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Hess KC, Liu J, Manfredi G, Mühlschlegel FA, Buck J, Levin LR, Barrientos A. A mitochondrial CO2-adenylyl cyclase-cAMP signalosome controls yeast normoxic cytochrome c oxidase activity. FASEB J 2014; 28:4369-80. [PMID: 25002117 PMCID: PMC4202101 DOI: 10.1096/fj.14-252890] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 06/16/2014] [Indexed: 12/30/2022]
Abstract
Mitochondria, the major source of cellular energy in the form of ATP, respond to changes in substrate availability and bioenergetic demands by employing rapid, short-term, metabolic adaptation mechanisms, such as phosphorylation-dependent protein regulation. In mammalian cells, an intramitochondrial CO2-adenylyl cyclase (AC)-cyclic AMP (cAMP)-protein kinase A (PKA) pathway regulates aerobic energy production. One target of this pathway involves phosphorylation of cytochrome c oxidase (COX) subunit 4-isoform 1 (COX4i1), which modulates COX allosteric regulation by ATP. However, the role of the CO2-sAC-cAMP-PKA signalosome in regulating COX activity and mitochondrial metabolism and its evolutionary conservation remain to be fully established. We show that in Saccharomyces cerevisiae, normoxic COX activity measured in the presence of ATP is 55% lower than in the presence of ADP. Moreover, the adenylyl cyclase Cyr1 activity is present in mitochondria, and it contributes to the ATP-mediated regulation of COX through the normoxic subunit Cox5a, homologue of human COX4i1, in a bicarbonate-sensitive manner. Furthermore, we have identified 2 phosphorylation targets in Cox5a (T65 and S43) that modulate its allosteric regulation by ATP. These residues are not conserved in the Cox5b-containing hypoxic enzyme, which is not regulated by ATP. We conclude that across evolution, a CO2-sAC-cAMP-PKA axis regulates normoxic COX activity.
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Affiliation(s)
| | - Jingjing Liu
- Department of Biochemistry and Molecular Biology and
| | - Giovanni Manfredi
- Brain and Mind Research Institute, Weill Cornell Medical College, New York, New York, USA
| | | | | | | | - Antoni Barrientos
- Department of Biochemistry and Molecular Biology and Department of Neurology, University of Miami Miller School of Medicine, Miami, Florida, USA; and
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2
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Daley JM, Zakaria C, Ramotar D. The endonuclease IV family of apurinic/apyrimidinic endonucleases. Mutat Res 2010; 705:217-27. [PMID: 20667510 DOI: 10.1016/j.mrrev.2010.07.003] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Revised: 07/03/2010] [Accepted: 07/14/2010] [Indexed: 11/17/2022]
Abstract
Apurinic/apyrimidinic (AP) endonucleases are versatile DNA repair enzymes that possess a variety of nucleolytic activities, including endonuclease activity at AP sites, 3' phosphodiesterase activity that can remove a variety of ligation-blocking lesions from the 3' end of DNA, endonuclease activity on oxidative DNA lesions, and 3' to 5' exonuclease activity. There are two families of AP endonucleases, named for the bacterial counterparts endonuclease IV (EndoIV) and exonuclease III (ExoIII). While ExoIII family members are present in all kingdoms of life, EndoIV members exist in lower organisms but are curiously absent in plants, mammals and some other vertebrates. Here, we review recent research on these enzymes, focusing primarily on the EndoIV family. We address the role(s) of EndoIV members in DNA repair and discuss recent findings from each model organism in which the enzymes have been studied to date.
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Affiliation(s)
- James M Daley
- Centre de Recherche, Hôpital Maisonneuve-Rosemont, Université de Montréal, 5415 de L'Assomption, Montréal, QC H1T 2M4, Canada
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3
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Steininger S, Ahne F, Winkler K, Kleinschmidt A, Eckardt-Schupp F, Moertl S. A novel function for the Mre11-Rad50-Xrs2 complex in base excision repair. Nucleic Acids Res 2009; 38:1853-65. [PMID: 20040573 PMCID: PMC2847237 DOI: 10.1093/nar/gkp1175] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Mre11/Rad50/Xrs2 (MRX) complex in Saccharomyces cerevisiae has well-characterized functions in DNA double-strand break processing, checkpoint activation, telomere length maintenance and meiosis. In this study, we demonstrate an involvement of the complex in the base excision repair (BER) pathway. We studied the repair of methyl-methanesulfonate-induced heat-labile sites in chromosomal DNA in vivo and the in vitro BER capacity for the repair of uracil- and 8-oxoG-containing oligonucleotides in MRX-deficient cells. Both approaches show a clear BER deficiency for the xrs2 mutant as compared to wildtype cells. The in vitro analyses revealed that both subpathways, long-patch and short-patch BER, are affected and that all components of the MRX complex are similarly important for the new function in BER. The investigation of the epistatic relationship of XRS2 to other BER genes suggests a role of the MRX complex downstream of the AP-lyases Ntg1 and Ntg2. Analysis of individual steps in BER showed that base recognition and strand incision are not affected by the MRX complex. Reduced gap-filling activity and the missing effect of aphidicoline treatment, an inhibitor for polymerases, on the BER efficiency indicate an involvement of the MRX complex in providing efficient polymerase activity.
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Affiliation(s)
- Sylvia Steininger
- Institute of Radiation Biology, Helmholtz Centre Munich - German Research Centre for Environmental Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg, Germany
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4
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Ma W, Resnick MA, Gordenin DA. Apn1 and Apn2 endonucleases prevent accumulation of repair-associated DNA breaks in budding yeast as revealed by direct chromosomal analysis. Nucleic Acids Res 2008; 36:1836-46. [PMID: 18267974 PMCID: PMC2346603 DOI: 10.1093/nar/gkm1148] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Base excision repair (BER) provides relief from many DNA lesions. While BER enzymes have been characterized biochemically, BER functions within cells are much less understood, in part because replication bypass and double-strand break (DSB) repair can also impact resistance to base damage. To investigate BER in vivo, we examined the repair of methyl methanesulfonate (MMS) induced DNA damage in haploid G1 yeast cells, so that replication bypass and recombinational DSB repair cannot occur. Based on the heat-lability of MMS-induced base damage, an assay was developed that monitors secondary breaks in full-length yeast chromosomes where closely spaced breaks yield DSBs that are observed by pulsed-field gel electrophoresis. The assay detects damaged bases and abasic (AP) sites as heat-dependent breaks as well as intermediate heat-independent breaks that arise during BER. Using a circular chromosome, lesion frequency and repair kinetics could be easily determined. Monitoring BER in single and multiple glycosylase and AP-endonuclease mutants confirmed that Mag1 is the major enzyme that removes MMS-damaged bases. This approach provided direct physical evidence that Apn1 and Apn2 not only repair cellular base damage but also prevent break accumulation that can result from AP sites being channeled into other BER pathway(s).
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Affiliation(s)
- Wenjian Ma
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences (NIH, DHHS), Research Triangle Park, NC 27709, USA
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5
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Boiteux S, Guillet M. Abasic sites in DNA: repair and biological consequences in Saccharomyces cerevisiae. DNA Repair (Amst) 2004; 3:1-12. [PMID: 14697754 DOI: 10.1016/j.dnarep.2003.10.002] [Citation(s) in RCA: 371] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Apurinic/apyrimidinic (AP) sites are one of the most frequent spontaneous lesions in DNA. They are potentially mutagenic and lethal lesions that can block DNA replication and transcription. In addition, cleavage of AP sites by AP endonucleases or AP lyases generates DNA single-strand breaks (SSBs) with 5'- or 3'-blocked ends, respectively. Therefore, we suggest that AP sites and 3'- or 5'-blocked SSBs, we name "honorary AP sites", constitute a single class of lesions. In this review, we describe the different mechanisms used by the budding yeast Saccharomyces cerevisiae to remove or tolerate AP sites and related SSBs. In wild-type cells, AP sites are primarily repaired by the base excision repair (BER) pathway, with the nucleotide excision repair (NER) pathway as a back up activity. BER is initiated by one of the two AP endonucleases, Apn1 or Apn2. Three DNA N-glycosylases/AP lyases, Ntg1, Ntg2 and Ogg1, can also incise AP sites in DNA. Rad27, a structure specific endonuclease, is involved in the repair of 5'-blocked ends, whereas Apn1, Apn2 and Rad1-Rad10 are involved in the removal of 3'-blocked ends using their 3'-phosphodiesterase and 3'-flap endonuclease activities, respectively. AP sites can stall DNA replication forks, as well as they block in vitro DNA synthesis by DNA polymerase delta. Restart of stalled forks can occur through a recombination-associated pathway initiated by the Mus81-Mms4 endonuclease or mutagenic translesion DNA synthesis (TLS). The mutagenic bypass of AP sites is a two-polymerases affair with an inserter DNA polymerase (Poldelta, Poleta or Rev1) and an extender DNA polymerase (Polzeta). Under normal growth conditions, inactivation of Apn1, Apn2 and Rad1-Rad10 causes cell death. Therefore, the burden of spontaneous AP sites is not compatible with life, in the absence of excision repair pathways. These results in yeast demonstrate that AP sites are critical endogenous DNA damages that cause genetic instability and by analogy could be associated with degenerative pathologies in human.
