1 School of Biology, Institute of Genetics, University of Nottingham, University Park, Nottingham NG7 2RD, UK
2 Department of Biology, Georgia State University, University Plaza, Atlanta, GA 30303, USA
Correspondence
Simon V. Avery
Simon.Avery{at}nottingham.ac.uk
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ABSTRACT |
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INTRODUCTION |
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Cr is a highly toxic non-essential metal which is used in the production of steel and other alloys, in metal finishes and leather tanning. Waste from such processes (in addition to the high natural abundance of Cr) has made Cr a serious environmental pollutant. It is widely hypothesized that toxicity due to Cr (as well as many other metals) may arise due to enhanced generation of reactive oxygen species (ROS) and oxidative damage in Cr-exposed organisms. Cr, like other redox-active metals, may catalyse Fenton-type reactions to promote free radical formation (Halliwell & Gutteridge, 1999). However, most of the existing evidence that links oxidative processes to Cr toxicity is correlation-based, typified by enhanced oxidation in Cr-exposed organisms. While valuable, such evidence has not helped to resolve whether such oxidation effects are actually important for Cr toxicity. One reason for the absence of more robust evidence is the experimental limitations imposed on studies of this nature by animal models. The budding yeast Saccharomyces cerevisiae provides an attractive alternative system for elucidating the mechanism(s) of metal toxicity (Avery, 2001
). Moreover, Cr toxicity towards yeasts and other micro-organisms is of interest in its own right, from both environmental and biotechnological perspectives (White et al., 1998
; Cervantes et al., 2001
).
Cr exists primarily in the Cr(III) and Cr(VI) oxidation states, the latter, hexavalent species being considered the more toxic in the environment due to its higher solubility and mobility. Cr(VI) accumulated by organisms is reduced to Cr(III) with the concomitant production of intermediate Cr(V) and Cr(IV) products and oxygen- and carbon-based radicals (Cervantes et al., 2001; O'Brien et al., 2001
; Ackerley et al., 2004
). These species are known to be associated with a spectrum of DNA lesions occurring during Cr(VI) exposure (Aiyar et al., 1991
; Luo et al., 1996
; O'Brien et al., 2002
; Reynolds et al., 2004
), many of which are oxidative in nature. However, a quadruple apn1/rad1/ntg1/ntg2 mutant of S. cerevisiae, which is impaired in the repair of abasic sites in DNA and is hypersensitive to oxidizing agents such as menadione and hydrogen peroxide (Swanson et al., 1999
), did not display hypersensitivity to Cr(VI) (O'Brien et al., 2002
). Protection against Cr by ROS-scavenging molecules and other antioxidants has been reported in several organisms (Pourahmad & O'Brien, 2001
; Pesti et al., 2002
). In S. cerevisiae, Cr has been shown to affect mitochondrial function (Henderson, 1989
; Fernandes et al., 2002
), and the antioxidant protein alkyl hydroperoxide reductase (Ahp1p) protects against Cr toxicity (Nguyen-Nhu & Knoops, 2002
). However, while generally this type of evidence is consistent with a role for ROS in Cr toxicity, it is not necessarily demonstrative. For example, many antioxidant molecules or proteins have non-specific activities (e.g. metal-binding as well as ROS-scavenging functions), making it difficult to assign associated phenotypes with antioxidant properties specifically (Avery, 2001
).
In this paper we use the power of yeast genetics to test whether oxidative mechanisms are a cause of Cr toxicity in S. cerevisiae. In particular, we exploit the specificity of engineered Cu,Zn-superoxide dismutase (Sod1) variant proteins and of cellular oxidative damage-repair systems to show that Cr toxicity is oxidative in nature, with cellular proteins being primary targets.
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METHODS |
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Culture conditions and assessment of Cr toxicity.
