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Aouida M, Khodami-Pour A, Ramotar D. Novel role for the Saccharomyces cerevisiae oligopeptide transporter Opt2 in drug detoxification. Biochem Cell Biol 2009; 87:653-61. [PMID: 19767828 DOI: 10.1139/o09-045] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Saccharomyces cerevisiae Opt2 is a member of the oligopeptide transporter family that was initially identified to transport tetra- and pentapeptides. Mutants deleted for the OPT2 gene exhibit no growth defects under normal culture conditions. We identified OPT2 from a high-throughput screen that when deleted results in mutants that displayed sensitivity to the anticancer agent bleomycin. The opt2Delta mutant was also reisolated in two additional genome-wide screens designed to identify mutants that are sensitive to the immunosuppressant rapamycin and the divalent metal ion zinc. However, the role of Opt2 in protecting cells against these agents was not investigated. Herein, we show that opt2Delta mutants are also sensitive to a wide variety of toxic agents that are typically detoxified by the vacuoles. Mutants lacking two other related oligopeptide transporters, Opt1 and Ygl114w, showed no significant sensitivities to these drugs, indicating a specific role for Opt2 in drug detoxification. The sensitivities of the opt2Delta mutants were not related to an increased drug uptake but rather to the presence of several small vesicles instead of a functional large vacuole. We propose that Opt2 has a novel function involving the fusion of vesicles to form a mature vacuole.
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Affiliation(s)
- Mustapha Aouida
- Maisonneuve-Rosemont Hospital, Research Center, 5415 Boul. de l'Assomption, Montreal, QC H1T 2M4, Canada
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52
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Massignan T, Stewart RS, Biasini E, Solomon IH, Bonetto V, Chiesa R, Harris DA. A novel, drug-based, cellular assay for the activity of neurotoxic mutants of the prion protein. J Biol Chem 2009; 285:7752-65. [PMID: 19940127 DOI: 10.1074/jbc.m109.064949] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
In prion diseases, the infectious isoform of the prion protein (PrP(Sc)) may subvert a normal, physiological activity of the cellular isoform (PrP(C)). A deletion mutant of the prion protein (Delta105-125) that produces a neonatal lethal phenotype when expressed in transgenic mice provides a window into the normal function of PrP(C) and how it can be corrupted to produce neurotoxic effects. We report here the surprising and unexpected observation that cells expressing Delta105-125 PrP and related mutants are hypersensitive to the toxic effects of two classes of antibiotics (aminoglycosides and bleomycin analogues) that are commonly used for selection of stably transfected cell lines. This unusual phenomenon mimics several essential features of Delta105-125 PrP toxicity seen in transgenic mice, including rescue by co-expression of wild type PrP. Cells expressing Delta105-125 PrP are susceptible to drug toxicity within minutes, suggesting that the mutant protein enhances cellular accumulation of these cationic compounds. Our results establish a screenable cellular phenotype for the activity of neurotoxic forms of PrP, and they suggest possible mechanisms by which these molecules could produce their pathological effects in vivo.
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Affiliation(s)
- Tania Massignan
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63110, USA
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53
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dos Santos SC, Sá-Correia I. Genome-Wide Identification of Genes Required for Yeast Growth Under Imatinib Stress: Vacuolar H+-ATPase Function Is an Important Target of This Anticancer Drug. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2009; 13:185-98. [DOI: 10.1089/omi.2008.0086] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Sandra C. dos Santos
- IBB—Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Técnico, Lisboa, Portugal
| | - Isabel Sá-Correia
- IBB—Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Técnico, Lisboa, Portugal
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Suzuki S, Tada S, Fukuoka M, Taketani H, Tsukakoshi Y, Matsushita M, Oda K, Kusumoto KI, Kashiwagi Y, Sugiyama M. A novel transformation system using a bleomycin resistance marker with chemosensitizers for Aspergillus oryzae. Biochem Biophys Res Commun 2009; 383:42-7. [PMID: 19324021 DOI: 10.1016/j.bbrc.2009.03.108] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2009] [Accepted: 03/20/2009] [Indexed: 10/21/2022]
Abstract
Aspergillus oryzae is resistant to many kinds of antibiotics, which hampers their use to select transformants. In fact, the fungus is resistant to over 200microg/ml of bleomycin (Bm). By enhancing the susceptibility of A. oryzae to Bm using Triton X-100 as a detergent and an ATP-binding cassette (ABC) pump inhibitor, chlorpromazine, to the growing medium, we established a novel transformation system by Bm selection for A. oryzae. In a medium containing these reagents, A. oryzae showed little growth even in the presence of 30microg Bm/ml. Based on these findings, we constructed a Bm-resistance expression cassette (BmR), in which blmB encoding Bm N-acetyltransferase from Bm-producing Streptomyces verticillus was expressed under the control of a fungal promoter. We obtained a gene knockout mutant efficiently by Bm selection, i.e., the chromosomal ligD coding region was successfully replaced by BmR using ligD disruption cassette consisted of ligD flanking sequence and BmR through homologous recombination.
