Double-stranded DNA translocase activity of transcription factor TFIIH and the mechanism of RNA polymerase II open complex formation

James Fishburn, Eric Tomko, Eric Galburt, Steven Hahn

Research output: Contribution to journalArticlepeer-review

80 Scopus citations

Abstract

Formation of the RNA polymerase II (Pol II) open complex (OC) requires DNA unwinding mediated by the transcription factor TFIIH helicase-related subunit XPB/Ssl2. Because XPB/Ssl2 binds DNA downstream from the location of DNA unwinding, it cannot function using a conventional helicase mechanism. Here we show that yeast TFIIH contains an Ssl2-dependent double-stranded DNA translocase activity. Ssl2 tracks along one DNA strand in the 5′ → 3′ direction, implying it uses the nontemplate promoter strand to reel downstream DNA into the Pol II cleft, creating torsional strain and leading to DNA unwinding. Analysis of the Ssl2 and DNA-dependent ATPase activity of TFIIH suggests that Ssl2 has a processivity of approximately one DNA turn, consistent with the length of DNA unwound during transcription initiation. Our results can explain why maintaining the OC requires continuous ATP hydrolysis and the function of TFIIH in promoter escape. Our results also suggest that XPB/Ssl2 uses this translocase mechanism during DNA repair rather than physically wedging open damaged DNA.

Original languageEnglish
Pages (from-to)3961-3966
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume112
Issue number13
DOIs
StatePublished - Mar 31 2015

Keywords

  • DNA helicase
  • DNA unwinding
  • Transcription initiation

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