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  • Hyper-resistance  (2)
  • Interstrand cross-links  (2)
  • Oxidative stress  (2)
  • 1
    ISSN: 1432-0983
    Keywords: Platinum compounds ; Yeast ; Repair mutants ; Interstrand cross-links ; DNA degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Four haploid yeast strains differing in proficiency for DNA repair were treated with cis- or transDDP. The wild type was least sensitive while the excision-deficient mutants rad1, rad2 and snm1exhibited higher sensitivities to either platinum compound. In all four strains tested cisDDP showed a two- to five-fold higher cytotoxicity than equimolar concentrations of transDDP. DNA interstrand cross-linking was caused by both agents in all strains. However, transDDP introduced more DNA cross-links at exposure times up to 6 h while cisDDP was the more active cross-linking agent at longer times. There was no clear-cut correlation of the number of DNA interstrand cross-links with survival. Formaldehyde-treated cells showed DNA with lower buoyant density due to proteinase K sensitive DNA-protein cross-linking; this effect was not observed after treatment with either platinum compound. Post-treatment incubation of wild-type cells exposed to cisDDP led to degradation of DNA by single and double-strand breaks, parallel with further increase of DNA interstrand cross-linking. DNA from transDDP-treated cells did not show extensive degradation although interstrand cross-links were lost during liquid holding.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0983
    Keywords: Multi-copy plasmid ; Hyper-resistance ; 4-NQO ; MNNG ; Triaziquone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Screening of a multi-copy vector-based yeast genomic library in haploid cells of wild-type Saccharomyces cerevisiae yielded transformants hyper-resistant to various chemical mutagens. Genetical analysis of the yeast insert DNAs revealed three genes SNG1, SNQ2, and SNQ3 that confer the phenotype hyper-resistance to MNNG, to 4-NQO and triaziquone, and to mutagens 4-NQO, MNNG, and triaziquone, respectively. Integration of the gene disruption-constructs into the haploid yeast genome yielded viable null-mutants with a mutagen-sensitive phenotype. Thus, copy number of these non-essential yeast genes determines the relative resistance to certain chemical mutagens, with zero copies yielding a phenotype of mutagen sensitivity and multiple copies one of mutagen hyper-resistance, respectively.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0983
    Keywords: Key words Glutathione ; Yap1 ; H2O2 ; t-BOOH ; Glucose repression ; Oxidative stress ; Diauxic shift
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Resistance of haploid yeast to hydrogen peroxide and to tert-butylhydroperoxide strongly increases when 4% glucose is replaced by glycerol or ethanol as the carbon source of the complex medium. Using a GSH1-promoter-lacZ-fusion reporter construct we could demonstrate that GSH1 is one of the genes that are up-regulated during the shift from fermentative to oxidative metabolism. A gsh1 mutant did not exhibit respiratory growth resistance to H2O2, whereas it was only slightly impaired in acquiring resistance against t-BOOH in the same experimental conditions. An isogenic Δyap1 mutant, although more sensitive to oxidative stress than the wild-type (WT), could increase resistance to both peroxides by a similar factor as observed for the WT when shifted from 4% glucose to a non-fermentable carbon source. This indicates that in this case induction of resistance to oxidative stress is independent from Yap1 and from the Yap1-mediated stress response via the STRE motif.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 29 (1996), S. 437-440 
    ISSN: 1432-0983
    Keywords: Yeast ; Formaldehyde ; Hyper-resistance ; Alcohol dehydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In an attempt to clone genes involved in resistance to formaldehyde we have screened a genomic library based on the episomal plasmid YEp24 for the ability to increase resistance to formaldehyde in a wild-type strain. In addition toSFA, the gene encoding the formaldehyde dehydrogenase Adh5, an enzyme most potent in formaldehyde de-toxification, we isolated a second plasmid that conferred a less pronounced but significant hyper-resistance to formaldehyde. Its passenger DNA contained the geneADH1, encoding alcohol dehydrogenase 1 (EC 1.1.1.1), which could be shown to be responsible for the observed hyper-resistance phenotype. Construction of anadh1-0 mutant revealed that yeast lacking a functionalADH1 gene is sensitive to formaldehyde. While glutathione is essential for Adh5-mediated formaldehyde de-toxification, Adh1 reduced formaldehyde best in the absence of this thiol compound. Evidence is presented that formaldehyde is a substrate for Adh1 in vivo and in vitro and that its cellular de-toxification employs a reductive step that may yield methanol.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0983
    Keywords: Key words Psoralen sensitivity ; Cytochrome oxidase ; Saccharomyces cerevisiae ; Oxidative stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The yeast gene PSO7 was cloned from a genomic library by complementation of the pso7-1 mutant's sensitivity phenotype to 4-nitroquinoline-1-oxide (4NQO). Sequence analysis revealed that PSO7 is allelic to the 1.1-kb ORF of the yeast gene COX11 which is located on chromosome XVI and encodes a protein of 28-kDa localized in the inner mitochondrial membrane. Allelism of PSO7/COX11 was verified by non-complementation of 4NQO-sensitivity in diploids homo- and hetero-allelic for the pso7-1 and cox11::TRP1 mutant alleles. Sensitivity to 4NQO was the same in exponentially growing cells of the pso7-1 mutant and the cox11::TRP1 disruptant. Allelism of COX11 and PSO7 indicates that the pso7 mutant's sensitivity to photoactivated 3-carbethoxypsoralen and to 4NQO is not caused by defective DNA repair, but rather is due to an altered metabolism of the pro-mutagen 4NQO in the absence of cytochrome oxidase (Cox) in pso7-1/cox11::TRP1 mutants/disruptants. Lack of Cox might also lead to a higher reactivity of the active oxygen species produced by photoactivated 3-carbethoxypsoralen. The metabolic state of the cells is important for their sensitivity phenotype since the largest enhancement of sensitivity to 4NQO between wild-type (WT) and the pso7 mutant occurs in exponentially growing cells, while cells in stationary phase or growing cells in phosphate buffer have the same 4NQO resistance, irrespective of their WT/mutant status. Strains containing the pso7-1 or cox11::TRP1 mutant allele were also sensitive to the oxidative stress-generating agents H2O2 and paraquat. Mutant pso7-1, as well as disruptant cox11::TRP1, harboured mitochondria that in comparison to WT contained less than 5% and no detectable Cox activity, respectively.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 231 (1992), S. 194-200 
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; DNA repair ; Nitrogen mustard ; Interstrand cross-links ; Nucleotide sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A 3.2 kb yeast DNA fragment containing the DNA interstrand cross-link-specific repair gene SNM1 has been sequenced. Two genes were identified. SNM1 has an open reading frame of 1983 by and codes for a 661 amino acid protein. Hydrophobic analysis shows that the protein is most probably not directly membrane bound. The second gene, UGX1, has an open reading frame of 573 by coding for a polypeptide of 191 amino acid residues. The two genes are arranged head to head and share a 192 by divergent promoter region that contains three TATAAA motives, two for the SNM1 and one for the UGX1 locus. Gene UGX1 has no apparent influence on the sensitivity of the cell to cross-linking nitrogen mustard, as its disruption in wild type does not increase sensitivity to nitrogen mustard and the presence of multiple copies of the gene fails to complement the nitrogen mustard sensitivity phenotype of snm1 disruption mutants. Northern analysis revealed that the expression of SNM1 yields an average of 0.3 copies/cell of a 2.4 kb transcript, while expression of UGX1 yields higher levels of a 0.8 kb poly(A)+ RNA.
    Type of Medium: Electronic Resource
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