, Michael S. Kobor3,4
, Minkyu Kim1
, Jack Greenblatt3
, and Stephen Buratowski1,5
1Harvard Medical School, Department of Biological Chemistry and Molecular Pharmacology, Boston, Massachusetts 02115, USA; 2Department of Biochemistry and Molecular Biology, College of Pharmacy, Sungkyunkwan University, Suwon, Korea; 3Banting and Best Department of Medical Research and Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario M5G 1L6, Canada
The C-terminal domain (CTD) of the RNA polymerase II (Pol II) largest subunit is hyperphosphorylated during transcription. Using an in vivo cross-linking/chromatin immunoprecipitation assay, we found previously that different phosphorylated forms of RNA Pol II predominate at different stages of transcription. At promoters, the Pol II CTD is phosphorylated at Ser 5 by the basal transcription factor TFIIH. However, in coding regions, the CTD is predominantly phosphorylated at Ser 2. Here we show that the elongation-associated phosphorylation of Ser 2 is dependent upon the Ctk1 kinase, a putative yeast homolog of Cdk9/P-TEFb. Furthermore, mutations in the Fcp1 CTD phosphatase lead to increased levels of Ser 2 phosphorylation. Both Ctk1 and Fcp1 cross-link to promoter and coding regions, suggesting that they associate with the elongating polymerase. Both Ctk1 and Fcp1 have been implicated in regulation of transcription elongation. Our results suggest that this regulation may occur by modulating levels of Ser 2 phosphorylation, which in turn, may regulate the association of elongation factors with the polymerase.
Transcription, phosphorylation, mRNA processing, mRNA capping enzyme, RNA polymerase II
4 Present address: Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA 94720, USA.
5 Corresponding author.
Article and publication are at http://www.genesdev.org/cgi/doi/10.1101/gad.935901.
Received August 8, 2001.
Accepted October 18, 2001.
Cold Spring Harbor Laboratory Press