title: A pro-apoptotic function of iASPP by stabilizing p300 and CBP through inhibition of BRMS1 E3 ubiquitin ligase activity.
abstract: The p53 family and its cofactors are potent inducers of apoptosis and form a barrier to cancer. Here, we investigated the impact of the supposedly inhibitory member of the apoptosis-stimulating protein of p53, iASPP, on the activity of the p53 homolog TAp73, and its cofactors p300 and CBP. We found that iASPP interacted with and stabilized the histone acetyltransferase p300 and its homolog CBP upon cisplatin treatment. Vice versa, iASPP depletion by shRNA resulted in decreased amounts of p300 and CBP, impaired binding of p300 and TAp73 to target site promoters, reduced induction of pro-apoptotic TAp73 target genes, and impaired apoptosis. Mechanistically, we observed that the p300-regulatory E3 ubiquitin ligase BRMS1 could rescue the degradation of p300 and CBP in cisplatin-treated, iASPP-depleted cells. This argues that iASPP stabilizes p300 and CBP by interfering with their BRMS1-mediated ubiquitination, thereby contributing to apoptotic susceptibility. In line, iASPP overexpression partially abolished the interaction of BRMS1 and CBP upon DNA damage. Reduced levels of iASPP mRNA and protein as well as CBP protein were observed in human melanoma compared with normal skin tissue and benign melanocytic nevi. In line with our findings, iASPP overexpression or knockdown of BRMS1 each augmented p300/CBP levels in melanoma cell lines, thereby enhancing apoptosis upon DNA damage. Taken together, destabilization of p300/CBP by downregulation of iASPP expression levels appears to represent a molecular mechanism that contributes to chemoresistance in melanoma cells.
authors: Department of Molecular Oncology, University Medical Center Göttingen, Göttingen, Germany.
authors: D
authors: D
authors: Kramer
authors: Department of Dermatology, Venereology and Allergology, University Medical Center Göttingen, Göttingen, Germany.
authors: M
authors: M
authors: Schön
authors: Department of Medical Statistics, University Medical Center Göttingen, Göttingen, Germany.
authors: M
authors: M
authors: Bayerlová
authors: Department of Hematology and Medical Oncology, University Medical Center Göttingen, Göttingen, Germany.
authors: A
authors: A
authors: Bleckmann
authors: Department of Dermatology, Venereology and Allergology, University Medical Center Göttingen, Göttingen, Germany.
authors: M P
authors: MP
authors: Schön
authors: Institute of Tumor Biology and Experimental Therapy, Georg Speyer Haus, Frankfurt am Main,Germany.
authors: M
authors: M
authors: Zörnig
authors: Department of Molecular Oncology, University Medical Center Göttingen, Göttingen, Germany.
authors: M
authors: M
authors: Dobbelstein
mesh_terms: D017209:Apoptosis; D050882:CREB-Binding Protein / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle; D047369:Chromatin Immunoprecipitation; D050881:E1A-Associated p300 Protein / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008545:Melanoma / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C410024:BRMS1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; C119612:PPP1R13L protein, human; D012097:Repressor Proteins; D050882:CREB-Binding Protein; D050881:E1A-Associated p300 Protein; C494360:EP300 protein, human