May regulate the intracellular trafficking of RAN. Promotes guanine nucleotide release from RAN and inhibits binding of new GTP by preventing the binding of the RAN guanine nucleotide exchange factor RCC1. Regulates the levels of GTP-bound RAN in the nucleus, and thereby plays a role in the regulation of RAN-dependent mitotic spindle dynamics. Enhances the expression of SCN5A at the cell membrane in cardiomyocytes. Monomer. Interacts with RAN, both RAN-GTP and RAN-GDP. Competes with RCC1 for a common binding site on RAN and thereby inhibits RCC1-mediated nucleotide exchange (By similarity). Forms a complex with RAN-GTP and RANBP1 (By similarity). Interacts with the cytoplasmic loop 2 of SCN5A (By similarity). May shuttle between the nucleus and cytoplasm. Belongs to the MOG1 family.