title: Differential binding of an SRF/NK-2/MEF2 transcription factor complex in normal versus neoplastic smooth muscle tissues.
abstract: The malignant potential of smooth muscle tumors correlates strongly with the disappearance of gamma-smooth muscle isoactin, a lineage-specific marker of smooth muscle development. In this paper, we identify a 36-base pair regulatory motif containing an AT-rich domain, CArG box, and a non-canonical NK-2 homeodomain-binding site that has the capacity to regulate smooth muscle-specific gene expression in cultured intestinal smooth muscle cells. Serum-response factor associates with an NK-2 transcription factor via protein-protein interactions and binds to the core CArG box element. Our studies suggest that the NK-2 transcription factor that associates with serum-response factor during smooth muscle differentiation is Nkx2-3. Myocyte-specific enhancer factor 2 binding to this regulatory complex was also observed but limited to uterine smooth muscle tissues. Smooth muscle neoplasms displayed altered transcription factor binding when compared with normal myometrium. Differential nuclear accessibility of serum-response factor protein during smooth muscle differentiation and neoplastic transformation was also observed. Thus, we have identified a unique regulatory complex whose differential binding properties and nuclear accessibility are associated with modulating gamma-smooth muscle isoactin-specific gene expression in both normal and neoplastic tissues.
authors.affiliation: Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Phiel
authors.forename: V
authors.initials: V
authors.lastname: Gabbeta
authors.forename: L M
authors.initials: LM
authors.lastname: Parsons
authors.forename: D
authors.initials: D
authors.lastname: Rothblat
authors.forename: R P
authors.initials: RP
authors.lastname: Harvey
authors.forename: K M
authors.initials: KM
authors.lastname: McHugh
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D029721:Drosophila Proteins; D018398:Homeodomain Proteins / Q000378:metabolism*; D064326:MEF2 Transcription Factors; D051379:Mice; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000166:cytology* / Q000378:metabolism; D018006:Myogenic Regulatory Factors; D009369:Neoplasms / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D051381:Rats; D026362:Serum Response Factor; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D009687:Nuclear Proteins; D026362:Serum Response Factor; D014157:Transcription Factors; C094797:vnd protein, Drosophila