Evidence of altered histone interactions, as investigated by removal of histones, in chromatin isolated from rat liver nuclei by a conventional method.

It is shown that the release of the slightly lysine-rich histones f2a2 and f2b by 0.4 M ammonium sulfate from conventionally isolated chromatin is diminished in comparison to the lysed nuclei. The change in extractability is further demonstrated by the application of ethidium bromide. At a molar input ratio of 0.09 (moles ethidium bromide/moles nucleotide) and 0.4 M ammonium sulfate the slightly lysine-rich histones are released from the chromatin to 70 - 80% if the lysed nuclei are used. At 0.1 M ammonium sulfate ethidium bromide effected also a release of 50 % of histone f1. Comparable effects could not be observed with chromatin prepared in a conventional way but instead a tendency towards loss of histone f3 in the presence of ethidium bromide was observed.