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Pai CC, Durley SC, Cheng WC, Chiang NY, Peters J, Kasparek T, Blaikley E, Wee BY, Walker C, Kearsey SE, Buffa F, Murray JM, Humphrey TC. Homologous recombination suppresses transgenerational DNA end resection and chromosomal instability in fission yeast. Nucleic Acids Res 2023; 51:3205-3222. [PMID: 36951111 PMCID: PMC10123110 DOI: 10.1093/nar/gkad160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Revised: 02/13/2023] [Accepted: 02/23/2023] [Indexed: 03/24/2023] Open
Abstract
Chromosomal instability (CIN) drives cell-to-cell heterogeneity, and the development of genetic diseases, including cancer. Impaired homologous recombination (HR) has been implicated as a major driver of CIN, however, the underlying mechanism remains unclear. Using a fission yeast model system, we establish a common role for HR genes in suppressing DNA double-strand break (DSB)-induced CIN. Further, we show that an unrepaired single-ended DSB arising from failed HR repair or telomere loss is a potent driver of widespread CIN. Inherited chromosomes carrying a single-ended DSB are subject to cycles of DNA replication and extensive end-processing across successive cell divisions. These cycles are enabled by Cullin 3-mediated Chk1 loss and checkpoint adaptation. Subsequent propagation of unstable chromosomes carrying a single-ended DSB continues until transgenerational end-resection leads to fold-back inversion of single-stranded centromeric repeats and to stable chromosomal rearrangements, typically isochromosomes, or to chromosomal loss. These findings reveal a mechanism by which HR genes suppress CIN and how DNA breaks that persist through mitotic divisions propagate cell-to-cell heterogeneity in the resultant progeny.
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Affiliation(s)
- Chen-Chun Pai
- MRC Oxford Institute for Radiation Oncology & Biology, Department of Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Samuel C Durley
- MRC Oxford Institute for Radiation Oncology & Biology, Department of Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Wei-Chen Cheng
- MRC Oxford Institute for Radiation Oncology & Biology, Department of Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Nien-Yi Chiang
- MRC Oxford Institute for Radiation Oncology & Biology, Department of Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Jennifer Peters
- MRC Oxford Institute for Radiation Oncology & Biology, Department of Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Torben Kasparek
- MRC Oxford Institute for Radiation Oncology & Biology, Department of Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Elizabeth Blaikley
- MRC Oxford Institute for Radiation Oncology & Biology, Department of Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Boon-Yu Wee
- MRC Oxford Institute for Radiation Oncology & Biology, Department of Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Carol Walker
- MRC Oxford Institute for Radiation Oncology & Biology, Department of Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Stephen E Kearsey
- Department of Biology, University of Oxford, Zoology Research and Administration Building, Mansfield Road, Oxford OX1 3SZ, UK
| | - Francesca Buffa
- MRC Oxford Institute for Radiation Oncology & Biology, Department of Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Johanne M Murray
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, SussexBN1 9RQ, UK
| | - Timothy C Humphrey
- MRC Oxford Institute for Radiation Oncology & Biology, Department of Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
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Kolobynina KG, Rapp A, Cardoso MC. Chromatin Ubiquitination Guides DNA Double Strand Break Signaling and Repair. Front Cell Dev Biol 2022; 10:928113. [PMID: 35865631 PMCID: PMC9294282 DOI: 10.3389/fcell.2022.928113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 06/16/2022] [Indexed: 11/13/2022] Open
Abstract
Chromatin is the context for all DNA-based molecular processes taking place in the cell nucleus. The initial chromatin structure at the site of the DNA damage determines both, lesion generation and subsequent activation of the DNA damage response (DDR) pathway. In turn, proceeding DDR changes the chromatin at the damaged site and across large fractions of the genome. Ubiquitination, besides phosphorylation and methylation, was characterized as an important chromatin post-translational modification (PTM) occurring at the DNA damage site and persisting during the duration of the DDR. Ubiquitination appears to function as a highly versatile “signal-response” network involving several types of players performing various functions. Here we discuss how ubiquitin modifiers fine-tune the DNA damage recognition and response and how the interaction with other chromatin modifications ensures cell survival.
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Li Y, Guo J, Zhang H, Lam CW, Luo W, Zhou H, Zhang W. Protective Effect of Thymidine on DNA Damage Induced by Hydrogen Peroxide in Human Hepatocellular Cancer Cells. ACS OMEGA 2020; 5:21796-21804. [PMID: 32905386 PMCID: PMC7469367 DOI: 10.1021/acsomega.0c02843] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 08/04/2020] [Indexed: 06/11/2023]
Abstract
Intracellular ribonucleotide (RN) and deoxyribonucleotide (dRN) pool sizes are critical for the fidelity of DNA synthesis. They are likely to be severely perturbed by many factors which disrupt the integrity and stability of DNA, leading to DNA damage. Exogenously supplied nucleosides are able to increase the deoxynucleoside triphosphate pools, then reverse the DNA damage, and decrease the oncogene-induced transformation dramatically. In this study, the impact of thymidine on the hydrogen peroxide (H2O2)-induced DNA damage was investigated in HepG2 liver cancer cells. From the result of the comet assay, the tail length of cells in the thymidine 600 μM + H2O2 1.0 mM group was dramatically decreased from 42.1 ± 10.8 to 21.9 ± 2.4 μm compared to that exposed with 1.0 mM H2O2 (p < 0.05), suggesting that pretreatment of thymidine reduced the DNA damage of HepG2 cells. Although the RN and dRN contents decreased in the damage group, most of them presented increasing tendency when pretreated with thymidine, especially the key metabolites dCTP, which was mainly related with the decline in the rate of DNA synthesis. The restoration also showed a significant G0/G1 phase arrest of cell cycle progression from 44.6 ± 2.2 to 56.6 ± 0.4% after pretreated with thymidine (p < 0.05). In conclusion, our data demonstrated that the pretreatment with thymidine had a potential protective ability against oxidative damage for DNA in HepG2 cells through the perturbation of RN and dRN pools as well as cell cycle arrest, which should provide new insights into the molecular basis of preventing H2O2-induced oxidative DNA damage in mammalian cells.
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CRL4Cdt2 ubiquitin ligase regulates Dna2 and Rad16 (XPF) nucleases by targeting Pxd1 for degradation. PLoS Genet 2020; 16:e1008933. [PMID: 32692737 PMCID: PMC7394458 DOI: 10.1371/journal.pgen.1008933] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 07/31/2020] [Accepted: 06/15/2020] [Indexed: 01/19/2023] Open
Abstract
Structure-specific endonucleases (SSEs) play key roles in DNA replication, recombination, and repair. SSEs must be tightly regulated to ensure genome stability but their regulatory mechanisms remain incompletely understood. Here, we show that in the fission yeast Schizosaccharomyces pombe, the activities of two SSEs, Dna2 and Rad16 (ortholog of human XPF), are temporally controlled during the cell cycle by the CRL4Cdt2 ubiquitin ligase. CRL4Cdt2 targets Pxd1, an inhibitor of Dna2 and an activator of Rad16, for degradation in S phase. The ubiquitination and degradation of Pxd1 is dependent on CRL4Cdt2, PCNA, and a PCNA-binding degron motif on Pxd1. CRL4Cdt2-mediated Pxd1 degradation prevents Pxd1 from interfering with the normal S-phase functions of Dna2. Moreover, Pxd1 degradation leads to a reduction of Rad16 nuclease activity in S phase, and restrains Rad16-mediated single-strand annealing, a hazardous pathway of repairing double-strand breaks. These results demonstrate a new role of the CRL4Cdt2 ubiquitin ligase in genome stability maintenance and shed new light on how SSE activities are regulated during the cell cycle. Structure-specific endonucleases are enzymes that process DNA intermediates generated in DNA replication, recombination, and repair. Proper regulation of these enzymes is critical for maintaining genome stability. Dna2 and XPF are two such enzymes present across eukaryotes, from yeasts to humans. Here, we show that in the fission yeast Schizosaccharomyces pombe, the activities of Dna2 and Rad16 (the equivalent of human XPF) are temporally controlled during the cell cycle by the CRL4Cdt2 ubiquitin E3 ligase. In the S phase of the cell cycle, CRL4Cdt2 promotes the degradation of Pxd1, which is an inhibitor of Dna2 and an activator of Rad16. Through targeting Pxd1 for degradation, CRL4Cdt2 increases the activity of Dna2 in S phase and is important for the normal S-phase function of Dna2. Meanwhile, the degradation of Pxd1 reduces the activity of Rad16 in S phase, and curtails Rad16-dependent single-strand annealing, a mutagenic DNA repair pathway. Our findings uncover a new mechanism regulating two important endonucleases during the cell cycle, and reveal a new way of coordinating endonucleases to safeguard genome stability.
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Regulation of Histone Ubiquitination in Response to DNA Double Strand Breaks. Cells 2020; 9:cells9071699. [PMID: 32708614 PMCID: PMC7407225 DOI: 10.3390/cells9071699] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 07/10/2020] [Accepted: 07/14/2020] [Indexed: 12/11/2022] Open
Abstract
Eukaryotic cells are constantly exposed to both endogenous and exogenous stressors that promote the induction of DNA damage. Of this damage, double strand breaks (DSBs) are the most lethal and must be efficiently repaired in order to maintain genomic integrity. Repair of DSBs occurs primarily through one of two major pathways: non-homologous end joining (NHEJ) or homologous recombination (HR). The choice between these pathways is in part regulated by histone post-translational modifications (PTMs) including ubiquitination. Ubiquitinated histones not only influence transcription and chromatin architecture at sites neighboring DSBs but serve as critical recruitment platforms for repair machinery as well. The reversal of these modifications by deubiquitinating enzymes (DUBs) is increasingly being recognized in a number of cellular processes including DSB repair. In this context, DUBs ensure proper levels of ubiquitin, regulate recruitment of downstream effectors, dictate repair pathway choice, and facilitate appropriate termination of the repair response. This review outlines the current understanding of histone ubiquitination in response to DSBs, followed by a comprehensive overview of the DUBs that catalyze the removal of these marks.