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Affiliation(s)
- Serge Boiteux
- CEA, DSV, Département de Radiobiologie et Radiopathologie, UMR 217 CNRS, "Radiobiologie Moléculaire et Cellulaire", BP 6, F-92265, Fontenay aux Roses, France.
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6
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Teresa Pellicer M, Felisa Nuñez M, Aguilar J, Badia J, Baldoma L. Role of 2-phosphoglycolate phosphatase of Escherichia coli in metabolism of the 2-phosphoglycolate formed in DNA repair. J Bacteriol 2003; 185:5815-21. [PMID: 13129953 PMCID: PMC193966 DOI: 10.1128/jb.185.19.5815-5821.2003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The enzyme 2-phosphoglycolate phosphatase from Escherichia coli, encoded by the gph gene, was purified and characterized. The enzyme was highly specific for 2-phosphoglycolate and showed good catalytic efficiency (k(cat)/K(m)), which enabled the conversion of this substrate even at low intracellular concentrations. A comparison of the structural and functional features of this enzyme with those of 2-phosphoglycolate phosphatases of different origins showed a high similarity of the sequences, implying the use of the same catalytic mechanism. Western blot analysis revealed constitutive expression of the gph gene, regardless of the carbon source used, growth stage, or oxidative stress conditions. We showed that this housekeeping enzyme is involved in the dissimilation of the intracellular 2-phosphoglycolate formed in the DNA repair of 3'-phosphoglycolate ends. DNA strand breaks of this kind are caused by agents such as the radiomimetic compound bleomycin. The differential response between a 2-phosphoglycolate phosphatase-deficient mutant and its parental strain after treatment with bleomycin allowed us to connect the intracellular formation of 2-phosphoglycolate with the production of glycolate, which is subsequently incorporated into general metabolism. We thus provide evidence for a salvage function of 2-phosphoglycolate phosphatase in the metabolism of a two-carbon compound generated by the cellular DNA repair machinery.
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Affiliation(s)
- Maria Teresa Pellicer
- Department of Biochemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain
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7
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Ramotar D, Wang H. Protective mechanisms against the antitumor agent bleomycin: lessons from Saccharomyces cerevisiae. Curr Genet 2003; 43:213-24. [PMID: 12698269 DOI: 10.1007/s00294-003-0396-1] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2003] [Revised: 03/17/2003] [Accepted: 03/18/2003] [Indexed: 10/26/2022]
Abstract
Bleomycin is a small glycopeptide antibiotic used in combination therapy for the treatment of a few types of human cancer. The antitumor effect of bleomycin is most likely caused by its ability to bind to DNA and induce the formation of toxic DNA lesions via a free radical reactive (Fe.bleomycin) complex. However, the chemotherapeutic potential of bleomycin is limited, as it causes pulmonary fibrosis and tumor resistance at high doses. The chemical structure and modes of action of bleomycin have been extensively studied and these provide a foundation towards improving the therapeutic value of the drug. This review provides a first account of the current state of knowledge of the cellular processes that can allow the yeast Saccharomyces cerevisiae to evade the lethal effects of bleomycin. This model organism is likely to provide rapid clues in our understanding of bleomycin resistance in tumor cells.
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Affiliation(s)
- Dindial Ramotar
- Maisonneuve-Rosemont Hospital, Guy-Bernier Research Center, 5415 Boulevard de l'Assomption, H1T 2M4, Montreal, Quebec, Canada.
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8
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Morey NJ, Doetsch PW, Jinks-Robertson S. Delineating the requirements for spontaneous DNA damage resistance pathways in genome maintenance and viability in Saccharomyces cerevisiae. Genetics 2003; 164:443-55. [PMID: 12807766 PMCID: PMC1462586 DOI: 10.1093/genetics/164.2.443] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Cellular metabolic processes constantly generate reactive species that damage DNA. To counteract this relentless assault, cells have developed multiple pathways to resist damage. The base excision repair (BER) and nucleotide excision repair (NER) pathways remove damage whereas the recombination (REC) and postreplication repair (PRR) pathways bypass the damage, allowing deferred removal. Genetic studies in yeast indicate that these pathways can process a common spontaneous lesion(s), with mutational inactivation of any pathway increasing the burden on the remaining pathways. In this study, we examine the consequences of simultaneously compromising three or more of these pathways. Although the presence of a functional BER pathway alone is able to support haploid growth, retention of the NER, REC, or PRR pathway alone is not, indicating that BER is the key damage resistance pathway in yeast and may be responsible for the removal of the majority of either spontaneous DNA damage or specifically those lesions that are potentially lethal. In the diploid state, functional BER, NER, or REC alone can support growth, while PRR alone is insufficient for growth. In diploids, the presence of PRR alone may confer a lethal mutation load or, alternatively, PRR alone may be insufficient to deal with potentially lethal, replication-blocking lesions.
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Affiliation(s)
- Natalie J Morey
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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9
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Demple B, DeMott MS. Dynamics and diversions in base excision DNA repair of oxidized abasic lesions. Oncogene 2002; 21:8926-34. [PMID: 12483509 DOI: 10.1038/sj.onc.1206178] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Bruce Demple
- Department of Cancer Cell Biology, Harvard School of Public Health, Boston, MA 02115, USA.
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10
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Xiao W, Chow BL, Hanna M, Doetsch PW. Deletion of the MAG1 DNA glycosylase gene suppresses alkylation-induced killing and mutagenesis in yeast cells lacking AP endonucleases. Mutat Res 2001; 487:137-47. [PMID: 11738940 DOI: 10.1016/s0921-8777(01)00113-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
DNA base excision repair (BER) is initiated by DNA glycosylases that recognize and remove damaged bases. The phosphate backbone adjacent to the resulting apurinic/apyrimidinic (AP) site is then cleaved by an AP endonuclease or glycosylase-associated AP lyase to invoke subsequent BER steps. We have used a genetic approach in Saccharomyces cerevisiae to address whether AP sites are blocks to DNA replication and the biological consequences if AP sites persist in the genome. We found that yeast cells deficient in the two AP endonucleases (apn1 apn2 double mutant) are extremely sensitive to killing by methyl methanesulfonate (MMS), a model DNA alkylating agent. Interestingly, this sensitivity can be reduced up to 2500-fold by deleting the MAG1 3-methyladenine DNA glycosylase gene, suggesting that Mag1 not only removes lethal base lesions, but also benign lesions and possibly normal bases, and that the resulting AP sites are highly toxic to the cells. This rescuing effect appears to be specific for DNA alkylation damage, since the mag1 mutation reduces killing effects of two other DNA alkylating agents, but does not alter the sensitivity of apn cells to killing by UV, gamma-ray or H(2)O(2). Our mutagenesis assays indicate that nearly half of spontaneous and almost all MMS-induced mutations in the AP endonuclease-deficient cells are due to Mag1 DNA glycosylase activity. Although the DNA replication apparatus appears to be incapable of replicating past AP sites, Polzeta-mediated translesion synthesis is able to bypass AP sites, and accounts for all spontaneous and MMS-induced mutagenesis in the AP endonuclease-deficient cells. These results allow us to delineate base lesion flow within the BER pathway and link AP sites to other DNA damage repair and tolerance pathways.
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Affiliation(s)
- W Xiao
- Department of Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E5.
