title: Transactivation of E2F-regulated genes by polyomavirus large T antigen: evidence for a two-step mechanism.
abstract: Polyomavirus large T antigen transactivates a variety of genes whose products are involved in S phase induction. These genes are regulated by the E2F family of transcription factors, which are under the control of the pocket protein retinoblastoma protein and its relatives p130 and p107. The viral protein causes a dissociation of E2F-pocket protein complexes that results in transactivation of the genes. This reaction requires the N-terminal binding site for pocket proteins and the J domain that binds chaperones. We found earlier that a mutation of the zinc finger located within the C-terminal domain, a region assumed to function mainly in the replication of viral DNA, also interferes with transactivation. Here we show that binding of the histone acetyltransferase coactivator complex CBP/p300-PCAF to the C terminus correlates with the ability of large T antigen to transactivate genes. This interaction results in promoter-specific acetylation of histones. Inactive mutant proteins with changes within the C-terminal domain were nevertheless able to dissociate the E2F pocket protein complexes, indicating that this dissociation is a necessary but insufficient step in the T antigen-induced transactivation of genes. It has to be accompanied by a second step involving the T antigen-mediated recruitment of a histone acetyltransferase complex.
authors.affiliation: Medical University of Vienna, Department of Medical Biochemistry, Division of Molecular Biology, Vienna Biocenter, Dr. Bohrgasse 9, A-1030 Vienna, Austria.
authors.forename: Maria
authors.initials: M
authors.lastname: Nemethova
authors.forename: Michael
authors.initials: M
authors.lastname: Smutny
authors.forename: Erhard
authors.initials: E
authors.lastname: Wintersberger
mesh_terms: D000409:Alanine / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D002843:Chromatin / Q000378:metabolism; D004247:DNA / Q000032:analysis; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D050684:E2F Transcription Factors; D024202:Electrophoretic Mobility Shift Assay; D004622:Embryo, Mammalian / Q000166:cytology; D005347:Fibroblasts / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D017930:Genes, Reporter; D015151:Immunoblotting; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D011233:Precipitin Tests; D017434:Protein Structure, Tertiary; D051381:Rats; D041701:Swiss 3T3 Cells; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D000952:Antigens, Polyomavirus Transforming; D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D014157:Transcription Factors; D004247:DNA; D008156:Luciferases; D000409:Alanine