Enhanced binding of RNAP II CTD phosphatase FCP1 to RAP74 following CK2 phosphorylation

The study demonstrated that the phosphorylation of S942-S944 occurs in a semiordered fashion with the initial phosphorylation occurring at either S492 or S944 followed by a second phosphorylation to yield the S942/S944 diphosphorylated species. The results provided new functional and structural information on the role of phosphorylation in the recognition of acidic-rich activation domains involved in transcriptional regulation, and bring insights into how CK2 and TFIIF regulate FCP1 function.