Schmitt T L, Espinoza C R, Loos U
Department of Internal Medicine I, University of Ulm, Germany.
Horm Metab Res. 2000 Jan;32(1):1-5. doi: 10.1055/s-2007-978576.
To investigate the existence of potential enhancer or silencer elements in the 5'-flanking region of the human Na+/I-symporter (NIS) gene, we cloned 2,512 bp of genomic DNA further upstream of the previously defined proximal promoter. When tested in reporter gene assays, this sequence had no transcriptional activity per se, but was able to repress the activity of the heterologous SV40 promoter. Conversely, when fused to the homologous NIS gene promoter and thus comprising 3,800 bp 5'-flanking region, the transcription of the proximal NIS promoter was stimulated in the human cell lines FTC-133 (from thyroid) and HeLa, but inhibited in the rat thyroid cell line FRTL-5. This might be due to differences between the upstream regions of the rat and human NIS gene. Comparative analysis with standard promoters (SV40) led to the conclusion that the 5'-flanking region of the human NIS gene also exhibited transcriptional activity in non-thyroid cells. Thyroid-stimulating hormone (TSH) had a moderately stimulating effect on the full length NIS reporter gene construct in FRTL-5 cells. This stimulation is presumably mediated by a putative cAMP responsive element found in the first half of the cloned sequence.
为了研究人类钠/碘同向转运体（NIS）基因5'侧翼区域中潜在增强子或沉默子元件的存在情况，我们克隆了先前定义的近端启动子上游2512 bp的基因组DNA。在报告基因检测中，该序列本身没有转录活性，但能够抑制异源SV40启动子的活性。相反，当与同源NIS基因启动子融合，从而包含3800 bp的5'侧翼区域时，近端NIS启动子的转录在人类细胞系FTC-133（来自甲状腺）和HeLa中受到刺激，但在大鼠甲状腺细胞系FRTL-5中受到抑制。这可能是由于大鼠和人类NIS基因上游区域的差异所致。与标准启动子（SV40）的比较分析得出结论，人类NIS基因的5'侧翼区域在非甲状腺细胞中也表现出转录活性。促甲状腺激素（TSH）对FRTL-5细胞中的全长NIS报告基因构建体有适度的刺激作用。这种刺激可能是由克隆序列前半部分中发现的一个假定的cAMP反应元件介导的。
