Mazzolini Laurent, Broban Anaïs, Froment Carine, Burlet-Schiltz Odile, Besson Arnaud, Manenti Stéphane, Dozier Christine
a Centre de Recherche en Cancérologie de Toulouse, INSERM UMR1037, CNRS ERL5294 , Université Toulouse III Paul Sabatier , Toulouse , France.
b Equipe labellisée LIGUE contre le Cancer , CNRS ERL5294 , Toulouse , France.
Cell Cycle. 2016 Oct 17;15(20):2742-52. doi: 10.1080/15384101.2016.1220455. Epub 2016 Aug 11.
The Cdc25A phosphatase is an essential activator of CDK-cyclin complexes at all steps of the eukaryotic cell cycle. The activity of Cdc25A is itself regulated in part by positive and negative feedback regulatory loops performed by its CDK-cyclin substrates that occur in G1 as well as during the G1/S and G2/M transitions. However, the regulation of Cdc25A during G2 phase progression before mitotic entry has not been intensively characterized. Here, we identify by mass spectrometry analysis a new phosphorylation event of Cdc25A on Serine283. Phospho-specific antibodies revealed that the phosphorylation of this residue appears in late S/G2 phase of an unperturbed cell cycle and is performed by CDK-cyclin complexes. Overexpression studies of wild-type and non-phosphorylatable mutant forms of Cdc25A indicated that Ser283 phosphorylation increases the G2/M-promoting activity of the phosphatase without impacting its stability or subcellular localization. Our results therefore identify a new positive regulatory loop between Cdc25A and its CDK-cyclin substrates which contributes to accelerate entry into mitosis through the regulation of Cdc25A activity in G2.
Cdc25A磷酸酶是真核细胞周期各阶段CDK-细胞周期蛋白复合物的重要激活剂。Cdc25A的活性本身部分受其CDK-细胞周期蛋白底物在G1期以及G1/S和G2/M转换过程中形成的正反馈和负反馈调节环调控。然而，有丝分裂进入前G2期进程中Cdc25A的调控尚未得到深入研究。在此，我们通过质谱分析鉴定出Cdc25A丝氨酸283位点的一个新磷酸化事件。磷酸化特异性抗体显示，该位点的磷酸化出现在未受干扰的细胞周期的S/G2晚期，由CDK-细胞周期蛋白复合物介导。对野生型和不可磷酸化突变型Cdc25A的过表达研究表明，丝氨酸283位点的磷酸化增强了该磷酸酶促进G2/M期转换的活性，而不影响其稳定性或亚细胞定位。因此，我们的研究结果确定了Cdc25A与其CDK-细胞周期蛋白底物之间一个新的正反馈调节环，该调节环通过调控G2期Cdc25A的活性，促进有丝分裂的进入。
