Project description:Prdm16 is a transcription factor that drives a complete program of brown adipocyte differentiation, but the mechanism by which Prdm16 activates gene transcription remains unknown. Utilizing ChIP-seq teqhnique, we found that Prdm16 binds to chromatin at/near many brown fat-selective genes in BAT. Interestingly, Prdm16-deficiency dramatically reduced the binding of Med1 to Prdm16-target sites. Indeed, Prdm16 binds and recruits Med1 to BAT-enriched genes and the loss of Prdm16 caused a fundamental change in chromatin architecture at key BAT-selective genes and also reduced transcirptional activity. Moreover, Prdm16, through its interaction with Med1, defines and regulates the activity of super-enhancers that drive the expression of cell identity genes. Together, these data demonstrate that Prdm16 drives gene transcription by recruiting Med1 to control chromatin architecture and super-enhancers. Brown adipose tissues were collected from Prdm16 knockout and wiletype 9-month-old mice and ChIP-seq was performed for Prdm16, PolII, Med1, and H3K27ac.
Project description:The autoimmune regulator, AIRE, induces the transcription of thousands of peripheral tissue genes (PTGs) in thymic epithelial cells (TECs) to mediate immunological tolerance. The chromatin state required for optimal AIRE function in TECs and how this state is induced remains unclear. Using RNA-seq and ATAC-seq, we tested the role of the histone acetyltransferase, KAT7 (also known as HBO1 or MYST2), which is essential for acetylation of histone 3 lysine 14 (H3K14), in TEC differentiation, AIRE-mediated PTG expression and thymic tolerance. We find that KAT7 is required for optimal expansion of medullary TEC and has a major role in the expression of AIRE-dependent PTGs, associated with enhanced chromatin accessibility at these gene loci in TECs. Mice with TEC-specific Kat7 deletion develop organ-specific autoimmunity with features resembling those observed in Aire-deficient mice. These findings highlight critical roles for KAT7-mediated acetylation in promoting a chromatin state at PTG loci that enables AIRE function and the establishment of immunological tolerance.
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.
Project description:Male gender is protective against multiple sclerosis and other T cell-mediated autoimmune diseases. This protection may be due, in part, to higher androgen levels in males. Androgen binds to the androgen receptor (AR) to regulate gene expression, but how androgen protects against autoimmunity is not well-understood. Autoimmune Regulator (Aire) prevents autoimmunity by promoting self-antigen expression in medullary thymic epithelial cells, such that developing T cells that recognize these self-antigens within the thymus undergo clonal deletion. Here, we show that androgen upregulates Aire-mediated thymic tolerance to protect against autoimmunity. Androgen recruits AR to Aire promoter regions, with consequent enhancement of Aire transcription. In mice and humans, thymic Aire expression is higher in males compared to females. Androgen administration and male gender protect against autoimmunity in a multiple sclerosis mouse model in an Aire-dependent manner. Thus, androgen control of an intrathymic Aire-mediated tolerance mechanism contributes to gender differences in autoimmunity. RNA-seq comparison of male vs. female expression in mTEC cells. Pools of 10 mice each were used for each replicate (two for male and two for female)
Project description:Prdm16 is a transcription factor that drives a complete program of brown adipocyte differentiation, but the mechanism by which Prdm16 activates gene transcription remains unknown. Utilizing ChIP-seq teqhnique, we found that Prdm16 binds to chromatin at/near many brown fat-selective genes in BAT. Interestingly, Prdm16-deficiency dramatically reduced the binding of Med1 to Prdm16-target sites. Indeed, Prdm16 binds and recruits Med1 to BAT-enriched genes and the loss of Prdm16 caused a fundamental change in chromatin architecture at key BAT-selective genes and also reduced transcirptional activity. Moreover, Prdm16, through its interaction with Med1, defines and regulates the activity of super-enhancers that drive the expression of cell identity genes. Together, these data demonstrate that Prdm16 drives gene transcription by recruiting Med1 to control chromatin architecture and super-enhancers.
Project description:Proinflammatory stimuli rapidly and globally remodel chromatin landscape, thereby enabling transcriptional responses. Yet, the mechanisms coupling chromatin regulators to the master regulatory inflammatory transcription factor NF-kB remain poorly understood. We report in human endothelial cells (ECs) that activated NF-kB binds to enhancers, provoking a rapid, global redistribution of BRD4 preferentially at super-enhancers, large enhancer domains highly bound by chromatin regulators. Newly established NF-kB super-enhancers drive nearby canonical inflammatory response genes. In both ECs and macrophages BET bromodomain inhibition prevents super-enhancer formation downstream of NF-kB activation, abrogating proinflammatory transcription. In TNFa-activated endothelium this culminates in functional suppression of leukocyte rolling, adhesion and transmigration. Sustained BET bromodomain inhibitor treatment of LDLr -/- animals suppresses atherogenesis, a disease process rooted in pathological vascular inflammation involving endothelium and macrophages. These data establish BET-bromodomains as key effectors of inflammatory response through their role in the dynamic, global reorganization of super-enhancers during NF-kB activation. ChIP-Seq for various transcription factors, RNA Polymerase II, and histone modifications in human endothelial cells
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.