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Journal of Virology, December 1998, p. 9806-9817, Vol. 72, No. 12
Institute for Medical Microbiology,
Received 15 June 1998/Accepted 10 September 1998
The equine herpesvirus 1 (EHV-1) IR6 protein forms typical rod-like
structures in infected cells, influences virus growth at elevated
temperatures, and determines the virulence of EHV-1 Rac strains
(Osterrieder et al., Virology 226:243-251, 1996). Experiments to
further elucidate the functions and properties of the IR6 protein were
conducted. It was shown that the IR6 protein of wild-type RacL11 virus
colocalizes with nuclear lamins very late in infection as demonstrated
by confocal laser scan microscopy and coimmunoprecipitation
experiments. In contrast, the mutated IR6 protein encoded by the RacM24
strain did not colocalize with the lamin proteins at any time
postinfection (p.i.). Electron microscopical examinations of ultrathin
sections were performed on cells infected at 37 and 40°C, the
latter being a temperature at which the IR6-negative RacH virus and the
RacM24 virus are greatly impaired in virus replication. These analyses
revealed that nucleocapsid formation is efficient at 40°C
irrespective of the virus strain. However, whereas cytoplasmic virus
particles were readily observed at 16 h p.i. in cells infected
with the wild-type EHV-1 RacL11 or an IR6-recombinant RacH virus
(HIR6-1) at 40°C, virtually no capsid translocation to the cytoplasm
was obvious in RacH- or RacM24-infected cells at the elevated
temperature, demonstrating that the IR6 protein is involved in
nucleocapsid egress. Transient transfection assays using RacL11 or
RacM24 IR6 plasmid DNA and COS7 or Rk13 cells, infection
studies using a gB-negative RacL11 mutant (L11
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
The Equine Herpesvirus 1 IR6 Protein That Colocalizes with
Nuclear Lamins Is Involved in Nucleocapsid Egress and Migrates from
Cell to Cell Independently of Virus Infection
gB) which is deficient
in direct cell-to-cell spread, and studies using lysates of
IR6-transfected cells demonstrated that the wild-type IR6 protein is
transported from cell to cell in the absence of virus infection and can
enter cells by a yet unknown mechanism.
*
Corresponding author. Mailing address: Institute of
Molecular and Cellular Virology, Friedrich-Loeffler-Institutes, Federal Research Centre for Virus Diseases of Animals, D-17498 Insel Riems, Germany. Phone: 49-38351-7266. Fax: 49-38351-7151. E-mail:
klaus.osterrieder{at}rie.bfav.de.
Journal of Virology, December 1998, p. 9806-9817, Vol. 72, No. 12
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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