Three loci related to the src oncogene and tyrosine-specific protein kinase activity in Drosophila.

Rous sarcoma virus (RSV) is an acutely oncogenic avian retrovirus which induces sarcomas in animals and transforms fibroblasts in cell culture. Genetic analysis indicates that the viral src gene (v-src) mediates neoplastic transformation. The product of v-src is a 60,000 molecular weight (MW) phosphoprotein (pp60v-src) possessing the enzymatic activity of a tyrosine-specific protein kinase. The viral src gene is derived from a cellular gene (c-src) which also encodes a 60,000 MW phosphoprotein (pp60c-src) with tyrosine-specific protein kinase activity. Both birds and mammals are known to possess c-src. Shilo and Weinberg have reported that the genome of the fruit fly, Drosophila melanogaster, contains nucleotide sequences that are homologous to v-src. We report here the molecular cloning and chromosomal mapping of three loci from the Drosophila genome that contain such sequences. We also show that Drosophila contain both phosphotyrosine and a tyrosine-specific protein kinase activity immunoprecipitated by antisera directed against pp60v-src. It should now be possible to identify the precise locus that encodes a src-specific protein kinase in Drosophila, and to explore the role of c-src in the growth and development of D. melanogaster.