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Affiliation(s)
- Satoshi Suzuki
- Department of Molecular Microbiology and Biotechnology, Hiroshima University, Kasumi, Minami-ku, Japan
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Thorsen M, Perrone GG, Kristiansson E, Traini M, Ye T, Dawes IW, Nerman O, Tamás MJ. Genetic basis of arsenite and cadmium tolerance in Saccharomyces cerevisiae. BMC Genomics 2009; 10:105. [PMID: 19284616 PMCID: PMC2660369 DOI: 10.1186/1471-2164-10-105] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Accepted: 03/12/2009] [Indexed: 11/10/2022] Open
Abstract
Background Arsenic and cadmium are widely distributed in nature and pose serious threats to the environment and human health. Exposure to these nonessential toxic metals may result in a variety of human diseases including cancer. However, arsenic and cadmium toxicity targets and the cellular systems contributing to tolerance acquisition are not fully known. Results To gain insight into metal action and cellular tolerance mechanisms, we carried out genome-wide screening of the Saccharomyces cerevisiae haploid and homozygous diploid deletion mutant collections and scored for reduced growth in the presence of arsenite or cadmium. Processes found to be required for tolerance to both metals included sulphur and glutathione biosynthesis, environmental sensing, mRNA synthesis and transcription, and vacuolar/endosomal transport and sorting. We also identified metal-specific defence processes. Arsenite-specific defence functions were related to cell cycle regulation, lipid and fatty acid metabolism, mitochondrial biogenesis, and the cytoskeleton whereas cadmium-specific defence functions were mainly related to sugar/carbohydrate metabolism, and metal-ion homeostasis and transport. Molecular evidence indicated that the cytoskeleton is targeted by arsenite and that phosphorylation of the Snf1p kinase is required for cadmium tolerance. Conclusion This study has pin-pointed core functions that protect cells from arsenite and cadmium toxicity. It also emphasizes the existence of both common and specific defence systems. Since many of the yeast genes that confer tolerance to these agents have homologues in humans, similar biological processes may act in yeast and humans to prevent metal toxicity and carcinogenesis.
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Affiliation(s)
- Michael Thorsen
- Department of Cell and Molecular Biology/Microbiology, University of Gothenburg, S-405 30 Gothenburg, Sweden.
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56
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Caba E, Aubrecht J. Functional Genomic Approaches for Studying Genotoxicity and Carcinogenesis. Genomics 2008. [DOI: 10.3109/9781420067064-10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Caba E, Aubrecht J. Genomic Approaches for Investigating Mechanisms of Genotoxicity. Toxicol Mech Methods 2008; 16:69-77. [DOI: 10.1080/15376520600558291] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Dawson K, Toone WM, Jones N, Wilkinson CRM. Loss of regulators of vacuolar ATPase function and ceramide synthesis results in multidrug sensitivity in Schizosaccharomyces pombe. EUKARYOTIC CELL 2008; 7:926-37. [PMID: 18441123 PMCID: PMC2446650 DOI: 10.1128/ec.00037-08] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Accepted: 04/11/2008] [Indexed: 11/20/2022]
Abstract
We undertook a screen to isolate determinants of drug resistance in fission yeast and identified two genes that, when mutated, result in sensitivity to a range of structurally unrelated compounds, some of them commonly used in the clinic. One gene, rav1, encodes the homologue of a budding yeast protein which regulates the assembly of the vacuolar ATPase. The second gene, lac1, encodes a homologue of genes that are required for ceramide synthesis. Both mutants are sensitive to the chemotherapeutic agent doxorubicin, and using the naturally fluorescent properties of this compound, we found that both rav1 and lac1 mutations result in an increased accumulation of the drug in cells. The multidrug-sensitive phenotype of rav1 mutants can be rescued by up-regulation of the lag1 gene which encodes a homologue of lac1, whereas overexpression of either lac1 or lag1 confers multidrug resistance on wild-type cells. These data suggest that changing the amount of ceramide synthase activity in cells can influence innate drug resistance. The function of Rav1 appears to be conserved, as we show that SpRav1 is part of a RAVE-like complex in fission yeast and that loss of rav1 results in defects in vacuolar (H(+))-ATPase activity. Thus, we conclude that loss of normal V-ATPase function results in an increased sensitivity of Schizosaccharomyces pombe cells to drugs. The rav1 and lac1 genes are conserved in both higher eukaryotes and various pathogenic fungi. Thus, our data could provide the basis for strategies to sensitize tumor cells or drug-resistant pathogenic fungi to drugs.
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Affiliation(s)
- Keren Dawson
- Paterson Institute for Cancer Research, University of Manchester, Wilmslow Road, Manchester M20 4BX, United Kingdom
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Abstract
The sequencing of the human genome promised the identification of disease-causing genes and, subsequently, therapies for those diseases. However, when identifying the genetic basis of a disease, it is not uncommon to discover an abnormal protein whose normal function is unknown. The genetic manipulations required to assign function to genes is often extremely difficult, if not impossible, in human cells. Model organisms have been used to facilitate understanding of gene function because of the ease of genetic manipulations and because many features of eukaryotic physiology have been conserved across phyla. Yeast is a simple eukaryote with a tractable genome, a short generation time, and a large network of researchers who have generated a vast arsenal of research tools. These traits make yeast ideally suited to help reveal the function of genes implicated in human disease.
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Chen J, Ghorai MK, Kenney G, Stubbe J. Mechanistic studies on bleomycin-mediated DNA damage: multiple binding modes can result in double-stranded DNA cleavage. Nucleic Acids Res 2008; 36:3781-90. [PMID: 18492718 PMCID: PMC2441780 DOI: 10.1093/nar/gkn302] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The bleomycins (BLMs) are a family of natural glycopeptides used clinically as antitumor agents. In the presence of required cofactors (Fe(2+) and O(2)), BLM causes both single-stranded (ss) and double-stranded (ds) DNA damage with the latter thought to be the major source of cytotoxicity. Previous biochemical and structural studies have demonstrated that BLM can mediate ss cleavage through multiple binding modes. However, our studies have suggested that ds cleavage occurs by partial intercalation of BLM's bithiazole tail 3' to the first cleavage site that facilitates its re-activation and re-organization to the second strand without dissociation from the DNA where the second cleavage event occurs. To test this model, a BLM A5 analog (CD-BLM) with beta-cyclodextrin attached to its terminal amine was synthesized. This attachment presumably precludes binding via intercalation. Cleavage studies measuring ss:ds ratios by two independent methods were carried out. Studies using [(32)P]-hairpin technology harboring a single ds cleavage site reveal a ss:ds ratio of 6.7 +/- 1.2:1 for CD-BLM and 3.4:1 and 3.1 +/- 0.3:1 for BLM A2 and A5, respectively. In contrast with BLM A5 and A2, however, CD-BLM mediates ds-DNA cleavage through cooperative binding of a second CD-BLM molecule to effect cleavage on the second strand. Studies using the supercoiled plasmid relaxation assay revealed a ss:ds ratio of 2.8:1 for CD-BLM in comparison with 7.3:1 and 5.8:1, for BLM A2 and A5, respectively. This result in conjunction with the hairpin results suggest that multiple binding modes of a single BLM can lead to ds-DNA cleavage and that ds cleavage can occur using one or two BLM molecules. The significance of the current study to understanding BLM's action in vivo is discussed.
