OXIDATIVE STRESS AND SIGNAL-TRANSDUCTION

Reactive oxygen intermediates (ROIs) are an evolutionarily ancient thr eat to all organisms. Both prokaryotic and higher eukaryotic cells are able to alter their genetic program in response to changes in the in the intracellular levels of ROIs. In bacteria and yeast, this response leads to the new synthesis of proteins that protect cells from the co nsequences of oxidative damage, such as DNA strand breaks, lipid perox idation and oxidative damage of proteins. Intriguingly, higher organis ms have also evolved cellular mechanisms to actively produce ROIs. The re is increasing evidence that ROIs fulfil an important role as second messengers involved in signal transduction. We have proposed that ROI s have been consented throughout evolution as universal pathogen messe ngers turning on genes with important functions in the immune response and cell proliferation. The higher eukaryotic transcription factors N F-kappa B and AP-1 will be described as proteins which are regulated b y ROIs under a great variety of pathogenic conditions and initiate the new expression of genes with important roles in immune, inflammatory and other pathogen-related genetic responses.