Mitotic regulation of the APC activator proteins CDC20 and CDH1
Mitotic regulation of the APC activator proteins CDC20 and CDH1
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DOI：
10.1091/mbc.11.5.1555
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发表时间：
2000-05-01
影响因子：
3.3
通讯作者：
Peters, JM
中科院分区：
文献类型：
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作者：
Kramer, ER;Scheuringer, N;Peters, JM
中期CDC20和末期CDH1对泛素蛋白连接酶后期促进复合体（APC）或环小体的有序激活分别是后期和有丝分裂退出所必需的。在这里，我们证明CDC20只能结合并激活体外有丝分裂磷酸化形式的爪蟾和人类APC。相比之下，CDC20磷酸化和非磷酸化形式的分析表明，CDC20磷酸化既不是APC激活的充分条件，也不是APC激活的必要条件。基于这些结果，并观察到APC磷酸化与体内APC激活相关，我们提出有丝分裂APC磷酸化是控制APC（CDC20）激活适当时间的重要机制。我们进一步表明，CDH1在S期、G2期和M期被磷酸化，并且CDH1水平在细胞周期中波动。体外，磷酸化的CDH1既不结合APC，也不像非磷酸化的CDH1那样有效地激活APC。在体外和体内，非磷酸化CDH1突变体构成性地激活APC，而模仿CDH1磷酸化形式的突变体则构成性地失活。这些结果表明，有丝分裂激酶在调节APC（CDC20）和APC（CDH1）中具有拮抗作用；APC亚基的磷酸化是允许APC被CDC20激活所必需的，而CDH1的磷酸化阻止了CDH1对APC的激活。这些机制可以解释APC被CDC20和CDH1激活的时间顺序，并可能有助于确保在有丝分裂后期发生之前不启动退出。
The ordered activation of the ubiquitin protein ligase anaphase-promoting complex (APC) or cyclosome by CDC20 in metaphase and by CDH1 in telophase is essential for anaphase and for exit from mitosis, respectively. Here, we show that CDC20 can only bind to and activate the mitotically phosyhorylated form of the Xenopus and the human APC in vitro. In contrast, the analysis of phosphorylated and nonphosphorylated forms of CDC20 suggests that CDC20 phosphorylation is neither sufficient nor required for APC activation On the basis of these results and the observation that APC phosphorylation correlates with APC activation in vivo, we propose that mitotic APC phosyhorylation is an important mechanism that controls the proper timing of APC(CDC20) activation. We further show that CDH1 is phosphorylated in vivo during S, G2, and M phase and that CDH1 levels fluctuate during the cell cycle. In vitro, phosphorylated CDH1 neither binds to nor activates the APC as efficiently as does nonphosphorylated CDH1. Nonphosphorylatable CDH1 mutants constitutively activate APC in vitro and in vivo, whereas mutants mimicking the phosphorylated form of CDH1 are constitutively inactive. These results suggest that mitotic kinases have antagonistic roles in regulating APC(CDC20) and APC(CDH1); the phosphorylation of APC subunits is required to allow APC activation by CDC20, whereas the phosphorylation of CDH1 prevents activation of the APC by CDH1. These mechanisms can explain the temporal order of APC activation by CDC20 and CDH1 and may help to ensure that exit from mitosis is not initiated before anaphase has occurred.