Study on defect in human UGTIAI gene promoter associated with hyperbilirubinemia and mechanism of the UGTIAI in duction

udp -葡萄糖醛酸糖基转移酶UGT1A1通过与葡萄糖醛酸结合，在潜在的神经毒性胆红素解毒中起关键作用。我们发现了一种多态性，该多态性导致UGT1A1基因苯巴比妥反应增强子模块的核苷酸编号-3263处T到G的替换，从而显着降低了荧光素酶报告试验显示的转录活性。这些双杂合子的血浆总胆红素水平明显高于单独携带其中一种或另一种突变的对照组，表明复合杂合子突变可能导致更强烈的UGT1A1活性降低。我们的研究结果表明，UGT1A1基因启动子（T-3263G和A[TA]_7TAA）和/或基因外显子1 （G211A）突变的纯合性和复合杂合性可以解释大多数吉尔伯特综合征患者的高胆红素血症。此外，我们还鉴定了UDP-glucu . More ronosyltransferase UGT1A1 5'上游区域，该区域可通过包括黄酮类化合物在内的各种药物诱导UGT1A1在荧光素酶报告基因上，并具有转录增强子的特性。对白杨素和利福平的反应活性与290 bp远端增强子模块（-3483/-3194）相同，其中报告活性被核受体[组成型雄甾烷受体（CAR）和孕烷X受体（PXR）]和转录因子[芳烃受体（AhR）]的激活剂增强。利用UGT1A1 290-bp报告基因的转激活实验，我们评估了不同黄酮类化合物对UGT1A1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5,7-二羟黄酮以时间和剂量依赖的方式增加报告活性。在CAR和PXR表达载体共转染的HepG2细胞中，Chrysin和利福平诱导野生型报告基因和t - 3263g突变基因的激活程度相似。综上所述，UGT1A1是通过一个290 bp的报告基因的反激活而被黄酮类化合物和外源生物诱导的，该基因是一个包含CAR、PXR和AhR基序的多组分增强子。少

The UDP-glucuronosyltransferase UGT1A1 plays a critical role in the detoxification of potentially neurotoxic bilirubin by conjugating it with glucuronic acid. We identified a polymorphism that results in a T to G substitution at nucleotide number -3263 of the phenobarbital-responsive enhancer module of the UGT1A1 gene, thereby significantly decreaseing transcriptional activity as indicated by the luciferase-reporter assay. Plasma total bilirubin levels in these double heterozygotes were significantly higher than those in control subjects carrying one or other of these mutations singly, indicating that compound heterozygous mutations may result in more strongly reduced UGT1A1 activity. Our results indicate that homozygocity and compound heterozygocity for mutations in the UGT1A1 gene promoter (T-3263G and A[TA]_7TAA) and/or exon 1 of the gene (G211A) could explain the hyperbilirubinemia seen in the majority of individuals with Gilbert's syndrome. Furthermore, we identified the UDP-glucu … More ronosyltransferase UGT1A1 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-respones activities were traced to the same element as a 290-bp distal enhancer module (-3483/-3194), in which the reporter activites 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. 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. 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. Less