title: N-Methyl-N-nitrosourea-induced DNA damage detected by the comet assay in Vicia faba nuclei during all interphase stages is not restricted to chromatid aberration hot spots.
abstract: The genotoxic effect of the monofunctional alkylating agent N:-methyl-N:-nitrosourea (MNU) on root-tip nuclei of the field bean, Vicia faba, has been tested by comparative application of three protocols of the comet assay. While the alkaline denaturation/alkaline electrophoresis (A/A) procedure proved to be most sensitive at low doses, the alkaline denaturation/neutral electrophoresis (A/N) procedure yielded an optimal dose-response curve within a wider dose range. With the neutral electrophoresis without alkaline denaturation (N/N) procedure only minimal response was found. MNU-mediated single-strand breaks occurred in nuclei of all interphase stages. Detection of tandemly repeated FOK:I elements on comets by fluorescence in situ hybridization showed an average involvement of these heterochromatin-specific sequences in MNU-mediated single-strand breaks. This, together with previous results, suggests that the pronounced clustering of chromosomal aberrations in heterochromatic regions after treatment with S phase-dependent mutagens is mainly due to an error-prone interference of recombinative repair and replication in damaged basic repeats of large tandem repeat arrays.
authors.affiliation: Institute of Plant Genetics and Crop Plant Research (IPK), D-06466 Gatersleben, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Menke
authors.forename: A
authors.initials: A
authors.lastname: Meister
authors.forename: I
authors.initials: I
authors.lastname: Schubert
mesh_terms: D000477:Alkylating Agents; D002453:Cell Cycle / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D002469:Cell Separation; D002842:Chromatids / Q000235:genetics*; D002869:Chromosome Aberrations; D002875:Chromosomes / Q000187:drug effects; D020552:Comet Assay; D004249:DNA Damage / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004586:Electrophoresis; D005434:Flow Cytometry; D017404:In Situ Hybridization, Fluorescence; D007399:Interphase / Q000187:drug effects*; D008770:Methylnitrosourea; D010944:Plants / Q000187:drug effects
chemical_list: D000477:Alkylating Agents; D008770:Methylnitrosourea