Analysis of DNase-I-hypersensitive sites at the 3′ end of the cystic fibrosis transmembrane conductance regulator gene (CFTR)

The cystic fibrosis transmembrane conductance regulator gene (CFTR) exhibits a complex pattern of expression that shows temporal and spatial regulation, although the control mechanisms are not fully known, We have mapped DNase-I-hypersensitive sites (DHSs) flanking the CFTR gene with the aim of identifying potential regulatory elements. We previously characterized DHSs at -79.5 and -20.9 kb with respect to the CFTR translational start site and a regulatory element in the first intron of the gene at 185+10 kb. We have now mapped five DHSs lying 3' to the CFTR gene at 4574 + 5.4, + 6.8, + 7.0, + 7.4 and + 15.6 kb that show some degree of tissue specificity. The DHSs are seen in chromatin extracted from human primary epithelial cells and cell lines; the presence of the + 15.6 kb site is tissue-specific in transgenic mice carrying a human CFTR yeast artificial chromosome. Further analysis of the 4574+15.6 kb DHS implicates the involvement of CCAAT-enhancer-binding protein (C/EBP), cAMP-response-element-binding protein (CREB)/activating transcription factor (ATF) and activator protein 1 (AP-1) family transcription factors at this regulatory element.