Transcriptional Response of Yeast to Aflatoxin B1: Recombinational Repair InvolvingRAD51andRAD1

Keller-Seitz, Monika U.; Certa, Ulrich; Sengstag, Christian; Würgler, Friedrich E.; Sun, Mingzeng; Fasullo, Michael

doi:10.1091/mbc.e04-05-0375

Cited by 40 publications

(49 citation statements)

References 65 publications

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“…3) also suggests that both NER and HRR act on one or more common substrates. These results are consistent with the involvement of Rad1, required in NER (81), in the repair of AFB 1 -induced DNA damage via recombinational repair (48). In the absence of the two repair pathways, these AFB 1 -induced DNA lesions are channeled into a mutagenic repair pathway mediated by REV3.…”

Section: Discussionsupporting

confidence: 86%

“…Both pathways are also involved in the repair of UV damage (8). Our data are also consistent with the loss of AFB 1 -induced recombination in a diploid rad51 mutant transformed with human CYP1A1 (48). It could be that replication forks collapse when encountering AFB 1 -DNA adducts, leaving single strands whose repair is likely to be dependent on Rad51 (19).…”

Section: Discussionsupporting

confidence: 86%

“…Early studies indicated that AFB 1 is strongly recombinogenic but only weakly mutagenic in yeast (87). Our work offers an explanation of these observations, in that wild-type cells readily and faithfully repair AFB 1 -induced damage using homologous recombination and nucleotide excision repair, consistent with the role of recombinational repair in the repair of AFB 1 -induced DNA damage in another study (48). Our data suggest that, in the absence of these pathways, the mutagenesis that ensues is via the error-prone translesion synthesis pathway and requires a functional DNA damage checkpoint.…”

Section: Discussionsupporting

confidence: 83%

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Expression of a Human Cytochrome P450 in Yeast Permits Analysis of Pathways for Response to and Repair of Aflatoxin-Induced DNA Damage

Guo

Breeden

Zarbl

et al. 2005

Molecular and Cellular Biology

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Aflatoxin B 1 (AFB 1 ) is a human hepatotoxin and hepatocarcinogen produced by the mold Aspergillus flavus. In humans, AFB 1 is primarily bioactivated by cytochrome P450 1A2 (CYP1A2) and 3A4 to a genotoxic epoxide that forms N 7 -guanine DNA adducts. A series of yeast haploid mutants defective in DNA repair and cell cycle checkpoints were transformed with human CYP1A2 to investigate how these DNA adducts are repaired. Cell survival and mutagenesis following aflatoxin B 1 treatment was assayed in strains defective in nucleotide excision repair (NER) (rad14), postreplication repair (PRR) (rad6, rad18, mms2, and rad5), homologous recombinational repair (HRR) (rad51 and rad54), base excision repair (BER) (apn1 apn2), nonhomologous end-joining (NHEJ) (yku70), mismatch repair (MMR) (pms1), translesion synthesis (TLS) (rev3), and checkpoints (mec1-1, mec1-1 rad53, rad9, and rad17). Together our data suggest the involvement of homologous recombination and nucleotide excision repair, postreplication repair, and checkpoints in the repair and/or tolerance of AFB 1 -induced DNA damage in the yeast model. Rev3 appears to mediate AFB 1 -induced mutagenesis when error-free pathways are compromised. The results further suggest unique roles for Rad5 and abasic endonuclease-dependent DNA intermediates in regulating AFB 1 -induced mutagenicity.Mutagenic substances, including many environmental contaminants, are structurally diverse and range from simple compounds such as methylating agents to bulky DNA damaging agents (57). Differences in DNA repair capacity may play an important role in determination of individual susceptibility to endogenous and exogenous mutagens (88). DNA repair and mutagenesis have been less well studied for bulky mutagens, partly because the majority of them require efficient bioactivation by biotransformation enzymes that are absent in many in vitro study models (35).A yeast model has been established in this study to delineate the mechanisms involved in the elimination and/or tolerance of DNA damage produced by a bulky mutagen, aflatoxin B 1 (AFB 1 ). A natural toxin produced by the common fungal mold Aspergillus flavus (21), AFB 1 is one of the most potent mutagens ever characterized in eukaryotes (12,31,62). It requires biotransformation by cytochrome P450 (CYP450)-dependent monooxygenases to the reactive, yet highly unstable AFB 1 -8,9-exo-epoxide (AFBO) to become toxic and carcinogenic (21). AFBO can react with the N 7 guanine residue of DNA to form an unstable trans-8,9-dihydro-(N 7 -guanyl)-9-hydroxy-aflatoxin B 1 adduct (AFB 1 -N 7 -Gua) that is thought to either be removed hydrolytically to form an abasic (AP) site or to undergo a hydrolytic reaction that opens the guanine imidazole ring, forming a stable and persistent formamidopyrimidine (AFB 1 -FAPY) derivative (61,93). Studies have shown that human CYP1A2 (hCYP1A2) is the high-affinity CYP450 enzyme active at the low AFB 1 concentrations typically encountered in dietary exposures (26). Consequences of AFB 1 -induced DNA lesions include chromoso...

