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Balboni B, Marotta R, Rinaldi F, Milordini G, Varignani G, Girotto S, Cavalli A. An integrative structural study of the human full-length RAD52 at 2.2 Å resolution. Commun Biol 2024; 7:956. [PMID: 39112549 PMCID: PMC11306251 DOI: 10.1038/s42003-024-06644-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2024] [Accepted: 07/27/2024] [Indexed: 08/10/2024] Open
Abstract
Human RAD52 (RAD52) is a DNA-binding protein involved in many DNA repair mechanisms and genomic stability maintenance. In the last few years, this protein was discovered to be a promising novel pharmacological target for anticancer strategies. Although the interest in RAD52 has exponentially grown in the previous decade, most information about its structure and mechanism still needs to be elucidated. Here, we report the 2.2 Å resolution cryo-EM reconstruction of the full-length RAD52 (FL-RAD52) protein. This allows us to describe the hydration shell of the N-terminal region of FL-RAD52, which is structured in an undecamer ring. Water molecules coordinate with protein residues to promote stabilization inside and among the protomers and within the inner DNA binding cleft to drive protein-DNA recognition. Additionally, through a multidisciplinary approach involving SEC-SAXS and computational methods, we comprehensively describe the highly flexible and dynamic organization of the C-terminal portion of FL-RAD52. This work discloses unprecedented structural details on the FL-RAD52, which will be critical for characterizing its mechanism of action and inhibitor development, particularly in the context of novel approaches to synthetic lethality and anticancer drug discovery.
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Affiliation(s)
- Beatrice Balboni
- Computational and Chemical Biology, Istituto Italiano di Tecnologia, Genoa, Italy
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
| | - Roberto Marotta
- Electron Microscopy Facility (EMF), Istituto Italiano di Tecnologia, Genoa, Italy
| | - Francesco Rinaldi
- Computational and Chemical Biology, Istituto Italiano di Tecnologia, Genoa, Italy
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
| | - Giulia Milordini
- Computational and Chemical Biology, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Giulia Varignani
- Computational and Chemical Biology, Istituto Italiano di Tecnologia, Genoa, Italy
- Department of Pharmacy and Biotechnology, University of Bologna, Bologna, Italy
| | - Stefania Girotto
- Computational and Chemical Biology, Istituto Italiano di Tecnologia, Genoa, Italy.
- Structural Biophysics Facility, Istituto Italiano di Tecnologia, Genoa, Italy.
| | - Andrea Cavalli
- Computational and Chemical Biology, Istituto Italiano di Tecnologia, Genoa, Italy.
- CECAM, Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne, Switzerland.
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2
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Charifi F, Churikov D, Eckert-Boulet N, Minguet C, Jourquin F, Hardy J, Lisby M, Simon MN, Géli V. Rad52 SUMOylation functions as a molecular switch that determines a balance between the Rad51- and Rad59-dependent survivors. iScience 2021; 24:102231. [PMID: 33748714 PMCID: PMC7966982 DOI: 10.1016/j.isci.2021.102231] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 02/01/2021] [Accepted: 02/22/2021] [Indexed: 12/21/2022] Open
Abstract
Functional telomeres in yeast lacking telomerase can be restored by rare Rad51- or Rad59-dependent recombination events that lead to type I and type II survivors, respectively. We previously proposed that polySUMOylation of proteins and the SUMO-targeted ubiquitin ligase Slx5-Slx8 are key factors in type II recombination. Here, we show that SUMOylation of Rad52 favors the formation of type I survivors. Conversely, preventing Rad52 SUMOylation partially bypasses the requirement of Slx5-Slx8 for type II recombination. We further report that SUMO-dependent proteasomal degradation favors type II recombination. Finally, inactivation of Rad59, but not Rad51, impairs the relocation of eroded telomeres to the Nuclear Pore complexes (NPCs). We propose that Rad59 cooperates with non-SUMOylated Rad52 to promote type II recombination at NPCs, resulting in the emergence of more robust survivors akin to ALT cancer cells. Finally, neither Rad59 nor Rad51 is required by itself for the survival of established type II survivors.
