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Nucleic acid-independent retrovirus assembly can be driven by dimerization.
Marc C Johnson1, Heather M Scobie, Yu May Ma
1Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA. mcj7@cornell.edu
Journal of Virology
|October 22, 2002
Summary
Retroviral Gag protein assembly into virus-like particles (VLPs) requires the nucleocapsid (NC) domain. Replacing NC with a dimerization domain shows nucleic acid acts to promote Gag dimer formation for VLP assembly.
Area of Science:
- Virology
- Molecular Biology
- Biochemistry
Background:
- Retroviral virus-like particles (VLPs) assemble from the Gag polyprotein.
- Capsid (CA) and nucleocapsid (NC) domains of Gag, along with nucleic acid, are typically required for VLP assembly.
- The precise role of NC-nucleic acid interactions in promoting Gag assembly remains unclear.
Purpose of the Study:
- To investigate the role of the NC domain in retroviral Gag protein assembly.
- To elucidate the mechanism by which NC-nucleic acid interactions facilitate VLP formation.
Main Methods:
- Deletion and replacement of the NC domain in Rous sarcoma virus Gag protein.
- Expression of modified Gag proteins in baculovirus-infected insect cells.
- Analysis of VLP formation and budding at the plasma membrane using electron microscopy.
Main Results:
- Deletion of the NC domain abolished VLP formation and budding.
- Replacing the NC domain with a leucine zipper dimerization domain restored spherical VLP formation.
- Insertion of a flexible linker altered particle morphology, leading to tubular structures, suggesting critical positioning of dimerization domains.
Conclusions:
- The NC domain's function in VLP assembly can be mimicked by a foreign dimerization domain.
- Nucleic acid likely functions to promote Gag dimer formation rather than acting as a scaffold.
- Gag dimers are essential intermediates for the polymerization of the Gag shell during retroviral assembly.