Rapid characterization of Cas endonuclease systems, PAM sequences and guide RNA elements
Compositions and methods are provided for rapid characterization of Cas endonuclease systems and the elements comprising such systems, including, but not limiting to, rapid characterization of PAM sequences, guide RNA elements and Cas endonucleases. Type II Cas9 endonuclease systems originating from Brevibacillus laterosporus, Lactobacillus reuteri Mlc3, Lactobacillus rossiae DSM 15814, Pediococcus pentosaceus SL4, Lactobacillus nodensis JCM 14932, Sulfurospirillum sp. SCADC, Bifidobacterium thermophilum DSM 20210, Loktanella vestfoldensis, Sphingomonas sanxanigenens NX02, Epilithonimonas tenax DSM 16811, Sporocytophaga myxococcoides are described herein. The present disclosure also describes methods for genome modification of a target sequence in the genome of a cell, for gene editing, and for inserting a polynucleotide of interest into the genome of a cell.
1. A method for identification of a Protospacer-Adjacent-Motif (PAM) sequence, the method comprising:
a) providing a library of circular double-stranded plasmid DNA, wherein each one of said plasmid DNA comprises a randomized Protospacer-Adjacent-Motif sequence integrated adjacent to a target sequence that can be recognized by a guide RNA/Cas endonuclease complex;
b) providing to said library of plasmids a guide RNA and a Cas endonuclease protein, wherein said guide RNA and Cas endonuclease protein can form a complex that is capable of introducing a double strand break into the said target sequence, thereby creating a library of cleavage products;
c) ligating 3′ deoxyAdenine to the cleavage products;
d) ligating adaptors to the library of cleavage products of (c) allowing for the library of cleavage products to be amplified;
e) amplifying the library of cleavage products of (d) such that the cleavage products containing the randomized PAM sequence are enriched, thereby producing a library of enriched PAM-sided targets;
f) sequencing the library of (a) and the library of enriched PAM-sided targets of (e) and identifying the nucleotide sequence adjacent to the target sequences in the cleavage products of (b) on either strand of the plasmid DNA, wherein said nucleotide sequence represents a putative Protospacer-Adjacent-Motif sequences; and,
g) determining the fold enrichment of each nucleotide within the putative Protospacer-Adjacent-Motif sequence relative to the plasmid DNA library of (a).
2. The method of anyone of claim 1 , wherein the randomized PAM sequence comprises at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 randomized nucleotides.
3. The method of claim 1 , wherein the target sequence is at least 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 nucleotides in length.
4. The method of claim 1 , wherein the Cas endonuclease protein is provided as a purified protein, a cell lysate comprising said Cas endonuclease, a dilution of a cell lysate comprising said Cas endonuclease, an in-vitro translation mixture or an dilution of an in-vitro translation mixture.
5. The method of claim 1 , wherein the Cas endonuclease protein is a Cas9 protein.
6. The method of claim 1 , wherein the Cas endonuclease comprises an HNH domain and an RuvC domain.
7. The method of claim 1 , wherein the Cas endonuclease, the guide RNA, or both in step (b) is(are) provided as a purified molecule(s).
8. The method of claim 1 , wherein the Cas endonuclease, the guide RNA, or both in step (b) is(are) provided as part of a cell lysate.
9. The method of claim 1 , wherein the Cas endonuclease, the guide RNA, or both in step (b) is(are) provided as in vitro transcription product(s).
10. The method of claim 5 , wherein the Cas9 protein is from Streptococcus thermophilus.