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Affiliation(s)
- Ferose Charifi
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Aix Marseille University, Institut Paoli-Calmettes, Marseille, 13009, France
| | - Dmitri Churikov
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Aix Marseille University, Institut Paoli-Calmettes, Marseille, 13009, France
| | | | - Christopher Minguet
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Aix Marseille University, Institut Paoli-Calmettes, Marseille, 13009, France
| | - Frédéric Jourquin
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Aix Marseille University, Institut Paoli-Calmettes, Marseille, 13009, France
| | - Julien Hardy
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Aix Marseille University, Institut Paoli-Calmettes, Marseille, 13009, France
| | - Michael Lisby
- Department of Biology, University of Copenhagen, Copenhagen N, Denmark
| | - Marie-Noëlle Simon
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Aix Marseille University, Institut Paoli-Calmettes, Marseille, 13009, France
| | - Vincent Géli
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Aix Marseille University, Institut Paoli-Calmettes, Marseille, 13009, France
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3
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Zan H, Tat C, Qiu Z, Taylor JR, Guerrero JA, Shen T, Casali P. Rad52 competes with Ku70/Ku86 for binding to S-region DSB ends to modulate antibody class-switch DNA recombination. Nat Commun 2017; 8:14244. [PMID: 28176781 PMCID: PMC5309807 DOI: 10.1038/ncomms14244] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 12/12/2016] [Indexed: 12/13/2022] Open
Abstract
Antibody class-switch DNA recombination (CSR) is initiated by AID-introduced DSBs in the switch (S) regions targeted for recombination, as effected by Ku70/Ku86-mediated NHEJ. Ku-deficient B cells, however, undergo (reduced) CSR through an alternative(A)-NHEJ pathway, which introduces microhomologies in S-S junctions. As microhomology-mediated end-joining requires annealing of single-strand DNA ends, we addressed the contribution of single-strand annealing factors HR Rad52 and translesion DNA polymerase θ to CSR. Compared with their Rad52+/+ counterparts, which display normal CSR, Rad52-/- B cells show increased CSR, fewer intra-Sμ region recombinations, no/minimal microhomologies in S-S junctions, decreased c-Myc/IgH translocations and increased Ku70/Ku86 recruitment to S-region DSB ends. Rad52 competes with Ku70/Ku86 for binding to S-region DSB ends. It also facilitates a Ku-independent DSB repair, which favours intra-S region recombination and mediates, particularly in Ku absence, inter-S-S recombination, as emphasized by the significantly greater CSR reduction in Rad52-/- versus Rad52+/+ B cells on Ku86 knockdown.
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Affiliation(s)
- Hong Zan
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
| | - Connie Tat
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
| | - Zhifang Qiu
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
| | - Julia R. Taylor
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
| | - Justin A. Guerrero
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
| | - Tian Shen
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
| | - Paolo Casali
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas School of Medicine, UT Health Science Center, San Antonio, Texas 78229, USA
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Nair A, Agarwal R, Chittela RK. Biochemical characterization of plant Rad52 protein from rice (Oryza sativa). PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2016; 106:108-117. [PMID: 27156135 DOI: 10.1016/j.plaphy.2016.04.048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 04/28/2016] [Accepted: 04/28/2016] [Indexed: 06/05/2023]
Abstract
DNA damage in living cells is repaired by two main pathways, homologous recombination (HR) and non-homologous end joining (NHEJ). Of all the genes promoting HR, Rad52 (Radiation sensitive 52) is an important gene which is found to be highly conserved across different species. It was believed that RAD52 is absent in plant systems until lately. However, recent genetic studies have shown the presence of RAD52 homologues in plants. Rad52 homologues in plant systems have not yet been characterized biochemically. In the current study, we bring out the biochemical properties of rice Rad52-2a protein. OsRad52-2a was over-expressed in Escherichia coli BL21 (DE3) cells and the protein was purified. The identity of purified OsRad52-2a protein was confirmed via peptide mass fingerprinting. Gel filtration and native PAGE analysis indicated that the OsRad52-2a protein in its native state probably formed an undecameric structure. Purified OsRad52-2a protein showed binding to single stranded DNA, double stranded DNA. Protein also mediated the renaturation of complementary single strands into duplex DNA in both agarose gel and FRET based assays. Put together, OsRad52-2a forms oligomeric structures and binds to ssDNA/dsDNA for mediating an important function like renaturation during homologous recombination. This study represents the first report on biochemical properties of OsRad52-2a protein from important crop like rice. This information will help in dissecting the recombination and repair machinery in plant systems.
