Development of bio-dosimetry for the evaluation of low dose radiation and carcinogenic risk estimation

我们尝试用DNA损伤反应蛋白建立过敏小鼠模型和分子生物剂量学来估计辐射暴露后的致癌风险和剂量。辐射暴露致敏小鼠模型的建立erev1蛋白属于翻译DNA聚合酶家族。Rev1负责易出错的翻译合成，并在DNA损伤诱导的突变中发挥作用。REV1是脱氧胞基转移酶，包含dCMP相反的模板碱基位点。为了建立辐射暴露的过敏小鼠模型，我们在锌诱导的组成型转录激活启动子下培养了过表达Rev1基因的转基因小鼠（Tg）。我们成功建立了表达Rev1转基因的7tg小鼠细胞系。我们检测了辐射暴露后t细胞受体（TCR）的敏感性和突变频率，发现Tg小鼠的TCR突变频率高于正常小鼠2。为了开发低剂量辐射分子生物剂量学，我们重点研究了DNA损伤后磷酸化的组蛋白H2AX复合物（γ-H2AX）的功能分析，并在细胞核中显示为病灶。我们发现H2AX在诱导dsb后具有很高的流动性。我们进一步发现，动员不依赖于磷酸化，而是依赖于泛素化，而H2AX的泛素化反过来又受到TIP60组蛋白乙酰化酶的调节，这暗示了TIP60在DNA修复中的作用。这些结果表明H2AX的动员是DNA DSB修复的早期和必要步骤。

We have tried to develop the hypersensitive mouse model and molecular bio-dosimery using DNA damage response proteins for the estimation of carcinogenic risk and dose after radiation exposure.1.Development of hypersensitive mouse model for radiation exposureRev1 protein belongs to a family of translesion DNA polymerases. Rev1 is responsible for error-prone translesion synthesis and play a role in mutagenesis induced by DNA damage. REV1 is deoxycytidyltransferase that incorporates dCMP opposite template abasic sites.In order to develop hypersensitive mouse model for radiation exposure, We have developed transgenic mouse (Tg) over expressing Rev1 gene under the constitutive zinc-induced transcriptional activation promoter. We've succeeded in establishing 7 Tg mouse line expressing Rev1 transgene. We examined sensitivity and mutation frequency of T-cell receptor (TCR) after radiation exposure, and found that Tg mouse was apt to have higher mutation frequency of TCR than normal mouse.2.Development of molecular bio-dosimery for low dose radiationIn order to develop molecular bio-dosimery, We have focused our research on functional analysis of Histone H2AX complex which is phosphorylated after induction of DNA damage (γ-H2AX) and visualized as foci in cell nucleus. We found that H2AX became highly mobile after induction of DSBs. We further find that mobilization depends not on phosphorylation but rather on ubiquitination, and that ubiquitination of H2AX is, in turn, regulated by TIP60 histone acetylase which implicates TIP60 in DNA repair. These results suggest that mobilization of H2AX is an early and necessary step in repair of DNA DSB.