Homodimerization of RBPMS2 through a new RRM-interaction motif is necessary to control smooth muscle plasticity.
Bottom Line: RBPMS2 contains only one RNA recognition motif (RRM) while this motif is often repeated in tandem or associated with other functional domains in RRM-containing proteins.We also show that this specific motif is conserved among its homologs and paralogs in vertebrates and in its insect and worm orthologs (CPO and MEC-8, respectively) suggesting a conserved molecular mechanism of action.Our study demonstrates that RBPMS2 possesses an RRM domain harboring both RNA-binding and protein-binding properties and that the newly identified RRM-homodimerization motif is crucial for the function of RBPMS2 at the cell and tissue levels.
Affiliation: INSERM U1046, Université Montpellier 1, Université Montpellier 2, 34295 Montpellier, France.Show MeSH
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Mentions: To further investigate whether RBPMS2 homodimerization has a role in its biological function, we expressed chick RBPMS2 or the chick mutant of human RBPMS2-L49E (RBPMS2-L40E) in the gastrointestinal mesenchyme of stage-10 chicken embryos using an avian replication-competent retroviral misexpression system (10,18). In accordance with our previous results (9), sustained RBPMS2 expression resulted in a dramatic alteration of the stomach morphology: the proventriculus, which is the glandular part of the chick stomach, was hypertrophied and the gizzard was denser and malformed in comparison to controls that overexpressed GFP alone (Figure 4A). In contrast, sustained expression of RBPMS2-L40E did not induce any morphological change (n = 26, stomachs; Figure 4B). Moreover, while misexpression of wild-type RBPMS2 in the gastrointestinal mesenchyme upregulated NOGGIN mRNA expression in comparison to controls (Figure 4C, left and middle panels), misexpression of RBPMS2-L40E did not (n = 17 infected stomachs; Figure 4C, right panel). Lastly, we verified the homodimerization status of Myc-RBPMS2, Myc-RBPMS2-L40E and GFP proteins in DF1 cell line by glutaraldehyde crosslinking. Interestingly, whereas fixed protein extract from GFP (as positive control) or Myc-RBPMS2 expressing cells displays well-defined homodimeric forms, no clear dimerization was observed in fixed protein extract from Myc-RBPMS2-L40 expressing cells (Figure 4D). Altogether these results demonstrate that RBPMS2 homodimerization is essential for RBPMS2-mediated upregulation of NOGGIN.
Affiliation: INSERM U1046, Université Montpellier 1, Université Montpellier 2, 34295 Montpellier, France.