12th Conference on Retroviruses and Opportunistic Infections Boston, Massachusetts - February 22-25, 2005

Conf Retrovir Opportunistic Infect 2005 Feb 22-25;12:abstract no. 36

Chad Swanson, M Ahmad, and M Malim
King's Coll London, UK

BACKGROUND: Very little is known about the ribonucleoprotein (RNP) complexes that form on the HIV genomic transcript, or how these regulate the fate of the genomic RNA. Because cells support different RNA nuclear export pathways, pathway selection may affect the identity of proteins that constitute the RNP. Different retroviruses have evolved to use different RNA nuclear export pathways. M-PMV’s genome transcript uses the NXF1 pathway via a cis-acting element, the CTE, while HIV RRE/Rev-dependent HIV transcripts use the Crm1 pathway. Thus, utilization of the Crm1-dependent or NXF1-dependent export pathway by HIV gag-pol RNA could regulate RNP formation and the fate of the RNA and translated protein. Here, we examine this issue in terms of virus assembly.

METHODS: HIV assembly and budding were analyzed by immunoprecipitation/Western blot on transfected cell lysates and supernatants. An ELISA was used to quantitate the amount of virion-like particles in supernatants. Intracellular localization of Gag was analyzed by indirect immunofluorescence.

RESULTS: While human cells are permissive for HIV assembly, murine cells are non-permissive with a defect in plasma membrane trafficking of Gag. We have tested several different RNA nuclear export elements for their ability to modulate intracellular Gag trafficking and budding. All of these constructs have wild type Gag-Pol and are efficiently expressed.

CONCLUSIONS: Differential use of RNA nuclear export pathways can modulate Gag trafficking and assembly. In human cells, altering the gag-pol RNA nuclear export pathway affects the intracellular trafficking of Gag and its ability to form virion-like particles. In murine cells, the fundamental assembly block appears to be due to a defect in the nuclear history of the RNA because Gag trafficking and virion-like particle formation can be rescued by altering the nuclear RNA export pathway from Rev/RRE/Crm1 to 4xCTE/NXF1. We hypothesize that the nuclear export element modulates cytosolic localization of gag-pol RNA to an assembly permissive microdomain and are currently characterizing RNA binding proteins that may regulate this process.

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Copyright © 2005 - Foundation for Retrovirology and Human Health. Reproduction of this abstract (other than one copy for personal reference) must be cleared through the Foundation for Retrovirology and Human Health. Licensed (AIDSLINE) from National Library of Medicine.