Zoncheddu A, Accomando R, Orunesu M
Boll Soc Ital Biol Sper. 1979 Nov 15;55(21):2222-7.
Rat liver RNA polymerase I solubilized from isolated nuclei and present in a soluble form in the cytoplasmic fraction has been analyzed by phosphocellulose chromatography 3 hours after the administration of cycloheximide. The antibiotic did not induce any change in the chromatographic properties of both nuclear and cytoplasmic RNA polymerase I. They appeared to remain in the IB and IA forms, characteristic of the transcribing (IB) and non-transscribing (IA) enzyme. While the level of the nuclear enzyme was not modified, the level of the cytoplasmic one appeared significantly increased. These results support previous ones indicating that the cycloheximide-induced inhibition of ribosomal RNA synthesis cannot be merely explained by a decrease in the nuclear or cellular level of RNA polymerase I. The cellular level of RNA polymerase I, taking into account the relative proportion of the enzyme found in nuclei and cytoplasm, appeared to be slightly increased. Cycloheximide administration did not seem to result in the appearance, in intact nuclei, of enzyme molecules in a free form or as blocked transcription complexes. It is concluded that the antibiotic affects the catalytic efficiency rather than the number of RNA polymerase I molecules actually engaged in the transcription of ribosomal cistrone.
在给予环己酰亚胺3小时后，通过磷酸纤维素色谱法对从分离的细胞核中溶解并以可溶形式存在于细胞质部分的大鼠肝脏RNA聚合酶I进行了分析。该抗生素并未引起细胞核和细胞质RNA聚合酶I的色谱性质发生任何变化。它们似乎仍保持在IB和IA形式，这是转录型（IB）和非转录型（IA）酶的特征。虽然细胞核酶的水平未发生改变，但细胞质酶的水平却显著升高。这些结果支持了先前的研究结果，表明环己酰亚胺诱导的核糖体RNA合成抑制不能仅仅通过RNA聚合酶I的细胞核或细胞水平降低来解释。考虑到在细胞核和细胞质中发现的酶的相对比例，RNA聚合酶I的细胞水平似乎略有增加。给予环己酰亚胺似乎并未导致完整细胞核中出现游离形式的酶分子或作为受阻转录复合物的酶分子。得出的结论是，该抗生素影响催化效率而非实际参与核糖体顺反子转录的RNA聚合酶I分子数量。
