Induction of the SOS DNA repair response in Escherichia coli by nitric oxide donating agents: dinitrosyl iron complexes with thiol-containing ligandsand S-nitrosothiols

The ability of nitric oxide (NO) donor compounds to induce the SOS DIVA rep air response in Escherichia coli is reported. Dinitrosyl iron complexes wit h glutathione and cysteine (DNIC) are the most potent SOS-inducers. S-Nitro sothiols (RSNO) mediate a similar response at 10-100 mu M, but the response decreases sharply at concentrations above 0.5 mM. Pretreatment of the cell s with the chelating agent o-phenanthroline (OP) prevents induction of the SOS response by all agents used. On the other hand, the toxicity of S-nitro sothiols is higher than that of DNIC. The EPR study shows the appearance of an EPR DNIC-type signal after incubation of the cells with S-nitrosoglutat hione because of mutual transformation between RSNO and DNIC in the presenc e of accessible iron inside the cells, Pretreatment of the cells with OP le ads to a decrease in this signal. Analysis of NO donor effects reveals a du al role of the iron ions in reactivity and toxicity of the compounds studie d, i.e. (i) stabilization of the cytotoxic RSNO and (ii) generation of the SOS signal. (C) 1999 Federation of European Biochemical Societies.