The smooth muscle gamma-actin gene promoter is a molecular target for the mouse bagpipe homologue, mNkx3-1, and serum response factor.
An evolutionarily conserved vertebrate homologue of the Drosophila NK-3 homeodomain gene bagpipe, Nkx3-1, is expressed in vascular and visceral mesoderm-derived muscle tissues and may influence smooth muscle cell differentiation. Nkx3-1 was evaluated for mediating smooth muscle gamma-actin (SMGA) gene activity, a specific marker of smooth muscle differentiation. Expression of mNkx3-1 ... in heterologous CV-1 fibroblasts was unable to elicit SMGA promoter activity but required the coexpression of serum response factor (SRF) to activate robust SMGA transcription. A novel complex element containing a juxtaposed Nkx-binding site (NKE) and an SRF-binding element (SRE) in the proximal promoter region was found to be necessary for the Nkx3-1/SRF coactivation of SMGA transcription. Furthermore, Nkx3-1 and SRF associate through protein-protein interactions and the homeodomain region of Nkx3-1 facilitated SRF binding to the complex NKE.SRE. Mutagenesis of Nkx3-1 revealed an inhibitory domain within its C-terminal segment. In addition, mNkx3-1/SRF cooperative activity required an intact Nkx3-1 homeodomain along with the MADS box of SRF, which contains DNA binding and dimerization structural domains, and the contiguous C-terminal SRF activation domain. Thus, SMGA is a novel target for Nkx3-1, and the activity of Nkx3-1 on the SMGA promoter is dependent upon SRF.
Mesh Terms:
Actins, Animals, Base Sequence, Binding Sites, Birds, Cell Differentiation, Cell Line, Conserved Sequence, DNA-Binding Proteins, Drosophila Proteins, Electrophoresis, Polyacrylamide Gel, Fibroblasts, Glutathione Transferase, Haplorhini, Homeodomain Proteins, Humans, Mesoderm, Mice, Molecular Sequence Data, Muscle, Smooth, Mutagenesis, Site-Directed, Nuclear Proteins, Plasmids, Precipitin Tests, Promoter Regions, Genetic, Protein Binding, Protein Structure, Tertiary, Recombinant Fusion Proteins, Sequence Homology, Nucleic Acid, Serum Response Factor, Transcription Factors, Transcription, Genetic, Transcriptional Activation, Transfection
Actins, Animals, Base Sequence, Binding Sites, Birds, Cell Differentiation, Cell Line, Conserved Sequence, DNA-Binding Proteins, Drosophila Proteins, Electrophoresis, Polyacrylamide Gel, Fibroblasts, Glutathione Transferase, Haplorhini, Homeodomain Proteins, Humans, Mesoderm, Mice, Molecular Sequence Data, Muscle, Smooth, Mutagenesis, Site-Directed, Nuclear Proteins, Plasmids, Precipitin Tests, Promoter Regions, Genetic, Protein Binding, Protein Structure, Tertiary, Recombinant Fusion Proteins, Sequence Homology, Nucleic Acid, Serum Response Factor, Transcription Factors, Transcription, Genetic, Transcriptional Activation, Transfection
J. Biol. Chem.
Date: Dec. 15, 2000
PubMed ID: 10993896
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