Induction of human γ globin gene expression by histone deacetylase inhibitors

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Abstract
We investigated the induction of human γ globin gene activity by 3 classes of histone deacetylase inhibitors: amide analogues of trichostatin A, hydroxamic acid analogues of trapoxin, and scriptaid and its analogues. The screening consisted of measuring the effects of these compounds on γ and β human gene promoter activity by using cultures of GM979 cells stably transfected with a construct containing a γ promoter linked to firefly luciferase and a β promoter linked to renilla luciferase. Compounds belonging to all 3 classes induced γ gene promoter activity in the screening assay in low micromolar concentrations. Histone deacetylase (HDAC) inhibitors increased acetylation of histone H4 and induced the expression of endogenous murine embryonic genes. They also increased the levels of γ mRNA and the frequency of fetal hemoglobin-containing erythroblasts in erythroid burst-forming unit (BFUe) cultures from healthy adult individuals. Compounds that displayed very similar degrees of inhibition of the HDAC activity in an HDAC enzymatic assay differed strikingly on their effects on γ gene promoter activity, raising the possibility of selectivity of HDACs that interact with the γ globin gene chromatin.