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J. Virol., 09 1997, 6339-6347, Vol 71, No. 9
S Mahalingam, V Ayyavoo, M Patel, T Kieber-Emmons and DB Weiner
The vpr gene product of human immunodeficiency virus type 1 (HIV-1) is a
virion-associated protein that is essential for efficient viral replication
in monocytes/macrophages. Vpr is primarily localized in the nucleus when
expressed in the absence of other viral proteins. Vpr is packaged
efficiently into viral particles through interactions with the p6 domain of
the Gag precursor polyprotein p55gag. We developed a panel of expression
vectors encoding Vpr molecules mutated in the amino- terminal helical
domain, leucine-isoleucine (LR) domain, and carboxy- terminal domain to map
the different functional domains and to define the interrelationships
between virion incorporation, nuclear localization, cell cycle arrest, and
differentiation functions of Vpr. We observed that substitution mutations
in the N-terminal domain of Vpr impaired both nuclear localization and
virion packaging, suggesting that the helical structure may play a vital
role in modulating both of these biological properties. The LR domain was
found to be involved in the nuclear localization of Vpr. In contrast, cell
cycle arrest appears to be largely controlled by the C-terminal domain of
Vpr. The LR and C- terminal domains do not appear to be essential for
virion incorporation of Vpr. Interestingly, we found that two Vpr mutants
harboring single amino acid substitutions (A30L and G75A) retained the
ability to translocate to the nucleus but were impaired in the cell cycle
arrest function. In contrast, mutation of Leu68 to Ser resulted in a
protein that localizes in the cytoplasm while retaining the ability to
arrest host cell proliferation. We speculate that the nuclear localization
and cell cycle arrest functions of Vpr are not interrelated and that these
functions are mediated by separable putative functional domains of Vpr.
Copyright © 1997, American Society for Microbiology
Nuclear import, virion incorporation, and cell cycle arrest/differentiation are mediated by distinct functional domains of human immunodeficiency virus type 1 Vpr
Department of Pathology, School of Medicine, University of Pennsylvania Medical Center, Philadelphia 19104, USA.
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