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Affiliation(s)
- Anuradha Nair
- Bio-molecular Damage and Repair Section, Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400085, India
| | - Rachna Agarwal
- Bio-molecular Damage and Repair Section, Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400085, India
| | - Rajani Kant Chittela
- Bio-molecular Damage and Repair Section, Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai, 400085, India.
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Vijayraghavan S, Tsai FL, Schwacha A. A Checkpoint-Related Function of the MCM Replicative Helicase Is Required to Avert Accumulation of RNA:DNA Hybrids during S-phase and Ensuing DSBs during G2/M. PLoS Genet 2016; 12:e1006277. [PMID: 27556397 PMCID: PMC4996524 DOI: 10.1371/journal.pgen.1006277] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 08/04/2016] [Indexed: 01/10/2023] Open
Abstract
The Mcm2-7 complex is the catalytic core of the eukaryotic replicative helicase. Here, we identify a new role for this complex in maintaining genome integrity. Using both genetic and cytological approaches, we find that a specific mcm allele (mcm2DENQ) causes elevated genome instability that correlates with the appearance of numerous DNA-damage associated foci of γH2AX and Rad52. We further find that the triggering events for this genome instability are elevated levels of RNA:DNA hybrids and an altered DNA topological state, as over-expression of either RNaseH (an enzyme specific for degradation of RNA in RNA:DNA hybrids) or Topoisomerase 1 (an enzyme that relieves DNA supercoiling) can suppress the mcm2DENQ DNA-damage phenotype. Moreover, the observed DNA damage has several additional unusual properties, in that DNA damage foci appear only after S-phase, in G2/M, and are dependent upon progression into metaphase. In addition, we show that the resultant DNA damage is not due to spontaneous S-phase fork collapse. In total, these unusual mcm2DENQ phenotypes are markedly similar to those of a special previously-studied allele of the checkpoint sensor kinase ATR/MEC1, suggesting a possible regulatory interplay between Mcm2-7 and ATR during unchallenged growth. As RNA:DNA hybrids primarily result from transcription perturbations, we suggest that surveillance-mediated modulation of the Mcm2-7 activity plays an important role in preventing catastrophic conflicts between replication forks and transcription complexes. Possible relationships among these effects and the recently discovered role of Mcm2-7 in the DNA replication checkpoint induced by HU treatment are discussed.
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Affiliation(s)
- Sriram Vijayraghavan
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Feng-Ling Tsai
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Anthony Schwacha
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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Pillet F, Chopinet L, Formosa C, Dague E. Atomic Force Microscopy and pharmacology: from microbiology to cancerology. Biochim Biophys Acta Gen Subj 2013; 1840:1028-50. [PMID: 24291690 DOI: 10.1016/j.bbagen.2013.11.019] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 11/18/2013] [Accepted: 11/20/2013] [Indexed: 02/06/2023]
Abstract
BACKGROUND Atomic Force Microscopy (AFM) has been extensively used to study biological samples. Researchers take advantage of its ability to image living samples to increase our fundamental knowledge (biophysical properties/biochemical behavior) on living cell surface properties, at the nano-scale. SCOPE OF REVIEW AFM, in the imaging modes, can probe cells morphological modifications induced by drugs. In the force spectroscopy mode, it is possible to follow the nanomechanical properties of a cell and to probe the mechanical modifications induced by drugs. AFM can be used to map single molecule distribution at the cell surface. We will focus on a collection of results aiming at evaluating the nano-scale effects of drugs, by AFM. Studies on yeast, bacteria and mammal cells will illustrate our discussion. Especially, we will show how AFM can help in getting a better understanding of drug mechanism of action. MAJOR CONCLUSIONS This review demonstrates that AFM is a versatile tool, useful in pharmacology. In microbiology, it has been used to study the drugs fighting Candida albicans or Pseudomonas aeruginosa. The major conclusions are a better understanding of the microbes' cell wall and of the drugs mechanism of action. In cancerology, AFM has been used to explore the effects of cytotoxic drugs or as an innovative diagnostic technology. AFM has provided original results on cultured cells, cells extracted from patient and directly on patient biopsies. GENERAL SIGNIFICANCE This review enhances the interest of AFM technologies for pharmacology. The applications reviewed range from microbiology to cancerology.
