This domain binds to the phosphorylated C-terminal domain (CTD) of RNA polymerase II [1,2]. This domain is known as the CTD-interacting domain (CID).

1: Snapshots of the RNA processing factor SCAF8 bound to different phosphorylated forms of the carboxyl-terminal domain of RNA polymerase II. Becker R, Loll B, Meinhart A; J Biol Chem. 2008;283:22659-22669. PMID:18550522

2: Cooperative interaction of transcription termination factors with the RNA polymerase II C-terminal domain. Lunde BM, Reichow SL, Kim M, Suh H, Leeper TC, Yang F, Mutschler H, Buratowski S, Meinhart A, Varani G; Nat Struct Mol Biol. 2010;17:1195-1201. PMID:20818393