The nuclear pore complex: a protein machine bridging the nucleus and cytoplasm.

Compositional analysis of nuclear pore complexes (NPCs) is nearing completion, and efforts are now focused on understanding how these protein machines work. Recent analysis of soluble transport factor interactions with NPC proteins reveals distinct and overlapping pathways for movement between the nucleus and cytoplasm. New fluorescence- and microscopy-based strategies have been used to monitor the pathway of NPC assembly and to reveal the dynamics of the NPC during transport.