Host: The Japan Radiation Research Society
The bystander effect for chromosomal aberrations and SCEs was examined in Chinese Hamster cell lines deficient in either non-homologous end joining or homologous recombination.
Dose-response curve for induction of chromosomal aberrations was curvilinear for all cell lines, with a great effect occurring at low fluences owing to aberrations arising in bystander cells. These aberrations were predominately of the chromatid type.
We are presently examining the HR repair defective cell lines in different Rad 51 paralogs, as well as a cell line deficient in BRCA-2. The frequencies of SCEs measured in three non-irradiated wild type cell lines were approximately 0.3 SCE per chromosome, whereas only 0.16 SCE per chromosome was observed in two Rad 51C -/- cell lines. SCE frequencies significantly higher than the baseline line level were induced in wild type cells. On the other hand, induction of SCE was minimal or absent after α-particle irradiation in all of the mutant cell lines. These results suggest that Rad 51 paralogs may contribute to DNA damage repair processes involved in the induction of SCEs in bystander cells by very low fluences of α-Particles.
