1
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Tang Q, Liu Y, Liu Y, Zhu F, Yu Q, Chen H, Chen L, Ma S, Xu H, Chen K, Li G. Bombyx mori Flap endonuclease 1 correlates with the repair of ultraviolet-induced DNA damage. JOURNAL OF INSECT PHYSIOLOGY 2022; 142:104424. [PMID: 35878701 DOI: 10.1016/j.jinsphys.2022.104424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 07/19/2022] [Accepted: 07/20/2022] [Indexed: 06/15/2023]
Abstract
Solar ultraviolet radiation (UV) can cause DNA damage in microorganisms. Flap endonuclease 1 (FEN1) is a structure-specific nuclease and plays important roles in DNA replication and repair. At present, the properties and functions of FEN1 have not been characterized in detail in invertebrates such as Bombyx mori. In this study, Bombyx mori FEN1 (BmFEN1) was expressed in E. coli, and was shown to have nuclease activity that nonspecifically cleaved DNA in vitro. However, inside the cell, BmFEN1 did not cleave DNA randomly. Truncated BmFEN1 missing the nuclear localization signal (346-380 aa) still had the nuclease activity, but was no longer precisely localized to the sites of UV-induced DNA damage. It was further found that BmFEN1 favored the faster repair of UV-damaged DNA. The present study will provide a reference for further understanding the functions of BmFEN1 and UV-induced DNA damage repair mechanisms in insects.
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Affiliation(s)
- Qi Tang
- School of Life Sciences, Jiangsu University, 301# Xuefu Road, Zhenjiang 212013, China
| | - Yue Liu
- School of Life Sciences, Jiangsu University, 301# Xuefu Road, Zhenjiang 212013, China
| | - Yutong Liu
- School of Life Sciences, Jiangsu University, 301# Xuefu Road, Zhenjiang 212013, China
| | - Feifei Zhu
- School of Life Sciences, Jiangsu University, 301# Xuefu Road, Zhenjiang 212013, China
| | - Qian Yu
- School of Life Sciences, Jiangsu University, 301# Xuefu Road, Zhenjiang 212013, China
| | - Huiqing Chen
- School of Life Sciences, Jiangsu University, 301# Xuefu Road, Zhenjiang 212013, China
| | - Liang Chen
- School of Life Sciences, Jiangsu University, 301# Xuefu Road, Zhenjiang 212013, China
| | - Shangshang Ma
- School of Life Sciences, Jiangsu University, 301# Xuefu Road, Zhenjiang 212013, China
| | - Huixin Xu
- School of Life Sciences, Jiangsu University, 301# Xuefu Road, Zhenjiang 212013, China
| | - Keping Chen
- School of Life Sciences, Jiangsu University, 301# Xuefu Road, Zhenjiang 212013, China.
| | - Guohui Li
- School of Life Sciences, Jiangsu University, 301# Xuefu Road, Zhenjiang 212013, China.
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2
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Carreira R, Aguado FJ, Hurtado-Nieves V, Blanco MG. Canonical and novel non-canonical activities of the Holliday junction resolvase Yen1. Nucleic Acids Res 2021; 50:259-280. [PMID: 34928393 PMCID: PMC8754655 DOI: 10.1093/nar/gkab1225] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 11/12/2021] [Accepted: 12/01/2021] [Indexed: 11/14/2022] Open
Abstract
Yen1 and GEN1 are members of the Rad2/XPG family of nucleases that were identified as the first canonical nuclear Holliday junction (HJ) resolvases in budding yeast and humans due to their ability to introduce two symmetric, coordinated incisions on opposite strands of the HJ, yielding nicked DNA products that could be readily ligated. While GEN1 has been extensively characterized in vitro, much less is known about the biochemistry of Yen1. Here, we have performed the first in-depth characterization of purified Yen1. We confirmed that Yen1 resembles GEN1 in many aspects, including range of substrates targeted, position of most incisions they produce or the increase in the first incision rate by assembly of a dimer on a HJ, despite minor differences. However, we demonstrate that Yen1 is endowed with additional nuclease activities, like a nick-specific 5′-3′ exonuclease or HJ arm-chopping that could apparently blur its classification as a canonical HJ resolvase. Despite this, we show that Yen1 fulfils the requirements of a canonical HJ resolvase and hypothesize that its wider array of nuclease activities might contribute to its function in the removal of persistent recombination or replication intermediates.
