Journal of Virology, January 2001, p. 323-340, Vol. 75, No. 1
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.1.323-340.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Institute of Human Nutrition1 and Departments of Anatomy and Cell Biology,2 Microbiology,3 and Pediatrics,5 College of Physicians and Surgeons, Columbia University, New York, New York 10032, and Departments of Pediatrics and Microbiology/Immunology, Stanford University School of Medicine, Stanford, California 943054
Received 14 August 2000/Accepted 28 September 2000
Varicella-zoster virus (VZV) is enveloped in the
trans-Golgi network (TGN). Here we report that
glycoprotein I (gI) is required within the TGN for VZV
envelopment. Enveloping membranous TGN cisternae were microscopically
identified in cells infected with intact VZV. These sacs curved around,
and ultimately enclosed, nucleocapsids. Tegument coated the concave
face of these sacs, which formed the viral envelope, but the convex
surface was tegument-free. TGN cisternae of cells infected with VZV
mutants lacking gI (gI
) or its C (gI
C)-
or N-terminal (gI
N)-terminal domains were uniformly
tegument coated and adhered to one another, forming bizarre membranous
stacks. Viral envelopment was compromised, and no virions were
delivered to post-Golgi structures. The TGN was not gI-immunoreactive
in cells infected with the gI
or gI
N
mutants, but it was in cells infected with gI
C (because the ectodomains of gI and gE interact). The presence in the TGN of gI
lacking a C-terminal domain, therefore, was not sufficient to maintain
enveloping cisternae. In cells infected with intact VZV or with
gI
, gI
N, or gI
C mutants,
ORF10p immunoreactivity was concentrated on the cytosolic face of TGN
membranes, suggesting that it interacts with the cytosolic domains of
glycoproteins. Because of the gE-gI interaction,
cotransfected cells that expressed gE or gI were able to target
truncated forms of the other to the TGN. Our data suggest that the
C-terminal domain of gI is required to segregate viral and cellular
proteins in enveloping TGN cisternae.
Present address: Department of Medicine, Harvard Medical School,
Boston, Mass.
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