Yeast strains were routinely maintained on YEPD agar or, for plasmid maintenance, on YNB agar supplemented with the appropriate amino acids or nucleic acid bases (Ausubel et al., 2004). For experiments, organisms were cultured at 30 °C, 120 r.p.m., to mid-/late-exponential phase (OD600
2·0) either in liquid YEPD or in YNB medium for experiments involving plasmid-bearing strains. For enumeration of viable cells on CrO3-supplemented agar, the experimental cultures were adjusted to an OD600 of
0·0004 in sterile YEPD broth and 200 µl aliquots were plated onto YEPD agar supplemented with CrO3 at the desired concentration. Colony-forming ability was determined after 8 d at 30 °C.
For spotting experiments, experimental cultures were each adjusted to an OD600 of 2·5, 0·25, 0·025, 0·0025 and 0·00025. Samples (4 µl) from each dilution were spotted onto YEPD agar, supplemented with CrO3 as specified. Growth was examined after incubation for 4 d at 30 °C. Where specified, plates were incubated anaerobically in an N2 atmosphere. For experiments involving linolenic acid (18 : 3), media were prepared with tergitol (Nonidet P-4-; Sigma) to solubilize the fatty acid and 1 µl aliquots were spotted from dilution series starting at an OD600 of
5·0. The final tergitol concentration was 1 % (w/v); tergitol has no adverse effect on yeast growth (Howlett & Avery, 1997
).
Analysis of protein oxidation.
At intervals during exposure to 0·5 mM CrO3 in liquid medium, cell samples were harvested by centrifugation and flash-frozen. Protein extracts were prepared from the cells as outlined previously (Shanmuganathan et al., 2004). The methods for 2D protein separation and Western blotting were exactly as described by Shanmuganathan et al. (2004)
. Briefly, proteins were loaded onto immobilized pH gradient strips [pH 310; Amersham Pharmacia (or pH 4·55·5 for identification of heat-shock proteins)] and, after isoelectric focusing, protein carbonyls were derivatized with 2,4-dinitrophenylhydrazine (DNPH). After 2D separation and electroblotting, the derivatized proteins were probed with rabbit anti-DNP as primary antibody (Molecular Probes Inc.; 1 : 16 000 dilution) and peroxidase-linked goat anti-rabbit IgG as secondary antibody (Sigma; 1 : 16 000 dilution). Carbonylated proteins were immunodetected with a chemiluminescent peroxidase substrate, West femtoM (Pierce), using a Fuji LAS3000 Image Analyser with pre-cooled camera. Quantification of carbonylated protein and normalization against protein abundance and protein loading were as described previously (Shanmuganathan et al., 2004
).
For preliminary identification of proteins after 2D resolution, images from SYPROruby (Molecular Probes)-stained gels were compared to the 2D yeast proteome databases www.ibgc.u-bordeaux2.fr/YPM and www.expasy.org/images/swiss-2dpage/publi/yeast-high.gif. The identities of specified proteins within the protein arrays were subsequently confirmed by MALDI-MS (Voyager DE Pro; Applied Biosystems) as described previously (Shanmuganathan et al., 2004).
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RESULTS |
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The 8-oxoG DNA glycosylase Ogg1p specifically repairs oxidative DNA damage, 8-oxoG being a critical mutagenic lesion (Kasprzak, 2002). Here, wild-type and ogg1
cells were compared for Cr sensitivity, but no difference was apparent (data not shown). We obtained the same result also with an ogg1
/rad30
double mutant, which is susceptible to a synergistic increase in oxidative DNA lesions (Haracska et al., 2000
) and in pro-oxidant sensitivity (Willetts, 2004
) versus the ogg1
and rad30
single mutants. The results indicated that DNA oxidation arising during Cr exposure is unlikely to be a primary cause of Cr toxicity in yeast (see also Discussion).
To determine whether protein oxidation was involved in the mechanism of Cr toxicity, cells defective for the peptide methionine sulfoxide reductases MsrA and MsrB were tested. These MSR enzymes have complementary activities, reducing different stereoisomers of oxidized methionine (Met) residues in proteins (methionine-S-sulfoxide and methionine-R-sulfoxide, respectively) (Kryukov et al., 2002). MSRs provide the only characterized protein oxidation repair activity of cells. Single msra
and msrb
mutant strains exhibited marked sensitivity to Cr compared to wild-type cells, and this phenotype was accentuated in a double msra
/msrb
mutant (Fig. 3a, b
). Thus, the colony-forming ability of msra
/msrb
cells was diminished by approximately three orders of magnitude at 0·8 mM CrO3, a concentration at which colony formation by wild-type cells was barely affected (Fig. 3b
). To determine whether the MSRs may be broadly required for metal resistance in yeast, the growth of msra
/msrb
single and double mutants was also tested in the presence of Cu(NO3)2 (1016 mM) and Cd(NO3)2 (50200 µM), but these strains were no more sensitive to Cu or Cd than the wild-type (data not shown).
