State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China.
State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
J Virol. 2018 Aug 29;92(18). doi: 10.1128/JVI.00499-18. Print 2018 Sep 15.
Human myxovirus resistance protein 2 (huMxB) has been shown to be a determinant type I interferon (IFN)-induced host factor involved in the inhibition of human immunodeficiency virus type 1 (HIV-1) as well as many other primate lentiviruses. This blocking occurs after the reverse transcription of viral RNA and ahead of integration into the host DNA, which is closely connected to the ability of the protein to bind the viral capsid. To date, Mx2s derived from nonprimate animals have shown no capacity for HIV-1 suppression. In this study, we examined the restrictive effect of equine Mx2 (eqMx2) on both equine infectious anemia virus (EIAV) and HIV-1 and investigated possible mechanisms for its specific function. We demonstrated that IFN-α/β upregulates the expression of eqMx2 in equine monocyte-derived macrophages (eMDMs). The overexpression of eqMx2 significantly suppresses the replication of EIAV, HIV-1, and simian immunodeficiency viruses (SIVs) but not that of murine leukemia virus (MLV). The knockdown of eqMx2 transcription weakens the inhibition of EIAV replication by type I interferon. Interestingly, data from immunofluorescence assays suggest that the subcellular localization of eqMx2 changes following virus infection, from being dispersed in the cytoplasm to being accumulated at the nuclear envelope. Furthermore, eqMx2 blocks the nuclear uptake of the proviral genome by binding to the viral capsid. The N-terminally truncated mutant of eqMx2 lost the ability to bind the viral capsid as well as the restriction effect for lentiviruses. These results improve our understanding of the Mx2 protein in nonprimate animals. Previous research has shown that the antiviral ability of Mx2s is confined to primates, particularly humans. EIAV has been shown to be insensitive to restriction by human MxB. Here, we describe the function of equine Mx2. This protein plays an important role in the suppression of EIAV, HIV-1, and SIVs. The antiviral activity of eqMx2 depends on its subcellular location as well as its capsid binding capacity. Our results showed that following viral infection, eqMx2 changes its original cytoplasmic location and accumulates at the nuclear envelope, where it binds to the viral capsid and blocks the nuclear entry of reverse-transcribed proviral DNAs. In contrast, huMxB does not bind to the EIAV capsid and shows no EIAV restriction effect. These studies expand our understanding of the function of the equine Mx2 protein.
人溶瘤病毒抗性蛋白 2（huMxB）已被证明是一种决定 I 型干扰素（IFN）诱导的宿主因子，参与抑制人类免疫缺陷病毒 1 型（HIV-1）以及许多其他灵长类慢病毒。这种阻断发生在病毒 RNA 逆转录之后，整合到宿主 DNA 之前，这与该蛋白结合病毒衣壳的能力密切相关。迄今为止，源自非灵长类动物的 Mx2 对 HIV-1 的抑制没有显示出能力。在这项研究中，我们研究了马 Mx2（eqMx2）对马传染性贫血病毒（EIAV）和 HIV-1 的限制作用，并探讨了其特定功能的可能机制。我们证明 IFN-α/β 上调了马单核细胞衍生巨噬细胞（eMDMs）中 eqMx2 的表达。eqMx2 的过表达显著抑制了 EIAV、HIV-1 和猴免疫缺陷病毒（SIV）的复制，但不抑制鼠白血病病毒（MLV）的复制。eqMx2 转录的敲低削弱了 I 型干扰素对 EIAV 复制的抑制作用。有趣的是，免疫荧光分析的数据表明，病毒感染后 eqMx2 的亚细胞定位发生变化，从细胞质弥散到核膜聚集。此外，eqMx2 通过与病毒衣壳结合来阻止前病毒基因组的核摄取。N 端截断突变体的 eqMx2 失去了与病毒衣壳结合的能力，也失去了对慢病毒的限制作用。这些结果提高了我们对非灵长类动物 Mx2 蛋白的理解。先前的研究表明，Mx2s 的抗病毒能力仅限于灵长类动物，特别是人类。EIAV 对人 MxB 的限制作用不敏感。在这里，我们描述了马 Mx2 的功能。这种蛋白在抑制 EIAV、HIV-1 和 SIVs 中发挥重要作用。eqMx2 的抗病毒活性取决于其亚细胞定位和衣壳结合能力。我们的结果表明，病毒感染后，eqMx2 改变了其原有的细胞质位置，聚集在核膜上，在那里它与病毒衣壳结合，并阻止逆转录前病毒 DNA 的核内进入。相比之下，huMxB 不与 EIAV 衣壳结合，对 EIAV 没有限制作用。这些研究扩展了我们对马 Mx2 蛋白功能的理解。
