title: Transcriptional regulation by Pol II(G) involving mediator and competitive interactions of Gdown1 and TFIIF with Pol II.
abstract: Pol II(G) is a distinct form of RNA polymerase II that contains the tightly associated Gdown1 polypeptide (encoded by POLR2M). Unlike Pol II, Pol II(G) is highly dependent upon Mediator for robust activator-dependent transcription in a biochemically defined in vitro system. Here, in vitro studies show that Gdown1 competes with TFIIF for binding to the RPB1 and RPB5 subunits of Pol II, thereby inhibiting an essential function of TFIIF in preinitiation complex assembly, but also that Mediator can actually facilitate Pol II(G) binding to the promoter prior to subsequent Mediator functions. Complementary ChIP and RNAi analyses reveal that Pol II(G) is recruited to promoter regions of subsets of actively transcribed genes, where it appears to restrict transcription. These and other results suggest that Pol II(G) may act to modulate some genes while simultaneously, as a poised (noninitiated) polymerase, setting the stage for Mediator-dependent enhancement of their activity.
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY 10065, USA.
authors.forename: Miki
authors.initials: M
authors.lastname: Jishage
authors.forename: Sohail
authors.initials: S
authors.lastname: Malik
authors.forename: Ulrich
authors.initials: U
authors.lastname: Wagner
authors.forename: Beatrix
authors.initials: B
authors.lastname: Uberheide
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Ishihama
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Hu
authors.forename: Brian T
authors.initials: BT
authors.lastname: Chait
authors.forename: Averell
authors.initials: A
authors.lastname: Gnatt
authors.forename: Bing
authors.initials: B
authors.lastname: Ren
authors.forename: Robert G
authors.initials: RG
authors.lastname: Roeder
mesh_terms: D001667:Binding, Competitive; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D056892:Mediator Complex / Q000378:metabolism / Q000502:physiology; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D019473:Transcription Factors, TFII / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D056892:Mediator Complex; C433812:POLR2M protein, human; D019473:Transcription Factors, TFII; D012319:RNA Polymerase II; D012321:DNA-Directed RNA Polymerases; C517511:POLR2E protein, human; C056604:transcription factor TFIIF