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Affiliation(s)
- Raquel Carreira
- Department of Biochemistry and Molecular Biology, CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), Santiago de Compostela, A Coruña 15782, Spain
| | - F Javier Aguado
- Department of Biochemistry and Molecular Biology, CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), Santiago de Compostela, A Coruña 15782, Spain
| | - Vanesa Hurtado-Nieves
- Department of Biochemistry and Molecular Biology, CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), Santiago de Compostela, A Coruña 15782, Spain
| | - Miguel G Blanco
- Department of Biochemistry and Molecular Biology, CIMUS, Universidade de Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), Santiago de Compostela, A Coruña 15782, Spain
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3
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Bellendir SP, Rognstad DJ, Morris LP, Zapotoczny G, Walton WG, Redinbo MR, Ramsden DA, Sekelsky J, Erie DA. Substrate preference of Gen endonucleases highlights the importance of branched structures as DNA damage repair intermediates. Nucleic Acids Res 2017; 45:5333-5348. [PMID: 28369583 PMCID: PMC5435919 DOI: 10.1093/nar/gkx214] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 02/16/2017] [Accepted: 03/21/2017] [Indexed: 11/20/2022] Open
Abstract
Human GEN1 and yeast Yen1 are endonucleases with the ability to cleave Holliday junctions (HJs), which are proposed intermediates in recombination. In vivo, GEN1 and Yen1 function secondarily to Mus81, which has weak activity on intact HJs. We show that the genetic relationship is reversed in Drosophila, with Gen mutants having more severe defects than mus81 mutants. In vitro, DmGen, like HsGEN1, efficiently cleaves HJs, 5΄ flaps, splayed arms, and replication fork structures. We find that the cleavage rates for 5΄ flaps are significantly higher than those for HJs for both DmGen and HsGEN1, even in vast excess of enzyme over substrate. Kinetic studies suggest that the difference in cleavage rates results from a slow, rate-limiting conformational change prior to HJ cleavage: formation of a productive dimer on the HJ. Despite the stark difference in vivo that Drosophila uses Gen over Mus81 and humans use MUS81 over GEN1, we find the in vitro activities of DmGen and HsGEN1 to be strikingly similar. These findings suggest that simpler branched structures may be more important substrates for Gen orthologs in vivo, and highlight the utility of using the Drosophila model system to further understand these enzymes.
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Affiliation(s)
| | | | - Lydia P. Morris
- Lineberger Comprehensive Cancer Center, Chapel Hill, NC 27599, USA
| | | | | | - Matthew R. Redinbo
- Department of Chemistry, Chapel Hill, NC 27599, USA
- Integrative Program for Biological and Genome Sciences, Chapel Hill, NC 27599, USA
| | - Dale A. Ramsden
- Curriculum in Genetics and Molecular Biology, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, Chapel Hill, NC 27599, USA
- Department of Biochemistry and Biophysics, Chapel Hill, NC 27599, USA
| | - Jeff Sekelsky
- Curriculum in Genetics and Molecular Biology, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, Chapel Hill, NC 27599, USA
- Integrative Program for Biological and Genome Sciences, Chapel Hill, NC 27599, USA
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Dorothy A. Erie
- Department of Chemistry, Chapel Hill, NC 27599, USA
- Integrative Program for Biological and Genome Sciences, Chapel Hill, NC 27599, USA
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4
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Shah Punatar R, Martin MJ, Wyatt HDM, Chan YW, West SC. Resolution of single and double Holliday junction recombination intermediates by GEN1. Proc Natl Acad Sci U S A 2017; 114:443-450. [PMID: 28049850 PMCID: PMC5255610 DOI: 10.1073/pnas.1619790114] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Genetic recombination provides an important mechanism for the repair of DNA double-strand breaks. Homologous pairing and strand exchange lead to the formation of DNA intermediates, in which sister chromatids or homologous chromosomes are covalently linked by four-way Holliday junctions (HJs). Depending on the type of recombination reaction that takes place, intermediates may have single or double HJs, and their resolution is essential for proper chromosome