Coexposure to benzo[a]pyrene plus UVA induced DNA double strand breaks: visualization of Ku assembly in the nucleus having DNA lesions.
Benzo[a]pyrene (BaP) is a ubiquitous environmental pollutant with potential carcinogenicity. It has been shown that BaP, upon UVA irradiation, synergistically induced oxidative DNA damage, but other DNA damage was not confirmed. In this study, we examined whether coexposure to BaP plus UVA induces double strand breaks (DSBs) using xrs-5 cells, deficient in the repair of DSBs (Ku80 mutant), and whether Ku translocates involving the formation of DSBs. BaP plus UVA had a significant cytotoxic effect on CHO-K1 cells and an even more drastic effect on Ku80-deficient, xrs-5 cells, suggesting that the DSBs were generated by coexposure to BaP plus UVA. The DSBs were repaired in CHO-K1 cells within 30 min, but not in xrs-5 cells, indicating the involvement of a non-homologous end joining, which needs Ku proteins. Furthermore, we succeeded in visualizing that Ku80 rapidly assembled to the exposed region, in which DSBs might be generated, and clarified that the presence of both Ku70 and Ku80 was important for their accumulation.
Laboratory of Radiation Biology, Graduate School of Nutritional and Environmental Sciences, University of Shizuoka, Shizuoka, Japan.
Tatsushi
T
Toyooka
Yuko
Y
Ibuki
Manabu
M
Koike
Norio
N
Ohashi
Sentaro
S
Takahashi
Rensuke
R
Goto
D000818:Animals; D001564:Benzo(a)pyrene / Q000494:pharmacology*; D016466:CHO Cells; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D006224:Cricetinae; D004247:DNA / Q000187:drug effects* / Q000528:radiation effects*; D004265:DNA Helicases; D004587:Electrophoresis, Agar Gel; D000072200:Ku Autoantigen; D018613:Microscopy, Confocal; D009153:Mutagens / Q000494:pharmacology*; D009154:Mutation; D013997:Time Factors; D014466:Ultraviolet Rays
D002352:Carrier Proteins; D009153:Mutagens; D001564:Benzo(a)pyrene; D004247:DNA; D004265:DNA Helicases; C106893:XRCC5 protein, human; D000072200:Ku Autoantigen