Mutants of CAS12A nuclease and methods for making and using same

Abstract

The present invention relates to variants of Cas12a nucleases with altered protospacer adjacent motif recognition specificity. The present invention further relates to methods for making the CRISPR-CAS nuclease variants and for using the variants to modify nucleic acids.

Description

[Technical field]

[0001] [STATEMENT REGARDING ELECTRONIC FILING OF SEQUENCE LISTING] A sequence listing in ASCII text format submitted under 37 CFR § 1.821, entitled 1499.7WO_ST25.txt, created on Oct. 13, 2020, and submitted via EFS-Web, with a size of 257,774 bytes, is provided in lieu of a paper copy. This sequence listing is incorporated herein by reference for its disclosure.

[0002] [PRIORITY STATEMENT] This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 62 / 916,392, filed October 17, 2019, the entire contents of which are incorporated herein by reference.

[0003] [Field of the Invention] The present invention relates to variants of Cas12a CRISPR-Cas nucleases with altered protospacer adjacent motif recognition specificity.The invention further relates to methods of making the CRISPR-Cas nuclease variants and to methods of using the variants to modify nucleic acids. [Background technology]

[0004] Genome editing / modification is a process that utilizes site-specific nucleases, such as CRISPR-Cas nucleases, to introduce variation into targeted genomic locations.Cas9, the most widely used nuclease for genome modification, can introduce mutations in genomic regions upstream of NGG motifs (e.g., protospacer adjacent motifs (PAMs)).Other Cas nucleases have different PAM recognition specificities.If the PAM specificities of these nucleases are particularly strict, they can reduce the usefulness of the nuclease for genome modification by limiting the number of genomic target sites available for modification by the nuclease. Summary of the Invention [Problem to be solved by the invention]

[0005] To address the shortcomings in the art, the present invention provides engineered CRISPR-Cas nucleases with improved PAM specificity, and methods for designing, identifying, and selecting such CRISPR-Cas nucleases. [Means for solving the problem]

[0006] One aspect of the invention provides a modified Lachnospiraceae bacterium CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) Cas12a (LbCas12a) polypeptide, wherein the modified LbCas12a polypeptide has at least 80% identity to the amino acid sequence of SEQ ID NO:1 (LbCas12a) and the following positions with respect to the position numbering of SEQ ID NO:1: K116, K120, K121, D122, E125, T148, T149, T152, D156, E159, Q529, G532, D535, K538, D541, Y542, L585, K591, M592, K595, V596, S599, K600, K601, Y616, Y617, Y619, Y620, Y621, Y622, Y623, Y624, Y625, Y626, Y627, Y628, Y629, Y630, Y631, Y632, Y633, Y634, Y635, Y636, Y637, Y638, Y639, Y640, Y641, Y642, Y643, Y644, Y645, Y646, Y647, Y648, Y649, Y650, Y651, Y652, Y653, Y654, Y655, Y656, Y657, Y658, Y659, Y666, Y667, Y668, Y670, Y671, Y672, Y673, Y674, Y675, Y676, Y677, Y678, Y6 In one embodiment, the present invention relates to an amino acid sequence comprising, essentially consisting of, or consisting of an amino acid sequence having, in any combination, a mutation at one or more (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or more) of W646, and / or W649 (which may be a mutation at one or more of the following positions with respect to the position numbering of SEQ ID NO:1: K116, K120, K121, D122, E125, T152, D156, E159, G532, D535, K538, D541, and / or K595).

[0007] A second aspect of the present invention provides a V-type Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-associated (Cas) (CRISPR-Cas) system comprising: (a) (i) a modified LbCas12a polypeptide of the present invention or a nucleic acid encoding a modified LbCas12a polypeptide of the present invention, and (ii) a fusion protein comprising a polypeptide of interest or a nucleic acid encoding a polypeptide of interest; and (b) a guide nucleic acid (CRISPR RNA, CRISPR DNA, crRNA, crDNA) comprising a spacer sequence and a repeat sequence, wherein the guide nucleic acid is capable of forming a complex with the modified LbCas12a polypeptide or the fusion protein, and the spacer sequence is capable of hybridizing to the target nucleic acid, thereby guiding the modified LbCas12a polypeptide and the polypeptide of interest to the target nucleic acid, thereby modifying or modulating the target nucleic acid.

[0008] A third aspect of the present invention provides a method for modifying a target nucleic acid, the method comprising the step of contacting the target nucleic acid with (a) (i) a modified LbCas12a polypeptide of the present invention, or a fusion protein comprising a modified LbCas12a polypeptide of the present invention, and (ii) a guide nucleic acid (e.g., CRISPR RNA, CRISPR DNA, crRNA, crDNA); (b) a complex comprising a modified LbCas12a polypeptide of the present invention and a guide nucleic acid; (c) a composition comprising (i) a modified lbCas12a polypeptide of the present invention, or a fusion protein of the present invention, and (ii) a guide nucleic acid; and / or (d) a system of the present invention, thereby modifying the target nucleic acid.

[0009] A fourth aspect of the present invention provides a method for modifying a target nucleic acid, the method comprising contacting a cell or cell-free system containing the target nucleic acid with (a) (i) a polynucleotide encoding a modified LbCas12a polypeptide of the present invention, or an expression cassette or vector comprising same, and (ii) a guide nucleic acid, or an expression cassette or vector comprising same; and / or (b) (i) a complex or fusion protein comprising a modified LbCas12a polypeptide of the present invention, and (ii) a nucleic acid construct encoding, or an expression cassette or vector comprising same, a guide nucleic acid, thereby modifying the target nucleic acid.

[0010] A fifth aspect of the invention provides a method of editing a target nucleic acid, the method comprising contacting the target nucleic acid with (a)(i) a fusion protein comprising a modified LbCas12a polypeptide of the invention and (a)(ii) a guide nucleic acid; (b) a complex comprising the fusion protein of the invention and a guide nucleic acid; (c) a composition comprising the fusion protein of the invention and a guide nucleic acid; and / or (d) a system of the invention, thereby editing the target nucleic acid.

[0011] A sixth aspect of the present invention provides a method for editing a target nucleic acid, the method comprising contacting a cell or cell-free system comprising a target nucleic acid with (a)(i) a polynucleotide encoding a fusion protein comprising a modified LbCas12a polypeptide of the present invention, or an expression cassette or vector comprising the same, and (a)(ii) a guide nucleic acid, or an expression cassette or vector comprising the same; and / or (b) a nucleic acid construct encoding a complex comprising a fusion protein comprising a modified LbCas12a polypeptide of the present invention and a guide nucleic acid, or an expression cassette or vector comprising the same; and / or (c) a system of the present invention, thereby editing the target nucleic acid.

[0012] A seventh aspect of the present invention provides a method for constructing a randomized DNA library comprising double-stranded nucleic acid molecules for determining the protospacer adjacent motif (PAM) requirement / specificity of a CRISPR-Cas nuclease having a PAM recognition site at the 5' end of the protospacer, the method comprising: preparing two or more double-stranded nucleic acid molecules comprising: (a) synthesizing a non-target oligonucleotide (first) strand and a target oligonucleotide (second) strand for each of the two or more double-stranded nucleic acid molecules, wherein the non-target oligonucleotide strand comprises from 5' to 3': (i) a first sequence having about 5 to about 15 nucleotides, (ii) a second sequence having at least four randomized nucleotides, (iii) a protospacer sequence comprising about 16 to about 25 nucleotides, and (iv) a third sequence having about 5 to about 20 nucleotides, a first sequence having about 5-15 nucleotides, (i), immediately adjacent to the 5'-terminus of a second sequence, (ii), which second sequence, (ii), is immediately adjacent to the 5'-terminus of a protospacer sequence, (iii), which protospacer sequence, is immediately adjacent to the 5'-terminus of a third sequence, (iv); the target oligonucleotide (second) strand is complementary to a non-target oligonucleotide strand; and (b) annealing the non-target oligonucleotide strand to a complementary target oligonucleotide strand to produce a double-stranded nucleic acid molecule, wherein the first sequence comprises a restriction site (at its 5'-terminus) and the third sequence comprises a restriction site (at its 3'-terminus), and wherein the first sequence, (i), the protospacer sequence, (iii), and the third sequence, (iv), of each of the two or more double-stranded nucleic acid molecules are identical, thereby constructing a randomized DNA library comprising double-stranded nucleic acid molecules.

[0013] An eighth aspect of the present invention provides a method for constructing a randomized DNA library comprising double-stranded nucleic acid molecules for determining the protospacer adjacent motif (PAM) requirement / specificity of a CRISPR-Cas nuclease having a PAM recognition site at the 3' end of the protospacer, the method comprising: preparing two or more double-stranded nucleic acid molecules comprising: (a) synthesizing a non-target oligonucleotide (first) strand and a target oligonucleotide (second) strand for each of the two or more double-stranded nucleic acid molecules, wherein the non-target oligonucleotide strand comprises from 5' to 3': (i) a first sequence having about 5 to about 20 nucleotides, (ii) a protospacer sequence comprising about 16 to about 25 nucleotides, (iii) a second sequence having at least four randomized nucleotides, and (iv) a third sequence having about 5 to about 15 nucleotides, wherein (i) a first sequence having about 5-20 nucleotides immediately adjacent to the 5'-terminus of the protospacer sequence of (ii), a second sequence of (iii) immediately adjacent to the 3'-terminus of the protospacer sequence of (iii), and a third sequence of (iv) immediately adjacent to the 3'-terminus of the second sequence of (iii); the target oligonucleotide (second) strand is complementary to the non-target oligonucleotide strand; and (b) annealing the non-target oligonucleotide strand to the complementary target oligonucleotide strand to produce a double-stranded nucleic acid molecule, wherein the first sequence (i) comprises a restriction site (at its 5'-terminus) and the third sequence (iv) comprises a restriction site (at its 3'-terminus), and wherein the first sequence (i), the protospacer sequence (ii) and the third sequence (iv) of each of the two or more double-stranded nucleic acid molecules are identical, thereby constructing a randomized DNA library comprising double-stranded nucleic acid molecules.

[0014] A ninth aspect of the present invention provides a randomized DNA library for determining the protospacer adjacent motif (PAM) requirement / specificity of a CRISPR-Cas nuclease having a PAM recognition site at the 5' end of the protospacer, the randomized DNA library comprising two or more double-stranded nucleic acid molecules, each comprising: (a) a non-target oligonucleotide (first) strand and a target oligonucleotide (second) strand, wherein the non-target oligonucleotide strand comprises, from 5' to 3', (i) about 5 to about 15 nucleotides. (ii) a first sequence having at least four randomized nucleotides (e.g., at least 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 nucleotides, and any range or value therein); (iii) a second sequence having at least about 16 to about 25 nucleotides, e.g., about 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 nucleotides; a protospacer sequence, and (iv) a third sequence having about 5 to about 20 nucleotides (e.g., about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 nucleotides, and any range or value therein), wherein the first sequence having about 5 to 15 nucleotides in (i) is immediately adjacent to the 5'-terminus of the second sequence in (ii), which second sequence in (ii) is immediately adjacent to the 5'-terminus of the protospacer sequence in (iii), and the protospacer sequence is immediately adjacent to the 5'-terminus of the protospacer sequence in (iv). the target oligonucleotide (second) strand is complementary to the non-target oligonucleotide strand; and (b) the non-target oligonucleotide strand anneals to the complementary target oligonucleotide strand to produce a double-stranded nucleic acid molecule, wherein the first sequence comprises a restriction site (at its 5' end) and the third sequence comprises a restriction site (at its 3' end), and wherein the first sequence (i), the protospacer sequence (iii) and the third sequence (iv) of each of the two or more double-stranded nucleic acid molecules are identical.

[0015] A tenth aspect of the present invention provides a randomized DNA library for determining the protospacer adjacent motif (PAM) requirement / specificity of a CRISPR-Cas nuclease having a PAM recognition site at the 3' end of the protospacer, the randomized DNA library comprising two or more double-stranded nucleic acid molecules, each comprising: (a) a non-target oligonucleotide (first) strand and a target oligonucleotide (second) strand, wherein the non-target oligonucleotide strand comprises, from 5' to 3', (i) about 5 to about 20 nucleotides. (ii) a protospacer sequence comprising about 16 to about 25 nucleotides, e.g., about 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 nucleotides; (iii) at least four randomized nucleotides (e.g., at least 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 nucleotides, and any range or value therein); (iv) a protospacer sequence comprising about 16 to about 25 nucleotides, e.g., about 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 nucleotides; (v) a protospacer sequence comprising at least four randomized nucleotides (e.g., at least 4, 5, 6, 7, 8, 9, 10, or more, and any range or value therein); and (iv) a third sequence having from about 5 to about 15 nucleotides (e.g., about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 nucleotides, and any range or value therein), wherein the first sequence having from about 5 to about 20 nucleotides in (i) is immediately adjacent to the 5'-terminus of the protospacer sequence in (ii), the second sequence in (iii) is immediately adjacent to the 3'-terminus of the protospacer sequence in (iii), and the third sequence in (iv) is from about 5 to about 15 nucleotides (e.g., about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 nucleotides, and any range or value therein), ) is immediately adjacent to the 3'-terminus of a second sequence; the target oligonucleotide (second) strand is complementary to the non-target oligonucleotide strand; and (b) the non-target oligonucleotide strand anneals to the complementary target oligonucleotide strand to produce a double-stranded nucleic acid molecule, where the first sequence comprises a restriction site (at its 5'-terminus) and the third sequence comprises a restriction site (at its 3'-terminus), and where the first sequence (i), protospacer sequence (ii) and third sequence (iv) of each of the two or more double-stranded nucleic acid molecules are identical.

[0016] The present invention further provides expression cassettes and / or vectors comprising polynucleotides encoding the CRISPR-Cas nucleases and / or fusion proteins of the present invention, and / or cells comprising the polynucleotides, polypeptides and / or fusion proteins of the present invention, and / or kits comprising the same.

[0017] These and other aspects of the invention are set forth in greater detail in the following description of the invention.

[0018] [Brief description of the sequence] SEQ ID NOs:1-17, 49, 50 and 51 are exemplary nucleotide sequences encoding Cas12a nucleases. SEQ ID NOs:18-22 are exemplary adenosine deaminases. SEQ ID NOs:23-25 ​​and SEQ ID NOs:42-48 are exemplary cytosine deaminases. SEQ ID NO:26 is an exemplary nucleotide sequence encoding a uracil-DNA glycosylase inhibitor (UGI). SEQ ID NOs: 27-29 provide an example of a protospacer adjacent motif location for a V-type CRISPR-Cas12a nuclease. SEQ ID NOs:30-39 provide examples of nucleotide sequences useful for generating randomized libraries of the invention, eg, for use in in vitro cleavage assays. SEQ ID NOs: 40-41 are exemplary regulatory sequences encoding promoters and introns. SEQ ID NO:52 provides the nucleotide sequence of an exemplary expression cassette. SEQ ID NO:53 provides the nucleotide sequence of an exemplary vector. SEQ ID NOs:54-61 provide exemplary spacer sequences. SEQ ID NO:62 provides an exemplary CRISPR RNA. [Brief description of the drawings]

[0019] [Figure 1]1 shows a diagram of an exemplary PAM library preparation of the present invention. In this method, 5' phosphorylated oligonucleotides are annealed and cloned into a pUC19 vector digested with EcoRI and SphI. The vector is linearized with ScaI (the AGTACT sequence is not recognized by Lbcpf1). Top strand (SEQ ID NO:32); bottom strand (SEQ ID NO:33). [Diagram 2] The average protospacer adjacent motifs (PAMs) per gene within the coding sequence for maize (top panel) and soybean (bottom panel) are shown. The LbCpf1 gene can access much less gene sequence than the Cas9 mutants. [Diagram 3] The average accessible cytosines (panels A, B) and adenines (panels C, D) restricted by PAM in maize (panels A, C) and soybean (panels B, D) are shown. As shown, LbCpf1 cytosines and adenines are much less accessible than the Cas9 mutants. [Figure 4] A diagram showing a simplified PAM determination assay from Gao et al. (Nat Biotechnol 35(8):789-792(2017)) is provided. The amplified fragments represent sequences that were not cleaved by the CRISPR-Cas nuclease, and the non-amplified fragments are those that were cleaved by the CRISPR-Cas nuclease. Sequencing and comparison to a no enzyme control identifies nucleic acid sequences that were not amplified (i.e., those present in the control population but not in the edited population), and thus sequences that are recognized and cleaved by the nuclease. Top panel: top sequence (SEQ ID NO:36), middle sequence (SEQ ID NO:37), bottom sequence (SEQ ID NO:38); middle panel: top sequence (SEQ ID NO:39), middle sequence (SEQ ID NO:37); bottom panel: top sequence (SEQ ID NO:36), middle sequence (SEQ ID NO:37). [Diagram 5]The average of the 3 Illumina MiSeq NGS reads for the PAMDA library plotted from highest to lowest counts. The 1024 library members containing NNNNN follow a normal distribution with a mean of 39 reads. [Figure 6] Cell sorting results of negative controls, including wtLbCas12a and a crRNA that did not target the plasmid spacer. [Figure 7] Cell sorting results of wtLbCas12a and crRNA targeting the plasmid spacer. [Figure 8] Cell sorting results of crRNA targeting LbCas12a-K595Y and the plasmid spacer. [Figure 9] Cell sorting results of LbCas12a-G532R-K595R double mutant control and crRNA targeting the plasmid spacer. [Figure 10] Cell sorting results of crRNA targeting the plasmid spacer and the LbCas12a-T152R-K595Y double mutation (the combination of two point mutations in this study). [Figure 11] Cell sorting results of crRNA targeting the plasmid spacer and the LbCas12a-T152R-K538W-K595Y triple mutation (combination of three point mutations). [Figure 12] Total normalized NGS counts for two separate no-crRNA control and wild-type dLbCas12a and reporter libraries. [Figure 13] Normalized PAM-SCANR scores of single point mutations for each of the 256 4-nucleotide PAMs. The line through the graph indicates the highest observed score, 1.67, for either of the two negative controls. [Figure 14] Normalized PAM-SCANR scores of combinatorial mutations for each of the 256 4-nucleotide PAMs. [Figure 15]We show that the combination of mutants K538W and K595Y results in an enzyme, LbCas12a-K538W-K595Y, with a unique PAM recognition sequence. In some cases, the shared PAM recognition motif from K538W (vertical shading) or K595Y (horizontal shading) is recognized by the combined mutant, but often the combination results in an entirely novel PAM recognition sequence (thatched). [Figure 16] We show that combinations of multiple expanded PAM mutations can produce unique, although sometimes additive, PAM recognition sequences. [Figure 17] Compare all non-TTTV PAMs (grey boxes) that scored above 1.67 by PAN-SCANR for K595Y (left) and T152R (right). All (except one) of the PAM-SCANR positive PAMs above the 1.67 cutoff had PAM depletion scores above the 9.2 cutoff in vitro. [Figure 18] The percentage of indels formed in HEK293T cells for each TTTV-containing spacer is shown. The percentage of individual indels is shown as a circle, square, or triangle for TTTC, TTTA, and TTTG, respectively. Also shown are the mean line and rounded values ​​for each spacer. [Figure 19] The maximum observed indel percentage of LbCas12a_K595Y HEK293T per PAM tested is shown. Values ​​above 0.1% are outside the sequencing noise and represent bona fide indels. [Figure 20] The maximum observed indel percentage of LbCas12a_T152R HEK293T per PAM tested is shown. Values ​​above 0.1% are outside the sequencing noise and represent bona fide indels. [Figure 21]The maximum observed percentage of indels in LbCas12a_K538W HEK293T per PAM tested is shown. Values ​​above 0.1% are outside the sequencing noise and represent bona fide indels. [Fig. 22A-22B] Linear correlation between Indel% (max) and normalized bacterial PAM-SCANR scores for LbCas12a-T152R (Figure 22A) and LbCas12a-K595Y (Figure 22B). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention is described below with reference to the accompanying drawings and examples in which embodiments of the invention are shown. This description is not intended to be a detailed catalog of all the different ways in which the invention may be implemented or all the features that may be added to the invention. For example, features illustrated with respect to one embodiment may be incorporated in other embodiments, and features illustrated with respect to a particular embodiment may be deleted from that embodiment. Thus, it is contemplated that the present invention may exclude or omit, in some embodiments of the invention, any feature or combination of features shown herein. Moreover, numerous variations and additions to the various embodiments suggested herein will be apparent to those skilled in the art in light of this disclosure and do not depart from the invention. Thus, the following description is intended to illustrate some particular embodiments of the invention, and is not intended to exhaustively specify all permutations, combinations, and variations thereof.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the present invention in this specification is for the purpose of describing specific embodiments only and is not intended to be limiting of the present invention.

[0022] All publications, patent applications, patents, and other references cited herein are incorporated by reference in their entirety for the teachings relevant to the sentence and / or paragraph in which the reference is set forth.

[0023] Unless the context indicates otherwise, it is expressly intended that the various features of the invention described herein can be used in any combination. Moreover, it is also contemplated that in some embodiments of the invention, any feature or combination of features described herein can be excluded or omitted. For example, if the specification states that a composition comprises components A, B, and C, it is expressly intended that any of A, B, or C, or any combination thereof, can be omitted and negated, either alone or in any combination.

[0024] As used in the description of this invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise.

[0025] Also, as used herein, "and / or" refers to and includes any and all possible combinations of one or more of the associated listed items, as well as the lack of combinations when interpreted in the alternative ("or").

[0026] The term "about" as used herein, when referring to a measurable value, such as an amount or concentration, means to include the specified value as well as a variation of ±10%, ±5%, ±1%, ±0.5%, or even ±0.1% of the specified value. For example, "about X", where X is a measurable value, means to include X and a variation of ±10%, ±5%, ±1%, ±0.5%, or even ±0.1% of X. Ranges provided herein for measurable values ​​may include any other ranges and / or individual values ​​therein.

[0027] As used herein, phrases such as "between X and Y" and "between about X and Y" should be interpreted to include X and Y. As used herein, phrases such as "between about X and Y" mean "between about X and about Y," and phrases such as "from about X to Y" mean "from about X to about Y."

[0028] The recitation of ranges of values ​​herein is merely intended to serve as a shorthand method of referring individually to each individual value falling within the range, unless otherwise indicated herein, and each individual value is incorporated herein as if it were individually recited herein. For example, if the range 10 to 15 is disclosed, then 11, 12, 13, and 14 are also disclosed.

[0029] As used in this specification, the terms "comprise", "comprises" and "comprising" specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0030] The transitional phrase "consisting essentially of" as used herein means that the claims should be construed to include the specified materials or steps recited in the claims and that do not materially affect the basic and novel feature(s) of the claimed invention. Thus, the term "consisting essentially of" when used in the claims of the present invention is not intended to be construed as the equivalent of "comprising."

[0031] As used herein, the terms "increase," "increasing," "enhance," "enhancing," "improve," and "improving" (and grammatical variations thereof) describe an increase of at least about 25%, 50%, 75%, 100%, 150%, 200%, 300%, 400%, 500% or more compared to a control.

[0032] As used herein, the terms "reduce," "reduced," "reducing," "reduction," "diminish," and "decrease" (and grammatical variations thereof) describe a reduction of at least about 5%, 10%, 15%, 20%, 25%, 35%, 50%, 75%, 80%, 85%, 90%, 95%, 97%, 98%, 99%, or 100%, for example, as compared to a control. In certain embodiments, the reduction results in no or essentially no detectable activity or amount (i.e., an insignificant amount, e.g., less than about 10% or even 5%).

[0033] A "heterologous" or "recombinant" nucleotide sequence is a nucleotide sequence that is not naturally associated with a host cell into which it is introduced and includes non-naturally occurring multiple copies of a naturally occurring nucleotide sequence.

[0034] A "native" or "wild-type" nucleic acid, nucleotide sequence, polypeptide, or amino acid sequence refers to a naturally occurring or endogenous nucleic acid, nucleotide sequence, polypeptide, or amino acid sequence. Thus, for example, a "wild-type mRNA" is an mRNA that occurs naturally in an organism or is endogenous to an organism. A "homologous" nucleic acid sequence is a nucleotide sequence that is naturally associated with a host cell into which it is introduced.

