title: Critical roles for the serine 20, but not the serine 15, phosphorylation site and for the polyproline domain in regulating p53 turnover.
abstract: The p53 tumour suppressor protein is a short-lived transcription factor that becomes stabilized in response to a wide range of cellular stresses. Ubiquitination and the targeting of p53 for degradation by the proteasome are mediated by Mdm2 (mouse double minute clone 2), a negative regulatory partner of p53. Previous studies have suggested that DNA-damage-induced phosphorylation of p53 at key N-terminal sites has a pivotal role in regulating the interaction with Mdm2 but the precise role of phosphorylation of serines 15 and 20 is still unclear. Here we show that replacement of serine 15 and a range of other key N-terminal phosphorylation sites with alanine, which cannot be phosphorylated, has little effect on the ubiquitination and degradation of full-length human p53. In contrast, replacement of serine 20 makes p53 highly sensitive to Mdm2-mediated turnover. These results define distinct roles for serines 15 and 20, two sites previously demonstrated to be dependent on phosphorylation through mechanisms mediated by DNA damage and ATM (ataxia telangiectasia mutated). We also show that the polyproline region of p53, a domain that has a key role in p53-induced apoptosis, exerts a critical influence over the Mdm2-mediated turnover of p53.
authors.affiliation: Biomedical Research Centre, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK.
authors.forename: N
authors.initials: N
authors.lastname: Dumaz
authors.forename: D M
authors.initials: DM
authors.lastname: Milne
authors.forename: L J
authors.initials: LJ
authors.lastname: Jardine
authors.forename: D W
authors.initials: DW
authors.lastname: Meek
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D001665:Binding Sites / Q000235:genetics; D019556:COS Cells; D018797:Cell Cycle Proteins; D004249:DNA Damage; D004268:DNA-Binding Proteins; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D016296:Mutagenesis; D009687:Nuclear Proteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D012694:Serine / Q000737:chemistry; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D012694:Serine; C497206:MDM2 protein, human; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; C576897:Atr protein, mouse; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases