The long-term objective of our ongoing, multi-project research program is to understand molecular mechanisms for cellular regulation by signal transduction. Most of our project focus on cellular transducers that have oncogenic potential in the absence of regulation. We think that many oncogenes are likely to interact in common signal transduction pathways designed for regulation of cellular proliferation. Our projects include study of growth factor receptors at the cell surface, signal transduction networks in the cytoplasm, and transcription factors operating in the nucleus. Our research projects are: 1: Regulation of mammalian Ras exchange factor Sos 2: Regulation of hematopoiesis by epidermal growth factor receptor 3: Regulation of transcription factor E2F 4: Regulation of gene expression by prolactin 5: Regulation of cellular proliferation by p53 Our program project grant includes five investigators at the State university of new York at Stony Brook. Our interdisciplinary approaches include cell biology, molecular biology, genetics, and structure. During the past 15 years, our program has evolved from a study of tumor-virus- associated oncogenes to our present emphasis on signal transduction.