Visualization of distinct substrate-recruitment pathways in the yeast exosome by EM
Visualization of distinct substrate-recruitment pathways in the yeast exosome by EM
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DOI：
10.1038/nsmb.2736
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发表时间：
2014-01-01
影响因子：
16.8
通讯作者：
Wang, Hong-Wei
中科院分区：
文献类型：
--
作者：
Liu, Jun-Jie;Bratkowski, Matthew A.;Wang, Hong-Wei
真核外泌体是一种多亚基复合物，通常由催化失活核心和 Rrp44 蛋白组成，其中包含 3' 至 5' 外切和内切 RNA 酶活性。 RNA 底物已被证明可以通过核心募集到达 Rrp44 的外切 RNA 酶 (EXO) 位点。使用单颗粒电镜和生化分析，我们提供了存在两种不同的底物招募途径的视觉证据。在穿过核心的途径中，单链底物从核心引导至 Rrp44 引起 Rrp44 的特征性构象变化。在另一种直接进入途径中，不会发生这种构象变化，并且RNA底物被可视化以避开核心并直接进入Rrp44的EXO位点。我们的结果为真核外泌体的几种 RNA 加工情况提供了机制解释，并表明了该复合物的底物特异性降解模式。
The eukaryotic exosome is a multisubunit complex typically composed of a catalytically inactive core and the Rrp44 protein, which contains 3'-to-5' exo- and endo-RNase activities. RNA substrates have been shown to be recruited through the core to reach Rrp44's exo-RNase (EXO) site. Using single-particle EM and biochemical analysis, we provide visual evidence that two distinct substrate-recruitment pathways exist. In the through-core route, channeling of the single-stranded substrates from the core to Rrp44 induces a characteristic conformational change in Rrp44. In the alternative direct-access route, this conformational change does not take place, and the RNA substrate is visualized to avoid the core and enter Rrp44's EXO site directly. Our results provide mechanistic explanations for several RNA processing scenarios by the eukaryotic exosome and indicate substrate-specific modes of degradation by this complex.