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Affiliation(s)
- Jingyang Chen
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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61
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Ruotolo R, Marchini G, Ottonello S. Membrane transporters and protein traffic networks differentially affecting metal tolerance: a genomic phenotyping study in yeast. Genome Biol 2008; 9:R67. [PMID: 18394190 PMCID: PMC2643938 DOI: 10.1186/gb-2008-9-4-r67] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2007] [Revised: 02/26/2008] [Accepted: 04/07/2008] [Indexed: 01/01/2023] Open
Abstract
Genomic phenotyping was used to assess the role of all non-essential S. cerevisiae proteins in modulating cell viability after exposure to cadmium, nickel and other metals. Background The cellular mechanisms that underlie metal toxicity and detoxification are rather variegated and incompletely understood. Genomic phenotyping was used to assess the roles played by all nonessential Saccharomyces cerevisiae proteins in modulating cell viability after exposure to cadmium, nickel, and other metals. Results A number of novel genes and pathways that affect multimetal as well as metal-specific tolerance were discovered. Although the vacuole emerged as a major hot spot for metal detoxification, we also identified a number of pathways that play a more general, less direct role in promoting cell survival under stress conditions (for example, mRNA decay, nucleocytoplasmic transport, and iron acquisition) as well as proteins that are more proximally related to metal damage prevention or repair. Most prominent among the latter are various nutrient transporters previously not associated with metal toxicity. A strikingly differential effect was observed for a large set of deletions, the majority of which centered on the ESCRT (endosomal sorting complexes required for transport) and retromer complexes, which - by affecting transporter downregulation and intracellular protein traffic - cause cadmium sensitivity but nickel resistance. Conclusion The data show that a previously underestimated variety of pathways are involved in cadmium and nickel tolerance in eukaryotic cells. As revealed by comparison with five additional metals, there is a good correlation between the chemical properties and the cellular toxicity signatures of various metals. However, many conserved pathways centered on membrane transporters and protein traffic affect cell viability with a surprisingly high degree of metal specificity.
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Affiliation(s)
- Roberta Ruotolo
- Department of Biochemistry and Molecular Biology, Viale G.P. Usberti 23/A, University of Parma, I-43100 Parma, Italy
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62
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McGary KL, Lee I, Marcotte EM. Broad network-based predictability of Saccharomyces cerevisiae gene loss-of-function phenotypes. Genome Biol 2008; 8:R258. [PMID: 18053250 PMCID: PMC2246260 DOI: 10.1186/gb-2007-8-12-r258] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Revised: 10/16/2007] [Accepted: 12/05/2007] [Indexed: 11/10/2022] Open
Abstract
Loss-of-function phenotypes of yeast genes can be predicted from the loss-of-function phenotypes of their neighbours in functional gene networks. This could potentially be applied to the prediction of human disease genes. We demonstrate that loss-of-function yeast phenotypes are predictable by guilt-by-association in functional gene networks. Testing 1,102 loss-of-function phenotypes from genome-wide assays of yeast reveals predictability of diverse phenotypes, spanning cellular morphology, growth, metabolism, and quantitative cell shape features. We apply the method to extend a genome-wide screen by predicting, then verifying, genes whose disruption elongates yeast cells, and to predict human disease genes. To facilitate network-guided screens, a web server is available .
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Affiliation(s)
- Kriston L McGary
- Center for Systems and Synthetic Biology, Institute for Cellular and Molecular Biology, University of Texas at Austin, 2500 Speedway, Austin, Texas 78712, USA.
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63
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Heterozygous screen in Saccharomyces cerevisiae identifies dosage-sensitive genes that affect chromosome stability. Genetics 2008; 178:1193-207. [PMID: 18245329 DOI: 10.1534/genetics.107.084103] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
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.
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64
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Kundaje A, Lianoglou S, Li X, Quigley D, Arias M, Wiggins CH, Zhang L, Leslie C. Learning regulatory programs that accurately predict differential expression with MEDUSA. Ann N Y Acad Sci 2007; 1115:178-202. [PMID: 17934055 DOI: 10.1196/annals.1407.020] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Inferring gene regulatory networks from high-throughput genomic data is one of the central problems in computational biology. In this paper, we describe a predictive modeling approach for studying regulatory networks, based on a machine learning algorithm called MEDUSA. MEDUSA integrates promoter sequence, mRNA expression, and transcription factor occupancy data to learn gene regulatory programs that predict the differential expression of target genes. Instead of using clustering or correlation of expression profiles to infer regulatory relationships, MEDUSA determines condition-specific regulators and discovers regulatory motifs that mediate the regulation of target genes. In this way, MEDUSA meaningfully models biological mechanisms of transcriptional regulation. MEDUSA solves the problem of predicting the differential (up/down) expression of target genes by using boosting, a technique from statistical learning, which helps to avoid overfitting as the algorithm searches through the high-dimensional space of potential regulators and sequence motifs. Experimental results demonstrate that MEDUSA achieves high prediction accuracy on held-out experiments (test data), that is, data not seen in training. We also present context-specific analysis of MEDUSA regulatory programs for DNA damage and hypoxia, demonstrating that MEDUSA identifies key regulators and motifs in these processes. A central challenge in the field is the difficulty of validating reverse-engineered networks in the absence of a gold standard. Our approach of learning regulatory programs provides at least a partial solution for the problem: MEDUSA's prediction accuracy on held-out data gives a concrete and statistically sound way to validate how well the algorithm performs. With MEDUSA, statistical validation becomes a prerequisite for hypothesis generation and network building rather than a secondary consideration.
