Transcriptional Co-Regulators and Macrophage Gene Expression

描述（由申请人提供）：许多核受体以反式方式抑制信号通路的转录反应，这是其生物学功能的一个核心方面，但其潜在机制在发育和体内平衡中仍然是一个重要且未解决的问题。在本基金资助期间进行的研究表明，糖皮质激素受体（GR）、过氧化物酶体增殖体激活受体y （PPAR?）和肝X受体（LXRs）以启动子特异性和核受体特异性的方式抑制toll样受体激活的反应。目前的建议试图在全基因组范围内定义负责这些特定抑制程序的潜在机制。初步研究表明PPAR？通过阻止NCoR共抑制复合物的信号依赖性解离，抑制巨噬细胞中的炎症反应基因子集。令人惊讶的是，这一机制涉及PPAR？配体结合域，哪个靶向PPAR？炎性基因启动子的NCoR/ hdac共抑制复合物。聚合PPAR？NCoR/HDAC3复合物阻止了泛素化/igS蛋白体机制的募集，这些机制通常介导它们的信号依赖性去除。在果蝇Schneider细胞中的研究表明，这种依赖于summoylylation的转抑制途径在进化上是保守的，并且被孤儿和配体依赖的核受体所利用。基于这些观察结果，我们建议在全基因组范围内探索sumo化和NCoR共抑制复合物在核受体依赖性先天免疫反应转抑制中的作用。提出了三个具体目标。特异性目的i将验证核受体的聚合化是基因表达炎症程序转抑制中广泛使用的机制的假设。特异性目的2将验证核受体的sumoylation通过阻止共抑制因子/共激活因子交换来介导基因表达炎症程序的抑制的假设。特异性目的3将检验nor共抑制复合物的功能是由组蛋白甲基转移酶SMYDs调节的假设。这些研究的结果可能会导致对炎症反应转抑制机制的新见解，可以用于开发新的治疗方法。

DESCRIPTION (provided by applicant): Many nuclear receptors act in trans to repress transcriptional responses to signaling pathways as a central aspect of their biological functions, but the underlying mechanisms remain an important and unresolved question in development and homeostasis. Studies performed during the current funding period of this grant demonstrated that the glucocorticoid receptor (GR), the peroxisome proliferator-activated receptor y (PPAR?) and liver X receptors (LXRs) repress responses to toll-like receptor activation in a promoter-, and nuclear receptor-specific manner. The current proposal seeks to define the underlying mechanisms responsible for these specific programs of repression on a genome-wide scale. Preliminary studies indicate that PPAR? represses a subset of inflammatory response genes in macrophages by preventing the signal- dependent dissociation of NCoR co-repressor complexes. Surprisingly, this mechanism involves ligand- dependent sumoylation of the PPAR? ligand binding domain, which targets PPAR? to NCoR/HDACs co- repressor complexes on inflammatory gene promoters. The interaction of sumoylated PPAR? with NCoR/HDAC3 complexes prevents the recruitment of ubiquitylation/igS proteosome machinery that normally mediates their signal-dependent removal. Studies in Drosophila Schneider cells suggests that this sumoylation-dependent transrepression pathway is evolutionarily conserved and is utilized by both orphan and ligand-dependent nuclear receptors. Based on these observations, we propose to explore the roles of sumoylation and NCoR co-repressor complexes in nuclear receptor-dependent transrepression of innate immune responses on a genome-wide scale. Three Specific Aims are proposed. Specific Aim i will test the hypothesis that sumoylation of nuclear receptors is a broadly used mechanism in transrepression of inflammatory programs of gene expression. Specific Aim 2 will test the hypothesis that sumoylation of nuclear receptors mediates repression of inflammatory programs of gene expression by preventing co- repressor/co-activator exchange. Specific Aim 3 will test the hypothesis that the function of NCoR co- repressor complexes is modulated by the histone methyltransferase SMYDs. The results of these studies are likely to lead to new insights into the mechanisms underlying transrepression of inflammatory responses that can be exploited for development of novel therapeutic approaches.