Requirement of ATM-dependent pathway for the repair of a subset of DNA double strand breaks created by restriction endonucleases.
BACKGROUND
DNA double strand breaks induced by DNA damaging agents, such ionizing radiation, are repaired by multiple DNA repair pathways including non-homologous end-joining (NHEJ) repair and homologous recombination (HR) repair. ATM-dependent DNA damage checkpoint regulates a part of DNA repair pathways, however, the exact role of ATM activity remains to be elucidated. In order to define the molecular structure of DNA double strand breaks requiring ATM activity we examined repair of DNA double strand breaks induced by different restriction endonucleases in normal human diploid cells treated with or without ATM-specific inhibitor.


RESULTS
Synchronized G1 cells were treated with various restriction endonucleases. DNA double strand breaks were detected by the foci of phosphorylated ATM at serine 1981 and 53BP1. DNA damage was detectable 2 hours after the treatment, and the number of foci decreased thereafter. Repair of the 3'-protruding ends created by Pst I and Sph I was efficient irrespective of ATM function, whereas the repair of a part of the blunt ends caused by Pvu II and Rsa I, and 5'-protruding ends created by Eco RI and Bam HI, respectively, were compromised by ATM inhibition.


CONCLUSIONS
Our results indicate that ATM-dependent pathway plays a pivotal role in the repair of a subset of DNA double strand breaks with specific end structures.
Suzuki
Keiji
K
Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
Takahashi
Maiko
M
Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
Oka
Yasuyoshi
Y
Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
Yamauchi
Motohiro
M
Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
Suzuki
Masatoshi
M
Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
Yamashita
Shunichi
S
Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.