Trans amplifying rnas comprising chemically modified nucleobases

Abstract

This application is directed to, in part, chemically modified trans amplifying RNAs, and methods of use thereof for payload expression in cells and subjects.

Description

[0001]TRANS AMPLIFYING RNAS COMPRISING CHEMICALLY MODIFIED NUCLEOBASES FIELD This disclosure relates to chemically modified polynucleotides encoding gene products and methods for their use in modulating gene expression in cells and subjects. RELATED APPLICATIONS This application claims the benefit under 35 U.S.C. § 119(e) of US Provisional Application No.63 / 595,690, filed November 2, 2023, entitled “TRANS AMPLIFYING RNAS COMPRISING CHEMICALLY MODIFIED NUCLEOBASES” and US Provisional Application No.63 / 662,498, filed June 21, 2024, entitled “TRANS AMPLIFYING RNAS COMPRISING CHEMICALLY MODIFIED NUCLEOBASES” the content of each of which is hereby incorporated by reference herein in its entirety for all purposes. REFERENCE TO AN ELECTRONIC SEQUENCE LISTING The content of the electronic sequence listing (A141470000WO00-SEQ-ARM.xml; Size: 25,199 bytes; and Date of Creation: October 29, 2024) is herein incorporated by reference in its entirety. BACKGROUND Despite their promise, ribonucleic acid (RNA)-based therapeutics face major barriers in production and use. The rapid degradation of foreign polynucleotides by host immune factors requires large quantities of RNA to generate effective doses, greatly limiting production capacity and development timelines. Moreover, administration of large doses of RNA increases the possibility of undesired secondary effects in subjects as a result of their administration, limiting their widespread applicability. New developments in RNA technologies aimed at resolving these issues include the utilization of self-amplifying RNA (saRNA) and, more recently, trans- amplifying RNA (taRNA), two next-generation RNA constructs useful for expressing a desired product in a cell. Briefly, saRNA and taRNA both encode alphaviral replicases, which are able to transcribe and synthesize copies of a compatible RNA sequence encoding a payload for expression in a host. In saRNA, replicase-encoding and payload-encoding sequences are part of 12531064.1 the same >9000 nucleotide construct (i.e., on one continuous strand), which the replicase then replicates (i.e., self-amplifies). taRNA instead comprise replicase-encoding sequences and payload-encoding sequences on separate, smaller constructs, such that replication of the payload-encoding sequence by the replicase occurs in trans. These two amplifying RNA constructs allow for smaller starting doses of polynucleotides while also providing for similar or greater expression than contemporary RNA therapeutics (i.e., mRNA). Described herein are taRNAs comprising chemically modified nucleotides and methods for use thereof. SUMMARY While the development of taRNAs is relatively new, saRNA constructs have been a point of focus for amplified RNA therapeutics, with mixed results. Preclinical studies and clinical trials suggest saRNA can induce immune responses at ultralow doses in some subjects, albeit inconsistently and ineffectively—a result thought to be mediated by increased innate immune recognition leading to degradation by host immune factors Pollock, K. C. (2022). EClinicalMedicine, 44. Accordingly, efforts to reduce immune recognition and degradation of saRNA are underway, with attempts focusing on adapting techniques which have been successfully implemented in mRNA vaccines, including the introduction of chemically modified nucleotides. Despite success in mRNA, incorporation of chemically modified nucleotides reportedly results in a substantial loss of expression of the payload in saRNA, possibly due to impaired interactions of the replicase and saRNA. Several references report that chemically modified nucleotides are rarely tolerated in saRNA, such that expression of modified saRNA is reduced relative to expression of unmodified saRNA (Voigt, E. G., et al., (2022). NPJ Vaccines, 7(1), 136; Minnaert, A.-K. H., et al. (2021). Advanced drug delivery reviews, 176, 113900), with one study finding that modified pyrimidines, such as m1Ψ, render saRNA incapable of replication (McGee, J., et al. (2023). bioRxiv, 2023-09). Though the mechanisms by which these chemical modifications interfere with saRNA function are yet unclear, one prominent theory suggests that chemical modifications may impair replicase interactions with saRNA constructs (Maruggi, G. C., et al (2019). Molecular Therapy, 27(4), 757-772; McGee, J., et al. (2023). bioRxiv, 2023- 09). Overall, incorporation of chemically modified nucleotides into saRNA yield mixed results, with the majority of studies finding modified nucleotide incorporation detrimental. However, the inventors have surprisingly been able to successfully incorporate a variety of chemically modified nucleotides into taRNAs with benefits that have not been observed in 12531064.1 saRNAs. For example, in some aspects, chemically modified taRNAs of the instant disclosure dramatically increase fold expression of payload-encoding constructs and significantly reduce immunogenicity compared to unmodified taRNA. Further, the inventors have shown that numerous chemical modifications to taRNA increase payload expression, including those which have been unsuccessfully incorporated in saRNA, such as modified uridines (e.g., m1Ψ). In some aspects, this disclosure describes a trans-amplifying ribonucleic acid (RNA) (taRNA) comprising a first RNA polynucleotide (i.e., a replicase construct) comprising a nucleic acid encoding a replicase; and a second RNA polynucleotide (i.e., trans replicon construct (trRNA)) comprising a nucleic acid encoding a payload, wherein about 25% to about 100% of adenine (A), cytidine (C), guanine (G), and / or uridine (U) in the first RNA polynucleotide and / or the second RNA polynucleotide comprise a -methyl, an -O methyl, a pseudouridine, a methyl- pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, about 25% to about 100% of A in the first and / or second RNA polynucleotide of a taRNA are 2'-O-methyl-adenosine-5'-triphosphase(2'OMe-ATP), N6- methyladenosine-5'-triphosphate (m6ATP), and / or 2'-O-methyl-N6-methyladenosine-5'- triphosphate (2'OMe-m6ATP). In some embodiments, about 25% to about 100% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-ATP. In some embodiments, about 25% to about 75% of A in the first and / or second RNA polynucleotides of a taRNA are 2’OMe-ATP. In some embodiments, about 40% to about 60% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-ATP. In some embodiments, about 50% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-ATP. In some embodiments, about 60% to about 90% of A in the first and / or second RNA polynucleotides in a taRNA are 2'OMe-ATP. In some embodiments, about 75% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-ATP. In some embodiments, about 75% to about 100% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-ATP. In some embodiments, about 90% to about 100% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-ATP. In some embodiments, about 100% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-ATP. In some embodiments, about 25% to about 100% of A in the first and / or second RNA polynucleotides of a taRNA are m6ATP. In some embodiments, about 25% to about 75% of A in the first and / or second RNA polynucleotides of a taRNA are m6ATP. In some embodiments, about 40% to about 60% of A in the first and / or second RNA polynucleotides of a taRNA are 12531064.1 m6ATP. In some embodiments, about 50% of A in the first and / or second RNA polynucleotides of a taRNA are m6ATP. In some embodiments, about 75% to about 100% of A in the first and / or second RNA polynucleotides of a taRNA are m6ATP. In some embodiments, about 90% to about 100% of A in the first and / or second RNA polynucleotides of a taRNA are m6ATP. In some embodiments, about 100% of A in the first and / or second RNA polynucleotides of the taRNA are m6ATP. In some embodiments, about 25% to about 100% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-m6ATP. In some embodiments, about 25% to about 75% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-m6ATP. In some embodiments, about 40% to about 60% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-m6ATP. In some embodiments, about 50% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-m6ATP. In some embodiments, about 75% to about 100% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-m6ATP. In some embodiments, about 90% to about 100% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-m6ATP. In some embodiments, about 100% of A in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-m6ATP. In some embodiments, about 25% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 5-methylcytidine-5'-triphosphate (m5c), 2'-O-methylcytidine-5'- triphosphate (2'OMe-CTP), N4-acetylcytidine triphosphate (ac4CTP), 5-methylcytidine-5'- triphosphate (5moC), and / or 5-methylcytosine (5mC). In some embodiments, 25% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5c. In some embodiments, about 25% to about 75% of C in the first and / or second RNA polynucleotides of a taRNA are m5c. In some embodiments, about 25% to about 40% of C in the first and / or second RNA polynucleotides of a taRNA are m5c. In some embodiments, about 25% of C in the first and / or second RNA polynucleotides of a taRNA are m5c. In some embodiments, about 40% to about 60% of C in the first and / or second RNA polynucleotides of a taRNA are m5c. In some embodiments, about 50% of C in the first and / or second RNA polynucleotides of a taRNA are m5c. In some embodiments, about 75% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5c. In some embodiments, about 90% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5c. In some embodiments, about 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5c. 12531064.1 In some embodiments, about 25% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-CTP. In some embodiments, about 25% to about 40% of C in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-CTP. In some embodiments, about 25% of C in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-CTP. In some embodiments, about 40% to about 60% of C in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-CTP. In some embodiments, about 50% of C in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-CTP. In some embodiments, about 60% to about 90% of C in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-CTP. In some embodiments, about 75% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-CTP. In some embodiments, about 75% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-CTP. In some embodiments, about 90% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-CTP. In some embodiments, about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-CTP. In some embodiments, about 25% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are ac4CTP. In some embodiments, about 25% to about 75% of C in the first and / or second RNA polynucleotides of a taRNA are ac4CTP. In some embodiments, about 40% to about 60% of C in the first and / or second RNA polynucleotides of a taRNA are ac4CTP. In some embodiments, about 50% of C in the first and / or second RNA polynucleotides of a taRNA are ac4CTP. In some embodiments, about 75% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are ac4CTP. In some embodiments, about 90% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are ac4CTP. In some embodiments, about 100% of C in the first and / or second RNA polynucleotides of a taRNA are ac4CTP. In some embodiments, wherein about 25% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 5moC. In some embodiments, about 25% to about 75% of C in the first and / or second RNA polynucleotides of a taRNA are 5moC. In some embodiments, about 40% to about 60% of C in the first and / or second RNA polynucleotides of a taRNA are 5moC. In some embodiments, about 50% of C in the first and / or second RNA polynucleotides of a taRNA are 5moC. In some embodiments, about 75% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 5moC. In some embodiments, about 75% of C in the first and / or second RNA polynucleotides of a taRNA are 5moC. In some embodiments, about 90% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 12531064.1 5moC. In some embodiments, about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 5moC. In some embodiments, 25% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are 5mC. In some embodiments, about 25% to about 75% of C in the first and / or second RNA polynucleotides of a taRNA are 5mC. In some embodiments, 40% to about 60% of C in the first and / or second RNA polynucleotides of a taRNA are 5mC. In some embodiments, about 50% of C in the first and / or second RNA polynucleotides of a taRNA are 5mC. In some embodiments, about 75% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 5mC. In some embodiments, about 90% to about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 5mC. In some embodiments, about 100% of C in the first and / or second RNA polynucleotides of a taRNA are 5mC. In some embodiments, 25% to 100% of G in the first and / or second RNA polynucleotides of a taRNA are 2'-O-methylguanosine-5'-O-triphosphate (2'OMe-GTP). In some embodiments, about 25% to about 100% of G in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-GTP. In some embodiments, about 25% to about 75% of G in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-GTP. In some embodiments, about 40% to about 60% of G in the first and / or second RNA polynucleotides of a taRNA are 2'OMe- GTP. In some embodiments, about 50% of G in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-GTP. In some embodiments, about 75% to about 100% of G in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-GTP. In some embodiments, about 90% to about 100% of G in the first and / or second RNA polynucleotides of a taRNA are 2'OMe- GTP. In some embodiments, 100% of G in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-GTP. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 5-methyluridine-5'-triphosophate (m5U), 2-thiouridine-5'- triphosphate (2-Thio-UTP), 2'-O-methyluridine-5'-triphosphase (2'OMe-UTP), 5- methoxyuridine-5'-triphosphate (5'-moUTP), 5-methoxymethyl uridine (5'-moMe-UTP), 1- methoxymethylpseudouridine (N1-methoxymethyl Ψ), pseudouridine-5'-triphosphate (Ψ), 2'-O- methylpseudouridine-5'-triphosphate (2'OMeΨTP), N1-methyl-pseudourine-5'-triphosphate (N1MeΨTP), N1-methyl-2'-O-methylpseudouridine-5'-triphosphate (N1Me2'OMeΨTP), N1- ethylpseudouridine-5'-triphosphate (N1ethylΨTP), and / or N1-methyl-pseudouridine In some embodiments, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are m5U. In some embodiments, about 25% to about 75% of U 12531064.1 in the first and / or second RNA polynucleotides of a taRNA are m5U. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are m5U. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are m5U. In some embodiments, about 60% to about 90% of U in the first and / or second RNA polynucleotides of a taRNA are m5U. In some embodiments, about 75% of U in the first and / or second RNA polynucleotides of a taRNA are m5U. In some embodiments, about 90% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are m5U. In some embodiments, about 100% of U in the first and / or second RNA polynucleotides of a taRNA are m5U. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 2-Thio-UTP. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP. In some embodiments, about 25% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP. In some embodiments, about 25% to about 40% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP. In some embodiments, about 25% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP. In some embodiments, about 60% to about 90% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP. In some embodiments, about 75% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP. In some embodiments, about 90% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP. In some embodiments, about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP. In some embodiments, about 25% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP. In some embodiments, about 60% to about 90% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP. In some embodiments, about 75% of U in the first and / or second RNA polynucleotides of a taRNA are 12531064.1 5'-moUTP. In some embodiments, about 90% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP. In some embodiments, about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP. In some embodiments, at least 95% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP. In some embodiments, at least 98% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP. In some embodiments, at least 99% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP. In some embodiments, 100% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moMe-UTP . In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1-methoxymethyl Ψ. In some embodiments, about 25% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1- methoxymethyl Ψ. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are N1-methoxymethyl Ψ. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are N1- methoxymethyl Ψ. In some embodiments, about 60% to about 90% of U in the first and / or second RNA polynucleotides of a taRNA are N1-methoxymethyl Ψ. In some embodiments, about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1- methoxymethyl Ψ. In some embodiments, about 90% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1-methoxymethyl Ψ. In some embodiments, about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1- methoxymethyl Ψ. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are Ψ. In some embodiments, about 25% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are Ψ. In some embodiments, about 25% to about 40% of U in the first and / or second RNA polynucleotides of a taRNA are Ψ. In some embodiments, about 25% of U in the first and / or second RNA polynucleotides of a taRNA are Ψ. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are Ψ. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are Ψ. In some embodiments, about 75% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are Ψ. In some embodiments, about 90% to about 100% of U in the first and / or second RNA polynucleotides of 12531064.1 a taRNA are Ψ. In some embodiments, about 100% of U in the first and / or second RNA polynucleotides of a taRNA are Ψ. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMeΨTP. In some embodiments, about 25% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMeΨTP. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMeΨTP. In some embodiments, 50% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMeΨTP. In some embodiments, about 60% to about 90% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMeΨTP. In some embodiments, 75% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMeΨTP. In some embodiments, about 90% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMeΨTP. In some embodiments, about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMeΨTP. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP. In some embodiments, about 25% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP. In some embodiments, about 25% to about 40% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP. In some embodiments, about 25% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP. In some embodiments, about 60% to about 90% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP. In some embodiments, about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP. In some embodiments, about 75% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP. In some embodiments, about 90% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP. In some embodiments, about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1Me2'OMeΨTP. In some embodiments, about 25% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1Me2'OMeΨTP. In some embodiments, about 40% to about 60% of U in the first and / or second RNA 12531064.1 polynucleotides of a taRNA are N1Me2'OMeΨTP. In some embodiments, 50% of U in the first and / or second RNA polynucleotides of a taRNA are N1Me2'OMeΨTP. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1ethylΨTP. In some embodiments, about 25% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1ethylΨTP. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are N1ethylΨTP. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are N1ethylΨTP. In some embodiments, about 75% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1ethylΨTP. In some embodiments, about 90% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1ethylΨTP. In some embodiments, about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1ethylΨTP. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are m1Ψ. In some embodiments, about 25% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are m1Ψ. In some embodiments, about 25% to about 40% of U in the first and / or second RNA polynucleotides of a taRNA are m1Ψ. In some embodiments, about 25% of U in the first and / or second RNA polynucleotides of a taRNA are m1Ψ. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are m1Ψ. In some embodiments, 50% of U in the first and / or second RNA polynucleotides of a taRNA are m1Ψ. In some embodiments, about 60% to about 90% of U in the first and / or second RNA polynucleotides of a taRNA are m1Ψ. In some embodiments, about 75% of U in the first and / or second RNA polynucleotides of a taRNA are m1Ψ. In some embodiments, about 75% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are m1Ψ. In some embodiments, about 90% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are m1Ψ. In some embodiments, about 100% of U in the first and / or second RNA polynucleotides of a taRNA are m1Ψ. In some embodiments, about 25% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 25% to about 50% of U in the first and / or second RNA polynucleotides of the same taRNA are 5'-moUTP. In some embodiments, about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 25% of U in the first and / or second RNA polynucleotides of the same taRNA are 5'-moUTP. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA 12531064.1 are N1MeΨTP and about 50% of U in the first and / or second RNA polynucleotides of the same taRNA are 5'-moUTP. In some embodiments, about 40% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 25% to about 60% of U in the first and / or second RNA polynucleotides of the same taRNA are 2'OMe-UTP. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 40% to about 60% U in the first and / or second RNA polynucleotides of the same taRNA are 2'OMe-UTP. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 50% of U in the first and / or second RNA polynucleotides of the same taRNA are 2'OMe-UTP. In some embodiments, about 60% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 25% to about 40% of U in the first and / or second RNA polynucleotides of the same taRNA are 2'OMe-UTP. In some embodiments, about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 25% of U in the first and / or second RNA polynucleotides of the same taRNA are 2'OMe-UTP. In some embodiments, about 40% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP and about 40% to about 75% of U in the first and / or second RNA polynucleotides of the same taRNA are 5'-moUTP. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP and about 40% to about 60% U in the first and / or second RNA polynucleotides of the same taRNA are 5'-moUTP. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP and about 50% of U in the first and / or second RNA polynucleotides of the same taRNA are 5'-moUTP. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 25% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are 5mC. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 40% to about 60% of C in the first and / or second RNA polynucleotides of the same taRNA are 5mC. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 50% of C in the first and / or second RNA polynucleotides of the same taRNA are 5mC. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 60% to about 90% of C in the first and / or second RNA polynucleotides of the same taRNA are 5mC. In 12531064.1 some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 75% of C in the first and / or second RNA polynucleotides of the same taRNA are 5mC. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 90% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are 5mC. In some embodiments, 50% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are 5mC. In some embodiments, about 60% to about 90% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 40% to about 60% of C in the first and / or second RNA polynucleotides of the same taRNA are 5mC. In some embodiments, about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 50% of C in the first and / or second RNA polynucleotides of the same taRNA are 5mC. In some embodiments, less than 5% (e.g., less than 4%, less than 3%, less than 2%, less than 1%) of nucleotides of the first RNA polynucleotide are modified. In some embodiments, none of nucleotides of the first RNA polynucleotide are modified. In some embodiments, about 60% to about 90% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 60% to about 90% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 75% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 60% to about 90% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 90% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 75% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 40% to about 60% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 50% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 90% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 60% to about 90% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 100% of U in the first and / or second 12531064.1 RNA polynucleotides of a taRNA are N1MeΨTP and about 75% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 90% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 90% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 100% of U in the first and / or second RNA polynucleotides of a taRNA are N1MeΨTP and about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 25% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP and about 75% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 25% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP and about 75% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP and about 90% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP and about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 60% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP and about 60% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 75% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP and about 75% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 90% to about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP and about 90% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 100% of U in the first and / or second RNA polynucleotides of a taRNA are 5'-moUTP and about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 40% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP and about 40% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 25% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe- UTP and about 75% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 40% to about 60% of U in the first and / or 12531064.1 second RNA polynucleotides of a taRNA are 2'OMe-UTP and about 90% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP and about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 25% to about 75% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP, about 25% to about 75% of U in the first and / or second RNA polynucleotides of the same taRNA are 5'-moUTP, and about 60% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP, about 40% to about 60% of U in the first and / or second RNA polynucleotides of the same taRNA are 5'-moUTP, and about 75% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 40% to about 60% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP, about 40% to about 60% of U in the first and / or second RNA polynucleotides of the same taRNA are 5'-moUTP, and about 90% to about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, about 50% of U in the first and / or second RNA polynucleotides of a taRNA are 2'OMe-UTP, about 50% of U in the first and / or second RNA polynucleotides of the same taRNA are 5'-moUTP, and about 100% of C in the first and / or second RNA polynucleotides of the same taRNA are m5C. