HISTONE ACETYLTRANSFERASE IS ASSOCIATED WITH THE NUCLEAR MATRIX

Only a small fraction of the adult chicken erythrocyte histones is inv olved in dynamic acetylation. me have reported previously that the rap idly acetylated and deacetylated H4 histones are primarily associated with the transcriptionally active DNA-enriched chromatin fragments tha t remain attached to the residual nuclear material following micrococc al nuclease digestion and chromatin solubilization. Furthermore, this nuclear fraction contained most of the histone deacetylase activity. I n this study we show that the bulk of the nuclear histone acetyltransf erase activity is located with the insoluble residual nuclear material . We demonstrate that in vitro the enzymes associated with the residua l nuclear material catalyze reversible acetylation when the endogenous histones of the nuclear skeleton-bound chromatin fragments are used a s substrate. Nuclear matrices isolated from adult chicken immature ery throcyte and trout liver nuclei had 60-76% of the nuclear histone acet yltransferase activity. Procedures that solubilized the internal nucle ar matrix also resulted in the release of the enzyme from the nuclear matrix. Together, our observations suggest that histone acetyltransfer ase and deacetylase are associated with the internal nuclear matrix, a nd one of the functions of these enzymes may be to mediate a dynamic a ttachment between transcriptionally active chromatin and the nuclear m atrix.