Patent Publication Number: US-2022220460-A1

Title: Enzymes with ruvc domains

Description:
CROSS-REFERENCE 
     This application is a continuation of International Application No. PCT/US20/18432, filed on Feb. 14, 2020, entitled “ENZYMES WITH RUVC DOMAINS”, which application claims the benefit of U.S. Provisional Application Nos. 62/874, 414 filed on Jul. 15, 2019, 62/805,899 filed on Feb. 14, 2019, 62/805,868 filed on Feb. 14, 2019, and 62/805,878 filed on Feb. 14, 2019, each of which is incorporated by reference herein in their entireties. This application is related to International Application No. PCT/US21/31136 entitled “ENZYMES WITH RUVC DOMAINS”, filed on May 6, 2021, which claims priority to U.S. Provisional Application No. 63/180,570, entitled “ENZYMES WITH RUVC DOMAINS”, filed on Apr. 27, 2021; U.S. Provisional Application No. 63/116,155, entitled “ENZYMES WITH RUVC DOMAINS”, filed on Nov. 19, 2020;U.S. Provisional Application No. 63/032,464, entitled “ENZYMES WITH RUVC DOMAINS”, filed on May 29, 2020; and U.S. Provisional Application No. 63/022,320, entitled “ENZYMES WITH RUVC DOMAINS”, filed on May 8, 2020, each of which is incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     Cas enzymes along with their associated Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) guide ribonucleic acids (RNAs) appear to be a pervasive (˜45% of bacteria, ˜84% of archaea) component of prokaryotic immune systems, serving to protect such microorganisms against non-self nucleic acids, such as infectious viruses and plasmids by CRISPR-RNA guided nucleic acid cleavage. While the deoxyribonucleic acid (DNA) elements encoding CRISPR RNA elements may be relatively conserved in structure and length, their CRISPR-associated (Cas) proteins are highly diverse, containing a wide variety of nucleic acid-interacting domains. While CRISPR DNA elements have been observed as early as 1987, the programmable endonuclease cleavage ability of CRISPR/Cas complexes has only been recognized relatively recently, leading to the use of recombinant CRISPR/Cas systems in diverse DNA manipulation and gene editing applications. 
     SEQUENCE LISTING 
     The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Jun. 30, 2020, is named 55921_703_504_SL.txt and is 23,363,499 bytes in size. 
     SUMMARY 
     In some aspects, the present disclosure provides for an engineered nuclease system, comprising: (a) an endonuclease comprising a RuvC_III domain and an HNH domain, wherein the endonuclease is derived from an uncultivated microorganism, wherein the endonuclease is a class 2, type II Cas endonuclease; and (b) an engineered guide ribonucleic acid structure configured to form a complex with the endonuclease comprising: (i) a guide ribonucleic acid sequence configured to hybridize to a target deoxyribonucleic acid sequence; and (ii) a tracr ribonucleic acid sequence configured to bind to the endonuclease. In some embodiments, the RuvC_III domain comprises a sequence with at least 70%, at least 75%, at least 80% or at least 90% sequence identity to any one of SEQ ID NOs: 1827-3637. 
     In some aspects, the present disclosure provides for an engineered nuclease system comprising: (a) an endonuclease comprising a RuvC_III domain having at least 75% sequence identity to any one of SEQ ID NOs: 1827-3637; and (b) an engineered guide ribonucleic acid structure configured to form a complex with the endonuclease comprising: (i) a guide ribonucleic acid sequence configured to hybridize to a target deoxyribonucleic acid sequence; and (ii) a tracr ribonucleic acid sequence configured to bind to the endonuclease. 
     In some aspects, the present disclosure provides for an engineered nuclease system comprising: (a) an endonuclease configured to bind to a protospacer adjacent motif (PAM) sequence comprising SEQ ID NOs: 5512-5537, wherein the endonuclease is a class 2, type II Cas endonuclease; and (b) an engineered guide ribonucleic acid structure configured to form a complex with the endonuclease comprising: (i) a guide ribonucleic acid sequence configured to hybridize to a target deoxyribonucleic acid sequence; and (ii) a tracr ribonucleic acid sequence configured to bind to the endonuclease. 
     In some embodiments, the endonuclease is derived from an uncultivated microorganism. In some embodiments, the endonuclease has not been engineered to bind to a different PAM sequence. In some embodiments, the endonuclease is not a Cas9 endonuclease, a Cas14 endonuclease, a Cas12a endonuclease, a Cas12b endonuclease, a Cas 12c endonuclease, a Cas12d endonuclease, a Cas12e endonuclease, a Cas13a endonuclease, a Cas13b endonuclease, a Cas13c endonuclease, or a Cas 13d endonuclease. In some embodiments, the endonuclease has less than 80% identity to a Cas9 endonuclease. In some embodiments, the endonuclease further comprises an HNH domain. In some embodiments, the tracr ribonucleic acid sequence comprises a sequence with at least 80% sequence identity to about 60 to 90 consecutive nucleotides selected from any one of SEQ ID NOs: 5476-5511 and SEQ ID NO: 5538. 
     In some aspects, the present disclosure provides for an engineered nuclease system comprising, (a) an engineered guide ribonucleic acid structure comprising: (i) a guide ribonucleic acid sequence configured to hybridize to a target deoxyribonucleic acid sequence; and (ii) a tracr ribonucleic acid sequence configured to bind to an endonuclease, wherein the tracr ribonucleic acid sequence comprises a sequence with at least 80% sequence identity to about 60 to 90 consecutive nucleotides selected from any one of SEQ ID NOs: 5476-5511 and SEQ ID NO: 5538; and (b) a class 2, type II Cas endonuclease configured to bind to the engineered guide ribonucleic acid. In some embodiments, the endonuclease is configured to bind to a protospacer adjacent motif (PAM) sequence selected from the group comprising SEQ ID NOs: 5512-5537. 
     In some embodiments, the engineered guide ribonucleic acid structure comprises at least two ribonucleic acid polynucleotides. In some embodiments, the engineered guide ribonucleic acid structure comprises one ribonucleic acid polynucleotide comprising the guide ribonucleic acid sequence and the tracr ribonucleic acid sequence. 
     In some embodiments, the guide ribonucleic acid sequence is complementary to a prokaryotic, bacterial, archaeal, eukaryotic, fungal, plant, mammalian, or human genomic sequence. In some embodiments, the guide ribonucleic acid sequence is 15-24 nucleotides in length. In some embodiments, the endonuclease comprises one or more nuclear localization sequences (NLSs) proximal to an N- or C-terminus of the endonuclease. In some embodiments, the NLS comprises a sequence selected from SEQ ID NOs: 5597-5612. 
     In some embodiments, the engineered nuclease system further comprises a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least 20 nucleotides 5′ to the target deoxyribonucleic acid sequence, a synthetic DNA sequence of at least 10 nucleotides, and a second homology arm comprising a sequence of at least 20 nucleotides 3′ to the target sequence. In some embodiments, the first or second homology arm comprises a sequence of at least 40, 80, 120, 150, 200, 300, 500, or 1,000 nucleotides. 
     In some embodiments, the system further comprises a source of Mg 2+ . 
     In some embodiments, the endonuclease and the tracr ribonucleic acid sequence are derived from distinct bacterial species within a same phylum. In some embodiments, the endonuclease is derived from a bacterium belonging to a genus  Dermabacter.  In some embodiments, the endonuclease is derived from a bacterium belonging to  Phylum Verrucomicrobia, Phylum Candidatus Peregrinibacteria,  or  Phylum Candidatus  Melainabacteria. In some embodiments, the endonuclease is derived from a bacterium comprising a 16S rRNA gene having at least 90% identity to any one of SEQ ID NOs: 5592-5595. 
     In some embodiments, the HNH domain comprises a sequence with at least 70% or at least 80% identity to any one of SEQ ID NOs: 5638-5460. In some embodiments, the endonuclease comprises SEQ ID NOs: 1-1826 or a variant thereof having at least 55% identity thereto. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 1827-1830 or SEQ ID NOs: 1827-2140. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 3638-3641 or SEQ ID NOs: 3638-3954. In some embodiments, the endonuclease comprises at least 1, at least 2, at least 3, at least 4, or at least 5 peptide motifs selected from the group consisting of SEQ ID NOs: 5615-5632. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 1-4 or SEQ ID NOs: 1-319. 
     In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 5461-5464, SEQ ID NOs: 5476-5479, or SEQ ID NOs: 5476-5489. In some embodiments, the guide RNA structure comprises an RNA sequence predicted to comprise a hairpin consisting of a stem and a loop, wherein the stem comprises at least 10, at least 12 or at least 14 base-paired ribonucleotides, and an asymmetric bulge within 4 base pairs of the loop. 
     In some embodiments, the endonuclease is configured to bind to a PAM comprising a sequence selected from the group consisting of SEQ ID NOs: 5512-5515 or SEQ ID NOs: 5527-5530. 
     In some embodiments: (a) the endonuclease comprises a sequence at least 70%, at least 80%, or at least 90% identical to SEQ ID NO: 1827; (b) the guide RNA structure comprises a sequence at least 70%, at least 80%, or at least 90% identical to at least one of SEQ ID NO: 5461 or SEQ ID NO: 5476; and (c) the endonuclease is configured to bind to a PAM comprising SEQ ID NO: 5512 or SEQ ID NO: 5527. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, at least 80%, or at least 90% identical to SEQ ID NO: 1828; (b) the guide RNA structure comprises a sequence at least 70%, at least 80%, or at least 90% identical to at least one of SEQ ID NO: 5462 or SEQ ID NO: 5477; and (c) the endonuclease is configured to bind to a PAM comprising SEQ ID NO: 5513 or SEQ ID NO: 5528. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, at least 80%, or at least 90% identical to SEQ ID NO: 1829; (b) the guide RNA structure comprises a sequence at least 70%, at least 80%, or at least 90% identical to at least one of SEQ ID NO: 5463 or SEQ ID NO: 5478; and (c) the endonuclease is configured to bind to a PAM comprising SEQ ID NO: 5514 or SEQ ID NO: 5529. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, at least 80%, or at least 90% identical to SEQ ID NO: 1830; (b) the guide RNA structure comprises a sequence at least 70%, at least 80%, or at least 90% identical to at least one of SEQ ID NO: 5464 or SEQ ID NO: 5479; and (c) the endonuclease is configured to bind to a PAM comprising SEQ ID NO: 5515 or SEQ ID NO: 5530. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 2141-2142 or SEQ ID NOs: 2141-2241. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 3955-3956 or SEQ ID NOs: 3955-4055. In some embodiments, the endonuclease comprises at least 1, at least 2, at least 3, at least 4, or at least 5 peptide motifs selected from the group consisting of SEQ ID NOs: 5632-5638. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 320-321 or SEQ ID NOs: 320-420. In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 5465, SEQ ID NOs: 5490-5491 or SEQ ID NOs: 5490-5494. In some embodiments, the guide RNA structure comprises a tracr ribonucleic acid sequence comprising a hairpin comprising at least 8, at least 10, or at least 12 base-paired ribonucleotides. In some embodiments, the endonuclease is configured to bind to a PAM comprising a sequence selected from the group consisting of SEQ ID NOs: 5516 and SEQ ID NOs: 5531. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 2141; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5490; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5531. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 2142; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5465 or SEQ ID NO: 5491; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5516. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 2245-2246. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 4059-4060. In some embodiments, the endonuclease comprises at least 1, at least 2, at least 3, at least 4, or at least 5 peptide motifs selected from the group consisting of SEQ ID NOs: 5639-5648. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 424-425. In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 5498-5499 and SEQ ID NO: 5539. In some embodiments, the guide RNA structure comprises a guide ribonucleic acid sequence predicted to comprise a hairpin with an uninterrupted base-paired region comprising at least 8 nucleotides of a guide ribonucleic acid sequence and at least 8 nucleotides of a tracr ribonucleic acid sequence, and wherein the tracr ribonucleic acid sequence comprises, from 5′ to 3′, a first hairpin and a second hairpin, wherein the first hairpin has a longer stem than the second hairpin. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 2242-2244 or SEQ ID NOs: 2247-2249. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 4056-4058 and SEQ ID NOs 4061-4063. In some embodiments, the endonuclease comprises at least 1, at least 2, at least 3, at least 4, or at least 5 peptide motifs selected from the group consisting of SEQ ID NOs: 5639-5648. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 421-423 or SEQ ID NOs: 426-428. In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 5466-5467, SEQ ID NOs: 5495-5497, SEQ ID NO: 5500-5502, and SEQ ID NO: 5539. In some embodiments, the guide RNA structure comprises a guide ribonucleic acid sequence predicted to comprise a hairpin with an uninterrupted base-paired region comprising at least 8 nucleotides of a guide ribonucleic acid sequence and at least 8 nucleotides of a tracr ribonucleic acid sequence, and wherein the tracr ribonucleic acid sequence comprises, from 5′ to 3′, a first hairpin and a second hairpin, wherein the first hairpin has a longer stem than the second hairpin. In some embodiments, the endonuclease is configured to binding to a PAM comprising a sequence selected from the group consisting of SEQ ID NOs: 5517-5518 or SEQ ID NOs: 5532-5534. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 2247; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5500; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5517 or SEQ ID NO: 5532. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 2248; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5501; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5518 or SEQ ID NOs: 5533. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 2249; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5502; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5534. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 2253 or SEQ ID NOs: 2253-2481. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 4067 or SEQ ID NOs: 4067-4295. In some embodiments, the endonuclease comprises a peptide motif according to SEQ ID NO: 5649. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 432 or SEQ ID NOs: 432-660. In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 5468 or SEQ ID NO: 5503. In some embodiments, the endonuclease is configured to binding to a PAM comprising a sequence selected from the group consisting of SEQ ID NOs: 5519. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 2253; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5468 or SEQ ID NO: 5503; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5519. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 2482-2489. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 4296-4303. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of or SEQ ID NOs: 661-668. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of or SEQ ID NOs: 2490-2498. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 4304-4312. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 669-677. In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 5504. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 2499 or SEQ ID NOs: 2499-2750. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 4313 or SEQ ID NOs: 4313-4564. In some embodiments, the endonuclease comprises at least 1, at least 2, at least 3, at least 4, or at least 5 peptide motifs selected from the group consisting of SEQ ID NOs: 5650-5667. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 678 or SEQ ID NOs: 678-929. In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5469 or SEQ ID NO: 5505. In some embodiments, the endonuclease is configured to binding to a PAM comprising SEQ ID NOs: 5520 or SEQ ID NOs: 5535. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 2499; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5469 or SEQ ID NO: 5505; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5520 or SEQ ID NO: 5535. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 2751 or SEQ ID NOs: 2751-2913. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 4565 or SEQ ID NOs: 4565-4727. In some embodiments, the endonuclease comprises at least 1, at least 2, at least 3, at least 4, or at least 5 peptide motifs selected from the group consisting of SEQ ID NOs: 5668-5678. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 930 or SEQ ID NOs: 930-1092. In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5470 or SEQ ID NOs: 5506. In some embodiments, the endonuclease is configured to binding to a PAM comprising a sequence selected from the group consisting of SEQ ID NOs: 5521 or SEQ ID NOs: 5536. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 2751; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5470 or SEQ ID NO: 5506; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5521 or SEQ ID NO: 5536. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 2914 or SEQ ID NOs: 2914-3174. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 4728 or SEQ ID NOs: 4728-4988. In some embodiments, the endonuclease comprises at least 1, at least 2, or at least 3 peptide motifs selected from the group consisting of SEQ ID NOs: 5676-5678. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 1093 or SEQ ID NOs: 1093-1353. In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 5471, SEQ ID NO: 5507, and SEQ ID NOs: 5540-5542. In some embodiments, the guide RNA structure comprises a tracr ribonucleic acid sequence predicted to comprise at least two hairpins comprising less than 5 base-paired ribonucleotides. In some embodiments, the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5522. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 2914; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5471 or SEQ ID NO: 5507; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5522. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 3175 or SEQ ID NOs: 3175-3330. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 4989 or SEQ ID NOs: 4989-5146. In some embodiments, the endonuclease comprises at least 1, at least 2, at least 3, at least 4, or at least 5 peptide motifs selected from the group consisting of SEQ ID NOs: 5679-5686. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 1354 or SEQ ID NOs: 1354-1511. In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 5472 or SEQ ID NOs: 5508. In some embodiments, the endonuclease is configured to binding to a PAM comprising a sequence selected from the group consisting of SEQ ID NO: 5523 or SEQ ID NO: 5537. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 3175; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5472 or SEQ ID NO: 5508; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5523 or SEQ ID NO: 5537. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 3331 or SEQ ID NOs: 3331-3474. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NOs: 5147 or SEQ ID NOs: 5147-5290. In some embodiments, the endonuclease comprises at least 1, at least 2, at least 3, at least 4, or at least 5 peptide motifs selected from the group consisting of SEQ ID NOs: 5674-5675 and SEQ ID NOs: 5687-5693. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 1512 or SEQ ID NOs: 1512-1655. In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 5473 or SEQ ID NO: 5509. In some embodiments, the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5524. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 3331; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5473 or SEQ ID NO: 5509; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5524. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 3475 or SEQ ID NOs: 3475-3568. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 5291 or SEQ ID NOs: 5291-5389. In some embodiments, the endonuclease comprises at least 1, at least 2, at least 3, at least 4, or at least 5 peptide motifs selected from the group consisting of SEQ ID NOs: 5694-5699. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 1656 or SEQ ID NOs: 1656-1755. In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5474 or SEQ ID NO: 5510. In some embodiments, the endonuclease is configured to binding to a PAM comprising SEQ ID NOs: 5525. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 3475; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5474 or SEQ ID NO: 5510; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5525. 
     In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 3569 or SEQ ID NOs: 3569-3637. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 5390 or SEQ ID NOs: 5390-5460. In some embodiments, the endonuclease comprises at least 1, at least 2, at least 3, at least 4, or at least 5 peptide motifs selected from the group consisting of SEQ ID NOs: 5700-5717. In some embodiments, the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to a sequence selected from the group consisting of SEQ ID NO: 1756 or SEQ ID NOs: 1756-1826. In some embodiments, the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5475 or SEQ ID NOs: 5511. In some embodiments, the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5526. In some embodiments: (a) the endonuclease comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 3569; (b) the guide RNA structure comprises a sequence at least 70%, 80%, or 90% identical to SEQ ID NO: 5475 or SEQ ID NO: 5511; and (c) the endonuclease is configured to binding to a PAM comprising SEQ ID NO: 5526. In some embodiments, the sequence identity is determined by a BLASTP, CLUSTALW, MUSCLE, MAFFT, or Smith-Waterman homology search algorithm. In some embodiments, the sequence identity is determined by the BLASTP homology search algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some aspects, the present disclosure provides for an engineered guide ribonucleic acid polynucleotide comprising: (a) a DNA-targeting segment comprising a nucleotide sequence that is complementary to a target sequence in a target DNA molecule; and (b) a protein-binding segment comprising two complementary stretches of nucleotides that hybridize to form a double-stranded RNA (dsRNA) duplex, wherein the two complementary stretches of nucleotides are covalently linked to one another with intervening nucleotides, and wherein the engineered guide ribonucleic acid polynucleotide is configured to forming a complex with an endonuclease comprising a RuvC_III domain having at least 75% sequence identity to any one of SEQ ID NOs: 1827-3637 and targeting the complex to the target sequence of the target DNA molecule. In some embodiments, the DNA-targeting segment is positioned 5′ of both of the two complementary stretches of nucleotides. 
     In some embodiments: (a) the protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to a sequence selected from the group consisting of SEQ ID NOs: 5476-5479 or SEQ ID NOs: 5476-5489; (b) the protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to a sequence selected from the group consisting of (SEQ ID NOs: 5490-5491 or SEQ ID NOs: 5490-5494) and SEQ ID NO: 5538; (c) the protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to a sequence selected from the group consisting of SEQ ID NOs: 5498-5499; (d) the protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to a sequence selected from the group consisting of SEQ ID NOs: 5495-5497 and SEQ ID NOs: 5500-5502; (e) the protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to SEQ ID NO: 5503; (0 the protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to SEQ ID NO: 5504; (g) the protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to SEQ ID NOs: 5505; (h) protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to SEQ ID NO: 5506; (i) protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to SEQ ID NO: 5507; (j) the protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to SEQ ID NO: 5508; (k) the protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to SEQ ID NO: 5509; (1) the protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to SEQ ID NO: 5510; or (m) the protein binding segment comprises a sequence having at least 70%, at least 80%, or at least 90% identity to SEQ ID NO: 5511. 
     In some embodiments: (a) the guide ribonucleic acid polynucleotide comprises an RNA sequence comprising a hairpin comprising a stem and a loop, wherein the stem comprises at least 10, at least 12, or at least 14 base-paired ribonucleotides, and an asymmetric bulge within 4 base pairs of the loop; (b) the guide ribonucleic acid polynucleotide comprises a tracr ribonucleic acid sequence predicted to comprise a hairpin comprising at least 8, at least 10, or at least 12 base-paired ribonucleotides; (c) the guide ribonucleic acid polynucleotide comprises a guide ribonucleic acid sequence predicted to comprise a hairpin with an uninterrupted base-paired region comprising at least 8 nucleotides of a guide ribonucleic acid sequence and at least 8 nucleotides of a tracr ribonucleic acid sequence, and wherein the tracr ribonucleic acid sequence comprises, from 5′ to 3′, a first hairpin and a second hairpin, wherein the first hairpin has a longer stem than the second hairpin; or (d) the guide ribonucleic acid polynucleotide comprises a tracr ribonucleic acid sequence predicted to comprise at least two hairpins comprising less than 5 base-paired ribonucleotides. 
     In some aspects, the present disclosure provides for a deoxyribonucleic acid polynucleotide encoding any of the engineered guide ribonucleic acid polynucleotides described herein. 
     In some aspects, the present disclosure provides for a nucleic acid comprising an engineered nucleic acid sequence optimized for expression in an organism, wherein the nucleic acid encodes a class 2, type II Cas endonuclease comprising a RuvC_III domain and an HNH domain, and wherein the endonuclease is derived from an uncultivated microorganism. 
     In some aspects, the present disclosure provides for a nucleic acid comprising an engineered nucleic acid sequence optimized for expression in an organism, wherein the nucleic acid encodes an endonuclease comprising a RuvC_III domain having at least 70% sequence identity to any one of SEQ ID NOs: 1827-3637. In some embodiments, the endonuclease comprises an HNH domain having at least 70% or at least 80% sequence identity to any one of SEQ ID NOs: 3638-5460. In some embodiments, the endonuclease comprises SEQ ID NOs: 5572-5591 or a variant thereof having at least 70% sequence identity thereto. In some embodiments, the endonuclease comprises a sequence encoding one or more nuclear localization sequences (NLSs) proximal to an N- or C-terminus of the endonuclease. In some embodiments, the NLS comprises a sequence selected from SEQ ID NOs: 5597-5612. 
     In some embodiments, the organism is prokaryotic, bacterial, eukaryotic, fungal, plant, mammalian, rodent, or human. In some embodiments, the organism is  E. coli,  and: (a) the nucleic acid sequence has at least 70%, 80%, or 90% identity to a sequence selected from the group consisting of SEQ ID NOs: 5572-5575; (b) the nucleic acid sequence has at least 70%, 80%, or 90% identity to a sequence selected from the group consisting of SEQ ID NOs: 5576-5577; (c) the nucleic acid sequence has at least 70%, 80%, or 90% identity to a sequence selected from the group consisting of SEQ ID NOs: 5578-5580; (d) the nucleic acid sequence has at least 70%, 80%, or 90% identity to SEQ ID NO: 5581; (e) the nucleic acid sequence has at least 70%, 80%, or 90% identity to SEQ ID NO: 5582; (f) the nucleic acid sequence has at least 70%, 80%, or 90% identity to SEQ ID NO: 5583; (g) the nucleic acid sequence has at least 70%, 80%, or 90% identity to SEQ ID NO: 5584; (h) the nucleic acid sequence has at least 70%, 80%, or 90% identity to SEQ ID NO: 5585; (i) the nucleic acid sequence has at least 70%, 80%, or 90% identity to SEQ ID NO: 5586; or (j) the nucleic acid sequence has at least 70%, 80%, or 90% identity to SEQ ID NO: 5587. In some embodiments, the organism is human, and: (a) the nucleic acid sequence has at least 70%, 80%, or 90% identity to SEQ ID NO: 5588 or SEQ ID NO: 5589; or (b) the nucleic acid sequence has at least 70%, 80%, or 90% identity to SEQ ID NO: 5590 or SEQ ID NO: 5591. 
     In some aspects, the present disclosure provides for a vector comprising a nucleic acid sequence encoding a class 2, type II Cas endonuclease comprising a RuvC_III domain and an HNH domain, wherein the endonuclease is derived from an uncultivated microorganism. 
     In some aspects, the present disclosure provides for a vector comprising the any of the nucleic acids described herein. In some embodiments, the vector further comprises a nucleic acid encoding an engineered guide ribonucleic acid structure configured to form a complex with the endonuclease comprising: (a) a guide ribonucleic acid sequence configured to hybridize to a target deoxyribonucleic acid sequence; and (b) a tracr ribonucleic acid sequence configured to binding to the endonuclease. In some embodiments, the vector is a plasmid, a minicircle, a CELiD, an adeno-associated virus (AAV) derived virion, or a lentivirus. 
     In some aspects, the present disclosure provides for a cell comprising any of the vectors described herein. 
     In some aspects, the present disclosure provides for a method of manufacturing an endonuclease, comprising cultivating any of the cells described herein. 
     In some aspects, the present disclosure provides for a method for binding, cleaving, marking, or modifying a double-stranded deoxyribonucleic acid polynucleotide, comprising: (a) contacting the double-stranded deoxyribonucleic acid polynucleotide with a class 2, type II Cas endonuclease in complex with an engineered guide ribonucleic acid structure configured to bind to the endonuclease and the double-stranded deoxyribonucleic acid polynucleotide; (b) wherein the double-stranded deoxyribonucleic acid polynucleotide comprises a protospacer adjacent motif (PAM); and (c) wherein the PAM comprises a sequence selected from the group consisting of SEQ ID NOs: 5512-5526 or SEQ ID NOs: 5527-5537. In some embodiments, the double-stranded deoxyribonucleic acid polynucleotide comprises a first strand comprising a sequence complementary to a sequence of the engineered guide ribonucleic acid structure and a second strand comprising the PAM. In some embodiments, the PAM is directly adjacent to the 3′ end of the sequence complementary to the sequence of the engineered guide ribonucleic acid structure. In some embodiments, the class 2, type II Cas endonuclease is not a Cas9 endonuclease, a Cas14 endonuclease, a Cas12a endonuclease, a Cas12b endonuclease, a Cas 12c endonuclease, a Cas12d endonuclease, a Cas12e endonuclease, a Cas13a endonuclease, a Cas13b endonuclease, a Cas13c endonuclease, or a Cas 13d endonuclease. In some embodiments, the class 2, type II Cas endonuclease is derived from an uncultivated microorganism. In some embodiments, the double-stranded deoxyribonucleic acid polynucleotide is a eukaryotic, plant, fungal, mammalian, rodent, or human double-stranded deoxyribonucleic acid polynucleotide. 
     In some embodiments: (a) the PAM comprises a sequence selected from the group consisting of SEQ ID NOs: 5512-5515 and SEQ ID NOs: 5527-5530; (b) the PAM comprises SEQ ID NO: 5516 or SEQ ID NO: 5531; (c) the PAM comprises SEQ ID NO: 5539; (d) the PAM comprises SEQ ID NO: 5517 or SEQ ID NO: 5518; (e) the PAM comprises SEQ ID NO: 5519; (f) the PAM comprises SEQ ID NO: 5520 or SEQ ID NO: 5535; (g) the PAM comprises SEQ ID NO: 5521 or SEQ ID NO: 5536; (h) the PAM comprises SEQ ID NO: 5522; (i) the PAM comprises SEQ ID NO: 5523 or SEQ ID NO: 5537; (j) the PAM comprises SEQ ID NO: 5524; (k) the PAM comprises SEQ ID NO: 5525; or (l) the PAM comprises SEQ ID NO: 5526. 
     In some aspects, the present disclosure provides for a method of modifying a target nucleic acid locus, the method comprising delivering to the target nucleic acid locus any of the engineered nuclease systems described herein, wherein the endonuclease is configured to form a complex with the engineered guide ribonucleic acid structure, and wherein the complex is configured such that upon binding of the complex to the target nucleic acid locus, the complex modifies the target nucleic locus. In some embodiments, modifying the target nucleic acid locus comprises binding, nicking, cleaving, or marking the target nucleic acid locus. In some embodiments, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). In some embodiments, the target nucleic acid comprises genomic DNA, viral DNA, viral RNA, or bacterial DNA. In some embodiments, the target nucleic acid locus is in vitro. In some embodiments, the target nucleic acid locus is within a cell. In some embodiments, the cell is a prokaryotic cell, a bacterial cell, a eukaryotic cell, a fungal cell, a plant cell, an animal cell, a mammalian cell, a rodent cell, a primate cell, or a human cell. 
     In some embodiments, delivering the engineered nuclease system to the target nucleic acid locus comprises delivering the nucleic acid of any of claims  135 - 140  or the vector of any of claims  142 - 146 . In some embodiments, delivering the engineered nuclease system to the target nucleic acid locus comprises delivering a nucleic acid comprising an open reading frame encoding the endonuclease. In some embodiments, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. In some embodiments, the engineered nuclease system to the target nucleic acid locus comprises delivering a capped mRNA containing the open reading frame encoding the endonuclease. In some embodiments, the engineered nuclease system to the target nucleic acid locus comprises delivering a translated polypeptide. In some embodiments, the engineered nuclease system to the target nucleic acid locus comprises delivering a deoxyribonucleic acid (DNA) encoding the engineered guide ribonucleic acid structure operably linked to a ribonucleic acid (RNA) pol III promoter. In some embodiments, the endonuclease induces a single-stranded break or a double-stranded break at or proximal to the target locus. 
     Additional aspects and advantages of the present disclosure will become readily apparent to those skilled in this art from the following detailed description, wherein only illustrative embodiments of the present disclosure are shown and described. As will be realized, the present disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
     INCORPORATION BY REFERENCE 
     All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings (also “Figure” and “FIG.” herein), of which: 
         FIG. 1  depicts typical organizations of CRISPR/Cas loci of different classes and types. 
         FIG. 2  depicts the architecture of a natural Class2/Type II crRNA/tracrRNA pair, compared to a hybrid sgRNA wherein both are joined. 
         FIG. 3  depicts schematics showing organization of CRISPR loci encoding enzymes from the MG1 family. 
         FIG. 4  depicts schematics showing organization of CRISPR loci encoding enzymes from the MG2 family. 
         FIG. 5  depicts schematics showing organization of CRISPR loci encoding enzymes from the MG3 family. 
         FIG. 6  depicts a structure-based alignment of an enzyme of the present disclosure (MG1-1) versus Cas9 from  Staphylococcus aureus  (SEQ ID NO:5613). 
         FIG. 7  depicts a structure-based alignment of an enzyme of the present disclosure (MG2-1) versus Cas9 from  Staphylococcus aureus  (SEQ ID NO:5613). 
         FIG. 8  depicts a structure-based alignment of an enzyme of the present disclosure (MG3-1) versus Cas9 from  Actinomyces naeslundii  (SEQ ID NO: 5614). 
         FIGS. 9A, 9B, 9C, 9D, 9E, 9F, 9G, and 9H  depicts a structure-based alignment of MG1 family enzymes MG1-1 through MG1-6 (SEQ ID NOs: 5, 6, 9, 1, 2, and 3). 
         FIG. 10  depicts in vitro cleavage of DNA by MG1-4 in complex with its corresponding sgRNA containing targeting sequences of varying lengths. 
         FIG. 11  depicts in cell cleavage of  E. coli  genomic DNA using MG1-4 along with its corresponding sgRNA. Shown are dilution series of cells transformed with MG1-4 along with target or non-target spacer (top); bottom panel shows the data quantitated, where the left bar represents non-target sgRNA and the right bar represents target sgRNA. 
         FIG. 12  depicts in cell indel formation generated by transfection of HEK cells with MG1-4 or MG1-6 constructs described in Example 11 alongside their corresponding sgRNAs containing various different targeting sequences targeting various locations in the human genome. 
         FIG. 13  depicts vitro cleavage of DNA by MG3-6 in complex with its corresponding sgRNA containing targeting sequences of varying lengths. 
         FIG. 14  depicts in cell cleavage of  E. coli  genomic DNA using MG3-7 along with its corresponding sgRNA. Shown are dilution series of cells transformed with MG3-7 along with target or non-target spacer (top); bottom panel shows the data quantitated, where the left bar represents non-target sgRNA and the right bar represents target sgRNA. 
         FIG. 15  depicts in cell indel formation generated by transfection of HEK cells with MG3-7 constructs described in Example 13 alongside their corresponding sgRNAs containing various different targeting sequences targeting various locations in the human genome. 
         FIG. 16  depicts in vitro cleavage of DNA by MG15-1 in complex with its corresponding sgRNA containing targeting sequences of varying lengths. 
         FIGS. 17, 18, 19, and 20  depict agarose gels showing the results of PAM vector library cleavage in the presence of TXTL extracts containing various MG family nucleases and their corresponding tracrRNAs or sgRNAs. 
         FIGS. 21, 22, 23, 24, 25 and 26  depict predicted structures (predicted e.g., as in Example 7) of corresponding sgRNAs of MG enzymes described herein. 
         FIGS. 27, 28, 29, 30, 31, 32 and 33  depict seqLogo representations of PAM sequences derived via NGS as described herein (e.g. as described in Example 6). 
         FIG. 34  depicts in cell cleavage of  E. coli  genomic DNA using MG2-7 along with its corresponding sgRNA. Shown are dilution series of cells transformed with MG2-7 along with target or non-target spacer (top); bottom panel shows the data quantitated, where the right bar represents non-target sgRNA and the left bar represents target sgRNA. 
         FIG. 35  depicts in cell cleavage of  E. coli  genomic DNA using MG14-1 along with its corresponding sgRNA. Shown are dilution series of cells transformed with MG14-1 along with target or non-target spacer (top); bottom panel shows the data quantitated, where the right bar represents non-target sgRNA and the left bar represents target sgRNA. 
         FIG. 36  depicts in cell cleavage of  E. coli  genomic DNA using MG15-1 along with its corresponding sgRNA. Shown are dilution series of cells transformed with MG15-1 along with target or non-target spacer (top); bottom panel shows the data quantitated, where the right bar represents non-target sgRNA and the left bar represents target sgRNA. 
         FIGS. 37-39  depicts in cell indel formation generated by transfection of HEK cells with MG1-4, MG1-6 and MG1-7 constructs described in Example 11 alongside their corresponding sgRNAs containing various different targeting sequences targeting various locations in the human genome. 
         FIGS. 40-42  depicts in cell indel formation generated by transfection of HEK cells with MG3-6, MG3-7 and MG3-8 constructs described in Example 13 alongside their corresponding sgRNAs containing various different targeting sequences targeting various locations in the human genome. 
         FIG. 43  depicts in cell indel formation generated by transfection of HEK cells with MG14-1 constructs described in Example 14 alongside their corresponding sgRNAs containing various different targeting sequences targeting various locations in the human genome. 
         FIG. 44  depicts in cell indel formation generated by transfection of HEK cells with MG18-1 constructs described in Example 17 alongside their corresponding sgRNAs containing various different targeting sequences targeting various locations in the human genome. 
     
