Oligomerization properties of fragile-X mental-retardation protein (FMRP) and the fragile-X-related proteins FXR1P and FXR2P

The absence of fragile-X mental-retardation protein (FMRP) results in fragile-X syndrome. Two other fragile-X-related (FXR) proteins have been described, FXR1P and FXR2P, which are both very similar in amino acid sequence to FMRP. Interaction between the three proteins as well as with themselves has been demonstrated. The FXR proteins are believed to play a role in RNA metabolism. To characterize a possible functional role of the interacting proteins the complex formation of the FXR proteins was studied in mammalian cells. Double immunofluorescence analysis in COS cells over-expressing either FMRP ISO12/FXR1P or FMRP ISO12/FXR2P confirmed heterotypic interactions. However, Western-blotting studies on cellular homogenates containing physiological amounts of the three proteins gave different indications. Gel-filtration experiments under physiological as well as EDTA conditions showed that the FXR proteins were in complexes of > 600 kDa, as parts of messenger ribonuclear protein (mRNP) particles associated with polyribosomes. Salt treatment shifted FMRP, FXR1P and FXR2P into distinct intermediate complexes, with molecular masses between 200 and 300 kDa. Immunoprecipitations of FMRP as well as FXR1P from the dissociated complexes revealed that the vast majority of the FXR proteins do not form heteromeric complexes. Further analysis by [35S]methionine labelling in vivo followed by immunoprecipitation indicated that no proteins other than the FXR proteins were present in these complexes. These results suggest that the FXR proteins form homo-multimers preferentially under physiological conditions in mammalian cells, and might participate in mRNP particles with separate functions.

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Dicer-Derived MicroRNAs Are Utilized by the Fragile X Mental Retardation Protein for Assembly on Target RNAs

Journal of Biomedicine and Biotechnology ◽

10.1155/jbb/2006/64347 ◽

2006 ◽

Vol 2006 ◽

pp. 1-12 ◽

Cited By ~ 36

Author(s):

Isabelle Plante ◽

Laetitia Davidovic ◽

Dominique L. Ouellet ◽

Lise-Andrée Gobeil ◽

Sandra Tremblay ◽

...

Keyword(s):

Mental Retardation ◽

Translational Control ◽

Mammalian Cells ◽

Rna Binding ◽

Fragile X ◽

Rna Sequences ◽

Fragile X Mental Retardation ◽

Mental Retardation Protein ◽

Rnp Complex

In mammalian cells, fragile X mental retardation protein (FMRP) has been reported to be part of a microRNA (miRNA)-containing effector ribonucleoprotien (RNP) complex believed to mediate translational control of specific mRNAs. Here, using recombinant proteins, we demonstrate that human FMRP can act as a miRNA acceptor protein for the ribonuclease Dicer and facilitate the assembly of miRNAs on specific target RNA sequences. The miRNA assembler property of FMRP was abrogated upon deletion of its single-stranded (ss) RNA binding K-homology domains. The requirement of FMRP for efficient RNA interference (RNAi) in vivo was unveiled by reporter gene silencing assays using various small RNA inducers, which also supports its involvement in an ss small interfering RNA (siRNA)-containing RNP (siRNP) effector complex in mammalian cells. Our results define a possible role for FMRP in RNA silencing and may provide further insight into the molecular defects in patients with the fragile X syndrome.

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DrosophilaTorsin Protein Regulates Motor Control and Stress Sensitivity and Forms a Complex with Fragile-X Mental Retardation Protein

Neural Plasticity ◽

10.1155/2016/6762086 ◽

2016 ◽

Vol 2016 ◽

pp. 1-14 ◽

Cited By ~ 2

Author(s):

Phuong Nguyen ◽

Jong Bok Seo ◽

Hyo-Min Ahn ◽

Young Ho Koh

Keyword(s):

Mental Retardation ◽

Protein Complexes ◽

Fragile X ◽

Stress Sensitivity ◽

Altered Expression ◽

Fragile X Mental Retardation ◽

Evolutionarily Conserved ◽

Mental Retardation Protein ◽

Synaptic Boutons

We investigated unknownin vivofunctions of Torsin by usingDrosophilaas a model. Downregulation ofDrosophilaTorsin (DTor) by DTor-specific inhibitory double-stranded RNA (RNAi) induced abnormal locomotor behavior and increased susceptibility to H2O2. In addition, altered expression of DTor significantly increased the numbers of synaptic boutons. One important biochemical consequence of DTor-RNAi expression in fly brains was upregulation of alcohol dehydrogenase (ADH). Altered expression of ADH has also been reported inDrosophilaFragile-X mental retardation protein (DFMRP) mutant flies. Interestingly, expression of DFMRP was altered in DTor mutant flies, and DTor and DFMRP were present in the same protein complexes. In addition, DTor and DFMRP immunoreactivities were partially colocalized in several cellular organelles in larval muscles. Furthermore, there were no significant differences between synaptic morphologies ofdfmrpnull mutants anddfmrpmutants expressing DTor-RNAi. Taken together, our evidences suggested that DTor and DFMRP might be present in the same signaling pathway regulating synaptic plasticity. In addition, we also found that human Torsin1A and human FMRP were present in the same protein complexes, suggesting that this phenomenon is evolutionarily conserved.

