Gene Center Munich and Center of Integrated Protein Science-Munich (CiPS-M), Department of Biochemistry, University of Munich, Munich, Germany.
Nature. 2018 Jun;558(7709):249-253. doi: 10.1038/s41586-018-0193-0. Epub 2018 Jun 6.
The formation of eukaryotic ribosomal subunits extends from the nucleolus to the cytoplasm and entails hundreds of assembly factors. Despite differences in the pathways of ribosome formation, high-resolution structural information has been available only from fungi. Here we present cryo-electron microscopy structures of late-stage human 40S assembly intermediates, representing one state reconstituted in vitro and five native states that range from nuclear to late cytoplasmic. The earliest particles reveal the position of the biogenesis factor RRP12 and distinct immature rRNA conformations that accompany the formation of the 40S subunit head. Molecular models of the late-acting assembly factors TSR1, RIOK1, RIOK2, ENP1, LTV1, PNO1 and NOB1 provide mechanistic details that underlie their contribution to a sequential 40S subunit assembly. The NOB1 architecture displays an inactive nuclease conformation that requires rearrangement of the PNO1-bound 3' rRNA, thereby coordinating the final rRNA folding steps with site 3 cleavage.
真核核糖体亚基的形成从核仁延伸到细胞质，需要数百种组装因子。尽管核糖体形成的途径存在差异，但只有真菌具有高分辨率的结构信息。在这里，我们展示了晚期人 40S 组装中间体的冷冻电镜结构，代表了一种在体外重建的状态和五种从核到晚期细胞质的天然状态。最早的颗粒揭示了生物发生因子 RRP12 的位置以及伴随 40S 亚基头部形成的不同不成熟 rRNA 构象。晚期作用的组装因子 TSR1、RIOK1、RIOK2、ENP1、LTV1、PNO1 和 NOB1 的分子模型提供了其对顺序 40S 亚基组装贡献的机制细节。NOB1 结构显示出无活性的核酸酶构象，需要重新排列与 PNO1 结合的 3' rRNA，从而将最终的 rRNA 折叠步骤与位点 3 切割协调起来。