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Affiliation(s)
- Flavien Pillet
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse Cedex 4, France; Université de Toulouse, UPS, INSA, INP, ISAE, UT1, UTM, LAAS, ITAV, F-31077 Toulouse Cedex 4, France
| | - Louise Chopinet
- CNRS, IPBS-UMR 5089, BP64182, 205 route de Narbonne, F-31077 Toulouse Cedex 4, France; Université de Toulouse, UPS, INSA, INP, ISAE, UT1, UTM, LAAS, ITAV, F-31077 Toulouse Cedex 4, France
| | - Cécile Formosa
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse Cedex 4, France; Université de Toulouse, UPS, INSA, INP, ISAE, UT1, UTM, LAAS, ITAV, F-31077 Toulouse Cedex 4, France; CNRS, UMR 7565, SRSMC, Vandoeuvre-lès-Nancy, France; Université de Lorraine, UMR 7565, Faculté de Pharmacie, Nancy, France
| | - Etienne Dague
- CNRS, LAAS, 7 avenue du colonel Roche, F-31077 Toulouse Cedex 4, France; Université de Toulouse, UPS, INSA, INP, ISAE, UT1, UTM, LAAS, ITAV, F-31077 Toulouse Cedex 4, France; CNRS; ITAV-USR 3505; F31106 Toulouse, France.
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7
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Buechner CN, Tessmer I. DNA substrate preparation for atomic force microscopy studies of protein-DNA interactions. J Mol Recognit 2013; 26:605-17. [DOI: 10.1002/jmr.2311] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 08/14/2013] [Accepted: 08/15/2013] [Indexed: 12/16/2022]
Affiliation(s)
- Claudia N. Buechner
- Rudolf Virchow Center for Experimental Biomedicine; University of Wuerzburg; Josef Schneider Str. 2 97080 Wuerzburg Germany
| | - Ingrid Tessmer
- Rudolf Virchow Center for Experimental Biomedicine; University of Wuerzburg; Josef Schneider Str. 2 97080 Wuerzburg Germany
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8
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Manthey GM, Bailis AM. Rad51 inhibits translocation formation by non-conservative homologous recombination in Saccharomyces cerevisiae. PLoS One 2010; 5:e11889. [PMID: 20686691 PMCID: PMC2912366 DOI: 10.1371/journal.pone.0011889] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 07/07/2010] [Indexed: 11/24/2022] Open
Abstract
Chromosomal translocations are a primary biological response to ionizing radiation (IR) exposure, and are likely to result from the inappropriate repair of the DNA double-strand breaks (DSBs) that are created. An abundance of repetitive sequences in eukaryotic genomes provides ample opportunity for such breaks to be repaired by homologous recombination (HR) between non-allelic repeats. Interestingly, in the budding yeast, Saccharomyces cerevisiae the central strand exchange protein, Rad51 that is required for DSB repair by gene conversion between unlinked repeats that conserves genomic structure also suppresses translocation formation by several HR mechanisms. In particular, Rad51 suppresses translocation formation by single-strand annealing (SSA), perhaps the most efficient mechanism for translocation formation by HR in both yeast and mammalian cells. Further, the enhanced translocation formation that emerges in the absence of Rad51 displays a distinct pattern of genetic control, suggesting that this occurs by a separate mechanism. Since hypomorphic mutations in RAD51 in mammalian cells also reduce DSB repair by conservative gene conversion and stimulate non-conservative repair by SSA, this mechanism may also operate in humans and, perhaps contribute to the genome instability that propels the development of cancer.
