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J. Virol., Aug 1997, 6049-6054, Vol 71, No. 8
B He, J Chou, R Brandimarti, I Mohr, Y Gluzman and B Roizman
Earlier studies have shown that infection of human cells by herpes simplex
virus 1 (HSV-1) results in the activation of RNA-dependent protein kinase
(PKR) but that the alpha subunit of eIF-2 is not phosphorylated and that
protein synthesis is unaffected. In the absence of the viral gamma(1)34.5
gene, eIF-2alpha is phosphorylated and protein synthesis is prematurely
shut off (J. Chou, J. J. Chen, M. Gross, and B. Roizman, Proc. Natl. Acad.
Sci. USA 92:10516-10520, 1995). A second recent paper reported the
selection of second-site suppressor mutants characterized by near-wild-type
protein synthesis in cells infected with gamma(1)34.5- mutants (I. Mohr and
Y. Gluzman, EMBO J. 15:4759-4766, 1996). Here, we report the properties of
the spontaneous HSV-1 suppressor mutant Sup-1, which is characterized by
spontaneous deletion of 503 bp encompassing the domain of the alpha47 gene
and junction with the inverted repeats flanking the unique short (U(S))
sequence of the HSV-1 DNA resulting in the juxtaposition of the alpha47
promoter to the coding domain of the U(S)11 gene. This mutant does not
exhibit the shutoff of protein synthesis characteristic of the
gamma(1)34.5- virus. Specifically, Sup-1 in SK-N-SH human neuroblastoma
cells (i) did not exhibit the function of the alpha47 gene characterized by
a reduction in the transport of peptides across the endoplasmic reticulum
of permealized cells consistent with the absence of alpha47 gene sequences,
(ii) accumulated U(S)11 protein at levels analogous to those of the
wild-type parent but the protein was made at earlier times after infection,
as would be expected from a change in the promoter, and (iii) activated PKR
like that of the parent, gamma(1)34.5- virus, but (iv) did not cause
premature shutoff of protein synthesis and therefore was similar to the
wild-type parent virus rather than the gamma(1)34.5- virus from which it
was derived. We conclude that the mechanism by which Sup-1 blocks the
shutoff of protein synthesis associated with phosphorylation of eIF-2alpha
by the activated PKR is not readily explainable by a secondary mutation
characterized by a deletion.
Copyright © 1997, American Society for Microbiology
Suppression of the phenotype of gamma(1)34.5- herpes simplex virus 1: failure of activated RNA-dependent protein kinase to shut off protein synthesis is associated with a deletion in the domain of the alpha47 gene
The Marjorie B. Kovler Viral Oncology Laboratories, The University of Chicago, Illinois 60637, USA.
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