Spontaneous mutagenesis in haploid and diploid Saccharomyces cerevisiae

Ohnishi, Gaku; Endo, Katsumi; Doi, Akiko; Fujita, Atsushige; Daigaku, Yasukazu; Nunoshiba, Tatsuo; Yamamoto, Kazuo

doi:10.1016/j.bbrc.2004.10.120

Cited by 43 publications

(67 citation statements)

References 25 publications

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Section: Resultsmentioning

confidence: 99%

“…Quantitative assessment of conversion to canavanine resistance assessed the combined effects of loss of the endogenous chromosome V containing the wild-type CAN1 gene, mitotic recombination of the CAN1 locus to can1-100, or point mutation in the CAN1 gene. However, spontaneous point mutations account for only 1-2% of the canavanine-resistant mutants (Ohnishi et al 2004) and thus do not significantly contribute to this assay.Chromosome V instability was measured by fluctuation analysis using a modification of the Lea and Coulson method of the median (see materials and methods) Five independent estimations of chromosome V instability for the rad9D/rad9D and wild-type strains were performed to show reproducibility of the assay with estimated mutation rates of 3.37E-05 and 7.86E-06, respectively (see Figure 2A). To confirm that the mutant strains exhibiting increased CF loss also had increased instability of chromosome V, we performed fluctuation analysis on 40 of the 398 increased CF loss strains and 10 mutagenized strains that did not show sectored colonies.…”

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confidence: 99%

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Heterozygous Screen in Saccharomyces cerevisiae Identifies Dosage-Sensitive Genes That Affect Chromosome Stability

Strome

Kimmel

et al. 2008

Genetics

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Current techniques for identifying mutations that convey a small increased cancer risk or those that modify cancer risk in carriers of highly penetrant mutations are limited by the statistical power of epidemiologic studies, which require screening of large populations and candidate genes. To identify dosage-sensitive genes that mediate genomic stability, we performed a genomewide screen in Saccharomyces cerevisiae for heterozygous mutations that increase chromosome instability in a checkpoint-deficient diploid strain. We used two genome stability assays sensitive enough to detect the impact of heterozygous mutations and identified 172 heterozygous gene disruptions that affected chromosome fragment (CF) loss, 45% of which also conferred modest but statistically significant instability of endogenous chromosomes. Analysis of heterozygous deletion of 65 of these genes demonstrated that the majority increased genomic instability in both checkpoint-deficient and wild-type backgrounds. Strains heterozygous for COMA kinetochore complex genes were particularly unstable. Over 50% of the genes identified in this screen have putative human homologs, including CHEK2, ERCC4, and TOPBP1, which are already associated with inherited cancer susceptibility. These findings encourage the incorporation of this orthologous gene list into cancer epidemiology studies and suggest further analysis of heterozygous phenotypes in yeast as models of human disease resulting from haplo-insufficiency. C ANCERS are commonly characterized as having an abnormal number of chromosomes, termed aneuploidy, which arises due to genomic instability. Aneuploidy has been proposed as a mutagenic mechanism and a driving force of tumor progression and not just a phenotype of the disease (Weaver and Cleveland 2006). Many of the genes whose disruption results in aneuploidy were first identified in budding yeast on the basis of analysis of haploid strains containing null mutations. Aneuploidy can be caused by inherited or somatic mutations in genes that function in the maintenance of genomic stability, such as those involved in centrosome formation,chromosomemetabolism,andcellcyclecheckpoints. Among these, cell cycle checkpoint pathways play an especially important role in maintaining genomic integrity when cells are challenged with genotoxic agents or other stressors (Zhou and Elledge 2000).Mutations in checkpoint genes including, BRCA1, PTEN, ATM, and CHEK2, lead to increases in breast cancer susceptibility (Li et al. 1997;Nathanson and Weber 2001;Meijers-Heijboer et al. 2002;King et al. 2003). Women who inherit BRCA1 mutations have an increased lifetime breast cancer risk of 50-80% (12% risk in the general population) and an ovarian cancer risk of 15-65% (1.5% risk in the general population). However, the age of cancer onset and type and number of cancers can vary, even among women carrying the same mutation. One mechanism for this variation is the presence of unlinked genetic loci, which modify this risk (Rebbeck 2002). For instance, ovarian cancer ...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Heterozygous Screen in Saccharomyces cerevisiae Identifies Dosage-Sensitive Genes That Affect Chromosome Stability

Strome

Kimmel

et al. 2008

Genetics

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“…In an eŠort to understand the two-step process of diploid phenotype change, we constructed S. cerevisiae cells carrying a can1 -/CAN1 ＋ heterozygous allele and examined the mutational changes that occurred. The mutation frequency of the can1 -/CAN1 ＋ (Can S ) heterozygote to can1 -/can1 -(Can R ) was 1.03×10 -4 per cell per generation (16), which is about 100-fold higher than that in the haploid allele. The diŠerence might re‰ect diŠerences in the mechanism of Can R formation; in haploid cells, point mutations such as base substitutions and frameshifts predominate, whereas in the diploid heterozygous state, any genetic alteration that functionally inactivates the wild-type allele, such as gene conversion, allelic crossover, gross rearrangement of a chromosome or chromosome loss, can lead to Can R .…”