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Milo S, Harari-Misgav R, Hazkani-Covo E, Covo S. Limited DNA Repair Gene Repertoire in Ascomycete Yeast Revealed by Comparative Genomics. Genome Biol Evol 2020; 11:3409-3423. [PMID: 31693105 PMCID: PMC7145719 DOI: 10.1093/gbe/evz242] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/31/2019] [Indexed: 12/11/2022] Open
Abstract
Ascomycota is the largest phylogenetic group of fungi that includes species important to human health and wellbeing. DNA repair is important for fungal survival and genome evolution. Here, we describe a detailed comparative genomic analysis of DNA repair genes in Ascomycota. We determined the DNA repair gene repertoire in Taphrinomycotina, Saccharomycotina, Leotiomycetes, Sordariomycetes, Dothideomycetes, and Eurotiomycetes. The subphyla of yeasts, Saccharomycotina and Taphrinomycotina, have a smaller DNA repair gene repertoire comparing to Pezizomycotina. Some genes were absent from most, if not all, yeast species. To study the conservation of these genes in Pezizomycotina, we used the Gain Loss Mapping Engine algorithm that provides the expectations of gain or loss of genes given the tree topology. Genes that were absent from most of the species of Taphrinomycotina or Saccharomycotina showed lower conservation in Pezizomycotina. This suggests that the absence of some DNA repair in yeasts is not random; genes with a tendency to be lost in other classes are missing. We ranked the conservation of DNA repair genes in Ascomycota. We found that Rad51 and its paralogs were less conserved than other recombinational proteins, suggesting that there is a redundancy between Rad51 and its paralogs, at least in some species. Finally, based on the repertoire of UV repair genes, we found conditions that differentially kill the wine pathogen Brettanomyces bruxellensis and not Saccharomyces cerevisiae. In summary, our analysis provides testable hypotheses to the role of DNA repair proteins in the genome evolution of Ascomycota.
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Affiliation(s)
- Shira Milo
- Department of Plant Pathology and Microbiology, Hebrew University, Rehovot, Israel
| | - Reut Harari-Misgav
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, Israel
| | - Einat Hazkani-Covo
- Department of Natural and Life Sciences, The Open University of Israel, Ra'anana, Israel
| | - Shay Covo
- Department of Plant Pathology and Microbiology, Hebrew University, Rehovot, Israel
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Covo S. Genomic Instability in Fungal Plant Pathogens. Genes (Basel) 2020; 11:E421. [PMID: 32295266 PMCID: PMC7230313 DOI: 10.3390/genes11040421] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 03/29/2020] [Accepted: 04/10/2020] [Indexed: 02/07/2023] Open
Abstract
Fungi and fungal-like organisms (oomycetes) that cause diseases in plants have impacted human communities for centuries and probably from the dawn of agriculture. In modern agriculture, there is a constant race between new strategies to manage fungal plant pathogens and their ability to adapt. An important component in this race is fungal genetic diversity. Mechanisms such as sexual and parasexual recombination that contribute to the creation of novel allele combinations in fungal plant pathogens are briefly discussed in the first part of this review. Advances in genomics have enabled the investigation of chromosomal aberrations of agriculturally important fungal isolates at the nucleotide level. Some of these cases are summarized in the second part of this review; it is claimed that the effect of chromosomal aberrations on pathogenicity should be studied mechanistically. More data on the effect of gene copy number variations on phenotypes that are relevant to agriculture are especially needed. Genome rearrangements through translocations have shaped the genome of fungal plant pathogens by creating lineage-specific chromosome territories encoding for genes participating in plant diseases. Pathogenicity chromosomes are unique cases of such lineage-specific genetic elements, interestingly these chromosomes can be transferred horizontally and thus transforming a non-pathogenic strain to a pathogenic one. The third part of this review describes our attempts to reveal mutators in fungal plant pathogens by identifying fungi that lack important DNA repair genes or respond to DNA damage in an unconventional way. We found that a group of fungal plant pathogens lack conserved genes that are needed for an important Holliday junction resolution pathway. In addition, in Fusarium oxysporum, the rate-limiting step in dNTP production is not induced under DNA replication stress. This is very different from organisms from bacteria to humans. It remains to be seen if these mechanisms promote genetic instability in fungal plant pathogens.
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Affiliation(s)
- Shay Covo
- Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University, Rehovot 76100001, Israel
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Schizosaccharomyces pombe Assays to Study Mitotic Recombination Outcomes. Genes (Basel) 2020; 11:genes11010079. [PMID: 31936815 PMCID: PMC7016768 DOI: 10.3390/genes11010079] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 01/07/2020] [Accepted: 01/07/2020] [Indexed: 01/16/2023] Open
Abstract
The fission yeast—Schizosaccharomyces pombe—has emerged as a powerful tractable system for studying DNA damage repair. Over the last few decades, several powerful in vivo genetic assays have been developed to study outcomes of mitotic recombination, the major repair mechanism of DNA double strand breaks and stalled or collapsed DNA replication forks. These assays have significantly increased our understanding of the molecular mechanisms underlying the DNA damage response pathways. Here, we review the assays that have been developed in fission yeast to study mitotic recombination.
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Fouad S, Wells OS, Hill MA, D'Angiolella V. Cullin Ring Ubiquitin Ligases (CRLs) in Cancer: Responses to Ionizing Radiation (IR) Treatment. Front Physiol 2019; 10:1144. [PMID: 31632280 PMCID: PMC6781834 DOI: 10.3389/fphys.2019.01144] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 08/22/2019] [Indexed: 12/19/2022] Open
Abstract
Treatment with ionizing radiation (IR) remains the cornerstone of therapy for multiple cancer types, including disseminated and aggressive diseases in the palliative setting. Radiotherapy efficacy could be improved in combination with drugs that regulate the ubiquitin-proteasome system (UPS), many of which are currently being tested in clinical trials. The UPS operates through the covalent attachment of ATP-activated ubiquitin molecules onto substrates following the transfer of ubiquitin from an E1, to an E2, and then to the substrate via an E3 enzyme. The specificity of ubiquitin ligation is dictated by E3 ligases, which select substrates to be ubiquitylated. Among the E3s, cullin ring ubiquitin ligases (CRLs) represent prototypical multi-subunit E3s, which use the cullin subunit as a central assembling scaffold. CRLs have crucial roles in controlling the cell cycle, hypoxia signaling, reactive oxygen species clearance and DNA repair; pivotal factors regulating the cancer and normal tissue response to IR. Here, we summarize the findings on the involvement of CRLs in the response of cancer cells to IR, and we discuss the therapeutic approaches to target the CRLs which could be exploited in the clinic.
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Affiliation(s)
- Shahd Fouad
- Medical Research Council Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, United Kingdom
| | - Owen S Wells
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | - Mark A Hill
- Medical Research Council Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, United Kingdom
| | - Vincenzo D'Angiolella
- Medical Research Council Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, United Kingdom
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Andreadis C, Hulme L, Wensley K, Liu JL. The TOR pathway modulates cytoophidium formation in Schizosaccharomyces pombe. J Biol Chem 2019; 294:14686-14703. [PMID: 31431504 PMCID: PMC6779450 DOI: 10.1074/jbc.ra119.009913] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Revised: 08/09/2019] [Indexed: 12/30/2022] Open
Abstract
CTP synthase (CTPS) has been demonstrated to form evolutionarily-conserved filamentous structures termed cytoophidia whose exact cellular functions remain unclear, but they may play a role in intracellular compartmentalization. We have previously shown that the mammalian target of rapamycin complex 1 (mTORC1)-S6K1 pathway mediates cytoophidium assembly in mammalian cells. Here, using the fission yeast Schizosaccharomyces pombe as a model of a unicellular eukaryote, we demonstrate that the target of rapamycin (TOR)-signaling pathway regulates cytoophidium formation (from the S. pombe CTPS ortholog Cts1) also in S. pombe Conducting a systematic analysis of all viable single TOR subunit-knockout mutants and of several major downstream effector proteins, we found that Cts1 cytoophidia are significantly shortened and often dissociate when TOR is defective. We also found that the activities of the downstream effector kinases of the TORC1 pathway, Sck1, Sck2, and Psk1 S6, as well as of the S6K/AGC kinase Gad8, the major downstream effector kinase of the TORC2 pathway, are necessary for proper cytoophidium filament formation. Interestingly, we observed that the Crf1 transcriptional corepressor for ribosomal genes is a strong effector of Cts1 filamentation. Our findings connect TOR signaling, a major pathway required for cell growth, with the compartmentalization of the essential nucleotide synthesis enzyme CTPS, and we uncover differences in the regulation of its filamentation among higher multicellular and unicellular eukaryotic systems.
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Affiliation(s)
- Christos Andreadis
- School of Life Sciences and Technology, ShanghaiTech University, 201210 Shanghai, China
| | - Lydia Hulme
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom
| | - Katherine Wensley
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom
| | - Ji-Long Liu
- School of Life Sciences and Technology, ShanghaiTech University, 201210 Shanghai, China .,MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom
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Cohen R, Milo S, Sharma S, Savidor A, Covo S. Ribonucleotide reductase from Fusarium oxysporum does not Respond to DNA replication stress. DNA Repair (Amst) 2019; 83:102674. [PMID: 31375409 DOI: 10.1016/j.dnarep.2019.102674] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 07/22/2019] [Accepted: 07/22/2019] [Indexed: 12/14/2022]
Abstract
Ribonucleotide reductase (RNR) catalyzes the rate limiting step in dNTP biosynthesis and is tightly regulated at the transcription and activity levels. One of the best characterized responses of yeast to DNA damage is up-regulation of RNR transcription and activity and consequently, elevation of the dNTP pools. Hydroxyurea is a universal inhibitor of RNR that causes S phase arrest. It is used in the clinic to treat certain types of cancers. Here we studied the response of the fungal plant pathogen Fusarium oxysporum to hydroxyurea in order to generate hypotheses that can be used in the future in development of a new class of pesticides. F. oxysporum causes severe damage to more than 100 agricultural crops and specifically threatens banana cultivation world-wide. Although the recovery of F. oxysporum from transient hydroxyurea exposure was similar to the one of Saccharomyces cerevisiae, colony formation was strongly inhibited in F. oxysporum in comparison with S. cerevisiae. As expected, genomic and phosphoproteomic analyses of F. oxysporum conidia (spores) exposed to hydroxyurea showed hallmarks of DNA replication perturbation and activation of recombination. Unexpectedly and strikingly, RNR was not induced by either hydroxyurea or the DNA-damaging agent methyl methanesulfonate as determined at the RNA and protein levels. Consequently, dNTP concentrations were significantly reduced, even in response to a low dose of hydroxyurea. Methyl methanesulfonate treatment did not induce dNTP pools in F. oxysporum, in contrast to the response of RNR and dNTP pools to DNA damage and hydroxyurea in several tested organisms. Our results are important because the lack of a feedback mechanism to increase RNR expression in F. oxysporum is expected to sensitize the pathogen to a fungal-specific ribonucleotide inhibitor. The potential impact of our observations on F. oxysporum genome stability and genome evolution is discussed.
