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Three loci related to the src oncogene and tyrosine-specific protein kinase activity in Drosophila
Abstract:
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.
Insights
The Rous sarcoma virus (RSV) v-src gene product, a tyrosine kinase, has counterparts in fruit flies (Drosophila melanogaster). This study identifies homologous DNA sequences and related kinase activity in Drosophila, paving the way for understanding cellular src (c-src) functions.
Area of Science:
- Molecular Biology
- Genetics
- Virology
Background:
- Rous sarcoma virus (RSV) contains an oncogenic viral src (v-src) gene.
- The v-src gene product is a 60,000 MW phosphoprotein (pp60v-src) with tyrosine-specific protein kinase activity.
- Cellular homologs (c-src) exist in birds and mammals, but their function is unclear.
Purpose of the Study:
- To investigate the presence and nature of src-homologous sequences in Drosophila melanogaster.
- To determine if Drosophila possess tyrosine-specific protein kinase activity related to pp60v-src.
- To lay the groundwork for studying the role of c-src in Drosophila development.
Main Methods:
- Molecular cloning of src-homologous loci from the Drosophila genome.
- Chromosomal mapping of these cloned loci.
- Immunoprecipitation using anti-pp60v-src antisera to detect phosphotyrosine and kinase activity.
Main Results:
- Three loci in the Drosophila genome homologous to v-src were molecularly cloned and mapped.
- Drosophila possess phosphotyrosine.
- Tyrosine-specific protein kinase activity, immunoprecipitable by anti-pp60v-src, was detected in Drosophila.
Conclusions:
- Drosophila melanogaster harbors genetic elements homologous to the viral src gene.
- The presence of related phosphotyrosine and kinase activity suggests functional conservation.
- Further research can now pinpoint the specific Drosophila locus encoding a src-like kinase and explore its developmental roles.