Structure of the herpes simplex virus portal-vertex.
Structure of the herpes simplex virus portal-vertex.
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DOI：
10.1371/journal.pbio.2006191
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发表时间：
2018-06
期刊：
影响因子：
9.8
通讯作者：
Bhella D
中科院分区：
文献类型：
--
作者：
McElwee M;Vijayakrishnan S;Rixon F;Bhella D
疱疹病毒包括许多重要的人类病原体，如单纯疱疹病毒、巨细胞病毒、水痘-带状疱疹病毒和致癌性EB病毒和卡波西肉瘤相关疱疹病毒。疱疹病毒粒子包含一个大的二十面体衣壳，在一个独特的5倍顶点有一个门户，类似于在有尾噬菌体中看到的。门户是病毒基因组在病毒体形态发生期间进入衣壳的分子马达。当基因组通过核孔注射到新宿主细胞的核中以引发感染时，基因组也通过门顶离开衣壳。疱疹病毒门顶的结构研究已被证明具有挑战性，由于尾状门顶相关被膜（PVAT）的尺寸小，以及位于核衣壳和病毒包膜之间的被膜层的存在，模糊了门顶的视图。在这里，我们显示了单纯疱疹病毒的门户顶点在亚纳米分辨率的结构，解决了电子冷冻显微镜（cryoEM）和单粒子三维重建。这导致了一些新的发现，包括两个以前未知的门户相关结构的存在，占据了通常由五子和Ta三重体占据的位置。我们的数据显示PVAT由10个拷贝的pUL 25的C-末端结构域组成，它们独特地排列为两层星形密度。我们的门户顶点的3D重建还表明，病毒基因组的一端延伸到门户以外的方式描述的一些噬菌体，但以前没有看到在任何真核病毒。最后，我们表明，病毒基因组始终包装在一个高度有序的左手线轴，形成同心壳的DNA。我们的数据提供了对一类重要的人类病原体生物学至关重要的分子机器结构的新见解。疱疹病毒家族包括许多重要的人类病原体，如引起唇疱疹的单纯疱疹病毒和人巨细胞病毒，这是先天性异常的主要原因。已知几种疱疹病毒会导致癌症。疱疹病毒组装有包膜的病毒颗粒（病毒体），其中包含一个大的含DNA的二十面体衣壳。病毒体组装开始于受感染细胞的细胞核中，其中病毒基因组通过位于独特的5重对称轴（门户顶点）处的门户马达被泵入预先组装的衣壳中。我们已经使用低温电子显微镜和三维图像重建，以解决8毫米分辨率的单纯疱疹病毒1型的门顶结构。我们的结构揭示了几个以前未知的功能，包括一个新的五聚体组装，展示了一个卷曲螺旋基序，包括两个α-螺旋的存在。这取代了五邻体，五邻体是在其他5重对称轴（五邻体顶点）处看到的主要衣壳蛋白的五聚体。我们的数据使我们能够假设一个身份的小尾状结构，以前确定在门户顶点，并称为门户顶点相关的皮层（PVAT）。最后，我们的3D重建显示，病毒DNA被包装在衣壳内，作为一个左旋线轴，排列在同心壳中。我们的数据呈现了一个分子机器的结构视图，该分子机器在人类病原体的一个重要家族的复制周期中起着关键作用。
Herpesviruses include many important human pathogens such as herpes simplex virus, cytomegalovirus, varicella-zoster virus, and the oncogenic Epstein–Barr virus and Kaposi sarcoma–associated herpesvirus. Herpes virions contain a large icosahedral capsid that has a portal at a unique 5-fold vertex, similar to that seen in the tailed bacteriophages. The portal is a molecular motor through which the viral genome enters the capsid during virion morphogenesis. The genome also exits the capsid through the portal-vertex when it is injected through the nuclear pore into the nucleus of a new host cell to initiate infection. Structural investigations of the herpesvirus portal-vertex have proven challenging, owing to the small size of the tail-like portal-vertex–associated tegument (PVAT) and the presence of the tegument layer that lays between the nucleocapsid and the viral envelope, obscuring the view of the portal-vertex. Here, we show the structure of the herpes simplex virus portal-vertex at subnanometer resolution, solved by electron cryomicroscopy (cryoEM) and single-particle 3D reconstruction. This led to a number of new discoveries, including the presence of two previously unknown portal-associated structures that occupy the sites normally taken by the penton and the Ta triplex. Our data revealed that the PVAT is composed of 10 copies of the C-terminal domain of pUL25, which are uniquely arranged as two tiers of star-shaped density. Our 3D reconstruction of the portal-vertex also shows that one end of the viral genome extends outside the portal in the manner described for some bacteriophages but not previously seen in any eukaryote viruses. Finally, we show that the viral genome is consistently packed in a highly ordered left-handed spool to form concentric shells of DNA. Our data provide new insights into the structure of a molecular machine critical to the biology of an important class of human pathogens. The herpesvirus family includes many important human pathogens such as herpes simplex viruses that cause cold-sores and human cytomegalovirus, a major cause of congenital abnormalities. Several herpes viruses are known to cause cancer. Herpes viruses assemble enveloped virus particles (virions) that incorporate a large DNA-containing icosahedral capsid. Virion assembly commences in the nucleus of an infected cell, where the viral genome is pumped into preassembled capsids by a portal motor that is located at a unique 5-fold symmetry axis: the portal-vertex. We have used cryogenic electron microscopy and 3D image reconstruction to solve the structure of the portal-vertex of herpes simplex virus type 1 at 8 Å resolution. Our structure reveals the presence of several previously unknown features including a novel pentameric assembly that exhibits a coiled-coil motif comprising two α-helices. This substitutes the penton, a pentamer of the major capsid protein that is seen at other 5-fold symmetry axes (penton-vertices). Our data allowed us to postulate an identity for the small tail-like structure previously identified at the portal-vertex and termed the portal-vertex–associated tegument (PVAT). Finally, our 3D reconstruction reveals that the viral DNA is packaged within the capsid as a left-handed spool that is arranged in concentric shells. Our data present a structural view of a molecular machine that plays a critical role in the replication cycle of an important family of human pathogens.
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