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Romero H, Rösch TC, Hernández-Tamayo R, Lucena D, Ayora S, Alonso JC, Graumann PL. Single molecule tracking reveals functions for RarA at replication forks but also independently from replication during DNA repair in Bacillus subtilis. Sci Rep 2019; 9:1997. [PMID: 30760776 PMCID: PMC6374455 DOI: 10.1038/s41598-018-38289-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 12/18/2018] [Indexed: 12/19/2022] Open
Abstract
RarA is a widely conserved protein proposed to be involved in recombination-dependent replication. We present a cell biological approach to identify functional connections between RarA and other proteins using single molecule tracking. We found that 50% of RarA molecules were static, mostly close to replication forks and likely DNA-bound, while the remaining fraction was highly dynamic throughout the cells. RarA alternated between static and dynamic states. Exposure to H2O2 increased the fraction of dynamic molecules, but not treatment with mitomycin C or with methyl methanesulfonate, which was exacerbated by the absence of RecJ, RecD2, RecS and RecU proteins. The ratio between static and dynamic RarA also changed in replication temperature-sensitive mutants, but in opposite manners, dependent upon inhibition of DnaB or of DnaC (pre)primosomal proteins, revealing an intricate function related to DNA replication restart. RarA likely acts in the context of collapsed replication forks, as well as in conjunction with a network of proteins that affect the activity of the RecA recombinase. Our novel approach reveals intricate interactions of RarA, and is widely applicable for in vivo protein studies, to underpin genetic or biochemical connections, and is especially helpful for investigating proteins whose absence does not lead to any detectable phenotype.
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Affiliation(s)
- Hector Romero
- SYNMIKRO, LOEWE-Zentrum für Synthetische Mikrobiologie, Philipps-Universität Marburg, Hans-Meerwein-Straße, Mehrzweckgebäude, 35043, Marburg, Germany
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032, Marburg, Germany
- Department Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin St., 28049, Cantoblanco, Madrid, Spain
| | - Thomas C Rösch
- SYNMIKRO, LOEWE-Zentrum für Synthetische Mikrobiologie, Philipps-Universität Marburg, Hans-Meerwein-Straße, Mehrzweckgebäude, 35043, Marburg, Germany
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032, Marburg, Germany
| | - Rogelio Hernández-Tamayo
- SYNMIKRO, LOEWE-Zentrum für Synthetische Mikrobiologie, Philipps-Universität Marburg, Hans-Meerwein-Straße, Mehrzweckgebäude, 35043, Marburg, Germany
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032, Marburg, Germany
| | - Daniella Lucena
- SYNMIKRO, LOEWE-Zentrum für Synthetische Mikrobiologie, Philipps-Universität Marburg, Hans-Meerwein-Straße, Mehrzweckgebäude, 35043, Marburg, Germany
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032, Marburg, Germany
| | - Silvia Ayora
- Department Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin St., 28049, Cantoblanco, Madrid, Spain
| | - Juan C Alonso
- Department Microbial Biotechnology, Centro Nacional de Biotecnología, CNB-CSIC, 3 Darwin St., 28049, Cantoblanco, Madrid, Spain.
| | - Peter L Graumann
- SYNMIKRO, LOEWE-Zentrum für Synthetische Mikrobiologie, Philipps-Universität Marburg, Hans-Meerwein-Straße, Mehrzweckgebäude, 35043, Marburg, Germany.
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032, Marburg, Germany.
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52
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Weaver GM, Mettrick KA, Corocher TA, Graham A, Grainge I. Replication fork collapse at a protein-DNA roadblock leads to fork reversal, promoted by the RecQ helicase. Mol Microbiol 2018; 111:455-472. [PMID: 30466158 DOI: 10.1111/mmi.14166] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/09/2018] [Indexed: 11/27/2022]
Abstract
Proteins that bind DNA are the cause of the majority of impediments to replication fork progression and can lead to subsequent collapse of the replication fork. Failure to deal with fork collapse efficiently leads to mutation or cell death. Several models have been proposed for how a cell processes a stalled or collapsed replication fork; eukaryotes and bacteria are not dissimilar in terms of the general pathways undertaken to deal with these events. This study shows that replication fork regression, the combination of replication fork reversal leading to formation of a Holliday Junction along with exonuclease digestion, is the preferred pathway for dealing with a collapsed fork in Escherichia coli. Direct endo-nuclease activity at the replication fork was not observed. The protein that had the greatest effect on these fork processing events was the RecQ helicase, while RecG and RuvABC, which have previously been implicated in this process, were found to play a lesser role. Eukaryotic RecQ homologues, BLM and WRN, have also been implicated in processing events following replication fork collapse and may reflect a conserved mechanism. Finally, the SOS response was not induced by the protein-DNA roadblock under these conditions, so did not affect fork processing.
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Affiliation(s)
- Georgia M Weaver
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
| | - Karla A Mettrick
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
| | - Tayla-Ann Corocher
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
| | - Adam Graham
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
| | - Ian Grainge
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia
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53
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A tough row to hoe: when replication forks encounter DNA damage. Biochem Soc Trans 2018; 46:1643-1651. [PMID: 30514768 DOI: 10.1042/bst20180308] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 11/05/2018] [Accepted: 11/07/2018] [Indexed: 01/12/2023]
Abstract
Eukaryotic cells continuously experience DNA damage that can perturb key molecular processes like DNA replication. DNA replication forks that encounter DNA lesions typically slow and may stall, which can lead to highly detrimental fork collapse if appropriate protective measures are not executed. Stabilization and protection of stalled replication forks ensures the possibility of effective fork restart and prevents genomic instability. Recent efforts from multiple laboratories have highlighted several proteins involved in replication fork remodeling and DNA damage response pathways as key regulators of fork stability. Homologous recombination factors such as RAD51, BRCA1, and BRCA2, along with components of the Fanconi Anemia pathway, are now known to be crucial for stabilizing stalled replication forks and preventing nascent strand degradation. Several checkpoint proteins have additionally been implicated in fork protection. Ongoing work in this area continues to shed light on a sophisticated molecular pathway that balances the action of DNA resection and fork protection to maintain genomic integrity, with important implications for the fate of both normal and malignant cells following replication stress.
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54
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Warren GM, Stein RA, Mchaourab HS, Eichman BF. Movement of the RecG Motor Domain upon DNA Binding Is Required for Efficient Fork Reversal. Int J Mol Sci 2018; 19:ijms19103049. [PMID: 30301235 PMCID: PMC6213257 DOI: 10.3390/ijms19103049] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Revised: 09/29/2018] [Accepted: 10/04/2018] [Indexed: 01/20/2023] Open
Abstract
RecG catalyzes reversal of stalled replication forks in response to replication stress in bacteria. The protein contains a fork recognition (“wedge”) domain that binds branched DNA and a superfamily II (SF2) ATPase motor that drives translocation on double-stranded (ds)DNA. The mechanism by which the wedge and motor domains collaborate to catalyze fork reversal in RecG and analogous eukaryotic fork remodelers is unknown. Here, we used electron paramagnetic resonance (EPR) spectroscopy to probe conformational changes between the wedge and ATPase domains in response to fork DNA binding by Thermotoga maritima RecG. Upon binding DNA, the ATPase-C lobe moves away from both the wedge and ATPase-N domains. This conformational change is consistent with a model of RecG fully engaged with a DNA fork substrate constructed from a crystal structure of RecG bound to a DNA junction together with recent cryo-electron microscopy (EM) structures of chromatin remodelers in complex with dsDNA. We show by mutational analysis that a conserved loop within the translocation in RecG (TRG) motif that was unstructured in the RecG crystal structure is essential for fork reversal and DNA-dependent conformational changes. Together, this work helps provide a more coherent model of fork binding and remodeling by RecG and related eukaryotic enzymes.
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Affiliation(s)
- Garrett M Warren
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA.
| | - Richard A Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA.
| | - Hassane S Mchaourab
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA.
| | - Brandt F Eichman
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA.
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55
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Yates M, Maréchal A. Ubiquitylation at the Fork: Making and Breaking Chains to Complete DNA Replication. Int J Mol Sci 2018; 19:E2909. [PMID: 30257459 PMCID: PMC6213728 DOI: 10.3390/ijms19102909] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 09/20/2018] [Accepted: 09/24/2018] [Indexed: 12/11/2022] Open
Abstract
The complete and accurate replication of the genome is a crucial aspect of cell proliferation that is often perturbed during oncogenesis. Replication stress arising from a variety of obstacles to replication fork progression and processivity is an important contributor to genome destabilization. Accordingly, cells mount a complex response to this stress that allows the stabilization and restart of stalled replication forks and enables the full duplication of the genetic material. This response articulates itself on three important platforms, Replication Protein A/RPA-coated single-stranded DNA, the DNA polymerase processivity clamp PCNA and the FANCD2/I Fanconi Anemia complex. On these platforms, the recruitment, activation and release of a variety of genome maintenance factors is regulated by post-translational modifications including mono- and poly-ubiquitylation. Here, we review recent insights into the control of replication fork stability and restart by the ubiquitin system during replication stress with a particular focus on human cells. We highlight the roles of E3 ubiquitin ligases, ubiquitin readers and deubiquitylases that provide the required flexibility at stalled forks to select the optimal restart pathways and rescue genome stability during stressful conditions.
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Affiliation(s)
- Maïlyn Yates
- Department of Biology, Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada.
| | - Alexandre Maréchal
- Department of Biology, Université de Sherbrooke, Sherbrooke, QC J1K 2R1, Canada.
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56
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Wilson JJ, Chow KH, Labrie NJ, Branca JA, Sproule TJ, Perkins BRA, Wolf EE, Costa M, Stafford G, Rosales C, Mills KD, Roopenian DC, Hasham MG. Enhancing the efficacy of glycolytic blockade in cancer cells via RAD51 inhibition. Cancer Biol Ther 2018; 20:169-182. [PMID: 30183475 PMCID: PMC6343731 DOI: 10.1080/15384047.2018.1507666] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Targeting the early steps of the glycolysis pathway in cancers is a well-established therapeutic strategy; however, the doses required to elicit a therapeutic effect on the cancer can be toxic to the patient. Consequently, numerous preclinical and clinical studies have combined glycolytic blockade with other therapies. However, most of these other therapies do not specifically target cancer cells, and thus adversely affect normal tissue. Here we first show that a diverse number of cancer models – spontaneous, patient-derived xenografted tumor samples, and xenografted human cancer cells – can be efficiently targeted by 2-deoxy-D-Glucose (2DG), a well-known glycolytic inhibitor. Next, we tested the cancer-cell specificity of a therapeutic compound using the MEC1 cell line, a chronic lymphocytic leukemia (CLL) cell line that expresses activation induced cytidine deaminase (AID). We show that MEC1 cells, are susceptible to 4,4ʹ-Diisothiocyano-2,2ʹ-stilbenedisulfonic acid (DIDS), a specific RAD51 inhibitor. We then combine 2DG and DIDS, each at a lower dose and demonstrate that this combination is more efficacious than fludarabine, the current standard- of- care treatment for CLL. This suggests that the therapeutic blockade of glycolysis together with the therapeutic inhibition of RAD51-dependent homologous recombination can be a potentially beneficial combination for targeting AID positive cancer cells with minimal adverse effects on normal tissue. Implications: Combination therapy targeting glycolysis and specific RAD51 function shows increased efficacy as compared to standard of care treatments in leukemias.
