title: Head module control of mediator interactions.
abstract: Yeast Mediator proteins interacting with Med17(Srb4) have been expressed at a high level with the use of recombinant baculoviruses and recovered in homogeneous form as a seven subunit, 223 kDa complex. Electron microscopy and single-particle analysis identify this complex as the Mediator head module. The recombinant head module complements "headless" Mediator for the initiation of transcription in vitro. The module interacts with an RNA polymerase II-TFIIF complex, but not with the polymerase or TFIIF alone. This interaction is lost in the presence of a DNA template and associated RNA transcript, recapitulating the release of Mediator that occurs upon the initiation of transcription. Disruption of the head module in a temperature-sensitive mutant in vivo leads to the release of middle and tail modules from a transcriptionally active promoter. The head module evidently controls Mediator-RNA polymerase II and Mediator-promoter interactions.
authors.affiliation: Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Takagi
authors.forename: Guillermo
authors.initials: G
authors.lastname: Calero
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Komori
authors.forename: Jesse A
authors.initials: JA
authors.lastname: Brown
authors.forename: Andreas H
authors.initials: AH
authors.lastname: Ehrensberger
authors.forename: Andy
authors.initials: A
authors.lastname: Hudmon
authors.forename: Francisco
authors.initials: F
authors.lastname: Asturias
authors.forename: Roger D
authors.initials: RD
authors.lastname: Kornberg
mesh_terms: D016367:Baculoviridae / Q000235:genetics; D056892:Mediator Complex; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012319:RNA Polymerase II / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D035181:TATA-Box Binding Protein / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D035581:Transcription Factor TFIIB / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D019473:Transcription Factors, TFII / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: C107274:MED6 protein, S cerevisiae; C421882:MED8 protein, S cerevisiae; D056892:Mediator Complex; D046912:Multiprotein Complexes; D011993:Recombinant Fusion Proteins; C074748:SRB2 protein, S cerevisiae; C082148:SRB4 protein, S cerevisiae; C082149:SRB5 protein, S cerevisiae; C082150:SRB6 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D035181:TATA-Box Binding Protein; D015534:Trans-Activators; D035581:Transcription Factor TFIIB; D014157:Transcription Factors; D019473:Transcription Factors, TFII; D012319:RNA Polymerase II; C056604:transcription factor TFIIF