The Purα/Purβ single-strand DNA-binding proteins attenuate smooth-muscle actin gene transactivation in myofibroblasts.
Expression of smooth muscle alpha-actin (SMαA) is essential for myofibroblast-mediated wound contraction following tissue injury. The Pur α/β and YB-1 transcriptional repressors govern the DNA-binding activity of serum response factor (SRF) and phosphorylated Smad3 (pSmad3) transcriptional activators during induction of SMαA gene expression in human pulmonary myofibroblasts. In quiescent fibroblasts, Pur α exhibited a novel function in enhancing stability of pre-existing SRF complexes with SMαA core promoter DNA, whereas Pur β was more effective in disrupting SRF-DNA interaction. Pur proteins were less efficient competitors of pre-existing, core-promoter complexes containing both SRF and pSmad3 in nuclear extracts from TGFβ1-activated myofibroblasts. TGFβ1 signaling dissociated a SRF/Pur protein complex with concurrent formation of a transient pSmad3/MRTF-A/Pur β complex during early phase myofibroblast differentiation. Pur β was replaced by Pur α in the pSmad3/MRTF-A complex in mature myofibroblasts. Combining all three repressors potently inhibited SRF and pSmad3 binding to promoter DNA in quiescent fibroblasts and TGFβ1-activated myofibroblasts, respectively. The results point to dynamic interplay between transcriptional activators and repressors in regulating SMαA gene output during myofibroblast differentiation. Therapeutic targeting of nucleoprotein complexes regulating the SMαA promoter may prevent excessive myofibroblast accumulation associated with chronic cardiopulmonary fibrosis and dysfunctional tissue remodeling.
Department of Physiology and Cell Biology, Ohio State Biochemistry Program, and Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, Ohio, USA.
Seethalakshmi
S
Hariharan
Robert J
RJ
Kelm
Arthur Roger
AR
Strauch
D000199:Actins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002454:Cell Differentiation; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005355:Fibrosis; D006801:Humans; D008168:Lung / Q000378:metabolism* / Q000473:pathology; D058628:Myofibroblasts / Q000378:metabolism* / Q000473:pathology; D015514:Oncogene Proteins, Fusion / Q000378:metabolism; D010766:Phosphorylation; D011658:Pulmonary Fibrosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D034622:RNA Interference; D027602:Serum Response Element; D026362:Serum Response Factor / Q000378:metabolism; D015398:Signal Transduction; D051900:Smad3 Protein / Q000378:metabolism; D013997:Time Factors; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D015854:Up-Regulation
C541116:ACTA2 protein, human; D000199:Actins; D004268:DNA-Binding Proteins; C431575:MRTFA protein, human; D015514:Oncogene Proteins, Fusion; C501130:PURA protein, human; C491579:PURB protein, human; C497790:SMAD3 protein, human; D026362:Serum Response Factor; D051900:Smad3 Protein; C508960:TGFB1 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1