title: HAUSP is required for p53 destabilization.
abstract: p53 ubiquitination is the principal mechanism by which p53 levels are regulated in the cell. HAUSP (also known as USP7) has been proposed to serve as a substrate-specific deubiquitinase of p53, and an increase in p53 levels was reported upon overexpression of HAUSP. We have disrupted the HAUSP genomic locus by homologous recombination and shown that HAUSP ablation results in a phenotype opposite to that predicted. Rather than decreasing p53 levels associated with increased p53 ubiquitination, the absence of HAUSP resulted in p53 accumulation accompanied by decreased p53 ubiquitination. The p53 protein in HAUSP-deficient cells was active, as assessed by the induction of its transcriptional targets and growth arrest. The basis for this phenotype was traced to the increased ubiquitination of MDM2, a negative regulator of p53 levels. These results demonstrate that MDM2, rather than p53, is the substrate for HAUSP under physiologic conditions and document a fascinating and unexpected twist to the regulation of the p53/MDM2 axis.
authors.affiliation: The Howard Hughes Medical Institute, The Sidney Kimmel Comprehensive Cancer Center, Program in Cellular and Molecular Medicine, The Johns Hopkins University Medical Institutions, Baltimore, Maryland, USA. jcummins@jhmi.edu
authors.forename: Jordan M
authors.initials: JM
authors.lastname: Cummins
authors.forename: Bert
authors.initials: B
authors.lastname: Vogelstein
mesh_terms: D045744:Cell Line, Tumor; D010450:Endopeptidases / Q000172:deficiency / Q000378:metabolism / Q000502:physiology*; D045325:HCT116 Cells; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D013379:Substrate Specificity; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D043222:Ubiquitin Thiolesterase; D000076084:Ubiquitin-Specific Peptidase 7; D014452:Ubiquitins / Q000378:metabolism
chemical_list: D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D014452:Ubiquitins; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D010450:Endopeptidases; C464569:USP7 protein, human; D043222:Ubiquitin Thiolesterase; D000076084:Ubiquitin-Specific Peptidase 7