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11
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He YH, Wu M, Kobune M, Xu Y, Kelley MR, Martin WJ. Expression of yeast apurinic/apyrimidinic endonuclease (APN1) protects lung epithelial cells from bleomycin toxicity. Am J Respir Cell Mol Biol 2001; 25:692-8. [PMID: 11726394 DOI: 10.1165/ajrcmb.25.6.4550] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Bleomycin is a well-established anti-tumor drug. Its major untoward effect, pulmonary toxicity, has limited its usage. In this study, we used a DNA repair protein, yeast apurinic/apyrimidinic endonuclease (APN1) to reduce the toxicity of bleomycin on lung cells. A549 cells, an alveolar epithelial cell line, were transduced by MIEG3 retroviral vector encoding both enhanced green fluorescent protein (EGFP) and APN1. Transduced cells were sorted by fluorescent-activated cell sorter (FACS) analysis and were cloned. The APN1 expression of transduced A549 cell population and four selected clones expressing different levels of EGFP was confirmed by Northern, Western, and apurinic/apyrimidinic (AP) endonuclease activity analyses. The expression of APN1 was positively correlated with the expression of EGFP. The protective effect of APN1 against bleomycin was determined by single cell gel electrophoresis/Comet assay and by clonogenic survival assay following bleomycin treatment. The A549 population expressing APN1 showed a significant reduction of DNA damage in the presence of 20, 50, and 100 microg/ml bleomycin; similarly, the APN1-expressing A549 population also demonstrated increased survival in the presence of bleomycin compared with the vector-transduced A549 population. In selected clones, three of four APN1-expressing clones resulted in significantly improved cell survival. The current study suggests that the yeast DNA repair protein, APN1, can reduce bleomycin toxicity to target lung cells.
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Affiliation(s)
- Y H He
- Department of Medicine, Section of Hematology/Oncology, Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202-2879, USA
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12
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Vance JR, Wilson TE. Repair of DNA strand breaks by the overlapping functions of lesion-specific and non-lesion-specific DNA 3' phosphatases. Mol Cell Biol 2001; 21:7191-8. [PMID: 11585902 PMCID: PMC99894 DOI: 10.1128/mcb.21.21.7191-7198.2001] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Saccharomyces cerevisiae, the apurinic/apyrimidinic (AP) endonucleases Apn1 and Apn2 act as alternative pathways for the removal of various 3'-terminal blocking lesions from DNA strand breaks and in the repair of abasic sites, which both result from oxidative DNA damage. Here we demonstrate that Tpp1, a homologue of the 3' phosphatase domain of polynucleotide kinase, is a third member of this group of redundant 3' processing enzymes. Unlike Apn1 and Apn2, Tpp1 is specific for the removal of 3' phosphates at strand breaks and does not possess more general 3' phosphodiesterase, exonuclease, or AP endonuclease activities. Deletion of TPP1 in an apn1 apn2 mutant background dramatically increased the sensitivity of the double mutant to DNA damage caused by H2O2 and bleomycin but not to damage caused by methyl methanesulfonate. The triple mutant was also deficient in the repair of 3' phosphate lesions left by Tdp1-mediated cleavage of camptothecin-stabilized Top1-DNA covalent complexes. Finally, the tpp1 apn1 apn2 triple mutation displayed synthetic lethality in combination with rad52, possibly implicating postreplication repair in the removal of unrepaired 3'-terminal lesions resulting from endogenous damage. Taken together, these results demonstrate a clear role for the lesion-specific enzyme, Tpp1, in the repair of a subset of DNA strand breaks.
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Affiliation(s)
- J R Vance
- Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan 48109-0602, USA
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13
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Morey NJ, Greene CN, Jinks-Robertson S. Genetic analysis of transcription-associated mutation in Saccharomyces cerevisiae. Genetics 2000; 154:109-20. [PMID: 10628973 PMCID: PMC1460922 DOI: 10.1093/genetics/154.1.109] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
High levels of transcription are associated with elevated mutation rates in yeast, a phenomenon referred to as transcription-associated mutation (TAM). The transcription-associated increase in mutation rates was previously shown to be partially dependent on the Rev3p translesion bypass pathway, thus implicating DNA damage in TAM. In this study, we use reversion of a pGAL-driven lys2DeltaBgl allele to further examine the genetic requirements of TAM. We find that TAM is increased by disruption of the nucleotide excision repair or recombination pathways. In contrast, elimination of base excision repair components has only modest effects on TAM. In addition to the genetic studies, the lys2DeltaBgl reversion spectra of repair-proficient low and high transcription strains were obtained. In the low transcription spectrum, most of the frameshift events correspond to deletions of AT base pairs whereas in the high transcription strain, deletions of GC base pairs predominate. These results are discussed in terms of transcription and its role in DNA damage and repair.
