title: Increased frequency of formation of interphase ring-chromosomes in radiosensitive irs-1 cells exposed to X-rays.
abstract: Induction and rejoining of interphase chromosome breaks were measured, after exposure to X-rays, in plateau-phase Chinese hamster V79 cells and in a radiosensitive mutant cell line derived from them, iris-1, using premature chromosome condensation (PCC). There was no difference in the induction of interphase chromosome breaks per Gy between the radiosensitive mutant cells and wild-type V79 cells despite the large differences in their radiosensitivity; an induction of 2.85 +/- 0.05 breaks/cell/Gy was measured in both cell lines. Also, rejoining of interphase chromosome breaks proceeded in the two cell lines with similar kinetics (t1/2 = 26.2 min). In contrast, ring chromosome formation was higher in irs-1 cells, as compared to wild-type V79 cells (0.78 versus 0.44 after 6 h of repair). These results confirm previous observations suggesting that a general deficiency in the rejoining of DNA dsb is unlikely to be a direct cause of the increased radiosensitivity of irs-1 cells, and are consistent with the hypothesis that the increased radiosensitivity of these cells derives from an increase in the probability of misrepair.
authors.affiliation: Thomas Jefferson University, Department of Radiation Oncology and Nuclear Medicine, Philadelphia, PA 19107.
authors.forename: R
authors.initials: R
authors.lastname: Okayasu
authors.forename: G E
authors.initials: GE
authors.lastname: Pantelias
authors.forename: G
authors.initials: G
authors.lastname: Iliakis
mesh_terms: D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D005821:Genetic Techniques; D007399:Interphase / Q000528:radiation effects*; D007700:Kinetics; D012044:Regression Analysis; D012303:Ring Chromosomes