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Reconstitution of selective HIV-1 RNA packaging in vitro by membrane-bound Gag assemblies.

ABSTRACT: HIV-1 Gag selects and packages a dimeric, unspliced viral RNA in the context of a large excess of cytosolic human RNAs. As Gag assembles on the plasma membrane, the HIV-1 genome is enriched relative to cellular RNAs by an unknown mechanism. We used a minimal system consisting of purified RNAs, recombinant HIV-1 Gag and giant unilamellar vesicles to recapitulate the selective packaging of the 5' untranslated region of the HIV-1 genome in the presence of excess competitor RNA. Mutations in the CA-CTD domain of Gag which subtly affect the self-assembly of Gag abrogated RNA selectivity. We further found that tRNA suppresses Gag membrane binding less when Gag has bound viral RNA. The ability of HIV-1 Gag to selectively package its RNA genome and its self-assembly on membranes are thus interdependent on one another.

SUBMITTER: Carlson LA

PROVIDER: S-EPMC4946900 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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Reconstitution of selective HIV-1 RNA packaging in vitro by membrane-bound Gag assemblies.

Carlson Lars-Anders LA Bai Yun Y Keane Sarah C SC Doudna Jennifer A JA Hurley James H JH

eLife 20160625

HIV-1 Gag selects and packages a dimeric, unspliced viral RNA in the context of a large excess of cytosolic human RNAs. As Gag assembles on the plasma membrane, the HIV-1 genome is enriched relative to cellular RNAs by an unknown mechanism. We used a minimal system consisting of purified RNAs, recombinant HIV-1 Gag and giant unilamellar vesicles to recapitulate the selective packaging of the 5' untranslated region of the HIV-1 genome in the presence of excess competitor RNA. Mutations in the CA- ...[more]

PMID: 27343348

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Project description:During immature capsid assembly, HIV-1 genome packaging is initiated when Gag first associates with unspliced HIV-1 RNA by a poorly understood process. Previously, we defined a pathway of sequential intracellular HIV-1 capsid assembly intermediates; here we sought to identify the intermediate in which HIV-1 Gag first associates with unspliced HIV-1 RNA. In provirus-expressing cells, unspliced HIV-1 RNA was not found in the soluble fraction of the cytosol, but instead was largely in complexes ≥30S. We did not detect unspliced HIV-1 RNA associated with Gag in the first assembly intermediate, which consists of soluble Gag. Instead, the earliest assembly intermediate in which we detected Gag associated with unspliced HIV-1 RNA was the second assembly intermediate (~80S intermediate), which is derived from a host RNA granule containing two cellular facilitators of assembly, ABCE1 and the RNA granule protein DDX6. At steady-state, this RNA-granule-derived ~80S complex was the smallest assembly intermediate that contained Gag associated with unspliced viral RNA, regardless of whether lysates contained intact or disrupted ribosomes, or expressed WT or assembly-defective Gag. A similar complex was identified in HIV-1-infected T cells. RNA-granule-derived assembly intermediates were detected in situ as sites of Gag colocalization with ABCE1 and DDX6; moreover these granules were far more numerous and smaller than well-studied RNA granules termed P bodies. Finally, we identified two steps that lead to association of assembling Gag with unspliced HIV-1 RNA. Independent of viral-RNA-binding, Gag associates with a broad class of RNA granules that largely lacks unspliced viral RNA (step 1). If a viral-RNA-binding domain is present, Gag further localizes to a subset of these granules that contains unspliced viral RNA (step 2). Thus, our data raise the possibility that HIV-1 packaging is initiated not by soluble Gag, but by Gag targeted to a subset of host RNA granules containing unspliced HIV-1 RNA.

Dataset Information

Reconstitution of selective HIV-1 RNA packaging in vitro by membrane-bound Gag assemblies.

Publications

Reconstitution of selective HIV-1 RNA packaging in vitro by membrane-bound Gag assemblies.

Similar Datasets

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