1
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Arter M, Keeney S. Divergence and conservation of the meiotic recombination machinery. Nat Rev Genet 2024; 25:309-325. [PMID: 38036793 DOI: 10.1038/s41576-023-00669-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/03/2023] [Indexed: 12/02/2023]
Abstract
Sexually reproducing eukaryotes use recombination between homologous chromosomes to promote chromosome segregation during meiosis. Meiotic recombination is almost universally conserved in its broad strokes, but specific molecular details often differ considerably between taxa, and the proteins that constitute the recombination machinery show substantial sequence variability. The extent of this variation is becoming increasingly clear because of recent increases in genomic resources and advances in protein structure prediction. We discuss the tension between functional conservation and rapid evolutionary change with a focus on the proteins that are required for the formation and repair of meiotic DNA double-strand breaks. We highlight phylogenetic relationships on different time scales and propose that this remarkable evolutionary plasticity is a fundamental property of meiotic recombination that shapes our understanding of molecular mechanisms in reproductive biology.
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Affiliation(s)
- Meret Arter
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Scott Keeney
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
- Howard Hughes Medical Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
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2
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Meir A, Raina VB, Rivera CE, Marie L, Symington LS, Greene EC. The separation pin distinguishes the pro- and anti-recombinogenic functions of Saccharomyces cerevisiae Srs2. Nat Commun 2023; 14:8144. [PMID: 38065943 PMCID: PMC10709652 DOI: 10.1038/s41467-023-43918-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 11/23/2023] [Indexed: 12/18/2023] Open
Abstract
Srs2 is an Sf1a helicase that helps maintain genome stability in Saccharomyces cerevisiae through its ability to regulate homologous recombination. Srs2 downregulates HR by stripping Rad51 from single-stranded DNA, and Srs2 is also thought to promote synthesis-dependent strand annealing by unwinding D-loops. However, it has not been possible to evaluate the relative contributions of these two distinct activities to any aspect of recombination. Here, we used a structure-based approach to design an Srs2 separation-of-function mutant that can dismantle Rad51-ssDNA filaments but is incapable of disrupting D-loops, allowing us to assess the relative contributions of these pro- and anti-recombinogenic functions. We show that this separation-of-function mutant phenocopies wild-type SRS2 in vivo, suggesting that the ability of Srs2 to remove Rad51 from ssDNA is its primary role during HR.
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Affiliation(s)
- Aviv Meir
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY, 10032, USA
| | - Vivek B Raina
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY, 10032, USA
| | - Carly E Rivera
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY, 10032, USA
| | - Léa Marie
- Department of Microbiology & Immunology, Columbia University, New York, NY, 10032, USA
- Institute of Pharmacology and Structural Biology (IPBS), French National Centre for Scientific Research (CNRS), Université Toulouse III, Toulouse, France
| | - Lorraine S Symington
- Department of Microbiology & Immunology, Columbia University, New York, NY, 10032, USA
- Department of Genetics & Development, Columbia University, New York, NY, 10032, USA
| | - Eric C Greene
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY, 10032, USA.
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3
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Meir A, Greene EC. Srs2 and Pif1 as Model Systems for Understanding Sf1a and Sf1b Helicase Structure and Function. Genes (Basel) 2021; 12:1319. [PMID: 34573298 PMCID: PMC8469786 DOI: 10.3390/genes12091319] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 08/23/2021] [Accepted: 08/24/2021] [Indexed: 01/19/2023] Open
Abstract
Helicases are enzymes that convert the chemical energy stored in ATP into mechanical work, allowing them to move along and manipulate nucleic acids. The helicase superfamily 1 (Sf1) is one of the largest subgroups of helicases and they are required for a range of cellular activities across all domains of life. Sf1 helicases can be further subdivided into two classes called the Sf1a and Sf1b helicases, which move in opposite directions on nucleic acids. The results of this movement can range from the separation of strands within duplex nucleic acids to the physical remodeling or removal of nucleoprotein complexes. Here, we describe the characteristics of the Sf1a helicase Srs2 and the Sf1b helicase Pif1, both from the model organism Saccharomyces cerevisiae, focusing on the roles that they play in homologous recombination, a DNA repair pathway that is necessary for maintaining genome integrity.
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Affiliation(s)
| | - Eric C. Greene
- Department of Biochemistry & Molecular Biophysics, Columbia University, New York, NY 10032, USA;
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4
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Resolvases, Dissolvases, and Helicases in Homologous Recombination: Clearing the Road for Chromosome Segregation. Genes (Basel) 2020; 11:genes11010071. [PMID: 31936378 PMCID: PMC7017083 DOI: 10.3390/genes11010071] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/29/2019] [Accepted: 01/01/2020] [Indexed: 12/13/2022] Open
Abstract
The execution of recombinational pathways during the repair of certain DNA lesions or in the meiotic program is associated to the formation of joint molecules that physically hold chromosomes together. These structures must be disengaged prior to the onset of chromosome segregation. Failure in the resolution of these linkages can lead to chromosome breakage and nondisjunction events that can alter the normal distribution of the genomic material to the progeny. To avoid this situation, cells have developed an arsenal of molecular complexes involving helicases, resolvases, and dissolvases that recognize and eliminate chromosome links. The correct orchestration of these enzymes promotes the timely removal of chromosomal connections ensuring the efficient segregation of the genome during cell division. In this review, we focus on the role of different DNA processing enzymes that collaborate in removing the linkages generated during the activation of the homologous recombination machinery as a consequence of the appearance of DNA breaks during the mitotic and meiotic programs. We will also discuss about the temporal regulation of these factors along the cell cycle, the consequences of their loss of function, and their specific role in the removal of chromosomal links to ensure the accurate segregation of the genomic material during cell division.
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5
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Jenkins SS, Gore S, Guo X, Liu J, Ede C, Veaute X, Jinks-Robertson S, Kowalczykowski SC, Heyer WD. Role of the Srs2-Rad51 Interaction Domain in Crossover Control in Saccharomyces cerevisiae. Genetics 2019; 212:1133-1145. [PMID: 31142613 PMCID: PMC6707447 DOI: 10.1534/genetics.119.302337] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 05/22/2019] [Indexed: 02/05/2023] Open
Abstract
Saccharomyces cerevisiae Srs2, in addition to its well-documented antirecombination activity, has been proposed to play a role in promoting synthesis-dependent strand annealing (SDSA). Here we report the identification and characterization of an SRS2 mutant with a single amino acid substitution (srs2-F891A) that specifically affects the Srs2 pro-SDSA function. This residue is located within the Srs2-Rad51 interaction domain and embedded within a protein sequence resembling a BRC repeat motif. The srs2-F891A mutation leads to a complete loss of interaction with Rad51 as measured through yeast two-hybrid analysis and a partial loss of interaction as determined through protein pull-down assays with purified Srs2, Srs2-F891A, and Rad51 proteins. Even though previous work has shown that internal deletions of the Srs2-Rad51 interaction domain block Srs2 antirecombination activity in vitro, the Srs2-F891A mutant protein, despite its weakened interaction with Rad51, exhibits no measurable defect in antirecombination activity in vitro or in vivo Surprisingly, srs2-F891A shows a robust shift from noncrossover to crossover repair products in a plasmid-based gap repair assay, but not in an ectopic physical recombination assay. Our findings suggest that the Srs2 C-terminal Rad51 interaction domain is more complex than previously thought, containing multiple interaction sites with unique effects on Srs2 activity.
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Affiliation(s)
- Shirin S Jenkins
- Department of Microbiology and Molecular Genetics, University of California, Davis, California 95616
| | - Steven Gore
- Department of Microbiology and Molecular Genetics, University of California, Davis, California 95616
| | - Xiaoge Guo
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina 27710
| | - Jie Liu
- Department of Microbiology and Molecular Genetics, University of California, Davis, California 95616
| | - Christopher Ede
- Department of Microbiology and Molecular Genetics, University of California, Davis, California 95616
| | - Xavier Veaute
- CEA, CIGEx, F-92265 Fontenay-aux-Roses Cedex, France
| | - Sue Jinks-Robertson
- Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina 27710
| | - Stephen C Kowalczykowski
- Department of Microbiology and Molecular Genetics, University of California, Davis, California 95616
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616
| | - Wolf-Dietrich Heyer
- Department of Microbiology and Molecular Genetics, University of California, Davis, California 95616
- Department of Molecular and Cellular Biology, University of California, Davis, California 95616
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6
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Srs2 helicase prevents the formation of toxic DNA damage during late prophase I of yeast meiosis. Chromosoma 2019; 128:453-471. [DOI: 10.1007/s00412-019-00709-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 05/07/2019] [Accepted: 05/15/2019] [Indexed: 12/24/2022]
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7
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Hunt LJ, Ahmed EA, Kaur H, Ahuja JS, Hulme L, Chou TC, Lichten M, Goldman ASH. S. cerevisiae Srs2 helicase ensures normal recombination intermediate metabolism during meiosis and prevents accumulation of Rad51 aggregates. Chromosoma 2019; 128:249-265. [PMID: 31069484 PMCID: PMC6823294 DOI: 10.1007/s00412-019-00705-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 04/04/2019] [Accepted: 04/24/2019] [Indexed: 01/06/2023]
Abstract
We investigated the meiotic role of Srs2, a multi-functional DNA helicase/translocase that destabilises Rad51-DNA filaments and is thought to regulate strand invasion and prevent hyper-recombination during the mitotic cell cycle. We find that Srs2 activity is required for normal meiotic progression and spore viability. A significant fraction of srs2 mutant cells progress through both meiotic divisions without separating the bulk of their chromatin, although in such cells sister centromeres often separate. Undivided nuclei contain aggregates of Rad51 colocalised with the ssDNA-binding protein RPA, suggesting the presence of persistent single-strand DNA. Rad51 aggregate formation requires Spo11-induced DSBs, Rad51 strand-invasion activity and progression past the pachytene stage of meiosis, but not the DSB end-resection or the bias towards interhomologue strand invasion characteristic of normal meiosis. srs2 mutants also display altered meiotic recombination intermediate metabolism, revealed by defects in the formation of stable joint molecules. We suggest that Srs2, by limiting Rad51 accumulation on DNA, prevents the formation of aberrant recombination intermediates that otherwise would persist and interfere with normal chromosome segregation and nuclear division.
