Lee, Jaesuk Lim, Kayeong Kim, Annie Mok, Young Geun Chung, Eugene Cho, Sung-Ik Lee, Ji Min Kim, Jin-Soo 2024-01-19T10:01:12Z 2024-01-19T10:01:12Z 2023-04-27 2023-03 2041-1723 https://pubs.kist.re.kr/handle/201004/113910 Cas9 nickases (nCas9s) produce nicks or single-strand breaks in the DNA. Here the authors analyse the on- and off-target nicks generated by these nickases, and show that nCas9 (H840A) but not nCas9 (D10A) can cleave both strands and produce unwanted DNA double-strand breaks. Unlike CRISPR-Cas9 nucleases, which yield DNA double-strand breaks (DSBs), Cas9 nickases (nCas9s), which are created by replacing key catalytic amino-acid residues in one of the two nuclease domains of S. pyogenesis Cas9 (SpCas9), produce nicks or single-strand breaks. Two SpCas9 variants, namely, nCas9 (D10A) and nCas9 (H840A), which cleave target (guide RNA-pairing) and non-target DNA strands, respectively, are widely used for various purposes, including paired nicking, homology-directed repair, base editing, and prime editing. In an effort to define the off-target nicks caused by these nickases, we perform Digenome-seq, a method based on whole genome sequencing of genomic DNA treated with a nuclease or nickase of interest, and find that nCas9 (H840A) but not nCas9 (D10A) can cleave both strands, producing unwanted DSBs, albeit less efficiently than wild-type Cas9. To inactivate the HNH nuclease domain further, we incorporate additional mutations into nCas9 (H840A). Double-mutant nCas9 (H840A + N863A) does not exhibit the DSB-inducing behavior in vitro and, either alone or in fusion with the M-MLV reverse transcriptase (prime editor, PE2 or PE3), induces a lower frequency of unwanted indels, compared to nCas9 (H840A), caused by error-prone repair of DSBs. When incorporated into prime editor and used with engineered pegRNAs (ePE3), we find that the nCas9 variant (H840A + N854A) dramatically increases the frequency of correct edits, but not unwanted indels, yielding the highest purity of editing outcomes compared to nCas9 (H840A). English Nature Publishing Group Prime editing with genuine Cas9 nickases minimizes unwanted indels Article 10.1038/s41467-023-37507-8 1 Nature Communications, v.14, no.1 Nature Communications 14 1 Y scie scopus 000961133600027 2-s2.0-85151316474 Multidisciplinary Sciences Science & Technology - Other Topics Article WIDE TARGET SPECIFICITIES GENOMIC DNA RNA BASE