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Section: Discussionsupporting

confidence: 86%

Section: Discussionsupporting

confidence: 86%

Section: Discussionsupporting

confidence: 83%

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Expression of a Human Cytochrome P450 in Yeast Permits Analysis of Pathways for Response to and Repair of Aflatoxin-Induced DNA Damage

Guo

Breeden

Zarbl

et al. 2005

Molecular and Cellular Biology

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“…The expression of the RAD1 gene, the product of which plays a crucial role in the repair of DNA double-strand breaks by homologous recombination, was shown to be downregulated in response to oxidative stimulus in AMD patients (Strunnikova et al 2005). The coordinated involvement of Rad51 and Rad1 in recombinational repair of DNA damage implicates the potential role of RAD51-dependent DNA repair in circumstances of elevated oxidative reaction species (Keller-Seitz et al 2004).…”

Section: Discussionmentioning

confidence: 98%

In-depth analyses unveil the association and possible functional involvement of novel RAD51B polymorphisms in age-related macular degeneration

Chu

Meyerle

Liang

et al. 2014

AGE

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The contribution of DNA damage to the pathogenesis of age-related macular degeneration (AMD) has been reported. Recently, a genomewide association study detected the association of a single-nucleotide polymorphism (SNP) in RAD51B (rs8017304 A>G) with AMD. RAD51B is involved in recombinational repair of DNA double-strand breaks. We analyzed RAD51B influence on AMD using two cohorts from Caucasian and Han Chinese populations. The Caucasian set replicated the rs8017304 A>G association and revealed two novel AMD-associated SNPs in RAD51B, rs17105278 T>C and rs4902566 C>T. Under the dominant model, these two SNPs exhibit highly significant disease risk. SNP-SNP interaction analysis on rs17105278 T>C and rs4902566 C>T homozygous demonstrated a synergistic effect on AMD risk, reaching an odds ratio multifold higher than wellestablished AMD susceptibility loci in genes such as CFH, HTRA1, and ARMS2. Functional study revealed lower RAD51B mRNA expression in cultured primary human fetal retinal pigment epithelium (hfRPE) carrying rs17105278 T>C variants than in hfRPE carrying rs17105278 wild type. We concluded that the risk of developing AMD exhibits dose dependency as well as an epistatic combined effect in rs17105278 T>C and rs4902566 C>T carriers and that the elevated risk for rs17105278 T>C carriers may be due to decreased transcription of RAD51B. This study further confirms the role of DNA damage/DNA repair in AMD pathogenesis.

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“…Several of these pathways are also involved in tolerance to aflatoxin B 1 in mammalian cells [9]. Additionally, microarray experiments on aflatoxin B 1 treated yeast cells expressing CYP1A2 showed that expression of genes involved in DNA synthesis and repair, cell cycle regulation, or protein degradation and synthesis was significantly altered [25,130].…”

Section: Cytochrome P450-related Toxicity In Yeastmentioning

confidence: 99%

Yeast as a Humanized Model Organism for Biotransformation-Related Toxicity

Leeuwen

Vermeulen

Vos

2012

CDM

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High drug attrition rates due to toxicity, the controversy of experimental animal usage, and the EU REACH regulation demanding toxicity profiles of a high number of chemicals demonstrate the need for new, in vitro toxicity models with high predictivity and throughput. Metabolism by cytochrome P450s (P450s) is one of the main causes of drug toxicity. As some of these enzymes are highly polymorphic leading to large differences is metabolic capacity, isotype-specific test systems are needed. In this review, we will discuss the use of yeast expressing (mammalian) P450s as a powerful, additional model system in drug safety. We will discuss the various cellular model systems for bioactivation-related toxicity and subsequently describe the properties of yeast as a model system, including the endogenous bioactivation enzymes present, the heterologous expression of (mammalian) P450s and the application of yeasts expressing heterologous P450s and/or other biotransformation enzymes in toxicity studies. All major human drug-metabolizing P450s have been successfully expressed in yeast and various mutagenicity tests have been performed with these humanized yeast strains. The few examples of non-mutagenic toxicity studies with these strains and of the combination of P450s with phase II or other human enzymes show the potential of yeast as a model system in metabolism-related toxicity studies. The wide variety of genome-wide screens available in yeast, combined with its well-annotated genome, also facilitate follow-up studies on the genes involved in toxicity. Unless indicated otherwise "yeast" will refer to baker's yeast Saccharomyces cerevisiae.

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Transcriptional Response of Yeast to Aflatoxin B₁: Recombinational Repair InvolvingRAD51andRAD1

Cited by 40 publications

References 65 publications

Expression of a Human Cytochrome P450 in Yeast Permits Analysis of Pathways for Response to and Repair of Aflatoxin-Induced DNA Damage

Expression of a Human Cytochrome P450 in Yeast Permits Analysis of Pathways for Response to and Repair of Aflatoxin-Induced DNA Damage

In-depth analyses unveil the association and possible functional involvement of novel RAD51B polymorphisms in age-related macular degeneration

Yeast as a Humanized Model Organism for Biotransformation-Related Toxicity

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