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Cr exposure causes protein oxidation, targeting glycolytic enzymes and heat-shock proteins
If, as the above results showed, protein oxidation is important for Cr toxicity, then this should be reflected also by increased levels of protein oxidation during Cr exposure. Protein oxidation during Cr exposure has not been examined previously to our knowledge, so protein oxidation was monitored here before and during incubation of cells in the presence of CrO3, by immunodetection of protein carbonyls (Cabiscol et al., 2000; Costa et al., 2002
; Shanmuganathan et al., 2004
). The assay of protein carbonyl content is particularly useful since this modification reports relatively accurately on the fraction of oxidatively damaged protein with impaired function in total protein samples (Requena et al., 2001
). Note that oxidized Met does not contribute to the protein carbonyl signal, so determination of protein carbonyls provided independent corroboration of protein oxidation (cf. data in Fig. 3
). A non-lethal concentration of 0·5 mM CrO3 was selected for these experiments, so that protein extracts were representative of all the Cr-treated cells in cultures (a higher dose may give rise to membrane permeabilization and protein leakage from some cells but not others, yielding non-representative protein extracts). Cr caused rapid, but transient oxidation of total-soluble proteins (Fig. 4a
; proteins with pI in the range of 310 were examined). Increased protein carbonyl levels were evident within 5 min of Cr exposure. Most Cr-dependent protein oxidation occurred between 15 and 30 min, after which time total carbonyl levels were approximately 20-fold higher than those of control cells that were not exposed to Cr. There was a subsequent decline in the level of protein carbonylation, but this index of protein oxidation was still approximately 10-fold higher after 60 min than that of cells before Cr exposure. There were no significant changes in total-protein oxidation in parallel, untreated control flasks (not shown).
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DISCUSSION |
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Cell-cycle- and age-dependent fluctuations in Sod1p have been found to drive variation in the Cu resistances of individual cells of S. cerevisiae (Sumner et al., 2003). Here, the similar gradients (albeit non-superimposed) of Cr dose-response curves for wild-type and sod1
cells (Fig. 1
) together with a relatively weak cell cycle dependency of Cr resistance (data not shown) indicated that, while Sod1p is critical for culture-averaged Cr resistance, it does not appear to drive cell-to-cell heterogeneity in Cr resistance. This different effect to that seen with Cu, combined with the fact that Cu-binding by Sod1p confers Cu resistance (Culotta et al., 1995
) whereas the enzyme's superoxide dismutase activity gives Cr resistance (this study), is consistent with these differing functions of Sod1p being subject to distinct regulatory controls.
Phospholipid hydroperoxide glutathione peroxidases (PHGPxs) are capable of reducing phospholipid hydroperoxides in biological membranes and so they repair oxidative damage, specifically, to membrane lipids. In yeast cells, expression of the PHGPx-like enzymes Gpx13 confers resistance to agents which have a lipid peroxidation-dependent mode of action (Avery & Avery, 2001; Avery et al., 2004
). This was exploited here to show that Cr toxicity towards S. cerevisiae does not require lipid peroxidation. This outcome was different to that obtained recently with another metal, Cd (Avery et al., 2004
). In that study, Cd resistance in S. cerevisiae was shown to depend specifically on the phospholipid hydroperoxidase activity of Gpx3p, dissected away from other Gpx3p-dependent activities such as transduction of redox-stress signals (Delaunay et al., 2002
). Evidently, none of the Gpx3p-dependent activities (including phospholipid hydroperoxidase activity) is important for Cr resistance. Consistent with this, enrichment of S. cerevisiae with an oxidation-sensitive polyunsaturated fatty acid did not sensitize the cells to Cr, unlike the outcome found previously for Cu and Cd (Avery et al., 1996
; Howlett & Avery, 1997
). In addition, the adverse effects of Cr on yeast mitochondrial function were found elsewhere to occur in the apparent absence of lipid peroxidation (Fernandes et al., 2002
).
