BACH1, the master regulator of oxidative stress, modulates CFTR gene expression [4C-seq]. BACH1, the master regulator of oxidative stress, modulates CFTR gene expression [4C-seq]

The cystic fibrosis transmembrane conductance regulator (CFTR) gene lies within a TAD in which multiple cis-regulatory elements (CREs) and transcription factors (TFs) regulate its cell-specific expression. The CREs are recruited to the gene promoter by a looping mechanism that depends upon both architectural proteins and specific TFs. An siRNA screen to identify TFs coordinating CFTR expression in airway epithelial cells suggested an activating role for BTB Domain and CNC Homolog 1 (BACH1). BACH1 is a ubiquitous master regulator of the cellular response to oxidative stress. Here we show that BACH1 may have a dual effect on CFTR expression by direct occupancy of CREs at physiological oxygen (~8%), while indirectly modulating expression under conditions of oxidative stress. Hence BACH1, can activate or repress the same gene, to fine tune expression in response to environmental cues such as cell stress. Furthermore, our 4C-seq data suggest that BACH1 can also directly regulate CFTR gene expression by modulating locus architecture through occupancy at known enhancers and structural elements, and depletion of BACH1 alters the higher order chromatin structure. Overall design: Analysis of the 3D chromatin architecture at the CFTR locus to determine interaction frequencies between elements which lead to changes in CFTR gene regulatory patterns upon BACH1 Knockdown.

囊性纤维化跨膜传导调节因子（cystic fibrosis transmembrane conductance regulator, CFTR）基因位于一个拓扑关联结构域（TAD）内，该结构域中多种顺式调控元件（CREs）与转录因子（TFs）共同调控其细胞特异性表达。顺式调控元件通过同时依赖结构蛋白与特定转录因子的染色质环化机制，被招募至基因启动子区域。为鉴定可协调气道上皮细胞中CFTR表达的转录因子，研究人员开展了小干扰RNA（siRNA）筛选，该筛选结果提示BTB结构域与CNC同源物1（BACH1）具有激活性功能。BACH1是调控细胞氧化应激应答的普遍核心调控因子。本研究表明，在生理氧浓度（约8%）条件下，BACH1可通过直接结合顺式调控元件对CFTR表达产生双重调控作用；而在氧化应激状态下，则可间接调控CFTR的表达。由此可见，BACH1可对同一基因同时发挥激活与抑制功能，从而根据细胞应激等环境信号精细调控基因表达水平。此外，本研究的染色体构象捕获高通量测序（4C-seq）数据显示，BACH1还可通过结合已知增强子与结构元件来调控基因座的三维染色质结构，进而直接调控CFTR基因的表达；敲低BACH1的表达会改变细胞的高级染色质结构。整体实验设计：对CFTR基因座的三维染色质结构进行分析，以测定各调控元件间的相互作用频率，进而明确BACH1基因敲低后CFTR基因调控模式的变化。