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and at least 90% of U in the first and / or second RNA polynucleotides of the same taRNA comprise a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and at least 95% of U in the first and / or second RNA polynucleotides of the same taRNA comprise a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and at least 98% of U in the first and / or second RNA polynucleotides of the same taRNA comprise a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and at least 99% of U in the first and / or second RNA polynucleotides of the same taRNA comprise a -methyl, an -O methyl, a pseudouridine, a 12531064.1 methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and 100% of U in the first and / or second RNA polynucleotides of the same taRNA comprise a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and at least 90% of U in the first and / or second RNA polynucleotides of the same taRNA are m5U, 2-Thio-UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe- UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and at least 95% of U in the first and / or second RNA polynucleotides of the same taRNA are m5U, 2-Thio-UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and at least 98% of U in the first and / or second RNA polynucleotides of the same taRNA are m5U, 2-Thio-UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and at least 99% of U in the first and / or second RNA polynucleotides of the same taRNA are m5U, 2-Thio- UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and 100% of U in the first and / or second RNA polynucleotides of the same taRNA are m5U, 2-Thio-UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and at least 90% of U in the first and / or second RNA polynucleotides of the same taRNA are m5U, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1- methoxymethyl Ψ, N1Me2'OMeΨTP, and / or N1ethylΨTP. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and at least 95% of U in the first and / or second RNA polynucleotides of the same taRNA are m5U, 2'OMe-UTP, 5'- moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, N1Me2'OMeΨTP, and / or N1ethylΨTP. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are 12531064.1 m5C and at least 98% of U in the first and / or second RNA polynucleotides of the same taRNA are m5U, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, N1Me2'OMeΨTP, and / or N1ethylΨTP. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and at least 99% of U in the first and / or second RNA polynucleotides of the same taRNA are m5U, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1- methoxymethyl Ψ, N1Me2'OMeΨTP, and / or N1ethylΨTP. In some embodiments, 50% to 100% of C in the first and / or second RNA polynucleotides of a taRNA are m5C and 100% of U in the first and / or second RNA polynucleotides of the same taRNA are m5U, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, N1Me2'OMeΨTP, and / or N1ethylΨTP. In some embodiments, the replicase encoded by the first RNA polynucleotide of a taRNA (i.e., the replicase construct) is an alphavirus replicase. In some embodiments, the replicase is a Sindbis virus (SINV) replicase. In some embodiments, the replicase is a Semliki Forest virus (SFV) replicase. In some embodiments, the first RNA polynucleotide of a taRNA comprises a 5' UTR. In some embodiments, the first RNA polynucleotide of a taRNA comprises a human alpha-globin (HBA) 5' UTR. In some embodiments, the first RNA polynucleotide of a taRNA comprises a 5' UTR comprising the sequence set forth in SEQ ID NO: 5. In some embodiments, the first RNA polynucleotide of a taRNA comprises a 3’ UTR. In some embodiments, the first RNA polynucleotide of a taRNA comprises a HBA 3' UTR. In some embodiments, the first RNA polynucleotide of a taRNA comprises a 3' UTR comprising the sequence set forth in SEQ ID NO: 6. In some embodiments, the second RNA polynucleotide of a taRNA comprises a conserved sequence element (CSE). In some embodiments, the second RNA polynucleotide of a taRNA comprises a 5' UTR. In some embodiments, the second RNA polynucleotide of a taRNA comprises a 5' UTR comprising a CSE which can be recognized by the replicase. In some embodiments, the second RNA polynucleotide of a taRNA comprises a SINV 5' UTR. In some embodiments, the second RNA polynucleotide of a taRNA comprises a SFV 5' UTR. In some embodiments, the second RNA polynucleotide of a taRNA comprises a 3' UTR. In some embodiments, the second RNA polynucleotide of a taRNA comprises a SINV 3' UTR. In some embodiments, the second RNA polynucleotide of a taRNA comprises a SFV 3' UTR. In some embodiments, the first RNA polynucleotide of a taRNA comprises SEQ ID NO: 1 and has one or more of the chemical modifications described herein. 12531064.1 In some embodiments, the second RNA polynucleotide of a taRNA comprises any one of SEQ ID NOs: 2-4 and has one or more of the chemical modifications described herein. In some aspects, described herein are cells comprising one or more taRNAs described herein. In some aspects, described herein are methods of expressing a payload in a cell. In some embodiments, a method described herein comprises transfecting a cell with one or more of the taRNAs described herein. In some aspects, described herein are methods of expressing a payload in a subject. In some embodiments, a method described herein comprises administering to a subject one or more of the taRNAs described herein. In some embodiments, a subject is a mammal. In some embodiments, a subject is a human. BRIEF DESCRIPTION OF DRAWINGS FIG.1 is a schematic showing a self-amplifying ribonucleic acid (RNA) (saRNA) construct (top) vs a trans amplifying RNA (taRNA) construct (bottom). An saRNA construct comprises a 5' conserved sequence element (CSE), a replicase-encoding sequence, a gene of interest, and a 3' CSE, on one polynucleotide. A taRNA comprises two separate polynucleotides: a first RNA polynucleotide comprising a 5' untranslated region (UTR), a replicase-encoding sequence, and a 3' UTR; and a second RNA polynucleotide comprising a 5' CSE, a gene encoding sequence, and a 3’ CSE. FIG.2 shows GFP expression in BHK-21 cells treated with chemically modified taRNAs having a 5'-HBA-UTR-SFV replicase-3’-HBA-UTR replicase construct (SEQ ID NO: 1) and a 5'-SINV-UTR-GFP-3'- SINV-UTR trRNA (SEQ ID NO: 2). BHK-21 cells were treated with 25ng of the replicase construct and 5ng of a trRNA having the following chemically modified uridine (U) (from left to right): unmodified U (UTP); 50% m1Ψ; 50% Ψ; or 50% 2'OMe-UTP. FIG.3 shows expression of GFP in 3T3 fibroblast cells treated with chemically modified taRNAs having a 5'-HBA-UTR-SFV replicase-3’-HBA-UTR replicase construct (SEQ ID NO: 1) and a T3A-5'-SINV-UTR-GFP-3'-SFV-UTR trRNA (SEQ ID NO: 3). GFP expression was measured (relative fluorescence units; RFU) in 3T3 fibroblasts treated with 25ng of the replicase construct and 5ng of trRNA having the following chemically modified U (from left to right) unmodified U (UTP); 50% m1Ψ; 100% m1Ψ; or 50% 2'OMe-UTP. Bars represent standard error. 12531064.1 FIGs.4A-4C show effects of chemical modification on taRNA-mediated payload expression. FIG.4A shows expression of GFP in BHK-21 cells transfected with or without chemically modified taRNA having a 5'-HBA-UTR-SFV replicase-3’-HBA-UTR replicase (SEQ ID NO: 1) and a T3A-5'-SINV-UTR-GFP-3'-SFV-UTR trRNA (SEQ ID NO: 3). GFP expression was measured (RFU) in BHK-21 cells treated with: no treatment; water; a SFV replicase construct (“replicase”) only; an unmodified trRNA; and a replicase with: trRNA having 50% of U replaced with Ψ; trRNA having 100% of U replaced with Ψ; taRNA having 50% of U replaced with m1Ψ; trRNA having 100% of U replaced with m1Ψ; trRNA having 50% of U replaced with m6A; trRNA having 100% of A replaced with m6A; trRNA having 50% of C replaced with m5C; trRNA having 100% of C replaced with m5C; trRNA having 50% of A replaced with 2'OMe-ATP; trRNA having 100% of A replaced with 2'OMe-ATP; trRNA having 50% of G replaced with 2'OMe-GTP; trRNA having 100% of G replaced with 2'OMe-GTP; trRNA having 50% of C replaced with 2'OMe-CTP; trRNA having 100% of G replaced with 2'OMe-CTP; trRNA having 50% of U replaced with 2'OMe-UTP; trRNA having 100% of U replaced with 2'OMe-UTP; and unmodified mRNA encoding GFP. FIG.4B shows expression of SEAP in BHK-21 cells transfected with taRNA having a 5'-HBA-UTR-SFV replicase-3’-HBA-UTR replicase construct (SEQ ID NO: 1) and a T3A-5'- SINV-UTR-SEAP-3'-SFV-UTR trRNA (SEQ ID NO: 4). SEAP expression was measured (RFU) in BHK-21 cells treated with: no treatment; water; the replicase construct (“replicase”) only; the unmodified trRNA and an unmodified mRNA encoding SEAP; the unmodified taRNA (replicase and trRNA); the replicase construct and an unmodified mRNA encoding SEAP; and the replicase construct and the trRNA having: 50% of U replaced with N1MeΨTP; trRNA having 75% of U replaced with N1MeΨTP; trRNA having 100% of U replaced with N1MeΨTP; trRNA having 50% of U replaced with 2’OMe-UTP; a trRNA having 75% of U replaced with 2’OMe-UTP; a trRNA having 50%of U replaced with 2’OMe-UTP and 50% of U replaced with N1MeΨTP; a trRNA having 25%of U replaced with 2’OMe-UTP and 75% of U replaced with N1MeΨTP; a trRNA having 100% m5C; a trRNA having 50% of U replaced with N1MeΨTP and 50% of C replaced with m5C; a trRNA having 50% of U replaced with N1MeΨTP and 75% of C replaced with m5C; a trRNA having 50% of U replaced with N1MeΨTP and 100% of C replaced with m m5C; a trRNA having 75% of U replaced with N1MeΨTP and 50% of C replaced with m5C; a trRNA having 75% of U replaced with N1MeΨTP and 75% of C replaced with m5C; a trRNA having 75% of U replaced with N1MeΨTP and 100% of C replaced with m5C; a trRNA having 100% of U replaced with N1MeΨTP and 50% of C replaced with m5C; a trRNA having 12531064.1 100% of U replaced with N1MeΨTP and 75% of C replaced with m5C; a trRNA having 100% of U replaced with N1MeΨTP and 100% of C replaced with m5C; a trRNA having 50% of U replaced with 5'-moUTP; a trRNA having 75% of U replaced with 5'-moUTP; a trRNA having 100% of U replaced with 5'-moUTP; a trRNA having 50% of U replaced with N1MeΨTP and 50% of U replaced with 5'-moUTP; and a trRNA having 75% of U replaced with N1MeΨTP and 25% of U replaced with 5'-moUTP. Expression was measured at 6 hours (black) or 24 hours (white) post-transfection. FIG.4C shows expression of SEAP in RAW cells transfected with or without chemically modified taRNA comprising an SFV replicase construct and a T3A-5'-SINV-UTR- SEAP-3'-SFV-UTR trRNA. SEAP expression was measured (RFU) in BHK-21 cells treated with: no treatment; water; a SFV replicase construct (“replicase”) only; an unmodified trRNA; an mRNA encoding SEAP and having N1MeΨTP; an unmodified taRNA (replicase and taRNA); a replicase construct and an unmodified mRNA encoding SEAP; and a replicase with: trRNA having 50% of U replaced with N1MeΨTP; trRNA having 75% of U replaced with N1MeΨTP; trRNA having 100% of U replaced with N1MeΨTP; trRNA having 50% of U replaced with 2’OMe-UTP; a trRNA having 75% of U replaced with 2’OMe-UTP; a trRNA having 50% of U replaced with 2’OMe-UTP and 50% of U replaced with N1MeΨTP; a trRNA having 25% of U replaced with 2’OMe-UTP and 75% of U replaced with N1MeΨTP; a trRNA having 100% m5C; a trRNA having 50% of U replaced with N1MeΨTP and 50% of C replaced with m5C; a trRNA having 50% of U replaced with N1MeΨTP and 75% of C replaced with m5C; a trRNA having 50% of U replaced with N1MeΨTP and 100% of C replaced with m5C; a trRNA having 75% of U replaced with N1MeΨTP and 50% of C replaced with m5C; a trRNA having 75% of U replaced with N1MeΨTP and 75% of C replaced with m5C; a trRNA having 75% of U replaced with N1MeΨTP and 100% of C replaced with m5C; a trRNA having 100% of U replaced with N1MeΨTP and 50% of C replaced with m5C; a trRNA having 100% of U replaced with N1MeΨTP and 75% of C replaced with m5C; a trRNA having 100% of U replaced with N1MeΨTP and 100% of C replaced with m5C; a trRNA having 50% of U replaced with 5'- moUTP; a trRNA having 75% of U replaced with 5'-moUTP; a trRNA having 100% of U replaced with 5'-moUTP; a trRNA having 50% of U replaced with N1MeΨTP and 50% of U replaced with 5'-moUTP; and a trRNA having 75% of U replaced with N1MeΨTP and 25% of U replaced with 5'-moUTP. Expression was measured at 6 hours (black) or 24 hours (white) post- transfection. 12531064.1 FIG.5 shows immunogenic responses of A549 cells transfected with taRNA comprising a 5'-HBA-UTR-SFV replicase-3’-HBA-UTR replicase construct consisting of SEQ ID NO: 1 and a T3A-5'-SINV-UTR-SEAP-3'-SFV-UTR trRNA consisting of SEQ ID NO: 4. A549 cells were treated with chemically modified trRNAs having U modified as follows: unmodified U (UTP); 50% of U replaced with m1Ψ; 100% of U replaced with m1Ψ; or 50% of U replaced with 2'OMe-UTP. Fold-induction of ISG54 in treated cells, relative to untreated cells, is shown for four doses (ng / well) of each chemically modified taRNA. Bars represent standard error. FIG.6 shows SEAP expression (LU) vs IFNβ induction (pg / mL) in human BJ fibroblasts transfected with taRNA comprising a 5'-HBA-UTR-SFV replicase-3’-HBA-UTR replicase construct (SEQ ID NO: 1) and chemically modified 5'-oeE3L-CVB3-SEAP-3'-SFV- UTR trRNA (SEQ ID NO: 7). BJ cells were treated with chemically modified trRNAs having 50% or 100% modified U; or 50% or 100% modified U and 100% modified C. trRNA were chemically modified as follows: unmodified control (UTP); unmodified oeSTR (SEQ ID NO: 8); 100% of C replaced with m5C and 50% of U replaced with 5'-moUTP; 100% of C replaced with m5C, 50% of U replaced with 5'-moUTP, and 50% of U replaced with 2'OMe-UTP (2'OMe- U); 100% of C replaced with m5C and 50% of U replaced with 2'OMe-U; 100% of C replaced with m5C and 100% of U replaced with 5'-moUTP; 50% of U replaced with 5'-moUTP and 50% of U replaced with 2'OMe-U. FIGs.7A-7C show chemical structures for Adenine nucleotides having chemical modifications. FIG.7A shows the chemical structure of 2'-O-methyl-adenosine-5'- triphosphase(2'OMe-ATP). FIG.7B shows the chemical structure of N6-methyladenosine-5'- triphosphate (m6ATP). FIG.7C shows the chemical structure of 2'-O-methyl-N6- methyladenosine-5'-triphosphate (2'OMe-m6ATP). FIGs.8A-8E show chemical structures for Cytidine nucleotides having chemical modifications. FIG.8A shows the chemical structure of 5-methylcytidine-5'-triphosphate (m5C). FIG.8B shows the chemical structure of 2'-O-methylcytidine-5'-triphosphate (2'OMe-CTP). FIG.8C shows the chemical structure of N4-acetylcytidine triphosphate (ac4CTP). FIG.8D shows the chemical structure of 5-methoxycytidine (5moC). FIG.8E shows the chemical structure of 5-methylcytosine (5mC). FIG.9 shows the chemical structure of 2'-O-methylguanosine-5'-O-triphosphate (2'OMe-GTP). FIGs.10A-10L show chemical structures for Uridine nucleotides having chemical modifications. FIG.10A shows the chemical structure of 5-methyluridine-5'-triphosophate 12531064.1 (m5U). FIG.10B shows the chemical structure of 2-thiouridine-5'-triphosphate (2-Thio-UTP). FIG.10C shows the chemical structure of 2'-O-methyluridine-5'-triphosphase (2'OMe-UTP). FIG.10D shows the chemical structure of 5-methoxyuridine-5'-triphosphate (5'-moUTP). FIG. 10E shows the chemical structure of 5-methoxymethyl uridine (5'-moMe-UTP). FIG.10F shows the chemical structure of 1-methoxymethylpseudouridine (N1-methoxymethyl Ψ). FIG. 10G shows the chemical structure of pseudouridine-5'-triphosphate (Ψ). FIG.10H shows the chemical structure of 2'-O-methylpseudouridine-5'-triphosphate (2'OMeΨTP). FIG.10I shows the chemical structure of N1-methyl-pseudourine-5'-triphosphate (N1MeΨTP). FIG.10J shows the chemical structure of N1-methyl-2'-O-methylpseudouridine-5'-triphosphate (N1Me2'OMeΨTP). FIG.10K shows the chemical structure of N1-ethylpseudouridine-5'- triphosphate (N1ethylΨTP). FIG.10L shows the chemical structure of N1-methylpseudouridine (m1Ψ). DETAILED DESCRIPTION In some aspects, this disclosure describes a trans-amplifying ribonucleic acid (RNA) (taRNA) comprising a first RNA polynucleotide comprising a nucleic acid encoding a replicase, and a second RNA polynucleotide comprising a nucleic acid encoding a payload; wherein about 25% to about 100% of adenine (A), cytidine (C), guanine (G), and / or uridine (U) in the first RNA polynucleotide and / or the second RNA polynucleotide comprise a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. A “trans-amplifying RNA,” hereinafter referred to as “taRNA,” comprises a first and second RNA polynucleotide, wherein the first RNA polynucleotide encodes a replicase, the second RNA polynucleotide encodes a payload, and wherein the second RNA polynucleotide can be replicated by the encoded replicase in trans. The first and second RNA polynucleotides of a taRNA are separate molecules (i.e., not a single continuous strand of RNA). The terms “replicase construct” and “trans replicon” (trRNA) construct are used synonymously herein to refer to the first and second RNA polynucleotides of a taRNA, respectively. As used herein, a “construct” refers to an artificial (i.e., not naturally occurring) polynucleotide. The “replicase construct” (i.e., the first RNA polynucleotide) refers to mRNA which comprises nucleic acids encoding a replicase and does not comprise nucleic acids encoding the payload. In some embodiments, the replicase construct is a non-replicating mRNA. As used herein, the term “non-replicating mRNA” refers to an mRNA which is processed for translation 12531064.1 into a gene product or else degraded, and which does not self-replicate. Once introduced to an environment comprising translational machinery (such as a cell), replicase constructs can be translated to generate the encoded replicase. A “replicase” is an RNA-dependent RNA polymerase capable of transcribing (i.e., reading) an RNA template to produce an RNA (e.g., trRNA). A replicase construct may encode a modified replicase from an RNA virus, for example, an alphavirus. The term “alphavirus” refers to an RNA virus belonging to the Togaviridae family. In some embodiments, the alphavirus comprises a single-stranded RNA genome encoding at least nsP1, nsP2, nsP3, nsP4, E1, E2, E3, 6K / TF and capsid proteins. In some embodiments, a replicase construct of a taRNA encodes a replicase derived from a Semliki forest virus (SFV) (SFV replicase). In some embodiments, a replicase construct of a taRNA encodes a replicase derived from a Sindbis virus (SINV) (SINV replicase). In some embodiments, a taRNA comprises a replicase construct encoding an alphavirus replicase. Typically, an alphaviral replicase comprises a complex formed by the non-structural proteins nsP1, nsP2, nsP3, and nsP4. Once expressed, alphaviral replicase may interact with a RNA polynucleotide comprising one or more conserved sequence elements and generate mirrored copies of it, which can be subsequently translated. A “conserved sequence element,” hereinafter referred to as “CSE,” refers to a recognition site for an alphavirus replicase. Typically, a CSE functions as a core promoter or enhancer for initiation of replication of a downstream sequence, such that a 5'-CSE may initiate synthesis of a plus-strand and a 3'-CSE may initiate synthesis of a minus-strand. A polynucleotide may comprise one or more 5'-CSEs and / or 3'-CSEs. In some embodiments, a CSE forms one or more secondary structure, such as one or more stem-loops. Non-limiting examples of CSEs include CSE1, CSE2, CSE3, CSE4, and variants or derivatives thereof. Replicase constructs necessarily do not comprise a CSE; thus, once the replicase of a replicase construct is translated, the encoded replicase cannot replicate the replicase construct. In some embodiments, a replicase construct comprises one or more untranslated regions. An “untranslated region,,” hereinafter referred to as “UTR,” is a region in a polynucleotide which may be transcribed, but is not translated into a gene product. UTRs may act as stabilizing elements and / or provide regulation of transcription of a gene or transgene. Typically, UTRs are found upstream and / or downstream of a gene or transgene. A UTR located directly upstream of a start codon operably linked to a gene or transgene is referred to herein as a 5'-UTR. As a skilled artisan will understand, 5'-UTRs may comprise sequence elements which play roles in regulation of expression (e.g., Kozak sequences) or structural elements which alter stability of the molecule 12531064.1 (e.g., 5' cap structures). A UTR located directly downstream of a stop codon operably linked to a gene or transgene is referred to herein as a 3'-UTR.3'-UTRs may comprise structural elements which alter the stability of a construct and / or provide transcriptional control, including, but not limited to AU-rich elements and polyA tails. A variety of 5'-UTRs and a 3'-UTRs are known to those of ordinary skill in the art. UTRs may be naturally occurring or synthetic. In some embodiments, a polynucleotide comprises a 5'-UTR and / or a 3'-UTR. In some embodiments, a replicase construct comprises a 5'-UTR. In some embodiments, a replicase construct comprises a 3'-UTR. In some embodiments, a replicase construct comprises a 5'-UTR and a 3'-UTR. In some embodiments, a replicase construct comprises a 5'-UTR derived from human alpha-globin (5'- HBA-UTR). An exemplary 5'-HBA-UTR is provided in SEQ ID NO: 5. In some embodiments, a replicase construct comprises a 3'-UTR derived from human alpha-globin (3'-HBA-UTR). An exemplary 5'-HBA-UTR is provided in SEQ ID NO: 6. In some embodiments, a replicase construct comprises a 5'-HBA-UTR and a 3'-HBA-UTR. In some embodiments, a replicase construct comprises a 5'-HBA-UTR, a Semliki Forest Virus replicase-encoding sequence, and a 3'-HBA-UTR (5'-HBA-UTR-SFV replicase-3'-HBA-UTR). An exemplary 5'-HBA-UTR-SFV replicase-3'-HBA-UTR construct is provided in SEQ ID NO: 1. The term “trans replicon construct” (i.e., second RNA polynucleotide), hereinafter referred to as “trRNA,” refers to an RNA construct capable of being replicated by a replicase of a taRNA. A trRNA comprises at least a payload-encoding sequence and one or more CSEs. In some embodiments, a trRNA comprises a nucleic acid payload or a nucleic acid encoding a payload, and one or more CSEs. The trRNA does not comprise the replicase that amplifies the trRNA. As used herein, a “payload” refers to one or more gene products of interest for delivery to or expression by an organism. A payload may be a functional nucleic acid (e.g., RNA), a protein, a peptide or protein fragment, or a fusion protein. In some embodiments, a payload is a selectable marker. As used herein, a “selectable marker” is a peptide or protein that can be used to screen cells by artificial selection. Non-limiting examples of selectable markers include antibiotic resistance proteins (e.g., ampicillin, puromycin) and negative selection markers (e.g., thymidine kinase). In some embodiments, a payload is a reporter. A “reporter” is a peptide or protein which alters the appearance of a cell such that cells can be visually or optically screened for presence or absence of the peptide or protein. In some embodiments, a reporter is an enzyme which alters the appearance of a cell, such as beta-galactosidase. In some embodiments, a reporter is a peptide or peptide fragment (e.g., secreted embryonic alkaline phosphatase (SEAP)) which can be detected in combination with additional reagents (e.g., assay-specific media). In 12531064.1 some embodiments, a reporter is a fluorophore, such as, but not limited to, green fluorescent protein (GFP), red fluorescent protein (RFP), blue fluorescent protein (BFP), yellow fluorescent protein (YFP), or any derivative thereof. In some embodiments, a payload is “therapeutic payload,” here referring to a gene product useful for treating or preventing a disease or disorder. In some embodiments, a therapeutic payload knocks down, knocks in, increases, inhibits, or otherwise modulates gene expression. In some embodiments, a therapeutic payload replaces or edits an endogenous gene or gene product. In some embodiments, a therapeutic payload is a nucleic acid payload or a “functional RNA.” Non-limiting examples of functional RNA include short hairpin RNA (shRNA), microRNA (miRNA), artificial microRNA (amiRNA), small interfering RNA (siRNA), or circular RNA (circRNA). In some embodiments, a therapeutic payload is a protein. A therapeutic protein may replace or interfere with activity of deficient or absent endogenous proteins; augment activity of existing metabolic or synthetic pathways; provide a novel function or activity; or interfere with the activity of a pathogen or toxic molecule. Non-limiting examples of therapeutic proteins suitable for use as payloads include membrane proteins, membrane- associated proteins, secreted proteins, intracellular proteins, immunomodulatory proteins, antigens, antibodies, or fragments thereof. The simultaneous expression of a replicase and presence of a trRNA in a cell can thus result in amplification of the trRNA and its encoded payload. trRNA constructs comprise one or more CSEs. In some embodiments, a trRNA comprises one or more CSEs, wherein the CSEs are present in a payload-encoding sequence. In some embodiments, a trRNA comprises one or more CSEs, wherein the CSEs are present in one or more UTRs. In some embodiments, a trRNA comprises a 5'-UTR having one or more CSEs. In some embodiments, a trRNA comprises a 3'-UTR having one or more CSEs. In some embodiments, a trRNA comprises a 5'-UTR having one or more CSEs, a payload-encoding sequence, and a 3'-UTR having one or more CSEs. In some embodiments, a trRNA comprises a 5'-UTR having one or more CSEs, a payload-encoding sequence having one or more CSEs, and a 3’-UTR having one or more CSEs. In some embodiments, a trRNA comprises UTRs having one or more CSEs, wherein the UTRs are derived from one or more alphaviruses. A skilled artisan will appreciate that UTRs derived from alphaviruses comprise one or more CSEs unless stated otherwise. In some embodiments, a trRNA comprises a 5'-UTR derived from a first alphavirus and a 3'-UTR derived from a second alphavirus. In some embodiments, a trRNA comprises a 3'-UTR comprising one or more repeat sequence elements (RSE). 