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Studies on a temperature-sensitive mutant of fowl plague virus having a mutation in gene 7 coding for the M protein
Abstract:
A fowl plague virus (FPV) temperature-sensitive mutant, ts 303/1 having a ts mutation in gene 7 coding for the matrix (M) protein has been obtained. The mutant induced synthesis of virus-specific RNA and polypeptides as well as ribonuclear protein (RNP) formation in cells under non-permissive conditions; however, haemagglutinin cleavage was reduced, functionally active haemagglutinin and neuraminidase were absent and virions were not formed. In mutant-infected cells at 36 degrees C haemagglutinin cleavage was also reduced and virions formed had an altered NP:M ratio as well as a decreased haemagglutinin content. A population of virions formed under these conditions was heterogeneous both in morphology and in buoyant density. The data obtained suggest that a mutation in the M proteins of orthomyxoviruses can affect processing of the haemagglutinin and impair final stages of virion morphogenesis.
Insights
A temperature-sensitive mutant of fowl plague virus (FPV) with a matrix (M) protein mutation impairs virion formation. This mutation affects haemagglutinin processing and morphogenesis, crucial for viral assembly.
Area of Science:
- Virology
- Molecular Biology
- Protein Biochemistry
Background:
- Fowl plague virus (FPV) is an avian influenza virus with segmented RNA genome.
- The matrix (M) protein plays a critical role in the assembly and release of orthomyxoviruses.
- Temperature-sensitive (ts) mutants are valuable tools for studying viral replication and protein function.
Purpose of the Study:
- To investigate the role of the M protein in FPV replication and virion morphogenesis.
- To characterize a novel ts mutant of FPV affecting M protein function.
- To elucidate the impact of M protein mutations on viral protein processing and assembly.
Main Methods:
- Generation and characterization of a temperature-sensitive FPV mutant (ts 303/1) with a mutation in the M protein gene (gene 7).
- Analysis of viral RNA and polypeptide synthesis under permissive and non-permissive conditions.
- Assessment of haemagglutinin cleavage, neuraminidase activity, and virion formation.
- Biochemical analysis of virion composition, including NP:M ratio and haemagglutinin content.
- Evaluation of virion morphology and buoyant density.
Main Results:
- The ts 303/1 mutant synthesized viral RNA, polypeptides, and formed ribonucleoprotein complexes under non-permissive conditions.
- Haemagglutinin cleavage was reduced, and functional haemagglutinin and neuraminidase were absent in mutant-infected cells at non-permissive temperatures, preventing virion formation.
- At a semi-permissive temperature (36°C), haemagglutinin cleavage remained reduced, and formed virions exhibited an altered NP:M ratio and decreased haemagglutinin content.
- Virions produced under semi-permissive conditions were heterogeneous in morphology and buoyant density.
Conclusions:
- A mutation in the M protein of FPV can significantly impair haemagglutinin processing.
- The M protein is essential for the final stages of virion morphogenesis in orthomyxoviruses.
- M protein dysfunction leads to the production of defective virions with altered composition and heterogeneity.