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Phosphorylation of the N and M1 proteins of rabies virus
Abstract:
Phosphorylation of rabies virus proteins was followed in vivo and in vitro. The N and M1 proteins were both found to be phosphorylated. The M1 protein was present in the virion in two phosphorylated states, but only the hypophosphorylated form of M1 was found in infected cells. The hypothesis that some of the M1 molecules become hyperphosphorylated during the maturation process by a membrane-bound kinase was examined. The phosphorylation of the viral proteins by the kinase present in purified rabies virions was studied using an in vitro transcriptase assay: under the conditions of the assay, additional phosphate groups were rapidly attached to the N protein. The M1 protein was similarly hyperphosphorylated although more slowly. Whether the hyperphosphorylation of the N protein is responsible for the poor efficiency of the in vitro transcriptase reaction is not clear. No detectable change in the phosphorylation of cellular proteins was observed in the course of rabies virus infection.
Insights
Rabies virus N and M1 proteins undergo phosphorylation. M1 protein exists in two forms in virions, but only one in infected cells, suggesting a maturation-related phosphorylation event.
Area of Science:
- Virology
- Molecular Biology
- Protein Biochemistry
Background:
- Rabies virus is a significant human and animal pathogen.
- Understanding viral protein modification, like phosphorylation, is crucial for viral replication and pathogenesis.
- The phosphorylation status of rabies virus proteins in vivo and in vitro remains incompletely understood.
Purpose of the Study:
- To investigate the phosphorylation patterns of rabies virus proteins during infection and in vitro.
- To explore the role of viral kinases in protein phosphorylation and maturation.
- To determine if cellular protein phosphorylation is altered during rabies virus infection.
Main Methods:
- In vivo and in vitro analysis of rabies virus protein phosphorylation.
- Use of purified rabies virions and an in vitro transcriptase assay.
- Comparison of protein phosphorylation states in infected cells versus purified virions.
Main Results:
- Both N and M1 proteins of rabies virus are phosphorylated.
- M1 protein exhibits two phosphorylated states in virions, with only the hypophosphorylated form detected in infected cells.
- In vitro assays showed hyperphosphorylation of N and M1 proteins by a virion-associated kinase.
- No significant changes in cellular protein phosphorylation were observed during rabies virus infection.
Conclusions:
- Rabies virus M1 protein undergoes phosphorylation changes potentially linked to maturation.
- A virion-associated kinase contributes to the hyperphosphorylation of viral proteins in vitro.
- The hyperphosphorylation of the N protein may impact in vitro transcription efficiency.
- Rabies virus infection does not appear to broadly affect cellular protein phosphorylation.