Patterns of histone acetylation in Physarum polycephalum. H2A and H2B acetylation is functionally distinct from H3 and H4 acetylation.

Histone acetylation has previously been correlated with both chromosome replication and transcription. We present evidence that (a) confirms both correlations in the true slime mold, Physarum polycephalum and (b) shows that quite a different pattern of acetate turnover is associated with replication compared with transcription. The pattern associated with replication involves turnover of acetate on all four core histones on species containing one or two acetates per molecule. This pattern was resolved from the transcription-associated pattern by three different procedures: (a) detailed analysis of gels of histones pulse-labelled with acetate; (b) the pattern of acetylation of histones pulse-labelled with [3H]lysine; and (c) the pattern of acetylation of soluble histones. The pattern associated with transcription is restricted to histones H3 and H4 and occurs mostly on highly acetylated species. This pattern was resolved by (a) analysis of gels of histones pulse-labelled with acetate; (b) the pattern of histone acetylation in G2 phase of the cell cycle; and (c) the pattern of histone acetylation in the presence of cycloheximide.