This project, as well as project number ZO1-CP-04852-01-LVC, studies the biochemical and biophysical properties of nucleic acids and polypeptides of mammalian and human putative oncornaviruses. A summary of our major findings for the this fiscal year are as follows: 1. Poly(A), poly(C), and poly(G)-rich sequences or tracts have been detected in the RNA of leukemia and sarcoma viruses. 2. Poly(U)-rich sequences have not been detected in the RNA of leukemia and sarcoma viruses. 3. Four classes of viral RNA subunits have been identified according to their polynucleotide tract composition. 4. The four classes of subunits have been assembled into a genomic model for mammalian oncornaviruses. 5. These studies represent a possible molecular approach to cancer therapy.