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Affiliation(s)
- John J Wilson
- a Research Department , The Jackson Laboratory , Bar Harbor , Maine , USA
| | - Kin-Hoe Chow
- a Research Department , The Jackson Laboratory , Bar Harbor , Maine , USA
| | - Nathan J Labrie
- a Research Department , The Jackson Laboratory , Bar Harbor , Maine , USA
| | - Jane A Branca
- a Research Department , The Jackson Laboratory , Bar Harbor , Maine , USA
| | - Thomas J Sproule
- a Research Department , The Jackson Laboratory , Bar Harbor , Maine , USA
| | - Bryant R A Perkins
- a Research Department , The Jackson Laboratory , Bar Harbor , Maine , USA
| | - Elise E Wolf
- a Research Department , The Jackson Laboratory , Bar Harbor , Maine , USA
| | - Mauro Costa
- a Research Department , The Jackson Laboratory , Bar Harbor , Maine , USA
| | - Grace Stafford
- a Research Department , The Jackson Laboratory , Bar Harbor , Maine , USA
| | - Christine Rosales
- a Research Department , The Jackson Laboratory , Bar Harbor , Maine , USA
| | | | - Derry C Roopenian
- a Research Department , The Jackson Laboratory , Bar Harbor , Maine , USA
| | - Muneer G Hasham
- a Research Department , The Jackson Laboratory , Bar Harbor , Maine , USA
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57
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Ordabayev YA, Nguyen B, Niedziela-Majka A, Lohman TM. Regulation of UvrD Helicase Activity by MutL. J Mol Biol 2018; 430:4260-4274. [PMID: 30171840 DOI: 10.1016/j.jmb.2018.08.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 08/03/2018] [Accepted: 08/23/2018] [Indexed: 11/18/2022]
Abstract
Escherichia coli UvrD is a superfamily 1 helicase/translocase involved in multiple DNA metabolic processes including methyl-directed mismatch DNA repair. Although a UvrD monomer can translocate along single-stranded DNA, a UvrD dimer is needed for processive helicase activity in vitro. E. coli MutL, a regulatory protein involved in methyl-directed mismatch repair, stimulates UvrD helicase activity; however, the mechanism is not well understood. Using single-molecule fluorescence and ensemble approaches, we find that a single MutL dimer can activate latent UvrD monomer helicase activity. However, we also find that MutL stimulates UvrD dimer helicase activity. We further find that MutL enhances the DNA-unwinding processivity of UvrD. Hence, MutL acts as a processivity factor by binding to and presumably moving along with UvrD to facilitate DNA unwinding.
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Affiliation(s)
- Yerdos A Ordabayev
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., Box 8231, St. Louis, MO 63110, United States
| | - Binh Nguyen
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., Box 8231, St. Louis, MO 63110, United States
| | - Anita Niedziela-Majka
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., Box 8231, St. Louis, MO 63110, United States
| | - Timothy M Lohman
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 S. Euclid Ave., Box 8231, St. Louis, MO 63110, United States.
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58
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Carrasco B, Seco EM, López-Sanz M, Alonso JC, Ayora S. Bacillus subtilis RarA modulates replication restart. Nucleic Acids Res 2018; 46:7206-7220. [PMID: 29947798 PMCID: PMC6101539 DOI: 10.1093/nar/gky541] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 06/05/2018] [Indexed: 02/01/2023] Open
Abstract
The ubiquitous RarA/Mgs1/WRNIP protein plays a crucial, but poorly understood role in genome maintenance. We show that Bacillus subtilis RarA, in the apo form, preferentially binds single-stranded (ss) over double-stranded (ds) DNA. SsbA bound to ssDNA loads RarA, and for such recruitment the amphipathic C-terminal domain of SsbA is required. RarA is a DNA-dependent ATPase strongly stimulated by ssDNA–dsDNA junctions and SsbA, or by dsDNA ends. RarA, which may interact with PriA, does not stimulate PriA DNA unwinding. In a reconstituted PriA-dependent DNA replication system, RarA inhibited initiation, but not chain elongation. The RarA effect was not observed in the absence of SsbA, or when the host-encoded preprimosome and the DNA helicase are replaced by proteins from the SPP1 phage with similar function. We propose that RarA assembles at blocked forks to maintain genome integrity. Through its interaction with SsbA and with a preprimosomal component, RarA might impede the assembly of the replicative helicase, to prevent that recombination intermediates contribute to pathological DNA replication restart.
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Affiliation(s)
- Begoña Carrasco
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, (CNB-CSIC), Cantoblanco 28049, Madrid, Spain
| | - Elena M Seco
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, (CNB-CSIC), Cantoblanco 28049, Madrid, Spain
| | - María López-Sanz
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, (CNB-CSIC), Cantoblanco 28049, Madrid, Spain
| | - Juan C Alonso
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, (CNB-CSIC), Cantoblanco 28049, Madrid, Spain
| | - Silvia Ayora
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, (CNB-CSIC), Cantoblanco 28049, Madrid, Spain
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59
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Liao H, Ji F, Helleday T, Ying S. Mechanisms for stalled replication fork stabilization: new targets for synthetic lethality strategies in cancer treatments. EMBO Rep 2018; 19:embr.201846263. [PMID: 30108055 DOI: 10.15252/embr.201846263] [Citation(s) in RCA: 122] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 07/06/2018] [Accepted: 07/20/2018] [Indexed: 01/24/2023] Open
Abstract
Timely and faithful duplication of the entire genome depends on completion of replication. Replication forks frequently encounter obstacles that may cause genotoxic fork stalling. Nevertheless, failure to complete replication rarely occurs under normal conditions, which is attributed to an intricate network of proteins that serves to stabilize, repair and restart stalled forks. Indeed, many of the components in this network are encoded by tumour suppressor genes, and their loss of function by mutation or deletion generates genomic instability, a hallmark of cancer. Paradoxically, the same fork-protective network also confers resistance of cancer cells to chemotherapeutic drugs that induce high-level replication stress. Here, we review the mechanisms and major pathways rescuing stalled replication forks, with a focus on fork stabilization preventing fork collapse. A coherent understanding of how cells protect their replication forks will not only provide insight into how cells maintain genome stability, but also unravel potential therapeutic targets for cancers refractory to conventional chemotherapies.
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Affiliation(s)
- Hongwei Liao
- Department of Pharmacology & Key Laboratory of Respiratory Disease of Zhejiang Province, Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital, Institute of Respiratory Diseases, Zhejiang University School of Medicine, Hangzhou, China
| | - Fang Ji
- Department of Pharmacology & Key Laboratory of Respiratory Disease of Zhejiang Province, Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital, Institute of Respiratory Diseases, Zhejiang University School of Medicine, Hangzhou, China
| | - Thomas Helleday
- Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden .,Sheffield Cancer Centre, Department of Oncology and Metabolism, University of Sheffield, Sheffield, UK
| | - Songmin Ying
- Department of Pharmacology & Key Laboratory of Respiratory Disease of Zhejiang Province, Department of Respiratory and Critical Care Medicine, Second Affiliated Hospital, Institute of Respiratory Diseases, Zhejiang University School of Medicine, Hangzhou, China
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60
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Zhai B, DuPrez K, Han X, Yuan Z, Ahmad S, Xu C, Gu L, Ni J, Fan L, Shen Y. The archaeal ATPase PINA interacts with the helicase Hjm via its carboxyl terminal KH domain remodeling and processing replication fork and Holliday junction. Nucleic Acids Res 2018; 46:6627-6641. [PMID: 29846688 PMCID: PMC6061704 DOI: 10.1093/nar/gky451] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 05/05/2018] [Accepted: 05/09/2018] [Indexed: 11/27/2022] Open
Abstract
PINA is a novel ATPase and DNA helicase highly conserved in Archaea, the third domain of life. The PINA from Sulfolobus islandicus (SisPINA) forms a hexameric ring in crystal and solution. The protein is able to promote Holliday junction (HJ) migration and physically and functionally interacts with Hjc, the HJ specific endonuclease. Here, we show that SisPINA has direct physical interaction with Hjm (Hel308a), a helicase presumably targeting replication forks. In vitro biochemical analysis revealed that Hjm, Hjc, and SisPINA are able to coordinate HJ migration and cleavage in a concerted way. Deletion of the carboxyl 13 amino acid residues impaired the interaction between SisPINA and Hjm. Crystal structure analysis showed that the carboxyl 70 amino acid residues fold into a type II KH domain which, in other proteins, functions in binding RNA or ssDNA. The KH domain not only mediates the interactions of PINA with Hjm and Hjc but also regulates the hexameric assembly of PINA. Our results collectively suggest that SisPINA, Hjm and Hjc work together to function in replication fork regression, HJ formation and HJ cleavage.
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Affiliation(s)
- Binyuan Zhai
- State Key Laboratory of Microbial Technology, Microbiology and Biotechnology Institute, Shandong University, 72 Binhai Road, Jimo, Qingdao, Shandong, 266237, P.R. China
| | - Kevin DuPrez
- Department of Biochemistry, University of California, Riverside, CA 92521, USA
| | - Xiaoyun Han
- State Key Laboratory of Microbial Technology, Microbiology and Biotechnology Institute, Shandong University, 72 Binhai Road, Jimo, Qingdao, Shandong, 266237, P.R. China
| | - Zenglin Yuan
- State Key Laboratory of Microbial Technology, Microbiology and Biotechnology Institute, Shandong University, 72 Binhai Road, Jimo, Qingdao, Shandong, 266237, P.R. China
| | - Sohail Ahmad
- State Key Laboratory of Microbial Technology, Microbiology and Biotechnology Institute, Shandong University, 72 Binhai Road, Jimo, Qingdao, Shandong, 266237, P.R. China
| | - Cheng Xu
- State Key Laboratory of Microbial Technology, Microbiology and Biotechnology Institute, Shandong University, 72 Binhai Road, Jimo, Qingdao, Shandong, 266237, P.R. China
| | - Lichuan Gu
- State Key Laboratory of Microbial Technology, Microbiology and Biotechnology Institute, Shandong University, 72 Binhai Road, Jimo, Qingdao, Shandong, 266237, P.R. China
| | - Jinfeng Ni
- State Key Laboratory of Microbial Technology, Microbiology and Biotechnology Institute, Shandong University, 72 Binhai Road, Jimo, Qingdao, Shandong, 266237, P.R. China
| | - Li Fan
- Department of Biochemistry, University of California, Riverside, CA 92521, USA
| | - Yulong Shen
- State Key Laboratory of Microbial Technology, Microbiology and Biotechnology Institute, Shandong University, 72 Binhai Road, Jimo, Qingdao, Shandong, 266237, P.R. China
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61
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Pasero P, Vindigni A. Nucleases Acting at Stalled Forks: How to Reboot the Replication Program with a Few Shortcuts. Annu Rev Genet 2018; 51:477-499. [PMID: 29178820 DOI: 10.1146/annurev-genet-120116-024745] [Citation(s) in RCA: 86] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In a lifetime, a human being synthesizes approximately 2×1016 meters of DNA, a distance that corresponds to 130,000 times the distance between the Earth and the Sun. This daunting task is executed by thousands of replication forks, which progress along the chromosomes and frequently stall when they encounter DNA lesions, unusual DNA structures, RNA polymerases, or tightly-bound protein complexes. To complete DNA synthesis before the onset of mitosis, eukaryotic cells have evolved complex mechanisms to process and restart arrested forks through the coordinated action of multiple nucleases, topoisomerases, and helicases. In this review, we discuss recent advances in understanding the role and regulation of nucleases acting at stalled forks with a focus on the nucleolytic degradation of nascent DNA, a process commonly referred to as fork resection. We also discuss the effects of deregulated fork resection on genomic instability and on the unscheduled activation of the interferon response under replication stress conditions.
