title: Visualization of distinct substrate-recruitment pathways in the yeast exosome by EM.
abstract: 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.
authors: Ministry of Education Key Laboratory of Protein Science, Tsinghua-Peking Joint Center for Life Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.|Joint Graduate Program of Peking-Tsinghua-NBIS, Tsinghua University, Beijing 100084, China.
authors: Jun-Jie
authors: JJ
authors: Liu
authors: Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
authors: Matthew A
authors: MA
authors: Bratkowski
authors: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA.
authors: Xueqi
authors: X
authors: Liu
authors: Ministry of Education Key Laboratory of Protein Science, Tsinghua-Peking Joint Center for Life Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors: Chu-Ya
authors: CY
authors: Niu
authors: Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
authors: Ailong
authors: A
authors: Ke
authors: Ministry of Education Key Laboratory of Protein Science, Tsinghua-Peking Joint Center for Life Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.|Joint Graduate Program of Peking-Tsinghua-NBIS, Tsinghua University, Beijing 100084, China.
authors: Hong-Wei
authors: HW
authors: Wang
mesh_terms: D055354:Exosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D013379:Substrate Specificity