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Affiliation(s)
- Laura J Hunt
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, S10 2TN, UK.,Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, BN1 9RQ, UK
| | - Emad A Ahmed
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, S10 2TN, UK.,Immunology and Molecular Physiology Lab., Zoology Department, Faculty of Science, Assiut University, Markaz El-Fath, 71515, Egypt
| | - Hardeep Kaur
- Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, 20892, USA.,Department of Biochemistry and Structural Biology, UT Health San Antonio, San Antonio, TX, 78229, USA
| | - Jasvinder S Ahuja
- Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, 20892, USA
| | - Lydia Hulme
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, S10 2TN, UK
| | - Ta-Chung Chou
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, S10 2TN, UK.,All First Tech Co., Ltd, 32467, No 146-2. Hung Chun Road, Ping Zhen Dist, Taoyuan City, Taiwan
| | - Michael Lichten
- Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, 20892, USA
| | - Alastair S H Goldman
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, S10 2TN, UK. .,Faculty of Life Sciences, The University of Bradford, Bradford, BD7 1AZ, UK.
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8
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Crickard JB, Greene EC. Helicase Mechanisms During Homologous Recombination in Saccharomyces cerevisiae. Annu Rev Biophys 2019; 48:255-273. [PMID: 30857400 DOI: 10.1146/annurev-biophys-052118-115418] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Helicases are enzymes that move, manage, and manipulate nucleic acids. They can be subdivided into six super families and are required for all aspects of nucleic acid metabolism. In general, all helicases function by converting the chemical energy stored in the bond between the gamma and beta phosphates of adenosine triphosphate into mechanical work, which results in the unidirectional movement of the helicase protein along one strand of a nucleic acid. The results of this translocation activity can range from separation of strands within duplex nucleic acids to the physical remodeling or removal of nucleoprotein complexes. In this review, we focus on describing key helicases from the model organism Saccharomyces cerevisiae that contribute to the regulation of homologous recombination, which is an essential DNA repair pathway for fixing damaged chromosomes.
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Affiliation(s)
- J Brooks Crickard
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; ,
| | - Eric C Greene
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; ,
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9
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Abstract
Homologous recombination (HR) is a universally conserved mechanism used to maintain genomic integrity. In eukaryotes, HR is used to repair the spontaneous double strand breaks (DSBs) that arise during mitotic growth, and the programmed DSBs that form during meiosis. The mechanisms that govern mitotic and meiotic HR share many similarities, however, there are also several key differences, which reflect the unique attributes of each process. For instance, even though many of the proteins involved in mitotic and meiotic HR are the same, DNA target specificity is not: mitotic DSBs are repaired primarily using the sister chromatid as a template, whereas meiotic DBSs are repaired primarily through targeting of the homologous chromosome. These changes in template specificity are induced by expression of meiosis-specific HR proteins, down-regulation of mitotic HR proteins, and the formation of meiosis-specific chromosomal structures. Here, we compare and contrast the biochemical properties of key recombination intermediates formed during the pre-synapsis phase of mitotic and meiotic HR. Throughout, we try to highlight unanswered questions that will shape our understanding of how homologous recombination contributes to human cancer biology and sexual reproduction.
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10
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The Main Role of Srs2 in DNA Repair Depends on Its Helicase Activity, Rather than on Its Interactions with PCNA or Rad51. mBio 2018; 9:mBio.01192-18. [PMID: 30018112 PMCID: PMC6050964 DOI: 10.1128/mbio.01192-18] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Homologous recombination (HR) is a mechanism that repairs a variety of DNA lesions. Under certain circumstances, however, HR can generate intermediates that can interfere with other cellular processes such as DNA transcription or replication. Cells have therefore developed pathways that abolish undesirable HR intermediates. The Saccharomyces cerevisiae yeast Srs2 helicase has a major role in one of these pathways. Srs2 also works during DNA replication and interacts with the clamp PCNA. The relative importance of Srs2’s helicase activity, Rad51 removal function, and PCNA interaction in genome stability remains unclear. We created a new SRS2 allele [srs2(1-850)] that lacks the whole C terminus, containing the interaction site for Rad51 and PCNA and interactions with many other proteins. Thus, the new allele encodes an Srs2 protein bearing only the activity of the DNA helicase. We find that the interactions of Srs2 with Rad51 and PCNA are dispensable for the main role of Srs2 in the repair of DNA damage in vegetative cells and for proper completion of meiosis. On the other hand, it has been shown that in cells impaired for the DNA damage tolerance (DDT) pathways, Srs2 generates toxic intermediates that lead to DNA damage sensitivity; we show that this negative Srs2 activity requires the C terminus of Srs2. Dissection of the genetic interactions of the srs2(1-850) allele suggest a role for Srs2’s helicase activity in sister chromatid cohesion. Our results also indicate that Srs2’s function becomes more central in diploid cells. Homologous recombination (HR) is a key mechanism that repairs damaged DNA. However, this process has to be tightly regulated; failure to regulate it can lead to genome instability. The Srs2 helicase is considered a regulator of HR; it was shown to be able to evict the recombinase Rad51 from DNA. Cells lacking Srs2 exhibit sensitivity to DNA-damaging agents, and in some cases, they display defects in DNA replication. The relative roles of the helicase and Rad51 removal activities of Srs2 in genome stability remain unclear. To address this question, we created a new Srs2 mutant which has only the DNA helicase domain. Our study shows that only the DNA helicase domain is needed to deal with DNA damage and assist in DNA replication during vegetative growth and in meiosis. Thus, our findings shift the view on the role of Srs2 in the maintenance of genome integrity.
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11
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Yeast Srs2 Helicase Promotes Redistribution of Single-Stranded DNA-Bound RPA and Rad52 in Homologous Recombination Regulation. Cell Rep 2018; 21:570-577. [PMID: 29045827 DOI: 10.1016/j.celrep.2017.09.073] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 09/06/2017] [Accepted: 09/22/2017] [Indexed: 12/20/2022] Open
Abstract
Srs2 is a super-family 1 helicase that promotes genome stability by dismantling toxic DNA recombination intermediates. However, the mechanisms by which Srs2 remodels or resolves recombination intermediates remain poorly understood. Here, single-molecule imaging is used to visualize Srs2 in real time as it acts on single-stranded DNA (ssDNA) bound by protein factors that function in recombination. We demonstrate that Srs2 is highly processive and translocates rapidly (∼170 nt per second) in the 3'→5' direction along ssDNA saturated with replication protein A (RPA). We show that RPA is evicted from DNA during the passage of Srs2. Remarkably, Srs2 also readily removes the recombination mediator Rad52 from RPA-ssDNA and, in doing so, promotes rapid redistribution of both Rad52 and RPA. These findings have important mechanistic implications for understanding how Srs2 and related nucleic acid motor proteins resolve potentially pathogenic nucleoprotein intermediates.
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12
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De Tullio L, Kaniecki K, Greene EC. Single-Stranded DNA Curtains for Studying the Srs2 Helicase Using Total Internal Reflection Fluorescence Microscopy. Methods Enzymol 2018; 600:407-437. [PMID: 29458768 DOI: 10.1016/bs.mie.2017.12.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Helicases are crucial participants in many types of DNA repair reactions, including homologous recombination. The properties of these enzymes can be assayed by traditional bulk biochemical analysis; however, these types of assays cannot directly access some types of information. In particular, bulk biochemical assays cannot readily access information that may be obscured in population averages. Single-molecule assays offer the potential advantage of being able to visualize the molecules in question in real time, thus providing direct access to questions relating to translocation velocity, processivity, and insights into how helicases may behave on different types of substrates. Here, we describe the use of single-stranded DNA (ssDNA) curtains as an assay for directly viewing the behavior of the Saccharomyces cerevisiae Srs2 helicase on single molecules of ssDNA. When used with total internal reflection fluorescence microscopy, these methods can be used to track the binding and movements of individual helicase complexes, and allow new insights into helicase behaviors at the single-molecule level.
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13
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Niu H, Klein HL. Multifunctional roles of Saccharomyces cerevisiae Srs2 protein in replication, recombination and repair. FEMS Yeast Res 2017; 17:fow111. [PMID: 28011904 DOI: 10.1093/femsyr/fow111] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 12/22/2016] [Indexed: 11/12/2022] Open
Abstract
The Saccharomyces cerevisiae Srs2 DNA helicase has important roles in DNA replication, recombination and repair. In replication, Srs2 aids in repair of gaps by repair synthesis by preventing gaps from being used to initiate recombination. This is considered to be an anti-recombination role. In recombination, Srs2 plays both prorecombination and anti-recombination roles to promote the synthesis-dependent strand annealing recombination pathway and to inhibit gaps from initiating homologous recombination. In repair, the Srs2 helicase actively promotes gap repair through an interaction with the Exo1 nuclease to enlarge a gap for repair and to prevent Rad51 protein from accumulating on single-stranded DNA. Finally, Srs2 helicase can unwind hairpin-forming repeat sequences to promote replication and prevent repeat instability. The Srs2 activities can be controlled by phosphorylation, SUMO modification and interaction with key partners at DNA damage or lesions sites, which include PCNA and Rad51. These interactions can also limit DNA polymerase function during recombinational repair independent of the Srs2 translocase or helicase activity, further highlighting the importance of the Srs2 protein in regulating recombination. Here we review the myriad roles of Srs2 that have been documented in genome maintenance and distinguish between the translocase, helicase and additional functions of the Srs2 protein.
