A role of iron ions in the SOS DNA repair response induced by nitric oxidein Escherichia coli

An induction of the SOS DNA repair response by physiological nitric oxide d onors (dinitrosyl iron complexes (DNIC) with thiols and S-nitrosothiols (RS NO)) was studied in E. coli cells. DNIC with thiols were the most effective SOS-inducers. Being more toxic, RSNO mediated a similar response at 10-100 mu M, but they were inactive at concentrations above 0.5 mM. Pretreatment of the cells with chelating agents, o-phenanthroline and picolinic acid, pr evented induction of the SOS response by all NO-donors used and led to a de crease in the DNIC-type EPR signal that appeared after incubation of the ce lls with DNIC or S-nitrosoglutathione (GSNO). Analysis of these effects rev ealed a dual role of iron ions in reactivity and toxicity of the NO-donatin g agents. On one hand, they could stabilize GSNO in the form of less toxic DNIC, and, on the other hand, they took part in the formation of the SOS-in ducing signal by NO-donating agents.