Expression of the VP2 protein of murine norovirus by a translation termination-reinitiation strategy.
Expression of the VP2 protein of murine norovirus by a translation termination-reinitiation strategy.
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DOI：
10.1371/journal.pone.0008390
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发表时间：
2009-12-22
期刊：
影响因子：
3.7
通讯作者：
Brierley I
中科院分区：
文献类型：
--
作者：
Napthine S;Lever RA;Powell ML;Jackson RJ;Brown TD;Brierley I
杯状病毒小鼠诺如病毒(MNV)的微小病毒结构蛋白VP2的表达被认为是通过依赖于密码子的终止重新启动翻译的不寻常机制发生的。在这个过程中，在翻译上游开放阅读框架(ORF)并在终止密码子终止后，仍有一部分40S亚基与mRNA相关，并在下游ORF的8月重新启动，下游ORF通常非常接近。与此一致，MNV的VP2起始密码子(AUG)与五核苷酸UAA UG中上游VP1 ORF(UAA)的终止密码子重叠。在这里，我们确认MNV VP2的表达是由终止-重新启动调节的，并定义了mRNA序列要求。有效的复活依赖于紧靠UAA UG位点上游的43个核苷酸的RNA。化学和酶探测表明，该区域的RNA不是高度结构的，包括与18S rRNA螺旋26(基序1)互补的必要碱基。Motif 1相对于UAA UG位点的相对位置影响该过程的效率。MNV的终止-再引发也被发现对起始抑制剂依地因相对不敏感。MNV的终止-重新启动信号与BM2流感病毒的信号最为相似。与使用这一策略的其他病毒类似，在VP1终止密码子终止后，mRNA和rRNA之间的碱基配对可能在将40S亚基与mRNA捆绑在一起的过程中发挥作用。我们的数据也表明，对VP2 ORF Aug的准确识别并不是该系统中有效重新启动翻译的先决条件。
Expression of the minor virion structural protein VP2 of the calicivirus murine norovirus (MNV) is believed to occur by the unusual mechanism of termination codon-dependent reinitiation of translation. In this process, following translation of an upstream open reading frame (ORF) and termination at the stop codon, a proportion of 40S subunits remain associated with the mRNA and reinitiate at the AUG of a downstream ORF, which is typically in close proximity. Consistent with this, the VP2 start codon (AUG) of MNV overlaps the stop codon of the upstream VP1 ORF (UAA) in the pentanucleotide UAA UG. Here, we confirm that MNV VP2 expression is regulated by termination-reinitiation and define the mRNA sequence requirements. Efficient reintiation is dependent upon 43 nt of RNA immediately upstream of the UAA UG site. Chemical and enzymatic probing revealed that the RNA in this region is not highly structured and includes an essential stretch of bases complementary to 18S rRNA helix 26 (Motif 1). The relative position of Motif 1 with respect to the UAA UG site impacts upon the efficiency of the process. Termination-reinitiation in MNV was also found to be relatively insensitive to the initiation inhibitor edeine. The termination-reinitiation signal of MNV most closely resembles that of influenza BM2. Similar to other viruses that use this strategy, base-pairing between mRNA and rRNA is likely to play a role in tethering the 40S subunit to the mRNA following termination at the VP1 stop codon. Our data also indicate that accurate recognition of the VP2 ORF AUG is not a pre-requisite for efficient reinitiation of translation in this system.
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