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J. Virol., Jul 1997, 4892-4903, Vol 71, No. 7
R Schneider, M Campbell, G Nasioulas, BK Felber and GN Pavlakis
The expression of gag, pol, and env of human immunodeficiency virus type 1
(HIV-1) depends on the presence of the viral Rev protein. This dependence
is, at least in part, due to the presence of negatively acting sequences
(inhibitory or instability elements [INS]) located within unspliced and
partially spliced mRNAs. The positive interaction of Rev with the
Rev-responsive element in these mRNAs counteracts the negative effects of
the inhibitory sequences. Here, we demonstrate that in addition to the
previously identified INS1 within p17gag, several other INS elements exist
within the gag/pol region of HIV-1. These elements act independently of
each other and were eliminated by mutagenesis after the introduction of
multiple point mutations not affecting the coding region, leading to
constitutive high levels of Gag expression. Expression vectors containing
an intact or nearly intact p55gag region allowed the production of immature
viral particles in mammalian cells in the absence of any other HIV
proteins. The introduction of additional mutations in the protease region
allowed efficient production of Gag/protease, which resulted in processing
of the Pr55gag precursor and production of mature Gag particles with a
lentivirus-like conical-core structure. The elimination of a newly
identified INS element within pol and the previously identified CRS located
within int was accomplished by the same methodology. Sequence comparisons
of the identified inhibitory elements revealed no apparent homologies and
demonstrated that these sequences are not splice sites. These results
demonstrate that the elimination of INS elements leads to efficient
expression of HIV-1 mRNAs in the absence of Rev or any posttranscriptional
activating mechanisms.
Copyright © 1997, American Society for Microbiology
Inactivation of the human immunodeficiency virus type 1 inhibitory elements allows Rev-independent expression of Gag and Gag/protease and particle formation
Human Retrovirus Section, National Cancer Institute-Frederick Cancer Research and Development Center, ABL-Basic Research Program, Maryland 21702-1201, USA.
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