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Affiliation(s)
- Rotem Cohen
- Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University, Rehovot, 76100, Israel
| | - Shira Milo
- Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University, Rehovot, 76100, Israel
| | - Sushma Sharma
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden
| | - Alon Savidor
- de Botton Institute for Protein Profiling, the Nancy and Stephen Grand Israel National Center for Personalized Medicine, Weizmann Institute of Science, Rehovot, 76100, Israel
| | - Shay Covo
- Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University, Rehovot, 76100, Israel.
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12
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Milo-Cochavi S, Pareek M, Delulio G, Almog Y, Anand G, Ma LJ, Covo S. The response to the DNA damaging agent methyl methanesulfonate in a fungal plant pathogen. Fungal Biol 2019; 123:408-422. [PMID: 31053330 DOI: 10.1016/j.funbio.2019.03.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 02/27/2019] [Accepted: 03/05/2019] [Indexed: 12/31/2022]
Abstract
DNA damage can cause mutations that in fungal plant pathogens lead to hypervirulence and resistance to pesticides. Almost nothing is known about the response of these fungi to DNA damage. We performed transcriptomic and phosphoproteomic analyses of Fusarium oxysporum exposed to methyl methanesulfonate (MMS). At the RNA level we observe massive induction of DNA repair pathways including the global genome nucleotide excision. Cul3, Cul4, several Ubiquitin-like ligases and components of the proteasome are significantly induced. In agreement, we observed drug synergism between a proteasome inhibitor and MMS. While our data suggest that Yap1 and Xbp1 networks are similarly activated in response to damage in yeast and F. oxysporum we were able to observe modules that were MMS-responsive in F. oxysporum and not in yeast. These include transcription/splicing modules that are upregulated and respiration that is down-regulated. In agreement, MMS treated cells are much more sensitive to a respiration inhibitor. At the phosphoproteomic level, Adenylate cyclase, which generates cAMP, is phosphorylated in response to MMS and forms a network of phosphorylated proteins that include cell cycle regulators and several MAPKs. Our analysis provides a starting point in understanding how genomic changes in response to DNA damage occur in Fusarium species.
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Affiliation(s)
- Shira Milo-Cochavi
- Department of Plant Pathology and Microbiology, Hebrew University, Rehovot, 7610001, Israel
| | - Manish Pareek
- Department of Plant Pathology and Microbiology, Hebrew University, Rehovot, 7610001, Israel
| | - Gregory Delulio
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA 01003, USA
| | - Yael Almog
- Department of Plant Pathology and Microbiology, Hebrew University, Rehovot, 7610001, Israel
| | - Gautam Anand
- Department of Plant Pathology and Microbiology, Hebrew University, Rehovot, 7610001, Israel
| | - Li-Jun Ma
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA 01003, USA
| | - Shay Covo
- Department of Plant Pathology and Microbiology, Hebrew University, Rehovot, 7610001, Israel.
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13
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Pai CC, Hsu KF, Durley SC, Keszthelyi A, Kearsey SE, Rallis C, Folkes LK, Deegan R, Wilkins SE, Pfister SX, De León N, Schofield CJ, Bähler J, Carr AM, Humphrey TC. An essential role for dNTP homeostasis following CDK-induced replication stress. J Cell Sci 2019; 132:jcs226969. [PMID: 30674555 PMCID: PMC6451416 DOI: 10.1242/jcs.226969] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 01/02/2019] [Indexed: 02/03/2023] Open
Abstract
Replication stress is a common feature of cancer cells, and thus a potentially important therapeutic target. Here, we show that cyclin-dependent kinase (CDK)-induced replication stress, resulting from Wee1 inactivation, is synthetic lethal with mutations disrupting dNTP homeostasis in fission yeast. Wee1 inactivation leads to increased dNTP demand and replication stress through CDK-induced firing of dormant replication origins. Subsequent dNTP depletion leads to inefficient DNA replication, DNA damage and to genome instability. Cells respond to this replication stress by increasing dNTP supply through histone methyltransferase Set2-dependent MBF-induced expression of Cdc22, the catalytic subunit of ribonucleotide reductase (RNR). Disrupting dNTP synthesis following Wee1 inactivation, through abrogating Set2-dependent H3K36 tri-methylation or DNA integrity checkpoint inactivation results in critically low dNTP levels, replication collapse and cell death, which can be rescued by increasing dNTP levels. These findings support a 'dNTP supply and demand' model in which maintaining dNTP homeostasis is essential to prevent replication catastrophe in response to CDK-induced replication stress.
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Affiliation(s)
- Chen-Chun Pai
- CRUK-MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, ORCRB, Roosevelt Drive, Oxford, OX3 7DQ, UK
| | - Kuo-Feng Hsu
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, OX1 3TA, UK
- Department of Surgery, Tri-Service General Hospital, National Defense Medical Centre, Taipei 114, Taiwan
| | - Samuel C Durley
- CRUK-MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, ORCRB, Roosevelt Drive, Oxford, OX3 7DQ, UK
| | - Andrea Keszthelyi
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, Sussex, BN1 9RQ, UK
| | - Stephen E Kearsey
- Department of Zoology, University of Oxford, Zoology Research & Administration Building, Mansfield Road, Oxford, OX1 3PS, UK
| | - Charalampos Rallis
- Research Department of Genetics, Evolution & Environment, University College London, London, WC1E 6BT, UK
- School of Health, Sport and Bioscience, University of East London, Stratford Campus, E15 4LZ, London, UK
| | - Lisa K Folkes
- CRUK-MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, ORCRB, Roosevelt Drive, Oxford, OX3 7DQ, UK
| | - Rachel Deegan
- CRUK-MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, ORCRB, Roosevelt Drive, Oxford, OX3 7DQ, UK
| | - Sarah E Wilkins
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, OX1 3TA, UK
| | - Sophia X Pfister
- CRUK-MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, ORCRB, Roosevelt Drive, Oxford, OX3 7DQ, UK
| | - Nagore De León
- Department of Zoology, University of Oxford, Zoology Research & Administration Building, Mansfield Road, Oxford, OX1 3PS, UK
| | - Christopher J Schofield
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, OX1 3TA, UK
| | - Jürg Bähler
- Research Department of Genetics, Evolution & Environment, University College London, London, WC1E 6BT, UK
| | - Antony M Carr
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, Sussex, BN1 9RQ, UK
| | - Timothy C Humphrey
- CRUK-MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, ORCRB, Roosevelt Drive, Oxford, OX3 7DQ, UK
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14
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Mlak R, Powrózek T, Brzozowska A, Homa-Mlak I, Mazurek M, Małecka-Massalska T. RRM1 gene expression evaluated in the liquid biopsy (blood cfRNA) as a non-invasive, predictive factor for radiotherapy-induced oral mucositis and potential prognostic biomarker in head and neck cancer patients. Cancer Biomark 2018; 22:657-667. [DOI: 10.3233/cbm-171082] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Radosław Mlak
- Department of Human Physiology, Medical University of Lublin, Lublin, Poland
| | - Tomasz Powrózek
- Department of Human Physiology, Medical University of Lublin, Lublin, Poland
| | - Anna Brzozowska
- Department of Oncology, Medical University of Lublin, Lublin, Poland
| | - Iwona Homa-Mlak
- Department of Human Physiology, Medical University of Lublin, Lublin, Poland
| | - Marcin Mazurek
- Department of Human Physiology, Medical University of Lublin, Lublin, Poland
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15
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Abstract
DNA double-strand breaks (DSBs), arising during normal DNA metabolism or following exposure to mutagenic agents such as ionizing radiation can lead to chromosomal rearrangements and genome instability, and are potentially lethal if unrepaired. Therefore, understanding the mechanisms of DSB repair and misrepair, and identifying the factors involved in these processes is of biological as well as medical interest. Here we describe a DSB assay in Schizosaccharomyces pombe that can be used to identify and quantify different repair, misrepair, and failed repair events resulting from a site-specific DSB within the context of a nonessential minichromosome, Ch16 This assay can be used to determine the contribution of most genes or genetic backgrounds to DSB repair and genome stability, and can also provide mechanistic insights into their function.
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Affiliation(s)
- Chen-Chun Pai
- CRUK-MRC Institute for Radiation Oncology, University of Oxford, Department of Oncology, ORCRB, Oxford OX3 7DQ, United Kingdom
| | - Elizabeth Blaikley
- CRUK-MRC Institute for Radiation Oncology, University of Oxford, Department of Oncology, ORCRB, Oxford OX3 7DQ, United Kingdom
| | - Timothy C Humphrey
- CRUK-MRC Institute for Radiation Oncology, University of Oxford, Department of Oncology, ORCRB, Oxford OX3 7DQ, United Kingdom
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16
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Abstract
The fission yeast Schizosaccharomyces pombe is an excellent model organism to study DNA metabolism, in which the DNA replication and repair mechanisms are evolutionarily conserved. In this introduction we describe a range of methods commonly used to study aspects of DNA metabolism in fission yeast, focusing on approaches used for the analysis of genome stability, DNA replication, and DNA repair. We describe the use of a minichromosome, Ch16, for monitoring different aspects of genome stability. We introduce two-dimensional gel electrophoresis and immunofluorescent visualization of combed DNA molecules for the analysis of DNA replication. Further, we introduce a pulsed field gel electrophoresis (PFGE) assay to physically monitor chromosome integrity, which can be used in conjunction with a DNA double-strand break (DSB) repair assay to genetically quantitate different DSB repair and misrepair outcomes, including gross chromosomal rearrangements, in fission yeast.
