**5. Acknowledgements**

Our work was supported in part by Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sport, Science and Technology of Japan to Y.M. Y.M. also received supports from Foundation for Promotion of Cancer Research, Sato Memorial Foundation for Cancer Research, Public Trust Haraguchi Memorial Cancer Research Fund and Osaka Cancer Research Foundation. A part of the work is the result of "Initiating Events in the Recognition and Repair of DNA Double-Strand Breaks" carried out under the Strategic Promotion Program for Basic Nuclear Research, the Ministry of Education, Culture, Sport, Science and Technology, Japan.
