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Characterization of an integrase mutant of feline immunodeficiency virus
K Tomonaga1, S I Itagaki, H Kashiwase
1Department of Veterinary Microbiology, University of Tokyo, Japan.
Abstract:
The role of the integrase region of feline immunodeficiency virus (FIV) in viral replication was examined using an integrase mutant clone of FIV which carries a frameshift mutation in the region. Upon transfection, although the integrase mutant was able to release virus-like particles into the supernatant from the transfected cells, the virions produced by the mutant contained unprocessed gag precursor protein and undetectable levels of reverse transcriptase activity. Furthermore, the mutant virions were unable to direct the synthesis of viral DNA after infection in target cells. To understand this phenotype of the integrase mutant in more detail, we constructed a gag-pol expression plasmid from an FIV molecular clone and assayed roles of the integrase region on virus particle formation following transfection. When an inframe deletion was introduced into the protease region of the expression plasmid, the mutant was able to efficiently release gag- and gag-pol precursor proteins into the supernatant from the transfected cells. An expression plasmid with mutations in both the protease and integrase regions, however, failed to release the gag-pol precursor protein from the cells. These results suggested an essential role for the integrase region for efficient incorporation of the gag-pol precursor into the virions.
Insights
The integrase region of feline immunodeficiency virus (FIV) is crucial for viral replication. Mutations in this region prevent proper processing and packaging of viral proteins, hindering virus assembly and infectivity.
Area of Science:
- Virology
- Molecular Biology
- Retroviral Research
Background:
- Feline immunodeficiency virus (FIV) is a lentivirus that infects cats.
- Viral replication is a complex process involving multiple viral proteins.
- The integrase enzyme plays a critical role in the retroviral life cycle.
Purpose of the Study:
- To investigate the specific role of the integrase region in FIV replication.
- To elucidate the function of FIV integrase in viral particle formation and infectivity.
Main Methods:
- Construction and transfection of FIV integrase mutant clones.
- Analysis of viral particle release and protein processing.
- Assay of reverse transcriptase activity and viral DNA synthesis in target cells.
- Construction of gag-pol expression plasmids with mutations in protease and integrase regions.
Main Results:
- FIV integrase mutants released virus-like particles but contained unprocessed gag precursor protein and lacked reverse transcriptase activity.
- Mutant virions were deficient in directing viral DNA synthesis post-infection.
- Mutations affecting both protease and integrase regions abolished gag-pol precursor protein release.
- The integrase region is essential for efficient gag-pol precursor incorporation into virions.
Conclusions:
- The integrase region of FIV is essential for efficient viral replication.
- Integrase plays a critical role in the proper processing and packaging of viral proteins into infectious virions.
- Understanding FIV integrase function can inform strategies against lentiviral infections.