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Affiliation(s)
- Hengyao Niu
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405, USA
| | - Hannah L Klein
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY 10016, USA
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14
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Liu J, Ede C, Wright WD, Gore SK, Jenkins SS, Freudenthal BD, Todd Washington M, Veaute X, Heyer WD. Srs2 promotes synthesis-dependent strand annealing by disrupting DNA polymerase δ-extending D-loops. eLife 2017; 6. [PMID: 28535142 PMCID: PMC5441872 DOI: 10.7554/elife.22195] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 04/29/2017] [Indexed: 01/12/2023] Open
Abstract
Synthesis-dependent strand annealing (SDSA) is the preferred mode of homologous recombination in somatic cells leading to an obligatory non-crossover outcome, thus avoiding the potential for chromosomal rearrangements and loss of heterozygosity. Genetic analysis identified the Srs2 helicase as a prime candidate to promote SDSA. Here, we demonstrate that Srs2 disrupts D-loops in an ATP-dependent fashion and with a distinct polarity. Specifically, we partly reconstitute the SDSA pathway using Rad51, Rad54, RPA, RFC, DNA Polymerase δ with different forms of PCNA. Consistent with genetic data showing the requirement for SUMO and PCNA binding for the SDSA role of Srs2, Srs2 displays a slight but significant preference to disrupt extending D-loops over unextended D-loops when SUMOylated PCNA is present, compared to unmodified PCNA or monoubiquitinated PCNA. Our data establish a biochemical mechanism for the role of Srs2 in crossover suppression by promoting SDSA through disruption of extended D-loops. DOI:http://dx.doi.org/10.7554/eLife.22195.001
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Affiliation(s)
- Jie Liu
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, United States
| | - Christopher Ede
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, United States
| | - William D Wright
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, United States
| | - Steven K Gore
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, United States
| | - Shirin S Jenkins
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, United States
| | - Bret D Freudenthal
- Department of Biochemistry, University of Iowa Carver College of Medicine, Iowa City, United States
| | - M Todd Washington
- Department of Biochemistry, University of Iowa Carver College of Medicine, Iowa City, United States
| | | | - Wolf-Dietrich Heyer
- Department of Microbiology and Molecular Genetics, University of California, Davis, Davis, United States.,Department of Molecular and Cellular Biology, University of California, Davis, Davis, United States
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15
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Lorenz A. Modulation of meiotic homologous recombination by DNA helicases. Yeast 2017; 34:195-203. [PMID: 27930825 DOI: 10.1002/yea.3227] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 11/28/2016] [Accepted: 11/28/2016] [Indexed: 12/20/2022] Open
Abstract
DNA helicases are ATP-driven motor proteins which translocate along DNA capable of dismantling DNA-DNA interactions and/or removing proteins bound to DNA. These biochemical capabilities make DNA helicases main regulators of crucial DNA metabolic processes, including DNA replication, DNA repair, and genetic recombination. This budding topic will focus on reviewing the function of DNA helicases important for homologous recombination during meiosis, and discuss recent advances in how these modulators of meiotic recombination are themselves regulated. The emphasis is placed on work in the two model yeasts, Saccharomyces cerevisiae and Schizosaccharomyces pombe, which has vastly expanded our understanding of meiotic homologous recombination, a process whose correct execution is instrumental for healthy gamete formation, and thus functioning sexual reproduction. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Alexander Lorenz
- Institute of Medical Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK
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16
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Silva S, Altmannova V, Eckert-Boulet N, Kolesar P, Gallina I, Hang L, Chung I, Arneric M, Zhao X, Buron LD, Mortensen UH, Krejci L, Lisby M. SUMOylation of Rad52-Rad59 synergistically change the outcome of mitotic recombination. DNA Repair (Amst) 2016; 42:11-25. [PMID: 27130983 DOI: 10.1016/j.dnarep.2016.04.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 04/02/2016] [Accepted: 04/05/2016] [Indexed: 11/18/2022]
Abstract
Homologous recombination (HR) is essential for maintenance of genome stability through double-strand break (DSB) repair, but at the same time HR can lead to loss of heterozygosity and uncontrolled recombination can be genotoxic. The post-translational modification by SUMO (small ubiquitin-like modifier) has been shown to modulate recombination, but the exact mechanism of this regulation remains unclear. Here we show that SUMOylation stabilizes the interaction between the recombination mediator Rad52 and its paralogue Rad59 in Saccharomyces cerevisiae. Although Rad59 SUMOylation is not required for survival after genotoxic stress, it affects the outcome of recombination to promote conservative DNA repair. In some genetic assays, Rad52 and Rad59 SUMOylation act synergistically. Collectively, our data indicate that the described SUMO modifications affect the balance between conservative and non-conservative mechanisms of HR.
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Affiliation(s)
- Sonia Silva
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Veronika Altmannova
- Department of Biology, Masaryk University, Kamenice 5/A7, 62500 Brno, Czech Republic
| | - Nadine Eckert-Boulet
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Peter Kolesar
- Department of Biology, Masaryk University, Kamenice 5/A7, 62500 Brno, Czech Republic
| | - Irene Gallina
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Lisa Hang
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Inn Chung
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Milica Arneric
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Xiaolan Zhao
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Line Due Buron
- Department of Systems Biology, Technical University of Denmark, Building 223, 2800 Kgs. Lyngby, Denmark
| | - Uffe H Mortensen
- Department of Systems Biology, Technical University of Denmark, Building 223, 2800 Kgs. Lyngby, Denmark
| | - Lumir Krejci
- Department of Biology, Masaryk University, Kamenice 5/A7, 62500 Brno, Czech Republic; National Centre for Biomolecular Research, Masaryk University, Kamenice 5/A4, Brno 625 00, Czech Republic; International Clinical Research Center, Center for Biomolecular and Cellular Engineering, St. Anne's University Hospital Brno, Brno, Czech Republic
| | - Michael Lisby
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark.
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Kolesar P, Altmannova V, Silva S, Lisby M, Krejci L. Pro-recombination Role of Srs2 Protein Requires SUMO (Small Ubiquitin-like Modifier) but Is Independent of PCNA (Proliferating Cell Nuclear Antigen) Interaction. J Biol Chem 2016; 291:7594-607. [PMID: 26861880 DOI: 10.1074/jbc.m115.685891] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Indexed: 11/06/2022] Open
Abstract
Srs2 plays many roles in DNA repair, the proper regulation and coordination of which is essential. Post-translational modification by small ubiquitin-like modifier (SUMO) is one such possible mechanism. Here, we investigate the role of SUMO in Srs2 regulation and show that the SUMO-interacting motif (SIM) of Srs2 is important for the interaction with several recombination factors. Lack of SIM, but not proliferating cell nuclear antigen (PCNA)-interacting motif (PIM), leads to increased cell death under circumstances requiring homologous recombination for DNA repair. Simultaneous mutation of SIM in asrs2ΔPIMstrain leads to a decrease in recombination, indicating a pro-recombination role of SUMO. Thus SIM has an ambivalent function in Srs2 regulation; it not only mediates interaction with SUMO-PCNA to promote the anti-recombination function but it also plays a PCNA-independent pro-recombination role, probably by stimulating the formation of recombination complexes. The fact that deletion of PIM suppresses the phenotypes of Srs2 lacking SIM suggests that proper balance between the anti-recombination PCNA-bound and pro-recombination pools of Srs2 is crucial. Notably, sumoylation of Srs2 itself specifically stimulates recombination at the rDNA locus.
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Affiliation(s)
- Peter Kolesar
- From the Department of Biology and National Centre for Biomolecular Research, Masaryk University, 62500 Brno, Czech Republic
| | | | - Sonia Silva
- the Department of Biology, University of Copenhagen, Copenhagen 2200, Denmark, and
| | - Michael Lisby
- the Department of Biology, University of Copenhagen, Copenhagen 2200, Denmark, and
| | - Lumir Krejci
- From the Department of Biology and National Centre for Biomolecular Research, Masaryk University, 62500 Brno, Czech Republic, the International Clinical Research Center, Center for Biomolecular and Cellular Engineering, St. Anne's University Hospital in Brno, 60200 Brno, Czech Republic
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18
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Xu X, Blackwell S, Lin A, Li F, Qin Z, Xiao W. Error-free DNA-damage tolerance in Saccharomyces cerevisiae. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2015; 764:43-50. [DOI: 10.1016/j.mrrev.2015.02.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Revised: 01/07/2015] [Accepted: 02/06/2015] [Indexed: 12/18/2022]
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19
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Charlot F, Chelysheva L, Kamisugi Y, Vrielynck N, Guyon A, Epert A, Le Guin S, Schaefer DG, Cuming AC, Grelon M, Nogué F. RAD51B plays an essential role during somatic and meiotic recombination in Physcomitrella. Nucleic Acids Res 2014; 42:11965-78. [PMID: 25260587 PMCID: PMC4231755 DOI: 10.1093/nar/gku890] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The eukaryotic RecA homologue Rad51 is a key factor in homologous recombination and recombinational repair. Rad51-like proteins have been identified in yeast (Rad55, Rad57 and Dmc1), plants and vertebrates (RAD51B, RAD51C, RAD51D, XRCC2, XRCC3 and DMC1). RAD51 and DMC1 are the strand-exchange proteins forming a nucleofilament for strand invasion, however, the function of the paralogues in the process of homologous recombination is less clear. In yeast the two Rad51 paralogues, Rad55 and Rad57, have been shown to be involved in somatic and meiotic HR and they are essential to the formation of the Rad51/DNA nucleofilament counterbalancing the anti-recombinase activity of the SRS2 helicase. Here, we examined the role of RAD51B in the model bryophyte Physcomitrella patens. Mutant analysis shows that RAD51B is essential for the maintenance of genome integrity, for resistance to DNA damaging agents and for gene targeting. Furthermore, we set up methods to investigate meiosis in Physcomitrella and we demonstrate that the RAD51B protein is essential for meiotic homologous recombination. Finally, we show that all these functions are independent of the SRS2 anti-recombinase protein, which is in striking contrast to what is found in budding yeast where the RAD51 paralogues are fully dependent on the SRS2 anti-recombinase function.
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Affiliation(s)
- Florence Charlot
- INRA, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France AgroParisTech, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France
| | - Liudmila Chelysheva
- INRA, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France AgroParisTech, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France
| | - Yasuko Kamisugi
- Centre for Plant Sciences, Faculty of Biological Sciences, Leeds University, Leeds LS2 9JT, UK
| | - Nathalie Vrielynck
- INRA, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France AgroParisTech, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France
| | - Anouchka Guyon
- INRA, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France AgroParisTech, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France
| | - Aline Epert
- INRA, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France AgroParisTech, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France
| | - Sylvia Le Guin
- INRA, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France AgroParisTech, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France
| | - Didier G Schaefer
- Laboratoire de Biologie Moleculaire et Cellulaire, Institut de Biologie, Universite de Neuchatel, rue Emile-Argand 11, CH-2007 Neuchatel, Switzerland
| | - Andrew C Cuming
- Centre for Plant Sciences, Faculty of Biological Sciences, Leeds University, Leeds LS2 9JT, UK
| | - Mathilde Grelon
- INRA, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France AgroParisTech, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France
| | - Fabien Nogué
- INRA, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France AgroParisTech, Institut Jean-Pierre Bourgin UMR1318, Saclay Plant Sciences, Versailles, France
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20
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Burgess RC, Sebesta M, Sisakova A, Marini VP, Lisby M, Damborsky J, Klein H, Rothstein R, Krejci L. The PCNA interaction protein box sequence in Rad54 is an integral part of its ATPase domain and is required for efficient DNA repair and recombination. PLoS One 2013; 8:e82630. [PMID: 24376557 PMCID: PMC3869717 DOI: 10.1371/journal.pone.0082630] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 10/25/2013] [Indexed: 11/19/2022] Open
Abstract
Rad54 is an ATP-driven translocase involved in the genome maintenance pathway of homologous recombination (HR). Although its activity has been implicated in several steps of HR, its exact role(s) at each step are still not fully understood. We have identified a new interaction between Rad54 and the replicative DNA clamp, proliferating cell nuclear antigen (PCNA). This interaction was only mildly weakened by the mutation of two key hydrophobic residues in the highly-conserved PCNA interaction motif (PIP-box) of Rad54 (Rad54-AA). Intriguingly, the rad54-AA mutant cells displayed sensitivity to DNA damage and showed HR defects similar to the null mutant, despite retaining its ability to interact with HR proteins and to be recruited to HR foci in vivo. We therefore surmised that the PCNA interaction might be impaired in vivo and was unable to promote repair synthesis during HR. Indeed, the Rad54-AA mutant was defective in primer extension at the MAT locus as well as in vitro, but additional biochemical analysis revealed that this mutant also had diminished ATPase activity and an inability to promote D-loop formation. Further mutational analysis of the putative PIP-box uncovered that other phenotypically relevant mutants in this domain also resulted in a loss of ATPase activity. Therefore, we have found that although Rad54 interacts with PCNA, the PIP-box motif likely plays only a minor role in stabilizing the PCNA interaction, and rather, this conserved domain is probably an extension of the ATPase domain III.
