Absence of Ku70 gene obliterates X-ray-induced lacZ mutagenesis of small deletions in mouse tissues.
With the goal of understanding the role of non-homologous end-joining repair in the maintenance of genetic information at the tissue level, we studied mutations induced by radiation and subsequent repair of DNA double-strand breaks in Ku70 gene-deficient lacZ transgenic mice. The local mutation frequencies and types of mutations were analyzed on a lacZ gene that had been chromosomally integrated, which allowed us to monitor DNA sequence alterations within this 3.1-kbp region. The mutagenic process leading to the development of the most frequently observed small deletions in wild-type mice after exposure to 20 Gy of X rays was suppressed in Ku70(-/-) mice in the three tissues examined: spleen, liver and brain. Examination of DNA break rejoining and the phosphorylation of histone H2AX in Ku70-deficient and -proficient mice revealed that Ku70 deficiency decreased the frequency of DNA rejoining, suggesting that DNA rejoining is one of the causes of radiation-induced deletion mutations. Limited but statistically significant DNA rejoining was found in the liver and brain of Ku70-deficient mice 3.5 days after irradiation, showing the presence of a DNA double-strand break repair system other than non-homologous end joining. These data indicate a predominant role of non-homologous end joining in the production of radiation-induced mutations in vivo.
Uehara
Yoshihiko
Y
Department of Cell Biology, Graduate School of Medicine, Tohoku University, 2-1 Seiryo-machi, Aoba-ku, Sendai, Japan.
Ikehata
Hironobu
H
Komura
Jun-ichiro
J
Ito
Ari
A
Ogata
Masaki
M
Itoh
Tsunetoshi
T
Hirayama
Ryoichi
R
Furusawa
Yoshiya
Y
Ando
Koichi
K
Paunesku
Tatjana
T
Woloschak
Gayle E
GE
Komatsu
Kenshi
K
Matsuura
Shinya
S
Ikura
Tsuyoshi
T
Kamiya
Kenji
K
Ono
Tetsuya
T
D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D017353:Gene Deletion; D000072200:Ku Autoantigen; D007763:Lac Operon / Q000235:genetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D016296:Mutagenesis / Q000235:genetics / Q000528:radiation effects*; D011829:Radiation Dosage; D014781:Viscera / Q000378:metabolism* / Q000528:radiation effects*; D014965:X-Rays
D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen