The final step in 5.8S rRNA processing is cytoplasmic in Saccharomyces cerevisiae.
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.
Thomson
Emma
E
Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh EH9 3JR, Scotland, UK.
Tollervey
David
D
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
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