Thyroid Hormone Receptors Bind to an Element in the Connexin43 Promoter
Thyroid Hormone Receptors Bind to an Element in the Connexin43 Promoter
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DOI：
10.1515/bc.2000.120
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发表时间：
2000-09
期刊：
影响因子：
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通讯作者：
A. Stock;H. Sies
中科院分区：
文献类型：
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作者：
A. Stock;H. Sies
摘要甲状腺激素刺激大鼠肝WB-F344上皮细胞缝隙连接通讯，上调缝隙连接蛋白43的mRNA和蛋白水平。在目前的工作中，我们分析了甲状腺激素治疗的Wistar大鼠的肝脏和心脏样本中连接蛋白43的表达。与对照组相比，大鼠肝脏组织中缝隙连接蛋白43基因的表达增加了2.1倍，而心脏组织中没有变化。检测了大鼠连接蛋白43启动子区的甲状腺激素反应元件；在−480到−464位置鉴定了一个候选序列，包括一个配体依赖的转录因子的结合位点。这个可能的调控元件，Rcx−480，包含一个被三个碱基对分隔的直接重复结构(DR3型元件)。在体外翻译蛋白的凝胶迁移率改变分析中，Rcx−480元件与甲状腺激素受体α/维甲酸X受体α异源二聚体形成的复合体比与维生素D受体/维甲酸X受体α异源二聚体形成的复合物更强。在3，3‘，5-三碘-L-甲状腺原氨酸处理的Cos-7细胞中，通过该元件可观察到启动子的激活。当Rcx−480元件的3‘半位点或间隔区发生实验突变时，出现结合丢失，而在5’半位点引入突变时，观察到更强的结合。
Abstract Thyroid hormones stimulate gap junctional communication in rat liver WB-F344 epithelial cells, elevating connexin43 mRNA and protein levels. In the present work we analysed connexin43 expression in liver and heart samples from thyroid hormone-treated Wistar rats. Connexin43 mRNA was elevated 2.1-fold in rat liver samples as compared to controls, while there was no change in heart. Thyroid hormone response elements in the rat connexin43 promoter region were examined; a candidate sequence, including a binding site for ligand-dependent transcription factors, was identified at position −480 to −464. This putative regulatory element, rCx−480, contains a direct repeat structure separated by three base pairs (DR3-type element). In electrophoretic mobility shift assays using in vitro translated proteins, the rCx−480 element formed stronger complexes with thyroid hormone receptor α/retinoid X receptor α heterodimers than with vitamin D receptor/retinoid X receptor α heterodimers. In transfected Cos-7 cells, promoter activation was observed via this element after treatment with 3,3′,5-triiodo-L-thyronine. Loss of binding was seen when the 3′ half-site or the spacer region of the rCx−480 element were experimentally mutated, while a stronger binding was observed with mutations introduced in the 5′ halfsite.