title: Regulation of 130-kDa smooth muscle myosin light chain kinase expression by an intronic CArG element.
abstract: The 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.
authors.affiliation: From the Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202.
authors.forename: Meng
authors.initials: M
authors.lastname: Chen
authors.forename: Wenwu
authors.initials: W
authors.lastname: Zhang
authors.forename: Xiao
authors.initials: X
authors.lastname: Lu
authors.forename: April M
authors.initials: AM
authors.lastname: Hoggatt
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Gunst
authors.forename: Ghassan S
authors.initials: GS
authors.lastname: Kassab
authors.forename: Johnathan D
authors.initials: JD
authors.lastname: Tune
authors.forename: B Paul
authors.initials: BP
authors.lastname: Herring
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D005786:Gene Expression Regulation; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000235:genetics* / Q000378:metabolism; D007438:Introns / Q000235:genetics; D019394:Ki-67 Antigen / Q000378:metabolism; D051379:Mice; D009119:Muscle Contraction / Q000235:genetics*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D026362:Serum Response Factor / Q000378:metabolism
chemical_list: D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D019394:Ki-67 Antigen; D020033:Protein Isoforms; D012097:Repressor Proteins; D026362:Serum Response Factor; C077048:Hnrnpab protein, mouse; D009219:Myosin-Light-Chain Kinase
keywords: Calcium Calmodulin-dependent Protein Kinase (CaMK); Contractile Protein; Intestine; Myosin; Serum Response Factor; Smooth Muscle