[0035] As used herein, the terms "nucleic acid", "nucleic acid molecule", "nucleotide sequence" and "polynucleotide" refer to RNA or DNA, linear or branched, single or double stranded, or hybrids thereof. The terms also encompass RNA / DNA hybrids. When dsRNA is produced synthetically, less common bases such as inosine, 5-methylcytosine, 6-methyladenine, hypoxanthine and others can also be used for pairing antisense, dsRNA and ribozymes. For example, polynucleotides containing C-5 propyne analogs of uridine and cytidine have been shown to bind RNA with high affinity and are potent antisense inhibitors of gene expression. Other modifications can also be made, such as modifications to the phosphodiester backbone of RNA or the 2'-hydroxy in the ribose sugar group.

[0036] The term "nucleotide sequence" as used herein refers to a heteropolymer of nucleotides or the sequence of these nucleotides from the 5' to 3' end of a nucleic acid molecule, including DNA or RNA molecules, including cDNA, DNA fragments or portions, genomic DNA, synthetic (e.g., chemically synthesized) DNA, plasmid DNA, mRNA, and antisense RNA, any of which may be single-stranded or double-stranded. The terms "nucleotide sequence," "nucleic acid," "nucleic acid molecule," "nucleic acid construct," "oligonucleotide," and "polynucleotide" are also used interchangeably herein to refer to a heteropolymer of nucleotides. Nucleic acid molecules and / or nucleotide sequences provided herein are presented herein in the 5' to 3' direction, from left to right, and are represented using the standard code for representing nucleotide symbols as set forth in the United States Sequence Rules, 37 CFR §§ 1.821-1.825 and World Intellectual Property Organization (WIPO) Standard ST.25. As used herein, the "5' region" can refer to the region of a polynucleotide closest to the 5' end of the polynucleotide. Thus, for example, an element in a 5' region of a polynucleotide can be located anywhere from the first nucleotide located at the 5' end of the polynucleotide to a nucleotide located in the middle of the polynucleotide. As used herein, a "3' region" can refer to the region of a polynucleotide that is closest to the 3' end of the polynucleotide. Thus, for example, an element in a 3' region of a polynucleotide can be located anywhere from the first nucleotide located at the 3' end of the polynucleotide to a nucleotide located in the middle of the polynucleotide.

[0037] The term "gene" as used herein refers to a nucleic acid molecule that can be used to produce mRNA, antisense RNA, miRNA, anti-microRNA antisense oligodeoxyribonucleotide (AMO), and the like. A gene may or may not be capable of being used to produce a functional protein or gene product. A gene can include both coding and non-coding regions (e.g., introns, regulatory elements, promoters, enhancers, termination sequences, and / or 5' and 3' untranslated regions). A gene may be "isolated," thereby meaning a nucleic acid that is substantially or essentially free from components that are normally found associated with the nucleic acid in its natural state. Such components include other cellular materials, culture medium from recombinant production, and / or various chemicals used in the chemical synthesis of the nucleic acid.

[0038] The term "mutation" refers to point mutations (e.g., missense, or nonsense, or single base pair insertions or deletions resulting in a frameshift), insertions, deletions, and / or truncations. When a mutation is a substitution of a residue in an amino acid sequence with another residue, or a deletion or insertion of one or more residues in a sequence, the mutation is typically described by specifying the original residue followed by the position of that residue in the sequence and the identity of the newly substituted residue.

[0039] The term "complementary" or "complementarity" as used herein refers to the natural binding of polynucleotides by base pairing under permissive salt and temperature conditions. For example, the sequence "AGT" (5' to 3') binds to the complementary sequence "TCA" (3' to 5'). Complementarity between two single-stranded molecules can be "partial," where only a portion of the nucleotides bind, or "complete," where there is total complementarity between the single-stranded molecules. The degree of complementarity between nucleic acid strands has a significant effect on the efficiency and strength of hybridization between nucleic acid strands.

[0040] "Complement," as used herein, can mean 100% complementarity with a comparator nucleotide sequence, or it can mean less than 100% complementarity (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc. complementarity).

[0041] A "portion" or "fragment" of a nucleotide sequence of the present invention is understood to mean a nucleotide sequence of reduced length compared to a reference nucleic acid or nucleotide sequence (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more nucleotides reduced) comprising, consisting essentially of, and / or consisting of a nucleotide sequence of contiguous nucleotides identical or nearly identical (e.g., 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% identical) to the reference nucleic acid or nucleotide sequence. Such a nucleic acid fragment or portion according to the invention may, where appropriate, be included within a larger polynucleotide of which it is a component. As an example, the repeat sequence of the guide nucleic acid of the invention may comprise a portion of a wild-type CRISPR-Cas repeat sequence (e.g., a wild-type Cas9 repeat, a wild-type Cas12a repeat, etc.).

[0042] Different nucleic acids or proteins with homology are referred to herein as "homologs". The term "homologs" includes homologous sequences from the same and other species and orthologous sequences from the same and other species. "Homology" refers to the level of similarity between two or more nucleic acid and / or amino acid sequences in terms of percentage of positional identity (i.e., sequence similarity or identity). Homology also refers to the concept of similar functional properties between different nucleic acids or proteins. Thus, the compositions and methods of the present invention further include homologs to the nucleotide and polypeptide sequences of the present invention. "Orthologs" as used herein refers to homologous nucleotide and / or amino acid sequences in different species that arose from a common ancestral gene during speciation. Homologs of the nucleotide sequences of the present invention have substantial sequence identity (e.g., at least about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100%) to the above-mentioned nucleotide sequences of the present invention.

[0043] "Sequence identity," as used herein, refers to the degree to which two optimally aligned polynucleotide or polypeptide sequences are invariant throughout the window of alignment of the components (eg, nucleotides or amino acids). "Identity" can be readily calculated by known methods, including but not limited to those described in Computational Molecular Biology (Lesk, AM, ed.) Oxford University Press, New York (1988); Biocomputing: Informatics and Genome Projects (Smith, DW, ed.) Academic Press, New York (1993); Computer Analysis of Sequence Data, Part I (Griffin, AM, and Griffin, HG, eds.) Humana Press, New Jersey (1994); Sequence Analysis in Molecular Biology (von Heinje, G., ed.) Academic Press (1987); and Sequence Analysis Primer (Gribskov, M. and Devereux, J., eds.) Stockton Press, New York (1991).

[0044] The term "percent sequence identity" or "percent identity" as used herein refers to the percentage of identical nucleotides in a linear polynucleotide sequence of a reference ("query") polynucleotide molecule (or its complementary strand) compared to a test ("subject") polynucleotide molecule (or its complementary strand) when the two sequences are optimally aligned. In some embodiments, "percent identity" can refer to the percentage of identical amino acids in an amino acid sequence compared to a reference polypeptide.

[0045] The phrase "substantially identical" or "substantial identity" as used herein in the context of two nucleic acid molecules, nucleotide sequences or protein sequences refers to two or more sequences or subsequences that have at least about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% nucleotide or amino acid residue identity when compared and aligned for maximum correspondence as measured using one of the following sequence comparison algorithms or by visual inspection. In some embodiments of the invention, the substantial identity exists over a region of contiguous nucleotides of the nucleotide sequences of the invention that is about 10 nucleotides to about 20 nucleotides, about 10 nucleotides to about 25 nucleotides, about 10 nucleotides to about 30 nucleotides, about 15 nucleotides to about 25 nucleotides, about 30 nucleotides to about 40 nucleotides, about 50 nucleotides to about 60 nucleotides, about 70 nucleotides to about 80 nucleotides, about 90 nucleotides to about 100 nucleotides, or more nucleotides in length, and any range therein (up to the full length of the sequence). In some embodiments, the nucleotide sequences can be substantially identical over at least about 20 nucleotides (e.g., about 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 nucleotides). In some embodiments, the substantially identical nucleotide or protein sequence performs substantially the same function as the nucleotide (or encoded protein sequence) to which it is substantially identical.

[0046] For sequence comparison, typically one sequence serves as a reference sequence, to which test sequences are compared.When using sequence comparison algorithm, test and reference sequences are input into computer, subsequence coordinates are designated as necessary, and sequence algorithm program parameters are designated.The sequence comparison algorithm then calculates the percent sequence identity for the test sequence(s) compared to the reference sequence based on the designated program parameters.

[0047] Optimal sequence alignment for aligning a comparison window is well known to those skilled in the art and may be performed by tools such as the Smith and Waterman local homology algorithm, the Needleman and Wunsch homology alignment algorithm, the Pearson and Lipman similarity search method, or by computerized implementations of algorithms such as GAP, BESTFIT, FASTA, and TFASTA available as part of the GCG® Wisconsin Package® (Accelrys Inc., San Diego, CA). The "identity fraction" for an aligned segment of a test sequence and a reference sequence is the number of identical elements shared by the two aligned sequences divided by the total number of elements in the reference sequence segment (i.e., the entire reference sequence, or a smaller defined portion of the reference sequence). The sequence identity percentage is expressed as the identity fraction multiplied by 100. The comparison of one or more polynucleotide sequences may be to a full-length polynucleotide sequence or a portion thereof, or to a longer polynucleotide sequence. For purposes of the present invention, "percent identity" may be determined using BLASTX version 2.0 for translated nucleotide sequences and BLASTN version 2.0 for polynucleotide sequences.

[0048] Two nucleotide sequences may be considered to be substantially complementary if the two sequences hybridize to each other under stringent conditions. In some exemplary embodiments, two nucleotide sequences that are considered to be substantially complementary hybridize to each other under highly stringent conditions.

[0049] "Stringent hybridization conditions" and "stringent hybridization wash conditions" in the context of nucleic acid hybridization experiments such as Southern and Northern hybridization are sequence dependent and will vary under different environmental parameters. A comprehensive guide to nucleic acid hybridization can be found in Tijssen Laboratory Techniques in Biochemistry and Molecular Biology-Hybridization with Nucleic Acid Probes part I chapter 2 "Overview of principles of hybridization and the strategy of nucleic acid probe assays", Elsevier, New York (1993). In general, highly stringent hybridization and wash conditions are those that meet the thermal melting point (T m ) is chosen to be approximately 5°C lower than

[0050] T m is the temperature (under defined ionic strength and pH) at which 50% of the target sequence hybridizes to a perfectly matched probe. Very stringent conditions are the T mAn example of stringent hybridization conditions for hybridization of complementary nucleotide sequences with more than 100 complementary residues on a filter in a Southern or Northern blot is 50% formamide with 1 mg heparin at 42° C., with overnight hybridization. An example of very stringent washing conditions is 0.15 M NaCl at 72° C. for about 15 minutes. An example of stringent washing conditions is a 0.2×SSC wash at 65° C. for 15 minutes (see Sambrook, below, for a description of SSC buffers). Often, a low stringency wash is performed before a high stringency wash to remove background probe signal. An example of a medium stringency wash, for example for a duplex of more than 100 nucleotides, is 1×SSC at 45° C. for 15 minutes. An example of a low stringency wash, for example for duplexes of more than 100 nucleotides, is 4-6×SSC at 40° C. for 15 minutes. For short probes (e.g., about 10-50 nucleotides), stringent conditions typically include a salt concentration of less than about 1.0 M Na ion, typically about 0.01-1.0 M Na ion (or other salts) (pH 7.0-8.3), and a temperature typically at least about 30° C. Stringent conditions can also be achieved by the addition of destabilizing agents such as formamide. In general, a signal-to-noise ratio of 2-fold (or higher) than that observed for an unrelated probe in a particular hybridization assay indicates detection of specific hybridization. Nucleotide sequences that do not hybridize to each other under stringent conditions are substantially identical if the proteins they encode are substantially identical. This can occur, for example, when copies of nucleotide sequences are made using the maximum codon degeneracy permitted by the genetic code.

[0051] Any nucleotide sequence, polynucleotide and / or recombinant nucleic acid construct of the present invention can be codon-optimized for expression in any organism of interest. Codon optimization is well known in the art and involves modification of nucleotide sequences for codon usage bias using a species-specific codon usage table. The codon usage table is generated based on sequence analysis of the most highly expressed genes for the organism / species of interest. If the nucleotide sequence is expressed in the nucleus, the codon usage table is generated based on sequence analysis of the most highly expressed nuclear genes for the species of interest. The modification of the nucleotide sequence is determined by comparing the codons present in the native polynucleotide sequence with the species-specific codon usage table. As is understood in the art, codon optimization of a nucleotide sequence results in a nucleotide sequence having less than 100% identity to a native nucleotide sequence (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, or 99.9%, and any range or value therein), yet encodes a polypeptide having the same function as that encoded by the original, native nucleotide sequence. Thus, in some embodiments of the invention, polynucleotides, nucleic acid constructs, expression cassettes, and / or vectors of the invention (e.g., comprising / encoding a polypeptide, fusion protein, complex, e.g., a modified CRISPR-Cas nuclease of the invention) are codon-optimized for expression in a particular species of interest, e.g., a particular plant species, a particular bacterial species, a particular animal species, etc.In some embodiments, the codon-optimized nucleic acid constructs, polynucleotides, expression cassettes, and / or vectors of the invention have about 70% to about 99.9% (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9% or 100%) or more identity to the polynucleotides, nucleic acid constructs, expression cassettes, and / or vectors of the invention that are not codon-optimized.

[0052] In any of the embodiments described herein, the polynucleotides or nucleic acid constructs of the present invention may be operably associated with various promoters and / or other regulatory elements for expression in plants and / or cells of plants. Thus, in some embodiments, the polynucleotides or nucleic acid constructs of the present invention may further comprise one or more promoters, introns, enhancers, and / or terminators operably linked to one or more nucleotide sequences. In some embodiments, the promoter may be operably associated with an intron (e.g., Ubi1 promoter and intron). In some embodiments, the promoter associated with an intron may be referred to as a "promoter region" (e.g., Ubi1 promoter and intron).

[0053] By "operably linked" or "operably associated" as used herein in reference to a polynucleotide, it is meant that the indicated elements are functionally associated with each other, and generally also physically associated. Thus, as used herein, the term "operably linked" or "operably associated" refers to nucleotide sequences on a single nucleic acid molecule that are functionally related. Thus, a first nucleotide sequence operably linked to a second nucleotide sequence refers to a situation in which the first nucleotide sequence is placed in a functional relationship with the second nucleotide sequence. For example, a promoter is operably associated with a nucleotide sequence if the promoter acts to transcribe or express the nucleotide sequence. Those skilled in the art will understand that a control sequence (e.g., a promoter) need not be contiguous with the nucleotide sequence with which it is operably associated, so long as the control sequence functions to direct expression. Thus, for example, an intervening transcribed but not translated nucleic acid sequence may be present between the promoter and the nucleotide sequence, and the promoter can still be considered to be "operably linked" to the nucleotide sequence.

[0054] The term "linked" as used herein in reference to a polypeptide refers to the attachment of one polypeptide to another. A polypeptide may be linked to another polypeptide (at the N-terminus or C-terminus) directly (e.g., via a peptide bond) or via a linker.

[0055] The term "linker" is art-recognized and refers to a chemical group or molecule that links two molecules or moieties, such as two domains of a fusion protein, such as an LbCas12a CRISPR-Cas nuclease domain and a polypeptide of interest (e.g., a nucleic acid editing domain, a deaminase domain, an adenosine deaminase, a cytosine deaminase). A linker may consist of a single linking molecule, or may include more than one linking molecule. In some embodiments, a linker can be an organic molecule, group, polymer, or chemical moiety, such as a bivalent organic moiety. In some embodiments, a linker can be an amino acid or a peptide.In some embodiments, the peptide linker is from about 4 to about 100 or more amino acids in length, e.g., about 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 109, 109, 108, 109, 109, 110, 111, 112, 113, 114, 115 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100 or more amino acids in length (e.g., about 4 to about 40, about 4 to about 50, about 4 to about 60, about 5 to about 40, about 5 to about 50, about 5 to about 60, about 9 to about 40, about 9 to about 50, about 9 to about 60, about 10 to about 40, about 10 to about 50, about 10 to about 60, or about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 amino acids to about 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 5 It may be 3, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100 or more amino acids in length. In some embodiments, the peptide linker may be a GS linker.

[0056] A "promoter" is a nucleotide sequence that controls or regulates the transcription of a nucleotide sequence (e.g., a coding sequence) that is operably associated with the promoter. The coding sequence controlled or regulated by a promoter may code for a polypeptide and / or a functional RNA. Typically, a "promoter" refers to a nucleotide sequence that contains a binding site for RNA polymerase II and directs the initiation of transcription. Generally, promoters are found 5', or upstream, to the start of the coding region of the corresponding coding sequence. Promoters may contain other elements that act as regulators of gene expression; for example, promoter regions. These include the TATA box consensus sequence, and often the CAAT box consensus sequence (Breathnach and Chambon, (1981) Annu. Rev. Biochem. 50:349). In plants, the CAAT box may be replaced by an AGGA box (Messing et al., (1983) in Genetic Engineering of Plants, T. Kosuge, C. Meredith and A. Hollaender (eds.), Plenum Press, pp. 211-227). In some embodiments, the promoter region may contain at least one intron (e.g., SEQ ID NO: 40 or SEQ ID NO: 41).

[0057] Promoters useful in the present invention can include, for example, constitutive, inducible, temporally regulated, developmentally regulated, chemically regulated, tissue-preferred and / or tissue-specific promoters for use in the preparation of recombinant nucleic acid molecules, e.g., "synthetic nucleic acid constructs" or "protein-RNA complexes." These various types of promoters are known in the art.

[0058] The choice of promoter may vary depending on the time and space requirements of expression, and may vary based on the host cell to be transformed.Promoters for many different organisms are well known in the art.Based on the extensive knowledge existing in the art, suitable promoters can be selected for a specific host organism of interest.Thus, for example, much is known about the upstream promoters of highly constitutively expressed genes in model organisms, and such knowledge can be easily accessed and implemented in other systems as appropriate.

[0059] In some embodiments, promoters functional in plants can be used with the constructs of the present invention.Non-limiting examples of promoters useful for driving expression in plants include the promoter of Rubisco small subunit gene 1 (PrbcS1), the promoter of actin gene (Pactin), the promoter of nitrate reductase gene (Pnr) and the promoter of duplicated carbonic anhydrase gene 1 (Pdca1) (see Walker et al. Plant Cell Rep. 23: 727-735 (2005); Li et al. Gene 403: 132-142 (2007); Li et al. Mol Biol. Rep. 37: 1143-1154 (2010)). PrbcS1 and Pactin are constitutive promoters, while Pnr and Pdca1 are inducible promoters. Pnr is induced by nitrate and repressed by ammonium (Li et al. Gene 403:132-142 (2007)), and Pdca1 is induced by salt (Li et al. Mol Biol. Rep. 37:1143-1154 (2010)).

[0060] Examples of constitutive promoters useful in plants include, but are not limited to, the cestrum virus promoter (cmp) (U.S. Pat. No. 7,166,770), the rice actin 1 promoter (Wang et al. (1992) Mol. Cell. Biol. 12:3399-3406; and U.S. Pat. No. 5,641,876), the CaMV 35S promoter (Odell et al. (1985) Nature 313:810-812), the CaMV 19S promoter (Lawton et al. (1987) Plant Mol. Biol. 9:315-324), the nos promoter (Ebert et al. (1987) Proc. Natl. Acad. Sci USA 84:5745-5749), the Adh promoter (Walker et al. (1987) Proc. Natl. Acad. Sci USA 84:5745-5749), the β-actin ... al. (1987) Proc. Natl. Acad. Sci. USA 84:6624-6629), sucrose synthase promoter (Yang & Russell (1990) Proc. Natl. Acad. Sci. USA 87:4144-4148), and ubiquitin promoter. Constitutive promoters derived from ubiquitin have accumulated in many cell types. Ubiquitin promoters have been cloned from several plant species for use in transgenic plants, such as sunflower (Binet et al., 1991. Plant Science 79:87-94), maize (Christensen et al., 1989. Plant Molec. Biol. 12:619-632), and Arabidopsis (Norris et al. 1993. Plant Molec. Biol. 21:895-906). The maize ubiquitin promoter (UbiP) has been developed in a transgenic monocotyledonous plant system, and its sequence and the vector constructed for monocotyledonous plant transformation are disclosed in patent publication EP 0 342 926. The ubiquitin promoter is suitable for the expression of the nucleotide sequence of the present invention in transgenic plants, particularly monocotyledonous plants.In addition, promoter expression cassettes described by McElroy et al. (Mol. Gen. Genet. 231:150-160 (1991)) can be readily modified for expression of the nucleotide sequences of the present invention and are particularly suitable for use in monocotyledonous hosts.

[0061] In some embodiments, tissue-specific / tissue-preferred promoters can be used for the expression of heterologous polynucleotides in plant cells. Tissue-specific or preferred expression patterns include, but are not limited to, green tissue-specific or preferred, root-specific or preferred, stem-specific or preferred, flower-specific or preferred, or pollen-specific or preferred. Promoters suitable for expression in green tissues include many of those that regulate genes involved in photosynthesis, many of which have been cloned from both monocotyledonous and dicotyledonous plants. In one embodiment, a promoter useful in the present invention is the maize PEPC promoter from the phosphoenol carboxylase gene (Hudspeth & Grula, Plant Molec. Biol. 12:579-589 (1989)). Non-limiting examples of tissue-specific promoters include those associated with genes encoding seed storage proteins (e.g., β-conglycinin, cruciferin, napin and phaseolin), zein or oil body proteins (e.g., oleosin), or proteins involved in fatty acid biosynthesis, including acyl carrier protein, stearoyl-ACP desaturase and fatty acid desaturase (fad2-1), and other nucleic acids expressed during embryo development (e.g., Bce4, see, e.g., Kridl et al. (1991) Seed Sci. Res. 1:209-219; and European Patent No. 255378). Tissue-specific or tissue-preferred promoters useful for expression of the nucleotide sequences of the present invention in plants, particularly maize, include, but are not limited to, those that direct expression in roots, pith, leaves or pollen. Such promoters are disclosed, for example, in WO 93 / 07278, which is incorporated herein by reference in its entirety.Other non-limiting examples of tissue-specific or tissue-preferred promoters useful in the present invention include the cotton Rubisco promoter disclosed in U.S. Pat. No. 6,040,504; the rice sucrose synthase promoter disclosed in U.S. Pat. No. 5,604,121; the root-specific promoter described by de Framond (FEBS 290:103-106 (1991); EP 0452269 (Ciba-Geigy)); the stem-specific promoter driving expression of the maize trpA gene described in U.S. Pat. No. 5,625,136 (Ciba-Geigy); the cestrum yellow leaf curling virus promoter disclosed in WO 01 / 73087; and, without limitation, the ProOsLPS10 and ProOsLPS11 promoters from rice (Nguyen et al. Plant Biotechnol. Reports 9(5):297-306(2015)), ZmSTK2_USP from maize (Wang et al. Genome 60(6):485-495(2017)), LAT52 and LAT59 from tomato (Twell et al. Development 109(3):705-713(1990)), Zm13 (U.S. Patent No. 10,421,972), the PLA2-δ promoter from Arabidopsis (U.S. Patent No. 7,141,424), and / or the ZmC5 promoter from maize (International PCT Publication No. WO1999 / 042587).

