Characterization of a nuclear retention sequence within the 3' region of the HIV-2 envelope gene

During the phenotypic analysis of mutations in the HIV-2 envelope protein (gp140), we have identified a mutant that expresses high levels of gp140 in the absence of the Rev protein. This mutant was obtained by deletion of a 190-base pair fragment at the end of the env coding region. Northern blot analysis of RNAs produced by transfected HeLa cells showed that this fragment inhibits the cytoplasmic transport of unspliced env-specific RNAs in the absence of Rev. The "inhibitory element" was only active in the sense orientation and appeared to be specific for unspliced HIV-2 env RNAs, suggesting that it may have an important regulatory role for HIV-2 expression.