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Affiliation(s)
- Glenn M. Manthey
- Department of Molecular and Cellular Biology, Beckman Research Institute, City of Hope National Medical Center, Duarte, California, United States of America
| | - Adam M. Bailis
- Department of Molecular and Cellular Biology, Beckman Research Institute, City of Hope National Medical Center, Duarte, California, United States of America
- * E-mail:
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Blunt-ended DNA double-strand breaks induced by endonucleases PvuII and EcoRV are poor substrates for repair in Saccharomyces cerevisiae. DNA Repair (Amst) 2010; 9:617-26. [PMID: 20356803 DOI: 10.1016/j.dnarep.2010.02.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Revised: 01/11/2010] [Accepted: 02/12/2010] [Indexed: 12/26/2022]
Abstract
Most mechanistic studies of repair of DNA double-strand breaks (DSBs) produced by in vivo expression of endonucleases have utilized enzymes that produce cohesive-ended DSBs such as HO, I-SceI and EcoRI. We have developed systems for expression of PvuII and EcoRV, nucleases that produce DSBs containing blunt ends, using a modified GAL1 promoter that has reduced basal activity. Expression of PvuII and EcoRV caused growth inhibition and strong cell killing in both haploid and diploid yeast cells. Surprisingly, there was little difference in sensitivities of wildtype cells and mutants defective in homologous recombination, nonhomologous end-joining (NHEJ), or both pathways. Physical analysis using standard and pulsed field gel electrophoresis demonstrated time-dependent breakage of chromosomal DNA within cells. Although ionizing radiation-induced DSBs were largely repaired within 4h, no repair of PvuII-induced breaks could be detected in diploid cells, even after arrest in G2/M. Rare survivors of PvuII expression had an increased frequency of chromosome XII deletions, an indication that a fraction of the induced DSBs could be repaired by an error-prone process. These results indicate that, unlike DSBs with complementary single-stranded DNA overhangs, blunt-ended DSBs in yeast chromosomes are poor substrates for repair by either NHEJ or recombination.
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Deng X, Prakash A, Dhar K, Baia GS, Kolar C, Oakley GG, Borgstahl GEO. Human replication protein A-Rad52-single-stranded DNA complex: stoichiometry and evidence for strand transfer regulation by phosphorylation. Biochemistry 2009; 48:6633-43. [PMID: 19530647 PMCID: PMC2710861 DOI: 10.1021/bi900564k] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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The eukaryotic single-stranded DNA-binding protein, replication protein A (RPA), is essential in DNA metabolism and is phosphorylated in response to DNA-damaging agents. Rad52 and RPA participate in the repair of double-stranded DNA breaks (DSBs). It is known that human RPA and Rad52 form a complex, but the molecular mass, stoichiometry, and exact role of this complex in DSB repair are unclear. In this study, absolute molecular masses of individual proteins and complexes were measured in solution using analytical size-exclusion chromatography coupled with multiangle light scattering, the protein species present in each purified fraction were verified via sodium dodecyl sulfate−polyacrylamide gel electrophoresis (SDS−PAGE)/Western analyses, and the presence of biotinylated ssDNA in the complexes was verified by chemiluminescence detection. Then, employing UV cross-linking, the protein partner holding the ssDNA was identified. These data show that phosphorylated RPA promoted formation of a complex with monomeric Rad52 and caused the transfer of ssDNA from RPA to Rad52. This suggests that RPA phosphorylation may regulate the first steps of DSB repair and is necessary for the mediator function of Rad52.
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Affiliation(s)
- Xiaoyi Deng
- The Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, 987696 Nebraska Medical Center, Omaha, Nebraska 68198-7696, USA
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Meyer DH, Bailis AM. Telomerase deficiency affects the formation of chromosomal translocations by homologous recombination in Saccharomyces cerevisiae. PLoS One 2008; 3:e3318. [PMID: 18830407 PMCID: PMC2553005 DOI: 10.1371/journal.pone.0003318] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Accepted: 09/11/2008] [Indexed: 01/17/2023] Open
Abstract
Telomerase is a ribonucleoprotein complex required for the replication and protection of telomeric DNA in eukaryotes. Cells lacking telomerase undergo a progressive loss of telomeric DNA that results in loss of viability and a concomitant increase in genome instability. We have used budding yeast to investigate the relationship between telomerase deficiency and the generation of chromosomal translocations, a common characteristic of cancer cells. Telomerase deficiency increased the rate of formation of spontaneous translocations by homologous recombination involving telomere proximal sequences during crisis. However, telomerase deficiency also decreased the frequency of translocation formation following multiple HO-endonuclease catalyzed DNA double-strand breaks at telomere proximal or distal sequences before, during and after crisis. This decrease correlated with a sequestration of the central homologous recombination factor, Rad52, to telomeres determined by chromatin immuno-precipitation. This suggests that telomerase deficiency results in the sequestration of Rad52 to telomeres, limiting the capacity of the cell to repair double-strand breaks throughout the genome. Increased spontaneous translocation formation in telomerase-deficient yeast cells undergoing crisis is consistent with the increased incidence of cancer in elderly humans, as the majority of our cells lack telomerase. Decreased translocation formation by recombinational repair of double-strand breaks in telomerase-deficient yeast suggests that the reemergence of telomerase expression observed in many human tumors may further stimulate genome rearrangement. Thus, telomerase may exert a substantial effect on global genome stability, which may bear significantly on the appearance and progression of cancer in humans.
