Hypomethylation of the interferon‐γ gene correlates with its expression by primary T‐lineage cells

Abstract

To determine the potential role of methylation in the regulation of interferon-gamma (IFN-gamma) gene transcription by T cells, primary T-lineage cell populations were analyzed for the extent of methylation of three CpG sites within or near transcriptional activator elements in the 5' flank and first intron of the human IFN-gamma gene. A striking correlation was observed between the capacity of the IFN-gamma gene to be expressed and the degree of hypomethylation. The IFN-gamma gene was virtually completely methylated at all sites in thymocytes, neonatal T cells, and adult CD45RAhiCD45R0lo (antigenically naive) CD4 T cells, cell types that all have a low or undetectable capacity to express the IFN-gamma gene. In contrast, there was substantial hypomethylation in T-lineage cell types with relatively high capacities to express the IFN-gamma gene, including adult CD8 T cells and adult CD45RAloCD45R0hi (memory/effector) CD4 T cells. These results suggest that hypomethylation of the IFN-gamma genetic locus may be an important determinant of IFN-gamma gene expression in vivo by T-lineage cells.

Differential Patterns of Methylation of the IFN-γ Promoter at CpG and Non-CpG Sites Underlie Differences in IFN-γ Gene Expression Between Human Neonatal and Adult CD45RO− T Cells

“…Previous studies using methylation-sensitive restriction mapping have investigated the status of the Ϫ54 CpG site in human CD4 ϩ and CD8 ϩ T cells (18,23). We have extended these studies by the use of a sensitive bisulfite sequencing technique that allows measurement of methylated cytosine in any context over a DNA region of interest.…”

“…Sequencing of 500 ng plasmid DNA was performed with T7 primer (5Ј-TAA TAC GAC TCA CTA TAG GG) and BigDye Terminator Ready Reaction Mix (PE Applied Biosystems, Foster City, CA) according to the manufacturer's instructions, except that the cycle-sequencing PCR parameters were varied to compensate for AT-rich bisulfite-treated DNA using an annealing temperature of 45°C and extension at 55°C. (18,23), and, conversely, a hypermethylated IFN-␥ promoter can disrupt nuclear factor binding (17,24). The positions of CpG sites that, when methylated, may be potentially disruptive to nuclear factor binding are identified in Fig.…”

“…Of particular interest here are earlier investigations that used methylation-sensitive restriction mapping to identify the methylation status of a single SnaBI site in the proximal IFN-␥ promoter in adult human CD4 ϩ and CD8 ϩ cells (18). In addition, treatment of human neonatal naive T cells with 5-aza-2Ј-deoxycytidine was shown to markedly up-regulate their capacity to produce IFN-␥ (19).…”

Nature versus nurture in T cell cytokine production

“…Several other reports have shown that epigenetic mechanisms involving DNA methylation and/or chromatin conformation are key features of IFN-␥, IL-2, IL-3, and IL-4 expression in T cells [53][54][55][56][57][58][59]. In the case of the IL-2 and IL-4 genes, epigenetic mechanisms may allow differential regulation of individual alleles of the same cytokine gene in single T cells [60][61][62][63].…”

An IFNG SNP with an estrogen-like response element selectively enhances promoter expression in peripheral but not lamina propria T cells

“…11,[13][14][15]22 Studies by other groups have indicated that regulation of IFN-g gene expression in primary T cells differs from that observed in tumor T-cell lines, and likewise, differs in naïve compared to memory T-cell subsets. [23][24][25] Differential cytokine gene regulation may be controlled, in part, Novel ERE-like cis-element in IFNG promoter R Gonsky et al by DNA methylation patterns. The increased IFN-g expression in Th0 or Th1, compared to Th2, cells is correlated with the hypomethylated status of IFNG.…”