Dual phosphorylation controls Cdc25 phosphatases and mitotic entry
Dual phosphorylation controls Cdc25 phosphatases and mitotic entry
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DOI：
10.1038/ncb994
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发表时间：
2003-06-01
影响因子：
21.3
通讯作者：
Fornace, AJ
中科院分区：
文献类型：
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作者：
Bulavin, DV;Higashimoto, Y;Fornace, AJ
CDC25C蛋白磷酸酶在14-3-3结合位点Ser216上的磷酸化负调控是细胞在正常条件下和DNA损伤后阻止有丝分裂进入的重要调节机制。在有丝分裂过程中，CDC25C在Ser216上不被磷酸化，电离辐射(IR)既不能诱导Ser216的磷酸化，也不能与14-3-3结合。在这里，我们证明了在有丝分裂过程中，CDC25C在Ser214上被磷酸化，这反过来又阻止了Ser216的磷酸化。在有丝分裂过程中，Ser214到Ala的突变重组了Ser216的磷酸化和14-3-3的结合。将外源CDC25C(S214A)导入内源性CDC25C缺失的HeLa细胞，可显著延迟有丝分裂的进入。这种作用在S214A/S216A双突变体中被完全逆转，这意味着S214A突变体的抑制作用完全依赖于Ser216的磷酸化。类似的调控机制也适用于另一种有丝分裂磷酸酶，即CDc25B，以及包括非洲爪哇在内的其他物种的有丝分裂磷酸酶。我们认为，这一途径确保了CDC2在有丝分裂开始后保持活跃，是维持细胞周期转换正确顺序的关键控制机制。
Negative regulation of the Cdc25C protein phosphatase by phosphorylation on Ser 216, the 14-3-3-binding site, is an important regulatory mechanism used by cells to block mitotic entry under normal conditions and after DNA damage. During mitosis, Cdc25C is not phosphorylated on Ser 216 and ionizing radiation (IR) does not induce either phosphorylation of Ser 216, or binding to 14-3-3. Here, we show that Cdc25C is phosphorylated on Ser 214 during mitosis, which in turn prevents phosphorylation of Ser 216. Mutation of Ser 214 to Ala reconstitutes Ser 216 phosphorylation and 14-3-3 binding during mitosis. Introduction of exogenous Cdc25C(S214A) into HeLa cells depleted of endogenous Cdc25C results in a substantial delay to mitotic entry. This effect was fully reversed in a S214A/S216A double-mutant, implying that the inhibitory effect of S214A mutant was entirely dependent on Ser 216 phosphorylation. A similar regulatory mechanism may also apply to another mitotic phosphatase, Cdc25B, as well as mitotic phosphatases of other species, including Xenopus laevis. We propose that this pathway ensures that Cdc2 remains active once mitosis is initiated and is a key control mechanism for maintaining the proper order of cell-cycle transitions.