CArG elements control smooth muscle subtype-specific expression of smooth muscle myosin in vivo.
Expression of smooth muscle myosin heavy chain (SM-MHC) is tightly controlled depending on the differentiated state of smooth muscle cells (SMCs). To better understand the mechanisms that regulate transcription of the SM-MHC gene in vivo, we tested the function of several conserved CArG elements contained within the -4200 to +11,600 region of this gene that we had previously shown to drive SMC-specific expression in transgenic mice. CArG1 in the 5'-flanking sequence was required for all SMCs, while CArG2 and a novel intronic CArG element were differentially required in SMC subtypes. Of particular note, mutation of the intronic CArG selectively abolished expression in large arteries. A promoter construct containing three repeats of a conserved 227-bp intronic CArG-containing region was sufficient to direct transcription in vascular SMCs in transgenic mice, although this construct was also expressed in skeletal and cardiac muscle. These results support a model in which transcriptional regulation of SM-MHC is controlled by multiple positive and negative modular control regions that differ between SMCs and non-SMCs and among SMC subtypes. We also demonstrated that the CArG elements of the endogenous SM-MHC gene were bound by SRF in chromatin.
Manabe
I
I
Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, USA.
Owens
G K
GK
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D002843:Chromatin; D004268:DNA-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007438:Introns; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D016296:Mutagenesis; D018995:Myosin Heavy Chains / Q000235:genetics*; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D051381:Rats; D026362:Serum Response Factor; D014158:Transcription, Genetic
D002843:Chromatin; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D026362:Serum Response Factor; D018995:Myosin Heavy Chains