Small GTPase required for proper nuclear import of RNA polymerase II (RNAPII) (PubMed:20855544, PubMed:21768307). May act at an RNAP assembly step prior to nuclear import (PubMed:21768307). Forms an interface between the RNA polymerase II enzyme and chaperone/scaffolding proteins, suggesting that it is required to connect RNA polymerase II to regulators of protein complex formation (PubMed:17643375). May be involved in nuclear localization of XPA (PubMed:11058119). Heterodimer with GPN3 (PubMed:21768307). Binds to RNA polymerase II (RNAPII) (PubMed:17643375, PubMed:20864038, PubMed:21844196). Interacts directly with RNAPII subunits RPB4 and RPB7 and the CTD of RPB1 (PubMed:21768307). Interacts with XPA (PubMed:11058119). Shuttles between the nucleus and the cytoplasm. Expressed ubiquitously. Belongs to the GPN-loop GTPase family.