Distinct roles of ATR and DNA-PKcs in triggering DNA damage responses in ATM-deficient cells
Distinct roles of ATR and DNA-PKcs in triggering DNA damage responses in ATM-deficient cells
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DOI：
10.1038/embor.2009.60
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发表时间：
2009-06-01
期刊：
影响因子：
7.7
通讯作者：
Burma, Sandeep
中科院分区：
文献类型：
--
作者：
Tomimatsu, Nozomi;Mukherjee, Bipasha;Burma, Sandeep
细胞对DNA双链断裂的反应包括直接激活突变的共济失调毛细血管扩张症(ATM)和以ATM/Mre11/细胞周期依赖的方式间接激活共济失调毛细血管扩张症和Rad3相关基因(ATR)。在这里，我们报告了关键的检查点信号蛋白-P53，1号染色体的结构维持(SMC1)，P53结合蛋白1(53BP1)，检查点激酶(Chk)1和Chk2-被ATR以ATM/Mre11/细胞周期无关的方式迅速磷酸化，尽管水平很低。我们观察到复制蛋白A(RPA)和ATR在ATM缺陷细胞中DNA损伤部位的顺序募集，这为观察到的磷酸化提供了机制基础。ATR的招募和随后的磷酸化不需要Mre11，而是依赖于Exo1。我们表明，这些低水平的磷酸化具有重要的生物学意义，因为ATM缺陷细胞实施了依赖ATR的早期G2/M检查点。ATR对于辐射后的ATM缺陷细胞所特有的G2晚期积累也是必不可少的。有趣的是，参与染色质重塑的KRAB相关蛋白1(KAP-1)的磷酸化除了ATM外，还受到DNA依赖的蛋白激酶催化亚单位(DNA-PKcs)的时空调控。我们假设，参与细胞周期检查点信号传递的ATM底物可以被ATR独立地最低限度地磷酸化，而参与染色质重塑的一小部分蛋白质除了被ATM外，还被DNA-PKcs磷酸化。
The cellular response to DNA double-strand breaks involves direct activation of ataxia telangiectasia mutated (ATM) and indirect activation of ataxia telangiectasia and Rad3 related (ATR) in an ATM/Mre11/cell-cycle-dependent manner. Here, we report that the crucial checkpoint signalling proteins-p53, structural maintainance of chromosomes 1 (SMC1), p53 binding protein 1 (53BP1), checkpoint kinase (Chk)1 and Chk2-are phosphorylated rapidly by ATR in an ATM/Mre11/cell-cycle-independent manner, albeit at low levels. We observed the sequential recruitment of replication protein A (RPA) and ATR to the sites of DNA damage in ATM-deficient cells, which provides a mechanistic basis for the observed phosphorylations. The recruitment of ATR and consequent phosphorylations do not require Mre11 but are dependent on Exo1. We show that these low levels of phosphorylation are biologically important, as ATM-deficient cells enforce an early G2/M checkpoint that is ATR-dependent. ATR is also essential for the late G2 accumulation that is peculiar to irradiated ATM-deficient cells. Interestingly, phosphorylation of KRAB associated protein 1 (KAP-1), a protein involved in chromatin remodelling, is mediated by DNA-dependent protein kinase catalytic subunit (DNA-PKcs) in a spatio-temporal manner in addition to ATM. We posit that ATM substrates involved in cell-cycle checkpoint signalling can be minimally phosphorylated independently by ATR, while a small subset of proteins involved in chromatin remodelling are phosphorylated by DNA-PKcs in addition to ATM.