title: A cell-cycle stage-related chromosomal X-ray hypersensitivity in larval neuroblasts of Drosophila mei-9 and mei-41 mutants suggesting defective DNA double-strand break repair.
abstract: We have examined the chromosomal X-ray hypersensitivity in relation to the cell cycle in larval neuroblasts of the mutagen-sensitive and excision repair-defective mutant mei-9 and of the mutagen-sensitive and post-replication repair-defective mutant mei-41 of Drosophila melanogaster. When compared to wild-type cells, cells bearing the mei-9L1 allele produced unusually high levels in particular of chromatid deletions and to a lesser extent also of isochromatid deletions, but virtually no exchange aberrations. The chromosomal hypersensitivity is apparent at M1 when cells are irradiated in S or G2 but not when irradiated in G1. On the other hand, following irradiation cells bearing the mei-41D5 allele predominantly produce chromosome deletions. Also dicentric and chromatid exchange formation is enhanced with a moderate increase in chromatid deletions. The phases of major sensitivity are the S and G1. Mei-9 and mei-41 mutants have been classified to date as proficient in DNA double-strand break repair. The data presented in this paper revealed an S-independent clastogenic hypersensitivity of mei-9 and mei-41 cells. They are interpreted as indicative evidence for the presence of impaired DNA double-strand break repair. The cell-cycle-related difference in the ratio of chromatid- versus chromosome-type deletions in both mutants suggests repair defects at partially different phases of the cell cycle in mei-9 and mei-41 mutant cells.
authors.affiliation: Strahlenbiologisches Institut, Universität Zürich, Switzerland.
authors.forename: P M
authors.initials: PM
authors.lastname: Schweizer
mesh_terms: D000705:Anaphase / Q000528:radiation effects; D000818:Animals; D002453:Cell Cycle / Q000528:radiation effects*; D002869:Chromosome Aberrations; D004247:DNA / Q000528:radiation effects*; D004260:DNA Repair / Q000528:radiation effects*; D004331:Drosophila melanogaster / Q000235:genetics*; D005404:Fixatives; D007399:Interphase / Q000528:radiation effects; D007814:Larva / Q000528:radiation effects; D008677:Metaphase / Q000528:radiation effects; D009154:Mutation; D009474:Neurons / Q000528:radiation effects; D013692:Telophase / Q000528:radiation effects; D013936:Thymidine
chemical_list: D005404:Fixatives; D004247:DNA; D013936:Thymidine