Characterization of a thyroid hormone-mediated short-loop feedback control of TSH receptor gene in an anaplastic human thyroid cancer cell line
Characterization of a thyroid hormone-mediated short-loop feedback control of TSH receptor gene in an anaplastic human thyroid cancer cell line
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DOI：
10.1677/joe.0.1750459
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发表时间：
2002-11-01
影响因子：
4
通讯作者：
Lin, KH
中科院分区：
文献类型：
--
作者：
Chen, ST;Lin, JD;Lin, KH
促甲状腺激素受体(TSHR)基因在甲状腺癌的去分化过程中经常丢失，该过程涉及多种核转录因子的干扰。我们已经证实，甲状腺激素受体β1(TRbeta1)与间变性人甲状腺癌细胞系ARO中TSHR基因的表达缺失有关。为了证明TRbeta1调节TSHR基因的表达，我们进行了凝胶迁移率改变和3，5，3‘-三碘甲腺原氨酸(T3)反式激活实验。不出所料，TRbeta1通过与维甲酸X受体异源二聚结合合成的含有TSHR启动子序列的寡聚体。当使用包含最小TSHR启动子的嵌合报告pTRCAT5‘-146进行T3反式激活实验时，两个高表达TRbeta1的ARO细胞(ARO1和ARO2)表现出比其亲本细胞更高的基础活性。因此，T3仅在ARO1和ARO2细胞中抑制报告基因的活性，而在ARO细胞中不抑制。在报告基因pTRCAT5‘-146Cre中产生cAMP反应元件(Cre)的点突变导致ARO细胞中T3诱导的报告基因抑制，而不改变ARO1和ARO2细胞中的基础或T3诱导的活性。我们认为，T3对TSHR基因表达的调控作用是由转录因子和启动子DNA序列决定的。
The expression of TSH receptor (TSHR) gene is frequently lost in thyroid cancers during the process of dedifferentiation that involves perturbation of several nuclear transcription factors. We have established that thyroid hormone receptor beta1 (TRbeta1) is associated with the loss of TSHR gene expression in an anaplastic human thyroid cancer cell line, ARO. To demonstrate that TRbeta1 regulates TSHR gene expression, we performed electrophoresis mobility shift and 3,5,3'-triiodothyronine (T3) transactivation assays. As expected, TRbeta1 bound the synthesized oligomer containing TSHR promoter sequence by heterodimerizing with retinoid X receptor. When a chimeric reporter pTRCAT5'-146 enclosing the minimal TSHR promoter was applied for T3 transactivation assay, two TRbeta1-overexpressing transfectants of ARO cells (ARO1 and ARO2) demonstrated higher basal activity than their parental cells. Consequentially, T3 suppressed the reporter gene activity only in ARO1 and ARO2, but not in ARO cells. A point mutation creating a cAMP response element (CRE) in the reporter pTRCAT5'-146 CRE led to T3-induced suppression of the reporter gene in ARO cells without changing the basal or T3-induced activities in ARO1 and ARO2 cells. We conclude that the regulatory effect of T3 on TSHR gene expression is TR- and promoter DNA sequence-determined.