Cryo-EM structure of 90S small ribosomal subunit precursors in transition states
Cryo-EM structure of 90S small ribosomal subunit precursors in transition states
复制标题
DOI：
10.1126/science.aba9690
复制
发表时间：
2020-09-18
期刊：
影响因子：
56.9
通讯作者：
Ye, Keqiong
中科院分区：
文献类型：
--
作者：
Du, Yifei;An, Weidong;Ye, Keqiong
90S前核糖体是小核糖体亚基的大型早期组装中间体，经过结构改变形成40s前核糖体。在这里，我们通过测定酿酒酵母中间体从90年代到40年代前的低温电镜结构，深入了解了这种转变。完整的转化被RNA解旋酶Dhr1的缺失所阻断。一系列的结构快照显示，切除的5 ‘外部转录间隔物（5 ’ ETS）在90S内被降解，推动了组装因子的逐步拆卸和核糖体的成熟。核外泌体是一种RNA降解机器，通过解旋酶Mtr4停靠在90S上，并准备好消化5 ‘ ETS的3’端。分辨率在3.2 ~ 8.6埃之间的结构揭示了关键中间体和5′ETS降解在90S过程中的关键作用。
The 90S preribosome is a large, early assembly intermediate of small ribosomal subunits that undergoes structural changes to give a pre-40S ribosome. Here, we gained insight into this transition by determining cryo-electron microscopy structures of Saccharomyces cerevisiae intermediates in the path from the 90S to the pre-40S. The full transition is blocked by deletion of RNA helicase Dhr1. A series of structural snapshots revealed that the excised 5 ' external transcribed spacer (5 ' ETS) is degraded within 90S, driving stepwise disassembly of assembly factors and ribosome maturation. The nuclear exosome, an RNA degradation machine, docks on the 90S through helicase Mtr4 and is primed to digest the 3' end of the 5 ' ETS. The structures resolved between 3.2- and 8.6-angstrom resolution reveal key intermediates and the critical role of 5 ' ETS degradation in 90S progression.