title: A comparison of the roles of p53 mutation and AraC inhibition in the enhancement of bleomycin-induced chromatid aberrations in mouse and human cells.
abstract: Previous studies have shown that p53 is involved in the repair of bleomycin-induced DNA damage, and that the frequency of bleomycin-induced chromatid aberrations is elevated in G(2)-treated p53 null transgenic mouse embryo fibroblasts (MEF) as compared to isogenic controls. To further characterize p53-mediated DNA repair, we studied the effect of p53 status on the ability of the DNA repair inhibitor 1-ss-D-arabinofuranosylcytosine (AraC) to sensitize MEF to bleomycin-induced chromatid aberrations. Both p53+/+ and p53-/- MEF were treated in G(2) with 0 to 7.5 microg/ml bleomycin in the presence or absence of AraC (5x10(-5) M). The frequency of bleomycin-induced chromatid aberrations was significantly higher in p53-/- cells than wild-type cells in the absence of AraC. AraC treatment significantly increased the frequency of bleomycin-induced chromatid aberrations in p53+/+ MEF to the levels in p53-/- (no AraC) but had no effect in p53-/- MEF. These results suggest that an AraC-sensitive DNA repair component is altered or absent in p53-/- cells. Similar results were observed in p53-mutant WTK1 and wild-type TK6 human lymphoblast cells exposed to 0 to 3 microg/ml bleomycin in G(2). However, AraC did cause a small increase in bleomycin sensitivity in WTK1 cells. This difference from the p53-/- MEF response may be due to differences in p53-mutant phenotype. To determine whether mutation of p53 alters DNA replication fidelity, p53+/+ and p53-/- MEF were exposed to 0 to 1 microg/ml mitomycin C (MMC). MMC did not induce chromosome aberrations in either cell line treated in G(2) but did with the same effectiveness in both cell lines treated in S-phase. Thus, p53 deficiency does not affect DNA replication fidelity or the repair of MMC-induced DNA damage.
authors.affiliation: Chemical Industry Institute of Toxicology, Research Triangle Park, NC 27709, USA.
authors.forename: T
authors.initials: T
authors.lastname: Allio
authors.forename: E M
authors.initials: EM
authors.lastname: Donner
authors.forename: R J
authors.initials: RJ
authors.lastname: Preston
mesh_terms: D000818:Animals; D001761:Bleomycin / Q000494:pharmacology*; D002460:Cell Line; D002478:Cells, Cultured; D002869:Chromosome Aberrations / Q000235:genetics*; D003561:Cytarabine / Q000494:pharmacology*; D004260:DNA Repair / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D016195:G2 Phase; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D016685:Mitomycin / Q000494:pharmacology; D008940:Mitotic Index / Q000187:drug effects; D009154:Mutation; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D016196:S Phase; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
chemical_list: D019384:Nucleic Acid Synthesis Inhibitors; D016159:Tumor Suppressor Protein p53; D003561:Cytarabine; D001761:Bleomycin; D016685:Mitomycin