Model for the chromatin organization within the human IL-12(p35) promoter region. A tentative assignment of nucleosome positions in this region based on nuclease digestion is shown and aligned with the nuclease-hypersensitive sites. Sites of cutting by DNase I and MNase are depicted by solid bars for basal conditions. Because MNase preferentially digests DNA in linker regions between nucleosomes, it is possible to locate nucleosomes within the p35 region. The DNA domain between nuc-2 and nuc-3 is strongly hypersensitive to DNase I and MNase cleavage. It is therefore likely to represent a nucleosome-free region. Empty boxes indicate increase in DNase I and MNase hypersensitivities on LPS/IFN-γ stimulation. The 4 arrows refer to the cutting sites of BstXI (nt –298), AlwNI (nt –256), BanI (nt –185), and SmaI (nt –178), which become more accessible on activation. Taken together, these results strongly suggest that nuc-2 (black circle) is selectively remodeled on p35 transcriptional activation.