Parcs/Gpn3 is required for the nuclear accumulation of RNA polymerase II

► Silencing of Parcs/Gpn3 completely inhibited proliferation in MCF-12A but affected less in MDA-MB-231 cells. ► RNA polymerase II co-immunoprecipitated with Parcs/Gpn3. ► Parcs/Gpn3 depletion inhibited overall transcription in MCF-12A but not in MDA-MB-231 cells. ► Parcs/Gpn3 depletion caused a cytoplasmic localization of Rpb1 in MCF-12A but not in MDA-MB-231 cells. ► Parcs/Gpn3 depletion significantly increased Rpb1 protein levels in MCF-12A cells.