BASIS FOR TRANSFORMATION BY FUJINAMI SARCOMA VIRUS

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The objective of the proposed research is to understand how protein- tyrosine kinase oncongenes transform cells. The major emphasis is on the fps gene of Fujinami sarcoma virus. We will characterize signal transduction pathways used by v-fps to transform cells. We have developed a pharmaco-genetic approach for identifying signal transduction intermediates used by the v-fps gene product to transduce signals to the nucleus. Elevating the protein-tyrosine kinase activity of a temperature-sensitive derivative of v-fps, leads to the rapid transcriptional activation of the recently characterized 9E3 gene whose expression correlates with transformation (Sugano et al., Cell 49, 1321,-328, 1987). Drugs that interfere with known signal transduction intermediates are used to block the induction of 9E3 gene expression. In this way, we can determine if specific signal transduction intermediates are required for v-fps to induce expression of the transformation-related 9E3 gene. The pharmacological approach involves the generation of detailed drug- sensitivity profiles (DSPs) for inhibitors of signal transduction that are diagnostic for the involvement of specific signal transduction intermediates. Using several protein kinase C requirement. In addition, we have preliminary data suggesting a requirement for protein kinase C, a cholera toxin-sensitive G-protein, phospholipase C, and phospholipase A2 in the v-fps induction of 9E3 gene expression. Experiments proposed here will directly demonstrate the involvement of these implicated signal transduction intermediates in transformation by v-fps. The data to be generated from these studies may provide new targets and strategies for cancer chemotherapy in cases where protein-tyrosine kinase activity has been implicated.