Effects of histone acetylation on the solubility and folding of the chromatin fiber

The folding ability of chromatin fractions containing approximately identic al nucleosome numbers and the same linker histone composition, but with dif ferent extents of core histone acetylation, were analyzed by analytical ult racentrifugation. It was found that the acetylated fractions consistently e xhibited a relatively small but significantly lower extent of compaction th an that of their native nonacetylated counterparts. This was regardless of the extent of the size distribution heterogeneity of the fractions analyzed . Furthermore the acetylated chromatin fibers exhibited an enhanced solubil ity in both NaCl and MgCl2, which is neither the result of a differential b inding affinity of the linker histones to chromatin nor of an alteration in the relative amounts of the histone H1 variants.