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J. Virol., Jan 1998, 104-112, Vol 72, No. 1
X Hu, EJ Wolffe, AS Weisberg, LJ Carroll and B Moss
The vaccinia virus early transcription factor (VETF) is a DNA binding
protein comprised of 70- and 82-kDa subunits encoded by the D6R and A8L
genes, respectively. A previous investigation suggested a novel role for
the 70-kDa subunit in the morphogenesis of vaccinia virus particles. The
principal objectives of the present study were to determine if the 82-kDa
subunit of VETF is also required for morphogenesis and, if so, whether the
block occurs before or after the incorporation of the genome into the
assembling virus particle. To address these and other questions, we
constructed and characterized a conditionally lethal recombinant vaccinia
virus in which the A8L gene is stringently repressed by the Escherichia
coli lac operator system. The amount of 82-kDa protein synthesized could be
regulated by the amount of inducer: from undetectable to higher than normal
levels. Virus replication, as determined by plaque formation or virus yield
upon synchronous infection, was dependent on inducer. Nevertheless, de novo
synthesis of the 82-kDa subunit was not required for viral early,
intermediate, and late gene expression or DNA replication. Overexpression
of the A8L gene alone, produced by high concentrations of inducer,
inhibited viral late protein synthesis, whereas overexpression of the D6R
gene alone or both VETF genes simultaneously had little inhibitory effect.
Laser confocal fluorescence and quantitative electron microscopic analyses
revealed that immature and DNA-containing intermediate stage particles
accumulated in the absence of inducer, indicating that the A8L protein has
a role in morphogenesis of the core and subsequent events.
Copyright © 1998, American Society for Microbiology
Repression of the A8L gene, encoding the early transcription factor 82- kilodalton subunit, inhibits morphogenesis of vaccinia virions
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892-0445, USA.
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