Radiation-induced strand scissions in bacterial DNA and their enzymatic repair

Abstract Abundant evidence indicates that lesions induced in DNA, unless they are repaired, may lead to death of cells exposed to ionizing radiations. Although sugar and base damage undoubtedly occur, the lesions which have been most readily quantifiable by biophysical methods and which, if unrepaired, correlate most closely with lethality are single‐strand and especially double‐strand chain breaks. Evidence is presented for the existence of several different systems for the repair of single‐strand breaks, and some of the relevant enzymes are tentatively identified. Chemical inhibitors of these repair processes have been demonstrated. Since these inhibitors act after irradiation and since the consequence of their action is to enhance lethality, they comprise a new class of radiosensitizers.