[0062] Further examples of plant tissue specific / tissue preferred promoters include, but are not limited to, the root hair specific cis-element (RHE) (Kim et al. The Plant Cell 18:2958-2970 (2006)), the root specific promoters RCc3 (Jeong et al. Plant Physiol. 153:185-197 (2010)) and RB7 (U.S. Pat. No. 5,459,252), the lectin promoter (Lindstrom et al. (1990) Der. Genet. 11:160-167; and Vodkin (1983) Prog. Clin. Biol. Res. 138:87-98), the corn alcohol dehydrogenase 1 promoter (Dennis et al. (1984) Nucleic Acids Res. 12:3983-4000), the S-adenosyl-L-methionine synthase (SAMS) (Vander Mijnsbrugge et al. (1996) Plant and Cell Physiology, 37(8):1108-1115), maize light-harvesting complex promoter (Bansal et al. (1992) Proc. Natl. Acad. Sci. USA 89:3654-3658), maize heat shock protein promoter (O'Dell et al. (1985) EMBOJ. 5:451-458; and Rochester et al. (1986) EMBOJ. 5:451-458), pea small subunit RuBP carboxylase promoter (Cashmore, "Nuclear genes encoding the small subunit of ribulose-l,5-bisphosphate carboxylase" pp.29-39 In: Genetic Engineering of Plants (Hollaender ed., Plenum Press 1983; and Poulsen et al. al. (1986) Mol. Gen. Genet. 205:193-200), the mannopine synthase promoter of the Ti plasmid (Langridge et al. (1989) Proc. Natl. Acad. Sci. USA 86:3219-3223), the Ti plasmid nopaline synthase promoter (Langridge et al.(1989), supra), the petunia chalcone isomerase promoter (van Tunen et al. (1988) EMBOJ. 7:1257-1263), the bean glycine-rich protein 1 promoter (Keller et al. (1989) Genes Dev. 3:1639-1646), the truncated CaMV 35S promoter (O'Dell et al. (1985) Nature 313:810-812), the potato patatin promoter (Wenzler et al. (1989) Plant Mol. Biol. 13:347-354), a root cell promoter (Yamamoto et al. (1990) Nucleic Acids Res. 18:7449), and the maize zein promoter (Kriz et al. (1987) Mol. Gen. Genet. 207:90-98; Langridge et al. (1989) Mol. Gen. Genet. 207:90-98). (1983) Cell 34:1015-1022; Reina et al. (1990) Nucleic Acids Res. 18:6425; Reina et al. (1990) Nucleic Acids Res. 18:7449; and Wandelt et al. (1989) Nucleic Acids Res. 17:2354), the globulin-1 promoter (Belanger et al. (1991) Genetics 129:863-872), the α-tubulin cab promoter (Sullivan et al. (1989) Mol. Gen. Genet. 215:431-440), the PEPCase promoter (Hudspeth & Grula (1989) Plant Mol. Biol. 12:579-589), the R gene complex-associated promoter (Chandler et al. (1989) Plant Cell 1:1175-1183), and the chalcone synthase promoter (Franken et al. (1991) EMBO J. 10:2605-2612).

[0063] Useful for species-specific expression is the pea vicilin promoter (Czako et al. (1992) Mol. Gen. Genet. 235:33-40; as well as the species-specific promoters disclosed in U.S. Pat. No. 5,625,136. Useful promoters for expression in mature leaves are those that are switched on during senescence, such as the SAG promoter from Arabidopsis (Gan et al. (1995) Science 270:1986-1988).

[0064] Additionally, promoters functional in chloroplasts can be used. Non-limiting examples of such promoters include the bacteriophage T3 gene 9 5'UTR and other promoters disclosed in U.S. Patent No. 7,579,516. Other promoters useful in the present invention include, but are not limited to, the S-E9 small subunit RuBP carboxylase promoter and the Kunitz trypsin inhibitor gene promoter (Kti3).

[0065] Additional regulatory elements useful in the present invention include, but are not limited to, introns, enhancers, termination sequences and / or 5' and 3' untranslated regions.

[0066] Introns useful in the present invention may be introns identified and isolated in plants, and inserted into expression cassettes used in plant transformation. As will be understood by those skilled in the art, introns may contain sequences necessary for self-excision, which are integrated in frame into the nucleic acid construct / expression cassette. Introns may be used as spacers to separate multiple protein coding sequences in one nucleic acid construct, or introns may be used within one protein coding sequence, for example, to stabilize mRNA. When used within a protein coding sequence, they are inserted "in frame" with the excision site included. Introns may be associated with promoters to improve or modify expression. By way of example, promoter / intron combinations useful in the present invention include, but are not limited to, the maize Ubi1 promoter and intron combination.

[0067] Non-limiting examples of introns useful in the present invention include introns from the ADHI gene (e.g., Adh1-S introns 1, 2 and 6), introns from the ubiquitin gene (Ubi1), introns from the Rubisco small subunit (rbcS) gene, introns from the Rubisco large subunit (rbcL) gene, introns from the actin gene (e.g., the actin-1 intron), introns from the pyruvate dehydrogenase kinase gene (pdk), introns from the nitrate reductase gene (nr), introns from the dual carbonic anhydrase gene 1 (Tdca1), introns from the psbA gene, introns from the atpA gene, or any combination thereof. As a non-limiting example, a nucleic acid construct of the present invention may encode a base editor comprising an optimized CRISPR-Cas nuclease (e.g., SEQ ID NOs: 1-11 or 23-25) and a deaminase, wherein the nucleic acid construct further comprises a promoter comprising / associated with an intron. As a further non-limiting example, a nucleic acid construct of the invention may encode a base editor comprising an optimized CRISPR-Cas nuclease (e.g., SEQ ID NOs: 1-11 or 23-25) and a deaminase, where the nuclease and / or deaminase comprise one or more introns, and the nucleic acid construct may further comprise a promoter comprising / associated with an intron.

[0068] In some embodiments, the polynucleotide and / or nucleic acid construct of the present invention may be an "expression cassette" or may be included in an expression cassette. As used herein, "expression cassette" refers to a recombinant nucleic acid molecule that includes, for example, a nucleic acid construct of the present invention (e.g., encoding a modified LbCas12a of the present invention), where the nucleic acid construct is operably associated with at least a control sequence (e.g., a promoter). Thus, some embodiments of the present invention provide, for example, an expression cassette designed to express a nucleic acid construct of the present invention (e.g., a nucleic acid construct of the present invention encoding a modified LbCas12a of the present invention).

[0069] An expression cassette comprising a nucleic acid construct of the invention may be chimeric, meaning that at least one of its components is heterologous to at least one of its other components (e.g., a promoter from a host organism operably linked to a polynucleotide of interest to be expressed in the host organism, where the polynucleotide of interest is from an organism different from the host or is not normally found in association with that promoter). Expression cassettes may be of natural origin, but have been obtained in recombinant form useful for heterologous expression.

[0070] The expression cassette can also include a transcription and / or translation termination region (i.e., a termination region) and / or an enhancer region that is functional in the selected host cell. A variety of transcription terminators and enhancers are known in the art and are available for use in the expression cassette. The transcription terminator is responsible for transcription termination and correct mRNA polyadenylation. The termination region and / or enhancer region can be native to the transcription initiation region, for example, native to the gene encoding the LbCas12a nuclease encoded by the nucleic acid construct of the present invention, native to the host cell, or native to another source (e.g., foreign or heterologous to the promoter, the gene encoding the LbCas12a nuclease encoded by the nucleic acid construct of the present invention, the host cell, or any combination thereof). The enhancer region may be native to the gene encoding the LbCas12a nuclease encoded by the nucleic acid construct of the present invention, may be native to the host cell, or may be of another origin (e.g., foreign or heterologous to the promoter, the gene encoding the LbCas12a nuclease encoded by the nucleic acid construct of the present invention, the host cell, or any combination thereof).

[0071] The expression cassette of the present invention may include a nucleotide sequence encoding a selectable marker that can be used to select transformed host cells. As used herein, a "selectable marker" refers to a nucleotide sequence that, when expressed, confers a distinct phenotype on host cells expressing the marker, such that such transformed cells can be distinguished from those that do not possess the marker. Such a nucleotide sequence may encode either a selectable marker or a screenable marker, depending on whether the marker confers a characteristic that can be selected by chemical means, for example, by using a selection agent (such as an antibiotic), or whether the marker is a simple characteristic that can be identified through observation or testing, for example, by screening (e.g., fluorescence). Many examples of suitable selectable markers are known in the art and can be used in the expression cassettes described herein.

[0072] In addition to expression cassettes, the nucleic acid molecules / constructs and polynucleotide sequences described herein may be used in the context of vectors. The term "vector" refers to a composition for transferring, delivering, or introducing a nucleic acid(s) into a cell. A vector includes a nucleic acid construct that includes the nucleotide sequence(s) to be transferred, delivered, or introduced. Vectors for use in transforming host organisms are well known in the art. Non-limiting examples of general classes of vectors include viral vectors, plasmid vectors, phage vectors, phagemid vectors, cosmid vectors, fosmid vectors, bacteriophages, artificial chromosomes, minicircles, or Agrobacterium binary vectors in double-stranded or single-stranded, linear or circular form, which may or may not be self-transmissible or motile. In some embodiments, viral vectors can include, but are not limited to, retroviral, lentiviral, adenoviral, adeno-associated, or herpes simplex viral vectors. A vector as defined herein can transform a prokaryotic or eukaryotic host by integration into a cell genome or can exist extrachromosomally (e.g., an autonomously replicating plasmid with an origin of replication). Further included is a shuttle vector, which means a DNA vehicle capable of replication, naturally or by design, in two different host organisms, which may be selected from actinomycetes and related species, bacteria and eukaryotes (e.g., higher plants, mammals, yeast or fungal cells). In some embodiments, the nucleic acid in the vector is under the control of and operably linked to a suitable promoter or other regulatory element for transcription in the host cell. The vector may be a bifunctional expression vector that functions in multiple hosts. In the case of genomic DNA, this may include its own promoter and / or other regulatory element, and in the case of cDNA, it may be under the control of a suitable promoter and / or other regulatory element for expression in the host cell. Thus, the nucleic acid construct of the present invention and / or the expression cassette comprising it may be included in a vector as described herein and known in the art.In some embodiments, the vector may be a high copy number vector (e.g., a high copy number E. coli vector; e.g., pUC, pBluescript, pGEM, etc.). Thus, for example, the libraries of the invention may be constructed using high copy number vectors.

[0073] As used herein, "contact," "contacting," "contacted," and grammatical variations thereof refer to placing components of a desired reaction together under appropriate conditions to perform the desired reaction (e.g., transformation, transcriptional regulation, genome editing, nicking, and / or cleavage). Thus, for example, a target nucleic acid can be contacted with (a) a polynucleotide and / or nucleic acid construct of the present invention encoding a modified LbCas12a nuclease of the present invention and (b) a guide nucleic acid under conditions in which the polynucleotide / nucleic acid construct is expressed to produce a modified LbCas12a nuclease, where the nuclease forms a complex with the guide nucleic acid and the complex hybridizes to the target nucleic acid, thereby modifying the target nucleic acid. In some embodiments, the target nucleic acid can be contacted with (a) a modified LbCas12a nuclease of the invention and / or a fusion protein comprising the same (e.g., a modified LbCas12a nuclease of the invention and a polypeptide of interest (e.g., a deaminase)) and (b) a guide nucleic acid, where the modified LbCas12a nuclease forms a complex with the guide nucleic acid and the complex hybridizes to the target nucleic acid, thereby modifying the target nucleic acid. As described herein, the target nucleic acid can be contacted with a polynucleotide / nucleic acid construct / polypeptide of the invention before, simultaneously with, or after contact with the guide nucleic acid.

[0074] As used herein, "modifying" or "modification" in reference to a target nucleic acid includes editing (e.g., mutation), covalent modification, replacement / substitution of nucleic acid / nucleotide bases, deletion, truncation, nicking, and / or transcriptional regulation of the target nucleic acid.

[0075] "Introducing," "introduce," "introduced" (and grammatical variations thereof) in the context of a polynucleotide of interest means presenting a nucleotide sequence of interest (e.g., a polynucleotide, a nucleic acid construct, and / or a guide nucleic acid) to a host organism or a cell of the organism (e.g., a host cell; e.g., a plant cell) in a manner that allows the nucleotide sequence to access the interior of the cell. Thus, for example, a polynucleotide of the invention encoding a modified LbCas12a nuclease as described herein and a guide nucleic acid can be introduced into a cell of an organism, thereby transforming the cell with the modified LbCas12a nuclease and the guide nucleic acid.

[0076] The term "transformation" as used herein refers to the introduction of heterologous nucleic acid into a cell. The transformation of a cell may be stable or transient. Thus, in some embodiments, a host cell or host organism may be stably transformed by a polynucleotide / nucleic acid molecule of the present invention. In some embodiments, a host cell or host organism may be transiently transformed by a polynucleotide / nucleic acid construct of the present invention.

[0077] "Transient transformation" in the context of a polynucleotide means that the polynucleotide is introduced into a cell and does not integrate into the genome of the cell.

[0078] By "stably introduce" or "stably introduced" in the context of a polynucleotide introduced into a cell, it is intended that the introduced polynucleotide is stably integrated into the genome of the cell, thus stably transforming the cell with the polynucleotide.

[0079] As used herein, "stable transformation" or "stably transformed" means that a nucleic acid molecule is introduced into a cell and integrated into the genome of the cell. Thus, the integrated nucleic acid molecule can be inherited by its progeny, more specifically, by multiple generations of progeny. As used herein, "genome" includes nuclear and plastid genomes, and thus includes, for example, the integration of a nucleic acid into a chloroplast or mitochondrial genome. As used herein, stable transformation can also refer to a transgene that is maintained extrachromosomally, for example, as a minichromosome or plasmid.

[0080] Transient transformation can be detected, for example, by enzyme-linked immunosorbent assay (ELISA) or Western blot, which can detect the presence of peptides or polypeptides encoded by one or more transgenes introduced into the organism. Stable transformation of cells can be detected, for example, by Southern blot hybridization assay of the genomic DNA of the cells with a nucleic acid sequence that specifically hybridizes with the nucleotide sequence of the transgene introduced into the organism (e.g., a plant). Stable transformation of cells can be detected, for example, by Northern blot hybridization assay of the RNA of the cells with a nucleic acid sequence that specifically hybridizes with the nucleotide sequence of the transgene introduced into the host organism. Stable transformation of cells can also be detected by polymerase chain reaction (PCR) or other amplification reactions well known in the art, which result in the amplification of transgene sequences that can be detected according to standard methods, for example, using specific primer sequences that hybridize with the target sequence(s) of the transgene. Transformation can also be detected by direct sequencing and / or hybridization protocols well known in the art.

[0081] Thus, in some embodiments, the nucleotide sequences, polynucleotides, and / or nucleic acid constructs of the present invention and / or expression cassettes and / or vectors comprising them may be expressed transiently and / or they may be stably integrated into the genome of a host organism. Thus, in some embodiments, the nucleic acid constructs of the present invention (e.g., encoding the modified LbCas12a nuclease of the present invention or a fusion protein thereof; e.g., a fusion protein comprising the modified LbCas12a nuclease linked to a polynucleotide of interest, e.g., a deaminase domain) (wherein the nucleic acid construct encoding the modified LbCas12a nuclease is codon-optimized for expression in an organism (e.g., a plant, a mammal, a fungus, a bacterium, etc.)) may be transiently introduced into the cells of the organism along with a guide nucleic acid, and thus the DNA is not maintained within the cell.

[0082] The polynucleotide / nucleic acid constructs of the invention can be introduced into cells by any method known to those of skill in the art. In some embodiments of the invention, the transformation of a cell comprises nuclear transformation. In other embodiments, the transformation of a cell comprises plastid transformation (e.g., chloroplast transformation). In further embodiments, the polynucleotide / nucleic acid constructs of the invention can be introduced into cells via conventional breeding techniques.

[0083] Procedures for transforming both eukaryotes and prokaryotes are well known and routine in the art and are described throughout the literature (see, e.g., Jiang et al. 2013. Nat. Biotechnol. 31:233-239; Ran et al. Nature Protocols 8:2281-2308 (2013)).

[0084] Thus, the nucleotide sequence can be introduced into the host organism or into its cells by any number of methods well known in the art. The method of the present invention does not depend on a particular method to introduce one or more nucleotide sequences into an organism, only to access the inside of at least one cell of the organism. If more than one nucleotide sequence is introduced, they can be assembled as part of a single nucleic acid construct, or can be located on the same or different nucleic acid constructs as separate nucleic acid constructs. Thus, the nucleotide sequence can be introduced into the cell of interest in a single transformation event and / or in separate transformations, or, if relevant, the nucleotide sequence can be incorporated into the plant, for example, as part of a breeding protocol.

[0085] The present invention relates to Cas12a nucleases that have been engineered to contain a non-native PAM recognition site / sequence (e.g., Cas12a nucleases that contain a non-native PAM recognition specificity in addition to or in place of the native PAM recognition specificity for that particular Cas12a nuclease). Additionally, the present invention relates to methods for designing, identifying, and selecting Cas12a nucleases with desirable properties, including improved PAM recognition specificity.

[0086] As used herein in reference to an engineered Cas12a polypeptide, "altered PAM specificity" means that the PAM specificity of the nuclease is altered from that of a wild-type nuclease (e.g., a non-native PAM sequence is recognized in addition to and / or instead of the native PAM sequence. For example, an engineered Cas12a nuclease has altered PAM specificity if it recognizes a PAM sequence other than and / or in addition to the native Cas12a PAM sequence of TTTV (V=A, C, or G).

[0087] The present invention relates to LbCas12a nucleases with altered PAM recognition specificity. In some embodiments, the present invention provides altered Lachnospiraceae bacterium CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) Cas12a (LbCas12a) polypeptides, wherein the altered LbCas12a polypeptides have at least 80% identity (e.g., about 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100% identity; e.g., about 80% to about 100%, about 85% to about 100%, about 90% to about 100% identity) to the amino acid sequence of SEQ ID NO:1 (LbCas12a). about 95% to about 100%), and the following positions with respect to the position numbering of SEQ ID NO:1: K116, K120, K121, D122, E125, T148, T149, T152, D156, E159, Q529, G532, D535, K538, D541, Y542, L585, K591, M592, K595, V596, S599, K600, K601, Y616, Y646, and and / or mutations at one or more (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or more) of W649, and may also include mutations at one or more of the following positions with respect to the position numbering of SEQ ID NO:1: K116, K120, K121, D122, E125, T152, D156, E159, G532, D535, K538, D541, and / or K595. In some embodiments, the mutations in the Cas12a (LbCas12a) polypeptide comprise, consist essentially of, or consist of mutations in any combination at one or more of the following positions with respect to the position numbering of SEQ ID NO:1: K116, K120, K121, D122, E125, T152, D156, E159, G532, D535, K538, D541, and / or K595.Thus, the modified LbCas12a polypeptides of the invention can comprise a single nucleotide polynucleotide at any one of the following positions with respect to the position numbering of SEQ ID NO:1: K116, K120, K121, D122, E125, T148, T149, T152, D156, E159, Q529, G532, D535, K538, D541, Y542, L585, K591, M592, K595, V596, S599, K600, K601, Y616, Y646, and / or W649. It may comprise a mutation or a combination of mutations at any two or more of the following positions, with respect to the position numbering of SEQ ID NO:1: K116, K120, K121, D122, E125, T148, T149, T152, D156, E159, Q529, G532, D535, K538, D541, Y542, L585, K591, M592, K595, V596, S599, K600, K601, Y616, Y646, and / or W649.

[0088] In some embodiments, the mutations in the Cas12a (LbCas12a) polypeptide are the following mutations with respect to position numbering in SEQ ID NO:1: K116N, K116R, K120H, K120N, K120Q, K120R, K120T, K121D, K121G, K121H, K121Q, K121R, K121S, K121T, D122H, D122K, D122N, D122R, E125K, E125Q, E125R, E125Y, T148A, T148C, T148H, T148S, T149C, T149F, T149G, T149H, T149N , T149P, T149S, T149V, T152E, T152F, T152H, T152K, T152L, T152Q, T152R, T 152W, T152Y, D156E, D156H, D156I, D156K, D156L, D156Q, D156R, D156W, D156 Y, E159K, E159Q, E159R, E159Y, Q529A, Q529D, Q529F, Q529G, Q529H, Q529N, Q529P, Q529S, Q529T, Q529W, G532A, G532C, G532D, G532F, G532H, G532K, G53 2L, G532N, G532Q, G532S, D535A, D535H, D535K, D535N, D535S, D535T, D535V , K538C, K538F, K538G, K538H, K538L, K538M, K538Q, K538R, K538V, K538W, K5 38Y, D541A, D541E, D541H, D541I, D541N, D541R, D541Y, Y542F, Y542H, Y542 K, Y542L, Y542M, Y542N, Y542R, Y542T, Y542V, L585F, L585G, L585H, K591A, K 591F, K591G, K591H, K591R, K591S, K591W, K591Y, M592A, M592E, M592Q, K59 5H, K595L, K595M, K595Q, K595R, K595S, K595W, K595Y, V596H, V596T, S599G, S599H, S599N, K600G, K600H, K600R, K601H, K601Q, K601R, K601T, Y616E, Y61 6F, Y616H, Y616K, Y616R, Y646E, Y646H, Y646K, Y646N, Y646Q, Y646R, Y646W,The Cas12a polypeptide may comprise, consist essentially of, or consist of one or more of W649H, W649K, W649R, W649S, and / or W649Y. As will be understood, any single Cas12a polypeptide with two or more mutations contains only a single mutation at any given position. Thus, for example, a polypeptide may have a mutation at position D535, any one of D535A, D535H, D535K, D535N, D535S, D535T, or D535V, but the same polypeptide may further comprise a mutation at any one or more of the other positions described herein. In some embodiments, the mutations in the Cas12a (LbCas12a) polypeptide are K116N, K116R, K120H, K120N, K120Q, K120R, K120T, K121D, K121G, K121H, K121Q, K121R, K121S, K121T, D122H, D122K ... 122N, D122R, E125K, E125Q, E125R, E125Y, T152E, T152F, T152H, T152K, T152L, T152Q, T152R, T 152W, T152Y, D156E, D156H, D156I, D156K, D156L, D156Q, D156R, D156W, D156Y, E159K, E159Q, E1 59R, E159Y, G532A, G532C, G532D, G532F, G532H, G532K, G532L, G532N, G532Q, G532S, D535A, D5 35H, D535K, D535N, D535S, D535T, D535V, K538C, K538F, K538G, K538H, K538L, K538M, K538Q, K53 In some embodiments, the mutations in the Cas12a (LbCas12a) polypeptide comprise, consist essentially of, or consist of one or more of the following mutations in any combination: K116R, K116N, K120Y, K121S, K121R, D122H, D122N, E125K ...T152R, T152K, T152Y, T152Q, T152E, T152F, D156R, D156W, D156Q, D156H, D156I, D156V, D156L, D156E, E159K, E159R, G532N, G532S, G532H, G532K, G532R, G532L, D535N, D535H, D535T, D535, S D535A, D535W, K538R The Cas12a polypeptide may comprise, consist essentially of, or consist of one or more of the following mutations: K538V, K538Q, K538W, K538Y, K538F, K538H, K538L, K538M, K538C, K538G, K538A, D541E, K595R, K595Q, K595Y, K595W, K595H, K595S, and / or K595M. As will be appreciated, any single Cas12a polypeptide with two or more mutations will include a single mutation at any given position. Thus, for example, a polypeptide may have a mutation at position D535 at any one of D535A, D535H, D535K, D535N, D535S, D535T, or D535V, and may further include a mutation at any other position described herein.

[0089] In some embodiments, the mutations do not include, consist essentially of, or consist of D156R, G532R, K538R, K538V, Y542R, or K595R mutations with respect to the position numbering of SEQ ID NO: 1. In some embodiments, the mutations in the Cas12a (LbCas12a) polypeptide do not include, consist essentially of, or consist of a combination of G532R and K595R mutations, a combination of G532R, K538V, and Y542R mutations, or a combination of D156R, G532R, and K532R mutations with respect to the position numbering of SEQ ID NO: 1.

[0090] In some embodiments, the modified LbCas12a polypeptide may include one or more amino acid mutations of SEQ ID NO:1 as set forth in Table 2 (in Example 2).

[0091] In some embodiments, modified LbCas12a polypeptides may comprise altered protospacer adjacent motif (PAM) specificity compared to wild-type LbCas12a (e.g., SEQ ID NO: 1). Modified LbCas12a polypeptides of the invention may comprise altered PAM specificity, including but not limited to NNNG, NNNT, NNNA, NNNC, NNG, NNT, NNC, NNA, NG, NT, NC, NA, NN, NNN, NNNN, where each N in each sequence is independently selected from any of T, C, G, or A. In some embodiments, altered PAM specificity may include but is not limited to TTTA, TTTC, TTTG, TTTT, TTCA, TTCC, TTCG, TTCT, ATTC, CTTA, CTTC, CTTG, GTTC, TATA, TATC, CTCC, TCCG, TACA, TCCG, TACA, TCCG, TCCC, TCCA, and / or TATG. In some embodiments, the altered PAM specificity can be NNNN, where each N in each sequence is independently selected from any of T, C, G, or A.

[0092] In addition to having altered PAM recognition specificity, the modified LbCas12a nuclease may further comprise a mutation within the nuclease active site (e.g., RuvC domain) (e.g., deadLbCas12a, dLbCas12a). Such modifications may result in an LbCas12a polypeptide with reduced or no nuclease activity (e.g., nickase activity).

