RNA Pol II CTD phosphorylation and interaction with CE Authored: Matthews, L, Rice, AP, 2005-07-27 00:00:00 Edited: Matthews, L, 2005-07-26 23:29:22 Reactome Database ID Release 43167160 Reactome, http://www.reactome.org ReactomeREACT_6237 To facilitate co-transcriptional capping, and thereby restrict the cap structure to RNAs made by RNA polymerase II, the capping enzymes bind directly to the RNA polymerase II. The C-terminal domain of the largest Pol II subunit contains several phosphorylation sites on its heptapeptide repeats. The capping enzyme guanylyltransferase and the methyltransferase bind specifically to CTD phosphorylated at Serine 5 within the CTD. Kinase subunit of TFIIH, Cdk7, catalyzes this phosphorylation event that occurs near the promoter. In addition, it has been shown that binding of capping enzyme to the Serine-5 phosphorylated CTD stimulates guanylyltransferase activity in vitro. PathwayStep3554 PathwayStep3555 PathwayStep3553 PathwayStep3552 PathwayStep3551 Activation of GT SPT5 subunit of Pol II binds the RNA triphosphatase (RTP) RNA Polymerase II CTD (phosphorylated) binds to CE Phosphorylation (Ser5) of RNA pol II CTD Extrusion of 5'-end of 30 nt long HIV-1 transcript through the pore in Pol II complex