Kloetzel P M, Johnson R M, Sommerville J
Eur J Biochem. 1982 Oct;127(2):301-8. doi: 10.1111/j.1432-1033.1982.tb06870.x.
A ribonucleoprotein fraction that contains most of the rapidly labelled hnRNA has been isolated from gently ruptured oocytes of Triturus cristatus. This fraction consists of large aggregates of ribonucleoprotein and has a high (30:1) ratio of protein to RNA. The labelled RNA is contained in ribonucleoprotein particles that have a density of 1.27 g/cm3 in Cs2SO4 gradients (1.39 g/cm3 after formaldehyde fixation in CSCl gradients). Evidence is presented that the particles are associated in vivo with a fibrillar protein network. When the ribonucleoprotein aggregates are treated with ribonuclease, high salt concentration and nonionic detergent, a fibrillar protein residue is produced which contains many species of protein but a few that have electrophoretic characteristics that are identical to major ribonucleoprotein particle proteins. Isolated labelled hnRNA has been shown to bind specifically polypeptides of molecular weight 60 000 and 54 000 that are found in both particle and fibril preparations. In binding assays in vitro, these polypeptides are found to interact with mRNA to a lesser extent and not with rRNA. The isolated 60 000-Mr and 54 000-Mr proteins have the dual ability of forming ribonucleoprotein 'particles' with hnRNA and of polymerizing to generate 10-nm fibrillar structures in the absence of RNA. The possible cellular functions of these proteins are discussed.
从轻度破裂的美西螈卵母细胞中分离出了一种核糖核蛋白组分，其中含有大部分快速标记的核内不均一RNA（hnRNA）。该组分由核糖核蛋白的大聚集体组成，蛋白质与RNA的比例很高（30:1）。标记的RNA包含在核糖核蛋白颗粒中，这些颗粒在硫酸铯梯度中的密度为1.27 g/cm³（在氯化铯梯度中用甲醛固定后为1.39 g/cm³）。有证据表明，这些颗粒在体内与纤维状蛋白质网络相关联。当核糖核蛋白聚集体用核糖核酸酶、高盐浓度和非离子去污剂处理时，会产生一种纤维状蛋白质残渣，其中含有多种蛋白质，但少数几种蛋白质的电泳特征与主要核糖核蛋白颗粒蛋白相同。已证明分离出的标记hnRNA能特异性结合分子量为60000和54000的多肽，这些多肽在颗粒和纤维制剂中均有发现。在体外结合试验中，发现这些多肽与mRNA的相互作用程度较小，与rRNA则不相互作用。分离出的分子量为60000和54000的蛋白质具有双重能力，既能与hnRNA形成核糖核蛋白“颗粒”，又能在没有RNA的情况下聚合生成10纳米的纤维状结构。文中讨论了这些蛋白质可能的细胞功能。
