Borthwick N M, Bell P A
Mol Cell Endocrinol. 1978 Jan;9(3):269-78. doi: 10.1016/0303-7207(78)90069-2.
Treatment of rat thymus cells with the glucocorticoids cortisol and dexamethasone resulted in the stimulation of RNA polymerase B activity within 10 min of steroid addition. This early effect was followed by the inhibition of both RNA polymerase A and B activities. These effects were glucocorticoid-specific and were inhibited by the antiglucocorticoid cortexolone. The inhibitory effect of dexamethasone on RNA polymerase A activity was abolished by prior treatment of the cells with alpha-amanitin, cordycepin or cycloheximide, but cycloheximide was only capable of inhibiting the steroid effect measured at 3 h if added within 10--20 min after steroid addition. Cycloheximide had no effect on the steroid-mediated inhibition of RNA polymerase B activity. Control RNA polymerase A activities were unaffected by the presence of inhibitors of RNA and protein synthesis. It is concluded that the inhibition of ribosomal RNA synthesis by glucocorticoids is dependent on protein synthesis, but that basal RNA polymerase A activity in rat thymus cells is not stringently coupled to protein synthesis.
用糖皮质激素皮质醇和地塞米松处理大鼠胸腺细胞，在添加类固醇后10分钟内RNA聚合酶B的活性受到刺激。这种早期效应之后是RNA聚合酶A和B的活性均受到抑制。这些效应具有糖皮质激素特异性，并被抗糖皮质激素皮质酮所抑制。地塞米松对RNA聚合酶A活性的抑制作用可通过先用α-鹅膏蕈碱、虫草素或环己酰亚胺处理细胞而消除，但环己酰亚胺只有在添加类固醇后10至20分钟内添加，才能抑制3小时时测得的类固醇效应。环己酰亚胺对类固醇介导的RNA聚合酶B活性抑制无影响。对照RNA聚合酶A的活性不受RNA和蛋白质合成抑制剂存在的影响。结论是，糖皮质激素对核糖体RNA合成的抑制依赖于蛋白质合成，但大鼠胸腺细胞中的基础RNA聚合酶A活性与蛋白质合成并非紧密偶联。
