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Proceedings: The time resolution of the effects of oxygen and radio-sensitizers on the DNA strand break and repair process in E. coli polA.

British Journal of Cancer
Nature Publishing Group
Publication Date
  • Research Article
  • Biology


760 PROCEEDINGS OF THE EUROPEAN SOCIETY FOR RADIATION BIOLOGY thymidine incorporation into DNA of spleen cells under conditions, under which either DNA synthesis or repair after y- or UV irradiation takes place. There are substances which inhibit either only the semiconservative DNA synthesis (vinblastine, isonicotinic acid hydrazide) or only DNA repair (mixture of penicillin G and procaine penicillin G) or both (cyclophosphamide, phenylbutazone, procarbazine, nalidixic acid). Vincristine shows no effect on the thymidine incorporation in DNA, but by density gradient centrifugation it has been found that it influences the ligase reaction. Two DNA polymerases had been isolated from spleen cells, one of the low molecular and one of the high molecular weight type. The influences of the described drugs on these enzymes and on a deoxyribonuclease I from beef pancreas have also been tested in in vitro systems. In all cases, it has been found that there is no effect or only a very small one, compared with the action of well- known inhibitors as e.g. ethidium bromide and p-chloromercuribenzoate, and this cannot be responsible for the suppressions found in DNA repair and semiconservative synthesis. THE TIME RESOLUTION OF THE EFFECTS OF OXYGEN AND RADIO- SENSITIZERS ON THE DNA STRAND BREAK AND REPAIR PROCESS IN E. COLI polA-. 0. SAPORA and P. S. LOVEROCK, Physics Department, Institute of Cancer Research, Sutton. By use of a rapid lysis technique the radiation induced yield of SSBs in the repair deficient strain of E. coli polA- was studied with a time resolution down to 0-2 sec. The time dependence of the repair processes including incision of base damage and polymerase III dependent strand rejoining were followed. Addition of oxygen after anoxic irradiation demonstrated that the polymerase III enzyme system and at least part of the incision process are completely inhibited under hypoxia. Oxygen or the radiosensitizer PNAP, when present during irradiation, produced the same yield of SSBs initially alth

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