Rosen C A, Ennis H L, Cohen P S
J Virol. 1982 Dec;44(3):932-8. doi: 10.1128/JVI.44.3.932-938.1982.
An mRNA-ribonucleoprotein particle (mRNP) was found in vesicular stomatitis virus (VSV)-infected Chinese hamster ovary cells. The particle was present 3 and 4.5 h after infection but was barely discernible at 2 h. The mRNP (buoyant density, 1.56 g/cm3), which cosedimented with viral nucleocapsid in a sucrose density gradient at approximately 120 to 160S, was separable from nucleocapsid (buoyant density, 1.31 g/cm3) by CsCl density gradient centrifugation. It contained all five VSV mRNAs and, almost exclusively, viral N protein. Some host mRNA and host protein was also present in the particle. The intact mRNP was incapable of stimulating protein synthesis in an in vitro protein-synthesizing system, although the VSV mRNA isolated from the particle by phenol extraction was functional in vitro. In contrast, intact polysomes stimulated cell-free protein synthesis to the same extent as purified polysomal mRNA. By 4.5 h after infection, 97% of the functional mRNA in vivo was associated with the mRNP, and only 3% was on polysomes. The amount of polysomal mRNA at 4.5 h after infection was only 31% of that found at 2 h after infection; this was reflected by the 76% decrease observed in the rate of in vivo protein synthesis at 4.5 h relative to that found at 2 h. Thus, it appears that the mRNP serves as an organelle which sequesters the large excess of VSV mRNA that is normally made during secondary transcription.
在感染水泡性口炎病毒（VSV）的中国仓鼠卵巢细胞中发现了一种信使核糖核酸 - 核糖核蛋白颗粒（mRNP）。该颗粒在感染后3小时和4.5小时出现，但在2小时时几乎难以辨认。mRNP（浮力密度为1.56 g/cm³）在蔗糖密度梯度中与病毒核衣壳共沉降，沉降系数约为120至160S，通过氯化铯密度梯度离心可与核衣壳（浮力密度为1.31 g/cm³）分离。它包含所有五种VSV信使核糖核酸，并且几乎只含有病毒N蛋白。颗粒中还存在一些宿主信使核糖核酸和宿主蛋白。完整的mRNP在体外蛋白质合成系统中不能刺激蛋白质合成，尽管通过苯酚提取从颗粒中分离出的VSV信使核糖核酸在体外具有功能。相比之下，完整的多核糖体刺激无细胞蛋白质合成的程度与纯化的多核糖体信使核糖核酸相同。感染后4.5小时，体内97%的功能性信使核糖核酸与mRNP相关联，只有3%存在于多核糖体上。感染后4.5小时多核糖体信使核糖核酸的量仅为感染后2小时的31%；这反映在与2小时相比，4.5小时体内蛋白质合成速率下降了76%。因此，mRNP似乎作为一种细胞器，隔离了在二次转录过程中通常产生的大量过量VSV信使核糖核酸。
