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Immature small ribosomal subunits can engage in translation initiation in Saccharomyces cerevisiae
Author(s) -
Soudet Julien,
Gélugne JeanPaul,
BelhabichBaumas Kamila,
CaizerguesFerrer Michèle,
Mougin Annie
Publication year - 2010
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2009.307
Subject(s) - eukaryotic small ribosomal subunit , biology , ribosome , ribosomal rna , translation (biology) , eukaryotic ribosome , saccharomyces cerevisiae , ribosomal protein , eukaryotic large ribosomal subunit , microbiology and biotechnology , protein biosynthesis , polysome , messenger rna , genetics , rna , yeast , gene
It is generally assumed that, in Saccharomyces cerevisiae , immature 40S ribosomal subunits are not competent for translation initiation. Here, we show by different approaches that, in wild‐type conditions, a portion of pre‐40S particles (pre‐SSU) associate with translating ribosomal complexes. When cytoplasmic 20S pre‐rRNA processing is impaired, as in Rio1p‐ or Nob1p‐depleted cells, a large part of pre‐SSUs is associated with translating ribosomes complexes. Loading of pre‐40S particles onto mRNAs presumably uses the canonical pathway as translation‐initiation factors interact with 20S pre‐rRNA. However, translation initiation is not required for 40S ribosomal subunit maturation. We also provide evidence suggesting that cytoplasmic 20S pre‐rRNAs that associate with translating complexes are turned over by the no go decay (NGD) pathway, a process known to degrade mRNAs on which ribosomes are stalled. We propose that the cytoplasmic fate of 20S pre‐rRNA is determined by the balance between pre‐SSU processing kinetics and sensing of ribosome‐like particles loaded onto mRNAs by the NGD machinery, which acts as an ultimate ribosome quality check point.