims 27 to 34.Attorney Docket No.45817-0022WO1 / MTX977.20 37. The method of claim 36, further comprising administering to the human subject an effective amount of (i) an argininosuccinate lyase (ASL) polypeptide, (ii) an mRNA comprising an ORF encoding the ASL polypeptide, (iii) a pharmaceutical composition comprising the ASL polypeptide or the mRNA comprising an ORF encoding the ASL polypeptide, or (iv) a lipid nanoparticle comprising an ASL polypeptide or an mRNA comprising an ORF encoding the ASL polypeptide.

38. A method for treating adenylosuccinate lyase deficiency (ASLD) in a human subject in need thereof, the method comprising administering to the human subject (a) an effective amount of (i) the polypeptide of any one of claims 1 to 6, (ii) the mRNA of any one of claims 7 to 25, (iii) the pharmaceutical composition of claim 26, or (vi) the lipid nanoparticle of any one of claims 27 to 34, and (b) an effective amount of (i) an argininosuccinate lyase (ASL) polypeptide, (ii) an mRNA comprising an ORF encoding the ASL polypeptide, (iii) a pharmaceutical composition comprising the ASL polypeptide or the mRNA comprising an ORF encoding the ASL polypeptide, or (iv) a lipid nanoparticle comprising the ASL polypeptide or the mRNA comprising an ORF encoding the ASL polypeptide.

39. The method of claim 37 or 38, wherein the ASL polypeptide comprises an amino acid sequence that is at least 80% identical to the amino acid sequence of SEQ ID NO:28, wherein the amino acid sequence comprises an amino acid other than lysine (K) at the position corresponding to position 51 of SEQ ID NO:28, and wherein the polypeptide catalyzes the conversion of citrulline and aspartate into argininosuccinate.

40. The method of claim 39, wherein the amino acid sequence comprises an arginine (R) at the position corresponding to position 51 of SEQ ID NO:

28.

41. The method of claim 39 or 40, wherein the ASL polypeptide is at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99% identical to SEQ ID NO:28.Attorney Docket No.45817-0022WO1 / MTX977.20 42. The method of claim 39, wherein the polypeptide comprises the amino acid sequence of SEQ ID NO:

7.

43. The method of claim 37 or 38, wherein the ASL polypeptide comprises the sequence of SEQ ID NO:7, and wherein the ORF encoding the ASL polypeptide is at least 90%, at least 95%, at least 97%, at least 98%, at least 99%, or 100% identical to the nucleotide sequence of SEQ ID NO:15.

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