Abstract
We investigated the contribution of epigenetic mechanisms in MHC2TA transcriptional silencing in uveal melanoma. Although no correlation was observed between impaired CIITA transcript levels after IFN-gamma induction and DNA methylation of MHC2TA promoter IV (CIITA-PIV), an association was found with high levels of trimethylated histone H3-lysine 27 (3Me-K27-H3) in CIITA-PIV chromatin. The 3Me-K27-H3 modification correlated with a strong reduction in RNA polymerase II-recruitment to CIITA-PIV. Interestingly, we observed that none of these epigenetic modifications affected recruitment of activating transcription factors to this promoter. Subsequently, we demonstrated the presence of the histone methyltransferase EZH2 in CIITA-PIV chromatin, which is known to be a component of the Polycomb repressive complex 2 and able to triple methylate histone H3-lysine 27. RNA interference-mediated down-regulation of EZH2 expression resulted in an increase in CIITA transcript levels after IFN-gamma induction. Our data therefore reveal that EZH2 contributes to silencing of IFN-gamma-inducible transcription of MHC2TA in uveal melanoma cells.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Base Sequence
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Cell Line, Tumor
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DNA-Binding Proteins / physiology*
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Enhancer of Zeste Homolog 2 Protein
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Gene Expression Regulation, Neoplastic / immunology*
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Gene Silencing / immunology
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Histocompatibility Antigens Class II / biosynthesis*
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Histocompatibility Antigens Class II / genetics*
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Humans
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Interferon-gamma / physiology*
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Melanoma / genetics
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Melanoma / immunology*
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Melanoma / metabolism
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Molecular Sequence Data
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Nuclear Proteins / antagonists & inhibitors*
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Nuclear Proteins / biosynthesis
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Nuclear Proteins / genetics
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Polycomb Repressive Complex 2
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Promoter Regions, Genetic / immunology
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RNA Interference / immunology
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Trans-Activators / antagonists & inhibitors*
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Trans-Activators / biosynthesis
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Trans-Activators / genetics
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Transcription Factors / physiology*
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Transcription, Genetic / immunology
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Uveal Neoplasms / genetics
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Uveal Neoplasms / immunology*
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Uveal Neoplasms / metabolism
Substances
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DNA-Binding Proteins
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Histocompatibility Antigens Class II
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MHC class II transactivator protein
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Nuclear Proteins
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Trans-Activators
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Transcription Factors
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Interferon-gamma
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EZH2 protein, human
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Enhancer of Zeste Homolog 2 Protein
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Polycomb Repressive Complex 2