Control of the SCFSkp2-Cks1 ubiquitin ligase by the APC/CCdh1 ubiquitin ligase
Control of the SCFSkp2-Cks1 ubiquitin ligase by the APC/CCdh1 ubiquitin ligase
复制标题
DOI：
10.1038/nature02330
复制
发表时间：
2004-03-11
期刊：
影响因子：
64.8
通讯作者：
Pagano, M
中科院分区：
文献类型：
--
作者：
Bashir, T;Dorrello, NV;Pagano, M
Skp 2及其辅因子Cks 1是SCFSkp 2-Cks 1（Skp 1/Cul 1/F-box蛋白）泛素连接酶复合物的底物靶向亚基，该复合物通过诱导细胞周期蛋白依赖性激酶抑制剂p21和p27的降解来调节进入S期（参考文献1）。Skp 2是一种癌蛋白，通常在人类癌症中表达增加（2）;然而，调节其细胞丰度的机制尚不清楚。在这里，我们表明Skp 2和Cks 1蛋白在G1中都不稳定，并且它们的降解是由遍在蛋白连接酶APC/C-Cdh 1（后期促进复合物/环体及其激活剂Cdh 1）介导的。在G1细胞中通过RNA干扰沉默Cdh 1稳定Skp 2和Cks 1，从而增加p21和p27蛋白水解。Cdh 1的缺失也增加了S期细胞的百分比，而Skp 2的伴随下调逆转了这种效应，表明Skp 2是APC/C-Cdh 1的重要靶点。不能结合APC/C-Cdh 1的稳定Skp 2突变体的表达诱导过早进入S期。因此，诱导Skp 2和Cks 1降解G1代表了APC/C-Cdh 1防止SCFSkp 2-Cks 1底物的非程序性降解并维持G1状态的主要机制。
Skp2 and its cofactor Cks1 are the substrate-targeting subunits of the SCFSkp2-Cks1 (Skp1/Cul1/F-box protein) ubiquitin ligase complex that regulates entry into S phase by inducing the degradation of the cyclin-dependent kinase inhibitors p21 and p27 (ref. 1). Skp2 is an oncoprotein that often shows increased expression in human cancers(2); however, the mechanism that regulates its cellular abundance is not well understood. Here we show that both Skp2 and Cks1 proteins are unstable in G1 and that their degradation is mediated by the ubiquitin ligase APC/C-Cdh1 (anaphase-promoting complex/cyclosome and its activator Cdh1). Silencing of Cdh1 by RNA interference in G1 cells stabilizes Skp2 and Cks1, with a consequent increase in p21 and p27 proteolysis. Depletion of Cdh1 also increases the percentage of cells in S phase, whereas concomitant downregulation of Skp2 reverses this effect, showing that Skp2 is an essential target of APC/C-Cdh1. Expression of a stable Skp2 mutant that cannot bind APC/C-Cdh1 induces premature entry into S phase. Thus, the induction of Skp2 and Cks1 degradation in G1 represents a principal mechanism by which APC/C-Cdh1 prevents the unscheduled degradation of SCFSkp2-Cks1 substrates and maintains the G1 state.