Does the Topology of Closed Supercoiled DNA Affect Its Radiation Sensitivity.(Reannouncement with New Availability Information)

摘要

Several families of negatively supercoiled topoisomers of the plasmid pIBI30 were(60)Co gamma-irradiated and assayed for the induction of strand scission by agarose gel electrophoresis. Form-I DNA for all topoisomers decreased exponentially with increasing dose. The radiation sensitivity (1/D37) was dependent on the average linking difference (delta L) associated with a given supercoiled family. For /delta L/ < 2.5 the radiation sensitivity of DNA decreased with increasing /delta L/, whereas for /delta L/ > 2.5 enhanced radiation sensitivity was observed with increasing /delta L/. These results are in agreement with data reported by Miller, et al. (1991) also for pIBI30 (250kV X-irradiated), but are inconsistent with experiments by Milligan, et al. (1992) for 137Cs gamma-irradiated pUC18. Our results are suggestive of several mechanisms that could be operative in explaining the dependence of DNA radiation sensitivity on topology.