Hashimoto S, Schmid W, Schütz G
Proc Natl Acad Sci U S A. 1984 Nov;81(21):6637-41. doi: 10.1073/pnas.81.21.6637.
The enzyme tyrosine aminotransferase (Tyr-ATase; L-tyrosine:2-oxoglutarate aminotransferase, EC 2.6.1.5), which is synthesized in rat liver, is induced by glucocorticoids, insulin, and glucagon or its intracellular mediator cAMP. We have used cloned TyrATase genomic and cDNA sequences to study the mechanism of induction by cAMP. RNA blot analysis shows that cAMP causes a rapid 5-fold increase in TyrATase mRNA concentration in rat liver. Transcription in isolated rat liver nuclei was studied to determine the relative rate of transcription of the TyrATase gene after cAMP administration. We show that the accumulation of TyrATase mRNA after cAMP stimulation is a consequence of transcriptional activation of the TyrATase gene. Combined dexamethasone and cAMP treatment leads to higher TyrATase mRNA concentrations than each inducer alone, which implies that dexamethasone and cAMP act by distinct mechanisms.
酪氨酸转氨酶（Tyr-ATase；L-酪氨酸：2-氧代戊二酸转氨酶，EC 2.6.1.5）在大鼠肝脏中合成，可被糖皮质激素、胰岛素、胰高血糖素或其细胞内介质cAMP诱导。我们利用克隆的酪氨酸转氨酶基因组和cDNA序列研究了cAMP的诱导机制。RNA印迹分析表明，cAMP可使大鼠肝脏中酪氨酸转氨酶mRNA浓度迅速增加5倍。研究了分离的大鼠肝细胞核中的转录情况，以确定给予cAMP后酪氨酸转氨酶基因的相对转录速率。我们发现，cAMP刺激后酪氨酸转氨酶mRNA的积累是酪氨酸转氨酶基因转录激活的结果。地塞米松和cAMP联合处理导致的酪氨酸转氨酶mRNA浓度高于单独使用每种诱导剂时，这表明地塞米松和cAMP的作用机制不同。
