Inactivation and mutagenesis on isolated DNA IV. possibility of integration of lethal damage into the chromosome of Bacillus subtilis during transformation

Postreplication repair of ultraviolet-irradiated transforming deoxyribonucleic acid in Bacillus subtilis

“…However, it soon became clear that pyrimidine dimers, the major lesions induced by UV irradiation, do not act with a high probability to terminate the recombination region, although pyrimidine diners are clearly the major inacti-vating lesions (35). Data have been presented (4,6,21) that imply that segments of DNA contining pyrmimdine dimers are integrated by transformed cells; i.e., the fate of a genetic marker located on an irradiated transforming DNA molecule must be determined partially by the ability of the recipient cell to repair integrated lesions. It is probable that repair processes contribute to the observed shape of the dose-response curve.…”

Integration and Repair of Ultraviolet-Irradiated Transforming Deoxyribonucleic Acid in Haemophilus influenzae

“…Estimates of the extent of integration of UV-irradiated transforming DNA have been made by measurement of (i) the sedimentation velocity of radioactively labeled DNA from cells exposed to transforming DNA (10), (ii) the amount of recipient label specifically released from competent cells exposed to ' Present address: Nuclear Institute for Agriculture and Biology, Lyallpur, Pakistan. irradiated transforming DNA (9), (iii) the biological activity of donor and recombinant DNA extracted from transforming cells and assayed on repair-proficient and -deficient strains (5), and (iv) the ability of genetically unmarked, irradiated DNA to compete with unirradiated DNA in transformation (3). All such estimates indicate that blockage of integration cannot account for a very large fraction of the inactivation of transforming DNA by UV radiation, in accord with the evidence that UV lesions can be integrated (2,6,15) and can even be lethal to the recipient cell (1).…”