Functional Comparison of Mx1 from Two Different Mouse Species Reveals the Involvement of Loop L4 in the Antiviral Activity against Influenza A Viruses
Functional Comparison of Mx1 from Two Different Mouse Species Reveals the Involvement of Loop L4 in the Antiviral Activity against Influenza A Viruses
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DOI：
10.1128/jvi.01744-15
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发表时间：
2015-08
影响因子：
5.4
通讯作者：
Judith Verhelst;J. Spitaels;C. Nürnberger;D. De Vlieger;T. Ysenbaert;P. Staeheli;W. Fiers;X. Saelens
中科院分区：
文献类型：
--
作者：
Judith Verhelst;J. Spitaels;C. Nürnberger;D. De Vlieger;T. Ysenbaert;P. Staeheli;W. Fiers;X. Saelens
干扰素诱导的Mx1基因是哺乳动物防御流感病毒的重要组成部分。小家鼠Mx1通过抑制病毒核糖核蛋白（vRNP）的聚合酶活性来抑制甲型流感病毒复制和转录。在这里，我们比较了Mx 1从小家鼠A2G的抗流感病毒活性与它的直系同源物从小家鼠spretus。结果表明，M. spretus Mx 1的抗肿瘤活性低于M. Mx1肌M. musculus Mx1序列与M. spretus Mx1序列显示25个氨基酸的差异，其中一半以上存在于GT3结构域，其中2个存在于L4环。然而，来自两种小鼠物种的Mx1的体外GTdR活性相似。替换M中L4环中的一个残基。spretus Mx1通过A2G Mx1的相应残基增强其抗病毒活性。我们还表明，L4环的缺失阻止Mx1与甲型流感病毒核蛋白的结合，因此，取消了小鼠Mx1的抗病毒活性。这些结果表明小鼠Mx1的L4环是抗病毒活性的决定因素。我们的研究结果表明，来自不同哺乳动物的Mx蛋白使用共同的机制来抑制甲型流感病毒。重要性Mx蛋白在脊椎动物中是进化保守的，并抑制多种病毒。尽管如此，它们抗病毒机制的确切细节在很大程度上仍然未知。对两个在进化过程中相对最近出现分歧的物种的Mx基因进行功能比较可以为这些机制提供新的见解。我们发现，小家鼠A2G Mx1和小家鼠Mx1都靶向流感病毒核蛋白。我们还发现，小鼠Mx1中的L4环对于其抗病毒活性至关重要，正如最近报道的灵长类MxA。这表明人类和小鼠Mx蛋白在7500万年的进化过程中有所不同，它们通过共同的机制识别和抑制甲型流感病毒。
ABSTRACT The interferon-induced Mx1 gene is an important part of the mammalian defense against influenza viruses. Mus musculus Mx1 inhibits influenza A virus replication and transcription by suppressing the polymerase activity of viral ribonucleoproteins (vRNPs). Here, we compared the anti-influenza virus activity of Mx1 from Mus musculus A2G with that of its ortholog from Mus spretus. We found that the antiviral activity of M. spretus Mx1 was less potent than that of M. musculus Mx1. Comparison of the M. musculus Mx1 sequence with the M. spretus Mx1 sequence revealed 25 amino acid differences, over half of which were present in the GTPase domain and 2 of which were present in loop L4. However, the in vitro GTPase activity of Mx1 from the two mouse species was similar. Replacement of one of the residues in loop L4 in M. spretus Mx1 by the corresponding residue of A2G Mx1 increased its antiviral activity. We also show that deletion of loop L4 prevented the binding of Mx1 to influenza A virus nucleoprotein and, hence, abolished the antiviral activity of mouse Mx1. These results indicate that loop L4 of mouse Mx1 is a determinant of antiviral activity. Our findings suggest that Mx proteins from different mammals use a common mechanism to inhibit influenza A viruses. IMPORTANCE Mx proteins are evolutionarily conserved in vertebrates and inhibit a wide range of viruses. Still, the exact details of their antiviral mechanisms remain largely unknown. Functional comparison of the Mx genes from two species that diverged relatively recently in evolution can provide novel insights into these mechanisms. We show that both Mus musculus A2G Mx1 and Mus spretus Mx1 target the influenza virus nucleoprotein. We also found that loop L4 in mouse Mx1 is crucial for its antiviral activity, as was recently reported for primate MxA. This indicates that human and mouse Mx proteins, which have diverged by 75 million years of evolution, recognize and inhibit influenza A viruses by a common mechanism.