The nuclear pore complex (NPC) serves as the sole bidirectional gateway
of macromolecules in and out of the nucleus. Owing to its size and complexity
(~1,000 protein subunits, ~110 MDa in humans), the NPC has
remained one of the foremost challenges for structure determination. Structural
studies have now provided atomic-resolution crystal structures of most
nucleoporins. The acquisition of these structures, combined with biochemical
reconstitution experiments, cross-linking mass spectrometry, and
cryo–electron tomography, has facilitated the determination of the
near-atomic overall architecture of the symmetric core of the human, fungal, and
algal NPCs. Here, we discuss the insights gained from these new advances and
outstanding issues regarding NPC structure and function. The powerful
combination of bottom-up and top-down approaches toward determining the
structure of the NPC offers a paradigm for uncovering the architectures of other
complex biological machines to near-atomic resolution.