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gag-Related polypeptides encoded by replication-defective avian oncoviruses
Abstract:
The content of viral structural (gag) protein sequences in polypeptides encoded by replication-defective avian erythroblastosis virus (AEV) and myelocytomatosis virus MC29 was assessed by immunological and peptide analyses. Direct comparison with gag proteins of the associated helper viruses revealed that MC29 110K polypeptide contained p19, p12, and p27, whereas the AEV 75K polypeptide had sequences related only to p19 and p12. Both of these polypeptides contained some information that was unrelated to gag, pol, or env gene products. In addition, no homology was detected between these unique peptides of MC29 110K and AEV 75K. The AEV 75K polypeptide shared strain-specific tryptic peptides with the p19 encoded by its naturally occurring helper virus; this observation suggests that gag-related sequences in 75K were originally derived from the helper viral gag gene. Digestion of oxidized MC29 110K and AEV 75K proteins with the Staphylococcus aureus V8 protease generated a fragment which comigrated with N-acetylmethionylsulfoneglutamic acid, a blocked dipeptide which is the putative amino-terminal sequence of structural protein p19 and gag precursor Pr76gag. This last finding is evidence that the gag sequences are located at the N-terminal end of the MC29 110K and AEV 75K polypeptides.
Insights
Replication-defective avian erythroblastosis virus (AEV) and myelocytomatosis virus MC29 contain viral structural (gag) protein sequences. These gag sequences are located at the N-terminal end of the viral polypeptides.
Area of Science:
- Virology
- Molecular Biology
- Oncogenic Viruses
Background:
- Replication-defective avian retroviruses encode complex polypeptides.
- Understanding the protein content of these polypeptides is crucial for viral pathogenesis.
Purpose of the Study:
- To determine the viral structural (gag) protein sequence content in polypeptides from avian erythroblastosis virus (AEV) and myelocytomatosis virus MC29.
- To investigate the origin and location of gag-related sequences within these viral polypeptides.
Main Methods:
- Immunological analyses were employed to assess protein content.
- Peptide analyses, including Staphylococcus aureus V8 protease digestion, were performed.
- Comparison with gag proteins of associated helper viruses was conducted.
Main Results:
- MC29 110K polypeptide contained p19, p12, and p27 gag sequences, while AEV 75K had p19 and p12.
- Both polypeptides contained non-gag, non-pol, non-env information with no homology between unique peptides.
- Gag sequences were identified at the N-terminal end of both MC29 110K and AEV 75K polypeptides.
Conclusions:
- AEV 75K gag-related sequences likely originated from the helper viral gag gene.
- The N-terminal location of gag sequences in AEV and MC29 polypeptides was confirmed.
- These findings contribute to understanding the structure and potential function of viral oncogene products.