    
    
     BRIEF DESCRIPTION OF THE SEQUENCE LISTING 
     The Sequence Listing filed herewith provides exemplary polynucleotide and polypeptide sequences for use in methods, compositions and systems according to the disclosure. Below are exemplary descriptions of sequences therein. 
     MG1 
     SEQ ID NOs: 1-319 show the full-length peptide sequences of MG1 nucleases. 
     SEQ ID NOs: 1827-2140 show the peptide sequences of RuvC_III domains of MG1 nucleases above. 
     SEQ ID NOs: 3638-3955 show the peptide of HNH domains of MG1 nucleases above. 
     SEQ ID NOs: 5476-5479 show the nucleotide sequences of MG1 tracrRNAs derived from the same loci as MG1 nucleases above (e.g., same loci as SEQ ID NO:1-4, respectively). 
     SEQ ID NOs: 5461-5464 show the nucleotide sequences of sgRNAs engineered to function with an MG1 nuclease (e.g., SEQ ID NO:1-4, respectively), where Ns denote nucleotides of a targeting sequence. 
     SEQ ID NOs: 5572-5575 show nucleotide sequences for  E. coli  codon-optimized coding sequences for MG1 family enzymes (SEQ ID NOs: 1-4). 
     SEQ ID NOs: 5588-5589 show nucleotide sequences for human codon-optimized coding sequences for MG1 family enzymes (SEQ ID NOs: 1 and 3). 
     SEQ ID NOs: 5616-5632 show peptide motifs characteristic of MG1 family enzymes. MG2 
     SEQ ID NOs: 320-420 show the full-length peptide sequences of MG2 nucleases. 
     SEQ ID NOs: 2141-2241 show the peptide sequences of RuvC_III domains of MG2 nucleases above. 
     SEQ ID NOs: 3955-4055 show the peptide of HNH domains of MG2 nucleases above. 
     SEQ ID NOs: 5490-5494 show the nucleotide sequences of MG2 tracrRNAs derived from the same loci as MG2 nucleases above (e.g., same loci as SEQ ID NOs: 320, 321, 323, 325, and 326, respectively). 
     SEQ ID NO: 5465 shows the nucleotide sequence of an sgRNA engineered to function with an MG2 nuclease (e.g., SEQ ID NO: 321 above). 
     SEQ ID NOs: 5572-5575 show nucleotide sequences for  E. coli  codon-optimized coding sequences for MG2 family enzymes. 
     SEQ ID NOs: 5631-5638 show peptide sequences characteristic of MG2 family enzymes. 
     MG3 
     SEQ ID NOs: 421-431 show the full-length peptide sequences of MG3 nucleases. 
     SEQ ID NOs: 2242-2252 show the peptide sequences of RuvC_III domains of MG3 nucleases above. 
     SEQ ID NOs: 4056-4066 show the peptide of HNH domains of MG3 nucleases above. 
     SEQ ID NOs: 5495-5502 show the nucleotide sequences of MG3 tracrRNAs derived from the same loci as MG3 nucleases above (e.g., same loci as SEQ ID NOs: 421-428, respectively). 
     SEQ ID NOs: 5466-5467 show the nucleotide sequence of sgRNAs engineered to function with an MG3 nuclease (e.g., SEQ ID NOs: 421-423). 
     SEQ ID NOs: 5578-5580 show nucleotide sequences for  E. coli  codon-optimized coding sequences for MG3 family enzymes. 
     SEQ ID NOs: 5639-5648 show peptide sequences characteristic of MG3 family enzymes. 
     MG4 
     SEQ ID NOs: 432-660 show the full-length peptide sequences of MG4 nucleases. 
     SEQ ID NOs: 2253-2481 show the peptide sequences of RuvC_III domains of MG4 nucleases above. 
     SEQ ID NOs: 4067-4295 show the peptide of HNH domains of MG4 nucleases above. 
     SEQ ID NO: 5503 shows the nucleotide sequences of an MG4 tracrRNA derived from the same loci as MG4 nucleases above. 
     SEQ ID NO: 5468 shows the nucleotide sequence of sgRNAs engineered to function with an MG4 nuclease. 
     SEQ ID NO: 5649 shows a peptide sequence characteristic of MG4 family enzymes. MG6 
     SEQ ID NOs: 661-668 show the full-length peptide sequences of MG6 nucleases. 
     SEQ ID NOs: 2482-2489 show the peptide sequences of RuvC_III domains of MG6 nucleases above. 
     SEQ ID NOs: 4296-4303 show the peptide of HNH domains of MG3 nucleases above. 
     MG7 
     SEQ ID NOs: 669-677 show the full-length peptide sequences of MG7 nucleases. 
     SEQ ID NOs: 2490-2498 show the peptide sequences of RuvC_III domains of MG7 nucleases above. 
     SEQ ID NOs: 4304-4312 show the peptide of HNH domains of MG3 nucleases above. 
     SEQ ID NO: 5504 shows the nucleotide sequence of an MG7 tracrRNA derived from the same loci as MG7 nucleases above. 
     MG14 
     SEQ ID NOs: 678-929 show the full-length peptide sequences of MG14 nucleases. 
     SEQ ID NOs: 2499-2750 show the peptide sequences of RuvC_III domains of MG14 nucleases above. 
     SEQ ID NOs: 4313-4564 show the peptide of HNH domains of MG14 nucleases above. 
     SEQ ID NO: 5505 shows the nucleotide sequences of MG14 tracrRNA derived from the same loci as MG14 nucleases above. 
     SEQ ID NO: 5581 shows a nucleotide sequence for an  E. coli  codon-optimized coding sequences for an MG14 family enzyme. 
     SEQ ID NOs: 5650-5667 show peptide sequences characteristic of MG14 family enzymes. 
     MG15 
     SEQ ID NOs: 930-1092 show the full-length peptide sequences of MG15 nucleases. 
     SEQ ID NOs: 2751-2913 show the peptide sequences of RuvC_III domains of MG15 nucleases above. 
     SEQ ID NOs: 4565-4727 show the peptide of HNH domains of MG15 nucleases above. 
     SEQ ID NO: 5506 shows the nucleotide sequences of MG15 tracrRNA derived from the same loci as MG15 nucleases above. 
     SEQ ID NOs: 5470 shows the nucleotide sequence of an sgRNA engineered to function with an MG15 nuclease. 
     SEQ ID NO: 5582 shows a nucleotide sequence for an  E. coli  codon-optimized coding sequences for an MG15 family enzyme. 
     SEQ ID NOs: 5668-5675 show peptide sequences characteristic of MG15 family enzymes. 
     MG16 
     SEQ ID NOs: 1093-1353 show the full-length peptide sequences of MG16 nucleases. 
     SEQ ID NOs: 2914-3174 show the peptide sequences of RuvC_III domains of MG16 nucleases above. 
     SEQ ID NOs: 4728-4988 show the peptide of HNH domains of MG16 nucleases above. 
     SEQ ID NOs: 5507 show the nucleotide sequences of an MG16 tracrRNA derived from the same loci as MG3 nucleases above. 
     SEQ ID NOs: 5471 shows the nucleotide sequence of sgRNAs engineered to function with an MG16 nuclease. 
     SEQ ID NO: 5583 shows a nucleotide sequence for an  E. coli  codon-optimized coding sequences for an MG16 family enzyme. 
     SEQ ID NOs: 5676-5678 show peptide sequences characteristic of MG16 family enzymes. 
     MG18 
     SEQ ID NOs: 1354-1511 show the full-length peptide sequences of MG18 nucleases. 
     SEQ ID NOs: 3175-3330 show the peptide sequences of RuvC_III domains of MG18 nucleases above. 
     SEQ ID NOs: 4989-5146 show the peptide of HNH domains of MG18 nucleases above. 
     SEQ ID NO: 5508 shows the nucleotide sequences of MG18 tracrRNA derived from the same loci as MG18 nucleases above. 
     SEQ ID NOs: 5472 shows the nucleotide sequence of an sgRNA engineered to function with an MG18 nuclease. 
     SEQ ID NO: 5584 shows a nucleotide sequence for an  E. coli  codon-optimized coding sequences for an MG18 family enzyme. 
     SEQ ID NOs: 5679-5686 show peptide sequences characteristic of MG18 family enzymes. 
     MG21 
     SEQ ID NOs: 1512-1655 show the full-length peptide sequences of MG21 nucleases. 
     SEQ ID NOs: 3331-3474 show the peptide sequences of RuvC_III domains of MG21 nucleases above. 
     SEQ ID NOs: 5147-5290 show the peptide of HNH domains of MG21 nucleases above. 
     SEQ ID NOs: 5509 show the nucleotide sequence of an MG21 tracrRNA derived from the same loci as MG21 nucleases above. 
     SEQ ID NOs: 5473 shows the nucleotide sequence of an sgRNA engineered to function with an MG21 nuclease. 
     SEQ ID NO: 5585 shows a nucleotide sequence for an  E. coli  codon-optimized coding sequences for an MG21 family enzyme. 
     SEQ ID NOs: 5687-5692 and 5674-5675 show peptide sequences characteristic of MG21 family enzymes. 
     MG22 
     SEQ ID NOs: 1656-1755 show the full-length peptide sequences of MG22 nucleases. 
     SEQ ID NOs: 3475-3568 show the peptide sequences of RuvC_III domains of MG22 nucleases above. 
     SEQ ID NOs: 5291-5389 show the peptide of HNH domains of MG22 nucleases above. 
     SEQ ID NO: 5510 show the nucleotide sequence of an MG22 tracrRNA derived from the same loci as MG22 nucleases above. 
     SEQ ID NOs: 5474 shows the nucleotide sequence of an sgRNAs engineered to function with an MG22 nuclease. 
     SEQ ID NO: 5586 shows a nucleotide sequence for an  E. coli  codon-optimized coding sequences for an MG22 family enzyme. 
     SEQ ID NOs: 5694-5699 show peptide sequences characteristic of MG22 family enzymes. 
     MG23 
     SEQ ID NOs: 1756-1826 show the full-length peptide sequences of MG23 nucleases. 
     SEQ ID NOs: 3569-3637 show the peptide sequences of RuvC_III domains of MG23 nucleases above. 
     SEQ ID NOs: 5390-5460 show the peptide of HNH domains of MG23 nucleases above. 
     SEQ ID NO: 5511 shows the nucleotide sequences of an MG23 tracrRNA derived from the same loci as MG23 nucleases above. 
     SEQ ID NOs: 5475 shows the nucleotide sequence of an sgRNA engineered to function with an MG23 nuclease. 
     SEQ ID NO: 5587 shows a nucleotide sequence for an  E. coli  codon-optimized coding sequences for an MG23 family enzyme. 
     SEQ ID NOs: 5700-5717 show peptide sequences characteristic of MG23 family enzymes. 
     DETAILED DESCRIPTION 
     While various embodiments of the invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions may occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed. 
     The practice of some methods disclosed herein employ, unless otherwise indicated, techniques of immunology, biochemistry, chemistry, molecular biology, microbiology, cell biology, genomics and recombinant DNA. See for example Sambrook and Green, Molecular Cloning: A Laboratory Manual, 4th Edition (2012); the series Current Protocols in Molecular Biology (F. M. Ausubel, et al. eds.); the series Methods In Enzymology (Academic Press, Inc.), PCR 2: A Practical Approach (M. J. MacPherson, B. D. Hames and G. R. Taylor eds. (1995)), Harlow and Lane, eds. (1988) Antibodies, A Laboratory Manual, and Culture of Animal Cells: A Manual of Basic Technique and Specialized Applications, 6th Edition (R. I. Freshney, ed. (2010)) (which is entirely incorporated by reference herein). 
     As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and/or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”. 
     The term “about” or “approximately” means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e., the limitations of the measurement system. For example, “about” can mean within one or more than one standard deviation, per the practice in the art. Alternatively, “about” can mean a range of up to 20%, up to 15%, up to 10%, up to 5%, or up to 1% of a given value. 
     As used herein, a “cell” generally refers to a biological cell. A cell may be the basic structural, functional and/or biological unit of a living organism. A cell may originate from any organism having one or more cells. Some non-limiting examples include: a prokaryotic cell, eukaryotic cell, a bacterial cell, an archaeal cell, a cell of a single-cell eukaryotic organism, a protozoa cell, a cell from a plant (e.g., cells from plant crops, fruits, vegetables, grains, soy bean, corn, maize, wheat, seeds, tomatoes, rice, cassava, sugarcane, pumpkin, hay, potatoes, cotton, cannabis, tobacco, flowering plants, conifers, gymnosperms, ferns, clubmosses, hornworts, liverworts, mosses), an algal cell, (e.g.,  Botryococcus braunii, Chlamydomonas reinhardtii, Nannochloropsis gaditana, Chlorella pyrenoidosa, Sargassum patens C. Agardh,  and the like), seaweeds (e.g., kelp), a fungal cell (e.g., a yeast cell, a cell from a mushroom), an animal cell, a cell from an invertebrate animal (e.g., fruit fly, cnidarian, echinoderm, nematode, etc.), a cell from a vertebrate animal (e.g., fish, amphibian, reptile, bird, mammal), a cell from a mammal (e.g., a pig, a cow, a goat, a sheep, a rodent, a rat, a mouse, a non-human primate, a human, etc.), and etcetera. Sometimes a cell is not originating from a natural organism (e.g., a cell can be a synthetically made, sometimes termed an artificial cell). 
     The term “nucleotide,” as used herein, generally refers to a base-sugar-phosphate combination. A nucleotide may comprise a synthetic nucleotide. A nucleotide may comprise a synthetic nucleotide analog. Nucleotides may be monomeric units of a nucleic acid sequence (e.g., deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)). The term nucleotide may include ribonucleoside triphosphates adenosine triphosphate (ATP), uridine triphosphate (UTP), cytosine triphosphate (CTP), guanosine triphosphate (GTP) and deoxyribonucleoside triphosphates such as dATP, dCTP, dITP, dUTP, dGTP, dTTP, or derivatives thereof. Such derivatives may include, for example, [αS]dATP, 7-deaza-dGTP and 7-deaza-dATP, and nucleotide derivatives that confer nuclease resistance on the nucleic acid molecule containing them. The term nucleotide as used herein may refer to dideoxyribonucleoside triphosphates (ddNTPs) and their derivatives. Illustrative examples of dideoxyribonucleoside triphosphates may include, but are not limited to, ddATP, ddCTP, ddGTP, ddITP, and ddTTP. A nucleotide may be unlabeled or detectably labeled, such as using moieties comprising optically detectable moieties (e.g., fluorophores). Labeling may also be carried out with quantum dots. Detectable labels may include, for example, radioactive isotopes, fluorescent labels, chemiluminescent labels, bioluminescent labels and enzyme labels. Fluorescent labels of nucleotides may include but are not limited fluorescein, 5-carboxyfluorescein (FAM), 2′7′-dimethoxy-4′5-dichloro-6-carboxyfluorescein (JOE), rhodamine, 6-carboxyrhodamine (R6G), N,N,N′,N′-tetramethyl-6-carboxyrhodamine (TAMRA), 6-carboxy-X-rhodamine (ROX), 4-(4′dimethylaminophenylazo) benzoic acid (DABCYL), Cascade Blue, Oregon Green, Texas Red, Cyanine and 5-(2′-aminoethyl)aminonaphthalene-1-sulfonic acid (EDANS). Specific examples of fluorescently labeled nucleotides can include [R6G]dUTP, [TAMRA]dUTP, [R110]dCTP, [R6G]dCTP, [TAMRA]dCTP, [JOE]ddATP, [R6G]ddATP, [FAM]ddCTP, [R110]ddCTP, [TAMRA]ddGTP, [ROX]ddTTP, [dR6G]ddATP, [dR110]ddCTP, [dTAMRA]ddGTP, and [dROX]ddTTP available from Perkin Elmer, Foster City, Calif.; FluoroLink DeoxyNucleotides, FluoroLink Cy3-dCTP, FluoroLink Cy5-dCTP, FluoroLink Fluor X-dCTP, FluoroLink Cy3-dUTP, and FluoroLink Cy5-dUTP available from Amersham, Arlington Heights, Ill.; Fluorescein-15-dATP, Fluorescein-12-dUTP, Tetramethyl-rodamine-6-dUTP, IR770-9-dATP, Fluorescein-12-ddUTP, Fluorescein-12-UTP, and Fluorescein-15-2′-dATP available from Boehringer Mannheim, Indianapolis, Ind.; and Chromosome Labeled Nucleotides, BODIPY-FL-14-UTP, BODIPY-FL-4-UTP, BODIPY-TMR-14-UTP, BODIPY-TMR-14-dUTP, BODIPY-TR-14-UTP, BODIPY-TR-14-dUTP, Cascade Blue-7-UTP, Cascade Blue-7-dUTP, fluorescein-12-UTP, fluorescein-12-dUTP, Oregon Green 488-5-dUTP, Rhodamine Green-5-UTP, Rhodamine Green-5-dUTP, tetramethylrhodamine-6-UTP, tetramethylrhodamine-6-dUTP, Texas Red-5-UTP, Texas Red-5-dUTP, and Texas Red-12-dUTP available from Molecular Probes, Eugene, Oreg. Nucleotides can also be labeled or marked by chemical modification. A chemically-modified single nucleotide can be biotin-dNTP. Some non-limiting examples of biotinylated dNTPs can include, biotin-dATP (e.g., bio-N6-ddATP, biotin-14-dATP), biotin-dCTP (e.g., biotin-11-dCTP, biotin-14-dCTP), and biotin-dUTP (e.g., biotin-11-dUTP, biotin-16-dUTP, biotin-20-dUTP). 
     The terms “polynucleotide,” “oligonucleotide,” and “nucleic acid” are used interchangeably to generally refer to a polymeric form of nucleotides of any length, either deoxyribonucleotides or ribonucleotides, or analogs thereof, either in single-, double-, or multi-stranded form. A polynucleotide may be exogenous or endogenous to a cell. A polynucleotide may exist in a cell-free environment. A polynucleotide may be a gene or fragment thereof. A polynucleotide may be DNA. A polynucleotide may be RNA. A polynucleotide may have any three-dimensional structure and may perform any function. A polynucleotide may comprise one or more analogs (e.g., altered backbone, sugar, or nucleobase). If present, modifications to the nucleotide structure may be imparted before or after assembly of the polymer. Some non-limiting examples of analogs include: 5-bromouracil, peptide nucleic acid, xeno nucleic acid, morpholinos, locked nucleic acids, glycol nucleic acids, threose nucleic acids, dideoxynucleotides, cordycepin, 7-deaza-GTP, fluorophores (e.g., rhodamine or fluorescein linked to the sugar), thiol containing nucleotides, biotin linked nucleotides, fluorescent base analogs, CpG islands, methyl-7-guanosine, methylated nucleotides, inosine, thiouridine, pseudourdine, dihydrouridine, queuosine, and wyosine. Non-limiting examples of polynucleotides include coding or non-coding regions of a gene or gene fragment, loci (locus) defined from linkage analysis, exons, introns, messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA), short interfering RNA (siRNA), short-hairpin RNA (shRNA), micro-RNA (miRNA), ribozymes, cDNA, recombinant polynucleotides, branched polynucleotides, plasmids, vectors, isolated DNA of any sequence, isolated RNA of any sequence, cell-free polynucleotides including cell-free DNA (cfDNA) and cell-free RNA (cfRNA), nucleic acid probes, and primers. The sequence of nucleotides may be interrupted by non-nucleotide components. 
     The terms “transfection” or “transfected” generally refer to introduction of a nucleic acid into a cell by non-viral or viral-based methods. The nucleic acid molecules may be gene sequences encoding complete proteins or functional portions thereof. See, e.g., Sambrook et al., 1989, Molecular Cloning: A Laboratory Manual, 18.1-18.88. 
     The terms “peptide,” “polypeptide,” and “protein” are used interchangeably herein to generally refer to a polymer of at least two amino acid residues joined by peptide bond(s). This term does not connote a specific length of polymer, nor is it intended to imply or distinguish whether the peptide is produced using recombinant techniques, chemical or enzymatic synthesis, or is naturally occurring. The terms apply to naturally occurring amino acid polymers as well as amino acid polymers comprising at least one modified amino acid. In some cases, the polymer may be interrupted by non-amino acids. The terms include amino acid chains of any length, including full length proteins, and proteins with or without secondary and/or tertiary structure (e.g., domains). The terms also encompass an amino acid polymer that has been modified, for example, by disulfide bond formation, glycosylation, lipidation, acetylation, phosphorylation, oxidation, and any other manipulation such as conjugation with a labeling component. The terms “amino acid” and “amino acids,” as used herein, generally refer to natural and non-natural amino acids, including, but not limited to, modified amino acids and amino acid analogues. Modified amino acids may include natural amino acids and non-natural amino acids, which have been chemically modified to include a group or a chemical moiety not naturally present on the amino acid. Amino acid analogues may refer to amino acid derivatives. The term “amino acid” includes both D-amino acids and L-amino acids. 
     As used herein, the “non-native” can generally refer to a nucleic acid or polypeptide sequence that is not found in a native nucleic acid or protein. Non-native may refer to affinity tags. Non-native may refer to fusions. Non-native may refer to a naturally occurring nucleic acid or polypeptide sequence that comprises mutations, insertions and/or deletions. A non-native sequence may exhibit and/or encode for an activity (e.g., enzymatic activity, methyltransferase activity, acetyltransferase activity, kinase activity, ubiquitinating activity, etc.) that may also be exhibited by the nucleic acid and/or polypeptide sequence to which the non-native sequence is fused. A non-native nucleic acid or polypeptide sequence may be linked to a naturally-occurring nucleic acid or polypeptide sequence (or a variant thereof) by genetic engineering to generate a chimeric nucleic acid and/or polypeptide sequence encoding a chimeric nucleic acid and/or polypeptide. 
     The term “promoter”, as used herein, generally refers to the regulatory DNA region which controls transcription or expression of a gene and which may be located adjacent to or overlapping a nucleotide or region of nucleotides at which RNA transcription is initiated. A promoter may contain specific DNA sequences which bind protein factors, often referred to as transcription factors, which facilitate binding of RNA polymerase to the DNA leading to gene transcription. A ‘basal promoter’, also referred to as a ‘core promoter’, may generally refer to a promoter that contains all the basic necessary elements to promote transcriptional expression of an operably linked polynucleotide. Eukaryotic basal promoters typically, though not necessarily, contain a TATA-box and/or a CAAT box. 
     The term “expression”, as used herein, generally refers to the process by which a nucleic acid sequence or a polynucleotide is transcribed from a DNA template (such as into mRNA or other RNA transcript) and/or the process by which a transcribed mRNA is subsequently translated into peptides, polypeptides, or proteins. Transcripts and encoded polypeptides may be collectively referred to as “gene product.” If the polynucleotide is derived from genomic DNA, expression may include splicing of the mRNA in a eukaryotic cell. 
     As used herein, “operably linked”, “operable linkage”, “operatively linked”, or grammatical equivalents thereof generally refer to juxtaposition of genetic elements, e.g., a promoter, an enhancer, a polyadenylation sequence, etc., wherein the elements are in a relationship permitting them to operate in the expected manner. For instance, a regulatory element, which may comprise promoter and/or enhancer sequences, is operatively linked to a coding region if the regulatory element helps initiate transcription of the coding sequence. There may be intervening residues between the regulatory element and coding region so long as this functional relationship is maintained. 
     A “vector” as used herein, generally refers to a macromolecule or association of macromolecules that comprises or associates with a polynucleotide and which may be used to mediate delivery of the polynucleotide to a cell. Examples of vectors include plasmids, viral vectors, liposomes, and other gene delivery vehicles. The vector generally comprises genetic elements, e.g., regulatory elements, operatively linked to a gene to facilitate expression of the gene in a target. 
     As used herein, “an expression cassette” and “a nucleic acid cassette” are used interchangeably generally to refer to a combination of nucleic acid sequences or elements that are expressed together or are operably linked for expression. In some cases, an expression cassette refers to the combination of regulatory elements and a gene or genes to which they are operably linked for expression. 
     A “functional fragment” of a DNA or protein sequence generally refers to a fragment that retains a biological activity (either functional or structural) that is substantially similar to a biological activity of the full-length DNA or protein sequence. A biological activity of a DNA sequence may be its ability to influence expression in a manner known to be attributed to the full-length sequence. 
     As used herein, an “engineered” object generally indicates that the object has been modified by human intervention. According to non-limiting examples: a nucleic acid may be modified by changing its sequence to a sequence that does not occur in nature; a nucleic acid may be modified by ligating it to a nucleic acid that it does not associate with in nature such that the ligated product possesses a function not present in the original nucleic acid; an engineered nucleic acid may synthesized in vitro with a sequence that does not exist in nature; a protein may be modified by changing its amino acid sequence to a sequence that does not exist in nature; an engineered protein may acquire a new function or property. An “engineered” system comprises at least one engineered component. 
     As used herein, “synthetic” and “artificial” are used interchangeably to refer to a protein or a domain thereof that has low sequence identity (e.g., less than 50% sequence identity, less than 25% sequence identity, less than 10% sequence identity, less than 5% sequence identity, less than 1% sequence identity) to a naturally occurring human protein. For example, VPR and VP64 domains are synthetic transactivation domains. 
     The term “tracrRNA” or “tracr sequence”, as used herein, can generally refer to a nucleic acid with at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or 100% sequence identity and/or sequence similarity to a wild type exemplary tracrRNA sequence (e.g., a tracrRNA from  S. pyogenes S. aureus,  etc or SEQ ID NOs: 5476-5511). tracrRNA can refer to a nucleic acid with at most about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% sequence identity and/or sequence similarity to a wild type exemplary tracrRNA sequence (e.g., a tracrRNA from  S. pyogenes S. aureus,  etc). tracrRNA may refer to a modified form of a tracrRNA that can comprise a nucleotide change such as a deletion, insertion, or substitution, variant, mutation, or chimera. A tracrRNA may refer to a nucleic acid that can be at least about 60% identical to a wild type exemplary tracrRNA (e.g., a tracrRNA from  S. pyogenes S. aureus,  etc) sequence over a stretch of at least 6 contiguous nucleotides. For example, a tracrRNA sequence can be at least about 60% identical, at least about 65% identical, at least about 70% identical, at least about 75% identical, at least about 80% identical, at least about 85% identical, at least about 90% identical, at least about 95% identical, at least about 98% identical, at least about 99% identical, or 100% identical to a wild type exemplary tracrRNA (e.g., a tracrRNA from  S. pyogenes S. aureus,  etc) sequence over a stretch of at least 6 contiguous nucleotides. Type II tracrRNA sequences can be predicted on a genome sequence by identifying regions with complementarity to part of the repeat sequence in an adjacent CRISPR array. 
     As used herein, a “guide nucleic acid” can generally refer to a nucleic acid that may hybridize to another nucleic acid. A guide nucleic acid may be RNA. A guide nucleic acid may be DNA. The guide nucleic acid may be programmed to bind to a sequence of nucleic acid site-specifically. The nucleic acid to be targeted, or the target nucleic acid, may comprise nucleotides. The guide nucleic acid may comprise nucleotides. A portion of the target nucleic acid may be complementary to a portion of the guide nucleic acid. The strand of a double-stranded target polynucleotide that is complementary to and hybridizes with the guide nucleic acid may be called the complementary strand. The strand of the double-stranded target polynucleotide that is complementary to the complementary strand, and therefore may not be complementary to the guide nucleic acid may be called noncomplementary strand. A guide nucleic acid may comprise a polynucleotide chain and can be called a “single guide nucleic acid.” A guide nucleic acid may comprise two polynucleotide chains and may be called a “double guide nucleic acid.” If not otherwise specified, the term “guide nucleic acid” may be inclusive, referring to both single guide nucleic acids and double guide nucleic acids. A guide nucleic acid may comprise a segment that can be referred to as a “nucleic acid-targeting segment” or a “nucleic acid-targeting sequence.” A nucleic acid-targeting segment may comprise a sub-segment that may be referred to as a “protein binding segment” or “protein binding sequence” or “Cas protein binding segment”. 
     The term “sequence identity” or “percent identity” in the context of two or more nucleic acids or polypeptide sequences, generally refers to two (e.g., in a pairwise alignment) or more (e.g., in a multiple sequence alignment) sequences that are the same or have a specified percentage of amino acid residues or nucleotides that are the same, when compared and aligned for maximum correspondence over a local or global comparison window, as measured using a sequence comparison algorithm. Suitable sequence comparison algorithms for polypeptide sequences include, e.g., BLASTP using parameters of a wordlength (W) of 3, an expectation (E) of 10, and the BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment for polypeptide sequences longer than 30 residues; BLASTP using parameters of a wordlength (W) of 2, an expectation (E) of 1000000, and the PAM30 scoring matrix setting gap costs at 9 to open gaps and 1 to extend gaps for sequences of less than 30 residues (these are the default parameters for BLASTP in the BLAST suite available at https://blast.ncbi.nlm.nih.gov); CLUSTALW with parameters of; the Smith-Waterman homology search algorithm with parameters of a match of 2, a mismatch of −1, and a gap of −1; MUSCLE with default parameters; MAFFT with parameters retree of 2 and maxiterations of 1000; Novafold with default parameters; HMMER hmmalign with default parameters. 
     Included in the current disclosure are variants of any of the enzyme described herein with one or more conservative amino acid substitutions. Such conservative substitutions can be made in the amino acid sequence of a polypeptide without disrupting the three-dimensional structure or function of the polypeptide. Conservative substitutions can be accomplished by substituting amino acids with similar hydrophobicity, polarity, and R chain length for one another. Additionally or alternatively, by comparing aligned sequences of homologous proteins from different species, conservative substitutions can be identified by locating amino acid residues that have been mutated between species (e.g. non-conserved residues) without altering the basic functions of the encoded proteins. Such conservatively substituted variants may include variants with at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of the endonuclease protein sequences described herein (e.g. MG1, MG2, MG3, MG4, MG6, MG7, MG14, MG15, MG16, MG18, MG21, MG22, or MG23 family endonucleases described herein). In some embodiments, such conservatively substituted variants are functional variants. Such functional variants can encompass sequences with substitutions such that the activity of critical active site residues of the endonuclease are not disrupted. 
     Conservative substitution tables providing functionally similar amino acids are available from a variety of references (see, for e.g., Creighton, Proteins: Structures and Molecular Properties (W H Freeman &amp; Co.; 2nd edition (December 1993)). The following eight groups each contain amino acids that are conservative substitutions for one another:
     1) Alanine (A), Glycine (G);   2) Aspartic acid (D), Glutamic acid (E);   3) Asparagine (N), Glutamine (Q);   4) Arginine (R), Lysine (K);   5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V);   6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W);   7) Serine (S), Threonine (T); and   8) Cysteine (C), Methionine (M).   