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Affiliation(s)
- N J Morey
- Graduate Program in Genetics and Molecular Biology, Emory University, Atlanta, Georgia 30322, USA
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14
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Bennett RA. The Saccharomyces cerevisiae ETH1 gene, an inducible homolog of exonuclease III that provides resistance to DNA-damaging agents and limits spontaneous mutagenesis. Mol Cell Biol 1999; 19:1800-9. [PMID: 10022867 PMCID: PMC83973 DOI: 10.1128/mcb.19.3.1800] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The recently sequenced Saccharomyces cerevisiae genome was searched for a gene with homology to the gene encoding the major human AP endonuclease, a component of the highly conserved DNA base excision repair pathway. An open reading frame was found to encode a putative protein (34% identical to the Schizosaccharomyces pombe eth1(+) [open reading frame SPBC3D6.10] gene product) with a 347-residue segment homologous to the exonuclease III family of AP endonucleases. Synthesis of mRNA from ETH1 in wild-type cells was induced sixfold relative to that in untreated cells after exposure to the alkylating agent methyl methanesulfonate (MMS). To investigate the function of ETH1, deletions of the open reading frame were made in a wild-type strain and a strain deficient in the known yeast AP endonuclease encoded by APN1. eth1 strains were not more sensitive to killing by MMS, hydrogen peroxide, or phleomycin D1, whereas apn1 strains were approximately 3-fold more sensitive to MMS and approximately 10-fold more sensitive to hydrogen peroxide than was the wild type. Double-mutant strains (apn1 eth1) were approximately 15-fold more sensitive to MMS and approximately 2- to 3-fold more sensitive to hydrogen peroxide and phleomycin D1 than were apn1 strains. Elimination of ETH1 in apn1 strains also increased spontaneous mutation rates 9- or 31-fold compared to the wild type as determined by reversion to adenine or lysine prototrophy, respectively. Transformation of apn1 eth1 cells with an expression vector containing ETH1 reversed the hypersensitivity to MMS and limited the rate of spontaneous mutagenesis. Expression of ETH1 in a dut-1 xthA3 Escherichia coli strain demonstrated that the gene product functionally complements the missing AP endonuclease activity. Thus, in apn1 cells where the major AP endonuclease activity is missing, ETH1 offers an alternate capacity for repair of spontaneous or induced damage to DNA that is normally repaired by Apn1 protein.
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Affiliation(s)
- R A Bennett
- Department of Cancer Cell Biology, Harvard School of Public Health, Boston, Massachusetts 02115, USA.
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15
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Johnson RE, Torres-Ramos CA, Izumi T, Mitra S, Prakash S, Prakash L. Identification of APN2, the Saccharomyces cerevisiae homolog of the major human AP endonuclease HAP1, and its role in the repair of abasic sites. Genes Dev 1998; 12:3137-43. [PMID: 9765213 PMCID: PMC317187 DOI: 10.1101/gad.12.19.3137] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/1998] [Accepted: 08/14/1998] [Indexed: 11/24/2022]
Abstract
Abasic (AP) sites arise in DNA through spontaneous base loss and enzymatic removal of damaged bases. APN1 encodes the major AP-endonuclease of Saccharomyces cerevisiae. Human HAP1 (REF1) encodes the major AP endonuclease which, in addition to its role in DNA repair, functions as a redox regulatory protein. We identify APN2, the yeast homolog of HAP1 and provide evidence that Apn1 and Apn2 represent alternate pathways for repairing AP sites. The apn1Delta apn2Delta strain displays a highly elevated level of MMS-induced mutagenesis, which is dependent on the REV3, REV7, and REV1 genes. Our findings indicate that AP sites are highly cytotoxic and mutagenic in eukaryotes, and that the REV3, REV7-encoded DNA polymerase zeta mediates the mutagenic bypass of AP sites.
