Hepatocyte nuclear factor 4α contributes to thyroid hormone homeostasis by cooperatively regulating the type 1 iodothyronine deiodinase gene with GATA4 and Kruppel-like transcription factor 9
Hepatocyte nuclear factor 4α contributes to thyroid hormone homeostasis by cooperatively regulating the type 1 iodothyronine deiodinase gene with GATA4 and Kruppel-like transcription factor 9
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DOI：
10.1128/mcb.02154-07
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发表时间：
2008-06-01
影响因子：
5.3
通讯作者：
Sakai, Juro
中科院分区：
文献类型：
--
作者：
Ohguchi, Hiroto;Tanaka, Toshiya;Sakai, Juro
1型碘甲状腺原氨酸脱碘酶（Dio1）是一种催化甲状腺激素生物活化的硒酶，在肝脏中高度表达。肝细胞核因子4 α (HNF4 α)缺失小鼠肝脏中Diol mRNA和酶活性水平显著降低，从而解释了其肝脏特异性表达。与这种缺陷相一致的是，这些小鼠的血清T(4)和rT(3)浓度与注射了HNF4的对照组相比升高；然而，血清T(3)水平不变。小鼠Diol基因启动子分析表明，HNF4 α在小鼠Dio1基因的反激活中起关键作用。缺失和替换突变分析表明，近端HNF4 α位点（直接重复1 [TGGACAAA GGTGC]； HNF4 α - re）对于HNF4 α对小鼠Dio1基因的反激活至关重要。小鼠Dio1也受到甲状腺激素信号的刺激，但甲状腺激素受体的直接作用尚未报道。我们还发现甲状腺激素诱导的kruppel样因子9 （KLF9）通过位于HNF4 α - re两侧的两个CACCC序列非常有效地刺激小鼠Dio1启动子。此外，KLF9与HNF4 α和GATA4一起协同激活小鼠Dio1启动子，表明小鼠Dio1通过一种需要KLF9预先诱导的间接机制受到甲状腺激素的调节。此外，我们发现GATA4的c端锌指结构域（Cf）与HNF4 α的激活功能2之间以及GATA4的Cf相邻的基本结构域与KLF9的c端结构域之间的物理相互作用都是这种协同反应所必需的。综上所述，这些结果表明HNF4 α通过GATA4和KLF9对小鼠Dio1基因的转录调控来调节甲状腺激素的稳态。
Type 1 iodothyronine deiodinase (Dio1), a selenoenzyme catalyzing the bioactivation of thyroid hormone, is highly expressed in the liver. Diol mRNA and enzyme activity levels are markedly reduced in the livers of hepatocyte nuclear factor 4 alpha (HNF4 alpha)-null mice, thus accounting for its liver-specific expression. Consistent with this deficiency, serum T(4) and rT(3) concentrations are elevated in these mice compared with those in HNF4 alpha-floxed control littermates; however, serum T(3) levels are unchanged. Promoter analysis of the mouse Diol gene demonstrated that HNF4 alpha plays a key role in the transactivation of the mouse Dio1 gene. Deletion and substitution mutation analyses demonstrated that a proximal HNF4 alpha site (direct repeat 1 [TGGACAAA GGTGC]; HNF4 alpha-RE) is crucial for transactivation of the mouse Dio1 gene by HNF4 alpha. Mouse Dio1 is also stimulated by thyroid hormone signaling, but a direct role for thyroid hormone receptor action has not been reported. We also showed that thyroid hormone- inducible Kruppel-like factor 9 (KLF9) stimulates the mouse Dio1 promoter very efficiently through two CACCC sequences that are located on either side of HNF4 alpha-RE. Furthermore, KLF9 functions together with HNF4 alpha and GATA4 to synergistically activate the mouse Dio1 promoter, suggesting that Dio1 is regulated by thyroid hormone in the mouse through an indirect mechanism requiring prior KLF9 induction. In addition, we showed that physical interactions between the C-terminal zinc finger domain (Cf) of GATA4 and activation function 2 of HNF4 alpha and between the basic domain adjacent to Cf of GATA4 and a C-terminal domain of KLF9 are both required for this synergistic response. Taken together, these results suggest that HNF4 alpha regulates thyroid hormone homeostasis through transcriptional regulation of the mouse Dio1 gene with GATA4 and KLF9.