量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum Science and Technology.
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The DNA double-strand break (DSB) is the most deleterious of the ionizing radiation- induced DNA damages. Two major repair pathways for DSBs have been well studied, nonhomologous end-joining and homologous recombination. It is known that high linear energy transfer radiation, such as heavy ion beams, induces complex DSBs with clustered damages at the end and that, as a result, the efficiency of nonhomologous end- joining in repairing these DSBs is diminished. We have shown that more than 80% of complex DSBs in S/G2 human cells are subjected to DNA end resection, an early step in homologous recombination to generate single-strand DNA. Furthermore, recent work, including ours, revealed that a subpopulation of human G1 cells exhibit resection activity following ionizing radiation, which is dependent on CtIP, as in other cell cycle phases, and also dependent on the complexity of the DSB. Collectively, this recent progress indicates that the complexity of the DSB structure drastically enhances end resection, with CtIP being a significant factor required for complex DSB repair throughout the cell cycle. We further revealed that the ATR pathway, which is activated by end resection, plays a pivotal role in regulating early G2/M arrest in ATM-deficient cells exposed to high linear energy transfer ion beams. This suggests that the complexity of the DSB also influences the choice of the signaling pathway via the enhanced resection. Additionally, we discuss a possibility that CtIP has an additional function (or functions) after the initiation of resection. In conclusion, new findings and insight are pivotal to allow innovative progress in heavy ion-particle therapy by shedding light on the whole response at the molecular level in cells exposed to heavy ion beams.
DNA Repair Processes and Checkpoint Pathways in Human Cells Exposed to Heavy Ion Beams
