Relationship between core histone acetylation and histone H1(0) gene activity.

In this study we show a striking correlation between histone H1(0) gene expression and histone acetylation. Trichostatin A, a highly specific inhibitor of histone deacetylase, efficiently induces H1(0) gene expression. Moreover, using a cell line sensitive to trichostatin A (FM3A) and a derived cell line selected for its resistance to this inhibitor (TR303), it is shown that the level of H1(0) gene expression is related to the extent of chromatin acetylation. After showing the S-phase-dependent activation of H1(0) gene expression, we demonstrate that hyperacetylation has a dominant effect on H1(0) gene expression, since it enhances the expression of the gene independent of the position of cells in the cell cycle. This response to deacetylase inhibitors is specific to H1(0), since it is not shared by other cell-cycle-dependent histone genes (H1 and H4). Finally, by transfection of trichostatin-A-resistant and trichostatin-A-sensitive cells with a plasmid containing a H1(0) promoter, we show that the exogenous H1(0) promoter is also highly sensitive to trichostatin A treatment and that activation of transcription follows exactly the same pattern as activation of the endogenous gene. These data show that histone acetylation may be used to modulate H1(0) gene activity and offers insight into a possible mechanism in which the developmentally regulated chromatin acetylation acts to potentiate H1(0) gene expression.