Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Hungarian Academy of Sciences, "Lendület" Immunogenomics Research Group, University of Debrecen, Debrecen, Hungary.
Mol Cell Endocrinol. 2018 Aug 15;471:63-74. doi: 10.1016/j.mce.2017.07.034. Epub 2017 Jul 31.
Macrophages are able to differentiate into classically polarized (M1) or alternatively polarized (M2) states upon encountering pro-inflammatory cytokines such as interferon (IFN) γ or anti-inflammatory cytokines such as interleukin (IL) -4/IL-13, respectively. Moreover, macrophages are known to regulate lipid metabolism via multiple members of the nuclear hormone receptor family, including the retinoid X receptors (RXR). It has been also documented that cytokines are able to modulate macrophage responses to lipid signals but the nature of these interactions and the underlying mechanisms of these processes especially at the level of the chromatinized genome are not well understood. Previous work from our laboratory suggested that STAT6 is a facilitator of nuclear receptor mediated transcriptional activity acting at the genome level. This prompted us to investigate genome-wide DNA binding events and the development of cistromes in human CD14+ monocyte-derived macrophages upon exposure to IL-4. We determined the impact of IL-4 on the PU.1, RXR and STAT6 cistromes within the active enhancer regions marked by H3K27-acetylation using chromatin immunoprecipitation followed by deep sequencing and integrated bioinformatics analyses. We found that about 2/3rd of the IL-4 induced STAT6 peaks co-localized with RXR peaks. These STAT6/RXR co-peaks differed at least in part from the non-overlapping RXR peaks regarding the most enriched de novo transcription factor binding motifs. Interestingly, RXR-binding was not regulated at the STAT6/RXR co-bound enhancers following IL-4 stimulation, but differential enhancer interactions were observed between the IL-4/STAT6 and RXR signaling pathways acting in a gene selective manner. Our results suggest that there is a novel, so far uncharacterized cistromic crosstalk between RXR and STAT6 that is likely to contribute to the formation of the active enhancer repertoire, transcriptome and differential signal-specific gene regulation of polarized macrophages.
巨噬细胞在遇到促炎细胞因子（如干扰素 (IFN) γ）或抗炎细胞因子（如白细胞介素 (IL) -4/IL-13）时，能够分别分化为经典极化（M1）或替代极化（M2）状态。此外，已知巨噬细胞通过核激素受体家族的多个成员来调节脂质代谢，包括视黄酸 X 受体 (RXR)。已经有文献记录表明细胞因子能够调节巨噬细胞对脂质信号的反应，但这些相互作用的性质和这些过程的潜在机制，特别是在染色质基因组水平上，尚未得到很好的理解。我们实验室之前的工作表明，STAT6 是核受体介导的转录活性的促进剂，作用于基因组水平。这促使我们研究人类 CD14+单核细胞衍生的巨噬细胞在暴露于 IL-4 时全基因组 DNA 结合事件和 cistromes 的发展。我们使用染色质免疫沉淀 followed by deep sequencing 和整合生物信息学分析，确定了 IL-4 对活性增强子区域内的 PU.1、RXR 和 STAT6 cistromes 的影响，这些增强子区域由 H3K27-乙酰化标记。我们发现，大约 2/3 的 IL-4 诱导的 STAT6 峰与 RXR 峰共定位。这些 STAT6/RXR 共峰至少在部分上与非重叠的 RXR 峰在最丰富的从头转录因子结合基序上不同。有趣的是，在 IL-4 刺激后，RXR 结合在 STAT6/RXR 共结合增强子上不受调节，但在 IL-4/STAT6 和 RXR 信号通路之间观察到差异增强子相互作用，这些作用以基因选择性方式进行。我们的结果表明，RXR 和 STAT6 之间存在一种新的、迄今为止尚未表征的 cistromic 串扰，这可能有助于形成活跃的增强子库、转录组和极化巨噬细胞中差异信号特异性基因调控。
