Repair of I-SceI induced DSB at a specific site of chromosome in human cells: influence of low-dose, low-dose-rate gamma-rays.
We investigated the influence of low-dose, low-dose-rate gamma-ray irradiation on DNA double strand break (DSB) repair in human lymphoblastoid TK6 cells. A single DSB was introduced at intron 4 of the TK+ allele (chromosome 17) by transfection with the I-SceI expression vector pCBASce. We assessed for DSB repair due to non-homologous end-joining (NHEJ) by determining the generation of TK-deficient mutants in the TK6 derivative TSCE5 (TK +/-) carrying an I-SceI recognition site. We similarly estimated DSB repair via homologous recombination (HR) at the same site in the derived compound heterozygote (TK-/-) cell line TSCER2 that carries an additional point mutation in exon 5. The NHEJ repair of DSB was barely influenced by pre-irradiation of the cells with 30 mGy gamma-rays at 1.2 mGy h(-1). DSB repair by HR, in contrast, was enhanced by approximately 50% after pre-irradiation of the cells under these conditions. Furthermore, when I-SceI digestion was followed by irradiation at a dose of 8.5 mGy, delivered at a dose rate of only 0.125 mGy h(-1), HR repair efficiency was enhanced by approximately 80%. This experimental approach can be applied to characterize DSB repair in the low-dose region of ionizing radiation.
Yatagai
Fumio
F
Advanced Development and Support Center, The Institute of Physical and Chemical Research (RIKEN), Saitama 351-0198, Japan. yatagai@postman.riken.go.jp
Suzuki
Masao
M
Ishioka
Noriaki
N
Ohmori
Hitoshi
H
Honma
Masamitsu
M
D002460:Cell Line; D002877:Chromosomes, Human / Q000502:physiology* / Q000528:radiation effects*; D004249:DNA Damage / Q000502:physiology*; D004260:DNA Repair / Q000502:physiology* / Q000528:radiation effects*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics*; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D006801:Humans; D008214:Lymphocytes / Q000502:physiology* / Q000528:radiation effects*; D011829:Radiation Dosage; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*
D029701:Saccharomyces cerevisiae Proteins; C037725:SCEI protein, S cerevisiae; D015252:Deoxyribonucleases, Type II Site-Specific