Endonuclease IV Is the Main Base Excision Repair Enzyme Involved in DNA Damage Induced by UVA Radiation and Stannous Chloride

Abstract

Stannous chloride (SnCl2) and UVA induce DNA lesions through ROS. The aim of this work was to study the toxicity induced by UVA preillumination, followed bySnCl2treatment.E. coliBER mutants were used to identify genes which could play a role in DNA lesion repair generated by these agents. The survival assays showed (i) Thenfomutant was the most sensitive toSnCl2; (ii) lethal synergistic effect was observed after UVA pre-illumination, plusSnCl2incubation, thenfomutant being the most sensitive; (iii) wild type andnfomutants, transformed with pBW21 plasmid (nfo+) had their survival increased following treatments. The alkaline agarose gel electrophoresis assays pointed that (i) UVA induced DNA breaks andfpgmutant was the most sensitive; (ii)SnCl2-induced DNA strand breaks were higher than those from UVA andnfomutant had the slowest repair kinetics; (iii)UVA+SnCl2promoted an increase in DNA breaks thanSnCl2and, again,nfomutant displayed the slowest repair kinetics. In summary, Nfo protectsE. colicells against damage induced bySnCl2andUVA+SnCl2.