title: A fourth complementation group among ionizing radiation-sensitive Chinese hamster cell mutants defective in DNA double-strand break repair.
abstract: The XR-V9B mutant of Chinese hamster V79 cells which exhibits hypersensitivity to ionizing radiation was isolated by the replica plating technique. The increased sensitivity of XR-V9B cells to X rays (approximately 4-fold, as judged by the D10) was accompanied by increased sensitivity to other DNA-damaging agents such as bleomycin (approximately 17-fold), VP16 (approximately 6-fold), and adriamycin (approximately 5-fold). Only a slightly increased sensitivity was observed after exposure to UV radiation, MMS, or mitomycin C (1.4-, 1.7-, and 2-fold, respectively). As measured by neutral elution after exposure to X rays, XR-V9B cells showed a defect in the rejoining of double-strand breaks (DSBs); after 4 h of repair more than 50% of DSBs remained in comparison to 5% in wild-type cells. No difference was observed in the kinetics of single-strand break rejoining between XR-V9B and wild-type cells, as measured by alkaline elution. To determine whether XR-V9B represents a new complementation group among ionizing radiation-sensitive Chinese hamster cell mutants defective in DSB repair, XR-V9B cells were fused with XR-V15B, XR-1, and V-3 cells, which have impaired DSB rejoining and belong to three different complementation groups. In all cases, the derived hybrids regained the sensitivity of wild-type cells when exposed to X rays, indicating that the XR-V9B mutant represents a new fourth complementation group among X-ray-sensitive Chinese hamster cell mutants defective in DSB repair.
authors.affiliation: MGC-Department of Radiation Genetics and Chemical Mutagenesis, State University of Leiden, Sylvius Laboratory, The Netherlands.
authors.forename: M Z
authors.initials: MZ
authors.lastname: Zdzienicka
authors.forename: N
authors.initials: N
authors.lastname: van Wessel
authors.forename: G P
authors.initials: GP
authors.lastname: van der Schans
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D006224:Cricetinae; D004260:DNA Repair; D005816:Genetic Complementation Test; D009154:Mutation; D011836:Radiation Tolerance