DNaseI hypersensitivity in primary erythroid cells. (Top) A portion of the Gata1 locus is shown. Coordinates (below the horizontal line) are in kilobases in respect to the Gata1 IE promoter. The black arrows show the position of mHS−25/6; the gray bar, the position of the probe used in the DNaseI hypersensitive mapping and R1, the position of EcoRI sites. (Below) Nuclei from E14.5 murine fetal liver cells were digested with increasing concentrations of DNaseI (triangle). No exogenous DNaseI was added to nuclei in the first lane. DNA was then extracted and digested with EcoRI and a Southern blot hybridized to the probe shown in the top panel. Size markers on the left are in kilobases. The blot shows 2 DHSs, mHS−25 and mHS−26, and the limited digest (LD).