title: TFIIH XPB mutants suggest a unified bacterial-like mechanism for promoter opening but not escape.
abstract: DNA helicases open the duplex during DNA replication, repair and transcription. However, RNA polymerase II is the only member of its family with this requirement; RNA polymerases I and III and bacterial RNA polymerases open DNA without a helicase. In this report, characterization of XPB mutants indicates that its helicase activity is not used for RNA polymerase II promoter opening, which is instead driven by its ATPase activity. The mutants have parallels in sigma(54) bacterial transcription and this suggests a similar mode of opening DNA for both RNA polymerases, involving ATP-dependent enzyme conformational changes. Promoter escape is defective in these XPB mutants, suggesting that the XPB helicase acts as an ATP-driven motor to reorganize the tightly wrapped multiprotein eukaryotic preinitiation complex during the remodeling that precedes elongation and the coupling to RNA processing events.
authors.affiliation: Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, PO Box 951569, Los Angeles, California 90095-1569, USA.
authors.forename: Yin Chun
authors.initials: YC
authors.lastname: Lin
authors.forename: Wai S
authors.initials: WS
authors.lastname: Choi
authors.forename: Jay D
authors.initials: JD
authors.lastname: Gralla
mesh_terms: D004247:DNA / Q000378:metabolism*; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D011196:Potassium Permanganate; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology*; D012319:RNA Polymerase II / Q000378:metabolism; D012568:Schizosaccharomyces; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics; D051758:Transcription Factor TFIIH; D019473:Transcription Factors, TFII / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*; D043324:beta-Fructofuranosidase / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; D029702:Schizosaccharomyces pombe Proteins; D019473:Transcription Factors, TFII; D011196:Potassium Permanganate; C072022:XPBC-ERCC-3 protein; D051758:Transcription Factor TFIIH; D004247:DNA; D012319:RNA Polymerase II; C468429:INV1 protein, S pombe; D043324:beta-Fructofuranosidase; D004265:DNA Helicases