Ling Chen, Huang Jing, Yan Zhijiang, Li Yongjiang, Ohzeki Mioko, Ishiai Masamichi, Xu Dongyi, Takata Minoru, Seidman Michael, Wang Weidong
Lab of Genetics, National Institute on Aging, National Institute of Health , Baltimore, MD, USA.
Lab of Molecular Gerontology, National Institute on Aging, National Institute of Health , Baltimore, MD, USA.
Cell Discov. 2016 Dec 20;2:16047. doi: 10.1038/celldisc.2016.47. eCollection 2016.
The recruitment of FANCM, a conserved DNA translocase and key component of several DNA repair protein complexes, to replication forks stalled by DNA interstrand crosslinks (ICLs) is a step upstream of the Fanconi anemia (FA) repair and replication traverse pathways of ICLs. However, detection of the FANCM recruitment has been technically challenging so that its mechanism remains exclusive. Here, we successfully observed recruitment of FANCM at stalled forks using a newly developed protocol. We report that the FANCM recruitment depends upon its intrinsic DNA translocase activity, and its DNA-binding partner FAAP24. Moreover, it is dependent on the replication checkpoint kinase, ATR; but is independent of the FA core and FANCD2-FANCI complexes, two essential components of the FA pathway, indicating that the FANCM recruitment occurs downstream of ATR but upstream of the FA pathway. Interestingly, the recruitment of FANCM requires its direct interaction with Bloom syndrome complex composed of BLM helicase, Topoisomerase 3α, RMI1 and RMI2; as well as the helicase activity of BLM. We further show that the FANCM-BLM complex interaction is critical for replication stress-induced FANCM hyperphosphorylation, for normal activation of the FA pathway in response to ICLs, and for efficient traverse of ICLs by the replication machinery. Epistasis studies demonstrate that FANCM and BLM work in the same pathway to promote replication traverse of ICLs. We conclude that FANCM and BLM complex work together at stalled forks to promote both FA repair and replication traverse pathways of ICLs.
FANCM是一种保守的DNA转位酶,也是几种DNA修复蛋白复合物的关键组成部分,它被招募到因DNA链间交联(ICL)而停滞的复制叉上,这是范可尼贫血(FA)修复和ICL复制穿越途径上游的一个步骤。然而,检测FANCM的招募在技术上具有挑战性,因此其机制仍然未知。在这里,我们使用新开发的方案成功观察到FANCM在停滞叉处的招募。我们报告说,FANCM的招募取决于其内在的DNA转位酶活性及其DNA结合伙伴FAAP24。此外,它依赖于复制检查点激酶ATR;但独立于FA核心以及FA途径的两个重要组成部分FANCD2 - FANCI复合物,这表明FANCM的招募发生在ATR下游但FA途径上游。有趣的是,FANCM的招募需要它与由BLM解旋酶、拓扑异构酶3α、RMI1和RMI2组成的布卢姆综合征复合物直接相互作用;以及BLM的解旋酶活性。我们进一步表明,FANCM - BLM复合物相互作用对于复制应激诱导的FANCM过度磷酸化、对ICL响应时FA途径的正常激活以及复制机制对ICL的有效穿越至关重要。上位性研究表明,FANCM和BLM在促进ICL复制穿越的同一途径中起作用。我们得出结论,FANCM和BLM复合物在停滞叉处共同发挥作用,以促进ICL的FA修复和复制穿越途径。