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Temporal-specific roles of fragile X mental retardation protein in the development of the hindbrain auditory circuit

Development ◽

10.1242/dev.188797 ◽

2020 ◽

Vol 147 (21) ◽

pp. dev188797

Author(s):

Xiaoyu Wang ◽

Ayelet Kohl ◽

Xiaoyan Yu ◽

Diego A. R. Zorio ◽

Avihu Klar ◽

...

Keyword(s):

Mental Retardation ◽

Rna Binding ◽

Fragile X ◽

Neuronal Cell ◽

High Specificity ◽

Fragile X Mental Retardation ◽

Midline Crossing ◽

Mental Retardation Protein ◽

Axonal Targeting

ABSTRACTFragile X mental retardation protein (FMRP) is an RNA-binding protein abundant in the nervous system. Functional loss of FMRP leads to sensory dysfunction and severe intellectual disabilities. In the auditory system, FMRP deficiency alters neuronal function and synaptic connectivity and results in perturbed processing of sound information. Nevertheless, roles of FMRP in embryonic development of the auditory hindbrain have not been identified. Here, we developed high-specificity approaches to genetically track and manipulate throughout development of the Atoh1+ neuronal cell type, which is highly conserved in vertebrates, in the cochlear nucleus of chicken embryos. We identified distinct FMRP-containing granules in the growing axons of Atoh1+ neurons and post-migrating NM cells. FMRP downregulation induced by CRISPR/Cas9 and shRNA techniques resulted in perturbed axonal pathfinding, delay in midline crossing, excess branching of neurites, and axonal targeting errors during the period of circuit development. Together, these results provide the first in vivo identification of FMRP localization and actions in developing axons of auditory neurons, and demonstrate the importance of investigating early embryonic alterations toward understanding the pathogenesis of neurodevelopmental disorders.

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A highly conserved protein family interacting with the fragile X mental retardation protein (FMRP) and displaying selective interactions with FMRP-related proteins FXR1P and FXR2P

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.151231598 ◽

2001 ◽

Vol 98 (15) ◽

pp. 8844-8849 ◽

Cited By ~ 198

Author(s):

A. Schenck ◽

B. Bardoni ◽

A. Moro ◽

C. Bagni ◽

J.-L. Mandel

Keyword(s):

Mental Retardation ◽

Fragile X ◽

Protein Family ◽

Fragile X Mental Retardation ◽

Mental Retardation Protein ◽

Related Proteins ◽

Selective Interactions

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Hypothesis: A Role for Fragile X Mental Retardation Protein in Mediating and Relieving MicroRNA-Guided Translational Repression?

Journal of Biomedicine and Biotechnology ◽

10.1155/jbb/2006/16806 ◽

2006 ◽

Vol 2006 ◽

pp. 1-7 ◽

Cited By ~ 3

Author(s):

Isabelle Plante ◽

Patrick Provost

Keyword(s):

Mental Retardation ◽

Messenger Rna ◽

Mammalian Cells ◽

Fragile X ◽

Strand Exchange ◽

Translational Repression ◽

Fragile X Mental Retardation ◽

Mental Retardation Protein ◽

Cellular Signal ◽

Reverse Strand

MicroRNA (miRNA)-guided messenger RNA (mRNA) translational repression is believed to be mediated by effector miRNA-containing ribonucleoprotein (miRNP) complexes harboring fragile X mental retardation protein (FMRP). Recent studies documented the nucleic acid chaperone properties of FMRP and characterized its role and importance in RNA silencing in mammalian cells. We propose a model in which FMRP could facilitate miRNA assembly on target mRNAs in a process involving recognition of G quartet structures. Functioning within a duplex miRNP, FMRP may also mediate mRNA targeting through a strand exchange mechanism, in which the miRNA*of the duplex is swapped for the mRNA. Furthermore, FMRP may contribute to the relief of miRNA-guided mRNA repression through a reverse strand exchange reaction, possibly initiated by a specific cellular signal, that would liberate the mRNA for translation. Suboptimal utilization of miRNAs may thus account for some of themolecular defects in patients with the fragile X syndrome.

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