Escorts unspliced or incompletely spliced viral pre-mRNAs (late transcripts) out of the nucleus of infected cells. These pre-mRNAs carry a recognition sequence called Rev responsive element (RRE) located in the env gene, that is not present in fully spliced viral mRNAs (early transcripts). This function is essential since most viral proteins are translated from unspliced or partially spliced pre-mRNAs which cannot exit the nucleus by the pathway used by fully processed cellular mRNAs (By similarity). Homomultimer; when bound to the RRE. Multimeric assembly is essential for activity (By similarity). The presence of both nuclear import and nuclear export signals leads to continuous shuttling between the nucleus and cytoplasm. The RNA-binding motif binds to the RRE, a stem-and-loop structure present in incompletely spliced viral pre-mRNAs. This region also contains the NLS which mediates nuclear localization. These overlapping functions prevent Rev bound to RRE from undesirable return to the nucleus. When Rev binds the RRE, the NLS becomes masked while the NES remains accessible (By similarity). PubMed:1323707 sequence does not seem to originate from isolate Petaluma as described, but rather from the strain San Diego.