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Affiliation(s)
- Francisco Antequera
- Instituto de Biología Funcional y Genómica, CSIC/Universidad de Salamanca, Salamanca 37007, Spain
| | - Timothy C Humphrey
- CRUK-MRC Oxford Institute for Radiation Oncology, University of Oxford, OX3 7DQ, United Kingdom
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17
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Pai CC, Kishkevich A, Deegan RS, Keszthelyi A, Folkes L, Kearsey SE, De León N, Soriano I, de Bruin RAM, Carr AM, Humphrey TC. Set2 Methyltransferase Facilitates DNA Replication and Promotes Genotoxic Stress Responses through MBF-Dependent Transcription. Cell Rep 2017; 20:2693-2705. [PMID: 28903048 PMCID: PMC5608972 DOI: 10.1016/j.celrep.2017.08.058] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 06/10/2017] [Accepted: 08/17/2017] [Indexed: 11/24/2022] Open
Abstract
Chromatin modification through histone H3 lysine 36 methylation by the SETD2 tumor suppressor plays a key role in maintaining genome stability. Here, we describe a role for Set2-dependent H3K36 methylation in facilitating DNA replication and the transcriptional responses to both replication stress and DNA damage through promoting MluI cell-cycle box (MCB) binding factor (MBF)-complex-dependent transcription in fission yeast. Set2 loss leads to reduced MBF-dependent ribonucleotide reductase (RNR) expression, reduced deoxyribonucleoside triphosphate (dNTP) synthesis, altered replication origin firing, and a checkpoint-dependent S-phase delay. Accordingly, prolonged S phase in the absence of Set2 is suppressed by increasing dNTP synthesis. Furthermore, H3K36 is di- and tri-methylated at these MBF gene promoters, and Set2 loss leads to reduced MBF binding and transcription in response to genotoxic stress. Together, these findings provide new insights into how H3K36 methylation facilitates DNA replication and promotes genotoxic stress responses in fission yeast.
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Affiliation(s)
- Chen-Chun Pai
- CRUK-MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, ORCRB, Roosevelt Drive, Oxford OX3 7DQ, UK.
| | - Anastasiya Kishkevich
- MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6B, UK
| | - Rachel S Deegan
- CRUK-MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, ORCRB, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Andrea Keszthelyi
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, Sussex BN1 9RQ, UK
| | - Lisa Folkes
- CRUK-MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, ORCRB, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Stephen E Kearsey
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
| | - Nagore De León
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
| | - Ignacio Soriano
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
| | | | - Antony M Carr
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, Sussex BN1 9RQ, UK
| | - Timothy C Humphrey
- CRUK-MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, ORCRB, Roosevelt Drive, Oxford OX3 7DQ, UK.
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18
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Abstract
Cullin 4B (CUL4B) is a scaffold of the Cullin4B-Ring E3 ligase complex (CRL4B) that plays an important role in proteolysis and is implicated in tumorigenesis. Aberrant expression of CUL4B has been reported in various types of human diseases. Recently, studies have shown that CUL4B was overexpressed in a multitude of solid neoplasms and affect the expression of several tumor suppressor genes. In this review, we aim to summarize the biological function of CUL4B in order to better understand its pathogenesis in human cancers.
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Affiliation(s)
- Ying Li
- Department of Hematology, Shandong Provincial Hospital Affiliated to Shandong University, No.324, Jingwu Road, Jinan, 250021 Shandong People's Republic of China
| | - Xin Wang
- Department of Hematology, Shandong Provincial Hospital Affiliated to Shandong University, No.324, Jingwu Road, Jinan, 250021 Shandong People's Republic of China.,Shandong University School of Medicine, Jinan, 250012 Shandong People's Republic of China
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19
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Deoxynucleoside Salvage in Fission Yeast Allows Rescue of Ribonucleotide Reductase Deficiency but Not Spd1-Mediated Inhibition of Replication. Genes (Basel) 2017; 8:genes8050128. [PMID: 28441348 PMCID: PMC5448002 DOI: 10.3390/genes8050128] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 04/10/2017] [Accepted: 04/20/2017] [Indexed: 12/12/2022] Open
Abstract
In fission yeast, the small, intrinsically disordered protein S-phase delaying protein 1 (Spd1) blocks DNA replication and causes checkpoint activation at least in part, by inhibiting the enzyme ribonucleotide reductase, which is responsible for the synthesis of DNA building blocks. The CRL4Cdt2 E3 ubiquitin ligase mediates degradation of Spd1 and the related protein Spd2 at S phase of the cell cycle. We have generated a conditional allele of CRL4Cdt2, by expressing the highly unstable substrate-recruiting protein Cdt2 from a repressible promoter. Unlike Spd1, Spd2 does not regulate deoxynucleotide triphosphate (dNTP) pools; yet we find that Spd1 and Spd2 together inhibit DNA replication upon Cdt2 depletion. To directly test whether this block of replication was solely due to insufficient dNTP levels, we established a deoxy-nucleotide salvage pathway in fission yeast by expressing the human equilibrative nucleoside transporter 1 (hENT1) and the Drosophila deoxynucleoside kinase. We present evidence that this salvage pathway is functional, as 2 µM of deoxynucleosides in the culture medium is able to rescue the growth of two different temperature-sensitive alleles controlling ribonucleotide reductase. However, salvage completely failed to rescue S phase delay, checkpoint activation, and damage sensitivity, which was caused by CRL4Cdt2 inactivation, suggesting that Spd1—in addition to repressing dNTP synthesis—together with Spd2, can inhibit other replication functions. We propose that this inhibition works at the point of the replication clamp proliferating cell nuclear antigen, a co-factor for DNA replication.
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20
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Pai CC, Kearsey SE. A Critical Balance: dNTPs and the Maintenance of Genome Stability. Genes (Basel) 2017; 8:genes8020057. [PMID: 28146119 PMCID: PMC5333046 DOI: 10.3390/genes8020057] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 01/24/2017] [Indexed: 01/14/2023] Open
Abstract
A crucial factor in maintaining genome stability is establishing deoxynucleoside triphosphate (dNTP) levels within a range that is optimal for chromosomal replication. Since DNA replication is relevant to a wide range of other chromosomal activities, these may all be directly or indirectly affected when dNTP concentrations deviate from a physiologically normal range. The importance of understanding these consequences is relevant to genetic disorders that disturb dNTP levels, and strategies that inhibit dNTP synthesis in cancer chemotherapy and for treatment of other disorders. We review here how abnormal dNTP levels affect DNA replication and discuss the consequences for genome stability.
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Affiliation(s)
- Chen-Chun Pai
- CRUK-MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, ORCRB, Roosevelt Drive, Oxford OX3 7DQ, UK.
| | - Stephen E Kearsey
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
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21
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Ashton TM, Fokas E, Kunz-Schughart LA, Folkes LK, Anbalagan S, Huether M, Kelly CJ, Pirovano G, Buffa FM, Hammond EM, Stratford M, Muschel RJ, Higgins GS, McKenna WG. The anti-malarial atovaquone increases radiosensitivity by alleviating tumour hypoxia. Nat Commun 2016; 7:12308. [PMID: 27453292 PMCID: PMC4962491 DOI: 10.1038/ncomms12308] [Citation(s) in RCA: 147] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 06/17/2016] [Indexed: 02/06/2023] Open
Abstract
Tumour hypoxia renders cancer cells resistant to cancer therapy, resulting in markedly worse clinical outcomes. To find clinical candidate compounds that reduce hypoxia in tumours, we conduct a high-throughput screen for oxygen consumption rate (OCR) reduction and identify a number of drugs with this property. For this study we focus on the anti-malarial, atovaquone. Atovaquone rapidly decreases the OCR by more than 80% in a wide range of cancer cell lines at pharmacological concentrations. In addition, atovaquone eradicates hypoxia in FaDu, HCT116 and H1299 spheroids. Similarly, it reduces hypoxia in FaDu and HCT116 xenografts in nude mice, and causes a significant tumour growth delay when combined with radiation. Atovaquone is a ubiquinone analogue, and decreases the OCR by inhibiting mitochondrial complex III. We are now undertaking clinical studies to assess whether atovaquone reduces tumour hypoxia in patients, thereby increasing the efficacy of radiotherapy.
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Affiliation(s)
- Thomas M. Ashton
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Emmanouil Fokas
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Leoni A. Kunz-Schughart
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
- OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, TU Dresden, and Helmholtz-Zentrum Dresden–Rossendorf, Institute of Radiooncology, Dresden, P.O. Box 41, 01307, Germany
| | - Lisa K. Folkes
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Selvakumar Anbalagan
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Melanie Huether
- OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, TU Dresden, and Helmholtz-Zentrum Dresden–Rossendorf, Institute of Radiooncology, Dresden, P.O. Box 41, 01307, Germany
| | - Catherine J. Kelly
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Giacomo Pirovano
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Francesca M. Buffa
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Ester M. Hammond
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Michael Stratford
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Ruth J. Muschel
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Geoff S. Higgins
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - William Gillies McKenna
- CRUK/MRC Oxford Institute for Radiation Oncology, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
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22
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CRL4(Wdr70) regulates H2B monoubiquitination and facilitates Exo1-dependent resection. Nat Commun 2016; 7:11364. [PMID: 27098497 PMCID: PMC4844679 DOI: 10.1038/ncomms11364] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 03/18/2016] [Indexed: 01/16/2023] Open
Abstract
Double-strand breaks repaired by homologous recombination (HR) are first resected to form single-stranded DNA, which binds replication protein A (RPA). RPA attracts mediators that load the Rad51 filament to promote strand invasion, the defining feature of HR. How the resection machinery navigates nucleosome-packaged DNA is poorly understood. Here we report that in Schizosaccharomyces pombe a conserved DDB1-CUL4-associated factor (DCAF), Wdr70, is recruited to DSBs as part of the Cullin4-DDB1 ubiquitin ligase (CRL4(Wdr70)) and stimulates distal H2B lysine 119 mono-ubiquitination (uH2B). Wdr70 deletion, or uH2B loss, results in increased loading of the checkpoint adaptor and resection inhibitor Crb2(53BP1), decreased Exo1 association and delayed resection. Wdr70 is dispensable for resection upon Crb2(53BP1) loss, or when the Set9 methyltransferase that creates docking sites for Crb2 is deleted. Finally, we establish that this histone regulatory cascade similarly controls DSB resection in human cells.
