Article

The C terminus of fragile X mental retardation protein interacts with the multi-domain Ran-binding protein in the microtubule-organising centre

National Institute for Medical Research, London NW7 1AA, UK.
Journal of Molecular Biology (Impact Factor: 4.33). 11/2004; 343(1):43-53. DOI: 10.1016/j.jmb.2004.08.024
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ABSTRACT Absence of the fragile X mental retardation protein (FMRP) causes fragile X syndrome, the most common form of hereditary mental retardation. FMRP is a mainly cytoplasmic protein thought to be involved in repression of translation, through a complex network of protein-protein and protein-RNA interactions. Most of the currently known protein partners of FMRP recognise the conserved N terminus of the protein. No interaction has yet been mapped to the highly charged, poorly conserved C terminus, so far thought to be involved in RNA recognition through an RGG motif. In the present study, we show that a two-hybrid bait containing residues 419-632 of human FMRP fishes out a protein that spans the sequence of the Ran-binding protein in the microtubule-organising centre (RanBPM/RanBP9). Specific interaction of RanBPM with FMRP was confirmed by in vivo and in vitro assays. In brain tissue sections, RanBPM is highly expressed in the neurons of cerebral cortex and the cerebellar purkinje cells, in a pattern similar to that described for FMRP. Sequence analysis shows that RanBPM is a multi-domain protein. The interaction with FMRP was mapped in a newly identified CRA motif present in the RanBPM C terminus. Our results suggest that the functional role of RanBPM binding is modulation of the RNA-binding properties of FMRP.

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    • "It was previously suggested that RanBPM interacted with microtubules, but this observation was later dismissed as the original study used an antibody that did not recognize RanBPM (Nakamura et al., 1998; Nishitani et al., 2001). Some studies have subsequently suggested a potential role for RanBPM in microtubule regulation (Menon et al., 2004; Togashi et al., 2006), although a direct association of RanBPM with microtubules remains to be confirmed. Interestingly, the highly similar protein RanBP10, whose expression is restricted to hematopoietic cell lineages, has been shown to function in platelet microtubule organization through an interaction with b1-tubulin (Kunert et al., 2009; Schulze et al., 2008). "
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    ABSTRACT: In conditions of proteasomal impairment, the build-up of damaged or misfolded proteins activates a cellular response leading to the recruitment of damaged proteins into perinuclear aggregates called aggresomes. Aggresome formation involves the retrograde transport of cargo proteins along the microtubule network and is dependent on the histone deacetylase HDAC6. Here we show that ionizing radiation (IR) promotes Ran-Binding Protein M (RanBPM) relocalization into discrete perinuclear foci where it co-localizes with aggresome components ubiquitin, dynein and HDAC6, suggesting that the RanBPM perinuclear clusters correspond to aggresomes. RanBPM was also recruited to aggresomes following treatment with the proteasome inhibitor MG132 and the DNA-damaging agent etoposide. Strikingly, aggresome formation by HDAC6 was markedly impaired in RanBPM shRNA cells, but was restored by re-expression of RanBPM. RanBPM was found to interact with HDAC6 and to inhibit its deacetylase activity. This interaction was abrogated by a RanBPM deletion of its LisH/CTLH domain, which also prevented aggresome formation, suggesting that RanBPM promotes aggresome formation through an association with HDAC6. Our results suggest that RanBPM regulates HDAC6 activity and is a central regulator of aggresome formation.
    Biology Open 05/2014; 3(6). DOI:10.1242/bio.20147021 · 2.42 Impact Factor
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    • "YPEL5 binding site of RanBPM protein Eleven partial cDNA clones for YPEL5-binding protein screened by Y2H covered various regions of RanBPM protein and their minimum overlapping region (MOR) corresponded to a distinct region of 146– 330 aa (Fig. 5A). Human RanBPM has four domains, namely SPRY, LisH, CTLH and CRA (Fig. 5A) [9]. The MOR corresponds to almost entire SPRY domain; hence, the SPRY domain was considered necessary for binding of YPEL5. "
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    • "While the presence of RNA-binding and protein interaction domains in the N-terminal amino acids of FMRP and the FXR paralogs have been noted for some time, a role for C-terminal amino acids had been less clear. Recent studies of the hFMRP C-terminal peptide strongly indicate that it has protein interaction capacity, as judged by yeast two-hybrid screening using the C-terminal peptide as a bait (Menon et al., 2004), and the finding that a C-terminal truncation of hFMRP inhibits its interaction with kinesin (Dictenberg et al., 2008). A comparison of the C-terminal 81 amino acids encoded by exons 16-17 of FMR1 and the terminal 81 amino acids of dFMR1 shows significant conservation, with 31 of 81 residues (38%) being identical or similar (Figure 1E). "
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