[0093] In some embodiments, a V-type Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) associated (Cas) (CRISPR-Cas) system is provided, the system comprising: (a) a fusion protein comprising: (i) a modified LbCas12a nuclease of the present invention or a nucleic acid encoding a modified LbCas12a nuclease of the present invention, and (ii) a polypeptide of interest or a nucleic acid encoding a polypeptide of interest; and (b) a guide nucleic acid (CRISPR RNA, CRISPR DNA, crRNA, crDNA) comprising a spacer sequence and a repeat sequence, where the guide nucleic acid is capable of forming a complex with the modified LbCas12a nuclease or the fusion protein, and the spacer sequence is capable of hybridizing to the target nucleic acid, thereby guiding the modified LbCas12a nuclease and the polypeptide of interest to the target nucleic acid, whereby the system is capable of modifying (e.g., cleaving or editing) or modulating (e.g., transcriptionally modulating) the target nucleic acid. In some embodiments, the system comprises a polypeptide of interest (e.g., a fusion protein) linked to the C-terminus and / or N-terminus of the engineered LbCas12a nuclease, optionally via a peptide linker.

[0094] Further provided herein is a fusion protein comprising the modified Cas12a nuclease of the present invention. In some embodiments, the fusion protein may comprise a polypeptide of interest linked to the C-terminus and / or N-terminus of the modified LbCas12a. In some embodiments, the present invention provides a fusion protein comprising the modified LbCas12a (and may comprise an intervening linker linking the polypeptide of interest).

[0095] Any linker known in the art or subsequently identified that does not interfere with the activity of the fusion protein may be used. A linker that does not "interfere" with the activity of the fusion protein is one that does not reduce or eliminate the activity of the polypeptides (e.g., nuclease and / or polypeptide of interest) of the fusion protein; that is, the nuclease activity, nucleic acid binding activity, editing activity, and / or any other activity of the nuclease or polypeptide of interest is maintained in the fusion protein in which the nuclease and polypeptide of interest are linked to each other via a linker. In some embodiments, the peptide linker may be linked (e.g., at its N-terminus) to the C-terminus of the modified LbCas12a, and the fusion protein may further comprise a polypeptide of interest linked to the C-terminus of the linker. In some embodiments, the peptide linker may be linked (e.g., at its C-terminus) to the N-terminus of the modified LbCas12a, and the fusion protein may further comprise a polypeptide of interest linked to the N-terminus of the linker. In some embodiments, the modified LbCas12a of the present invention may be linked (directly or via a linker) to a linker and / or a polypeptide of interest at both its C-terminus and N-terminus.

[0096] In some embodiments, linkers useful in the present invention may be amino acids or peptides. In some embodiments, peptide linkers useful in the present invention may be from about 4 to about 100 or more amino acids in length, e.g., about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 1 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100 or more amino acids in length (e.g., about 4 to about 40, about 4 to about 50, about 4 to about 60 , about 5 to about 40, about 5 to about 50, about 5 to about 60, about 9 to about 40, about 9 to about 50, about 9 to about 60, about 10 to about 40, about 10 to about 50, about 10 to about 60, or about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 amino acids to about 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, , 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100 or more amino acids in length). In some embodiments, the peptide linker may be a GS linker.

[0097] Polypeptides of interest useful according to the invention can include, but are not limited to, polypeptides or protein domains having deaminase (deamination) activity, nickase activity, recombinase activity, transposase activity, methylase activity, glycosylase (DNA glycosylase) activity, glycosylase inhibitor activity (e.g., uracil-DNA glycosylase inhibitor (UGI)). demethylase activity, transcription activator activity, transcription repressor activity, transcription release factor activity, histone modifying activity, nuclease activity, single-stranded RNA cleavage activity, double-stranded RNA cleavage activity, restriction endonuclease activity (e.g., Fok1), nucleic acid binding activity, methyltransferase activity, DNA repair activity, DNA damage activity, dismutase activity, alkylation activity, depurination activity, oxidation activity, pyrimidine dimer formation activity, integrase activity, transposase activity, polymerase activity, ligase activity, helicase activity, and / or photolyase activity.

[0098] In some embodiments, the polypeptide of interest may comprise at least one polypeptide or protein domain having deaminase activity. In some embodiments, the at least one polypeptide or protein domain may be an adenine deaminase domain. The adenine deaminase (or adenosine deaminase) useful in the present invention may be any known or later identified adenine deaminase from any organism (see, for example, U.S. Pat. No. 10,113,163, which is incorporated herein by reference for its disclosure of adenine deaminase). Adenine deaminase can catalyze the hydrolytic deamination of adenine or adenosine. In some embodiments, adenine deaminase can catalyze the hydrolytic deamination of adenosine or deoxyadenosine to inosine or deoxyinosine, respectively. In some embodiments, adenosine deaminase can catalyze the hydrolytic deamination of adenine or adenosine in DNA. In some embodiments, the adenine deaminase encoded by a nucleic acid construct of the invention can produce an A to G conversion in the sense (e.g., "+"; template) strand of a target nucleic acid or a T to C conversion in the antisense (e.g., "-", complementary) strand of a target nucleic acid.

[0099] In some embodiments, the adenosine deaminase may be a variant of a naturally occurring adenine deaminase. Thus, in some embodiments, the adenosine deaminase useful in the present invention may be about 70% to 100% identical to a wild-type adenine deaminase (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% identical to a naturally occurring adenine deaminase, and any range or value therein). In some embodiments, the deaminase or deaminase is not naturally occurring and may be referred to as an engineered, mutated, or evolved adenosine deaminase. Thus, for example, an engineered, mutated, or evolved adenine deaminase polypeptide or adenine deaminase domain may be about 70% to 99.9% identical to a naturally occurring adenine deaminase polypeptide / domain (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, 101%, 102%, 103%, 104%, 105%, 106%, 107%, 108%, 109 ... 5%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8% or 99.9% identical, and any range or value therein). In some embodiments, the adenosine deaminase may be from a bacterium, (e.g., Escherichia coli, Staphylococcus aureus, Haemophilus influenzae, Caulobacter crescentus, etc.). In some embodiments, the polynucleotide encoding the adenine deaminase polypeptide / domain may be codon-optimized for expression in the organism.

[0100] In some embodiments, the adenine deaminase domain is a wild-type tRNA-specific adenosine deaminase domain, e.g., a tRNA-specific adenosine deaminase (TadA) and / or a mutated / evolved adenosine deaminase domain, e.g., a mutated / evolved tRNA-specific adenosine deaminase domain (TadA). * ). In some embodiments, the TadA domain may be from E. coli. In some embodiments, TadA may be modified, e.g., truncated, and may have one or more N-terminal and / or C-terminal amino acids deleted relative to full-length TadA (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 6, 17, 18, 19, or 20 N-terminal and / or C-terminal amino acid residues deleted compared to full-length TadA. In some embodiments, the TadA polypeptide or TadA domain does not include an N-terminal methionine. In some embodiments, wild-type E. coli TadA comprises the amino acid sequence of SEQ ID NO: 18. In some embodiments, the mutated / evolved E. coli TadA comprises the amino acid sequence of SEQ ID NO: 19. * comprises the amino acid sequence of SEQ ID NO: 19-22. In some embodiments, TadA / TadA * The polynucleotide encoding may be codon-optimized for expression in an organism.

[0101] The cytosine deaminase (or cytidine deaminase) useful in the present invention may be any known or later identified cytosine deaminase from any organism (see, for example, U.S. Pat. No. 10,167,457, which is incorporated herein by reference for its disclosure of cytosine deaminases). In some embodiments, at least one polypeptide or protein domain may be a cytosine deaminase polypeptide or domain. In some embodiments, the cytosine deaminase polypeptide / domain may be an apolipoprotein B mRNA editing catalytic polypeptide-like (APOBEC) domain. In some embodiments, the polypeptide of interest may comprise at least one polypeptide or protein domain having glycosylase inhibitor activity. In some embodiments, the polypeptide of interest may be a uracil-DNA glycosylase inhibitor (UGI) polypeptide / domain. In some embodiments, the nucleic acid construct encoding the modified LbCas12a nuclease and cytosine deaminase domain of the invention (e.g., encoding a fusion protein comprising a modified LbCas12a nuclease and cytosine deaminase domain) may further encode a uracil-DNA glycosylase inhibitor (UGI), where the UGI is codon-optimized for expression in an organism. In some embodiments, the invention provides a fusion protein comprising a modified LbCas12a nuclease, a cytosine deaminase domain, and a UGI, and / or one or more polynucleotides encoding the same, where the one or more polynucleotides may be codon-optimized for expression in an organism.

[0102] Cytosine deaminase catalyzes the hydrolytic deamination of cytidine or deoxycytidine to uridine or deoxyuridine, respectively. In some embodiments, the deaminase or deaminase domain can be a cytidine deaminase domain that catalyzes the hydrolytic deamination of cytosine to uracil. In some embodiments, the cytosine deaminase can be a mutant of naturally occurring cytosine deaminase, including but not limited to, primate (e.g., human, monkey, chimpanzee, gorilla), dog, cow, rat, or mouse. Thus, in some embodiments, cytosine deaminases useful in the present invention may be about 70% to about 100% identical to a wild-type cytosine deaminase (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100% identical to a naturally occurring cytosine deaminase, and any range or value therein). In some embodiments, a polynucleotide encoding a cytosine deaminase polypeptide / domain may be codon-optimized for expression in an organism.

[0103] In some embodiments, the cytosine deaminase useful in the present invention may be an apolipoprotein B mRNA editing complex (APOBEC) family deaminase. In some embodiments, the cytosine deaminase may be APOBEC1 deaminase, APOBEC2 deaminase, APOBEC3A deaminase, APOBEC3B deaminase, APOBEC3C deaminase, APOBEC3D deaminase, APOBEC3F deaminase, APOBEC3G deaminase, APOBEC3H deaminase, APOBEC4 deaminase, human activation-induced deaminase (hAID), rAPOBEC1, FERNY, and / or CDA1, and may be pmCDA1, atCDA1 (e.g., At2g19570), and evolved versions thereof. In some embodiments, the cytosine deaminase may be APOBEC1 deaminase having the amino acid sequence of SEQ ID NO:23, SEQ ID NO:44, or SEQ ID NO:46. In some embodiments, the cytosine deaminase may be APOBEC3A deaminase having the amino acid sequence of SEQ ID NO:24. In some embodiments, the cytosine deaminase may be CDA1 deaminase, which may be CDA1 having the amino acid sequence of SEQ ID NO:25 or SEQ ID NO:43. In some embodiments, the cytosine deaminase may be FERNY deaminase, which may be FERNY having the amino acid sequence of SEQ ID NO:42 or SEQ ID NO:45. In some embodiments, the cytosine deaminase may be human activation-induced deaminase (hAID) having the amino acid sequence of SEQ ID NO:47 or SEQ ID NO:48. In some embodiments, a cytosine deaminase useful in the invention can be about 70% to about 100% identical (e.g., 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical) to the amino acid sequence of a naturally occurring cytosine deaminase (e.g., an evolved deaminase).In some embodiments, the cytosine deaminase useful in the invention is about 70% to about 99.5% identical (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, 101%, 102%, 103%, 104%, 105%, 106%, 107%, 108%, 109%, 110%, 111%, 112%, 113%, 114%, 115%, 116%, 117%, 118%, 119%, 120%, 121%, 122%, 123%, 124%, 125%, 126%, 127%, 128%, 129%, 130%, 131%, 132%, 133%, 134%, 135%, 136%, 137%, 138%, 139%, 140%, 141%, 142%, 143%, 144%, 145%, 146%, 147%, 148%, 149%, 150%, 151%, 152%, 153%, 154%, 155%, 156%, 157%, 158%, 159%, 160%, 161%, 162%, 163%, 164%, 165%, 166%, 167%, 168%, 169%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.5% identical) (e.g., at least 80%, at least 85%, at least 90%, at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to the amino acid sequence of SEQ ID NO:23, SEQ ID NO:24, SEQ ID NO:25, or SEQ ID NO:42-48). In some embodiments, the polynucleotide encoding the cytosine deaminase may be codon-optimized for expression in an organism, and the codon-optimized polypeptide may be about 70% to 99.5% identical to the reference polynucleotide.

[0104] A "uracil glycosylase inhibitor" (UGI) useful in the present invention can be any protein capable of inhibiting the uracil-DNA glycosylase base excision repair enzyme. In some embodiments, the UGI domain comprises wild-type UGI or a fragment thereof. In some embodiments, a UGI domain useful in the present invention can be about 70% to about 100% identical (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100% identical and any range or value therein) to the amino acid sequence of a naturally occurring UGI domain. In some embodiments, the UGI domain may comprise the amino acid sequence of SEQ ID NO:26 or a polypeptide having about 70% to about 99.5% identity to the amino acid sequence of SEQ ID NO:26 (e.g., at least 80%, at least 85%, at least 90%, at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or at least 99.5% identical to the amino acid sequence of SEQ ID NO:26). For example, in some embodiments, the UGI domain may comprise a fragment of the amino acid sequence of SEQ ID NO:26 that is 100% identical to a portion of contiguous nucleotides of the amino acid sequence of SEQ ID NO:26 (e.g., about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 contiguous nucleotides; e.g., about 10, 15, 20, 25, 30, 35, 40, 45, to about 50, 55, 60, 65, 70, 75, 80 contiguous nucleotides). In some embodiments, the UGI domain may be a variant of a known UGI (e.g., SEQ ID NO: 26) having 70% to about 99.5% identity to a known UGI (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5% identity, and any range or value therein).In some embodiments, a polynucleotide encoding UGA may be codon-optimized for expression in an organism, and the codon-optimized polypeptide may be about 70% to about 99.5% identical to a reference polynucleotide.

[0105] In some embodiments, a modified LbCas12a nuclease may contain a mutation in its nuclease active site (e.g., RuvC). A modified LbCas12a nuclease that has a mutation in its nuclease active site(s) and no longer contains nuclease activity is generally referred to as "dead" (e.g., dLbCas12a). In some embodiments, a modified LbCas12a domain or polypeptide that has a mutation in its nuclease active site(s) may have impaired or reduced activity (e.g., nickase activity) compared to the same LbCas12a nuclease without the mutation.

[0106] The modified LbCas12a nuclease of the present invention can be used in combination with a guide RNA (gRNA, CRISPR array, CRISPR RNA, crRNA) designed to function with the modified LbCas12a nuclease to modify target nucleic acid. The guide nucleic acid useful in the present invention comprises at least a spacer sequence and a repeat sequence. The guide nucleic acid can form a complex with the LbCas12a nuclease domain encoded and expressed by the polynucleotide / nucleic acid construct of the present invention that encodes the modified LbCas12a nuclease, and the spacer sequence can hybridize to the target nucleic acid, thereby guiding the nucleic acid construct (e.g., modified LbCas12a nuclease (and / or polypeptide of interest)) to the target nucleic acid, where the target nucleic acid can be modified (e.g., cleaved or edited) or adjusted (e.g., transcriptionally adjusted) by the modified LbCas12a nuclease (and / or encoded deaminase domain and / or polypeptide of interest). As an example, a nucleic acid construct encoding an LbCas12a domain (e.g., a fusion protein) linked to a cytosine deaminase domain can be used in combination with an LbCas12a guide nucleic acid to modify a target nucleic acid, where the cytosine deaminase domain of the fusion protein deaminates a cytosine base in the target nucleic acid, thereby editing the target nucleic acid. In a further example, a nucleic acid construct encoding an LbCas12a domain (e.g., a fusion protein) linked to an adenine deaminase domain can be used in combination with an LbCas12a guide nucleic acid to modify a target nucleic acid, where the adenine deaminase domain of the fusion protein deaminates an adenosine base in the target nucleic acid, thereby editing the target nucleic acid.

[0107] As used herein, "guide nucleic acid", "guide RNA", "gRNA", "CRISPR RNA / DNA", "crRNA" or "crDNA" refers to a nucleic acid that includes at least one spacer sequence that is complementary to (and hybridizes with) a target nucleic acid (e.g., a protospacer), and at least one repeat sequence (e.g., a repeat of a V-type Cas12a CRISPR-Cas system, or a fragment or portion thereof), where the repeat sequence can be linked to the 5'-end and / or 3'-end of the spacer sequence. The design of the gRNA of the present invention can be based on the V-type Cas12a system.

[0108] In some embodiments, the Cas12a gRNA may comprise, from 5' to 3', a repeat sequence (either full length or a portion thereof ("handle"); e.g., a pseudoknot-like structure) and a spacer sequence.

[0109] In some embodiments, a guide nucleic acid may contain more than one "repeat sequence-spacer" sequence (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, or more repeat-spacer sequences) (e.g., repeat-spacer-repeat, e.g., repeat-spacer-repeat-spacer-repeat-spacer-repeat-spacer-repeat-spacer, etc.). Guide nucleic acids of the invention are synthetic, man-made, and not found in nature. gRNAs can be made quite long and can be used as aptamers (as in the MS2 recruitment strategy) or other RNA structures hanging off the spacer.

[0110] "Repeat sequence" as used herein refers to, for example, any repeat sequence of a wild-type Cas12a locus (e.g., LbCas12a locus) or a repeat sequence of a synthetic crRNA that is functional with the LbCas12a nuclease encoded by the nucleic acid construct of the present invention. The repeat sequence useful in the present invention can be any known or later identified repeat sequence of a Cas12a locus, or can be a synthetic repeat designed to function in a Cas12aV-type CRISPR-Cas system. The repeat sequence may include a hairpin structure and / or a stem-loop structure. In some embodiments, the repeat sequence may form a pseudoknot-like structure at its 5' end (e.g., a "handle"). Thus, in some embodiments, the repeat sequence can be identical or substantially identical to a repeat sequence from a wild-type V CRISPR-Cas locus (e.g., a wild-type Cas12a locus). Repeat sequences from a wild-type Cas12a locus can be determined by established algorithms, for example, using CRISPRfinder provided by CRISPRdb (see Grissa et al. Nucleic Acids Res. 35 (Web Server issue): W52-7). In some embodiments, a repeat sequence or a portion thereof is linked at its 3' end to the 5' end of a spacer sequence, thereby forming a repeat-spacer sequence (e.g., guide RNA, crRNA).

[0111] In some embodiments, the repeat sequence comprises, consists essentially of, or consists of at least 10 nucleotides (e.g., about 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50-100 or more nucleotides, or any range or value therein; e.g., about), depending on the particular repeat and regardless of whether the guide RNA comprising the repeat is processed. In some embodiments, the repeat sequence comprises, consists essentially of, or consists of about 10 to about 20, about 10 to about 30, about 10 to about 45, about 10 to about 50, about 15 to about 30, about 15 to about 40, about 15 to about 45, about 15 to about 50, about 20 to about 30, about 20 to about 40, about 20 to about 50, about 30 to about 40, about 40 to about 80, about 50 to about 100, or more nucleotides.

[0112] The repeat sequence linked to the 5' end of the spacer sequence can include a portion of the repeat sequence (e.g., 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 or more consecutive nucleotides of the wild-type repeat sequence). In some embodiments, the portion of the repeat sequence linked to the 5' end of the spacer sequence can be about 5 to about 10 contiguous nucleotides in length (e.g., about 5, 6, 7, 8, 9, 10 nucleotides) and can have at least 90% identity (e.g., at least about 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more) to the identical region (e.g., the 5' end) of the wild-type CRISPR Cas repeat nucleotide sequence. In some embodiments, the portion of the repeat sequence can include a pseudoknot-like structure at its 5' end (e.g., a "handle").

[0113] A "spacer sequence" as used herein is a nucleotide sequence that is complementary to a target nucleic acid (e.g., a target DNA) (e.g., a protospacer). A spacer sequence can be fully complementary or substantially complementary (e.g., at least about 70% complementary (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more, and any range or value therein)) to a target nucleic acid. Thus, in some embodiments, a spacer sequence can have 1, 2, 3, 4, or 5 mismatches compared to a target nucleic acid, and the mismatches can be contiguous or non-contiguous. In some embodiments, the spacer sequence can have about 70% complementarity to the target nucleic acid. In other embodiments, the spacer nucleotide sequence can have about 80% complementarity to the target nucleic acid. In still other embodiments, the spacer nucleotide sequence can have about 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 99.5% complementarity to the target nucleic acid (protospacer), etc. In some embodiments, the spacer sequence is 100% complementary to the target nucleic acid. The spacer sequence can have a length of about 15 nucleotides to about 30 nucleotides (e.g., about 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 nucleotides, or any range or value therein). Thus, in some embodiments, the spacer sequence may have perfect or substantial complementarity over a region of the target nucleic acid (e.g., a protospacer), which may be at least about 15 nucleotides to about 30 nucleotides in length. In some embodiments, the spacer may be about 20, 21, 22, 23, 24, or 25 nucleotides in length. In some embodiments, the spacer may be 23 nucleotides in length.

[0114] In some embodiments, the 5' region of the spacer sequence of the guide RNA may be identical to the target nucleic acid while the 3' region of the spacer may be substantially complementary to the target nucleic acid (e.g., type V CRISPR-Cas), or the 3' region of the spacer sequence of the guide RNA may be identical to the target nucleic acid while the 5' region of the spacer may be substantially complementary to the target nucleic acid (e.g., type II CRISPR-Cas), and thus the overall complementarity of the spacer sequence to the target nucleic acid may be less than 100%. Thus, for example, in a guide for a type V CRISPR-Cas system, for example, the first 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 nucleotides in the 5' region of a 20 nucleotide spacer sequence (i.e., the seed region) may be 100% complementary to the target nucleic acid, and the remaining nucleotides in the 3' region of the spacer sequence may be substantially complementary (e.g., at least about 70% complementary) to the target nucleic acid. In some embodiments, the first 1-8 nucleotides (e.g., the first 1, 2, 3, 4, 5, 6, 7, 8, nucleotides, and any range therein) at the 5' end of the spacer sequence can be 100% complementary to the target nucleic acid, and the remaining nucleotides in the 3' region of the spacer sequence can be substantially complementary (e.g., at least about 50% complementary (e.g., about 50%, 55%, 60%, 65%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more)) to the target nucleic acid.

[0115] In some embodiments, the seed region of the spacer can be about 8 to about 10 nucleotides in length, about 5 to about 6 nucleotides in length, or about 6 nucleotides in length.

[0116] As used herein, a "target nucleic acid", "target DNA", "target nucleotide sequence", "target region", or "target region in a genome" refers to a region of an organism's genome that is fully complementary (100% complementary) or substantially complementary (e.g., at least 70% complementary (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or more, and any range or value therein)) to a spacer sequence in a guide RNA of the present invention. In some embodiments, a target region useful for a V-type CRISPR-Cas system (e.g., LbCas12a) is located immediately 3' to a PAM sequence in the genome of an organism (e.g., a plant genome, an animal genome, a bacterial genome). In some embodiments, the target region can be selected from any at least 15 contiguous nucleotides (e.g., 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or more nucleotides, and any range or value therein; e.g., from about 19 to about 25 nucleotides, from about 20 to about 24 nucleotides in length, etc.) located immediately adjacent to the PAM sequence.

[0117] "Protospacer sequence" refers to a target nucleic acid, specifically a portion of a target nucleic acid (e.g., or a target region within a genome) that is completely or substantially complementary to (and hybridizes with) a spacer sequence of a CRISPR repeat-spacer sequence (e.g., guide RNA, CRISPR array, crRNA).

[0118] In the case of the Type V CRISPR-Cas Cas12a system, the protospacer sequence is flanked (immediately adjacent) to a protospacer adjacent motif (PAM) that is located at the 5' end of the non-targeted strand and the 3' end of the targeted strand (see below for an example). JPEG0007644755000001.jpg29166

[0119] A canonical Cas12a PAM is T-rich. In some embodiments, the canonical Cas12a PAM sequence may be 5'-TTN, 5'-TTTN, or 5'-TTTV.

[0120] The polypeptides, fusion proteins and / or systems of the invention may be encoded by a polynucleotide or nucleic acid construct. In some embodiments, the polynucleotide / nucleic acid construct encoding the polypeptides, fusion proteins and / or systems of the invention may be operatively associated with regulatory elements (e.g., promoters, terminators, etc.) for expression in an organism of interest and / or cells of an organism of interest as described herein. In some embodiments, the polynucleotide / nucleic acid construct encoding the polypeptides, fusion proteins and / or systems of the invention may be codon-optimized for expression in an organism.

[0121] In some embodiments, the invention provides a complex comprising (a) a modified LbCas12a polypeptide of the invention or a fusion protein of the invention and (b) a guide nucleic acid (e.g., CRISPR RNA, CRISPR DNA, crRNA, crDNA).