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23
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Aronica L, Kasparek T, Ruchman D, Marquez Y, Cipak L, Cipakova I, Anrather D, Mikolaskova B, Radtke M, Sarkar S, Pai CC, Blaikley E, Walker C, Shen KF, Schroeder R, Barta A, Forsburg SL, Humphrey TC. The spliceosome-associated protein Nrl1 suppresses homologous recombination-dependent R-loop formation in fission yeast. Nucleic Acids Res 2015; 44:1703-17. [PMID: 26682798 PMCID: PMC4770224 DOI: 10.1093/nar/gkv1473] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 12/03/2015] [Indexed: 01/07/2023] Open
Abstract
The formation of RNA–DNA hybrids, referred to as R-loops, can promote genome instability and cancer development. Yet the mechanisms by which R-loops compromise genome instability are poorly understood. Here, we establish roles for the evolutionarily conserved Nrl1 protein in pre-mRNA splicing regulation, R-loop suppression and in maintaining genome stability. nrl1Δ mutants exhibit endogenous DNA damage, are sensitive to exogenous DNA damage, and have defects in homologous recombination (HR) repair. Concomitantly, nrl1Δ cells display significant changes in gene expression, similar to those induced by DNA damage in wild-type cells. Further, we find that nrl1Δ cells accumulate high levels of R-loops, which co-localize with HR repair factors and require Rad51 and Rad52 for their formation. Together, our findings support a model in which R-loop accumulation and subsequent DNA damage sequesters HR factors, thereby compromising HR repair at endogenously or exogenously induced DNA damage sites, leading to genome instability.
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Affiliation(s)
- Lucia Aronica
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, Vienna A-1030, Austria Department of Oncology, Stanford University, Stanford 94305, USA
| | - Torben Kasparek
- CRUK/MRC Oxford Institute for Radiation Oncology, Oxford OX37DQ , UK
| | - David Ruchman
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, Vienna A-1030, Austria
| | - Yamile Marquez
- Department of Medical Biochemistry, Max F. Perutz Laboratories,Medical University of Vienna, Vienna A-1030, Austria
| | - Lubos Cipak
- Cancer Research Institute, Slovak Academy of Sciences, Bratislava 81438, Slovakia
| | - Ingrid Cipakova
- Cancer Research Institute, Slovak Academy of Sciences, Bratislava 81438, Slovakia
| | - Dorothea Anrather
- Max F. Perutz Laboratories, Mass Spectrometry Facility, Vienna A-1030, Austria
| | - Barbora Mikolaskova
- Cancer Research Institute, Slovak Academy of Sciences, Bratislava 81438, Slovakia
| | - Maximilian Radtke
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, Vienna A-1030, Austria
| | - Sovan Sarkar
- CRUK/MRC Oxford Institute for Radiation Oncology, Oxford OX37DQ , UK
| | - Chen-Chun Pai
- CRUK/MRC Oxford Institute for Radiation Oncology, Oxford OX37DQ , UK
| | | | - Carol Walker
- CRUK/MRC Oxford Institute for Radiation Oncology, Oxford OX37DQ , UK
| | - Kuo-Fang Shen
- University of Southern California, Los Angeles 90089-0911, USA
| | - Renee Schroeder
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, Vienna A-1030, Austria
| | - Andrea Barta
- Department of Medical Biochemistry, Max F. Perutz Laboratories,Medical University of Vienna, Vienna A-1030, Austria
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24
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Tiwana GS, Prevo R, Buffa FM, Yu S, Ebner DV, Howarth A, Folkes LK, Budwal B, Chu KY, Durrant L, Muschel RJ, McKenna WG, Higgins GS. Identification of vitamin B1 metabolism as a tumor-specific radiosensitizing pathway using a high-throughput colony formation screen. Oncotarget 2015; 6:5978-89. [PMID: 25788274 PMCID: PMC4467415 DOI: 10.18632/oncotarget.3468] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 01/22/2015] [Indexed: 12/20/2022] Open
Abstract
Colony formation is the gold standard assay for determining reproductive cell death after radiation treatment, since effects on proliferation often do not reflect survival. We have developed a high-throughput radiosensitivity screening method based on clonogenicity and screened a siRNA library against kinases. Thiamine pyrophosphokinase-1 (TPK1), a key component of Vitamin B1/thiamine metabolism, was identified as a target for radiosensitization. TPK1 knockdown caused significant radiosensitization in cancer but not normal tissue cell lines. Other means of blocking this pathway, knockdown of thiamine transporter-1 (THTR1) or treatment with the thiamine analogue pyrithiamine hydrobromide (PyrH) caused significant tumor specific radiosensitization. There was persistent DNA damage in cells irradiated after TPK1 and THTR1 knockdown or PyrH treatment. Thus this screen allowed the identification of thiamine metabolism as a novel radiosensitization target that affects DNA repair. Short-term modulation of thiamine metabolism could be a clinically exploitable strategy to achieve tumor specific radiosensitization.
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Affiliation(s)
- Gaganpreet S. Tiwana
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, Department of Oncology, University of Oxford, Oxford, UK
| | - Remko Prevo
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, Department of Oncology, University of Oxford, Oxford, UK
| | - Francesca M. Buffa
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, Department of Oncology, University of Oxford, Oxford, UK
| | - Sheng Yu
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, Department of Oncology, University of Oxford, Oxford, UK
| | - Daniel V. Ebner
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Alison Howarth
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Lisa K. Folkes
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, Department of Oncology, University of Oxford, Oxford, UK
| | - Balam Budwal
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, Department of Oncology, University of Oxford, Oxford, UK
| | - Kwun-Ye Chu
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, Department of Oncology, University of Oxford, Oxford, UK
| | - Lisa Durrant
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, Department of Oncology, University of Oxford, Oxford, UK
| | - Ruth J. Muschel
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, Department of Oncology, University of Oxford, Oxford, UK
| | - W. Gillies McKenna
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, Department of Oncology, University of Oxford, Oxford, UK
| | - Geoff S. Higgins
- Cancer Research UK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories, Department of Oncology, University of Oxford, Oxford, UK
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25
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Guarino E, Cojoc G, García-Ulloa A, Tolić IM, Kearsey SE. Real-time imaging of DNA damage in yeast cells using ultra-short near-infrared pulsed laser irradiation. PLoS One 2014; 9:e113325. [PMID: 25409521 PMCID: PMC4237433 DOI: 10.1371/journal.pone.0113325] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 10/22/2014] [Indexed: 01/12/2023] Open
Abstract
Analysis of accumulation of repair and checkpoint proteins at repair sites in yeast nuclei has conventionally used chemical agents, ionizing radiation or induction of endonucleases to inflict localized damage. In addition to these methods, similar studies in mammalian cells have used laser irradiation, which has the advantage that damage is inflicted at a specific nuclear region and at a precise time, and this allows accurate kinetic analysis of protein accumulation at DNA damage sites. We show here that it is feasible to use short pulses of near-infrared laser irradiation to inflict DNA damage in subnuclear regions of yeast nuclei by multiphoton absorption. In conjunction with use of fluorescently-tagged proteins, this allows quantitative analysis of protein accumulation at damage sites within seconds of damage induction. PCNA accumulated at damage sites rapidly, such that maximum accumulation was seen approximately 50 s after damage, then levels declined linearly over 200-1000 s after irradiation. RPA accumulated with slower kinetics such that hardly any accumulation was detected within 60 s of irradiation, and levels subsequently increased linearly over the next 900 s, after which levels were approximately constant (up to ca. 2700 s) at the damage site. This approach complements existing methodologies to allow analysis of key damage sensors and chromatin modification changes occurring within seconds of damage inception.
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Affiliation(s)
- Estrella Guarino
- Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Gheorghe Cojoc
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | | | - Iva M. Tolić
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
| | - Stephen E. Kearsey
- Department of Zoology, University of Oxford, Oxford, United Kingdom
- * E-mail:
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Maniam S, Coutts AS, Stratford MR, McGouran J, Kessler B, La Thangue NB. Cofactor Strap regulates oxidative phosphorylation and mitochondrial p53 activity through ATP synthase. Cell Death Differ 2014; 22:156-63. [PMID: 25168243 DOI: 10.1038/cdd.2014.135] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 06/16/2014] [Accepted: 07/22/2014] [Indexed: 12/18/2022] Open
Abstract
Metabolic reprogramming is a hallmark of cancer cells. Strap (stress-responsive activator of p300) is a novel TPR motif OB-fold protein that contributes to p53 transcriptional activation. We show here that, in addition to its established transcriptional role, Strap is localised at mitochondria where one of its key interaction partners is ATP synthase. Significantly, the interaction between Strap and ATP synthase downregulates mitochondrial ATP production. Under glucose-limiting conditions, cancer cells are sensitised by mitochondrial Strap to apoptosis, which is rescued by supplementing cells with an extracellular source of ATP. Furthermore, Strap augments the apoptotic effects of mitochondrial p53. These findings define Strap as a dual regulator of cellular reprogramming: first as a nuclear transcription cofactor and second in the direct regulation of mitochondrial respiration.
