The long goal of this proposal is to understand the roles of the naturally occurring polycations, the polyamines, in normal and neoplastic cell proliferation and in cellular responses to stress. A major hypothesis to be tested in the proposed work is that multiple metabolic pathways are coordinately regulated in mammalian cells, and that one coordinately regulated pathway includes enzymes involved in polyamine biosynthesis, such as ornithine decarboxylase, certain stress-induced proteins, such as the Mr=70,000 heat shock protein, and specific growth-associated proteins, including p53 and those encoded by the oncogenes c-myc, c-fos and v-myb. Since it is known that the polyamines putrescine and spermidine can regulate aspects of ornithine decarboxylase expression in a post-transcriptional manner, the proposed work will, first, explore specific mechanisms of this polyamine-dependent post-transcriptional regulation of ornithine decarboxylase and, second, determine whether the expression of other proteins sharing common features, such as long 5' untranslated leader sequences in their encoding mRNAs and common amino acid sequences which appear to characterize their rapid degradation rates, is also regulated in a polyamine-dependent fashion. This work will utilize cell-free synthesis of appropriately modified mRNAs, coupled with translation in polyamine-depleted reticulocyte lysates, to document effects of polyamines on mRNA translation. Modified cDNAs will be transfected into cells to investigate specific aspects of protein degradation. A final specific aim will investigate the mechanism of elevated ornithine decarboxylase activity in certain premalignant tissues, such as those from humans with Barrett's esophagus. These latter studies will ask whether the elevated enzyme activity is to a post-transcriptional process affecting either translation mRNA or the stability of the protein. The results of these studies will impact our understanding of the regulation of mammalian normal and tumor cell growth, and contribute to our knowledge of how cells respond to certain toxic stresses, such as those used in certain forms of cancer treatment. The findings of this work should be of interest to a variety of cancer researchers and could find applications in both the chemoprevention or therapy of human cancers.
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