INACTIVATION OF THE HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INHIBITORY ELEMENTS ALLOWS REV-INDEPENDENT EXPRESSION OF GAG AND GAG PROTEASE AND PARTICLE FORMATION/

The expression of gag, pol, and env of human immunodeficiency virus ty pe 1 (HIV-1) depends on the presence of the viral Rev protein, This de pendence is, at least in part, due to the presence of negatively actin g 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 negati ve effects of the inhibitory sequences, Here, we demonstrate that in a ddition to the previously identified INS1 within p17(gag), several oth er INS elements exist within the gag/pol region of HIV-1 These element s act independently of each other and were eliminated by mutagenesis a fter the introduction of multiple paint mutations not affecting the co ding region, leading to constitutive high levels of Gag expression, Ex pression vectors containing an intact or nearly intact p55(gag) region allowed the production of immature viral particles in mammalian cells in the absence of any other HN proteins, The introduction of addition al mutations in the protease region allowed efficient production of Ga g/protease, which resulted in processing of the Pr55(gag) precursor an d production of mature Gag particles with a lentivirus-like conical-co re structure, The elimination of a newly identified INS clement within pol and the previously identified CRS located within int was accompli shed by tile same methodology, Sequence comparisons of the identified inhibitory elements revealed no apparent homologies and demonstrated t hat these sequences are not splice sites, These results demonstrate th at the elimination of INS elements leads to efficient expression of HI V-1 mRNAs in the absence of Rev or any posttranscriptional activating mechanisms.