Matsui H, Yazawa H, Suzuki N, Hosoya T
Biochem J. 1986 May 1;235(3):699-705. doi: 10.1042/bj2350699.
The activity of the template-engaged form of RNA polymerase I from livers of adrenalectomized rats was about 50-60% of that of normal control rats, and increased about 2-fold at 6 h after the administration of dexamethasone. However, no change was found in the activity of the 'free' form of RNA polymerase I or the template-engaged form of RNA polymerase II. Immunochemical studies using guinea-pig anti-(RNA polymerase I) serum disclosed that the total number of RNA polymerase I molecules did not vary during the treatment with dexamethasone. Cycloheximide caused a rapid decrease in the template-engaged form of RNA polymerase I activity in normal rats and in dexamethasone-treated (6 h) adrenalectomized rats, to the value in adrenalectomized rats, but affected it only slightly in adrenalectomized rats. The elongation rate of rRNA-precursor synthesis in liver nuclei was not affected by a change in the concentration of circulating dexamethasone. From these results, it is concluded that about half the rRNA-precursor synthesis in rat liver is regulated by glucocorticoids, probably through the synthesis of short-lived protein(s) which may play a role in conversion of the 'dormant' form of RNA polymerase I into the 'engaged' form.
肾上腺切除大鼠肝脏中与模板结合形式的RNA聚合酶I的活性约为正常对照大鼠的50 - 60%，在给予地塞米松6小时后增加约2倍。然而，未发现“游离”形式的RNA聚合酶I或与模板结合形式的RNA聚合酶II的活性有变化。使用豚鼠抗（RNA聚合酶I）血清进行的免疫化学研究表明，在用地塞米松治疗期间，RNA聚合酶I分子的总数没有变化。环己酰亚胺导致正常大鼠和用地塞米松处理（6小时）的肾上腺切除大鼠中与模板结合形式的RNA聚合酶I活性迅速下降至肾上腺切除大鼠中的水平，但对肾上腺切除大鼠的影响仅轻微。肝细胞核中rRNA前体合成的延伸速率不受循环地塞米松浓度变化的影响。从这些结果可以得出结论，大鼠肝脏中约一半的rRNA前体合成受糖皮质激素调节，可能是通过合成可能在将“休眠”形式的RNA聚合酶I转化为“结合”形式中起作用的短命蛋白质来实现的。