segregation. In mitotic cells, double HJs are primarily dissolved by the BLM helicase-TopoisomeraseIIIα-RMI1-RMI2 (BTR) complex, whereas single HJs (and double HJs that have escaped the attention of BTR) are resolved by structure-selective endonucleases known as HJ resolvases. These enzymes are ubiquitous in nature, because they are present in bacteriophage, bacteria, archaea, and simple and complex eukaryotes. The human HJ resolvase GEN1 is a member of the XPG/Rad2 family of 5'-flap endonucleases. Biochemical studies of GEN1 revealed that it cleaves synthetic DNA substrates containing a single HJ by a mechanism similar to that shown by the prototypic HJ resolvase, Escherichia coli RuvC protein, but it is unclear whether these substrates fully recapitulate the properties of recombination intermediates that arise within a physiological context. Here, we show that GEN1 efficiently cleaves both single and double HJs contained within large recombination intermediates. Moreover, we find that GEN1 exhibits a weak sequence preference for incision between two G residues that reside in a T-rich region of DNA. These results contrast with those obtained with RuvC, which exhibits a strict requirement for the consensus sequence 5'-A/TTTG/C-3'.
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Affiliation(s)
- Rajvee Shah Punatar
- DNA Recombination and Repair Laboratory, The Francis Crick Institute, London NW1 1AT, United Kingdom
| | - Maria Jose Martin
- DNA Recombination and Repair Laboratory, The Francis Crick Institute, London NW1 1AT, United Kingdom
| | - Haley D M Wyatt
- DNA Recombination and Repair Laboratory, The Francis Crick Institute, London NW1 1AT, United Kingdom
| | - Ying Wai Chan
- DNA Recombination and Repair Laboratory, The Francis Crick Institute, London NW1 1AT, United Kingdom
| | - Stephen C West
- DNA Recombination and Repair Laboratory, The Francis Crick Institute, London NW1 1AT, United Kingdom
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5
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Wu Y, Qian Y, Zhou G, Lv J, Yan Q, Dong X. Effect of GEN1 interference on the chemosensitivity of the breast cancer MCF-7 and SKBR3 cell lines. Oncol Lett 2016; 11:3597-3604. [PMID: 27284361 PMCID: PMC4887781 DOI: 10.3892/ol.2016.4489] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 03/01/2016] [Indexed: 12/20/2022] Open
Abstract
Chemotherapy is a notable method for the treatment of breast cancer. Numerous genes associated with the sensitivity of cancer to chemotherapy have been found. In recent years, evidence has suggested that a particular structure termed Holliday junction (HJ) plays a crucial role in cancer chemosensitivity. Targeting HJ resolvases, such as structure-specific endonuclease subunit SLX4 (Slx4) and MUS81 structure-specific endonuclease subunit (Mus81), significantly increases the chemosensitivity of tumor cells. Flap endonuclease GEN homolog 1 (GEN1) is a HJ resolvase that belongs to the Rad2/xeroderma pigmentosum complementation group G nuclease family. Whether GEN1 affects the chemosensitivity of tumor cells in a similar manner to Slx4 and Mus81 remains unknown. The aim of the present study was to determine the effect of GEN1 interference on the chemosensitivity of breast cancer cell lines. The investigation of the function of GEN1 was performed using MCF-7 and SKBR3 cells. Short hairpin RNA was used to suppress the expression of GEN1, and western blot analysis and reverse transcription-quantitative polymerase chain reaction were used to detect gene expression. In addition, a cell counting kit-8 assay was performed to detect the viability of cells and flow cytometry was performed to test apoptosis levels. Suppression of GEN1 in SKBR3 cells effectively increased the sensitivity to the chemotherapeutic drug 5-fluorouracil (5-FU), while MCF-7 cells showed no significant change in sensitivity following GEN1 suppression. However, when GEN1 was targeted in addition to Mus81, the MCF-7 cells also demonstrated a significantly increased sensitivity to 5-FU. In addition, when the level of Mus81 was low, GEN1 expression was increased under a low concentration of 5-FU. The present results suggest that GEN1 may play different roles in different breast cancer cell lines. The function of GEN1 may be affected by the level of Mus81 in the cell line. In addition, GEN1 interference may improve the sensitivity to chemotherapy induced by targeting Mus81 alone.
