Chk1, but not Chk2, inhibits Cdc25 phosphatases by a novel common mechanism
Chk1, but not Chk2, inhibits Cdc25 phosphatases by a novel common mechanism
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DOI：
10.1038/sj.emboj.7600328
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发表时间：
2004-08-18
期刊：
影响因子：
11.4
通讯作者：
Sagata, N
中科院分区：
文献类型：
--
作者：
Uto, K;Inoue, D;Sagata, N
Cdc 25磷酸酶激活细胞周期蛋白依赖性激酶（Cdks），从而促进细胞周期进程。在脊椎动物中，Chk 1和Chk 2在多个N-末端位点磷酸化Cdc 25 A，并靶向其快速降解以响应遗传毒性应激。在这里，我们表明，Chk 1，而不是Chk 2，磷酸化非洲爪蟾Cdc 25 A在一个新的C-末端位点（Thr 504），并抑制其从C-末端与各种Cdk-细胞周期蛋白复合物，包括Cdk 1-细胞周期蛋白A，Cdk 1-细胞周期蛋白B，和Cdk 2-细胞周期蛋白E相互作用。引人注目的是，这种抑制，而不是降解本身，Cdc 25 A是必不可少的Chk 1诱导的细胞周期停滞和早期胚胎中的DNA复制检查点。14-3-3蛋白与Chk 1-磷酸化的Thr 504结合，但这种结合不是Thr 504磷酸化的抑制作用所必需的。一个C-末端位点可能相当于Thr 504存在于所有已知的Cdc 25家族成员从酵母到人类，其磷酸化的Chk 1（而不是Chk 2）也可以抑制所有检查Cdc 25家族成员的C-末端与他们的Cdk-细胞周期蛋白底物相互作用。因此，Chk 1，而不是Chk 2似乎抑制几乎所有的Cdc 25磷酸酶的一种新的共同机制。
Cdc25 phosphatases activate cyclin-dependent kinases (Cdks) and thereby promote cell cycle progression. In vertebrates, Chk1 and Chk2 phosphorylate Cdc25A at multiple N-terminal sites and target it for rapid degradation in response to genotoxic stress. Here we show that Chk1, but not Chk2, phosphorylates Xenopus Cdc25A at a novel C-terminal site (Thr504) and inhibits it from C-terminally interacting with various Cdk-cyclin complexes, including Cdk1-cyclin A, Cdk1-cyclin B, and Cdk2-cyclin E. Strikingly, this inhibition, rather than degradation itself, of Cdc25A is essential for the Chk1-induced cell cycle arrest and the DNA replication checkpoint in early embryos. 14-3-3 proteins bind to Chk1-phosphorylated Thr504, but this binding is not required for the inhibitory effect of Thr504 phosphorylation. A C-terminal site presumably equivalent to Thr504 exists in all known Cdc25 family members from yeast to humans, and its phosphorylation by Chk1 (but not Chk2) can also inhibit all examined Cdc25 family members from C-terminally interacting with their Cdk-cyclin substrates. Thus, Chk1 but not Chk2 seems to inhibit virtually all Cdc25 phosphatases by a novel common mechanism.