12531064.1 In some embodiments, a trRNA comprises a 5'-UTR and / or 3'-UTR derived from a Semliki Forest virus (SFV), hereinafter referred to as a “SFV-UTR”. In some embodiments, a trRNA comprises a 5'-UTR and / or 3'-UTR derived from a Sindbis virus (SINV), hereinafter referred to as a “SINV-UTR”. In some embodiments, a trRNA comprises a 5'-UTR and 3'-UTR from the same virus. Non-limiting examples include a trRNA comprising a 5'-UTR derived from a SINV (5'-SINV-UTR), and a 3'-UTR derived from a SINV (3'-SINV-UTR) or a trRNA comprising a 5'-UTR derived from a SFV (5'-SFV-UTR), and a 3'-UTR derived from a SFV (3'- SFV-UTR). In some embodiments, a trRNA comprises a 5'-UTR and 3'-UTR from different viruses. Non-limiting examples include a trRNA comprising a 5'-SINV-UTR and a 3'-SFV- UTR. In some embodiments, a trRNA comprises a 5'-SINV-UTR, a payload-encoding sequence, and a 3'-SINV-UTR. In some embodiments, a trRNA comprises a 5'-SFV-UTR, a payload-encoding sequence, and a 3'-SFV-UTR. In some embodiments, a trRNA comprises a 5'- SINV-UTR, a payload-encoding sequence, and a 3'-SFV-UTR. In some embodiments, a trRNA comprises a 5'-SINV-UTR, a payload-encoding sequence comprising a CSE, and a 3'-SINV- UTR. In some embodiments, a trRNA comprises a 5'-SFV-UTR, a payload-encoding sequence comprising a CSE, and a 3'-SFV-UTR. In some embodiments, a trRNA comprises a 5'-SINV- UTR, a payload-encoding sequence comprising a CSE, and a 3'-SFV-UTR. In some embodiments, a trRNA is a trRNA having the sequence set forth in any one of SEQ ID NO: 2-4. In some embodiments, a taRNA comprises a compatible replicase construct and trRNA construct. A replicase construct and trRNA construct are considered “compatible” when a trRNA comprises a CSE to which the replicase encoded by the replicase construct can bind, such that the trans replicon is replicated. In some embodiments, a compatible replicase construct and CSE are derived from the same alphavirus. In some embodiments, a replicase derived from a SFV is capable of binding to a trRNA comprising a CSE from an SFV. In some embodiments, a replicase derived from a SINV is capable of binding to a trRNA comprising a CSE from an SINV. In some embodiments, a compatible replicase construct and CSE are derived from different alphaviruses. In some embodiments, a replicase derived from a SFV is capable of binding to a trRNA comprising a CSE from a SINV. In some embodiments, a replicase derived from a SINV is capable of binding to a trRNA comprising a CSE from an SFV. In some embodiments, a taRNA comprises a replicase construct having the sequence of SEQ ID NOs: 1 and comprises any of the chemical modifications described herein. 12531064.1 In some embodiments, a taRNA comprises a trRNA construct having the sequence of any one of SEQ ID NOs: 2-4 and comprises any of the chemical modifications described herein. In some embodiments, a taRNA comprises replicase constructs and trRNA constructs in about equal amounts (e.g., a molar ratio of replicase construct:trRNA of about 1:1). In some embodiments, a taRNA comprises more replicase constructs than trRNA (e.g., a molar ratio of replicase construct:trRNA construct of about 5:1, 10:1, 100:1, 1000:1, or more). Chemical Modifications In some embodiments, the first RNA polynucleotide (i.e., the replicase construct) and / or the second RNA polynucleotide (i.e., the trRNA) of a taRNA comprise one or more chemically modified A, T, G and / or C nucleotides. In some embodiments, the chemically modified nucleotides comprise a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an - acetyl, a -thio, and / or an -ethyl chemical modification. As used herein, a “polynucleotide” is a polymer of nucleotides (e.g., polynucleotide monomers). The skilled artisan will understand that unmodified RNA polynucleotides typically comprise combinations of adenine (A), cytidine (C), guanosine (G), and uridine (U). Each type of nucleotide of a polynucleotide may be unmodified or chemically modified as described herein. Chemical modifications may be made to any nucleotide which is generally known or recognized in the art (e.g., A, C, G, thymidine (T), and U). Any region of a nucleotide or polynucleotide may be modified; for example, at sugars, nucleobases, and / or glycosidic linkages. In some embodiments, chemical modifications are located in the sugar of a nucleotide, for example, at the 2' position of a ribose or deoxyribose. Chemical modifications to a sugar of a nucleotide may comprise, for example, the addition of a -methyl or an -O-methyl (i.e., methoxy) group. In some embodiments, chemical modifications are located on the nucleobase. Chemical modifications to a nucleobase may comprise, for example, addition of or replacement of an oxygen with a -methyl, -acetyl, -ethyl, or -thio group in a nucleobase. In some embodiments, chemical modifications are located in the glycosidic linkages of a nucleobase to a ribose. Chemical modifications to glycosidic linkages may comprise, for example, changing a nitrogen- carbon bond to a carbon-carbon bond, such that a uridine is transformed into a pseudouridine. The skilled artisan will appreciate that chemically modified nucleotides may comprise one or more modifications to sugars, nucleobases, glycosidic linkages, or any combination thereof. In some embodiments, a certain amount of one or more types of nucleotides (e.g., A, C, G, U) in an RNA polynucleotide are chemically modified (e.g., about 25% to about 100% of C 12531064.1 are chemically modified), and the remaining types of nucleotides are not chemically modified (e.g., 100% of A, 100% of G, 100% of U, and 0% to about 75% of C are not chemically modified). In some embodiments, a certain amount of two or more types of nucleotides in an RNA polynucleotide are chemically modified (e.g., about 25% to about 100% of C are chemically modified and about 25% to about 100% of U are chemically modified), and the remaining types of nucleotides are not chemically modified (e.g., 100% of A and 100% of G are not chemically modified). In some embodiments, a certain amount of three or more types of nucleotides in an RNA polynucleotide are chemically modified (e.g., about 25% to about 100% of C are chemically modified, about 25% to about 100% of U are chemically modified, and about 100% of A are chemically modified), and the remaining nucleotide type is not chemically modified (e.g., 100% of G are not chemically modified). In some embodiments, a certain amount of each nucleotide in an RNA polynucleotide is chemically modified (e.g., about 25% to about 100% of C are chemically modified, about 25% to about 100% of U are chemically modified, about 100% of A are chemically modified, and about 100% of G are chemically modified). Chemically modified nucleotides may be synthesized using any method generally known to those of skill in the art, for example chemical synthesis, enzymatic synthesis, or recombination. Chemically modified nucleotides may be introduced during synthesis or post- synthesis of polynucleotides, such that the resulting polynucleotides comprise one or more modified nucleotides. Base pairings between chemically modified nucleotides encompasses not only the standard adenosine-thymine, adenosine-uracil, or guanosine-cytosine base pairs, but also pairings formed between unmodified nucleotides and / or modified nucleotides comprising non-standard or otherwise modified bases. In some aspects, this disclosure describes a taRNA comprising a first RNA polynucleotide (i.e., replicase construct) and a second RNA polynucleotide (i.e., trRNA), wherein about 25% to about 100% of A, C, G, and / or U in the first RNA polynucleotide (i.e., replicase construct) and / or second RNA polynucleotide (i.e., trRNA) are chemically modified. In some aspects, this disclosure describes a taRNA comprising a replicase construct and a trRNA, wherein about 25% to about 100% of A, C, G, and / or U in the first RNA polynucleotide (i.e., replicase construct) are chemically modified. In some aspects, this disclosure describes a taRNA comprising a replicase construct and a trRNA, wherein about 25% to about 100% of A, C, G, and / or U in the second RNA polynucleotide (i.e., trRNA) are chemically modified. 12531064.1 As used herein, the term “about” means approximately. In the context of numerical ranges, the term “about” refers to ±5% of the numerical values cited. For example, “about 25% to about 75%” should be understood to include any value between 25% and 75% (inclusive), but also any value between 20-25% and 75-80%. About does not refer to percentages that are above 100% (e.g., above 100% of a chemical modification). A skilled artisan will understand that when a polynucleotide is described as comprising a percent range of a chemically modified nucleotide, this percentage is relative to the total amount of the equivalent unmodified nucleotide. For example, an unmodified RNA having a sequence comprising 25% U may be chemically modified to comprise “about 50% pseudouridine,” such that 50% of the U are replaced with pseudouridine; the resulting chemically modified RNA would thus comprise about 12.5% pseudouridine. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of A, C, G, and / or U in the first RNA polynucleotide (i.e., replicase construct) and / or in the second RNA polynucleotide (i.e., trRNA) comprise: a -methyl, an -O methyl, a pseudouridine, a methyl- pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some aspects, this disclosure describes taRNA wherein about 25 to 100% of the A, C, G, and / or U in the first RNA polynucleotide (i.e., replicase construct) and the second RNA polynucleotide (i.e., trRNA) are 2'-O-methyl-adenosine-5'-triphosphase(2'OMe-ATP), N6- methyladenosine-5'-triphosphate (m6ATP), 2'-O-methyl-N6-methyladenosine-5'-triphosphate (2'OMe-m6ATP), 5-methylcytidine-5'-triphosphate (m5C), 2'-O-methylcytidine-5'-triphosphate (2'OMe-CTP), N4-acetylcytidine triphosphate (ac4CTP), 5-methoxycytidine (5moC), 5- methylcytosine (5mC), 2'-O-methylguanosine-5'-O-triphosphate (2'OMe-GTP), 5- methyluridine-5'-triphosophate (m5U), 2-thiouridine-5'-triphosphate (2-Thio-UTP), 2'-O- methyluridine-5'-triphosphase (2'OMe-UTP), 5-methoxyuridine-5'-triphosphate (5'-moUTP), 5- methoxymethyl uridine (5'-moMe-UTP), 1-methoxymethylpseudouridine (N1-methoxymethyl Ψ), pseudouridine-5'-triphosphate (Ψ), 2'-O-methylpseudouridine-5'-triphosphate (2'OMeΨTP), N1-methyl-pseudourine-5'-triphosphate (N1MeΨTP), N1-methyl-2'-O-methylpseudouridine-5'- triphosphate (N1Me2'OMeΨTP), N1-ethylpseudouridine-5'-triphosphate (N1ethylΨTP), and / or N1-methyl-pseudouridine (m1Ψ). In some aspects, this disclosure describes taRNA wherein about 25 to 100% of the A, C, G, and / or U in the first RNA polynucleotide (i.e., replicase construct) are 2'OMe-ATP, m6ATP, 2'OMe-m6ATP, m5C, 2'OMe-CTP, ac4CTP, 5moC, 5mC, 2'OMe-GTP, m5U, 2-Thio-UTP, 12531064.1 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. JIn some aspects, this disclosure describes taRNA wherein about 25 to 100% of the A, C, G, and / or U in the second RNA polynucleotide (i.e., trRNA) are 2'OMe-ATP, m6ATP, 2'OMe- m6ATP, m5C, 2'OMe-CTP, ac4CTP, 5moC, 5mC, 2'OMe-GTP, m5U, 2-Thio-UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ . Chemical Modifications of Adenine (A) In some aspects, this disclosure describes a taRNA comprising a replicase construct and a trRNA wherein about 25% to 100% of A in the first RNA polynucleotide (i.e., replicase construct) and / or the second RNA polynucleotide (i.e., trRNA) are 2'-O-methyl-adenosine-5'- triphosphase (2'OMe-ATP), N6-methyladenosine-5'-triphosphate (m6ATP), and / or 2'-O-methyl- N6-methyladenosine-5'-triphosphate (2'OMe-m6ATP). In some aspects, this disclosure describes a taRNA comprising a first RNA polynucleotide (i.e., replicase construct) and a second RNA polynucleotide (trRNA) wherein about 25% to 100% of A in the first RNA polynucleotide (i.e., replicase construct) are 2'OMe- ATP, m6ATP, 2'-and / or 2'OMe-m6ATP. In some aspects, this disclosure describes a taRNA comprising a first RNA polynucleotide (i.e., replicase construct) and a second RNA polynucleotide (i.e., trRNA) wherein about 25% to 100% of A in the trRNA are 2'OMe-ATP, m6ATP, 2'-and / or 2'OMe-m6ATP. 2'-O-methyl-adenosine-5'-triphosphase (2'OMe-ATP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of A in the taRNA (i.e., about 25% to about 100% of total A in the replicase construct and the trRNA) are 2'OMe-ATP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of A in a taRNA are 2'OMe-ATP. In some embodiments, about 50%, about 75%, or about 100% of A in a taRNA are 2'OMe-ATP. In some embodiments, about 50% of A in a taRNA are 2'OMe-ATP. In some embodiments, about 75% of A in a taRNA are 2'OMe-ATP. In some embodiments, about 100% of A in a taRNA are 2'OMe- ATP. In some embodiments, 50% of A in a taRNA are 2'OMe-ATP. In some embodiments, 75% of A in a taRNA are 2'OMe-ATP. In some embodiments, 100% of A in a taRNA are 2'OMe-ATP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of A in the replicase construct are 2'OMe-ATP. In some embodiments, about 25% to about 75%, 12531064.1 about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of A in the replicase construct are 2'OMe-ATP. In some embodiments, about 50%, about 75%, or about 100% of A in the replicase construct are 2'OMe-ATP. In some embodiments, about 50% of A in the replicase construct are 2'OMe-ATP. In some embodiments, about 75% of A in the replicase construct are 2'OMe-ATP. In some embodiments, about 100% of A in the replicase construct are 2'OMe-ATP. In some embodiments, 50% of A in the replicase construct are 2'OMe-ATP. In some embodiments, 75% of A in the replicase construct are 2'OMe-ATP. In some embodiments, 100% of A in the replicase construct are 2'OMe-ATP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of A in the trRNA are 2'OMe-ATP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of A in the trRNA are 2'OMe- ATP. In some embodiments, about 50%, about 75%, or about 100% of A in the trRNA are 2'OMe-ATP. In some embodiments, about 50% of A in the trRNA are 2'OMe-ATP. In some embodiments, about 75% of A in the trRNA are 2'OMe-ATP. In some embodiments, about 100% of A in the trRNA are 2'OMe-ATP. In some embodiments, 50% of A in the trRNA are 2'OMe-ATP. In some embodiments, 75% of A in the trRNA are 2'OMe-ATP. In some embodiments, 100% of A in the trRNA are 2'OMe-ATP. N6-methyladenosine-5'-triphosphate (m6ATP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of A in the taRNA (i.e., about 25% to about 100% of total A in the replicase construct and the trRNA) are m6ATP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of A in a taRNA are m6ATP. In some embodiments, about 50% or about 100% of A in a taRNA are m6ATP. In some embodiments, about 50% of A in a taRNA are m6ATP. In some embodiments, about 100% of A in a taRNA are m6ATP. In some embodiments, 50% of A in a taRNA are m6ATP. In some embodiments, 100% of A in a taRNA are m6ATP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of A in the replicase construct are m6ATP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of A in the replicase construct are m6ATP. In some embodiments, about 50% or about 100% of A in the replicase construct are m6ATP. In some embodiments, about 50% of A in the replicase construct are m6ATP. In some embodiments, about 100% of A in the replicase construct are m6ATP. In some 12531064.1 embodiments, 50% of A in the replicase construct are m6ATP. In some embodiments, 100% of A in the replicase construct are m6ATP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of A in the trRNA are m6ATP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of A in the trRNA are m6ATP. In some embodiments, about 50% or about 100% of A in the trRNA are m6ATP. In some embodiments, about 50% of A in the trRNA are m6ATP. In some embodiments, about 100% of A in a trRNA are m6ATP. In some embodiments, 50% of A in the trRNA are m6ATP. In some embodiments, 100% of A in the trRNA are m6ATP. 2'-O-methyl-N6-methyladenosine-5'-triphosphate (2'OMe-m6ATP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of A in the taRNA (i.e., about 25% to about 100% of total A in the replicase construct and the trRNA) are 2'OMe-m6ATP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of A in a taRNA are 2'OMe-m6ATP. In some embodiments, about 50% or about 100% of A in a taRNA are 2'OMe-m6ATP. In some embodiments, about 50% of A in a taRNA are 2'OMe-m6ATP. In some embodiments, about 100% of A in a taRNA are 2'OMe-m6ATP. In some embodiments, 50% of A in a taRNA are 2'OMe-m6ATP. In some embodiments, 100% of A in a taRNA are 2'OMe-m6ATP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of A in the replicase construct are 2'OMe-m6ATP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of A in the replicase construct are 2'OMe-m6ATP. In some embodiments, about 50% or about 100% of A in the replicase construct are 2'OMe-m6ATP. In some embodiments, about 50% of A in the replicase construct are 2'OMe-m6ATP. In some embodiments, about 100% of A in the replicase construct are 2'OMe-m6ATP. In some embodiments, 50% of A in the replicase construct are 2'OMe-m6ATP. In some embodiments, 100% of A in the replicase construct are 2'OMe-m6ATP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of A in the trRNA are 2'OMe-m6ATP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of A in the trRNA are 2'OMe- m6ATP. In some embodiments, about 50% or about 100% of A in the trRNA are 2'OMe-m6ATP. In some embodiments, about 50% of A in the trRNA are 2'OMe-m6ATP. In some embodiments, 12531064.1 about 100% of A in the trRNA are 2'OMe-m6ATP. In some embodiments, 50% of A in the trRNA are 2'OMe-m6ATP. In some embodiments, 100% of A in the trRNA are 2'OMe-m6ATP. Chemical Modifications of Cytidine (C) In some aspects, this disclosure describes taRNA comprising a first RNA polynucleotide (i.e., replicase construct) and a second RNA polynucleotide (i.e., trRNA), wherein about 25% to 100% of C in the first RNA polynucleotide (i.e., replicase construct) and / or the second RNA polynucleotide (i.e., trRNA) are 5-methylcytidine-5'-triphosphate (m5c), 2'-O-methylcytidine-5'- triphosphate (2'OMe-CTP), N4-acetylcytidine triphosphate (ac4CTP), 5-methylcytidine-5'- triphosphate (5moC), and / or 5-methylcytosine (5mC). In some aspects, this disclosure describes taRNA comprising a replicase construct and a trRNA, wherein about 25% to 100% of C in the replicase construct are m5c, 2'OMe-CTP, ac4CTP, 5moC, and / or 5mC. In some aspects, this disclosure describes taRNA comprising a replicase construct and a trRNA, wherein about 25% to 100% of C in the trRNA are m5c, 2'OMe-CTP, ac4CTP, 5moC, and / or 5mC. 5-methylcytidine-5'-triphosphate (m5c) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the taRNA (i.e., about 25% to about 100% of total C in the replicase construct and the trRNA) are m5c. In some embodiments, about 25% to about 75%, about 25% to about 40%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of C in a taRNA are m5c. In some embodiments, about 25%, about 50%, or about 100% of C in a taRNA are m5c. In some embodiments, about 25% of C in a taRNA are m5c. In some embodiments, about 50% of C in a taRNA are m5c. In some embodiments, about 100% of C in a taRNA are m5c. In some embodiments, 25% of C in a taRNA are m5c. In some embodiments, 50% of C in a taRNA are m5c. In some embodiments, 100% C in a taRNA are m5c. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the replicase construct are m5c. In some embodiments, about 25% to about 75%, about 25% to about 40%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of C in the replicase construct are m5c. In some embodiments, about 25%, about 50%, or about 100% of C in a taRNA are m5c. In some embodiments, about 25% of C in the replicase construct are m5c. In some embodiments, about 50% of C in the replicase construct are m5c. In some embodiments, about 100% of C in the replicase construct are m5c. In some embodiments, 25% 12531064.1 of C in a taRNA are m5c. In some embodiments, 50% of C in the replicase construct are m5c. In some embodiments, 100% C in the replicase construct are m5c. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the trRNA are m5c. In some embodiments, about 25% to about 75%, about 25% to about 40%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of C in the trRNA are m5c. In some embodiments, about 25%, about 50%, or about 100% of C in the trRNA are m5c. In some embodiments, about 25% of C in the trRNA are m5c. In some embodiments, about 50% of C in the trRNA are m5c. In some embodiments, about 100% of C in the trRNA are m5c. In some embodiments, 25% of C in the trRNA are m5c. In some embodiments, 50% of C in the trRNA are m5c. In some embodiments, 100% C in the trRNA are m5c. 2'-O-methylcytidine-5'-triphosphate (2'OMe-CTP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the taRNA (i.e., about 25% to about 100% of total C in the replicase construct and the trRNA) are 2'OMe-CTP. In some embodiments, about 25% to about 40%, about 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of C in a taRNA are 2'OMe-CTP. In some embodiments, about 25%, about 50%, about 75%, or about 100% of C in a taRNA are 2'OMe-CTP. In some embodiments, about 25% of C in a taRNA are 2'OMe-CTP. In some embodiments, about 50% of C in a taRNA are 2'OMe-CTP. In some embodiments, about 75% of C in a taRNA are 2'OMe-CTP. In some embodiments, about 100% of C in a taRNA are 2'OMe-CTP. In some embodiments, 25% of C in a taRNA are 2'OMe-CTP. In some embodiments, 50% of C in a taRNA are 2'OMe-CTP. In some embodiments, 75% of C in a taRNA are 2'OMe-CTP. In some embodiments, 100% of C in a taRNA are 2'OMe-CTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the replicase construct are 2'OMe-CTP. In some embodiments, about 25% to about 40%, about 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of C in the replicase construct are 2'OMe-CTP. In some embodiments, about 25%, about 50%, about 75%, or about 100% of C in the replicase construct are 2'OMe-CTP. In some embodiments, about 25% of C in the replicase construct are 2'OMe-CTP. In some embodiments, about 50% of C in the replicase construct are 2'OMe-CTP. In some embodiments, about 75% of C in the replicase construct are 2'OMe-CTP. In some embodiments, about 100% of C in the replicase construct are 2'OMe-CTP. In some embodiments, 25% of C in the replicase construct are 2'OMe-CTP. In some embodiments, 50% of C in the replicase construct are 2'OMe-CTP. In 12531064.1 some embodiments, 75% of C in the replicase construct are 2'OMe-CTP. In some embodiments, 100% of C in the replicase construct are 2'OMe-CTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the trRNA are 2'OMe-CTP. In some embodiments, about 25% to about 40%, about 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of C in the trRNA are 2'OMe-CTP. In some embodiments, about 25%, about 50%, about 75%, or about 100% of C in the trRNA are 2'OMe-CTP. In some embodiments, about 25% of C in the trRNA are 2'OMe-CTP. In some embodiments, about 50% of C in the trRNA are 2'OMe-CTP. In some embodiments, about 75% of C in the trRNA are 2'OMe-CTP. In some embodiments, about 100% of C in the trRNA are 2'OMe-CTP. In some embodiments, 25% of C in the trRNA are 2'OMe-CTP. In some embodiments, 50% of C in the trRNA are 2'OMe-CTP. In some embodiments, 75% of C in the trRNA are 2'OMe-CTP. In some embodiments, 100% of C in the trRNA are 2'OMe-CTP. N4-acetylcytidine triphosphate (ac4CTP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the taRNA (i.e., about 25% to about 100% of total C in the replicase construct and the trRNA) are ac4CTP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of C in a taRNA are ac4CTP. In some embodiments, about 50% or about 100% of C in a taRNA are ac4CTP. In some embodiments, about 50% of C in a taRNA are ac4CTP. In some embodiments, about 100% of C in a taRNA are ac4CTP. In some embodiments, 50% of C in a taRNA are ac4CTP. In some embodiments, 100% of C in a taRNA are ac4CTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the replicase construct are ac4CTP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of C in the replicase construct are ac4CTP. In some embodiments, about 50% or about 100% of C in the replicase construct are ac4CTP. In some embodiments, about 50% of C in the replicase construct are ac4CTP. In some embodiments, about 100% of C in the replicase construct are ac4CTP. In some embodiments, 50% of C in the replicase construct are ac4CTP. In some embodiments, 100% of C in the replicase construct are ac4CTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the trRNA are ac4CTP. In some embodiments, about 25% to about 75%, about 40% to about 12531064.1 60%, about 75% to about 100%, or about 90% to about 100% of C in the trRNA are ac4CTP. In some embodiments, about 50% or about 100% of C in the trRNA are ac4CTP. In some embodiments, about 50% of C in the trRNA are ac4CTP. In some embodiments, about 100% of C in the trRNA are ac4CTP. In some embodiments, 50% of C in the trRNA are ac4CTP. In some embodiments, 100% of C in the trRNA are ac4CTP. 5-methylcytidine-5'-triphosphate (5moC) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the taRNA (i.e., about 25% to about 100% of total C in the replicase construct and the trRNA) are 5moC. In some embodiments, about 25% to about 75%, about 40 to about 60%, about 60% to about 90%, or about 90% to about 100% of C in a taRNA are 5moC. In some embodiments, about 50%, about 75%, or about 100% of C in a taRNA are 5moC. In some embodiments, about 50% of C in a taRNA are 5moC. In some embodiments, about 75% of C in a taRNA are 5moC. In some embodiments, about 100% of C in a taRNA are 5moC. In some embodiments, 50% of C in a taRNA are 5moC. In some embodiments, 75% of C in a taRNA are 5moC. In some embodiments, 100% of C in a taRNA are 5moC. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the replicase construct are 5moC. In some embodiments, about 25% to about 75%, about 40 to about 60%, about 60% to about 90%, or about 90% to about 1100% of C in the replicase construct are 5moC. In some embodiments, about 50%, about 75%, or about 100% of C in the replicase construct are 5moC. In some embodiments, about 50% of C in the replicase construct are 5moC. In some embodiments, about 75% of C in the replicase construct are 5moC. In some embodiments, about 100% of C in the replicase construct are 5moC. In some embodiments, 50% of C in the replicase construct are 5moC. In some embodiments, 75% of C in the replicase construct are 5moC. In some embodiments, 100% of C in the replicase construct are 5moC. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the trRNA are 5moC. In some embodiments, about 25% to about 75%, about 40 to about 60%, about 60% to about 90%, or about 90% to about 1100% of C in the trRNA are 5moC. In some embodiments, about 50%, about 75%, or about 100% of C in the trRNA are 5moC. In some embodiments, about 50% of C in the trRNA are 5moC. In some embodiments, about 75% of C in the trRNA are 5moC. In some embodiments, about 100% of C in the trRNA are 5moC. In some embodiments, 50% of C in the trRNA are 5moC. In some embodiments, 75% of C in the trRNA are 5moC. In some embodiments, 100% of C in the trRNA are 5moC. 12531064.1 5-methylcytosine (5mC) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the taRNA (i.e., about 25% to about 100% of total C in the replicase construct and the trRNA) are 5mC. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of C in a taRNA are 5mC. In some embodiments, about 50% or about 100% of C in a taRNA are 5mC. In some embodiments, about 50% of C in a taRNA are 5mC. In some embodiments, about 100% of C in a taRNA are 5mC. In some embodiments, 50% of C in a taRNA are 5mC. In some embodiments, 100% of C in a taRNA are 5mC. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the replicase construct are 5mC. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of C in the replicase construct are 5mC. In some embodiments, about 50% or about 100% of C in the replicase construct are 5mC. In some embodiments, about 50% of C in the replicase construct are 5mC. In some embodiments, about 100% of C in the replicase construct are 5mC. In some embodiments, 50% of C in the replicase construct are 5mC. In some embodiments, 100% of C in the replicase construct are 5mC. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of C in the trRNA are 5mC. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of C in the trRNA are 5mC. In some embodiments, about 50% or about 100% of C in the trRNA are 5mC. In some embodiments, about 50% of C in the trRNA are 5mC. In some embodiments, about 100% of Cin the trRNA are 5mC. In some embodiments, 50% of C in the trRNA are 5mC. In some embodiments, 100% of C in the trRNA are 5mC. Chemical Modifications of Guanosine (G) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of G in the taRNA (i.e., about 25% to about 100% of total G in the replicase construct and the trRNA) are 2'OMe-GTP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of G in a taRNA are 2'OMe-GTP. In some embodiments, about 50% or about 100% of G in a taRNA are 2'OMe-GTP. In some embodiments, about 50% of G in a taRNA are 2'OMe-GTP. In some embodiments, about 100% 12531064.1 of G in a taRNA are 2'OMe-GTP. In some embodiments, 50% of G in a taRNA are 2'OMe-GTP. In some embodiments, 100% of G in a taRNA are 2'OMe-GTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of G in the replicase construct are 2'OMe-GTP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of G in the replicase construct are 2'OMe-GTP. In some embodiments, about 50% or about 100% of G in the replicase construct are 2'OMe-GTP. In some embodiments, about 50% of G in the replicase construct are 2'OMe-GTP. In some embodiments, about 100% of G in the replicase construct are 2'OMe-GTP. In some embodiments, 50% of G in the replicase construct are 2'OMe-GTP. In some embodiments, 100% of G in the replicase construct are 2'OMe-GTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of G in the trRNA are 2'OMe-GTP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of G in the trRNA are 2'OMe-GTP. In some embodiments, about 50% or about 100% of G in the trRNA are 2'OMe- GTP. In some embodiments, about 50% of G in the trRNA are 2'OMe-GTP. In some embodiments, about 100% of G in the trRNA are 2'OMe-GTP. In some embodiments, 50% of G in the trRNA are 2'OMe-GTP. In some embodiments, 100% of G in the trRNA are 2'OMe-GTP. Chemical Modifications of Uridine (U) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are 5-methyluridine-5'-triphosophate (m5U), 2-thiouridine-5'-triphosphate (2-Thio-UTP), 2'-O- methyluridine-5'-triphosphase (2'OMe-UTP), 5-methoxyuridine-5'-triphosphate (5'-moUTP), 5- methoxymethyl uridine (5'-moMe-UTP), 1-methoxymethylpseudouridine (N1-methoxymethyl Ψ), pseudouridine-5'-triphosphate (Ψ), 2'-O-methylpseudouridine-5'-triphosphate (2'OMeΨTP), N1-methyl-pseudourine-5'-triphosphate (N1MeΨTP), N1-methyl-2'-O-methylpseudouridine-5'- triphosphate (N1Me2'OMeΨTP), N1-ethylpseudouridine-5'-triphosphate (N1ethylΨTP), and / or N1-methyl-pseudouridine (m1Ψ). In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are m5U, 2-Thio-UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1- methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. 12531064.1 In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are m5U, 2-Thio-UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. 5-methyluridine-5'-triphosophate In some aspects, this disclosure taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are m5U. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in a taRNA are m5U. In some embodiments, about 50%, about 75%, or about 100% of U in a taRNA are m5U. In some embodiments, about 50% of U in a taRNA are m5U. In some embodiments, about 75% of U in a taRNA are m5U. In some embodiments, about 100% of U in a taRNA are m5U. In some embodiments, 50% of U in a taRNA are m5U. In some embodiments, 75% of U in a taRNA are m5U. In some embodiments, 100% of U in a taRNA are m5U. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are m5U. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 60% to about 90%, about 75% to about 100%, or about 90% to about 100% of U in the replicase construct are m5U. In some embodiments, about 50%, about 75%, or about 100% of U in the replicase construct are m5U. In some embodiments, about 50% of U in the replicase construct are m5U. In some embodiments, about 75% of U in the replicase construct are m5U. In some embodiments, about 100% of U in the replicase construct are m5U. In some embodiments, 50% of U in the replicase construct are m5U. In some embodiments, 75% of U in the replicase construct are m5U. In some embodiments, 100% of U in the replicase construct are m5U. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are m5U. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in the trRNA are m5U. In some embodiments, about 50%, about 75%, or about 100% of U in the trRNA are m5U. In some embodiments, about 50% of U in the trRNA are m5U. In some embodiments, about 75% of U in the trRNA are m5U. In some embodiments, about 100% of U in the trRNA are m5U. In some embodiments, 50% of U in the trRNA are m5U. In some embodiments, 75% of U in the trRNA are m5U. In some embodiments, 100% of U in the trRNA are m5U. 12531064.1 2-thiouridine-5'-triphosphate (2-Thio-UTP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are 2-Thio-UTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are 2-Thio-UTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are 2-Thio-UTP. 2'-O-methyluridine-5'-triphosphase (2'OMe-UTP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are 2'OMe-UTP. In some embodiments, about 25% to about 75%, about 25% to about 40%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in a taRNA are 2'OMe-UTP. In some embodiments, about 25%, about 50%, about 75%, or about 100% of U in a taRNA are 2'OMe-UTP. In some embodiments, about 25% of U in a taRNA are 2'OMe-UTP. In some embodiments, about 50% of U in a taRNA are 2'OMe-UTP. In some embodiments, about 75% of U in a taRNA are 2'OMe-UTP. In some embodiments, about 100% of U in a taRNA are 2'’OMe-UTP. In some embodiments, 25% of U in a taRNA are 2'OMe-UTP. In some embodiments, 50% of U in a taRNA are 2'OMe-UTP. In some embodiments, 75% of U in a taRNA are 2'OMe-UTP. In some embodiments, 100% of U in a taRNA are 2'OMe-UTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are 2'OMe-UTP. In some embodiments, about 25% to about 75%, about 25% to about 40%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in the replicase construct are 2'OMe-UTP. In some embodiments, about 25%, about 50%, about 75%, or about 100% of U in the replicase construct are 2'OMe-UTP. In some embodiments, about 25% of U in the replicase construct are 2'OMe-UTP. In some embodiments, about 50% of U in the replicase construct are 2'OMe-UTP. In some embodiments, about 75% of U in the replicase construct are 2'OMe-UTP. In some embodiments, about 100% of U in the replicase construct are 2'OMe-UTP. In some embodiments, 25% of U in the replicase construct are 2'OMe-UTP. In some embodiments, 50% of U in the replicase construct are 2'OMe-UTP. In some embodiments, 75% of U in the replicase construct are 2'OMe-UTP. In some embodiments, 100% of U in the replicase construct are 2'OMe-UTP. 12531064.1 In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are 2'OMe-UTP. In some embodiments, about 25% to about 75%, about 25% to about 40%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in the trRNA are 2'OMe-UTP. In some embodiments, about 25%, about 50%, about 75%, or about 100% of U in the trRNA are 2'OMe-UTP. In some embodiments, about 25% of U in the trRNA are 2'OMe-UTP. In some embodiments, about 50% of U in the trRNA are 2'OMe-UTP. In some embodiments, about 75% of U in the trRNA are 2'OMe-UTP. In some embodiments, about 100% of U in the trRNA are 2'OMe-UTP. In some embodiments, 25% of U in the trRNA are 2'OMe-UTP. In some embodiments, 50% of U in the trRNA are 2'OMe-UTP. In some embodiments, 75% of U in the trRNA are 2'OMe-UTP. In some embodiments, 100% of U in the trRNA are 2'OMe-UTP. 5-methoxyuridine-5'-triphosphate (5'-moUTP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are 5'-moUTP. In some embodiments, 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in a taRNA are 5'-moUTP. In some embodiments, about 50%, about 75%, or about 100% of U in a taRNA are 5'-moUTP. In some embodiments, about 50% of U in a taRNA are 5'-moUTP. In some embodiments, about 75% of U in a taRNA are 5'-moUTP. In some embodiments, about 100% of U in a taRNA are 5'- moUTP. In some embodiments, 50% of U in a taRNA are 5'-moUTP. In some embodiments, 75% of U in a taRNA are 5'-moUTP. In some embodiments, 100% of U in a taRNA are 5'- moUTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are 5'-moUTP. In some embodiments, 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in the replicase construct are 5'-moUTP. In some embodiments, about 50%, about 75%, or about 100% of U in the replicase construct are 5'-moUTP. In some embodiments, about 50% of U in the replicase construct are 5'-moUTP. In some embodiments, about 75% of U in the replicase construct are 5'- moUTP. In some embodiments, about 100% of U in the replicase construct are 5'-moUTP. In some embodiments, 50% of U in the replicase construct are 5'-moUTP. In some embodiments, 75% of U in the replicase construct are 5'-moUTP. In some embodiments, 100% of U in the replicase construct are 5'-moUTP. 12531064.1 In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are 5'-moUTP. In some embodiments, 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in the trRNA are 5'-moUTP. In some embodiments, about 50%, about 75%, or about 100% of U in the trRNA are 5'-moUTP. In some embodiments, about 50% of U in the trRNA are 5'-moUTP. In some embodiments, about 75% of U in the trRNA are 5'-moUTP. In some embodiments, about 100% of U in the trRNA are 5'-moUTP. In some embodiments, 50% of U in the trRNA are 5'-moUTP. In some embodiments, 75% of U in the trRNA are 5'-moUTP. In some embodiments, 100% of U in the trRNA are 5'-moUTP. 5-methoxymethyl uridine (5'-moMe-UTP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are 5'- methoxymethyl uridine. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are 5'-methoxymethyl uridine. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are 5'-methoxymethyl uridine. 1-methoxymethylpseudouridine (N1-methoxymethyl Ψ) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are N1-methoxymethyl Ψ. In some embodiments, 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in a taRNA are N1-methoxymethyl Ψ. In some embodiments, about 50%, about 75%, or about 100% of U in a taRNA are N1- methoxymethyl Ψ. In some embodiments, about 50% of U in a taRNA are N1-methoxymethyl Ψ. In some embodiments, about 75% of U in a taRNA are N1-methoxymethyl Ψ. In some embodiments, about 100% of U in a taRNA are N1-methoxymethyl Ψ. In some embodiments, 50% of U in a taRNA are N1-methoxymethyl Ψ. In some embodiments, 75% of U in a taRNA are N1-methoxymethyl Ψ. In some embodiments, 100% of U in a taRNA are N1-methoxymethyl Ψ. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are N1MeΨTP. In some embodiments, 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in the replicase 12531064.1 construct are N1-methoxymethyl Ψ. In some embodiments, about 50%, about 75%, or about 100% of U in the replicase construct are N1-methoxymethyl Ψ. In some embodiments, about 50% of U in the replicase construct are N1-methoxymethyl Ψ. In some embodiments, about 75% of U in the replicase construct are N1-methoxymethyl Ψ. In some embodiments, about 100% of U in the replicase construct are N1-methoxymethyl Ψ. In some embodiments, 50% of U in the replicase construct are N1-methoxymethyl Ψ. In some embodiments, 75% of U in the replicase construct are N1-methoxymethyl Ψ. In some embodiments, 100% of U in the replicase construct are N1-methoxymethyl Ψ. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are N1MeΨTP. In some embodiments, 25% to about 75%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in the trRNA are N1- methoxymethyl Ψ. In some embodiments, about 50%, about 75%, or about 100% of U in the trRNA are N1-methoxymethyl Ψ. In some embodiments, about 50% of U in the trRNA are N1- methoxymethyl Ψ. In some embodiments, about 75% of U in the trRNA are N1-methoxymethyl Ψ. In some embodiments, about 100% of U in the trRNA are N1-methoxymethyl Ψ. In some embodiments, 50% of U in the trRNA are N1-methoxymethyl Ψ. In some embodiments, 75% of U in the trRNA are N1-methoxymethyl Ψ. In some embodiments, 100% of U in the trRNA are N1-methoxymethyl Ψ. Pseudouridine-5'-triphosphate (Ψ) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are Ψ. In some embodiments, about 25% to about 75%, about 25 % to about 40%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of U in a taRNA are Ψ. In some embodiments, about 25%, about 50%, or about 100% of U in a taRNA are Ψ. In some embodiments, about 25% of U in a taRNA are Ψ. In some embodiments, about 50% of U in a taRNA are Ψ. In some embodiments, about 100% of U in a taRNA are Ψ. In some embodiments, 25% of U in a taRNA are Ψ. In some embodiments, 50% of U in a taRNA are Ψ. In some embodiments, 100% of U in a taRNA are Ψ. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are Ψ. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 25 % to about 40%, about 75% to about 100%, or about 90% to about 100% of U in the replicase construct are Ψ. In some embodiments, about 25%, about 50%, or about 12531064.1 100% of U in the replicase construct are Ψ. In some embodiments, about 25% of U in the replicase construct are Ψ. In some embodiments, about 50% of U in the replicase construct are Ψ. In some embodiments, about 100% of U in the replicase construct are Ψ. In some embodiments, 25% of U in the replicase construct are Ψ. In some embodiments, 50% of U in the replicase construct are Ψ. In some embodiments, 100% of U in the replicase construct are Ψ. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are Ψ. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 25 % to about 40%, about 75% to about 100%, or about 90% to about 100% of U in the trRNA are Ψ. In some embodiments, about 25%, about 50%, or about 100% of U in the trRNA are Ψ. In some embodiments, about 25% of U in the trRNA are Ψ. In some embodiments, about 50% of U in the trRNA are Ψ. In some embodiments, about 100% of U in the trRNA are Ψ. In some embodiments, 25% of U in the trRNA are Ψ. In some embodiments, 50% of U in the trRNA are Ψ. In some embodiments, 100% of U in the trRNA are Ψ. 2'-O-methylpseudouridine-5'-triphosphate (2'OMeΨTP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are 2'OMeΨTP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 60% to about 90%, about 75% to about 100%, or about 90% to about 100% of U in a taRNA are 2'OMeΨTP. In some embodiments, about 50%, about 75%, or about 100% of U in a taRNA are 2'OMeΨTP. In some embodiments, about 50% of U in a taRNA are 2'OMeΨTP. In some embodiments, about 75% of U in a taRNA are 2'OMeΨTP. In some embodiments, about 100% of U in a taRNA are 2'OMeΨTP. In some embodiments, 50% of U in a taRNA are 2'OMeΨTP. In some embodiments, 75% of U in a taRNA are 2'OMeΨTP. In some embodiments, 100% of U in a taRNA are 2'OMeΨTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are 2'OMeΨTP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 60% to about 90%, about 75% to about 100%, or about 90% to about 100% of U in the replicase construct are 2'OMeΨTP. In some embodiments, about 50%, about 75%, or about 100% of U in the replicase construct are 2'OMeΨTP. In some embodiments, about 50% of U in the replicase construct are 2'OMeΨTP. In some embodiments, about 75% of U in the replicase construct are 2'OMeΨTP. In some embodiments, about 100% of U in the replicase construct are 2'OMeΨTP. In some embodiments, 50% of U in the replicase construct are 12531064.1 2'OMeΨTP. In some embodiments, 75% of U in the replicase construct are 2'OMeΨTP. In some embodiments, 100% of U in the replicase construct are 2'OMeΨTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are 2'OMeΨTP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 60% to about 90%, about 75% to about 100%, or about 90% to about 100% of U in the trRNA are 2'OMeΨTP. In some embodiments, about 50%, about 75%, or about 100% of U in the trRNA are 2'OMeΨTP. In some embodiments, about 50% of U in the trRNA are 2'OMeΨTP. In some embodiments, about 75% of U in the trRNA are 2'OMeΨTP. In some embodiments, about 100% of U in the trRNA are 2'OMeΨTP. In some embodiments, 50% of U in the trRNA are 2'OMeΨTP. In some embodiments, 75% of U in the trRNA are 2'OMeΨTP. In some embodiments, 100% of U in the trRNA are 2'OMeΨTP. N1-methyl-pseudourine-5'-triphosphate (N1MeΨTP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are N1MeΨTP. In some embodiments, about 25% to about 75%, about 25% to about 40%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in a taRNA are N1MeΨTP. In some embodiments, about 25%, about 50%, about 75%, or about 100% of U in a taRNA are N1MeΨTP. In some embodiments, about 25% of U in a taRNA are N1MeΨTP. In some embodiments, about 50% of U in a taRNA are N1MeΨTP. In some embodiments, about 75% of U in a taRNA are N1MeΨTP. In some embodiments, about 100% of U in a taRNA are N1MeΨTP. In some embodiments, 25% of U in a taRNA are N1MeΨTP. In some embodiments, 50% of U in a taRNA are N1MeΨTP. In some embodiments, 75% of U in a taRNA are N1MeΨTP. In some embodiments, 100% of U in a taRNA are N1MeΨTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are N1MeΨTP. In some embodiments, 25% to about 40%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in the replicase construct are N1MeΨTP. In some embodiments, about 25%, about 50%, about 75%, or about 100% of U in the replicase construct are N1MeΨTP. In some embodiments, about 25% of U in the replicase construct are N1MeΨTP. In some embodiments, about 50% of U in the replicase construct are N1MeΨTP. In some embodiments, about 75% of U in the replicase construct are N1MeΨTP. In some embodiments, about 100% of U in the replicase construct are N1MeΨTP. In some embodiments, 25% of U in the replicase construct are N1MeΨTP. In some embodiments, 12531064.1 50% of U in the replicase construct are N1MeΨTP. In some embodiments, 75% of U in the replicase construct are N1MeΨTP. In some embodiments, 100% of U in the replicase construct are N1MeΨTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are N1MeΨTP. In some embodiments, 25% to about 40%, about 40% to about 60%, about 60% to about 90%, or about 90% to about 100% of U in the trRNA are N1MeΨTP. In some embodiments, about 25%, about 50%, about 75%, or about 100% of U in the trRNA N1MeΨTP. In some embodiments, about 25% of U in the trRNA are N1MeΨTP. In some embodiments, about 50% of U in the trRNA are N1MeΨTP. In some embodiments, about 75% of U in the trRNA are N1MeΨTP. In some embodiments, about 100% of U in the trRNA are N1MeΨTP. In some embodiments, 25% of U in the trRNA are N1MeΨTP. In some embodiments, 50% of U in the trRNA are N1MeΨTP. In some embodiments, 75% of U in the trRNA are N1MeΨTP. In some embodiments, 100% of U in the trRNA are N1MeΨTP. N1-methyl-2'-O-methylpseudouridine-5'-triphosphate (N1Me2'OMeΨTP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are N1Me2'OMeΨTP. In some embodiments, about 25% to about 75% or about 40% to about 60% of U in a taRNA are N1Me2'OMeΨTP. In some embodiments, about 50% of U in a taRNA are N1Me2'OMeΨTP.. In some embodiments, 50% of U in a taRNA are N1Me2'OMeΨTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are N1Me2'OMeΨTP. In some embodiments, about 25% to about 75% or about 40% to about 60% of U in the replicase construct are N1Me2'OMeΨTP. In some embodiments, about 50% of U in the replicase construct are N1Me2'OMeΨTP.. In some embodiments, 50% of U in the replicase construct are N1Me2'OMeΨTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are N1Me2'OMeΨTP. In some embodiments, about 25% to about 75% or about 40% to about 60% of U in the trRNA are N1Me2'OMeΨTP. In some embodiments, about 50% of U in the trRNA are N1Me2'OMeΨTP. In some embodiments, 50% of U in the trRNA are N1Me2'OMeΨTP. N1-ethylpseudouridine-5'-triphosphate (N1ethylΨTP) In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) 12531064.1 are N1ethylΨTP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of U in a taRNA are N1ethylΨTP. In some embodiments, about 50% or about 100% of U in a taRNA are N1ethylΨTP. In some embodiments, about 50% of U in a taRNA are N1ethylΨTP. In some embodiments, about 100% of U in a taRNA are N1ethylΨTP. In some embodiments, 50% of U in a taRNA are N1ethylΨTP. In some embodiments, 100% of U in a taRNA are N1ethylΨTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) in the replicase construct are N1ethylΨTP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of U in the replicase construct are N1ethylΨTP. In some embodiments, about 50% or about 100% of U in the replicase construct are N1ethylΨTP. In some embodiments, about 50% of U in the replicase construct are N1ethylΨTP. In some embodiments, about 100% of U in the replicase construct are N1ethylΨTP. In some embodiments, 50% of U in the replicase construct are N1ethylΨTP. In some embodiments, 100% of U in the replicase construct are N1ethylΨTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) in the trRNA are N1ethylΨTP. In some embodiments, about 25% to about 75%, about 40% to about 60%, about 75% to about 100%, or about 90% to about 100% of U in the trRNA are N1ethylΨTP. In some embodiments, about 50% or about 100% of U in the trRNA are N1ethylΨTP. In some embodiments, about 50% of U in the trRNA are N1ethylΨTP. In some embodiments, about 100% of U in the trRNA are N1ethylΨTP. In some embodiments, 50% of U in the trRNA are N1ethylΨTP. In some embodiments, 100% of U in the trRNA are N1ethylΨTP. N1-methyl-pseudouridine In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are m1Ψ. In some embodiments, about 25% to about 75%, about 25% to about 40%, about 40% to about 60%, about 60% to about 90%, about 75% to about 100%, or about 90% to about 100% of U in a taRNA are m1Ψ. In some embodiments, about 25%, about 50%, about 75%, or about 100% of U in a taRNA are m1Ψ. In some embodiments, about 25% of U in a taRNA are m1Ψ. In some embodiments, about 50% of U in a taRNA are m1Ψ. In some embodiments, about 75% of U in a taRNA are m1Ψ. In some embodiments, about 100% of U in a taRNA are m1Ψ. In some 12531064.1 embodiments, 25% of U in a taRNA are m1Ψ. In some embodiments, 50% of U in a taRNA are m1Ψ. In some embodiments, 75% of U in a taRNA are m1Ψ. In some embodiments, 100% of U in a taRNA are m1Ψ. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are m1Ψ. In some embodiments, about 25% to about 75%, about 25% to about 40%, about 40% to about 60%, about 60% to about 90%, about 75% to about 100%, or about 90% to about 100% of U in the replicase construct are m1Ψ. In some embodiments, about 25%, about 50%, about 75%, or about 100% of U in the replicase construct are m1Ψ. In some embodiments, about 25% of U in the replicase construct are m1Ψ. In some embodiments, about 50% of U in the replicase construct are m1Ψ. In some embodiments, about 75% of U in the replicase construct are m1Ψ. In some embodiments, about 100% of U in the replicase construct are m1Ψ. In some embodiments, 25% of U in the replicase construct are m1Ψ. In some embodiments, 50% of U in the replicase construct are m1Ψ. In some embodiments, 75% of U in the replicase construct are m1Ψ. In some embodiments, 100% of U in the replicase construct are m1Ψ. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are m1Ψ. In some embodiments, about 25% to about 75%, about 25% to about 40%, about 40% to about 60%, about 60% to about 90%, about 75% to about 100%, or about 90% to about 100% of U in the trRNA are m1Ψ. In some embodiments, about 25%, about 50%, about 75%, or about 100% of U in the trRNA are m1Ψ. In some embodiments, about 25% of U in the trRNA are m1Ψ. In some embodiments, about 50% of U in the trRNA are m1Ψ. In some embodiments, about 75% of U in the trRNA are m1Ψ. In some embodiments, about 100% of U in the trRNA are m1Ψ. In some embodiments, 25% of U in the trRNA are m1Ψ. In some embodiments, 50% of U in the trRNA are m1Ψ. In some embodiments, 75% of U in the trRNA are m1Ψ. In some embodiments, 100% of U in the trRNA are m1Ψ. In some aspects, this disclosure describes taRNA wherein about 25% to about 75% of U in the taRNA (i.e., about 25% to about 75% of total U in the replicase construct and the trRNA) are N1MeΨTP and about 25% to about 50% of U in the taRNA (i.e., about 25% to about 50% of total U in the replicase construct and the trRNA) are 5'-moUTP. In some embodiments, about 75% of U are N1MeΨTP and about 25% of U are 5'-moUTP. In some embodiments, 75% of U are N1MeΨTP and 25% of U are 5'-moUTP. 12531064.1 In some aspects, this disclosure describes taRNA wherein about 25% to about 75% of U in the replicase construct are N1MeΨTP and about 25% to about 50% of U in the replicase construct are 5'-moUTP. In some embodiments, about 75% of U in the replicase construct are N1MeΨTP and about 25% of U in the replicase construct are 5'-moUTP. In some embodiments, 75% of U in the replicase construct are N1MeΨTP and 25% of U in the replicase construct are 5'-moUTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 75% of U in the trRNA are N1MeΨTP and about 25% to about 50% of U in the trRNA are 5'-moUTP. In some embodiments, about 75% of U in the trRNA are N1MeΨTP and about 25% of U in the trRNA are 5'-moUTP. In some embodiments, 75% of U in the trRNA are N1MeΨTP and 25% of U in the trRNA are 5'-moUTP. In some aspects, this disclosure describes taRNA wherein about 40% to about 75% of U in the taRNA (i.e., about 40% to about 75% of total U in the replicase construct and the trRNA) are N1MeΨTP and about 25% to about 60% of U in the taRNA (i.e., about 25% to about 60% of total U in the replicase construct and the trRNA) are 2'OMe-UTP. In some embodiments, about 40% to about 60% or 60% to about 75% of U in the taRNA are N1MeΨTP and about 25% to about 40% or about 40% to about 60% of U in the taRNA are 2'OMe-UTP. In some embodiments, about 50% or about 75% of U in the taRNA are N1MeΨTP and about 25% or about 50% of U in the taRNA are 2'OMe-UTP. In some embodiments, about 50% of U in the taRNA are N1MeΨTP and about 50% of U in the taRNA are 2'OMe-UTP. In some embodiments, about 75% of U in the taRNA are N1MeΨTP and about 25% of U in the taRNA are 2'OMe-UTP. In some embodiments, 50% of U in the taRNA are N1MeΨTP and 50% of U in the taRNA are 2'OMe-UTP. In some embodiments, 75% of U in the taRNA are N1MeΨTP and 25% of U in the taRNA are 2'OMe-UTP. In some aspects, this disclosure describes taRNA wherein about 40% to about 75% of U in the replicase construct are N1MeΨTP and about 25% to about 60% of U in the replicase construct are 2'OMe-UTP. In some embodiments, about 40% to about 60% or 60% to about 75% of U in the replicase construct are N1MeΨTP and about 25% to about 40% or about 40% to about 60% of U in the replicase construct are 2'OMe-UTP. In some embodiments, about 50% or about 75% of U in the replicase construct are N1MeΨTP and about 25% or about 50% of U in the replicase construct are 2'OMe-UTP. In some embodiments, about 50% of U in the replicase 12531064.1 construct are N1MeΨTP and about 50% of U in the replicase construct are 2'OMe-UTP. In some embodiments, about 75% of U in the replicase construct are N1MeΨTP and about 25% of U in the replicase construct are 2'OMe-UTP. In some embodiments, 50% of U in the replicase construct are N1MeΨTP and 50% of U in the replicase construct are 2'OMe-UTP. In some embodiments, 75% of U in the replicase construct are N1MeΨTP and 25% of U in the replicase construct are 2'OMe-UTP. In some aspects, this disclosure describes taRNA wherein about 40% to about 75% of U in the trRNA are N1MeΨTP and about 25% to about 60% of U in the trRNA are 2'OMe-UTP. In some embodiments, about 40% to about 60% or 60% to about 75% of U in the trRNA are N1MeΨTP and about 25% to about 40% or about 40% to about 60% of U in the trRNA are 2'OMe-UTP. In some embodiments, about 50% or about 75% of U in the trRNA are N1MeΨTP and about 25% or about 50% of U in the trRNA are 2'OMe-UTP. In some embodiments, about 50% of U in the trRNA are N1MeΨTP and about 50% of U in the trRNA are 2'OMe-UTP. In some embodiments, about 75% of U in the trRNA are N1MeΨTP and about 25% of U in the trRNA are 2'OMe-UTP. In some embodiments, 50% of U in the trRNA are N1MeΨTP and 50% of U in the trRNA are 2'OMe-UTP. In some embodiments, 75% of U in the trRNA are N1MeΨTP and 25% of U in the trRNA are 2'OMe-UTP. 5'-moUTP and 2'OMe-UTP In some aspects, this disclosure describes taRNA wherein about 25% to about 75% of U in the taRNA (i.e., about 25% to about 75% of total U in the replicase construct and the trRNA) are 5'-moUTP and about 25% to about 75% of U in the taRNA (e.g., about 40% to about 75% of total U in the replicase construct and the trRNA) are 2'OMe-UTP. In some embodiments, about 40% to about 75% of U in the taRNA are 5'-moUTP. In some embodiments, about 40% to about 75% of U in the taRNA are 2'OMe-UTP. In some embodiments, about 40% to about 60% of U in the taRNA are 5'-moUTP and about 40% to about 60% of U in the taRNA are 2'OMe-UTP. In some embodiments, about 50% of U in the taRNA are 5'-moUTP and about 50% of U in the taRNA are 2'OMe-UTP. In some embodiments, 50% of U in the taRNA are 5'-moUTP and 50% of U in the taRNA are 2'OMe-UTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 75% of U in the replicase construct are 5'-moUTP and about 25% to about 75% of U in the replicase construct are 2'OMe-UTP. In some aspects, this disclosure describes taRNA wherein about 40% to about 75% of U in the replicase construct are 5'-moUTP. In some embodiments, about 40% to 12531064.1 about 75% of U in the replicase construct are 2'OMe-UTP. In some embodiments, about 40% to about 60% of U in the replicase construct are 5'-moUTP and about 40% to about 60% of U in the replicase construct are 2'OMe-UTP. In some embodiments, about 50% of U in the replicase construct are 5'-moUTP and about 50% of U in the replicase construct are 2'OMe-UTP. In some embodiments, 50% of U in the replicase construct are 5'-moUTP and 50% of U in the replicase construct are 2'OMe-UTP. In some aspects, this disclosure describes taRNA wherein about 25% to about 75% of U in the trRNA are 5'-moUTP and about 25% to about 75% of U in the trRNA are 2'OMe-UTP. In some aspects, this disclosure describes taRNA wherein about 40% to about 75% of U in the trRNA are 5'-moUTP and about 40% to about 75% of U in the trRNA are 2'OMe-UTP. In some embodiments, about 40% to about 60% of U in the trRNA are 5'-moUTP and about 40% to about 60% of U in the trRNA are 2'OMe-UTP. In some embodiments, about 50% of U in the trRNA are 5'-moUTP and about 50% of U in the trRNA are 2'OMe-UTP. In some embodiments, 50% of U in the trRNA are 5'-moUTP and 50% of U in the trRNA are 2'OMe-UTP. Exemplary Combinations of Chemical Modifications In some aspects, this disclosure describes taRNA having a combination of different nucleotides comprising different chemical modifications, such that two or more (e.g., 2, 3, or 4) of A, C, G, and / or U in the taRNA (e.g., replicase construct, trRNA, or both) are chemically modified. In some aspects, this disclosure describes taRNA wherein two or more of A, C, G, and / or U of the first RNA polynucleotide (i.e., the replicase construct) and / or the second RNA polynucleotide (i.e., the trRNA) of a taRNA comprise a chemical modification. In some embodiments, this disclosure describes taRNA wherein about 25% to about 100% of two or more of A, C, G and U in the first RNA polynucleotide (i.e., the replicase construct) and / or the second RNA polynucleotide (i.e., the trRNA) comprise: a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, this disclosure describes taRNA wherein about 25% to about 100% of A and C in the first RNA polynucleotide (i.e., the replicase construct) and / or the second RNA polynucleotide (i.e., the trRNA) comprise: a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, about 25% to about 100% of A in the taRNA (e.g., in the replicase construct, the 12531064.1 trRNA, or both) are 2'OMe-ATP, m6ATP, 2'-and / or 2'OMe-m6ATP and about 25% to about 100% of C in the taRNA (e.g., in the replicase construct, the trRNA, or both) are m5c, 2'OMe- CTP, ac4CTP, 5moC, and / or 5mC. In some embodiments, this disclosure describes taRNA wherein about 25% to about 100% of A and G in the first RNA polynucleotide (i.e., the replicase construct) and / or the second RNA polynucleotide (i.e., the trRNA) comprise: a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, about 25% to about 100% of A in the taRNA (e.g., in the replicase construct, the trRNA, or both) are 2'OMe-ATP, m6ATP, 2'-and / or 2'OMe-m6ATP and about 25% to about 100% of G in the taRNA (e.g., in the replicase construct, the trRNA, or both) are 2'OMe-GTP. In some embodiments, this disclosure describes taRNA wherein about 25% to about 100% of A and U in the first RNA polynucleotide (i.e., the replicase construct) and / or the second RNA polynucleotide (i.e., the trRNA) comprise: a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, about 25% to about 100% of A in the taRNA (e.g., in the replicase construct, the trRNA, or both) are 2'OMe-ATP, m6ATP, 2'-and / or 2'OMe-m6ATP and about 25% to about 100% of U in the taRNA (e.g., in the replicase construct, the trRNA, or both) are m5U, 2-Thio- UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. In some embodiments, this disclosure describes taRNA wherein about 25% to about 100% of C and G in the first RNA polynucleotide (i.e., the replicase construct) and / or the second RNA polynucleotide (i.e., the trRNA) comprise: a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, about 25% to about 100% of C in the taRNA (e.g., in the replicase construct, the trRNA, or both) are m5c, 2'OMe-CTP, ac4CTP, 5moC, and / or 5mc, and about 25% to about 100% of G in the taRNA (e.g., in the replicase construct, the trRNA, or both) are 2'OMe-GTP. In some embodiments, this disclosure describes taRNA wherein about 25% to about 100% of C and about 25% to about 100% of U in the first RNA polynucleotide (i.e., the replicase construct) and / or the second RNA polynucleotide (i.e., the trRNA) comprise: a - methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an - ethyl chemical modification. In some embodiments, about 25% to about 100% of C in the taRNA (e.g., in the replicase construct, the trRNA, or both) are m5c, 2'OMe-CTP, ac4CTP, 5moC, and / or 5mc, and about 25% to about 100% of U in the taRNA (e.g., in the replicase 12531064.1 construct, the trRNA, or both) are m5U, 2-Thio-UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. In some embodiments, this disclosure describes taRNA wherein about 25% to about 100% of three or more of A, C, G and U in the replicase construct and / or in the trRNA comprise: a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an - ethyl chemical modification. In some embodiments, this disclosure describes taRNA wherein about 25% to about 100% of A, C, and G in the replicase construct and / or in the trRNA comprise: a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, about 25% to about 100% of A in the taRNA (e.g., in the replicase construct, the trRNA, or both) are 2'OMe-ATP, m6ATP, 2'-and / or 2'OMe-m6ATP; about 25% to about 100% of C in the taRNA (e.g., in the replicase construct, the trRNA, or both) are m5c, 2'OMe-CTP, ac4CTP, 5moC, and / or 5mC; and about 25% to about 100% of G in the taRNA (e.g., in the replicase construct, the trRNA, or both) are 2'OMe-GTP. In some embodiments, this disclosure describes taRNA wherein about 25% to about 100% of A, C, and U in the replicase construct and / or in the trRNA comprise: a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, about 25% to about 100% of A in the taRNA (e.g., in the replicase construct, the trRNA, or both) are 2'OMe-ATP, m6ATP, 2'-and / or 2'OMe-m6ATP; about 25% to about 100% of C in the taRNA (e.g., in the replicase construct, the trRNA, or both) are m5c, 2'OMe-CTP, ac4CTP, 5moC, and / or 5mC; and about 25% to about 100% of U in the taRNA (e.g., in the replicase construct, the trRNA, or both) are m5U, 2-Thio-UTP, 2'OMe- UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. In some embodiments, this disclosure describes taRNA wherein about 25% to about 100% of A, G, and U in the replicase construct and / or in the trRNA comprise: a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, about 25% to about 100% of A in the taRNA (e.g., in the replicase construct, the trRNA, or both) are 2'OMe-ATP, m6ATP, 2'-and / or 2'OMe-m6ATP; about 25% to about 100% of G in the taRNA (e.g., in the replicase construct, the trRNA, or both) are 2'OMe-GTP; and about 25% to about 100% of U in the taRNA (e.g., in the replicase 12531064.1 construct, the trRNA, or both) are m5U, 2-Thio-UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. In some embodiments, this disclosure describes taRNA wherein about 25% to about 100% of C, G, and U in the replicase construct and / or in the trRNA comprise: a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, about 25% to about 100% of C in the taRNA (e.g., in the replicase construct, the trRNA, or both) are m5c, 2'OMe-CTP, ac4CTP, 5moC, and / or 5mC; about 25% to about 100% of G in the taRNA (e.g., in the replicase construct, the trRNA, or both) are 2'OMe-GTP; and about 25% to about 100% of U in the taRNA (e.g., in the replicase construct, the trRNA, or both) are m5U, 2-Thio-UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1- methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. In some embodiments, this disclosure describes taRNA wherein about 25% to about 100% of A, C, G, and U in the replicase construct and / or in the trRNA comprise: a -methyl, an - O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. In some embodiments, about 25% to about 100% of A in the taRNA (e.g., in the replicase construct, the trRNA, or both) are 2'OMe-ATP, m6ATP, 2'-and / or 2'OMe-m6ATP; about 25% to about 100% of C in the taRNA (e.g., in the replicase construct, the trRNA, or both) are m5c, 2'OMe-CTP, ac4CTP, 5moC, and / or 5mC; about 25% to about 100% of G in the taRNA (e.g., in the replicase construct, the trRNA, or both) are 2'OMe-GTP; and about 25% to about 100% of U in the taRNA (e.g., in the replicase construct, the trRNA, or both) are m5U, 2- Thio-UTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, Ψ, 2'OMeΨTP, N1MeΨTP, N1Me2'OMeΨTP, N1ethylΨTP, and / or m1Ψ. Combinations of m5c and chemically modified U In preferred embodiments, about 25% to about 100% of C in the taRNA (e.g., in the replicase construct, the trRNA, or both) are m5c and about 25% to about 100% of U in the taRNA (e.g., in the replicase construct, the trRNA, or both) are chemically modified (e.g., comprise a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification). As shown in the section entitled “Examples” below, such combinations can be especially useful for reducing immunogenicity and increasing taRNA- mediate payload expression. Certain examples of such combinations are provided below. 12531064.1 Exemplary combinations of N1MeΨTP and m5c In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are N1MeΨTP and about 25% to about 100% of C in the taRNA (i.e., about 25% to about 100% of total C in the replicase construct and the trRNA) are m5c. In some embodiments, about 40% to about 60%, 60% to about 90%, or about 90% to about 100% of U in the taRNA are N1MeΨTP and about 40% to about 60%, about 60% to about 90%, about 90% to about 100% of C in the taRNA are m5c. In some embodiments, about 50%, about 75%, or about 100% of U in the taRNA are N1MeΨTP and about 50%, about 75%, or about 100% of C in the taRNA are m5c. In some embodiments, about 50% of U in the taRNA are N1MeΨTP and about 50% of C in the taRNA are m5c. In some embodiments, about 50% of U in the taRNA are N1MeΨTP and about 75% of C in the taRNA are m5c. In some embodiments, about 50% of U in the taRNA are N1MeΨTP and about 100% of C in the taRNA are m5c. In some embodiments, about 75% of U in the taRNA are N1MeΨTP and about 50% of C in the taRNA are m5c. In some embodiments, about 75% of U in the taRNA are N1MeΨTP and about 75% of C in the taRNA are m5c. In some embodiments, about 100% of U in the taRNA are N1MeΨTP and about 50% of C in the taRNA are m5c. In some embodiments, about 100% of U in the taRNA are N1MeΨTP and about 75% of C in the taRNA are m5c. In some embodiments, about 100% of U in the taRNA are N1MeΨTP and about 100% of C in the taRNA are m5c. In some embodiments, 50% of U in the taRNA are N1MeΨTP and 50% of C in the taRNA are m5c. In some embodiments, 50% of U in the taRNA are N1MeΨTP and 75% of C in the taRNA are m5c. In some embodiments, 50% of U in the taRNA are N1MeΨTP and 100% of C in the taRNA are m5c. In some embodiments, 75% of U in the taRNA are N1MeΨTP and 50% of C in the taRNA are m5c. In some embodiments, 75% of U in the taRNA are N1MeΨTP and 75% of C in the taRNA are m5c. In some embodiments, 100% of U in the taRNA are N1MeΨTP and 50% of C in the taRNA are m5c. In some embodiments, 100% of U in the taRNA are N1MeΨTP and 75% of C in the taRNA are m5c. In some embodiments, 100% of U in the taRNA are N1MeΨTP and 100% of C in the taRNA are m5c. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are N1MeΨTP and about 25% to about 100% of C in the replicase construct are m5c. In some embodiments, about 40% to about 60%, 60% to about 90%, or about 90% to about 100% of U in the replicase construct are N1MeΨTP and about 40% to about 60%, about 60% to about 90%, about 90% to about 100% of C in the replicase construct are m5c. In some embodiments, about 50%, about 75%, or about 100% of U in the replicase construct are 12531064.1 N1MeΨTP and about 50%, about 75%, or about 100% of C in the replicase construct are m5c. In some embodiments, about 50% of U in the replicase construct are N1MeΨTP and about 50% of C in the replicase construct are m5c. In some embodiments, about 50% of U in the replicase construct are N1MeΨTP and about 75% of C in the replicase construct are m5c. In some embodiments, about 50% of U in the replicase construct are N1MeΨTP and about 100% of C in the replicase construct are m5c. In some embodiments, about 75% of U in the replicase construct are N1MeΨTP and about 50% of C in the replicase construct are m5c. In some embodiments, about 75% of U in the replicase construct are N1MeΨTP and about 75% of C in the replicase construct are m5c. In some embodiments, about 100% of U in the replicase construct are N1MeΨTP and about 50% of C in the replicase construct are m5c. In some embodiments, about 100% of U are N1MeΨTP and about 75% of C in the replicase construct are m5c. In some embodiments, about 100% of U in the replicase construct are N1MeΨTP and about 100% of C in the replicase construct are m5c. In some embodiments, 50% of U in the replicase construct are N1MeΨTP and 50% of C in the replicase construct are m5c. In some embodiments, 50% of U in the replicase construct are N1MeΨTP and 75% of C in the replicase construct are m5c. In some embodiments, 50% of U in the replicase construct are N1MeΨTP and 100% of C in the replicase construct are m5c. In some embodiments, 75% of U in the replicase construct are N1MeΨTP and 50% of C in the replicase construct are m5c. In some embodiments, 75% of U in the replicase construct are N1MeΨTP and 75% of C in the replicase construct are m5c.In some embodiments, 100% of U in the replicase construct are N1MeΨTP and 50% of C in the replicase construct are m5c. In some embodiments, 100% of U in the replicase construct are N1MeΨTP and 75% of C in the replicase construct are m5c. In some embodiments, 100% of U in the replicase construct are N1MeΨTP and 100% of C in the replicase construct are m5c. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are N1MeΨTP and about 25% to about 100% of C in the trRNA are m5c. In some embodiments, about 40% to about 60%, 60% to about 90%, or about 90% to about 100% of U in the trRNA are N1MeΨTP and about 40% to about 60%, about 60% to about 90%, about 90% to about 100% of C in the trRNA are m5c. In some embodiments, about 50%, about 75%, or about 100% of U in the trRNA are N1MeΨTP and about 50%, about 75%, or about 100% of C in the trRNA are m5c. In some embodiments, about 50% of U in the trRNA are N1MeΨTP and about 50% of C in the trRNA are m5c. In some embodiments, about 50% of U in the trRNA are N1MeΨTP and about 75% of C in the trRNA are m5c. In some embodiments, about 50% of U in the trRNA are N1MeΨTP and about 100% of C in the trRNA are m5c. In some embodiments, 12531064.1 about 75% of U in the trRNA are N1MeΨTP and about 50% of C in the trRNA are m5c. In some embodiments, about 75% of U in the trRNA are N1MeΨTP and about 75% of C in the trRNA are m5c. In some embodiments, about 100% of U in the trRNA are N1MeΨTP and about 50% of C in the trRNA are m5c. In some embodiments, about 100% of U are N1MeΨTP and about 75% of C in the trRNA are m5c. In some embodiments, about 100% of U in the trRNA are N1MeΨTP and about 100% of C in the trRNA are m5c. In some embodiments, 50% of U in the trRNA are N1MeΨTP and 50% of C in the trRNA are m5c. In some embodiments, 50% of U in the trRNA are N1MeΨTP and 75% of C in the trRNA are m5c. In some embodiments, 50% of U in the trRNA are N1MeΨTP and 100% of C in the trRNA are m5c. In some embodiments, 75% of U in the trRNA are N1MeΨTP and 50% of C in the trRNA are m5c. In some embodiments, 75% of U in the trRNA are N1MeΨTP and 75% of C in the trRNA are m5c. In some embodiments, 100% of U in the trRNA are N1MeΨTP and 50% of C in the trRNA are m5c. In some embodiments, 100% of U in the trRNA are N1MeΨTP and 75% of C in the trRNA are m5c. In some embodiments, 100% of U in the trRNA are N1MeΨTP and 100% of C in the trRNA are m5c. Exemplary combinations of 5'-moUTP and m5c In some aspects, this disclosure describes taRNA wherein about 40% to about 100% of U in the taRNA (i.e., about 40% to about 100% of total U in the replicase construct and the trRNA) are 5'-moUTP and about 75% to about 100% of C in the taRNA (i.e., about 75% to about 100% of total C in the replicase construct and the trRNA) are m5c. In some embodiments, about 40% to about 60%, 60% to about 90%, or about 90% to about 100% of U in the taRNA are 5'-moUTP and about 75% to about 90% or about 90% to about 100% of C in the taRNA are m5c. In some embodiments, about 50% or about 100% of U in the taRNA are 5'-moUTP and about 100% of C in the taRNA are m5c. In some embodiments, about 50% of U in the taRNA are 5'-moUTP and about 100% of C in the taRNA are m5c. In some embodiments, about 100% of U in the taRNA are 5'-moUTP and about 100% of C in the taRNA are m5c. In some embodiments, 50% of U in the taRNA are 5'-moUTP and 100% of C in the taRNA are m5c. In some embodiments, 100% of U in the taRNA are 5'-moUTP and 100% of C in the taRNA are m5c. In some aspects, this disclosure describes taRNA wherein about 40% to about 100% of U in the replicase construct are 5'-moUTP and about 75% to about 100% of C in the replicase construct are m5c. In some embodiments, about 40% to about 60% or about 90% to about 100% of U in the replicase construct are 5'-moUTP and about 90% to about 100% of C in the replicase construct are m5c. In some embodiments, about 50% or about 100% of U in the replicase 12531064.1 construct are 5'-moUTP and about 100% of C in the replicase construct are m5c. In some embodiments, about 50% of U in the replicase construct are 5'-moUTP and about 100% of C in the replicase construct are m5c. In some embodiments, about 100% of U in the replicase construct are 5'-moUTP and about 100% of C in the replicase construct are m5c. In some embodiments, 50% of U in the replicase construct are 5'-moUTP and 100% of C in the replicase construct are m5c. In some embodiments, 100% of U in the replicase construct are 5'-moUTP and 100% of C in the replicase construct are m5c. In some aspects, this disclosure describes taRNA wherein about 40% to about 100% of U in the trRNA are 5'-moUTP and about 75% to about 100% of C in the trRNA are m5c. In some embodiments, about 40% to about 60% or about 90% to about 100% of U in the trRNA are 5'- moUTP and about 90% to about 100% of C in the trRNA are m5c. In some embodiments, about 50% or about 100% of U in the trRNA are 5'-moUTP and about 100% of C in the trRNA are m5c. In some embodiments, about 50% of U in the trRNA are 5'-moUTP and about 100% of C in the trRNA are m5c. In some embodiments, about 100% of U in the trRNA are 5'-moUTP and about 100% of C in the trRNA are m5c. In some embodiments, 50% of U in the trRNA are 5'- moUTP and 100% of C in the trRNA are m5c. In some embodiments, 100% of U in the trRNA are 5'-moUTP and 100% of C in the trRNA are m5c. Exemplary combinations of 2'OMe-UTP and m5c In some aspects, this disclosure describes taRNA wherein about 40% to about 75% of U in the taRNA (i.e., about 40% to about 75% of total U in the replicase construct and the trRNA) are 2'OMe-UTP and about 75% to about 100% of C in the taRNA (i.e., about 75% to about 100% of total C in the replicase construct and the trRNA) are m5c. In some embodiments, about 40% to about 60% of U in the taRNA are 2'OMe-UTP and about 90% to about 100% of C in the taRNA are m5c. In some embodiments, about 50% of U in the taRNA are 2'OMe-UTP and about 100% of C in the taRNA are m5c. In some embodiments, about 50% of U in the taRNA are 2'OMe-UTP and about 100% of C in the taRNA are m5c. In some aspects, this disclosure describes taRNA wherein about 40% to about 75% of U in the replicase construct are 2'OMe-UTP and about 75% to about 100% of C in the replicase construct are m5c. In some embodiments, about 40% to about 60% of U in the replicase construct are 2'OMe-UTP and about 90% to about 100% of C in the replicase construct are m5c. In some embodiments, about 50% of U in the replicase construct are 2'OMe-UTP and about 12531064.1 100% of C in the replicase construct are m5c. In some embodiments, about 50% of U in the replicase construct are 2'OMe-UTP and about 100% of C in the replicase construct are m5c. In some aspects, this disclosure describes taRNA wherein about 40% to about 75% of U in the trRNA are 2'OMe-UTP and about 75% to about 100% of C in the trRNA are m5c. In some embodiments, about 40% to about 60% of U in the trRNA are 2'OMe-UTP and about 90% to about 100% of C in the trRNA are m5c. In some embodiments, about 50% of U in the trRNA are 2'OMe-UTP and about 100% of C in the trRNA are m5c. In some embodiments, about 50% of U in the trRNA are 2'OMe-UTP and about 100% of C in the trRNA are m5c. Exemplary combinations of 2'OMe-UTP, 5'-moUTP, and m5c In some aspects, this disclosure describes taRNA wherein about 25% to about 75% of U in the taRNA (i.e., about 25% to about 75% of total U in the replicase construct and the trRNA) are 2'OMe-UTP, about 25% to about 75% of U in the taRNA (i.e., about 25% to about 75% of total U in the replicase construct and the trRNA) are 5'-moUTP, and about 40% to about 100% of C in the taRNA (i.e., about 40% to about 100% of total C in the replicase construct and the trRNA) are m5c. In some embodiments, about 40% to about 60% of U in the taRNA are 2'OMe- UTP, about 40% to about 60% of U in the taRNA are 5'-moUTP, and about 90% to about 100% of C in the taRNA are m5c. In some embodiments, about 50% of U in the taRNA are 2'OMe- UTP, about 50% of U in the taRNA are 5'-moUTP, and about 100% of C in the taRNA are m5c. In some embodiments, 50% of U in the taRNA are 2'OMe-UTP, 50% of U in the taRNA are 5'- moUTP, and 100% of C in the taRNA are m5c. In some aspects, this disclosure describes taRNA wherein about 25% to about 75% of U in the replicase construct are 2'OMe-UTP, about 25% to about 75% of U in the replicase construct are 5'-moUTP, and about 40% to about 100% of C in the replicase construct are m5c. In some embodiments, about 40% to about 60% of U in the replicase construct are 2'OMe-UTP, about 40% to about 60% of U in the replicase construct are 5'-moUTP, and about 90% to about 100% of C in the replicase construct are m5c. In some embodiments, about 50% of U in the replicase construct are 2'OMe-UTP, about 50% of U in the replicase construct are 5'-moUTP, and about 100% of C in the replicase construct are m5c. In some embodiments, 50% of U in the replicase construct are 2'OMe-UTP, 50% of U in the replicase construct are 5'-moUTP, and 100% of C in the replicase construct are m5c. In some aspects, this disclosure describes taRNA wherein about 25% to about 75% of U in the trRNA are 2'OMe-UTP, about 25% to about 75% of U in the trRNA are 5'-moUTP, and 12531064.1 about 40% to about 100% of C in the trRNA are m5c. In some embodiments, about 40% to about 60% of U in the trRNA are 2'OMe-UTP, about 40% to about 60% of U in the trRNA are 5'- moUTP, and about 90% to about 100% of C in the trRNA are m5c. In some embodiments, about 50% of U in the trRNA are 2'OMe-UTP, about 50% of U in the trRNA are 5'-moUTP, and about 100% of C in the trRNA are m5c. In some embodiments, 50% of U in the trRNA are 2'OMe- UTP, 50% of U in the trRNA are 5'-moUTP, and 100% of C in the trRNA are m5c. Exemplary combinations of m5U and m5c In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are m5U and about 25% to about 100% of C in the taRNA (i.e., about 25% to about 100% of total C in the replicase construct and the trRNA) are m5c. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are m5U and about 25% to about 100% of C in the replicase construct are m5c. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA are m5U and about 25% to about 100% of C in the taRNA are m5c. Exemplary combinations of 5'-moMe-UTP and m5c In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are 5'-moMe-UTP and about 25% to about 100% of C in the trRNA (i.e., about 25% to about 100% of total C in the replicase construct and the trRNA) are m5c. In some aspects, this disclosure describes replicase construct wherein about 25% to about 100% of U in the trRNA are 5'-moMe-UTP and about 25% to about 100% of C in the replicase construct are m5c. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA are 5'-moMe-UTP and about 25% to about 100% of C in the taRNA are m5c. Exemplary combinations of N1-methoxymethyl Ψ and m5c In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are N1-methoxymethyl Ψ and about 25% to about 100% of C in the taRNA (i.e., about 25% to about 100% of total C in the replicase construct and the trRNA) are m5c. 12531064.1 In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are N1-methoxymethyl Ψ and about 25% to about 100% of C in the replicase construct are m5c. In some aspects, this disclosure describes trRNA wherein about 25% to about 100% of U in the trRNA are N1-methoxymethyl Ψ and about 25% to about 100% of C in the taRNA are m5c. Exemplary combinations of N1Me2'OMeΨTP and m5c In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are N1Me2'OMeΨTP and about 25% to about 100% of C in the taRNA (i.e., about 25% to about 100% of total C in the replicase construct and the trRNA) are m5c. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are N1Me2'OMeΨTP and about 25% to about 100% of C in the replicase construct are m5c. In some aspects, this disclosure describes trRNA wherein about 25% to about 100% of U in the trRNA are N1Me2'OMeΨTP and about 25% to about 100% of C in the trRNA are m5c. Exemplary combinations of N1ethylΨTP and m5c In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the taRNA (i.e., about 25% to about 100% of total U in the replicase construct and the trRNA) are N1ethylΨTP and about 25% to about 100% of C in the taRNA (i.e., about 25% to about 100% of total C in the replicase construct and the trRNA) are m5c. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the replicase construct are N1ethylΨTP and about 25% to about 100% of C in the replicase construct are m5c. In some aspects, this disclosure describes taRNA wherein about 25% to about 100% of U in the trRNA are N1ethylΨTP and about 25% to about 100% of C in the trRNA are m5c. Compositions and Methods of Use In some embodiments, this disclosure describes a cell comprising one or more of any of the taRNAs described herein. In some aspects, the taRNAs described herein may be used to express a payload in a mammalian cell. Mammalian cells may be derived from any mammal, including, but not limited to, mice, hamsters, pigs, cows, sheep, goats, horses, and primates, 12531064.1 including humans. In some embodiments, the taRNA described herein are used to express payloads in isolated cells from established cell lines generally known in the art, such as 3T3, A549, BHK21, C127, CHO, HeLa, HEK, HT-1080, Huh7, Jurkat, NS0, PER.C6, Sp2 / 0, Vero, and derivatives thereof. In some embodiments, the taRNA described herein are used to express payloads in cells isolated from a subject (e.g., immune cells). In some embodiments, the taRNAs described herein are transfected into a cell. The term “transfection” refers to the process by which cells uptake foreign polynucleotides into the cytoplasm, in the absence of viral vectors. Non-limiting examples of transfection include electroporation, heat shock, liposome-mediated delivery, nanoparticle-mediated delivery, microinjections, sonoporation, photoporation, magnetofection, hydroporation, biolistics, continuous infusion, impalefection, and any technique known to those of ordinary skill in the art. In some embodiments, a cell transfected with a taRNA is transfected with the replicase construct and trans replicon construct concurrently (i.e., at the same time). In some embodiments, a cell transfected with a taRNA is transfected with the replicase construct and trans replicon construct sequentially; for example, the replicase construct may be transfected at a first time point and a trans replicon construct transfected at a second, later, time point. Once one or more foreign polynucleotides have entered the cytoplasm of a cell, the polynucleotides may be expressed by the cell. In some embodiments, a cell transfected with a taRNA expresses the replicase encoded by the replicase construct. In some embodiments, a cell transfected with a taRNA expresses (i.e., translates) the payload encoded by the trans replicon construct or its replicants. In some aspects, the taRNAs described herein may be used to express a payload in a subject. taRNAs described herein may be administered to a subject using any method known to those of ordinary skill in the art, such as injection (e.g., intravenous, intraocular, intravitreal, intramuscular, intradermal, intracardiac, intraperitoneal, and subcutaneous). In some embodiments, the taRNAs described herein are formulated as a pharmaceutical composition. A “pharmaceutical composition” refers to a composition comprising taRNAs formulated with one or more pharmaceutically acceptable excipients. In some embodiments, taRNAs are formulated in a carrier (e.g., lipidoid, liposome, lipid nanoparticle, polymer, lipoplex, ligand). In some embodiments, one or more cells transfected with taRNAs may be administered to the subject. In some embodiments, taRNAs are administered to mammalian subjects. Non-limiting examples of mammalian subjects include mice, hamsters, pigs, cows, sheep, goats, horses, and primates, including humans. In some embodiments, taRNAs are administered to human subjects. 12531064.1 In some embodiments, taRNAs are expressed in a cell-free system, for example, using in vitro transcription. EXEMPLARY SEQUENCES 12531064.1 12531064.1 12531064.1 12531064.1 12531064.1 5 12531064.1 EXAMPLES Example 1: Increased efficiency of in vitro transcription with incorporation of chemical modifications Chemically modified taRNAs having trRNAs encoding EGFP or SEAP were produced by in vitro transcription using a linearized DNA template. The final volume of each IVT reaction was 20 to 250uL. This reaction mixture was incubated for 2-3 hours (37ºC), after which DnaseI and DnaseI buffer were added, and the mixture was incubated for an additional 30-minute period (37ºC). After the full incubation period, RNA was isolated using NEB Monarch RNA Cleanup kits according to manufacturer instructions, then eluted into 100µL Rnase-free water. Total RNA produced (ng) was measured via Nanodrop for each construct. RNA integrity was assessed via denaturing gel electrophoresis or Agilent Fragment Analyzer. RNA was stored at -20ºC or 80ºC. IVT yield for or each construct is reported below in Table 1 as the percentage of RNA produced relative to starting template DNA. Table 1. IVT Yield with incorporation of a single type of chemically modified nucleotide 12531064.1 12531064.1 IVT yield of unmodified trRNA varied, with unmodified T3A constructs generally outperforming unmodified SINV / SINV constructs. Surprisingly, it was found that IVT yield for numerous modified trRNAs remained high—more than 5x higher for some constructs than starting DNA templates. IVT Yield of chemically modified taRNA was dependent on the chemical modification made to a nucleotide, but not the base of the nucleotide. For example, while 2’Ome-m6ATP (chemically modified A) constructs generally reduced IVT regardless of percent chemically modification (% Mod.), 2’OMe-ATP (a different chemically modified A), improved IVT Yield as much as 30x. 12531064.1 In stark contrast to reports that chemical modifications to pyrimidine bases (C and U) render saRNA constructs ineffective, several chemical modifications to C and U in trRNAs were tolerated and even yielded significant improvements to IVT Yield. N1meΨTP and 2'OMe-UTP improved IVT Yield as more than 60x, while m5C and 2'OMe-CTP increased IVT Yield by 25- 35x. Similarly, contrary to reports in saRNA, up to 100% replacement of U with Ψ was tolerated in taRNA, with as much as 13x IVT Yield. Notably, % incorporation of chemically modified nucleotides to trRNA yielded different effects on IVT Yield. For example, 50% replacement of A with 2'OMe-ATP improved IVT Yield by as much as 30x, but 100% replacement reduced IVT Yield to below 1x. Similar relationships were found across constructs, suggesting that both the chemical modification made to a nucleotide and percent incorporation of the chemically modified nucleotide into taRNA influence transcription. For example, maximum incorporation (100%) of some chemically modified nucleotides—such as 2'OMe-UTP—was deleterious, while lower percentage incorporation (e.g., 25%, 50%) of the same nucleotide significantly increased IVT Yield. Still other chemically modified nucleotides—such as m5C—were not tolerated when incorporated at lower percentages, but, surprisingly, yielded substantial improvements at 100% modification. Overall, it was found that taRNA expression can benefit from incorporation of a variety of chemically modified nucleotides into trRNA, including those previously described in the art as not tolerated in saRNA. Importantly, improvements to trRNA yield depended both on the chemical modification introduced to nucleotides of the trRNA as well as the percent incorporation. This phenomenon is further documented below in Table 2. Table 2. IVT yield of chemically modified trRNA by percent modification, relative to unmodified trRNA 12531064.1 Example 2. Increased efficiency of in vitro transcription with incorporation of combinations of chemically modified nucleotides taRNA were modified to incorporate N1meΨTP and 5'-moUTP, 2'OMe-UTP, or m5C into trRNA at varying ranges, using the methods described in Example 1. IVT yield of trRNA having multiple modified nucleotides are shown in Table 3 below. Two of the tested trRNA constructs included two types of chemically modified U. For example, one construct was chemically modified such that 75% of U were N1meΨTP and the remaining 25% of U were 5'-moUTP, such that 100% of U were chemically modified overall. Surprisingly, both combinations of chemically modified U were tolerated, such that expression was at least at baseline even at maximum incorporation of the chemically modified U (100% total). A third type of construct included combinations of N1meΨTP and m5C at various levels of incorporation, including 100% N1meΨTP and 100% m5C in the same construct. Overall, most 12531064.1 combinations of chemically modified nucleotides yielded significant improvements in expression, ranging from 5.24-fold (about 50% N1meΨTP and about 50% m5C) to 8.75-fold (about 75% N1meΨTP and about 75% m5C) increases. No tested combination of chemically modified nucleotides decreased IVT Yield. Example 3. Payload expression from chemically modified taRNAs In these proof-of-concept experiments, various cell types were co-transfected with taRNAs having a replicase construct encoding an SFV replicase and a chemically modified trRNA encoding GFP. As shown in FIG.2, BHK-21 cells were transfected with taRNAs having chemically modified trRNAs (50% m1Ψ; 50% Ψ; or 50% 2'OMe-UTP) comprising a payload encoding GFP. Surprisingly, cells treated with any of the three chemically modified trRNA, including trRNA having m1Ψ and Ψ, resulted in equal or improved expression of GFP relative to cells treated with trRNA having only unmodified U (UTP). Though these chemical modifications have been widely unsuccessful in saRNA, the instant results demonstrate that these chemically modified taRNAs can still be used to express payloads in cells, and that chemical modifications can even increase payload expression. FIG.3 shows quantification of similar experiments in 3T3 fibroblasts treated with taRNAs having chimeric T3A 5'-SINV-UTR-GFP-3'-SFV-UTR trRNAs.3T3 fibroblasts were treated with taRNAs having trRNA in which 0%, 50% or 100% of U were m1Ψ or 2'OMe-UTP. Cells treated with chemically modified trRNA show increases in payload expression (measured by relative fluorescence (RFU)) relative to 3T3 fibroblasts treated with unmodified trRNA. The effect of chemical modifications on taRNA-mediated payload expression were tested in BHK-21 cells or RAW cells, results of which are shown in FIGs.4A-4C.6 hours or 24 hours following transfection, GFP or SEAP expression in the cells was observed via plate reader. FIG.4A shows that, consistent with the cell-free findings described in Examples 1 and 2, taRNA-mediated GFP expression in BHK-21 cells treated with chemically modified trRNAs were variable; while some chemically modified nucleotides, in specific percent incorporation, improved expression of GFP, other modified nucleotides reduced expression. Surprisingly, trRNA having 50% of U being m1Ψ or 50% of C being 2'OMe-CTP resulted in the highest levels of GFP expression (here, measured in RFU). Notably, 100% incorporation of these chemically U and / or C into trRNA dramatically reduced GFP expression, confirming that for many modified nucleotides, some ranges, but not others, are tolerated. Accordingly, only two of the chemically 12531064.1 modified nucleotides tested in this experiment resulted in consistently poor expression across ranges: Ψ and m6A. For all other chemically modified nucleotides tested, some range of percent incorporation was tolerated, and for no chemically modified nucleotide were all ranges of percent incorporation tolerated. FIG.4B shows that several of the conditions containing chemically modified nucleotides had similar levels of SEAP at 24 hours, the conditions produced with 5'-moUTP led to higher levels of expression at 6 hours. Surprisingly, combinations of chemically modified nucleotides in trRNA having 5'-moUTP yielded the highest levels of SEAP expression. Finally, similar findings were made for SEAP expression in RAW cells, as shown in FIG.4C. Example 4: Reduced immunogenicity of chemically modified taRNAs In this experiment, A549 cells were transfected with taRNAs having chemically modified trRNAs at increasing dosages, then evaluated for expression of interferon stimulated gene 54 (ISG54) as a measure of induced immunogenicity. Results are shown in FIG.5 as fold- induction (ISG54 expression / unmodified). Cells treated with taRNAs having chemically modified trRNAs with 50% U being m1Ψ; 100% U being m1Ψ; or 50% U being 2'OMe-UTP showed significantly decreased fold-induction of ISG54 relative to cells treated with unmodified taRNA. Notably, taRNA having a trRNA with 100% of U being m1Ψ resulted in about an 80% reduction in fold-induced ISG54 expression. Importantly, all tested taRNAs showed substantially reduced immunogenicity, even at high doses. Example 5: Reduced immunogenicity and increased payload expression of in vitro transcription with incorporation of chemical modified trRNA In this experiment, human BJ fibroblasts were transfected with taRNAs having trRNAs comprising combinations of chemical modifications, then evaluated for expression of both SEAP, as a measure of payload expression, and interferon β (IFNβ), as a measure of induced immunogenicity. Chemically modified trRNAs were prepared with combinations of m5C modifications or m5C and 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1-methoxymethyl Ψ, N1ethylΨTP, m5U, or N1Me2'OMeΨTP; IVT yield of these are shown in Table 4 below. Table 4. IVT Yield with incorporation of multiple types of chemically modified nucleotides 12531064.1 Cells were treated with 5'-HBA-UTR-SFV replicase-3'-HBA-UTR replicase construct (SEQ ID NO: 1) and chemically modified trRNAs as described above, including: unmodified control (UTP); unmodified oeSTR (SEQ ID NO: 8); 100% of C replaced with m5C and 50% of U replaced with 5'-moUTP; 100% of C replaced with m5C, 50% of U replaced with 5'-moUTP, and 50% of U replaced with 2'OMe-UTP (2’OMe-U); 100% of C replaced with m5C and 50% of U replaced with 2'OMe-U; 100% of C replaced with m5C and 100% of U replaced with 5'- moUTP; or 50% of U replaced with 5'-moUTP and 50% of U replaced with 2'OMe-U. taRNAs showed high expression of SEAP and increased IFNβ induction, likely a result of increased amplification. Notably, taRNA including a modification of m5C were not only 12531064.1 capable of expressing the SEAP payload, but exhibited increased expression of SEAP relative to control. Overall, these results show that, unlike saRNAs, taRNAs tolerate several types of chemical modifications at specific range incorporation without the loss of efficiency- and often, with enhanced expression- while also exhibiting reduced immunogenicity. EMBODIMENTS Embodiment 1. A trans-amplifying ribonucleic acid (RNA) (taRNA) comprising: (a) a first RNA polynucleotide comprising a nucleic acid encoding a replicase; and (b) a second RNA polynucleotide comprising a nucleic acid encoding a payload, wherein about 25% to about 100% of adenine (A), cytidine (C), guanine (G), and / or uridine (U) in the first RNA polynucleotide and / or the second RNA polynucleotide comprise a - methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an - ethyl chemical modification. Embodiment 2. The taRNA of embodiment 1, wherein about 25% to about 100% of A in the first and / or second RNA polynucleotides are 2'-O-methyl-adenosine-5'- triphosphase(2'OMe-ATP), N6-methyladenosine-5'-triphosphate (m6ATP), or 2'-O-methyl-N6- methyladenosine-5'-triphosphate (2'OMe-m6ATP). Embodiment 3. The taRNA of embodiment 2, wherein about 25% to about 100% of A in the first and / or second RNA polynucleotides are 2'OMe-ATP. Embodiment 4. The taRNA of embodiment 3, wherein about 25% to about 75% of A in the first and / or second RNA polynucleotides are 2'OMe-ATP. Embodiment 5. The taRNA of embodiment 4, wherein about 40% to about 60% of A in the first and / or second RNA polynucleotides are 2'OMe-ATP. Embodiment 6. The taRNA of embodiment 5, wherein about 50% of A in the first and / or second RNA polynucleotides are 2'OMe-ATP. Embodiment 7. The taRNA of embodiment 3, wherein about 60% to about 90% of A in the first and / or second RNA polynucleotides are 2'OMe-ATP. Embodiment 8. The taRNA of embodiment 7, wherein about 75% of A in the first and / or second RNA polynucleotides are 2'OMe-ATP. 12531064.1 Embodiment 9. The taRNA of embodiment 3, wherein about 75% to about 100% of A in the first and / or second RNA polynucleotides are 2'OMe-ATP. Embodiment 10. The taRNA of embodiment 9, wherein about 90% to about 100% of A in the first and / or second RNA polynucleotides are 2'OMe-ATP. Embodiment 11. The taRNA of embodiment 10, wherein about 100% of A in the first and / or second RNA polynucleotides are 2'OMe-ATP. Embodiment 12. The taRNA of embodiment 2, wherein about 25% to about 100% of A in the first and / or second RNA polynucleotides are m6ATP. Embodiment 13. The taRNA of embodiment 12, wherein about 25% to about 75% of A in the first and / or second RNA polynucleotides are m6ATP. Embodiment 14. The taRNA of embodiment 13, wherein about 40% to about 60% of A in the first and / or second RNA polynucleotides are m6ATP. Embodiment 15. The taRNA of embodiment 14, about 50% of A in the first and / or second RNA polynucleotides are m6ATP. Embodiment 16. The taRNA of embodiment 12, wherein about 75% to about 100% of A in the first and / or second RNA polynucleotides are m6ATP. Embodiment 17. The taRNA of embodiment 16, wherein about 90% to about 100% of A in the first and / or second RNA polynucleotides are m6ATP. Embodiment 18. The taRNA of embodiment 17, about 100% of A in the first and / or second RNA polynucleotides are m6ATP. Embodiment 19. The taRNA of embodiment 2, wherein about 25% to about 100% of A in the first and / or second RNA polynucleotides are 2'OMe-m6ATP. Embodiment 20. The taRNA of embodiment 19, wherein about 25% to about 75% of A in the first and / or second RNA polynucleotides are 2'OMe-m6ATP. Embodiment 21. The taRNA of embodiment 20, wherein about 40% to about 60% of A in the first and / or second RNA polynucleotides are 2'OMe-m6ATP. Embodiment 22. The taRNA of embodiment 21, wherein about 50% of A in the first and / or second RNA polynucleotides are 2'OMe-m6ATP. 12531064.1 Embodiment 23. The taRNA of embodiment 19, wherein about 75% to about 100% of A in the first and / or second RNA polynucleotides are 2'OMe-m6ATP. Embodiment 24. The taRNA of embodiment 23, wherein about 90% to about 100% of A in the first and / or second RNA polynucleotides are 2'OMe-m6ATP. Embodiment 25. The taRNA of embodiment 24, wherein about 100% of A in the first and / or second RNA polynucleotides are 2'OMe-m6ATP. Embodiment 26. The taRNA of embodiment 1, wherein about 25% to about 100% of C in the first and / or second RNA polynucleotides are 5-methylcytidine-5'-triphosphate (m5c), 2'-O- methylcytidine-5'-triphosphate (2'OMe-CTP), N4-acetylcytidine triphosphate (ac4CTP), 5- methylcytidine-5'-triphosphate (5moC), or 5-methylcytosine (5mC). Embodiment 27. The taRNA of embodiment 26, wherein about 25% to about 100% of C in the first and / or second RNA polynucleotides are m5c. Embodiment 28. The taRNA of embodiment 27, wherein about 25% to about 75% of C in the first and / or second RNA polynucleotides are m5c. Embodiment 29. The taRNA of embodiment 28, wherein about 25% to about 40% of C in the first and / or second RNA polynucleotides are m5c. Embodiment 30. The taRNA of embodiment 29, wherein about 25% of C in the first and / or second RNA polynucleotides are m5c. Embodiment 31. The taRNA of embodiment 30, wherein about 40% to about 60% of C in the first and / or second RNA polynucleotides are m5c. Embodiment 32. The taRNA of embodiment 29, wherein about 50% of C in the first and / or second RNA polynucleotides are m5c. Embodiment 33. The taRNA of embodiment 27, wherein about 75% to about 100% of C in the first and / or second RNA polynucleotides are m5c. Embodiment 34. The taRNA of embodiment 33, wherein about 90% to about 100% of C in the first and / or second RNA polynucleotides are m5c. Embodiment 35. The taRNA of embodiment 32, wherein about 100% of C in the first and / or second RNA polynucleotides are m5c. 12531064.1 Embodiment 36. The taRNA of embodiment 26, wherein about 25% to about 100% of C in the first and / or second RNA polynucleotides are 2'OMe-CTP. Embodiment 37. The taRNA of embodiment 36, wherein about 25% to about 40% of C in the first and / or second RNA polynucleotides are 2'OMe-CTP. Embodiment 38. The taRNA of embodiment 37, wherein about 25% of C in the first and / or second RNA polynucleotides are 2'OMe-CTP. Embodiment 39. The taRNA of embodiment 36, wherein about 40% to about 60% of C in the first and / or second RNA polynucleotides are 2'OMe-CTP. Embodiment 40. The taRNA of embodiment 39, wherein about 50% of C in the first and / or second RNA polynucleotides are 2'OMe-CTP. Embodiment 41. The taRNA of embodiment 36, wherein about 60% to about 90% of C in the first and / or second RNA polynucleotides are 2'OMe-CTP. Embodiment 42. The taRNA of embodiment 40, wherein about 75% to about 100% of C in the first and / or second RNA polynucleotides are 2'OMe-CTP. Embodiment 43. The taRNA of embodiment 36, wherein about 75% to about 100% of C in the first and / or second RNA polynucleotides are 2'OMe-CTP. Embodiment 44. The taRNA of embodiment 40, wherein about 90% to about 100% of C in the first and / or second RNA polynucleotides are 2'OMe-CTP. Embodiment 45. The taRNA of embodiment 44, wherein about 100% of C in the first and / or second RNA polynucleotides are 2'OMe-CTP. Embodiment 46. The taRNA of embodiment 27, wherein about 25% to about 100% of C in the first and / or second RNA polynucleotides are ac4CTP. Embodiment 47. The taRNA of embodiment 46, wherein about 25% to about 75% of C in the first and / or second RNA polynucleotides are ac4CTP. Embodiment 48. The taRNA of embodiment 47, wherein about 40% to about 60% of C in the first and / or second RNA polynucleotides are ac4CTP. Embodiment 49. The taRNA of embodiment 48, wherein about 50% of C in the first and / or second RNA