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Affiliation(s)
- Anshul Kundaje
- Department of Computer Science, Center for Computational Learning Systems, Columbia University, New York, NY 10065, USA
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65
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Pike BL, Heierhorst J. Mdt1 facilitates efficient repair of blocked DNA double-strand breaks and recombinational maintenance of telomeres. Mol Cell Biol 2007; 27:6532-45. [PMID: 17636027 PMCID: PMC2099617 DOI: 10.1128/mcb.00471-07] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
DNA recombination plays critical roles in DNA repair and alternative telomere maintenance. Here we show that absence of the SQ/TQ cluster domain-containing protein Mdt1 (Ybl051c) renders Saccharomyces cerevisiae particularly hypersensitive to bleomycin, a drug that causes 3'-phospho-glycolate-blocked DNA double-strand breaks (DSBs). mdt1Delta also hypersensitizes partially recombination-defective cells to camptothecin-induced 3'-phospho-tyrosyl protein-blocked DSBs. Remarkably, whereas mdt1Delta cells are unable to restore broken chromosomes after bleomycin treatment, they efficiently repair "clean" endonuclease-generated DSBs. Epistasis analyses indicate that MDT1 acts in the repair of bleomycin-induced DSBs by regulating the efficiency of the homologous recombination pathway as well as telomere-related functions of the KU complex. Moreover, mdt1Delta leads to severe synthetic growth defects with a deletion of the recombination facilitator and telomere-positioning factor gene CTF18 already in the absence of exogenous DNA damage. Importantly, mdt1Delta causes a dramatic shift from the usually prevalent type II to the less-efficient type I pathway of recombinational telomere maintenance in the absence of telomerase in liquid senescence assays. As telomeres resemble protein-blocked DSBs, the results indicate that Mdt1 acts in a novel blocked-end-specific recombination pathway that is required for the efficiency of both drug-induced DSB repair and telomerase-independent telomere maintenance.
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Affiliation(s)
- Brietta L Pike
- St. Vincent's Institute of Medical Research, 9 Princes Street, Fitzroy, VIC 3065, Australia
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66
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Tounekti K, Aouida M, Leduc A, Poschmann J, Yang X, Belhadj O, Ramotar D. Deletion of the chromatin remodeling gene SPT10 sensitizes yeast cells to a subclass of DNA-damaging agents. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2006; 47:707-17. [PMID: 17078097 DOI: 10.1002/em.20260] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The Saccharomyces cerevisiae SPT10 protein possesses a DNA-binding domain that is fused to a putative histone acetyltransferase domain. It binds specifically to upstream-activating sequence elements in the core histone promoters and plays a direct role in histone gene regulation. SPT10 is also required for cell-cycle-specific K56 acetylation at histone genes, allowing the recruitment of the nucleosome remodeling factor Snf5 and subsequent regulation of gene transcription. We reisolated the SPT10 gene in a functional genome-wide screen designed to identify haploid yeast mutants that are hypersensitive to the antitumor drug bleomycin, which acts by damaging DNA. In addition to bleomycin, we show that spt10Delta mutants are also hypersensitive to a limited set of genotoxic agents that create DNA strand breaks, but not to 254-nm ultraviolet light or 4-nitroquinoline-1-oxide, which generate helix distortion. The hypersensitivities of the spt10Delta mutant to the genotoxic agents are rescued by a single copy plasmid carrying the SPT10 gene. We further showed that spt10Delta mutants displayed a modest twofold increase spontaneous mutant frequency, as compared to the parent. Following exposure to bleomycin, these mutants accumulate unrepaired lesions, e.g., DNA strand breaks with blocked 3'-ends in the chromosomal DNA. This defect is not due to the altered expression level or the enzymatic activities of a key DNA repair enzyme, APN1, which is known to repair DNA strand breaks with blocked ends. We propose that SPT10 mediates repair of a subset of DNA lesions by acetylating histones to promote recruitment of DNA repair enzymes.
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Affiliation(s)
- Kaouther Tounekti
- Laboratoire de Biochimie et de Biotechnologie, Faculte des Sciences de Tunis, Université Tunis El-Manar, Tunis, Tunisia
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67
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McCullock S, Kinard T, McCullough L, Formosa T. blm3-1 Is an Allele of UBP3, a Ubiquitin Protease that Appears to Act During Transcription of Damaged DNA. J Mol Biol 2006; 363:660-72. [PMID: 16997324 DOI: 10.1016/j.jmb.2006.08.073] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2006] [Revised: 08/05/2006] [Accepted: 08/25/2006] [Indexed: 12/16/2022]
Abstract
Yeast Blm10 and mammalian PA200 proteins share significant sequence similarity and both cap the ends of 20 S proteasomes and enhance degradation of some peptide substrates. Blm10 was identified as a suppressor of the yeast blm3-1 mutation, and initially was thought to be the Blm3 protein. Both the blm3-1 and blm10-Delta mutations were reported to cause sensitivity to bleomycin and other forms of DNA damage, suggesting a role for Blm10/PA200-proteasome complexes in DNA repair. We have been unable to observe significant DNA damage sensitivity in blm10-Delta mutants in several genetic backgrounds, and we have therefore further investigated the relationship between BLM10 and blm3-1. We find that blm3-1 is a nonsense mutation in the ubiquitin protease gene UBP3. Deleting UBP3 causes phenotypes similar to those caused by blm3-1, but neither causes a general defect in DNA repair. Ubp3 has several known functions, and genetic interaction data presented here suggest an additional role in transcriptional elongation. The phenotypes caused by blm3-1 and ubp3-Delta mutations are not suppressed by over-expression of BLM10, nor are they affected by deletion of BLM10. These results remove key components of the previously reported connection between Blm10/PA200-proteasome complexes and DNA repair, and they suggest a novel way to interpret sensitivity to bleomycin as resulting from defects in transcription elongation.
