Dual Regulation of Cdc25A by Chk1 and p53-ATF3 in DNA Replication Checkpoint Control
Dual Regulation of Cdc25A by Chk1 and p53-ATF3 in DNA Replication Checkpoint Control
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DOI：
10.1074/jbc.m808118200
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发表时间：
2009-02-13
影响因子：
4.8
通讯作者：
Yu, Qiang
中科院分区：
文献类型：
--
作者：
Demidova, Anastasia R.;Aau, Mei Yee;Yu, Qiang
真核细胞通过激活促进细胞周期停滞和DNA修复的信号通路来应对DNA损伤和复制分叉停滞。对蛋白激酶小干扰文库的系统筛选表明，Chk1、共济失调性毛细血管扩张突变(ATM)和RAD3相关(ATR)是导致拓扑异构酶I抑制剂喜树碱诱导的S期内检查点的主要激酶。众所周知，ATR-Chk1介导的蛋白降解CDc25A蛋白磷酸酶是激活这种检查点的重要机制。在这里，我们描述了CDc25A下调表达的另一种机制，以响应发生在转录水平的DNA损伤。我们发现，通过DNA损伤激活肿瘤抑制因子P53导致了对CDc25A转录的抑制，这是直接与CDc25A启动子结合的转录抑制因子ATF3激活的结果。在同时缺乏Chk1和P53的细胞中，CDC25A对喜树碱诱导的DNA损伤的下调作用被完全取消，导致细胞周期检查点的严重缺陷和有丝分裂中显著的细胞死亡。我们的发现揭示了两种独立的机制在调节DNA损伤反应中的CDc25A。虽然Chk1通过快速磷酸化和蛋白质周转来影响CDc25A，但P53-ATF3对CDc25A转录的抑制是维持细胞周期停滞所必需的。
Eukaryotic cells respond to DNA damage and stalled replication forks by activating signaling pathways that promote cell cycle arrest and DNA repair. A systematic screening of the protein kinase small interfering RNA library reveals that Chk1 and ataxia telangiectasia-mutated (ATM) and Rad3-related (ATR) are the main kinases responsible for intra-S-phase checkpoint upon topoisomerase I inhibitor camptothecin-induced DNA damage. It is well known that ATR-Chk1-mediated protein degradation of Cdc25A protein phosphatase is a crucial mechanism conferring this checkpoint activation. Here we describe another mechanism underlying Cdc25A down-regulation in response to DNA damage that occurs at the transcriptional level. We show that activation of tumor suppressor p53 by DNA damage results in inhibition of Cdc25A transcription as a result of activation of transcriptional repressor ATF3 that directly binds to the Cdc25A promoter. In cells deficient in both Chk1 and p53, Cdc25A down-regulation upon camptothecin-induced DNA damage is completely abolished, leading to severe defects in cell cycle checkpoints and remarkable cell death in mitosis. Our findings reveal two independent mechanisms acting in concert in regulation of Cdc25A in DNA damage response. Although Chk1 affects Cdc25A via rapid phosphorylation and protein turnover, inhibition of Cdc25A transcription by p53-ATF3 is required for the maintenance of cell cycle arrest.