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Affiliation(s)
- Yunlu Wu
- Clinical Laboratory Center, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China; The Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Science, Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Ying Qian
- Clinical Laboratory Center, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China
| | - Guozhong Zhou
- Clinical Laboratory Center, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China
| | - Juan Lv
- Clinical Laboratory Center, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China
| | - Qiuyue Yan
- Clinical Laboratory Center, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China; The Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Science, Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
| | - Xuejun Dong
- Clinical Laboratory Center, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China; The Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Science, Wenzhou Medical University, Wenzhou, Zhejiang 325000, P.R. China
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6
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Lee SH, Princz LN, Klügel MF, Habermann B, Pfander B, Biertümpfel C. Human Holliday junction resolvase GEN1 uses a chromodomain for efficient DNA recognition and cleavage. eLife 2015; 4:e12256. [PMID: 26682650 PMCID: PMC5039027 DOI: 10.7554/elife.12256] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 12/17/2015] [Indexed: 12/22/2022] Open
Abstract
Holliday junctions (HJs) are key DNA intermediates in homologous recombination. They link homologous DNA strands and have to be faithfully removed for proper DNA segregation and genome integrity. Here, we present the crystal structure of human HJ resolvase GEN1 complexed with DNA at 3.0 Å resolution. The GEN1 core is similar to other Rad2/XPG nucleases. However, unlike other members of the superfamily, GEN1 contains a chromodomain as an additional DNA interaction site. Chromodomains are known for their chromatin-targeting function in chromatin remodelers and histone(de)acetylases but they have not previously been found in nucleases. The GEN1 chromodomain directly contacts DNA and its truncation severely hampers GEN1's catalytic activity. Structure-guided mutations in vitro and in vivo in yeast validated our mechanistic findings. Our study provides the missing structure in the Rad2/XPG family and insights how a well-conserved nuclease core acquires versatility in recognizing diverse substrates for DNA repair and maintenance.
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Affiliation(s)
- Shun-Hsiao Lee
- Department of Structural Cell Biology, Molecular Mechanisms of DNA Repair, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Lissa Nicola Princz
- Department of Molecular Cell Biology, DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Maren Felizitas Klügel
- Department of Structural Cell Biology, Molecular Mechanisms of DNA Repair, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Bianca Habermann
- Computational Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Boris Pfander
- Department of Molecular Cell Biology, DNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Christian Biertümpfel
- Department of Structural Cell Biology, Molecular Mechanisms of DNA Repair, Max Planck Institute of Biochemistry, Martinsried, Germany
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7
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Blanco MG, Matos J. Hold your horSSEs: controlling structure-selective endonucleases MUS81 and Yen1/GEN1. Front Genet 2015; 6:253. [PMID: 26284109 PMCID: PMC4519697 DOI: 10.3389/fgene.2015.00253] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 07/13/2015] [Indexed: 12/21/2022] Open
Abstract
Repair of DNA lesions through homologous recombination promotes the establishment of stable chromosomal interactions. Multiple helicases, topoisomerases and structure-selective endonucleases (SSEs) act upon recombining joint molecules (JMs) to disengage chromosomal connections and safeguard chromosome segregation. Recent studies on two conserved SSEs – MUS81 and Yen1/GEN1– uncovered multiple layers of regulation that operate to carefully tailor JM-processing according to specific cellular needs. Temporal restriction of SSE function imposes a hierarchy in pathway usage that ensures efficient JM-processing while minimizing reciprocal exchanges between the recombining DNAs. Whereas a conserved strategy of fine-tuning SSE functions exists in different model systems, the precise molecular mechanisms to implement it appear to be significantly different. Here, we summarize the current knowledge on the cellular switches that are in place to control MUS81 and Yen1/GEN1 functions.
