THE NUCLEAR-PORE COMPLEX

The nuclear pore complex (NPC) creates an aqueous channel across the n uclear envelope through which macromolecular transport between nucleus and cytoplasm occurs, Nucleocytoplasmic traffic is bidirectional and involves diverse substrates, including protein and RNA, It is unclear whether import and export ate mechanistically similar, but evidence su ggests that numerous pathways may be involved, The discovery of filame nts that extend out from each side of the NPC suggests that the NPC ma y also have a structural role, perhaps providing a connection between cytoskeletal elements of the nucleus and cytoplasm. If this suggestion is valid, it remains to be determined whether this aspect of NPC func tion is related to its role in nuclear transport. This review discusse s recent development regarding the structure of the NPC, characterizat ion of its constituent proteins (nucleoporins), the mechanism by which transport occurs, the function of individual nucleoporins, and the pa thway of NPC assembly and disassembly.