The rev protein of human immunodeficiency virus type 1 (HIV-1), a phosphoprotein of 20 kDa apparent molecular mass, is essential to target the mRNA for virion polypeptides into the cytoplasm. This effect is mediated by a specific RNA stretch (rev-responsive element = RRE) localized within a 3′-terminal segment of the mRNA encoding virion proteins. We present evidence that rev expressed as a β-galactosidase fusion protein in E. coli forms a complex with in vitro transcripts containing the RRE; it can be precipitated by monoclonal antibodies with rev or β-galactosidasespecificity. In addition, specific binding of rev protein to RNA could be demonstrated by Northwestern blotting.