polynucleotides are ac4CTP. 12531064.1 Embodiment 50. The taRNA of embodiment 46, wherein about 75% to about 100% of C in the first and / or second RNA polynucleotides are ac4CTP. Embodiment 51. The taRNA of embodiment 50, wherein about 90% to about 100% of C in the first and / or second RNA polynucleotides are ac4CTP. Embodiment 52. The taRNA of embodiment 51, wherein about 100% of C in the first and / or second RNA polynucleotides are ac4CTP. Embodiment 53. The taRNA of embodiment 26, wherein about 25% to about 100% of C in the first and / or second RNA polynucleotides are 5moC. Embodiment 54. The taRNA of embodiment 53, wherein about 25% to about 75% of C in the first and / or second RNA polynucleotides are 5moC. Embodiment 55. The taRNA of embodiment 54, wherein about 40% to about 60% of C in the first and / or second RNA polynucleotides are 5moC. Embodiment 56. The taRNA of embodiment 55, wherein about 50% of C in the first and / or second RNA polynucleotides are 5moC. Embodiment 57. The taRNA of embodiment 54, wherein about 75% to about 100% of C in the first and / or second RNA polynucleotides are 5moC. Embodiment 58. The taRNA of embodiment 57, wherein about 75% of C in the first and / or second RNA polynucleotides are 5moC. Embodiment 59. The taRNA of embodiment 57, wherein about 90% to about 100% of C in the first and / or second RNA polynucleotides are 5moC. Embodiment 60. The taRNA of embodiment 59, wherein about 100% of C in the first and / or second RNA polynucleotides are 5moC. Embodiment 61. The taRNA of embodiment 46, wherein 25% to 100% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 62. The taRNA of embodiment 61, wherein about 25% to about 75% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 63. The taRNA of embodiment 62, wherein about 40% to about 60% of C in the first and / or second RNA polynucleotides are 5mC. 12531064.1 Embodiment 64. The taRNA of embodiment 38, wherein about 50% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 65. The taRNA of embodiment 61, wherein about 75% to about 100% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 66. The taRNA of embodiment 65, wherein about 90% to about 100% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 67. The taRNA of embodiment 66, wherein about 100% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 68. The taRNA of embodiment 1, wherein about 25% to about 100% of G in the first and / or second RNA polynucleotides are 2'-O-methylguanosine-5'-O-triphosphate (2'OMe-GTP). Embodiment 69. The taRNA of embodiment 68, wherein about 25% to about 100% of G in the first and / or second RNA polynucleotides are 2'OMe-GTP. Embodiment 70. The taRNA of embodiment 69, wherein about 25% to about 75% of G in the first and / or second RNA polynucleotides are 2'OMe-GTP. Embodiment 71. The taRNA of embodiment 70, wherein about 40% to about 60% of G in the first and / or second RNA polynucleotides are 2'OMe-GTP. Embodiment 72. The taRNA of embodiment 71, wherein about 50% of G in the first and / or second RNA polynucleotides are 2'OMe-GTP. Embodiment 73. The taRNA of embodiment 69, wherein about 75% to about 100% of G in the first and / or second RNA polynucleotides are 2'OMe-GTP. Embodiment 74. The taRNA of embodiment 73, wherein about 90% to about 100% of G in the first and / or second RNA polynucleotides are 2'OMe-GTP. Embodiment 75. The taRNA of embodiment 74, wherein about 100% of G in the first and / or second RNA polynucleotides are 2'OMe-GTP. Embodiment 76. The taRNA of embodiment 1, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are 5-methyluridine-5'-triphosophate (m5U), 2- thiouridine-5'-triphosphate (2-Thio-UTP), 2'-O-methyluridine-5'-triphosphase (2'OMe-UTP), 5- 12531064.1 methoxyuridine-5'-triphosphate (5'-moUTP), 5-methoxymethyl uridine (5'-moMe-UTP), 1- methoxymethylpseudouridine (N1-methoxymethyl Ψ), pseudouridine-5'-triphosphate (Ψ), 2'-O- methylpseudouridine-5'-triphosphate (2'OMeΨTP), N1-methyl-pseudourine-5'-triphosphate (N1MeΨTP), N1-methyl-2'-O-methylpseudouridine-5'-triphosphate (N1Me2'OMeΨTP), N1- ethylpseudouridine-5'-triphosphate (N1ethylΨTP), or N1-methyl-pseudouridine (m1Ψ). Embodiment 77. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are m5U. Embodiment 78. The taRNA of embodiment 77, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are m5U. Embodiment 79. The taRNA of embodiment 78, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are m5U. Embodiment 80. The taRNA of embodiment 79, wherein about 50% of U in the first and / or second RNA polynucleotides are m5U. Embodiment 81. The taRNA of embodiment 77, wherein about 60% to about 90% of U in the first and / or second RNA polynucleotides are m5U. Embodiment 82. The taRNA of embodiment 81, wherein about 75% of U in the first and / or second RNA polynucleotides are m5U. Embodiment 83. The taRNA of embodiment 77, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are m5U. Embodiment 84. The taRNA of embodiment 81, wherein about 100% of U in the first and / or second RNA polynucleotides are m5U. Embodiment 85. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are 2-Thio-UTP. Embodiment 86. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. Embodiment 87. The taRNA of embodiment 86, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. 12531064.1 Embodiment 88. The taRNA of embodiment 87, wherein about 25% to about 40% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. Embodiment 89. The taRNA of embodiment 88, wherein about 25% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. Embodiment 90. The taRNA of embodiment 87, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. Embodiment 91. The taRNA of embodiment 90, wherein about 50% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. Embodiment 92. The taRNA of embodiment 89, wherein about 60% to about 90% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. Embodiment 93. The taRNA of embodiment 92, wherein about 75% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. Embodiment 94. The taRNA of embodiment 86, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. Embodiment 95. The taRNA of embodiment 94, wherein about 100% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. Embodiment 96. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 97. The taRNA of embodiment 96, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 98. The taRNA of embodiment 97, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 99. The taRNA of embodiment 98, wherein about 50% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 100. The taRNA of embodiment 96, wherein about 60% to about 90% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 101. The taRNA of embodiment 100, wherein about 75% of U in the first and / or second RNA polynucleotides are 5'-moUTP. 12531064.1 Embodiment 102. The taRNA of embodiment 100, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 103. The taRNA of embodiment 100, wherein about 100% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 104. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are 5'-moMe-UTP . Embodiment 105. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are N1-methoxymethyl Ψ. Embodiment 106. The taRNA of embodiment 105, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are N1-methoxymethyl Ψ. Embodiment 107. The taRNA of embodiment 106, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are N1-methoxymethyl Ψ. Embodiment 108. The taRNA of embodiment 107, wherein about 50% of U in the first and / or second RNA polynucleotides are N1-methoxymethyl Ψ. Embodiment 109. The taRNA of embodiment 105, wherein about 60% to about 90% of U in the first and / or second RNA polynucleotides are N1-methoxymethyl Ψ. Embodiment 110. The taRNA of embodiment 109, wherein about 75% of U in the first and / or second RNA polynucleotides are N1-methoxymethyl Ψ. Embodiment 111. The taRNA of embodiment 109, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are N1-methoxymethyl Ψ. Embodiment 112. The taRNA of embodiment 109, wherein about 100% of U in the first and / or second RNA polynucleotides are N1-methoxymethyl Ψ. Embodiment 113. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are Ψ. Embodiment 114. The taRNA of embodiment 113, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are Ψ. Embodiment 115. The taRNA of embodiment 114, wherein about 25% to about 40% of U in the first and / or second RNA polynucleotides are Ψ. 12531064.1 Embodiment 116. The taRNA of embodiment 115, wherein about 25% of U in the first and / or second RNA polynucleotides are Ψ. Embodiment 117. The taRNA of embodiment 114, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are Ψ. Embodiment 118. The taRNA of embodiment 115, wherein about 50% of U in the first and / or second RNA polynucleotides are Ψ. Embodiment 119. The taRNA of embodiment 113, wherein about 75% to about 100% of U in the first and / or second RNA polynucleotides are Ψ. Embodiment 120. The taRNA of embodiment 119, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are Ψ. Embodiment 121. The taRNA of embodiment 118, wherein about 100% of U in the first and / or second RNA polynucleotides are Ψ. Embodiment 122. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are 2'OMeΨTP. Embodiment 123. The taRNA of embodiment 122, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are 2'OMeΨTP. Embodiment 124. The taRNA of embodiment 123, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are 2'OMeΨTP. Embodiment 125. The taRNA of embodiment 124, wherein about 50% of U in the first and / or second RNA polynucleotides are 2'OMeΨTP. Embodiment 126. The taRNA of embodiment 122, wherein about 60% to about 90% of U in the first and / or second RNA polynucleotides are 2'OMeΨTP. Embodiment 127. The taRNA of embodiment 126, wherein about 75% of U in the first and / or second RNA polynucleotides are 2'OMeΨTP. Embodiment 128. The taRNA of embodiment 126, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are 2'OMeΨTP. Embodiment 129. The taRNA of embodiment 126, wherein about 100% of U in the first and / or second RNA polynucleotides are 2'OMeΨTP. 12531064.1 Embodiment 130. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are N1MeΨTP. Embodiment 131. The taRNA of embodiment 130, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are N1MeΨTP. Embodiment 132. The taRNA of embodiment 131, wherein about 25% to about 40% of U in the first and / or second RNA polynucleotides are N1MeΨTP. Embodiment 133. The taRNA of embodiment 132, wherein about 25% of U in the first and / or second RNA polynucleotides are N1MeΨTP. Embodiment 134. The taRNA of embodiment 131, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are N1MeΨTP. Embodiment 135. The taRNA of embodiment 134, wherein about 50% of U in the first and / or second RNA polynucleotides are N1MeΨTP. Embodiment 136. The taRNA of embodiment 130, wherein about 60% to about 90% of U in the first and / or second RNA polynucleotides are N1MeΨTP. Embodiment 137. The taRNA of embodiment 136, wherein about 75% of U in the first and / or second RNA polynucleotides are N1MeΨTP. Embodiment 138. The taRNA of embodiment 130, wherein about 75% to about 100% of U in the first and / or second RNA polynucleotides are N1MeΨTP. Embodiment 139. The taRNA of embodiment 138, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are N1MeΨTP. Embodiment 140. The taRNA of embodiment 139, wherein about 100% of U in the first and / or second RNA polynucleotides are N1MeΨTP. Embodiment 141. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are N1Me2'OMeΨTP. Embodiment 142. The taRNA of embodiment 141, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are N1Me2'OMeΨTP. Embodiment 143. The taRNA of embodiment 142, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are N1Me2'OMeΨTP. 12531064.1 Embodiment 144. The taRNA of embodiment 143, wherein about 50% of U in the first and / or second RNA polynucleotides are N1Me2'OMeΨTP. Embodiment 145. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are N1ethylΨTP. Embodiment 146. The taRNA of embodiment 145, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are N1ethylΨTP. Embodiment 147. The taRNA of embodiment 146, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are N1ethylΨTP. Embodiment 148. The taRNA of embodiment 147, wherein about 50% of U in the first and / or second RNA polynucleotides are N1ethylΨTP. Embodiment 149. The taRNA of embodiment 145, wherein about 75% to about 100% of U in the first and / or second RNA polynucleotides are N1ethylΨTP. Embodiment 150. The taRNA of embodiment 149, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are N1ethylΨTP. Embodiment 151. The taRNA of embodiment 150, wherein about 100% of U in the first and / or second RNA polynucleotides are N1ethylΨTP. Embodiment 152. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are m1Ψ. Embodiment 153. The taRNA of embodiment 152, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are m1Ψ. Embodiment 154. The taRNA of embodiment 153, wherein about 25% to about 40% of U in the first and / or second RNA polynucleotides are m1Ψ. Embodiment 155. The taRNA of embodiment 154, wherein about 25% of U in the first and / or second RNA polynucleotides are m1Ψ. Embodiment 156. The taRNA of embodiment 153, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are m1Ψ. Embodiment 157. The taRNA of embodiment 156, wherein about 50% of U in the first and / or second RNA polynucleotides are m1Ψ. 12531064.1 Embodiment 158. The taRNA of embodiment 152, wherein about 60% to about 90% of U in the first and / or second RNA polynucleotides are m1Ψ. Embodiment 159. The taRNA of embodiment 158, wherein about 75% of U in the first and / or second RNA polynucleotides are m1Ψ. Embodiment 160. The taRNA of embodiment 152, wherein about 75% to about 100% of U in the first and / or second RNA polynucleotides are m1Ψ. Embodiment 161. The taRNA of embodiment 160, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are m1Ψ. Embodiment 162. The taRNA of embodiment 161, wherein about 100% of U in the first and / or second RNA polynucleotides are m1Ψ. Embodiment 163. The taRNA of embodiment 130, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 25% to about 50% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 164. The taRNA of embodiment 163, about 75% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 25% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 165. The taRNA of embodiment 163, about 50% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 50% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 166. The taRNA of embodiment 130, wherein about 40% to about 75% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 25% to about 60% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. Embodiment 167. The taRNA of embodiment 166, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 40% to about 60% U in the first and / or second RNA polynucleotides are 2'OMe-UTP. Embodiment 168. The taRNA of embodiment 167, wherein about 50% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 50% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. 12531064.1 Embodiment 169. The taRNA of embodiment 166, wherein about 60% to about 75% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 25% to about 40% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP. Embodiment 170. The taRNA of embodiment 169, wherein about 75% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 25% of U in the first and / or second RNA are 2'OMe-UTP. Embodiment 171. The taRNA of embodiment 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 25% to about 100% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 172. The taRNA of embodiment 171, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 40% to about 60% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 173. The taRNA of embodiment 172, wherein about 50% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 50% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 174. The taRNA of embodiment 171, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 60% to about 90% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 175. The taRNA of embodiment 174, wherein about 50% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 75% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 176. The taRNA of embodiment 171, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 90% to about 100% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 177. The taRNA of embodiment 176, wherein about 50% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 100% of C in the first and / or second RNA polynucleotides are 5mC. 12531064.1 Embodiment 178. The taRNA of embodiment 171, wherein about 60% to about 90% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 40% to about 60% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 179. The taRNA of embodiment 178, wherein about 75% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 50% of C in the first and / or second RNA polynucleotides are 5mC. Embodiment 180. The taRNA of embodiment 171, wherein about 60% to about 90% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 60% to about 90% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 181. The taRNA of embodiment 180, wherein about 75% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 75% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 182. The taRNA of embodiment 171, wherein about 60% to about 90% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 90% to about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 183. The taRNA of embodiment 171, wherein about 75% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 184. The taRNA of embodiment 171, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 40% to about 60% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 185. The taRNA of embodiment 184, wherein about 100% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 50% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 186. The taRNA of embodiment 171, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 60% to about 90% of C in the first and / or second RNA polynucleotides are m5C. 12531064.1 Embodiment 187. The taRNA of embodiment 186, wherein about 100% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 75% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 188. The taRNA of embodiment 171, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 90% to about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 189. The taRNA of embodiment 188, wherein about 100% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 190. The taRNA of embodiment 76, wherein about 40% to about 75% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP and about 40% to about 75% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 191. The taRNA of embodiment 190, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP and about 40% to about 60% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 192. The taRNA of embodiment 190 or 191, wherein about 50% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP and about 50% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 193. The taRNA of any one of embodiments 190-192, wherein about 50% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP and about 50% of U in the first and / or second RNA polynucleotides are 5'-moUTP. Embodiment 194. The taRNA of embodiment 26 or 76, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are 5'-moUTP and about 75% to about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 195. The taRNA of embodiment 194, wherein about 25% to about 60% of U in the first and / or second RNA polynucleotides are 5'-moUTP and about 75% to about 100% of C in the first and / or second RNA polynucleotides are m5C. 12531064.1 Embodiment 196. The taRNA of embodiment 194 or 195, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are 5'-moUTP and about 90% to about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 197. The taRNA of any one of embodiments 194 to 196, wherein about 50% of U in the first and / or second RNA polynucleotides are 5'-moUTP and about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 198. The taRNA of embodiment 197, wherein about 60% to about 100% of U in the first and / or second RNA polynucleotides are 5'-moUTP and about 75% to about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 199. The taRNA of embodiment 194, 197 or 198, wherein about 75% to about 100% of U in the first and / or second RNA polynucleotides are 5'-moUTP and about 75% to about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 200. The taRNA of any one of embodiments 194 or 197 to 199, wherein about 90% to about 100% of U in the first and / or second RNA polynucleotides are 5'-moUTP and about 90% to about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 201. The taRNA of any one of embodiments 194 or 197 to 200, wherein about 100% of U in the first and / or second RNA polynucleotides are 5'-moUTP and about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 202. The taRNA of embodiment 26 or 76, wherein about 40% to about 75% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP and about 75% to about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 203. The taRNA of embodiment 202, wherein about 25% to about 60% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP and about 75% to about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 204. The taRNA of embodiment 202 or 203, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP and about 60% to about 100% of C in the first and / or second RNA polynucleotides are m5C. 12531064.1 Embodiment 205. The taRNA of any one of embodiments 202 to 204, wherein about 50% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP and about 90% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 207. The taRNA of embodiment 26 or 76, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP, about 25% to about 75% of U in the first and / or second RNA polynucleotides are 5'-moUTP, and about 75% to about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 208. The taRNA of embodiment 207, wherein about 40% to about 60% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP, about 40% to about 60% of U in the first and / or second RNA polynucleotides are 5'-moUTP, and about 90% to about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 209. The taRNA of embodiment 207 or 208, wherein about 50% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP, about 50% of U in the first and / or second RNA polynucleotides are 5'-moUTP, and about 100% of C in the first and / or second RNA polynucleotides are m5C. Embodiment 210. The taRNA of any one of embodiments 1 to 209, wherein the replicase is an alphavirus replicase. Embodiment 211. The taRNA of embodiment 210, wherein the alphavirus is a Sindbis virus (SINV). Embodiment 212. The taRNA of embodiment 120, wherein the alphavirus is a Semliki Forest virus (SFV). Embodiment 213. The taRNA of any one of embodiments 1 to 120, wherein the first RNA polynucleotide does not comprise a conserved sequence element (CSE). Embodiment 214. The taRNA of any one of embodiments 1 to 213, wherein the first RNA polynucleotide comprises a 5' UTR. Embodiment 215. The taRNA of embodiment 214, wherein the 5' UTR is a human alpha- globin (HBA) 5' UTR. Embodiment 216. The taRNA of embodiment 215, wherein the 5' UTR comprises the sequence set forth in SEQ ID NO: 5. 12531064.1 Embodiment 217. The taRNA of any one of embodiments 1 to 216, wherein the first RNA polynucleotide comprises a 3’ UTR. Embodiment 218. The taRNA of embodiment 217, wherein the 3' UTR is a HBA 3' UTR. Embodiment 219. The taRNA of any one of embodiments 1 to 216, wherein the 3' UTR comprises the sequence set forth in SEQ ID NO: 6. Embodiment 220. The taRNA of any one of embodiments 1 to 213, wherein the second RNA polynucleotide comprises a CSE. Embodiment 221. The taRNA of any one of embodiments 1 to 220, wherein the second RNA polynucleotide comprises a 5' UTR. Embodiment 222. The taRNA of embodiment 221, wherein the 5' UTR comprises a conserved sequence element (CSE) which can be recognized by the replicase. Embodiment 223. The taRNA of embodiment 222, wherein the 5' UTR of the second RNA polynucleotide is a SINV 5' UTR. Embodiment 224. The taRNA of embodiment 222, wherein the 5' UTR of the second RNA polynucleotide is a SFV 5' UTR. Embodiment 225. The taRNA of any one of embodiments 1 to 224, wherein the second RNA polynucleotide comprises a 3' UTR. Embodiment 226. The taRNA of embodiment 225, wherein the 3' UTR comprises a conserved sequence element (CSE) which can be recognized by the replicase. Embodiment 227. The taRNA of embodiment 226, wherein the 5' UTR of the second RNA polynucleotide is a SINV 3' UTR. Embodiment 228. The taRNA of embodiment 226, wherein the 3' UTR of the second RNA polynucleotide is a SFV 3' UTR. Embodiment 229. The taRNA of any one of embodiments 1 to 228, wherein the first RNA polynucleotide comprises SEQ ID NO: 1, having the chemical modifications of any one of embodiments 1 to 209. 12531064.1 Embodiment 230. The taRNA of any one of embodiments 1 to 229, wherein the second RNA polynucleotide comprises any one of SEQ ID NOs: 2-4 having the chemical modifications of any one of embodiments 1 to 209. Embodiment 231. A cell comprising the taRNA of any one of embodiments 1 to 230. Embodiment 232. A method of expressing a payload in a cell, the method comprising: transfecting a cell with the taRNA of any one of embodiments 1 to 230. Embodiment 233. A method for expressing a payload in a subject, the method comprising administering to a subject the taRNA of any one of embodiments 1 to 230. Embodiment 234. The method of embodiment 233, wherein the subject is a mammal. Embodiment 235. The method of embodiment 234, wherein the subject is a human. Embodiment 236. A trans-amplifying ribonucleic acid (RNA) (taRNA) comprising: (a) a first RNA polynucleotide comprising a nucleic acid encoding a replicase; and (b) a second RNA polynucleotide comprising a nucleic acid encoding a payload, wherein about 25% to about 100% of cytidine (C) and uridine (U) in the first RNA polynucleotide and / or the second RNA polynucleotide comprise a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification. Embodiment 237. The taRNA of embodiment 236, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are N1-methyl-pseudourine-5'-triphosphate (N1MeΨTP), 5- 2'-O-methyluridine-5'-triphosphase (2'OMe-UTP), 5-methoxyuridine-5'- triphosphate (5'-moUTP), 5-methoxymethyl uridine (5'-moMe-UTP), N1-ethylpseudouridine-5'- triphosphate (N1ethylΨTP), 5-methyluridine-5'-triphosophate (m5U), or N1-methyl-2'-O- methylpseudouridine-5'-triphosphate (N1Me2'OMeΨTP). Embodiment 238. The taRNA of embodiment 236 or 237, wherein about 25% to about 100% of C in the first and / or second RNA polynucleotides are 5-methylcytidine-5'-triphosphate (m5c). 12531064.1

