Hyperactive Nickase Activity Improves Adenine Base Editing

Base editing technologies enable
programmable single-nucleotide
changes in target DNA without double-stranded DNA breaks. Adenine
base editors (ABEs) allow precise conversion of adenine (A) to guanine
(G). However, limited availability of optimized deaminases as well
as their variable efficiencies across different target sequences can
limit the ability of ABEs to achieve effective adenine editing. Here,
we explored the use of a TurboCas9 nickase in an ABE to improve its
genome editing activity. The resulting TurboABE exhibits amplified
editing efficiency on a variety of adenine target sites without increasing
off-target editing in DNA and RNA. An interesting feature of TurboABE
is its ability to significantly improve the editing frequency at bases
with normally inefficient editing rates in the editing window of each
target DNA. Development of improved ABEs provides new possibilities
for precise genetic modification of genes in living cells.

碱基编辑（Base editing）技术可在不产生双链DNA断裂（double-stranded DNA breaks）的前提下，实现靶标DNA的可编程单核苷酸改造。腺嘌呤碱基编辑器（Adenine Base Editors, ABEs）能够精准将腺嘌呤（A）转化为鸟嘌呤（G）。然而，优化型脱氨酶的供应有限，且其编辑效率因靶序列不同存在显著差异，这限制了ABEs实现高效腺嘌呤编辑的能力。
本研究探索了将TurboCas9切口酶（TurboCas9 nickase）应用于ABEs系统以提升其基因组编辑活性的方案。所获得的TurboABE可在多种腺嘌呤靶位点上提升编辑效率，且不会增加DNA与RNA层面的脱靶编辑风险。TurboABE的一项显著特性是，它可显著提升位于各靶标DNA编辑窗口内、原本编辑效率极低的碱基的编辑频率。
优化型ABEs的开发为活细胞内基因的精准遗传修饰提供了全新的可能性。