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Updated: Aug 14, 2026
Detection of Viral RNA by Fluorescence in situ Hybridization (FISH)
Published on: May 5, 2012
Feline immunodeficiency virus Vif localizes to the nucleus
U Chatterji1, C K Grant, J H Elder
1Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Insights
Feline immunodeficiency virus (FIV) Vif protein is found in the nucleus when milder fixation methods are used, suggesting its primary role in infection begins there. This differs from previous findings with human immunodeficiency virus (HIV) Vif.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- The Vif protein plays a crucial role in the lifecycle of lentiviruses, including feline immunodeficiency virus (FIV) and human immunodeficiency virus (HIV).
- Understanding Vif's expression and localization is key to deciphering its function in viral replication and pathogenesis.
Purpose of the Study:
- To characterize the expression and subcellular localization of FIV Vif protein in infected cells.
- To investigate the potential interaction of FIV Vif with viral Gag antigens and its presence in virions.
Main Methods:
- Production of monoclonal antibodies against recombinant FIV Vif.
- Western blotting and immunoprecipitation to detect FIV Vif in infected cells.
- Immunofluorescence microscopy with varying fixation protocols (methanol vs. formaldehyde) to determine Vif localization.
- Analysis of colocalization and coprecipitation with Gag antigens.
Main Results:
- A specific 29-kDa FIV Vif protein species was detected in infected cells.
- Methanol fixation revealed predominantly cytoplasmic localization of FIV Vif, similar to HIV-1 Vif and FIV Gag.
- Milder formaldehyde fixation demonstrated strong nuclear localization of FIV Vif, distinct from Rev localization.
- No colocalization or coprecipitation with Gag antigens was observed, and Vif was not detected in purified FIV virions.
Conclusions:
- FIV Vif exhibits context-dependent subcellular localization, appearing in the nucleus under specific conditions.
- The nuclear localization of FIV Vif suggests its critical function may initiate within the nucleus during the viral infection cycle.
- These findings provide new insights into the intracellular mechanisms of FIV replication.
Abstract:
Monoclonal antibodies prepared against recombinant Vif derived from the 34TF10 strain of feline immunodeficiency virus (FIV) were used to assess the expression and localization of Vif in virus-infected cells. Analyses by Western blotting and by immunoprecipitation from cells infected with FIV-34TF10 revealed the presence of a single 29-kDa species specific for virus-infected cells. Confirmation of antibody specificity was also performed by specific immunoprecipitation of in vitro-transcribed and -translated recombinant Vif. Localization experiments were also performed on virus-infected cells, using different fixation procedures. Results for methanol fixation protocols similar to those reported for localization of human immunodeficiency virus (HIV) Vif showed a predominant cytoplasmic localization for FIV Vif, very similar to localization of HIV type 1 Vif and virtually identical to the localization observed for the Gag antigens of the virus. However, with milder fixation procedures that used 2% formaldehyde at 4 degrees C, FIV Vif was strongly evident in the nucleus. The localization was distinct from the nuclear localization noted with Rev and did not involve the nucleolus. Attempts to show colocalization or coprecipitation of Vif with Gag antigens were unsuccessful. In addition, Vif was not detected in purified FIV virions. The results are consistent with the notion that the primary role of Vif in virus infection initiates in the nucleus.
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