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.
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.
Menke
M
M
Institute of Plant Genetics and Crop Plant Research (IPK), D-06466 Gatersleben, Germany.
Meister
A
A
Schubert
I
I
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
D000477:Alkylating Agents; D008770:Methylnitrosourea