Anderson K V, Lengyel J A
Cell. 1980 Oct;21(3):717-27. doi: 10.1016/0092-8674(80)90435-3.
The rates of synthesis and turnover of histone mRNA in Drosophila embryos were determined by hybridization of in vivo and in vitro labeled embryonic RNA to Drosophila histone DNA of the recombinant plasmid cDm500. There is a large store of maternal histone mRNA, equivalent to at least 7 X 10(7) copies of each of the five classes of histone mRNA per embryo. Embryonic synthesis of histone mRNA begins at 90 min after oviposition, making the histone genes among the first to be transcribed by embryonic nuclei. Embryonic histone mRNA accumulates rapidly during the blastoderm and gastrula stages. The peak in the rate of histone mRNA synthesis per embryo coincides with the peak in the rate of DNA synthesis per embryo, which occurs at 6 hr after oviposition. After 6 hr, as the rate of DNA synthesis per embryo decreases, the rate of histone mRNA synthesis and the total mass of histone mRNA per embryo both drop sharply. The rate of histone mRNA synthesis per gene falls more than 60 fold in the first 13 hr after oviposition, from 1.3 -2.5 copies per gene-min at 2 hr to 0.02-0.03 copies per gene-min at 13 hr. From measurements of the mass of histone mRNA per embryo and of the rate of accumulation of newly synthesized histone mRNA at a number of stages of early embryogenesis we determined that the cytoplasmic half-life of histone mRNA decreases approximately 7 fold during early Drosophila development, from 2.3 hr at blastoderm to 20 min by the end of gastrulation. Thus the level of expression of histone genes in Drosophila development is controlled not only by the size of the maternal mRNA pool and changes in the rate of histone mRNA synthesis, but also by changes in the rate of histone mRNA turnover.
通过将体内和体外标记的胚胎RNA与重组质粒cDm500的果蝇组蛋白DNA杂交，测定了果蝇胚胎中组蛋白mRNA的合成速率和周转情况。每个胚胎中存在大量母源组蛋白mRNA储备，相当于五类组蛋白mRNA中每一类至少7×10⁷个拷贝。组蛋白mRNA的胚胎合成在产卵后90分钟开始，使组蛋白基因成为最早被胚胎细胞核转录的基因之一。胚胎组蛋白mRNA在囊胚期和原肠胚期迅速积累。每个胚胎中组蛋白mRNA合成速率的峰值与每个胚胎中DNA合成速率的峰值相吻合，后者发生在产卵后6小时。6小时后，随着每个胚胎中DNA合成速率下降，组蛋白mRNA合成速率和每个胚胎中组蛋白mRNA的总量均急剧下降。每个基因的组蛋白mRNA合成速率在产卵后的前13小时下降超过60倍，从2小时时的每个基因每分钟1.3 - 2.5个拷贝降至13小时时的每个基因每分钟0.02 - 0.03个拷贝。通过对早期胚胎发育多个阶段每个胚胎中组蛋白mRNA的量以及新合成组蛋白mRNA积累速率的测量，我们确定组蛋白mRNA的细胞质半衰期在果蝇早期发育过程中大约下降7倍，从囊胚期的2.3小时降至原肠胚期末的20分钟。因此，果蝇发育过程中组蛋白基因的表达水平不仅受母源mRNA库大小和组蛋白mRNA合成速率变化的控制，还受组蛋白mRNA周转速率变化的控制。
