title: Role of homologous recombination in the alpha-particle-induced bystander effect for sister chromatid exchanges and chromosomal aberrations.
abstract: The bystander effect for sister chromatid exchanges (SCEs) and chromosomal aberrations was examined in hamster cell lines deficient in either DNA-PKcs (V3 cells, deficient in nonhomologous end joining, NHEJ) or RAD51C (irs3 cells, deficient in homologous recombination, HR). Cells synchronized in G0/G1 phase were irradiated with very low fluences of alpha particles such that < 1% of the nuclei were traversed by an alpha particle. Wild-type cells showed a prominent bystander response for SCE induction; an even greater effect was observed in V3 cells. On the other hand, no significant induction of SCE was observed in the irs3 RAD51C-deficient bystander cells irradiated at various stages in the cell cycle. Whereas a marked bystander effect for chromosomal aberrations occurred in V3 cells, the induction of chromosomal aberrations in irs3 bystander cells was minimal and similar to that of wild-type cells. Based on these findings, we hypothesize that HR is essential for the induction of SCE in bystander cells; however, HR is unable to repair the DNA damage induced in NHEJ-deficient bystander cells that leads to either SCE or chromosomal aberrations.
authors.affiliation: Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, Colorado 80523, USA.
authors.forename: H
authors.initials: H
authors.lastname: Nagasawa
authors.forename: Y
authors.initials: Y
authors.lastname: Peng
authors.forename: P F
authors.initials: PF
authors.lastname: Wilson
authors.forename: Y-C
authors.initials: YC
authors.lastname: Lio
authors.forename: D J
authors.initials: DJ
authors.lastname: Chen
authors.forename: J S
authors.initials: JS
authors.lastname: Bedford
authors.forename: J B
authors.initials: JB
authors.lastname: Little
mesh_terms: D000512:Alpha Particles; D000818:Animals; D024201:Bystander Effect; D002869:Chromosome Aberrations; D006224:Cricetinae; D003412:Cricetulus; D004307:Dose-Response Relationship, Radiation; D011995:Recombination, Genetic; D012854:Sister Chromatid Exchange