Figure 4.

New generations of genome editing tools- base and prime editing. (A) Cytosine and adenine base editors (CBEs or ABEs), consist of a nickase Cas9 (nCas9) fused to a deaminase that nicks the opposite strand inducing a DNA repair pathway response, resulting in the conversion of C:G into T:A or A:T into G:C base pairs in the editing site. (B) In the prime editing (PE) method, a PE gRNA (pegRNA) complexes to the fused retroviral reverse transcriptase (RT)- nCas9 complex, tethering it to the target site. After the nicking of the target strand by nCas9, the RT synthesizes a new DNA strand using the sequence included in the pegRNA as a template, and thus introducing the desired edit.