Effect of Rev on the Cytoplasmic Localization of Intron-Containing Human Immunodeficiency Virus Type 1 RNA

Abstract

Human immunodeficiency virus type 1 (HIV-1) proteins are expressed from both intron-containing and completely spliced RNAs. Rev, an HIV-1 regulatory protein, is necessary for the expression of intron-containing RNAs. The effect of Rev on the subcellular localization of intron-containing HIV-1 RNA was examined byin situRNA hybridization. In the presence of Rev, intron-containing HIV-1 RNA accumulated at the nuclear membrane and within the cytoplasm of transfected cells. In the absence of Rev, intron-containing HIV-1 RNA accumulated within the nucleus. In ∼20% of the cells transfected in the absence of Rev, intron-containing HIV-1 RNA was also found in the cytoplasm. Differences in the subcytoplasmic localization of intron-containing HIV-1 RNA in the presence and absence of Rev were not observed usingin situRNA hybridization. To determine the effect of Rev on RNA localization within the cytoplasm, an extensive fractionation protocol involving both hypotonic and detergent lysis was used. In the presence of Rev, 40.9 ± 4.6% of the cytoplasmic intron-containing HIV-1 RNA was released by hypotonic lysis. A similar fractionation profile was seen for several other translated viral and cellular RNAs. However, in the absence of Rev, only 16.5 ± 5.1% of the cytoplasmic intron-containing HIV-1 RNA was released on hypotonic lysis (P< 0.005). Thus the cytoplasmic fractionation pattern of this RNA was altered in the absence of Rev.