Fibrates increase human REV-ERBα expression in liver via a novel peroxisome proliferator-activated receptor response element
Fibrates increase human REV-ERBα expression in liver via a novel peroxisome proliferator-activated receptor response element
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DOI：
10.1210/me.13.3.400
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发表时间：
1999-03-01
影响因子：
--
通讯作者：
Staels, B
中科院分区：
文献类型：
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作者：
Gervois, P;Chopin-Delannoy, S;Staels, B
贝特类药物是广泛使用的降血脂药物，其通过调节参与脂质和脂蛋白代谢的基因表达发挥作用。然而，贝特类通过核受体过氧化物酶体增殖物激活受体-α（PPAR α）与由间隔一个核苷酸（DR 1）的AGGTCA基序的直接重复组成的反应元件相互作用来激活基因转录，贝特类和PPAR α的负基因调控机制在很大程度上是未知的。在本研究中，我们证明贝特类药物诱导核受体Rev-erb α的表达，这是一种基因转录的负调节因子。贝特类药物增加原代人肝细胞和HepG 2肝母细胞瘤细胞中Rev-erb α mRNA水平。在HepG 2细胞中，贝特类还诱导Rev-erb α蛋白合成速率。用由人Rev-erb α启动子驱动的报告基因构建体进行的转染研究表明，贝特类通过PPAR α在转录水平诱导Rev-erb α表达。定点诱变实验确定了与先前确定的Rev-erb α负性自身调节Rev-DR 2元件一致的PPAR反应元件。电迁移率变动分析实验表明，PPAR α作为异二聚体与9-顺式-视黄酸受体结合至DR 2元件的亚组，其5'侧接富含A/T的序列，例如在Rev-DR 2中。PPARalpha和Rev-erb alpha与Rev-DR 2位点的结合亲和力相似。总之，这些数据证明了人Rev-erb α作为PPAR α靶基因，并鉴定了DR 2位点的子集作为新型PPAR α反应元件。最后，PPARalpha和Rev-erb alpha信号通路通过竞争结合这些反应元件而相互干扰。
Fibrates are widely used hypolipidemic drugs that act by modulating the expression of genes involved in lipid and lipoprotein metabolism. Whereas the activation of gene transcription by fibrates occurs via the nuclear receptor peroxisome proliferator-activated receptor-alpha (PPAR alpha) interacting with response elements consisting of a direct repeat of the AGGTCA motif spaced by one nucleotide (DR1), the mechanisms of negative gene regulation by fibrates and PPAR alpha are largely unknown. In the present study, we demonstrate that fibrates induce the expression of the nuclear receptor Rev-erb alpha, a negative regulator of gene transcription. Fibrates increase Rev-erb alpha mRNA levels both in primary human hepatocytes and in HepG2 hepatoblastoma cells. In HepG2 cells, fibrates furthermore induce Rev-erb alpha protein synthesis rates. Transfection studies with reporter constructs driven by the human Rev-erb alpha promoter revealed that fibrates induce Rev-erb alpha expression at the transcriptional level via PPAR alpha. Site-directed mutagenesis experiments identified a PPAR response element that coincides with the previously identified Rev-erb alpha negative autoregulatory Rev-DR2 element. Electromobility shift assay experiments indicated that PPAR alpha binds as heterodimer with 9-cis-retinoic acid receptor to a subset of DR2 elements 5' flanked by an A/T-rich sequence such as in the Rev-DR2. PPAR alpha and Rev-erb alpha bind with similar affinities to the Rev-DR2 site. In conclusion, these data demonstrate human Rev-erb alpha as a PPAR alpha target gene and identify a subset of DR2 sites as novel PPAR alpha response elements. Finally, the PPAR alpha and Rev-erb alpha signaling pathways crosstalk through competition for binding to those response elements.