Expression of the smooth muscle myosin heavy chain gene is regulated by a negative-acting GC-rich element located between two positive-acting serum response factor-binding elements.
To identify cis- and trans-acting factors that regulate smooth muscle-specific gene expression, we studied the smooth muscle myosin heavy chain gene, a rigorous marker of differentiated smooth muscle. A comparison of smooth muscle myosin heavy chain promoter sequences from multiple species revealed the presence of a highly conserved 227-base pair domain (nucleotides -1321 to -1095 in rat). Results of a deletion analysis of a 4.3-kilobase pair segment of the rat promoter (nucleotides -4220 to +88) demonstrated that this domain was necessary for maximal transcriptional activity in smooth muscle cells. Gel-shift analysis and site-directed mutagenesis demonstrated that one true CArG and another CArG-like element contained within this domain were both recognized by the serum response factor and were both required for the positive activity attributable to this domain. Additional studies demonstrated that mutation of a GC-rich sequence within the 227-base pair conserved domain resulted in a nearly 100% increase in transcriptional activity. Gel-shift analysis showed that this GC-rich repressor element was recognized by both Sp1 and Sp3. These data demonstrate that transcriptional control of the smooth muscle myosin heavy chain gene is highly complex, involving both negative and positive regulatory elements, including CArG sequences found in the promoters of multiple smooth muscle differentiation marker genes.
Madsen
C S
CS
Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, USA.
Hershey
J C
JC
Hautmann
M B
MB
White
S L
SL
Owens
G K
GK
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D018983:DNA Footprinting; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D051379:Mice; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000235:genetics*; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011817:Rabbits; D051381:Rats; D012689:Sequence Homology, Nucleic Acid; D016329:Sp1 Transcription Factor / Q000378:metabolism; D051705:Sp3 Transcription Factor; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000378:metabolism
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D016329:Sp1 Transcription Factor; C497122:Sp3 protein, mouse; C497123:Sp3 protein, rat; D014157:Transcription Factors; D051705:Sp3 Transcription Factor; D018995:Myosin Heavy Chains