The effects of radioprotectors on DNA polymerase I-directed repair synthesis and DNA strand breaks in toluene-treated and X-irradiated Escherichia coli.

In Escherichia coli made permeable to nucleotides by toluene treatment, a DNA polymerase I-directed repair synthesis is induced by exposure to X rays. This repair synthesis may be amplified and easily measured through inhibition of DNA ligase action. In an effort to learn more of the relationship between X-ray-induced strand breaks in cellular DNA and the extent of this repair synthesis, experiments designed to compare the influence of radioprotectors on both strand-break production and repair synthesis have been carried out. The results show that cysteamine, sodium formate, and glycerol not only protect against strand breaks but also reduce DNA polymerase I-directed repair synthesis. However, I-, an efficient hydroxyl radical scavenger, is not as effective a protective agent against strand breaks and does not measurably affect repair synthesis in our system.