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Affiliation(s)
- Miguel G Blanco
- Department of Biochemistry and Molecular Biology, Center for Research in Molecular Medicine and Chronic Diseases, University of Santiago de Compostela , Santiago de Compostela, Spain
| | - Joao Matos
- Institute of Biochemistry, Swiss Federal Institute of Technology in Zürich , Zürich, Switzerland
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8
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Mus81-Mms4 and Yen1 resolve a novel anaphase bridge formed by noncanonical Holliday junctions. Nat Commun 2014; 5:5652. [PMID: 25466415 DOI: 10.1038/ncomms6652] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 10/24/2014] [Indexed: 02/07/2023] Open
Abstract
Downregulation of separase, condensin, Smc5/6, topoisomerase II and Cdc14 in Saccharomyces cerevisiae yields anaphase bridges formed by unresolved sister chromatids (SCBs). Here we report that the overlapping actions of the structure-selective endonucleases (SSEs) Mus81-Mms4/EME1 and Yen1/GEN1, but not Slx1-Slx4, are also essential to prevent the formation of spontaneous SCBs that depend on the homologous recombination pathway. We further show that the frequency of SCBs is boosted after mild replication stress and that they contain joint molecules enriched in non-canonical forms of the Holliday junction (HJ), including nicked-HJ (nHJ). We show that SCBs are mostly reversible upon activation of either Mus81-Mms4 or Yen1 in late anaphase, which is concomitant with the disappearance of non-canonical HJs and restoration of viable progeny. On the basis of these findings, we propose a model where unresolved recombination intermediates are a source of mitotic SCBs, and Mus81-Mms4 and Yen1 play a central role in their resolution in vivo.
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9
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Schwartz EK, Wright WD, Ehmsen KT, Evans JE, Stahlberg H, Heyer WD. Mus81-Mms4 functions as a single heterodimer to cleave nicked intermediates in recombinational DNA repair. Mol Cell Biol 2012; 32:3065-80. [PMID: 22645308 PMCID: PMC3434506 DOI: 10.1128/mcb.00547-12] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Accepted: 05/18/2012] [Indexed: 11/20/2022] Open
Abstract
The formation of crossovers is a fundamental genetic process. The XPF-family endonuclease Mus81-Mms4 (Eme1) contributes significantly to crossing over in eukaryotes. A key question is whether Mus81-Mms4 can process Holliday junctions that contain four uninterrupted strands. Holliday junction cleavage requires the coordination of two active sites, necessitating the assembly of two Mus81-Mms4 heterodimers. Contrary to this expectation, we show that Saccharomyces cerevisiae Mus81-Mms4 exists as a single heterodimer both in solution and when bound to DNA substrates in vitro. Consistently, immunoprecipitation experiments demonstrate that Mus81-Mms4 does not multimerize in vivo. Moreover, chromatin-bound Mus81-Mms4 does not detectably form higher-order multimers. We show that Cdc5 kinase activates Mus81-Mms4 nuclease activity on 3' flaps and Holliday junctions in vitro but that activation does not induce a preference for Holliday junctions and does not induce multimerization of the Mus81-Mms4 heterodimer. These data support a model in which Mus81-Mms4 cleaves nicked recombination intermediates such as displacement loops (D-loops), nicked Holliday junctions, or 3' flaps but not intact Holliday junctions with four uninterrupted strands. We infer that Mus81-dependent crossing over occurs in a noncanonical manner that does not involve the coordinated cleavage of classic Holliday junctions.
