LeMaire M F, Thummel C S
Department of Human Genetics, Howard Hughes Medical Institute, University of Utah Medical Center, Salt Lake City 84132.
Mol Cell Biol. 1990 Nov;10(11):6059-63. doi: 10.1128/mcb.10.11.6059-6063.1990.
The E74 gene is one of a small set of early genes induced by the steroid hormone ecdysone at the onset of metamorphosis in the fruit fly, Drosophila melanogaster. This complex gene directs the synthesis of a 60-kilobase (kb) primary transcript that is spliced to form the 6-kb E74A mRNA. In a previous study, we found that ecdysone directly activates the E74A promoter and determined that RNA polymerase II transcribes this gene at a rate of approximately 1.1 kb/min. This elongation rate accounts for most of the 1-hour delay seen between the addition of ecdysone and the appearance of cytoplasmic E74A mRNA (C. S. Thummel, K. C. Burtis, and D. S. Hogness, Cell 61:101-111, 1990). We show here that nascent E74A transcripts are spliced, and we propose a model for the order of that splicing. This study provides, for the first time, direct biochemical evidence for splicing of a low-abundance cellular RNA before transcription termination and polyadenylation.
E74基因是果蝇黑腹果蝇变态发育开始时由类固醇激素蜕皮激素诱导产生的一小部分早期基因之一。这个复杂的基因指导合成一个60千碱基（kb）的初级转录本，该转录本经过剪接形成6 kb的E74A mRNA。在先前的一项研究中，我们发现蜕皮激素直接激活E74A启动子，并确定RNA聚合酶II以大约1.1 kb/分钟的速率转录该基因。这个延伸速率解释了在添加蜕皮激素和细胞质E74A mRNA出现之间观察到的大部分1小时延迟（C. S. 萨默尔、K. C. 伯蒂斯和D. S. 霍格尼斯，《细胞》61:101 - 111，1990）。我们在此表明新生的E74A转录本会被剪接，并提出了一个关于该剪接顺序的模型。这项研究首次提供了在转录终止和多聚腺苷酸化之前低丰度细胞RNA剪接的直接生化证据。
