title: Platelet-derived growth factor-BB represses smooth muscle cell marker genes via changes in binding of MKL factors and histone deacetylases to their promoters.
abstract: A hallmark of smooth muscle cell (SMC) phenotypic switching is suppression of SMC marker gene expression. Although myocardin has been shown to be a key regulator of this process, the role of its related factors, MKL1 and MKL2, in SMC phenotypic switching remains unknown. The present studies were aimed at determining if: 1) MKL factors contribute to the expression of SMC marker genes in cultured SMCs; and 2) platelet-derived growth factor-BB (PDGF-BB)-induced repression of SMC marker genes is mediated by suppression of MKL factors. Results of gain- and loss-of-function experiments showed that MKL factors regulated the expression of single and multiple CArG [CC(AT-rich)(6)GG]-containing SMC marker genes, such as smooth muscle (SM) alpha-actin and telokin, but not CArG-independent SMC marker genes such as smoothelin-B. Treatment with PDGF-BB reduced the expression of CArG-containing SMC marker genes, as well as myocardin expression in cultured SMCs, while it had no effect on expression of MKL1 and MKL2. However, of interest, PDGF-BB induced the dissociation of MKL factors from the CArG-containing region of SMC marker genes, as determined by chromatin immunoprecipitation assays. This dissociation was caused by the competition between MKL factors and phosphorylated Elk-1 at early time points, but subsequently by the reduction in acetylated histone H4 levels at these promoter regions mediated by histone deacetylases, HDAC2, HDAC4, and HDAC5. Results provide novel evidence that PDGF-BB-induced repression of SMC marker genes is mediated through combinatorial mechanisms, including downregulation of myocardin expression and inhibition of the association of myocardin/MKL factors with CArG-containing SMC marker gene promoters.
authors.affiliation: Dept. of Molecular Physiology and Biological Physics, Univ. of Virginia, MR5 Rm. 1220, 415 Lane Road, Charlottesville, VA 22908, USA.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yoshida
authors.forename: Qiong
authors.initials: Q
authors.lastname: Gan
authors.forename: Yueting
authors.initials: Y
authors.lastname: Shang
authors.forename: Gary K
authors.initials: GK
authors.lastname: Owens
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001011:Aorta / Q000166:cytology; D000077214:Becaplermin; D015415:Biomarkers / Q000378:metabolism; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D010446:Peptide Fragments; D010455:Peptides / Q000378:metabolism; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000502:physiology*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020574:Proto-Oncogene Proteins c-sis; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D050807:ets-Domain Protein Elk-1 / Q000378:metabolism
chemical_list: D000199:Actins; D015415:Biomarkers; D003598:Cytoskeletal Proteins; D009124:Muscle Proteins; D010446:Peptide Fragments; D010455:Peptides; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D034741:RNA, Small Interfering; C491051:Smtn protein, rat; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D000077214:Becaplermin; C060640:telokin; D009219:Myosin-Light-Chain Kinase; D006655:Histone Deacetylases