Larsen P R, Harney J W, Moore D D
J Biol Chem. 1986 Nov 5;261(31):14373-6.
We have located sequences within the rat growth hormone (rGH) promoter region which are required for pituitary cell-type specific responsiveness to T3 (thyroid hormone, 3,5,3'-L-triiodothyronine). Transient transfections with a series of plasmids containing as few as 202 nucleotides upstream of the start site of the rat growth hormone mRNA showed specific induction by T3 in rat pituitary cell lines. Both the magnitude and the kinetics of this response were similar to those of the endogenous rGH gene, showing a strong early induction followed by a decline in T3 effect. Deletion of an additional 19 base pairs (to -183 relative to the start site) eliminated this induction. Plasmids containing sequences up to -237 or -202 showed significant promoter activity but no T3 responsiveness in transfections of mouse fibroblasts or monkey kidney cells. The presence of high affinity nuclear T3 binding proteins was demonstrated in both cell types. These results show that sequences between -183 and -202 are required for pituitary cell specific T3 regulation of the rGH promoter. The lack of T3 responsiveness in non-pituitary cells suggests that such regulation may be mediated by factors present in pituitary cells and absent in other cells.
我们已经在大鼠生长激素（rGH）启动子区域中定位到了一些序列，这些序列是垂体细胞类型对T3（甲状腺激素，3,5,3'-L-三碘甲状腺原氨酸）产生特异性反应所必需的。用一系列质粒进行瞬时转染，这些质粒包含大鼠生长激素mRNA起始位点上游少至202个核苷酸的序列，结果显示在大鼠垂体细胞系中T3能特异性诱导其表达。这种反应的强度和动力学与内源性rGH基因的相似，表现为早期强烈诱导，随后T3效应下降。再缺失19个碱基对（相对于起始位点至-183）则消除了这种诱导作用。在转染小鼠成纤维细胞或猴肾细胞时，含有至-237或-202序列的质粒显示出显著的启动子活性，但无T3反应性。在这两种细胞类型中均证实存在高亲和力核T3结合蛋白。这些结果表明，-183至-202之间的序列是垂体细胞特异性T3调节rGH启动子所必需的。非垂体细胞中缺乏T3反应性表明，这种调节可能是由垂体细胞中存在而其他细胞中不存在的因子介导的。
