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Vaccinia virus H7-protein is required for the organization of the viral scaffold protein into hexamers.

ABSTRACT: Viruses of the giant virus family are characterized by a structurally conserved scaffold-capsid protein that shapes the icosahedral virion. The vaccinia virus (VACV) scaffold protein D13, however, transiently shapes the newly assembled viral membrane in to a sphere and is absent from the mature brick-shaped virion. In infected cells D13, a 62 kDa polypeptide, forms trimers that arrange in hexamers and a honey-comb like lattice. Membrane association of the D13-lattice may be mediated by A17, an abundant 21 kDa viral membrane protein. Whether membrane binding mediates the formation of the honey-comb lattice or if other factors are involved, remains elusive. Here we show that H7, a 17 kDa protein conserved among poxviruses, mediates proper formation of D13-hexamers, and hence the honey comb lattice and spherical immature virus. Without H7 synthesis D13 trimers assemble into a large 3D network rather than the typical well organized scaffold layer observed in wild-type infection, composed of short D13 tubes of discrete length that are tightly associated with the endoplasmic reticulum (ER). The data show an unexpected role for H7 in D13 organization and imply that formation of the honey-comb, hexagonal, lattice is essential for VACV membrane assembly and production of infectious progeny. The data are discussed with respect to scaffold proteins of other giant viruses.

SUBMITTER: Tonnemacher S

PROVIDER: S-EPMC9338303 | biostudies-literature | 2022 Jul

REPOSITORIES: biostudies-literature

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Vaccinia virus H7-protein is required for the organization of the viral scaffold protein into hexamers.

Tonnemacher Susanne S Folly-Klan Marcia M Gazi Anastasia D AD Schäfer Simon S Pénard Esthel E Eberle Regina R Kunz Renate R Walther Paul P Krijnse Locker Jacomine J

Scientific reports 20220729 1

Viruses of the giant virus family are characterized by a structurally conserved scaffold-capsid protein that shapes the icosahedral virion. The vaccinia virus (VACV) scaffold protein D13, however, transiently shapes the newly assembled viral membrane in to a sphere and is absent from the mature brick-shaped virion. In infected cells D13, a 62 kDa polypeptide, forms trimers that arrange in hexamers and a honey-comb like lattice. Membrane association of the D13-lattice may be mediated by A17, an a ...[more]

PMID: 35906465

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Project description:UnlabelledPoxviridae are viruses with a large linear double-stranded DNA genome coding for up to 250 open reading frames and a fully cytoplasmic replication. The double-stranded DNA genome is covalently circularized at both ends. Similar structures of covalently linked extremities of the linear DNA genome are found in the African swine fever virus (asfarvirus) and in the Phycodnaviridae We are studying the machinery which replicates this peculiar genome structure. From our work with vaccinia virus, we give first insights into the overall structure and function of the essential poxvirus virus helicase-primase D5 and show that the active helicase domain of D5 builds a hexameric ring structure. This hexamer has ATPase and, more generally, nucleoside triphosphatase activities that are indistinguishable from the activities of full-length D5 and that are independent of the nature of the base. In addition, hexameric helicase domains bind tightly to single- and double-stranded DNA. Still, the monomeric D5 helicase construct truncated within the D5N domain leads to a well-defined structure, but it does not have ATPase or DNA-binding activity. This shows that the full D5N domain has to be present for hexamerization. This allowed us to assign a function to the D5N domain which is present not only in D5 but also in other viruses of the nucleocytoplasmic large DNA virus (NCLDV) clade. The primase domain and the helicase domain were structurally analyzed via a combination of small-angle X-ray scattering and, when appropriate, electron microscopy, leading to consistent low-resolution models of the different proteins.ImportanceSince the beginning of the 1980s, research on the vaccinia virus replication mechanism has basically stalled due to the absence of structural information. As a result, this important class of pathogens is less well understood than most other viruses. This lack of information concerns in general viruses of the NCLDV clade, which use a superfamily 3 helicase for replication, as do poxviruses. Here we provide for the first time information about the domain structure and DNA-binding activity of D5, the poxvirus helicase-primase. This result not only refines the current model of the poxvirus replication fork but also will lead in the long run to a structural basis for antiviral drug design.

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Vaccinia virus H7-protein is required for the organization of the viral scaffold protein into hexamers.

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Vaccinia virus H7-protein is required for the organization of the viral scaffold protein into hexamers.

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