Ray B K, Brendler T G, Adya S, Daniels-McQueen S, Miller J K, Hershey J W, Grifo J A, Merrick W C, Thach R E
Proc Natl Acad Sci U S A. 1983 Feb;80(3):663-7. doi: 10.1073/pnas.80.3.663.
Host and reovirus mRNAs compete with one another for translation in infected cells. Kinetic analysis has suggested that the site of competition is a message discriminatory initiation factor which must bind to the mRNA before it can interact with the 40S ribosomal subunit. The present communication describes an in vitro assay which can detect message discriminatory activities. A competitive situation is established by using reovirus and globin mRNAs, and then the specificity with which this competition is relieved by added components is measured. Among the various initiation factors surveyed with this assay, two have the properties expected of the mRNA discriminatory factor. These are eukaryotic initiation factor 4A and a "cap binding protein" complex. Inasmuch as the cap binding protein complex contains a subunit similar or identical to the initiation factor eIF-4A, it seems likely that only one form of the latter factor may be active in vivo. In vitro, both factors relieve competition among both capped and uncapped reovirus mRNAs according to similar hierarchies. These results suggest that some feature other than the m7G cap, such as nucleotide sequence or secondary structure, is recognized by the discriminatory factor.
宿主和呼肠孤病毒的信使核糖核酸（mRNA）在受感染细胞中相互竞争进行翻译。动力学分析表明，竞争位点是一种对信使有识别作用的起始因子，它必须先与mRNA结合，然后才能与40S核糖体亚基相互作用。本通讯描述了一种能够检测信使识别活性的体外测定方法。通过使用呼肠孤病毒和珠蛋白mRNA建立竞争情况，然后测量添加成分缓解这种竞争的特异性。在用该测定法检测的各种起始因子中，有两种具有信使识别因子所预期的特性。它们是真核起始因子4A和一种“帽结合蛋白”复合物。由于帽结合蛋白复合物包含一个与起始因子eIF - 4A相似或相同的亚基，看来后者因子可能只有一种形式在体内具有活性。在体外，这两种因子都按照相似的层级关系缓解加帽和未加帽的呼肠孤病毒mRNA之间的竞争。这些结果表明，除了m7G帽之外的某些特征，如核苷酸序列或二级结构等，被识别因子所识别。
