Serum response factor neutralizes Pur alpha- and Pur beta-mediated repression of the fetal vascular smooth muscle alpha-actin gene in stressed adult cardiomyocytes.
Mouse hearts subjected to repeated transplant surgery and ischemia-reperfusion injury develop substantial interstitial and perivascular fibrosis that was spatially associated with dysfunctional activation of fetal smooth muscle alpha-actin (SM alpha A) gene expression in graft ventricular cardiomyocytes. Compared with cardiac fibroblasts in which nuclear levels of the Sp1 and Smad 2/3 transcriptional-activating proteins increased markedly after transplant injury, the most abundant SM alpha A gene-activating protein in cardiomyocyte nuclei was serum response factor (SRF). Additionally, cardiac intercalated discs in heart grafts contained substantial deposits of Pur alpha, an mRNA-binding protein and known negative modulator of SRF-activated SM alpha A gene transcription. Activation of fetal SM alpha A gene expression in perfusion-isolated adult cardiomyocytes was linked to elevated binding of a novel protein complex consisting of SRF and Pur alpha to a purine-rich DNA element in the SM alpha A promoter called SPUR, previously shown to be required for induction of SM alpha A gene transcription in injury-activated myofibroblasts. Increased SRF binding to SPUR DNA plus one of two nearby CArG box consensus elements was observed in SM alpha A-positive cardiomyocytes in parallel with enhanced Pur alpha:SPUR protein:protein interaction. The data suggest that de novo activation of the normally silent SM alpha A gene in reprogrammed adult cardiomyocytes is linked to elevated interaction of SRF with fetal-specific CArG and injury-activated SPUR elements in the SM alpha A promoter as well as the appearance of novel Pur alpha protein complexes in both the nuclear and cytosolic compartments of these cells.
Zhang
Aiwen
A
Dept. of Physiology and Cell Biology, Davis Heart and Lung Research, Institute Biomedical Research Tower, Rm. 314, 460 West 12th Ave., The Ohio State Univ. College of Medicine, Columbus, OH 43210-1252, USA.
David
Jason J
JJ
Subramanian
Sukanya V
SV
Liu
Xiaoying
X
Fuerst
Matthew D
MD
Zhao
Xue
X
Leier
Carl V
CV
Orosz
Charles G
CG
Kelm
Robert J
RJ
Strauch
Arthur R
AR
D000005:Abdomen / Q000601:surgery; D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005355:Fibrosis; D005786:Gene Expression Regulation; D006084:Graft Rejection / Q000235:genetics / Q000378:metabolism; D016027:Heart Transplantation; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008822:Mice, Transgenic; D009131:Muscle, Smooth, Vascular / Q000196:embryology / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000235:genetics / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D026362:Serum Response Factor / Q000378:metabolism*; D015398:Signal Transduction; D013312:Stress, Physiological / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D016042:Transplantation, Heterotopic; D020257:Ventricular Remodeling
D000199:Actins; D004268:DNA-Binding Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D026362:Serum Response Factor; D014157:Transcription Factors; C508559:PurA protein, rat; C508560:PurB protein, rat; C121485:Pura protein, mouse; C108770:Purb protein, mouse; C498862:Acta2 protein, rat