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Genetic analysis of the vaccinia virus I6 telomere-binding protein uncovers a key role in genome encapsidation

Grubisha, Olivera ORCID: and Traktman, P. 2003. Genetic analysis of the vaccinia virus I6 telomere-binding protein uncovers a key role in genome encapsidation. Journal of Virology 77 (20) , pp. 10929-10942. 10.1128/JVI.77.20.10929-10942.2003

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The linear, double-stranded DNA genome of vaccinia virus contains covalently closed hairpin termini. These hairpin termini comprise a terminal loop and an A+T-rich duplex stem that has 12 extrahelical bases. DeMasi et al. have shown previously that proteins present in infected cells and in virions form distinct complexes with the telomeric hairpins and that these interactions require the extrahelical bases. The vaccinia virus I6 protein was identified as the protein showing the greatest specificity and affinity for interaction with the viral hairpins (J. DeMasi, S. Du, D. Lennon, and P. Traktman, J. Virol. 75:10090-10105, 2001). To gain insight into the role of I6 in vivo, we generated eight recombinant viruses bearing altered alleles of I6 in which clusters of charged amino acids were changed to alanine residues. One allele (temperature-sensitive I6-12 [tsI6-12]) conferred a tight ts phenotype and was used to examine the stage(s) of the viral life cycle that was affected at the nonpermissive temperature. Gene expression, DNA replication, and genome resolution proceeded normally in this mutant. However, proteolytic processing of structural proteins, which accompanies virus maturation, was incomplete. Electron microscopic studies confirmed a severe block in morphogenesis in which immature, but no mature, virions were observed. Instead, aberrant spherical virions and large crystalloids were seen. When purified, these aberrant virions were found to have normal protein content but to be devoid of viral DNA. We propose that the binding of I6 to viral telomeres directs genome encapsidation into the virus particle.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Biosciences
Publisher: American Society for Microbiology
ISSN: 0022-538X
Funders: 2004-01-21
Date of First Compliant Deposit: 6 August 2018
Date of Acceptance: 21 July 2003
Last Modified: 06 May 2023 03:25

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