DNA binding proteins from keloid fibroblasts form unique complexes with the human fibronectin promoter

Keloids are pathological lesions characterized by enhanced expression of extracellular matrix molecules including fibronectin. A molecular dissection of the human fibronectin promoter was performed to identify DNA-protein interactions that correlate with altered fibronectin gene expression by keloid fibroblasts. DNA mobility shift patterns generated by nuclear extracts from skin, scar, and keloid fibroblasts were identical at a consensus CRE at -170 of the human fibronectin promoter whereas extracts from keloid fibroblasts formed complexes at a CRE/AP-1-like sequence at -415 that differed from those generated by skin and scar fibroblast extracts. The DNA-protein interactions identified at -415 were sensitive to altered serum concentrations in skin and scar but not keloid fibroblast cultures. The effects of forskolin and TGF-beta on fibronectin expression correlated with changes in the DNA-protein complexes assembled on the -170 and -415 cis elements, respectively. Oligonucleotides containing consensus CRE and AP-1 sequences did not compete for binding of nuclear proteins to the CRE/AP-1-like domain at -415, suggesting that this is a unique cis element. These studies indicate that the human fibronectin promoter contains two cis elements on which related but nonidentical complexes form. Alterations in the complexes interacting with the sequence at -415 may be responsible for the differences in fibronectin gene expression among quiescent skin, mature scar, and keloid fibroblasts.