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Affiliation(s)
- Philippe Pasero
- Institute of Human Genetics, CNRS UMR9002, University of Montpellier, 34396 Montpellier, France;
| | - Alessandro Vindigni
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA;
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62
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Abstract
Accurate transmission of the genetic information requires complete duplication of the chromosomal DNA each cell division cycle. However, the idea that replication forks would form at origins of DNA replication and proceed without impairment to copy the chromosomes has proven naive. It is now clear that replication forks stall frequently as a result of encounters between the replication machinery and template damage, slow-moving or paused transcription complexes, unrelieved positive superhelical tension, covalent protein-DNA complexes, and as a result of cellular stress responses. These stalled forks are a major source of genome instability. The cell has developed many strategies for ensuring that these obstructions to DNA replication do not result in loss of genetic information, including DNA damage tolerance mechanisms such as lesion skipping, whereby the replisome jumps the lesion and continues downstream; template switching both behind template damage and at the stalled fork; and the error-prone pathway of translesion synthesis.
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Affiliation(s)
- Kenneth J Marians
- Molecular Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA;
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63
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Abstract
In all organisms, replication impairments are an important source of genome rearrangements, mainly because of the formation of double-stranded DNA (dsDNA) ends at inactivated replication forks. Three reactions for the formation of dsDNA ends at replication forks were originally described for Escherichia coli and became seminal models for all organisms: the encounter of replication forks with preexisting single-stranded DNA (ssDNA) interruptions, replication fork reversal, and head-to-tail collisions of successive replication rounds. Here, we first review the experimental evidence that now allows us to know when, where, and how these three different reactions occur in E. coli. Next, we recall our recent studies showing that in wild-type E. coli, spontaneous replication fork breakage occurs in 18% of cells at each generation. We propose that it results from the replication of preexisting nicks or gaps, since it does not involve replication fork reversal or head-to-tail fork collisions. In the recB mutant, deficient for double-strand break (DSB) repair, fork breakage triggers DSBs in the chromosome terminus during cell division, a reaction that is heritable for several generations. Finally, we recapitulate several observations suggesting that restart from intact inactivated replication forks and restart from recombination intermediates require different sets of enzymatic activities. The finding that 18% of cells suffer replication fork breakage suggests that DNA remains intact at most inactivated forks. Similarly, only 18% of cells need the helicase loader for replication restart, which leads us to speculate that the replicative helicase remains on DNA at intact inactivated replication forks and is reactivated by the replication restart proteins.
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64
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Bhat KP, Cortez D. RPA and RAD51: fork reversal, fork protection, and genome stability. Nat Struct Mol Biol 2018; 25:446-453. [PMID: 29807999 PMCID: PMC6006513 DOI: 10.1038/s41594-018-0075-z] [Citation(s) in RCA: 233] [Impact Index Per Article: 38.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 04/23/2018] [Accepted: 04/26/2018] [Indexed: 01/23/2023]
Abstract
Replication protein A (RPA) and RAD51 are DNA-binding proteins that help maintain genome stability during DNA replication. These proteins regulate nucleases, helicases, DNA translocases, and signaling proteins to control replication, repair, recombination, and the DNA damage response. Their different DNA-binding mechanisms, enzymatic activities, and binding partners provide unique functionalities that cooperate to ensure that the appropriate activities are deployed at the right time to overcome replication challenges. Here we review and discuss the latest discoveries of the mechanisms by which these proteins work to preserve genome stability, with a focus on their actions in fork reversal and fork protection.
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Affiliation(s)
- Kamakoti P Bhat
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - David Cortez
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
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65
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Genetic Evidence for Roles of Yeast Mitotic Cyclins at Single-Stranded Gaps Created by DNA Replication. G3-GENES GENOMES GENETICS 2018; 8:737-752. [PMID: 29279302 PMCID: PMC5919743 DOI: 10.1534/g3.117.300537] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Paused or stalled replication forks are major threats to genome integrity; unraveling the complex pathways that contribute to fork stability and restart is crucial. Experimentally, fork stalling is induced by growing the cells in presence of hydroxyurea (HU), which depletes the pool of deoxynucleotide triphosphates (dNTPs) and slows down replication progression in yeast. Here, I report an epistasis analysis, based on sensitivity to HU, between CLB2, the principal mitotic cyclin gene in Saccharomyces cerevisiae, and genes involved in fork stability and recombination. clb2Δ cells are not sensitive to HU, but the strong synergistic effect of clb2Δ with most genes tested indicates, unexpectedly, that CLB2 has an important role in DNA replication, in the stability and restart of stalled forks, and in pathways dependent on and independent of homologous recombination. Results indicate that CLB2 functions in parallel with the SGS1 helicase and EXO1 exonuclease to allow proper Rad51 recombination, but also regulates a combined Sgs1–Exo1 activity in a pathway dependent on Mec1 and Rad53 checkpoint protein kinases. The data argue that Mec1 regulates Clb2 to prevent a deleterious Sgs1–Exo1 activity at paused or stalled forks, whereas Rad53 checkpoint activation regulates Clb2 to allow a necessary Sgs1–Exo1 activity at stalled or collapsed forks. Altogether, this study indicates that Clb2 regulates the activity of numerous nucleases at single-stranded gaps created by DNA replication. A model is proposed for the function and regulation of Clb2 at stalled forks. These data provide new perspectives on the role of mitotic cyclins at the end of S phase.
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66
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Tomko EJ, Lohman TM. Modulation of Escherichia coli UvrD Single-Stranded DNA Translocation by DNA Base Composition. Biophys J 2017; 113:1405-1415. [PMID: 28978435 DOI: 10.1016/j.bpj.2017.08.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 08/15/2017] [Accepted: 08/16/2017] [Indexed: 10/18/2022] Open
Abstract
Escherichia coli UvrD is an SF1A DNA helicase/translocase that functions in chromosomal DNA repair and replication of some plasmids. UvrD can also displace proteins such as RecA from DNA in its capacity as an anti-recombinase. Central to all of these activities is its ATP-driven 3'-5' single-stranded (ss) DNA translocation activity. Previous ensemble transient kinetic studies have estimated the average translocation rate of a UvrD monomer on ssDNA composed solely of deoxythymidylates. Here we show that the rate of UvrD monomer translocation along ssDNA is influenced by DNA base composition, with UvrD having the fastest rate along polypyrimidines although decreasing nearly twofold on ssDNA containing equal amounts of the four bases. Experiments with DNA containing abasic sites and polyethylene glycol spacers show that the ssDNA base also influences translocation processivity. These results indicate that changes in base composition and backbone insertions influence the translocation rates, with increased ssDNA base stacking correlated with decreased translocation rates, supporting the proposal that base-stacking interactions are involved in the translocation mechanism.
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Affiliation(s)
- Eric J Tomko
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri
| | - Timothy M Lohman
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri.
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67
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Zhao B, Zhang W, Cun Y, Li J, Liu Y, Gao J, Zhu H, Zhou H, Zhang R, Zheng P. Mouse embryonic stem cells have increased capacity for replication fork restart driven by the specific Filia-Floped protein complex. Cell Res 2017; 28:69-89. [PMID: 29125140 DOI: 10.1038/cr.2017.139] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 07/12/2017] [Accepted: 08/22/2017] [Indexed: 12/15/2022] Open
Abstract
Pluripotent stem cells (PSCs) harbor constitutive DNA replication stress during their rapid proliferation and the consequent genome instability hampers their applications in regenerative medicine. It is therefore important to understand the regulatory mechanisms of replication stress response in PSCs. Here, we report that mouse embryonic stem cells (ESCs) are superior to differentiated cells in resolving replication stress. Specifically, ESCs utilize a unique Filia-Floped protein complex-dependent mechanism to efficiently promote the restart of stalled replication forks, therefore maintaining genomic stability. The ESC-specific Filia-Floped complex resides on replication forks under normal conditions. Replication stress stimulates their recruitment to stalling forks and the serine 151 residue of Filia is phosphorylated in an ATR-dependent manner. This modification enables the Filia-Floped complex to act as a functional scaffold, which then promotes the stalling fork restart through a dual mechanism: both enhancing recruitment of the replication fork restart protein, Blm, and stimulating ATR kinase activation. In the Blm pathway, the scaffolds recruit the E3 ubiquitin ligase, Trim25, to the stalled replication forks, and in turn Trim25 tethers and concentrates Blm at stalled replication forks through ubiquitination. In differentiated cells, the recruitment of the Trim25-Blm complex to replication forks and the activation of ATR signaling are much less robust due to lack of the ESC-specific Filia-Floped scaffold. Thus, our study reveals that ESCs utilize an additional and unique regulatory layer to efficiently promote the stalled fork restart and maintain genomic stability.
