Induction of vascular smooth muscle alpha-actin gene transcription in transforming growth factor beta1-activated myofibroblasts mediated by dynamic interplay between the Pur repressor proteins and Sp1/Smad coactivators.
The mouse vascular smooth muscle alpha-actin (SMA) gene enhancer is activated in fibroblasts by transforming growth factor beta1 (TGFbeta1), a potent mediator of myofibroblast differentiation and wound healing. The SMA enhancer contains tandem sites for the Sp1 transcriptional activator protein and Puralpha and beta repressor proteins. We have examined dynamic interplay between these divergent proteins to identify checkpoints for possible control of myofibroblast differentiation during chronic inflammatory disease. A novel element in the SMA enhancer named SPUR was responsible for both basal and TGFbeta1-dependent transcriptional activation in fibroblasts and capable of binding Sp1 and Pur proteins. A novel Sp1:Pur:SPUR complex was dissociated when SMA enhancer activity was increased by TGFbeta1 or Smad protein overexpression. Physical association of Pur proteins with Smad2/3 was observed as was binding of Smads to an upstream enhancer region that undergoes DNA duplex unwinding in TGFbeta1-activated myofibroblasts. Purbeta repression of the SMA enhancer could not be relieved by TGFbeta1, whereas repression mediated by Puralpha was partially rescued by TGFbeta1 or overexpression of Smad proteins. Interplay between Pur repressor isoforms and Sp1 and Smad coactivators may regulate SMA enhancer output in TGFbeta1-activated myofibroblasts during episodes of wound repair and tissue remodeling.
Department of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, College of Medicine and Public Health, The Ohio State University, Columbus, OH 43210, USA.
Sukanya V
SV
Subramanian
John A
JA
Polikandriotis
Robert J
RJ
Kelm
Jason J
JJ
David
Charles G
CG
Orosz
Arthur R
AR
Strauch
D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009419:Nerve Tissue Proteins; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D051785:Smad Proteins; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D053773:Transforming Growth Factor beta1
D000199:Actins; D004268:DNA-Binding Proteins; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; C121485:Pura protein, mouse; D051785:Smad Proteins; D016329:Sp1 Transcription Factor; C508961:Tgfb1 protein, mouse; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D004247:DNA