Specific sequences in the fragile X syndrome protein FMR1 and the FXR proteins mediate their binding to 60S ribosomal subunits and the interactions among them

Mikiko C. Siomi, Yan Zhang, Haruhiko Siomi, Gideon Dreyfuss

Research output: Contribution to journalArticle

207 Citations (Scopus)

Abstract

Fragile X syndrome, the most common form of hereditary mental retardation, usually results from lack of expression of the FMR1 gene. The FMR1 protein is a cytoplasmic RNA-binding protein. The RNA-binding activity of FMR1 is an essential feature of FMR1, as fragile X syndrome can also result from the expression of mutant FMR1 protein that is impaired in RNA binding. Recently, we described two novel cytoplasmic proteins, FXR1 and FXR2, which are both very similar in amino acid sequence to FMR1 and which also interact strongly with FMR1 and with each other. To understand the function of FMR1 and the FXR proteins, we carried out cell fractionation and sedimentation experiments with monoclonal antibodies to these proteins to characterize the complexes they form. Here, we report that the FMR1 and FXR proteins are associated with ribosomes, predominantly with 60S large ribosomal subunits. The FXR proteins are associated with 60S ribosomal subunits even in cells that lack FMR1 and that are derived from a fragile X syndrome patient, indicating that FMR1 is not required for this association. We delineated the regions of FMR1 that mediate its binding to 60S ribosomal subunits and the interactions among the FMR1-FXR family members. Both regions contain sequences predicted to have a high propensity to form coiled coil interactions, and the sequences are highly evolutionarily conserved in this protein family. The association of the FMR1, FXR1, and FXR2 proteins with ribosomes suggests they have functions in translation or mRNA stability.

Original languageEnglish
Pages (from-to)3825-3832
Number of pages8
JournalMolecular and Cellular Biology
Volume16
Issue number7
DOIs
Publication statusPublished - 1996 Jan 1
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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