Prototype foamy virus gag nuclear localization: a novel pathway among retroviruses

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

Abstract

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 glycine-arginine-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 ΔGRII 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.

Details

Original languageEnglish
Pages (from-to)9276-9285
Number of pages10
JournalJournal of Virology
Volume85
Issue number18
Publication statusPublished - Sept 2011
Peer-reviewedYes

External IDs

Scopus 80052494157
PubMed 21715475
PubMedCentral PMC3165767
ORCID /0000-0002-0320-4223/work/151983045

Keywords

Keywords

  • Active Transport, Cell Nucleus, Binding Sites, Cell Line, Cell Nucleus/chemistry, Gene Products, gag/genetics, Humans, Microscopy, Fluorescence/methods, Mutant Proteins/genetics, Protein Sorting Signals, Spumavirus/physiology, Virus Replication