Föhe C, Dikomey E
Institute of Biophysics and Radiobiology, University of Hamburg, Germany.
Int J Radiat Biol. 1994 Dec;66(6):697-704.
DNA base damage was measured in Chinese hamster ovary cells X-irradiated under aerobic conditions using an extract of the bacterium Micrococcus luteus. The glycosylases and endonucleases present in this extract recognize damaged bases and convert them into strand breaks (termed endonuclease-sensitive sites, enss). Strand breaks were detected by the alkaline unwinding technique. The induction of enss was measured for X-ray doses ranging up to 45 Gy. The relative frequency of all enss related to all radiation induced strand breaks was 1.7 +/- 0.4. Repair of enss was studied for a radiation dose of 45 Gy. The number of enss was found to decrease exponentially with time after irradiation with a half-time of tau enss = 37 +/- 8 min. The repair kinetics that were also measured for all X-ray-induced DNA strand breaks were found to consist of three phases: fast, intermediate and slow. The intermediate phase was fitted under the assumption that this phase results from the formation and repair of secondary single-strand breaks generated by enzymatic incision at the sites of base damage repair. The relative frequency of base damage derived from this fit was 1.8 +/- 0.5 and the half-time of base damage repair was tau in = 32 +/- 6 min. The agreement of this half-time with the half-time obtained when base damage was measured directly using the M. luteus assay gives support to the interpretation that the intermediate phase of the total repair curve represents the kinetics of secondary strand breaks resulting from base damage by enzymatic incision.
在中国仓鼠卵巢细胞中，使用藤黄微球菌提取物对有氧条件下X射线辐照后的DNA碱基损伤进行了测量。该提取物中存在的糖基化酶和核酸内切酶可识别受损碱基并将其转化为链断裂（称为核酸内切酶敏感位点，enss）。通过碱性解旋技术检测链断裂。测量了高达45 Gy的X射线剂量下enss的诱导情况。与所有辐射诱导的链断裂相关的所有enss的相对频率为1.7±0.4。研究了45 Gy辐射剂量下enss的修复情况。发现enss的数量在辐照后随时间呈指数下降，半衰期为τenss = 37±8分钟。还测量了所有X射线诱导的DNA链断裂的修复动力学，发现其由三个阶段组成：快速、中间和缓慢。中间阶段是在假设该阶段是由碱基损伤修复位点的酶切产生的二级单链断裂的形成和修复导致的情况下拟合的。由此拟合得出的碱基损伤相对频率为1.8±0.5，碱基损伤修复的半衰期为τin = 32±6分钟。当使用藤黄微球菌测定法直接测量碱基损伤时获得的半衰期与该半衰期的一致性支持了以下解释：总修复曲线的中间阶段代表了酶切导致碱基损伤产生的二级链断裂的动力学。