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Affiliation(s)
- Damon H. Meyer
- Division of Molecular Biology, Beckman Research Institute of the City of Hope, Duarte, California, United States of America
- City of Hope Graduate School of Biological Sciences, Duarte, California, United States of America
| | - Adam M. Bailis
- Division of Molecular Biology, Beckman Research Institute of the City of Hope, Duarte, California, United States of America
- * E-mail:
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12
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McIlwraith MJ, West SC. DNA repair synthesis facilitates RAD52-mediated second-end capture during DSB repair. Mol Cell 2008; 29:510-6. [PMID: 18313388 DOI: 10.1016/j.molcel.2007.11.037] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Revised: 09/27/2007] [Accepted: 11/05/2007] [Indexed: 11/27/2022]
Abstract
Homologous recombination (HR) is essential for the repair of DNA double-strand breaks (DSBs) in mitotic and meiotic cells. HR occurs through a series of steps involving DSB resection, invasion of single-stranded DNA into homologous duplex DNA to form a D loop, repair synthesis, and second-end capture. We show that DNA repair synthesis, catalyzed by human DNA polymerase eta (poleta) acting upon the priming strand of a D loop, leads to capture and annealing of the second end of a resected DSB in reactions mediated by RAD52 protein. Second-end capture products were not detected when poleta was replaced by other polymerases such as poldelta or poliota. RAD52 could not be replaced by RAD51. We also found that the RAD52-dependent reaction was stimulated by the single-strand binding protein RPA, but not by E. coli SSB. Following repair synthesis and second-end capture, de novo DNA synthesis was observed from the captured second DNA end.
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Affiliation(s)
- Michael J McIlwraith
- Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Herts EN6 3LD, UK
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13
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de Vries FAT, Zonneveld JBM, de Groot AJ, Koning RI, van Zeeland AA, Pastink A. Schizosaccharomyces pombe Rad22A and Rad22B have similar biochemical properties and form multimeric structures. Mutat Res 2006; 615:143-52. [PMID: 17208257 DOI: 10.1016/j.mrfmmm.2006.11.032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Revised: 11/10/2006] [Accepted: 11/28/2006] [Indexed: 10/23/2022]
Abstract
The Saccharomyces cerevisiae Rad52 protein has a crucial role in the repair of DNA double-strand breaks by homologous recombination. In vitro, Rad52 displays DNA binding and strand annealing activities and promotes Rad51-mediated strand exchange. Schizosaccharomyces pombe has two Rad52 homologues, Rad22A and Rad22B. Whereas rad22A deficient strains exhibit severe defects in repair and recombination, rad22B mutants have a much less severe phenotype. To better understand the role of Rad22A and Rad22B in double-strand break repair, both proteins were purified to near homogeneity. Using gel retardation and filter binding assays, binding of Rad22A and Rad22B to short single-stranded DNAs was demonstrated. Binding of Rad22A to double-stranded oligonucleotides or linearized plasmid molecules containing blunt ends or short single-stranded overhangs could not be detected. Rad22B also does not bind efficiently to short duplex oligonucleotides but binds readily to DNA fragments containing 3'-overhangs. Rad22A as well as Rad22B efficiently promote annealing of complementary single-stranded DNAs. In the presence of Rad22A annealing of complementary DNAs is almost 90%. Whereas in reactions containing Rad22B the maximum level of annealing is 60%, most likely due to inhibition of the reaction by duplex DNA. Gel-filtration experiments and electron microscopic analyses indicate self-association of Rad22A and Rad22B and the formation of multimeric structures as has been observed for Rad52 in yeast and man.
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Affiliation(s)
- Femke A T de Vries
- Department of Toxicogenetics, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands
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