Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
National Institute of Biological Sciences, Beijing 102206, China.
Science. 2020 Sep 18;369(6510):1477-1481. doi: 10.1126/science.aba9690.
The 90 preribosome is a large, early assembly intermediate of small ribosomal subunits that undergoes structural changes to give a pre-40 ribosome. Here, we gained insight into this transition by determining cryo-electron microscopy structures of intermediates in the path from the 90 to the pre-40 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 90, driving stepwise disassembly of assembly factors and ribosome maturation. The nuclear exosome, an RNA degradation machine, docks on the 90 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 90 progression.
90 前核糖体是小核糖体亚基的一个大型早期组装中间产物，它会发生结构变化，从而形成前 40 核糖体。在这里，我们通过确定从 90 到前 40 的路径中的中间产物的低温电子显微镜结构，深入了解了这一转变。RNA 解旋酶 Dhr1 的缺失会阻止整个转变。一系列结构快照显示，被切除的 5' 外部转录间隔区 (5' ETS) 在 90 内被降解，从而逐步去除组装因子并促进核糖体成熟。核 exosome 是一种 RNA 降解机器，通过解旋酶 Mtr4 与 90 结合，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的中间产物，以及 5' ETS 降解在 90 进展中的关键作用。
