title: The co-activator p300 associates physically with and can mediate the action of the distal enhancer of the FGF-4 gene.
abstract: Distal enhancers commonly regulate gene expression. However, the mechanisms of transcriptional mediation by distal enhancers remain largely unknown. To better understand distal enhancer-mediated transcription, we examined the regulation of the FGF-4 gene. The FGF-4 gene is regulated during early development by a powerful distal enhancer located downstream of the promoter in exon 3. Sox-2 and Oct-3 bind to the enhancer and are required for the activation of the FGF-4 gene. Previously, we implicated the co-activator p300 as a mediator of Sox-2/Oct-3 synergistic activation of a heterologous promoter, suggesting that p300 may play a role in mediating enhancer activation of the FGF-4 gene. In this study, we provide both functional and physical evidence that p300 plays an important role in the action of the FGF-4 enhancer. Specifically, we show that E1a, but not a mutant form of E1a that is unable to bind p300, inhibits enhancer activation of the FGF-4 promoter. We also demonstrate that Gal4/p300 fusion proteins can stimulate the FGF-4 promoter when bound to the FGF-4 enhancer. Additionally, we present evidence that p300 mediation of the FGF-4 enhancer requires acetyltransferase activity. Importantly, we also show that Sox-2 and p300 are physically associated with the endogenous FGF-4 enhancer but weakly associated with the endogenous FGF-4 promoter. These results are consistent with a model of transitory interaction between the distal enhancer and the FGF-4 promoter. Our results also suggest that intragenic distal enhancers may use mechanisms that differ from extragenic distal enhancers.
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha 68198, USA.
authors.forename: Tamara
authors.initials: T
authors.lastname: Nowling
authors.forename: Cory
authors.initials: C
authors.lastname: Bernadt
authors.forename: Lance
authors.initials: L
authors.lastname: Johnson
authors.forename: Michelle
authors.initials: M
authors.lastname: Desler
authors.forename: Angie
authors.initials: A
authors.lastname: Rizzino
mesh_terms: D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism; D050881:E1A-Associated p300 Protein; D004742:Enhancer Elements, Genetic; D005091:Exons; D051519:Fibroblast Growth Factor 4; D005346:Fibroblast Growth Factors / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D024002:HMGB Proteins; D051379:Mice; D008954:Models, Biological; D008957:Models, Genetic; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism* / Q000502:physiology*; D050814:Octamer Transcription Factor-3; D020161:Physical Chromosome Mapping; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D055748:SOXB1 Transcription Factors; D015534:Trans-Activators / Q000378:metabolism* / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; C496446:Fgf4 protein, mouse; D051519:Fibroblast Growth Factor 4; D024002:HMGB Proteins; D009687:Nuclear Proteins; D050814:Octamer Transcription Factor-3; C494174:Pou5f1 protein, mouse; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D055748:SOXB1 Transcription Factors; C527783:Sox2 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D005346:Fibroblast Growth Factors; D015500:Chloramphenicol O-Acetyltransferase; D050881:E1A-Associated p300 Protein; C494361:Ep300 protein, mouse