Like other retroviruses, the integrated proviral form of the human immunodeficiency virus (HIV) produces a multicistronic precursor transcript that can be spliced in various ways to express individual viral genes. The rev gene product of HIV is a regulatory protein that controls expression of the different viral mRNA species. Acting through a poorly-understood post-transcriptional mechanism, rev is required for the expression of virion structural proteins; this, mutant HIV provirus that lack a functional rev gene fail to produce infectious viral particles. Pharmacologic or genetic interventions aimed at inhibiting rev function might therefore provide a means to maintain viral latency, block HIV replication, and slow the progression of disease in infected persons. Using techniques of molecular genetics, we will investigate the functional architecture and mechanism of action of the rev protein and of a rev-responsive element (RRE) in the viral genome, searching for potential targets for therapeutic intervention. The effects of systematic mutations in rev and in the RRE will be evaluated in a transient-transfection assay. Modified forms of rev whose activity can be precisely controlled will be used to dissect the sequence of events in the response to this protein. We will test the ability of oligonucleotide sequences derived from the RRE, or of mutants forms of the rev protein itself, to block the activity of wild-type rev. Using stably-transfected reporter cell lines, we will develop a rapid assay system that could be used to screen potential pharmacologic inhibitors of this critical viral function. The information to be gained will be of value in designing antiviral gene therapy or specific chemotherapeutic agents, and will also provide insight into the enigmatic post-transcriptional mechanisms that control cellular, as well as viral, gene expression.