The repetitive C-terminal domain of RNA polymerase II: Multiple conformational states drive the transcription cycle

RNA polymerase (RNAP) 11 is a complex multisubunit enzyme responsible for the synthesis of mRNA in eukaryotic cells. The largest subunit contains at its C-terminus a unique domain, designated the CTD, comprised of tandem repeats of the consensus sequence Tyr(1)Ser(2)Pro(3)Thr(4)Ser(5)Pro(6)Ser(7). This repeat occurs 52 times in mammalian RNAP II. The CTD is subject to extensive phosphorylation at specific points in the transcription cycle by distinct CTD kinases that phosphorylate certain positions within the consensus repeat. The level and pattern of phosphorylation is determined by the concerted action of CTD kinases and CTD phosphatases. The highly dynamic modification by multiple CTD kinases and phosphatases generate distinct conformations of the CTD that facilitate the recruitment of specific macromolecular assemblies to RNAP II. These CTD interacting proteins influence formation of a preinitiation complex at the promoter and couple processing of the primary transcript to the elongation complex. (C) 2003 The Japan Chemical journal Forum and Wiley Periodicals, Inc.