Skinner M A, Ebner D, Siddell S G
J Gen Virol. 1985 Mar;66 ( Pt 3):581-92. doi: 10.1099/0022-1317-66-3-581.
The sequence of a 5'-proximal region of mRNA 5 of coronavirus MHV-JHM was determined by chain-terminator sequencing of cDNA subcloned in M13. The sequence contained two long open reading frames of 321 bases and 264 bases, overlapping by five bases but in different frames. Both open reading frames are initiated by AUG codons in sequence contexts that are relatively infrequently used as initiator codons. The smaller, downstream open reading frame encoded a neutral protein (mol. wt. 10200) with a hydrophobic amino terminus. The larger, 5'-proximal open reading frame encoded a basic protein (mol. wt. 12400) which lacks internal methionine residues. With the exception of the AUG codon initiating the downstream open reading frame, no internal AUG codons were found within the sequence covered by the upstream open reading frame. These results suggest that the MHV-JHM mRNA 5 is translated to produce two proteins by a mechanism involving internal initiation of protein synthesis. Preliminary evidence is presented showing that the downstream open reading frame is functional in vivo.
通过对克隆于M13的cDNA进行链终止测序，确定了冠状病毒MHV-JHM的mRNA 5的5'-近端区域的序列。该序列包含两个长开放阅读框，分别为321个碱基和264个碱基，它们重叠5个碱基但阅读框不同。两个开放阅读框均由AUG密码子起始，其序列上下文相对较少用作起始密码子。较小的下游开放阅读框编码一种中性蛋白（分子量10200），其氨基末端具有疏水性。较大的5'-近端开放阅读框编码一种碱性蛋白（分子量12400），该蛋白缺乏内部甲硫氨酸残基。除了起始下游开放阅读框的AUG密码子外，在上游开放阅读框覆盖的序列内未发现内部AUG密码子。这些结果表明，MHV-JHM的mRNA 5通过涉及蛋白质合成内部起始的机制翻译产生两种蛋白质。初步证据表明下游开放阅读框在体内具有功能。
