Human immunodeficiency virus type 1 rev protein as a negative trans-regulator.

Even though the rev gene of the human immunodeficiency virus type 1 (HIV-1) is essential for viral replication, high levels of rev also downregulate viral gene expression. As the degree of rev protein expression exceeds expression of wild-type virus, a gradient of decreasing viral mRNA synthesis becomes evident. The target sequence for this downregulation resides outside of trans-activating region (TAR) and upstream from the enhancer sequences in the long terminal repeat (LTR), suggesting that regulation is at a transcriptional level.