Characterization of the src Gene of a Rous Sarcoma Virus Mutant Temperature-sensitive for Cell Transformation

The src gene is responsible for oncogenic transformation induced by RNA tumor viruses. Both non-conditional and conditional mutants in the src gene have been isolated. Nonconditional mutants of helper-independent sarcoma viruses, commonly designated as transformation-defective (td), are formed in many nondefective avian sarcoma virus (ASV) preparations and, if not freshly cloned, these preparations usually contain transformation-defective mutants in excess of the nondefective virus (Coffin and Billeter 1976). Thus, there is a strong tendency for nondefective RNA tumor viruses to delete most if not all of the src gene and to yield spontaneous transformation-defective segregants. Numerous conditional mutants temperature-sensitive (ts) for cell transformation (temperature-sensitive src) have been isolated after mutagenization of nondefective strains of avian tumor viruses. Recently, we have reported that one of such temperature-sensitive src mutants, LA23 (Wyke 1975), shows an unusual behavior in that it does not yield transformation-defective segregants even after several passages at high multiplicity in...