Human Immunodeficiency Virus Type 1 Preferentially Encapsidates Genomic RNAs That Encode Pr55Gag: Functional Linkage between Translation and RNA Packaging
| Autor: | David E. Ott, Elena Chertova, Dexter T.K. Poon |
|---|---|
| Rok vydání: | 2002 |
| Předmět: |
viruses
Gene Products gag RNA-dependent RNA polymerase Biology Cell Line 03 medical and health sciences Virology Humans Point Mutation RNA Messenger Protein Precursors 030304 developmental biology 0303 health sciences Virus Assembly 030302 biochemistry & molecular biology Intron RNA Non-coding RNA Molecular biology Antisense RNA RNA silencing RNA editing Protein Biosynthesis HIV-1 RNA Viral Small nuclear RNA |
| Zdroj: | Virology. 293:368-378 |
| ISSN: | 0042-6822 |
| DOI: | 10.1006/viro.2001.1283 |
| Popis: | Full-length retroviral RNA serves as both messenger and genomic RNA. Therefore, an unspliced RNA could play both roles: viral mRNA could be bound in cis by the same Gag polyprotein that it produced, becoming a packaged genomic RNA. To test this possibility, we used in vivo packaging experiments which coexpressed wild-type NL4-3 RNA and NL4-3-based mutant RNA that, ideally, could not translate Gag. However, mutating the gag initiator produced a mutant (pNLX) that expressed a truncated Gag, Gag*, initiated at methionine 10 in the CA region (142 of Pr55Gag). Gag* can be rescued into virions by Gag and, as it contains the NC domain, could package RNA in cis. To eliminate NC and the CA dimerization domain, a nonsense mutation in CA at residue 99 was introduced into pNLX to produce pNLXX, which expresses an RNA that should only be packaged in trans. Cotransfection packaging experiments revealed that wild-type genomic RNA was packaged at an 8-fold greater level than NLXX RNA given equal expression of both RNAs. Experiments that varied the relative amounts of these RNAs in the cell found that the wild-type RNA was encapsidated with a packaging preference (i.e., the relative amount of this RNA in virions versus cells) of 6- to 13-fold over the NLXX RNA, showing that the NLXX RNA did not efficiently compete with NL4-3 RNA. These data suggest that the wild-type RNA's ability to express Pr55Gag and, by inference, actively translate Gag confers an advantage in packaging over the nearly identical NLXX RNA. In contrast, the NLX RNA competed with wild-type RNA at a 1-to-3 preference. This ratio is similar to the amounts of Gag* rescued by Gag, suggesting that the presence of Gag* assists in the encapsidation of NLX RNA. Together, our data link translation and particle formation to the packaging of viral RNA and support a model of cis packaging where nascent Gag proteins encapsidate their cognate RNA. |
| Databáze: | OpenAIRE |
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