Olfactomedin 2, a novel regulator for transforming growth factor-β-induced smooth muscle differentiation of human embryonic stem cell-derived mesenchymal cells.
Bottom Line: Olfm2 also inhibited HERP1 expression.Moreover, blockade of Olfm2 expression inhibited TGF-β-induced SRF binding to SM gene promoters in a chromatin setting, whereas overexpression of Olfm2 dose dependently enhanced SRF binding.These results demonstrate that Olfm2 mediates TGF-β-induced SM gene transcription by empowering SRF binding to CArG box in SM gene promoters.
Affiliation: Department of Physiology and Pharmacology, University of Georgia, Athens, GA 30602.Show MeSH
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Mentions: Although Olfm2 is a nuclear factor likely involving the SM gene transcription, analysis of Olfm2 protein structure using DNA-Binder software revealed that Olfm2 lacks the DNA-binding domain, suggesting that Olfm2 may serve as a coactivator for a key transcription factor that regulates SM differentiation. SRF is a key nuclear transcription factor regulating the expression of most SM marker genes by binding to highly conserved CArG box present within nearly all SM-specific promoters (Miano, 2003; Mack, 2011). Because Olfm2 is critical for SM marker expression, we sought to determine whether Olfm2 can induce SM marker expression in the absence of SRF. As shown in Figure 4, A–E, knockdown of SRF by shRNA blocked Olfm2-induced SM marker expression, suggesting that SRF was essential for Olfm2-induced SM differentiation. Moreover, CArG box mutations significantly inhibited Olfm2 induction of α-SMA and SM22α promoter activity (Figure 4, F and G), suggesting that CArG box is indispensable for Olfm2 function. These data demonstrate that Olfm2 mediates SM differentiation in a SRF/CArG-dependent manner.
Affiliation: Department of Physiology and Pharmacology, University of Georgia, Athens, GA 30602.