Abstract
BackgroundEfficient incorporation of the cellular cytidine deaminase APOBEC3G (APO3G) into HIV-1 virions is necessary for its antiviral activity. Even though cellular RNAs are known to be non-specifically incorporated into virus particles, we have previously found that encapsidation of APO3G into HIV-1 virions is specifically enhanced by viral genomic RNA. Intracellularly, APO3G was found to form large RNA-protein complexes involving a variety of cellular RNAs. The goal of this study was to investigate the possible contribution of host RNAs recently identified in intracellular APO3G ribonucleoprotein complexes to APO3G's encapsidation into HIV-1 virions.ResultsOur results show that 7SL RNA, a component of signal recognition particles, and hY1, hY3, hY4, hY5 RNAs were present in intracellular APO3G complexes and were packaged into HIV-1 particles lacking viral genomic RNA unlike APO3G, which was not packaged in significant amounts into genomic RNA-deficient particles. These results indicate that packaging of 7SL or hY RNAs is not sufficient for the packaging of APO3G into HIV-1 virions. We also tested the encapsidation of several other cellular RNAs including β-actin, GAPDH, α-tubulin, and small nuclear RNAs and determined their effect on the packaging of APO3G into nascent virions. Again, we were unable to observe any correlation between APO3G encapsidation and the packaging of any of these cellular RNAs.ConclusionThe results from this study support our previous conclusion that viral genomic RNA is a critical determinant for APO3G incorporation into HIV-1 virions. While most cellular RNAs tested in this study were packaged into viruses or virus-like particles we failed to identify a correlation between APO3G encapsidation and the packaging of these cellular RNAs.
Highlights
Efficient incorporation of the cellular cytidine deaminase APOBEC3G (APO3G) into HIV-1 virions is necessary for its antiviral activity
Our results demonstrate that cellular RNAs are not sufficient for the encapsidation of APO3G into HIV-1 particles and for the functional association with viral nucleoprotein complexes
Association of APO3G with cellular RNAs Cellular APO3G is present in high molecular mass (HMM) ribonucleoprotein complexes
Summary
Efficient incorporation of the cellular cytidine deaminase APOBEC3G (APO3G) into HIV-1 virions is necessary for its antiviral activity. Even though cellular RNAs are known to be nonspecifically incorporated into virus particles, we have previously found that encapsidation of APO3G into HIV-1 virions is enhanced by viral genomic RNA. In vitro studies demonstrated that the APO3G-Gag interaction is sensitive to RNase-treatment suggesting a possible role of RNA in APO3G encapsidation [9,11,14,17]. Consistent with these studies, we previously observed that efficient packaging of APO3G into vif-deficient HIV-1 particles required the presence of viral genomic RNA [18]. Other studies support the significance of viral genomic RNA for the encapsidation of APO3G into HIV1 particles [16,19,20]
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