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Journal of Virology, November 2000, p. 10535-10550, Vol. 74, No. 22
Departamento de Mejora Genética y
Biotecnología
Received 30 May 2000/Accepted 15 August 2000
The extracellular enveloped virus (EEV) form of vaccinia virus is
bound by an envelope which is acquired by wrapping of intracellular virus particles with cytoplasmic vesicles containing trans-Golgi network markers. Six virus-encoded proteins have been reported as
components of the EEV envelope. Of these, four proteins (A33R, A34R,
A56R, and B5R) are glycoproteins, one (A36R) is a nonglycosylated transmembrane protein, and one (F13L) is a palmitylated peripheral membrane protein. During infection, these proteins localize to the
Golgi complex, where they are incorporated into infectious virus that
is then transported and released into the extracellular medium. We have
investigated the fates of these proteins after expressing them
individually in the absence of vaccinia infection, using a Semliki
Forest virus expression system. Significant amounts of proteins A33R
and A56R efficiently reached the cell surface, suggesting that they do
not contain retention signals for intracellular compartments. In
contrast, proteins A34R and F13L were retained intracellularly but
showed distributions different from that of the normal infection.
Protein A36R was partially retained intracellularly, decorating both
the Golgi complex and structures associated with actin fibers. A36R was
also transported to the plasma membrane, where it accumulated at the
tips of cell projections. Protein B5R was efficiently targeted to the
Golgi region. A green fluorescent protein fusion with the last 42 C-terminal amino acids of B5R was sufficient to target the chimeric
protein to the Golgi region. However, B5R-deficient vaccinia virus
showed a normal localization pattern for other EEV envelope proteins.
These results point to the transmembrane or cytosolic domain of B5R
protein as one, but not the only, determinant of the retention of EEV
proteins in the wrapping compartment.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Intracellular Localization of Vaccinia Virus Extracellular
Enveloped Virus Envelope Proteins Individually Expressed Using a
Semliki Forest Virus Replicon
I.N.I.A., E-28040 Madrid,
Spain,1 and European Molecular
Biology Laboratory, Cell Biology Programme, 69117 Heidelberg,
Germany2
*
Corresponding author. Mailing address: Dpt. Mejora
Genética y Biotecnología, I.N.I.A., Ctra. La Coruña
km 7.5, E-28040 Madrid, Spain. Phone: 34-91-347 39 13. Fax: 34-91-357 22 93. E-mail: blasco{at}inia.es.
Dedicated to the memory of Spanish virologist Eladio
Viñuela.
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