Cytidine base editors are powerful genetic tools that catalyse cytidine to thymidine conversion at specific genomic loci, and further improvement of the editing range and efficiency is critical for their broader applications. Through insertion of a non-sequence-specific single-stranded DNA-binding domain from Rad51 protein between Cas9 nickase and the deaminases, serial hyper cytidine base editors were generated with substantially increased activity and an expanded editing window towards the protospacer adjacent motif in both cell lines and mouse embryos. Additionally, hyeA3A-BE4max selectively catalysed cytidine conversion in TC motifs with a broader editing range and much higher activity (up to 257-fold) compared with eA3A-BE4max. Moreover, hyeA3A-BE4max specifically generated a C-to-T conversion without inducing bystander mutations in the haemoglobin gamma gene promoter to mimic a naturally occurring genetic variant for amelioration of β-haemoglobinopathy, suggesting the therapeutic potential of the improved base editors.

中文翻译：

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通过融合单链DNA结合蛋白结构域来提高胞苷碱基编辑器的效率和靶向范围。

胞嘧啶碱基编辑器是强大的遗传工具，可在特定的基因组位点催化胞嘧啶核苷向胸腺嘧啶核苷的转化，进一步扩大编辑范围和效率对于其更广泛的应用至关重要。通过在Cas9切口酶和脱氨基酶之间插入Rad51蛋白的非序列特异性单链DNA结合结构域，产生了序列化的高胞苷碱基编辑器，其活性大大提高，并且向两个细胞中的原间隔子相邻基序扩展了编辑窗口系和小鼠胚胎。此外，与eA3A-BE4max相比，hyeA3A-BE4max具有更宽的编辑范围和更高的活性（高达257倍），可选择性地催化TC基序中的胞苷转化。此外，