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Influenza virus assembly and its defects
Abstract:
The most abundant protein within the influenza virus particles is membrane protein (M protein) which forms an inner virus membrane under a lipid bilayer and plays the role of mediator during the process of assembly of a virus particle on plasma membranes. Ehrlich ascites tumor cells (EAT) when infected with influenza virus, strain WSN, produced virus-like particles containing greatly reduced amounts of M protein. Such particles were extremely fragile and easily lost hemagglutinins. The loss of this glycoprotein was accompanied by a decrease in infectious activity. SDS-PAGE analysis of RNA duplexes formed after hybridization of intracellular labeled mRNAs and unlabeled virion RNA showed that the mRNA for M protein was synthesized in EAT nearly in the same amounts as in productively infected chicken fibroblasts. Accordingly, M protein was readily revealed when the polypeptides of infected EAT were analyzed by SDS-PAGE. Thus, the reduced amount of M protein in virus particles was likely not due to the decrease in its synthesis but rather to its defective structure or to its defective transport and misintegration into plasma membranes of EAT.
Insights
Influenza virus M protein (membrane protein) is crucial for virus assembly. In infected Ehrlich ascites tumor cells, reduced M protein in virus particles wasn
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Influenza virus membrane protein (M protein) is essential for virus assembly and forms the inner viral membrane.
- M protein mediates virus particle assembly on host plasma membranes.
Purpose of the Study:
- To investigate the cause of reduced M protein content in influenza virus-like particles produced by Ehrlich ascites tumor cells (EAT).
Main Methods:
- Infection of EAT with influenza virus (WSN strain).
- Analysis of virus-like particles for M protein content and hemagglutinin stability.
- SDS-PAGE analysis of RNA duplexes to compare M protein mRNA synthesis.
- SDS-PAGE analysis of infected EAT polypeptides.
Main Results:
- EAT infected with influenza virus produced fragile virus-like particles with significantly less M protein and hemagglutinins.
- M protein mRNA synthesis in EAT was comparable to that in chicken fibroblasts.
- M protein was detectable in infected EAT cell polypeptides, indicating synthesis occurred.
Conclusions:
- Reduced M protein in influenza virus particles from EAT is not due to decreased synthesis.
- Defective M protein structure or impaired transport/integration into EAT plasma membranes likely causes the deficiency.