title: The ataxia-telangiectasia related protein ATR mediates DNA-dependent phosphorylation of p53.
abstract: Levels of the tumour suppressor protein p53 are increased in response to a variety of DNA damaging agents. DNA damage-induced phosphorylation of p53 occurs at serine-15 in vivo. Phosphorylation of p53 at serine-15 leads to a stabilization of the polypeptide by inhibiting its interaction with Mdm2, a protein that targets p53 for ubiquitin-dependent degradation. However, the mechanisms by which DNA damage is signalled to p53 remain unclear. Here, we report the identification of a novel DNA-activated protein kinase that phosphorylates p53 on serine-15. Fractionation of HeLa nuclear extracts and biochemical analyses indicate that this kinase is distinct from the DNA-dependent protein kinase (DNA-PK) and corresponds to the human cell cycle checkpoint protein ATR. Immunoprecipitation studies of recombinant ATR reveal that catalytic activity of this polypeptide is required for DNA-stimulated phosphorylation of p53 on serine-15. These data suggest that ATR may function upstream of p53 in a signal transduction cascade initiated upon DNA damage and provide a biochemical assay system for ATR activity.
authors.affiliation: Wellcome Trust/Cancer Research Campaign Institute of Cancer and Developmental Biology, Department of Zoology, Cambridge University, UK.
authors.forename: N D
authors.initials: ND
authors.lastname: Lakin
authors.forename: B C
authors.initials: BC
authors.lastname: Hann
authors.forename: S P
authors.initials: SP
authors.lastname: Jackson
mesh_terms: D001260:Ataxia Telangiectasia / Q000201:enzymology / Q000378:metabolism*; D064007:Ataxia Telangiectasia Mutated Proteins; D002384:Catalysis; D018797:Cell Cycle Proteins / Q000502:physiology*; D004247:DNA / Q000502:physiology; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000502:physiology*; D012694:Serine / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins; D054462:p21-Activated Kinases
chemical_list: D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins; D004247:DNA; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D012694:Serine; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D054462:p21-Activated Kinases; C576324:ATM protein, human; C576597:ATR protein, human; C515903:PAK1 protein, human; C497263:PRKDC protein, human