CTD-dependent dismantling of the RNA polymerase II elongation complex by the pre-mRNA 3'-end processing factor, Pcf11.

Pcf11 is one of numerous proteins involved in pre-mRNA 3'-end processing and transcription termination. Using elongation complexes (ECs) formed from purified yeast RNA polymerase II (Pol II), we show that a 140-amino acid polypeptide from yeast Pcf11 is capable of dismantling the EC in vitro. This action depends on the C-terminal domain (CTD) of the largest subunit of Pol II and the CTD-interaction domain (CID) of Pcf11. Our experiments reveal a novel termination mechanism whereby Pcf11 bridges the CTD to the nascent transcript and causes dissociation of both Pol II and the nascent transcript from the DNA in the absence of nucleotide hydrolysis. We posit that conformational changes in the CTD are transduced through Pcf11 to the nascent transcript to cause termination.