Structure and Expression of a Smooth Muscle Cell-specific Gene, SM22

doi:10.1074/jbc.270.22.13460

Structure and Expression of a Smooth Muscle Cell-specific Gene, SM22(*)

From the (1) Department of Medicine, University of Chicago, Chicago, Illinois 60637

^§ To whom correspondence should be addressed:
Dept. of Medicine, University of Chicago MC 6088, 5841 S. Maryland Ave., Chicago, IL 60637.
Tel.: 312-702-2679; Fax: 312-702-2681.

Abstract

SM22α is expressed exclusively in smooth muscle-containing tissues of adult animals and is one of the earliest markers of differentiated smooth muscle cells (SMCs). To examine the molecular mechanisms that regulate SMC-specific gene expression, we have isolated and structurally characterized the murine SM22α gene. SM22α is a 6.2-kilobase single copy gene composed of five exons. SM22α mRNA is expressed at high levels in the aorta, uterus, lung, and intestine, and in primary cultures of rat aortic SMCs, and the SMC line, A7r5. In contrast to genes encoding SMC contractile proteins, SM22α gene expression is not decreased in proliferating SMCs. Transient transfection experiments demonstrated that 441 base pairs of SM22α 5′-flanking sequence was necessary and sufficient to program high level transcription of a luciferase reporter gene in both primary rat aortic SMCs and A7r5 cells. DNA sequence analyses revealed that the 441-base pair promoter contains two CArG/SRF boxes, a CACC box, and one potential MEF-2 binding site, cis-acting elements which are each important regulators of striated muscle transcription. Taken together, these studies have identified the murine SM22α promoter as an excellent model system for studies of developmentally regulated, lineage-specific gene expression in SMCs.

Footnotes

↵* This work was supported in part by United States Public Health Service Grants R01-HL48257 and U01 AI34566 (to J. S.) and R01HL51145 (to M. S. P.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The GenBank accession number for the murine SM22α cDNA is L41154. The GenBank accession number for the murine SM22α gene is L41161.
↵¹ The abbreviations used are:

SMC

smooth muscle cells

bp

base pair(s)

PCR

polymerase chain reaction

RSV

Rous sarcoma virus

kb

kilobase pair(s).
↵²F. Samaha and M. Parmacek, unpublished data.
↵³F. Samaha and M. Parmacek, unpublished observation.
↵⁴F. Samaha, J. Seltzer, and M. Parmacek, unpublished observation.