Claims

CLAIMS What is claimed is:

1. A trans-amplifying ribonucleic acid (RNA) (taRNA) comprising: a first RNA polynucleotide comprising a nucleic acid encoding a replicase; and a second RNA polynucleotide comprising a nucleic acid encoding a payload, wherein about 25% to about 100% of adenine (A), cytosine (C), guanosine (G), and / or uridine (U) in the first RNA polynucleotide and / or the second RNA polynucleotide comprise a - methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an - ethyl chemical modification.

2. The taRNA of claim 1, wherein 25% to 100% of C in the first RNA polynucleotide and / or the second RNA polynucleotide are 5-methylcytidine-5'-triphosphate (m5c).

3. The taRNA of claim 1, wherein 75% to 100% of C in the first RNA polynucleotide and / or the second RNA polynucleotide are 5-methylcytidine-5'-triphosphate (m5c).

4. The taRNA of claim 1, wherein about 100% of C in the first RNA polynucleotide and / or the second RNA polynucleotide are m5c.

5. The taRNA of any one of claims 1-4, wherein 25%-75% of U in the first RNA polynucleotide and / or the second RNA polynucleotide are 2'-O-methyluridine-5'-triphosphase (2'OMe-UTP) or 5-methoxyuridine-5'-triphosphate (5'-moUTP).

6. The taRNA of claim 5, wherein about 50% of U in the first RNA polynucleotide and / or the second RNA polynucleotide are 2'-O-methyluridine-5'-triphosphase (2'OMe-UTP) or 5- methoxyuridine-5'-triphosphate (5'-moUTP).

7. The taRNA of any one of claims 1-6, wherein about 100% of C in the second RNA polynucleotide are m5c and about 50% of U in the first RNA polynucleotide are 2'OMe-UTP or 5'-moUTP. 12531064.

18. The taRNA of any one of claims 1-7, wherein about 50% of U in the first RNA polynucleotide and / or the second RNA polynucleotide are unmodified.

9. The method of any one of claims 1-8, wherein less than 5% of nucleotides of the first RNA polynucleotide are modified.

10. The taRNA of claim 1, wherein about 25% to about 100% of cytidine (C) in the first RNA polynucleotide and / or the second RNA polynucleotide comprise a -methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an -ethyl chemical modification.

11. The taRNA of claim 10, wherein about 25% to about 100% of C in the first and / or second RNA polynucleotides are 5-methylcytidine-5'-triphosphate (m5c), 2'-O-methylcytidine- 5'-triphosphate (2'OMe-CTP), N4-acetylcytidine triphosphate (ac4CTP), 5-methylcytidine-5'- triphosphate (5moC), and / or 5-methylcytosine (5mC).

12. The taRNA of any one of claims 1, 10, or 11, wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are 5-methyluridine-5'-triphosophate (m5U), 2- thiouridine-5'-triphosphate (2-Thio-UTP), 2'-O-methyluridine-5'-triphosphase (2'OMe-UTP), 5- methoxyuridine-5'-triphosphate (5'-moUTP), 5-methoxymethyl uridine (5'-moMe-UTP), 1- methoxymethylpseudouridine (N1-methoxymethyl Ψ), pseudouridine-5'-triphosphate (Ψ), 2'-O- methylpseudouridine-5'-triphosphate (2'OMeΨTP), N1-methyl-pseudourine-5'-triphosphate (N1MeΨTP), N1-methyl-2'-O-methylpseudouridine-5'-triphosphate (N1Me2'OMeΨTP), N1- ethylpseudouridine-5'-triphosphate (N1ethylΨTP), and / or N1-methyl-pseudouridine13. The taRNA of claim 12, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 25% to about 50% of U in the first and / or second RNA polynucleotides are 5'-moUTP.

14. The taRNA of claim 12, wherein about 40% to about 75% of U in the first and / or second RNA polynucleotides are N1MeΨTP and about 25% to about 60% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP.

15. The taRNA of claim 12, wherein about 25% to about 75% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP and about 25% to about 75% of U in the first and / or second RNA polynucleotides are 5'-moUTP. 12531064.

116. The taRNA of claim 1, wherein about 25% to about 100% of C and about 25% to about 100% of U in the first RNA polynucleotide and / or the second RNA polynucleotide comprise a - methyl, an -O methyl, a pseudouridine, a methyl-pseudouridine, an -acetyl, a -thio, and / or an - ethyl chemical modification.

17. The taRNA of claim 1, wherein about 25% to about 100% of C in the first and / or second RNA polynucleotides are m5c and wherein about 25% to about 100% of U in the first and / or second RNA polynucleotides are N1MeΨTP, 2'OMe-UTP, 5'-moUTP, 5'-moMe-UTP, N1ethylΨTP, m5U, and / or N1Me2'OMeΨTP.

18. The taRNA any one of claims 1-17, wherein about 25% to about 100% of A in the first and / or second RNA polynucleotides are 2'-O-methyl-adenosine-5'-triphosphase(2'OMe-ATP), N6-methyladenosine-5'-triphosphate (m6ATP), and / or 2'-O-methyl-N6-methyladenosine-5'- triphosphate (2'OMe-m6ATP).

19. The taRNA of any one of claims 1-18, wherein about 25% to about 100% of G in the first and / or second RNA polynucleotides are 2'-O-methylguanosine-5'-O-triphosphate (2'OMe- GTP).

20. The taRNA of any one of claim 1-19, wherein the second RNA polynucleotide comprises, from 5’ to 3’: a 5’ untranslated region (UTR), the nucleic acid encoding the payload, and a 3’ UTR, wherein the 5’ UTR and / or the 3’ UTR comprises a conserved sequence element (CSE) that is cognate to the replicase encoded by the first RNA polynucleotide.

21. A trans-amplifying ribonucleic acid (RNA) (taRNA) comprising: a first RNA polynucleotide comprising a nucleic acid encoding a replicase; and a second RNA polynucleotide comprising a nucleic acid encoding a payload, wherein about 100% of C in the second RNA polynucleotide are m5c.

22. The taRNA of claim 20, wherein about 50% of U in the second RNA polynucleotide are 2'OMe-UTP or 5'-moUTP and about 50% of U in the second RNA polynucleotide are unmodified. 12531064.

123. A trans-amplifying ribonucleic acid (RNA) (taRNA) comprising: a first RNA polynucleotide comprising a nucleic acid encoding a replicase; and a second RNA polynucleotide comprising a nucleic acid encoding a payload, wherein about 25% to about 100% of C in the first and / or second RNA polynucleotides are m5C; and wherein: (a) about 60% to about 90% of U in the first and / or second RNA polynucleotides are N1MeΨTP; (b) about 25% to about 100% of U in the first and / or second RNA polynucleotides are 5'- moUTP; (c) about 40% to about 75% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP; or (d) about 25% to about 75% of U in the first and / or second RNA polynucleotides are 2'OMe-UTP and about 25% to about 75% of U in the first and / or second RNA polynucleotides are 5'-moUTP. 12531064.1

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