title: E6 oncoprotein represses p53-dependent gene activation via inhibition of protein acetylation independently of inducing p53 degradation.
abstract: The mechanism employed by DNA tumor viruses to inhibit p53-dependent transcription from chromatin is poorly understood. Here, we use in vitro-reconstituted chromatin and UV-irradiated cells to define the mechanism of human papillomavirus E6 oncoprotein in repressing p53-dependent transcription. We demonstrate that E6 does not prevent p53 or p300 recruitment to the chromatin but inhibits p300-mediated acetylation on p53 and nucleosomal core histones. This suppression of protein acetylation requires the E6-interacting regions of p300. Moreover, E6 mutants unable to interact with p53 or p300, but not deficient in inducing p53 degradation, fail to inhibit p53-mediated activation, indicating that a p53-E6-p300-containing protein complex is critical for repressing p53-targeted gene activation. That E6 acts as a molecular switch converting p53-p300 from an activating complex to a repressing entity on the chromatin, which occurs independently of E6AP-mediated protein degradation pathway, may represent a general mechanism for gene regulation.
authors.affiliation: Department of Biochemistry, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
authors.forename: Mary C
authors.initials: MC
authors.lastname: Thomas
authors.forename: Cheng-Ming
authors.initials: CM
authors.lastname: Chiang
mesh_terms: D000105:Acetyl Coenzyme A / Q000378:metabolism; D000107:Acetylation; D000123:Acetyltransferases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050881:E1A-Associated p300 Protein; D051548:Histone Acetyltransferases; D006657:Histones / Q000378:metabolism; D006801:Humans; D046911:Macromolecular Substances; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor
chemical_list: D000105:Acetyl Coenzyme A; D000123:Acetyltransferases; D018797:Cell Cycle Proteins; D002843:Chromatin; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050881:E1A-Associated p300 Protein; D051548:Histone Acetyltransferases; D006657:Histones; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral; D046988:Proteasome Endopeptidase Complex; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; C068651:E6 protein, Human papillomavirus type 16; C494361:Ep300 protein, mouse