The overall goal of this research is to investigate the mechanism(s) for the control and regulation of MnSOD expression in normal and tumor cells under normal growth conditions and under stress. It has been shown that tumor cells have reduced MnSOD activity when compared to their normal counterparts. The specific aims are to investigate whether this reduction of MnSOD activity in tumor cells is due to one or more mechanisms. Several questions will be examined. What is the specific activity of MnSOD in tumor cells when compared to their normal cell counterparts? Are there any differences in the structure of this protein between normal and tumor cells? Are the mitochondria of normal and tumor cells equally efficient at processing the precursor protein? Is transcription of the MnSOD gene in tumor cells reduced? Is the mRNA unstable or its processing delayed in tumor cells? Do the MnSOD genes differ in normal and tumor cells? Will oxidative damage or stress cause an induction of MnSOD in normal and tumor cells? If so, what level of control is responsible for this phenomena? To address these questions, three normal/tumor cell models (WI-38 and WI-38 SV-40 transformed, C3H/10T 1/2 Cl-8 and C3H10T 1/2 F-17 radiation transformed and HL-60 and HL-60 differentiated) will be used. The MnSOD protein, mRNA and gene content, structure, processing and function will be assessed by standard biochemical and molecular biology techniques. Gamma radiation, bleomycin and high oxygen concentration will be used to stress both normal and tumor cells under selected conditions. Alterations of the MnSOD protein, mRNA and gene content, structure, processing and function will be assessed by the same biochemical and molecular biology techniques used above. The results obtained from this study should contribute significantly to our understanding of the control and regulation of this metabolically important molecule. With this information, future studies can be designed to determine the role of MnSOD in cancer induction and therapy.