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Affiliation(s)
- Bo Zhao
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, China.,Yunnan Key Laboratory of Animal Reproduction, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, China
| | - Weidao Zhang
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, China.,Yunnan Key Laboratory of Animal Reproduction, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
| | - Yixian Cun
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, China
| | - Jingzheng Li
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, China.,Yunnan Key Laboratory of Animal Reproduction, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, China.,Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, Yunnan 650204, China
| | - Yan Liu
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, China.,Yunnan Key Laboratory of Animal Reproduction, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, China
| | - Jing Gao
- Department of Analytical Chemistry and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Hongwen Zhu
- Department of Analytical Chemistry and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Hu Zhou
- Department of Analytical Chemistry and CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Rugang Zhang
- Gene Expression and Regulation Program, The Wistar Institute Cancer Center, The Wistar Institute, Philadelphia, PA 19104, USA
| | - Ping Zheng
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, China.,Yunnan Key Laboratory of Animal Reproduction, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan 650223, China
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68
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Raguse M, Torres R, Seco EM, Gándara C, Ayora S, Moeller R, Alonso JC. Bacillus subtilis DisA helps to circumvent replicative stress during spore revival. DNA Repair (Amst) 2017; 59:57-68. [PMID: 28961460 DOI: 10.1016/j.dnarep.2017.09.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 08/24/2017] [Accepted: 09/08/2017] [Indexed: 02/06/2023]
Abstract
The mechanisms that allow to circumvent replicative stress, and to resume DNA synthesis are poorly understood in Bacillus subtilis. To study the role of the diadenylate cyclase DisA and branch migration translocase (BMT) RadA/Sms in restarting a stalled replication fork, we nicked and broke the circular chromosome of an inert mature haploid spore, damaged the bases, and measured survival of reviving spores. During undisturbed ripening, nicks and breaks should be repaired by pathways that do not invoke long-range end resection or genetic exchange by homologous recombination, after which DNA replication might be initiated. We found that DNA damage reduced the viability of spores that lacked DisA, BMT (RadA/Sms, RuvAB or RecG), the Holliday junction resolvase RecU, or the translesion synthesis DNA polymerases (PolY1 or PolY2). DisA and RadA/Sms, in concert with RuvAB, RecG, RecU, PolY1 or PolY2, are needed to bypass replication-blocking lesions. DisA, which binds to stalled or reversed forks, did not apparently affect initiation of PriA-dependent DNA replication in vitro. We propose that DisA is necessary to coordinate responses to replicative stress; it could help to circumvent damaged template bases that otherwise impede fork progression.
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Affiliation(s)
- Marina Raguse
- German Aerospace Center (DLReV), Institute of Aerospace Medicine, Radiation Biology Department, Space Microbiology Research Group, Linder Hoehe, D-51147 Cologne (Köln), Germany
| | - Rubén Torres
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología (CNB-CSIC), Darwin 3, Cantoblanco, 28049 Madrid, Spain
| | - Elena M Seco
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología (CNB-CSIC), Darwin 3, Cantoblanco, 28049 Madrid, Spain
| | - Carolina Gándara
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología (CNB-CSIC), Darwin 3, Cantoblanco, 28049 Madrid, Spain
| | - Silvia Ayora
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología (CNB-CSIC), Darwin 3, Cantoblanco, 28049 Madrid, Spain
| | - Ralf Moeller
- German Aerospace Center (DLReV), Institute of Aerospace Medicine, Radiation Biology Department, Space Microbiology Research Group, Linder Hoehe, D-51147 Cologne (Köln), Germany.
| | - Juan C Alonso
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología (CNB-CSIC), Darwin 3, Cantoblanco, 28049 Madrid, Spain.
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69
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Nguyen JHG, Viterbo D, Anand RP, Verra L, Sloan L, Richard GF, Freudenreich CH. Differential requirement of Srs2 helicase and Rad51 displacement activities in replication of hairpin-forming CAG/CTG repeats. Nucleic Acids Res 2017; 45:4519-4531. [PMID: 28175398 PMCID: PMC5416882 DOI: 10.1093/nar/gkx088] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 01/31/2017] [Indexed: 12/25/2022] Open
Abstract
Trinucleotide repeats are a source of genome instability, causing replication fork stalling, chromosome fragility, and impaired repair. Specialized helicases play an important role in unwinding DNA structures to maintain genome stability. The Srs2 helicase unwinds DNA hairpins, facilitates replication, and prevents repeat instability and fragility. However, since Srs2 is a multifunctional protein with helicase activity and the ability to displace Rad51 recombinase, it was unclear which functions were required for its various protective roles. Here, using SRS2 separation-of-function alleles, we show that in the absence of Srs2 recruitment to PCNA or in helicase-deficient mutants, breakage at a CAG/CTG repeat increases. We conclude that Srs2 interaction with PCNA allows the helicase activity to unwind fork-blocking CAG/CTG hairpin structures to prevent breaks. Independently of PCNA binding, Srs2 also displaces Rad51 from nascent strands to prevent recombination-dependent repeat expansions and contractions. By 2D gel electrophoresis, we detect two different kinds of structured intermediates or joint molecules (JMs). Some JMs are Rad51-independent and exhibit properties of reversed forks, including being processed by the Exo1 nuclease. In addition, in a helicase-deficient mutant, Rad51-dependent JMs are detected, probably corresponding to recombination between sisters. These results clarify the many roles of Srs2 in facilitating replication through fork-blocking hairpin lesions.
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Affiliation(s)
| | - David Viterbo
- Institut Pasteur, Department Genomes & Genetics, CNRS, UMR3525, Université Pierre et Marie Curie, UFR927, 25 rue du Dr Roux, F-75015 Paris, France
| | - Ranjith P Anand
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Lauren Verra
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Laura Sloan
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Guy-Franck Richard
- Institut Pasteur, Department Genomes & Genetics, CNRS, UMR3525, Université Pierre et Marie Curie, UFR927, 25 rue du Dr Roux, F-75015 Paris, France
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70
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Toulmin A, Baltierra-Jasso LE, Morten MJ, Sabir T, McGlynn P, Schröder GF, Smith BO, Magennis SW. Conformational Heterogeneity in a Fully Complementary DNA Three-Way Junction with a GC-Rich Branchpoint. Biochemistry 2017; 56:4985-4991. [PMID: 28820590 DOI: 10.1021/acs.biochem.7b00677] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
DNA three-way junctions (3WJs) are branched structures that serve as important biological intermediates and as components in DNA nanostructures. We recently derived the global structure of a fully complementary 3WJ and found that it contained unpaired bases at the branchpoint, which is consistent with previous observations of branch flexibility and branchpoint reactivity. By combining high-resolution single-molecule Förster resonance energy transfer, molecular modeling, time-resolved ensemble fluorescence spectroscopy, and the first 19F nuclear magnetic resonance observations of fully complementary 3WJs, we now show that the 3WJ structure can adopt multiple distinct conformations depending upon the sequence at the branchpoint. A 3WJ with a GC-rich branchpoint adopts an open conformation with unpaired bases at the branch and at least one additional conformation with an increased number of base interactions at the branchpoint. This structural diversity has implications for branch interactions and processing in vivo and for technological applications.
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Affiliation(s)
- Anita Toulmin
- The School of Chemistry, The University of Manchester , Oxford Road, Manchester M13 9PL, U.K.,The Photon Science Institute, The University of Manchester , Alan Turing Building, Oxford Road, Manchester M13 9PL, U.K
| | - Laura E Baltierra-Jasso
- The School of Chemistry, The University of Manchester , Oxford Road, Manchester M13 9PL, U.K.,The Photon Science Institute, The University of Manchester , Alan Turing Building, Oxford Road, Manchester M13 9PL, U.K.,School of Chemistry, WestCHEM, University of Glasgow , Joseph Black Building, University Avenue, Glasgow G12 8QQ, U.K
| | - Michael J Morten
- School of Chemistry, WestCHEM, University of Glasgow , Joseph Black Building, University Avenue, Glasgow G12 8QQ, U.K
| | - Tara Sabir
- The School of Chemistry, The University of Manchester , Oxford Road, Manchester M13 9PL, U.K.,The Photon Science Institute, The University of Manchester , Alan Turing Building, Oxford Road, Manchester M13 9PL, U.K
| | - Peter McGlynn
- Department of Biology, University of York , Wentworth Way, York YO10 5DD, U.K
| | - Gunnar F Schröder
- Institute of Complex Systems (ICS-6), Forschungszentrum Jülich , 52425 Jülich, Germany.,Physics Department, Heinrich-Heine Universität Düsseldorf , Düsseldorf, Germany
| | - Brian O Smith
- Institute of Molecular, Cell and Systems Biology, University of Glasgow , Glasgow G12 8QQ, U.K
| | - Steven W Magennis
- School of Chemistry, WestCHEM, University of Glasgow , Joseph Black Building, University Avenue, Glasgow G12 8QQ, U.K
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71
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Abstract
One major challenge during genome duplication is the stalling of DNA replication forks by various forms of template blockages. As these barriers can lead to incomplete replication, multiple mechanisms have to act concertedly to correct and rescue stalled replication forks. Among these mechanisms, replication fork regression entails simultaneous annealing of nascent and template strands, which leads to regression of replication forks and formation of four-way DNA junctions. In principle, this process can lead to either positive outcomes, such as DNA repair and replication resumption, or less desirable outcomes, such as misalignment between nascent and template DNA and DNA cleavage. While our understanding of replication fork regression and its various possible outcomes is still at an early stage, recent studies using combinational approaches in multiple organisms have begun to identify the enzymes that catalyze this DNA transaction and how these enzymes are regulated, as well as the specific manners by which fork regression can influence replication. This review summarizes these recent progresses. In keeping with the theme of this series of reviews, we focus on studies in yeast and compare to findings in higher eukaryotes. It is anticipated that these findings will form the basis for future endeavors to further elucidate replication fork remodeling and its implications for genome maintenance.
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72
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Abstract
Cells are exposed to various endogenous and exogenous insults that induce DNA damage, which, if unrepaired, impairs genome integrity and leads to the development of various diseases, including cancer. Recent evidence has implicated poly(ADP-ribose) polymerase 1 (PARP1) in various DNA repair pathways and in the maintenance of genomic stability. The inhibition of PARP1 is therefore being exploited clinically for the treatment of various cancers, which include DNA repair-deficient ovarian, breast and prostate cancers. Understanding the role of PARP1 in maintaining genome integrity is not only important for the design of novel chemotherapeutic agents, but is also crucial for gaining insights into the mechanisms of chemoresistance in cancer cells. In this Review, we discuss the roles of PARP1 in mediating various aspects of DNA metabolism, such as single-strand break repair, nucleotide excision repair, double-strand break repair and the stabilization of replication forks, and in modulating chromatin structure.
