Involvement of the cohesin protein, Smc1, in Atm-dependent and independent responses to DNA damage
Involvement of the cohesin protein, Smc1, in Atm-dependent and independent responses to DNA damage
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DOI：
10.1101/gad.970602
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发表时间：
2002-03-01
影响因子：
10.5
通讯作者：
Kastan, MB
中科院分区：
文献类型：
--
作者：
Kim, ST;Xu, B;Kastan, MB
染色体结构维持蛋白（SMC）在姐妹染色单体内聚、染色体凝聚、性染色体剂量补偿、DNA重组和修复等过程中发挥着重要作用。含有Smc1和Smc3蛋白异源二聚体的蛋白质复合物在姐妹染色单体内聚和DNA重组中都有特殊的作用。在这里，我们展示了蛋白激酶Atm，它属于磷脂酰肌醇3-激酶家族，调节细胞周期检查点和DNA重组和修复，在电离照射后磷酸化Smc1蛋白。Atm在体外和体内磷酸化957和966丝氨酸上的Smc1，在这些磷酸化位点突变的Smc1蛋白的表达消除了电离照射诱导的S期细胞周期检查点。电离辐照后Smc1中这些位点的最佳磷酸化也需要Atm底物Nbs1和Brca1的存在。在紫外线照射或羟基脲处理后，Smc1中的这些相同位点以不依赖于atm的方式磷酸化，从而表明必须有另一种激酶参与对这些细胞应激的反应。含有SMC1亚型突变的酵母和在这两个磷酸化位点过度表达SMC1突变的人细胞在电离照射后表现出存活率下降。这些结果表明，Smc1参与细胞对DNA损伤的反应，并将Smc1与Atm信号转导途径联系起来。
Structural maintenance of chromosomes (SMC) proteins play important roles in sister chromatid cohesion, chromosome condensation, sex-chromosome dosage compensation, and DNA recombination and repair. Protein complexes containing heterodimers of the Smc1 and Smc3 proteins have been implicated specifically in both sister chromatid cohesion and DNA recombination. Here, we show that the protein kinase, Atm, which belongs to a family of phosphatidylinositol 3-kinases that regulate cell cycle checkpoints and DNA recombination and repair, phosphorylates Smc1 protein after ionizing irradiation. Atm phosphorylates Smc1 on serines 957 and 966 in vitro and in vivo, and expression of an Smc1 protein mutated at these phosphorylation sites abrogates the ionizing irradiation-induced S phase cell cycle checkpoint. Optimal phosphorylation of these sites in Smc1 after ionizing irradiation also requires the presence of the Atm substrates Nbs1 and Brca1. These same sites in Smc1 are phosphorylated after treatment with UV irradiation or hydroxyurea in an Atm-independent manner, thus demonstrating that another kinase must be involved in responses to these cellular stresses. Yeast containing hypomorphic mutations in SMC1 and human cells overexpressing Smc1 mutated at both of these phosphorylation sites exhibit decreased survival following ionizing irradiation. These results demonstrate that Smc1 participates in cellular responses to DNA damage and link Smc1 to the Atm signal transduction pathway.