[pSer2, pSer5, pSer7]-CTD

[pSer2, pSer5, pSer7]-CTD, a substrate for CDK7 (cyclin dependent protein kinase), is a phosphorylated polypeptide at ser2, ser5 and ser7 sites of RNA polymerase II carboxy-terminal domain (CTD)[1].

[1]. Czudnochowski N, et al. Serine-7 but not serine-5 phosphorylation primes RNA polymerase II CTD for P-TEFb recognition. Nat Commun. 2012 May 15;3:842.