GTPase activator for RAN. Converts cytoplasmic GTP-bound RAN to GDP-bound RAN, which is essential for RAN-mediated nuclear import and export (PubMed:18305100). Mediates dissociation of cargo from nuclear export complexes containing XPO1, RAN and RANBP2 after nuclear export (By similarity). Required for postimplantation embryonic development (PubMed:8314081). Homodimer (PubMed:7891706). Interacts with RAN (PubMed:7891706). Forms a complex with RANBP2/NUP358, NXF1 and NXT1 (By similarity). Forms a tight complex in association with RANBP2 and UBE2I/UBC9, the ubiquitin-conjugating enzyme E2 (PubMed:11853669). Interacts with UBE2I; the interaction conjugates SUMO1 to RANGAP1, and subsequently stabilizes interactions of sumoylated RANGAP1 with RANBP2 (PubMed:9456312, PubMed:18305100, PubMed:11853669). The complex composed of RANBP2, SUMO1, RANGAP1 and UBE2I associates with nuclear pore complexes (By similarity). Identified in a complex composed of RAN, RANBP2, sumoylated RANGAP1, UBE2I and XPO1 (By similarity). Interacts with TRAF6 (By similarity). Interacts with SUMO1 and SENP1 (By similarity). Interacts (when sumoylated) with MYCBP2; interaction inhibits MYCBP2 E3 ubiquitin-protein ligase activity and promotes MYCBP2 translocation to the nucleus (PubMed:26304119). Cytoplasmic during interphase (PubMed:26506250). Detected at the nuclear envelope during interphase (PubMed:9442102, PubMed:9456312, PubMed:26506250). Shuttles between nucleus and cytoplasm (PubMed:26506250). Targeted to the nuclear pores after sumoylation. During mitosis, associates with mitotic spindles, but is essentially not detected at the spindle poles. Association with kinetochores appears soon after nuclear envelope breakdown and persists until late anaphase. Mitotic location also requires sumoylation (By similarity). Detected in adult brain, liver, kidney, intestine, uterus and ovary. Detected in embryos at 7.5 dpc, but not at 6 dpc. Phosphorylation occurs before nuclear envelope breakdown and continues throughout mitosis. Phosphorylated by the M-phase kinase cyclin B/Cdk1, in vitro. Differential timimg of dephosphorylation occurs during phases of mitosis. The phosphorylated form remains associated with RANBP2/NUP358 and the SUMO E2-conjugating enzyme, UBE2I, on nuclear pore complex (NPC) diassembly and during mitosis. Sumoylated (PubMed:26506250, PubMed:11853669). Sumoylation is necessary for targeting to the nuclear envelope (NE) (PubMed:16469311). Sumoylation is necessary for association with mitotic spindles and kinetochores during mitosis (By similarity). Also required for interaction with RANBP2 and is mediated by UBE2I (PubMed:9456312, PubMed:11853669). Desumoylated by HINT1 (PubMed:31088288). Embryonic development is arrested around 6 dpc. Belongs to the RNA1 family.