The forkhead box A transcription factors, FOXA1 and FOXA2, function as pioneer factors to open condensed chromatin and facilitate binding of other proteins. We showed previously that these factors are key components of a transcriptional network that drives enhancer function at the cystic fibrosis transmembrane conductance regulator (CFTR) locus in intestinal epithelial cells. The CFTR promoter apparently lacks tissue-specific regulatory elements and expression of the gene is controlled by multiple cis-acting elements, which coordinate gene expression in different cell types. Here we show that concurrent depletion of FOXA1 and FOXA2 represses CFTR expression and alters the three-dimensional architecture of the active locus by diminishing interactions between the promoter and intronic cis-acting elements. Reduction of FOXA1/A2 also modifies the enrichment profile of the active enhancer marks H3K27ac and H3K4me2 across the CFTR locus and alters chromatin accessibility at individual cis-elements. Moreover, loss of FOXA1/A2 suppresses the recruitment of other members of the transcriptional network including HNF1 and CDX2, to multiple cis-elements. These data reveal a complex molecular mechanism underlying the role of FOXA1/A2 in achieving high levels of CFTR expression in intestinal epithelial cells.
Keywords: CFTR; FOXA; chromatin remodeling; pioneer factor; transcriptional network.