Results obtained with cells defective for Ogg1p, a protein important for repairing oxidative DNA specifically, in conjunction with other evidence (O'Brien et al., 2002; see below), indicated that DNA oxidation is not a primary cause of Cr toxicity. Oxidation of guanine residues is a major form of DNA damage arising from metal-induced oxidative stress (Kasprzak, 2002
). Other forms of DNA damage are known to arise during cellular exposure to elevated Cr(VI) concentrations [e.g. CrDNA interstrand cross-links (O'Brien et al., 2002
; Reynolds et al., 2004
)], and it cannot be ruled out that selective formation of oxidative DNA lesions other than 8-oxoG could contribute to Cr toxicity. However, Cr treatment does enhance 8-oxoG formation, possibly as a result of diminished Ogg1p activity (Hodges & Chipman, 2002
), but just not at a level that causes Cr toxicity according to our results. Similarly, although Cr(VI) causes alternative oxidative lesions to DNA that are repairable by Apn1p in S. cerevisiae (Cheng et al., 1998
), even in a quadruple apn1/rad1/ntg1/ntg2 mutant, such lesions were not sufficient to elicit a Cr(VI) hypersensitivity phenotype (O'Brien et al., 2002
).
With regard to the above conclusions, it is acknowledged that there are overlaps in the induction pathways and activities of certain antioxidant proteins and such proteins may compensate functionally for each other. However, such overlaps are not maintained across the full spectrum of antioxidant gene functions (Jamieson, 1998) and the differential effects reported here underscore this point: the specificities of the Gpx, Ogg1 and Msr proteins for repair of oxidative damage to distinct macromolecular groups borne out by previous studies of differential activities and phenotypes associated with the corresponding deletion strains (Haracska et al., 2000
; Kryukov et al., 2002
; Avery et al., 2004
; Willetts, 2004
) enabled us to discriminate between these groups as the candidate toxicity targets of Cr. It is emphasized that the present data refer to functions that protect against the continuous presence of Cr, a situation that may be more likely to be experienced naturally, rather than recovery after a brief Cr stress.
Methionine sulfoxide reductase activity, the only protein oxidation repair activity known in biology, proved to be critical for Cr resistance. This result was particularly compelling since overexpression of the MSR-encoding yeast genes raised the lower threshold of Cr tolerance. In contrast to gene overexpression, gene deletion can alter (lower) the threshold of cellular metal resistance by sensitizing a new target to the metal, i.e. a primary target different to that in wild-type cells. Overexpression should be effective in altering (raising) the lower resistance threshold only with a gene product that helps to protect the normal target(s) of toxicity, or that is the target itself (Avery et al., 2004).
The observation that manipulation of both yeast MSR-encoding genes gave a stronger phenotype than either gene alone was consistent with certain MSR-dependent phenotypes reported in other studies (Kryukov et al., 2002; Koc et al., 2004
). While MSR enzymes have narrow specificity (for oxidized Met), Met residues are especially susceptible to metal-catalysed oxidation in proteins (Kim et al., 2001
). This, together with the potentially critical role of Met residues for function of individual proteins, and the protection of other residues that is considered to result from oxidation of surface exposed Met (Levine et al., 2000
), would explain why MSR expression has the marked impact on Cr resistance evident here. Note that protein oxidation was of course not restricted to Met residues, as demonstrated by the increased protein carbonyl levels observed during Cr exposure; carbonyl groups do not result from Met oxidation, but are the main oxidation products of other oxidation-susceptible residues such as Arg, Lys and Pro.
