Isolation and characterization of a new nucleolar protein, Nrap, that is conserved from yeast to humans

Genes Cells. 2002 Feb;7(2):115-32. doi: 10.1046/j.1356-9597.2001.00507.x.


Background: The nucleolus is the site of rRNA synthesis and processing in eukaryotic cells, but its composition remains poorly understood.

Results: We have identified a novel nucleolar RNA-associated protein (Nrap) which is highly conserved from yeast (Saccharomyces cerevisiae) to human, with homologues in mouse, Drosophila melanogaster, Caenorhabditis elegans, Arabidopsis thaliana, Schizosaccharomyces pombe, and other species. In the mouse, we have found that Nrap is ubiquitously expressed and is specifically localized in the nucleolus. We have also identified splice variants in human and mouse, and defined the intron-exon structure of the human Nrap gene. Nrap is inherited into daughter nuclei by associating with the condensed chromosomes during mitosis. RNase treatment of permeabilized cells indicated that the nucleolar localization of Nrap is RNA dependent. The effects of actinomycin D, cycloheximide and 5,6-dichloro-beta-d-ribofuranosyl-benzimidazole on Nrap expression and distribution in cultured cells suggest that Nrap is associated with the pre-rRNA transcript.

Conclusions: Nrap is a large nucleolar protein (of more than 1000 amino acids), and is a new class of protein with new structural and functional motifs. Nrap appears to be associated with ribosome biogenesis by interacting with pre-rRNA primary transcript.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / isolation & purification
  • Caenorhabditis elegans Proteins / genetics*
  • Caenorhabditis elegans Proteins / isolation & purification
  • Conserved Sequence
  • Drosophila Proteins / genetics*
  • Drosophila Proteins / isolation & purification
  • Evolution, Molecular
  • Humans
  • Mice
  • Molecular Sequence Data
  • Nuclear Proteins / genetics*
  • Nuclear Proteins / isolation & purification
  • Protein Isoforms / genetics
  • RNA-Binding Proteins
  • Saccharomyces cerevisiae Proteins / genetics*
  • Saccharomyces cerevisiae Proteins / isolation & purification
  • Schizosaccharomyces pombe Proteins / genetics*
  • Schizosaccharomyces pombe Proteins / isolation & purification
  • Sequence Alignment
  • Sequence Analysis, DNA
  • Species Specificity
  • Transcription, Genetic


  • Arabidopsis Proteins
  • Caenorhabditis elegans Proteins
  • Drosophila Proteins
  • NOL6 protein, human
  • Nrap protein, Arabidopsis
  • Nrap protein, Drosophila
  • Nrap protein, S cerevisiae
  • Nrap, mouse
  • Nuclear Proteins
  • Protein Isoforms
  • RNA-Binding Proteins
  • SPBC776.08c protein, S pombe
  • Saccharomyces cerevisiae Proteins
  • Schizosaccharomyces pombe Proteins
  • nol-6 protein, C elegans