     As used herein, the term “RuvC_III domain” generally refers to a third discontinuous segment of a RuvC endonuclease domain (the RuvC nuclease domain being comprised of three discontiguous segments, RuvC_I, RuvC_II, and RuvC_III). A RuvC domain or segments thereof can generally be identified by alignment to known domain sequences, structural alignment to proteins with annotated domains, or by comparison to Hidden Markov Models (HMMs) built based on known domain sequences (e.g., Pfam HMM PF18541 for RuvC_III). 
     As used herein, the term “HNH domain” generally refers to an endonuclease domain having characteristic histidine and asparagine residues. An HNH domain can generally be identified by alignment to known domain sequences, structural alignment to proteins with annotated domains, or by comparison to Hidden Markov Models (HMMs) built based on known domain sequences (e.g., Pfam HMM PF01844 for domain HNH). 
     Overview 
     The discovery of new Cas enzymes with unique functionality and structure may offer the potential to further disrupt deoxyribonucleic acid (DNA) editing technologies, improving speed, specificity, functionality, and ease of use. Relative to the predicted prevalence of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) systems in microbes and the sheer diversity of microbial species, relatively few functionally characterized CRISPR/Cas enzymes exist in the literature. This is partly because a huge number of microbial species may not be readily cultivated in laboratory conditions. Metagenomic sequencing from natural environmental niches that represent large numbers of microbial species may offer the potential to drastically increase the number of new CRISPR/Cas systems known and speed the discovery of new oligonucleotide editing functionalities. A recent example of the fruitfulness of such an approach is demonstrated by the 2016 discovery of CasX/CasY CRISPR systems from metagenomic analysis of natural microbial communities. 
     CRISPR/Cas systems are RNA-directed nuclease complexes that have been described to function as an adaptive immune system in microbes. In their natural context, CRISPR/Cas systems occur in CRISPR (clustered regularly interspaced short palindromic repeats) operons or loci, which generally comprise two parts: (i) an array of short repetitive sequences (30-40 bp) separated by equally short spacer sequences, which encode the RNA-based targeting element; and (ii) ORFs encoding the Cas encoding the nuclease polypeptide directed by the RNA-based targeting element alongside accessory proteins/enzymes. Efficient nuclease targeting of a particular target nucleic acid sequence generally requires both (i) complementary hybridization between the first 6-8 nucleic acids of the target (the target seed) and the crRNA guide; and (ii) the presence of a protospacer-adjacent motif (PAM) sequence within a defined vicinity of the target seed (the PAM usually being a sequence not commonly represented within the host genome). Depending on the exact function and organization of the system, CRISPR-Cas systems are commonly organized into 2 classes, 5 types and 16 subtypes based on shared functional characteristics and evolutionary similarity. 
     Class I CRISPR-Cas systems have large, multisubunit effector complexes, and comprise Types I, III, and IV. 
     Type I CRISPR-Cas systems are considered of moderate complexity in terms of components. In Type I CRISPR-Cas systems, the array of RNA-targeting elements is transcribed as a long precursor crRNA (pre-crRNA) that is processed at repeat elements to liberate short, mature crRNAs that direct the nuclease complex to nucleic acid targets when they are followed by a suitable short consensus sequence called a protospacer-adjacent motif (PAM). This processing occurs via an endoribonuclease subunit (Cas6) of a large endonuclease complex called Cascade, which also comprises a nuclease (Cas3) protein component of the crRNA-directed nuclease complex. Cas I nucleases function primarily as DNA nucleases. 
     Type III CRISPR systems may be characterized by the presence of a central nuclease, known as Cas10, alongside a repeat-associated mysterious protein (RAMP) that comprises Csm or Cmr protein subunits. Like in Type I systems, the mature crRNA is processed from a pre-crRNA using a Cas6-like enzyme. Unlike type I and II systems, type III systems appear to target and cleave DNA-RNA duplexes (such as DNA strands being used as templates for an RNA polymerase). 
     Type IV CRISPR-Cas systems possess an effector complex that consists of a highly reduced large subunit nuclease (csf1), two genes for RAMP proteins of the Cas5 (csf3) and Cas7 (csf2) groups, and, in some cases, a gene for a predicted small subunit; such systems are commonly found on endogenous plasmids. 
     Class II CRISPR-Cas systems generally have single-polypeptide multidomain nuclease effectors, and comprise Types II, V and VI. 
     Type II CRISPR-Cas systems are considered the simplest in terms of components. In Type II CRISPR-Cas systems, the processing of the CRISPR array into mature crRNAs does not require the presence of a special endonuclease subunit, but rather a small trans-encoded crRNA (tracrRNA) with a region complementary to the array repeat sequence; the tracrRNA interacts with both its corresponding effector nuclease (e.g. Cas9) and the repeat sequence to form a precursor dsRNA structure, which is cleaved by endogenous RNAse III to generate a mature effector enzyme loaded with both tracrRNA and crRNA. Cas II nucleases are known as DNA nucleases. Type 2 effectors generally exhibit a structure consisting of a RuvC-like endonuclease domain that adopts the RNase H fold with an unrelated HNH nuclease domain inserted within the folds of the RuvC-like nuclease domain. The RuvC-like domain is responsible for the cleavage of the target (e.g., crRNA complementary) DNA strand, while the HNH domain is responsible for cleavage of the displaced DNA strand. 
     Type V CRISPR-Cas systems are characterized by a nuclease effector (e.g. Cas12) structure similar to that of Type II effectors, comprising a RuvC-like domain. Similar to Type II, most (but not all) Type V CRISPR systems use a tracrRNA to process pre-crRNAs into mature crRNAs; however, unlike Type II systems which requires RNAse III to cleave the pre-crRNA into multiple crRNAs, type V systems are capable of using the effector nuclease itself to cleave pre-crRNAs. Like Type-II CRISPR-Cas systems, Type V CRISPR-Cas systems are again known as DNA nucleases. Unlike Type II CRISPR-Cas systems, some Type V enzymes (e.g., Cas12a) appear to have a robust single-stranded nonspecific deoxyribonuclease activity that is activated by the first crRNA directed cleavage of a double-stranded target sequence. 
     Type VI CRIPSR-Cas systems have RNA-guided RNA endonucleases. Instead of RuvC-like domains, the single polypeptide effector of Type VI systems (e.g. Cas13) comprises two HEPN ribonuclease domains. Differing from both Type II and V systems, Type VI systems also appear to not need a tracrRNA for processing of pre-crRNA into crRNA. Similar to type V systems, however, some Type VI systems (e.g., C2C2) appear to possess robust single-stranded nonspecific nuclease (ribonuclease) activity activated by the first crRNA directed cleavage of a target RNA. 
     Because of their simpler architecture, Class II CRISPR-Cas have been most widely adopted for engineering and development as designer nuclease/genome editing applications. 
     One of the early adaptations of such a system for in vitro use can be found in Jinek et al. (Science. 2012 Aug. 17; 337(6096):816-21, which is entirely incorporated herein by reference). The Jinek study first described a system that involved (i) recombinantly-expressed, purified full-length Cas9 (e.g., a Class II, Type II Cas enzyme) isolated from  S. pyogenes  SF370, (ii) purified mature ˜42 nt crRNA bearing a ˜20 nt 5′ sequence complementary to the target DNA sequence desired to be cleaved followed by a 3′ tracr-binding sequence (the whole crRNA being in vitro transcribed from a synthetic DNA template carrying a T7 promoter sequence); (iii) purified tracrRNA in vitro transcribed from a synthetic DNA template carrying a T7 promoter sequence, and (iv) Mg 2+ . Jinek later described an improved, engineered system wherein the crRNA of (ii) is joined to the 5′ end of (iii) by a linker (e.g., GAAA) to form a single fused synthetic guide RNA (sgRNA) capable of directing Cas9 to a target by itself (compare top and bottom panel of  FIG. 2 ). 
     Mali et al. (Science. 2013 Feb. 15; 339(6121): 823-826.), which is entirely incorporated herein by reference, later adapted this system for use in mammalian cells by providing DNA vectors encoding (i) an ORF encoding codon-optimized Cas9 (e.g., a Class II, Type II Cas enzyme) under a suitable mammalian promoter with a C-terminal nuclear localization sequence (e.g., SV40 NLS) and a suitable polyadenylation signal (e.g., TK pA signal); and (ii) an ORF encoding an sgRNA (having a 5′ sequence beginning with G followed by 20 nt of a complementary targeting nucleic acid sequence joined to a 3′ tracr-binding sequence, a linker, and the tracrRNA sequence) under a suitable Polymerase III promoter (e.g., the U6 promoter) . 
     MG1 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 1827-2140. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 1827-2140. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 1827-2140. The endonuclease may comprise a RuvC_III domain having at least about 70% sequence identity to any one of SEQ ID NOs: 1827-1831. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 1827-1831. In some cases, the endonuclease may comprise a RuvC_III domain substantially identical to any one of SEQ ID NOs: 1827-1831. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to SEQ ID NO: 1827. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to SEQ ID NO: 1828. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to SEQ ID NO: 1829. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to SEQ ID NO: 1830. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to SEQ ID NO: 1831. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 3638-3955. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 3638-3955. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 3638-3955. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 3638-3955. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 3638-3955. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 3638-3955. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 3638-3641. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 3638-3641. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 3638-3641. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 3638. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 3638. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 3638. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 3639. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 3639. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 3639. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 3640. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 3640. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 3640. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 3641. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 3641. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 3641. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1-6 or 9-319. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 1-6 or 9-319. In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs:1-4. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 1-4. In some cases, the endonuclease may comprise a peptide motif substantially identical to any one of SEQ ID NOs: 5615, 5616, or 5617. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 1-6 or 9-319, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1-319. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 below, or a combination thereof: 
     
       
         
           
               
             
               
                 TABLE 1  
               
             
            
               
                   
               
               
                 Example NLS Sequences that can be used with Cas Effectors 
               
               
                 According to the Disclosure 
               
            
           
           
               
               
               
            
               
                 Source 
                 NLS amino acid sequence 
                 SEQ ID NO: 
               
               
                   
               
               
                 SV40 
                 PKKKRKV 
                 5597 
               
               
                   
               
               
                 nucleoplasmin bipartite NLS 
                 KRPAATKKAGQAKKKK 
                 5598 
               
               
                   
               
               
                 c-myc NLS 
                 PAAKRVKLD 
                 5599 
               
               
                   
               
               
                 c-myc NLS 
                 RQRRNELKRSP 
                 5600 
               
               
                   
               
               
                 hRNPA1 M9 NLS 
                 NQSSNFGPMKGGNFGGRSSGPYGGGGQYFA 
                 5601 
               
               
                   
                 KPRNQGGY 
                   
               
               
                   
               
               
                 Importin-alpha IBB domain 
                 RMRIZFKNKGKDTAELRRRRVEVSVELRKAK 
                 5602 
               
               
                   
                 KDEQILKRRNV 
                   
               
               
                   
               
               
                 Myoma T protein 
                 VSRKRPRP 
                 5603 
               
               
                   
               
               
                 Myoma T protein 
                 PPKKARED 
                 5604 
               
               
                   
               
               
                 p53 
                 PQPKKKPL 
                 5605 
               
               
                   
               
               
                 mouse c-abl IV 
                 SALIKKKKKMAP 
                 5606 
               
               
                   
               
               
                 influenza virus NS1 
                 DRLRR 
                 5607 
               
               
                   
               
               
                 influenza virus NS1 
                 PKQKKRK 
                 5608 
               
               
                   
               
               
                 Hepatitis virus delta antigen 
                 RKLKKKIKKL 
                 5609 
               
               
                   
               
               
                 mouse Mx1 protein 
                 REKKKELKER 
                 5610 
               
               
                   
               
               
                 human poly(ADP-ribose) 
                 KRKGDEVDGVDEVAKKKSKK 
                 5611 
               
               
                 polymerase 
                   
                   
               
               
                   
               
               
                 steroid hormone receptor 
                 RKCLQAGMNLEARKTKK 
                 5612 
               
               
                 (human) glucocorticoid 
               
               
                   
               
            
           
         
       
     
     In some cases, the endonuclease may be recombinant (e.g., cloned, expressed, and purified by a suitable method such as expression in  E. coli  followed by epitope-tag purification). In some cases, the endonuclease may be derived from a bacterium with a 16S rRNA gene having at least about 90% identity to any one of SEQ ID NOs: 5592-5595. The endonuclease may be derived from a species having a 16S rRNA gene at least about 80%, at least about 82%, at least about 83%, at least about 84%, at least about 85%, at least about 86%, at least about 87%, at least about 88%, at least about 89%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 5592-5595. The endonuclease may be derived from a species having a 16S rRNA gene substantially identical to any one of SEQ ID NOs: 5592-5595. The endonuclease may be derived from a bacterium belonging to the  Phylum Verrucomicrobia  or the  Phylum Candidatus  Peregrinibacteria. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. The tracr sequence may have at least about 80% sequence identity to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of any one of SEQ ID NOs: 5476-5489. In some cases, the tracrRNA may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to at least about 60-90 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of any one of SEQ ID NOs: 5476-5489. In some cases, the tracrRNA may be substantially identical to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of any one of SEQ ID NOs: 5476-5489. The tracrRNA may comprise any of SEQ ID NOs: 5476-5489. 
     In some cases, the at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease may comprise a sequence having at least about 80% identity to any one of SEQ ID NOs: 5461-5464. The sgRNA may comprise a sequence having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 5461-5464. The sgRNA may comprise a sequence substantially identical to any one of SEQ ID NOs: 5461-5464. 
     In some cases, the system above may comprise two different sgRNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus, may modify the target nucleic acid locus. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 1827-2140. The deoxyribonucleic acid (DNA) containing an open reading frame encoding said endonuclease may comprise a sequence substantially identical to any of SEQ ID NOs: 5572-5575 or at variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 5572-5575. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     In some cases, the present disclosure may provide for an expression cassette comprising the system disclosed herein, or the nucleic acid described herein. In some cases, the expression cassette or nucleic acid may be supplied as a vector. In some cases, the expression cassette, nucleic acid, or vector may be supplied in a cell. In some cases, the cell is a cell of a bacterium with a 16S rRNA gene having at least about 90% (e.g., at least about 99%) identity to any one of SEQ ID NOs: 5592-5595. 
     MG2 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 2141-2241. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2141-2241. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 2141-2142. The endonuclease may comprise a RuvC_III domain having at least about 70% sequence identity to any one of SEQ ID NOs: 2141-2142. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2141-2142. In some cases, the endonuclease may comprise a RuvC_II domain substantially identical to any one of SEQ ID NOs: 2141-2142. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 3955-4055. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 3955-4055. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 3955-4055. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 3955-3956. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 3955-3956. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 3955-3956. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 320-420. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 320-420. In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs:320-321. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 320-321. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 320-420, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 320-420. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 or a combination thereof. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. The tracr sequence may have at least about 80% sequence identity to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of any one of SEQ ID NOs: 5490-5494. In some cases, the tracrRNA may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to at least about 60-90 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of any one of SEQ ID NOs: 5490-5494. In some cases, the tracrRNA may be substantially identical to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of any one of SEQ ID NOs: 5490-5494. The tracrRNA may comprise any of SEQ ID NOs: 5490-5494. 
     In some cases, the at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease may comprise a sequence having at least about 80% identity to SEQ ID NO: 5465. The sgRNA may comprise a sequence having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NO: 5465. The sgRNA may comprise a sequence substantially identical to SEQ ID NO: 5465. 
     In some cases, the system above may comprise two different sgRNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus of interest. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus of interest, may modify the target nucleic acid locus of interest. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 2141-2241. The deoxyribonucleic acid (DNA) containing an open reading frame encoding said endonuclease may comprise a sequence substantially identical to any of SEQ ID NOs: 5576-5577 or at variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 5576-5577. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     MG3 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 2242-2251. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2242-2251. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 2242-2251. The endonuclease may comprise a RuvC_III domain having at least about 70% sequence identity to any one of SEQ ID NOs: 2242-2244. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2242-2244. In some cases, the endonuclease may comprise a RuvC_III domain substantially identical to any one of SEQ ID NOs: 2242-2244. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4056-4066. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4056-4066. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4056-4066. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4056-4058. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4056-4058. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4056-4058. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 421-431. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 421-431. In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs:421-423. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 421-423. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 421-431, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 421-431. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 or a combination thereof. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. The tracr sequence may have at least about 80% sequence identity to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of any one of SEQ ID NOs: 5495-5502. In some cases, the tracrRNA may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to at least about 60-90 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of any one of SEQ ID NOs: 5495-5502. In some cases, the tracrRNA may be substantially identical to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of any one of SEQ ID NOs: 5495-5502. The tracrRNA may comprise any of SEQ ID NOs: 5495-5502. 
     In some cases, the at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease may comprise a sequence having at least about 80% identity to any one of SEQ ID NOs: 5466-5467. The sgRNA may comprise a sequence having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 5466-5467. The sgRNA may comprise a sequence substantially identical to any one of SEQ ID NOs: 5466-5467. 
     In some cases, the system above may comprise two different sgRNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus of interest. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus of interest, may modify the target nucleic acid locus of interest. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 2242-2251. The deoxyribonucleic acid (DNA) containing an open reading frame encoding said endonuclease may comprise a sequence substantially identical to any of SEQ ID NOs: 5578-5580 or at variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 5578-5580. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     MG4 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 2253-2481. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2253-2481. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 2253-2481. The endonuclease may comprise a RuvC_III domain having at least about 70% sequence identity to any one of SEQ ID NOs: 2253-2481. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2253-2481. In some cases, the endonuclease may comprise a RuvC_III domain substantially identical to any one of SEQ ID NOs: 2253-2481. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4067-4295. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4067-4295. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4067-4295. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4067-4295. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4067-4295. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4067-4295. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 432-660. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 432-660. In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 432-660. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 432-660. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 432-660, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 432-660. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 or a combination thereof. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. The tracr sequence may have at least about 80% sequence identity to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5503. In some cases, the tracrRNA may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to at least about 60-90 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5503. In some cases, the tracrRNA may be substantially identical to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5503. The tracrRNA may comprise SEQ ID NO: 5503. 
     In some cases, the at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease may comprise a sequence having at least about 80% identity to SEQ ID NO: 5468. The sgRNA may comprise a sequence having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NO: 5468. The sgRNA may comprise a sequence substantially identical to SEQ ID NO: 5468. 
     In some cases, the system above may comprise two different sgRNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus of interest. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus of interest, may modify the target nucleic acid locus of interest. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 2253-2481. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     MG6 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 2482-2489. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2482-2489. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 2482-2489. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4296-4303. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4296-4303. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4056-4066. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 661-668. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 661-668. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 661-668, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 661-668. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 or a combination thereof. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. 
     In some cases, the system above may comprise two different guide RNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus of interest. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus of interest, may modify the target nucleic acid locus of interest. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 2482-2489. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     MG7 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 2490-2498. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2490-2498. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 2490-2498. The endonuclease may comprise a RuvC_III domain having at least about 70% sequence identity to any one of SEQ ID NOs: 2490-2498. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2490-2498. In some cases, the endonuclease may comprise a RuvC_III domain substantially identical to any one of SEQ ID NOs: 2490-2498. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4304-4312. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4304-4312. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4304-4312. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4304-4312. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4304-4312. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4304-4312. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 669-677. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 669-677. In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 669-677. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 669-677. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 669-677, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 669-677. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 or a combination thereof. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. The tracr sequence may have at least about 80% sequence identity to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5504. In some cases, the tracrRNA may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to at least about 60-90 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5504. In some cases, the tracrRNA may be substantially identical to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5504. The tracrRNA may comprise SEQ ID NO: 5504. 
     In some cases, the system above may comprise two different sgRNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus of interest. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus of interest, may modify the target nucleic acid locus of interest. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 2490-2498. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     MG14 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 2499-2750. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2499-2750. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 2499-2750. The endonuclease may comprise a RuvC_III domain having at least about 70% sequence identity to any one of SEQ ID NOs: 2499-2750. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2499-2750. In some cases, the endonuclease may comprise a RuvC_III domain substantially identical to any one of SEQ ID NOs: 2499-2750. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4313-4564. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4313-4564. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4313-4564. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4313-4564. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4067-4295. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4313-4564. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 678-929. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 678-929. In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 678-929. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 678-929. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 678-929, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 678-929. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 or a combination thereof. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. The tracr sequence may have at least about 80% sequence identity to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5505. In some cases, the tracrRNA may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to at least about 60-90 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5505. In some cases, the tracrRNA may be substantially identical to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5505. The tracrRNA may comprise SEQ ID NO: 5505. 
     In some cases, the at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease may comprise a sequence having at least about 80% identity to SEQ ID NO: 5469. The sgRNA may comprise a sequence having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NO: 5469. The sgRNA may comprise a sequence substantially identical to SEQ ID NO: 5469. 
     In some cases, the system above may comprise two different sgRNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus of interest. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus of interest, may modify the target nucleic acid locus of interest. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 2499-2750. The deoxyribonucleic acid (DNA) containing an open reading frame encoding said endonuclease may comprise a sequence substantially identical to SEQ ID NO: 5581 or at variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NO: 5581. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     MG15 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 2751-2913. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2751-2913. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 2751-2913. The endonuclease may comprise a RuvC_III domain having at least about 70% sequence identity to any one of SEQ ID NOs: 2751-2913. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2751-2913. In some cases, the endonuclease may comprise a RuvC_III domain substantially identical to any one of SEQ ID NOs: 2751-2913. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4565-4727. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4565-4727. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4565-4727. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4565-4727. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4565-4727. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4565-4727. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 930-1092. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 930-1092. In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 930-1092. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 930-1092. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 930-1092, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 930-1092. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 or a combination thereof. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. The tracr sequence may have at least about 80% sequence identity to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5506. In some cases, the tracrRNA may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to at least about 60-90 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5506. In some cases, the tracrRNA may be substantially identical to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5506. The tracrRNA may comprise SEQ ID NO: 5506. 
     In some cases, the at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease may comprise a sequence having at least about 80% identity to SEQ ID NO: 5470. The sgRNA may comprise a sequence having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NO: 5470. The sgRNA may comprise a sequence substantially identical to SEQ ID NO: 5470. 
     In some cases, the system above may comprise two different sgRNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus of interest. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus of interest, may modify the target nucleic acid locus of interest. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 2751-2913. The deoxyribonucleic acid (DNA) containing an open reading frame encoding said endonuclease may comprise a sequence substantially identical to SEQ ID NO: 5582 or at variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NO: 5582. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     MG16 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 2914-3174. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2914-3174. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 2914-3174. The endonuclease may comprise a RuvC_III domain having at least about 70% sequence identity to any one of SEQ ID NOs: 2914-3174. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 2914-3174. In some cases, the endonuclease may comprise a RuvC_III domain substantially identical to any one of SEQ ID NOs: 2914-3174. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4728-4988. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4728-4988. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4728-4988. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4728-4988. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4728-4988. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4728-4988. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1093-1353. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 1093-1353. In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1093-1353. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 1093-1353. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 1093-1353, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1093-1353. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 or a combination thereof. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. The tracr sequence may have at least about 80% sequence identity to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5507. In some cases, the tracrRNA may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to at least about 60-90 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5507. In some cases, the tracrRNA may be substantially identical to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5507. The tracrRNA may comprise SEQ ID NO: 5507. 
     In some cases, the at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease may comprise a sequence having at least about 80% identity to SEQ ID NO: 5471. The sgRNA may comprise a sequence having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NO: 5471. The sgRNA may comprise a sequence substantially identical to SEQ ID NO: 5471. 
     In some cases, the system above may comprise two different sgRNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus of interest. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus of interest, may modify the target nucleic acid locus of interest. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 2914-3174. The deoxyribonucleic acid (DNA) containing an open reading frame encoding said endonuclease may comprise a sequence substantially identical to SEQ ID NO: 5583 or at variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NO: 5583. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     MG18 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 3175-3300. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 3175-3300. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 3175-3300. The endonuclease may comprise a RuvC_III domain having at least about 70% sequence identity to any one of SEQ ID NOs: 3175-3300. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 3175-3300. In some cases, the endonuclease may comprise a RuvC_III domain substantially identical to any one of SEQ ID NOs: 3175-3300. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4989-5146. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4989-5146. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4989-5146. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 4989-5146. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 4989-5146. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 4989-5146. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1354-1511. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 1354-1511. In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1354-1511. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 1354-1511. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 1354-1511, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1354-1511. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 or a combination thereof. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. The tracr sequence may have at least about 80% sequence identity to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5508. In some cases, the tracrRNA may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to at least about 60-90 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5508. In some cases, the tracrRNA may be substantially identical to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5508. The tracrRNA may comprise SEQ ID NO: 5508. 
     In some cases, the at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease may comprise a sequence having at least about 80% identity to SEQ ID NO: 5472. The sgRNA may comprise a sequence having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NO: 5472. The sgRNA may comprise a sequence substantially identical to SEQ ID NO: 5472. 
     In some cases, the system above may comprise two different sgRNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus of interest. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus of interest, may modify the target nucleic acid locus of interest. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 3175-3300. The deoxyribonucleic acid (DNA) containing an open reading frame encoding said endonuclease may comprise a sequence substantially identical to SEQ ID NOs: 5584 or at variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NOs: 5584. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     MG21 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 3331-3474. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 3331-3474. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 3331-3474. The endonuclease may comprise a RuvC_III domain having at least about 70% sequence identity to any one of SEQ ID NOs: 3331-3474. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 3331-3474. In some cases, the endonuclease may comprise a RuvC_III domain substantially identical to any one of SEQ ID NOs: 3331-3474. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 5147-5290. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 5147-5290. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 5147-5290. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 5147-5290. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 5147-5290. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 5147-5290. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1512-1655. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 1512-1655. In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1512-1655. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 1512-1655. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 1512-1655, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1512-1655. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 or a combination thereof. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. The tracr sequence may have at least about 80% sequence identity to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5509. In some cases, the tracrRNA may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to at least about 60-90 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5509. In some cases, the tracrRNA may be substantially identical to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5509. The tracrRNA may comprise SEQ ID NO: 5509. 
     In some cases, the at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease may comprise a sequence having at least about 80% identity to SEQ ID NO: 5473. The sgRNA may comprise a sequence having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NO: 5473. The sgRNA may comprise a sequence substantially identical to SEQ ID NO: 5473. 
     In some cases, the system above may comprise two different sgRNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus of interest. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus of interest, may modify the target nucleic acid locus of interest. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 3331-3474. The deoxyribonucleic acid (DNA) containing an open reading frame encoding said endonuclease may comprise a sequence substantially identical to SEQ ID NOs: 5585 or at variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NOs: 5585. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     MG22 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 3475-3568. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 3475-3568. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 3475-3568. The endonuclease may comprise a RuvC_III domain having at least about 70% sequence identity to any one of SEQ ID NOs: 3475-3568. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 3475-3568. In some cases, the endonuclease may comprise a RuvC_III domain substantially identical to any one of SEQ ID NOs: 3475-3568. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 5291-5389. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 5291-5389. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 5291-5389. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 5291-5389. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 5291-5389. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 5291-5389. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1656-1755. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 1656-1755. In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1656-1755. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 1656-1755. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 432-660, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1656-1755. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 or a combination thereof. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. The tracr sequence may have at least about 80% sequence identity to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5510. In some cases, the tracrRNA may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to at least about 60-90 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5510. In some cases, the tracrRNA may be substantially identical to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5510. The tracrRNA may comprise SEQ ID NO: 5510. 
     In some cases, the at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease may comprise a sequence having at least about 80% identity to SEQ ID NO: 5474. The sgRNA may comprise a sequence having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NO: 5474. The sgRNA may comprise a sequence substantially identical to SEQ ID NO: 5474. 
