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Identification and protein analysis of polyomavirus assembly intermediates from infected primary mouse embryo cells
Abstract:
A method is described for the isolation of polyoma virus assembly intermediates from infected mouse embryo cells. Sucrose gradient profiles revealed the presence of 90 S, 200 S, and 240 S intermediates. These intermediates were shown to be sensitive to a number of factors: ionic condition of the isolation buffer, presence of chelating agents and nonionic detergents during isolation, and sonication of nuclei during extraction of intermediates. Pulse-chase experiments demonstrated that the order of formation of the intermediates to be 90 S----240 S, with the 200 S particles as a possible intermediate form linking the 90 S and 240 S particles. Viral structural proteins VP1, VP2, and VP3 were shown to be present on all three intermediates, but the ratio of each protein varied on each intermediate species. Two-dimensional gel electrophoresis demonstrated that the distribution of the VP1 isoelectric focusing species were different among the three intermediates. Histone H1 was found exclusively with the 90 S species.
Insights
Researchers isolated polyoma virus assembly intermediates from mouse cells, identifying 90S, 200S, and 240S particles. Protein composition varied across these intermediates, revealing insights into viral assembly.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Polyoma virus assembly is a complex process involving multiple intermediate structures.
- Understanding these intermediates is crucial for deciphering viral replication and assembly mechanisms.
Purpose of the Study:
- To develop a method for isolating polyoma virus assembly intermediates.
- To characterize the properties and composition of these intermediates.
- To elucidate the sequential order of intermediate formation during viral assembly.
Main Methods:
- Isolation of polyoma virus assembly intermediates from infected mouse embryo cells using sucrose gradient centrifugation.
- Analysis of intermediate sensitivity to isolation conditions (ionic strength, chelating agents, detergents, sonication).
- Pulse-chase experiments to determine the order of intermediate formation.
- Characterization of viral structural proteins (VP1, VP2, VP3) and histone H1 association using techniques like two-dimensional gel electrophoresis.
Main Results:
- Identified three distinct polyoma virus assembly intermediates: 90S, 200S, and 240S.
- Demonstrated sensitivity of intermediates to isolation buffer conditions, chelating agents, detergents, and sonication.
- Established a potential formation order of 90S → 240S, with 200S as a possible linking intermediate.
- Showed differential ratios of viral structural proteins (VP1, VP2, VP3) across the intermediates.
- Observed distinct distributions of VP1 isoelectric focusing species among the intermediates.
- Found histone H1 exclusively associated with the 90S intermediate.
Conclusions:
- The study successfully isolated and characterized polyoma virus assembly intermediates.
- The findings provide insights into the sequential assembly pathway and the dynamic composition of viral intermediates.
- Differential protein composition suggests distinct roles for each intermediate in the viral assembly process.