Casanova J, Copp R P, Janocko L, Samuels H H
J Biol Chem. 1985 Sep 25;260(21):11744-8.
Thyroid hormone has been shown to rapidly stimulate the rate of rat growth hormone gene transcription which parallels the kinetics of binding of 3,5,3'-triiodo-L-thyronine (L-T3) to its nuclear receptor (Yaffe, B. M., and Samuels, H. H. (1984) J. Biol. Chem. 259, 6284-6291). We have constructed a chimeric gene to explore whether the 5'-flanking region of the rat growth hormone gene contains a DNA element which could mediate thyroid hormone control of growth hormone gene expression. The construct consists of 1.8 kilobase pairs of the 5'-flanking region extending 11 nucleotides downstream from the transcription initiation (cap) site ligated to Escherichia coli DNA containing the structural gene for the enzyme xanthine-guanine phosphoribosyltransferase. GC cells, a growth hormone producing rat pituitary cell line, were transfected with this chimeric gene and stable transformants in which the enzyme is regulated by L-T3 were isolated by positive selection using mycophenolic acid and xanthine. These stable transformants develop with relatively high frequency and show marked L-T3 stimulation of xanthine-guanine phosphoribosyltransferase mRNA which is initiated at the cap site of the growth hormone gene. This study provides the first evidence that the 5'-flanking region of the rat growth hormone gene contains a DNA regulatory element which can mediate control of gene expression by thyroid hormone.
甲状腺激素已被证明能迅速刺激大鼠生长激素基因的转录速率，这与3,5,3'-三碘-L-甲状腺原氨酸（L-T3）与其核受体的结合动力学相似（亚菲，B.M.，和塞缪尔斯，H.H.（1984年）《生物化学杂志》259，6284 - 6291）。我们构建了一个嵌合基因，以探究大鼠生长激素基因的5'侧翼区域是否包含一个能介导甲状腺激素对生长激素基因表达调控的DNA元件。该构建体由转录起始（帽）位点下游11个核苷酸处延伸的1.8千碱基对的5'侧翼区域与含有黄嘌呤 - 鸟嘌呤磷酸核糖转移酶结构基因的大肠杆菌DNA连接而成。GC细胞是一种产生生长激素的大鼠垂体细胞系，用这个嵌合基因转染，然后通过使用霉酚酸和黄嘌呤进行阳性选择，分离出其中该酶受L-T3调控的稳定转化体。这些稳定转化体以相对较高的频率产生，并显示出L-T3对从生长激素基因帽位点起始的黄嘌呤 - 鸟嘌呤磷酸核糖转移酶mRNA有显著刺激作用。这项研究首次证明大鼠生长激素基因的5'侧翼区域包含一个能介导甲状腺激素对基因表达调控的DNA调节元件。