     In some cases, the system above may comprise two different sgRNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus of interest. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus of interest, may modify the target nucleic acid locus of interest. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 3475-3568. The deoxyribonucleic acid (DNA) containing an open reading frame encoding said endonuclease may comprise a sequence substantially identical to SEQ ID NOs: 5586 or at variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NOs: 5586. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     MG23 Enzymes 
     In one aspect, the present disclosure provides for an engineered nuclease system comprising (a) an endonuclease. In some cases, the endonuclease is a Cas endonuclease. In some cases, the endonuclease is a Type II, Class II Cas endonuclease. The endonuclease may comprise a RuvC_III domain, wherein said RuvC_III domain has at least about 70% sequence identity to any one of SEQ ID NOs: 3569-3637. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the RuvC_III domain has at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 3569-3637. In some cases, the endonuclease may comprise a RuvC_III domain, wherein the substantially identical to any one of SEQ ID NOs: 3569-3637. The endonuclease may comprise a RuvC_III domain having at least about 70% sequence identity to any one of SEQ ID NOs: 3569-3637. In some cases, the endonuclease may comprise a RuvC_III domain having at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99% identity to any one of SEQ ID NOs: 3569-3637. In some cases, the endonuclease may comprise a RuvC_III domain substantially identical to any one of SEQ ID NOs: 3569-3637. 
     The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 5390-5460. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 5390-5460. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 5390-5460. The endonuclease may comprise an HNH domain having at least about 70% identity to any one of SEQ ID NOs: 5390-5460. In some cases, the endonuclease may comprise an HNH domain having at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identical to any one of SEQ ID NOs: 5390-5460. The endonuclease may comprise an HNH domain substantially identical to any one of SEQ ID NOs: 5390-5460. 
     In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1756-1826. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 1756-1826. In some cases, the endonuclease may comprise a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1756-1826. In some cases, the endonuclease may be substantially identical to any one of SEQ ID NOs: 1756-1826. 
     In some cases, the endonuclease may comprise a variant having one or more nuclear localization sequences (NLSs). The NLS may be proximal to the N- or C-terminus of said endonuclease. The NLS may be appended N-terminal or C-terminal to any one of SEQ ID NOs: 1756-1826, or to a variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to any one of SEQ ID NOs: 1756-1826. The NLS may be an SV40 large T antigen NLS. The NLS may be a c-myc NLS. The NLS can comprise a sequence with at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99% identity to any one of SEQ ID NOs: 5593-5608. The NLS can comprise a sequence substantially identical to any one of SEQ ID NOs: 5593-5608. The NLS can comprise any of the sequences in Table 1 or a combination thereof. 
     In some cases, sequence identity may be determined by the BLASTP, CLUSTALW, MUSCLE, MAFFT, Novafold, or Smith-Waterman homology search algorithm. The sequence identity may be determined by the BLASTP algorithm using parameters of a wordlength (W) of 3, an expectation (E) of 10, and using a BLOSUM62 scoring matrix setting gap costs at existence of 11, extension of 1, and using a conditional compositional score matrix adjustment. 
     In some cases, the system above may comprise (b) at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease bearing a 5′ targeting region complementary to a desired cleavage sequence. In some cases, the 5′ targeting region may comprises a PAM sequence compatible with the endonuclease. In some cases, the 5′ most nucleotide of the targeting region may be G. In some cases, the 5′ targeting region may be 15-23 nucleotides in length. The guide sequence and the tracr sequence may be supplied as separate ribonucleic acids (RNAs) or a single ribonucleic acid (RNA). The guide RNA may comprise a crRNA tracrRNA binding sequence 3′ to the targeting region. The guide RNA may comprise a tracrRNA sequence preceded by a 4-nucleotide linker 3′ to the crRNA tracrRNA binding region. The sgRNA may comprise, from 5′ to 3′: a non-natural guide nucleic acid sequence capable of hybridizing to a target sequence in a cell; and a tracr sequence. In some cases, the non-natural guide nucleic acid sequence and the tracr sequence are covalently linked. 
     In some cases, the tracr sequence may have a particular sequence. The tracr sequence may have at least about 80% to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of a natural tracrRNA sequence. The tracr sequence may have at least about 80% sequence identity to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5511. In some cases, the tracrRNA may have at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to at least about 60-90 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5511. In some cases, the tracrRNA may be substantially identical to at least about 60-100 (e.g., at least about 60, at least about 65, at least about 70, at least about 75, at least about 80, at least about 85, or at least about 90) consecutive nucleotides of SEQ ID NO: 5511. The tracrRNA may comprise SEQ ID NO: 5511. 
     In some cases, the at least one engineered synthetic guide ribonucleic acid (sgRNA) capable of forming a complex with the endonuclease may comprise a sequence having at least about 80% identity to SEQ ID NO: 5475. The sgRNA may comprise a sequence having at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NO: 5475. The sgRNA may comprise a sequence substantially identical to SEQ ID NO: 5475. 
     In some cases, the system above may comprise two different sgRNAs targeting a first region and a second region for cleavage in a target DNA locus, wherein the second region is 3′ to the first region. In some cases, the system above may comprise a single- or double-stranded DNA repair template comprising from 5′ to 3′: a first homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 5′ to the first region, a synthetic DNA sequence of at least about 10 nucleotides, and a second homology arm comprising a sequence of at least about 20 (e.g., at least about 40, 80, 120, 150, 200, 300, 500, or 1 kb) nucleotides 3′ to the second region. 
     In another aspect, the present disclosure provides a method for modifying a target nucleic acid locus of interest. The method may comprise delivering to the target nucleic acid locus any of the non-natural systems disclosed herein, including an enzyme and at least one synthetic guide RNA (sgRNA) disclosed herein. The enzyme may form a complex with the at least one sgRNA, and upon binding of the complex to the target nucleic acid locus of interest, may modify the target nucleic acid locus of interest. Delivering the enzyme to said locus may comprise transfecting a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise electroporating a cell with the system or nucleic acids encoding the system. Delivering the nuclease to said locus may comprise incubating the system in a buffer with a nucleic acid comprising the locus of interest. In some cases, the target nucleic acid locus comprises deoxyribonucleic acid (DNA) or ribonucleic acid (RNA). The target nucleic acid locus may comprise genomic DNA, viral DNA, viral RNA, or bacterial DNA. The target nucleic acid locus may be within a cell. The target nucleic acid locus may be in vitro. The target nucleic acid locus may be within a eukaryotic cell or a prokaryotic cell. The cell may be an animal cell, a human cell, bacterial cell, archaeal cell, or a plant cell. The enzyme may induce a single or double-stranded break at or proximal to the target locus of interest. 
     In cases where the target nucleic acid locus may be within a cell, the enzyme may be supplied as a nucleic acid containing an open reading frame encoding the enzyme having a RuvC_III domain having at least about 75% (e.g., at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%) identity to any one of SEQ ID NOs: 3569-3637. The deoxyribonucleic acid (DNA) containing an open reading frame encoding said endonuclease may comprise a sequence substantially identical to SEQ ID NOs: 5587 or at variant having at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% identity to SEQ ID NOs: 5587. In some cases, the nucleic acid comprises a promoter to which the open reading frame encoding the endonuclease is operably linked. The promoter may be a CMV, EF1a, SV40, PGK1, Ubc, human beta actin, CAG, TRE, or CaMKIIa promoter. The endonuclease may be supplied as a capped mRNA containing said open reading frame encoding said endonuclease. The endonuclease may be supplied as a translated polypeptide. The at least one engineered sgRNA may be supplied as deoxyribonucleic acid (DNA) containing a gene sequence encoding said at least one engineered sgRNA operably linked to a ribonucleic acid (RNA) pol III promoter. In some cases, the organism may be eukaryotic. In some cases, the organism may be fungal. In some cases, the organism may be human. 
     EXAMPLES 
     Example 1 
     Metagenomic Analysis for New Proteins 
     Metagenomic samples were collected from sediment, soil and animal. Deoxyribonucleic acid (DNA) was extracted with a Zymobiomics DNA mini-prep kit and sequenced on an Illumina HiSeq® 2500. Samples were collected with consent of property owners. Additional raw sequence data from public sources included animal microbiomes, sediment, soil, hot springs, hydrothermal vents, marine, peat bogs, permafrost, and sewage sequences. Metagenomic sequence data was searched using Hidden Markov Models generated based on known Cas protein sequences including type II Cas effector proteins. Novel effector proteins identified by the search were aligned to known proteins to identify potential active sites. This metagenomic workflow resulted in delineation of the MG1, MG2, MG3, MG4, MG6, MG14, MG15, MG16, MG18, MG21, MG22, and MG23 families of class II, type II CRISPR endonucleases described herein. 
     Example 2A 
     Discovery of an MG1 Family of CRISPR Systems 
     Analysis of the data from the metagenomic analysis of Example 1 revealed a new cluster of previously undescribed putative CRISPR systems initially comprising six members (MG1-1, MG1-2, MG1-3, MG1-4, MG1-5, and MG1-6 recorded as SEQ ID NOs: 5, 6, 1, 2, and 3 respectively). This family is characterized by an enzyme bearing HNH and RuvC domains. The RuvC domains of this family have a RuvC_III portion having low homology to previously described Cas9 family members. Although the initial family members have a maximum of 56.8% identity among them, all 6 enzymes exhibit a divergent RuvC_III portion of the RuvC domain and bear the common motif of RHHALDAMV (SEQ ID NO:5615), KHHALDAMC (SEQ ID NO:5616), or KHHALDAIC (SEQ ID NO:5617) . These motifs are not found in other described Cas9-like enzymes. The corresponding protein and nucleic acid sequences for these new enzymes and their relevant subdomains are presented in the sequence listing. Putative tracrRNA sequences were identified based on their location relative to the other genes and are presented as SEQ ID NOs: 5476-5479. The enzyme systems appear to derive from the  Phylum Verrucomicrobia,  the  Phylum Candidatus  Peregrinibacteria, or the  Phylum Candidatus  Melainabacteria based on the sequences of 16S rRNAs from genome bins containing the CRISPR systems. The 16S rRNA sequences are presented as SEQ ID NOs: 5592-5596). A detailed domain-level alignment of the CRISPR system sequences together calling out the features described by Shmakov et al. (Mol Cell. 2015 Nov. 5; 60(3):385-97), which is entirely incorporated by reference) is depicted in  FIGS. 9A, 9B, 9C, 9D, 9E, 9F, 9G, and 9H . A comparison of MG1-1, 1-2, and 1-3 versus additional proprietary protein datasets revealed additional protein sequences with similar architecture, presented as SEQ NOs: 7-319. These MG1 protein sequences led to the discovery of additional MG1 motifs as shown in SEQ ID NOs: 5618-5632. 
     Example 2B 
     Discovery of an MG2 Family of CRISPR Systems 
     Analysis of data from the metagenomic analysis of Example 1 revealed a new cluster of previously undescribed putative CRISPR systems comprising six members (MG2-1, MG2-2, MG2-3, MG2-5, and MG2-6). The corresponding protein and nucleic acid sequences for these new enzymes and exemplary subdomains are presented as SEQ ID NOs: 320, 322-325. Based on their location relative to the other genes, putative tracrRNA sequences were identified in the operon and are presented as SEQ ID NOs: 5490, 5492-5494, and 5538. A detailed domain-level alignment of these sequences versus Cas9 as outlined in Shmakov et al. (Mol Cell. 2015 Nov. 5; 60(3):385-97.), is depicted in  FIG. 7 . 
     A comparison of MG2-1, MG2-2, MG2-3, MG2-5, and MG2-6 versus additional proprietary protein datasets revealed additional protein sequences with similar architecture, presented as SEQ NOs: 321 and 326-420. Motifs commonly found in MG2 family members are presented as SEQ ID NOs: 5631-5638. 
     Example 2C 
     Discovery of an MG3 Family of CRISPR Systems 
     Analysis of the data from the metagenomic analysis of Example 1 revealed a new previously undescribed putative CRISPR system: MG3-1. The corresponding amino acid sequences for this new enzyme and its exemplary subdomains are presented as SEQ ID NOs: 424, 2245, and 4059. Based on proximity to the other elements in the operon, a putative tracrRNA containing sequence was identified and is included as SEQ ID NO: 5498. A detailed domain-level alignment of the sequence versus Cas9 from  Actinomyces naeslundii  is depicted in  FIG. 8 . 
     A comparison of MG3-1 versus additional proprietary protein datasets revealed additional protein sequences with similar architecture, presented as SEQ NOs: 421-423, 425-431. 
     Example 2D 
     Discovery of MG4, 7, 14, 15, 16, 18, 21, 22, 23 Families of CRISPR Systems 
     Analysis of the data from the metagenomic analysis of Example 1 revealed new clusters of previously undescribed putative CRISPR systems comprising 9 families of one member each (MG 4-5, MG7-2, MG14-1, MG15-1, MG16-2, MG18-1, MG21-1, MG22-1, MG23-1). The corresponding protein and nucleic acid sequences for these new enzymes and their exemplary subdomains are presented as SEQ ID NOs: 432, 669, 678, 930, 1093, 1354, 1512, 1656, 1756. Based on proximity to the other elements in the operon, a putative tracr containing sequence was identified for each family. These sequences are presented in the sequence listing as SEQ ID NOs: 5503-5511, respectively. 
     A comparison of MG 4-5, MG7-2, MG14-1, MG15-1, MG16-2, MG18-1, MG21-1, MG22-1, MG23-1 versus additional proprietary protein datasets revealed additional protein sequences with similar architecture, presented as SEQ NOs: 433-660, 670-677, 679-929, 931-1092, 1094-1353, 1355-1511, 1513-1655, 1657-1755, and 1757-1826. Motifs common to the nucleases of these sets of CRISPR systems are presented as SEQ ID NO: 5649 for MG4; SEQ ID NOs: 5650-5667 for MG14; 5668-5675 for MG15; SEQ ID NOs: 5676-5678 for MG16; SEQ ID NOs: 5679-5686 for MG18; SEQ ID NOs: 5687-5693 and SEQ ID NOs: 5674-5675 for MG21; SEQ ID NOs: 5694-5699 for MG22; and SEQ ID NOs: 5700-5717 for MG23. 
     Example 3 
     Prophetic—Determination of Protospacer-Adjacent Motif 
     Experiments are performed as in any of the examples in Karvelis et al. Methods. 2017 May 15; 121-122:3-8, which is entirely incorporated by reference herein, to identify the protospacer adjacent motif (PAM) sequence specificity for the novel enzymes described herein to allow for optimal synthetic sequence targeting. 
     In one example (in-vivo screen), cells bearing plasmids encoding any of the enzymes described herein and protospacer-targeting guide RNA are co-transformed with a plasmid library containing an antibiotic resistance gene, and a protospacer sequence flanked by a randomized PAM sequence. Plasmids containing functional PAMs are cleaved by the enzyme, leading to cell death. Deep-sequencing of the enzyme cleavage-resistant plasmid pool isolated from the surviving cells displays a set of depleted plasmids that contain functional cleavage-permitting PAMs. 
     In another example (in vitro screen), PAM library in the form of DNA plasmid or concatemeric repeats is subjected to cleavage by the RNP complex (e.g., including the enzyme, tracrRNA and crRNA or the enzyme and hybrid sgRNA) assembled in vitro or in cell lysates. Resulting free DNA ends from successful cleavage events are captured by adapter ligation, followed by the PCR amplification of the PAM-sided products. Amplified library of functional PAMs is subjected to deep sequencing and PAMs licensing DNA cleavage are identified. 
     Example 4 
     Prophetic—Use of Synthetic CRISPR System as described herein in a Mammalian Cell for Genome Editing 
     DNA/RNA sequences encoding (i) an ORF encoding codon-optimized enzyme under a cell-compatible promoter with a cell-compatible C-terminal nuclear localization sequence (e.g., SV40 NLS in the case of human cells) and a suitable polyadenylation signal (e.g., TK pA signal in the case of human cells); and (ii) an ORF encoding an sgRNA (having a 5′ sequence beginning with G followed by 20 nt of a complementary targeting nucleic acid sequence targeting genomic DNA followed by a corresponding compatible PAM identified via Example 3 and a 3′ tracr-binding sequence, a linker, and the tracrRNA sequence) under a suitable Polymerase III promoter (e.g., the U6 promoter in mammalian cells) are prepared. In some embodiments, these sequences are prepared on the same or separate plasmid vectors, which are transfected via a suitable technique into eukaryotic cells. In some embodiments, these sequences are prepared as separate DNA sequences, which are transfected or microinjected into cells. In some embodiments, these sequences are prepared as synthesized RNAs or in-vitro transcribed RNAs which are transfected or microinjected into cells. In some embodiments, these sequences are translated into proteins and transfected or microinjected into cells. 
     Whichever transfection method is selected, (i) and (ii) are introduced into cells. A period of incubation is allowed to pass so that the enzyme and/or sgRNA can be transcribed and/or translated into active form. After the incubation period, genomic DNA in the vicinity of the targeting sequence is analyzed (e.g., by sequencing). An indel is introduced into the genomic DNA in the vicinity of the targeting sequence as a result of enzyme-mediated cleavage and non-homologous end joining. 
     In some embodiments, (i) and (ii) are introduced into cells with a third repair nucleotide that encodes regions of the genome flanking the cleavage site of sizes 25 bp or larger, which will facilitate homology directed repair. Containing within these flanking sequences may be a single base pair mutation, a functional gene fragment, a foreign or native gene for expression, or several genes composing a biochemical pathway. 
     Example 5 
     Prophetic—Use of Synthetic CRISPR System as described herein In Vitro 
     Any of the enzymes described herein are cloned into a suitable  E. coli  expression plasmid containing a purification tag and are recombinantly expressed in  E. coli  and purified using the recombinant tag. RNAs comprising a 5′ G followed by a 20 nt targeting sequence and PAM sequence, a tracrRNA binding region of a compatible crRNA, a GAAA linker, and a compatible tracrRNA are synthesized by suitable solid-phase RNA synthesis methods. Recombinant enzymes and sgRNA are combined in a suitable cleavage buffer containing Mg2+ (e.g., 20 mM HEPES pH 7.5, 100 mM KC1, 5 mM MgCl 2 , 1 mM DTT, 5% glycerol) and the reaction is initiated by introducing a target DNA including a sequence complementary to the targeting sequence and PAM sequence. Cleavage of the DNA is monitored by a suitable assay (e.g., agarose gel electrophoresis followed by ethidium bromide staining (or similarly acting DNA-intercalating agent) and UV visualization). 
     Example 6 
     (General Protocol) PAM Sequence Identification/Confirmation for the Endonucleases described herein 
     PAM sequences were determined by sequencing plasmids containing randomly-generated PAM sequences that could be cleaved by putative endonucleases expressed in an  E. coli  lysate-based expression system (myTXTL, Arbor Biosciences). In this system, an  E. coli  codon optimized nucleotide sequence was transcribed and translated from a PCR fragment under control of a T7 promoter. A second PCR fragment with a tracr sequence under a T7 promoter and a minimal CRISPR array composed of a T7 promoter followed by a repeat-spacer-repeat sequence was transcribed in the same reaction. Successful expression of the endonuclease and tracr sequence in the TXTL system followed by CRISPR array processing provided active in vitro CRISPR nuclease complexes. 
     A library of target plasmids containing a spacer sequence matching that in the minimal array followed by 8N mixed bases (putative PAM sequences) was incubated with the output of the TXTL reaction. After 1-3 hr, the reaction was stopped and the DNA was recovered via a DNA clean-up kit, e.g., Zymo DCC, AMPure XP beads, QiaQuick etc. Adapter sequences were blunt-end ligated to DNA with active PAM sequences that had been cleaved by the endonuclease, whereas DNA that had not been cleaved was inaccessible for ligation. DNA segments comprising active PAM sequences were then amplified by PCR with primers specific to the library and the adapter sequence. The PCR amplification products were resolved on a gel to identify amplicons that corresponded to cleavage events. The amplified segments of the cleavage reaction were also used as template for preparation of an NGS library. Sequencing this resulting library, which was a subset of the starting 8N library, revealed the sequences which contain the correct PAM for the active CRISPR complex. For PAM testing with a single RNA construct, the same procedure was repeated except that an in vitro transcribed RNA was added along with the plasmid library and the tracr/minimal CRISPR array template was omitted. For endonucleases where NGS libraries were prepared, seqLogo (see e.g., Huber et al. Nat Methods. 2015 February; 12(2):115-21) representations were constructed and are presented in  FIGS. 27, 38, 29, 30, 31, 32, 33, 34, and 35 . The seqLogo module used to construct these representations takes the position weight matrix of a DNA sequence motif (e.g. a PAM sequence) and plots the corresponding sequence logo as introduced by Schneider and Stephens (see e.g. Schneider et al. Nucleic Acids Res. 1990 Oct. 25; 18(20):6097-100. The characters representing the sequence in the seqLogo representations have been stacked on top of each other for each position in the aligned sequences (e.g. PAM sequences). The height of each letter is proportional to its frequency, and the letters have been sorted so the most common one is on top. 
     Example 7 
     (General Protocol) RNA Folding of tracrRNA and sgRNA Structures 
     Folded structures of guide RNA sequences at 37° C. were computed using the method of Andronescu et al. Bioinformatics. 2007 Jul. 1; 23(13):i19-28, which is incorporated by reference herein in its entirety. Predicted structures of exemplary sgRNAs described herein are presented in  FIGS. 21, 22, 23, 24, 25, and 26 . 
     Example 8 
     (General Protocol) In Vitro Cleavage Efficiency of MG CRISPR Complexes 
     Endonucleases were expressed as His-tagged fusion proteins from an inducible T7 promoter in a protease deficient  E. coli  B strain. Cells expressing the His-tagged proteins were lysed by sonication and the His-tagged proteins were purified by Ni-NTA affinity chromatography on a HisTrap FF column (GE Lifescience) on an AKTA Avant FPLC (GE Lifescience). The eluate was resolved by SDS-PAGE on acrylamide gels (Bio-Rad) and stained with InstantBlue Ultrafast coomassie (Sigma-Aldrich). Purity was determined using densitometry of the protein band with ImageLab software (Bio-Rad). Purified endonucleases were dialyzed into a storage buffer composed of 50 mM Tris-HCl, 300 mM NaCl, 1 mM TCEP, 5% glycerol; pH 7.5 and stored at −80° C. 
     Target DNAs containing spacer sequences and PAM sequences (determined e.g., as in Example 6) were constructed by DNA synthesis. A single representative PAM was chosen for testing when the PAM had degenerate bases. The target DNAs comprised 2200 bp of linear DNA derived from a plasmid via PCR amplification with a PAM and spacer located 700 bp from one end. Successful cleavage resulted in fragments of 700 and 1500 bp. The target DNA, in vitro transcribed single RNA, and purified recombinant protein were combined in cleavage buffer (10 mM Tris, 100 mM NaCl, 10 mM MgCl 2 ) with an excess of protein and RNA and incubated for 5 minutes to 3 hours, usually 1 hr. The reaction was stopped via addition of RNAse A and incubation at 60 minutes. The reaction was then resolved on a 1.2% TAE agarose gel and the fraction of cleaved target DNA is quantified in ImageLab software. 
     Example 9 
     (General Protocol) Testing of Genome Cleavage Activity of MG CRISPR Complexes in  E. coli    
       E. coli  lacks the capacity to efficiently repair double-stranded DNA breaks. Thus, cleavage of genomic DNA can be a lethal event. Exploiting this phenomenon, endonuclease activity was tested in  E. coli  by recombinantly expressing an endonuclease and a tracrRNA in a target strain with spacer/target and PAM sequences integrated into its genomic DNA. 
     In this assay, the PAM sequence is specific for the endonuclease being tested as determined by the methods described in Example 6. sgRNA sequences were determined based upon the sequence and predicted structure of the tracrRNA. Repeat-anti-repeat pairings of 8-12 bp (generally 10 bp) were chosen, starting from the 5′ end of the repeat. The remaining 3′ end of the repeat and 5′ end of the tracrRNA were replaced with a tetraloop. Generally, the tetraloop was GAAA, but other tetraloops can be used, particularly if the GAAA sequence is predicted to interfere with folding. In these cases, a TTCG tetraloop was used. 
     Engineered strains with PAM sequences integrated into their genomic DNA were transformed with DNA encoding the endonuclease. Transformants were then made chemocompetent and transformed with 50 ng of single guide RNAs either specific to the target sequence (“on target”), or non-specific to the target (“non target”). After heat shock, transformations were recovered in SOC for 2 hrs at 37° C. Nuclease efficiency was then determined by a 5-fold dilution series grown on induction media. Colonies were quantified from the dilution series in triplicate. 
     Example 10a 
     (General Protocol) Testing of Genome Cleavage Activity of MG CRISPR Complexes in Mammalian Cells 
     To show targeting and cleavage activity in mammalian cells, the MG Cas effector protein sequences were tested in two mammalian expression vectors: (a) one with a C-terminal SV40 NLS and a 2A-GFP tag, and (b) one with no GFP tag and two SV40 NLS sequences, one on the N-terminus and one on the C-terminus. In some instances, nucleotide sequences encoding the endonucleases were codon-optimized for expression in mammalian cells. 
     The corresponding single guide RNA sequence (sgRNA) with targeting sequence attached is cloned into a second mammalian expression vector. The two plasmids are cotransfected into HEK293T cells. 72 hr after co-transfection of the expression plasmid and a sgRNA targeting plasmid into HEK293T cells, the DNA is extracted and used for the preparation of an NGS-library. Percent NHEJ is measured via indels in the sequencing of the target site to demonstrate the targeting efficiency of the enzyme in mammalian cells. At least 10 different target sites were chosen to test each protein&#39;s activity. 
     Example 10b 
     (General Protocol) Testing of Genome Cleavage Activity of MG CRISPR Complexes in Mammalian Cells 
     To show targeting and cleavage activity in mammalian cells, the MG Cas effector protein sequences were cloned into two mammalian expression vector: (a) one with flanking N and C-terminal SV40 NLS sequences, a C-terminal His tag, and a 2A-GFP tag at the C terminus after the His tag (Backbone 1), and (b) one with flanking NLS sequences and C-terminal His tag but no T2A GFP tag (Backbone 2). In some instances, nucleotide sequences encoding the endonucleases were the native sequence, codon-optimized for expression in  E. coli,  or codon-optimized for expression in mammalian cells. 
     The corresponding single guide RNA sequence (sgRNA) with targeting sequence attached was cloned into a second mammalian expression vector. The two plasmids were cotransfected into HEK293T cells. 72 hr after co-transfection of the expression plasmid and a sgRNA targeting plasmid into HEK293T cells, the DNA was extracted and used for the preparation of an NGS-library. Percent NHEJ was measured via indels in the sequencing of the target site to demonstrate the targeting efficiency of the enzyme in mammalian cells. About 7-12 different target sites were chosen for testing each protein&#39;s activity. An arbitrary threshold of 5% indels was used to identify active candidates. 
     Example 11 
     Characterization of MG1 Family Members 
     PAM Specificity, tracrRNA/sgRNA Validation 
     The targeted endonuclease activity of MG1 family endonuclease systems was confirmed using the myTXTL system described in Example 6. In this assay, PCR amplification of cleaved target plasmids yields a product that migrates at approximately 170 bp in the gel, as shown in  FIGS. 17-20 . Amplification products were observed for MG1-4 (dual guide: see gel 1, lane 3, single guide: see gel 6 lane 2), MG1-5 (gel 2 lane 10), MG1-6 (dual guide: see gel 5 lane 6, single guide see: gel 6 lane 5), and MG1-7 (dual guide: see gel 3 lane 13, single guide: see gel 3 lane 2) (protein SEQ ID NOs: 1-4, respectively). Sequencing the PCR products revealed active PAM sequences for these enzymes as shown in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 PAM sequence specificities and related data for MG1 enzymes 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 Enzyme 
                   
