IscB has a similar domain organization to Cas9, but the small size of IscB is better suited for delivery by adeno-associated virus. To improve the low editing efficiency of OgeuIscB (IscB from human gut metagenome) in mammalian cells, we developed high-efficiency miniature base editors by engineering OgeuIscB nickase and its cognate ωRNA, termed IminiBEs. We demonstrated the robust editing efficiency of IminiCBE (67% on average) or IminiABE (52% on average). Fusing non-specific DNA-binding protein Sso7d to IminiBEs increased the editing efficiency of low-efficiency sites by around two- to threefold, and we termed it SIminiBEs. In addition, IminiCBE and SIminiCBE recognize NNRR, NNRY and NNYR target-adjacent motifs, which broaden the canonical NWRRNA target-adjacent motif sites for the wild-type IscB nickase. Overall, IminiBEs and SIminiBEs are efficient miniature base editors for site-specific genomic mutations.

IscB 具有与 Cas9 相似的结构域组织，但 IscB 的小尺寸更适合通过腺相关病毒递送。为了提高哺乳动物细胞中 OgeuIscB （来自人肠道宏基因组的 IscB） 的低编辑效率，我们通过工程化 OgeuIscB 切口酶及其同源 ωRNA（称为 IminiBEs）开发了高效的微型碱基编辑器。我们证明了 IminiCBE（平均 67%）或 IminiABE（平均 52%）的稳健编辑效率。将非特异性 DNA 结合蛋白 Sso7d 与 IminiBE 融合可将低效位点的编辑效率提高约 2 到 3 倍，我们将其称为 SIminiBEs。此外，IminiCBE 和 SIminiCBE 可识别 NNRR、NNRY 和 NNYR 靶标相邻基序，从而拓宽野生型 IscB 切口酶的经典 NWRRNA 靶标相邻基序位点。总体而言，IminiBEs 和 SIminiBE 是位点特异性基因组突变的高效微型碱基编辑器。