Two binding sites for thyroid transcription factor 1 (TTF-1) determine the activity of the bovine thyroglobulin gene upstream enhancer element
Two binding sites for thyroid transcription factor 1 (TTF-1) determine the activity of the bovine thyroglobulin gene upstream enhancer element
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DOI：
10.1016/s0303-7207(98)00250-0
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发表时间：
1999-03-25
影响因子：
4.1
通讯作者：
Christophe, D
中科院分区：
文献类型：
--
作者：
Christophe-Hobertus, C;Christophe, D
位于牛甲状腺球蛋白基因上游的甲状腺特异性增强子元件已被证明含有三个连续的区域，这些区域在体外足迹实验中受到甲状腺转录因子1（TTF-I）的保护。个体TTF-I结合位点的功能相关性在原代培养的甲状腺细胞的瞬时测定中进行了研究。使用含有与受保护序列重叠的合成寡核苷酸的报告构建体，我们能够表明三个TTF-1结合位点中只有两个表现出转录增强活性。在完整的增强子序列的情况下，中心的“非活性”TTF-1位点可以被删除，而在测定中对增强子的活性没有任何影响，而两个末端“活性”TTF-1位点的存在先前已被证明是增强子功能严格需要的。因此，我们的研究结果表明，牛甲状腺球蛋白上游增强子的活性依赖于一对TTF-I结合位点的存在下，分离约30 bp。这些结果也强调需要实验评估的功能相关性TTF-I结合位点的足迹实验中确定。(C)1999爱思唯尔科学爱尔兰有限公司保留所有权利。
A thyroid-specific enhancer element located upstream from the bovine thyroglobulin gene had been shown to contain three contiguous regions that are protected by thyroid transcription factor 1 (TTF-I) in footprinting experiments in vitro. The functional relevance of the individual TTF-I binding sites was investigated in a transient assay in primary cultured thyrocytes. Using reporter constructs containing synthetic oligonucleotides overlapping the protected sequences we were able to show that only two out of the three TTF-1 binding sites exhibit transcription enhancing activity. Within the context of the complete enhancer sequence, the central 'inactive' TTF-1 site could be deleted whithout any consequence on the activity of the enhancer in the assay, whereas the presence of both terminal 'active' TTF-I sites had previously been shown to be strictly required for enhancer function. Our results thus show that the activity of the bovine thyroglobulin upstream enhancer relies on the presence of a pair of TTF-I binding sites separated by about 30 bp. These results also emphasize the need to assess experimentally the functional relevance of TTF-I binding sites identified in footprinting experiments. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.