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73
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Torres R, Romero H, Rodríguez-Cerrato V, Alonso JC. Interplay between Bacillus subtilis RecD2 and the RecG or RuvAB helicase in recombinational repair. DNA Repair (Amst) 2017; 55:40-46. [DOI: 10.1016/j.dnarep.2017.05.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 05/08/2017] [Accepted: 05/10/2017] [Indexed: 10/24/2022]
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74
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Morrow CA, Nguyen MO, Fower A, Wong IN, Osman F, Bryer C, Whitby MC. Inter-Fork Strand Annealing causes genomic deletions during the termination of DNA replication. eLife 2017; 6. [PMID: 28586299 PMCID: PMC5461108 DOI: 10.7554/elife.25490] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 05/22/2017] [Indexed: 11/29/2022] Open
Abstract
Problems that arise during DNA replication can drive genomic alterations that are instrumental in the development of cancers and many human genetic disorders. Replication fork barriers are a commonly encountered problem, which can cause fork collapse and act as hotspots for replication termination. Collapsed forks can be rescued by homologous recombination, which restarts replication. However, replication restart is relatively slow and, therefore, replication termination may frequently occur by an active fork converging on a collapsed fork. We find that this type of non-canonical fork convergence in fission yeast is prone to trigger deletions between repetitive DNA sequences via a mechanism we call Inter-Fork Strand Annealing (IFSA) that depends on the recombination proteins Rad52, Exo1 and Mus81, and is countered by the FANCM-related DNA helicase Fml1. Based on our findings, we propose that IFSA is a potential threat to genomic stability in eukaryotes. DOI:http://dx.doi.org/10.7554/eLife.25490.001
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Affiliation(s)
- Carl A Morrow
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Michael O Nguyen
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Andrew Fower
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Io Nam Wong
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Fekret Osman
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Claire Bryer
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Matthew C Whitby
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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75
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Activity and in vivo dynamics of Bacillus subtilis DisA are affected by RadA/Sms and by Holliday junction-processing proteins. DNA Repair (Amst) 2017; 55:17-30. [PMID: 28511132 DOI: 10.1016/j.dnarep.2017.05.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 05/03/2017] [Accepted: 05/04/2017] [Indexed: 12/18/2022]
Abstract
Bacillus subtilis c-di-AMP synthase DisA and RecA-related RadA/Sms are involved in the repair of DNA damage in exponentially growing cells. We provide genetic evidence that DisA or RadA/Sms is epistatic to the branch migration translocase (BMT) RecG and the Holliday junction (HJ) resolvase RecU in response to DNA damage. We provide genetic evidence damage. Functional DisA-YFP formed dynamic foci in exponentially growing cells, which moved through the nucleoids at a speed compatible with a DNA-scanning mode. DisA formed more static structures in the absence of RecU or RecG than in wild type cells, while dynamic foci were still observed in cells lacking the BMT RuvAB. Purified DisA synthesizes c-di-AMP, but interaction with RadA/Sms or with HJ DNA decreases DisA-mediated c-di-AMP synthesis. RadA/Sms-YFP also formed dynamic foci in growing cells, but the foci moved throughout the cells rather than just on the nucleoids, and co-localized rarely with DisA-YFP foci, suggesting that RadA/Sms and DisA interact only transiently in unperturbed conditions. Our data suggest a model in which DisA moving along dsDNA indicates absence of DNA damage/replication stress via normal c-di-AMP levels, while interaction with HJ DNA/halted forks leads to reduced c-di-AMP levels and an ensuing block in cell proliferation. RadA/Sms may be involved in modulating DisA activities.
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76
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Gervai JZ, Gálicza J, Szeltner Z, Zámborszky J, Szüts D. A genetic study based on PCNA-ubiquitin fusions reveals no requirement for PCNA polyubiquitylation in DNA damage tolerance. DNA Repair (Amst) 2017; 54:46-54. [PMID: 28458162 DOI: 10.1016/j.dnarep.2017.04.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 04/11/2017] [Accepted: 04/12/2017] [Indexed: 10/19/2022]
Abstract
Post-translational modifications of Proliferating Cell Nuclear Antigen (PCNA) play a key role in regulating the bypass of DNA lesions during DNA replication. PCNA can be monoubiquitylated at lysine 164 by the RAD6-RAD18 ubiquitin ligase complex. Through this modification, PCNA can interact with low fidelity Y family DNA polymerases to promote translesion synthesis. Monoubiquitylated PCNA can be polyubiquitylated on lysine 63 of ubiquitin by a further ubiquitin-conjugating complex. This modification promotes a template switching bypass process in yeast, while its role in higher eukaryotes is less clear. We investigated the function of PCNA ubiquitylation using a PCNAK164R mutant DT40 chicken B lymphoblastoma cell line, which is hypersensitive to DNA damaging agents such as methyl methanesulfonate (MMS), cisplatin or ultraviolet radiation (UV) due to the loss of PCNA modifications. In the PCNAK164R mutant we also detected cell cycle arrest following UV treatment, a reduced rate of damage bypass through translesion DNA synthesis on synthetic UV photoproducts, and an increased rate of genomic mutagenesis following MMS treatment. PCNA-ubiquitin fusion proteins have been reported to mimic endogenous PCNA ubiquitylation. We found that the stable expression of a PCNAK164R-ubiquitin fusion protein fully or partially rescued the observed defects of the PCNAK164R mutant. The expression of a PCNAK164R-ubiquitinK63R fusion protein, on which the formation of lysine 63-linked polyubiquitin chains is not possible, similarly rescued the cell cycle arrest, DNA damage sensitivity, reduction of translesion synthesis and increase of MMS-induced genomic mutagenesis. Template switching bypass was not affected by the genetic elimination of PCNA polyubiquitylation, but it was reduced in the absence of the recombination proteins BRCA1 or XRCC3. Our study found no requirement for PCNA polyubiquitylation to protect cells from replication-stalling DNA damage.
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Affiliation(s)
- Judit Z Gervai
- Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok krt. 2, Budapest, H-1117, Hungary
| | - Judit Gálicza
- Macromolecular Crystallography Group, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen, 37077, Germany
| | - Zoltán Szeltner
- Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok krt. 2, Budapest, H-1117, Hungary
| | - Judit Zámborszky
- Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok krt. 2, Budapest, H-1117, Hungary
| | - Dávid Szüts
- Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok krt. 2, Budapest, H-1117, Hungary.
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77
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Kolinjivadi AM, Sannino V, de Antoni A, Técher H, Baldi G, Costanzo V. Moonlighting at replication forks - a new life for homologous recombination proteins BRCA1, BRCA2 and RAD51. FEBS Lett 2017; 591:1083-1100. [PMID: 28079255 DOI: 10.1002/1873-3468.12556] [Citation(s) in RCA: 116] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 12/27/2016] [Accepted: 01/09/2017] [Indexed: 12/30/2022]
Abstract
Coordination between DNA replication and DNA repair ensures maintenance of genome integrity, which is lost in cancer cells. Emerging evidence has linked homologous recombination (HR) proteins RAD51, BRCA1 and BRCA2 to the stability of nascent DNA. This function appears to be distinct from double-strand break (DSB) repair and is in part due to the prevention of MRE11-mediated degradation of nascent DNA at stalled forks. The role of RAD51 in fork protection resembles the activity described for its prokaryotic orthologue RecA, which prevents nuclease-mediated degradation of DNA and promotes replication fork restart in cells challenged by DNA-damaging agents. Here, we examine the mechanistic aspects of HR-mediated fork protection, addressing the crosstalk between HR and replication proteins.
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Affiliation(s)
| | - Vincenzo Sannino
- DNA metabolism laboratory, IFOM-The Firc Institute of Molecular Oncology, Milan, Italy
| | - Anna de Antoni
- DNA metabolism laboratory, IFOM-The Firc Institute of Molecular Oncology, Milan, Italy
| | - Hervé Técher
- DNA metabolism laboratory, IFOM-The Firc Institute of Molecular Oncology, Milan, Italy
| | - Giorgio Baldi
- DNA metabolism laboratory, IFOM-The Firc Institute of Molecular Oncology, Milan, Italy
| | - Vincenzo Costanzo
- DNA metabolism laboratory, IFOM-The Firc Institute of Molecular Oncology, Milan, Italy
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78
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Yang Z, Nejad MI, Varela JG, Price NE, Wang Y, Gates KS. A role for the base excision repair enzyme NEIL3 in replication-dependent repair of interstrand DNA cross-links derived from psoralen and abasic sites. DNA Repair (Amst) 2017; 52:1-11. [PMID: 28262582 PMCID: PMC5424475 DOI: 10.1016/j.dnarep.2017.02.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Accepted: 02/13/2017] [Indexed: 12/23/2022]
Abstract
Interstrand DNA-DNA cross-links are highly toxic lesions that are important in medicinal chemistry, toxicology, and endogenous biology. In current models of replication-dependent repair, stalling of a replication fork activates the Fanconi anemia pathway and cross-links are "unhooked" by the action of structure-specific endonucleases such as XPF-ERCC1 that make incisions flanking the cross-link. This process generates a double-strand break, which must be subsequently repaired by homologous recombination. Recent work provided evidence for a new, incision-independent unhooking mechanism involving intrusion of a base excision repair (BER) enzyme, NEIL3, into the world of cross-link repair. The evidence suggests that the glycosylase action of NEIL3 unhooks interstrand cross-links derived from an abasic site or the psoralen derivative trioxsalen. If the incision-independent NEIL3 pathway is blocked, repair reverts to the incision-dependent route. In light of the new model invoking participation of NEIL3 in cross-link repair, we consider the possibility that various BER glycosylases or other DNA-processing enzymes might participate in the unhooking of chemically diverse interstrand DNA cross-links.
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Affiliation(s)
- Zhiyu Yang
- University of Missouri Department of Chemistry, 125 Chemistry Building Columbia, MO 65211, United States
| | - Maryam Imani Nejad
- University of Missouri Department of Chemistry, 125 Chemistry Building Columbia, MO 65211, United States
| | - Jacqueline Gamboa Varela
- University of Missouri Department of Chemistry, 125 Chemistry Building Columbia, MO 65211, United States
| | - Nathan E Price
- University of California-Riverside, Department of Chemistry, 501 Big Springs Road Riverside, CA 92521-0403, United States
| | - Yinsheng Wang
- University of California-Riverside, Department of Chemistry, 501 Big Springs Road Riverside, CA 92521-0403, United States
| | - Kent S Gates
- University of Missouri Department of Chemistry, 125 Chemistry Building Columbia, MO 65211, United States; University of Missouri Department of Biochemistry, 125 Chemistry Building Columbia, MO 65211, United States.
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79
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Nikolova T, Roos WP, Krämer OH, Strik HM, Kaina B. Chloroethylating nitrosoureas in cancer therapy: DNA damage, repair and cell death signaling. Biochim Biophys Acta Rev Cancer 2017; 1868:29-39. [PMID: 28143714 DOI: 10.1016/j.bbcan.2017.01.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 01/25/2017] [Accepted: 01/26/2017] [Indexed: 01/20/2023]
Abstract
Chloroethylating nitrosoureas (CNU), such as lomustine, nimustine, semustine, carmustine and fotemustine are used for the treatment of malignant gliomas, brain metastases of different origin, melanomas and Hodgkin disease. They alkylate the DNA bases and give rise to the formation of monoadducts and subsequently interstrand crosslinks (ICL). ICL are critical cytotoxic DNA lesions that link the DNA strands covalently and block DNA replication and transcription. As a result, S phase progression is inhibited and cells are triggered to undergo apoptosis and necrosis, which both contribute to the effectiveness of CNU-based cancer therapy. However, tumor cells resist chemotherapy through the repair of CNU-induced DNA damage. The suicide enzyme O6-methylguanine-DNA methyltransferase (MGMT) removes the precursor DNA lesion O6-chloroethylguanine prior to its conversion into ICL. In cells lacking MGMT, the formed ICL evoke complex enzymatic networks to accomplish their removal. Here we discuss the mechanism of ICL repair as a survival strategy of healthy and cancer cells and DNA damage signaling as a mechanism contributing to CNU-induced cell death. We also discuss therapeutic implications and strategies based on sequential and simultaneous treatment with CNU and the methylating drug temozolomide.
