Nup2p dynamically associates with the distal regions of the yeast nuclear pore complex

Nucleocytoplasmic transport is mediated by the interplay between soluble tr ansport factors and nucleoporins resident within the nuclear pore complex ( NPC). Understanding this process demands knowledge of components of both th e soluble and stationary phases and the interface between them, Here, we pr ovide evidence that Nup2p, previously considered to be a typical yeast nucl eoporin that binds import- and export-bound karyopherins, dynamically assoc iates with the NPC in a Ran-facilitated manner. When bound to the NPC, Nup2 p associates with regions corresponding to the nuclear basket and cytoplasm ic fibrils. On the nucleoplasmic face, where the Ran-GTP levels are predict ed to be high, Nup2p binds to Nup60p. Deletion of NUP60 kenders Nup2p nucle oplasmic and compromises Nup2p-mediated recycling of Kap60p/Srplp. Depletio n of Ran-GTP by metabolic poisoning, disruption of the Ran cycle, or in vit ro by cell lysis, results in a shift of Nup2p from the nucleoplasm to the c ytoplasmic face of the NPC. This mobility of Nup2p was also detected using heterokaryons where, unlike nucleoporins, Nup2p was observed to move from o ne nucleus to the other. Together, our data support a model in which Nup2p movement facilitates the transition between the import and export phases of nucleocytoplasmic transport.