Regulation of Human Cdc25A Stability by Serine 75 Phosphorylation Is Not Sufficient to Activate a S-phase Checkpoint
Regulation of Human Cdc25A Stability by Serine 75 Phosphorylation Is Not Sufficient to Activate a S-phase Checkpoint
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DOI：
10.4161/cc.2.5.482
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发表时间：
2003-01-01
期刊：
影响因子：
4.3
通讯作者：
Bulavin, Dmitry V.
中科院分区：
文献类型：
--
作者：
Goloudina, Anastasia;Yamaguchi, Hiroshi;Bulavin, Dmitry V.
Cdc 25 A磷酸酶的降解是胁迫的普遍特征。在Cdc 25 A稳定性的调节中，不同磷酸化位点的报道作用存在一些差异。使用一组多西环素诱导的磷酸化突变体，我们表明，人Cdc 25 A蛋白的稳定性依赖于在S75磷酸化。在非应激条件下和非有丝分裂细胞中，Cdc 25 A是不稳定的，其稳定性以Chk 1依赖性方式调节。在有丝分裂过程中，Cdc 25 A变得稳定，并且在DNA损伤后不会发生降解。我们进一步表明，Chk 1激酶调节Cdc 25 A的稳定性后，紫外线照射。与Chk 1激酶类似，p38 MAPK控制渗透胁迫后Cdc 25 A蛋白水平。使用磷酸化特异性抗体，我们发现这两种激酶可以在体外磷酸化S75和S123。UV照射后Chk 1或渗透胁迫后p38 MAPK的失活防止S期检查点和S75和S123磷酸化的激活。然而，引入稳定的Cdc 25 A（S75 A或S75/123 A）蛋白不足以克服该检查点。我们建议，调节人类Cdc 25 A的稳定性，其磷酸化在S75可能有助于S期检查点激活，只有在合作与其他监管机制。
Degradation of Cdc25A phosphatase is an ubiquitous feature of stress. There are some discrepancies in the reported roles for different phosphorylation sites in the regulation of Cdc25A stability. Using a panel of doxycycline-inducible phosphorylation mutants we show that the stability of human Cdc25A protein is dependent upon phosphorylation at S75. In non-stressed conditions and in non-mitotic cells, Cdc25A is unstable and its stability is regulated in a Chk1-dependent manner. During mitosis, Cdc25A becomes stable and does not undergo degradation after DNA damage. We further show that Chk1 kinase regulates Cdc25A stability after UV irradiation. Similar to Chk1 kinase, p38 MAPK controls Cdc25A protein level after osmotic stress. Using phospho-specific antibodies, we find that both kinases can phosphorylate S75 and S123 in vitro. Inactivation of either Chk1 after UV-irradiation or p38 MAPK after osmotic stress prevents activation of a S phase checkpoint and S75 and S123 phosphorylation. However, introduction of stable Cdc25A (S75A or S75/123A) proteins is not sufficient to overcome this checkpoint. We propose that regulation of human Cdc25A stability by its phosphorylation at S75 may contribute to S phase checkpoint activation only in cooperation with other regulatory mechanisms.