Activation of fibroblast procollagen alpha 1(I) transcription by mechanical strain is transforming growth factor-beta-dependent and involves increased binding of CCAAT-binding factor (CBF/NF-Y) at the proximal promoter.
During normal developmental tissue growth and in a number of diseases of the cardiopulmonary system, adventitial and interstitial fibroblasts are subjected to increased mechanical strain. This leads to fibroblast activation and enhanced collagen synthesis, but the underlying mechanisms involved remain poorly understood. In this study, we have begun to identify and characterize mechanical strain-responsive elements in the rat procollagen alpha 1(I) (COL1A1) gene and show that the activity of COL1A1 promoter constructs, transiently transfected into cardiac fibroblasts, was increased between 2- and 4-fold by continuous cyclic mechanical strain. This was accompanied by an approximately 3-fold increase in the levels of total active transforming growth factor-beta (TGF-beta) released into the medium. Inclusion of a pan-specific TGF-beta neutralizing antibody inhibited strain-induced COL1A1 promoter activation. Deletion analysis revealed the presence of two potential strain response regions within the proximal promoter, one of which contains an inverted CCAAT-box overlapping a GC-rich element. Both mechanical strain and exogenously added TGF-beta1 enhanced the binding activity of CCAAT-binding factor, CBF/NF-Y, at this site. Moreover, this element was sufficient to confer strain-responsiveness to an otherwise unresponsive SV40 promoter. In summary, this study demonstrates that strain-induced COL1A1 promoter activation in cardiac fibroblasts is TGF-beta-dependent and involves increased binding of CCAAT-binding factor at the proximal promoter. Furthermore, these findings suggest a novel and potentially important TGF-beta response element in the rat COL1A1 gene.
Lindahl
Gisela E
GE
Centre for Cardiopulmonary Biochemistry and Respiratory Medicine, Department of Medicine, Royal Free and University College Medical School, The Rayne Institute, 5 University Street, London WC1E 6JJ, United Kingdom. g.lindahl@ucl.ac.uk
Chambers
Rachel C
RC
Papakrivopoulou
Jenny
J
Dawson
Sally J
SJ
Jacobsen
Marianne C
MC
Bishop
Jill E
JE
Laurent
Geoffrey J
GJ
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D023081:CCAAT-Binding Factor / Q000378:metabolism*; D002478:Cells, Cultured; D003094:Collagen / Q000235:genetics*; D024042:Collagen Type I / Q000235:genetics*; D000090602:Collagen Type I, alpha 1 Chain; D016384:Consensus Sequence; D017077:Culture Media, Conditioned; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006321:Heart / Q000196:embryology / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D023081:CCAAT-Binding Factor; D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D017077:Culture Media, Conditioned; D016212:Transforming Growth Factor beta; D003094:Collagen