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The synthesis of polypeptides in influenza C virus-infected cells
Abstract:
The synthesis of virus-specific polypeptides was analyzed in MDCK cells infected with the JJ/50 strain of influenza C virus. In addition to three major structural proteins gp88, NP, and M, the synthesis of five polypeptides with molecular weights of 29,500 (C1), 27,500 (C2), 24,000 (C3), 19,000 (C4), and 14,000 (C5) was found in infected cells. None of these polypeptides were detected either in virions or in immunoprecipitates obtained after treatment of infected cell lysates with antiviral serum, suggesting that they are not viral structural proteins. Polypeptides C1-C5 were found to be synthesized in MDCK cells infected with different influenza C virus strains as well as in different host cell types infected with C/JJ/50. Further, it was observed that cellular protein synthesis was greatly reduced under hypertonic conditions, whereas the synthesis of C1-C5 was relatively unaffected. These results suggest that polypeptides C1-C5 are virus coded rather than host cell coded. Peptide mapping studies showed that each of polypeptides C3, C4, and C5 had a peptide composition similar to the M protein. The amount of C2 synthesized in infected cells was insufficient for mapping. This polypeptide was, however, found to rapidly disappear in pulse-chase experiments, suggesting that C2 is probably not unique but biosynthetically related to one of the other proteins. In contrast to these polypeptides, polypeptide C1 showed a map which is largely different from any major structural polypeptide. It therefore appears likely that C1 is a nonstructural protein of influenza C virus similar to the NS1 protein of influenza A and B viruses.
Insights
Researchers identified five new virus-coded polypeptides (C1-C5) in influenza C virus-infected cells. Polypeptides C3-C5 resemble the M protein, while C1 may be a nonstructural protein, distinct from major structural proteins.
Area of Science:
- Virology
- Molecular Biology
- Protein Synthesis
Background:
- Influenza C virus is a significant human pathogen.
- Understanding influenza virus protein synthesis is crucial for developing antiviral strategies.
- Previous research has characterized the major structural proteins of influenza C virus.
Purpose of the Study:
- To analyze the synthesis of virus-specific polypeptides in MDCK cells infected with influenza C virus.
- To characterize newly identified viral polypeptides and determine their relationship to structural proteins.
- To investigate the potential nonstructural nature of these novel polypeptides.
Main Methods:
- Infection of MDCK cells with influenza C virus (JJ/50 strain).
- Analysis of newly synthesized polypeptides using SDS-PAGE and peptide mapping.
- Pulse-chase experiments to assess polypeptide stability and biosynthetic relationships.
- Detection of polypeptides in virions and immunoprecipitates with antiviral serum.
Main Results:
- Five novel polypeptides (C1-C5) were synthesized in infected cells, distinct from major structural proteins (gp88, NP, M).
- Polypeptides C3, C4, and C5 showed peptide mapping similarities to the M protein.
- Polypeptide C1 exhibited a unique peptide map, suggesting it is a nonstructural protein.
- Polypeptide C2 was unstable and likely related to other viral proteins.
- Synthesis of C1-C5 was relatively resistant to hypertonic conditions that inhibit cellular protein synthesis, indicating virus-coded origin.
Conclusions:
- Influenza C virus encodes at least five novel polypeptides beyond its major structural proteins.
- Polypeptides C3-C5 are likely related to or derived from the M protein.
- Polypeptide C1 is a strong candidate for a nonstructural protein, analogous to NS1 of influenza A and B viruses.