It is known that Cr can bind to proteins and may be associated with enhanced protein degradation (Shrivastava & Nair, 2000, 2004
; Feng et al., 2003
). However, CrDNA interactions are also widely reported. Thus, it is emphasized that the current data do not necessarily mean that proteins are more strongly targeted than lipids or DNA by ROS formed during Cr exposure. Rather, our data show that the damage caused by ROS to proteins has greater consequences for whole-cell inhibition than effects on the other macromolecules. That protein oxidation is particularly important for Cr toxicity was also consistent with the fact that Cr exposure gave an approximate 20-fold increase in total carbonyl levels, whereas Cu maximally gives only an
8-fold increase (Shanmuganathan et al., 2004
), with the metals supplied at just sublethal concentrations in both cases. Moreover, MSR activity was found not to affect Cu (or Cd) resistance in the present study. Furthermore, Cu-induced protein oxidation returned to basal levels within 60 min, whereas protein carbonyl levels were still elevated 10-fold after the same period of Cr treatment. The decline in total carbonyl levels between 30 and 60 min exposure to Cr likely reflects selective degradation of oxidatively damaged proteins (Grune et al., 1997
).
Whereas the total carbonylation induced by Cr was relatively high, Cr targeted a similar range of yeast proteins to Cu (Shanmuganathan et al., 2004) and other pro-oxidants (Cabiscol et al., 2000
; Costa et al., 2002
). Enzymes involved in glycolysis or in the fermentation of pyruvate, as well as heat-shock proteins, were particularly susceptible to oxidative modification. These results are consistent with the hypothesis that the glycolytic pathway may become inactivated during (Cr-induced) oxidative stress, so promoting the production of glucose equivalents within the pentose phosphate pathway (Ravichandran et al., 1994
; Costa et al., 2002
; Shenton & Grant, 2003
). Such rerouting of the metabolic flux is considered to serve as a rapid adaptive response to oxidative stress, since it may provide additional reducing power in the form of NADPH2 necessary for the function of certain antioxidant enzymes (Godon et al., 1998
; Cabiscol et al., 2000
). Furthermore, rerouting may alleviate glucose repression of antioxidant gene transcription (Moradas-Ferreira et al., 1996
).
As in studies with other oxidants, detection of the complete spectrum of yeast proteins that are oxidatively targeted by Cr is limited here by the sensitivity of the 2D carbonyl assay. Nevertheless, the similar pattern of carbonylated proteins to that seen with H2O2 further supports an oxidative mode of Cr toxicity. Despite the similar subsets of proteins targeted, individual proteins exhibited differing relative susceptibilities specifically to Cr- or Cu-mediated oxidation. The proteins examined (Fig. 5) were all primarily cytosolic, suggesting that differential targeting by Cr and Cu is unlikely to be a result of differing protein or metal localization. Rather, the proteins may have differing binding affinities for Cr and Cu. Moreover, alongside higher induction of protein oxidation by Cr versus Cu (see above), these results suggested that the differing contribution of protein oxidation to the toxicities of Cr and Cu could also be explained by some selective targeting of the oxidative protein damage that is associated with each metal. Since this study uniquely establishes protein (methionine) oxidation as a primary cause of Cr toxicity, the 2D analyses presented also suggest some preliminary candidates albeit ones for which Met oxidation specifically has not been measured for future efforts to identify the specific protein target(s) of cellular Cr toxicity.
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ACKNOWLEDGEMENTS |
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REFERENCES |
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---|
Aiyar, J., Berkovits, H. J., Floyd, R. A. & Wetterhahn, K. E. (1991). Reaction of chromium(VI) with glutathione or with hydrogen peroxide: identification of reactive intermediates and their role in chromium(VI)-induced DNA damage. Environ Health Perspect 92, 5362.[Medline]
Ausubel, F., Brent, R., Kingston, R. E., Moore, D. D., Seidman, J. G., Smith, J. A. & Struhl, K. (2004). Current Protocols in Molecular Biology. New York: Wiley.
Avery, A. M. & Avery, S. V. (2001). Saccharomyces cerevisiae expresses three phospholipid hydroperoxide glutathione peroxidases. J Biol Chem 276, 3373033735.
Avery, A. M., Willetts, S. A. & Avery, S. V. (2004). Genetic dissection of the phospholipid hydroperoxidase activity of yeast Gpx3 reveals its functional importance. J Biol Chem 279, 4665246658.
