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Processing of 20S pre-rRNA to 18S ribosomal RNA in yeast requires Rrp10p, an essential non-ribosomal cytoplasmic protein.

Numerous non-ribosomal trans-acting factors involved in pre-ribosomal RNA processing have been characterized, but none of them is specifically required for the last cytoplasmic steps of 18S rRNA maturation. Here we demonstrate that Rio1p/Rrp10p is such a factor. Previous studies showed that the RIO1 gene is essential for cell viability and conserved from archaebacteria to man. We isolated a RIO1 mutant in a screen for mutations synthetically lethal with a mutant allele of GAR1, an essential gene required for 18S rRNA production and rRNA pseudouridylation. We show that RIO1 encodes a cytoplasmic non-ribosomal protein, and that depletion of Rio1p blocks 18S rRNA production leading to 20S pre-rRNA accumulation. In situ hybridization reveals that, in Rio1p depleted cells, 20S pre-rRNA localizes in the cytoplasm, demonstrating that its accumulation is not due to an export defect. This strongly suggests that Rio1p is involved in the cytoplasmic cleavage of 20S pre-rRNA at site D, producing mature 18S rRNA. Thus, Rio1p has been renamed Rrp10p (ribosomal RNA processing #10). Rio1p/Rrp10p is the first non-ribosomal factor characterized specifically required for 20S pre-rRNA processing.

Pubmed ID: 11483523


  • Vanrobays E
  • Gleizes PE
  • Bousquet-Antonelli C
  • Noaillac-Depeyre J
  • Caizergues-Ferrer M
  • GĂ©lugne JP


The EMBO journal

Publication Data

August 1, 2001

Associated Grants


Mesh Terms

  • Cytoplasm
  • Fungal Proteins
  • Nuclear Proteins
  • Protein Biosynthesis
  • RNA Precursors
  • RNA Processing, Post-Transcriptional
  • RNA, Fungal
  • RNA, Ribosomal, 18S
  • Ribonucleoproteins, Small Nucleolar
  • Ribosomes
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins