The Chemical Inhibition of the Repair of Single-strand Breaks in DNA: Post-irradiation Sensitization to X-rays

SummaryA class of radiosensitizers is discussed which irreversibly inhibits the repair of x-ray-induced single-strand breaks in DNA. Such agents are active when added after irradiation and potentiate x-ray-induced killing in rec+ strains of E. coli K-12, but have little effect on the viability of x-irradiated recA strains which are deficient in their ability to repair x-ray-induced single-strand breaks. Chromatographically-impure samples of hydroxyurea (but not pure samples) have the properties associated with this class of post-irradiation sensitizers.