Structures of immature EIAV Gag lattices reveal a conserved role for IP6 in lentivirus assembly
Structures of immature EIAV Gag lattices reveal a conserved role for IP6 in lentivirus assembly
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DOI：
10.1371/journal.ppat.1008277
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发表时间：
2020-01-01
期刊：
影响因子：
6.7
通讯作者：
Schur, Florian K. M.
中科院分区：
文献类型：
--
作者：
Dick, Robert A.;Xu, Chaoyi;Schur, Florian K. M.
逆转录病毒装配由多结构域结构蛋白Gag驱动。Gag的衣壳结构域（CA）之间的相互作用导致Gag多聚化，从而产生由基于二聚体、三聚体和六聚体蛋白质接触的蛋白质晶格形成的未成熟病毒颗粒。在逆转录病毒中，六聚体间和六聚体内的接触是不同的，尤其是在CA的N-末端亚结构域（CA（NTD））中。对于HIV-1，细胞分子肌醇六磷酸（IP 6）与未成熟的六聚体相互作用并使其稳定，并且是产生感染性病毒颗粒所必需的。我们使用体外组装，冷冻电子断层扫描和subtomography平均，原子分子动力学模拟和突变分析，研究艾滋病病毒相关的慢病毒马传染性贫血病毒（EIAV）。特别是，我们试图了解不成熟的慢病毒晶格的结构保守性和IP 6在EIAV组装中的作用。与HIV-1相似，IP 6强烈促进EIAV Gag蛋白在体外组装成病毒样颗粒（VLP），其具有三种形态上高度不同的形式：窄管，宽管和球体。这些VLP的亚4埃分辨率的结构表征出乎意料地表明，所有三种形态都基于具有保留的关键结构组分的未成熟晶格，突出了CA形成未成熟组装体的结构多功能性。EIAV和HIV之间的直接比较显示，两种慢病毒都保持着相似的不成熟界面，这些界面由保守和非保守残基建立。在EIAV和HIV-1中，IP 6通过CA（CTD）和SP内的保守赖氨酸残基调节未成熟组装。最后，我们证明了IP 6刺激慢病毒属中其他几种逆转录病毒的未成熟颗粒的体外组装，提示IP 6在慢病毒装配中的保守作用。作者摘要结构多聚蛋白Gag在所有逆转录病毒中是保守的，并通过寡聚化介导病毒装配成通过二聚体、三聚体和六聚体接触稳定的不完全晶格。尽管在二级和三级结构水平上高度保守，但逆转录病毒Gag的CA结构域之间的四级相互作用各不相同。最近，小细胞分子IP 6被鉴定为慢病毒HIV-1的组装辅因子。为了更好地了解逆转录病毒的结构变异性，并确定IP 6是否是其他慢病毒的组装辅因子，我们确定了HIV-1相关逆转录病毒EIAV的结构。使用冷冻电子断层扫描和亚断层平均，在体外组装，突变分析，和分子动力学模拟，我们确定和特征的EIAV不成熟的晶格结构。此外，我们发现IP 6是EIAV和其他慢病毒的装配辅因子。
Retrovirus assembly is driven by the multidomain structural protein Gag. Interactions between the capsid domains (CA) of Gag result in Gag multimerization, leading to an immature virus particle that is formed by a protein lattice based on dimeric, trimeric, and hexameric protein contacts. Among retroviruses the inter- and intra-hexamer contacts differ, especially in the N-terminal sub-domain of CA (CA(NTD)). For HIV-1 the cellular molecule inositol hexakisphosphate (IP6) interacts with and stabilizes the immature hexamer, and is required for production of infectious virus particles. We have used in vitro assembly, cryo-electron tomography and subtomogram averaging, atomistic molecular dynamics simulations and mutational analyses to study the HIV-related lentivirus equine infectious anemia virus (EIAV). In particular, we sought to understand the structural conservation of the immature lentivirus lattice and the role of IP6 in EIAV assembly. Similar to HIV-1, IP6 strongly promoted in vitro assembly of EIAV Gag proteins into virus-like particles (VLPs), which took three morphologically highly distinct forms: narrow tubes, wide tubes, and spheres. Structural characterization of these VLPs to sub-4 angstrom resolution unexpectedly showed that all three morphologies are based on an immature lattice with preserved key structural components, highlighting the structural versatility of CA to form immature assemblies. A direct comparison between EIAV and HIV revealed that both lentiviruses maintain similar immature interfaces, which are established by both conserved and non-conserved residues. In both EIAV and HIV-1, IP6 regulates immature assembly via conserved lysine residues within the CA(CTD) and SP. Lastly, we demonstrate that IP6 stimulates in vitro assembly of immature particles of several other retroviruses in the lentivirus genus, suggesting a conserved role for IP6 in lentiviral assembly.Author summary The structural polyprotein Gag is conserved among all retroviruses and mediates virus assembly via oligomerization into incomplete lattices that are stabilized by dimeric, trimeric and hexameric contacts. Despite a high degree of conservation at the secondary and tertiary structure level, the quaternary interactions between the CA domains of retroviral Gag vary. Recently, the small cellular molecule IP6 was identified as an assembly co-factor of the lentivirus HIV-1. To better understand the structural variability of retroviruses and to determine if IP6 is an assembly cofactor of other lentiviruses we determined the structure of the HIV-1 related retrovirus EIAV. Using cryo-electron tomography and subtomogram averaging, in vitro assembly, mutation analysis, and molecular dynamic simulations, we determined and characterized the structure of the EIAV immature lattice. Furthermore, we found that IP6 is an assembly cofactor of EIAV, and other lentiviruses.