Abstract
Transcriptional activation of the major histocompatibility complex (MHC) by IFNgamma is a key step in cell-mediated immunity. At an early stage of IFNgamma induction, chromatin carrying the entire MHC locus loops out from the chromosome 6 territory. We show here that JAK/STAT signalling triggers this higher-order chromatin remodelling and the entire MHC locus becomes decondensed prior to transcriptional activation of the classical HLA class II genes. A single point mutation of STAT1 that prevents phosphorylation is sufficient to abolish chromatin remodelling, thus establishing a direct link between the JAK/STAT signalling pathway and human chromatin architecture. The onset of chromatin remodelling corresponds with the binding of activated STAT1 and the chromatin remodelling enzyme BRG1 at specific sites within the MHC, and is followed by RNA-polymerase recruitment and histone hyperacetylation. We propose that the higher-order chromatin remodelling of the MHC locus is an essential step to generate a transcriptionally permissive chromatin environment for subsequent activation of classical HLA genes.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Acetylation / drug effects
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Antiviral Agents / pharmacology*
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Cell Line, Tumor
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Chromatin Assembly and Disassembly / drug effects
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Chromatin Assembly and Disassembly / physiology*
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DNA Helicases / genetics
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DNA Helicases / immunology
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DNA Helicases / metabolism
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Histones / genetics
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Histones / immunology
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Histones / metabolism
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Humans
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Immunity, Cellular / drug effects
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Immunity, Cellular / physiology
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Interferon-gamma / pharmacology*
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Major Histocompatibility Complex / drug effects
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Major Histocompatibility Complex / physiology*
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Nuclear Proteins / genetics
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Nuclear Proteins / immunology
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Nuclear Proteins / metabolism
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Phosphorylation / drug effects
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Protein Processing, Post-Translational / drug effects
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Protein Processing, Post-Translational / physiology*
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Quantitative Trait Loci / drug effects
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Quantitative Trait Loci / physiology
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STAT1 Transcription Factor / genetics
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STAT1 Transcription Factor / immunology
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STAT1 Transcription Factor / metabolism*
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Signal Transduction / drug effects
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Signal Transduction / physiology*
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Transcription Factors / genetics
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Transcription Factors / immunology
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Transcription Factors / metabolism
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Transcription, Genetic / drug effects
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Transcription, Genetic / physiology
Substances
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Antiviral Agents
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Histones
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Nuclear Proteins
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STAT1 Transcription Factor
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STAT1 protein, human
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Transcription Factors
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Interferon-gamma
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SMARCA4 protein, human
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DNA Helicases