Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom.
Genes Dev. 2011 Sep 1;25(17):1859-70. doi: 10.1101/gad.15699211.
One of the major DNA interstrand cross-link (ICL) repair pathways in mammalian cells is coupled to replication, but the mechanistic roles of the critical factors involved remain largely elusive. Here, we show that purified human SNM1A (hSNM1A), which exhibits a 5'-3' exonuclease activity, can load from a single DNA nick and digest past an ICL on its substrate strand. hSNM1A-depleted cells are ICL-sensitive and accumulate replication-associated DNA double-strand breaks (DSBs), akin to ERCC1-depleted cells. These DSBs are Mus81-induced, indicating that replication fork cleavage by Mus81 results from the failure of the hSNM1A- and XPF-ERCC1-dependent ICL repair pathway. Our results reveal how collaboration between hSNM1A and XPF-ERCC1 is necessary to initiate ICL repair in replicating human cells.
在哺乳动物细胞中，一种主要的 DNA 链间交联 (ICL) 修复途径与复制偶联，但涉及的关键因素的作用机制仍很大程度上难以捉摸。在这里，我们表明，纯化的人 SNM1A（hSNM1A），其表现出 5'-3'外切核酸酶活性，可以从单个 DNA 缺口加载并消化其底物链上的 ICL。hSNM1A 耗尽的细胞对 ICL 敏感，并积累与复制相关的 DNA 双链断裂（DSB），类似于 ERCC1 耗尽的细胞。这些 DSB 是 Mus81 诱导的，表明复制叉切割是由于 hSNM1A 和 XPF-ERCC1 依赖性 ICL 修复途径的失败所致。我们的结果揭示了 hSNM1A 和 XPF-ERCC1 之间的协作对于启动复制人类细胞中的 ICL 修复是如何必要的。
