Proofreading of pre-40S ribosome maturation by a translation initiation factor and 60S subunits

Nat Struct Mol Biol. 2012 Aug;19(8):744-53. doi: 10.1038/nsmb.2308. Epub 2012 Jul 1.


In the final steps of yeast ribosome synthesis, immature translation-incompetent pre-40S particles that contain 20S pre-rRNA are converted to the mature translation-competent subunits containing the 18S rRNA. An assay for 20S pre-rRNA cleavage in purified pre-40S particles showed that cleavage by the PIN domain endonuclease Nob1 was strongly stimulated by the GTPase activity of Fun12, the yeast homolog of cytoplasmic translation initiation factor eIF5b. Cleavage of the 20S pre-rRNA was also inhibited in vivo and in vitro by blocking binding of Fun12 to the 25S rRNA through specific methylation of its binding site. Cleavage competent pre-40S particles stably associated with Fun12 and formed 80S complexes with 60S ribosomal subunits. We propose that recruitment of 60S subunits promotes GTP hydrolysis by Fun12, leading to structural rearrangements within the pre-40S particle that bring Nob1 and the pre-rRNA cleavage site together.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Base Sequence
  • Binding Sites
  • Eukaryotic Initiation Factor-2 / chemistry
  • Eukaryotic Initiation Factor-2 / metabolism*
  • Guanosine Triphosphate / metabolism
  • Models, Molecular
  • Molecular Sequence Data
  • Nuclear Proteins / metabolism
  • Nucleic Acid Conformation
  • Protein Conformation
  • RNA Precursors / chemistry
  • RNA Precursors / genetics
  • RNA Precursors / metabolism
  • RNA Processing, Post-Transcriptional
  • RNA, Fungal / chemistry
  • RNA, Fungal / genetics
  • RNA, Fungal / metabolism
  • RNA, Ribosomal / chemistry
  • RNA, Ribosomal / genetics
  • RNA, Ribosomal / metabolism
  • Ribosome Subunits, Large, Eukaryotic / chemistry
  • Ribosome Subunits, Large, Eukaryotic / metabolism*
  • Ribosome Subunits, Small, Eukaryotic / chemistry
  • Ribosome Subunits, Small, Eukaryotic / metabolism*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism*


  • Eukaryotic Initiation Factor-2
  • FUN12 protein, S cerevisiae
  • NOB1 protein, S cerevisiae
  • Nuclear Proteins
  • RNA Precursors
  • RNA, Fungal
  • RNA, Ribosomal
  • Saccharomyces cerevisiae Proteins
  • RNA, ribosomal, 25S
  • Guanosine Triphosphate
  • Adenosine Triphosphate