Journal Article A comprehensive analysis of radiosensitization targets; functional inhibition of DNA methyltransferase 3B radiosensitizes by disrupting DNA damage regulation

Fujimori, Hiroaki  ,  Sato, Akira  ,  Kikuhara, Sota  ,  Wang, Junhui  ,  Hirai, Takahisa  ,  Sasaki, Yuka  ,  Murakami, Yasufumi  ,  Okayasu, Ryuichi  ,  Masutani, Mitsuko

5p.18231 , 2015-12-15 , Nature Publishing Group
A comprehensive genome-wide screen of radiosensitization targets in HeLa cells was performed using a shRNA-library/functional cluster analysis and DNMT3B was identified as a candidate target. DNMT3B RNAi increased the sensitivity of HeLa, A549 and HCT116 cells to both γ3-irradiation and carbon-ion beam irradiation. DNMT3B RNAi reduced the activation of DNA damage responses induced by γ3-irradiation, including HP1β-, γ3H2AX- and Rad51-foci formation. DNMT3B RNAi impaired damage-dependent H2AX accumulation and showed a reduced level of γ3H2AX induction after γ3-irradiation. DNMT3B interacted with HP1β in non-irradiated conditions, whereas irradiation abrogated the DNMT3B/HP1β complex but induced interaction between DNMT3B and H2AX. Consistent with radiosensitization, TP63, BAX, PUMA and NOXA expression was induced after γ3-irradiation in DNMT3B knockdown cells. Together with the observation that H2AX overexpression canceled radiosensitization by DNMT3B RNAi, these results suggest that DNMT3B RNAi induced radiosensitization through impairment of damage-dependent HP1β foci formation and efficient γ3H2AX-induction mechanisms including H2AX accumulation. Enhanced radiosensitivity by DNMT3B RNAi was also observed in a tumor xenograft model. Taken together, the current study implies that comprehensive screening accompanied by a cluster analysis enabled the identification of radiosensitization targets. Downregulation of DNMT3B, one of the targets identified using this method, radiosensitizes cancer cells by disturbing multiple DNA damage responses.

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