EFFECTS OF INTRACELLULAR CHELATABLE IRON AND OXIDATIVE STRESS ON TRANSCRIPTION OF CLASSICAL CELLULAR GLUTATHIONE-PEROXIDASE GENE IN MURINE ERYTHROLEUKEMIA-CELLS

The effect of intracellular chelatable iron levels and of oxidative st ress on nuclear classical cellular glutathione peroxidase (GSHPx-1) RN A nascent chain elongation (run-on transcription) and on the stability of cytoplasmic GSHPx-1 mRNA was investigated in murine erythroleukemi a (MEL) cells. The amount of iron in the intracellular low molecular m ass iron pool was changed by incubation of MEL cells transformed by Fr iend virus with iron donors or iron chelators. Transcription in vitro in isolated nuclei from treated cells showed that the treatment with i ron chelators (desferrioxamine (DFO), pyridoxal isonicotinoyl hydrazon e (PIH) decreased the rate of nuclear GSHPx-1 RNA nascent chain elonga tion in both uninduced and with 5 mmol hexamethylenebisacetamide (HMBA ) to erythroid differentiation induced MEL cells. Iron donors (diferri c transferrin, Fe-PIH or their combination) and t-butyl hydroperoxide (t-BuOOH) had the opposite effect on GSHPx-1 gene transcription in run -on experiments. On the other hand, 50 mu mol DFO or 2.5 mu mol t-BuOO H did not change the stability of cytoplasmic GSHPx-1 mRNA in both uni nduced and induced MEL cells treated with 5 mu mol actinomycin D and w ith or without these agents for 9 h. These findings indicate that iron and oxidative stress play their role at the transcriptional level of GSHPx-1 gene expression.