Histone deacetylase inhibitors induce apoptosis in peripheral blood lymphocytes along with histone H4 acetylation and the expression of the linker histone variant, H1 degrees.

The results of this study show that H1 degrees can be induced by sodium butyrate and trichostatin A in peripheral blood lymphocytes, a cell system which does not normally express this linker histone variant. Moreover, this induced expression was found to be correlated in a dose-dependent manner with the concomitant induction of apoptosis and increased levels of histone H4 acetylation. Sodium butyrate and trichostatin A, both inhibitors of histone deacetylases, are known to induce terminal differentiation and at the same time the induction of the linker histone variant, H1 degrees, in a number of tissue/cell systems. Moreover, aside from induced expression by histone deacetylase inhibitors, H1 degrees gene expression has also been tightly associated with the process of terminal differentiation in many physiological tissue/cell systems. The concomitant induction of H1 degrees expression along with apoptosis and histone acetylation in the same cell system has not been previously reported. Histone acetylation is known to be involved in chromatin remodelling events. Such events also occur during apoptosis. The association of H1 degrees gene expression with apoptosis, and not with differentiation in these cells, leads to more general implications as to a potential functional role of H1 degrees during chromatin remodelling.