GTPase activator for the nuclear Ras-related regulatory protein Ran, converting it to the putatively inactive GDP-bound state. Homodimer (By similarity). Interacts with WIP1 and WIP2 through its WPP domain. Component of Ran complexes at least composed of WIT1 or WIT2, RANGAP1 or RANGAP2, and WIP1 or WIP2 or WIP3. Interacts with WIT1. Localized in patchy areas at the nuclear envelope of interphase cells. During mitosis, associates with mitotic spindles at the anaphase. Associated to the microtubular phragmoplast and the surface of the daughter nuclei at the telophase. The WPP domain is required for the nuclear envelope localization. Belongs to the RNA1 family.