Determinants of thyrotrope-specific thyrotropin beta promoter activation - Cooperation of Pit-1 with another factor
Determinants of thyrotrope-specific thyrotropin beta promoter activation - Cooperation of Pit-1 with another factor
复制标题
DOI：
10.1074/jbc.271.1.385
复制
发表时间：
1996-01-05
影响因子：
4.8
通讯作者：
Ridgway, EC
中科院分区：
文献类型：
--
作者：
Haugen, BR;McDermott, MT;Ridgway, EC
促甲状腺素(TSH) β是TSH的一个亚基，其表达仅限于垂体前叶的促甲状腺细胞。我们利用促甲状腺素衍生的TtT-97促甲状腺肿瘤来研究TSH β启动子的组织特异性表达，促甲状腺素中的TSH β启动子活性由5'侧区-270和-80之间的序列赋予。我们最近报道了近端区域-133到-100 （P1）是促甲状腺癌启动子表达所必需的。该区域与垂体特异性转录因子Pit-1相互作用。虽然Pit-1似乎是促甲状腺激素中TSH β启动子活性所必需的，但在垂体源性细胞中，该转录因子并不足以单独激活启动子活性。在本报告中，我们在P1区域产生了一系列启动子突变，以确定其他蛋白质- dna相互作用并确定其功能意义。我们发现Pit-1与P1区域的远端部分相互作用，第二种蛋白质与该区域的近端部分相互作用，每种蛋白质都能够独立地与TSH β启动子相互作用，但两者都不能单独维持启动子活性。这两种蛋白似乎都是甲状腺特异启动子活性的必要条件，西南分析显示P1区域近端片段（-117至-88）与一个50 kda蛋白相互作用，有趣的是，该蛋白在垂体源性GH3细胞中未发现，可能代表甲状腺特异转录因子。对这种新发现的DNA结合蛋白的进一步表征将进一步加深我们对TSH β基因组织特异性表达的理解。
Thyrotropin (TSH) beta is a subunit of TSH, the expression of which is limited to the thyrotrope cells of the anterior pituitary gland, We have utilized the thyrotrope-derived TtT-97 thyrotropic tumors to investigate tissue specific expression of the TSH beta promoter, TSH beta promoter activity in thyrotropes is conferred by sequences between -270 and -80 of the 5'-flanking region, We have recently reported that the proximal region from -133 to -100 (P1) is required for promoter expression in thyrotropes. This region interacts with the pituitary-specific transcription factor Pit-1. While Pit-1 appears necessary for TSH beta promoter activity in thyrotropes, this transcription factor is not alone sufficient for promoter activity in pituitary-derived cells, In this report, we have generated a series of promoter mutations in the P1 region to identify additional protein-DNA interactions and determine their functional significance. We have found that Pit-1 interacts with the distal portion of the P1 region, and a second protein interacts with the proximal segment of this region, Each protein is able to independently interact with the TSH beta promoter, but neither alone can maintain promoter activity. Both proteins appear to be necessary for full promoter activity in thyrotropes, Southwestern analysis with the proximal segment of the P1 region (-117 to -88) reveals interaction with a 50-kDa protein, Interestingly, this protein is not found in the pituitary-derived GH3 cells and may represent a thyrotrope-specific transcription factor. Further characterization of this newly identified DNA binding protein will further our understanding of the tissue-specific expression of the TSH beta gene.