COMPARATIVE-STUDIES ON THE SRC PROTOONCOGENE AND ITS GENE-PRODUCT PP60C-SRC IN NORMAL AND NEOPLASTIC TISSUES OF LOWER-VERTEBRATES

1. Oncogenes appear to play an important role in the phsyiology of transformed as well as of normal cells. 2. The src oncogene is by far the most investigated oncogene in birds and mammals with respect to the biochemical characteristics of its tyrosine kinase activity, although the specific function of this enzymatic activity still remains to be uncovered. 3. Systematic studies on the src related kinase activity in lower animals are lacking. 4. To contribute to a better understanding of the function of the c-src gene, we performed a comparative study on lower chordates. 5. We were able to demonstrate the presence of c-src related sequences in Acrania, Cyclostomata, cartilagenous and bony fish. 6. By performing the pp60scr-specific immune complex assay we detected a tyrosine specific kinase activity, that shows the same biochemical properties as the pp60src from higher vertebrates. 7. The level of kinase activity is regulated in an organ specific manner. 8. In lymphocystis tumors of flat-fish and in stomatopapilloma of freshwater eels a considerable amount of pp60src kinase activity was found, which, however, never exceeded the levels found in the normal brain.