GTPase activator for the nuclear Ras-related regulatory protein Ran, converting it to the putatively inactive GDP-bound state (By similarity). Trans-acting factor necessary for meiotic distortion (PubMed:10073941). Distortion is only seen in individuals that carry the RanGAP tandem duplication and express a RanGAP truncated protein. Binding of truncated RanGAP product to the Responder(RSP) locus initiates events that lead to sperm dysfunction (PubMed:10073941). During oogenesis, plays a role in the biogenesis of annulate lamellae containing nuclear pore complex components (PubMed:31626769). Forms a complex with Nup358/RanBP2, sbr/Nxf1 and Nxt1 (PubMed:14729961). Associates with the nuclear pore complex via its interaction with Nup358/RanBP2 (PubMed:14729961, PubMed:17032737). Association to cytoplasmic side of the nuclear pore complex is promoted by Nup214 (PubMed:17032737). Co-localizes with Nup358/RanBP2 to annulate lamellae (PubMed:31626769). Both full-length and truncated protein are expressed in testis (at protein level) (PubMed:10073941). Expressed in oocytes and nurse cells (at protein level) (PubMed:31626769). Belongs to the RNA1 family.