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Journal of Virology, March 2000, p. 2855-2866, Vol. 74, No. 6
Laboratory of Molecular Microbiology,
National Institute of Allergy and Infectious Diseases, National
Institutes of Health, Bethesda, Maryland
20892-0460,1 and Department of
Pathology, George Washington University Medical Center, Washington,
D.C. 200372
Received 27 October 1999/Accepted 22 December 1999
Human immunodeficiency virus type 1 (HIV-1) particle formation and
the subsequent initiation of protease-mediated maturation occur
predominantly on the plasma membrane. However, the mechanism by which
HIV-1 assembly is targeted specifically to the plasma membrane versus
intracellular membranes is largely unknown. Previously, we observed
that mutations between residues 84 and 88 of the matrix (MA) domain of
HIV-1 Gag cause a retargeting of virus particle formation to an
intracellular site. In this study, we demonstrate that the mutant virus
assembly occurs in the Golgi or in post-Golgi vesicles. These particles
undergo core condensation in a protease-dependent manner, indicating
that virus maturation can occur not only on the plasma membrane but
also in the Golgi or post-Golgi vesicles. The intracellular assembly of
mutant particles is dependent on Gag myristylation but is not
influenced by p6Gag or envelope glycoprotein expression.
Previous characterization of viral revertants suggested a functional
relationship between the highly basic domain of MA (amino acids 17 to
31) and residues 84 to 88. We now demonstrate that mutations in the
highly basic domain also retarget virus particle formation to the Golgi
or post-Golgi vesicles. Although the basic domain has been implicated in Gag membrane binding, no correlation was observed between the impact
of mutations on membrane binding and Gag targeting, indicating that
these two functions of MA are genetically separable. Plasma membrane
targeting of Gag proteins with mutations in either the basic domain or
between residues 84 and 88 was rescued by coexpression with wild-type
Gag; however, the two groups of MA mutants could not rescue each other.
We propose that the highly basic domain of MA contains a major
determinant of HIV-1 Gag plasma membrane targeting and that mutations
between residues 84 and 88 disrupt plasma membrane targeting through an
effect on the basic domain.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Role of the Gag Matrix Domain in Targeting Human
Immunodeficiency Virus Type 1 Assembly
*
Corresponding author. Mailing address: Bldg. 4, Rm.
307, NIAID, NIH, 9000 Rockville Pike, Bethesda, MD 20892-0460. Phone: (301) 402-3215. Fax: (301) 402-0226. E-mail: EFreed{at}nih.gov.
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