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Affiliation(s)
- Rebecca C. Burgess
- Department of Genetics & Development, Columbia University Medical Center, New York, New York, United States of America
| | - Marek Sebesta
- National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
- International Clinical Research Centre, Centre for Biomolecular and Cellular Engineering, Saint Anne's University Hospital, Brno, Czech Republic
| | - Alexandra Sisakova
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
- International Clinical Research Centre, Centre for Biomolecular and Cellular Engineering, Saint Anne's University Hospital, Brno, Czech Republic
| | - Victoria P. Marini
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Michael Lisby
- Department of Molecular Biology, University of Copenhagen, Copenhagen N, Denmark
| | - Jiri Damborsky
- International Clinical Research Centre, Centre for Biomolecular and Cellular Engineering, Saint Anne's University Hospital, Brno, Czech Republic
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Hannah Klein
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York, United States of America
| | - Rodney Rothstein
- Department of Genetics & Development, Columbia University Medical Center, New York, New York, United States of America
| | - Lumir Krejci
- National Centre for Biomolecular Research, Masaryk University, Brno, Czech Republic
- Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
- International Clinical Research Centre, Centre for Biomolecular and Cellular Engineering, Saint Anne's University Hospital, Brno, Czech Republic
- * E-mail:
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21
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Liddell LC, Manthey GM, Owens SN, Fu BXH, Bailis AM. Alleles of the homologous recombination gene, RAD59, identify multiple responses to disrupted DNA replication in Saccharomyces cerevisiae. BMC Microbiol 2013; 13:229. [PMID: 24125552 PMCID: PMC3852934 DOI: 10.1186/1471-2180-13-229] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 10/04/2013] [Indexed: 11/26/2022] Open
Abstract
Background In Saccharomyces cerevisiae, Rad59 is required for multiple homologous recombination mechanisms and viability in DNA replication-defective rad27 mutant cells. Recently, four rad59 missense alleles were found to have distinct effects on homologous recombination that are consistent with separation-of-function mutations. The rad59-K166A allele alters an amino acid in a conserved α-helical domain, and, like the rad59 null allele diminishes association of Rad52 with double-strand breaks. The rad59-K174A and rad59-F180A alleles alter amino acids in the same domain and have genetically similar effects on homologous recombination. The rad59-Y92A allele alters a conserved amino acid in a separate domain, has genetically distinct effects on homologous recombination, and does not diminish association of Rad52 with double-strand breaks. Results In this study, rad59 mutant strains were crossed with a rad27 null mutant to examine the effects of the rad59 alleles on the link between viability, growth and the stimulation of homologous recombination in replication-defective cells. Like the rad59 null allele, rad59-K166A was synthetically lethal in combination with rad27. The rad59-K174A and rad59-F180A alleles were not synthetically lethal in combination with rad27, had effects on growth that coincided with decreased ectopic gene conversion, but did not affect mutation, unequal sister-chromatid recombination, or loss of heterozygosity. The rad59-Y92A allele was not synthetically lethal when combined with rad27, stimulated ectopic gene conversion and heteroallelic recombination independently from rad27, and was mutually epistatic with srs2. Unlike rad27, the stimulatory effect of rad59-Y92A on homologous recombination was not accompanied by effects on growth rate, cell cycle distribution, mutation, unequal sister-chromatid recombination, or loss of heterozygosity. Conclusions The synthetic lethality conferred by rad59 null and rad59-K166A alleles correlates with their inhibitory effect on association of Rad52 with double-strand breaks, suggesting that this may be essential for rescuing replication lesions in rad27 mutant cells. The rad59-K174A and rad59-F180A alleles may fractionally reduce this same function, which proportionally reduced repair of replication lesions by homologous recombination and growth rate. In contrast, rad59-Y92A stimulates homologous recombination, perhaps by affecting association of replication lesions with the Rad51 recombinase. This suggests that Rad59 influences the rescue of replication lesions by multiple recombination factors.
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Affiliation(s)
- Lauren C Liddell
- Department of Molecular and Cellular Biology, Beckman Research Institute of the City of Hope, 91010 Duarte, CA, USA.
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22
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Esta A, Ma E, Dupaigne P, Maloisel L, Guerois R, Le Cam E, Veaute X, Coïc E. Rad52 sumoylation prevents the toxicity of unproductive Rad51 filaments independently of the anti-recombinase Srs2. PLoS Genet 2013; 9:e1003833. [PMID: 24130504 PMCID: PMC3794917 DOI: 10.1371/journal.pgen.1003833] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Accepted: 08/12/2013] [Indexed: 11/18/2022] Open
Abstract
The budding yeast Srs2 is the archetype of helicases that regulate several aspects of homologous recombination (HR) to maintain genomic stability. Srs2 inhibits HR at replication forks and prevents high frequencies of crossing-over. Additionally, sensitivity to DNA damage and synthetic lethality with replication and recombination mutants are phenotypes that can only be attributed to another role of Srs2: the elimination of lethal intermediates formed by recombination proteins. To shed light on these intermediates, we searched for mutations that bypass the requirement of Srs2 in DNA repair without affecting HR. Remarkably, we isolated rad52-L264P, a novel allele of RAD52, a gene that encodes one of the most central recombination proteins in yeast. This mutation suppresses a broad spectrum of srs2Δ phenotypes in haploid cells, such as UV and γ-ray sensitivities as well as synthetic lethality with replication and recombination mutants, while it does not significantly affect Rad52 functions in HR and DNA repair. Extensive analysis of the genetic interactions between rad52-L264P and srs2Δ shows that rad52-L264P bypasses the requirement for Srs2 specifically for the prevention of toxic Rad51 filaments. Conversely, this Rad52 mutant cannot restore viability of srs2Δ cells that accumulate intertwined recombination intermediates which are normally processed by Srs2 post-synaptic functions. The avoidance of toxic Rad51 filaments by Rad52-L264P can be explained by a modification of its Rad51 filament mediator activity, as indicated by Chromatin immunoprecipitation and biochemical analysis. Remarkably, sensitivity to DNA damage of srs2Δ cells can also be overcome by stimulating Rad52 sumoylation through overexpression of the sumo-ligase SIZ2, or by replacing Rad52 by a Rad52-SUMO fusion protein. We propose that, like the rad52-L264P mutation, sumoylation modifies Rad52 activity thereby changing the properties of Rad51 filaments. This conclusion is strengthened by the finding that Rad52 is often associated with complete Rad51 filaments in vitro. Homologous recombination (HR) is essential for double-strand break repair and participates in post-replication restart of stalled and collapsed replication forks. However, HR can lead to genome rearrangements and has to be strictly controlled. The budding yeast Srs2 is involved in the prevention of high crossing-over frequencies and in the inhibition of HR at replication forks. Nevertheless, important phenotypes of srs2Δ mutants, like sensitivity to DNA damage and synthetic lethality with replication and recombination mutants, can only be attributed to another role of Srs2: the elimination of lethal intermediates formed by recombination proteins. The nature of these intermediates remains to be defined. In a screen designed to uncover mutations able to suppress srs2Δ phenotypes, we isolated a novel allele of Rad52 (rad52-L264P), the gene that codes for the major Rad51 nucleoprotein filament mediator. Interestingly, we observed that rad52-L264P bypasses the requirement for Srs2 without affecting DNA repair by HR. We also found that Rad52-L264P specifically prevents the formation of unproductive Rad51 filaments before strand invasion, allowing us to define Srs2 substrates. Further analysis showed that Rad52-L264P mimics the properties of the Rad52-SUMO conjugate, revealing that Rad52 assembles Rad51 filaments differently according to its sumoylation status.
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Affiliation(s)
- Aline Esta
- CEA, DSV, iRCM, SIGRR, LRGM, Fontenay-aux-Roses, France
| | - Emilie Ma
- CEA, DSV, iRCM, SIGRR, LRGM, Fontenay-aux-Roses, France
| | - Pauline Dupaigne
- Laboratoire de Microscopie Moléculaire et Cellulaire, UMR 8126, Interactions Moléculaires et Cancer, CNRS–Université Paris Sud–Institut de Cancérologie Gustave Roussy, Villejuif, France
| | | | | | - Eric Le Cam
- Laboratoire de Microscopie Moléculaire et Cellulaire, UMR 8126, Interactions Moléculaires et Cancer, CNRS–Université Paris Sud–Institut de Cancérologie Gustave Roussy, Villejuif, France
| | - Xavier Veaute
- CEA, DSV, iRCM, SIGRR, LRGM, Fontenay-aux-Roses, France
| | - Eric Coïc
- CEA, DSV, iRCM, SIGRR, LRGM, Fontenay-aux-Roses, France
- * E-mail:
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23
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Abstract
Homologous recombination is associated with the dynamic assembly and disassembly of DNA-protein complexes. Assembly of a nucleoprotein filament comprising ssDNA and the RecA homolog, Rad51, is a key step required for homology search during recombination. The budding yeast Srs2 DNA translocase is known to dismantle Rad51 filament in vitro. However, there is limited evidence to support the dismantling activity of Srs2 in vivo. Here, we show that Srs2 indeed disrupts Rad51-containing complexes from chromosomes during meiosis. Overexpression of Srs2 during the meiotic prophase impairs meiotic recombination and removes Rad51 from meiotic chromosomes. This dismantling activity is specific for Rad51, as Srs2 Overexpression does not remove Dmc1 (a meiosis-specific Rad51 homolog), Rad52 (a Rad51 mediator), or replication protein A (RPA; a single-stranded DNA-binding protein). Rather, RPA replaces Rad51 under these conditions. A mutant Srs2 lacking helicase activity cannot remove Rad51 from meiotic chromosomes. Interestingly, the Rad51-binding domain of Srs2, which is critical for Rad51-dismantling activity in vitro, is not essential for this activity in vivo. Our results suggest that a precise level of Srs2, in the form of the Srs2 translocase, is required to appropriately regulate the Rad51 nucleoprotein filament dynamics during meiosis.