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Affiliation(s)
- S Maniam
- Laboratory of Cancer Biology, Department of Oncology, Medical Science Division, University of Oxford, Oxford, UK
| | - A S Coutts
- Laboratory of Cancer Biology, Department of Oncology, Medical Science Division, University of Oxford, Oxford, UK
| | - M R Stratford
- Department of Oncology, Medical Science Division, University of Oxford, Oxford, UK
| | - J McGouran
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - B Kessler
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - N B La Thangue
- Laboratory of Cancer Biology, Department of Oncology, Medical Science Division, University of Oxford, Oxford, UK
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27
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Jahns MT, Vezon D, Chambon A, Pereira L, Falque M, Martin OC, Chelysheva L, Grelon M. Crossover localisation is regulated by the neddylation posttranslational regulatory pathway. PLoS Biol 2014; 12:e1001930. [PMID: 25116939 PMCID: PMC4130666 DOI: 10.1371/journal.pbio.1001930] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Accepted: 07/03/2014] [Indexed: 12/21/2022] Open
Abstract
A genetic study finds the neddylation pathway (known to-date for post-translational protein modification) is involved in regulating crossover localization but not crossover number during meiosis in Arabidopsis. Crossovers (COs) are at the origin of genetic variability, occurring across successive generations, and they are also essential for the correct segregation of chromosomes during meiosis. Their number and position are precisely controlled, however the mechanisms underlying these controls are poorly understood. Neddylation/rubylation is a regulatory pathway of posttranslational protein modification that is required for numerous cellular processes in eukaryotes, but has not yet been linked to homologous recombination. In a screen for meiotic recombination-defective mutants, we identified several axr1 alleles, disrupting the gene encoding the E1 enzyme of the neddylation complex in Arabidopsis. Using genetic and cytological approaches we found that axr1 mutants are characterised by a shortage in bivalent formation correlated with strong synapsis defects. We determined that the bivalent shortage in axr1 is not due to a general decrease in CO formation but rather due to a mislocalisation of class I COs. In axr1, as in wild type, COs are still under the control of the ZMM group of proteins. However, in contrast to wild type, they tend to cluster together and no longer follow the obligatory CO rule. Lastly, we showed that this deregulation of CO localisation is likely to be mediated by the activity of a cullin 4 RING ligase, known to be involved in DNA damage sensing during somatic DNA repair and mouse spermatogenesis. In conclusion, we provide evidence that the neddylation/rubylation pathway of protein modification is a key regulator of meiotic recombination. We propose that rather than regulating the number of recombination events, this pathway regulates their localisation, through the activation of cullin 4 RING ligase complexes. Possible targets for these ligases are discussed. During meiosis, two successive chromosomal divisions follow a single S phase, resulting in the formation of four haploid cells, each with half of the parental genetic material. This reduction in chromosome number occurs during the first meiotic division, when homologous chromosomes (paternal and maternal) are separated from each other. For this to happen, homologous chromosomes associate in structures called bivalents, where each chromosome is linked to its homologue by a point of contact known as chiasmata. These chiasmata reflect the formation of crossovers (COs), one of the manifestations of the exchange of genetic material occurring during homologous recombination. CO number varies little at around two per chromosome pair, and they tend to be evenly spaced on chromosomes. Thus, CO number and distribution are very tightly controlled. However, the mechanisms underlying these controls are very poorly understood. In this study, we identified a regulatory pathway of meiotic recombination. We show that this pathway does not regulate the amount of recombination events per se, but instead controls their localisation, as when it is defective, CO events cluster together in a few regions of the genome, leading to bivalent shortage and progeny aneuploidy with incorrect numbers of chromosomes. This regulatory pathway is a posttranslational protein modification system called neddylation (or rubylation in plants), known to be required for numerous cellular processes in eukaryotes. We identify an enzyme of the neddylation complex as a major regulator of meiotic recombination in Arabidopsis and show that this process may be also conserved in mammals.
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Affiliation(s)
- Marina Tagliaro Jahns
- INRA, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, Versailles, France
- AgroParisTech, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, Versailles, France
| | - Daniel Vezon
- INRA, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, Versailles, France
- AgroParisTech, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, Versailles, France
| | - Aurélie Chambon
- INRA, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, Versailles, France
- AgroParisTech, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, Versailles, France
| | - Lucie Pereira
- INRA, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, Versailles, France
- AgroParisTech, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, Versailles, France
| | - Matthieu Falque
- Institut National de la Recherche Agronomique, Unité Mixte de Recherche de Génétique Végétale, Université Paris-Sud, Gif-sur-Yvette, France
| | - Olivier C. Martin
- Institut National de la Recherche Agronomique, Unité Mixte de Recherche de Génétique Végétale, Université Paris-Sud, Gif-sur-Yvette, France
| | - Liudmila Chelysheva
- INRA, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, Versailles, France
- AgroParisTech, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, Versailles, France
| | - Mathilde Grelon
- INRA, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, Versailles, France
- AgroParisTech, Institut Jean-Pierre Bourgin, UMR 1318, ERL CNRS 3559, Saclay Plant Sciences, RD10, Versailles, France
- * E-mail:
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28
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Cukras S, Morffy N, Ohn T, Kee Y. Inactivating UBE2M impacts the DNA damage response and genome integrity involving multiple cullin ligases. PLoS One 2014; 9:e101844. [PMID: 25025768 PMCID: PMC4099125 DOI: 10.1371/journal.pone.0101844] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 06/12/2014] [Indexed: 12/28/2022] Open
Abstract
Protein neddylation is involved in a wide variety of cellular processes. Here we show that the DNA damage response is perturbed in cells inactivated with an E2 Nedd8 conjugating enzyme UBE2M, measured by RAD51 foci formation kinetics and cell based DNA repair assays. UBE2M knockdown increases DNA breakages and cellular sensitivity to DNA damaging agents, further suggesting heightened genomic instability and defective DNA repair activity. Investigating the downstream Cullin targets of UBE2M revealed that silencing of Cullin 1, 2, and 4 ligases incurred significant DNA damage. In particular, UBE2M knockdown, or defective neddylation of Cullin 2, leads to a blockade in the G1 to S progression and is associated with delayed S-phase dependent DNA damage response. Cullin 4 inactivation leads to an aberrantly high DNA damage response that is associated with increased DNA breakages and sensitivity of cells to DNA damaging agents, suggesting a DNA repair defect is associated. siRNA interrogation of key Cullin substrates show that CDT1, p21, and Claspin are involved in elevated DNA damage in the UBE2M knockdown cells. Therefore, UBE2M is required to maintain genome integrity by activating multiple Cullin ligases throughout the cell cycle.
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Affiliation(s)
- Scott Cukras
- Department of Cell Biology, Microbiology, and Molecular Biology, College of Arts and Sciences, University of South Florida, Tampa, Florida, United States of America
| | - Nicholas Morffy
- Department of Cell Biology, Microbiology, and Molecular Biology, College of Arts and Sciences, University of South Florida, Tampa, Florida, United States of America
| | - Takbum Ohn
- Department of Cellular & Molecular Medicine, College of Medicine, Chosun University, Gwangju, Republic of Korea
| | - Younghoon Kee
- Department of Cell Biology, Microbiology, and Molecular Biology, College of Arts and Sciences, University of South Florida, Tampa, Florida, United States of America
- * E-mail:
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29
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Aye Y, Li M, Long MJC, Weiss RS. Ribonucleotide reductase and cancer: biological mechanisms and targeted therapies. Oncogene 2014; 34:2011-21. [PMID: 24909171 DOI: 10.1038/onc.2014.155] [Citation(s) in RCA: 276] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 04/25/2014] [Accepted: 04/26/2014] [Indexed: 12/16/2022]
Abstract
Accurate DNA replication and repair is essential for proper development, growth and tumor-free survival in all multicellular organisms. A key requirement for the maintenance of genomic integrity is the availability of adequate and balanced pools of deoxyribonucleoside triphosphates (dNTPs), the building blocks of DNA. Notably, dNTP pool alterations lead to genomic instability and have been linked to multiple human diseases, including mitochondrial disorders, susceptibility to viral infection and cancer. In this review, we discuss how a key regulator of dNTP biosynthesis in mammals, the enzyme ribonucleotide reductase (RNR), impacts cancer susceptibility and serves as a target for anti-cancer therapies. Because RNR-regulated dNTP production can influence DNA replication fidelity while also supporting genome-protecting DNA repair, RNR has complex and stage-specific roles in carcinogenesis. Nevertheless, cancer cells are dependent on RNR for de novo dNTP biosynthesis. Therefore, elevated RNR expression is a characteristic of many cancers, and an array of mechanistically distinct RNR inhibitors serve as effective agents for cancer treatment. The dNTP metabolism machinery, including RNR, has been exploited for therapeutic benefit for decades and remains an important target for cancer drug development.
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Affiliation(s)
- Y Aye
- 1] Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA [2] Department of Biochemistry, Weill Cornell Medical College, New York, NY, USA
| | - M Li
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, USA
| | - M J C Long
- Graduate Program in Biochemistry, Brandeis University, Waltham, MA, USA
| | - R S Weiss
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, USA
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30
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Guarino E, Salguero I, Kearsey SE. Cellular regulation of ribonucleotide reductase in eukaryotes. Semin Cell Dev Biol 2014; 30:97-103. [PMID: 24704278 DOI: 10.1016/j.semcdb.2014.03.030] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Accepted: 03/26/2014] [Indexed: 12/22/2022]
Abstract
Synthesis of deoxynucleoside triphosphates (dNTPs) is essential for both DNA replication and repair and a key step in this process is catalyzed by ribonucleotide reductases (RNRs), which reduce ribonucleotides (rNDPs) to their deoxy forms. Tight regulation of RNR is crucial for maintaining the correct levels of all four dNTPs, which is important for minimizing the mutation rate and avoiding genome instability. Although allosteric control of RNR was the first discovered mechanism involved in regulation of the enzyme, other controls have emerged in recent years. These include regulation of expression of RNR genes, proteolysis of RNR subunits, control of the cellular localization of the small RNR subunit, and regulation of RNR activity by small protein inhibitors. This review will focus on these additional mechanisms of control responsible for providing a balanced supply of dNTPs.
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Affiliation(s)
- Estrella Guarino
- Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, United Kingdom.
| | - Israel Salguero
- Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, United Kingdom.
| | - Stephen E Kearsey
- Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, United Kingdom.
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31
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Purine metabolite and energy charge analysis of Trypanosoma brucei cells in different growth phases using an optimized ion-pair RP-HPLC/UV for the quantification of adenine and guanine pools. Exp Parasitol 2014; 141:28-38. [PMID: 24657574 DOI: 10.1016/j.exppara.2014.03.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 02/12/2014] [Accepted: 03/04/2014] [Indexed: 11/21/2022]
Abstract
Human African Trypanosomiasis (HAT) is caused by the protozoan parasite Trypanosoma brucei. Although trypanosomes are well-studied model organisms, only little is known about their adenine and guanine nucleotide pools. Besides being building blocks of RNA and DNA, these nucleotides are also important modulators of diverse biochemical cellular processes. Adenine nucleotides also play an important role in the regulation of metabolic energy. The energetic state of cells is evaluated by the energy charge which gives information about how much energy is available in form of high energy phosphate bonds of adenine nucleotides. A sensitive and reproducible ion-pair RP-HPLC/UV method was developed and optimized, allowing the quantification of guanine and adenine nucleosides/nucleotides in T. brucei. With this method, the purine levels and their respective ratios were investigated in trypanosomes during logarithmic, stationary and senescent growth phases. Results of this study showed that all adenine and guanine purines under investigation were in the low mM range. The energy charge was found to decrease from logarithmic to static and to senescent phase whereas AMP/ATP, ADP/ATP and GDP/GTP ratios increased in the same order. In addition, the AMP/ATP ratio varied as the square of the ADP/ATP ratio, indicating AMP to be the key energy sensor molecule in trypanosomes.
