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Journal of Virology, May 2000, p. 4004-4016, Vol. 74, No. 9
Institutes of Molecular
Biology1 and
Infectology,2
Friedrich-Loeffler-Institutes, Federal Research Centre for Virus
Diseases of Animals, D-17498 Insel Riems, Germany, and
Department of Molecular Biology, Princeton University,
Princeton, New Jersey 085443
Received 7 December 1999/Accepted 7 February 2000
Glycoproteins M (gM), E (gE), and I (gI) of pseudorabies virus
(PrV) are required for efficient formation of mature virions. The
simultaneous absence of gM and the gE/gI complex results in severe
deficiencies in virion morphogenesis and cell-to-cell spread, leading
to drastically decreased virus titers and a small-plaque phenotype (A. Brack, J. Dijkstra, H. Granzow, B. G. Klupp, and T. C. Mettenleiter, J. Virol. 73:5364-5372, 1999). Serial passaging in
noncomplementing cells of a virus mutant unable to express gM, gE, and
gI resulted in a reversion of the small-plaque phenotype and
restoration of infectious virus formation to the level of a
gM
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Role of the Cytoplasmic Tail of Pseudorabies Virus
Glycoprotein E in Virion Formation
mutant. Genetic analyses showed that reversion of the
phenotype was accompanied by a genomic rearrangement which led to the
fusion of a portion of the gE gene encoding the cytoplasmic domain to the 3' end of the glycoprotein D gene, resulting in expression of a
chimeric gD-gE protein. Since this indicated that the intracytoplasmic domain of gE was responsible for the observed phenotypic alterations, the UL10 (gM) gene was deleted in a PrV mutant, PrV-107, which specifically lacked the cytoplasmic tail of gE. Regarding one-step growth, plaque size, and virion formation as observed under the electron microscope, the mutant lacking gM and the gE cytoplasmic tail
proved to be very similar to the gE/I/M triple mutant. Thus, our data
indicate that it is the cytoplasmic tail of gE which is responsible for
the observed phenotypic effects in conjunction with deletion of gM. We
hypothesize that the cytoplasmic domain of gE specifically interacts
with components of the capsid and/or tegument, leading to efficient
secondary envelopment of intracytoplasmic capsids.
*
Corresponding author. Mailing address: Institute of
Molecular Biology, Friedrich-Loeffler-Institutes, Federal Research
Centre for Virus Diseases of Animals, D-17498 Insel Riems, Germany.
Phone: 49-38351-7102. Fax: 49-38351-7151. E-mail:
mettenleiter{at}rie.bfav.de.
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