The nuclear pore complex (NPC) is the bidirectional gate that mediates the exchange of macromolecules or their assemblies between nucleus and cytoplasm^1,2,3. The assembly intermediates of the ribosomal subunits, pre-60S and pre-40S particles, are among the largest cargoes of the NPC and the export of these gigantic ribonucleoproteins requires numerous export factors^4,5. Here we report the cryo-electron microscopy structure of native pre-60S particles trapped in the channel of yeast NPCs. In addition to known assembly factors, multiple factors with export functions are also included in the structure. These factors in general bind to either the flexible regions or subunit interface of the pre-60S particle, and virtually form many anchor sites for NPC binding. Through interactions with phenylalanine-glycine (FG) repeats from various nucleoporins of NPC, these factors collectively facilitate the passage of the pre-60S particle through the central FG repeat network of the NPC. Moreover, in silico analysis of the axial and radial distribution of pre-60S particles within the NPC shows that a single NPC can take up to four pre-60S particles simultaneously, and pre-60S particles are enriched in the inner ring regions close to the wall of the NPC with the solvent-exposed surface facing the centre of the nuclear pore. Our data suggest a translocation model for the export of pre-60S particles through the NPC.

^{核孔复合体 (NPC) 是双向门，它介导大分子或其组件在细胞核和细胞质1,2,3}之间的交换。核糖体亚基、60S 前和 40S 前颗粒的组装中间体是 NPC 最大的货物之一，这些巨大核糖核蛋白的输出需要大量输出因素^4,5. 在这里，我们报告了捕获在酵母 NPC 通道中的原生 60 年代前颗粒的冷冻电子显微镜结构。除了已知的装配因子外，该结构中还包含具有导出功能的多个因子。这些因素通常与 60 年代前粒子的柔性区域或亚基界面结合，并实际上形成许多 NPC 结合的锚点。通过与来自 NPC 的各种核孔蛋白的苯丙氨酸-甘氨酸 (FG) 重复序列的相互作用，这些因素共同促进了 60 年代前粒子通过 NPC 的中央 FG 重复网络。此外，对 NPC 内 60S 前粒子的轴向和径向分布的计算机分析表明，单个 NPC 最多可以同时吸收四个 60S 前粒子，pre-60S 颗粒富集在靠近 NPC 壁的内环区域，溶剂暴露表面面向核孔中心。我们的数据表明了通过 NPC 输出 60 年代前粒子的易位模型。