Nucleolar protein Nop12p participates in synthesis of 25S rRNA in Saccharomyces cerevisiae

Nucleic Acids Res. 2001 Jul 15;29(14):2938-49. doi: 10.1093/nar/29.14.2938.


A genetic screen for mutations synthetically lethal with temperature sensitive alleles of nop2 led to the identification of the nucleolar proteins Nop12p and Nop13p in Saccharomyces cerevisiae. NOP12 was identified by complementation of a synthetic lethal growth phenotype in strain YKW35, which contains a single nonsense mutation at codon 359 in an allele termed nop12-1. Database mining revealed that Nop12p was similar to a related protein, Nop13p. Nop12p and Nop13p are not essential for growth and each contains a single canonical RNA recognition motif (RRM). Both share sequence similarity with Nsr1p, a previously identified, non-essential, RRM-containing nucleolar protein. Likely orthologs of Nop12p were identified in Drosophila and Schizosaccharomyces pombe. Deletion of NOP12 resulted in a cold sensitive (cs) growth phenotype at 15 degrees C and slow growth at 20 and 25 degrees C. Growth of a nop12Delta strain at 15 and 20 degrees C resulted in impaired synthesis of 25S rRNA, but not 18S rRNA. A nop13 null strain did not produce an observable growth phenotype under the laboratory conditions examined. Epitope-tagged Nop12p, which complements the cs growth phenotype and restores normal 25S rRNA levels, was localized to the nucleolus by immunofluorescence microscopy. Epitope-tagged Nop13p was distributed primarily in the nucleolus, with a lesser portion localizing to the nucleoplasm. Thus, Nop12p is a novel nucleolar protein required for pre-25S rRNA processing and normal rates of cell growth at low temperatures.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alleles
  • Amino Acid Sequence
  • Cell Division / drug effects
  • Cell Division / genetics
  • Cold Temperature
  • Fungal Proteins / genetics
  • Fungal Proteins / physiology
  • Gene Deletion
  • Genetic Complementation Test
  • Molecular Sequence Data
  • Mutation
  • Nuclear Proteins / genetics*
  • Nuclear Proteins / physiology
  • Orotic Acid / analogs & derivatives
  • Orotic Acid / pharmacology
  • Phenotype
  • RNA Precursors / metabolism
  • RNA Processing, Post-Transcriptional
  • RNA, Ribosomal / biosynthesis*
  • RNA, Ribosomal / metabolism
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae / metabolism
  • Sequence Homology, Amino Acid


  • Fungal Proteins
  • Nuclear Proteins
  • RNA Precursors
  • RNA, Ribosomal
  • RNA, ribosomal, 25S
  • Orotic Acid
  • 5-fluoroorotic acid