Involvement of hepatocyte nuclear factor 4α in the different expression level between CYP2C9 and CYP2C19 in the human liver
Involvement of hepatocyte nuclear factor 4α in the different expression level between CYP2C9 and CYP2C19 in the human liver
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DOI：
10.1124/dmd.106.009365
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发表时间：
2006-06-01
影响因子：
3.9
通讯作者：
Chiba, Kan
中科院分区：
文献类型：
--
作者：
Kawashima, Sachiyo;Kobayashi, Kaoru;Chiba, Kan
CYP2C9和CYP2C19是临床上重要的药物代谢酶。CYP2C9的表达水平远高于CYP2C19，但导致这些基因表达水平差异的因素仍不清楚。肝细胞核因子4 α（hepatocyte nuclear factor 4 alpha，HNF 4 alpha）在调控P450基因等肝脏富集基因的表达中起重要作用。因此，我们假设HNF4 α有助于这些基因表达水平之间的差异。两个直接重复1（DR 1）元件位于CYP2C9和CYP2C19启动子。这些启动子的上游和下游元件具有相同的序列，并且HNF 4 α在体外可以与这两种元件结合。含有两个DR1元件的CYP2C9启动子的构建体的反式激活水平被HNF 4 α增加，而CYP2C19启动子的反式激活水平没有增加。在CYP2C9基因的上游或下游元件中引入突变消除了对HNF 4 α的反应性。我们还检查了HNF 4 α是否可以结合到体内CYP2C9和CYP2C19基因的启动子区域。染色质免疫沉淀试验结果表明，HNF 4 α可以结合到CYP2C9基因的启动子区，但不能结合到人肝脏中的CYP2C19启动子区。综上所述，我们的结果表明，HNF 4 α是一个因素，负责的CYP2C9和CYP2C19在人类肝脏的表达水平之间的差异。
CYP2C9 and CYP2C19 are clinically important drug-metabolizing enzymes. The expression level of CYP2C9 is much higher than that of CYP2C19, although the factor( s) responsible for the difference between the expression levels of these genes is still unclear. It has been reported that hepatocyte nuclear factor 4 alpha ( HNF4 alpha) plays an important role in regulation of the expression of liver-enriched genes, including P450 genes. Thus, we hypothesized that HNF4 alpha contributes to the difference between the expression levels of these genes. Two direct repeat 1 ( DR1) elements were located in both the CYP2C9 and CYP2C19 promoters. The upstream and downstream elements in these promoters had the same sequences, and HNF4 alpha could bind to both elements in vitro. The transactivation levels of constructs containing two DR1 elements of the CYP2C9 promoter were increased by HNF4 alpha, whereas those of the CYP2C19 promoter were not increased. The introduction of mutations into either the upstream or downstream element in the CYP2C9 gene abolished the responsiveness to HNF4 alpha. We also examined whether HNF4 alpha could bind to the promoter regions of the CYP2C9 and the CYP2C19 genes in vivo. The results of chromatin immunoprecipitation assays showed that HNF4 alpha could bind to the promoter region of the CYP2C9 gene but not to that of the CYP2C19 promoter in the human liver. Taken together, our results suggest that HNF4 alpha is a factor responsible for the difference between the expression levels of CYP2C9 and CYP2C19 in the human liver.