Intranuclear localization of histone acetylation in Physarum polycephalum and the structure of functionally active chromatin.

Based on studies of histone acetylation in vivo in Physarum polycephalum, we present the following hypotheses: (1) Transcription-specific histone acetylation on histones H3 and H4 is a localized process at the nuclear matrix; (2) Histone acetylation in the S phase, which is specific for newly synthesized histones, occurs in an intranuclear nonlocalized process. These hypotheses can explain: (1) the histone specificity of histone acetylation that is dependent on the functional state of the chromatin; (2) the apparent absence of turnover of histone acetylation in the bulk of the chromatin despite a definite low level of steady-state acetylation of all four core histones in bulk chromatin; (3) the pattern of butyrate-induced hyperacetylation observed for active and inactive chromatin.