Histone acetyltransferase is associated with the nuclear matrix.

Only a small fraction of the adult chicken erythrocyte histones is involved in dynamic acetylation. We have reported previously that the rapidly acetylated and deacetylated H4 histones are primarily associated with the transcriptionally active DNA-enriched chromatin fragments that remain attached to the residual nuclear material following micrococcal nuclease digestion and chromatin solubilization. Furthermore, this nuclear fraction contained most of the histone deacetylase activity. In this study we show that the bulk of the nuclear histone acetyltransferase activity is located with the insoluble residual nuclear material. We demonstrate that in vitro the enzymes associated with the residual nuclear material catalyze reversible acetylation when the endogenous histones of the nuclear skeleton-bound chromatin fragments are used as substrate. Nuclear matrices isolated from adult chicken immature erythrocyte and trout liver nuclei had 60-76% of the nuclear histone acetyltransferase activity. Procedures that solubilized the internal nuclear matrix also resulted in the release of the enzyme from the nuclear matrix. Together, our observations suggest that histone acetyltransferase and deacetylase are associated with the internal nuclear matrix, and one of the functions of these enzymes may be to mediate a dynamic attachment between transcriptionally active chromatin and the nuclear matrix.