Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pennsylvania 15261, USA.
AAPS J. 2012 Sep;14(3):581-90. doi: 10.1208/s12248-012-9370-5. Epub 2012 May 30.
Human arylamine N-acetyltransferase 1, (HUMAN)NAT1, is a phase II xenobiotic-metabolizing enzyme that plays an important role in drug and carcinogen biotransformation and cancer development. Its gene expression has been shown to be regulated by environmental factors. The purpose of the current study is to determine the involvement of nuclear receptors in transcriptional regulation of (HUMAN)NAT1 gene. We show that among the nuclear receptors examined, including the glucocorticoid receptor, retinoid acid receptor-related orphan receptor alpha, constitutive androstane receptor, pregnane X receptor, aryl hydrocarbon receptor, and retinoic acid receptor, the glucocorticoid receptor plays a dominant role in regulating (HUMAN)NAT1 gene expression through distal promoter (P3). The involvement of the glucocorticoid receptor in transcription regulation of (HUMAN)NAT1 gene expression was demonstrated by dexamethasone treatment, reporter assay using plasmid-containing 3 kbp of 5'-end region of promoter 3, and treatment of anti-glucocorticoid RU486 in primary culture of human hepatocytes and transfected HepG2 cells. In addition, translation inhibition did not affect dexamethasone-induced gene expression through P3, suggesting that dexamethasone effect is directly mediated by glucocorticoid receptor activation. Furthermore, deletion analysis revealed the presence of multiple responsive elements within the 3 kbp fragment of P3. Transfection assays in mice using hydrodynamics-based procedure and reporter gene assay in a mouse cell line revealed that glucocorticoid-induced NAT gene expression is species dependent. Dexamethasone treatment of transfected mice and mouse cell line decreased (MOUSE)Nat2 gene expression, (HUMAN)NAT1 homologue. These results suggest that glucocorticoids serve as a modulator for (HUMAN)NAT1 gene expression via the P3-containing 5'-flanking region.
人芳香胺 N-乙酰转移酶 1（HUMAN）NAT1 是一种 II 相异生物代谢酶，在药物和致癌物质的生物转化和癌症发展中发挥重要作用。其基因表达已被证明受到环境因素的调节。本研究的目的是确定核受体在（HUMAN）NAT1 基因转录调控中的作用。我们表明，在所研究的核受体中，包括糖皮质激素受体、视黄酸受体相关孤儿受体 α、组成型雄烷受体、孕烷 X 受体、芳烃受体和维甲酸受体，糖皮质激素受体通过远端启动子（P3）在调节（HUMAN）NAT1 基因表达中发挥主导作用。通过地塞米松处理、使用包含 3 kbp 5'-端启动子 3 区域的质粒的报告基因测定以及在人原代肝细胞和转染 HepG2 细胞中用抗糖皮质激素 RU486 处理，证明了糖皮质激素受体参与（HUMAN）NAT1 基因表达的转录调节。此外，翻译抑制作用不会影响通过 P3 诱导的地塞米松诱导的基因表达，表明地塞米松的作用是通过糖皮质激素受体的激活直接介导的。此外，缺失分析表明 P3 的 3 kbp 片段内存在多个反应元件。使用基于水动力的程序在小鼠中转染以及在小鼠细胞系中进行报告基因测定表明，糖皮质激素诱导的 NAT 基因表达具有物种依赖性。地塞米松处理转染的小鼠和小鼠细胞系降低了（MOUSE）Nat2 基因表达，（HUMAN）NAT1 同源物。这些结果表明，糖皮质激素通过包含 P3 的 5'-侧翼区域作为（HUMAN）NAT1 基因表达的调节剂。
