OVEREXPRESSION OF GENES OF POTENTIAL RELEVANCE TO DNA DAMAGE OF AGING

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Project 1 (formerly Project 6) will continue to evaluate both "candidate" and "anonymous" genes that have the potential to protect the DNA of aging mammalian cells from oxidative damage and mutagenesis. According to oxidative damage theories of aging, such genes are predicted to enhance life span and to retard age-related disorder's, particularly late-life neoplasms. A subset of candidate cDNA constructs that have been evaluated in cell culture have been used to synthesize transgenic mice overexpressing these cDNAs via an exceptionally strong, constitutive promoter/enhancer (chick beta actin/CMV enhancer). Duplicate lines of two such transgenics (and of a control line with comparable genetic background) (C57BL/6NNia x DBA/2NNia F1) will be expanded as aging cohorts and characterized as to expression of the transgene and the level of damage to DNA; methods for the latter will range from cytogenetic and micronucleation assays to determinations of frequencies and spectrum of mutation at the APRT locus. Among the transgenes being evaluated are those for human catalase, human superoxide dismutase-1 and -2, mouse gamma- glutamyl cysteine synthetase and yeast apurinic endonuclease. Special attention will be given to catalase constructs targeted to the nucleus; these will be mated with previously described SOD-1 transgenics . An initial set of experiments will also be undertaken with the long term goal of isolating anonymous avian genomic sequences that are responsible for our recent observations indicating that avian somatic cells are unusually resistant to oxidative stress.