                   
                   
                   
                   
                 Synthetic 
               
               
                   
                 protein 
                 Native 
                   
                 tracrRNA 
                 sgRNA 
                 Synthetic 
                 (single guide) 
               
               
                   
                 SEQ 
                 (dual guide) 
                 PAM SEQ 
                 SEQ 
                 SEQ 
                 (single guide) 
                 PAM SEQ 
               
               
                 Enzyme 
                 ID NO 
                 PAM 
                 ID NO: 
                 ID NO: 
                 ID NO: 
                 PAM 
                 ID NO: 
               
               
                   
               
               
                 MG1-4 
                 1 
                 nRRRAA 
                 5527 
                 5476 
                 5461 
                 nRRR 
                 5512 
               
               
                 MG1-5 
                 2 
                 nnnnCC 
                 5528 
                 5477 
                 5462 
                 nnnnYY 
                 5513 
               
               
                 MG1-6 
                 3 
                 nnRRAC 
                 5529 
                 5478 
                 5463 
                 nnRRAY 
                 5514 
               
               
                 MG1-7 
                 4 
                 nRRRAA 
                 5530 
                 5479 
                 5464 
                 nRRRAAG 
                 5515 
               
               
                   
               
            
           
         
       
     
     Synthetic single guide RNAs (sgRNAs) were designed based on the sequences and predicted structures of the tracrRNAs and are presented as SEQ ID NOs: 5461-5464. The PAM sequence screen of Example 6 was repeated with the sgRNAs. The results of this experiment are also presented in Table 2, which reveals that PAM specificity changed slightly when using sgRNAs. 
     Targeted Endonuclease Activity In Vitro 
     In vitro activity of the MG1-4 endonuclease system (protein SEQ ID NO: 1 with sgRNA SEQ ID NO: 5461) on a target DNA with a PAM sequence CAGGAAGG was verified using the method of Example 8. The single guide sequence reported above (SEQ ID NO: 5461) was used, with varying spacer/targeting sequence lengths from 18-24 nt replacing the Ns of the sequence. The results are shown in  FIG. 10 , wherein the left panel shows a gel demonstrating DNA cleavage by MG1-4 in combination with corresponding single guide sgRNAs having different targeting sequence lengths (18-24 nt), and the right panel shows the same data quantified as a bar graph. The data demonstrated that targeting sequences from 18-24 nucleotides were functional with the MG1-4/sgRNA system. 
     Targeted Endonuclease Activity in Bacterial Cells 
     In vivo activity of the MG1-4 endonuclease system (protein SEQ ID NO: 1, sgRNA SEQ ID NO: 5461) was tested with the PAM sequence CAGGAAGG as in Example 9. Transformed  E. coli  were plated in serial dilution, and the results (showing  E. coli  serial dilutions in the left panel and quantitated growth in the right panel) are presented in  FIG. 11 . A substantial reduction in the growth of  E. coli  expressing on target sgRNA compared to  E. coli  expressing non-target sgRNA indicates that genomic DNA was specifically cleaved by the endonuclease in  E. coli  cells. 
     Targeted Endonuclease Activity in Mammalian Cells (a) 
     The method of Example 10 was used to demonstrate targeting and cleavage activity in mammalian cells. Open reading frames encoding the MG1-4 (protein SEQ ID NO: 5527) and MG1-6 (protein SEQ ID NO: 5529) sequences were cloned into 2 mammalian expression vectors, one with a C-terminal SV40 NLS and a 2A-GFP tag ( E. coli  MG-BB) and one with no GFP tag and 2 NLS sequences, one on the N-terminus and one on the C-terminus ( E. coli  pMG5-BB). For MG1-6, the open reading frame was additionally codon-optimized for mammalian expression (SEQ ID NO: 5589) and cloned into the 2-NLS plasmid backbone (MG-16 hs). The results of this experiment are shown in  FIG. 12 . The endonuclease expression vectors were cotransfected into HEK293T cells with a second vector for expressing a sgRNA (e.g., SEQ ID NOs: 5512 or 5515) with a tracr sequence specific for the endonuclease and a guide sequence selected from Tables 3-4. 72 hr after co-transfection the DNA was extracted and used for the preparation of an NGS-library. Cleavage activity was detected by the appearance of internal deletions (NHEJ remnants) proximal to the sequence of the target site. Percent NHEJ was measured via indels in the sequencing of the target site to demonstrate the targeting efficiency of the enzyme in mammalian cells and is presented in  FIG. 12 . 
     
