The repairability of oxidative free radical mediated damage to DNA: a review.

Many DNA repair enzyme activities are present in both prokaryotic and eukaryotic organisms. Among these are DNA exo- and endonucleases and DNA glycosylases which remove oxidatively damaged portions of the DNA molecule, thereby initiating excision-repair. The existence of these enzymes may be taken as evidence that cellular DNA is continuously subject to endogenous oxidative stress. Many of the lesions introduced by ionizing and ultraviolet radiation are identical to those introduced into DNA by reactive oxygen species generated by activated white cells, and are substrates for the repair enzymes. The chemical nature of the lesions, their biologic effects, and the mechanism of their repairability are described.