In the absence of the rev gene, the hostRNA splicing machinery in the nucleus quickly splices the RNA so that only the regulatory proteins Rev and Tat and the accessory protein Nef can be produced. In the presence of rev, RNA is exported from the nucleus before it can be spliced, so that the structural proteins and RNA genome can be produced. This mechanism allows a positive feedback loop to allow HIV to overwhelm the host's defenses, and provides time-dependent regulation of replication.
Rev gene coding sequence is supplied in a separate plasmid along with structural and functional gene containing plasmid (gag-pol) for the safe production of HIV-1 in the laboratory for research purpose. Viral like particles (VLPs) production wont occur if this Rev protein production is missing.