DNA deaminase enzymes play key roles in immunity and have recently been harnessed for their biotechnological applications. In base editors (BEs), the combination of DNA deaminase mutator activity with CRISPR–Cas localization confers the powerful ability to directly convert one target DNA base into another. While efforts have been made to improve targeting efficiency and precision, all BEs so far use a constitutively active DNA deaminase. The absence of regulatory control over promiscuous deaminase activity remains a major limitation to accessing the widespread potential of BEs. Here, we reveal sites that permit splitting of DNA cytosine deaminases into two inactive fragments, whose reapproximation reconstitutes activity. These findings allow for the development of split-engineered BEs (seBEs), which newly enable small-molecule control over targeted mutator activity. We show that the seBE strategy facilitates robust regulated editing with BE scaffolds containing diverse deaminases, offering a generalizable solution for temporally controlling precision genome editing.

DNA 脱氨酶在免疫中起着关键作用，最近已被用于生物技术应用。在碱基编辑器 (BE) 中，DNA 脱氨酶突变体活性与 CRISPR-Cas 定位的结合赋予了将一个目标 DNA 碱基直接转化为另一个目标 DNA 碱基的强大能力。虽然已经努力提高靶向效率和精确度，但迄今为止所有 BE 都使用组成型活性 DNA 脱氨酶。缺乏对混杂脱氨酶活性的监管控制仍然是获取 BE 广泛潜力的主要限制。在这里，我们揭示了允许将 DNA 胞嘧啶脱氨酶分裂成两个无活性片段的位点，其重新近似可重建活性。这些发现允许开发分裂工程 BE (seBE)，它最近使小分子能够控制目标突变体活动。我们表明，seBE 策略有助于使用包含多种脱氨酶的 BE 支架进行稳健的调控编辑，为暂时控制精确基因组编辑提供了一个通用的解决方案。