NMR structure of a complex formed by the carboxyl-terminal domain of human RAP74 and a phosphorylated peptide from the central domain of the FCP1 phosphatase

Recycling of RNA polymerase II (RNAPII) requires dephosphorylation of the C-terminal domain (CTD) of the largest subunit of the polymerase. FCP1 enables the recycling of RNAPII via its CTD-specific phosphatase activity, which is stimulated by the RAP74 subunit of the general transcription factor TFIIF. Both the central (centFCP1) and C-terminal (cterFCP1) domains of FCP1 interact independently and specifically with the C-terminal domain of RAP74 (cterRAP74), suggesting that these interactions mediate the stimulatory effect of TFIIF on the CTD phosphatase activity of FCP1. Phosphorylation of FCP1 by casein kinase 2 on residues in its central (T584) and C-terminal (S942 and S944) domains stimulates its binding to RAP74 and its CTD phosphatase activity. To improve our understanding of the FCP1−RAP74 interactions, we previously determined the NMR structure of a complex formed by human cterRAP74 and cterFCP1. We now present the high-resolution NMR structure and thermodynamic characterization by isothermal titr...