A simple model for the role of Ran in NE assembly

In telophase, Ran (probably in its GDP-bound form) becomes recruited and concentrated on the surface of chromatin. Localized generation of RanGTP by the guanine nucleotide-exchange factor RCC1 recruits nucleoporins and vesicles through importin-beta, which acts as a localization factor. The interaction of RanGTP with importin-beta complexes causes their local release and assembly into nuclear pore complexes (NPCs), the fusion of vesicles to form a double membrane, and the restarting of nuclear transport. Importin-beta is released from Ran by the action of the Ran GTPase-activating proteins RanGAP1 and RanBP1 (Ran-binding protein-1) or RanBP2, which stimulate GTP hydrolysis by Ran. FXFG represents a Phe-Gly (FG) repeat sequence that some nucleoporins contain.