Role of Sp1 in the induction of p27 gene expression in vascular smooth muscle cells in vitro and after balloon angioplasty.
-The abnormal proliferation of vascular smooth muscle cells (VSMCs) plays an important role in atherosclerosis and restenosis. Although several studies have implicated the growth inhibitory protein p27(Kip1) (p27) in the control of myocyte growth and hypertrophy, little is known about the molecular mechanisms that regulate p27 expression in the cardiovascular system. In the present study, we demonstrate the interaction of the transcription factor Sp1 with 2 GC-rich sequences within the p27 promoter in cultured VSMCs. Importantly, point mutations that disrupted Sp1 binding markedly reduced p27 promoter activity, demonstrating that Sp1 is required for efficient p27 gene transcription in cultured VSMCs. Because p27 expression is upregulated after balloon angioplasty, we investigated Sp1 expression and activity in control and balloon-injured rat carotid arteries to assess the role of Sp1 as a physiological regulator of p27 expression. Although immunohistochemical analysis disclosed Sp1 protein expression in both control and balloon-injured arteries, a high level of Sp1 DNA-binding activity was found only in response to balloon angioplasty. Collectively, these results demonstrate that Sp1 is essential for maximum p27 promoter activity in VSMCs and suggest that posttranslational induction of Sp1 DNA-binding activity contributes to the induction of p27 expression and VSMC growth arrest at late time points after balloon angioplasty.
Unit of Vascular Biology, Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Científicas, Valencia, Spain. vandres@ibv.csic.es
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V
Andrés
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J
Ureña
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E
Poch
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Chen
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D
Goukassian
D000800:Angioplasty, Balloon; D000818:Animals; D001665:Binding Sites; D002339:Carotid Arteries / Q000378:metabolism; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004247:DNA / Q000235:genetics / Q000378:metabolism; D020862:GC Rich Sequence / Q000235:genetics; D005786:Gene Expression Regulation; D008297:Male; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D016329:Sp1 Transcription Factor / Q000378:metabolism* / Q000502:physiology; D025521:Tumor Suppressor Proteins
C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004247:DNA