Figure 3.

Schematically shown base modification with Nickase Cas9(nCas9), (A) The ABE system catalyzes the conversion of adenine into guanine via nCas9 and adenine deaminase. Adenine is deaminated by ABE to inosine (I), changing T-A to T-I. Repair machinery interprets I as G and repairs T-I as C-G; (B) the CBE system uses nCas9 and cytidine deaminase to catalyze the conversion of cytosine to uridine. UGI (uracil glycosylase inhibitor) inhibits U: G mismatch from being repaired back to C: G, causing U to ultimately change into T; (C) Prime editing is illustrated in a schematic by combining nCas9 with reverse transcriptase and a prime editing guide RNA (pegRNA). The reverse transcriptase may carry out a variety of transitions, insertions, and deletions, while prime editing mechanisms edit DNA without resulting in DSBs (Ahmad et al., 2021).