Brock M L, Shapiro D J
J Biol Chem. 1983 May 10;258(9):5449-55.
Estrogen regulates the synthesis of the egg yolk precursor protein, vitellogenin, by causing both a 20-60-fold increase in the absolute rate of total nuclear RNA synthesis and a selective increase of at least several thousand fold in the absolute rate of vitellogenin gene transcription. Vitellogenin gene transcription is undetectable in unstimulated and withdrawn Xenopus laevis liver cells and in cultured Xenopus kidney cells allowing us to set a very low upper limit (less than 1 transcript/vitellogenin gene/day) on potential basal rates of vitellogenin gene transcription. The elevated rates of vitellogenin mRNA accumulation previously observed during restimulation of withdrawn liver cells (secondary estrogen stimulation) appear to be due to an increased rate of vitellogenin gene transcription. Both the maximum transcription rate and the rapidity of the early response increase on secondary estrogen stimulation. Relative transcription rates were determined by hybridization of pulse-labeled nuclear RNA to vitellogenin cDNA clones immobilized on nitrocellulose filters. The conversion of relative transcription rates to absolute transcription rates, was facilitated by development of a sensitive high performance liquid chromatography method for quantitation of the specific radioactivity of the cellular UTP pool.
雌激素通过使总核RNA合成的绝对速率增加20至60倍以及使卵黄蛋白原基因转录的绝对速率选择性增加至少几千倍来调节卵黄蛋白原（一种卵黄前体蛋白）的合成。在未受刺激和已去除雌激素的非洲爪蟾肝细胞以及培养的非洲爪蟾肾细胞中，无法检测到卵黄蛋白原基因转录，这使我们能够为卵黄蛋白原基因转录的潜在基础速率设定一个非常低的上限（每天每个卵黄蛋白原基因少于1个转录本）。先前在对已去除雌激素的肝细胞进行再刺激（二次雌激素刺激）期间观察到的卵黄蛋白原mRNA积累速率升高，似乎是由于卵黄蛋白原基因转录速率增加所致。二次雌激素刺激时，最大转录速率和早期反应的快速性均增加。通过将脉冲标记的核RNA与固定在硝酸纤维素滤膜上的卵黄蛋白原cDNA克隆杂交来确定相对转录速率。一种用于定量细胞UTP池比放射性的灵敏高效液相色谱方法的开发，有助于将相对转录速率转换为绝对转录速率。
