Thymine DNA glycosylase represses myocardin-induced smooth muscle cell differentiation by competing with serum response factor for myocardin binding

Jiliang Zhou, Emily K. Blue, Guoqing Hu, B. Herring

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Myocardin is a serum response factor (SRF) co-activator that regulates transcription of many smooth muscle-specific genes and is essential for development of vascular smooth muscle. We used a yeast two-hybrid screen, with myocardin as bait in a search for factors that regulate myocardin transcriptional activity. From this screen, thymine DNA glycosylase (TDG) was identified as a myocardin-associated protein. TDG was originally identified as an enzyme involved in base excision repair of T:G mismatches caused by spontaneous deamination of methylated cytosines. However, TDG has also been shown to act as a transcriptional co-activator or co-repressor. The interaction between TDG and myocardin was confirmed in vitro by glutathione S-transferase pull down and in vivo by co-immunoprecipitation assays. We found that TDG abrogates myocardin induced expression of smooth muscle-specific genes and represses the trans-activation of the promoters of myocardin of these genes. Overexpression of TDG in SMCs down-regulated smooth muscle marker expression. Conversely, depletion of endogenous TDG in SMCs increased smooth muscle-specific myosin heavy chain (SM MHC) and Telokin gene expression. Glutathione S-transferase pull-down assays demonstrated that TDG binds to a region of myocardin that includes the SRF binding domain. Furthermore, TDG was found to compete with SRF for binding to myocardin in vitro and in vivo, suggesting that TDG can inhibit expression of smooth muscle-specific genes, at least in part, through disrupting SRF/myocardin interactions. Finally, we demonstrated that the glycosylase activity of TDG is not required for its inhibitory effects on myocardin function. This study reveals a previously unsuspected role for the repair enzyme TDG as a repressor of smooth muscle differentiation via competing with SRF for binding to myocardin.

Original languageEnglish (US)
Pages (from-to)35383-35392
Number of pages10
JournalJournal of Biological Chemistry
Volume283
Issue number51
DOIs
StatePublished - Dec 19 2008
Externally publishedYes

Fingerprint

Thymine DNA Glycosylase
Serum Response Factor
Smooth Muscle Myocytes
Muscle
Cell Differentiation
Cells
Smooth Muscle
Genes
Glutathione Transferase
myocardin
Assays
Repair
Smooth Muscle Myosins
Co-Repressor Proteins
Deamination
Myosin Heavy Chains
Cytosine
Essential Genes
Enzymes
Transcription

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Cite this

Thymine DNA glycosylase represses myocardin-induced smooth muscle cell differentiation by competing with serum response factor for myocardin binding. / Zhou, Jiliang; Blue, Emily K.; Hu, Guoqing; Herring, B.

In: Journal of Biological Chemistry, Vol. 283, No. 51, 19.12.2008, p. 35383-35392.

Research output: Contribution to journalArticle

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