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Affiliation(s)
- Shannon McCullock
- University of Utah School of Medicine, Department of Biochemistry, 15 N Medical Drive East RM 4100, Salt Lake City, UT 84112-5640, USA
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68
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Suter B, Auerbach D, Stagljar I. Yeast-based functional genomics and proteomics technologies: the first 15 years and beyond. Biotechniques 2006; 40:625-44. [PMID: 16708762 DOI: 10.2144/000112151] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Yeast-based functional genomics and proteomics technologies developed over the past decade have contributed greatly to our understanding of bacterial, yeast, fly, worm, and human gene functions. In this review, we highlight some of these yeast-based functional genomic and proteomic technologies that are advancing the utility of yeast as a model organism in molecular biology and speculate on their future uses. Such technologies include use of the yeast deletion strain collection, large-scale determination of protein localization in vivo, synthetic genetic array analysis, variations of the yeast two-hybrid system, protein microarrays, and tandem affinity purification (TAP)-tagging approaches. The integration of these advances with established technologies is invaluable in the drive toward a comprehensive understanding of protein structure and function in the cellular milieu.
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69
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Chang M, Parsons AB, Sheikh BH, Boone C, Brown GW. Genomic approaches for identifying DNA damage response pathways in S. cerevisiae. Methods Enzymol 2006; 409:213-35. [PMID: 16793404 DOI: 10.1016/s0076-6879(05)09013-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
DNA damage response pathways have been studied extensively in the budding yeast Saccharomyces cerevisiae, yet new genes with roles in the DNA damage response are still being identified. In this chapter we describe the use of functional genomic approaches in the identification of DNA damage response genes and pathways. These techniques take advantage of the S. cerevisiae gene deletion mutant collection, either as an ordered array or as a pool, and can be automated for high throughput.
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Affiliation(s)
- Michael Chang
- Biochemistry, University of Toronto, Toronto, Ontario, Canada
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Ustrell V, Pratt G, Gorbea C, Rechsteiner M. Purification and assay of proteasome activator PA200. Methods Enzymol 2005; 398:321-9. [PMID: 16275339 DOI: 10.1016/s0076-6879(05)98026-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
PA200, the most recently discovered activator of the 20S proteasome, is a nuclear protein thought to play a role in DNA repair. Homologs of PA200 have been found in rat, frog, birds, worms, and budding yeast, where it is called Blm3p (now known as Blm10p), but not in Drosophila or fission yeast. Western blots of SDS-PAGE transfers reveal 160 and 200K forms of mammalian PA200, and organ surveys demonstrate that the 200K species is highest in testis. PA200 purified from bovine testis binds the ends of the cylindrical 20S proteasome, forming volcano-shaped structures in negatively stained EM images. In vitro assays demonstrate that binding of PA200 activates peptide hydrolysis by the 20S proteasome. This chapter describes the purification and assay of bovine testis PA200.
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Affiliation(s)
- Vicença Ustrell
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84132-3201, USA
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71
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Cai H, Kauffman S, Naider F, Becker JM. Genomewide screen reveals a wide regulatory network for di/tripeptide utilization in Saccharomyces cerevisiae. Genetics 2005; 172:1459-76. [PMID: 16361226 PMCID: PMC1456296 DOI: 10.1534/genetics.105.053041] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Small peptides of two to six residues serve as important sources of amino acids and nitrogen required for growth by a variety of organisms. In the yeast Saccharomyces cerevisiae, the membrane transport protein Ptr2p, encoded by PTR2, mediates the uptake of di/tripeptides. To identify genes involved in regulation of dipeptide utilization, we performed a systematic, functional examination of this process in a haploid, nonessential, single-gene deletion mutant library. We have identified 103 candidate genes: 57 genes whose deletion decreased dipeptide utilization and 46 genes whose deletion enhanced dipeptide utilization. On the basis of Ptr2p-GFP expression studies, together with PTR2 expression analysis and dipeptide uptake assays, 42 genes were ascribed to the regulation of PTR2 expression, 37 genes were involved in Ptr2p localization, and 24 genes did not apparently affect Ptr2p-GFP expression or localization. The 103 genes regulating dipeptide utilization were distributed among most of the Gene Ontology functional categories, indicating a very wide regulatory network involved in transport and utilization of dipeptides in yeast. It is anticipated that further characterization of how these genes affect peptide utilization should add new insights into the global mechanisms of regulation of transport systems in general and peptide utilization in particular.
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Affiliation(s)
- Houjian Cai
- Department of Microbiology, University of Tennessee, Knoxville 37996-0845, USA
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72
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Huang RY, Eddy M, Vujcic M, Kowalski D. Genome-wide screen identifies genes whose inactivation confer resistance to cisplatin in Saccharomyces cerevisiae. Cancer Res 2005; 65:5890-7. [PMID: 15994967 DOI: 10.1158/0008-5472.can-04-4093] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
To identify novel genes that mediate cellular resistance to cisplatin, we have screened the collection of Saccharomyces cerevisiae deletion strains. We have found reproducibly 22 genes/open reading frames (ORF), which when deleted, confer resistance to cisplatin at a concentration that is lethal to wild-type cells. Complementation of individual deletion strains with the corresponding wild-type gene abolished cisplatin resistance, confirming that specific gene deletions caused the resistance. Twenty of the genes/ORFs identified have not been previously linked to cisplatin resistance and belong to several distinct functional groups. Major functional groups encode proteins involved in nucleotide metabolism, mRNA catabolism, RNA-polymerase-II-dependent gene regulation and vacuolar transport systems. In addition, proteins that function in ubiquitination, sphingolipid biogenesis, cyclic AMP-dependent signaling, DNA repair, and genome stability are also associated with cisplatin resistance. More than half of the identified genes are known to have sequences or functional homology to mammalian counterparts. Some deletion strains are cross-resistant to selected cytotoxic agents whereas hypersensitive to others. The sensitivity of certain resistant strains to other cytotoxic agents suggests that our findings may point to particular drug combinations that can overcome resistance caused by inactivation of specific genes.
