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Nucleosome positioning on the chromatin strand plays a critical role in regulating accessibility of DNA to transcription factors and chromatin modifying enzymes. Hence, detailed information on nucleosome depletion or movement at cis -acting regulatory elements has the potential to identify predicted binding sites for trans -acting factors. Using a novel method based on enrichment of mononucleosomal DNA by bacterial artificial chromosome hybridization, we mapped nucleosome positions by deep sequencing across 250 kb, encompassing the cystic fibrosis transmembrane conductance regulator ( CFTR ) gene. CFTR shows tight tissue-specific regulation of expression, which is largely determined by cis -regulatory elements that lie outside the gene promoter. Although multiple elements are known, the repertoire of transcription factors …