       
         
           
               
             
               
                 TABLE 3  
               
             
            
               
                   
               
               
                 MG1-4 mammalian targeting sequences 
               
            
           
           
               
               
               
               
            
               
                 MG1-4  
                 MG1-4  
                 Targeting sequence 
                 Targeted 
               
               
                 Target ID 
                 Targeting Sequence 
                 SEQ ID NO: 
                 Gene 
               
               
                   
               
               
                 1 
                 aatatgtagctgtttgggaggt 
                 5543 
                 VEGFA 
               
               
                   
               
               
                 2 
                 ctagggggcgctcggccaccac 
                 5544 
                 VEGFA 
               
               
                   
               
               
                 3 
                 tggctaaagagggaatgggctt 
                 5545 
                 VEGFA 
               
               
                   
               
               
                 4 
                 cacaccccggctctggctaaag 
                 5546 
                 VEGFA 
               
               
                   
               
               
                 5 
                 tcggaggagccgtggtccgcgc 
                 5547 
                 VEGFA 
               
               
                   
               
               
                 6 
                 gcggaccacggctcctccgaag 
                 5548 
                 VEGFA 
               
               
                   
               
               
                 7 
                 gtacaaacggcagaagctggag 
                 5549 
                 EMX1 
               
               
                   
               
               
                 8 
                 gaggaagggcctgagtccgagca 
                 5550 
                 EMX1 
               
               
                   
               
               
                 9 
                 aaggcaaacatcctgataatgg 
                 5551 
                 Apolipoprotein 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 MG1-6 mammalian targeting sequences 
               
            
           
           
               
               
               
               
            
               
                 MG1-6 
                 MG1-6  
                 Targeting sequence 
                   
               
               
                 Target ID 
                 Targeting Sequence 
                 SEQ ID NO: 
                 Targeted Gene 
               
               
                   
               
               
                  1 
                 tctttagccagagccggggtgt 
                 5552 
                 VEGFA 
               
               
                   
               
               
                  2 
                 tggaccccctatttctgacctc 
                 5553 
                 VEGFA 
               
               
                   
               
               
                  3 
                 atgggagcccttcttcttctgc 
                 5554 
                 EMX1 
               
               
                   
               
               
                  4 
                 tgccacgaagcaggccaatggg 
                 5555 
                 EMX1 
               
               
                   
               
               
                  5 
                 tggtgtctgtttgaggttgcta 
                 5556 
                 HBB-R01 
               
               
                   
               
               
                  6 
                 gggcaggttggtatcaaggtta 
                 5557 
                 HBB-R01 
               
               
                   
               
               
                  7 
                 aggtgctgacgtaggtagtgct 
                 5558 
                 FANCF 
               
               
                   
               
               
                  8 
                 gccctacttccgctttcacctt 
                 5559 
                 FANCF 
               
               
                   
               
               
                  9 
                 aatgtatgctggcttttaaggg 
                 5560 
                 IVS40 
               
               
                   
               
               
                 10 
                 gctcctttggctagggaagtgt 
                 5561 
                 IVS40 
               
               
                   
               
            
           
         
       
     
     Targeted Endonuclease Activity in Mammalian Cells (b) 
     MG1-4 target loci were chosen to test locations in the genome with the PAM nRRRAA (SEQ ID NO: 5527). The spacers corresponding to the chosen target sites were cloned into the sgRNA scaffold in the mammalian vector system Backbone 2 described in Example 10b. The sites are listed in Table 4a below. The activity of MG1-4 at various target sites is shown in Table 4a and  FIG. 37   
     
       
         
           
               
             
               
                 TABLE 4a  
               
             
            
               
                   
               
               
                 Activity of MG1-4 at various target sites 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 % NHEJ 
               
               
                 target ID 
                 target sequence 
                 PAM 
                 locus 
                 (mean ± std) 
               
               
                   
               
               
                  1 
                 aatatgtagctgtttgggaggt 
                 CAGAAA 
                 VEGFA 
                  1.62 ± 1.2 
               
               
                   
               
               
                  2 
                 ctagggggcgctcggccaccac 
                 AGGGAA 
                 VEGFA 
                 -0.07 ± 0 
               
               
                   
               
               
                  3 
                 tggctaaagagggaatgggctt 
                 TGGAAA 
                 VEGFA 
                 10.32 ± 2.75 
               
               
                   
               
               
                  4 
                 cacaccccggctctggctaaag 
                 AGGGAA 
                 VEGFA 
                  0.18 ± 0.53 
               
               
                   
               
               
                  5 
                 tcggaggagccgtggtccgcgc 
                 GGGGAA 
                 VEGFA 
                     0 ± 0.03 
               
               
                   
               
               
                  6 
                 gaagccgagccgagcggagccg 
                 CGAGAA 
                 VEGFA 
                  4.53 ± 1.73 
               
               
                   
               
               
                  7 
                 gcggaccacggctcctccgaag 
                 GAGGAA 
                 VEGFA 
                   0.3 ± 0.04 
               
               
                   
               
               
                  8 
                 gtacaaacggcagaagctggag 
                 GAAGAA 
                 EMX1 
                  0.23 ± 0.1 
               
               
                   
               
               
                 10 
                 Gaaggcaaacatcctgataatgg 
                 TGAAAA 
                 Apolipoprotein 
                  0.07 ± 0.06 
               
               
                   
               
            
           
         
       
     
     MG1-6 target loci were chosen to test locations in the genome with the PAM nnRRAC (SEQ ID NO: 5529). The spacers corresponding to the chosen target sites were cloned into the sgRNA scaffold in the mammalian vector system backbone 2 described in Example 10b. The sites are listed in Table 4b below. The activity of MG1-6 at various target sites is shown in Table 4b and  FIG. 38 . 
     
       
         
           
               
             
               
                 TABLE 4b  
               
             
            
               
                   
               
               
                 Activity of MG1-6 at various target sites. 
               
            
           
           
               
               
               
               
               
            
               
                 target ID 
                 target sequence 
                 PAM 
                 locus 
                 % NHEJ (mean ± std) 
               
               
                   
               
               
                  1 
                 tctttagccagagccggggtgt 
                 GCAGAC 
                 VEGFA 
                  0.385 ± 0.035 
               
               
                   
               
               
                  2 
                 tggaccccctatttctgacctc 
                 CCAAAC 
                 VEGFA 
                   0.65 ± 0.62 
               
               
                   
               
               
                  3 
                 atgggagcccttcttcttctgc 
                 TCGGAC 
                 EMX1 
                 -0.045 ± 0.105 
               
               
                   
               
               
                  4 
                 tgccacgaagcaggccaatggg 
                 GAGGAC 
                 EMX1 
                   0.96 ± 0.14 
               
               
                   
               
               
                  5 
                 tggtgtctgtttgaggttgcta 
                 GTGAAC 
                 HBB 
                  -0.09 ± 0.09 
               
               
                   
               
               
                  6 
                 gggcaggttggtatcaaggtta 
                 CAAGAC 
                 HBB 
                  4.915 ± 0.135 
               
               
                   
               
               
                  7 
                 aggtgctgacgtaggtagtgct 
                 TGAGAC 
                 FANCF 
                   3.85 ± 1.86 
               
               
                   
               
               
                  9 
                 aatgtatgctggcttttaaggg 
                 GGAAAC 
                 IVS40 
                 -0.215 ± 0.105 
               
               
                   
               
               
                 10 
                 gctcctttggctagggaagtgt 
                 TAAAAC 
                 IVS40 
                   3.03 ± 3.5 
               
               
                   
               
            
           
         
       
     
     MG1-7 target loci were chosen to test locations in the genome with the PAM nRRRAAG (SEQ ID NO: 5515). The spacers corresponding to the chosen target sites were cloned into the sgRNA scaffold in the mammalian vector system backbone 2 described in Example 10b. The sites are listed in Table 4c below. The activity of MG1-7 at various target sites is shown in Table 4c and  FIG. 39 . 
     
       
         
           
               
             
               
                 TABLE 4c  
               
             
            
               
                   
               
               
                 Activity of MG1-7 at various target sites 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 % NHEJ 
               
               
                 target ID 
                 target sequence 
                 PAM 
                 locus 
                 (mean ± std) 
               
               
                   
               
               
                  1 
                 atcaaactgtgagcatcttcag 
                 ggaaaag 
                 IVS40 
                 0.105 ± 0.88 
               
               
                   
               
               
                  2 
                 cagcgaatctactcagccagag 
                 caggaag 
                 IVS40 
                 0.075 ± 0.02 
               
               
                   
               
               
                  3 
                 ctttaacttgtgtgattctgga 
                 gaggaag 
                 IVS40 
                 −0.25 
               
               
                   
               
               
                  4 
                 agcttaattagctcctttggct 
                 agggaag 
                 IVS40 
                 0.545 ± 1.71 
               
               
                   
               
               
                  5 
                 ccatggtgcatctgactcctga 
                 ggagaag 
                 HBB 
                 0.005 ± 0.01 
               
               
                   
               
               
                  6 
                 tgcttgagaccgccagaagctc 
                 ggaaaag 
                 FANCF 
                  0.91 ± 0.38 
               
               
                   
               
               
                  7 
                 cgagaacagcccagaagttgga 
                 cgaaaag 
                 VEGFA 
                  5.49 ± 0.44 
               
               
                   
               
               
                  8 
                 cggaggagccgtggtccgcgcg 
                 ggggaag 
                 VEGFA 
                  0.27 ± 0.20 
               
               
                   
               
               
                  9 
                 atgtgtgagaaaaatttaatca 
                 taagaag 
                 Apolipoprotein 
                 −1.85 ± 1.89 
               
               
                   
               
               
                 10 
                 aggtccaagtaaaatttgtctt 
                 agaaaag 
                 Apolipoprotein 
                 −2.17 ± 2.55 
               
               
                   
               
               
                 11 
                 gtacaaacggcagaagctggag 
                 gaggaag 
                 EMX1 
                 0.775 ± 0.33 
               
               
                   
               
               
                 12 
                 aggaagggcctgagtccgagca 
                 gaagaag 
                 EMX1 
                  0.01 ± 0.01 
               
               
                   
               
               
                 13 
                 aagggcctgagtccgagcagaa 
                 gaagaag 
                 EMX1 
                 0.185 ± 0.22 
               
               
                   
               
            
           
         
       
     
     Example 12 
     Characterization of MG2 Family Members 
     PAM Specificity, tracrRNA/sgRNA Validation 
     The targeted endonuclease activity of MG2 family members was confirmed in the myTXTL system as described in Example 6. Results of this assay are shown in  FIGS. 17-20 . In the assay shown in  FIGS. 17-20 , active proteins that successfully cleave the library result in a band around 170 bp in the gel. Amplification products were observed for MG2-1 (see gel 2 lane 11 and gel 4 lane 6) and MG2-7 (see gel 11 lane 10) (SEQ ID NOs: 320 and 321, respectively). Sequencing the PCR products revealed active PAM sequences in Table 5 below: 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 PAM sequence specificities and related data for MG2 enzymes 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 Enzyme 
                   
                   
                   
                   
                   
                 Synthetic 
               
               
                   
                 protein 
                 Native 
                   
                 tracrRNA 
                 sgRNA 
                 Synthetic 
                 (single guide) 
               
               
                   
                 SEQ 
                 (dual guide) 
                 PAM SEQ 
                 SEQ 
                 SEQ 
                 (single guide) 
                 PAM SEQ 
               
               
                 Enzyme 
                 ID NO 
                 PAM 
                 ID NO: 
                 ID NO: 
                 ID NO: 
                 PAM 
                 ID NO: 
               
               
                   
               
               
                 MG2-1 
                 320 
                 nRCGTA 
                 5531 
                 5490 
                 N/A 
                 N/A 
                 N/A 
               
               
                 MG2-7 
                 321 
                 N/A 
                 N/A 
                 5491 
                 5465 
                 NNNRTA 
                 5516 
               
               
                   
               
            
           
         
       
     
     Targeted Endonuclease activity in Bacterial Cells 
     In vivo activity of the MG2-7 endonuclease system with a sgRNA (endonuclease SEQ ID NO: 321; sgRNA SEQ ID NO: 5465) and an AGCGTAAG PAM sequence was confirmed using the method described in Example 9. Transformed  E. coli  were plated in serial dilution, and the results (showing  E. coli  serial dilutions in the left panel and quantitated growth in the right panel) are presented in  FIG. 34 . A substantial reduction in the growth of  E. coli  expressing on target sgRNA compared to  E. coli  expressing non-target sgRNA indicates that genomic DNA was specifically cleaved by the MG1-4 endonuclease in  E. coli  cells. 
     Example 13 
     Characterization of MG3 Family Members 
     PAM Specificity, tracrRNA/sgRNA Validation 
     The targeted endonuclease activity of MG3 family members was confirmed using the myTXTL system as described in Example 6 using tracr sequences and CRISPR arrays. In this assay, PCR amplification of cleaved target plasmids yields a product that migrates at approximately 170 bp in the gel, as shown in  FIGS. 17-20 . Amplification products were observed for MG3-6 (dual guide: see gel 2 lane 8; single guide: see gel 3 lane 3), MG3-7 (dual guide: see gel 2 lane 3, single guide: see gel 3 lane 4), and MG3-8 (dual guide: see gel 9 lane 5) (SEQ ID NOs: 421, 422, and 423, respectively). Sequencing the PCR products revealed active PAM sequences in Table 6 below: 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 PAM sequence specificities and related data for MG3 enzymes 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 Enzyme 
                   
                   
                   
                   
                   
                 Synthetic 
               
               
                   
                 protein 
                 Native 
                   
                 tracrRNA 
                 sgRNA 
                 Synthetic 
                 (single guide) 
               
               
                   
                 SEQ 
                 (dual guide) 
                 PAM SEQ 
                 SEQ 
                 SEQ 
                 (single guide) 
                 PAM SEQ 
               
               
                 Enzyme 
                 ID NO 
                 PAM 
                 ID NO: 
                 ID NO: 
                 ID NO: 
                 PAM 
                 ID NO: 
               
               
                   
               
               
                 MG3-6 
                 421 
                 nnRGGTT 
                 5532 
                 5500 
                 5466 
                 nnGGG 
                 5517 
               
               
                 MG3-7 
                 422 
                 nnRnYAY 
                 5533 
                 5501 
                 5467 
                 nnGnTnT 
                 5518 
               
               
                 MG3-8 
                 423 
                 nnRGGTT 
                 5534 
                 5502 
                 N/A 
                 N/A 
                 N/A 
               
               
                   
               
            
           
         
       
     
     Synthetic single guide RNAs (sgRNAs) were designed based on the sequences and predicted structures of the tracrRNAs and are presented as SEQ ID NOs: 5466-5467. The PAM sequence screen of Example 6 was repeated with the sgRNAs. The results of this experiment are also presented in Table 6, which reveals that PAM specificity changed slightly when using sgRNAs. 
     Targeted Endonuclease Activity In Vitro 
     In vitro activity of the MG3-6 (endonuclease SEQ ID NO: 421) was verified with the PAM sequence GTGGGTTA using the method of Example 8. The single guide sequence reported above (SEQ ID NO: 5466) was used, with varying spacer/targeting sequence lengths from 18-24 nt replacing the Ns of the sequence. The results are shown in  FIG. 13 , wherein the top panel shows a gel demonstrating DNA cleavage by MG3-6 in combination with different sgRNAs having different targeting sequence lengths (18-24 nt), and the bottom panel shows the same data quantified as a bar graph. The data demonstrated that targeting sequences from 18-24 nucleotides were functional with the MG3-6/sgRNA system. 
     Targeted Endonuclease Activity in Bacterial Cells 
     In vivo activity of the MG3-7 endonuclease system (protein SEQ ID NO: 422; sgRNA SEQ ID NO: 5467) was tested with the PAM sequence TGGACCTG using the method of Example 9. Transformed  E. coli  were plated in serial dilution, and the results (showing  E. coli  serial dilutions in the top panel and quantitated growth in the bottom panel) are presented in  FIG. 14 . A substantial reduction in the growth of  E. coli  expressing on target sgRNA compared to  E. coli  expressing non-target sgRNA indicates that genomic DNA was being specifically cleaved by the MG3-7 endonuclease system. 
     Targeted Endonuclease Activity in Mammalian Cells (a) 
     The method of Example 10 was used to demonstrate targeting and cleavage activity in mammalian cells. Open reading frames encoding MG3-7 (protein SEQ ID NO: 422) was cloned into 2 mammalian expression vectors, one with a C-terminal SV40 NLS and a 2A-GFP tag ( E. coli  MG-BB) and one with no GFP tag and 2 NLS sequences, one on the N-terminus and one on the C-terminus ( E. coli  pMGS-BB). The endonuclease expression vectors were cotransfected into HEK293T cells with a second vector for expressing the sgRNA above with a guide sequence selected from Table 7. The results of this experiment are shown in  FIG. 12 .  72  hr after co-transfection DNA was extracted and used for the preparation of an NGS-library. Cleavage activity was detected by the appearance of internal deletions (NHEJ remnants) in the vicinity of the target site. Results are presented in  FIG. 15 . 
     The target site which were encoded on the sgRNA plasmids are shown in Table 7 below. 
     
       
         
           
               
             
               
                 TABLE 7 
               
             
            
               
                   
               
               
                 MG3-7 mammalian targeting sequences 
               
            
           
           
               
               
               
               
            
               
                 MG3-7 
                 MG3-7  
                 Targeting sequence 
                   
               
               
                 Target ID 
                 Targeting Sequence 
                 SEQ ID NO: 
                 Targeted Gene 
               
               
                   
               
               
                  1 
                 cccctatttctgacctcccaaa 
                 5563 
                 VEGFA 
               
               
                   
               
               
                  2 
                 tgtggttccagaaccggaggac 
                 5564 
                 EMX1 
               
               
                   
               
               
                  3 
                 ggccctgggcaggttggtatca 
                 5565 
                 HBB-R01 
               
               
                   
               
               
                  4 
                 tccttaaacctgtcttgtaacc 
                 5566 
                 HBB-R01 
               
               
                   
               
               
                  5 
                 ctgactcctgaggagaagtctg 
                 5567 
                 HBB-R01 
               
               
                   
               
               
                  6 
                 tccgagcttctggcggtctcaa 
                 5568 
                 FANCF 
               
               
                   
               
               
                  7 
                 tatcatttcgcggatgttccaa 
                 5569 
                 FANCF 
               
               
                   
               
               
                  8 
                 tcgggcagagggtgcatcacct 
                 5570 
                 Apolipoprotein 
               
               
                   
               
               
                  9 
                 ataataagcagaacttttagtg 
                 5571 
                 Fibrinogen 
               
               
                   
               
               
                 10 
                 gttttctttagttattaatttc 
                 5572 
                 Fibrinogen 
               
               
                   
               
            
           
         
       
     
     Targeted Endonuclease Activity in Mammalian Cells (b) 
     MG3-6 target loci were chosen to test locations in the genome with the PAM nnRGGTT (SEQ ID NO: 5532). The spacers corresponding to the chosen target sites were cloned into the sgRNA scaffold in the mammalian vector system backbone 1 described in Example 10b. The sites are listed in Table 7a below. The activity of MG3-6 at various target sites is shown in Table 7a and  FIG. 40 . 
     
       
         
           
               
             
               
                 TABLE 7a 
               
             
            
               
                   
               
               
                 Activity of MG3-6 at various target sites 
               
            
           
           
               
               
               
               
               
            
               
                 target 
                   
                   
                   
                 % NHEJ 
               
               
                 ID 
                 target sequence 
                 PAM 
                 locus 
                 (mean ± std) 
               
               
                   
               
               
                 target1 
                 gagtgactgaaacttcacagaa 
                 tagggtt 
                 Albumin 
                   9.755 ± 4.67 
               
               
                   
               
               
                 target2 
                 ttctatttatgagatcaacagc 
                 acaggtt 
                 Albumin 
                   32.75 ± 7.42 
               
               
                   
               
               
                 target3 
                 cagatgcaccatggtgtctgtt 
                 tgaggt 
                 HBB_R01 
                   2.525 ± 2.13 
               
               
                   
               
               
                 target5 
                 gaggccctgggcaggttggtat 
                 caaggtt 
                 HBB_R01 
                   25.16 ± 3.67 
               
               
                   
               
               
                 target6 
                 aggttggtatcaaggttacaag 
                 acaggtt 
                 HBB_R01 
                   35.27 ± 2.78 
               
               
                   
               
               
                 target7 
                 tcaactttcctggcaacttgcg 
                 gtaggtt 
                 Apolipoprotei 
                   21.57 ± 5.70 
               
               
                   
               
               
                 target8 
                 aggaacattcagttaagatagt 
                 ctaggtt 
                 Fibrinogen 
                  7.5675 ± 11.99 
               
               
                   
               
               
                 target9 
                 tttaaattatgaatccatctct 
                 aaaggtt 
                 Fibrinogen 
                 46.3175 ± 31.46 
               
               
                   
               
               
                 target10 
                 gagtgactgaaacttcacagaa 
                 tagggtt 
                 Albumin 
                  3.9325 ± 3.53 
               
               
                   
               
            
           
         
       
     
     MG3-7 target loci were chosen to test locations in the genome with the PAM nnRnTAC (SEQ ID NO: 5718). The spacers corresponding to the chosen target sites were cloned into the sgRNA scaffold in the mammalian vector systems described in Example 10b. The sites are listed in Table 7b below. The activity of MG3-7 at various target sites is shown in Table 7b and  FIG. 41 . 
     
       
         
           
               
             
               
                 TABLE 7b 
               
             
            
               
                   
               
               
                 Activity of MG3-7 at various target sites 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                 % NHEJ 
                   
               
               
                   
                   
                   
                   
                 backbone 2 
                 % NHEJ 
               
               
                 target ID 
                 target sequence 
                 PAM 
                 locus 
                 (mean ± std) 
                 backbone 1 
               
               
                   
               
               
                 1 
                 cccctatttctgacctcccaaa 
                 CAGCTAC 
                 VEGFA 
                  0.54 ± 0.44 
                   
               
               
                   
               
               
                 2 
                 tgtggttccagaaccggaggac 
                 AAAGTAC 
                 EMX1 
                 −0.09 ± 0.04 
                   
               
               
                   
               
               
                 3 
                 ggccctgggcaggttggtatca 
                 AGGTTAC 
                 HBB 
                 8.275 ± 0.3.12 
                 3.87 
               
               
                   
               
               
                 4 
                 tccttaaacctgtcttgtaacc 
                 TTGATAC 
                 HBB 
                  0.16 ± 0.20 
                   
               
               
                   
               
               
                 5 
                 ctgactcctgaggagaagtctg 
                 CCGTTAC 
                 HBB 
                 0.245 ± 0.16 
                   
               
               
                   
               
               
                 6 
                 tccgagcttctggcggtctcaa 
                 GCACTAC 
                 FANCF 
                  1.84 ± 0.10 
                 3.95 
               
               
                   
               
               
                 7 
                 tatcatttcgcggatgttccaa 
                 TCAGTAC 
                 FANCF 
                 0.325 ± 0.68 
                   
               
               
                   
               
               
                 8 
                 tcgggcagagggtgcatcacct 
                 GGACTAC 
                 Apolipoprotein 
                 13 
                 23.88 
               
               
                   
               
            
           
         
       
     
     MG3-8 target loci were chosen to test locations in the genome with the PAM nnRGGTT (SEQ ID NO: 5534). The spacers corresponding to the chosen target sites were cloned into the sgRNA scaffold in the mammalian vector system backbone 1 described in Example 10b. The sites are listed in Table 7c below. The activity of MG3-8 at various target sites is shown in Table 7c and  FIG. 42 . 
     