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Affiliation(s)
- Ruea-Yea Huang
- Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
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73
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Thornton G, Wilkinson CRM, Toone WM, Jones N. A novel pathway determining multidrug sensitivity in Schizosaccharomyces pombe. Genes Cells 2005; 10:941-51. [PMID: 16164595 DOI: 10.1111/j.1365-2443.2005.00891.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
In this study, we show that a mutation isolated during a screen for determinants of chemosensitivity in S. pombe results in loss of function of a previously uncharacterized protein kinase now named Hal4. Hal4 shares sequence homology to Hal4 and Hal5 in S. cerevisiae, and previous evidence indicates that these kinases positively regulate the major potassium transporter Trk1,2 and thereby maintain the plasma membrane potential. Disruption of this ion homeostasis pathway results in a hyperpolarized membrane and a concomitant increased sensitivity to cations. We demonstrate that a mutation in hal4+ results in hyperpolarization of the plasma membrane. In addition to the original selection agent, the hal4-1 mutant is sensitive to a variety of chemotherapeutic agents and stress-inducing compounds. Furthermore, this wider chemosensitive phenotype is also displayed by corresponding mutants in S. cerevisiae, and in a trk1deltatrk2delta double deletion mutant in S. pombe. We propose that this pathway and its role in regulating the plasma membrane potential may act as a pleiotropic determinant of sensitivity to chemotherapeutic agents.
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Affiliation(s)
- Gemma Thornton
- Paterson Institute for Cancer Research, Christie Hospital NHS Trust, Wilmslow Road, Manchester, M20 4BX, UK
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74
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Hellauer K, Lesage G, Sdicu AM, Turcotte B. Large-Scale Analysis of Genes that Alter Sensitivity to the Anticancer Drug Tirapazamine inSaccharomyces cerevisiae. Mol Pharmacol 2005; 68:1365-75. [PMID: 16061773 DOI: 10.1124/mol.105.012963] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Tirapazamine (TPZ) is an anticancer drug that targets topoisomerase II. TPZ is preferentially active under hypoxic conditions. The drug itself is not harmful to cells; rather, it is reduced to a toxic radical species by an NADPH cytochrome P450 oxidoreductase. Under aerobic conditions, the toxic compound reacts with oxygen to revert back to TPZ and a much less toxic radical species. We have used yeast (Saccharomyces cerevisiae) as a model to better understand the mechanism of action of TPZ. Overexpression of NCP1, encoding the yeast ortholog of the human P450 oxidoreductase, results in greatly increased sensitivity to TPZ. Likewise, overexpression of TOP2 (encoding topoisomerase II) leads to hypersensitivity to TPZ, suggesting that topoisomerase II is also a target of TPZ in yeast. Thus, our data show that yeast mimics human cells in terms of TPZ sensitivity. We have performed robot-aided screens for altered sensitivity to TPZ using a collection of approximately 4600 haploid yeast deletion strains. We have identified 117 and 73 genes whose deletion results in increased or decreased resistance to TPZ, respectively. For example, cells lacking various DNA repair genes are hypersensitive to TPZ. In contrast, deletion of genes encoding some amino acid permeases results in cells that are resistant to TPZ. This suggests that permeases may be involved in intracellular uptake of TPZ. Our discoveries in yeast may lead to a better understanding of TPZ biology in humans.
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Affiliation(s)
- Karen Hellauer
- Department of Medicine, Royal Victoria Hospital, McGill University, 687 Pine Avenue West, Montréal, Québec, Canada H3A 1A1
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75
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Rechsteiner M, Hill CP. Mobilizing the proteolytic machine: cell biological roles of proteasome activators and inhibitors. Trends Cell Biol 2005; 15:27-33. [PMID: 15653075 DOI: 10.1016/j.tcb.2004.11.003] [Citation(s) in RCA: 261] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Proteasomes perform the majority of proteolysis that occurs in the cytosol and nucleus of eukaryotic cells and, thereby, perform crucial roles in cellular regulation and homeostasis. Isolated proteasomes are inactive because substrates cannot access the proteolytic sites. PA28 and PA200 are activators that bind to proteasomes and stimulate the hydrolysis of peptides. Several protein inhibitors of the proteasome have also been identified, and the properties of these activators and inhibitors have been characterized biochemically. By contrast, their physiological roles--which have been reported to include production of antigenic peptides, proteasome assembly and DNA repair--are controversial. In this article, we briefly review the biochemical data and discuss the possible biological roles of PA28, PA200 and proteasome inhibitors.
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Affiliation(s)
- Martin Rechsteiner
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
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76
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Abstract
In the past, studies using the yeast Saccharomyces cerevisiae enabled major breakthroughs in the understanding of basic cellular and molecular processes. Today, the use of yeast is undergoing a "rebirth" in both fundamental and applied research. Indeed, advances in yeast technology have paved the way for a variety of new genome-wide screening approaches. Experimental strategies using yeast aim to unravel disease-related molecular events and to discover novel medicinal compounds. In this article, the impact of yeast as an experimental tool for disease-related studies is summarized and the use of yeast in high-throughput screenings for pharmacological purposes is evaluated. The recently applied and promising approach of so-called humanized yeast systems is also discussed.
