Different signaling pathways inhibit DNA methylation activity and up-regulate IFN-γ in human lymphocytes

DNA methylation is recognized increasingly for its prominent role in controlling diverse immune processes. In this study, we show that in Jurkat T cells and fresh peripheral lymphocytes, short-time incubation with protein kinase C activators or phosphatase inhibitors down-regulate DNA methylation activity in a dose-dependent manner. This inhibition correlates with the induction of the interferon-gamma (IFN-gamma) gene, which contains several CG sequences in its promoter. The expression of mRNA and protein of the different DNA methyltransferases did not decrease after the treatment. In addition, sulfydryl reagents have a strong inhibitory effect on DNA methylation activity and also induce IFN-gamma gene expression, thus suggesting a link between both effects.