Cell-free synthesis of two proteins unique to RNA of transforming virions of Rous sarcoma virus.

We have utilized a reticulocyte lysate system to translate the 35S RNA of Rous sarcoma virus. Autoradiograms of the protein products separated on sodium dodecyl sulfate/polyacrylamide gels reveal a heterogeneous mixture of proteins of sizes ranging from 13,000 to 180,000 daltons. In comparing the translational products from 35S RNA of Prague B Rous sarcoma virus with those formed from the RNA of a transformation-defective deletion mutant derived from Prague B, we have found that two proteins, 25,000 and 18,000 daltons, are missing from the latter. Neither of these proteins is immunoprecipitated by monospecific antisera against the structural proteins of avian RNA tumor viruses. The combined atomic mass of 43,000 daltons corresponds to the amount of genetic coding capacity (40,000-50,000 daltons in terms of protein products) deleted from the RNA of the transformation-defective viruses. We propose that these proteins are coded for by the putative oncogene (onc) or sarc (src) gene and that one or both of them may be responsible for the oncogenic transformation caused by these viruses in infected cells.