Chen, MengZhang, WenwuLu, XiaoHoggatt, April M.Gunst, Susan J.Kassab, Ghassan S.Tune, Johnathan D.Herring, B. Paul2015-09-172015-09-172013Chen, M., Zhang, W., Lu, X., Hoggatt, A. M., Gunst, S. J., Kassab, G. S., ... & Herring, B. P. (2013). Regulation of 130-kDa smooth muscle myosin light chain kinase expression by an intronic CArG element. Journal of Biological Chemistry, 288(48), 34647-34657.https://hdl.handle.net/1805/6977The mylk1 gene encodes a 220-kDa nonmuscle myosin light chain kinase (MLCK), a 130-kDa smooth muscle MLCK (smMLCK), as well as the non-catalytic product telokin. Together, these proteins play critical roles in regulating smooth muscle contractility. Changes in their expression are associated with many pathological conditions; thus, it is important to understand the mechanisms regulating expression of mylk1 gene transcripts. Previously, we reported a highly conserved CArG box, which binds serum response factor, in intron 15 of mylk1. Because this CArG element is near the promoter that drives transcription of the 130-kDa smMLCK, we examined its role in regulating expression of this transcript. Results show that deletion of the intronic CArG region from a β-galactosidase reporter gene abolished transgene expression in mice in vivo. Deletion of the CArG region from the endogenous mylk1 gene, specifically in smooth muscle cells, decreased expression of the 130-kDa smMLCK by 40% without affecting expression of the 220-kDa MLCK or telokin. This reduction in 130-kDa smMLCK expression resulted in decreased phosphorylation of myosin light chains, attenuated smooth muscle contractility, and a 24% decrease in small intestine length that was associated with a significant reduction of Ki67-positive smooth muscle cells. Overall, these data show that the CArG element in intron 15 of the mylk1 gene is necessary for maximal expression of the 130-kDa smMLCK and that the 130-kDa smMLCK isoform is specifically required to regulate smooth muscle contractility and small intestine smooth muscle cell proliferation.en-USPublisher PolicyCalcium Calmodulin-dependent Protein Kinase (CaMK)contractile proteinintestineArticle