Zhang Zhaolin, Leir Shih-Hsing, Harris Ann
Human Molecular Genetics Program, Lurie Children's Research Center, and Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, Illinois.
Am J Respir Cell Mol Biol. 2015 Mar;52(3):387-96. doi: 10.1165/rcmb.2014-0263OC.
Cystic fibrosis transmembrane conductance regulator gene (CFTR) expression in human airway epithelial cells involves the recruitment of distal cis-regulatory elements, which are associated with airway-selective DNase hypersensitive sites at -44 kb and -35 kb from the gene. The -35-kb site encompasses an enhancer that is regulated by the immune mediators interferon regulatory factor 1 and 2 and by nuclear factor Y. Here we investigate the -44-kb element, which also has enhancer activity in vitro in airway epithelial cells but is inactive in intestinal epithelial cells. This site contains an antioxidant response element (ARE) that plays a critical role in its function in airway cell lines and primary human bronchial epithelial cells. The natural antioxidant sulforaphane (SFN) induces nuclear translocation of nuclear factor, erythroid 2-like 2 (Nrf2), a transcription factor that regulates genes with AREs in their promoters, many of which are involved in response to injury. Under normal conditions, the -44-kb ARE is occupied by the repressor BTB and CNC homology 1, basic leucine zipper transcription factor (Bach1), and v-Maf avian musculoaponeurotic fibrosarcoma oncogene homolog K (MafK) heterodimers. After 2 hours of SFN treatment, Nrf2 displaces these repressive factors and activates CFTR expression. Site-directed mutagenesis shows that both the ARE and an adjacent NF-κB binding site are required for activation of the -44-kb element in airway epithelial cells. Moreover, this element is functionally linked to the -35-kb enhancer in modulating CFTR expression in response to environmental stresses in the airway.
囊性纤维化跨膜传导调节因子基因（CFTR）在人气道上皮细胞中的表达涉及远端顺式调节元件的募集，这些元件与该基因-44 kb和-35 kb处的气道选择性脱氧核糖核酸酶超敏位点相关。-35 kb位点包含一个增强子，该增强子受免疫介质干扰素调节因子1和2以及核因子Y的调控。在此，我们研究-44 kb元件，该元件在体外人气道上皮细胞中也具有增强子活性，但在肠上皮细胞中无活性。该位点包含一个抗氧化反应元件（ARE），其在气道细胞系和原代人支气管上皮细胞的功能中起关键作用。天然抗氧化剂萝卜硫素（SFN）诱导核因子红系2样2（Nrf2）的核转位，Nrf2是一种转录因子，可调节启动子中带有ARE的基因，其中许多基因参与损伤反应。在正常条件下，-44 kb的ARE被阻遏物BTB和CNC同源物1、碱性亮氨酸拉链转录因子（Bach1）以及v-Maf禽肌动蛋白神经纤维肉瘤癌基因同源物K（MafK）异二聚体占据。经SFN处理2小时后，Nrf2取代这些阻遏因子并激活CFTR表达。定点诱变表明，ARE和相邻的核因子κB结合位点对于气道上皮细胞中-44 kb元件的激活都是必需的。此外，在调节气道中CFTR表达以响应环境应激方面，该元件与-35 kb增强子在功能上相关联。
