7ajt | pdb_00007ajt
Cryo-EM structure of the 90S-exosome super-complex (state Pre-A1-exosome)
Structural highlights
FunctionNAT10_YEAST RNA cytidine acetyltransferase with specificity toward both 18S rRNA and tRNAs. Catalyzes the formation of N(4)-acetylcytidine (ac4C) at positions 1280 and 1773 in 18S rRNA. Required for early nucleolar cleavages of precursor rRNA at sites A0, A1 and A2 during 18S rRNA synthesis (PubMed:25086048, PubMed:25653167). Catalyzes the formation of ac4C at position 12 in serine and leucine tRNAs. Requires the tRNA-binding adapter protein TAN1 for full tRNA acetyltransferase activity but not for 18S rRNA acetylation (PubMed:25653167).[HAMAP-Rule:MF_03211][1] [2] Publication Abstract from PubMedRibosome assembly is catalyzed by numerous trans-acting factors and coupled with irreversible pre-rRNA processing, driving the pathway toward mature ribosomal subunits. One decisive step early in this progression is removal of the 5' external transcribed spacer (5'-ETS), an RNA extension at the 18S rRNA that is integrated into the huge 90S pre-ribosome structure. Upon endo-nucleolytic cleavage at an internal site, A(1), the 5'-ETS is separated from the 18S rRNA and degraded. Here we present biochemical and cryo-electron microscopy analyses that depict the RNA exosome, a major 3'-5' exoribonuclease complex, in a super-complex with the 90S pre-ribosome. The exosome is docked to the 90S through its co-factor Mtr4 helicase, a processive RNA duplex-dismantling helicase, which strategically positions the exosome at the base of 5'-ETS helices H9-H9', which are dislodged in our 90S-exosome structures. These findings suggest a direct role of the exosome in structural remodeling of the 90S pre-ribosome to drive eukaryotic ribosome synthesis. Structure of the Maturing 90S Pre-ribosome in Association with the RNA Exosome.,Lau B, Cheng J, Flemming D, La Venuta G, Berninghausen O, Beckmann R, Hurt E Mol Cell. 2021 Jan 21;81(2):293-303.e4. doi: 10.1016/j.molcel.2020.11.009. Epub , 2020 Dec 15. PMID:33326748[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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