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24
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Synthetic lethality between gene defects affecting a single non-essential molecular pathway with reversible steps. PLoS Comput Biol 2013; 9:e1003016. [PMID: 23592964 PMCID: PMC3617211 DOI: 10.1371/journal.pcbi.1003016] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 02/18/2013] [Indexed: 12/31/2022] Open
Abstract
Systematic analysis of synthetic lethality (SL) constitutes a critical tool for systems biology to decipher molecular pathways. The most accepted mechanistic explanation of SL is that the two genes function in parallel, mutually compensatory pathways, known as between-pathway SL. However, recent genome-wide analyses in yeast identified a significant number of within-pathway negative genetic interactions. The molecular mechanisms leading to within-pathway SL are not fully understood. Here, we propose a novel mechanism leading to within-pathway SL involving two genes functioning in a single non-essential pathway. This type of SL termed within-reversible-pathway SL involves reversible pathway steps, catalyzed by different enzymes in the forward and backward directions, and kinetic trapping of a potentially toxic intermediate. Experimental data with recombinational DNA repair genes validate the concept. Mathematical modeling recapitulates the possibility of kinetic trapping and revealed the potential contributions of synthetic, dosage-lethal interactions in such a genetic system as well as the possibility of within-pathway positive masking interactions. Analysis of yeast gene interaction and pathway data suggests broad applicability of this novel concept. These observations extend the canonical interpretation of synthetic-lethal or synthetic-sick interactions with direct implications to reconstruct molecular pathways and improve therapeutic approaches to diseases such as cancer.
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25
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Srs2 mediates PCNA-SUMO-dependent inhibition of DNA repair synthesis. EMBO J 2013; 32:742-55. [PMID: 23395907 PMCID: PMC3594751 DOI: 10.1038/emboj.2013.9] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 01/10/2013] [Indexed: 12/11/2022] Open
Abstract
Completion of DNA replication needs to be ensured even when challenged with fork progression problems or DNA damage. PCNA and its modifications constitute a molecular switch to control distinct repair pathways. In yeast, SUMOylated PCNA (S-PCNA) recruits Srs2 to sites of replication where Srs2 can disrupt Rad51 filaments and prevent homologous recombination (HR). We report here an unexpected additional mechanism by which S-PCNA and Srs2 block the synthesis-dependent extension of a recombination intermediate, thus limiting its potentially hazardous resolution in association with a cross-over. This new Srs2 activity requires the SUMO interaction motif at its C-terminus, but neither its translocase activity nor its interaction with Rad51. Srs2 binding to S-PCNA dissociates Polδ and Polη from the repair synthesis machinery, thus revealing a novel regulatory mechanism controlling spontaneous genome rearrangements. Our results suggest that cycling cells use the Siz1-dependent SUMOylation of PCNA to limit the extension of repair synthesis during template switch or HR and attenuate reciprocal DNA strand exchanges to maintain genome stability. An unexpected non-catalytic function of the recombination-attenuating helicase Srs2 further expands the manifold roles of PCNA modifications in ensuring genome stability.
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26
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Roles of DNA helicases in the mediation and regulation of homologous recombination. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 767:185-202. [PMID: 23161012 DOI: 10.1007/978-1-4614-5037-5_9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Homologous recombination (HR) is an evolutionarily conserved process that eliminates DNA double-strand breaks from chromosomes, repairs injured DNA replication forks, and helps orchestrate meiotic chromosome segregation. Recent studies have shown that DNA helicases play multifaceted roles in HR mediation and regulation. In particular, the S. cerevisiae Sgs1 helicase and its human ortholog BLM helicase are involved in not only the resection of the primary lesion to generate single-stranded DNA to prompt the assembly of the HR machinery, but they also function in somatic cells to suppress the formation of chromosome arm crossovers during HR. On the other hand, the S. cerevisiae Mph1 and Srs2 helicases, and their respective functional equivalents in other eukaryotes, suppress spurious HR events and favor the formation of noncrossovers via distinct mechanisms. Thus, the functional integrity of the HR process and HR outcomes are dependent upon these helicase enzymes. Since mutations in some of these helicases lead to cancer predisposition in humans and mice, studies on them have clear relevance to human health and disease.
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27
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Ceballos SJ, Heyer WD. Functions of the Snf2/Swi2 family Rad54 motor protein in homologous recombination. BIOCHIMICA ET BIOPHYSICA ACTA 2011; 1809:509-23. [PMID: 21704205 PMCID: PMC3171615 DOI: 10.1016/j.bbagrm.2011.06.006] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 05/27/2011] [Accepted: 06/06/2011] [Indexed: 11/25/2022]
Abstract
Homologous recombination is a central pathway to maintain genomic stability and is involved in the repair of DNA damage and replication fork support, as well as accurate chromosome segregation during meiosis. Rad54 is a dsDNA-dependent ATPase of the Snf2/Swi2 family of SF2 helicases, although Rad54 lacks classical helicase activity and cannot carry out the strand displacement reactions typical for DNA helicases. Rad54 is a potent and processive motor protein that translocates on dsDNA, potentially executing several functions in recombinational DNA repair. Rad54 acts in concert with Rad51, the central protein of recombination that performs the key reactions of homology search and DNA strand invasion. Here, we will review the role of the Rad54 protein in homologous recombination with an emphasis on mechanistic studies with the yeast and human enzymes. We will discuss how these results relate to in vivo functions of Rad54 during homologous recombination in somatic cells and during meiosis. This article is part of a Special Issue entitled: Snf2/Swi2 ATPase structure and function.
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Affiliation(s)
- Shannon J. Ceballos
- Department of Microbiology, University of California, Davis, Davis, CA 95616-8665
| | - Wolf-Dietrich Heyer
- Department of Microbiology, University of California, Davis, Davis, CA 95616-8665
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616-8665
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28
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Bustamante C, Cheng W, Mejia YX, Meija YX. Revisiting the central dogma one molecule at a time. Cell 2011; 144:480-97. [PMID: 21335233 PMCID: PMC3063003 DOI: 10.1016/j.cell.2011.01.033] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 01/21/2011] [Accepted: 01/26/2011] [Indexed: 12/24/2022]
Abstract
The faithful relay and timely expression of genetic information depend on specialized molecular machines, many of which function as nucleic acid translocases. The emergence over the last decade of single-molecule fluorescence detection and manipulation techniques with nm and Å resolution and their application to the study of nucleic acid translocases are painting an increasingly sharp picture of the inner workings of these machines, the dynamics and coordination of their moving parts, their thermodynamic efficiency, and the nature of their transient intermediates. Here we present an overview of the main results arrived at by the application of single-molecule methods to the study of the main machines of the central dogma.
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Affiliation(s)
- Carlos Bustamante
- Jason L. Choy Laboratory of Single-Molecule Biophysics, University of California, Berkeley, 94720, USA.
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29
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Sun W, Lorenz A, Osman F, Whitby MC. A failure of meiotic chromosome segregation in a fbh1Delta mutant correlates with persistent Rad51-DNA associations. Nucleic Acids Res 2010; 39:1718-31. [PMID: 21149262 PMCID: PMC3061084 DOI: 10.1093/nar/gkq977] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The F-box DNA helicase Fbh1 constrains homologous recombination in vegetative cells, most likely through an ability to displace the Rad51 recombinase from DNA. Here, we provide the first evidence that Fbh1 also serves a vital meiotic role in fission yeast to promote normal chromosome segregation. In the absence of Fbh1, chromosomes remain entangled or segregate unevenly during meiosis, and genetic and cytological data suggest that this results in part from a failure to efficiently dismantle Rad51 nucleofilaments that form during meiotic double-strand break repair.
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Affiliation(s)
- Weili Sun
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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30
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Abstract
Homologous recombination (HR) performs crucial functions including DNA repair, segregation of homologous chromosomes, propagation of genetic diversity, and maintenance of telomeres. HR is responsible for the repair of DNA double-strand breaks and DNA interstrand cross-links. The process of HR is initiated at the site of DNA breaks and gaps and involves a search for homologous sequences promoted by Rad51 and auxiliary proteins followed by the subsequent invasion of broken DNA ends into the homologous duplex DNA that then serves as a template for repair. The invasion produces a cross-stranded structure, known as the Holliday junction. Here, we describe the properties of Rad54, an important and versatile HR protein that is evolutionarily conserved in eukaryotes. Rad54 is a motor protein that translocates along dsDNA and performs several important functions in HR. The current review focuses on the recently identified Rad54 activities which contribute to the late phase of HR, especially the branch migration of Holliday junctions.
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Affiliation(s)
- Alexander V Mazin
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA.
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31
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Saponaro M, Callahan D, Zheng X, Krejci L, Haber JE, Klein HL, Liberi G. Cdk1 targets Srs2 to complete synthesis-dependent strand annealing and to promote recombinational repair. PLoS Genet 2010; 6:e1000858. [PMID: 20195513 PMCID: PMC2829061 DOI: 10.1371/journal.pgen.1000858] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Accepted: 01/25/2010] [Indexed: 11/27/2022] Open
Abstract
Cdk1 kinase phosphorylates budding yeast Srs2, a member of UvrD protein family, displays both DNA translocation and DNA unwinding activities in vitro. Srs2 prevents homologous recombination by dismantling Rad51 filaments and is also required for double-strand break (DSB) repair. Here we examine the biological significance of Cdk1-dependent phosphorylation of Srs2, using mutants that constitutively express the phosphorylated or unphosphorylated protein isoforms. We found that Cdk1 targets Srs2 to repair DSB and, in particular, to complete synthesis-dependent strand annealing, likely controlling the disassembly of a D-loop intermediate. Cdk1-dependent phosphorylation controls turnover of Srs2 at the invading strand; and, in absence of this modification, the turnover of Rad51 is not affected. Further analysis of the recombination phenotypes of the srs2 phospho-mutants showed that Srs2 phosphorylation is not required for the removal of toxic Rad51 nucleofilaments, although it is essential for cell survival, when DNA breaks are channeled into homologous recombinational repair. Cdk1-targeted Srs2 displays a PCNA–independent role and appears to have an attenuated ability to inhibit recombination. Finally, the recombination defects of unphosphorylatable Srs2 are primarily due to unscheduled accumulation of the Srs2 protein in a sumoylated form. Thus, the Srs2 anti-recombination function in removing toxic Rad51 filaments is genetically separable from its role in promoting recombinational repair, which depends exclusively on Cdk1-dependent phosphorylation. We suggest that Cdk1 kinase counteracts unscheduled sumoylation of Srs2 and targets Srs2 to dismantle specific DNA structures, such as the D-loops, in a helicase-dependent manner during homologous recombinational repair. Broken DNA molecules can be repaired by copying a homologous DNA sequence located elsewhere in the genome. This process, called homologous recombination, needs to be carefully regulated, because unwanted DNA exchanges can lead to genome rearrangements and cell death. Cdk1 kinase is required for cell cycle progression and phosphorylates DNA repair factors, such as Srs2, a protein that can both translocate on single-stranded DNA and open the two strands of DNA double helix. DNA translocation activity of Srs2 is crucial to prevent unwanted recombination, while DNA unwinding activity might be important to promote recombination. In this study, we used two srs2 mutants that constitutively express the unphosphorylated or Cdk1-dependent phosphorylated Srs2 protein isoforms. We found that Srs2 performs genetically distinct functions in preventing or promoting homologous recombination. Cdk1 targets Srs2 to promote accurate repair of double-stranded DNA breaks, but is not essential for the removal of toxic recombination intermediates assembled at single-stranded DNA breaks. Further, Cdk1 counteracts sumoylation of Srs2, which is responsible for recombination defects due to the lack of Srs2 phosphorylation. In summary, Cdk1-dependent Srs2 phosphorylation prevents its unscheduled sumoylation and targets the helicase to promote accurate homologous recombinational repair.
