RPRD1A and RPRD1B are human RNA polymerase II C-terminal domain scaffolds for Ser5 dephosphorylation

Mammalian RPRD proteins bind the phosphorylated CTD of RNA pol II with different affinities. Structural elucidation and characterization of their CTD interaction domains reveal the basis of RPRD binding preferences and a role in directing CTD dephosphorylation.