5′ CArG degeneracy in smooth muscle α-actin is required for injury-induced gene suppression in vivo

Jennifer A. Hendrix, Brian R. Wamhoff, Oliver G. McDonald, Sanjay Sinha, Tadashi Yoshida, Gary K. Owens

Research output: Contribution to journalArticle

79 Citations (Scopus)

Abstract

CC(A/T)6GG-dependent (CArG-dependent) and serum response factor-dependent (SRF-dependent) mechanisms are required for gene expression in smooth muscle cells (SMCs). However, an unusual feature of many SMC-selective promoter CArG elements is that they contain a conserved single G or C substitution in their central A/T-rich region, which reduces binding affinity for ubiquitously expressed SRF. We hypothesized that this CArG degeneracy contributes to cell-specific expression of smooth muscle α-actin in vivo, since substitution of c-fos consensus CArGs for the degenerate CArGs resulted in relaxed specificity in cultured cells. Surprisingly, our present results show that these substitutions have no effect on smooth muscle-specific transgene expression during normal development and maturation in transgenic mice. However, these substitutions significantly attenuated injury-induced downregulation of the mutant transgene under conditions where SRF expression was increased but expression of myocardin, a smooth muscle-selective SRF coactivator, was decreased. Finally, chromatin immunoprecipitation analyses, together with cell culture studies, suggested that myocardin selectively enhanced SRF binding to degenerate versus consensus CArG elements. Our results indicate that reductions in myocardin expression and the degeneracy of CArG elements within smooth muscle promoters play a key role in phenotypic switching of smooth muscle cells in vivo, as well as in mediating responses of CArG-dependent smooth muscle genes and growth regulatory genes under conditions in which these 2 classes of genes are differentially expressed.

Original languageEnglish
Pages (from-to)418-427
Number of pages10
JournalJournal of Clinical Investigation
Volume115
Issue number2
DOIs
Publication statusPublished - 2005 Jan 1
Externally publishedYes

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Smooth Muscle
Actins
Wounds and Injuries
Smooth Muscle Myocytes
Genes
Transgenes
Serum Response Factor
Chromatin Immunoprecipitation
Regulator Genes
Transgenic Mice
Cultured Cells
Down-Regulation
Cell Culture Techniques
Gene Expression
Growth
myocardin

ASJC Scopus subject areas

  • Medicine(all)

Cite this

5′ CArG degeneracy in smooth muscle α-actin is required for injury-induced gene suppression in vivo. / Hendrix, Jennifer A.; Wamhoff, Brian R.; McDonald, Oliver G.; Sinha, Sanjay; Yoshida, Tadashi; Owens, Gary K.

In: Journal of Clinical Investigation, Vol. 115, No. 2, 01.01.2005, p. 418-427.

Research output: Contribution to journalArticle

Hendrix, Jennifer A. ; Wamhoff, Brian R. ; McDonald, Oliver G. ; Sinha, Sanjay ; Yoshida, Tadashi ; Owens, Gary K. / 5′ CArG degeneracy in smooth muscle α-actin is required for injury-induced gene suppression in vivo. In: Journal of Clinical Investigation. 2005 ; Vol. 115, No. 2. pp. 418-427.
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