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Affiliation(s)
- R E Johnson
- Sealy Center for Molecular Science, University of Texas Medical Branch, Galveston, Texas 77555-1061, USA
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16
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Ramotar D, Belanger E, Brodeur I, Masson JY, Drobetsky EA. A yeast homologue of the human phosphotyrosyl phosphatase activator PTPA is implicated in protection against oxidative DNA damage induced by the model carcinogen 4-nitroquinoline 1-oxide. J Biol Chem 1998; 273:21489-96. [PMID: 9705277 DOI: 10.1074/jbc.273.34.21489] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The model carcinogen 4-nitroquinoline 1-oxide (4-NQO) has historically been characterized as "UV-mimetic" with respect to its genotoxic properties. However, recent evidence indicates that 4-NQO, unlike 254-nm UV light, may exert significant cytotoxic and/or mutagenic potential via the generation of reactive oxygen species. To elucidate the response of eukaryotic cells to 4-NQO-induced oxidative stress, we isolated Saccharomyces cerevisiae mutants exhibiting hypersensitivity to the cytotoxic effects of this mutagen. One such mutant, EBY1, was cross-sensitive to the oxidative agents UVA and diamide while retaining parental sensitivities to 254-nm UV light, methyl methanesulfonate, and ionizing radiation. A complementing gene (designated yPTPA1), restoring full UVA and 4-NQO resistance to EBY1 and encoding a protein that shares 40% identity with the human phosphotyrosyl phosphatase activator hPTPA, has been isolated. Targeted deletion of yPTPA1 in wild type yeast engendered the identical pattern of mutagen hypersensitivity as that manifested by EBY1, in addition to a spontaneous mutator phenotype that was markedly enhanced upon exposure to either UVA or 4-NQO but not to 254-nm UV or methyl methanesulfonate. Moreover, the yptpa1 deletion mutant exhibited a marked deficiency in the recovery of high molecular weight DNA following 4-NQO exposure, revealing a defect at the level of DNA repair. These data (i) strongly support a role for active oxygen intermediates in determining the genotoxic outcome of 4-NQO exposure and (ii) suggest a novel mechanism in yeast involving yPtpa1p-mediated activation of a phosphatase that participates in the repair of oxidative DNA damage, implying that hPTPA may exert a similar function in humans.
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Affiliation(s)
- D Ramotar
- Hôpital Maisonneuve-Rosemont, Centre de Recherche, Université de Montréal, Montréal, Québec H1T 2M4, Canada.
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Ramotar D, Vadnais J, Masson JY, Tremblay S. Schizosaccharomyces pombe apn1 encodes a homologue of the Escherichia coli endonuclease IV family of DNA repair proteins. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1396:15-20. [PMID: 9524207 DOI: 10.1016/s0167-4781(97)00160-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The Apn1 protein of the budding yeast Saccharomyces cerevisiae is a DNA repair enzyme that hydrolyzes apurinic/apyrimidinic (AP) sites and removes 3'-blocking groups present at single strand breaks of damaged DNA. Yeast cells lacking Apn1 are hypersensitive to DNA damaging agents that produce AP sites and DNA strand breaks with blocked 3'-termini. In this study, we showed that the fission yeast Schizosaccharomyces pombe bears a homologue, Spapn1, that is 45% identical to S. cerevisiae Apn1. However, the Spapn1 gene is apparently not expressed. Active expression of S. cerevisiae Apn1 in S. pombe conferred no additional resistance to DNA damaging agents. These data suggest that the pathway by which S. pombe repairs AP sites is independent of a functional Apn1-like AP endonuclease.
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Affiliation(s)
- D Ramotar
- Maisonneuve-Rosemont Hospital, Research Center, Montreal, Que., Canada.
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Wang Z, Wu X, Friedberg EC. Molecular mechanism of base excision repair of uracil-containing DNA in yeast cell-free extracts. J Biol Chem 1997; 272:24064-71. [PMID: 9295360 DOI: 10.1074/jbc.272.38.24064] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Base excision repair (BER) constitutes a ubiquitous excision repair mechanism, which is responsible for the removal of multiple types of damaged and inappropriate bases in DNA. We have employed a yeast cell-free system to examine the biochemical mechanism of the BER pathway in lower eukaryotes. Using uracil-containing DNA as a model substrate, we demonstrate that yeast BER requires Apn1 protein, an Escherichia coli endonuclease IV homolog. In extracts of an apn1 deletion mutant, the 5'-incision at AP (apurinic/apyrimidinic) sites is not detectable, supporting the notion that yeast contains only one major 5'-AP endonuclease. The processing of the 5'-deoxyribose phosphate moieties was found to be a rate-limiting step. During BER of uracil-containing DNA, repair patch sizes of 1-5 nucleotides were detected, with single nucleotide repair patches predominant.
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Affiliation(s)
- Z Wang
- Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536, USA.
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Ramotar D. The apurinic–apyrimidinic endonuclease IV family of DNA repair enzymes. Biochem Cell Biol 1997. [DOI: 10.1139/o97-046] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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