Chromatin regulation by the nuclear receptor PPARbeta/delta

配体调控的核受体PPARβ/δ既可以激活转录，也可以抑制转录，但对这些功能的调节、机制原理和生物学后果还只有部分了解。通过使用染色质免疫沉淀(ChIP)测序和转录图谱的组合，我们已经定义了靶基因对PPARβ/δ配体或PPARβ/δ耗竭的三种不同类型的转录反应。这些不同的靶基因反应的分子基础将在拟议的项目中讨论。我们的数据还表明，远程相互作用可能是PPARβ/δ转录调控的重要组成部分。我们将通过全基因组芯片技术(CHIA-PET)、基因特异的染色体构象分析和功能丧失方法来分析DNA环的形成和功能含义。此外，我们还发现了PPARβ/δ的新的相互作用伙伴，包括SRCAP的一个亚基p18HAMLET，它可以将组蛋白变异体H2A.Z插入到核小体中，从而通过调控编码肌肉生成素的Myog基因在肌肉发生中发挥重要作用，我们将其确定为PPARβ/δ靶标。因此，我们将分析PPARβ/δ对H2A.Z基因特异性和全局性组织的影响，并将其与转录谱和PPARβ/δ在肌细胞分化中的作用相关联。最后，我们确定了PIAS2是PPARβ/δ的相互作用伙伴，并且发现PPARβ/δ是以一种配体依赖的方式多糖基化的。我们现在计划研究配体介导的SUMO化调节机制，并研究其功能后果。

The ligand-regulated nuclear receptor PPARβ/δ can both activate and repress transcription, but the regulation, mechanistic principles and biological consequences of these functions are only partly understood. By using a combination of chromatin immunoprecipitation (ChIP) sequencing and transcriptional profiling we have defined three distinct types of transcriptional responses of target genes to PPARβ/δ ligands or PPARβ/δ depletion. The molecular basis of these distinct target gene responses will be addressed in the proposed project. Our data also suggest that long-range interactions may be an important component of transcriptional regulation by PPARβ/δ. We will analyze the formation and functional implications of DNA looping by genome-wide ChIP-based technologies (ChIA-PET), gene-specific chromosome conformation assays and loss-of-function approaches. Furthermore, we have discovered new interaction partners of PPARβ/δ, including p18HAMLET, a subunit of SRCAP, which can insert histone variant H2A.Z into nucleosomes and thereby plays an essential role in myogenesis through regulation of the myogenin-encoding Myog gene, which we identified as a PPARβ/δ target. We will therefore analyze the influence of PPARβ/δ on genespecific and global organization of H2A.Z and correlate this with transcriptional profiling and the function of PPARβ/δ in myogenic differentiation. Finally, we have identified PIAS2 as an interaction partner of PPARβ/δ, and found that PPARβ/δ is polySUMOylated in a ligand-dependent way. We now plan to study the mechanism of ligand-mediated regulation of SUMOylation and to investigate its functional consequences.