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J. Virol., 11 1995, 6810-6818, Vol 69, No. 11
M Huang, JM Orenstein, MA Martin and EO Freed
The human immunodeficiency virus type 1 (HIV-1) Gag protein precursor,
Pr55Gag, contains at its C-terminal end a proline-rich, 6-kDa domain
designated p6. Two functions have been proposed for p6: incorporation of
the HIV-1 accessory protein Vpr into virus particles and virus particle
production. To characterize the role of p6 in the HIV-1 life cycle and to
map functional domains within p6, we introduced a number of nonsense and
single and multiple amino acid substitution mutations into p6. Following
the introduction of the mutations into the full- length HIV-1 molecular
clone pNL4-3, the effects on Gag protein expression and processing, virus
particle production, and virus infectivity were analyzed. The production of
mutant virus particles was also examined by transmission electron
microscopy. The results indicate that (i) p6 is required for efficient
virus particle production from a full-length HIV-1 molecular clone; (ii) a
Pro-Thr-Ala-Pro sequence, located between residues 7 and 10 of p6, is
critical for virus particle production; (iii) mutations outside the
Pro-Thr-Ala-Pro motif have little or no effect on virus assembly and
release; (iv) the p6 defect is manifested at a late stage in the budding
process; and (v) mutations in p6 that severely reduce virion production in
HeLa cells also block or significantly delay the establishment of a
productive infection in the CEM (12D-7) T-cell line. We further demonstrate
that mutational inactivation of the viral protease reverses the p6 defect,
suggesting a functional linkage between p6 and the proteolytic processing
of the Gag precursor protein during the budding of progeny virions.
Copyright © 1995, American Society for Microbiology
p6Gag is required for particle production from full-length human immunodeficiency virus type 1 molecular clones expressing protease
Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892-0460, USA.
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