FIG. 8.

Binding of five GAL4-AH molecules does not substantially affect the histone NH₂ tail-DNA interactions in reconstituted particle preparations containing either hypoacetylated or hyperacetylated histones. (A) ³²P-labeled hypoacetylated 150-bp (I) and 180-bp (II) DNA particles containing or not containing five GAL4-AH molecules were laser irradiated at identical doses, and the covalent complexes containing individual cross-linked histones were immunoprecipitated with specific antihistone antibodies (see Materials and Methods for details). The amount of immunoprecipitated DNA was measured by Cerenkov counting. A histogram showing the percentage of immunoprecipitated individual covalent histone-DNA complexes in the presence of five nucleosome-bound GAL4-AH molecules relative to that in the absence of bound GAL-AH is shown. +, presence of five GAL4-AH factors; −, absence of these factors. The results are averaged over three independent experiments with each of the antibodies used. a.u., arbitrary units. (B) Same as panel A but with 180-bp DNA particles reconstituted with either hypoacetylated or hyperacetylated histones. N, particles containing hypoacetylated histones; H, particles containing hyperacetylated histones. The data represent average values from several experiments. For hypoacetylated nucleosomes, six, four, and five independent immunoprecipitations were carried out with antibodies against H2A, H2B, and H4, respectively. The results for hyperacetylated nucleosomes are averaged over three independent experiments with each of the antibodies used.