Institute of Cancer Genetics, Columbia University, New York, NY 10032, USA.
Graduate School of Science, Osaka University, Toyonaka, Japan.
Cell Rep. 2017 Oct 31;21(5):1375-1385. doi: 10.1016/j.celrep.2017.10.032.
DNA interstrand crosslinks (ICLs) that are repaired in non-dividing cells must be recognized independently of replication-associated DNA unwinding. Using cell-free extracts from Xenopus eggs that support neither replication nor transcription, we establish that ICLs are recognized and processed by the mismatch repair (MMR) machinery. We find that ICL repair requires MutSα (MSH2-MSH6) and the mismatch recognition FXE motif in MSH6, strongly suggesting that MutSα functions as an ICL sensor. MutSα recruits MutLα and EXO1 to ICL lesions, and the catalytic activity of both these nucleases is essential for ICL repair. As anticipated for a DNA unwinding-independent recognition process, we demonstrate that least distorting ICLs fail to be recognized and repaired by the MMR machinery. This establishes that ICL structure is a critical determinant of repair efficiency outside of DNA replication.
DNA 链间交联 (ICLs) 在非分裂细胞中必须独立于与复制相关的 DNA 解旋进行修复。使用既不支持复制也不支持转录的非洲爪蟾卵无细胞提取物，我们确定 ICLs 是由错配修复 (MMR) 机制识别和处理的。我们发现 ICL 修复需要 MutSα (MSH2-MSH6) 和 MSH6 中的错配识别 FXE 基序，这强烈表明 MutSα 作为 ICL 传感器发挥作用。MutSα 将 MutLα 和 EXO1 募集到 ICL 损伤部位，这两种核酸酶的催化活性对 ICL 修复都是必不可少的。正如对 DNA 解旋非依赖性识别过程的预期，我们证明了扭曲最小的 ICL 无法被 MMR 机制识别和修复。这表明 ICL 结构是复制外修复效率的关键决定因素。
