8qcf
From Proteopedia
yeast cytoplasmic exosome-Ski2 complex degrading a RNA substrate
Structural highlights
FunctionRRP45_YEAST Non-catalytic component of the RNA exosome complex which has 3'->5' exoribonuclease activity and participates in a multitude of cellular RNA processing and degradation events. In the nucleus, the RNA exosome complex is involved in proper maturation of stable RNA species such as rRNA, snRNA and snoRNA, in the elimination of RNA processing by-products and non-coding 'pervasive' transcripts, such as antisense RNA species and cryptic unstable transcripts (CUTs), and of mRNAs with processing defects, thereby limiting or excluding their export to the cytoplasm. In the cytoplasm, the RNA exosome complex is involved in general mRNA turnover and in RNA surveillance pathways, preventing translation of aberrant mRNAs. The catalytic inactive RNA exosome core complex of 9 subunits (Exo-9) is proposed to play a pivotal role in the binding and presentation of RNA for ribonucleolysis, and to serve as a scaffold for the association with catalytic subunits and accessory proteins or complexes. RRP45 is part of the hexameric ring of RNase PH domain-containing subunits proposed to form a central channel which threads RNA substrates for degradation.[1] [2] Publication Abstract from PubMedThe Ski2-Ski3-Ski8 (Ski238) helicase complex directs cytoplasmic mRNAs toward the nucleolytic exosome complex for degradation. In yeast, the interaction between Ski238 and exosome requires the adaptor protein Ski7. We determined different cryo-EM structures of the Ski238 complex depicting the transition from a rigid autoinhibited closed conformation to a flexible active open conformation in which the Ski2 helicase module has detached from the rest of Ski238. The open conformation favors the interaction of the Ski3 subunit with exosome-bound Ski7, leading to the recruitment of the exosome. In the Ski238-Ski7-exosome holocomplex, the Ski2 helicase module binds the exosome cap, enabling the RNA to traverse from the helicase through the internal exosome channel to the Rrp44 exoribonuclease. Our study pinpoints how conformational changes within the Ski238 complex regulate exosome recruitment for RNA degradation. We also reveal the remarkable conservation of helicase-exosome RNA channeling mechanisms throughout eukaryotic nuclear and cytoplasmic exosome complexes. Concerted structural rearrangements enable RNA channeling into the cytoplasmic Ski238-Ski7-exosome assembly.,Keidel A, Kogel A, Reichelt P, Kowalinski E, Schafer IB, Conti E Mol Cell. 2023 Oct 19:S1097-2765(23)00803-1. doi: 10.1016/j.molcel.2023.09.037. PMID:37879335[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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