title: Modular organization of the E2F1 activation domain and its interaction with general transcription factors TBP and TFIIH.
abstract: The transcriptional activator E2F1 regulates the expression of genes at the G1/S boundary. We have characterized interactions of the E2F1 activation domain with two general transcription factors, the TATA-box binding protein (TBP) and TFIIH. Two distinct binding sites on E2F1 were identified for TBP (amino acids 386-417 and 415-437) each of which supported activation in mammalian cells when expressed as a fusion to a heterologous DNA-binding domain. Neither of these minimal activation domains independently bound TFIIH; rather, the TFIIH binding site of E2F1 overlaps both domains. Loss of TFIIH-binding by E2F1 resulted in a 60-65% reduction in transactivation, suggesting that the E2F1/TFIIH interaction is important, but not essential, for transactivation. The retinoblastoma protein (Rb) binds directly to E2F1 and represses E2F1-mediated transactivation. We have demonstrated that recombinant Rb can compete with TBP and the p62 subunit of TFIIH for binding to immobilized E2F1. A tumorigenic form of Rb deficient in repressing E2F1-mediated transactivation is likewise deficient in displacing TBP from E2F1. We propose that competition between Rb and both TBP and TFIIH for binding to E2F1 is a mechanism by which Rb inhibits transactivation by E2F1.
authors.affiliation: Banting and Best Department of Medical Research, University of Toronto, Ontario, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Pearson
authors.forename: J
authors.initials: J
authors.lastname: Greenblatt
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002846:Chromatography, Affinity; D004268:DNA-Binding Proteins / Q000378:metabolism*; D029721:Drosophila Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D056465:Retinoblastoma-Binding Protein 1; D029701:Saccharomyces cerevisiae Proteins; D035381:TATA-Binding Protein Associated Factors; D035181:TATA-Box Binding Protein; D015534:Trans-Activators; D050680:Transcription Factor DP1; D035362:Transcription Factor TFIID; D051758:Transcription Factor TFIIH; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D019473:Transcription Factors, TFII
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C088053:Dp transcription factor, Drosophila; D029721:Drosophila Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D029701:Saccharomyces cerevisiae Proteins; C490039:TAF6 protein, S cerevisiae; D035381:TATA-Binding Protein Associated Factors; D035181:TATA-Box Binding Protein; D015534:Trans-Activators; D050680:Transcription Factor DP1; D035362:Transcription Factor TFIID; D014157:Transcription Factors; D019473:Transcription Factors, TFII; D051758:Transcription Factor TFIIH