Section: Dna Sequence Alteration In E Coli Mutator Strainsmentioning

confidence: 88%

“…LOH is the most commonly reported event linked with diseases including cancer (15). Ohnishi et al (16) argued that gene conversion, allelic crossover and chromosome loss, but …”

Section: Introductionmentioning

confidence: 99%

Spontaneous Mutagenesis in Escherichia coli and Saccharomyces cerevisiae

Imai

Tago

Endo

et al. 2006

Genes and Environment

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In this article, we described the spontaneously occurring mutation speciˆcities of defects that are involved in translesion polymerase, mutS mismatch correction and polA mismatch correction in Escherichia coli. We argue that 1) there is no contribution of translesion polymerase to E. coli chromosomal mutation, 2) mutS system recognizes and corrects transition and frameshift mismatches and 3) polA system recognizes and corrects deletion, frameshift and transition mismatches. We also characterized the genetic alterations that inactivate either the CAN1 gene of Saccharomyces cerevisiae haploid cells or heterozygously situated in diploid cells. The characteristics of mutation in haploid yeast are essentially consistent with those in E. coli, suggesting that similar mechanisms are operating to form spontaneous mutation. CAN1 ＋ /can1 -(Can S ) to can1 -/can1 -(Can R ) mutations in diploid cells could occur through recombination, mainly allelic crossover and gene conversion.

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“…X-rays (and MMS is also assumed to) induce DSBs; on the other hand, UV induces mainly pyrimidine dimers and 6-4 photoproducts but not DSBs (Kupiec, 2000). Thus, with regard to the DNA (Ohnishi et al, 2004;Daigaku et al, 2004Daigaku et al, , 2006. The diploid cells are heterozygous for the mutagenic target CAN1.…”

Section: Introductionmentioning

confidence: 99%

Effects of Saccharomyces cerevisiae mec1, tel1, and mre11 mutations on spontaneous and methylmethane sulfonate-induced genome instability

et al. 2010

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In eukaryotes, together with the Mre11/Rad50/Xrs2 (or Nbs1) complex, a family of related protein kinases (the ATM family) is involved in checkpoint activation in response to DNA double-strand breaks. In Saccharomyces cerevisiae, two members of this family, MEC1 and TEL1, have functionally redundant roles in DNA damage repair. Strains with mutations in their mec1 as well as mre11 genes are very sensitive to DNA damaging agents, show defective induction of damageinduced cell-cycle checkpoints, and defective damage-induced homologous recombination. However, the fact that both the mec1Δ and mre11Δ strains exhibit the spontaneous hyper-recombination phenotype is paradoxical in light of the homologous recombination defects in these strains. In this study, we constructed yeast mec1, tel1, and mre11 null mutations and characterized their genome stability properties. Spontaneous and methylmethane sulfonate (MMS)-induced point mutations, base-substitutions, and frameshifts occurred to an almost equal extent in the wild-type, mec1Δ, tel1Δ, and mre11Δ strains. Thus, Mec1, Tel1, and Mre11 do not play roles in the point mutation response. We then found that the mec1Δ, mre11Δ, and mec1Δ tel1Δ strains demonstrated increased rates of spontaneous loss of heterozygosity (LOH), which includes crossover, gene conversion, and chromosome loss, compared with the wild-type strain. In the tel1Δ strain, the rate of spontaneous LOH was as low as that in the wild-type strain. Finally, no induction of LOH by MMS was observed in the mec1Δ, mre11Δ, or mec1Δ tel1Δ strain; however, it was detected in the wild-type and tel1Δ strains upon exposure to MMS. The elevated level of spontaneous LOH but not MMS-induced LOH in the mec1Δ, mre11Δ, and mec1Δ tel1Δ strains suggests the presence of high levels of spontaneous recombinogenic DNA damage, which differs from the damage induced by MMS treatment, in these strains.

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Spontaneous mutagenesis in haploid and diploid Saccharomyces cerevisiae

Cited by 43 publications

References 25 publications

Heterozygous Screen in Saccharomyces cerevisiae Identifies Dosage-Sensitive Genes That Affect Chromosome Stability

Heterozygous Screen in Saccharomyces cerevisiae Identifies Dosage-Sensitive Genes That Affect Chromosome Stability

Spontaneous Mutagenesis in Escherichia coli and Saccharomyces cerevisiae

Effects of Saccharomyces cerevisiae mec1, tel1, and mre11 mutations on spontaneous and methylmethane sulfonate-induced genome instability

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