Recent studies revealed that promoting the BER pathway by UNG or other DNA repair proteins fusion to SpCas9 CBEs can convert target C:G base pair into G:C or A:T base pair rather than the expected T:A product . Given that a high portion of unexpected C-to-G byproduct existed with CBEdSt1Cas9, we anticipated that fusion of UNG to CBEdSt1Cas9 would generate new base editors. We thus fused E. coli UNG (eUNG) to the C terminus of dSt1Cas9 in CBEdSt1Cas9 to create a new base editor CGBEWT and compared the base editing efficiencies of CGBEWT and CBEdSt1Cas9. As shown in Fig. , CGBEWT can efficiently achieve C-to-G conversions with enhanced editing product purity at all the five tested sites.