MUTAGENESIS BY METAL-INDUCED OXYGEN RADICALS

To assess the contribution of reactive oxygen species (ROS) to metal-i nduced mutagenesis, we have determined the spectrum of mutations in th e lacZ alpha gene after exposure of M13mp2 DNA to Fe2+, Cu2+, acid Ni2 +. With iron and copper ions, mutations are clustered and are predomin antly single base substitutions. Fe, Cu, and phorbol ester-stimulated neutrophils also produced tandem double CC-->TT mutations. This mutati on may provide a marker for the role of oxidative damage in carcinogen esis. Mutagenesis by Ni2+ required the complexing of the metal to a tr ipeptide and the addition of H2O2. To assess the contribution of ROS i n mammalian cells, we determined the spectrum of mutations produced wh en purified DNA polymerses and -beta synthesized DNA using a template that had been damaged by ROS. The mutation spectra produced by the two polymerases indicates that these enzymes substitute different nucleot ides opposite the same lesions.