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Affiliation(s)
| | | | | | - James E. Evans
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, California, USA
| | - Henning Stahlberg
- Center for Cellular Imaging and Nano Analytics, University Basel, Basel, Switzerland
| | - Wolf-Dietrich Heyer
- Department of Microbiology
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, California, USA
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10
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Yang Y, Ishino S, Yamagami T, Kumamaru T, Satoh H, Ishino Y. The OsGEN-L protein from Oryza sativa possesses Holliday junction resolvase activity as well as 5'-flap endonuclease activity. J Biochem 2012; 151:317-27. [DOI: 10.1093/jb/mvr145] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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11
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Andersen SL, Kuo HK, Savukoski D, Brodsky MH, Sekelsky J. Three structure-selective endonucleases are essential in the absence of BLM helicase in Drosophila. PLoS Genet 2011; 7:e1002315. [PMID: 22022278 PMCID: PMC3192830 DOI: 10.1371/journal.pgen.1002315] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Accepted: 08/03/2011] [Indexed: 02/03/2023] Open
Abstract
DNA repair mechanisms in mitotically proliferating cells avoid generating crossovers, which can contribute to genome instability. Most models for the production of crossovers involve an intermediate with one or more four-stranded Holliday junctions (HJs), which are resolved into duplex molecules through cleavage by specialized endonucleases. In vitro studies have implicated three nuclear enzymes in HJ resolution: MUS81–EME1/Mms4, GEN1/Yen1, and SLX4–SLX1. The Bloom syndrome helicase, BLM, plays key roles in preventing mitotic crossover, either by blocking the formation of HJ intermediates or by removing HJs without cleavage. Saccharomyces cerevisiae mutants that lack Sgs1 (the BLM ortholog) and either Mus81–Mms4 or Slx4–Slx1 are inviable, but mutants that lack Sgs1 and Yen1 are viable. The current view is that Yen1 serves primarily as a backup to Mus81–Mms4. Previous studies with Drosophila melanogaster showed that, as in yeast, loss of both DmBLM and MUS81 or MUS312 (the ortholog of SLX4) is lethal. We have now recovered and analyzed mutations in Drosophila Gen. As in yeast, there is some redundancy between Gen and mus81; however, in contrast to the case in yeast, GEN plays a more predominant role in responding to DNA damage than MUS81–MMS4. Furthermore, loss of DmBLM and GEN leads to lethality early in development. We present a comparison of phenotypes occurring in double mutants that lack DmBLM and either MUS81, GEN, or MUS312, including chromosome instability and deficiencies in cell proliferation. Our studies of synthetic lethality provide insights into the multiple functions of DmBLM and how various endonucleases may function when DmBLM is absent. The maintenance of a stable genome is crucial to organismal survival. Genome stability is perpetually threatened by spontaneous DNA damage, and DNA repair proteins are required to accurately and efficiently repair DNA damage in ways that minimize genome alterations. Some repair pathways are linked to increased risk of genome changes. One example is repair associated with the production of crossovers between homologous chromosomes. The DNA helicase BLM suppresses genome changes by promoting non-crossover forms of repair; without BLM, spontaneous crossovers, deletions, and genome rearrangements increase. Using Drosophila as a model organism, our studies reveal the complex interactions between BLM and three structure-selective endonucleases with overlapping substrate specificities and partial functional redundancy. Loss of BLM and any one of the nucleases results in severe genome instability, reduced cell proliferation, and, ultimately, death of the animal. Our work suggests that these nucleases differentially rescue the loss of functions of BLM associated with problems that arise during DNA replication, illuminating the complexity of repair mechanisms required to maintain genome stability during replication. Further, our work advances models of replication-associated repair by suggesting specific roles for BLM and structure-selective endonucleases.