[0122] In some embodiments, the invention provides a composition comprising (a) a modified LbCas12a polypeptide of the invention or a fusion protein of the invention and (b) a guide nucleic acid.

[0123] In some embodiments, the present invention provides an expression cassette and / or vector comprising the polynucleotide / nucleic acid construct of the present invention. In some embodiments, an expression cassette and / or vector comprising the polynucleotide / nucleic acid construct of the present invention and / or one or more guide nucleic acids may be provided. In some embodiments, the nucleic acid construct encoding the modified CRISPR-Cas nuclease of the present invention and / or the fusion protein comprising the modified CRISPR-Cas nuclease may be included in the same or separate expression cassette or vector as that comprising the guide nucleic acid. When the nucleic acid construct is included in a separate expression cassette or vector as that comprising the guide nucleic acid, the target nucleic acid may be contacted (e.g. provided) with the expression cassette or vector comprising the nucleic acid construct of the present invention before, simultaneously with, or after the expression cassette comprising the guide nucleic acid is provided (e.g. contacted with the target nucleic acid).

[0124] In some embodiments, the invention provides expression cassettes and / or vectors encoding the compositions and / or complexes of the invention or comprising the systems of the invention.

[0125] In some embodiments, polynucleotides, nucleic acid constructs, expression cassettes and / or vectors of the invention that have been optimized for expression in an organism may be about 70% to about 100% identical (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5% or 100%, and any value or range therein) to a polynucleotide, nucleic acid construct, expression cassette and / or vector encoding the same modified CRISPR-Cas nuclease or fusion protein of the invention but that has not been codon optimized for expression in an organism. Organisms for which a polynucleotide or nucleic acid construct may be optimized may include, but are not limited to, animals, plants, fungi, archaea, or bacteria. In some embodiments, a polynucleotide or nucleic acid construct of the invention is codon optimized for expression in a plant.

[0126] In some embodiments, the invention provides cells comprising one or more polynucleotides, guide nucleic acids, nucleic acid constructs, systems, expression cassettes and / or vectors of the invention.

[0127] The nucleic acid constructs of the invention (e.g., encoding a modified CRISPR-Cas nuclease of the invention and / or a fusion protein comprising a modified CRISPR-Cas nuclease of the invention) and expression cassettes / vectors comprising same can be used to modify target nucleic acids and / or their expression in vivo (e.g., in an organism or cells of an organism (e.g., a plant)) and in vitro (e.g., in a cell or a cell-free system).

[0128] The invention further provides methods of altering the PAM specificity of a Cas12a polypeptide. In some embodiments, methods of altering the PAM specificity are provided comprising introducing mutations into a Cas12a polypeptide, wherein the mutations are at amino acid residues K116, K120, K121, D122, E125, T148, T149, T152, D156, E159, Q529, D535, K538, D541, Y542, L585, K591, M592, K595, V596, S599, K600, K601, Y616, Y646, W649 with respect to position numbering of SEQ ID NO:1. In some embodiments, the mutations introduced into the Cas12a polypeptide are, with respect to the position numbering of SEQ ID NO:1, K116R, K116N, K120R, K120H, K120N, K120T, K120Y, K120Q, K121S, K121T, K121H, K121R, K121G, K121D, K121Q, D ...S, K121T, K121S, K121T, K121S, K121S, K 2R, D122K, D122H, D122E, D122N, E125R, E125K, E125Q, E125Y, T148H, T148S, T148A, T148 C, T149A, T149C, T149S, T149G, T149H, T149P, T149F, T149N, T149D, T149V, T152R, T152K, T152W, T152Y, T152H, T152Q, T152E, T152L, T152F, D156R, D156K, D156Y, D156W, D156Q, D 156H, D156I, D156V, D156L, D156E, E159K, E159R, E159H, E159Y, E159Q, Q529N, Q529T, Q52 9H, Q529A, Q529F, Q529G, Q529G, Q529S, Q529P, Q529W, Q529D, G532D, G532N, G532S, G532 H, G532F, G532K, G532R, G532Q, G532A, G532L, G532C, D535N, D535H, D535V, D535T, D535, S D535A, D535W, D535K, K538RK538V, K538Q, K538W, K538Y, K538F, K538H, K538L, K538M, K538C, K538G, K538A, K538P , D541N, D541H, D541R, D541K, D541Y, D541I, D541A, D541S, D541E, Y542R, Y542K, Y542H , Y542Q, Y542F, Y542L, Y542M, Y542P, Y542V, Y542N, Y542T, L585G, L585H, L585F, K591W , K591F, K591Y, K591H, K591R, K591S, K591A, K591G, K591P, M592R, M592K, M592Q, M592E , M592A, K595R, K595Q, K595Y, K595L, K595W, K595H, K595E, K595S, K595D, K595M, V596 T, V596H, V596G, V596A, S599G, S599H, S599N, S599D, K600R, K600H, K600G, K601R, K601 H, K601Q, K601T, Y616K, Y616R, Y616E, Y616F, Y616H, Y646R, Y646E, Y646K, Y646H, Y646Q, Y646W, Y646N, W649H, W649K, W649Y, W649R, W649E, W649S, W649V, and / or W649T. In some embodiments, the mutations introduced into the Cas12a polypeptide are at amino acid residue positions: K116, K120, K121, D122, E125, T152, D156, E159, G532, D535, K538, D541, and / or K595 with respect to the position numbering of SEQ ID NO:1, where the mutations are K116R, K116N, K120Y ... 21S, K121R, D122H, D122N, E125K, T152R, T152K, T152Y, T152Q, T152E, T152F, D156R, D156W, D156Q, D156H, D156 I, D156V, D156L, D156E, E159K, E159R, G532N, G532S, G532H, G532K, G532R, G532L, D535N, D535H, D535T, D535, S D535A, D535W, K538RThe mutation may be K538V, K538Q, K538W, K538Y, K538F, K538H, K538L, K538M, K538C, K538G, K538A, D541E, K595R, K595Q, K595Y, K595W, K595H, K595S, and / or K595M. The mutation introduced may be a single mutation or a combination of two or more mutations. As will be understood, any single Cas12a polypeptide with two or more mutations contains only a single mutation at any given position. In some embodiments, the Cas12a polypeptide with altered PAM specificity by the methods of the invention is an LbCas12a polypeptide (Lachnospiraceae bacterium).

[0129] The modified Cas12a polypeptide or nuclease (e.g., LbCas12a nuclease) of the present invention can be used to modify a target nucleic acid in a cell or cell-free system (e.g., to modify a target nucleic acid, to modify the genome of a cell / organism). Thus, in some embodiments, a method of modifying a target nucleic acid is provided, the method comprising contacting the target nucleic acid with (a) (i) a modified LbCas12a polypeptide of the present invention, or a fusion protein of the present invention (e.g., a modified LbCas12a polypeptide of the present invention and a polypeptide of interest (e.g., a deaminase)) and (ii) a guide nucleic acid; (b) (i) a complex of the present invention comprising a modified LbCas12a polypeptide or fusion protein of the present invention, and (ii) a guide nucleic acid; (c) (i) a composition comprising a modified LbCas12a polypeptide of the present invention, or a fusion protein of the present invention, and (ii) a guide nucleic acid; and / or (d) a system of the present invention, thereby modifying the target nucleic acid. In some embodiments, a method for modifying / altering the genome of a cell or organism is provided, the method comprising contacting a target nucleic acid in the genome of the cell / organism with (a) (i) a modified LbCas12a polypeptide of the invention, or a fusion protein of the invention (e.g., a modified LbCas12a polypeptide of the invention and a polypeptide of interest (e.g., a deaminase)) and (ii) a guide nucleic acid; (b) a complex of the invention comprising (i) a modified LbCas12a polypeptide or fusion protein of the invention and (ii) a guide nucleic acid; (c) a composition comprising (i) a modified CRISPR-Cas nuclease of the invention (e.g., a modified LbCas12a polypeptide) or a fusion protein of the invention and (ii) a guide nucleic acid; and / or (d) a system of the invention, thereby modifying / altering the genome of the cell or organism. In some embodiments, the cell or organism is a plant cell or plant.

[0130] In some embodiments, a method of modifying a target nucleic acid is provided, the method comprising contacting a cell or cell-free system comprising the target nucleic acid with (a) (i) a polynucleotide of the invention (e.g., encoding a modified LbCas12a polypeptide of the invention, or encoding a fusion protein comprising a modified LbCas12a polypeptide of the invention and a polypeptide of interest (e.g., a deaminase), or an expression cassette or vector comprising same, and (ii) a guide nucleic acid, or an expression cassette and / or vector comprising same; and / or (b) a nucleic acid construct encoding a complex of the invention comprising a modified LbCas12a polypeptide of the invention, or a fusion protein comprising a modified LbCas12a polypeptide of the invention and a polypeptide of interest (e.g., a deaminase), or an expression cassette and / or vector comprising same, wherein the contacting is performed under conditions in which the polynucleotide and / or nucleic acid construct is expressed to produce a modified LbCas12a polypeptide and / or fusion protein that forms a complex with the guide nucleic acid, thereby modifying the target nucleic acid.In some embodiments, methods of modifying / altering the genome of a cell and / or organism are provided, comprising contacting a cell and / or a cell within the organism comprising a target nucleic acid with (a) (i) a polynucleotide of the invention (e.g., encoding a modified LbCas12a polypeptide of the invention, or encoding a fusion protein comprising a modified LbCas12a polypeptide of the invention and a polypeptide of interest (e.g., a deaminase), or an expression cassette or vector comprising same, and (ii) a guide nucleic acid, or an expression cassette and / or vector comprising same; and / or (b) a nucleic acid construct encoding a complex of the invention comprising a modified LbCas12a polypeptide of the invention, or a fusion protein comprising a modified LbCas12a polypeptide of the invention and a polypeptide of interest (e.g., a deaminase), or an expression cassette and / or vector comprising same, wherein the contacting is under conditions in which the polynucleotide and / or nucleic acid construct is expressed and a modified LbCas12a polypeptide and / or fusion protein is produced which forms a complex with the guide nucleic acid, thereby modifying the target nucleic acid.

[0131] In some embodiments, the invention provides a method of editing a target nucleic acid, the method comprising contacting the target nucleic acid with (a)(i) a fusion protein of the invention (comprising an engineered LbCas12a polypeptide of the invention and a polypeptide of interest (e.g., a deaminase)), and (a)(ii) a guide nucleic acid; (b) a complex comprising the fusion protein of the invention and a guide nucleic acid; (c) a composition comprising the fusion protein of the invention and a guide nucleic acid; and / or (d) a system of the invention, thereby editing the target nucleic acid.

[0132] In some embodiments, the invention provides a method of editing a target nucleic acid, the method comprising contacting a cell or cell-free system comprising the target nucleic acid with (a)(i) a polynucleotide encoding a fusion protein of the invention (e.g., a modified LbCas12a polypeptide of the invention and a polypeptide of interest (e.g., a deaminase)) or an expression cassette and / or vector comprising the same, and (a)(ii) a guide nucleic acid or an expression cassette and / or vector comprising the same; (b) a nucleic acid construct encoding a complex comprising the fusion protein of the invention and the guide nucleic acid or an expression cassette and / or vector comprising the same; and / or (c) a system of the invention, wherein the contacting is performed under conditions in which the polynucleotide and / or nucleic acid construct is expressed and a modified CRISPR-Cas nuclease and / or fusion protein is produced, which forms a complex with the guide nucleic acid, thereby editing the target nucleic acid.

[0133] CRISPR-Cas nucleases with engineered PAM recognition specificities can be used in many ways, including but not limited to, in creating indels (NHEJ), homology-directed repair, as genomic recognition elements without nuclease function (dead Cpf1), as genomic recognition elements with partially functional nuclease (nickase Cpf1), in fusion proteins for catalytic editing of genomic DNA (DNA base editors), in fusion proteins for catalytic editing of RNA (RNA base editors), for targeting other macromolecules to specific genomic regions; for targeting small chemicals to specific genomic regions, for labeling specific genomic regions, and / or CRISPR-directed genome recombination strategies.

[0134] When provided on a different nucleic acid construct, expression vector, and / or vector, the nucleic acid construct of the invention can be contacted with the target nucleic acid before, simultaneously with, or after contacting the guide nucleic acid with the target nucleic acid.

[0135] The modified CRISPR-Cas nucleases and polypeptides of the present invention and the nucleic acid constructs encoding them can be used to modify target nucleic acids in any organism, including, but not limited to, animals, plants, fungi, archaea, or bacteria. Animals can include, but are not limited to, mammals, insects, fish, birds, etc. Exemplary mammals for which the present invention may be useful include, but are not limited to, primates (human and non-human, e.g., chimpanzees, baboons, monkeys, gorillas, etc.), cats, dogs, mice, rats, ferrets, gerbils, hamsters, cows, pigs, horses, goats, donkeys, or sheep.

[0136] The target nucleic acid of any plant or plant part can be modified and / or edited (e.g., mutated, e.g., base edited, truncated, nicked, etc.) using the nucleic acid constructs of the present invention. Any plant (or grouping of plants into, e.g., genera or higher classifications), including angiosperms, gymnosperms, monocots, dicots, C3, C4, CAM plants, bryophytes, ferns and / or ferns other than the class Pteridophytes, microalgae, and / or macroalgae, can be modified using the nucleic acid constructs of the present invention. Plants and / or plant parts useful in the present invention can be plants and / or plant parts of any plant species / variety / cultivar. The term "plant part" as used herein includes, but is not limited to, embryos, pollen, ovules, seeds, leaves, stems, buds, flowers, branches, fruits, grains, ears, cobs, husks, petioles, roots, root tips, anthers, plant cells (including intact plant cells in plants and / or plant parts, plant protoplasts, plant tissues, plant cell tissue cultures, plant calli, plant clumps, etc.). As used herein, "buds" refers to parts above ground level, including leaves and stems. Furthermore, as used herein, "plant cells" refers to the structural and physiological units of plants, including cell walls, and may also refer to protoplasts. Plant cells can be in the form of isolated single cells, or can be cultured cells, or can be part of a higher organized unit, such as, for example, plant tissues or plant organs.

[0137] Non-limiting examples of plants useful in the present invention include turfgrasses (e.g., bluegrass, bentgrass, ryegrass, fescue), feather reed grass, tufted hair grass, miscanthus, arundo, switchgrass, vegetable crops including: artichoke, kohlrabi, arugula, leek, asparagus, lettuce (e.g., head, leaf, romaine), malanga, melons (e.g., muskmelon, watermelon, cranberry, honeydew, cantaloupe), brassica crops (e.g., Brussels sprouts, cabbage, cauliflower, broccoli, collards, kale, Chinese cabbage, bok choy), cardoni, carrots, napa, okra, tuna, and the like. Onion, celery, parsley, chickpeas, parsnips, chicory, peppers, potatoes, cucurbits (e.g., cucumber, zucchini, toadflax, pumpkin, honeydew melon, watermelon, cantaloupe), radishes, dry bulb onions, rutabaga, eggplant, burdock, endive, shallot, endive, garlic, spinach, leeks, toadflax, leafy vegetables, beets (e.g., sugar beet and fodder beet), sweet potato, chard, horseradish, tomatoes, turnips, and spices;Fruit crops, such as apples, apricots, cherries, nectarines, peaches, pears, plums, prunes, cherries, quince, figs, nuts (e.g. chestnuts, pecans, pistachios, hazelnuts, pistachios, peanuts, walnuts, macadamia nuts, almonds, etc.), citrus fruits (e.g. clementines, kumquats, oranges, grapefruit, tangerines, mandarins, lemons, limes, etc.), blueberries, black raspberries, boysenberries, cranberries, currants, gooseberries, loganberries, raspberries, strawberries, blackberries, grapes (e.g. wine and table), avocados, bananas, kiwis, persimmons, pomegranates, pineapples, tropical fruits, pome fruits, melons, mandarins, grapes, grapefruits, grape ... go, papaya, and lychee, crop plants such as clover, alfalfa, timothy grass, evening primrose, meadowfoam, corn / maize (e.g., field, sweet, popcorn), hops, jojoba, buckwheat, safflower, quinoa, wheat, rice, barley, rye, millet, sorghum, oats, lyco, sorghum, tobacco, kapok, legumes (beans (e.g., green and dry), lentils, peas, soybeans), oilseed plants (e.g., rapeseed, canola, mustard, poppy, olive, sunflower, coconut, castor oil plant, cocoa beans, peanuts, oil palm, soybean, camellia, etc.), duckweed, Arabidopsis, fiber plants (cotton, flax, hemp, jute), hemp (e.g., Cannabis sativa, sativa, Cannabis indica, and Cannabis ruderalis), Lauraceae (e.g. cinnamon, camphor), or plants, such as coffee, sugar cane, tea, and rubber plants; and / or bedding plants, such as flowering plants, cacti, succulents and / or ornamental plants (e.g. roses, tulips, violets), and trees, such as forest trees (broad-leaved and evergreen, e.g. conifers;For example, elm, ash, oak, maple, fir, spruce, cedar, pine, birch, cypress, eucalyptus, willow), as well as shrubs and other seedlings. In some embodiments, the nucleic acid constructs of the invention and / or expression cassettes and / or vectors encoding same may be used to modify corn, soybean, wheat, canola, rice, tomato, pepper, sunflower, raspberry, blackberry, black raspberry, and / or cherry.

[0138] The present invention further includes kits for carrying out the methods of the present invention. The kits of the present invention may include reagents, buffers, and / or instruments for mixing, measuring, selecting, labeling, etc., as well as instructions suitable for modifying the target nucleic acid, etc.

[0139] In some embodiments, the present invention provides a kit comprising one or more polynucleotides and / or nucleic acid constructs of the present invention, and / or expression cassettes and / or vectors comprising same, and may include instructions for their use. In some embodiments, the kit may further comprise a polypeptide of interest and / or a polynucleotide encoding same and an expression cassette and / or vector comprising same. In some embodiments, the guide nucleic acid may be provided on the same expression cassette and / or vector as the nucleic acid construct of the present invention. In some embodiments, the guide nucleic acid may be provided on a separate expression cassette or vector from the one comprising the nucleic acid construct of the present invention.

[0140] Thus, in some embodiments, a kit is provided that includes a nucleic acid construct comprising (a) a polynucleotide encoding a modified CRISPR-Cas nuclease provided herein and (b) a promoter driving expression of the polynucleotide of (a). In some embodiments, the kit may further include a nucleic acid construct encoding a guide nucleic acid, where the construct includes a cloning site for cloning a nucleic acid sequence identical or complementary to a target nucleic acid sequence into the backbone of the guide nucleic acid.

[0141] In some embodiments, the kit may include a nucleic acid construct comprising / encoding one or more nuclear localization signals, where the nuclear localization signals are fused to a CRISPR-Cas nuclease. In some embodiments, a kit is provided that includes a nucleic acid construct of the invention encoding a modified CRISPR-Cas nuclease of the invention, and / or an expression cassette and / or vector comprising the same, where the nucleic acid construct, expression cassette and / or vector may further encode one or more selectable markers useful for identifying transformants (e.g., nucleic acids encoding antibiotic resistance genes, herbicide resistance genes, etc.). In some embodiments, the nucleic acid construct may be an mRNA encoding one or more introns within the encoded CRISPR-Cas nuclease. In some embodiments, the kit may include a promoter, and a promoter and intron, for use in expressing the polypeptides and nucleic acid constructs of the invention.

[0142] Methods for modifying the PAM specificity of CRISPR-Cas nucleases and related compositions CRISPR-Cas system is directed to target nucleic acid using two main criteria: the homology of guide RNA to the target DNA sequence, and the presence of a protospacer adjacent motif (PAM) of a specific sequence. Different CRISPR-Cas nucleases have different PAM sequence requirements (e.g., NGG for SpCas9, or TTTV for LbCas12a (Cpf1), where V is any non-thymidine nucleotide). Screening new CRISPR nucleases or their mutants for their PAM requirements can be complex and unpredictable, since there are so many repeat possibilities. In vitro assays, especially PAM determination assays (PAMDA), can be used to screen the PAM specificity for any particular CRISPR nuclease or its mutants. These assays rely on randomized portions of DNA adjacent to a defined / known protospacer sequence. A guide RNA can be designed to target a known protospacer sequence, and if the randomized PAM region contains the appropriate DNA sequence (e.g., recognized by a CRISPR nuclease or a mutant thereof), the CRISPR nuclease can bind and cleave the target.

[0143] PAM recognition sites for CRISPR-Cas nucleases can be assessed using a PAM site depletion assay (e.g., PAM depletion assay) or PAM determination assay (PAMDA) (Kleinstiver et al. Nat Biotechnol 37:276-282 (2019)). For a PAM depletion assay, a library of plasmids with randomized nucleotides (base pairs) adjacent to a protospacer are tested for cleavage by a CRISPR nuclease in bacteria (e.g., E. coli). The plasmids may contain, for example, a polynucleotide that confers antibiotic resistance adjacent to the randomized PAM sequence. Sequences that are not cleaved upon exposure to CRISPR-Cas nuclease allow cells to survive in the presence of antibiotics due to the presence of an antibiotic resistance gene, while plasmids with targetable PAMs are cleaved and depleted from the library due to cell death. Sequencing of the surviving (uncut) population of plasmids allows for the calculation of a post-selection PAM depletion value, which is compared to a library not exposed to CRISPR-Cas nuclease. The sequences that are depleted from the sequence pool in the experimental library contain the PAM sequence(s) recognized by the CRISPR-Cas nuclease.

[0144] Another method that can be used to identify PAM sequences is the PAM Determination Assay (PAMDA) (Kleinstiver et al. Nat Biotechnol 37:276-282 (2019)). In this case, cleavage is performed outside of living cells. In PAMDA, a single DNA strand is synthesized with a randomized portion of nucleotides next to a defined protospacer sequence. Oligonucleotides are annealed to the 3' end of the synthesized DNA strand and extended with exonuclease minus (-exo) Klenow fragment, polymerizing across the defined and randomized sequences. This produces a duplex library, which is then cleaved with a restriction endonuclease and cloned into bacteria to amplify the total DNA. The plasmid is extracted and linearized with another restriction endonuclease to create a linear template. The template is contacted with a CRISPR-Cas nuclease-guide RNA complex. Only sequences containing the PAM recognized by the CRISPR-Cas nuclease are cleaved. Both the experimental and control libraries (not exposed to CRISPR-Cas nuclease) are then amplified by PCR. Only sequences that are not cleaved by CRISPR-Cas nuclease are amplified. The PCR amplified sequences from the control and experimental libraries (treated with CRISPR-Cas nuclease) are sequenced and compared. The PAM sequence present in the control (not exposed to CRISPR-Cas nuclease) library but not in the experimental library is the PAM sequence recognized by the CRISPR-Cas nuclease (thereby allowing the protospacer to be cleaved).

[0145] A randomized PAM library is prepared for in vitro evaluation of nuclease requirements. The steps described for this method include preparation of an unbiased randomized DNA library containing all PAM sequences to be evaluated, cloning into a plasmid, introduction of the library into bacteria to increase the total amount of starting DNA, extraction of the plasmid, linearization of the plasmid with a restriction enzyme to remove supercoils, exposure of the linearized molecule to CRIPSR-Cas nuclease, amplification of the fragments (e.g., PCR), and final sequence analysis (e.g., next generation sequencing, NGS). The initial steps of unbiased library creation and restriction digestion require at least two restriction enzymes, Klenow extension, and cleaning of the product before ligation into a vector. The use of two to three restriction enzymes typically removes some PAM sequences from the library, introducing bias into the library. Additionally, subsequent Klenow extension and washing steps may also remove PAM sequences, thereby introducing further bias into the library. To avoid sequence loss and produce more complete and unbiased libraries, the present invention provides a novel method for generating randomized PAM libraries using overlapping solid synthetic oligonucleotides (e.g., annealed oligonucleotides) with overhangs instead of restriction endonucleases and Klenow extension (see, e.g., FIG. 1b).The randomized PAM libraries produced using the methods of the present invention can then be used to test the PAM specificity of CRISPR-Cas nucleases with a higher degree of accuracy than was previously available with libraries produced by prior art methods.