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32
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Blaikley EJ, Tinline-Purvis H, Kasparek TR, Marguerat S, Sarkar S, Hulme L, Hussey S, Wee BY, Deegan RS, Walker CA, Pai CC, Bähler J, Nakagawa T, Humphrey TC. The DNA damage checkpoint pathway promotes extensive resection and nucleotide synthesis to facilitate homologous recombination repair and genome stability in fission yeast. Nucleic Acids Res 2014; 42:5644-56. [PMID: 24623809 PMCID: PMC4027169 DOI: 10.1093/nar/gku190] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
DNA double-strand breaks (DSBs) can cause chromosomal rearrangements and extensive loss of heterozygosity (LOH), hallmarks of cancer cells. Yet, how such events are normally suppressed is unclear. Here we identify roles for the DNA damage checkpoint pathway in facilitating homologous recombination (HR) repair and suppressing extensive LOH and chromosomal rearrangements in response to a DSB. Accordingly, deletion of Rad3ATR, Rad26ATRIP, Crb253BP1 or Cdc25 overexpression leads to reduced HR and increased break-induced chromosome loss and rearrangements. We find the DNA damage checkpoint pathway facilitates HR, in part, by promoting break-induced Cdt2-dependent nucleotide synthesis. We also identify additional roles for Rad17, the 9-1-1 complex and Chk1 activation in facilitating break-induced extensive resection and chromosome loss, thereby suppressing extensive LOH. Loss of Rad17 or the 9-1-1 complex results in a striking increase in break-induced isochromosome formation and very low levels of chromosome loss, suggesting the 9-1-1 complex acts as a nuclease processivity factor to facilitate extensive resection. Further, our data suggest redundant roles for Rad3ATR and Exo1 in facilitating extensive resection. We propose that the DNA damage checkpoint pathway coordinates resection and nucleotide synthesis, thereby promoting efficient HR repair and genome stability.
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Affiliation(s)
- Elizabeth J Blaikley
- CRUK-MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, OX3 7DQ, UK
| | - Helen Tinline-Purvis
- CRUK-MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, OX3 7DQ, UK
| | - Torben R Kasparek
- CRUK-MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, OX3 7DQ, UK
| | - Samuel Marguerat
- Department of Genetics, Evolution and Environment, and UCL Cancer Institute, University College London, London WC1E 6BT, UK
| | - Sovan Sarkar
- CRUK-MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, OX3 7DQ, UK
| | - Lydia Hulme
- CRUK-MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, OX3 7DQ, UK
| | - Sharon Hussey
- CRUK-MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, OX3 7DQ, UK
| | - Boon-Yu Wee
- CRUK-MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, OX3 7DQ, UK
| | - Rachel S Deegan
- CRUK-MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, OX3 7DQ, UK
| | - Carol A Walker
- CRUK-MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, OX3 7DQ, UK
| | - Chen-Chun Pai
- CRUK-MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, OX3 7DQ, UK
| | - Jürg Bähler
- Department of Genetics, Evolution and Environment, and UCL Cancer Institute, University College London, London WC1E 6BT, UK
| | - Takuro Nakagawa
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka 560-0043, Osaka, Japan
| | - Timothy C Humphrey
- CRUK-MRC Gray Institute for Radiation Oncology and Biology, University of Oxford, OX3 7DQ, UK
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Vejrup-Hansen R, Fleck O, Landvad K, Fahnøe U, Broendum SS, Schreurs AS, Kragelund BB, Carr AM, Holmberg C, Nielsen O. Spd2 assists Spd1 in modulation of RNR architecture but does not regulate deoxynucleotide pools. J Cell Sci 2014; 127:2460-70. [DOI: 10.1242/jcs.139816] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In yeasts, small intrinsically disordered proteins (IDPs) modulate ribonucleotide reductase (RNR) activity to ensure an optimal supply of dNTPs for DNA synthesis. The S. pombe Spd1 protein can directly inhibit the large RNR subunit (R1), import the small subunit (R2) into the nucleus and induce an architectural change in the R1-R2 holocomplex. Here, we report the characterization of Spd2, a protein with homology to Spd1. We show that Spd2 is a CRL4Cdt2 controlled IDP that functions together with Spd1 in the DNA damage response and in modulation of RNR architecture. However, Spd2 does not regulate dNTP pools and R2 nuclear import. Furthermore, deletion of spd2 only weakly suppresses the Rad3ATR checkpoint dependency of CRL4Cdt2 mutants. However, when we raised intracellular dNTP pools by inactivation of RNR feedback inhibition, deletion of spd2 could suppress the checkpoint dependency of CRL4Cdt2 mutant cells to the same extent as spd1. Collectively, these observations suggest that Spd1 on its own regulates dNTP pools, while it together with Spd2 modulates RNR architecture and sensitizes cells to DNA damage.
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34
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Flórez-Zapata NMV, Reyes-Valdés MH, Hernandez-Godínez F, Martínez O. Transcriptomic landscape of prophase I sunflower male meiocytes. FRONTIERS IN PLANT SCIENCE 2014; 5:277. [PMID: 24982667 PMCID: PMC4059168 DOI: 10.3389/fpls.2014.00277] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2014] [Accepted: 05/27/2014] [Indexed: 05/06/2023]
Abstract
Meiosis is a form of specialized cell division that generates gametes, allowing recombination of alleles and halving the chromosome number. Arabidopsis and maize are the plant models that have been most extensively studied to determine the genes involved in meiosis. Here we present an RNA-seq study in which gene expression in male meiocytes isolated during prophase I was compared to that in somatic tissues of the sunflower HA89 line. We sampled more than 490 million gene tags from these libraries, assembled them de novo into a sunflower transcriptome. We obtained expression data for 36,304 sunflower genes, of which 19,574 (54%) were differentially expressed (DE) between meiocytes and somatic tissue. We also determined the functional categories and metabolic pathways that are DE in these libraries. As expected, we found large differences between the meiotic and somatic transcriptomes, which is in accordance with previous studies in Arabidopsis and maize. Furthermore, most of the previously implicated meiotic genes were abundantly and DE in meiocytes and a large repertoire of transcription factors (TF) and genes related to silencing are expressed in the sunflower meiocytes. We detected TFs which appear to be exclusively expressed in meiocytes. Our results allow for a better understanding of the conservation and differences in the meiotic transcriptome of plants.
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Affiliation(s)
- Nathalia M. V. Flórez-Zapata
- Laboratorio Nacional de Genómica para la Biodiversidad (Langebio), Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional(Cinvestav) Irapuato, México
| | - M. H. Reyes-Valdés
- Department of Plant Breeding, Universidad Autónoma Agraria Antonio NarroSaltillo, México
| | - Fernando Hernandez-Godínez
- Laboratorio Nacional de Genómica para la Biodiversidad (Langebio), Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional(Cinvestav) Irapuato, México
| | - Octavio Martínez
- Laboratorio Nacional de Genómica para la Biodiversidad (Langebio), Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional(Cinvestav) Irapuato, México
- *Correspondence: Octavio Martínez, Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, K. 9.6 Libramiento Norte Carretera Irapuato-León, Irapuato 36821, México e-mail:
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35
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Fleck O, Vejrup-Hansen R, Watson A, Carr AM, Nielsen O, Holmberg C. Spd1 accumulation causes genome instability independently of ribonucleotide reductase activity but functions to protect the genome when deoxynucleotide pools are elevated. J Cell Sci 2013; 126:4985-94. [PMID: 23986475 DOI: 10.1242/jcs.132837] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cullin4, Ddb1 and Cdt2 are core subunits of the ubiquitin ligase complex CRL4(Cdt2), which controls genome stability by targeting Spd1 for degradation during DNA replication and repair in fission yeast. Spd1 has an inhibitory effect on ribonucleotide reductase (RNR), the activity of which is required for deoxynucleotide (dNTP) synthesis. The failure to degrade Spd1 in mutants where CRL4(Cdt2) is defective leads to DNA integrity checkpoint activation and dependency. This correlates with a lower dNTP pool. Pools are restored in a spd1-deleted background and this also suppresses checkpoint activation and dependency. We hypothesized that fission yeast with RNR hyperactivity would display a mutator phenotype on their own, but also possibly repress aspects of the phenotype associated with the inability to target Spd1 for degradation. Here, we report that a mutation in the R1 subunit of ribonucleotide reductase cdc22 (cdc22-D57N), which alleviated allosteric feedback inhibition, caused a highly elevated dNTP pool that was further increased by deleting spd1. The Δspd1 cdc22-D57N double mutant had elevated mutation rates and was sensitive to damaging agents that cause DNA strand breaks, demonstrating that Spd1 can protect the genome when dNTP pools are high. In ddb1-deleted cells, cdc22-D57N also potently elevated RNR activity, but failed to allow cell growth independently of the intact checkpoint. Our results provide evidence that excess Spd1 interferes with other functions in addition to its inhibitory effect on ribonucleotide reduction to generate replication stress and genome instability.
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Affiliation(s)
- Oliver Fleck
- Cell Cycle and Genome Stability Group, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen N, Denmark
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36
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Abstract
Correct regulation of DNA nucleotide biosynthesis is emerging as a key issue of importance for genome integrity. The fission yeast Spd1 protein can modulate the activity of ribonucleotide reductase (RNR) by at least three different mechanisms. Now a paper reports that Spd1 turnover is linked to ongoing DNA synthesis.
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Affiliation(s)
- Christian Holmberg
- Cell cycle and Genome Stability Group, Department of Biology, University of Copenhagen, Ole Maaløes vej 5, DK-2200 Copenhagen N, Denmark
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37
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D'Angiolella V, Esencay M, Pagano M. A cyclin without cyclin-dependent kinases: cyclin F controls genome stability through ubiquitin-mediated proteolysis. Trends Cell Biol 2012. [PMID: 23182110 DOI: 10.1016/j.tcb.2012.10.011] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cell cycle transitions are driven by the periodic oscillations of cyclins, which bind and activate cyclin-dependent kinases (CDKs) to phosphorylate target substrates. Cyclin F uses a substrate recruitment strategy similar to that of the other cyclins, but its associated catalytic activity is substantially different. Indeed, cyclin F is the founding member of the F-box family of proteins, which are the substrate recognition subunits of Skp1-Cul1-F-box protein (SCF) ubiquitin ligase complexes. Here, we discuss cyclin F function and recently identified substrates of SCF(cyclin)(F) involved in deoxyribonucleotide triphosphate (dNTP) production, centrosome duplication, and spindle formation. We highlight the relevance of cyclin F in controlling genome stability through ubiquitin-mediated proteolysis and the implications for cancer development.
