MDC1 is a mediator of the mammalian DNA damage checkpoint
MDC1 is a mediator of the mammalian DNA damage checkpoint
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DOI：
10.1038/nature01446
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发表时间：
2003-02-27
期刊：
影响因子：
64.8
通讯作者：
Elledge, SJ
中科院分区：
文献类型：
--
作者：
Stewart, GS;Wang, B;Elledge, SJ
为了对抗细胞持续暴露于破坏DNA的物质中，细胞进化出了复杂的调节网络，称为检查点，以感知DNA损伤并协调DNA复制、细胞周期阻滞和DNA修复(1)。最近有研究表明，组蛋白H2A变体H2AX特异性地控制DNA修复蛋白在DNA损伤位点的募集（2-4）。在这里，我们发现了一种新的BRCA1羧基末端（BRCT）和叉头相关（FHA）结构域蛋白MDC1 （DNA损伤检查点蛋白1的介质），它与H2AX一起促进修复蛋白募集到DNA断裂位点，此外，它还控制损伤诱导的细胞周期阻滞检查点。MDC1在暴露于电离辐射后几分钟内形成与γ - h2ax灶广泛共定位的灶。H2AX是MDC1病灶形成所必需的，MDC1与磷酸化的H2AX形成复合物。此外，这种相互作用是磷酸化依赖的，因为含有H2AX磷酸化位点的肽以磷酸化依赖的方式结合MDC1。我们通过使用小干扰RNA （siRNA）表明，缺乏MDC1的细胞对电离辐射敏感，MDC1控制损伤诱导的53BP1， BRCA1和MRN灶的形成，部分通过促进有效的H2AX磷酸化。此外，缺乏MDC1的细胞在暴露于电离辐射后也不能正常激活s期内和G2/M期细胞周期检查点，这与无法正常调节Chk1有关。这些结果强调了MDC1在介导DNA损伤信号转导中的关键作用。
To counteract the continuous exposure of cells to agents that damage DNA, cells have evolved complex regulatory networks called checkpoints to sense DNA damage and coordinate DNA replication, cell-cycle arrest and DNA repair(1). It has recently been shown that the histone H2A variant H2AX specifically controls the recruitment of DNA repair proteins to the sites of DNA damage(2-4). Here we identify a novel BRCA1 carboxy-terminal (BRCT) and forkhead-associated (FHA) domain-containing protein, MDC1 (mediator of DNA damage checkpoint protein 1), which works with H2AX to promote recruitment of repair proteins to the sites of DNA breaks and which, in addition, controls damage-induced cell-cycle arrest checkpoints. MDC1 forms foci that co-localize extensively with gamma-H2AX foci within minutes after exposure to ionizing radiation. H2AX is required for MDC1 foci formation, and MDC1 forms complexes with phosphorylated H2AX. Furthermore, this interaction is phosphorylation dependent as peptides containing the phosphorylated site on H2AX bind MDC1 in a phosphorylation-dependent manner. We have shown by using small interfering RNA (siRNA) that cells lacking MDC1 are sensitive to ionizing radiation, and that MDC1 controls the formation of damage-induced 53BP1, BRCA1 and MRN foci, in part by promoting efficient H2AX phosphorylation. In addition, cells lacking MDC1 also fail to activate the intra-S phase and G2/M phase cell-cycle checkpoints properly after exposure to ionizing radiation, which was associated with an inability to regulate Chk1 properly. These results highlight a crucial role for MDC1 in mediating transduction of the DNA damage signal.