[0146] Thus, in some embodiments, the present invention provides a method for constructing a randomized DNA library comprising double-stranded nucleic acid molecules for determining the protospacer adjacent motif (PAM) requirement / specificity of a CRISPR-Cas nuclease having a PAM recognition site at the 5' end of the protospacer, the method comprising the steps of preparing two or more double-stranded nucleic acid molecules: (a) synthesizing a non-target oligonucleotide (first) strand and a target oligonucleotide (second) strand for each of the two or more double-stranded nucleic acid molecules, wherein the non-target oligonucleotides are The nucleotide strand comprises from 5' to 3': (i) a first sequence having about 5 to about 15 nucleotides (e.g., about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 nucleotides, and any range therein); (ii) a second sequence having at least four randomized nucleotides (e.g., at least 4, 5, 6, 7, 8, 9, 10, or more, and any range therein); (ii) a second sequence having about 16 to about 25 nucleotides (e.g., about 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 nucleotides); and and any range therein), and (iv) a third sequence having about 5 to about 20 nucleotides (e.g., about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 nucleotides, and any range therein), wherein the first sequence having about 5 to 15 nucleotides in (i) is immediately adjacent to the 5' terminus of the second sequence in (ii), the second sequence in (ii) is immediately adjacent to the 5' terminus of the protospacer sequence in (iii), and the protospacer sequence is immediately adjacent to the 5' terminus of the third sequence in (iv). the target oligonucleotide (second) strand is complementary to the non-target oligonucleotide strand; and (b) annealing the non-target oligonucleotide strand to the complementary target oligonucleotide strand to produce double-stranded nucleic acid molecules, where the first sequence comprises a restriction site (at its 5' end) and the third sequence comprises a restriction site (at its 3' end), where the first sequence (i), the protospacer sequence (iii) and the third sequence (iv) of each of the two or more double-stranded nucleic acid molecules are identical, thereby constructing a randomized DNA library comprising double-stranded nucleic acid molecules.In some embodiments, the target strand and / or the non-target strand may be 5' phosphorylated.

[0147] In some embodiments, the present invention provides a method for constructing a randomized DNA library comprising double-stranded nucleic acid molecules for determining the protospacer adjacent motif (PAM) requirement / specificity of a CRISPR-Cas nuclease having a PAM recognition site at the 3' end of the protospacer, the method comprising: preparing two or more double-stranded nucleic acid molecules comprising: (a) synthesizing a non-target oligonucleotide (first) strand and a target oligonucleotide (second) strand for each of the two or more double-stranded nucleic acid molecules, wherein the non-target oligonucleotide strand is 5' to 3' comprising: (i) a first sequence having about 5 to about 20 nucleotides (e.g., about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 nucleotides, and any range therein); (ii) a protospacer sequence having about 16 to about 25 nucleotides (e.g., about 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 nucleotides, and any range therein); (iii) at least four randomized nucleotides (e.g., at least 4, 5, 6, 7, 8, 9, 10, or more); a second sequence having from about 5 to about 15 nucleotides (e.g., from about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 nucleotides, and any range therein), and (iv) a third sequence having from about 5 to about 15 nucleotides (e.g., from about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 nucleotides, and any range therein), wherein the first sequence having from about 5 to about 20 nucleotides of (i) is immediately adjacent to the 5'-terminus of the protospacer sequence of (ii), the second sequence of (iii) is immediately adjacent to the 3'-terminus of the protospacer sequence of (iii), and the third sequence of (iv) is immediately adjacent to the 3'-terminus of the second sequence of (iii); the (second) strand of nucleotides is complementary to the non-target oligonucleotide strand; and (b) annealing the non-target oligonucleotide strand to the complementary target oligonucleotide strand to produce double-stranded nucleic acid molecules, wherein the first sequence (i) comprises a restriction site (at its 5' end) and the third sequence (iv) comprises a restriction site (at its 3' end), wherein the first sequence (i), the protospacer sequence (ii) and the third sequence (iv) of each of the two or more double-stranded nucleic acid molecules are identical, thereby constructing a randomized DNA library comprising double-stranded nucleic acid molecules.In some embodiments, the target strand and / or the non-target strand may be 5' phosphorylated.

[0148] In some embodiments, the double-stranded nucleic acid molecule can be ligated into a vector to produce a vector comprising a randomized DNA library. In some embodiments, the vector can be a high copy number vector. In some embodiments, the randomized DNA library can be amplified, for example, by introducing the vector comprising the randomized DNA library into one or more bacterial cells and culturing the one or more bacterial cells. In some embodiments, the vector comprising the randomized DNA library can be isolated from one or more bacterial cells after culturing. The isolated vector can then be linearized (e.g., by contacting the vector with one or more restriction enzymes; e.g., ScaI or PfoI) for use in, for example, analyzing the PAM recognition specificity of CRISPR-Cas nuclease. In some embodiments, Pfo1 can be used to linearize the isolated vector.

[0149] In some embodiments, a randomized DNA library can be provided to determine the protospacer adjacent motif (PAM) requirement / specificity of a CRISPR-Cas nuclease having a PAM recognition site at the 5' end of the protospacer, the randomized DNA library comprising two or more double-stranded nucleic acid molecules, each of which comprises (a) a non-target oligonucleotide (first) strand and a target oligonucleotide (second) strand, wherein the non-target oligonucleotide strand comprises, from 5' to 3', (i) about 5 to about (ii) a first sequence having 15 nucleotides (e.g., about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 nucleotides, and any range therein); (iii) a second sequence having at least 4 randomized nucleotides (e.g., at least 4, 5, 6, 7, 8, 9, 10, or more, and any range therein); (iv) a second sequence having about 16 to about 25 nucleotides (e.g., about 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 nucleotides, and any range therein); and (iv) a third sequence having about 5 to about 20 nucleotides (e.g., about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 nucleotides, and any range therein), wherein the first sequence having about 5 to 15 nucleotides in (i) is immediately adjacent to the 5'-terminus of the second sequence in (ii), and the second sequence in (ii) is immediately adjacent to the 5'-terminus of the protospacer sequence in (iii), and the protospacer sequence is (iv). (a) the target oligonucleotide (second) strand is immediately adjacent to the 5' end of a third sequence of the target oligonucleotide; the target oligonucleotide (second) strand is complementary to the non-target oligonucleotide strand; and (b) the non-target oligonucleotide strand anneals to the complementary target oligonucleotide strand to produce a double-stranded nucleic acid molecule, where the first sequence comprises a restriction site (at its 5' end) and the third sequence comprises a restriction site (at its 3' end), and where the first sequence (i), the protospacer sequence (iii) and the third sequence (iv) of each of the two or more double-stranded nucleic acid molecules are identical. In some embodiments, the target strand and / or the non-target strand may be 5' phosphorylated.

[0150] In some embodiments, a randomized DNA library for determining the protospacer adjacent motif (PAM) requirement / specificity of a CRISPR-Cas nuclease having a PAM recognition site at the 3' end of the protospacer may be provided, the randomized DNA library comprising two or more double-stranded nucleic acid molecules, each of which comprises (a) a non-target oligonucleotide (first) strand and a target oligonucleotide (second) strand, wherein the non-target oligonucleotide strand comprises, from 5' to 3', (i) about 5 to about 20 nucleotides. (ii) a first sequence having at least about 16 to about 25 nucleotides (e.g., about 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 nucleotides, and any range therein); (iii) a protospacer sequence having at least four randomized nucleotides (e.g., at least 4, 5, 6, 7, 8, 9, 10, or more); and (iv) a third sequence having from about 5 to about 15 nucleotides (e.g., about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 nucleotides, and any range therein), wherein the first sequence having from about 5 to about 20 nucleotides in (i) is immediately adjacent to the 5'-terminus of the protospacer sequence in (ii), the second sequence in (iii) is immediately adjacent to the 3'-terminus of the protospacer sequence in (iii), and the third sequence in (iv) is from about 5 to about 15 nucleotides (e.g., about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 nucleotides, and any range therein), (i) immediately adjacent to the 3' end of the second sequence; the target oligonucleotide (second) strand is complementary to the non-target oligonucleotide strand; and (b) the non-target oligonucleotide strand anneals to the complementary target oligonucleotide strand to produce a double-stranded nucleic acid molecule, where the first sequence comprises a restriction site (at its 5' end) and the third sequence comprises a restriction site (at its 3' end), and where the first sequence (i), the protospacer sequence (ii) and the third sequence (iv) of each of the two or more double-stranded nucleic acid molecules are identical. In some embodiments, the target strand and / or the non-target strand may be 5' phosphorylated.

[0151] In some embodiments, the present invention provides a method for determining the protospacer adjacent motif (PAM) specificity of a CRISPR-Cas nuclease, the method comprising the steps of contacting a CRISPR-Cas nuclease with a randomized DNA library of the present invention; and sequencing double-stranded nucleic acid molecules of the randomized DNA library before (e.g., a control) and after contact with the CRISPR-Cas nuclease, wherein double-stranded nucleic acid molecules present in the randomized DNA library before contact with the CRISPR-Cas nuclease but not present in the randomized DNA library after contact with the CRISPR-Cas nuclease identify the PAM recognition sequence of the CRISPR-Cas nuclease, thereby determining the PAM specificity of the CRISPR-Cas nuclease.

[0152] In some embodiments, a method for determining the protospacer adjacent motif (PAM) specificity of a CRISPR-Cas nuclease comprises the steps of: contacting a CRISPR-Cas nuclease with a randomized DNA library of the invention; sequencing double-stranded nucleic acid molecules of the randomized DNA library before (e.g., a control) and after contact with the CRISPR-Cas nuclease; and identifying a PAM recognition sequence of the nuclease, wherein the identifying step comprises comparing the double-stranded nucleic acid molecules present in the library before contact with the CRISPR-Cas nuclease to the double-stranded nucleic acid molecules present in the library after contact with the CRISPR-Cas nuclease, wherein double-stranded nucleic acid molecules present in the randomized DNA library before contact with the CRISPR-Cas nuclease but not in the randomized DNA library after contact with the CRISPR-Cas nuclease identify the PAM specificity of the CRISPR-Cas nuclease.

[0153] The result of sequencing the randomized library before contacting can serve as a control for the result of sequencing after contacting.In some embodiments, determining the PAM specificity of CRISPR-Cas nuclease can comprise performing nucleic acid sequencing.In some embodiments, sequencing can comprise next generation sequencing (NGS).

[0154] Any CRISPR-Cas nuclease can be used in the methods of the present invention to modify PAM recognition specificity. Thus, CRISPR-Cas nucleases that can be modified to have different PAM specificity compared to the wild type include, but are not limited to, Cas9, C2c1, C2c3, Cas12a (also called Cpf1), Cas12b, Cas12c, Cas12d, Cas12e, Cas13a, Cas13b, Cas13c, Cas13d, Casl, CaslB, Cas2, Cas3, Cas3', Cas3'', Cas4, Cas5, Cas6, Cas7, Cas8, Cas9 (with Csnl and Csx12), and Csx13 (with Csx13). Also known as Cas10, Csyl, Csy2, Csy3, Csel, Cse2, Cscl, Csc2, Csa5, Csn2, Csm2, Csm3, Csm4, Csm5, Csm6, Cmrl, Cmr3, Cmr4, Cmr5, Cmr6, Csbl, Csb2, Csb3, Csxl7, Csxl4, Csx10, Csx16, CsaX, Csx3, Csxl, Csxl5, Csfl, Csf2, Csf3, Csf4(dinG), and / or Csf5 polypeptides or domains.

[0155] Cas12a is a type V Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas nuclease originally identified in Prevotella and Francisella species. Cas12a (previously called Cpf1) differs in several ways from the better known type II CRISPR Cas9 nuclease. For example, Cas9 recognizes a G-rich protospacer adjacent motif (PAM) (3'-NGG) that is 3' to its guide RNA (gRNA, sgRNA) binding site (protospacer, target nucleic acid, target DNA), whereas Cas12a recognizes a T-rich PAM (5'-TTN, 5'-TTTN) that is located 5' to the binding site (protospacer, target nucleic acid, target DNA). In fact, the orientation in which Cas9 and Cas12a bind their guide RNAs is almost opposite with respect to their N- and C-termini. Furthermore, the Cas12a enzyme uses a single guide RNA (gRNA, CRISPR array, crRNA) rather than the dual guide RNAs (sgRNA (e.g., crRNA and tracrRNA)) found in the native Cas9 system, and Cas12a processes its own gRNA. In addition, Cas12a nuclease activity produces protruding DNA double-stranded breaks instead of the blunt ends generated by Cas9 nuclease activity, and Cas12a relies on a single RuvC domain to cleave both DNA strands, whereas Cas9 utilizes the HNH and RuvC domains for cleavage.

[0156] The CRISPR Cas12a polypeptide or CRISPR Cas12a domain useful in the present invention may be any known or later identified Cas12a nuclease (see, e.g., U.S. Patent No. 9,790,490, incorporated by reference for its disclosure of Cpf1 (Cas12a) sequences). The term "Cas12a", "Cas12a polypeptide" or "Cas12a domain" refers to an RNA-guided nuclease comprising a Cas12a polypeptide, or a fragment thereof, which includes the guide nucleic acid binding domain of Cas12a, and / or the active, inactive, or partially active DNA cleavage domain of Cas12a. In some embodiments, the Cas12a useful in the present invention may include a mutation in the nuclease active site (e.g., the RuvC site of the Cas12a domain). A Cas12a domain or Cas12a polypeptide that has a mutation in its nuclease active site and therefore no longer contains nuclease activity is generally referred to as a deadCas12a (e.g., dCas12a). In some embodiments, a Cas12a domain or Cas12a polypeptide that has a mutation in its nuclease active site may have impaired / reduced activity (e.g., nickase activity) compared to an identical Cas12a polypeptide that does not have the same mutation.

[0157] In some embodiments, the Cas12a domain can include, but is not limited to, the amino acid sequence of any one of SEQ ID NOs: 1-17 (e.g., SEQ ID NOs: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, and / or 17), or a polynucleotide encoding same. In some embodiments, the fusion protein of the invention can include a Cas12a domain from Lachnospiraceae bacterium ND2006 Cas12a (LbCas12a) (e.g., SEQ ID NO: 1).

[0158] A CRISPR Cas9 polypeptide or CRISPR Cas9 domain useful in the present invention may be any known or later identified Cas9 nuclease. In some embodiments, a Cas9 polypeptide useful in the present invention comprises at least 70% identity (e.g., about 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.) to the amino acid sequence of any known Cas9. CRISPR-Cas9 systems are well known in the art and include, but are not limited to, Cas9 polypeptides from Legionella pneumophila str. Paris, Streptococcus thermophilus CNRZ1066, Streptococcus pyogenes MI, or Neisseria lactamica 020-06.

[0159] Other nucleases that may be useful in the present invention to identify novel PAM recognition sequences include, but are not limited to, C2c1, C2c3, Cas12b, Cas12c, Cas12d, Cas12e, Cas13a, Cas13b, Cas13c, Cas13d, Casl, CaslB, Cas2, Cas3, Cas3', Cas3'', Cas4, Cas5, Cas6, Cas7, Cas8, Cas9 (also known as Csnl and Csx12), Csnl, Csx13 ... including as10, Csyl, Csy2, Csy3, Csel, Cse2, Cscl, Csc2, Csa5, Csn2, Csm2, Csm3, Csm4, Csm5, Csm6, Cmrl, Cmr3, Cmr4, Cmr5, Cmr6, Csbl, Csb2, Csb3, Csxl7, Csxl4, Csx10, Csx16, CsaX, Csx3, Csxl, Csxl5, Csfl, Csf2, Csf3, Csf4(dinG), and / or Csf5.

[0160] The present invention will now be described with reference to the following examples. It should be understood that these examples are not intended to limit the scope of the claimed invention, but rather are intended to be illustrative of specific embodiments. Any variations in the exemplified methods that occur to those skilled in the art are intended to be included within the scope of the present invention. EXAMPLES

[0161] Example 1. Randomized Library An example of the method of the present invention for efficient and cost-effective generation of libraries for an efficient and cost-effective in vitro cleavage assay (PAM determination assay (PAMDA)) is provided. Two libraries were generated for protospacers 1 and 2 (see Table 1). Oligonucleotides with randomized 5 nucleotide sequences at the 5' end were synthesized and verified to occupy equal molar ratios of each protospacer sequence (Integrated DNA Technologies) (Table 1). Oligonucleotides for protospacer 1 (PM0518, PM0519) and oligonucleotides for protospacer 2 (PM0520, PM0521) were annealed by placing the mixture in a thermal cycler at 95°C for 5 minutes and cooling down to 25°C / room temperature at 0.1°C / sec.

[0162] JPEG0007644755000002.jpg97166

[0163] The annealed double-stranded fragment was directly ligated into SphI and EcoRI digested pUC19 vector. The ligated protospacer construct was transformed into XL1-Blue electrocompetent E. coli cells (Agilent) and allowed to recover in 1 ml SOC medium at 37°C for 1 h. Carbenicillin plates were used to check for the presence of the ligated product in E. coli cells. The transformed E. coli cells were grown in LB broth (200 ml) supplemented with carbenicillin (50 mg / mL) for 16 h. Plasmids containing the protospacer construct were purified using Zymo midiprep kit. Plasmids / vectors were subjected to deep sequencing to calculate the frequency of A / T / G / C at each PAM position using Illumina Miseq.

[0164] This method can be used to generate libraries for PAM determination using any protospacer oligonucleotide(s) of choice, where the annealed oligonucleotides may contain any suitable restriction site selected to maintain a full complement of the PAM sequence in the library.

[0165] Example 2 Lachnospiraceae bacterium ND2006 Cpf1 (LbCpf1) requires a very specific protospacer adjacent motif (PAM). The "TTTV" sequence occurs only about 1 out of 85 bases compared to random nucleotides. This contrasts with the relative promiscuity of NGG for SpCas9, which occurs about 1 out of 16 bases in random DNA, TTN for AaC2c1, which occurs about 1 out of 16 bases in random DNA, and xCas9 / Cas9-NG, whose NG PAM requirement occurs about 1 out of 4 bases. Cpf1 PAM is much less abundant than Cas9 PAM in maize and soybean genes (Figure 2). Furthermore, adenine and cytosine (current targets for base editors) are much less accessible to LbCpf1 based on their stringent PAM requirements (Figure 3).

[0166] The stringency shown in Figure 3 for CRISPR-Cas nucleases greatly reduces the generation of potential targets and new traits. The present invention relates to the creation of CRISPR-Cas nucleases with improved ratios of accessible PAM sequences, in particular LbCpf1 (Cas12a) nucleases (e.g., nucleases with PAM recognition sites occurring at a ratio of about 1:4 or better). Such engineered Cas12a PAM mutants can be used as nucleases (for NHEJ or HDR applications) or inactivated versions can be used as genome recognition elements in genome editing tools.

[0167] PAMDA assay The PAM determination assay (PAMDA) is useful to test the PAM requirement for a CRISPR enzyme with unknown PAM recognition. There is an in vitro assay that takes advantage of the ability of CRISPR-Cas nucleases to cleave the target sequence only after successful PAM binding. Briefly, a library of DNA substrates with randomized PAM sequences is incubated with CRISPR nuclease, and then the DNA is amplified by PCR. Only intact fragments (e.g., those not recognized by the nuclease) are amplified. Cleaved fragments (those recognized by the nuclease) are not amplified. DNA from both the library exposed to the nuclease and the control library (not exposed to the nuclease) are sequenced. The two sets of sequencing results are compared to determine which sequences were cleaved and therefore not present in the assembly of the sequence after exposure to the nuclease (see Figure 4 for an example). A modified PAMDA using multiple time points was used to determine PAM binding and subsequent cleavage.

[0168] LbCpf1 mutagenesis 186 point mutations (Table 2) were designed and individually tested in the PAMDA assay as described herein. Successful engineering could alter the PAM recognition sequence to generate a novel PAM-recognizing LbCpf1, or relax the PAM stringency to produce a more promiscuous LbCpf1.

[0169] JPEG0007644755000003.jpg211166JPEG0007644755000004.jpg171166

[0170] In addition to individual mutations, combinations of mutations that alter PAM recognition will be combined and evaluated by PAMDA to provide second generation LbCpf1 mutations.

[0171] Example 3. 186 mutations were tested using three methods: (1) An in vitro method known as the PAMDA assay (Kleinstiver et al. Nat Biotechnol 37,:276-282(2019)) uses purified protein and plasmid libraries to test each point mutation across a library. Depletion of library members was scored using next generation sequencing (NGS). Depletion was calculated relative to the library itself (to determine absolute activity against a particular PAM) or relative to cleavage by wild-type LbCas12a (to determine if the mutation confers novel PAM recognition compared to wild-type). (2) A bacterial method known as PAM-SCANR (Leenay et al. Mol Cell 62:137-147 (2016)) uses a library in Escherichia coli to test binding of Cas12a mutations to 256 possible PAM NNNN mutants. It does not test for cleavage, only binding. Because the mutations made were not anywhere near the catalytic region, binding is predicted to also reflect cleavage (later verified in a 293T assay). The advantage of PAM-SCANR is the ability to rapidly test point mutations as well as combinations of amino acid point mutations in a rapid and accurate manner. This assay can be more rigorous than in vitro cleavage assays. (3) Indel assay in human HEK293T cells. This assay provides valuable eukaryotic indel data. To obtain insertions and deletions in eukaryotes, multiple criteria must be met: CRISPR enzyme must be expressed and stable in the cell, crRNA must be expressed and processed correctly, a protein:RNA complex must be formed, the complex must be stable, the complex must be translocated into the nucleus in sufficient amounts, the target DNA must be accessible, the DNA must be well targeted by the specific guide RNA design, and double-strand breaks must occur at a high enough rate to generate occasional DNA repair mistakes due to insertions or deletions (indels). This makes the eukaryotic assay the most stringent assay in this study. Due to the low throughput of the experiment, several dozen PAMs were tested for each of the three point mutants described below rather than all 256. Because certain guides are often ineffective due to target accessibility, three different targets were chosen for each PAM mutant combination to avoid false negatives.

[0172] 1. In Vitro Determination of PAM Binding and Cleavage Construction of PAM plasmid-based libraries A DNA library was prepared consisting of 5 random nucleotides directly 5' of the 23 nucleotide spacer sequence. Although LbCas12a is known to have a 4 nucleotide protospacer adjacent motif (PAM), we decided to use 5 random nucleotides instead of 4 to allow for replication within the experiment. The spacer sequence used was 5'-GGAATCCCTTCTGCAGCACCTGG (SEQ ID NO: 30). The library contained the sequence 5'-NNNNNGGAATCCCTTCTGCAGCACCTGG (SEQ ID NO: 36). Having 5 random nucleotides results in 1024 possible PAMs being assayed in this library.

[0173] We used a novel method to generate this library. Rather than using a single randomized pool of PAM-spacer fusions and using a polymerase to generate the complementary strand as previously described (Kleinstiver et al. Nat Biotechnol 37,:276-282 (2019)), we opted for a more direct method. Two 5'-phosphorylated sequences were synthesized: 5'phos / CGATGTNNNNNGGAATCCCTTCTGCAGCACCTGGGCGCAGGTCACGAGG (SEQ ID NO: 32) and AATTCCTCGTGACCTGCGCCCAGGTGCTGCAGAAGGGATTCCNNNNNACATCGCATG / 5'phos (sequence number 35).

[0174] Upon heating and annealing, the complementary sequences between the two NNNNN sequences anneal and the resulting ends have overhangs that correspond to those generated by the SphI and EcoRI restriction endonucleases. The two oligonucleotides were annealed in equal molar ratios in a thermal cycler at 95°C for 5 minutes and cooled at 0.1°C / s to 25°C / room temperature.

[0175] The annealed double-stranded fragment was directly ligated into the pUC19 vector digested with SphI and EcoRI. The ligated spacer construct was transformed into XL1-Blue electrocompetent E. coli cells (Agilent) and allowed to recover in 1 ml of glucose-containing Super Optimal Broth (SOC) medium at 37°C for 1 h. A proportion of aliquots was plated on carbenicillin plates to confirm the presence of the ligated product. The remaining transformed cells were grown in 200 ml of Luria Broth (LB) supplemented with 50 mg / mL carbenicillin for 16 h. The spacer plasmid was purified using a plasmid midiprep kit (Zymo Research).

