This work is directed toward understanding the molecular basis of malignant transformation. A combination of site-directed mutagenesis and monoclonal antibody techniques is being used to analyze protein structure/function relationships. The concentration is initially on the v-sis oncogene. The combination of methods will then be applied to the analysis of other gene products. We will introduce specific mutations into a gene sequence and then assay the effect of this mutation on its biological activity. This activity will be tested by transfecting the gene directly into eukaryotic cells and also by introducing the gene into an expression vector containing viral LTRs and transfecting into two cells to produce a retroviral genome containing the gene sequence. The biological activity of each mutant sequence will be compared to the "wild type" gene and the effect(s) of the mutation will be determined. To analyze the gene activity at the protein level, monoclonal antibodies against specific epitopes on the gene product will be produced. These antibodies will be used to localize these proteins in cells, to detect pathways of post-translational modification for these proteins, and to define regions of the gene products that interact with other molecules. The information derived from these two types of analyses will be correlated to define structure/function relationships for these proteins. The analysis will focus on the v-sis oncogene, the N-ras oncogene, and genes that are defined as playing a role in the transformation of lymphocytes as defined in the lymphocyte transfection system that we have developed. (AG)