DNA-membrane association and the repair of double breaks in X-irradiated Micrococcus radiodurans

Oxidative Stress Resistance inDeinococcus radiodurans

“…DSBs can arise when SSBs occur in close proximity on opposite strands, when a cluster of radicals introduces strand breaks in both strands at one location, or through the excision repair of damaged bases present in close proximity on both strands. In irradiated D. radiodurans, DSBs are a result of a single event, as opposed to a double event, where two close SSBs in opposite chains yield a DSB (79). In the case of "double-event" breaks, the number of breaks would be proportional to the square of the dose and would be dependent on ionic strength, which was not found (79).…”

“…ROS generated by desiccation and ionizing radiation damage proteins, lipids, nucleic acids, and carbohydrates and induce potentially lethal double-strand DNA breaks (DSBs) in the bacterial genome. D. radiodurans can survive high doses of ionizing radiation, which break its genome into several hundred fragments (up to 2,000 DSBs per multigenomic cell) without causing considerable protein damage (79,122,135,307). The robustness of this bacterium is due to strong oxidative stress resistance mechanisms that protect proteins from oxidative damage (122) and a DNA repair process that accomplishes an efficient and precise reassembly of DNA fragments (572,676).…”

Rate zonal density gradient ultracentrifugation analysis of repair of radiation damage to the folded chromosome of Escherichia coli

“…Matsuyama (1968,1971) demonstrated repair of DS-breaks by neutral sucrose gradient analysis of gamma-irradiated Micrococcus radiodurans. Precise quanti tation of the breakage and repair rates was not possible, but repair was show.n to be inhibitable by chloramphenicol, tetracycline, and mitomycin D. Working with the same M. radiodurans, Burrell et al (1971) and Burrell and Dean (1975) also demonstrated repair of DS-breaks produced by X-irradiation. In their system, as many as 100 DS-breaks/genome could be repaired.…”

“…Several researchers have reported on the formation of very-heavy, membrane associated material during repair of ionizing radiation damage (Burrell et al~ 1971;Burrell and Dean, 1975;Baraldi and Sinskey, unpublished observations). During the latter stages of post-irradiation incubation observed in the pres~nt experiments, large amounts of material with sedimentation coefficients in excess of 3100S are formed.…”

Role of protein synthesis in the repair of sublethal x-ray damage in a mutant Chinese hamster ovary cell line

“…It is believed that these lesions may be sites of base damage (Elkind and Redpath, 1977 it occurs under both aerobic and hypoxic conditions; it occurs in all ages of the synchronized population; it is not inhibited by hydroxyurea, actinomycin 0, or puromycin, and it is almost completely absent at SoC (Altman et al, 1970). Enzymatic repair of double-strand breaks has been reported to occur in bacteri a (Burrell et al, 1971) and yeast (Resnick and Martin, 1976). Repair of double-strand breaks in mammalian cells has been reported but not conclusively documented (Hutchinson, 1978) •…”