Association of FMRP with ribosomal precursor particles in the nucleolus

Biochem Biophys Res Commun. 1996 Aug 5;225(1):27-33. doi: 10.1006/bbrc.1996.1126.


The fragile X syndrome, one of the most common forms of inherited mental retardation, is caused by an expansion of a polymorphic CGG repeat upstream the coding region of the FMR1 gene. These expansions are associated with hypermethylation of the FMR1 gene, which results in the absence of the gene product, the FMR1 protein (FMRP). The physiological function of FMRP remains to be determined. We studied the ultrastructural localization of FMRP at the electron microscopical level using the immunogold technique. FMRP is associated with ribosomes attached to the endoplasmic reticulum and with ribosomes free in the cytoplasm. In addition, FMRP is found in the nucleus where the protein is associated with the granular component of the nucleolus. The cellular function of FMRP is hypothesized in relation to its subcellular distribution.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Chlorocebus aethiops
  • Cloning, Molecular
  • Fragile X Mental Retardation Protein
  • Fragile X Syndrome / genetics
  • Humans
  • Immunoenzyme Techniques
  • Microscopy, Immunoelectron
  • Nerve Tissue Proteins / analysis
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism*
  • Promoter Regions, Genetic
  • RNA-Binding Proteins / metabolism*
  • Recombinant Proteins / analysis
  • Recombinant Proteins / biosynthesis
  • Ribosomes / metabolism*
  • Ribosomes / ultrastructure
  • Simian virus 40 / genetics
  • Transfection
  • Trinucleotide Repeats


  • FMR1 protein, human
  • Nerve Tissue Proteins
  • RNA-Binding Proteins
  • Recombinant Proteins
  • Fragile X Mental Retardation Protein