title: Functional association of Gdown1 with RNA polymerase II poised on human genes.
abstract: Most human genes are loaded with promoter-proximally paused RNA polymerase II (Pol II) molecules that are poised for release into productive elongation by P-TEFb. We present evidence that Gdown1, the product of the POLR2M gene that renders Pol II responsive to Mediator, is involved in Pol II elongation control. During in vitro transcription, Gdown1 specifically blocked elongation stimulation by TFIIF, inhibited the termination activity of TTF2, and influenced pausing factors NELF and DSIF, but did not affect the function of TFIIS or the mRNA capping enzyme. Without P-TEFb, Gdown1 led to the production of stably paused polymerases in the presence of nuclear extract. Supporting these mechanistic insights, ChIP-Seq demonstrated that Gdown1 mapped over essentially all poised polymerases across the human genome. Our results establish that Gdown1 stabilizes poised polymerases while maintaining their responsiveness to P-TEFb and suggest that Mediator overcomes a Gdown1-mediated block of initiation by allowing TFIIF function.
authors.affiliation: Molecular and Cellular Biology Program, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Cheng
authors.forename: Tiandao
authors.initials: T
authors.lastname: Li
authors.forename: Peter B
authors.initials: PB
authors.lastname: Rahl
authors.forename: Todd E
authors.initials: TE
authors.lastname: Adamson
authors.forename: Nicholas B
authors.initials: NB
authors.lastname: Loudas
authors.forename: Jiannan
authors.initials: J
authors.lastname: Guo
authors.forename: Katayoun
authors.initials: K
authors.lastname: Varzavand
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Cooper
authors.forename: Xiaopeng
authors.initials: X
authors.lastname: Hu
authors.forename: Averell
authors.initials: A
authors.lastname: Gnatt
authors.forename: Richard A
authors.initials: RA
authors.lastname: Young
authors.forename: David H
authors.initials: DH
authors.lastname: Price
mesh_terms: D006367:HeLa Cells; D006801:Humans; D012319:RNA Polymerase II / Q000378:metabolism / Q000502:physiology*; D019473:Transcription Factors, TFII / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: C433812:POLR2M protein, human; D019473:Transcription Factors, TFII; D012319:RNA Polymerase II; C056604:transcription factor TFIIF