RPB1 CTD(1615-1621-Lys)-Tn(1619)

DNA-directed RNA polymerase II (Pol II) subunit RPB1 contains a Carboxy Terminal Domain (CTD) composed of up to 52 heptapeptide repeats (YSPTSPS) that are essential for polymerase activity. The CTD Nonconsensus Repeat, Tyr-Ser-Pro-Thr-Ser-Pro-Ser, is heavily modified by phosphorylation, glycosylation and proline isomerization. The CTD acts as a tether to bring into close proximity the machinery necessary to synthesize and process Pol II transcripts.