Cryo-EM structure of a late pre-40S ribosomal subunit from Saccharomyces cerevisiae
Cryo-EM structure of a late pre-40S ribosomal subunit from Saccharomyces cerevisiae
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DOI：
10.7554/elife.30189
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发表时间：
2017-11-20
期刊：
影响因子：
7.7
通讯作者：
Beckmann, Roland
中科院分区：
文献类型：
--
作者：
Heuer, Andre;Thomson, Emma;Beckmann, Roland
对真核核糖体形成机制的理解需要对沿着复杂途径产生的众多组装中间体的详细结构知识。在这里，我们展示了3.6埃分辨率的40s前晚期粒子的结构，揭示了组装因子如何调节18s前rRNA的及时折叠的分子细节。该结构表明，相关的组装因子Tsr1、Enp1、Rio2和Pno1共同阻止了40S的最终成熟，而不是立体阻断40S的翻译活性位点，从而防止了tRNA和mRNA的过早结合和容易出错的翻译。此外，该结构解释了Pno1如何协调Nob1对18S rRNA的3'端切割，以及细胞质中晚期因子的去除如何确保成熟的40S亚基的结构完整性。
Mechanistic understanding of eukaryotic ribosome formation requires a detailed structural knowledge of the numerous assembly intermediates, generated along a complex pathway. Here, we present the structure of a late pre-40S particle at 3.6 angstrom resolution, revealing in molecular detail how assembly factors regulate the timely folding of pre-18S rRNA. The structure shows that, rather than sterically blocking 40S translational active sites, the associated assembly factors Tsr1, Enp1, Rio2 and Pno1 collectively preclude their final maturation, thereby preventing untimely tRNA and mRNA binding and error prone translation. Moreover, the structure explains how Pno1 coordinates the 3'end cleavage of the 18S rRNA by Nob1 and how the late factor's removal in the cytoplasm ensures the structural integrity of the maturing 40S subunit.