6odm
Herpes simplex virus type 1 (HSV-1) portal vertex-adjacent capsid/CATC, asymmetric unit
Structural highlights
Function[D3YPI2_HHV1] Capsid vertex-specific component that plays a role during viral DNA encapsidation, assuring correct genome cleavage and presumably stabilizing capsids that contain full-length viral genomes. Participates in the interaction between the capsid and the tegument through interaction with the large tegument protein/LTP.[HAMAP-Rule:MF_04025] [G8H8D9_HHV1] Structural component of the T=16 icosahedral capsid. The capsid is composed of pentamers and hexamers of major capsid protein/MCP, which are linked together by heterotrimers called triplexes. These triplexes are formed by a single molecule of triplex protein 1/TRX1 and two copies of triplex protein 2/TRX2. Additionally, TRX1 is required for efficient transport of TRX2 to the nucleus, which is the site of capsid assembly.[HAMAP-Rule:MF_04019] [H9E925_HHV1] Self-assembles to form an icosahedral capsid with a T=16 symmetry, about 200 nm in diameter, and consisting of 150 hexons and 12 pentons (total of 162 capsomers). Hexons form the edges and faces of the capsid and are each composed of six MCP molecules. In contrast, one penton is found at each of the 12 vertices. Eleven of the pentons are MCP pentamers, while the last vertex is occupied by the portal complex. The capsid is surrounded by a layer of proteinaceous material designated the tegument which, in turn, is enclosed in an envelope of host cell-derived lipids containing virus-encoded glycoproteins.[HAMAP-Rule:MF_04016] [Q1T724_HHV1] Structural component of the T=16 icosahedral capsid. The capsid is composed of pentamers and hexamers of major capsid protein/MCP, which are linked together by heterotrimers called triplexes. These triplexes are formed by a single molecule of triplex protein 1/TRX1 and two copies of triplex protein 2/TRX2. Additionally, TRX1 is required for efficient transport of TRX2 to the nucleus, which is the site of capsid assembly.[HAMAP-Rule:MF_04018] [A0A0B5E3K2_HHV1] Large tegument protein that plays multiple roles in the viral cycle. During viral entry, remains associated with the capsid while most of the tegument is detached and participates in the capsid transport toward the host nucleus. Plays a role in the routing of the capsid at the nuclear pore complex and subsequent uncoating. Within the host nucleus, acts as a deneddylase and promotes the degradation of nuclear CRLs (cullin-RING ubiquitin ligases) and thereby stabilizes nuclear CRL substrates, while cytoplasmic CRLs remain unaffected. These modifications prevent host cell cycle S-phase progression and create a favorable environment allowing efficient viral genome replication. Participates later in the secondary envelopment of capsids. Indeed, plays a linker role for the association of the outer viral tegument to the capsids together with the inner tegument protein.[HAMAP-Rule:MF_04044] [Q25BW6_HHV1] Participates in the assembly of the infectious particles by decorating the outer surface of the capsid shell and thus forming a layer between the capsid and the tegument. Complexes composed of the major capsid protein and small capsomere-interacting protein/SCP assemble together in the host cytoplasm and are translocated to the nucleus, where they accumulate and participate in capsid assembly.[HAMAP-Rule:MF_04020] [F8REV0_HHV1] Capsid vertex-specific component that plays a role during viral DNA encapsidation, assuring correct genome cleavage and presumably stabilizing capsids that contain full-length viral genomes.[HAMAP-Rule:MF_04017] Publication Abstract from PubMedHerpesviruses are enveloped viruses that are prevalent in the human population and are responsible for diverse pathologies, including cold sores, birth defects and cancers. They are characterized by a highly pressurized pseudo-icosahedral capsid-with triangulation number (T) equal to 16-encapsidating a tightly packed double-stranded DNA (dsDNA) genome(1-3). A key process in the herpesvirus life cycle involves the recruitment of an ATP-driven terminase to a unique portal vertex to recognize, package and cleave concatemeric dsDNA, ultimately giving rise to a pressurized, genome-containing virion(4,5). Although this process has been studied in dsDNA phages(6-9)-with which herpesviruses bear some similarities-a lack of high-resolution in situ structures of genome-packaging machinery has prevented the elucidation of how these multi-step reactions, which require close coordination among multiple actors, occur in an integrated environment. To better define the structural basis of genome packaging and organization in herpes simplex virus type 1 (HSV-1), we developed sequential localized classification and symmetry relaxation methods to process cryo-electron microscopy (cryo-EM) images of HSV-1 virions, which enabled us to decouple and reconstruct hetero-symmetric and asymmetric elements within the pseudo-icosahedral capsid. Here we present in situ structures of the unique portal vertex, genomic termini and ordered dsDNA coils in the capsid spooled around a disordered dsDNA core. We identify tentacle-like helices and a globular complex capping the portal vertex that is not observed in phages, indicative of herpesvirus-specific adaptations in the DNA-packaging process. Finally, our atomic models of portal vertex elements reveal how the fivefold-related capsid accommodates symmetry mismatch imparted by the dodecameric portal-a longstanding mystery in icosahedral viruses-and inform possible DNA-sequence recognition and headful-sensing pathways involved in genome packaging. This work showcases how to resolve symmetry-mismatched elements in a large eukaryotic virus and provides insights into the mechanisms of herpesvirus genome packaging. Cryo-EM structures of herpes simplex virus type 1 portal vertex and packaged genome.,Liu YT, Jih J, Dai X, Bi GQ, Zhou ZH Nature. 2019 Jun;570(7760):257-261. doi: 10.1038/s41586-019-1248-6. Epub 2019 May, 29. PMID:31142842[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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