Molecular-Cloning Of The Prcii Sarcoma Viral Genome And The Chicken Proto-Oncogene C-Fps

The class II avian sarcoma viruses comprise PRCII, PRCIIp, PRCV, URI, 16L, and Fujinami. The members of this class are all replication-defective viruses containing various amounts of a transforming sequence called v- fps . PRCII cntains the smallest amount of fps -specific sequences, transforms fibroblasts in tissue culture, but is only weakly tumorigenic. As a first step in understanding variations in pathogenicity among the class II avian sarcoma viruses and the mechanism by which the oncogene of these viruses was transduced from a single cellular locus, we have molecularly cloned the viral genome of PRCII, its related helper PRCII-AV, and the chicken proto-oncogene (c- fps ) from which v- fps derived. The fps -specific region within the cloned PRCII genome was shown to be 8–10 kb smaller than that of the Fujinami fps -specific region, in agreement with previous studies. Transfection of the cloned DNAs into primary chicken cells demonstrated that both clones (PRCII and PRCII-AV) are biologically active. The cloned PRCII genome is helper dependent and produces a gag -fusion phosphoprotein (P105) which is phosphorylated on a tyrosine residue. The cloned PRCII-AV genome produces infectious virus and can function as a helper for the cloned PRCII genome in transfection assays. Three overlapping recombinant a clones homologous to v- fps from a chicken genomic library have been isolated. One of these, λ-c- fps (2), contains all of the cellular sequences homologous to v- fps . In the aggregate, the three molecular clones may represent the entirety of c- fps .