Is DNA Polymerase involved in DNA Degradation following Ionizing Radiation ?

The main lethal events in X-irradiated bacteria are probably internucleotide chain breaks in DNA rather than the formation of mismatched regions, which suggests that in the case of ionizing irradiation DNA breakdown is not a part of the repair process.

Abstract

EXPOSURE of microorganisms to ultraviolet or ionizing irradiation results in a partial degradation of their DNA. In most bacterial strains irradiated with ultraviolet light the depolymerization is not very extensive and is usually considered to be part of the DNA repair systems1,2. This process excises the mismatched regions of a DNA molecule containing pyrimidine dimers and replaces them by a new stretch of correctly paired nucleotides. The degradation of DNA in X or γ-irradiated microorganisms is more drastic3,4, and parallels in extent both the radiosensitivity of bacterial strains and the radio-sensitivity of their growth phases5. This suggests that in the case of ionizing irradiation DNA breakdown is not a part of the repair process. Moreover, the main lethal events in X-irradiated bacteria are probably internucleotide chain breaks in DNA6,7 rather than the formation of mismatched regions. There is thus no need for such a drastic degradation before rejoining of the newly formed ends. The repair replication of DNA observed in ultraviolet-irradiated microorganisms has not been detected after X-irradiation8.