Avery, S. V. (2001). Metal toxicity in yeasts and the role of oxidative stress. Adv Appl Microbiol 49, 111142.[Medline]
Avery, S. V., Howlett, N. G. & Radice, S. (1996). Copper toxicity towards Saccharomyces cerevisiae: dependence on plasma-membrane fatty acid composition. Appl Environ Microbiol 62, 39603966.[Abstract]
Cabiscol, E., Piulats, E., Echave, P., Herrero, E. & Ros, J. (2000). Oxidative stress promotes specific protein damage in Saccharomyces cerevisiae. J Biol Chem 275, 2739327398.
Cervantes, C., Campos-Garcia, J., Devars, S., Gutierrez-Corona, F., Loza-Tavera, H., Torres-Guzman, J. C. & Moreno-Sanchez, R. (2001). Interactions of chromium with microorganisms and plants. FEMS Microbiol Rev 25, 335347.[CrossRef][Medline]
Cheng, L., Liu, S. J. & Dixon, K. (1998). Analysis of repair and mutagenesis of chromium-induced DNA damage in yeast, mammalian cells, and transgenic yeast. Environ Health Perspect Suppl 4 106, 10271032.
Ciriolo, M. R., Civitareale, P., Carri, M. T., Demartino, A., Galiazzo, F. & Rotilio, G. (1994). Purification and characterization of Ag,Zn-superoxide dismutase from Saccharomyces cerevisiae exposed to silver. J Biol Chem 269, 2578325787.
Costa, W. M. V., Amorim, M. A., Quintanilha, A. & Moradas-Ferreira, P. (2002). Hydrogen peroxide-induced carbonylation of key metabolic enzymes in Saccharomyces cerevisiae: the involvement of the oxidative stress response regulators Yap1 and Skn7. Free Rad Biol Med 33, 15071515.[CrossRef][Medline]
Culotta, V. C., Joh, H. D., Lin, S. J., Slekar, K. H. & Strain, J. (1995). A physiological role for Saccharomyces cerevisiae copper/zinc superoxide dismutase in copper buffering. J Biol Chem 270, 2999129997.
Dayan, A. D. & Paine, A. J. (2001). Mechanisms of chromium toxicity, carcinogenicity and allergenicity: review of the literature from 1985 to 2000. Human Exp Toxicol 20, 439451.[CrossRef][Medline]
Delaunay, A., Pflieger, D., Barrault, M. B., Vinh, J. & Toledano, M. B. (2002). A thiol peroxidase is an H2O2 receptor and redox-transducer in gene activation. Cell 111, 471481.[CrossRef][Medline]
Feng, W. Y., Li, B., Liu, J., Chai, Z. F., Zhang, P. Q., Gao, Y. X. & Zhao, J. J. (2003). Study of chromium-containing proteins in subcellular fractions of rat liver by enriched stable isotopic tracer technique and gel filtration chromatography. Anal Bioanal Chem 375, 363368.[Medline]
Fernandes, M. A. S., Santos, M. S., Alpoim, M. C., Madeira, V. M. C. & Vicente, J. A. F. (2002). Chromium(VI) interaction with plant and animal mitochondrial bioenergetics: a comparative study. J Biochem Mol Toxicol 16, 5363.[CrossRef][Medline]
Gadd, G. M. (1992). Metals and microorganisms a problem of definition. FEMS Microbiol Lett 100, 197203.[CrossRef]
Gietz, R. D. & Woods, R. A. (2002). Transformation of yeast by lithium acetate/single-stranded carrier DNA/polyethylene glycol method. Methods Enzymol 350, 8796.[CrossRef][Medline]
Godon, C., Lagniel, G., Lee, J., Buhler, J. M., Kieffer, S., Perrot, R., Boucherie, H., Toledano, M. B. & Labarre, J. (1998). The H2O2 stimulon in Saccharomyces cerevisiae. J Biol Chem 273, 2248022489.
Grune, T., Reinheckel, T. & Davies, K. J. A. (1997). Degradation of oxidized proteins in mammalian cells. Faseb J 11, 526534.
