title: The final step in 5.8S rRNA processing is cytoplasmic in Saccharomyces cerevisiae.
abstract: The 18S rRNA component of yeast (Saccharomyces cerevisiae) 40S ribosomes undergoes cytoplasmic 3' cleavage following nuclear export, whereas exported pre-60S subunits were believed to contain only mature 5.8S and 25S rRNAs. However, in situ hybridization detected 3'-extended forms of 5.8S rRNA in the cytoplasm, which were lost when Crm1-dependent preribosome export was blocked by treatment with leptomycin B (LMB). LMB treatment rapidly blocked processing of 6S pre-rRNA to 5.8S rRNA, leading to TRAMP-dependent pre-rRNA degradation. The 6S pre-rRNA was coprecipitated with the 60S export adapter Nmd3 and cytoplasmic 60S synthesis factor Lsg1. The longer 5.8S+30 pre-rRNA (a form of 5.8S rRNA 3' extended by approximately 30 nucleotides) is processed to 6S by the nuclear exonuclease Rrp6, and nuclear pre-rRNA accumulated in the absence of Rrp6. In contrast, 6S to 5.8S processing requires the cytoplasmic exonuclease Ngl2, and cytoplasmic pre-rRNA accumulated in strains lacking Ngl2. We conclude that nuclear pre-60S particles containing the 6S pre-rRNA bind Nmd3 and Crm1 and are exported to the cytoplasm prior to final maturation by Ngl2.
authors.affiliation: Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, Scotland, UK.
authors.forename: Emma
authors.initials: E
authors.lastname: Thomson
authors.forename: David
authors.initials: D
authors.lastname: Tollervey
mesh_terms: D003593:Cytoplasm / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism; D026721:RNA 3' End Processing; D012322:RNA Precursors / Q000235:genetics* / Q000378:metabolism; D034443:RNA Transport; D012331:RNA, Fungal / Q000235:genetics* / Q000378:metabolism; D012340:RNA, Ribosomal, 5.8S / Q000235:genetics* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D000097606:Exportin 1 Protein
chemical_list: D005231:Fatty Acids, Unsaturated; D028884:Karyopherins; D012322:RNA Precursors; D012331:RNA, Fungal; D012340:RNA, Ribosomal, 5.8S; D016601:RNA-Binding Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D000097606:Exportin 1 Protein; C117894:NMD3 protein, S cerevisiae; C038753:leptomycin B