title: Enhanced mutability at the tk locus in the radiosensitive double-strand break repair mutant xrs5.
abstract: The thymidine kinase locus (tk) has been utilised as the target locus to measure the induced mutation frequency following X-irradiation in the X-ray-sensitive xrs5 mutant and its parent CHO K1 line of Chinese hamster cells. Mutations to tk- cells were measured by plating cells in selective medium containing trifluorothymidine after a post-irradiation expression time of 4 days. Our results show that the mutation frequency was 3-4 times higher in the xrs5 mutant than in the CHO K1 cell line. This enhanced mutation frequency in xrs5 is though to result from the deficiency in DNA double-strand break repair in this cell line which also results in the enhanced cell killing and higher frequencies of chromosomal aberrations in response to X-irradiation. The findings of the present study suggest that DNA double-strand break is a critical lesion leading to mutations in irradiated cells.
authors.affiliation: Department of Biology and Preclinical Medicine, University of St. Andrews, Fife, Great Britain.
authors.forename: T A
authors.initials: TA
authors.lastname: Mussa
authors.forename: B
authors.initials: B
authors.lastname: Singh
authors.forename: P E
authors.initials: PE
authors.lastname: Bryant
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D002875:Chromosomes / Q000528:radiation effects*; D006224:Cricetinae; D004249:DNA Damage; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D009154:Mutation; D013937:Thymidine Kinase / Q000235:genetics*; D014271:Trifluridine
chemical_list: D013937:Thymidine Kinase; D014271:Trifluridine