Potentiation of the mutagenicity and recombinagenicity of bleomycin in yeast by unconventional intercalating agents

Abstract

Interactions between bleomycin (BLM) and conventional or unconventional intercalating agents were analyzed in an assay for mitotic gene conversion at the trp5 locus and reversion of the ilv1-92 allele in Saccharomyces cerevisiae strain D7. BLM is a potent recombinagen and mutagen in the assay. Various chemicals modulate the genetic activity of BLM, producing either antimutagenic effects or enhanced genotoxicity. Effects of cationic amino compounds include enhancement of BLM activity by aminoacridines and protection against BLM by aliphatic amines. The potentiation of BLM is similar to findings in a micronucleus-based BLM amplification assay in Chinese hamster V79 cells. In this study, the amplification of BLM activity was explored in yeast using known intercalators, compounds structurally related to known intercalators, and unconventional intercalators that were identified on the basis of computer modeling or results in the Chinese hamster BLM amplification assay. As shown in previous studies, the classical intercalator 9-aminoacridine (9AA) caused dose-dependent enhancement of BLM activity. Other compounds found to enhance the induction of mitotic recombination and point mutations in strain D7 were chlorpromazine, chloroquine, mefloquine, tamoxifen, diphenhydramine, benzophenone, and 3-hydroxybenzophenone. The increased activity was detectable by cotreatment of yeast with BLM and the modulator compound in growth medium or by separate interaction of the intercalator with DNA followed by BLM treatment of nongrowing cells in buffer. The data support the interpretation drawn from micronucleus assays in mammalian cells that BLM enhancement results from DNA intercalation and may be useful in detecting noncovalent interactions with DNA. Environ.

Adaptive response to hydrogen peroxide in yeast: Induction, time course, and relationship to dose–response models

“…These procedures tend to minimize variation between cultures and between experiments. In all experiments, the spontaneous frequencies of convertants and revertants were consistent with our historical controls and values in published literature [Zimmermann, , ; Hoffmann et al, , ].…”

A source of artifact in the lacZ reversion assay in Escherichia coli

“…mutagenesis or a precursor that may (or may not) be processed into frameshifts. We used compounds whose structures do not suggest intercalation but that are thought to intercalate on the basis of computer modeling [6,7], displacement of ethidium from DNA [8], and interaction with bleomycin in genotoxicity assays in Chinese hamster cells [9] and yeast [10]. We observed strong mutagenicity for reactive acridine derivatives, as expected, and weakly positive responses for the other compounds, some of which had earlier yielded negative results for mutagenicity in our laboratory and elsewhere.…”

“…The significance of differences from the untreated control was determined by ANOVA with a Bonferroni multiple comparisons test ( NS nonsignificant; * P < 0.05; ** P < 0.01; *** P < 0.001; **** P < 0.0001). mutagenicity assays [10,14], also caused a significant increase in revertant frequency (P < 0.001 *** ), albeit at much higher doses. One might conclude on the basis of the significant increases in revertant frequency that DPH is weakly mutagenic in CC109.…”

“…When minimal lactose was supplemented with ␣MG, the concentration of ␣MG was 0.2%. Yeast strain D7 was grown in YEPD rich medium [10]. Gene conversion at the trp5 locus was selected on yeast minimal medium containing adenine and isoleucine (YMAI), and numbers of viable cells were determined on the same medium supplemented with tryptophan (YMAIT) [10].…”

9-AAA inhibits growth and induces apoptosis in human melanoma A375 and rat prostate adenocarcinoma AT-2 and Mat-LyLu cell lines but does not affect the growth and viability of normal fibroblasts

“…This phenomenon may result in varying responses of cells, differing in membrane electric properties. In addition, 9-AAA was reported to affect electric charges on cell surface and ion fluxes across membrane channels (8)(9)(10)(11)(12)(14)(15)(16)(17). This may modify the penetration of 9-AAA into cells or an operation of signaling pathways and interactions among cells.…”