Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia, USA.
Mol Cell Biol. 2013 Apr;33(8):1632-44. doi: 10.1128/MCB.01503-12. Epub 2013 Feb 11.
The minichromosome maintenance protein homologs MCM8 and MCM9 have previously been implicated in DNA replication elongation and prereplication complex (pre-RC) formation, respectively. We found that MCM8 and MCM9 physically associate with each other and that MCM8 is required for the stability of MCM9 protein in mammalian cells. Depletion of MCM8 or MCM9 in human cancer cells or the loss of function MCM9 mutation in mouse embryo fibroblasts sensitizes cells to the DNA interstrand cross-linking (ICL) agent cisplatin. Consistent with a role in the repair of ICLs by homologous recombination (HR), knockdown of MCM8 or MCM9 significantly reduces HR repair efficiency. Chromatin immunoprecipitation analysis using human DR-GFP cells or Xenopus egg extract demonstrated that MCM8 and MCM9 proteins are rapidly recruited to DNA damage sites and promote RAD51 recruitment. Thus, these two metazoan-specific MCM homologs are new components of HR and may represent novel targets for treating cancer in combination with DNA cross-linking agents.
微染色体维持蛋白同源物 MCM8 和 MCM9 先前分别被认为参与 DNA 复制延伸和前复制复合物（pre-RC）的形成。我们发现 MCM8 和 MCM9 相互物理结合，并且在哺乳动物细胞中，MCM8 是 MCM9 蛋白稳定性所必需的。在人类癌细胞中耗尽 MCM8 或 MCM9 或在小鼠胚胎成纤维细胞中丧失功能的 MCM9 突变会使细胞对 DNA 链间交联（ICL）试剂顺铂敏感。与同源重组（HR）修复 ICL 的作用一致，MCM8 或 MCM9 的敲低显著降低了 HR 修复效率。使用人 DR-GFP 细胞或非洲爪蟾卵提取物进行染色质免疫沉淀分析表明，MCM8 和 MCM9 蛋白迅速被募集到 DNA 损伤部位，并促进 RAD51 的募集。因此，这两种后生动物特异性的 MCM 同源物是 HR 的新组成部分，并且可能与 DNA 交联剂联合用于治疗癌症的新靶点。