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Affiliation(s)
- Marco Saponaro
- Institute of Molecular Oncology Foundation, The Italian Foundation for Cancer Research and Dipartimento di Scienze Biomolecolari e Biotecnologie–University of Milan, Milan, Italy
| | - Devon Callahan
- Department of Biochemistry and Kaplan Cancer Center, New York University School of Medicine, New York, New York, United States of America
| | - Xiuzhong Zheng
- Department of Biochemistry and Kaplan Cancer Center, New York University School of Medicine, New York, New York, United States of America
| | - Lumir Krejci
- Department of Biology and National Center for Biomolecular Research, Masaryk University, Brno, Czech Republic
| | - James E. Haber
- Department of Biology and Rosenstiel Medical Center, Brandeis University, Waltham, Massachusetts, United States of America
| | - Hannah L. Klein
- Department of Biochemistry and Kaplan Cancer Center, New York University School of Medicine, New York, New York, United States of America
| | - Giordano Liberi
- Institute of Molecular Oncology Foundation, The Italian Foundation for Cancer Research and Dipartimento di Scienze Biomolecolari e Biotecnologie–University of Milan, Milan, Italy
- * E-mail:
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32
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Colavito S, Macris-Kiss M, Seong C, Gleeson O, Greene EC, Klein HL, Krejci L, Sung P. Functional significance of the Rad51-Srs2 complex in Rad51 presynaptic filament disruption. Nucleic Acids Res 2009; 37:6754-64. [PMID: 19745052 PMCID: PMC2777448 DOI: 10.1093/nar/gkp748] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The SRS2 (Suppressor of RAD Six screen mutant 2) gene encodes an ATP-dependent DNA helicase that regulates homologous recombination in Saccharomyces cerevisiae. Mutations in SRS2 result in a hyper-recombination phenotype, sensitivity to DNA damaging agents and synthetic lethality with mutations that affect DNA metabolism. Several of these phenotypes can be suppressed by inactivating genes of the RAD52 epistasis group that promote homologous recombination, implicating inappropriate recombination as the underlying cause of the mutant phenotype. Consistent with the genetic data, purified Srs2 strongly inhibits Rad51-mediated recombination reactions by disrupting the Rad51-ssDNA presynaptic filament. Srs2 interacts with Rad51 in the yeast two-hybrid assay and also in vitro. To investigate the functional relevance of the Srs2-Rad51 complex, we have generated srs2 truncation mutants that retain full ATPase and helicase activities, but differ in their ability to interact with Rad51. Importantly, the srs2 mutant proteins attenuated for Rad51 interaction are much less capable of Rad51 presynaptic filament disruption. An internal deletion in Srs2 likewise diminishes Rad51 interaction and anti-recombinase activity. We also present evidence that deleting the Srs2 C-terminus engenders a hyper-recombination phenotype. These results highlight the importance of Rad51 interaction in the anti-recombinase function of Srs2, and provide evidence that this Srs2 function can be uncoupled from its helicase activity.
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Affiliation(s)
- Sierra Colavito
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA
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33
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Prakash R, Satory D, Dray E, Papusha A, Scheller J, Kramer W, Krejci L, Klein H, Haber JE, Sung P, Ira G. Yeast Mph1 helicase dissociates Rad51-made D-loops: implications for crossover control in mitotic recombination. Genes Dev 2009; 23:67-79. [PMID: 19136626 DOI: 10.1101/gad.1737809] [Citation(s) in RCA: 206] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Eukaryotes possess mechanisms to limit crossing over during homologous recombination, thus avoiding possible chromosomal rearrangements. We show here that budding yeast Mph1, an ortholog of human FancM helicase, utilizes its helicase activity to suppress spontaneous unequal sister chromatid exchanges and DNA double-strand break-induced chromosome crossovers. Since the efficiency and kinetics of break repair are unaffected, Mph1 appears to channel repair intermediates into a noncrossover pathway. Importantly, Mph1 works independently of two other helicases-Srs2 and Sgs1-that also attenuate crossing over. By chromatin immunoprecipitation, we find targeting of Mph1 to double-strand breaks in cells. Purified Mph1 binds D-loop structures and is particularly adept at unwinding these structures. Importantly, Mph1, but not a helicase-defective variant, dissociates Rad51-made D-loops. Overall, the results from our analyses suggest a new role of Mph1 in promoting the noncrossover repair of DNA double-strand breaks.
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Affiliation(s)
- Rohit Prakash
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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34
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SUMOylation regulates Rad18-mediated template switch. Nature 2009; 456:915-20. [PMID: 19092928 DOI: 10.1038/nature07587] [Citation(s) in RCA: 212] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Accepted: 10/21/2008] [Indexed: 01/06/2023]
Abstract
Replication by template switch is thought to mediate DNA damage-bypass and fillings of gaps. Gap-filling repair requires homologous recombination as well as Rad18- and Rad5-mediated proliferating cell nuclear antigen (PCNA) polyubiquitylation. However, it is unclear whether these processes are coordinated, and the physical evidence for Rad18-Rad5-dependent template switch at replication forks is still elusive. Here we show, using genetic and physical approaches, that in budding yeast (Saccharomyces cerevisiae) Rad18 is required for the formation of X-shaped sister chromatid junctions (SCJs) at damaged replication forks through a process involving PCNA polyubiquitylation and the ubiquitin-conjugating enzymes Mms2 and Ubc13. The Rad18-Mms2-mediated damage-bypass through SCJs requires the small ubiquitin-like modifier (SUMO)-conjugating enzyme Ubc9 and SUMOylated PCNA, and is coordinated with Rad51-dependent recombination events. We propose that the Rad18-Rad5-Mms2-dependent SCJs represent template switch events. Altogether, our results unmask a role for PCNA ubiquitylation and SUMOylation pathways in promoting transient damage-induced replication-coupled recombination events involving sister chromatids at replication forks.
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35
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RTEL1 maintains genomic stability by suppressing homologous recombination. Cell 2008; 135:261-71. [PMID: 18957201 DOI: 10.1016/j.cell.2008.08.016] [Citation(s) in RCA: 294] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Revised: 07/16/2008] [Accepted: 08/11/2008] [Indexed: 12/20/2022]
Abstract
Homologous recombination (HR) is an important conserved process for DNA repair and ensures maintenance of genome integrity. Inappropriate HR causes gross chromosomal rearrangements and tumorigenesis in mammals. In yeast, the Srs2 helicase eliminates inappropriate recombination events, but the functional equivalent of Srs2 in higher eukaryotes has been elusive. Here, we identify C. elegans RTEL-1 as a functional analog of Srs2 and describe its vertebrate counterpart, RTEL1, which is required for genome stability and tumor avoidance. We find that rtel-1 mutant worms and RTEL1-depleted human cells share characteristic phenotypes with yeast srs2 mutants: lethality upon deletion of the sgs1/BLM homolog, hyperrecombination, and DNA damage sensitivity. In vitro, purified human RTEL1 antagonizes HR by promoting the disassembly of D loop recombination intermediates in a reaction dependent upon ATP hydrolysis. We propose that loss of HR control after deregulation of RTEL1 may be a critical event that drives genome instability and cancer.
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36
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Le Breton C, Dupaigne P, Robert T, Le Cam E, Gangloff S, Fabre F, Veaute X. Srs2 removes deadly recombination intermediates independently of its interaction with SUMO-modified PCNA. Nucleic Acids Res 2008; 36:4964-74. [PMID: 18658248 PMCID: PMC2528196 DOI: 10.1093/nar/gkn441] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Saccharomyces cerevisiae Srs2 helicase plays at least two distinct functions. One is to prevent recombinational repair through its recruitment by sumoylated Proliferating Cell Nuclear Antigen (PCNA), evidenced in postreplication-repair deficient cells, and a second one is to eliminate potentially lethal intermediates formed by recombination proteins. Both actions are believed to involve the capacity of Srs2 to displace Rad51 upon translocation on single-stranded DNA (ssDNA), though a role of its helicase activity may be important to remove some toxic recombination structures. Here, we described two new mutants, srs2R1 and srs2R3, that have lost the ability to hinder recombinational repair in postreplication-repair mutants, but are still able to remove toxic recombination structures. Although the mutants present very similar phenotypes, the mutated proteins are differently affected in their biochemical activities. Srs2R1 has lost its capacity to interact with sumoylated PCNA while the biochemical activities of Srs2R3 are attenuated (ATPase, helicase, DNA binding and ability to displace Rad51 from ssDNA). In addition, crossover (CO) frequencies are increased in both mutants. The different roles of Srs2, in relation to its eventual recruitment by sumoylated PCNA, are discussed.
