Steroid induction of mouse mammary tumor virus: effect upon synthesis and degradation of viral RNA
Steroid induction of mouse mammary tumor virus: effect upon synthesis and degradation of viral RNA
复制标题
类固醇诱导小鼠乳腺肿瘤病毒：对病毒 RNA 合成和降解的影响
作者：
H. Young;T. Y. Shih;E. Scolnick;W. Parks
类固醇激素已被证明在组织培养中诱导小鼠乳腺肿瘤病毒(MMTV)RNA、蛋白质和颗粒的产生是构成水平的10倍。然而，以前关于病毒RNA水平升高的数据并没有区分病毒特异性RNA合成的速度增加和病毒RNA降解的速度减慢。根据最近发展的Coffin等人的分析。为了测量病毒RNA的合成速度，小鼠乳腺肿瘤细胞系的短期标记实验表明，糖皮质激素地塞米松在添加激素后10分钟内刺激MMTV特异性RNA的合成增加3倍，在30-60分钟内刺激RNA合成达到5-10倍，而同一细胞中Moloney白血病病毒特异性RNA的合成不受类固醇的影响。脉冲标记和累积的MMTV RNA在地塞米松存在或不存在时的衰减率表明，该RNA的半衰期大于8小时。此外，激素刺激的MMTV RNA的衰减率似乎比基础MMTV RNA快，因此排除了在类固醇激素存在时MMTV RNA的稳定性增加作为RNA水平增加的基础。因此，激素对MMTV RNA合成作用的大小、快速和特异性表明了对转录的主要影响。
Steroid hormones have been demonstrated to induce in tissue culture the production of mouse mammary tumor viral (MMTV) RNA, proteins, and particles 10-fold compared with constitutive levels. However, previous data of increased viral RNA levels did not distinguish between an increased rate of viral-specific RNA synthesis and a slower rate of viral RNA degradation. According to the recently developed assay of Coffin et al. (1974) for measuring rates of viral RNA synthesis, short-term labeling experiments of a mouse mammary tumor cell line indicate that the glucocorticoid hormone dexamethasone stimulates a 3-fold increase in the synthesis of MMTV-specific RNA within 10 min after the addition of hormone and that stimulation of RNA synthesis reaches 5- to 10-fold within 30 to 60 min, while the synthesis of Moloney leukemia virus-specific RNA in the same cell is unaffected by steroids. The decay rates of pulse-labeled and accumulated MMTV RNA in the presence or absence of dexamethasone show this RNA to have a half-life of greater than 8 h. In addition, hormone-stimulated MMTV RNA appears to have an increased rate of decay compared to basal MMTV RNA, thus ruling out an increased stability of MMTV RNA in the presence of steroid hormones as the basis for increased RNA levels. Thus, the magnitude, rapidity, and specificity of hormone action on MMTV RNA synthesis indicate a primary effect upon transcription.