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Analysis of retroviral assembly using a vaccinia/T7-polymerase complementation system
Abstract:
The nature of protein-protein interactions during retroviral assembly is not well understood, and mutational analyses of the potential signals involved in the viral assembly process has been difficult, particularly with the avian retroviruses due to the level of viral proteins expressed in the clonal cell lines containing defective viral genomes. We describe here a complementation system in which the retroviral gag/pol and env gene products were expressed independently from different plasmids under the control of the bacteriophage T7 promoter, in avian cells. Coexpression of the T7 polymerase from a vaccinia virus vector resulted in a high level of biosynthesis of retroviral structural proteins and efficient assembly of virus particles. Electron microscopy and protein composition analyses demonstrated that these virions were indistinguishable from those produced from RSV-infected cells. Through the use of mutant glycoprotein genes it was possible to demonstrate the specificity of the assembly process and the applicability of this system to other retroviral systems is described.
Insights
Researchers developed a novel complementation system for studying avian retroviral assembly. This system enables high-level protein expression and efficient virus particle formation, aiding in the analysis of viral assembly processes.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Understanding retroviral protein interactions during assembly is challenging.
- Previous methods for avian retroviruses were limited by low protein expression.
Purpose of the Study:
- To establish a complementation system for studying avian retroviral assembly.
- To enable high-level expression of retroviral proteins and efficient virus production.
Main Methods:
- Utilized a complementation system with independent expression of gag/pol and env genes from plasmids.
- Employed bacteriophage T7 promoter and vaccinia virus vector for T7 polymerase coexpression in avian cells.
- Analyzed assembled virions using electron microscopy and protein composition.
Main Results:
- Achieved high-level biosynthesis of retroviral structural proteins.
- Demonstrated efficient assembly of virus particles indistinguishable from naturally produced virions.
- Confirmed the specificity of the retroviral assembly process using mutant glycoprotein genes.
Conclusions:
- The developed complementation system facilitates the study of retroviral assembly.
- This system is applicable to various retroviral systems for analyzing protein interactions and assembly mechanisms.