Key component of the Ran GTPase system, which comprises ran-1, ran-2 and ran-3 and is essential in nucleocytoplasmic transport. Promotes the exchange of Ran-bound GDP by GTP and regulates the onset of chromosome condensation in the S phase. Binds to the chromatin. RCC1 (ran-3)/RAN (ran-1) complex (together with other proteins) acts as a component of a signal transmission pathway that detects unreplicated DNA. Loss of ran-3 causes low levels of chromosomes to misalign on the metaphase plate and segregate incorrectly in early embryonic cell divisions.