Interacts with phosphorylated C-terminal heptapeptide repeat domain (CTD) of the largest RNA polymerase II subunit POLR2A, and participates in dephosphorylation of the CTD by RPAP2. May act as a negative regulator of cyclin-D1 (CCND1) and cyclin-E (CCNE1) in the cell cycle. May form a heterodimer with RPRD1B (PubMed:24997600). Associates with the RNA polymerase II subunit POLR2A (via CTD phosphorylated at 'Ser-2' and 'Ser-7' of the heptad repeats) (PubMed:22231121, PubMed:24997600, PubMed:24399136). Up-regulated in cells overexpressing CDKN2B. Belongs to the UPF0400 (RTT103) family. Probable cloning artifact.