The RNA-binding protein Staufen1 impairs myogenic differentiation via a c-myc-dependent mechanism.
Bottom Line: Cells overexpressing Staufen1 differentiated poorly, as evidenced by reductions in the differentiation and fusion indices and decreases in MyoD, myogenin, MEF2A, and MEF2C, independently of Staufen-mediated mRNA decay.By contrast, the knockdown of Staufen1 decreased c-myc levels in myoblasts.Collectively our results show that Staufen1 is highly expressed during early stages of differentiation/development and that it can impair differentiation by regulating c-myc, thereby highlighting the multifunctional role of Staufen1 in skeletal muscle cells.
Affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada.Show MeSH
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Mentions: It is well known that the transcription factor MEF2 synergizes with MyoD to control the myogenic program (Lilly et al., 1994; Molkentin et al., 1995; Berkes and Tapscott, 2005; Buckingham and Vincent, 2009; Bismuth and Relaix, 2010; Bentzinger et al., 2012). We therefore examined the mRNA levels of MEF2A and MEF2C by qRT-PCR in the Staufen1-HA–overexpressing clones. MEF2A and MEF2C mRNA levels were both decreased (p < 0.05) in Staufen1-HA–overexpressing clones compared with those seen in control cells (Figure 7, A and B). In these experiments, we observed a slightly greater variability in MEF2C mRNA levels within conditions. This likely explains why MEF2C mRNA levels are significantly decreased only at 48 h in clone #15. As mentioned in the Introduction, Staufen1 is believed to be involved in the control of mRNA stability by a mechanism referred to as Staufen1-mediated mRNA decay, which involves direct binding of Staufen1 to secondary structures present in the 3′UTR of target mRNAs, and subsequent mRNA decay (Kim et al., 2005). This degradation mechanism has been shown to target a specific subset of mRNAs, including Pax3, whereas other transcripts, such as myogenin, are unaffected (Gong et al., 2009).
Affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada.