Mitotic and G2 Checkpoint Control: Regulation of 14-3-3 Protein Binding by Phosphorylation of Cdc25C on Serine-216

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Science  05 Sep 1997:
Vol. 277, Issue 5331, pp. 1501-1505
DOI: 10.1126/science.277.5331.1501

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Human Cdc25C is a dual-specificity protein phosphatase that controls entry into mitosis by dephosphorylating the protein kinase Cdc2. Throughout interphase, but not in mitosis, Cdc25C was phosphorylated on serine-216 and bound to members of the highly conserved and ubiquitously expressed family of 14-3-3 proteins. A mutation preventing phosphorylation of serine-216 abrogated 14-3-3 binding. Conditional overexpression of this mutant perturbed mitotic timing and allowed cells to escape the G2 checkpoint arrest induced by either unreplicated DNA or radiation-induced damage. Chk1, a fission yeast kinase involved in the DNA damage checkpoint response, phosphorylated Cdc25C in vitro on serine-216. These results indicate that serine-216 phosphorylation and 14-3-3 binding negatively regulate Cdc25C and identify Cdc25C as a potential target of checkpoint control in human cells.

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