Mitotic and G ₂ Checkpoint Control: Regulation of 14-3-3 Protein Binding by Phosphorylation of Cdc25C on Serine-216

TLDR

Human Cdc25C is a dual‑specificity phosphatase that drives mitotic entry by dephosphorylating Cdc2. Phosphorylation of Cdc25C at serine‑216 during interphase promotes 14‑3‑3 binding; loss of this modification disrupts 14‑3‑3 association, alters mitotic timing, and permits escape from the G2 checkpoint, showing that serine‑216 phosphorylation and 14‑3‑3 binding negatively regulate Cdc25C and that Chk1 mediates this phosphorylation.

Abstract

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 G 2 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.