Journal Article

Trapping of messenger RNA by Fragile X Mental Retardation protein into cytoplasmic granules induces translation repression

Rachid Mazroui, Marc-Etienne Huot, Sandra Tremblay, Christine Filion, Yves Labelle and Edouard W. Khandjian

in Human Molecular Genetics

Volume 11, issue 24, pages 3007-3017
Published in print November 2002 | ISSN: 0964-6906
Published online November 2002 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/11.24.3007
Trapping of messenger RNA by Fragile X Mental Retardation protein into cytoplasmic granules induces translation repression

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Absence of Fragile X Mental Retardation Protein (FMRP), an RNA-binding protein, is responsible for the Fragile X syndrome, the most common form of inherited mental retardation. FMRP is a cytoplasmic protein associated with mRNP complexes containing poly(A)+mRNA. As a step towards understanding FMRP function(s), we have established the immortal STEK Fmr1 KO cell line and showed by transfection assays with FMR1-expressing vectors that newly synthesized FMRP accumulates into cytoplasmic granules. These structures contain mRNAs and several other RNA-binding proteins. The formation of these cytoplasmic granules is dependent on determinants located in the RGG domain. We also provide evidence that FMRP acts as a translation repressor following co-transfection with reporter genes. The FMRP-containing mRNPs are dynamic structures that oscillate between polyribosomes and cytoplasmic granules reminiscent of the Stress Granules that contain repressed mRNAs. We speculate that, in neurons, FMRP plays a role as a mRNA repressor in incompetent mRNP granules that have to be translocated from the cell body to distal locations such as dendritic spines and synaptosomes.

Journal Article.  7451 words.  Illustrated.

Subjects: Genetics and Genomics

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