Particle Assembly and Genome Packaging

Linial, Maxine L.; Eastman, Scott W.

doi:10.1007/978-3-642-55701-9_4

Cited by 36 publications

(41 citation statements)

References 58 publications

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“…Indeed, FV protease was mainly shown to process the Gag precursor (p71) into a smaller mature product (p68), a cleavage essential for infectivity and occurring during the late phase of the PFV replication cycle. Indeed, the infectious virion harbors a core composed mainly of these two Gag precursors, the ratio between these two molecular forms varying between virus preparations (21). Consequently, Gag-Gag interactions occurring in these apparently immature cores are likely distinct from those of other retroviral mature cores, and the recent model of retroviral core disassembly by CA dilution in the infected cells may therefore not account for FV uncoating (26).…”

Section: Discussionmentioning

confidence: 99%

Protease-Dependent Uncoating of a Complex Retrovirus

Lehmann-Che

Giron

Delelis

et al. 2005

J Virol

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Although retrovirus egress and budding have been partly unraveled, little is known about early stages of the replication cycle. In particular, retroviral uncoating, a process during which incoming retroviral cores are altered to allow the integration of the viral genome into host chromosomes, is poorly understood. To get insights into these early events of the retroviral cycle, we have used foamy complex retroviruses as a model. In this report, we show that a protease-defective foamy retrovirus is noninfectious, although it is still able to bud and enter target cells efficiently. Similarly, a retrovirus mutated in an essential viral protease-dependent cleavage site in the central part of Gag is noninfectious. Following entry, wild-type and mutant retroviruses are able to traffic along microtubules towards the microtubule-organizing center (MTOC). However, whereas nuclear import of Gag and of the viral genome was observed for the wild-type virus as early as 8 hours postinfection, incoming capsids and genome from mutant viruses remained at the MTOC. Interestingly, a specific viral protease-dependent Gag cleavage product was detected only for the wild-type retrovirus early after infection, demonstrating that cleavage of Gag by the viral protease at this stage of the virus life cycle is absolutely required for productive infection, an unprecedented observation among retroviruses.

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Section: Discussionmentioning

confidence: 99%

Protease-Dependent Uncoating of a Complex Retrovirus

Lehmann-Che

Giron

Delelis

et al. 2005

J Virol

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“…Retroviruses and retrotransposons assemble intracellular immature core particles around a RNA genome, and nascent particles collect in association with membranes or as intracellular clusters (Garfinkel et al 1985;Hansen et al 1992;Coffin et al 1997;Linial and Eastman 2003;Sfakianos et al 2003;Teysset et al 2003). An important aspect of the retrovirus life cycle is how the RNA genome and particle proteins are brought together during assembly to allow orderly progression of the life cycle.…”

Section: Introductionmentioning

confidence: 99%

Virus-like particles of the Ty3 retrotransposon assemble in association with P-body components

Beliakova-Bethell¹,

Beckham²,

Giddings³

et al. 2005

RNA

137

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Retroviruses and retrotransposons assemble intracellular immature core particles around a RNA genome, and nascent particles collect in association with membranes or as intracellular clusters. How and where genomic RNA are identified for retrovirus and retrotransposon assembly, and how translation and assembly processes are coordinated is poorly understood. To understand this process, the subcellular localization of Ty3 RNA and capsid proteins and virus-like particles was investigated. We demonstrate that mRNAs, proteins, and virus-like particles of the yeast Ty3 retrotransposon accumulate in association with cytoplasmic P-bodies, which are sites of mRNA translation repression, storage, and degradation. Deletions of genes encoding P-body proteins decreased Ty3 transposition and caused changes in the pattern of Ty3 foci, underscoring the biological significance of the association of Ty3 virus-like protein components and P-bodies. These results suggest the hypothesis that P-bodies may serve to segregate translation and assembly functions of the Ty3 genomic RNA to promote assembly of virus-like particles. Because Ty3 has features of a simple retrovirus and P-body functions are conserved between yeast and metazoan organisms, these findings may provide insights into host factors that facilitate retrovirus assembly.

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“…An NLS was identified in the C-terminal part of GRII (45,57), and a chromatin-binding site (CBS), which mediates interaction of Gag with H2A/H2B core histones, was identified in the N-terminal part (52). Parts of GRII are well conserved among all FV Gag proteins and, with the exception of feline FV (FFV) Gag, all known FV Gag proteins localize to the cell nucleus (3,24,30,36,53,55). Very recently, a NES was described for PFV Gag (40).…”

mentioning

confidence: 99%

Prototype Foamy Virus Gag Nuclear Localization: a Novel Pathway among Retroviruses

Müllers¹,

Stirnnagel²,

Kaulfuss³

et al. 2011

J Virol

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Gag nuclear localization has long been recognized as a hallmark of foamy virus (FV) infection. Two required motifs, a chromatin-binding site (CBS) and a nuclear localization signal (NLS), both located in glycinearginine-rich box II (GRII), have been described. However, the underlying mechanisms of Gag nuclear translocation are largely unknown. We analyzed prototype FV (PFV) Gag nuclear localization using a novel live-cell fluorescence microscopy assay. Furthermore, we characterized the nuclear localization route of Gag mutants tagged with the simian vacuolating virus 40-NLS (SV40-NLS) and also dissected the respective contributions of the CBS and the NLS. We found that PFV Gag does not translocate to the nucleus of interphase cells by NLS-mediated nuclear import and does not possess a functional NLS. PFV Gag nuclear localization occurred only by tethering to chromatin during mitosis. This mechanism was found for endogenously expressed Gag as well as for Gag delivered by infecting viral particles. Thereby, the CBS was absolutely essential, while the NLS was dispensable. Gag CBS-dependent nuclear localization was neither essential for infectivity nor necessary for Pol encapsidation. Interestingly, Gag localization was independent of the presence of Pol, Env, and viral RNA. The addition of a heterologous SV40-NLS resulted in the nuclear import of PFV Gag in interphase cells, rescued the nuclear localization deficiency but not the infectivity defect of a PFV Gag ⌬GRII mutant, and did not enhance FV's ability to infect G 1 /S-phase-arrested cells. Thus, PFV Gag nuclear localization follows a novel pathway among orthoretroviral Gag proteins.

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Particle Assembly and Genome Packaging

Cited by 36 publications

References 58 publications

Protease-Dependent Uncoating of a Complex Retrovirus

Protease-Dependent Uncoating of a Complex Retrovirus

Virus-like particles of the Ty3 retrotransposon assemble in association with P-body components

Prototype Foamy Virus Gag Nuclear Localization: a Novel Pathway among Retroviruses

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