Pelletier J, Kaplan G, Racaniello V R, Sonenberg N
Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
J Virol. 1988 Jul;62(7):2219-27. doi: 10.1128/JVI.62.7.2219-2227.1988.
Poliovirus mRNA contains a long 5' noncoding region of about 750 nucleotides (the exact number varies among the three virus serotypes), which contains several AUG codons upstream of the major initiator AUG. Unlike most eucaryotic mRNAs, poliovirus does not contain a m7GpppX (where X is any nucleotide) cap structure at its 5' end and is translated by a cap-independent mechanism. To study the manner by which poliovirus mRNA is expressed, we examined the translational efficiencies of a series of deletion mutants within the 5' noncoding region of the mRNA. In this paper we report striking translation system-specific differences in the ability of the altered mRNAs to be translated. The results suggest the existence of an inhibitory cis-acting element(s) within the 5' noncoding region of poliovirus (between nucleotides 70 and 381) which restricts mRNA translation in reticulocyte lysate, wheat germ extract, and Xenopus oocytes, but not in HeLa cell extracts. In addition, we show that HeLa cell extracts contain a trans-acting factor(s) that overcomes this restriction.
脊髓灰质炎病毒mRNA含有一个约750个核苷酸的长5'非编码区（确切数量在三种病毒血清型中有所不同），在主要起始AUG上游含有几个AUG密码子。与大多数真核生物mRNA不同，脊髓灰质炎病毒在其5'端不含有m7GpppX（其中X是任何核苷酸）帽结构，而是通过不依赖帽的机制进行翻译。为了研究脊髓灰质炎病毒mRNA的表达方式，我们检测了mRNA 5'非编码区内一系列缺失突变体的翻译效率。在本文中，我们报道了改变后的mRNA在翻译能力上存在显著的翻译系统特异性差异。结果表明，脊髓灰质炎病毒5'非编码区（核苷酸70至381之间）存在一个抑制性顺式作用元件，它限制了网织红细胞裂解物、小麦胚芽提取物和非洲爪蟾卵母细胞中的mRNA翻译，但在HeLa细胞提取物中则不然。此外，我们表明HeLa细胞提取物含有一种能克服这种限制的反式作用因子。
