Rev-dependent expression of human immunodeficiency virus type 1 gp160 in Drosophila melanogaster cells

Expression of the human immunodeficiency virus (HIV) structural proteins in mammalian cells is regulated posttranscriptionally by the viral Rev protein. Rev has been shown to trans-activate expression by relieving the nuclear sequestration of RNAs containing viral gag or env coding regions. We have studied the effects of Rev on expression of the HIV type 1 env gene in Drosophila melanogaster cells. We demonstrated that synthesis of the gp160 envelope protein was fully Rev dependent; that is, gp160 was produced only when Rev function was coexpressed in the cell. Analysis of total cellular RNA indicated that Rev did not significantly affect the overall levels of gp160 RNA production. Instead, mRNA encoding gp160 was found in the cytoplasm only in cells expressing Rev, whereas in cells lacking Rev, this RNA was present only in the nucleus. Furthermore, comparison of these results with the previously demonstrated Rev-independent expression of gp120 envelope protein with this system indicated that information contained in the gp41 coding region appears to be critical to the selective nuclear retention of gp160 transcripts in the absence of Rev. Our results clearly demonstrate that the mechanism of Rev action is conserved in the insect cell system, and, thus, Rev must function via cellular machinery common to most, if not all, higher cell systems.