Yu F L, Feigelson P
Proc Natl Acad Sci U S A. 1971 Sep;68(9):2177-80. doi: 10.1073/pnas.68.9.2177.
Four hours after intraperitoneal injection of cortisone acetate into rats, hepatic nuclei had an enhanced ability to incorporate labeled nucleoside triphosphates into RNA in vitro. When the nuclei were further fractionated into nucleolar and extranucleolar (nucleoplasmic) fractions, it was found that this hormonal effect was localized exclusively in the nucleolar fraction. This increased transcriptive activity potentially could be due to either (a) an increased availability of the DNA template or (b) an increase in the amount or catalytic efficiency of the RNA polymerase, or both. In order to distinguish between these possibilities, actinomycin D was used to inhibit the template function of endogenous nucleolar DNA and a synthetic template, polydeoxycytidylate, which is insensitive to actinomycin D and codes for polyriboguanylate synthesis, was used to evaluate RNA polymerase activity. These studies indicate that the increased RNA synthesis evident in nucleoli isolated from livers of rats four hours after cortisone treatment is largely a consequence of elevated levels of RNA polymerase.
给大鼠腹腔注射醋酸可的松四小时后，肝细胞核在体外将标记的核苷三磷酸掺入RNA的能力增强。当将细胞核进一步分离为核仁组分和核仁外（核质）组分时，发现这种激素效应仅局限于核仁组分。这种转录活性的增加可能是由于（a）DNA模板的可用性增加，或（b）RNA聚合酶的量或催化效率增加，或两者兼而有之。为了区分这些可能性，使用放线菌素D抑制内源性核仁DNA的模板功能，并使用对放线菌素D不敏感且编码聚核糖鸟苷酸合成的合成模板聚脱氧胞苷酸来评估RNA聚合酶活性。这些研究表明，可的松处理四小时后从大鼠肝脏分离的核仁中明显增加的RNA合成主要是RNA聚合酶水平升高的结果。
