The Use of Permeabilized Cell Systems to Study Nuclear Transport

Nucleocytoplasmic transport occurs through nuclear pore complexes (NPC), macromolecular structures which span the nuclear envelope (1 ). NPCs contain aqueous channels with a diameter of ~9 nm, allowing ions, metabolites, and small proteins to passively diffuse between the nucleus and the cytoplasm (2 ). Most proteins and RNAs, however, exceed the ~60-kDa diffusion limit and are transported through the NPC by mechanisms that are saturable (3 ), energy-dependent (4 ), and signal-mediated (6 ).