RNA polymerase II C-terminal heptarepeat domain Ser-7 phosphorylation is established in a mediator-dependent fashion.
The largest subunit of RNA polymerase II (RNAPII) C-terminal heptarepeat domain (CTD) is subject to phosphorylation during initiation and elongation of transcription by RNA polymerase II. Here we study the molecular mechanisms leading to phosphorylation of Ser-7 in the human enzyme. Ser-7 becomes phosphorylated before initiation of transcription at promoter regions. We identify cyclin-dependent kinase 7 (CDK7) as one responsible kinase. Phosphorylation of both Ser-5 and Ser-7 is fully dependent on the cofactor complex Mediator. A subform of Mediator associated with an active RNAPII is critical for preinitiation complex formation and CTD phosphorylation. The Mediator-RNAPII complex independently recruits TFIIB and CDK7 to core promoter regions. CDK7 phosphorylates Ser-7 selectively in the context of an intact preinitiation complex. CDK7 is not the only kinase that can modify Ser-7 of the CTD. ChIP experiments with chemical inhibitors provide evidence that other yet to be identified kinases further phosphorylate Ser-7 in coding regions.
Boeing
Stefan
S
Institute of Molecular Tumor Biology, University of Muenster, Robert-Koch-Strasse 43, 48149 Muenster, Germany.
Rigault
Caroline
C
Heidemann
Martin
M
Eick
Dirk
D
Meisterernst
Michael
M
D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D056892:Mediator Complex / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D011687:Purines / Q000494:pharmacology; D012319:RNA Polymerase II / Q000737:chemistry* / Q000378:metabolism*; D020449:Repetitive Sequences, Amino Acid; D000077546:Roscovitine; D012694:Serine / Q000378:metabolism*; D013698:Templates, Genetic; D051758:Transcription Factor TFIIH / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D000095043:Cyclin-Dependent Kinase-Activating Kinase
D056892:Mediator Complex; D011687:Purines; D000077546:Roscovitine; D051758:Transcription Factor TFIIH; D012694:Serine; D004247:DNA; D018844:Cyclin-Dependent Kinases; D012319:RNA Polymerase II; D000095043:Cyclin-Dependent Kinase-Activating Kinase; C000722416:CDK7 protein, human