       
         
           
               
             
               
                 TABLE 7c  
               
             
            
               
                   
               
               
                 Activity of MG3-8 at various target sites 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 % NHEJ 
               
               
                 target ID 
                 target sequence 
                 PAM 
                 locus 
                 (mean ± std) 
               
               
                   
               
               
                 targetl 
                 gagtgactgaaacttcacagaa 
                 tagggtt 
                 Albumin 
                   10.81 ± 4.26 
               
               
                   
               
               
                 target2 
                 ttctatttatgagatcaacagc 
                 acaggtt 
                 Albumin 
                   30.48 ± 11.17 
               
               
                   
               
               
                 target3 
                 cagatgcaccatggtgtctgtt 
                 tgaggt 
                 HBB 
                  3.3925 ± 2.13 
               
               
                   
               
               
                 target4 
                 gaagttggtggtgaggccctgg 
                 gcaggtt 
                 HBB 
                  28.995 ± 11.87 
               
               
                   
               
               
                 target5 
                 gaggccctgggcaggttggtat 
                 caaggtt 
                 HBB 
                   28.69 ± 1.96 
               
               
                   
               
               
                 target6 
                 aggttggtatcaaggttacaag 
                 acaggtt 
                 HBB 
                 30.8575 ± 13.24 
               
               
                   
               
               
                 target7 
                 tcaactttcctggcaacttgcg 
                 gtaggtt 
                 Apolipoprotein 
                  7.9825 ± 3.23 
               
               
                   
               
               
                 target8 
                 aggaacattcagttaagatagt 
                 ctaggtt 
                 Fibrinogen 
                 20.2925 ± 17.10 
               
               
                   
               
               
                 target9 
                 tttaaattatgaatccatctct 
                 aaaggtt 
                 Fibrinogen 
                  35.533 ± 25.46 
               
               
                   
               
               
                 target10 
                 gagtgactgaaacttcacagaa 
                 tagggtt 
                 Albumin 
                     4.9 ± 0.71 
               
               
                   
               
            
           
         
       
     
     Example 13 
     Characterization of MG4 Family Members 
     PAM Specificity, tracrRNA/sgRNA Validation 
     The targeted endonuclease activity of MG4 family endonuclease systems was confirmed using the myTXTL system as described in Example 6. In this assay, PCR amplification of cleaved target plasmids yields a product that migrates at approximately 170 bp in the gel, as shown in  FIGS. 17-20 . Amplification products were observed for, MG4-2 (dual guide: see gel2 lane 9, single guide: see gel 10 lane 7) (SEQ ID NO: 432). Sequencing the PCR products revealed active PAM sequences shown in Table 8 below. 
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 PAM sequence specificities and related data for MG4 enzymes 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Enzyme 
                   
                   
                   
                 Synthetic 
               
               
                   
                 protein 
                 tracrRNA 
                 sgRNA 
                 Synthetic 
                 (single guide) 
               
               
                   
                 SEQ 
                 SEQ 
                 SEQ 
                 (single guide) 
                 PAM SEQ 
               
               
                 Enzyme 
                 ID NO 
                 ID NO: 
                 ID NO: 
                 PAM 
                 ID NO: 
               
               
                   
               
               
                 MG4-5 
                 432 
                 5503 
                 5468 
                 nnCCR 
                 5519 
               
               
                   
               
            
           
         
       
     
     Example 14 
     Characterization of MG14 Family Members 
     PAM Specificity, tracrRNA/sgRNA Validation 
     The targeted endonuclease activity of MG14 family members (was confirmed using the myTXTL system as described in Example 6. In this assay, PCR amplification of cleaved target plasmids yields a product that migrates at approximately 170 bp in the gel, as shown in  FIGS. 17-20 . Amplification products were observed for MG14-1 (dual guide: see gel 1 lane 4, single guide: see gel 3 lane 8) (SEQ ID NO: 678). Sequencing the PCR products revealed active PAM sequence specificities shown in Table 9 below. 
     
       
         
           
               
             
               
                 TABLE 9 
               
             
            
               
                   
               
               
                 PAM sequence specificities and related data for MG14 enzymes 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 Enzyme 
                 Native 
                   
                   
                   
                 Synthetic 
                 Synthetic 
               
               
                   
                 protein 
                 (dual guide) 
                 PAM 
                 tracrRNA 
                 sgRNA 
                 (single guide) 
                 (single guide) 
               
               
                   
                 SEQ 
                 PAM 
                 SEQ 
                 SEQ 
                 SEQ 
                 PAM 
                 PAM SEQ 
               
               
                 Enzyme 
                 ID NO 
                 determined 
                 ID NO: 
                 ID NO: 
                 ID NO: 
                 determined 
                 ID NO: 
               
               
                   
               
               
                 MG14-1 
                 678 
                 NNNNGGTA 
                 5535 
                 5505 
                 5469 
                 NNNGGRTA 
                 5520 
               
               
                   
               
            
           
         
       
     
     Targeted Endonuclease Activity in Bacterial Cells 
     In vivo activity of the MG14-1 endonuclease system with a sgRNA (endonuclease SEQ ID NO: 678; sgRNA SEQ ID NO: 5469) and a GGCGGGGA PAM sequence was confirmed using the method described in Example 9 . Transformed  E. coli  were plated in serial dilution, and the results (showing  E. coli  serial dilutions in the left panel and quantitated growth in the right panel) are presented in  FIG. 35 . A substantial reduction in the growth of  E. coli  expressing on target sgRNA compared to  E. coli  expressing non-target sgRNA indicates that genomic DNA was specifically cleaved by the MG1-4 endonuclease in  E. coli  cells. 
     Targeted Endonuclease Activity in Mammalian Cells 
     MG14-1 target loci were chosen to test locations in the genome with the PAM nnnnGGTA (SEQ ID NO: 5535). The spacers corresponding to the chosen target sites were cloned into the sgRNA scaffold in the mammalian vector system backbone 2 described in Example 10b. The sites are listed in Table 9a below. The activity of MG14-1 at various target sites is shown in Table 9a and  FIG. 43 . 
     
       
         
           
               
             
               
                 TABLE 9a  
               
             
            
               
                   
               
               
                 Activity of MG14-1 at various target sites 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 % NHEJ 
               
               
                 target ID 
                 target sequence 
                 PAM 
                 locus 
                 (mean ± std) 
               
               
                   
               
               
                  1 
                 cttattaataaaattcaaacat 
                 CCTAGGTA 
                 Albumin 
                  0.22 ± 1.04 
               
               
                   
               
               
                  2 
                 gttggtggtgaggccctgggca 
                 GGTTGGTA 
                 HBB 
                  0.67 ± 0.16 
               
               
                   
               
               
                  3 
                 ctagttaatggaataaaacatt 
                 TTATGGTA 
                 Fibrinogen 
                 0.15 
               
               
                   
               
               
                  4 
                 gcattataatgcaccaaggctt 
                 TATAGGTA 
                 Fibrinogen 
                 0.2 
               
               
                   
               
               
                  5 
                 gtggcggggtcccaggtgctga 
                 CGTAGGTA 
                 FANCF 
                  5.33 ± 4.13 
               
               
                   
               
               
                  6 
                 tgtccgccgccggccggggagg 
                 AGGTGGTA 
                 VEGFA 
                  4.88 ± 0.65 
               
               
                   
               
               
                  7 
                 ggtgatgcaccctctgcccgat 
                 GCTTGGTA 
                 Apolipoprotein 
                 −0.35 ± 0.59 
               
               
                   
               
               
                  8 
                 ccacatcaactttcctggcaac 
                 TTGCGGTA 
                 Apolipoprotein 
                 0.195 ± 0.98 
               
               
                   
               
               
                  9 
                 gctagttaatggaataaaacatt 
                 TTATGGTA 
                 Fibrinogen 
                 0.6 
               
               
                   
               
               
                 10 
                 gcattataatgcaccaaggctt 
                 TATAGGTA 
                 Fibrinogen 
                  1.17 ± 1.42 
               
               
                   
               
            
           
         
       
     
     Example 15 
     Characterization of MG15 Family Members 
     PAM Specificity, tracrRNA/sgRNA Validation 
     The targeted endonuclease activity of MG15 family members was confirmed using the myTXTL system as described in Example 6. In this assay, PCR amplification of cleaved target plasmids yields a product that migrates at approximately 170 bp in the gel, as shown in  FIGS. 17-20 . Amplification products were observed for MG15-1 (dual guide: see gel 7 lane 7, single guide: see gel 3 lane 9) (SEQ ID NO: 930). Sequencing the PCR products revealed active PAM sequence specificities detailed in Table 10 below. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 10 
               
               
                   
               
               
                   
                 Enzyme 
                   
                   
                   
                   
                   
                 Synthetic 
               
               
                   
                 protein 
                 Native 
                 PAM 
                 tracrRNA 
                 sgRNA 
                 Synthetic 
                 (single guide) 
               
               
                   
                 SEQ 
                 (dual guide) 
                 SEQ 
                 SEQ 
                 SEQ 
                 (single guide) 
                 PAM SEQ 
               
               
                 Enzyme 
                 ID NO 
                 PAM 
                 ID NO: 
                 ID NO: 
                 ID NO: 
                 PAM 
                 ID NO: 
               
               
                   
               
             
            
               
                 MG15-1 
                 930 
                 nnnnC 
                 5536 
                 5506 
                 5470 
                 nnnnC 
                 5521 
               
               
                   
               
            
           
         
       
     
     In Vitro Activity 
     In vitro activity of the MG15-1 endonuclease system (protein SEQ ID NO: 930; sgRNA SEQ ID NO:5470) was tested with the PAM sequence GGGTCAAA using the method of Example 8. The single guide sequence reported above (SEQ ID NO: 5470) was used, with varying spacer/targeting sequence lengths from 18-24 nt (replacing the Ns of the sequence). The results are shown in  FIG. 16 , wherein the top panel shows a gel demonstrating DNA cleavage by MG15-1 in combination with different sgRNAs having different targeting sequence lengths (18-24 nt), and the bottom panel shows the same data quantified as a bar graph. The data demonstrated that targeting sequences from 18-24 nucleotides were functional with the MG15-1/sgRNA system. 
     Targeted Endonuclease Activity in Bacterial Cells 
     In vivo activity of the MG15-1 endonuclease system with a sgRNA (endonuclease SEQ ID NO: 930; sgRNA SEQ ID NO: 5470) and a GGGTCAAA PAM sequence was confirmed using the method described in Example 9. Transformed  E. coli  were plated in serial dilution, and the results (showing  E. coli  serial dilutions in the left panel and quantitated growth in the right panel) are presented in  FIG. 35 . A substantial reduction in the growth of  E. coli  expressing on target sgRNA compared to  E. coli  expressing non-target sgRNA indicates that genomic DNA was specifically cleaved by the MG1-4 endonuclease in  E. coli  cells. 
     Example 16 
     Characterization of MG16 Family Members 
     PAM Specificity, tracrRNA/sgRNA Validation 
     The targeted endonuclease activity of MG16 family members was confirmed using the myTXTL system as described in Example 6. In this assay, PCR amplification of cleaved target plasmids yields a product that migrates at approximately 170 bp in the gel, as shown in  FIGS. 17-20 . Amplification products were observed for MG16-2 (see gel 11, lane 17) (SEQ ID NO: 1093). Sequencing the PCR products revealed active PAM sequence specificities detailed in Table 11 below. 
     
       
         
           
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                 PAM sequence specificities and related data for MG16 enzymes 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Enzyme 
                   
                   
                 Synthetic 
               
               
                   
                 protein 
                 sgRNA 
                 Synthetic 
                 (single guide) 
               
               
                   
                 SEQ 
                 SEQ 
                 (single guide) 
                 PAM SEQ 
               
               
                 Enzyme 
                 ID NO 
                 ID NO: 
                 PAM 
                 ID NO: 
               
               
                   
               
               
                 MG16-2 
                 1093 
                 5471 
                 nRTnCC 
                 5522 
               
               
                   
               
            
           
         
       
     
     Example 17 
     Characterization of MG18 Family Members 
     PAM Specificity, tracrRNA/sgRNA Validation 
     The targeted endonuclease activity of MG18 family members was confirmed using the myTXTL system as described in Example 6. In this assay, PCR amplification of cleaved target plasmids yields a product that migrates at approximately 170 bp in the gel, as shown in  FIGS. 17-20 . Amplification products were observed for MG18-1 (dual guide: see gel 9 lane 9, single guide: see gel 11 lane 12) (SEQ ID NO: 1354). Sequencing the PCR products revealed active PAM sequence specificities detailed in Table 12 below. 
     
       
         
           
               
             
               
                 TABLE 12 
               
             
            
               
                   
               
               
                 PAM sequence specificities and related data for MG18 enzymes 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 Enzyme 
                   
                   
                   
                   
                   
                 Synthetic 
               
               
                   
                 protein 
                 Native 
                 PAM 
                 tracrRNA 
                 sgRNA 
                 Synthetic 
                 (single guide) 
               
               
                   
                 SEQ 
                 (dual guide) 
                 SEQ 
                 SEQ 
                 SEQ 
                 (single guide) 
                 PAM SEQ 
               
               
                 Enzyme 
                 ID NO 
                 PAM 
                 ID NO: 
                 ID NO: 
                 ID NO: 
                 PAM 
                 ID NO: 
               
               
                   
               
               
                 MG18-1 
                 1354 
                 nRWART 
                 5537 
                 5508 
                 5472 
                 nnnRRT 
                 5523 
               
               
                   
               
            
           
         
       
     
     Targeted Endonuclease Activity in Mammalian Cells 
     MG18-1 target loci were chosen to test locations in the genome with the PAM nRWART (SEQ ID NO: 5537). The spacers corresponding to the chosen target sites were cloned into the sgRNA scaffold in the mammalian vector system backbone 1 described in Example 10b. The sites are in Table 12a below. The activity of MG18-1 at various target sites is shown in Table 12a and  FIG. 44 . 
     
       
         
           
               
             
               
                 TABLE 12a  
               
             
            
               
                   
               
               
                 Activity of MG18-1 at various target sites 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                   
                 % NHEJ 
               
               
                 target ID 
                 target sequence 
                 PAM 
                 locus 
                 (mean ± std) 
               
               
                   
               
               
                 target2 
                 tgcttattatggacaagtagca 
                 agaaat 
                 Fibrinogen 
                  9.003 ± 3.70 
               
               
                   
               
               
                 target4 
                 tccctgaagatgctcacagttt 
                 gatagt 
                 IVS40 
                   1.99 ± 2.56 
               
               
                   
               
               
                 target5 
                 ttttatttctcctgcatatgat 
                 gatagt 
                 IVS40 
                  6.303 ± 4.82 
               
               
                   
               
               
                 target8 
                 tgtggggcaaggtgaacgtgga 
                 tgaagt 
                 HBB 
                 14.897 ± 2.73 
               
               
                   
               
               
                 target9 
                 atggtgcatctgactcctgagg 
                 agaagt 
                 HBB 
                  0.387 ± 0.32 
               
               
                   
               
               
                 target10 
                 agaacagcccagaagttggacg 
                 aaaagt 
                 VEGFA 
                    4.3 ± 1.29 
               
               
                   
               
               
                 target11 
                 tcctccgaagcgagaacagccc 
                 agaagt 
                 VEGFA 
                  15.22 ± 2.40 
               
               
                   
               
            
           
         
       
     
     Example 18 
     Characterization of MG21 Family Members 
     PAM Specificity, tracrRNA/sgRNA Validation 
     The targeted endonuclease activity of MG21 family was confirmed using the myTXTL system as described in Example 6. In this assay, PCR amplification of cleaved target plasmids yields a product that migrates at approximately 170 bp in the gel, as shown in  FIGS. 17-20 . Amplification products were observed for MG21-1 (see gel 11 lane 2) (SEQ ID NO: 1512). Sequencing the PCR products revealed active PAM sequence specificities detailed in Table 13 below. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 13 
               
               
                   
               
               
                   
                 Enzyme 
                   
                   
                 Synthetic 
               
               
                   
                 protein 
                 sgRNA 
                 Synthetic 
                 (single guide) 
               
               
                   
                 SEQ 
                 SEQ 
                 (single guide) 
                 PAM SEQ 
               
               
                 Enzyme 
                 ID NO 
                 ID NO: 
                 PAM 
                 ID NO: 
               
               
                   
               
             
            
               
                 MG21-1 
                 1512 
                 5473 
                 nnRnR 
                 5524 
               
               
                   
               
            
           
         
       
     
     Example 19 
     Characterization of MG22 Family Members 
     PAM Specificity, tracrRNA/sgRNA Validation 
     The targeted endonuclease activity of MG22 family members was confirmed using the myTXTL system as described in Example 6. In this assay, PCR amplification of cleaved target plasmids yields a product that migrates at approximately 170 bp in the gel, as shown in  FIGS. 17-20 . In the assay shown  FIGS. 17-20 , active proteins that successfully cleave the library result in a band around 170 bp in the gel. Amplification products were observed for MG22-1 (see gel 11 lane 3) (protein SEQ ID NO: 1656). Sequencing the PCR products revealed active PAM sequence specificities detailed in Table 14 below. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 14 
               
               
                   
               
               
                   
                 Enzyme 
                 Native 
                   
                   
                   
                 Synthetic 
                 Synthetic 
               
               
                   
                 protein 
                 (dual guide) 
                 PAM 
                 tracrRNA 
                 sgRNA 
                 (single guide) 
                 (single guide) 
               
               
                   
                 SEQ 
                 PAM 
                 SEQ 
                 SEQ 
                 SEQ 
                 PAM 
                 PAM SEQ 
               
               
                 Enzyme 
                 ID NO 
                 determined 
                 ID NO: 
                 ID NO: 
                 ID NO: 
                 determined 
                 ID NO: 
               
               
                   
               
             
            
               
                 MG22-1 
                 1656 
                 N/A 
                 N/A 
                 5510 
                 5474 
                 nnRCnT 
                 5525 
               
               
                   
               
            
           
         
       
     
     Example 20 
     Characterization of MG23 Family Members 
     PAM Specificity, tracrRNA/sgRNA Validation 
     The targeted endonuclease activity of MG23 family members was confirmed using the myTXTL system as described in Example 6. In this assay, PCR amplification of cleaved target plasmids yields a product that migrates at approximately 170 bp in the gel, as shown in  FIGS. 17-20 . Amplification products were observed for MG23-1 (see gel 11 lane 4) (SEQ ID NO: 1756). Sequencing the PCR products revealed active PAM sequences specificities for these enzymes detailed Table 15 below. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 15 
               
               
                   
               
               
                   
                 Enzyme 
                   
                   
                   
                 Synthetic 
               
               
                   
                 protein 
                 tracrRNA 
                 sgRNA 
                 Synthetic 
                 (single guide) 
               
               
                   
                 SEQ 
                 SEQ 
                 SEQ 
                 (single guide) 
                 PAM SEQ 
               
               
                 Enzyme 
                 ID NO 
                 ID NO: 
                 ID NO: 
                 PAM 
                 ID NO: 
               
               
                   
               
             
            
               
                 MG23- 
                 1756 
                 5511 
                 5475 
                 nRRA 
                 5526 
               
               
                 1 
               
               
                   
               
            
           
         
       
     
     Systems of the present disclosure may be used for various applications, such as, for example, nucleic acid editing (e.g., gene editing), binding to a nucleic acid molecule (e.g., sequence-specific binding). Such systems may be used, for example, for addressing (e.g., removing or replacing) a genetically inherited mutation that may cause a disease in a subject, inactivating a gene in order to ascertain its function in a cell, as a diagnostic tool to detect disease-causing genetic elements (e.g. via cleavage of reverse-transcribed viral RNA or an amplified DNA sequence encoding a disease-causing mutation), as deactivated enzymes in combination with a probe to target and detect a specific nucleotide sequence (e.g. sequence encoding antibiotic resistance int bacteria), to render viruses inactive or incapable of infecting host cells by targeting viral genomes, to add genes or amend metabolic pathways to engineer organisms to produce valuable small molecules, macromolecules, or secondary metabolites, to establish a gene drive element for evolutionary selection, to detect cell perturbations by foreign small molecules and nucleotides as a biosensor. 
     While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. It is not intended that the invention be limited by the specific examples provided within the specification. While the invention has been described with reference to the aforementioned specification, the descriptions and illustrations of the embodiments herein are not meant to be construed in a limiting sense. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Furthermore, it shall be understood that all aspects of the invention are not limited to the specific depictions, configurations or relative proportions set forth herein which depend upon a variety of conditions and variables. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is therefore contemplated that the invention shall also cover any such alternatives, modifications, variations or equivalents. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.