Glucocorticoid receptor regulates the ANGPTL4 gene in a CTCF-mediated chromatin context in human hepatic cells. Homo sapiens

Glucocorticoid plays an essential role in various stress responses and metabolism, which is mediated by the glucocorticoid receptor (GR) in cells. This hormonal action is integrated to transcriptional control of the GR target genes in cell type-specific and condition-dependent manners. In this study, we report that GR regulates the angiopoietin-like 4 (ANGPTL4) gene in a CCCTC-binding factor (CTCF)-mediated chromatin context in human hepatic HepG2 cells. There were at least four CTCF-enriched sites and two GR-binding sites in the ANGPTL4 locus. Among them, major CTCF-enriched site was positioned nearly GR-bound enhancer of this gene. Using treatment with the synthetic glucocorticoid dexamethasone (Dex), our data showed that CTCF is required for proper induction and subsequent silencing of ANGPTL4 gene. Interestingly, this gene induction was diminished under the long-term Dex pretreatment. Although ANGPTL4 locus maintains stable higher-order chromatin conformation at the basal and the Dex-treated states, liganded GR activated the ANGPTL4 gene, but not the neighboring three genes, via the interactions between enhancer, promoter and CTCF sites. These results reveal that liganded GR spatiotemporally controls ANGPTL4 gene in the chromosomal context. Overall design: In total 2 samples; 1 input sample and 1 ChIP-seq sample

糖皮质激素（Glucocorticoid）在多种应激反应及代谢过程中发挥核心调控作用，其生理功能由细胞内的糖皮质激素受体（glucocorticoid receptor, GR）介导。该激素信号通路通过细胞类型特异性、条件依赖性的方式，整合调控GR靶基因的转录过程。本研究发现，在人肝癌HepG2细胞中，GR可通过CCCTC结合因子（CCCTC-binding factor, CTCF）介导的染色质环境调控血管生成素样4（ANGPTL4）基因的表达。ANGPTL4基因座中至少存在4个CTCF富集位点与2个GR结合位点，其中主要的CTCF富集位点紧邻该基因的GR结合增强子区域。通过合成糖皮质激素地塞米松（dexamethasone, Dex）处理实验，本研究结果证实，CTCF是ANGPTL4基因正常诱导及后续沉默过程的必需因子。值得注意的是，长期Dex预处理会削弱该基因的诱导表达效果。尽管在基础状态与Dex处理状态下，ANGPTL4基因座均维持稳定的高阶染色质构象，但配体结合型GR可通过增强子、启动子与CTCF位点之间的相互作用，激活ANGPTL4基因的表达，而不影响其邻近的3个基因。上述结果表明，配体结合型GR可在染色质环境中实现对ANGPTL4基因的时空特异性调控。总体实验设计：本研究共设置2组样本，分别为1份输入样本与1份染色质免疫共沉淀测序（ChIP-seq）样本。