T-bet antagonizes mSin3a recruitment and transactivates a fully methylated IFN-gamma promoter via a conserved T-box half-site.

Tong Y, Aune T, Boothby M
Proc Natl Acad Sci U S A. 2005 102 (6): 2034-9

PMID: 15684083 · PMCID: PMC548570 · DOI:10.1073/pnas.0409510102

Promoter DNA methylation is a major epigenetic mechanism for silencing genes and establishing commitment in cells differentiating from their precursors. The transcription factor T-bet is a key determinant of IFN-gamma gene expression in helper T cells, but the mechanisms by which it achieves this effect are not clear. It is shown here that T-bet binds to a highly conserved T-box half-site in the IFN-gamma promoter, is recruited to the endogenous IFN-gamma promoter in T lymphoid cells, and transactivates gene expression through this sequence in a manner dependent on consensus T-box residues. This conserved promoter site is methylated in a model T cell line, and enforced T-bet expression did not alter its complete methylation. T-bet transactivated the conserved core promoter in transfection assays and collaborated functionally with C/EBPbeta despite methylation of the conserved element. Importantly, enforced T-bet expression led to dissociation of the mSin3a corepressor from the endogenous, chromatinized IFN-gamma promoter without decreasing loading of the methyl-CpG binding protein MeCP2. These data indicate that T-bet can override repressive epigenetic modification by a mechanism in which this master regulator acts through a T-box half-site to enforce the activation of IFN-gamma gene expression in part by decreased loading of a corepressor on methylated DNA.

MeSH Terms (16)

Binding Sites CCAAT-Enhancer-Binding Proteins Chromosomal Proteins, Non-Histone DNA-Binding Proteins DNA Methylation Epigenesis, Genetic Humans Interferon-gamma Jurkat Cells Methyl-CpG-Binding Protein 2 Promoter Regions, Genetic Repressor Proteins Sin3 Histone Deacetylase and Corepressor Complex T-Box Domain Proteins Transcriptional Activation Transcription Factors

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