Rejoining of gamma-radiation-induced single-strand breaks in plasmid DNA by human cell extracts: Dependence on the concentration of the hydroxyl radical scavenger, Tris
- Medical Research Council Radiation and Genome Stability Unit, Harwell, Didcot, Oxon (United Kingdom)
The rejoining of single-strand breaks induced by {gamma} irradiation in plasmid DNA under different scavenging conditions is described using human cell extracts. As the scavenging capacity of the irradiated solution increases from 1.5 X 10{sup 7} to 3 X 10{sup 8} s{sup -1} using Tris-HCl as a scavenger, the ratio of single- to double-strand breaks is reduced from {approx}70:1 to 40:1. After irradiation, a proportion of DNA molecules have no initial strand breaks but contain damage that is converted to strand breaks when incubated either at 37{degrees}C or in the presence of cellular extract. Repair of damage by the extracts is dependent upon the scavenging capacity of the irradiated solution. Optimal rejoining is observed when the scavenging capacity is <1.5 X 10{sup 7} s{sup -1}, and results in the repair of some initial strand breaks. As the scavenging capacity increases to 3 X 10{sup 8} s{sup -1} the proportion of breaks repaired is significantly reduced. The relative increase in the yield of double-strand breaks and reduced repairability of single-strand breaks at a scavenging capacity of 3 X 10{sup 8} s{sup -1} is consistent with the concept that the severity of damage increases upon increasing the scavenger concentration. 26 refs., 5 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 478294
- Journal Information:
- Radiation Research, Journal Name: Radiation Research Journal Issue: 1 Vol. 145; ISSN 0033-7587; ISSN RAREAE
- Country of Publication:
- United States
- Language:
- English
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