Wasner G, Oshima H, Thompson E B, Simons S S
Steroid Hormones Section, National Institute of Diabetes, and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
Mol Endocrinol. 1988 Nov;2(11):1009-17. doi: 10.1210/mend-2-11-1009.
The enzyme tyrosine aminotransferase (TAT) is induced by unusually low concentrations of glucocorticoids in Fu5-5 cells. We have isolated clones of Fu5-5 cells infected with mouse mammary tumor virus (MMTV) in order to simultaneously compare the glucocorticoid regulation of the host cell gene, TAT, with that of another primary inducible gene, MMTV. In the two clones that were examined in detail, MMTV RNA induction occurred at 4- to 11-fold higher concentrations of dexamethasone than those needed for induction of TAT mRNA. Furthermore, the amount of agonist activity displayed by the irreversible antiglucocorticoid dexamethasone 21-mesylate was greater for the induction of TAT mRNA than for MMTV RNA. These results extend our previous observations of unequal sensitivity of induction of TAT enzyme activity in two hepatoma cell lines and show that differential glucocorticoid regulation of gene induction within the same cell can occur at a pretranslational step. The present data also indicate that the unusual properties of TAT gene induction are not shared by all primary, glucocorticoid-inducible responses of the same cell and imply that additional factors mediating differential regulation of glucocorticoid-responsive genes are involved.
在Fu5-5细胞中，酪氨酸转氨酶（TAT）可被异常低浓度的糖皮质激素诱导。我们分离了感染小鼠乳腺肿瘤病毒（MMTV）的Fu5-5细胞克隆，以便同时比较宿主细胞基因TAT与另一个主要的可诱导基因MMTV的糖皮质激素调节情况。在详细检测的两个克隆中，诱导MMTV RNA所需的地塞米松浓度比诱导TAT mRNA所需的浓度高4至11倍。此外，不可逆抗糖皮质激素甲磺酸地塞米松21酯诱导TAT mRNA的激动剂活性量大于诱导MMTV RNA的量。这些结果扩展了我们之前在两种肝癌细胞系中对TAT酶活性诱导敏感性不等的观察，并表明同一细胞内基因诱导的糖皮质激素差异调节可发生在翻译前步骤。目前的数据还表明，TAT基因诱导的异常特性并非该细胞所有主要的糖皮质激素诱导反应所共有，这意味着涉及介导糖皮质激素反应性基因差异调节的其他因素。
