TGF-beta stimulates collagen (I) in vascular smooth muscle cells via a short element in the proximal collagen promoter.
BACKGROUND
Accumulation of extracellular matrix contributes to the development of intimal hyperplasia. Transforming growth factor beta (TGF-beta) stimulates the production of several matrix proteins in vascular smooth muscle cells (SMC) including type I collagen, but the underlying mechanisms of TGF-beta's effects are not well understood.


METHODS
The effect of TGF-beta on type I collagen biosynthesis was determined by a [3H]proline incorporation assay and Northern blotting. The promoter of human alpha2(I) procollagen (COL1A2) gene was analyzed by transient transfection analysis and gel mobility shift assay.


RESULTS
Treatment of human vascular SMC with TGF-beta stimulated collagen synthesis and increased the level of alpha2(I) collagen mRNA. A collagen-luciferase reporter gene, constructed by linking the human COL1A2 promoter with the firefly luciferase gene, was transiently expressed in human SMC. Treatment with TGF-beta significantly stimulated the activity of this collagen-luciferase reporter. Using deletion analysis, we identified a 150 bp DNA fragment (-334 to -184) in the human COL1A2 promoter as the site through which TGF-beta mediates collagen gene expression in human SMC. Gel mobility shift assays demonstrated that this 150 bp DNA fragment formed conjugates with multiple nuclear factors derived from SMC, a process that was further enhanced by TGF-beta.


CONCLUSIONS
TGF-beta stimulates the human type I collagen gene via a DNA element located in the proximal region of its promoter. Interventions that disrupt interaction between this DNA element and nuclear factors may block the production of collagen in response to TGF-beta and consequently may have a significant effect on the development of intimal hyperplasia.
Kubota
Kenji
K
Department of Surgery, Division of Vascular Surgery, Weill Medical College of Cornell University, New York, New York 10021, USA.
Okazaki
Jin
J
Louie
Otway
O
Kent
K Craig
KC
Liu
Bo
B
D001665:Binding Sites; D015152:Blotting, Northern; D002467:Cell Nucleus / Q000737:chemistry; D002874:Chromosome Mapping; D003094:Collagen / Q000235:genetics*; D024042:Collagen Type I / Q000096:biosynthesis* / Q000235:genetics*; D004247:DNA / Q000378:metabolism; D006801:Humans; D008156:Luciferases / Q000235:genetics; D009131:Muscle, Smooth, Vascular / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D011392:Proline / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000494:pharmacology; D020218:Response Elements; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014316:Tritium
D024042:Collagen Type I; D012333:RNA, Messenger; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D014316:Tritium; D003094:Collagen; D004247:DNA; D011392:Proline; D008156:Luciferases