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Middle tumor antigen of polyomavirus transformation-defective mutant NG59 is associated with pp60c-src
Abstract:
We have found that lysis of mouse embryo cells infected with the polyomavirus host range transformation-defective (hr-t) mutant NG59 under gentle conditions that avoid ionic detergents results in detectable NG59-encoded middle tumor antigen (MTAg) associated with pp60c-src. This MTAg-pp60c-src complex could be immunoprecipitated from NG59-infected cell lysates by either sera from animals bearing polyomavirus-induced tumors or by monoclonal antibodies directed against MTAg. Immune complex kinase assays revealed that, whereas the pp60c-src associated with NG59 MTAg possessed tyrosyl kinase activity, the NG59 MTAg in this complex was not phosphorylated in these in vitro reactions. These results demonstrate that the point insertion mutation found in this transformation-deficient strain of polyomavirus encodes MTAg molecules capable of associating with pp60c-src and defines a limited region within MTAg which appears to be critical for stable MTAg-pp60c-src interactions.
Insights
Polyomavirus middle tumor antigen (MTAg) from a defective mutant associates with pp60c-src kinase. This interaction reveals a critical region within MTAg for stable binding and kinase activity.
Area of Science:
- Virology
- Molecular Biology
- Oncogenesis
Background:
- Polyomavirus infection can lead to cell transformation.
- The middle tumor antigen (MTAg) plays a role in viral oncogenesis.
- pp60c-src is a cellular tyrosine kinase implicated in cell signaling and cancer.
Purpose of the Study:
- To investigate the association between polyomavirus NG59-encoded MTAg and pp60c-src.
- To characterize the functional properties of the MTAg-pp60c-src complex.
- To identify regions within MTAg critical for pp60c-src interaction.
Main Methods:
- Gentle lysis of polyomavirus-infected mouse embryo cells.
- Immunoprecipitation using anti-MTAg antibodies or tumor-bearing animal sera.
- Immune complex kinase assays to assess tyrosyl kinase activity.
Main Results:
- NG59-MTAg was detected in association with pp60c-src in cell lysates.
- The MTAg-pp60c-src complex could be immunoprecipitated.
- Associated pp60c-src exhibited tyrosyl kinase activity, but MTAg was not phosphorylated in vitro.
Conclusions:
- The transformation-defective polyomavirus mutant NG59 encodes MTAg that associates with pp60c-src.
- A specific region within MTAg is crucial for stable interaction with pp60c-src.
- This interaction involves active pp60c-src kinase, suggesting a role in viral transformation mechanisms.