GO:0099122:   RNA polymerase II C-terminal domain binding
Interacting selectively and non-covalently with the C-terminal domain (CTD) of the largest subunit of RNA polymerase II. The CTD is comprised of repeats of a heptapeptide with the consensus sequence YSPTSPS. The number of repeats varies with the species and a minimum number of repeats is required for RNAP II function.