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Affiliation(s)
- Teodora Nikolova
- Institute of Toxicology, University Medical Center, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany.
| | - Wynand P Roos
- Institute of Toxicology, University Medical Center, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany
| | - Oliver H Krämer
- Institute of Toxicology, University Medical Center, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany
| | - Herwig M Strik
- Department of Neurology, University Medical Center, Baldinger Strasse, 35033 Marburg, Germany
| | - Bernd Kaina
- Institute of Toxicology, University Medical Center, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany.
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80
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The Causes and Consequences of Topological Stress during DNA Replication. Genes (Basel) 2016; 7:genes7120134. [PMID: 28009828 PMCID: PMC5192510 DOI: 10.3390/genes7120134] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 12/11/2016] [Accepted: 12/14/2016] [Indexed: 01/08/2023] Open
Abstract
The faithful replication of sister chromatids is essential for genomic integrity in every cell division. The replication machinery must overcome numerous difficulties in every round of replication, including DNA topological stress. Topological stress arises due to the double-stranded helical nature of DNA. When the strands are pulled apart for replication to occur, the intertwining of the double helix must also be resolved or topological stress will arise. This intrinsic problem is exacerbated by specific chromosomal contexts encountered during DNA replication. The convergence of two replicons during termination, the presence of stable protein-DNA complexes and active transcription can all lead to topological stresses being imposed upon DNA replication. Here we describe how replication forks respond to topological stress by replication fork rotation and fork reversal. We also discuss the genomic contexts where topological stress is likely to occur in eukaryotes, focusing on the contribution of transcription. Finally, we describe how topological stress, and the ways forks respond to it, may contribute to genomic instability in cells.
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81
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Replication intermediates that escape Dna2 activity are processed by Holliday junction resolvase Yen1. Nat Commun 2016; 7:13157. [PMID: 27779184 PMCID: PMC5093310 DOI: 10.1038/ncomms13157] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 09/08/2016] [Indexed: 12/29/2022] Open
Abstract
Cells have evolved mechanisms to protect, restart and repair perturbed replication forks, allowing full genome duplication, even under replication stress. Interrogating the interplay between nuclease-helicase Dna2 and Holliday junction (HJ) resolvase Yen1, we find the Dna2 helicase activity acts parallel to homologous recombination (HR) in promoting DNA replication and chromosome detachment at mitosis after replication fork stalling. Yen1, but not the HJ resolvases Slx1-Slx4 and Mus81-Mms4, safeguards chromosome segregation by removing replication intermediates that escape Dna2. Post-replicative DNA damage checkpoint activation in Dna2 helicase-defective cells causes terminal G2/M arrest by precluding Yen1-dependent repair, whose activation requires progression into anaphase. These findings explain the exquisite replication stress sensitivity of Dna2 helicase-defective cells, and identify a non-canonical role for Yen1 in the processing of replication intermediates that is distinct from HJ resolution. The involvement of Dna2 helicase activity in completing replication may have implications for DNA2-associated pathologies, including cancer and Seckel syndrome.
DNA replication stress drives genome instability and cancer. Here, Ölmezer and colleagues show that the helicase activity of multifunctional enzyme Dna2 suppresses dead-end replication structures that impair chromosome segregation if not removed by Holliday junction resolvase Yen1 in yeast.
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82
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Beyene GT, Balasingham SV, Frye SA, Namouchi A, Homberset H, Kalayou S, Riaz T, Tønjum T. Characterization of the Neisseria meningitidis Helicase RecG. PLoS One 2016; 11:e0164588. [PMID: 27736945 PMCID: PMC5063381 DOI: 10.1371/journal.pone.0164588] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2016] [Accepted: 09/27/2016] [Indexed: 11/19/2022] Open
Abstract
Neisseria meningitidis (Nm) is a Gram-negative oral commensal that opportunistically can cause septicaemia and/or meningitis. Here, we overexpressed, purified and characterized the Nm DNA repair/recombination helicase RecG (RecGNm) and examined its role during genotoxic stress. RecGNm possessed ATP-dependent DNA binding and unwinding activities in vitro on a variety of DNA model substrates including a Holliday junction (HJ). Database searching of the Nm genomes identified 49 single nucleotide polymorphisms (SNPs) in the recGNm including 37 non-synonymous SNPs (nsSNPs), and 7 of the nsSNPs were located in the codons for conserved active site residues of RecGNm. A transient reduction in transformation of DNA was observed in the Nm ΔrecG strain as compared to the wildtype. The gene encoding recGNm also contained an unusually high number of the DNA uptake sequence (DUS) that facilitate transformation in neisserial species. The differentially abundant protein profiles of the Nm wildtype and ΔrecG strains suggest that expression of RecGNm might be linked to expression of other proteins involved in DNA repair, recombination and replication, pilus biogenesis, glycan biosynthesis and ribosomal activity. This might explain the growth defect that was observed in the Nm ΔrecG null mutant.
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Affiliation(s)
| | | | - Stephan A. Frye
- Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway
| | - Amine Namouchi
- Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway
| | | | - Shewit Kalayou
- Department of Microbiology, University of Oslo, Oslo, Norway
| | - Tahira Riaz
- Department of Microbiology, University of Oslo, Oslo, Norway
| | - Tone Tønjum
- Department of Microbiology, University of Oslo, Oslo, Norway
- Department of Microbiology, Oslo University Hospital (Rikshospitalet), Oslo, Norway
- * E-mail:
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83
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Active Control of Repetitive Structural Transitions between Replication Forks and Holliday Junctions by Werner Syndrome Helicase. Structure 2016; 24:1292-1300. [PMID: 27427477 DOI: 10.1016/j.str.2016.06.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 05/11/2016] [Accepted: 06/05/2016] [Indexed: 11/20/2022]
Abstract
The reactivation of stalled DNA replication via fork regression invokes Holliday junction formation, branch migration, and the recovery of the replication fork after DNA repair or error-free DNA synthesis. The coordination mechanism for these DNA structural transitions by molecular motors, however, remains unclear. Here we perform single-molecule fluorescence experiments with Werner syndrome protein (WRN) and model replication forks. The Holliday junction is readily formed once the lagging arm is unwound, and migrated unidirectionally with 3.2 ± 0.03 bases/s velocity. The recovery of the replication fork was controlled by branch migration reversal of WRN, resulting in repetitive fork regression. The Holliday junction formation, branch migration, and migration direction reversal are all ATP dependent, revealing that WRN uses the energy of ATP hydrolysis to actively coordinate the structural transitions of DNA.
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84
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Paudyal SC, You Z. Sharpening the ends for repair: mechanisms and regulation of DNA resection. Acta Biochim Biophys Sin (Shanghai) 2016; 48:647-57. [PMID: 27174871 DOI: 10.1093/abbs/gmw043] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 04/12/2016] [Indexed: 12/23/2022] Open
Abstract
DNA end resection is a key process in the cellular response to DNA double-strand break damage that is essential for genome maintenance and cell survival. Resection involves selective processing of 5' ends of broken DNA to generate ssDNA overhangs, which in turn control both DNA repair and checkpoint signaling. DNA resection is the first step in homologous recombination-mediated repair and a prerequisite for the activation of the ataxia telangiectasia mutated and Rad3-related (ATR)-dependent checkpoint that coordinates repair with cell cycle progression and other cellular processes. Resection occurs in a cell cycle-dependent manner and is regulated by multiple factors to ensure an optimal amount of ssDNA required for proper repair and genome stability. Here, we review the latest findings on the molecular mechanisms and regulation of the DNA end resection process and their implications for cancer formation and treatment.
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Affiliation(s)
- Sharad C Paudyal
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Zhongsheng You
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO 63110, USA
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85
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Bianco P. Stalled replication fork rescue requires a novel DNA helicase. Methods 2016; 108:40-7. [PMID: 27282357 DOI: 10.1016/j.ymeth.2016.06.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 06/02/2016] [Accepted: 06/03/2016] [Indexed: 10/21/2022] Open
Abstract
During DNA replication, forks often stall and require restart. One mechanism for restart requires that the fork be moved in a direction opposite to that of replication. This reaction is known as fork regression. For this reaction to occur, the enzyme must couple unwinding of the nascent heteroduplex fork arms to the rewinding of nascent strands ahead of itself and to the parental duplex in its wake. As the arms of the fork are complementary, this reaction is isoenergetic making it challenging to study. To overcome this, a novel adaptation of magnetic tweezers was developed by the Croquette group. Here, a 1200bp hairpin was attached at opposite ends to a flow cell surface and a magnetic bead. By manipulating the bead with the magnets, force can be applied to unwind the hairpin or alternatively, released to allow the hairpin to rewind. This adaptation was used to study fork regression by RecG. The results show that this is an efficient regression enzyme, able to work against a large opposing force. Critically, it couples DNA unwinding to duplex rewinding and in the process, can displace bound proteins from fork arms.
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Affiliation(s)
- Piero Bianco
- Department of Microbiology and Immunology, Center for Single Molecule Biophysics, University at Buffalo, Buffalo, NY 14214, USA.
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86
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DNA replication and cancer: From dysfunctional replication origin activities to therapeutic opportunities. Semin Cancer Biol 2016; 37-38:16-25. [DOI: 10.1016/j.semcancer.2016.01.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 01/04/2016] [Accepted: 01/05/2016] [Indexed: 12/18/2022]
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87
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Song X, Ni J, Shen Y. Structure-Based Genetic Analysis of Hel308a in the Hyperthermophilic Archaeon Sulfolobus islandicus. J Genet Genomics 2016; 43:405-13. [PMID: 27317310 DOI: 10.1016/j.jgg.2016.03.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 03/06/2016] [Accepted: 03/07/2016] [Indexed: 10/22/2022]
Abstract
In archaea, the HEL308 homolog Hel308a (or Hjm) is implicated in stalled replication fork repair. The biochemical properties and structures of Hjm homologs are well documented, but in vivo mechanistic information is limited. Herein, a structure-based functional analysis of Hjm was performed in the genetically tractable hyperthermophilic archaeon, Sulfolobus islandicus. Results showed that domain V and residues within it, which affect Hjm activity and regulation, are essential and that the domain V-truncated mutants and site-directed mutants within domain V cannot complement hjm chromosomal deletion. Chromosomal hjm deletion can be complemented by ectopic expression of hjm under the control of its native promoter but not an artificial arabinose promoter. Cellular Hjm levels are kept constant under ultraviolet (UV) and methyl methanesulfonate (MMS) treatment conditions in a strain carrying a plasmid to induce Hjm overexpression. These results suggest that Hjm expression and activity are tightly controlled, probably at the translational level.
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Affiliation(s)
- Xueguo Song
- State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, China
| | - Jinfeng Ni
- State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, China
| | - Yulong Shen
- State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, China.
