title: Involvement of the DNA repair protein hHR23 in p53 degradation.
abstract: The stability of the tumor suppressor protein p53 is regulated via the ubiquitin-proteasome-dependent proteolytic pathway. Like most substrates of this pathway, p53 is modified by the attachment of polyubiquitin chains prior to proteasome-mediated degradation. However, the mechanism(s) involved in the delivery of polyubiquitylated p53 molecules to the proteasome are currently unclear. Here, we show that the human DNA repair protein hHR23 binds to polyubiquitylated p53 via its carboxyl-terminal ubiquitin-associated (Uba) domain shielding p53 from deubiquitylation in vitro and in vivo. In addition, downregulation of hHR23 expression within cells by RNA interference results in accumulation of p53. Since the Ubl domain of hHR23 has been shown to interact with the 26S proteasome, we propose that hHR23 is intrinsically involved in the delivery of polyubiquitylated p53 molecules to the proteasome. In this model, the Uba domain of hHR23 binds to polyubiquitin chains formed on p53 and protects them from deubiquitylation, while the Ubl domain delivers the polyubiquitylated p53 molecules to the proteasome.
authors.affiliation: Zentrum für Biochemie, Medizinische Fakultät, Universität zu Köln, 50931 Cologne, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Glockzin
authors.forename: Francois-Xavier
authors.initials: FX
authors.lastname: Ogi
authors.forename: Arnd
authors.initials: A
authors.lastname: Hengstermann
authors.forename: Martin
authors.initials: M
authors.lastname: Scheffner
authors.forename: Christine
authors.initials: C
authors.lastname: Blattner
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015536:Down-Regulation; D004355:Drug Stability; D006801:Humans; D066298:In Vitro Techniques; D008954:Models, Biological; D009687:Nuclear Proteins; D010447:Peptide Hydrolases / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D034741:RNA, Small Interfering / Q000235:genetics; D011817:Rabbits; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D016159:Tumor Suppressor Protein p53; D025801:Ubiquitin; C086985:RAD23A protein, human; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D045643:DNA Repair Enzymes