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对信号传导途径的转录反应，作为其生物学功能的中心方面，但潜在机制仍然是发育和稳态中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），过氧化物酶体增殖物激活受体γ（PPAR？）肝X受体（LXR）以启动子和核受体特异性方式抑制对Toll样受体激活的应答。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辅阻遏物复合物的信号依赖性解离来抑制巨噬细胞中炎症反应基因的亚群。令人惊讶的是，这一机制涉及配体依赖性小泛素化的过氧化物酶体增殖物激活受体？配体结合结构域，其靶向PPAR？NCoR/HDACs共阻遏物复合物。SUMO化的过氧化物酶体增殖体激活受体的相互作用？与NCoR/HDAC 3复合物的结合阻止了通常介导其信号依赖性去除的泛素化/igS蛋白体机制的募集。在果蝇Schneider细胞中的研究表明，这种SUMOYLATION依赖的反式阻遏途径是进化上保守的，被孤儿和配体依赖的核受体利用。基于这些观察，我们建议探索sumoylation和NCoR辅助阻遏物复合物在全基因组范围内的先天免疫反应的核受体依赖性反式阻遏中的作用。提出了三个具体目标。具体目标我将测试的假设，sumoylation核受体是一个广泛使用的机制，在反式阻遏炎症程序的基因表达。具体目标2将检验核受体的类小泛素化通过阻止共阻遏物/共激活物交换介导对基因表达的炎症程序的阻遏的假设。具体目标3将检验NCoR共阻遏物复合物的功能受组蛋白甲基转移酶SMYDs调节的假设。这些研究的结果可能会导致对炎症反应反式抑制机制的新见解，可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.