title: Sensitization of Escherichia coli C to gamma-radiation by 5-bromouracil incorporation.
abstract: Escherichia coli C cells, unifilarly substituted with 5-bromouracil (BrUra) were 2-25 times as sensitive as unsubstituted cells to killing by gamma-irradiation under aerobic conditions. The yield of DNA double-strand breaks in BrUra-substituted cells was increased by a factor only 1-55, suggesting that other lesions also contribute to cell-killing. Alkaline sucrose density gradient analysis of the 3H-thymine labelled DNA strand showed there was less repair of gamma-ray-induced single-strand breaks when BrUra was in the complementary strand. Since there are  more of these unrepaired breaks than can be accounted for by BrUra-induced DNA double-strand breakage, some fraction of the lethal events in BrUra-substituted E. coli cells may be unrepaired DNA single-strand breaks.
mesh_terms: D001976:Bromouracil / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D004269:DNA, Bacterial / Q000528:radiation effects; D004277:DNA, Single-Stranded / Q000528:radiation effects; D004926:Escherichia coli / Q000378:metabolism / Q000528:radiation effects*; D005720:Gamma Rays; D011836:Radiation Tolerance; D011838:Radiation-Sensitizing Agents / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D011838:Radiation-Sensitizing Agents; D001976:Bromouracil