Cdc6 determines utilization of p21WAF1/CIP1-dependent damage checkpoint in S phase cells
Cdc6 determines utilization of p21WAF1/CIP1-dependent damage checkpoint in S phase cells
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DOI：
10.1074/jbc.m802055200
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发表时间：
2008-06-27
影响因子：
4.8
通讯作者：
Okayama, Hiroto
中科院分区：
文献类型：
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作者：
Kan, Qiuming;Jinno, Shigeki;Okayama, Hiroto
当穿过G（1）的细胞被紫外线照射时，两个平行的损伤检查点通路被激活：Chk 1-Cdc 25 A和p53-p21（WAF 1/CIP 1），两者都靶向Cdk 2，但后者诱导持久的停滞。然而，在类似处理的S期进展细胞中，只有Cdc 25 A依赖性检查点是活跃的。我们最近发现，如果S期细胞被碱修饰剂（如甲磺酸甲酯（MMS）和顺铂）损伤，p21依赖性检查点可以被激活并诱导长时间的阻滞。但是，不同DNA损伤剂对p21依赖性检查点的差异激活的机制基础尚不清楚。在这里，我们报告说，治疗的S期细胞与MMS，但不是一个相当剂量的紫外线eliminating蛋白酶体介导的降解Cdc 6，组装的复制前复合物，这使得诱导p21结合Cdk 2，从而延长失活的Cdk 2和S期阻滞。一致的是，Cdc 6的增强表达在很大程度上消除了MMS诱导的S期阻滞和Cdk 2失活，而RNA干扰介导的Cdc 6敲除不仅消除了这种阻滞和失活，而且有效地激活了UV照射的S期细胞中的p21依赖的检查点。
When cells traversing G(1) are irradiated with UV light, two parallel damage checkpoint pathways are activated: Chk1-Cdc25A and p53-p21(WAF1/CIP1), both targeting Cdk2, but the latter inducing a long lasting arrest. In similarly treated S phase-progressing cells, however, only the Cdc25A-dependent checkpoint is active. We have recently found that the p21-dependent checkpoint can be activated and induce a prolonged arrest if S phase cells are damaged with a base-modifying agent, such as methyl methanesulfonate (MMS) and cisplatin. But the mechanistic basis for the differential activation of the p21-dependent checkpoint by different DNA damaging agents is not understood. Here we report that treatment of S phase cells with MMS but not a comparable dose of UV light elicits proteasome-mediated degradation of Cdc6, the assembler of pre-replicative complexes, which allows induced p21 to bind Cdk2, thereby extending inactivation of Cdk2 and S phase arrest. Consistently, enforced expression of Cdc6 largely eliminates the prolonged S phase arrest and Cdk2 inactivation induced with MMS, whereas RNA interference-mediated Cdc6 knockdown not only prolongs such arrest and inactivation but also effectively activates the p21-dependent checkpoint in the UV-irradiated S phase cells.