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Affiliation(s)
- Willem H Mager
- Department of Chemistry and Pharmaceutical Sciences, Faculty of Sciences, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
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77
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Aouida M, Leduc A, Poulin R, Ramotar D. AGP2 encodes the major permease for high affinity polyamine import in Saccharomyces cerevisiae. J Biol Chem 2005; 280:24267-76. [PMID: 15855155 DOI: 10.1074/jbc.m503071200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polyamines play essential functions in many aspects of cell biology. Plasma membrane transport systems for the specific uptake of polyamines exist in most eukaryotic cells but have been very recently identified at the molecular level only in the parasite Leishmania. We now report that the high affinity polyamine permease in Saccharomyces cerevisiae is identical to Agp2p, a member of the yeast amino acid transporter family that was previously identified as a carnitine transporter. Deletion of AGP2 dramatically reduces the initial velocity of spermidine and putrescine uptake and confers strong resistance to the toxicity of exogenous polyamines, and transformation with an AGP2 expression vector restored polyamine transport in agp2delta mutants. Yeast mutants deficient in polyamine biosynthesis required >10-fold higher concentrations of exogenous putrescine to restore cell proliferation upon deletion of the AGP2 gene. Disruption of END3, a gene required for an early step of endocytosis, increased the abundance of Agp2p, an effect that was paralleled by a marked up-regulation of spermidine transport velocity. Thus, AGP2 encodes the first eukaryotic permease that preferentially uses spermidine over putrescine as a high affinity substrate and plays a central role in the uptake of polyamines in yeast.
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Affiliation(s)
- Mustapha Aouida
- Guy-Bernier Research Center, Maisonneuve-Rosemont Hospital, Montreal, Quebec H1T 2M4, Canada
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78
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Tenreiro S, Vargas RC, Teixeira MC, Magnani C, Sá-Correia I. The yeast multidrug transporter Qdr3 (Ybr043c): localization and role as a determinant of resistance to quinidine, barban, cisplatin, and bleomycin. Biochem Biophys Res Commun 2005; 327:952-9. [PMID: 15649438 DOI: 10.1016/j.bbrc.2004.12.097] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2004] [Indexed: 12/29/2022]
Abstract
Saccharomyces cerevisiae ORF YBR043c, predicted to code for a transporter of the major facilitator superfamily required for multiple drug resistance, encodes a plasma membrane protein that confers resistance to quinidine and barban, as observed before for its close homologues QDR1 and QDR2. This ORF was, thus, named the QDR3 gene. The increased expression of QDR3, or QDR2, also leads to increased resistance to the anticancer agents cisplatin and bleomycin. However, no evidence for increased QDR3 expression in yeast cells exposed to all these inhibitory compounds was found. Transport assays support the concept that Qdr3 is involved, even if opportunistically, in the active export of quinidine out of yeast cell. A correlation was established between the efficiency of quinidine active export mediated by Qdr3p, Qdr2p or Qdr1p, and the efficacy of the expression of the encoding genes in alleviating the deleterious action of quinidine, as well as of the other compounds (QDR2>QDR3>>>QDR1).
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Affiliation(s)
- Sandra Tenreiro
- Biological Sciences Research Group, Centro de Engenharia Biológica e Química, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
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79
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Abstract
Bleomycins are a family of glycopeptide antibiotics that have potent antitumour activity against a range of lymphomas, head and neck cancers and germ-cell tumours. The therapeutic efficacy of the bleomycins is limited by development of lung fibrosis. The cytotoxic and mutagenic effects of the bleomycins are thought to be related to their ability to mediate both single-stranded and double-stranded DNA damage, which requires the presence of specific cofactors (a transition metal, oxygen and a one-electron reductant). Progress in understanding the mechanisms involved in the therapeutic efficacy of the bleomycins and the unwanted toxicity and elucidation of the biosynthetic pathway of the bleomycins sets the stage for developing a more potent, less toxic therapeutic agent.
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Affiliation(s)
- Jingyang Chen
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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80
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Ortega J, Heymann JB, Kajava AV, Ustrell V, Rechsteiner M, Steven AC. The axial channel of the 20S proteasome opens upon binding of the PA200 activator. J Mol Biol 2005; 346:1221-7. [PMID: 15713476 DOI: 10.1016/j.jmb.2004.12.049] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Revised: 12/16/2004] [Accepted: 12/21/2004] [Indexed: 11/17/2022]
Abstract
Proteasomes consist of a proteolytic core called the 20 S particle and ancillary factors that regulate its activity in various ways. PA200 has been identified as a large (200 kDa) nuclear protein that stimulates proteasomal hydrolysis of peptides. To characterize its interaction with the 20 S core, we have visualized PA200-20 S complexes by electron microscopy. Monomers of PA200 bind to one or both ends of the 20 S core. Reconstructed in three dimensions to 23 A resolution from cryo-electron micrographs of the singly bound complex, PA200 has an asymmetric dome-like structure with major and minor lobes. Taking into account previous bioinformatic analysis, it is likely to represent an irregular folding of an alpha-helical solenoid composed of HEAT-like repeats. PA200 makes contact with all alpha-subunits except alpha7, and this interaction induces an opening of the axial channel through the alpha-ring. Thus, the activation mechanism of PA200 is expressed via its allosteric effects on the 20 S core particle, perhaps facilitating release of digestion products or the entrance of substrates.
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Affiliation(s)
- Joaquin Ortega
- Laboratory of Structural Biology, National Institute of Arthritis, Musculoskeletal and Skin Diseases, National Institutes of Health, Bldg 50, Room 1517, 50 South Drive MSC 8025, Bethesda, MD 20892-8025, USA
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81
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Krogan NJ, Lam MHY, Fillingham J, Keogh MC, Gebbia M, Li J, Datta N, Cagney G, Buratowski S, Emili A, Greenblatt JF. Proteasome Involvement in the Repair of DNA Double-Strand Breaks. Mol Cell 2004; 16:1027-34. [PMID: 15610744 DOI: 10.1016/j.molcel.2004.11.033] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2004] [Revised: 08/17/2004] [Accepted: 10/21/2004] [Indexed: 11/23/2022]
Abstract
Affinity purification of the yeast 19S proteasome revealed the presence of Sem1 as a subunit. Its human homolog, DSS1, was found likewise to copurify with the human 19S proteasome. DSS1 is known to associate with the tumor suppressor protein BRCA2 involved in repair of DNA double-strand breaks (DSBs). We demonstrate that Sem1 is required for efficient repair of an HO-generated yeast DSB using both homologous recombination (HR) and nonhomologous end joining (NHEJ) pathways. Deletion of SEM1 or genes encoding other nonessential 19S or 20S proteasome subunits also results in synthetic growth defects and hypersensitivity to genotoxins when combined with mutations in well-established DNA DSB repair genes. Chromatin immunoprecipitation showed that Sem1 is recruited along with the 19S and 20S proteasomes to a DSB in vivo, and this recruitment is dependent on components of both the HR and NHEJ repair pathways, suggesting a direct role of the proteasome in DSB repair.
