Martin K A, Miller O L
Dev Biol. 1983 Aug;98(2):338-48. doi: 10.1016/0012-1606(83)90364-0.
Modified chromatin-spreading techniques have been used to prepare reproducible spreads of polysomes for EM visualization. We have analyzed polysomes of sea urchin (Lytechinus pictus) eggs and embryos to elucidate some of the events which occur during the burst of protein synthetic activity following fertilization. We have confirmed that the rise in protein synthesis after fertilization is concomitant with the recruitment of messenger RNA molecules into polysomes. The presence of ribosome-free tails is a structural feature of polysomes in which the mRNA is being translated for the first time. This structural marker has allowed us to derive an elongation rate of 1.5-1.8 amino acids/sec and a transit time of 5 min for the average-sized polysome in L. pictus embryos at 16 degrees C. We have also observed a difference between the structure and the average size of polysomes in the egg and embryo. Egg polysomes are longer (average size = 11.96 ribosomes, n = 671) than 1-hr embryo polysomes (average size = 7.14 ribosomes, n = 863) and 10% of the egg polysomes contain visible gaps while less than 1% of the 1-hr embryo polysomes contain internal ribosome-free regions. We speculate that such differences reflect the lower translation efficiency of the relatively dormant egg cell.
改良的染色质铺展技术已被用于制备用于电子显微镜观察的多核糖体的可重复铺展。我们分析了海胆（Lytechinus pictus）卵和胚胎的多核糖体，以阐明受精后蛋白质合成活性爆发期间发生的一些事件。我们已经证实，受精后蛋白质合成的增加与信使RNA分子募集到多核糖体中同时发生。无核糖体尾的存在是多核糖体的一种结构特征，其中mRNA正在首次被翻译。这种结构标记使我们能够得出在16摄氏度下，L. pictus胚胎中平均大小的多核糖体的延伸速率为1.5 - 1.8个氨基酸/秒，转运时间为5分钟。我们还观察到卵和胚胎中多核糖体的结构和平均大小之间的差异。卵多核糖体比1小时胚胎多核糖体更长（平均大小 = 11.96个核糖体，n = 671）（平均大小 = 7.14个核糖体，n = 863），并且10%的卵多核糖体含有可见间隙，而1小时胚胎多核糖体中不到1%含有内部无核糖体区域。我们推测这种差异反映了相对休眠的卵细胞较低的翻译效率。
