Effects of histone acetylation on nucleosome properties as evaluated by polyacrylamide gel electrophoresis and hydroxylapatite dissociation chromatography.

The release of acetylated histones from chick oviduct chromatin was analyzed by hydroxylapatite column chromatography. By raising of the NaCl concentration, acetylated histones were eluted from hydroxylapatite-bound chromatin depending on their release from nucleosomal DNA. Electrophoresis on acid-urea gel showed that hyperacetylated forms of histone H4 were eluted at a lower NaCl concentration than non-acetylated or hypoacetylated H4, suggesting that hyperacetylated H4 has decreased stability in nucleosomes. However, under milder ionic conditions which do not induce dissociation between histones and DNA, polyacrylamide gel electrophoresis of purified nucleosome cores showed no evidence for their unfolding or for increased accessibility by high mobility group protein-17.