Regulation of Cdc25A half-life in interphase by cyclin-dependent kinase 2 activity.
Cdc25A regulates cell cycle progression, has oncogenic and anti-apoptotic activity, and is over-expressed in many human tumors. Phosphorylation by Chk1 and Cds1/Chk2 down-regulates Cdc25A levels in response to genotoxic stresses. Nevertheless, it remains unclear whether Chk1 and Cds1/Chk2 are uniquely responsible for regulating Cdc25A stability during interphase or if other kinase activities contribute. Here we report that treatment of HeLa cells with the cyclin-dependent kinase inhibitor roscovitine caused a concentration- and time-dependent increase in Cdc25A protein levels. Transfection with dominant-negative Cdk mutants demonstrated that only a Cdk2 mutant increased Cdc25A protein levels; Cdk1 and Cdk3 mutants had no effect. The increased Cdc25A protein levels were the result of an increase in the half-life of the protein; no increase in Cdc25A mRNA levels was observed. These results demonstrate Cdk2 kinase activity contributes to the labile nature of Cdc25A during interphase and redefine the nature of the Cdc25A-Cdk2 autoamplification feedback loop.
Ducruet
Alexander P
AP
Department of Pharmacology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
Lazo
John S
JS
D042846:CDC2-CDC28 Kinases; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D006207:Half-Life; D006801:Humans; D007399:Interphase; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D020687:cdc25 Phosphatases / Q000378:metabolism*
D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; C517004:CDC25A protein, human; D020687:cdc25 Phosphatases