@misc{oai:repo.qst.go.jp:00061025,
 author = {Ban, Sadayuki and Okayasu, Ryuichi and Sagara, Masashi and Michikawa, Yuichi and Umetsu, Atsushi and Sakurai, Akio and Ishikawa, Ken-ichi and Okabe, Atsushi and Shimada, Yutaka and Inazawa, Jouji and Imai, Takashi and et.al and 伴 貞幸 and 岡安 隆一 and 相良 雅史 and 道川 祐市 and 梅津 篤 and 櫻井 亜希子 and 石川 顕一 and 岡部 篤史 and 今井 高志},
 month = {Jun},
 note = {DNA double strand breaks (DSBs) are the most deleterious and lethal form of DNA damage. DSBs are rejoined or repaired by two major pathways in mammalian cells: i.e. homologous recombination (HR) and non-homologous end-joining (NHEJ). DNA-PK is a nuclear, serine/threonine protein kinase consisting of three subunits of DNA-PKcs, Ku70 and Ku80, and involved in the NHEJ, V(D)J recombination and modulation of transcription [1]. Cells lacking DNA-PKcs activity are highly sensitive to DSBs-inducing agents such as ionizing radiations [2]. Douglas et al [3] identified 4 phosphorylation sites in the DNA-PKcs protein: i.e. Thr-2609, Ser-2612, Thr-2638 and Thr-2647. These sites were autophosphorylated with own DNA-PKcs. Chan et al [4] demonstrated that autophosphorylation of DNA-PKcs was required for the rejoining of DSBs. 
Radiation sensitivities of 31 human esophageal squamous cell carcinoma (ESCC) cell lines were investigated with a colony-formation assay. There was a large variation in radiosensitivity among 31 cell lines. In particular, the radiation sensitivity of one cell line (KYSE190) was distinct from a cluster of radiation sensitivities of other 30 cell lines. In order to understand the mechanism behind this hypersensitivity, we investigated the expression of ATM and DNA-PKcs proteins with a western-blotting method and the phosphorylation of DNA-PKcs with a immunohistochemical staining methd. The phosphorylation of DNA-PKcs was not observed in KYSE190 cells. No mutation was detected in the four phosphorylation sites, but one base change in FAT domain of DNA-PKcs gene was observed. These data seem to indicate that the high radiosensitivity of KYSE 190 cells results from the defect in the autophosphorylation of the DNA-PKcs protein., The 5th Japan-France Workshop on Radiobiology and Medical Imaging},
 title = {A deficiency in the phosphorylation of DNA-PKcs in a radiosensitive human ESCC cell line},
 year = {2004}
}