Activation of cyclin E/CDK2 is coupled to site-specific autophosphorylation and ubiquitin-dependent degradation of cyclin E
Activation of cyclin E/CDK2 is coupled to site-specific autophosphorylation and ubiquitin-dependent degradation of cyclin E
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DOI：
10.1002/j.1460-2075.1996.tb00793.x
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发表时间：
1996-08-15
期刊：
影响因子：
11.4
通讯作者：
Reed, SI
中科院分区：
文献类型：
--
作者：
Won, KA;Reed, SI
酵母菌筛选被用来鉴定导致蛋白质稳定的人细胞周期蛋白E的突变，以确定对细胞周期蛋白E周转重要的决定因素。Cyclin E C末端附近的C末端截断和错义突变都在体内赋予了高度稳定性，表明该区域的序列是关键的毛皮周转。以下观察表明，细胞周期蛋白Thr380上的CDK2/Cyclin E的自磷酸化作用调节细胞周期蛋白E的破坏：(I)Thr380突变为Ala使酵母和哺乳动物细胞中的细胞周期蛋白E稳定；(Ii)细胞周期蛋白E/CDK2在体外对细胞周期蛋白E进行自磷酸化，在哺乳动物细胞中细胞周期蛋白E是一种磷蛋白；(Iii)T380A突变消除了哺乳动物细胞和体外细胞中同一位置的磷酸化；(Iv)抑制体内的CDK2活性使细胞周期蛋白E稳定；(V)T380A突变阻止了细胞周期蛋白E的泛素化。这些结果提出了一种模型，其中细胞周期蛋白E/CDK2的激活与细胞周期蛋白E的转换通过位点特异性的磷酸化而耦合，这是泛素化和蛋白酶体处理的信号。
A yeast screen was developed to identify mutations in human cyclin E that lead to stabilization of the protein in order to identify determinants important for cyclin E turnover. Both C-terminal truncations and missense mutations near the C-terminus of cyclin E conferred hyperstability in vivo, suggesting that sequences in this region were critical fur turnover. The following observations indicate that autophosphorylation of CDK2/cyclin E on Thr380 of the cyclin regulates cyclin E destruction: (i) mutation of Thr380 to Ala stabilizes cyclin E in yeast and mammalian cells; (ii) cyclin E/CDK2 autophosphorylates on cyclin E in vitro and cyclin E is a phosphoprotein in vivo in mammalian cells; (iii) the T380A mutation eliminates phosphorylation on the same site in mammalian cells and in vitro; (iv) inhibiting CDK2 activity in vivo stabilizes cyclin E; (v) the T380A mutation prevents ubiquitination of cyclin E. These results suggest a model where activation of cyclinE/CDK2 is coupled to cyclin E turnover via site-specific phosphorylation, which acts as a signal for ubiquitination and proteasome processing.