Smith R E, Clark J M
Biochemistry. 1979 Apr 3;18(7):1366-71. doi: 10.1021/bi00574a037.
The mRNA guanyltransferase-mRNA methyltransferases of vaccinia virions can be used to introduce a 5'-terminal m7g(5')pp(5')Apm... capping group onto the RNA of satellite tobacco necrosis virus (STNV RNA) to yield intact capped STNV RNA. Studies with an in vitro system from wheat germ and limiting quantities of capped and uncapped STNV RNA show that the rates and extents of formation of initiation complexes of protein synthesis by intact capped and uncapped STNV RNA are identical, suggesting that 5'-terminal cap groups cannot function in the translation of STNV RNA. Also, the cap analogue pm7G equally inhibits the initiation and the translation of limiting quantities of both capped and uncapped STNV RNA. These contrasting observations suggest that the wheat germ system contains a pm7G sensitive protein and that STNV RNA has a tertiary structure that restricts the function of an added 5'-terminal capping group. This theory is supported by observations that fragmented capped STNV RNA is better at forming initiation complexes than is equally fragmented uncapped STNV RNA.
痘苗病毒粒子的mRNA鸟苷转移酶-mRNA甲基转移酶可用于将5'-末端m7g(5')pp(5')Apm...帽结构基团引入卫星烟草坏死病毒（STNV RNA）的RNA上，以产生完整的加帽STNV RNA。对来自小麦胚芽的体外系统以及有限量的加帽和未加帽STNV RNA的研究表明，完整的加帽和未加帽STNV RNA形成蛋白质合成起始复合物的速率和程度是相同的，这表明5'-末端帽结构基团在STNV RNA的翻译中不起作用。此外，帽类似物pm7G同样抑制有限量的加帽和未加帽STNV RNA的起始和翻译。这些相互矛盾的观察结果表明，小麦胚芽系统含有一种对pm7G敏感的蛋白质，并且STNV RNA具有一种三级结构，该结构限制了添加的5'-末端帽结构基团的功能。这一理论得到了以下观察结果的支持：片段化的加帽STNV RNA比同样片段化的未加帽STNV RNA更能形成起始复合物。