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88
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The RecQ DNA helicase Rqh1 constrains Exonuclease 1-dependent recombination at stalled replication forks. Sci Rep 2016; 6:22837. [PMID: 26957021 PMCID: PMC4783781 DOI: 10.1038/srep22837] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 02/22/2016] [Indexed: 01/28/2023] Open
Abstract
DNA double-strand break (DSB) repair by homologous recombination (HR) involves resection of the break to expose a 3' single-stranded DNA tail. In budding yeast, resection occurs in two steps: initial short-range resection, performed by Mre11-Rad50-Xrs2 and Sae2; and long-range resection catalysed by either Exo1 or Sgs1-Dna2. Here we use genetic assays to investigate the importance of Exo1 and the Sgs1 homologue Rqh1 for DNA repair and promotion of direct repeat recombination in the fission yeast Schizosaccharomyces pombe. We find that Exo1 and Rqh1 function in alternative redundant pathways for promoting survival following replication fork breakage. Exo1 promotes replication fork barrier-induced direct repeat recombination but intriguingly limits recombination induced by fork breakage. Direct repeat recombination induced by ultraviolet light depends on either Exo1 or Rqh1. Finally, we show that Rqh1 plays a major role in limiting Exo1-dependent direct repeat recombination induced by replication fork stalling but only a minor role in constraining recombination induced by fork breakage. The implications of our findings are discussed in the context of the benefits that long-range resection may bring to processing perturbed replication forks.
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89
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Berti M, Vindigni A. Replication stress: getting back on track. Nat Struct Mol Biol 2016; 23:103-9. [PMID: 26840898 PMCID: PMC5125612 DOI: 10.1038/nsmb.3163] [Citation(s) in RCA: 183] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 12/17/2015] [Indexed: 12/17/2022]
Abstract
The replication-stress response enables the DNA replication machinery to overcome DNA lesions or intrinsic replication-fork obstacles, and it is essential to ensure faithful transmission of genetic information to daughter cells. Multiple replication stress–response pathways have been identified in recent years, thus raising questions about the specific and possibly redundant functions of these pathways. Here, we review the emerging mechanisms of the replication-stress response in mammalian cells and consider how they may influence the dynamics of the core DNA replication complex.
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Affiliation(s)
- Matteo Berti
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | - Alessandro Vindigni
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
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90
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Mettrick KA, Grainge I. Stability of blocked replication forks in vivo. Nucleic Acids Res 2016; 44:657-68. [PMID: 26490956 PMCID: PMC4737137 DOI: 10.1093/nar/gkv1079] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 10/06/2015] [Accepted: 10/07/2015] [Indexed: 11/17/2022] Open
Abstract
Replication of chromosomal DNA must be carried out to completion in order for a cell to proliferate. However, replication forks can stall during this process for a variety of reasons, including nucleoprotein 'roadblocks' and DNA lesions. In these circumstances the replisome copying the DNA may disengage from the chromosome to allow various repair processes to restore DNA integrity and enable replication to continue. Here, we report the in vivo stability of the replication fork when it encounters a nucleoprotein blockage in Escherichia coli. Using a site-specific and reversible protein block system in conjunction with the temperature sensitive DnaC helicase loader and DnaB replicative helicase, we monitored the disappearance of the Y-shaped DNA replication fork structures using neutral-neutral 2D agarose gels. We show the replication fork collapses within 5 min of encountering the roadblock. Therefore, the stalled replication fork does not pause at a block in a stable confirmation for an extended period of time as previously postulated.
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Affiliation(s)
- Karla A Mettrick
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Ian Grainge
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia
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91
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Single-Molecule Observation of DNA Replication Repair Pathways in E. coli. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 915:5-16. [PMID: 27193534 DOI: 10.1007/978-3-319-32189-9_2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The method of action of many antibiotics is to interfere with DNA replication-quinolones trap DNA gyrase and topoisomerase proteins onto DNA while metronidazole causes single- and double-stranded breaks in DNA. To understand how bacteria respond to these drugs, it is important to understand the repair processes utilised when DNA replication is blocked. We have used tandem lac operators inserted into the chromosome bound by fluorescently labelled lac repressors as a model protein block to replication in E. coli. We have used dual-colour, alternating-laser, single-molecule narrowfield microscopy to quantify the amount of operator at the block and simultaneously image fluorescently labelled DNA polymerase. We anticipate use of this system as a quantitative platform to study replication stalling and repair proteins.
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92
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Brewer BJ, Payen C, Di Rienzi SC, Higgins MM, Ong G, Dunham MJ, Raghuraman MK. Origin-Dependent Inverted-Repeat Amplification: Tests of a Model for Inverted DNA Amplification. PLoS Genet 2015; 11:e1005699. [PMID: 26700858 PMCID: PMC4689423 DOI: 10.1371/journal.pgen.1005699] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 11/03/2015] [Indexed: 01/20/2023] Open
Abstract
DNA replication errors are a major driver of evolution—from single nucleotide polymorphisms to large-scale copy number variations (CNVs). Here we test a specific replication-based model to explain the generation of interstitial, inverted triplications. While no genetic information is lost, the novel inversion junctions and increased copy number of the included sequences create the potential for adaptive phenotypes. The model—Origin-Dependent Inverted-Repeat Amplification (ODIRA)—proposes that a replication error at pre-existing short, interrupted, inverted repeats in genomic sequences generates an extrachromosomal, inverted dimeric, autonomously replicating intermediate; subsequent genomic integration of the dimer yields this class of CNV without loss of distal chromosomal sequences. We used a combination of in vitro and in vivo approaches to test the feasibility of the proposed replication error and its downstream consequences on chromosome structure in the yeast Saccharomyces cerevisiae. We show that the proposed replication error—the ligation of leading and lagging nascent strands to create “closed” forks—can occur in vitro at short, interrupted inverted repeats. The removal of molecules with two closed forks results in a hairpin-capped linear duplex that we show replicates in vivo to create an inverted, dimeric plasmid that subsequently integrates into the genome by homologous recombination, creating an inverted triplication. While other models have been proposed to explain inverted triplications and their derivatives, our model can also explain the generation of human, de novo, inverted amplicons that have a 2:1 mixture of sequences from both homologues of a single parent—a feature readily explained by a plasmid intermediate that arises from one homologue and integrates into the other homologue prior to meiosis. Our tests of key features of ODIRA lend support to this mechanism and suggest further avenues of enquiry to unravel the origins of interstitial, inverted CNVs pivotal in human health and evolution. Chromosomal aberration such as gene amplification is a common event in human diseases and is often selected during adaptation of microorganism to stress. We proposed a replication-based model to explain the formation of a particular type of genomic aberration: internal inverted DNA amplification with retention of the distal end of the chromosome. In this study, using yeast as a model, we test the feasibility of several of these steps for the formation of an inverted amplification: a specific DNA replication anomaly (1) leading to the formation of a palindromic extrachromosomal circular molecule (2) followed by the homologous reintegration of this molecule into the genome (3). A significant feature of this mode of amplification is that the amplified sequences contain one or more replication origins. The instability of the inverted junctions can lead, through homology driven processes, to more complex genomic structures that contain a partial triplication within a duplicated segment, a structure commonly found associated with human disease.
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Affiliation(s)
- Bonita J. Brewer
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
- * E-mail:
| | - Celia Payen
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - Sara C. Di Rienzi
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - Megan M. Higgins
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - Giang Ong
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - Maitreya J. Dunham
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - M. K. Raghuraman
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
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93
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Ithurbide S, Bentchikou E, Coste G, Bost B, Servant P, Sommer S. Single Strand Annealing Plays a Major Role in RecA-Independent Recombination between Repeated Sequences in the Radioresistant Deinococcus radiodurans Bacterium. PLoS Genet 2015; 11:e1005636. [PMID: 26517555 PMCID: PMC4627823 DOI: 10.1371/journal.pgen.1005636] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 10/08/2015] [Indexed: 11/18/2022] Open
Abstract
The bacterium Deinococcus radiodurans is one of the most radioresistant organisms known. It is able to reconstruct a functional genome from hundreds of radiation-induced chromosomal fragments. Our work aims to highlight the genes involved in recombination between 438 bp direct repeats separated by intervening sequences of various lengths ranging from 1,479 bp to 10,500 bp to restore a functional tetA gene in the presence or absence of radiation-induced DNA double strand breaks. The frequency of spontaneous deletion events between the chromosomal direct repeats were the same in recA+ and in ΔrecA, ΔrecF, and ΔrecO bacteria, whereas recombination between chromosomal and plasmid DNA was shown to be strictly dependent on the RecA and RecF proteins. The presence of mutations in one of the repeated sequence reduced, in a MutS-dependent manner, the frequency of the deletion events. The distance between the repeats did not influence the frequencies of deletion events in recA+ as well in ΔrecA bacteria. The absence of the UvrD protein stimulated the recombination between the direct repeats whereas the absence of the DdrB protein, previously shown to be involved in DNA double strand break repair through a single strand annealing (SSA) pathway, strongly reduces the frequency of RecA- (and RecO-) independent deletions events. The absence of the DdrB protein also increased the lethal sectoring of cells devoid of RecA or RecO protein. γ-irradiation of recA+ cells increased about 10-fold the frequencies of the deletion events, but at a lesser extend in cells devoid of the DdrB protein. Altogether, our results suggest a major role of single strand annealing in DNA repeat deletion events in bacteria devoid of the RecA protein, and also in recA+ bacteria exposed to ionizing radiation. Deinococcus radiodurans is known for its exceptional ability to tolerate exposure to DNA damaging agents and, in particular, to very high doses of ionizing radiation. This exceptional radioresistance results from many features including efficient DNA double strand break repair. Here, we examine genome stability in D. radiodurans before and after exposure to ionizing radiation. Rearrangements between repeated sequences are a major source of genome instability and can be deleterious to the organism. Thus, we measured the frequency of recombination between direct repeats separated by intervening sequences of various lengths in the presence or absence of radiation-induced DNA double strand breaks. Strikingly, we showed that the frequency of deletions was as high in strains devoid of the RecA, RecF or RecO proteins as in wild type bacteria, suggesting a very efficient RecA-independent process able to generate genome rearrangements. Our results suggest that single strand annealing may play a major role in genome instability in the absence of homologous recombination.
