title: p53 stabilization in response to DNA damage requires Akt/PKB and DNA-PK.
abstract: The p53 protein is one of the major tumor suppressor proteins. In response to DNA damage, p53 is prevented from degradation and accumulates to high levels. Ionizing radiation leads to hypophosphorylation of the p53 ubiquitin ligase Mdm2 at sites where phosphorylation is critical for p53 degradation and to the phosphorylation and activation of Akt/PKB, a kinase that phosphorylates and inhibits GSK-3. GSK-3, which normally phosphorylates Mdm2, is inactivated in response to ionizing radiation. We show that p53 accumulates in lymphoblasts from patients with the hereditary disorder ataxia telangiectasia in response to ionizing radiation despite the absence of a functional ATM kinase. Also, knockdown of ATR did not prevent p53 accumulation in response to ionizing radiation. Instead, p53 stabilization in response to ionizing radiation depended on the inactivation of GSK-3 and the presence of Akt/PKB. Akt/PKB is a target of DNA-PK, a kinase that is activated after ionizing radiation. Correspondingly, down-regulation of DNA-PK prevented phosphorylation of Akt/PKB and GSK-3 after ionizing radiation and strongly reduced the accumulation of p53. We therefore propose a signaling cascade for the regulation of p53 in response to ionizing radiation that involves activation of DNA-PK and Akt/PKB and inactivation of GSK-3 and Mdm2.
authors.affiliation: Forschungszentrum Karlsruhe, Institute of Toxicology and Genetics, P.O. Box 3640, 76021 Karlsruhe, Germany. christine.blattner@itg.fzk.de
authors.forename: Karen A
authors.initials: KA
authors.lastname: Boehme
authors.forename: Roman
authors.initials: R
authors.lastname: Kulikov
authors.forename: Christine
authors.initials: C
authors.lastname: Blattner
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000235:genetics; D002460:Cell Line; D004247:DNA / Q000528:radiation effects; D004249:DNA Damage; D051747:DNA-Activated Protein Kinase / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics; D015536:Down-Regulation; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism; D011839:Radiation, Ionizing; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D004247:DNA; D051736:Proto-Oncogene Proteins c-mdm2; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3