Article
作者: Li, Dali ; Zhu, Biyun ; Xue, Niannian ; Yan, Yongchang ; Gao, Hongyi ; Luan, Changming ; Ru, Gaomeng ; Bai, Sijia ; Cheng, Yiyun ; Chen, Liang ; Li, Changqing ; Meng, Haowei ; Wang, Liren ; Hong, Mengjia ; Yi, Chengqi ; Liu, Mingyao ; Chen, Yuting ; Song, Gaojie ; Guan, Yuting ; Ding, Ruoyi ; Zhang, Dan ; Zhang, Shun ; Siwko, Stefan ; Wu, Hao ; Lei, Zhixin
Cytosine base editors (CBEs) efficiently generate precise C·G-to-T·A base conversions, but the activation-induced cytidine deaminase/apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (AID/APOBEC) protein family deaminase component induces considerable off-target effects and indels. To explore unnatural cytosine deaminases, we repurpose the adenine deaminase TadA-8e for cytosine conversion. The introduction of an N46L variant in TadA-8e eliminates its adenine deaminase activity and results in a TadA-8e-derived C-to-G base editor (Td-CGBE) capable of highly efficient and precise C·G-to-G·C editing. Through fusion with uracil glycosylase inhibitors and further introduction of additional variants, a series of Td-CBEs was obtained either with a high activity similar to that of BE4max or with higher precision compared to other reported accurate CBEs. Td-CGBE/Td-CBEs show very low indel effects and a background level of Cas9-dependent or Cas9-independent DNA/RNA off-target editing. Moreover, Td-CGBE/Td-CBEs are more efficient in generating accurate edits in homopolymeric cytosine sites in cells or mouse embryos, suggesting their accuracy and safety for gene therapy and other applications.