Shin Ha Youn, Willi Michaela, HyunYoo Kyung, Zeng Xianke, Wang Chaochen, Metser Gil, Hennighausen Lothar
Laboratory of Genetics and Physiology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Division of Bioinformatics, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.
Nat Genet. 2016 Aug;48(8):904-911. doi: 10.1038/ng.3606. Epub 2016 Jul 4.
Super-enhancers comprise dense transcription factor platforms highly enriched for active chromatin marks. A paucity of functional data led us to investigate the role of super-enhancers in the mammary gland, an organ characterized by exceptional gene regulatory dynamics during pregnancy. ChIP-seq analysis for the master regulator STAT5A, the glucocorticoid receptor, H3K27ac and MED1 identified 440 mammary-specific super-enhancers, half of which were associated with genes activated during pregnancy. We interrogated the Wap super-enhancer, generating mice carrying mutations in STAT5-binding sites within its constituent enhancers. Individually, the most distal site displayed the greatest enhancer activity. However, combinatorial mutation analysis showed that the 1,000-fold induction in gene expression during pregnancy relied on all enhancers. Disabling the binding sites of STAT5, NFIB and ELF5 in the proximal enhancer incapacitated the entire super-enhancer. Altogether, these data suggest a temporal and functional enhancer hierarchy. The identification of mammary-specific super-enhancers and the mechanistic exploration of the Wap locus provide insights into the regulation of cell-type-specific expression of hormone-sensing genes.
超级增强子由高度富集活性染色质标记的密集转录因子平台组成。由于功能数据匮乏，我们对超级增强子在乳腺中的作用展开研究，乳腺是一个在孕期具有特殊基因调控动态特征的器官。对主要调控因子STAT5A、糖皮质激素受体、H3K27ac和MED1进行染色质免疫沉淀测序（ChIP-seq）分析，确定了440个乳腺特异性超级增强子，其中一半与孕期激活的基因相关。我们对乳清酸性蛋白（Wap）超级增强子进行了研究，构建了在其组成增强子内STAT5结合位点带有突变的小鼠。单独来看，最远端的位点表现出最强的增强子活性。然而，组合突变分析表明，孕期基因表达1000倍的诱导依赖于所有增强子。使近端增强子中STAT5、NFIB和ELF5的结合位点失活会使整个超级增强子丧失功能。总之，这些数据表明存在一个时间和功能上的增强子层级结构。乳腺特异性超级增强子的鉴定以及对Wap基因座的机制探索为激素感应基因的细胞类型特异性表达调控提供了见解。
