Aire, guardian of immunological tolerance, binds to and activates super-enhancers [expression]
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE92509 | GEO | 2017/01/22
SECONDARY ACCESSION(S): PRJNA357834
REPOSITORIES: GEO
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Project description:Aire, guardian of immunological tolerance, binds to and activates super-enhancers
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Project description:Aire is a transcription factor that controls T cell tolerance by inducing the expression of a large repertoire of genes specifically in thymic stromal cells. It interacts with scores of protein partners of diverse functional classes. We found that Aire and some of its partners, notably those implicated in the DNA-damage response, preferentially localized to and activated long chromatin stretches that were overloaded with transcriptional regulators, known as super-enhancers. We also identified topoisomerase 1 as a cardinal Aire partner that colocalized on super-enhancers and was required for the interaction of Aire with all of its other associates. We propose a model that entails looping of super-enhancers to efficiently deliver Aire-containing complexes to local and distal transcriptional start sites.
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Project description:Autoimmune regulator (Aire) is a unique transcriptional regulator that induces promiscuous expression of thousands of tissue-restricted antigens (TRAs) in medullary thymic epithelial cells (mTECs), a step critical for induction of immunological self-tolerance. Although several recent studies provided very important molecular insights into how Aire operates, a more comprehensive understanding of this process still remains elusive. Here we demonstrate that a lysine deacetylase Sirtuin-1 (Sirt1) is predominantly expressed in mature Aire+ mTECs, where it is required for expression of Aire-dependent TRA genes and a subsequent induction of immunological self-tolerance. Our study elucidates a previously unknown molecular mechanism for Aire-mediated transcriptional regulation and uncovers a unique functional role for Sirt1 in preventing organ-specific autoimmunity. ~100ng of total RNA isolated by Trizol extraction from MHC-II low and high mTECs (pool of 3 mice) was used to generate poly-A-selected transcriptome libraries using the non-directionnal TruSeq V3 RNA Sample Prep Kit (without additional pre-amplification) following the manufacturer's protocols. Enrichment of DNA fragment with adapter molecules on both ends was done using 15 cycles of PCR amplification using the Illumina PCR mix and primer cocktail. Paired-end (2 × 100 bp) sequencing was performed using the Illumina HiSeq2000 machine.
2015-05-25 | E-GEOD-68190 | biostudies-arrayexpress
Project description:Super-enhancers (SEs), which consist of multiple enhancer elements, are occupied by master transcription factors and co-activators, such as Mediator, and are highly acetylated at histone H3K27. Here, we have characterized the SEs in terms of DNase I hypersensitive sites (DHSs) by analyzing publicly available chromatin immunoprecipitation (ChIP)-seq and DNase-seq data of K562 cells and compared with the DHSs in typical enhancers (TEs). DHSs in the SEs were highly marked by histone H3K4me1 than DHSs in TEs. Loss of H3K4me1 by the deletion of catalytic domains in histone methyltransferases MLL3 and MLL4 remarkably decreased histone H3K27ac and histone H3 depletion at SE DHSs than at TE DHSs. The levels of enhancer RNA (eRNA) transcripts and mRNA transcripts from the putative target genes were notably reduced at and near SE DHSs than TE DHSs following H3K4me1 loss. These results indicate that histone H3K4me1 is a marker for DHSs in SEs and that this modification has a more significant impact on the activation of SE DHSs than TE DHSs.
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Project description:Autoimmune regulator (Aire) is a unique transcriptional regulator that induces promiscuous expression of thousands of tissue-restricted antigens (TRAs) in medullary thymic epithelial cells (mTECs), a step critical for induction of immunological self-tolerance. Although several recent studies provided very important molecular insights into how Aire operates, a more comprehensive understanding of this process still remains elusive. Here we demonstrate that a lysine deacetylase Sirtuin-1 (Sirt1) is predominantly expressed in mature Aire+ mTECs, where it is required for expression of Aire-dependent TRA genes and a subsequent induction of immunological self-tolerance. Our study elucidates a previously unknown molecular mechanism for Aire-mediated transcriptional regulation and uncovers a unique functional role for Sirt1 in preventing organ-specific autoimmunity.
2015-05-25 | GSE68190 | GEO
Project description:Non-coding segments of the human genome are enriched in cis-regulatory modules that constitute functional elements, such as transcriptional enhancers and Super-enhancers. A hallmark of cancer pathogenesis is the dramatic dysregulation of the "archetype" gene expression profiles of normal human cells. Genomic variations can promote such deficiencies when occurring across enhancers and Super-enhancers, since they affect their mechanistic principles, their functional capacity and specificity, and the epigenomic features of the chromatin microenvironment across which these regulatory elements reside. Here, we comprehensively describe: fundamental mechanisms of gene expression dysregulation in cancers that involve genomic abnormalities within enhancers' and Super-enhancers' (SEs) sequences, which alter the expression of oncogenic transcription factors (TFs); cutting-edge technologies applied for the analysis of variation-enriched hotspots of the cancer genome; and pharmacological approaches for the treatment of Super-enhancers' aberrant function. Finally, we provide an intratumor meta-analysis, which highlights that genomic variations in transcription-factor-driven tumors are accompanied overexpression of genes, a portion of which encodes for additional cancer-related transcription factors.
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Project description:Aire induces ectopic expression of peripheral tissue antigens (PTAs) in thymic medullary epithelial cells, which promotes immunological tolerance. Beginning with a broad screen of histone peptides, we demonstrate that the mechanism by which this single factor controls the transcription of thousands of genes involves recognition of the amino-terminal tail of histone H3, but not of other histones, by one of Aire's plant homeodomain (PHD) fingers. Certain posttranslational modifications of H3 tails, notably dimethylation or trimethylation at H3K4, abrogated binding by Aire, whereas others were tolerated. Similar PHD finger-H3 tail-binding properties were recently reported for BRAF-histone deacetylase complex 80 and DNA methyltransferase 3L; sequence alignment, molecular modeling, and biochemical analyses showed these factors and Aire to have structure-function relationships in common. In addition, certain PHD1 mutations underlying the polyendocrine disorder autoimmune polyendocrinopathy-candidiases-ectodermaldystrophy compromised Aire recognition of H3. In vitro binding assays demonstrated direct physical interaction between Aire and nucleosomes, which was in part buttressed by its affinity to DNA. In vivo Aire interactions with chromosomal regions depleted of H3K4me3 were dependent on its H3 tail-binding activity, and this binding was necessary but not sufficient for the up-regulation of genes encoding PTAs. Thus, Aire's activity as a histone-binding module mediates the thymic display of PTAs that promotes self-tolerance and prevents organ-specific autoimmunity.
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