title: Chk2/hCds1 functions as a DNA damage checkpoint in G(1) by stabilizing p53.
abstract: Chk2/hcds1, the human homolog of the Saccharomyces cerevisiae RAD53/SPK1 and Schizosaccharomyces pombe cds1 DNA damage checkpoint genes, encodes a protein kinase that is post-translationally modified after DNA damage. Like its yeast homologs, the Chk2/hCds1 protein phosphorylates Cdc25C in vitro, suggesting that it arrests cells in G(2) in response to DNA damage. We expressed Chk2/hCds1 in human cells and analyzed their cell cycle profile. Wild-type, but not catalytically inactive, Chk2/hCds1 led to G(1) arrest after DNA damage. The arrest was inhibited by cotransfection of a dominant-negative p53 mutant, indicating that Chk2/hCds1 acted upstream of p53. In vitro, Chk2/hCds1 phosphorylated p53 on Ser-20 and dissociated preformed complexes of p53 with Mdm2, a protein that targets p53 for degradation. In vivo, ectopic expression of wild-type Chk2/hCds1 led to increased p53 stabilization after DNA damage, whereas expression of a dominant-negative Chk2/hCds1 mutant abrogated both phosphorylation of p53 on Ser-20 and p53 stabilization. Thus, in response to DNA damage, Chk2/hCds1 stabilizes the p53 tumor suppressor protein leading to cell cycle arrest in G(1).
authors.affiliation: Department of Molecular Genetics, The Wistar Institute, Philadelphia, Pennsylvania 19104, USA.
authors.forename: N H
authors.initials: NH
authors.lastname: Chehab
authors.forename: A
authors.initials: A
authors.lastname: Malikzay
authors.forename: M
authors.initials: M
authors.lastname: Appel
authors.forename: T D
authors.initials: TD
authors.lastname: Halazonetis
mesh_terms: D064447:Checkpoint Kinase 2; D004249:DNA Damage; D016193:G1 Phase; D006801:Humans; D009687:Nuclear Proteins; D010766:Phosphorylation; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2; D029702:Schizosaccharomyces pombe Proteins; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D029702:Schizosaccharomyces pombe Proteins; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C578634:CHEK2 protein, human; C578636:Cds1 protein, S pombe; D017346:Protein Serine-Threonine Kinases