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PRCII, a representative of a new class of avian sarcoma viruses
Abstract:
The Poultry Research Center Virus II (PRC II) is a replication-defective avian sarcoma virus with envelope determinants of the A and B subgroups. In nonproducing cells transformed by PRCII the products of the replicative genes gag, pol, and env are not demonstrable, but a single polyprotein of Mr 105,000 (p105) can be detected. P105 contains peptides of the gag proteins p19 and p27 plus transformation-specific sequences. It does not contain peptides of gPr95env of Pr180gag-pol (with the possible exception of one pol peptide). The transformation-specific sequences of p105 are distinct form those of p100 of avian carcinoma virus MH2, of p110 coded for by avian myelocytoma virus MC29, and of p75 or p40 of avian erythroblastosis virus AEV. They also show no resemblance to p60src of Rous sarcoma virus. P105 is phosphorylated on a tyrosine residue and has an associated phosphokinase activity. P105 appears to be capable of autophosphorylation and of phosphorylating homologous immunoglobulin.
Insights
Poultry Research Center Virus II (PRC II) is a replication-defective avian sarcoma virus. Its PRC II-transformed cells produce a unique p105 polyprotein with gag peptides and transformation-specific sequences, exhibiting phosphokinase activity.
Area of Science:
- Virology
- Molecular Biology
- Oncology
Background:
- Poultry Research Center Virus II (PRC II) is a replication-defective avian sarcoma virus.
- It possesses envelope determinants from subgroups A and B.
- Nonproducing cells transformed by PRC II do not express replicative gene products (gag, pol, env).
Purpose of the Study:
- To characterize the protein products of PRC II in transformed cells.
- To investigate the nature of the transformation-specific sequences.
- To determine the enzymatic activity of the detected polyprotein.
Main Methods:
- Cell transformation assays using PRC II.
- Polyacrylamide gel electrophoresis and Western blotting to detect viral proteins.
- Peptide mapping and phosphokinase assays to analyze protein composition and activity.
Main Results:
- A single polyprotein of Mr 105,000 (p105) was detected in PRC II-transformed cells.
- P105 contains gag peptides (p19, p27) and unique transformation-specific sequences, distinct from other avian retroviruses.
- P105 is phosphorylated on tyrosine and possesses associated phosphokinase activity, including autophosphorylation.
Conclusions:
- The p105 polyprotein is the primary product of PRC II in transformed cells.
- The transformation-specific sequences in p105 are novel and contribute to the oncogenic potential of PRC II.
- The phosphokinase activity of p105 suggests a role in cellular transformation mechanisms.