Jendrach M, Thiel V, Siddell S
Institute of Virology, University of Würzburg, Germany.
Arch Virol. 1999;144(5):921-33. doi: 10.1007/s007050050556.
The unique region of mRNA 5 of murine hepatitis virus contains two open reading frames, ORF 5a and ORF 5b. The downstream ORF 5b encodes the envelope (E) protein, an integral membrane protein of the virus. We have shown previously that the expression of ORF 5b is mediated by the internal entry of ribosomes. In the experiments reported here, we have used the in vitro translation of synthetic mRNAs to identify the region of mRNA 5 that mediates internal ribosome entry. Our results show that the 5' border of the MHV mRNA 5 IRES element is located between nucleotides 227 and 244 in ORF 5a, while the 3' border is located between nucleotides 140 and 172 in ORF 5b. The MHV mRNA 5 IRES element, therefore, contains not more than 280 nucleotides and encompasses the ORF 5b initiation codon. As evidenced by electrophoretic mobility shift assays, the IRES element of mRNA 5 interacts specifically with protein factors present in an L-cell lysate.
鼠肝炎病毒mRNA 5的独特区域包含两个开放阅读框，即ORF 5a和ORF 5b。下游的ORF 5b编码包膜（E）蛋白，它是病毒的一种整合膜蛋白。我们之前已经表明，ORF 5b的表达是由核糖体的内部进入介导的。在本文报道的实验中，我们利用合成mRNA的体外翻译来确定介导核糖体内部进入的mRNA 5区域。我们的结果表明，MHV mRNA 5内部核糖体进入位点（IRES）元件的5'边界位于ORF 5a中核苷酸227和244之间，而3'边界位于ORF 5b中核苷酸140和172之间。因此，MHV mRNA 5 IRES元件包含不超过280个核苷酸，并包含ORF 5b起始密码子。如电泳迁移率变动分析所示，mRNA 5的IRES元件与L细胞裂解物中存在的蛋白质因子特异性相互作用。
