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Evidence that the matrix protein of influenza C virus is coded for by a spliced mRNA
M Yamashita1, M Krystal, P Palese
1Department of Microbiology, Mount Sinai School of Medicine, City University of New York, New York 10029.
Abstract:
In contrast to influenza A and B viruses, which encode their matrix (M) proteins via an unspliced mRNA, the influenza C virus M protein appears to be coded for by a spliced mRNA from RNA segment 6. Although an open reading frame in RNA segment 6 of influenza C/JJ/50 virus could potentially code for a protein of 374 amino acids, a splicing event results in an mRNA coding for a 242-amino-acid M protein. The message for this protein represents the major M gene-specific mRNA species in C virus-infected cells. Despite the difference in coding strategies, there are sequence homologies among the M proteins of influenza A, B, and C viruses which confirm the evolutionary relationship of the three influenza virus types.
Insights
Influenza C virus uniquely uses spliced mRNA for its matrix (M) protein, unlike influenza A and B viruses. This finding highlights evolutionary relationships among influenza virus types despite differing coding strategies.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- Influenza A and B viruses synthesize matrix (M) proteins from unspliced messenger RNA (mRNA).
- The genetic mechanisms of influenza C virus replication and protein synthesis differ from other influenza types.
- Understanding M protein coding is crucial for influenza virus classification and evolution studies.
Purpose of the Study:
- To investigate the coding strategy of the matrix (M) protein in influenza C virus.
- To compare the M protein gene expression of influenza C virus with influenza A and B viruses.
- To explore the evolutionary connections between different influenza virus types based on M protein sequences.
Main Methods:
- Analysis of RNA segment 6 from influenza C virus.
- Identification of spliced mRNA species in infected cells.
- Sequence homology analysis of M proteins across influenza A, B, and C viruses.
Main Results:
- Influenza C virus M protein is encoded by a spliced mRNA derived from RNA segment 6.
- A splicing event results in a 242-amino-acid M protein, distinct from the potential 374-amino-acid product.
- This spliced mRNA is the predominant M gene-specific mRNA in influenza C virus-infected cells.
- Sequence homologies confirm evolutionary links between influenza A, B, and C virus M proteins.
Conclusions:
- Influenza C virus employs a distinct mRNA splicing strategy for M protein synthesis.
- Despite varied coding mechanisms, conserved sequences in M proteins indicate a shared ancestry among influenza virus types.
- This study clarifies a key difference in influenza C virus molecular biology and reinforces its relationship to other influenza viruses.