THE HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 REV PROTEIN SHUTTLES BETWEEN THE CYTOPLASM AND NUCLEAR COMPARTMENTS

A retroviral regulatory protein, Rev (regulator of virion protein expr ession), is made in cells infected by human immunodeficiency virus (HI V). Rev is essential for the completion of the retroviral life cycle a nd interacts with the host cell at some posttranscriptional step in or der to express the incompletely spliced HIV mRNAs from which HIV struc tural proteins are translated. Neither the host cell components nor th e mechanisms responsible for this important regulation have been defin ed. We now report that Rev is a nucleocytoplasmic shuttle protein whic h is continuously transported between the cytoplasm, the nucleoli, and nucleoplasmic speckles enriched in RNA splicing and processing factor s. The results show that Rev has the potential to interfere specifical ly with the splicing of the HIV pre-mRNA in the nucleoplasm and, next, guide such mRNAs to the cytoplasm for translation.