[0176] Verifying the PAM library The spacer vector was subjected to deep sequencing analysis to calculate the frequency of A / T / G / C at each position of PAM using Illumina MiSeq according to the manufacturer's protocol. Briefly, 10 ng of DNA was used as template for PCR. Phasing gene-specific forward and reverse PCR primers were designed to amplify across the target sites. Amplicon libraries were produced using a two-step PCR method, where a primary PCR with 5' tails allowed a secondary PCR to tag Illumina i5 and i7 adapter sequences and barcodes for sorting multiplexed samples. PCR amplification was performed with the following parameters: 98°C for 30 seconds; 25 cycles for PCR1 and 8 cycles for PCR2 (98°C for 10 seconds, 55°C for 20 seconds, 72°C for 30 seconds); 72°C for 5 minutes; hold at 12°C. PCR reactions were performed with Q5 High-Fidelity DNA Polymerase (New England BioLabs, Beverly, MA, United States). Secondary PCR amplicon samples were individually purified using AMPure XP beads according to the manufacturer's instructions (Beckman Coulter, Brea, CA, United States); all purified samples were quantified using a plate reader, pooled in equal molar ratios, and run on an AATI fragment analyzer (Agilent Technologies, Palo Alto, CA, United States). The pooled amplicon library was sequenced on an Illumina MiSeq (2X250 paired-end) using the MiSeq Reagent kit v2 (Illumina, San Diego, CA, United States).

[0177] Three separate reads were produced for the library and averaged. The resulting 1024 library members had an average read count of 39 reads and a standard deviation of 11.9 reads. The maximum number of average reads for any PAM sequence was 74 and the minimum was 12. The PAM counts followed a normal distribution (Figure 5).

[0178] Cloning of LbCas12a mutants A DNA cassette consisting of the LbCas12a sequence followed by the nucleoplasmin NLS and a 6x histidine tag was synthesized (GeneWiz) (SEQ ID NO: 52) and cloned between NcoI and XhoI into the pET28a vector to generate pWISE450 (SEQ ID NO: 53). An additional glycine was added to the sequence between Met-1 and Ser-2 to facilitate cloning. Throughout this document, numbering will exclude this extra glycine. As a result, 186 different amino acid point mutations (Table 2) were generated using a similar strategy resulting in 186 different plasmid vectors.

[0179] Expression and purification of LbCas12a mutants Glycerol stocks of each mutant in BL21 Star(DE3) cells (ThermoFisher Scientific) were used to inoculate 1 mL of medium containing 50 μg / mL kanamycin in a 24-well block. Cultures were sealed using AirPore tape sheets (Qiagen) and grown overnight at 37 °C with shaking. The following morning, 100 μL of the overnight culture was inoculated into 4 mL of ZYP autoinduction medium containing kanamycin and incubated at 37 °C with shaking to an OD600 nm range of 0.2-0.5. The temperature was reduced to 18 °C and cultures were grown overnight for protein expression. Cells were harvested by centrifugation and pellets were stored at -80 °C.

[0180] The following buffers were used for cell lysis and purification: Lysis buffer, containing non-ionic detergent, lysis agent, reducing agent, protease inhibitors, buffer, and salts. This solution was able to lyse bacteria, reduce viscosity, and allow downstream purification of enzymes free of interfering nucleases. Buffer A consisted of 20 mM Hepes-KOH (pH 7.5), 0.5 M NaCl, 10% glycerol, 2 mM TCEP, and 10 mM imidazole (pH 7.5). Buffer B was the same as buffer A but also contained 20 mM imidazole. Buffer C contained 20 mM Hepes-KOH (pH 7.5), 150 mM NaCl, 10% glycerol, 0.5 mM TCEP, and 200 mM imidazole (pH 7.5).

[0181] Purification was performed using a multi-well format. Two stainless steel 5 / 32'' BBs were added to all wells containing cell pellets. The pellets were resuspended in 0.5 mL of chilled lysis buffer and incubated at room temperature for 30 min with orbital mixing. Crude lysates (0.5 mL) were added to pre-equilibrated His MultiTrap™ plates (Cytiva LifeSciences). The plates were incubated at room temperature for 5 min to allow protein binding. The remaining steps were performed according to the manufacturer's instructions. Briefly, the plates were washed twice with 0.5 mL of buffer A, followed by one wash with 0.5 mL of buffer B, followed by elution in 0.2 mL of buffer C. Protein concentrations were determined using Pierce™ Coomassie Plus (Bradford) assay reagent. Protein eluates were stored at 4°C.

[0182] Test cleavage of the PAM library with wtLbCas12a Preliminary tests were performed to assess three aspects of the experiment: to ensure that the experiment was free of non-specific nucleases, to ensure that there was depletion in NTTTV PAMs from the library upon addition of crRNA guides, and to look at the extent of depletion at 15 minutes for CTTTA spiked samples.

[0183] Reaction conditions for test depletion were as follows: a total volume of 27 μL containing nuclease-free water, 3 μL NEB buffer 2.1 (New England Biolabs), 3 μL stock of 300 nM crRNA (5'-AAUUUCUACUAAGUGUAGAUGGAAUCCCUUCUGCAGCACCUGG-3' (SEQ ID NO: 62), Synthego Corporation), and purified wtLbCas12a (1 μL) at 1 μM stock was incubated at room temperature for 10 min. Reactions were started by adding 3 μL of a 10 ng / μL stock. Libraries were added neat or 1 μL of CTTTA-containing plasmid was added first at 0.75 ng / μL. All total volumes were 30 μL. Reactions were incubated at 37° C. for 15 min.

[0184] Table 3 provides the results of the experiment. Library counts for TTTV sequences ranged from 219 to 515 counts (column 2), adding wild-type protein purified as described in the absence of crRNA did not result in depletion of library members (column 3), adding crRNA and protein resulted in depletion of all NTTTVs containing PAMs (column 4), spiking the library with CTTTA resulted in an approximately 35-fold increase in CTTTA NGS counts (column 5), and adding wtLbCas12a and crRNA resulted in depletion of all library members (including a reduction of CTTTA from 10,776 to 193 counts). Also shown was a NACGA PAM-containing library member that showed no depletion under the conditions tested, as would be expected since ACGA is not the PAM recognized by LbCas12a. Thus, as shown in Table 3, NTTTV PAM library members are efficiently cleaved and depleted by wtLbCas12a, while a PAM not recognized by wtLbCas12a (NACGA) is not cleaved and depleted.

[0185] JPEG0007644755000005.jpg161166

[0186] The results in Table 3 show that (1) efficient and nuclease-free purification of wtLbCAs12a was achieved, (2) the library can be depleted under the conditions tested for members containing the PAM substrate, (3) depletion occurs upon addition of spacer-targeting crRNA, and (4) the enzyme-crRNA complex largely outnumbers the individual library members, as large amounts of the CTTTA substrate do not alter substrate depletion.

[0187] Cleavage of the PAM library by LbCas12a mutants The same reaction conditions were tested for each of the 186 PAM mutants as shown in the wtLbCas12a example. Three time points were selected for each mutation: 75, 435, and 900 seconds at 37°C. Library-alone controls were included. The products were subjected to Illumina HiSeq analysis (Genewiz). The data are reported in Table 4.

[0188] Handling absolute depletion scores We observed little difference in depletion between the four possibilities for any 5-nucleotide PAM. In other words: ANNNN, CNNNN, GNNNN, and TNNNN for any 4-nucleotide sequence had similar PAM depletion. This was consistent with what we observed in the wild-type LbCAs12a experiment, which showed that NTTTV sequences were all depleted in similar amounts regardless of whether N was A, C, G, or T (Table 3). Second, we observed that all three time points, 75, 435, and 900 seconds, had similar depletion. This indicated that the reaction was nearly complete just after 75 seconds at 37°C. Thus, we averaged all four 4ntPAMs from the 5nt library, averaging all three time points to effectively obtain 12 data points for each PAM. We then divided the average by the median library value for each PAM. This gave a depletion score for each 4-nucleotide PAM for all 186 mutants, where a depletion of 10 indicates that 90% of the four parental plasmid library members with that 4 nt PAM were depleted, and a score of 20 indicates 95% depletion.

[0189] The depletion score for wild-type LbCas12a is 9.2 for TTTV sequences, and therefore any mutant that cleaves PAM with a score of 9.2 or higher is considered effective using wild-type as a benchmark. For example, Table 4 shows that mutant LbCas12a-K595Y depletes 45 different PAM 4-mers from the library in vitro more than wtLbCas12a cleaves TTTV-containing sequences. This analysis was used to score each of the 186 mutants and determine the in vitro PAM recognition and cleavage by each of the mutants. The data, including the recognition sequence, is shown in Table 4, thereby showing the PAMDA depletion score of LbCas12a-K595Y to TTTV-containing sequences more than wtLbCas12a score (9.2).

[0190] JPEG0007644755000006.jpg219166 JPEG0007644755000007.jpg217166JPEG0007644755000008.jpg219166JPEG0007644755000009.jpg218166JPEG0007644755000010.jpg219166 JPEG0007644755000011.jpg221166JPEG0007644755000012.jpg217166JPEG0007644755000013.jpg219166JPEG0007644755000014.jpg255146

[0191] We observed 36 unique PAM sequences cleaved in vitro using two LbCas12a controls. This is consistent with the observation that in vitro wtLbCas12a can recognize and cleave many more sequences than just TTTV. TTCN, CTTN, TCTN, etc. have been shown to be recognized and cleaved by LbCas12a in vitro, whereas AsCas12a has only been shown to cleave TTTN (Zetsche et al. Cell 163:759-771 (2015)).

[0192] Several of the mutants increased the total number of PAM sequences recognized and cleaved in vitro compared to wtLbCas12a (Table 5). This speaks to the overall promiscuity conferred by individual mutations rather than absolute PAM recognition sequences. Some individual point mutants were more promiscuous than the wild type. For example, T152R recognized 57 different PAMs and K959Y recognized 45.

[0193] JPEG0007644755000015.jpg108166

[0194] Comparison of depletion to wild-type LbCas12a In vitro wtLbCas12a can recognize and cleave more sequences than TTTV alone (Zetsche et al. Cell 163:759-771 (2015)). TTCN, CTTN, TCTN, etc. have been shown to be recognized and cleaved by LbCas12a in vitro, while AsCas12a has only been shown to cleave TTTN (Zetsche et al. Cell 163:759-771 (2015)). The goal of this study was to expand the PAM recognition of LbCas12a beyond its wild-type capabilities. To achieve this goal, we used an analysis different from the library depletion scores alone. These scores are important for determining absolute PAM recognition and cleavage in vitro, but do not easily highlight changes to PAM recognition by the enzyme due to point mutations introduced.

[0195] First, the results of the 5-nucleotide depletion were collapsed into the 4-nucleotide PAMS as described above. Each time point was kept individual. The NGS total counts for each mutant-time point were normalized to 100 counts per PAM to account for loading differences on the NGS chip. The overall median for each 4nt PAM was then compared to each mutant-time point. This provided depletion relative to the wild type, not relative to the entire library. The results highlight which mutations altered the PAM recognition profile. We took a conservative approach and selected a depletion score of 4 or higher as an indication of new PAM recognition by the mutant. A depletion score of 4 indicated that that particular PAM-containing library member was cleaved 4-fold compared to the median of the wild type. For example, if 100 NGS counts remained for a PAM with GCGC for the wild type and 25 counts remained for a particular mutant-time point, a score of 4 was calculated.

[0196] A summary of each of the 186 mutations is provided in Table 6 below. Mutations provided in bold indicate that the mutation recognized and cleaved more than three new PAM sequences compared to wild type with a score above 4. Mutations provided in italics indicate that the mutant gained 1-3 new PAM sequences compared to wild type with a score above 4. Mutations in normal font (not bold or italicized) indicate that the point mutation did not cleave a new PAM sequence compared to wild type with a score above 4. Certain amino acids, e.g., T149, were found to be hot spots for engineering new PAM recognition motifs, even though aspartic acid 156 was changed to 10 different amino acids, 7 mutations recognized multiple new PAMs, 1 showed several new PAMs, and 2 did not gain new PAMs compared to wtLbCAs12a. In general, any position that showed differences in PAM recognition and cleavage compared to the wild type could be combined into double, triple, or multiple mutations to further alter PAM recognition. In total, 130 / 186 point mutations yielded no new PAMs above score 4 for wtLbCas12a (regular font / not bold or italic), 40 / 186 yielded many new PAMs (bold font), and 16 / 186 yielded 1-3 new PAMs (italic font). The overall 30% success rate (56 / 186) indicates that an effective method was used to design novel PAM recognition motifs by creating point mutations for LbCas12a.

[0197] Table 6. Summary table of 186 LbCas12a point mutations (Reference sequence: SEQ ID NO:1). JPEG0007644755000016.jpg112166

[0198] Many of the point mutations conferred novel PAM recognition to LbCas12a, allowing it to cleave DNA preceded by these sequences in vitro. Some mutations resulted in an increase in overall promiscuity, while others designed and tested were not shown to alter the recognition and cleavage of wtLbCas12a. In total, 130 / 186 point mutations did not acquire a new PAM for wtLbCas12a above a score of 4 (Table 6, regular font / not italics or bold), 40 / 186 acquired many new PAMs (Table 6, bold font), and 16 / 186 acquired 1-3 new PAMs (Table 6, italic font). The overall 30% success rate (56 / 186) indicates that an effective method was used to engineer novel PAM recognition motifs by creating point mutations for LbCas12a.

[0199] 2. Determining point mutations and combination binding in prokaryotes Combinations of individual mutations can alter PAM recognition much more than single mutations. However, such experiments must be rapidly scaled up to test a large number of combinations. Using only 40 mutations that gave rise to LbCas12a that recognize three or more new PAMs, we created a library of double mutants, for a total of 40 2 Thus, 1,600 enzymes could be tested. The triple mutant library was generated, resulting in 40 enzymes that had to be purified and assayed in replicates. 3That would yield 64,000 enzymes, which is not realistic. Therefore, we adopted a bacterial method known as PAM-SCANR (Leenay et al. Mol Cell 62, 137-147 (2016)) to evaluate combinatorial mutations. We used a library in E. coli to test the binding of Cas12a mutations to 256 possible PAM NNNN mutants. This assay does not test cleavage, but rather tests binding in vivo. Since the mutations made were not anywhere near the catalytic region, binding is expected to also reflect cleavage (this was later verified in the 293T assay). The advantage of PAM-SCANR is not only its ability to rapidly test point mutations, but also its ability to test combinations of amino acid point mutations in a fast and accurate manner. It also tends to be more rigorous than in vitro cleavage assays.

[0200] Reporter plasmids Plasmid pWISE1963 was used as the base vector to generate reporters with each of the 256 PAMS. The plasmid contains spectinomycin resistance, ColE1 origin of replication, LacI, and eGFP (under the control of the lac promoter). 256 gene blocks containing fragments between NotI and SmaI restriction sites (immediately 5' of the lacI promoter to the lacI gene) were synthesized by Twist Bioscience. Each fragment contained a different 4-mer PAM immediately 5' of the lacI promoter. Each gene block was cloned into pWISE1963 by restriction and ligation. Clones were selected for each mutant and the identity of the PAM was confirmed by Sanger sequencing.

[0201] CRISPR-Cas Plasmids Plasmid pWISE2031 was used as the base vector for the construction of all CRISPR-Cas plasmids. The plasmids contain chloramphenicol resistance, CloDF13 origin of replication, dLbCas12a driven by promoter BbaJ23108, and LbCas12a with crRNA targeting the lacI promoter driven by BbaJ23119 promoter. The negative control plasmid pWISE1961 contains the same components as pWISE2031, except that a non-targeting crRNA was used. Each point mutant and combinatorial mutant (pWISE2984-pWISE3007) was constructed via site-directed mutagenesis of pWISE2031 (Genewiz).

[0202] cell line JW0336, an E. coli cell line containing a chromosomal deletion of the lacI gene, was obtained from Dharmacon Horizon Discovery. Electrocompetent cells were prepared according to the protocol described (Sambrook, J., and Russell, DW (2006). Transformation of E. coli by Electroporation. Cold Spring Harb Protoc 2006, pdb.prot3933). E. coli JW0336 was used in all library transformation and cell sorting experiments.

[0203] Reporter library preparation Ten ng of each reporter plasmid described in the above section was pooled into a single tube to generate a library for transformation and amplification. One-twentieth of the pooled plasmid library (approximately 0.5 ng of each reporter) was transformed into supercompetent XL1-Blue according to the manufacturer's instructions. After 1 hour of recovery at 37°C with shaking at 225 rpm, the entire transformant was transferred to 1 L of LB spectinomycin and grown overnight at 37°C with shaking at 225 rpm. The next day, plasmid DNA was extracted from the overnight culture using the ZymoPURE Plasmid GigaPrep Kit according to the manufacturer's instructions. DNA was quantified by Nanodrop and used in all subsequent library transformations.

[0204] Library transformation and cell sorting 100 ng of reporter plasmid library and 100 ng of Crispr / Cas plasmid were co-transformed by electroporation into 40 uL of JW0336. Transformants were allowed to recover at 37°C with shaking at 225 rpm for 1 hour. At the end of recovery, 10 uL of transformants were removed, mixed with 90 uL of LB, and plated on LB agar plates containing chloramphenicol and spectinomycin to determine transformation efficiency. The remaining volume of recovery (990 uL) was transferred to an overnight culture containing 29 mL of LB with spectinomycin and chloramphenicol. The culture was grown overnight at 37°C with shaking at 225 rpm. The following morning, colonies on the transformation plates were counted to determine transformation efficiency; all but two transformations showed >2,000 transformants, corresponding to more than 10-fold coverage of the reporter library. The two samples that did not show 10x or greater coverage were repeated. Glycerol stocks of the overnight cultures were then prepared and stored at -80°C, and 6 mL of each culture was miniprepped using a Qiagen miniprep kit according to the manufacturer's instructions. These minipreps were labeled "pre-sort" and stored at 4°C.

[0205] One optical density (OD) of each overnight library culture was spun down in a tabletop microcentrifuge at 8,000 rpm for 5 min at 4°C. The supernatant was removed with a pipette and 1 mL of filter-sterilized 1x PBS buffer was added to each tube. The pellet was carefully resuspended by pipetting. The 1x PBS wash was repeated two more times and after the final resuspension, the cells (approximately 10 8 A total of 1000 cells / mL were placed on ice. Each sample was sorted on a Beckman-Coulter MoFlo XDP cell sorter. A negative control (WT-dLbCas12a+non-targeted crRNA+reporter library) and a positive control (WT-dLbCas12a+targeted crRNA+reporter library) were used to set the gating parameters for cell sorting. Samples were sorted in single cell purity mode, voltage 425, ssc voltage 535, fsc voltage (gain) 4.0. Typical speed of sorting was approximately 4000 events / sec. Each sample was sorted with a minimum of 1.0 × 10 6 events; cell sorting was performed until 50,000 GFP positive events were collected or until the sample was exhausted. If the sample was exhausted, a minimum of 200 GFP positive events were collected. GFP positive events were collected into a tube containing 2 mL of LB with spectinomycin and chloramphenicol. After sorting, the sample was diluted to 6 mL with additional LB with spectinomycin and chloramphenicol and then grown overnight at 37° C. with shaking at 225 rpm.

[0206] Examples of sorting are provided in Figures 6-11. Figure 6 shows cell sorting results for the negative control containing wtLbCas12a and crRNA that did not target the plasmid spacer. Cells sorted from the GFP high sample show no cells in the sorting fraction (left panel) and a single population of GFP signal indicated by a single peak (right panel). Figure 7 shows cell sorting results for crRNA targeting wtLbCas12a and a plasmid spacer. Cells sorted from the GFP high sample show no cells in the sorting fraction (left panel, GFP hi) and two populations of GFP signal indicated by two main peaks (right panel, GFP neg and GFP High). Cells sorted to GFP high are also shown to be fluorescent (lower right panel). Figure 8 shows cell sorting results for crRNA targeting LbCas12a-K595Y and a plasmid spacer. Cells sorted from the GFP high sample show cells in the sorting fraction (left panel, GFP hi) and populations indicated by two main peaks (right panel, GFP neg and GFP high). Figure 9 shows cell sorting results for the LbCas12a-G532R-K595R double mutant control (Gao et al. Nat Biotechnol 35, nbt.3900 (2017)) and crRNA targeting the plasmid spacer. Cells sorted from the GFP high sample show cells in the sorting fraction (left panel, GFP hi) and populations indicated by two main peaks (right panel). Figure 10 shows cell sorting results for the LbCas12a-T152R-K595Y double mutant, two combinations of point mutations used with crRNA targeting the plasmid spacer. Cells sorted from the GFP high sample show cells in the sorting fraction (left panel, GFP hi) and a population represented by two major peaks (right panel).Figure 11 shows cell sorting results of the triple mutation LbCas12a-T152R-K538W-K595Y, a triple mutation with three combinations of point mutations, with crRNA targeting a plasmid spacer. Cells sorted from the GFP high sample show cells in the sorting fraction (left, GFP hi) and the indicated populations (right, green line).

[0207] Next-generation sequencing The following morning, after sorting, glycerol stocks of each overnight culture were prepared and stored at -80 C. The remaining volume of each 6 mL culture was miniprepped using a Qiagen miniprep kit according to the manufacturer's instructions. These minipreps were labeled "post-sort" and stored at 4°C. Pre- and post-sort minipreps were quantified by nanodrop, diluted 10-fold, and handed off for sequencing on an Illumina Mi-Seq.

[0208] The spacer vector was subjected to deep sequencing analysis to calculate the frequency of A / T / G / C at each position of PAM using Illumina MiSeq according to the manufacturer's protocol. Briefly, 10 ng of DNA was used as template for PCR. Phasing gene-specific forward and reverse PCR primers were designed to amplify across the target sites. Amplicon libraries were produced using a two-step PCR method, where a primary PCR with 5' tails allowed a secondary PCR to tag Illumina i5 and i7 adapter sequences and barcodes for sorting multiplexed samples. PCR amplification was performed with the following parameters: 98°C for 30 seconds; 25 cycles for PCR1 and 8 cycles for PCR2 (98°C for 10 seconds, 55°C for 20 seconds, 72°C for 30 seconds); 72°C for 5 minutes; hold at 12°C. PCR reactions were performed with Q5 High-Fidelity DNA Polymerase (New England BioLabs, Beverly, MA, United States). Secondary PCR amplicon samples were individually purified using AMPure XP beads according to the manufacturer's instructions (Beckman Coulter, Brea, CA, United States); all purified samples were quantified using a plate reader, pooled in equal molar ratios, and run on an AATI fragment analyzer (Agilent Technologies, Palo Alto, CA, United States). The pooled amplicon library was sequenced on an Illumina MiSeq (2X250 paired-end) using the MiSeq Reagent kit v2 (Illumina, San Diego, CA, United States).

[0209] Sequencing results of highly fluorescent sorted cells Two negative control samples containing wtdLbCas12a and non-targeting crRNA were run in the presence of a 256-member reporter library. After normalization to 1.0, the values ​​for each member of the library were plotted as a histogram (Figure 12). Figure 12 shows the total normalized NGS counts for two separate no-crRNA controls and wild-type dLbCas12a and reporter library. Two separate samples were analyzed and combined (a total of 512 points representing 256 PAMs x 2). We chose a conservative 1.67 value (highest count) as the cutoff for these experiments, above which we scored PAM binding. The standard deviation was 0.16. Rather than choosing a multiple of the standard deviation as the cutoff, we chose 1.67, the absolute maximum value found in either of the two negative controls. This gave a very strict cutoff of more than 10 times the standard deviation of the data. In fact, only three PAM sequences were found above 1.5.

[0210] Pre-sort pools were all sequenced before sorting. The average reads / PAM was around 250-500 NGS reads depending on the sample. Highly fluorescent post-sort pools were sequenced and had similar read counts / PAM at around 250-500 reads / PAM. Both samples were then normalized to the control for small loading differences in each NGS run. The two values ​​were then subtracted and normalized to 1.0. Many PAM sequences were bound by the point mutation library above the 1.67 cutoff (Figure 13, Table 7).

[0211] JPEG0007644755000017.jpg245166JPEG0007644755000018.jpg189166

[0212] We combined three point mutations T152R, K538W, and K595Y in various combinations to generate double and triple dLbCas12a mutants (T152R+K538W, K538W+K595Y, and T152R+K538W+K595Y). This was compared to a previously described control developed in AsCas12a known as "RR" in which the LbCas12a mutation corresponds to the G532R+K595R control (Gao et al. Nat Biotechnol 35(8):789-792(2017)). "RR" has been described as capable of generating indels in the TYCV+CCCC sequence in AsCas12a and subsequently in LbCas12a.

