Fig. 2

Schematics of genome editing technology systems and genome modifications generated by different systems. A ZFNs technology contains an array of engineered zinc finger proteins fused to catalytic domain of the FokI endonuclease. B TALENs have arrays of the TAL effector fused with FokI. C CRISPR/Cas9 system which is composed of Cas9 protein and sgRNA. (D) The cytidine base editor (CBE). Green circle represents cytidine deaminase rAPOBEC1. Purple circle represents uracil glycosylase inhibitor (UGI). E The adenine base editor (ABE). Light purple circle represents adenine deaminase TadA. F Prime editing technology. The prime editor (PE) is made up of a fusion protein of nCas9 (H840A) with reverse transcriptase and a prime editing guide RNA (pegRNA). G ZFNs, TALENs and CRISPR/Cas9 deliver double strand breaks (DSBs). DNA repair pathway includes the DNA non-homologous end joining (NHEJ) repair pathway and homology directed repair (HDR) pathway. DNA repair pathway produce different forms of genome modifications. H CBE generates base substitution of C•G to A•T without DSBs. I ABE make base substitution of A•T to G•C without DSBs. J PE generate precise genome modification of DNA substitution, insertion and deletion