Temperature-sensitive transformation by Rous sarcoma virus and temperature-sensitive protein kinase activity

Area of Science:

• Oncology
• Virology
• Molecular Biology

Background:

• Rous sarcoma virus encodes p60src, a transforming protein with kinase activity.
• Temperature-sensitive mutants of Rous sarcoma virus allow investigation of p60src's role in cell transformation.

Purpose of the Study:

• To determine the correlation between cellular p60src concentration and chick cell transformation by Rous sarcoma virus mutants.
• To investigate the lability of protein kinase activity in temperature-sensitive mutants.

Main Methods:

• Quantification of virus-induced protein kinase activity via p60src immunoprecipitation with antitumor antiserum.
• Utilizing modified immunoprecipitation procedures to minimize inactivation of labile protein kinase activity.

Main Results:

• A correlation exists between active p60src levels and cell transformation.
• Some mutants exhibited 30-50% of wild-type p60src activity at non-permissive temperatures.
• Protein kinase activity in uninfected cells was significantly lower (3-5%) than in transformed cells.

Conclusions:

• The lability of p60src kinase activity in mutants further supports its essential role in Rous sarcoma virus-induced cell transformation.
• Transformation may result from quantitative changes in p60src activity or involve multiple viral functions.