Activator-dependent regulation of transcriptional pausing on nucleosomal templates.
Promoter-proximal pausing during transcriptional elongation is an important way of regulating many diverse genes, including human c-myc and c-fos, some HIV genes, and the Drosophila heat shock loci. To characterize the mechanisms that regulate pausing, we have established an in vitro system using the human hsp7O gene. We demonstrate that nucleosome formation increases by >100-fold the duration of a transcriptional pause on the human hsp7O gene in vitro at the same location as pausing is observed in vivo. Readthrough of this pause is increased by an activator that contains the human heat shock factor 1 (HSF1) transcriptional activation domains. Maximal effect of the activator requires that the system be supplemented with fractions that have hSWI/SNF activity, which has been shown previously to alter nucleosome structure. No significant readthrough is observed in the absence of activator, and neither the activator nor the hSWI/SNF fraction affected elongation on naked DNA; therefore, these results suggest that an activator can cause increased readthrough of promoter-proximal pausing by decreasing the inhibitory effect of nucleosomes on transcriptional elongation.
Brown
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Department of Genetics, Harvard Medical School, Boston, Massachusetts 02114, USA.
Imbalzano
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Kingston
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D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics*; D029721:Drosophila Proteins; D005656:Fungal Proteins / Q000235:genetics; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D006367:HeLa Cells; D000076249:Heat Shock Transcription Factors; D006801:Humans; D008969:Molecular Sequence Data; D009707:Nucleosomes / Q000235:genetics*; D011401:Promoter Regions, Genetic; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000235:genetics; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; C000619706:HSF1 protein, human; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D009707:Nucleosomes; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C089969:snf protein, Drosophila