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Proc Natl Acad Sci U S A. 2003 Jun 10;100(12):7129-34. Epub 2003 May 19.

Myocardin is a master regulator of smooth muscle gene expression.

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Department of Molecular Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, TX 75390-9148, USA.


Virtually all smooth muscle genes analyzed to date contain two or more essential binding sites for serum response factor (SRF) in their control regions. Because SRF is expressed in a wide range of cell types, it alone cannot account for smooth muscle-specific gene expression. We show that myocardin, a cardiac muscle- and smooth muscle-specific transcriptional coactivator of SRF, can activate smooth muscle gene expression in a variety of nonmuscle cell types via its association with SRF. Homodimerization of myocardin is required for maximal transcriptional activity and provides a mechanism for cooperative activation of smooth muscle genes by SRF-myocardin complexes bound to different SRF binding sites. These findings identify myocardin as a master regulator of smooth muscle gene expression and explain how SRF conveys smooth muscle specificity to its target genes.

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