Yatagai Fumio, Sugasawa Kaoru, Enomoto Shuichi, Honma Masamitsu
Metallomics Imaging Research Unit, Center for Molecular Imaging Science, The Institute of Physical and Chemical Research (RIKEN), Saitama, Japan.
J Radiat Res. 2009 Sep;50(5):407-13. doi: 10.1269/jrr.09050. Epub 2009 Aug 13.
In this review, we would like to introduce a unique approach for the estimation of radioadaptation. Recently, we proposed a new methodology for evaluating the repair efficiency of DNA double-strand breaks (DSB) using a model system. The model system can trace the fate of a single DSB, which is introduced within intron 4 of the TK gene on chromosome 17 in human lymphoblastoid TK6 cells by the expression of restriction enzyme I-SceI. This methodology was first applied to examine whether repair of the DSB (at the I-SceI site) can be influenced by low-dose, low-dose rate gamma-ray irradiation. We found that such low-dose IR exposure could enhance the activity of DSB repair through homologous recombination (HR). HR activity was also enhanced due to the pre-IR irradiation under the established conditions for radioadaptation (50 mGy X-ray-6 h-I-SceI treatment). Therefore, radioadaptation might account for the reduced frequency of homozygous loss of heterozygosity (LOH) events observed in our previous experiment (50 mGy X-ray-6 h-2 Gy X-ray). We suggest that the present evaluation of DSB repair using this I-SceI system, may contribute to our overall understanding of radioadaptation.
在本综述中，我们将介绍一种评估辐射适应性的独特方法。最近，我们提出了一种使用模型系统评估DNA双链断裂（DSB）修复效率的新方法。该模型系统可以追踪单个DSB的命运，通过限制性内切酶I-SceI的表达，在人淋巴母细胞TK6细胞17号染色体上的TK基因内含子4中引入单个DSB。该方法首先用于检验低剂量、低剂量率γ射线照射是否会影响DSB（在I-SceI位点）的修复。我们发现，这种低剂量的IR暴露可以通过同源重组（HR）增强DSB修复的活性。在既定的辐射适应条件（50 mGy X射线-6小时-I-SceI处理）下，预照射IR也会增强HR活性。因此，辐射适应可能是我们之前实验（50 mGy X射线-6小时-2 Gy X射线）中观察到的杂合性缺失（LOH）纯合事件频率降低的原因。我们认为，目前使用该I-SceI系统对DSB修复的评估，可能有助于我们全面理解辐射适应。
