Identification of an enhancer invlved in tissue-specific regulation of the rat fibronectin gene

Fibronectin (FN) is a widely distributed extracellular matrix protein that is essential for cell adhesion in a variety of biological processes such as wound healing, tissue development and remodelling and oncogenic transformation. Appropriate FN gene in response to specific factors or circumstances in vivo. In order to identify reulatory reions involved in tissue-specific expression of FN, we have examined the transcriptional activity of overlappin framents, within 4kb upstream of the rat FN gene, followin transfection into differetn cell types. Two reions conferred increases in transcription. The region between-1.08 and -2.6 displayed tissue-specificity and was active in fibroblasts but not hepatoma cells. The second region, between -3.2 and -3.9, was active in both cell types. Further characterization of the -1.08 to -2.6 sement demonstrated that it acts as an enhancer. Exonuclease III deletions of the 3′ and 5′ ends of the enhancer localized essential sequences between -1.5 and -1.7 and Indicate that this frament acts in concert with other sites between -1.08 and -2.6 to provided maximum enhacer activity. el mobility shift assays demonstrated fibroblast-specific bindin of nuclear protein(s) to a65 bp frament within the essential reion and DNase I foot printin localized this bindin toa 27 bp sequence. Deletion of the sequence abolished the activity of the 1.5 kb enhancer. These studies show that a novel DNA sequence at -1688 is involved in reulatin transciption of the FN FN ene in fibroblasts.