title: Immature large ribosomal subunits containing the 7S pre-rRNA can engage in translation in Saccharomyces cerevisiae.
abstract: Evolution has provided eukaryotes with mechanisms that impede immature and/or aberrant ribosomes to engage in translation. These mechanisms basically either prevent the nucleo-cytoplasmic export of these particles or, once in the cytoplasm, the release of associated assembly factors, which interfere with the binding of translation initiation factors and/or the ribosomal subunit joining. We have previously shown that aberrant yeast 40S ribosomal subunits containing the 20S pre-rRNA can engage in translation. In this study, we describe that cells harbouring the dob1-1 allele, encoding a mutated version of the exosome-assisting RNA helicase Mtr4, accumulate otherwise nuclear pre-60S ribosomal particles containing the 7S pre-rRNA in the cytoplasm. Polysome fractionation analyses revealed that these particles are competent for translation and do not induce elongation stalls. This phenomenon is rather specific since most mutations in other exosome components or co-factors, impairing the 3' end processing of the mature 5.8S rRNA, accumulate 7S pre-rRNAs in the nucleus. In addition, we confirm that pre-60S ribosomal particles containing either 5.8S + 30 or 5.8S + 5 pre-rRNAs also engage in translation elongation. We propose that 7S pre-rRNA processing is not strictly required for pre-60S r-particle export and that, upon arrival in the cytoplasm, there is no specific mechanism to prevent translation by premature pre-60S r-particles containing 3' extended forms of mature 5.8S rRNA.
authors.affiliation: a Instituto de Biomedicina de Sevilla ; Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla ; Seville , Spain.
authors.forename: Olga
authors.initials: O
authors.lastname: Rodríguez-Galán
authors.forename: Juan J
authors.initials: JJ
authors.lastname: García-Gómez
authors.forename: Dieter
authors.initials: D
authors.lastname: Kressler
authors.forename: Jesús
authors.initials: J
authors.lastname: de la Cruz
mesh_terms: D015152:Blotting, Northern; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D017404:In Situ Hybridization, Fluorescence; D008856:Microscopy, Fluorescence; D009154:Mutation; D014176:Protein Biosynthesis; D012322:RNA Precursors / Q000235:genetics* / Q000378:metabolism; D012331:RNA, Fungal / Q000235:genetics* / Q000378:metabolism; D012335:RNA, Ribosomal / Q000235:genetics* / Q000378:metabolism; D054683:Ribosome Subunits, Large, Eukaryotic / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D012322:RNA Precursors; D012331:RNA, Fungal; D012335:RNA, Ribosomal; D029701:Saccharomyces cerevisiae Proteins; C101004:MTR4 protein, S cerevisiae; D053487:DEAD-box RNA Helicases
keywords: DAPI, 4,6-diamidino-2-phenylindole; FISH, fluorescence in situ hybridization; Mtr4/Dob1; NRD, Non-functional rRNA decay; RNA exosome; RNA helicase; Ribosome biogenesis; TRAMP complexes, Trf/Air/Mtr4 complexes; Translation; pre-rRNA processing; pre-rRNA, precursor rRNA; r-particles, ribosomal particles; r-proteins, ribosomal proteins; r-subunits, ribosomal subunits; yeast