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Affiliation(s)
- Vincenzo D'Angiolella
- Department of Pathology, NYU Cancer Institute, New York University School of Medicine, New York, NY 10016, USA. vincenzo.d'
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38
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Abstract
Nucleoside analogs are frequently used to label newly synthesized DNA. These analogs are toxic in many cells, with the exception of the budding yeast. We show that Schizosaccharomyces pombe behaves similarly to metazoans in response to analogs 5-bromo-2'-deoxyuridine (BrdU) and 5-ethynyl-2'-deoxyuridine (EdU). Incorporation causes DNA damage that activates the damage checkpoint kinase Chk1 and sensitizes cells to UV light and other DNA-damaging drugs. Replication checkpoint mutant cds1Δ shows increased DNA damage response after exposure. Finally, we demonstrate that the response to BrdU is influenced by the ribonucleotide reductase inhibitor, Spd1, suggesting that BrdU causes dNTP pool imbalance in fission yeast, as in metazoans. Consistent with this, we show that excess thymidine induces G1 arrest in wild-type fission yeast expressing thymidine kinase. Thus, fission yeast responds to nucleoside analogs similarly to mammalian cells, which has implications for their use in replication and damage research, as well as for dNTP metabolism.
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39
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Hu CM, Yeh MT, Tsao N, Chen CW, Gao QZ, Chang CY, Lee MH, Fang JM, Sheu SY, Lin CJ, Tseng MC, Chen YJ, Chang ZF. Tumor cells require thymidylate kinase to prevent dUTP incorporation during DNA repair. Cancer Cell 2012; 22:36-50. [PMID: 22789537 DOI: 10.1016/j.ccr.2012.04.038] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Revised: 01/03/2012] [Accepted: 04/24/2012] [Indexed: 10/28/2022]
Abstract
The synthesis of dTDP is unique because there is a requirement for thymidylate kinase (TMPK). All other dNDPs including dUDP are directly produced by ribonucleotide reductase (RNR). We report the binding of TMPK and RNR at sites of DNA damage. In tumor cells, when TMPK function is blocked, dUTP is incorporated during DNA double-strand break (DSB) repair. Disrupting RNR recruitment to damage sites or reducing the expression of the R2 subunit of RNR prevents the impairment of DNA repair by TMPK intervention, indicating that RNR contributes to dUTP incorporation during DSB repair. We identified a cell-permeable nontoxic inhibitor of TMPK that sensitizes tumor cells to doxorubicin in vitro and in vivo, suggesting its potential as a therapeutic option.
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Affiliation(s)
- Chun-Mei Hu
- Graduate Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei, 11221 Taiwan
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40
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Sunder S, Greeson-Lott NT, Runge KW, Sanders SL. A new method to efficiently induce a site-specific double-strand break in the fission yeast Schizosaccharomyces pombe. Yeast 2012; 29:275-91. [PMID: 22674789 DOI: 10.1002/yea.2908] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Accepted: 05/03/2012] [Indexed: 12/16/2022] Open
Abstract
Double-strand DNA breaks are a serious threat to cellular viability and yeast systems have proved invaluable in helping to understand how these potentially toxic lesions are sensed and repaired. An important method to study the processing of DNA breaks in the budding yeast Saccharomyces cerevisiae is to introduce a unique double-strand break into the genome by regulating the expression of the site-specific HO endonuclease with a galactose inducible promoter. Variations of the HO site-specific DSB assay have been adapted to many organisms, but the methodology has seen only limited use in the fission yeast Schizosaccharomyces pombe because of the lack of a promoter capable of inducing endonuclease expression on a relatively short time scale (~1 h). We have overcome this limitation by developing a new assay in which expression of the homing endonuclease I-PpoI is tightly regulated with a tetracycline-inducible promoter. We show that induction of the I-PpoI endonuclease produces rapid cutting of a defined cleavage site (> 80% after 1 h), efficient cell cycle arrest and significant accumulation of the checkpoint protein Crb2 at break-adjacent regions in a manner that is analogous to published findings with DSBs produced by an acute exposure to ionizing irradiation. This assay provides an important new tool for the fission yeast community and, because many aspects of mammalian chromatin organization have been well-conserved in Sz. pombe but not in S. cerevisiae, also offers an attractive system to decipher the role of chromatin structure in modulating the repair of double-stranded DNA breaks.
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Affiliation(s)
- Sham Sunder
- Department of Biochemistry and Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH, USA
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41
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Ribonucleotide reductase activity is coupled to DNA synthesis via proliferating cell nuclear antigen. Curr Biol 2012; 22:720-6. [PMID: 22464192 DOI: 10.1016/j.cub.2012.02.070] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Revised: 02/06/2012] [Accepted: 02/29/2012] [Indexed: 11/24/2022]
Abstract
Synthesis of deoxynucleoside triphosphates (dNTPs) is required for both DNA replication and DNA repair and is catalyzed by ribonucleotide reductases (RNR), which convert ribonucleotides to their deoxy forms [1, 2]. Maintaining the correct levels of dNTPs for DNA synthesis is important for minimizing the mutation rate [3-7], and this is achieved by tight regulation of RNR [2, 8, 9]. In fission yeast, RNR is regulated in part by a small protein inhibitor, Spd1, which is degraded in S phase and after DNA damage to allow upregulation of dNTP supply [10-12]. Spd1 degradation is mediated by the activity of the CRL4(Cdt2) ubiquitin ligase complex [5, 13, 14]. This has been reported to be dependent on modulation of Cdt2 levels, which are cell cycle regulated, peaking in S phase, and which also increase after DNA damage in a checkpoint-dependent manner [7, 13]. We show here that Cdt2 level fluctuations are not sufficient to regulate Spd1 proteolysis and that the key step in this event is the interaction of Spd1 with the polymerase processivity factor proliferating cell nuclear antigen (PCNA), complexed onto DNA. This mechanism thus provides a direct link between DNA synthesis and RNR regulation.
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42
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RAD53 is limiting in double-strand break repair and in protection against toxicity associated with ribonucleotide reductase inhibition. DNA Repair (Amst) 2012; 11:317-23. [PMID: 22277748 DOI: 10.1016/j.dnarep.2011.12.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Revised: 11/28/2011] [Accepted: 12/24/2011] [Indexed: 02/08/2023]
Abstract
The yeast Chk2/Chk1 homolog Rad53 is a central component of the DNA damage checkpoint system. While it controls genotoxic stress responses such as cell cycle arrest, replication fork stabilization and increase in dNTP pools, little is known about the consequences of reduced Rad53 levels on the various cellular endpoints or about its roles in dealing with chronic vs. acute genotoxic challenges. Using a tetraploid gene dosage model in which only one copy of the yeast RAD53 is functional (simplex), we found that the simplex strain was not sensitive to acute UV radiation or chronic MMS exposure. However, the simplex strain was sensitized to chronic exposure of the ribonucleotide reductase inhibitor hydroxyurea (HU). Surprisingly, reduced RAD53 gene dosage did not affect sensitivity to HU acute exposure, indicating that immediate checkpoint responses and recovery from HU-induced stress were not compromised. Interestingly, cells of most of the colonies that arise after chronic HU exposure acquired heritable resistance to HU. We also found that short HU exposure before and after treatment of G₂ cells with ionizing radiation (IR) reduced the capability of RAD53 simplex cells to repair DSBs, in agreement with sensitivity of RAD53 simplex strain to high doses of IR. We propose that a modest reduction in Rad53 activity can impact the activation of the ribonucleotide reductase catalytic subunit Rnr1 following stress, reducing the ability to generate nucleotide pools sufficient for DNA repair and replication. At the same time, reduced Rad53 activity may lead to genome instability and to the acquisition of drug resistance before and/or during the chronic exposure to HU. These results have implications for developing drug enhancers as well as for understanding mechanisms of drug resistance in cells compromised for DNA damage checkpoint.
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Abstract
Eukaryotic cell cycle transitions are driven by E3 ubiquitin ligases that catalyze the ubiquitylation and destruction of specific protein targets. For example, the anaphase-promoting complex/cyclosome (APC/C) promotes the exit from mitosis via destruction of securin and mitotic cyclins, whereas CRL1(Skp2) allows entry into S phase by targeting the destruction of the cyclin-dependent kinase (CDK) inhibitor p27. Recently, an E3 ubiquitin ligase called CRL4(Cdt2) has been characterized, which couples proteolysis to DNA synthesis via an unusual mechanism that involves display of substrate degrons on the DNA polymerase processivity factor PCNA. Through its destruction of Cdt1, p21, and Set8, CRL4(Cdt2) has emerged as a master regulator that prevents rereplication in S phase. In addition, it also targets other factors such as E2F and DNA polymerase η. In this review, we discuss our current understanding of the molecular mechanism of substrate recognition by CRL4(Cdt2) and how this E3 ligase helps to maintain genome integrity.
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Affiliation(s)
- Courtney G Havens
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA
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Abbas T, Dutta A. CRL4Cdt2: master coordinator of cell cycle progression and genome stability. Cell Cycle 2011; 10:241-9. [PMID: 21212733 DOI: 10.4161/cc.10.2.14530] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Polyubiquitin-mediated degradation of proteins plays an essential role in various physiological processes including cell cycle progression, transcription and DNA replication and repair. Increasing evidence supports a vital role for the E3 ubiquitin ligase cullin-4, in conjunction with the substrate recognition factor Cdt2 (CRL4Cdt2), for the degradation of multiple cell cycle-regulated proteins to prevent genomic instability. In addition, it is critical for normal cell cycle progression by ensuring the timely destruction of various cell cycle proteins whose deregulated expression impairs cell cycle progression. Here, we summarize our current knowledge about the various roles of the CRL4Cdt2 E3 ubiquitin ligase, and how its activity contributes both to the preservation of genome integrity and to normal cell cycle progression, and how its deregulation may contribute to human cancer.
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Affiliation(s)
- Tarek Abbas
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA, USA
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