title: Retinoblastoma protein modulates gankyrin-MDM2 in regulation of p53 stability and chemosensitivity in cancer cells.
abstract: MDM2 is a key ubiquitin E3 ligase for p53 and its activity is critically regulated by a set of modulators, including ARF, p300, YY1 and recently by gankyrin, an oncoprotein frequently overexpressed in human heptocellular carcinomas. We have previously shown that MDM2 binds to and promotes retinoblastoma protein (Rb) degradation. Here we show that Rb inhibits MDM2 E3 ligase activity resulting in stabilization of p53. In addition, we demonstrated that Rb inhibits MDM2-mediated p53 ubiquitination in a gankyrin-dependent manner and the Rb-gankyrin interaction is critical for Rb-induced p53 stabilization. Furthermore, acute ablation of Rb facilitates gankyrin-mediated p53 destabilization, and desensitizes cancer cells for chemotherapy-induced apoptosis. These results indicate that Rb antagonizes gankyrin to inhibit MDM2-mediate p53 ubiquitination in cancer cells and suggest that the status of both p53 and Rb is important for efficacy of cancer chemotherapy.
authors.affiliation: Graduate Program in Molecular Medicine, Department of Medicine, Boston University School of Medicine, Boston, MA, USA.
authors.forename: W
authors.initials: W
authors.lastname: Qiu
authors.forename: J
authors.initials: J
authors.lastname: Wu
authors.forename: E M
authors.initials: EM
authors.lastname: Walsh
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: C-Y
authors.initials: CY
authors.lastname: Chen
authors.forename: J
authors.initials: J
authors.lastname: Fujita
authors.forename: Z-X J
authors.initials: ZX
authors.lastname: Xiao
mesh_terms: D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000378:metabolism*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D006801:Humans; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D054875:Ubiquitination; D050986:YY1 Transcription Factor / Q000378:metabolism
chemical_list: C403591:PSMD10 protein, human; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D050986:YY1 Transcription Factor; C494698:YY1 protein, human; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D046988:Proteasome Endopeptidase Complex