The human beta-globin locus control region (LCR) controls expression of the beta-globin gene family. It consists of four erythroid-cell-specific DNase I hypersensitive sites, HS1-4. DNAse I HS sites are thought to represent nucleosome-free regions of DNA which are available to trans-acting factors. NF-E2 binds two tandem AP1-like sites in HS2 which form the core of its enhancer activity. Interaction of NF-E2 with HS2 allows a second erythroid factor, GATA-1, to bind its nearby sites.