Halliwell, B. & Gutteridge, J. M. C. (1999). Free Radicals in Biology and Medicine, 3rd edn. Oxford: Oxford University Press.
Haracska, L., Yu, S. L., Johnson, R. E., Prakash, L. & Prakash, S. (2000). Efficient and accurate replication in the presence of 7,8-dihydro-8-oxoguanine by DNA polymerase . Nat Genet 25, 458461.[CrossRef][Medline]
Henderson, G. (1989). A comparison of the effects of chromate, molybdate and cadmium oxide on respiration in the yeast Saccharomyces cerevisiae. Biol Met 2, 8388.[CrossRef][Medline]
Hodges, N. J. & Chipman, J. K. (2002). Down-regulation of the DNA-repair endonuclease 8-oxo-guanine DNA glycosylase 1 (hOGG1) by sodium dichromate in cultured human A549 lung carcinoma cells. Carcinogenesis 23, 5560.
Howlett, N. G. & Avery, S. V. (1997). Induction of lipid peroxidation during heavy metal stress in Saccharomyces cerevisiae and influence of plasma membrane fatty acid unsaturation. Appl Environ Microbiol 63, 29712976.[Abstract]
Jamieson, D. J. (1998). Oxidative stress responses of the yeast Saccharomyces cerevisiae. Yeast 14, 15111527.[CrossRef][Medline]
Kasprzak, K. S. (2002). Oxidative DNA and protein damage in metal-induced toxicity and carcinogenesis. Free Rad Biol Med 32, 958967.[CrossRef][Medline]
Kim, Y. H., Berry, A. H., Spencer, D. S. & Stites, W. E. (2001). Comparing the effect on protein stability of methionine oxidation versus mutagenesis: steps toward engineering oxidative resistance in proteins. Prot Eng 14, 343347.
Koc, A., Gasch, A. P., Rutherford, J. C., Kim, H. Y. & Gladyshev, V. N. (2004). Methionine sulfoxide reductase regulation of yeast lifespan reveals reactive oxygen species-dependent and -independent components of aging. Proc Natl Acad Sci U S A 101, 79998004.
Kryukov, G. V., Kumar, R. A., Koc, A., Sun, Z. H. & Gladyshev, V. N. (2002). Selenoprotein R is a zinc-containing stereo-specific methionine sulfoxide reductase. Proc Natl Acad Sci U S A 99, 42454250.
Levine, R. L., Moskovitz, J. & Stadtman, E. R. (2000). Oxidation of methionine in proteins: roles in antioxidant defense and cellular regulation. IUBMB Life 50, 301307.[CrossRef][Medline]
Lu, Y., Roe, J. A., Bender, C. J., Peisach, J., Banci, L., Bertini, I., Gralla, E. B. & Valentine, J. S. (1996). New type 2 copper-cysteinate proteins. Copper site histidine-to-cysteine mutants of yeast copper-zinc superoxide dismutase. Inorg Chem 35, 16921700.[CrossRef][Medline]
Luo, H., Lu, Y., Shi, X., Mao, Y. & Delal, N. S. (1996). Chromium (IV)-mediated Fenton-like reaction causes DNA damage: implication to genotoxicity of chromate. Ann Clin Lab Sci 26, 185191.[Abstract]
Moradas-Ferreira, P., Costa, V., Piper, P. & Mager, W. (1996). The molecular defences against reactive oxygen species in yeast. Mol Microbiol 19, 651658.[CrossRef][Medline]
Nguyen-Nhu, N. T. & Knoops, B. (2002). Alkyl hydroperoxide reductase 1 protects Saccharomyces cerevisiae against metal ion toxicity and glutathione depletion. Toxicol Lett 135, 219228.[CrossRef][Medline]
Nishida, C. R., Gralla, E. B. & Valentine, J. S. (1994). Characterization of three yeast copper-zinc superoxide dismutase mutants analogous to those coded for in familial amyotrophic lateral sclerosis. Proc Natl Acad Sci U S A 91, 99069910.