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Affiliation(s)
- Nevan J Krogan
- Banting and Best Department of Medical Research, University of Toronto, 112 College Street, Toronto, Ontario M5G 1L6, Canada
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82
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Aouida M, Leduc A, Wang H, Ramotar D. Characterization of a transport and detoxification pathway for the antitumour drug bleomycin in Saccharomyces cerevisiae. Biochem J 2004; 384:47-58. [PMID: 15248838 PMCID: PMC1134087 DOI: 10.1042/bj20040392] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Revised: 06/17/2004] [Accepted: 07/13/2004] [Indexed: 11/17/2022]
Abstract
BLM (bleomycin) is effective in combination therapy against various cancers including testicular cancer. However, several other cancers such as colon cancer are refractory to BLM treatment. The exact mechanism for this differential response of cancer cells to the drug is not known. In the present study, we created fluorescently labelled BLM-A5, which retained nearly full genotoxic potential, and used this molecule to conduct the first study to understand the transport pathway of the drug in Saccharomyces cerevisiae. Uptake studies revealed that fluoro-BLM-A5 is transported into the cell in a concentration-dependent manner. Transport of a non-saturating concentration of fluoro-BLM-A5 was modest for the first 90 min, but thereafter it was sharply induced until 300 min. The inducible transport was completely abolished by the addition of cycloheximide, suggesting that BLM-A5 uptake into the cell is dependent on new protein synthesis. Interestingly, transport of fluoro-BLM-A5 was blocked if the cells were preincubated with increasing concentrations of spermine. Moreover, a mutant lacking the Ptk2 kinase, necessary for positively regulating polyamine transport, was defective in fluoro-BLM-A5 uptake and exhibited extreme resistance to the drug. A simple interpretation of these results is that BLM-A5 may enter the cell through the polyamine transport system. We showed further that after the uptake, fluoro-BLM-A5 accumulated into the vacuole of the parent, but localized to the cytoplasm of mutants disrupted for the END3 gene required for an early step of the endocytotic pathway. In general, mutants with a defect in the endocytic pathway to the vacuole were hypersensitive to BLM-A5. We suggest that BLM-A5 is transported across the yeast plasma membrane and sequestered into the vacuole for detoxification.
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Affiliation(s)
- Mustapha Aouida
- Guy-Bernier Research Center, Maisonneuve-Rosemont Hospital, University of Montreal, 5415, Boul. de l'Assomption, Montreal, Quebec, Canada H1T 2M4
| | - Anick Leduc
- Guy-Bernier Research Center, Maisonneuve-Rosemont Hospital, University of Montreal, 5415, Boul. de l'Assomption, Montreal, Quebec, Canada H1T 2M4
| | - Huijie Wang
- Guy-Bernier Research Center, Maisonneuve-Rosemont Hospital, University of Montreal, 5415, Boul. de l'Assomption, Montreal, Quebec, Canada H1T 2M4
| | - Dindial Ramotar
- Guy-Bernier Research Center, Maisonneuve-Rosemont Hospital, University of Montreal, 5415, Boul. de l'Assomption, Montreal, Quebec, Canada H1T 2M4
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83
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Perrone GG, Grant CM, Dawes IW. Genetic and environmental factors influencing glutathione homeostasis in Saccharomyces cerevisiae. Mol Biol Cell 2004; 16:218-30. [PMID: 15509654 PMCID: PMC539166 DOI: 10.1091/mbc.e04-07-0560] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Glutathione is an essential metabolite protecting cells against oxidative stress and aging. Here, we show that endogenously synthesized glutathione undergoes intercellular cycling during growth to stationary phase. Genome-wide screening identified approximately 270 yeast deletion mutants that overexcrete glutathione, predominantly in the reduced form, and identified a surprising set of functions important for glutathione homeostasis. The highest excretors were affected in late endosome/vacuolar functions. Other functions identified included nitrogen/carbon source signaling, mitochondrial electron transport, ubiquitin/proteasomal processes, transcriptional regulation, ion transport and the cellular integrity pathway. For many mutants the availability of branched chain amino acids and extracellular pH influenced both glutathione homeostasis and cell viability. For all mutants tested, the onset of glutathione excretion occurred when intracellular concentration exceeded the maximal level found in the parental strain; however, in some mutants prolonged excretion led to substantial depletion of intracellular glutathione. These results significantly contribute to understanding mechanisms affecting glutathione homeostasis in eukaryotes and may provide insight into the underlying cause of glutathione depletion in degenerative processes such as Parkinson's disease. The important implications of these data for use of the yeast deletion collection for the study of other phenomena also are discussed.
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Affiliation(s)
- Gabriel G Perrone
- School of Biotechnology and Biomolecular Sciences and Ramaciotti Centre for Gene Function Analysis, University of New South Wales, Sydney, New South Wales, Australia 2052
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84
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Abstract
We assess five years of usage of the major genome-wide collections of mutants from Saccharomyces cerevisiae: single deletion mutants, double mutants conferring 'synthetic' lethality and the 'TRIPLES' collection of mutants obtained by random transposon insertion. Over 100 experimental conditions have been tested and more than 5,000 novel phenotypic traits have been assigned to yeast genes using these collections.
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Affiliation(s)
- Bart Scherens
- Institut de Recherches Microbiologiques J.M. Wiame, Campus CERIA, Av. E. Gryson 1, 1070 Bruxelles, Belgium
| | - Andre Goffeau
- Institut des Sciences de la Vie, Université Catholique de Louvain, Croix du Sud 2-20, 1348 Louvain-la-Neuve, Belgium
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