Transcription factor TFIIH is required for promoter melting in vivo.
The Rad25 protein in yeast is a DNA helicase and a subunit of the general transcription factor TFIIH. While in vitro studies have led to the hypothesis that TFIIH helicase activity plays a role in promoter melting, in vivo tests are lacking. Using potassium permanganate, which preferentially modifies single-stranded DNA, we show that a temperature-sensitive rad25(ts) mutant severely reduces the normally extensive promoter melting observed in vivo on the highly expressed genes TDH2 and PDC1 and on the induced heat shock gene HSP82. Loss of promoter melting can be observed in as little as 30 s after a shift to the nonpermissive temperature and is accompanied by a dramatic reduction in transcription. These effects on the promoter are specific, since the mutation does not affect TATA box occupancy or, in the case of HSP82, recruitment of TATA-binding protein to the TATA element or that of heat shock factor to heat shock elements. Additionally, using the technique of formaldehyde cross-linking coupled with restriction endonuclease cleavage and ligation-mediated PCR, we were able to map the polymerase density on the promoter of HSP82. This high-resolution mapping allowed us to determine that the polymerase II (Pol II) density on the promoter is also dramatically reduced after inactivation of TFIIH. These data provide strong support for the hypothesis that TFIIH functions with Pol II in the transcriptionally required step of promoter melting and show, surprisingly, that the extent of TFIIH-dependent promoter melting observed in vivo is several times larger than that seen in vitro.
Guzmán
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Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853, USA.
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D004265:DNA Helicases / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D004271:DNA, Fungal / Q000737:chemistry* / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005800:Genes, Fungal; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics; D009691:Nucleic Acid Denaturation; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D035381:TATA-Binding Protein Associated Factors; D035362:Transcription Factor TFIID; D051758:Transcription Factor TFIIH; D014157:Transcription Factors / Q000502:physiology*; D019473:Transcription Factors, TFII
D004271:DNA, Fungal; D005656:Fungal Proteins; C074510:HSP82 protein, S cerevisiae; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C489575:SSL2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C490039:TAF6 protein, S cerevisiae; D035381:TATA-Binding Protein Associated Factors; D035362:Transcription Factor TFIID; D014157:Transcription Factors; D019473:Transcription Factors, TFII; D051758:Transcription Factor TFIIH; D012319:RNA Polymerase II; D004265:DNA Helicases