A minimal RNA polymerase III transcription system.
Transcription factor (TF) IIIB recruits RNA polymerase (pol) III for specific initiation of transcription. All three subunits of TFIIIB, TBP, Brf (the TFIIB-related subunit) and B", are required for transcription of supercoiled and linear duplex DNA, but we show here that B" is non-essential on a promoter that has been partly pre-opened by unpairing a short segment of the transcription bubble. These findings expose a striking similarity between transcriptional initiation by pol II, pol III and bacterial RNA polymerases: a preformed single-stranded DNA bubble upstream of the transcriptional start removes the dependence of pol II on TFIIE, TFIIH and ATP hydrolysis, and the dependence of pol III on B"; the favored placement of the transcription bubble for B"-independent transcription by pol III overlaps a DNA segment that interacts sequence specifically as single-stranded DNA with the sigma(70 )initiation subunit of Escherichia coli RNA polymerase holoenzyme.
Kassavetis
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GA
Department of Biology, Center for Molecular Genetics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA. gak@ucsd.edu
Letts
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GA
Geiduschek
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EP
D000255:Adenosine Triphosphate / Q000378:metabolism; D001483:Base Sequence; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D020035:Holoenzymes / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D020836:Protein Structure, Quaternary; D012320:RNA Polymerase III / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D012808:Sigma Factor / Q000378:metabolism; D035361:Transcription Factor TFIIIB; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism; D014158:Transcription, Genetic
C090956:BRF1 protein, S cerevisiae; D004271:DNA, Fungal; D020035:Holoenzymes; D029701:Saccharomyces cerevisiae Proteins; D012808:Sigma Factor; D035361:Transcription Factor TFIIIB; D014157:Transcription Factors; D000255:Adenosine Triphosphate; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases; D012320:RNA Polymerase III