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Affiliation(s)
- Cyrille Le Breton
- CEA-DSV-Institut de Radiobiologie Cellulaire et Moléculaire, UMR217 CNRS/CEA, F-92265 Fontenay aux Roses, France
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37
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Cromie GA, Hyppa RW, Smith GR. The fission yeast BLM homolog Rqh1 promotes meiotic recombination. Genetics 2008; 179:1157-67. [PMID: 18562672 PMCID: PMC2475723 DOI: 10.1534/genetics.108.088955] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Accepted: 03/31/2008] [Indexed: 01/04/2023] Open
Abstract
RecQ helicases are found in organisms as diverse as bacteria, fungi, and mammals. These proteins promote genome stability, and mutations affecting human RecQ proteins underlie premature aging and cancer predisposition syndromes, including Bloom syndrome, caused by mutations affecting the BLM protein. In this study we show that mutants lacking the Rqh1 protein of the fission yeast Schizosaccharomyces pombe, a RecQ and BLM homolog, have substantially reduced meiotic recombination, both gene conversions and crossovers. The relative proportion of gene conversions having associated crossovers is unchanged from that in wild type. In rqh1 mutants, meiotic DNA double-strand breaks are formed and disappear with wild-type frequency and kinetics, and spore viability is only moderately reduced. Genetic analyses and the wild-type frequency of both intersister and interhomolog joint molecules argue against these phenotypes being explained by an increase in intersister recombination at the expense of interhomolog recombination. We suggest that Rqh1 extends hybrid DNA and biases the recombination outcome toward crossing over. Our results contrast dramatically with those from the budding yeast ortholog, Sgs1, which has a meiotic antirecombination function that suppresses recombination events involving more than two DNA duplexes. These observations underscore the multiple recombination functions of RecQ homologs and emphasize that even conserved proteins can be adapted to play different roles in different organisms.
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Affiliation(s)
- Gareth A Cromie
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA
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38
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Abstract
Homologous recombination (HR) is a ubiquitous cellular pathway that mediates transfer of genetic information between homologous or near homologous (homeologous) DNA sequences. During meiosis it ensures proper chromosome segregation in the first division. Moreover, HR is critical for the tolerance and repair of DNA damage, as well as in the recovery of stalled and broken replication forks. Together these functions preserve genomic stability and assure high fidelity transmission of the genetic material in the mitotic and meiotic cell divisions. This review will focus on the Rad54 protein, a member of the Snf2-family of SF2 helicases, which translocates on dsDNA but does not display strand displacement activity typical for a helicase. A wealth of genetic, cytological, biochemical and structural data suggests that Rad54 is a core factor of HR, possibly acting at multiple stages during HR in concert with the central homologous pairing protein Rad51.
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Affiliation(s)
- Wolf-Dietrich Heyer
- Sections of Microbiology, University of California Davis, CA 95616-8665, USA.
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39
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Abstract
Homologous recombination is an important mechanism for the repair of double-strand breaks in DNA. One possible outcome of such repair is the reciprocal exchange or crossing over of DNA between chromosomes. Crossovers are beneficial during meiosis because, as well as generating genetic diversity, they promote proper chromosome segregation through the establishment of chiasmata. However, crossing over in vegetative cells can potentially result in loss of heterozygosity and chromosome rearrangements, which can be deleterious. Consequently, cells have evolved mechanisms to limit crossing over during vegetative growth while promoting it during meiosis. Here, we provide a brief review of how some of these mechanisms are thought to work.
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Affiliation(s)
- A Lorenz
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX13QU, UK
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40
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Lui DY, Peoples-Holst TL, Mell JC, Wu HY, Dean EW, Burgess SM. Analysis of close stable homolog juxtaposition during meiosis in mutants of Saccharomyces cerevisiae. Genetics 2006; 173:1207-22. [PMID: 16648640 PMCID: PMC1526657 DOI: 10.1534/genetics.105.050658] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A unique aspect of meiosis is the segregation of homologous chromosomes at the meiosis I division. The pairing of homologous chromosomes is a critical aspect of meiotic prophase I that aids proper disjunction at anaphase I. We have used a site-specific recombination assay in Saccharomyces cerevisiae to examine allelic interaction levels during meiosis in a series of mutants defective in recombination, chromatin structure, or intracellular movement. Red1, a component of the chromosome axis, and Mnd1, a chromosome-binding protein that facilitates interhomolog interaction, are critical for achieving high levels of allelic interaction. Homologous recombination factors (Sae2, Rdh54, Rad54, Rad55, Rad51, Sgs1) aid in varying degrees in promoting allelic interactions, while the Srs2 helicase appears to play no appreciable role. Ris1 (a SWI2/SNF2 related protein) and Dot1 (a histone methyltransferase) appear to play minor roles. Surprisingly, factors involved in microtubule-mediated intracellular movement (Tub3, Dhc1, and Mlp2) appear to play no appreciable role in homolog juxtaposition, unlike their counterparts in fission yeast. Taken together, these results support the notion that meiotic recombination plays a major role in the high levels of homolog interaction observed during budding yeast meiosis.
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Affiliation(s)
- Doris Y Lui
- Section of Molecular and Cellular Biology, University of California, Davis, California 95616, USA
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41
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Pfander B, Moldovan GL, Sacher M, Hoege C, Jentsch S. SUMO-modified PCNA recruits Srs2 to prevent recombination during S phase. Nature 2005; 436:428-33. [PMID: 15931174 DOI: 10.1038/nature03665] [Citation(s) in RCA: 467] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2004] [Accepted: 04/15/2005] [Indexed: 12/25/2022]
Abstract
Damaged DNA, if not repaired before replication, can lead to replication fork stalling and genomic instability; however, cells can switch to different damage bypass modes that permit replication across lesions. Two main bypasses are controlled by ubiquitin modification of proliferating cell nuclear antigen (PCNA), a homotrimeric DNA-encircling protein that functions as a polymerase processivity factor and regulator of replication-linked functions. Upon DNA damage, PCNA is modified at the conserved lysine residue 164 by either mono-ubiquitin or a lysine-63-linked multi-ubiquitin chain, which induce error-prone or error-free replication bypasses of the lesions. In S phase, even in the absence of exogenous DNA damage, yeast PCNA can be alternatively modified by the small ubiquitin-related modifier protein SUMO; however the consequences of this remain controversial. Here we show by genetic analysis that SUMO-modified PCNA functionally cooperates with Srs2, a helicase that blocks recombinational repair by disrupting Rad51 nucleoprotein filaments. Moreover, Srs2 displays a preference for interacting directly with the SUMO-modified form of PCNA, owing to a specific binding site in its carboxy-terminal tail. Our finding suggests a model in which SUMO-modified PCNA recruits Srs2 in S phase in order to prevent unwanted recombination events of replicating chromosomes.
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Affiliation(s)
- Boris Pfander
- Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
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42
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Suzuki K, Kato A, Sakuraba Y, Inoue H. Srs2 and RecQ homologs cooperate in mei-3-mediated homologous recombination repair of Neurospora crassa. Nucleic Acids Res 2005; 33:1848-58. [PMID: 15800214 PMCID: PMC1072801 DOI: 10.1093/nar/gki326] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Homologous recombination and post-replication repair facilitate restart of stalled or collapsed replication forks. The SRS2 gene of Saccharomyces cerevisiae encodes a 3′–5′ DNA helicase that functions both in homologous recombination repair and in post-replication repair. This study identifies and characterizes the SRS2 homolog in Neurospora crassa, which we call mus-50. A knockout mutant of N.crassa, mus-50, is sensitive to several DNA-damaging agents and genetic analyses indicate that it is epistatic with mei-3 (RAD51 homolog), mus-11 (RAD52 homolog), mus-48 (RAD55 homolog) and mus-49 (RAD57 homolog), suggesting a role for mus-50 in homologous recombination repair. However, epistasis evidence has presented that MUS50 does not participate in post-replication repair in N.crassa. Also, the N.crassa mus-25 (RAD54 homolog) mus-50 double mutant is viable, which is in contrast to the lethal phenotype of the equivalent rad54 srs2 mutant in S.cerevisiae. Tetrad analysis revealed that mus-50 in combination with mutations in two RecQ homologs, qde-3 and recQ2, is lethal, and this lethality is suppressed by mutation in mei-3, mus-11 or mus-25. Evidence is also presented for the two independent pathways for recovery from camptothecin-induced replication fork arrest: one pathway is dependent on QDE3 and MUS50 and the other pathway is dependent on MUS25 and RECQ2.
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Affiliation(s)
| | | | | | - Hirokazu Inoue
- To whom correspondence should be addressed. Tel: +81 48 858 3413; Fax: +81 48 858 3413;
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43
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Prakash R, Krejci L, Van Komen S, Anke Schürer K, Kramer W, Sung P. Saccharomyces cerevisiae MPH1 gene, required for homologous recombination-mediated mutation avoidance, encodes a 3' to 5' DNA helicase. J Biol Chem 2005; 280:7854-60. [PMID: 15634678 DOI: 10.1074/jbc.m413898200] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The MPH1 (mutator pHenotype 1) gene of Saccharomyces cerevisiae was identified on the basis of elevated spontaneous mutation rates of haploid cells deleted for this gene. Further studies showed that MPH1 functions to channel DNA lesions into an error-free DNA repair pathway. The Mph1 protein contains the seven conserved motifs of the superfamily 2 (SF2) family of nucleic acid unwinding enzymes. Genetic analyses have found epistasis of the mph1 deletion with mutations in the RAD52 gene group that mediates homologous recombination and DNA repair by homologous recombination. To begin dissecting the biochemical functions of the MPH1-encoded product, we have expressed it in yeast cells and purified it to near homogeneity. We show that Mph1 has a robust ATPase function that requires single-stranded DNA for activation. Consistent with its homology to members of the SF2 helicase family, we find a DNA helicase activity in Mph1. We present data to demonstrate that the Mph1 DNA helicase activity is fueled by ATP hydrolysis and has a 3' to 5' polarity with respect to the DNA strand on which this protein translocates. The DNA helicase activity of Mph1 is enhanced by the heterotrimeric single-stranded DNA binding protein replication protein A. These results, thus, establish Mph1 as an ATP-dependent DNA helicase, and the availability of purified Mph1 should facilitate efforts at deciphering the role of this protein in homologous recombination and mutation avoidance.
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Affiliation(s)
- Rohit Prakash
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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44
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Xu H, Boone C, Klein HL. Mrc1 is required for sister chromatid cohesion to aid in recombination repair of spontaneous damage. Mol Cell Biol 2004; 24:7082-90. [PMID: 15282308 PMCID: PMC479732 DOI: 10.1128/mcb.24.16.7082-7090.2004] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The SRS2 gene of Saccharomyces cerevisiae encoding a 3'-->5' DNA helicase is part of the postreplication repair pathway and functions to ensure proper repair of DNA damage arising during DNA replication through pathways that do not involve homologous recombination. Through a synthetic gene array analysis, genes that are essential when Srs2 is absent have been identified. Among these are MRC1, TOF1, and CSM3, which mediate the intra-S checkpoint response. srs2 Delta mrc1 Delta synthetic lethality is due to inappropriate recombination, as the lethality can be suppressed by genetic elimination of homologous recombination. srs2 Delta mrc1 Delta synthetic lethality is dependent on the role of Mrc1 in DNA replication but independent of the role of Mrc1 in a DNA damage checkpoint response. mrc1 Delta, tof1 Delta and csm3 Delta mutants have sister chromatid cohesion defects, implicating sister chromatid cohesion established at the replication fork as an important factor in promoting repair of stalled replication forks through gap repair.
