Yatagai Fumio, Suzuki Masao, Ishioka Noriaki, Ohmori Hitoshi, Honma Masamitsu
Advanced Development and Support Center, The Institute of Physical and Chemical Research (RIKEN), Saitama 351-0198, Japan.
Radiat Environ Biophys. 2008 Nov;47(4):439-44. doi: 10.1007/s00411-008-0179-7. Epub 2008 Jun 21.
We investigated the influence of low-dose, low-dose-rate gamma-ray irradiation on DNA double strand break (DSB) repair in human lymphoblastoid TK6 cells. A single DSB was introduced at intron 4 of the TK+ allele (chromosome 17) by transfection with the I-SceI expression vector pCBASce. We assessed for DSB repair due to non-homologous end-joining (NHEJ) by determining the generation of TK-deficient mutants in the TK6 derivative TSCE5 (TK +/-) carrying an I-SceI recognition site. We similarly estimated DSB repair via homologous recombination (HR) at the same site in the derived compound heterozygote (TK-/-) cell line TSCER2 that carries an additional point mutation in exon 5. The NHEJ repair of DSB was barely influenced by pre-irradiation of the cells with 30 mGy gamma-rays at 1.2 mGy h(-1). DSB repair by HR, in contrast, was enhanced by approximately 50% after pre-irradiation of the cells under these conditions. Furthermore, when I-SceI digestion was followed by irradiation at a dose of 8.5 mGy, delivered at a dose rate of only 0.125 mGy h(-1), HR repair efficiency was enhanced by approximately 80%. This experimental approach can be applied to characterize DSB repair in the low-dose region of ionizing radiation.
我们研究了低剂量、低剂量率γ射线照射对人淋巴母细胞TK6细胞中DNA双链断裂（DSB）修复的影响。通过转染I-SceI表达载体pCBASce，在TK +等位基因（17号染色体）的内含子4处引入单个DSB。我们通过检测携带I-SceI识别位点的TK6衍生物TSCE5（TK +/-）中TK缺陷型突变体的产生，评估非同源末端连接（NHEJ）导致的DSB修复。我们同样通过在携带外显子5中另一个点突变的衍生复合杂合子（TK-/-）细胞系TSCER2的同一位点进行同源重组（HR）来估计DSB修复。细胞预先接受1.2 mGy h(-1)的30 mGy γ射线照射，对DSB的NHEJ修复几乎没有影响。相比之下，在这些条件下细胞预先照射后，HR介导的DSB修复增强了约50%。此外，当I-SceI消化后以仅0.125 mGy h(-1)的剂量率给予8.5 mGy的照射时，HR修复效率提高了约80%。这种实验方法可用于表征电离辐射低剂量区域的DSB修复。
