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The lymphocytic choriomeningitis virus RING protein Z associates with eukaryotic initiation factor 4E and selectively
E J Campbell Dwyer1, H Lai, R C MacDonald
1Department of Biochemistry, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7.
Abstract:
Only a few host cell proteins that associate with arenaviruses have been identified. To date, the arenavirus Z protein associates with the promyelocytic leukemia protein PML and the ribosomal P proteins. The majority of PML is present in nuclear bodies which are translocated to the cytoplasm by infection with the arenavirus, lymphocytic choriomeningitis virus (LCMV). The Z protein is a small zinc-binding RING protein with an unknown function which is required for the viral life cycle. Here, we demonstrate an association between Z and the host cell translation factor, eukaryotic initiation factor 4E (eIF-4E) in infected and transfected cells. Z's association with both ribosomal proteins and this translation factor led us to investigate whether Z could modulate host cell translation. In cell culture, Z selectively represses protein production in an eIF-4E-dependent manner. Specifically, we see reduction in cyclin D1 protein production with no effect on glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in cells transfected with Z. Previous reports indicate that cyclin D1 is sensitive to eIF-4E levels, whereas GAPDH is not. Consistent with this, we observe preferential downregulation of cyclin D1 during infection and no effect on GAPDH. Further, no changes in RNA levels were observed for cyclin D1 or GAPDH transcripts. The interaction between eIF-4E and Z may provide a mechanism for slower growth observed in infected cells and a viral strategy for establishing chronic infection.
Insights
The lymphocytic choriomeningitis virus (LCMV) Z protein interacts with host translation factor eIF-4E, selectively repressing protein synthesis. This interaction may explain slower viral growth and chronic infection establishment.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Arenaviruses interact with a limited number of host cell proteins.
- The arenavirus Z protein binds to promyelocytic leukemia (PML) protein and ribosomal P proteins.
- LCMV infection causes translocation of PML from nuclear bodies to the cytoplasm.
Purpose of the Study:
- To investigate the association between the arenavirus Z protein and host cell factors.
- To determine if the Z protein modulates host cell translation.
- To elucidate the mechanism behind slower viral growth and chronic infection.
Main Methods:
- Co-immunoprecipitation assays to demonstrate protein-protein interactions.
- Cell culture experiments to assess protein production.
- Quantitative analysis of specific protein and RNA levels.
Main Results:
- The Z protein associates with eukaryotic initiation factor 4E (eIF-4E) in infected and transfected cells.
- Z protein selectively represses protein synthesis in an eIF-4E-dependent manner.
- Cyclin D1 protein production is reduced, while GAPDH is unaffected, with no changes in corresponding RNA levels.
Conclusions:
- The interaction between Z and eIF-4E provides a mechanism for selective host protein synthesis repression.
- This viral strategy may contribute to slower viral growth and the establishment of chronic LCMV infections.