Interaction of daunomycin with acetylated chromatin.

Anthracyclines are powerful chemotherapeutic agents for the treatment of many cancers. In many instances, they are currently used in combination with histone deacetylase inhibitors in order to enhance their efficiency. Not surprisingly and as part of their mode of action, these drugs interfere with gene expression, a process that has long been known to be mediated by histone acetylation. In this paper, we use analytical ultracentrifuge analysis, equilibrium dialysis, and circular dichroism to characterize the role of histone acetylation on the binding of antharcyclines to chromatin. We show that histone acetylation enhances the daunomycin-induced DNA dissociation from nucleosomes and decreases the extent of aggregation that results from the interaction in a way that is modulated by the presence or absence of linker histones. Histone acetylation increases the binding affinity of daunomycin by chromatin. Furthermore, the binding of anthracycline to acetylated chromatin sheds additional light into the conformational chromatin alterations resulting from core histone acetylation.