Nucleosome eviction or destabilization at promoters and enhancers results from the binding of specific regulatory factors responsible for transcriptional activation in eukaryotes [19, 20]. Open or accessible regions of the genome are, thus, regarded as the primary positions for regulatory elements [21] and have been historically characterized by nuclease hypersensitivity in vivo[22]. Notably, changes in chromatin structure have been implicated with many aspects of human health, as a result of mutations in chromatin remodelers that affect nucleosome positioning [23–25]. Therefore, current interest is placed on collecting and comparing genome-wide chromatin accessibility, to locate instrumental epigenetic changes that accompany cell differentiation, environmental signaling and disease development. Large collaborative projects such as ENCODE [26] have become part of this major effort.
