Mitotic Phosphorylation of Cdc25B Ser321 Disrupts 14-3-3 Binding to the High Affinity Ser323 Site
Mitotic Phosphorylation of Cdc25B Ser321 Disrupts 14-3-3 Binding to the High Affinity Ser323 Site
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DOI：
10.1074/jbc.m110.138412
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发表时间：
2010-11-05
影响因子：
4.8
通讯作者：
Gabrielli, Brian
中科院分区：
文献类型：
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作者：
Astuti, Puji;Boutros, Rose;Gabrielli, Brian
Cdc 25 B是进入有丝分裂的关键调节因子，其活性和定位受14-3-3二聚体的结合调节。Cdc 25 B上有三个14-3-3结合位点，其中Ser（323）是最高亲和力结合位点，并且与Cdc 25 C上的Ser（216）14-3-3结合位点高度同源。14-3-3与Ser（323）结合的丧失增加了细胞周期蛋白/Cdk底物对催化位点的接近，从而增加了其活性。它还影响Cdc 25 B的定位。因此，磷酸化和14-3-3结合到这个网站是必不可少的下调Cdc 25 B活性，阻断其有丝分裂促进功能。这个抑制信号是如何被释放，以允许Cdc 25 B激活和进入有丝分裂的问题尚未得到解决。在这里，我们表明，Ser（323）磷酸化维持到有丝分裂，但Ser（321）的磷酸化破坏了14-3-3与Ser（323）的结合，模拟抑制Ser（323）磷酸化对Cdc 25 B活性和定位的影响。未磷酸化的Ser（321）似乎具有稳定14-3-3与Ser（323）结合的作用，并且Ser羟基的损失似乎足以显著降低14-3-3结合。14-3-3结合丧失的结果是Ser（323）的去磷酸化。Ser（321）在有丝分裂中被Cdk 1磷酸化。Ser（321）的有丝分裂磷酸化通过破坏14-3-3与Ser（323）的结合并增强Ser（323）的去磷酸化以阻断14-3 -3与该位点的结合来维持Cdc 25 B的完全活化。
Cdc25B is a key regulator of entry into mitosis, and its activity and localization are regulated by binding of the 14-3-3 dimer. There are three 14-3-3 binding sites on Cdc25B, with Ser(323) being the highest affinity binding and is highly homologous to the Ser(216) 14-3-3 binding site on Cdc25C. Loss of 14-3-3 binding to Ser(323) increases cyclin/Cdk substrate access to the catalytic site, thereby increasing its activity. It also affects the localization of Cdc25B. Thus, phosphorylation and 14-3-3 binding to this site is essential for down-regulating Cdc25B activity, blocking its mitosis promoting function. The question of how this inhibitory signal is relieved to allow Cdc25B activation and entry into mitosis is yet to be resolved. Here, we show that Ser(323) phosphorylation is maintained into mitosis, but phosphorylation of Ser(321) disrupts 14-3-3 binding to Ser(323), mimicking the effect of inhibiting Ser(323) phosphorylation on both Cdc25B activity and localization. The unphosphorylated Ser(321) appears to have a role in stabilizing 14-3-3 binding to Ser(323), and loss of the Ser hydroxyl group appears to be sufficient to significantly reduce 14-3-3 binding. A consequence of loss of 14-3-3 binding is dephosphorylation of Ser(323). Ser(321) is phosphorylated in mitosis by Cdk1. The mitotic phosphorylation of Ser(321) acts to maintain full activation of Cdc25B by disrupting 14-3-3 binding to Ser(323) and enhancing the dephosphorylation of Ser(323) to block 14-3-3 binding to this site.