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Affiliation(s)
- Solenne Ithurbide
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif sur Yvette, France
| | - Esma Bentchikou
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif sur Yvette, France
| | - Geneviève Coste
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif sur Yvette, France
| | - Bruno Bost
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif sur Yvette, France
| | - Pascale Servant
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif sur Yvette, France
| | - Suzanne Sommer
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif sur Yvette, France
- * E-mail:
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94
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Thakur RS, Basavaraju S, Khanduja JS, Muniyappa K, Nagaraju G. Mycobacterium tuberculosis RecG protein but not RuvAB or RecA protein is efficient at remodeling the stalled replication forks: implications for multiple mechanisms of replication restart in mycobacteria. J Biol Chem 2015; 290:24119-39. [PMID: 26276393 DOI: 10.1074/jbc.m115.671164] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Indexed: 11/06/2022] Open
Abstract
Aberrant DNA replication, defects in the protection, and restart of stalled replication forks are major causes of genome instability in all organisms. Replication fork reversal is emerging as an evolutionarily conserved physiological response for restart of stalled forks. Escherichia coli RecG, RuvAB, and RecA proteins have been shown to reverse the model replication fork structures in vitro. However, the pathways and the mechanisms by which Mycobacterium tuberculosis, a slow growing human pathogen, responds to different types of replication stress and DNA damage are unclear. Here, we show that M. tuberculosis RecG rescues E. coli ΔrecG cells from replicative stress. The purified M. tuberculosis RecG (MtRecG) and RuvAB (MtRuvAB) proteins catalyze fork reversal of model replication fork structures with and without a leading strand single-stranded DNA gap. Interestingly, single-stranded DNA-binding protein suppresses the MtRecG- and MtRuvAB-mediated fork reversal with substrates that contain lagging strand gap. Notably, our comparative studies with fork structures containing template damage and template switching mechanism of lesion bypass reveal that MtRecG but not MtRuvAB or MtRecA is proficient in driving the fork reversal. Finally, unlike MtRuvAB, we find that MtRecG drives efficient reversal of forks when fork structures are tightly bound by protein. These results provide direct evidence and valuable insights into the underlying mechanism of MtRecG-catalyzed replication fork remodeling and restart pathways in vivo.
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Affiliation(s)
- Roshan Singh Thakur
- From the Department of Biochemistry, Indian Institute of Science, Bangalore-560012, India
| | - Shivakumar Basavaraju
- From the Department of Biochemistry, Indian Institute of Science, Bangalore-560012, India
| | - Jasbeer Singh Khanduja
- From the Department of Biochemistry, Indian Institute of Science, Bangalore-560012, India
| | - K Muniyappa
- From the Department of Biochemistry, Indian Institute of Science, Bangalore-560012, India
| | - Ganesh Nagaraju
- From the Department of Biochemistry, Indian Institute of Science, Bangalore-560012, India
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95
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Iannascoli C, Palermo V, Murfuni I, Franchitto A, Pichierri P. The WRN exonuclease domain protects nascent strands from pathological MRE11/EXO1-dependent degradation. Nucleic Acids Res 2015; 43:9788-803. [PMID: 26275776 PMCID: PMC4787784 DOI: 10.1093/nar/gkv836] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 08/06/2015] [Indexed: 11/17/2022] Open
Abstract
The WRN helicase/exonuclease protein is required for proper replication fork recovery and maintenance of genome stability. However, whether the different catalytic activities of WRN cooperate to recover replication forks in vivo is unknown. Here, we show that, in response to replication perturbation induced by low doses of the TOP1 inhibitor camptothecin, loss of the WRN exonuclease resulted in enhanced degradation and ssDNA formation at nascent strands by the combined action of MRE11 and EXO1, as opposed to the limited processing of nascent strands performed by DNA2 in wild-type cells. Nascent strand degradation by MRE11/EXO1 took place downstream of RAD51 and affected the ability to resume replication, which correlated with slow replication rates in WRN exonuclease-deficient cells. In contrast, loss of the WRN helicase reduced exonucleolytic processing at nascent strands and led to severe genome instability. Our findings identify a novel role of the WRN exonuclease at perturbed forks, thus providing the first in vivo evidence for a distinct action of the two WRN enzymatic activities upon fork stalling and providing insights into the pathological mechanisms underlying the processing of perturbed forks.
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Affiliation(s)
- Chiara Iannascoli
- Section of Experimental and Computational Carcinogenesis, Department of Environment and Primary Prevention, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
| | - Valentina Palermo
- Section of Experimental and Computational Carcinogenesis, Department of Environment and Primary Prevention, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
| | - Ivana Murfuni
- Section of Experimental and Computational Carcinogenesis, Department of Environment and Primary Prevention, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
| | - Annapaola Franchitto
- Section of Molecular Epidemiology, Department of Environment and Primary Prevention, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
| | - Pietro Pichierri
- Section of Experimental and Computational Carcinogenesis, Department of Environment and Primary Prevention, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
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96
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Abstract
Structure-prone DNA repeats are common components of genomic DNA in all kingdoms of life. In humans, these repeats are linked to genomic instabilities that result in various hereditary disorders, including many cancers. It has long been known that DNA repeats are not only highly polymorphic in length but can also cause chromosomal fragility and stimulate gross chromosomal rearrangements, i.e., deletions, duplications, inversions, translocations and more complex shuffles. More recently, it has become clear that inherently unstable DNA repeats dramatically elevate mutation rates in surrounding DNA segments and that these mutations can occur up to ten kilobases away from the repetitive tract, a phenomenon we call repeat-induced mutagenesis (RIM). This review describes experimental data that led to the discovery and characterization of RIM and discusses the molecular mechanisms that could account for this phenomenon.
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Affiliation(s)
- Kartik A Shah
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Sergei M Mirkin
- Department of Biology, Tufts University, Medford, MA 02155, USA.
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97
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Abstract
Homology-dependent exchange of genetic information between DNA molecules has a profound impact on the maintenance of genome integrity by facilitating error-free DNA repair, replication, and chromosome segregation during cell division as well as programmed cell developmental events. This chapter will focus on homologous mitotic recombination in budding yeast Saccharomyces cerevisiae. However, there is an important link between mitotic and meiotic recombination (covered in the forthcoming chapter by Hunter et al. 2015) and many of the functions are evolutionarily conserved. Here we will discuss several models that have been proposed to explain the mechanism of mitotic recombination, the genes and proteins involved in various pathways, the genetic and physical assays used to discover and study these genes, and the roles of many of these proteins inside the cell.
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98
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Gole B, Wiesmüller L. Leukemogenic rearrangements at the mixed lineage leukemia gene (MLL)-multiple rather than a single mechanism. Front Cell Dev Biol 2015; 3:41. [PMID: 26161385 PMCID: PMC4479792 DOI: 10.3389/fcell.2015.00041] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Accepted: 06/12/2015] [Indexed: 12/11/2022] Open
Abstract
Despite manifold efforts to achieve reduced-intensity and -toxicity regimens, secondary leukemia has remained the most severe side effect of chemotherapeutic cancer treatment. Rearrangements involving a short telomeric <1 kb region of the mixed lineage leukemia (MLL) gene are the most frequently observed molecular changes in secondary as well as infant acute leukemia. Due to the mode-of-action of epipodophyllotoxins and anthracyclines, which have widely been used in cancer therapy, and support from in vitro experiments, cleavage of this MLL breakpoint cluster hotspot by poisoned topoisomerase II was proposed to trigger the molecular events leading to malignant transformation. Later on, clinical patient data and cell-based studies addressing a wider spectrum of stimuli identified cellular stress signaling pathways, which create secondary DNA structures, provide chromatin accessibility, and activate nucleases other than topoisomerase II at the MLL. The MLL destabilizing signaling pathways under discussion, namely early apoptotic DNA fragmentation, transcription stalling, and replication stalling, may all act in concert upon infection-, transplantation-, or therapy-induced cell cycle entry of hematopoietic stem and progenitor cells (HSPCs), to permit misguided cleavage and error-prone DNA repair in the cell-of-leukemia-origin.
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Affiliation(s)
- Boris Gole
- Division of Gynecological Oncology, Department of Obstetrics and Gynecology, Ulm University Ulm, Germany
| | - Lisa Wiesmüller
- Division of Gynecological Oncology, Department of Obstetrics and Gynecology, Ulm University Ulm, Germany
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99
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Understanding DNA Repair in Hyperthermophilic Archaea: Persistent Gaps and Other Reasons to Focus on the Fork. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2015; 2015:942605. [PMID: 26146487 PMCID: PMC4471258 DOI: 10.1155/2015/942605] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 05/21/2015] [Indexed: 11/17/2022]
Abstract
Although hyperthermophilic archaea arguably have a great need for efficient DNA repair, they lack members of several DNA repair protein families broadly conserved among bacteria and eukaryotes. Conversely, the putative DNA repair genes that do occur in these archaea often do not generate the expected phenotype when deleted. The prospect that hyperthermophilic archaea have some unique strategies for coping with DNA damage and replication errors has intellectual and technological appeal, but resolving this question will require alternative coping mechanisms to be proposed and tested experimentally. This review evaluates a combination of four enigmatic properties that distinguishes the hyperthermophilic archaea from all other organisms: DNA polymerase stalling at dU, apparent lack of conventional NER, lack of MutSL homologs, and apparent essentiality of homologous recombination proteins. Hypothetical damage-coping strategies that could explain this set of properties may provide new starting points for efforts to define how archaea differ from conventional models of DNA repair and replication fidelity.
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100
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Thangavel S, Berti M, Levikova M, Pinto C, Gomathinayagam S, Vujanovic M, Zellweger R, Moore H, Lee EH, Hendrickson EA, Cejka P, Stewart S, Lopes M, Vindigni A. DNA2 drives processing and restart of reversed replication forks in human cells. ACTA ACUST UNITED AC 2015; 208:545-62. [PMID: 25733713 PMCID: PMC4347643 DOI: 10.1083/jcb.201406100] [Citation(s) in RCA: 264] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Following prolonged genotoxic stress, DNA2 and WRN functionally interact to degrade reversed replication forks and promote replication restart, thereby preventing aberrant processing of unresolved replication intermediates Accurate processing of stalled or damaged DNA replication forks is paramount to genomic integrity and recent work points to replication fork reversal and restart as a central mechanism to ensuring high-fidelity DNA replication. Here, we identify a novel DNA2- and WRN-dependent mechanism of reversed replication fork processing and restart after prolonged genotoxic stress. The human DNA2 nuclease and WRN ATPase activities functionally interact to degrade reversed replication forks with a 5′-to-3′ polarity and promote replication restart, thus preventing aberrant processing of unresolved replication intermediates. Unexpectedly, EXO1, MRE11, and CtIP are not involved in the same mechanism of reversed fork processing, whereas human RECQ1 limits DNA2 activity by preventing extensive nascent strand degradation. RAD51 depletion antagonizes this mechanism, presumably by preventing reversed fork formation. These studies define a new mechanism for maintaining genome integrity tightly controlled by specific nucleolytic activities and central homologous recombination factors.
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Affiliation(s)
- Saravanabhavan Thangavel
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104
| | - Matteo Berti
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104
| | - Maryna Levikova
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
| | - Cosimo Pinto
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
| | - Shivasankari Gomathinayagam
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104
| | - Marko Vujanovic
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
| | - Ralph Zellweger
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
| | - Hayley Moore
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Eu Han Lee
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - Eric A Hendrickson
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | - Petr Cejka
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
| | - Sheila Stewart
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Massimo Lopes
- Institute of Molecular Cancer Research, University of Zurich, CH-8057 Zurich, Switzerland
| | - Alessandro Vindigni
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104
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