Knöchel W, Tiedemann H
Biochim Biophys Acta. 1975 Feb 10;378(3):383-93. doi: 10.1016/0005-2787(75)90183-5.
Nuclear RNA from avian erythroblasts was isolated, fractionated by dimethylsulfoxide gradient centrifugation, and the fractions pooled according to increasing sedimentation values. Addition of 125I-labeled globin 9 S mRNA before centrifugation revealed a contamination of high molecular weight RNA by globin mRNA. However, the distribution of label was not identical to the distribution of globin synthesizing activity of unlabelled nuclear RNA when the RNA was translated in a cell-free system of Ehrlich ascites cells. Whereas more than 95% of 125I activity was found in the 0-20 S pool, only 33% of globin synthesizing activity of unlabelled nuclear RNA could be found in this pool. Most of the synthesizing activity was found in the 20-55 S pool and smaller amounts in even more rapidly sedimenting fractions. This conclusively demonstrates the existence of nuclear RNA with globin-coding sequences most probably representing the globin mRNA precursor. The precursor has a higher molecular weight than globin 9 S mRNA. Furthermore we could show that only a small percentage (smaller than 20%) of the proteins synthesized by addition of nuclear RNA from avian erythroblasts to the cell-free system represents globin chains. When 9 S mRNA is added to the cell-free system, more than 70% of the newly synthesized proteins are globin chains.
从禽类成红细胞中分离出核RNA，通过二甲基亚砜梯度离心进行分级分离，并根据沉降值增加对各组分进行合并。在离心前加入125I标记的珠蛋白9S mRNA，结果显示珠蛋白mRNA污染了高分子量RNA。然而，当RNA在艾氏腹水细胞无细胞体系中进行翻译时，标记的分布与未标记核RNA的珠蛋白合成活性分布并不相同。虽然在0 - 20S组分中发现超过95%的125I活性，但在该组分中仅能发现33%的未标记核RNA的珠蛋白合成活性。大部分合成活性存在于20 - 55S组分中，在沉降更快的组分中含量较少。这确凿地证明了存在具有珠蛋白编码序列的核RNA，很可能代表珠蛋白mRNA前体。该前体的分子量比珠蛋白9S mRNA高。此外，我们还能表明，向无细胞体系中添加禽类成红细胞的核RNA所合成的蛋白质中，只有一小部分（小于20%）是珠蛋白链。当向无细胞体系中添加9S mRNA时，新合成蛋白质中超过70%是珠蛋白链。
