Sp1, USF, and GAL4 activate transcription independently of TFIID-downstream promoter interactions.
One way specific transcription factors are thought to activate transcription initiation is by facilitating interactions between the general transcription factor TFIID and DNA sequences downstream of the TATA element. Examples supporting this model include transcription activation from the core adenovirus E4 promoter by either the human gene-specific transcription factor ATF or the acidic-domain fusion protein GAL4-AH. In these cases, appearance of downstream promoter binding by TFIID correlated directly with transcription activation by these proteins. Previously we had shown that downstream promoter binding by TFIID involved recognition of the initiator DNA control element and that the extent of this binding correlated directly with initiator-dependent transcription activation in vitro. We now report our use of DNase I footprinting and in vitro transcription to investigate the effects of various stimulatory transcription factors on TFIID binding and transcription efficiency from different initiator-containing promoters. Transcription factors investigated included Sp1, USF, and several GAL4-acidic domain fusion proteins. We found that none of these transcription factors appreciably affected downstream promoter binding by TFIID, whether qualitatively or quantitatively. In fact, all of these transcription factors stimulated transcription in vitro regardless of the strength of the initiator element present. When both elements were present, transcription stimulation mediated by proximally bound transcription factors and by TFIID-initiator interaction seemed to be synergistic. Taken together, our data would suggest that transcription activation by these two means occurs through different steps within the transcriptional process.
Wang
J C
JC
Department of Tumor Biology, University of Texas M.D. Anderson Cancer Center, Houston 77030.
Van Dyke
M W
MW
D001483:Base Sequence; D001665:Binding Sites; D015342:DNA Probes; D004268:DNA-Binding Proteins; D003850:Deoxyribonuclease I; D005656:Fungal Proteins / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D016385:TATA Box; D013698:Templates, Genetic; D035362:Transcription Factor TFIID; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D051720:Upstream Stimulatory Factors
D015342:DNA Probes; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D016329:Sp1 Transcription Factor; D035362:Transcription Factor TFIID; D014157:Transcription Factors; C497181:USF1 protein, human; D051720:Upstream Stimulatory Factors; D003850:Deoxyribonuclease I