Nucleosome positioning and inducible MNase hypersensitivity within the IL-12(p35) promoter. (A) THP-1 cells were either incubated with medium alone or stimulated with LPS (1 μg/mL) and IFN-γ (100 U/mL) for 4 hours. Nuclei were purified and digested with increasing concentrations of MNase, ranging from 0.015 to 0.12 U/mL. The major MNase-hypersensitive site is indicated by a gray box. Other MNase cutting sites are marked by arrowheads. Increase in MNase hypersensitivity on LPS/IFN-γ stimulation is indicated by a black extension of the gray box. (B) As a control, purified genomic DNA from THP-1 cells was digested in vitro with increasing concentrations of MNase (ranging from 0.00078 to 0.05 U/mL).