The induction of human UDP-glucuronosyltransferase 1A1 mediated through a distal enhancer module by flavonoids and xenobiotics
The induction of human UDP-glucuronosyltransferase 1A1 mediated through a distal enhancer module by flavonoids and xenobiotics
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DOI：
10.1016/j.bcp.2003.11.002
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发表时间：
2004-03-01
影响因子：
5.8
通讯作者：
Miwa, M
中科院分区：
文献类型：
--
作者：
Sugatani, J;Yamakawa, K;Miwa, M
我们鉴定了UDP-葡萄糖醛酸转移酶（UGT）1A 1 5 '上游区域，该区域赋予UGT 1A 1由各种试剂（包括类黄酮）诱导的荧光素酶报告基因，并具有转录增强子的特性。将利福平和利福平反应活性追溯到与290 bp远端增强子模块（-3483/-3194）相同的元件，其中报告活性通过核受体[组成型雄烷受体（CAR）和甾烷X受体（PXR）]和转录因子[芳烃受体（AhR）]的激活剂增强。利用UGT 1A 1 290 bp报告基因的反式激活实验，我们评估了各种黄酮类化合物对UGT 1A 1的诱导作用。在B环和没食子儿茶素二聚体中具有不同取代基的5，7-二羟基黄酮以时间和剂量依赖性方式增加报告活性。用黄酮类化合物处理HepG 2细胞24小时，UGT 1A 1和CYP 1A 1的mRNA和蛋白质表达升高，而CYP 2B 6、CYP 3A 4、CAR、PXR和AhR的mRNA水平没有改变。在共转染CAR和PXR表达载体的HepG 2细胞中，利福平和利福平诱导野生型报告基因和T-3263 G突变基因的激活程度相似。AhR核心结合区的突变最显著地抑制了白杨素和黄芩素对290-bp报告基因的激活，而四个假定的核受体基序（DR 4元件，PXRE. CARE和DR 3元件）部分降低其激活。综上所述，结果表明，UGT 1A 1是通过290 bp报告基因的反式激活而诱导的，该报告基因是含有CAR的多组分增强子。PXR和AhR基序。(C)2003年爱思唯尔公司All rights reserved.
We identified the UDP-glucuronosyltransferase (UGT) 1A1 5'-upstream region that confers UGT1A1 induction by various agents, including flavonoids, on a luciferase reporter gene and has the properties of a transcriptional enhancer. Chrysin- and rifampicin-response activities were traced to the same element as a 290-bp distal enhancer module (-3483/-3194), in which the reporter activities were enhanced by activators of nuclear receptors [constitutive androstane receptor (CAR) and pregnane X receptor (PXR)] and transcription factor [aryl hydrocarbon receptor (AhR)]. Utilizing transactivation experiments with the UGT1A1 290-bp reporter gene, we assessed UGT1A1 induction by various flavonoids. 5,7-Dihydroxyflavones with varying substituents in the B-ring and gallocatechin dimers increased the reporter activity in a time- and dose-dependent manner. The treatment of HepG2 cells with the flavonoids for 24 hr elevated the expression of mRNAs and proteins of UGT1A1 and CYP1A1, while the mRNA levels of CYP2B6, CYP3A4, CAR, PXR and AhR was not altered. Chrysin and rifampicin induced the activation of the wild-type reporter gene and T-3263G-mutated gene to a similar extent in HepG2 cells cotransfected with expression vectors of CAR and PXR. Mutation of the AhR core binding region most prominently suppressed the activation of the 290-bp reporter gene by chrysin and baicalein, while mutations of four putative nuclear receptor motifs (DR4 element, PXRE. CARE and DR3 element) partly decreased its activation. Taken together, the results indicate that UGT1A1 was induced in response to flavonoids and xenobiotics through the transactivation of the 290-bp reporter gene, that was a multi-component enhancer containing CAR. PXR and AhR motifs. (C) 2003 Elsevier Inc. All rights reserved.