[0213] The same methodology was applied to score combinatorial mutations. Pre- and post-sort pools, each with an average of ~250-500 MiSeq NGS reads per PAM library member, were sequenced. Pre- and post-sort pools were normalized, subtracted, and differences were normalized to 1.0. Many PAM sequences were combinatorially bound above the 1.67 cutoff (Figure 14, Table 8).

[0214] JPEG0007644755000019.jpg247166

[0215] Overall analysis of PAM-SCANR data Wild-type LbCas12a showed strong TTTV binding, while the LbCas12a-G532R-K595R control showed strong TYCV and CCCC binding. This mutation, called "RR", was developed in AsCas12a and shown to bind TYCV and CCCC (Gao et al. Nat Biotechnol 35(8):789-792(2017)). However, in vitro wtLbCas12a was shown to be able to recognize and cleave TTCN, CTTN, TCTN, etc., while AsCas12a was only shown to cleave TTTN (Zetsche et al., Cell 163:759-771(2015)). We speculate that the "RR" mutations placed in the LbCas12a context are more promiscuous than those placed in the AsCas12a context, which is what we observed for this control, where LbCas12a-RR recognized 45 sequences. Both wild-type and LbCas12a-RR results demonstrate the validity of the selection and sorting parameters.

[0216] The tested mutations clearly demonstrated that novel PAMs were recognized in vivo by the individual point mutations identified in vitro. For example, K595Y bound 13 PAMs above the 1.67 threshold, 11 of which were not recognized by wtLbCas12a, and none of which contained the TTTV sequence known to be bound by Cas12a. Similarly, T152R recognized 15 distinct PAMs, but in this case maintained the wild-type TTTV. All 12 tested point mutations each had a novel PAM-binding sequence that was different from the dLbCas12a control, other than the canonical TTTV motif.

[0217] Combination Effects We found that combining multiple point mutations does not result in linear addition of the PAM sequences of the point mutations (Figure 15). For example, the combination of LbCas12a point mutants K538W and K595Y results in the enzyme LbCas12a-K538W-K595Y, which in some cases shares the PAM recognition motif with K538W (vertical shading) or K595Y (horizontal shading), but more often results in a completely novel PAM recognition sequence (thatched). Using the same example, K538W recognizes AGCT, but K538W+K595Y does not. K595Y recognizes ACGC, but K538W+K595Y does not. CCCC is not recognized by either K538W or K595Y, but the double mutant binds to it with high affinity.

[0218] In general, combinations of mutations result in more PAM recognition than linear expansion. For example, K538W recognizes 6 PAM sequences and K595Y recognizes 13, but together they recognize 32 sequences (Figure 15). A simple additive effect would result in 19 PAMs for the double mutant, instead of the 32 we observed. Furthermore, only 11 of the 32 sequences recognized by the double mutant are recognized by either of the two single mutations. A similar pattern is observed when the three mutations are combined (Figure 16). The combination of T152R, K538W, and K595Y results in a triple mutation with PAM recognition different from any of the three individual mutations alone. For example: GGCA, GGCC, GGGC, and GGGG are recognized only when all three mutations are made to LbCas12a. None of these PAMs are bound by either the single or double mutations, but only when T152R, K538W, and K595Y are all mutated together.

[0219] Comparison of point mutant PAM recognition in PAM-SCANR versus in vitro PAMDA Considering the 12 point mutations tested as a whole, PAM-SCANR hits above 1.67 were well represented in the in vitro PAMDA depletion assay. Examples of K595Y and T152R are shown (Figure 17). Figure 17 compares all non-TTTV PAMs (gray boxes) that showed scores above 1.67 by PAN-SCANR for K595Y (left panel) and T152R (right panel). All (except one) of the PAM-SCANR positive PAMs above the 1.67 cutoff had PAM depletion scores above the 9.2 cutoff in vitro. However, the PAM-SCANR method and analysis were more rigorous than the in vitro assay and analysis. For example, 13 different PAMs were sorted, sequenced, and normalized to have values ​​above 1.67 in PAM-SCANR. This is in contrast to the PAMDA assay, which identified 45 sequences as readily cleaved in vitro, which is likely a function of relative concentrations in cells versus in vitro, but may also be a function of setting too strict a cutoff for PAM-SCANR or too permissive a cutoff for the PAMDA assay.

[0220] There are correlations between the data sets indicating that our engineering of residues away from the catalytic site affects PAM recognition and binding but not catalysis. If mutations at these residues affected nuclease activity along with PAM binding, there would be many hits in the PAM-SCANR assay (which measures binding but not cleavage) that would not show cleavage in the PAMDA assay. We have not seen that pattern. We observe that mutations that affected changes in binding (PAM-SCANR) also resulted in cleavage in vitro (PAMDA).

[0221] 3. Determining Joining, Breakage, and Indel Formation in Eukaryotes We selected three mutations, T152R, K538W, and K595Y, to test their ability to generate insertions or deletions (indels) in eukaryotic HEK293T cells. This assay provides valuable eukaryotic indel data. To obtain insertions and deletions in eukaryotes, multiple criteria must all be met: CRISPR enzyme must be expressed and stable in the cell, crRNA must be expressed and processed correctly, protein:RNA complex must be formed, the complex must be stable, the complex must be translocated into the nucleus in sufficient amounts, the target DNA must be accessible, the DNA must be well targeted by the specific guide RNA design, and double-strand breaks must occur at a high enough rate to generate occasional DNA repair mistakes by insertions or deletions (indels). This makes the eukaryotic assay the most rigorous assay in this study. Due to the low throughput of the experiment, we tested several dozen PAMs for each of the three point mutants described below, rather than all 256. Because certain guides are often ineffective due to target accessibility, three different targets were chosen for each PAM mutant combination to avoid false negatives.

[0222] Testing HEK293T cells Eukaryotic HEK293T (ATCC CRL-3216) cells were cultured in GlutaMax (ThermoFisher) supplemented with Dulbecco's modified Eagle's medium + 10% (v / v) FBS (FBS) at 37°C with 5% CO2. Wild-type and mutant LbCas12 were synthesized using solid synthesis and subsequently cloned into plasmids behind the CMV promoter. CRISPR RNA (crRNA) was cloned behind the human U6 promoter (Table 9). HEK293T cells were seeded on 48-well collagen-coated BioCoat plates (Corning). Cells were transfected at approximately 70% confluency. 750 ng of protein plasmid and 250 ng of crRNA expression plasmid were transfected using 1.5 μl per well of Lipofectamine 3000 (ThermoFisher Scientific) according to the manufacturer's protocol. Genomic DNA from transfected cells was harvested after 3 days, and indels were detected and quantified using high-throughput Illumina amplicon sequencing.

[0223] The spacer vector was subjected to deep sequencing analysis to calculate the frequency of A / T / G / C at each position of PAM using Illumina MiSeq according to the manufacturer's protocol. Briefly, 10 ng of DNA was used as template for PCR. Phasing gene-specific forward and reverse PCR primers were designed to amplify across the target sites. Amplicon libraries were produced using a two-step PCR method, where a primary PCR with 5' tails allowed a secondary PCR to tag Illumina i5 and i7 adapter sequences and barcodes for sorting multiplexed samples. PCR amplification was performed with the following parameters: 98°C for 30 seconds; 25 cycles for PCR1 and 8 cycles for PCR2 (98°C for 10 seconds, 55°C for 20 seconds, 72°C for 30 seconds); 72°C for 5 minutes; hold at 12°C. PCR reactions were performed with Q5 High-Fidelity DNA Polymerase (New England BioLabs, Beverly, MA, United States). Secondary PCR amplicon samples were individually purified using AMPure XP beads according to the manufacturer's instructions (Beckman Coulter, Brea, CA, United States); all purified samples were quantified using a plate reader, pooled in equal molar ratios, and run on an AATI fragment analyzer (Agilent Technologies, Palo Alto, CA, United States). The pooled amplicon library was sequenced on an Illumina MiSeq (2X250 paired-end) using the MiSeq Reagent kit v2 (Illumina, San Diego, CA, United States).

[0224] Wild-type control Wild-type LbCas12a (wtLbCas12a) recognizes TTTV (TTTA, TTTC, and TTTG). We tested the wild-type protein against TTTV using a crRNA spacer (Table 9) containing a 23-nucleotide spacer target (Figure 18).

[0225] JPEG0007644755000020.jpg78166

[0226] Protein and target selection There were many point mutations that showed increased PAM accessibility in PAMDA in vitro assay.Considering our many point mutations and 256 possible 4-nucleotide (nt) PAMs, it is effectively impossible to test all the effective PAM mutants against endogenous 293T cell targets due to the complexity, cost and time of experiment.Therefore, we selected three point mutations to test against a subset of PAMs.The three tested point mutations are T152R, K538W and K595Y.

[0227] Genomic targets in 293T cells were selected based on their PAM sequences. Genomic targets for three point mutations were randomly selected without any specific rules, except that they had the appropriate 4nt PAM and selected 23 nucleotides downstream from the PAM. Three different spacers were selected to assay each PAM. This is due to the observation that the activity of CRISPR enzymes is target-specific and often unpredictable.

[0228] On average, we observed that about half of the 23-nucleotide wtLbCas12a spacers tested were ineffective despite having the correct PAM TTTV sequence. With only three data points for each PAM and the observation that about 50% of targets do not produce indels, it is more informative to evaluate PAM recognition by visualizing the maximum indel percentage per PAM rather than the average over randomly designed spacers (Figures 19-21). If a larger number of spacers were assayed for each PAM, a statistical test could be used to evaluate their average editing efficiency.

[0229] Our overall transfection and assay conditions result in wild-type LbCAs12a generating indels in HEK293T cells at approximately 11-26% for TTTC, 10% for TTTA, and 4-10% for TTTG (Figure 18). These are HEK293T target sites and guides previously defined from the literature and are therefore predicted to be more effective than any randomly selected guide. Despite the random design of the crRNA guides for the mutants, many of the new Cas12a PAM recognition sites generated indels in the TTTV sequence at rates similar to the wild type (Figures 19-21). Any indels above 0.1% are above the noise of a sequencing assay read at 10,000 NGS read depth.

[0230] K595Y was able to generate indels in 25.5% of ACCG, 10.9% of CCGC, 10.1% of TCGC, 9.5% of CCCG, 8.3% of GCGC, 7.8% of CTGG, 6.3% of ACGG, 6.0% of CCCG, 5.3% of TGGC, etc. (Figure 19). All these numbers are within the range of TTTV control for wtLbCas12a, even though they were randomly designed. One main hallmark of Cas12a proteins is that they recognize T-rich PAMs (Zetsche et al. Cell 163:759-771 (2015)). This limits their usefulness in genome editing techniques. K595Y clearly prefers C- and G-rich PAMs, expanding the utility of Cas2a to targets previously targeted by the Cas9 CRISPR enzyme, which primarily utilizes G-rich PAMs (Jinek et al. Science 337, 816-821 (2012)). For K595Y, only 31 of a total of 256 possible 4-nucleotide PAMs were tested in 293T cells (or 12%). There are likely many other PAMs that can be recognized by K595Y in eukaryotic cells to generate indels.

[0231] T152R was able to generate indels in 11.5% of CCTC, 10.0% of CCTG, 9.6% of CCCA, 8.4% of GCCA, 7.2% of GCCC, 5.1% of CTGC, etc. (Figure 20). Interestingly, T152R maintained the TTTV recognition of wtLbCas12a by generating indels in 34.9% of TTTC, 10.2% of TTTA, and 6.2% of TTTG. It also picked up TTTT recognition, generating indels in 8.3%. For T152R, only 22 of a total of 256 possible 4-nucleotide PAMs were tested in 293T cells (or 9%). There may be many other PAMs that can be recognized by T152R to generate indels in eukaryotic cells.

[0232] As shown in Figure 21, 22 of the 28 PAM targets had activity above 0.1% background, suggesting that 79% of the tested PAMs are recognized and cleaved by this enzyme, which may be lower than desired for some applications. The six PAMs tested did not have editing above background for the three selected targets. All three TTTV targets still had good activity at 15.6%, 6.2%, and 5.8% for TTTC, TTTG, and TTTA, respectively. Other PAM sequences with indel formation above 1% included ATTA (3.5%), TTTT (3.2%), TGTC (1.8%), AGCG (1.8%), AGTC (1.6%), AGCA (1.4%), and GGTC (1.1%). This point mutation was used in combination with T152R and / or K595Y in PAM-SCANR experiments to generate a wide variety of PAM recognitions, but by itself bound relatively few PAMs using that assay. In the future, it may be a good choice to generate indels in HEK293T cells using double mutations rather than alone. As with the other two point mutations, only 28 of the 256 possible 4-nucleotide PAMs were tested (11%), and it is possible that this mutant may recognize PAMs or targets not tested here.

[0233] Correlation between HEK293T indels and PAM-SCANR binding A correlation was observed between the maximum observed indel percentage and the PAM-SCANR score for T152R and K595Y (Figures 22A-22B). Figures 22A-22B show the linear correlation between indel% (maximum) and normalized bacterial PAM-SCANR score for LbCas12a-T152R (Figure 22A) and LbCas12a-K595Y (Figure 22B).

[0234] Notably, any point mutation tested with a PAM-SCANR score above 1.5 produced indels at a rate greater than 5% in 293T cells, suggesting that any mutation tested in a PAM-SCANR experiment with a normalized score above 1.5 (rather than our strict 1.67 cutoff) may be capable of producing indels at a rate useful for most eukaryotic applications.

[0235] The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. The present invention is defined by the following claims, equivalents of which are included herein.

Claims

1. A modified Lachnospiraceae bacterium CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) Cas12a (LbCas12a) polypeptide, comprising: The modified LbCas12a polypeptide comprises an amino acid sequence having at least 90% identity to the amino acid sequence of SEQ ID NO: 1 (LbCas12a) and a K595Y mutation with respect to the position numbering of SEQ ID NO: 1; Modified LbCas12a polypeptide.

2. The modified LbCas12a polypeptide of claim 1, wherein the modified LbCas12a polypeptide comprises further mutations at one or more of the following positions with respect to the position numbering of SEQ ID NO:1: K116, K120, K121, D122, E125, T148, T149, T152, D156, E159, Q529, D535, K538, D541, Y542, L585, K591, M592, V596, S599, K600, K601, Y616, Y646 and / or W649.

3. The modified LbCas12a polypeptide is selected from the group consisting of K116R, K116N, K120R, K120H, K120N, K120T, K120Y, K120Q, K121S, K121T, K121H, K121R, K121G, K121D, K121Q, D122R, D122K, D122H, and / or D122H. , D122E, D122N, E125R, E125K, E125Q, E125Y, T148H, T148S, T148A, T148C, T149A, T149C, T1 49S, T149G, T149H, T149P, T149F, T149N, T149D, T149V, T152R, T152K, T152W, T152Y, T152H , T152Q, T152E, T152L, T152F, D156R, D156K, D156Y, D156W, D156Q, D156H, D156I, D156V, D1 56L, D156E, E159K, E159R, E159H, E159Y, E159Q, Q529N, Q529T, Q529H, Q529A, Q529F, Q529G , Q529G, Q529S, Q529P, Q529W, Q529D, G532D, G532N, G532S, G532H, G532F, G532K, G532R, G5 32Q, G532A, G532L, G532C, D535N, D535H, D535V, D535T, D535S, D535A, D535W, D535K, K538RK538V, K538Q, K538W, K538Y, K538F, K538H, K538L, K538M, K538C, K538G, K538A, K538P, D541N, D541H, D541R, D541K, D541Y, D541I, D541A, D541S, D541E, Y542R, Y542K, Y542H, Y542Q, Y542F, Y542L, Y542M, Y542P, Y542V, Y542N, Y542T, L585G, L585H, L585F, K591W, K591F, K591Y, K591H, K591R, K591S, K591A, K591G, K591P, M592R, M592K, M592Q, M592E, M592A, V596T, V596H, V596G, V596A, S599G, S599H, S599N, S599D, K600R, K600H, K600G, K601R, K601H, K601Q, K601T, Y616K, Y616R, comprising one or more of the following amino acid mutations: Y616E, Y616F, Y616H, Y646R, Y646E, Y646K, Y646H, Y646Q, Y646W, Y646N, W649H, W649K, W649Y, W649R, W649E, W649S, W649V, and / or W649T; The modified LbCas12a polypeptide of claim 1.

4. The modified LbCas12a polypeptide of any one of claims 1 to 3, wherein the modified LbCas12a polypeptide has altered PAM (protospacer adjacent motif) specificity.

5. The modified LbCas12a polypeptide of any one of claims 1 to 4, further comprising a mutation within a nuclease active site.

6. A modified Lachnospiraceae bacterium CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) Cas12a (LbCas12a) polypeptide, comprising: The modified LbCas12a polypeptide comprises an amino acid sequence having at least 90% identity to the amino acid sequence of SEQ ID NO:1 (LbCas12a) and a K595Y mutation with respect to the position numbering of SEQ ID NO:1; The modified LbCas12a polypeptide exhibits reduced PAM stringency and improved recognition of a novel protospacer adjacent motif (PAM) compared to wild-type LbCas12a (SEQ ID NO: 1). LbCas12a polypeptide.

7. 7. The modified LbCas12a polypeptide of claim 6, The modified LbCasl2a polypeptide comprises an additional mutation located at one or more of K116, K120, K121, D122, E125, T148, T149, T152, D156, E159, Q529, D535, G532, K538, D541, Y542, L585, K591, M592, V596, S599, K600, K601, Y616, Y646, or W649, with respect to the position numbering of SEQ ID NO: 1; LbCas12a polypeptide.

8. 8. The modified LbCas12a polypeptide of claim 7, Further mutations include, with respect to the position numbering of SEQ ID NO:1, K116R, K116N, K120R, K120H, K120N, K120T, K120Y, K120Q, K121S, K121T, K121H, K121R, K121G, K121D, K121Q, D122R, D122K, D122H, D122E, D122N, E125R, E125K, E125Q, E125Y, T148H, T148S, T148A, T148C, T149A, T149C, T149D, T149E, T149F, T149H, T149F ... 9S, T149G, T149H, T149P, T149F, T149N, T149D, T149V, E159K, E159R, E159H, E159Y, E159Q, Q529N, Q529T, Q529H, Q529A, Q529F, Q 529G, Q529G, Q529S, Q529P, Q529W, Q529D, D535N, D535H, D535V, D535T, D535S, D535A, D535W, D535K, D541N, D541H, D541R, D541K , D541Y, D541I, D541A, D541S, D541E, Y542R, Y542K, Y542H, Y542Q, Y542F, Y542L, Y542M, Y542P, Y542V, Y542N, Y542T, L585G, L58 5H, L585F, K591W, K591F, K591Y, K591H, K591R, K591S, K591A, K591G, K591P, M592R, M592K, M592Q, M592E, M592A, V596T, V596H, V 596G, V596A, S599G, S599H, S599N, S599D, K600R, K600H, K600G, K601R, K601H, K601Q, K601T, Y616K, Y616R, Y616E, Y616F, Y616H, Y646R, Y646E, Y646K, Y646H, Y646Q, Y646W, Y646N, W649H, W649K, W649Y, W649R, W649E, W649S, W649V, and / or W649T, LbCas12a polypeptide.

9. A modified LbCas12a polypeptide according to any one of claims 1 to 8, and a linker, The linker is linked to the C-terminus and / or N-terminus of the modified LbCas12a polypeptide; Fusion proteins.

10. The fusion protein of claim 9, The linker is a peptide linker. Fusion proteins.

11. A fusion protein comprising a modified LbCas12a polypeptide according to any one of claims 1 to 10 and a polypeptide of interest, The polypeptide of interest is linked to the C-terminus and / or N-terminus of the modified LbCas12a polypeptide; Fusion proteins.

12. 12. The fusion protein of claim 11 , The target polypeptide comprises at least one polypeptide or protein domain having deaminase (deamination) activity, nickase activity, recombinase activity, transposase activity, methylase activity, glycosylase (DNA glycosylase) activity, glycosylase inhibitor activity, demethylase activity, transcription activation activity, transcription repression activity, transcription release factor activity, histone modification activity, nuclease activity, single-stranded RNA cleavage activity, double-stranded RNA cleavage activity, restriction endonuclease activity, nucleic acid binding activity, methyltransferase activity, DNA repair activity, DNA damage activity, dismutase activity, alkylation activity, depurination activity, oxidation activity, pyrimidine dimer formation activity, integrase activity, transposase activity, polymerase activity, ligase activity, helicase activity, and / or photolyase activity; Fusion proteins.

13. The fusion protein of claim 11 or 12, The polypeptide of interest comprises at least one polypeptide or protein domain having deaminase activity; Fusion proteins.

14. The fusion protein of claim 12 or 13, wherein the at least one polypeptide has glycosylase inhibitor activity, and the at least one polypeptide may be a uracil-DNA glycosylase inhibitor (UGI).

15. A polynucleotide encoding a modified LbCas12a polypeptide according to any one of claims 1 to 8, or a fusion protein according to any one of claims 9 to 14.

16. The polynucleotide of claim 15, wherein the polynucleotide encoding the modified LbCasl2a polypeptide or the polynucleotide encoding the fusion protein is operably associated with a promoter, and the promoter may be a promoter region including an intron.

17. A complex comprising a modified LbCas12a polypeptide according to any one of claims 1 to 8, or a fusion protein according to any one of claims 9 to 14, and a guide nucleic acid.

18. A nucleic acid construct encoding the complex of claim 17.

19. A composition comprising: (a) a modified LbCas12a polypeptide according to any one of claims 1 to 8, or a fusion protein according to any one of claims 9 to 14, and (b) a guide nucleic acid.

20. 19. An expression cassette or vector comprising a polynucleotide according to claim 15 or 16, or a nucleic acid construct according to claim 18.

21. A V-shaped Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-associated (Cas) (CRISPR-Cas) system, Includes: (a) a fusion protein comprising: (i) a modified LbCas12a polypeptide according to any one of claims 1 to 8 or a nucleic acid encoding the modified LbCas12a polypeptide according to any one of claims 1 to 8, and (ii) a polypeptide of interest or a nucleic acid encoding said polypeptide of interest; and (b) a guide nucleic acid comprising a spacer sequence and a repeat sequence; wherein the guide nucleic acid is capable of forming a complex with the modified LbCasl2a polypeptide or the fusion protein, and the spacer sequence is capable of hybridizing to a target nucleic acid, thereby guiding the modified LbCasl2a polypeptide and the polypeptide of interest to the target nucleic acid, thereby modifying or adjusting the target nucleic acid; system.

22. The system of claim 21, wherein the target polypeptide is linked to the C-terminus and / or N-terminus of the modified LbCas12a polypeptide via a linker.

23. The system of claim 22, The linker is a peptide linker. system.

24. A system according to any one of claims 21 to 23, comprising: the target polypeptide comprises at least one polypeptide or protein domain having deaminase (deamination) activity, nickase activity, recombinase activity, transposase activity, methylase activity, glycosylase (DNA glycosylase) activity, glycosylase inhibitor activity, demethylase activity, transcription activation activity, transcription repression activity, transcription release factor activity, histone modification activity, nuclease activity, single-stranded RNA cleavage activity, double-stranded RNA cleavage activity, restriction endonuclease activity, nucleic acid binding activity, methyltransferase activity, DNA repair activity, DNA damage activity, dismutase activity, alkylation activity, depurination activity, oxidation activity, pyrimidine dimer formation activity, integrase activity, transposase activity, polymerase activity, ligase activity, helicase activity, and / or photolyase activity; system.

25. The system according to claim 21, further comprising: The polypeptide of interest comprises at least one polypeptide or protein domain having deaminase activity; system.

26. The system according to any one of claims 21 to 25, wherein the target polypeptide comprises a uracil-DNA glycosylase inhibitor (UGI).

27. 1. A method for modifying a target nucleic acid in vitro, comprising: The target nucleic acid (a) (i) a modified LbCas12a polypeptide according to any one of claims 1 to 8, or a fusion protein according to any one of claims 9 to 14, and (ii) a guide nucleic acid; (b) the complex of claim 17 and a guide nucleic acid; (c) a composition comprising (i) a modified LbCas12a polypeptide according to any one of claims 1 to 8, or a fusion protein according to any one of claims 9 to 14, and (ii) a guide nucleic acid; and / or (d) A system according to any one of claims 21 to 25. contacting the target nucleic acid with method.

28. 17. The method according to claim 15, comprising the steps of: kit.

29. The kit of claim 28, CRISPR-Cas12a guide nucleic acid and / or an expression cassette or vector containing the same, and / or instructions for use thereof; kit.

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