title: Cdk2 is required for p53-independent G2/M checkpoint control.
abstract: The activation of phase-specific cyclin-dependent kinases (Cdks) is associated with ordered cell cycle transitions. Among the mammalian Cdks, only Cdk1 is essential for somatic cell proliferation. Cdk1 can apparently substitute for Cdk2, Cdk4, and Cdk6, which are individually dispensable in mice. It is unclear if all functions of non-essential Cdks are fully redundant with Cdk1. Using a genetic approach, we show that Cdk2, the S-phase Cdk, uniquely controls the G(2)/M checkpoint that prevents cells with damaged DNA from initiating mitosis. CDK2-nullizygous human cells exposed to ionizing radiation failed to exclude Cdk1 from the nucleus and exhibited a marked defect in G(2)/M arrest that was unmasked by the disruption of P53. The DNA replication licensing protein Cdc6, which is normally stabilized by Cdk2, was physically associated with the checkpoint regulator ATR and was required for efficient ATR-Chk1-Cdc25A signaling. These findings demonstrate that Cdk2 maintains a balance of S-phase regulatory proteins and thereby coordinates subsequent p53-independent G(2)/M checkpoint activation.
authors.affiliation: Department of Radiation Oncology and Molecular Radiation Sciences and The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Jon H
authors.initials: JH
authors.lastname: Chung
authors.forename: Fred
authors.initials: F
authors.lastname: Bunz
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D000071877:Checkpoint Kinase 1; D051357:Cyclin-Dependent Kinase 2 / Q000172:deficiency / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism / Q000528:radiation effects; D004789:Enzyme Activation / Q000528:radiation effects; D004795:Enzyme Stability / Q000528:radiation effects; D016195:G2 Phase / Q000528:radiation effects; D045325:HCT116 Cells; D006801:Humans; D051379:Mice; D008938:Mitosis / Q000528:radiation effects; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000528:radiation effects; D011494:Protein Kinases / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000528:radiation effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport / Q000528:radiation effects; D011839:Radiation, Ionizing; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D020687:cdc25 Phosphatases / Q000378:metabolism
chemical_list: C103706:CDC6 protein, human; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D016159:Tumor Suppressor Protein p53; D011494:Protein Kinases; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C000605869:Chek1 protein, mouse; D017346:Protein Serine-Threonine Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D020687:cdc25 Phosphatases