O'Brien, T., Xu, J. & Patierno, S. R. (2001). Effects of glutathione on chromium-induced DNA crosslinking and DNA polymerase arrest. Mol Cell Biochem 222, 173182.[CrossRef][Medline]
O'Brien, T. J., Fornsaglio, J. L., Ceryak, S. & Patierno, S. R. (2002). Effects of hexavalent chromium on the survival and cell cycle distribution of DNA repair-deficient S. cerevisiae. DNA Repair 1, 617627.[CrossRef][Medline]
Pesti, M., Gazdag, Z., Emri, T., Farkas, N., Koosz, Z., Belagy, J. & Pocsi, I. (2002). Chromate sensitivity in fission yeast is caused by increased glutathione reductase activity and peroxide overproduction. J Basic Microbiol 42, 408419.[CrossRef][Medline]
Pourahmad, J. & O'Brien, P. J. (2001). Biological reactive intermediates that mediate chromium (VI) toxicity. Biol React Intermed VI Adv Exp Med Biol 500, 203207.
Ravichandran, V., Seres, T., Moriguchi, T., Thomas, J. A. & Johnston, R. B. (1994). S-thiolation of glyceraldehyde-3-phosphate dehydrogenase induced by the phagocytosis-associated respiratory burst in blood monocytes. J Biol Chem 269, 2501025015.
Requena, J. R., Chao, C. C., Levine, R. L. & Stadtman, E. R. (2001). Glutamic and aminoadipic semialdehydes are the main carbonyl products of metal-catalyzed oxidation of proteins. Proc Natl Acad Sci U S A 98, 6974.
Reynolds, M., Peterson, E., Quievryn, G. & Zhitkovich, A. (2004). Human nucleotide excision repair efficiently removes chromium-DNA phosphate adducts and protects cells against chromate toxicity. J Biol Chem 279, 3041930424.
Shanmuganathan, A., Avery, S. V., Willetts, S. A. & Houghton, J. E. (2004). Copper-induced oxidative stress in Saccharomyces cerevisiae targets enzymes of the glycolytic pathway. FEBS Lett 556, 253259.[CrossRef][Medline]
Shenton, D. & Grant, C. M. (2003). Protein S-thiolation targets glycolysis and protein synthesis in response to oxidative stress in the yeast Saccharomyces cerevisiae. Biochem J 374, 513519.[CrossRef][Medline]
Shrivastava, H. Y. & Nair, B. U. (2000). Protein degradation by peroxide catalyzed by chromium (III): role of coordinated ligand. Biochem Biophys Res Commun 270, 749754.[CrossRef][Medline]
Shrivastava, H. Y. & Nair, B. U. (2004). Fluorescence resonance energy transfer from tryptophan to a chromium(III) complex accompanied by non-specific cleavage of albumin: a step forward towards the development of a novel photoprotease. J Inorg Biochem 98, 991994.[CrossRef][Medline]
Sumner, E. R., Avery, A. M., Houghton, J. E., Robins, R. A. & Avery, S. V. (2003). Cell cycle- and age-dependent activation of Sod1p drives the formation of stress-resistant cell subpopulations within clonal yeast cultures. Mol Microbiol 50, 857870.[CrossRef][Medline]
Swanson, R. L., Morey, N. J., Doetsch, P. W. & Jinks-Robertson, S. (1999). Overlapping specificities of base excision repair, nucleotide excision repair, recombination, and translesion synthesis pathways for DNA base damage in Saccharomyces cerevisiae. Mol Cell Biol 19, 29292935.
Wei, J. P. J., Srinivasan, C., Han, H., Valentine, J. S. & Gralla, E. B. (2001). Evidence for a novel role of copper-zinc superoxide dismutase in zinc metabolism. J Biol Chem 276, 4479844803.
White, C., Sharman, A. K. & Gadd, G. M. (1998). An integrated microbial process for the bioremediation of soil contaminated with toxic metals. Nat Biotechnol 16, 572575.[CrossRef][Medline]
Willetts, S. A. (2004). Genetic and genomic approaches to understanding metal toxicity in Saccharomyces cerevisiae. PhD thesis, University of Nottingham.
Received 4 February 2005;
revised 10 March 2005;
accepted 16 March 2005.
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