title: Coactivators p300 and PCAF physically and functionally interact with the foamy viral trans-activator.
abstract: BACKGROUND
  Foamy virus Bel1/Tas trans-activators act as key regulators of gene expression and directly bind to Bel1 response elements (BRE) in both the internal and the 5'LTR promoters leading to strong transcriptional trans-activation. Cellular coactivators interacting with Bel1/Tas are unknown to date.
  
  
  RESULTS
  Transient expression assays, co-immunoprecipitation experiments, pull-down assays, and Western blot analysis were used to demonstrate that the coactivator p300 and histone acetyltransferase PCAF specifically interact with the retroviral trans-activator Bel1/Tas in vivo. Here we show that the Bel1/Tas-mediated trans-activation was enhanced by the coactivator p300, histone acetyltransferases PCAF and SRC-1 based on the crucial internal promoter BRE. The Bel1/Tas-interacting region was mapped to the C/H1 domain of p300 by co-immunoprecipitation and pull-down assays. In contrast, coactivator SRC-1 previously reported to bind to the C-terminal domain of p300 did not directly interact with the Bel1 protein but nevertheless enhanced Bel1/Tas-mediated trans-activation. Cotransfection of Bel1/Tas and p300C with an expression plasmid containing the C/H1domain partially inhibited the p300C-driven trans-activation.
  
  
  CONCLUSIONS
  Our data identify p300 and PCAF as functional partner molecules that directly interact with Bel1/Tas. Since the acetylation activities of the three coactivators reside in or bind to the C-terminal regions of p300, a C/H1 expression plasmid was used as inhibitor. This is the first report of a C/H1 domain-interacting retroviral trans-activator capable of partially blocking the strong Bel1/Tas-mediated activation of the C-terminal region of coactivator p300. The potential mechanisms and functional roles of the three histone and factor acetyltransferases p300, PCAF, and SRC-1 in Bel1/Tas-mediated trans-activation are discussed.
authors.affiliation: Department of Retroviral Gene Expression, German Cancer Research Center, Applied Tumor Virology, Heidelberg, Germany. h.bannert@dkfz-heidelberg.de
authors.forename: Helmut
authors.initials: H
authors.lastname: Bannert
authors.forename: Walter
authors.initials: W
authors.lastname: Muranyi
authors.forename: Vasily V
authors.initials: VV
authors.lastname: Ogryzko
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Nakatani
authors.forename: Rolf M
authors.initials: RM
authors.lastname: Flügel
mesh_terms: D000123:Acetyltransferases / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D006367:HeLa Cells / Q000737:chemistry / Q000378:metabolism; D051548:Histone Acetyltransferases; D006801:Humans; D007668:Kidney / Q000737:chemistry / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D009154:Mutation / Q000235:genetics / Q000502:physiology; D009687:Nuclear Proteins / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D025941:Protein Interaction Mapping / Q000379:methods; D017434:Protein Structure, Tertiary; D020218:Response Elements / Q000235:genetics; D012191:Retroviridae Proteins / Q000378:metabolism* / Q000502:physiology; D016092:Spumavirus / Q000235:genetics; D015534:Trans-Activators / Q000378:metabolism* / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics*; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor
chemical_list: D000123:Acetyltransferases; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D051548:Histone Acetyltransferases; D009687:Nuclear Proteins; D010455:Peptides; D012191:Retroviridae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C074061:bel1 protein, Human foamy virus