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Affiliation(s)
- Hong Xu
- Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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45
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Soustelle C, Vernis L, Fréon K, Reynaud-Angelin A, Chanet R, Fabre F, Heude M. A new Saccharomyces cerevisiae strain with a mutant Smt3-deconjugating Ulp1 protein is affected in DNA replication and requires Srs2 and homologous recombination for its viability. Mol Cell Biol 2004; 24:5130-43. [PMID: 15169880 PMCID: PMC419856 DOI: 10.1128/mcb.24.12.5130-5143.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Saccharomyces cerevisiae Srs2 protein is involved in DNA repair and recombination. In order to gain better insight into the roles of Srs2, we performed a screen to identify mutations that are synthetically lethal with an srs2 deletion. One of them is a mutated allele of the ULP1 gene that encodes a protease specifically cleaving Smt3-protein conjugates. This allele, ulp1-I615N, is responsible for an accumulation of Smt3-conjugated proteins. The mutant is unable to grow at 37 degrees C. At permissive temperatures, it still shows severe growth defects together with a strong hyperrecombination phenotype and is impaired in meiosis. Genetic interactions between ulp1 and mutations that affect different repair pathways indicated that the RAD51-dependent homologous recombination mechanism, but not excision resynthesis, translesion synthesis, or nonhomologous end-joining processes, is required for the viability of the mutant. Thus, both Srs2, believed to negatively control homologous recombination, and the process of recombination per se are essential for the viability of the ulp1 mutant. Upon replication, mutant cells accumulate single-stranded DNA interruptions. These structures are believed to generate different recombination intermediates. Some of them are fixed by recombination, and others require Srs2 to be reversed and fixed by an alternate pathway.
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Affiliation(s)
- Christine Soustelle
- Commissaritat à l'Energy Atomique, UMR 217 CNRS-CEA, DSV/DRR, Fontenay-aux-Roses, France
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46
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Aylon Y, Kupiec M. New insights into the mechanism of homologous recombination in yeast. Mutat Res 2004; 566:231-48. [PMID: 15082239 DOI: 10.1016/j.mrrev.2003.10.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2003] [Accepted: 10/02/2003] [Indexed: 01/09/2023]
Abstract
Genome stability is of primary importance for the survival and proper functioning of all organisms. Double-strand breaks (DSBs) arise spontaneously during growth, or can be created by external insults. Repair of DSBs by homologous recombination provides an efficient and fruitful pathway to restore chromosomal integrity. Exciting new work in yeast has lately provided insights into this complex process. Many of the proteins involved in recombination have been isolated and the details of the repair mechanism are now being unraveled at the molecular level. In this review, we focus on recent studies which dissect the recombinational repair of a single broken chromosome. After DSB formation, a decision is made regarding the mechanism of repair (recombination or non-homologous end-joining). This decision is under genetic control. Once committed to the recombination pathway, the broken chromosomal ends are resected by a still unclear mechanism in which the DNA damage checkpoint protein Rad24 participates. At this stage several proteins are recruited to the broken ends, including Rad51p, Rad52p, Rad55p, Rad57p, and possibly Rad54p. A genomic search for homology ensues, followed by strand invasion, promoted by the Rad51 filament with the participation of Rad55p, Rad57p and Rad54p. DNA synthesis then takes place, restoring the resected ends. Crossing-over formation depends on the length of the homologous recombining sequences, and is usually counteracted by the activity of the mismatch repair system. Given the conservation of the repair mechanisms and genes throughout evolution, these studies have profound implications for other eukaryotic organisms.
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Affiliation(s)
- Yael Aylon
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv 69978, Israel
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Smirnova M, Van Komen S, Sung P, Klein HL. Effects of tumor-associated mutations on Rad54 functions. J Biol Chem 2004; 279:24081-8. [PMID: 15056673 DOI: 10.1074/jbc.m402719200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Yeast RAD54 gene, a member of the RAD52 epistasis group, plays an important role in homologous recombination and DNA double strand break repair. Rad54 belongs to the Snf2/Swi2 protein family, and it possesses a robust DNA-dependent ATPase activity, uses free energy from ATP hydrolysis to supercoil DNA, and cooperates with the Rad51 recombinase in DNA joint formation. There are two RAD54-homologous genes in human cells, hRAD54 and RAD54B. Mutations in these human genes have been found in tumors. These tumor-associated mutations map to conserved regions of the hRad54 and hRad54B proteins. Here we introduced the equivalent mutations into the Saccharomyces cerevisiae RAD54 gene in an effort to examine the functional consequences of these gene changes. One mutant, rad54 G484R, showed sensitivity to DNA-damaging agents and reduced homologous recombination rates, indicating a loss of function. Even though the purified rad54 G484R mutant protein retained the ability to bind DNA and interact with Rad51, it was nearly devoid of ATPase activity and was similarly defective in DNA supercoiling and D-loop formation. Two other mutants, rad54 N616S and rad54 D442Y, were not sensitive to genotoxic agents and behaved like the wild type allele in homologous recombination assays. Consistent with the mild phenotype associated with the rad54 N616S allele, its encoded protein was similar to wild type Rad54 protein in biochemical attributes. Because dysfunctional homologous recombination gives rise to genome instability, our results are consistent with the premise that tumor-associated mutations in hRad54 and Rad54B could contribute to the tumor phenotype or enhance the genome instability seen in tumor cells.
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Affiliation(s)
- Marina Smirnova
- Department of Biochemistry and Kaplan Comprehensive Cancer Institute, New York University School of Medicine, New York, New York 10016, USA
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Van Komen S, Reddy MS, Krejci L, Klein H, Sung P. ATPase and DNA helicase activities of the Saccharomyces cerevisiae anti-recombinase Srs2. J Biol Chem 2003; 278:44331-7. [PMID: 12966095 DOI: 10.1074/jbc.m307256200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Saccharomyces cerevisiae SRS2 encodes an ATP-dependent DNA helicase that is needed for DNA damage checkpoint responses and that modulates the efficiency of homologous recombination. Interestingly, strains simultaneously mutated for SRS2 and a variety of DNA repair genes show low viability that can be overcome by inactivating homologous recombination, thus implicating inappropriate recombination as the cause of growth impairment in these mutants. Here, we report on our biochemical characterization of the ATPase and DNA helicase activities of Srs2. ATP hydrolysis by Srs2 occurs efficiently only in the presence of DNA, with ssDNA being considerably more effective than dsDNA in this regard. Using homopolymeric substrates, the minimal DNA length for activating ATP hydrolysis is found to be 5 nucleotides, but a length of 10 nucleotides is needed for maximal activation. In its helicase action, Srs2 prefers substrates with a 3' ss overhang, and approximately 10 bases of 3' overhanging DNA is needed for efficient targeting of Srs2 to the substrate. Even though a 3' overhang serves to target Srs2, under optimized conditions blunt-end DNA substrates are also dissociated by this protein. The ability of Srs2 to unwind helicase substrates with a long duplex region is enhanced by the inclusion of the single-strand DNA-binding factor replication protein A.
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Affiliation(s)
- Stephen Van Komen
- Institute of Biotechnology and Department of Molecular Medicine, University of Texas Health Science Center, San Antonio, Texas 78245, USA
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Krejci L, Van Komen S, Li Y, Villemain J, Reddy MS, Klein H, Ellenberger T, Sung P. DNA helicase Srs2 disrupts the Rad51 presynaptic filament. Nature 2003; 423:305-9. [PMID: 12748644 DOI: 10.1038/nature01577] [Citation(s) in RCA: 489] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2003] [Accepted: 03/20/2003] [Indexed: 11/08/2022]
Abstract
Mutations in the Saccharomyces cerevisiae gene SRS2 result in the yeast's sensitivity to genotoxic agents, failure to recover or adapt from DNA damage checkpoint-mediated cell cycle arrest, slow growth, chromosome loss, and hyper-recombination. Furthermore, double mutant strains, with mutations in DNA helicase genes SRS2 and SGS1, show low viability that can be overcome by inactivating recombination, implying that untimely recombination is the cause of growth impairment. Here we clarify the role of SRS2 in recombination modulation by purifying its encoded product and examining its interactions with the Rad51 recombinase. Srs2 has a robust ATPase activity that is dependent on single-stranded DNA (ssDNA) and binds Rad51, but the addition of a catalytic quantity of Srs2 to Rad51-mediated recombination reactions causes severe inhibition of these reactions. We show that Srs2 acts by dislodging Rad51 from ssDNA. Thus, the attenuation of recombination efficiency by Srs2 stems primarily from its ability to dismantle the Rad51 presynaptic filament efficiently. Our findings have implications for the basis of Bloom's and Werner's syndromes, which are caused by mutations in DNA helicases and are characterized by increased frequencies of recombination and a predisposition to cancers and accelerated ageing.
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Affiliation(s)
- Lumir Krejci
- Institute of Biotechnology and Department of Molecular Medicine, University of Texas Health Science Center at San Antonio, 15355 Lambda Drive, San Antonio, Texas 78245, USA.
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Veaute X, Jeusset J, Soustelle C, Kowalczykowski SC, Le Cam E, Fabre F. The Srs2 helicase prevents recombination by disrupting Rad51 nucleoprotein filaments. Nature 2003; 423:309-12. [PMID: 12748645 DOI: 10.1038/nature01585] [Citation(s) in RCA: 473] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2003] [Accepted: 03/17/2003] [Indexed: 12/22/2022]
Abstract
Homologous recombination is a ubiquitous process with key functions in meiotic and vegetative cells for the repair of DNA breaks. It is initiated by the formation of single-stranded DNA on which recombination proteins bind to form a nucleoprotein filament that is active in searching for homology, in the formation of joint molecules and in the exchange of DNA strands. This process contributes to genome stability but it is also potentially dangerous to cells if intermediates are formed that cannot be processed normally and thus are toxic or generate genomic rearrangements. Cells must therefore have developed strategies to survey recombination and to prevent the occurrence of such deleterious events. In Saccharomyces cerevisiae, genetic data have shown that the Srs2 helicase negatively modulates recombination, and later experiments suggested that it reverses intermediate recombination structures. Here we show that DNA strand exchange mediated in vitro by Rad51 is inhibited by Srs2, and that Srs2 disrupts Rad51 filaments formed on single-stranded DNA. These data provide an explanation for the anti-recombinogenic role of Srs2 in vivo and highlight a previously unknown mechanism for recombination control.
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Affiliation(s)
- Xavier Veaute
- CEA, DSV, Département de Radiobiologie et Radiopathologie, UMR217 CNRS/CEA, BP6, 92265 Fontenay aux Roses Cedex, France.
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