title: Increased susceptibility to delayed genetic effects of low dose X-irradiation in DNA repair deficient cells.
abstract: OBJECTIVE
  To examine whether the levels of micronuclei induction, as a marker for genomic instability in the progeny of X-irradiated cells, correlates with DNA repair function.
  
  
  METHODS
  Two repair deficient cell lines (X-ray repair cross-complementing 1 [XRCC1] deficient cell line [EM9] and X-ray repair cross complementing 5 [XRCC5; Ku80] deficient X-ray sensitive Chinese hamster ovary [CHO] cell line [xrs5]) were used in addition to wild-type CHO cells. These cells were irradiated with low doses of X-rays (up to 1 Gy). Seven days after irradiation, micronuclei formed in binucleated cells were counted. To assess the contribution of the bystander effect micronuclei induction was measured in progeny of non-irradiated cells co-cultured with cells that had been irradiated with 1Gy.
  
  
  RESULTS
  The delayed induction of micronuclei in 1 Gy-irradiated cells was observed in normal CHO and EM9 but not in xrs5. In the clone analysis, progenies of xrs5 under bystander conditions showed significantly higher levels of micronuclei, while CHO and EM9 did not.
  
  
  CONCLUSIONS
  Genomic instability induced by X-irradiation is associated with DSB (double-strand break) repair, even at low doses. It is also suggested that bystander signals, which lead to genomic instability, may be enhanced when DSB repair is compromised.
authors.affiliation: Advanced Molecular Imaging Center, School of Medicine, Oita University, Yufu city, Oita, Japan. kashino@oita-u.ac.jp
authors.forename: Genro
authors.initials: G
authors.lastname: Kashino
authors.forename: Keiji
authors.initials: K
authors.lastname: Suzuki
authors.forename: Seiji
authors.initials: S
authors.lastname: Kodama
authors.forename: Masami
authors.initials: M
authors.lastname: Watanabe
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Prise
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004260:DNA Repair / Q000235:genetics* / Q000528:radiation effects*; D015162:Micronucleus Tests; D011829:Radiation Dosage; D013997:Time Factors; D014965:X-Rays / Q000009:adverse effects