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Affiliation(s)
- Sabrina L Andersen
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
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12
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Schwartz EK, Heyer WD. Processing of joint molecule intermediates by structure-selective endonucleases during homologous recombination in eukaryotes. Chromosoma 2011; 120:109-27. [PMID: 21369956 PMCID: PMC3057012 DOI: 10.1007/s00412-010-0304-7] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 12/04/2010] [Accepted: 12/07/2010] [Indexed: 10/27/2022]
Abstract
Homologous recombination is required for maintaining genomic integrity by functioning in high-fidelity repair of DNA double-strand breaks and other complex lesions, replication fork support, and meiotic chromosome segregation. Joint DNA molecules are key intermediates in recombination and their differential processing determines whether the genetic outcome is a crossover or non-crossover event. The Holliday model of recombination highlights the resolution of four-way DNA joint molecules, termed Holliday junctions, and the bacterial Holliday junction resolvase RuvC set the paradigm for the mechanism of crossover formation. In eukaryotes, much effort has been invested in identifying the eukaryotic equivalent of bacterial RuvC, leading to the discovery of a number of DNA endonucleases, including Mus81-Mms4/EME1, Slx1-Slx4/BTBD12/MUS312, XPF-ERCC1, and Yen1/GEN1. These nucleases exert different selectivity for various DNA joint molecules, including Holliday junctions. Their mutant phenotypes and distinct species-specific characteristics expose a surprisingly complex system of joint molecule processing. In an attempt to reconcile the biochemical and genetic data, we propose that nicked junctions constitute important in vivo recombination intermediates whose processing determines the efficiency and outcome (crossover/non-crossover) of homologous recombination.
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Affiliation(s)
- Erin K. Schwartz
- Department of Microbiology, University of California—Davis, Davis, CA 95616 USA
| | - Wolf-Dietrich Heyer
- Department of Microbiology, University of California—Davis, Davis, CA 95616 USA
- Department of Molecular and Cellular Biology, University of California—Davis, Davis, CA 95616 USA
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13
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Bailly AP, Freeman A, Hall J, Déclais AC, Alpi A, Lilley DMJ, Ahmed S, Gartner A. The Caenorhabditis elegans homolog of Gen1/Yen1 resolvases links DNA damage signaling to DNA double-strand break repair. PLoS Genet 2010; 6:e1001025. [PMID: 20661466 PMCID: PMC2908289 DOI: 10.1371/journal.pgen.1001025] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2009] [Accepted: 06/14/2010] [Indexed: 11/30/2022] Open
Abstract
DNA double-strand breaks (DSBs) can be repaired by homologous recombination (HR), which can involve Holliday junction (HJ) intermediates that are ultimately resolved by nucleolytic enzymes. An N-terminal fragment of human GEN1 has recently been shown to act as a Holliday junction resolvase, but little is known about the role of GEN-1 in vivo. Holliday junction resolution signifies the completion of DNA repair, a step that may be coupled to signaling proteins that regulate cell cycle progression in response to DNA damage. Using forward genetic approaches, we identified a Caenorhabditis elegans dual function DNA double-strand break repair and DNA damage signaling protein orthologous to the human GEN1 Holliday junction resolving enzyme. GEN-1 has biochemical activities related to the human enzyme and facilitates repair of DNA double-strand breaks, but is not essential for DNA double-strand break repair during meiotic recombination. Mutational analysis reveals that the DNA damage-signaling function of GEN-1 is separable from its role in DNA repair. GEN-1 promotes germ cell cycle arrest and apoptosis via a pathway that acts in parallel to the canonical DNA damage response pathway mediated by RPA loading, CHK1 activation, and CEP-1/p53–mediated apoptosis induction. Furthermore, GEN-1 acts redundantly with the 9-1-1 complex to ensure genome stability. Our study suggests that GEN-1 might act as a dual function Holliday junction resolvase that may coordinate DNA damage signaling with a late step in DNA double-strand break repair. Coordination of DNA repair with cell cycle progression and apoptosis is a central task of the DNA damage response machinery. A key intermediate of recombinational repair and meiotic recombination, first proposed in 1964, involves four-stranded DNA structures. These intermediates have to be resolved upon completion of DNA repair to allow for proper chromosome segregation. Using forward genetics, we identified a Caenorhabditis elegans dual function DNA double-strand break repair and DNA damage signaling protein orthologous to the human GEN1 Holliday junction resolving enzyme. GEN-1 facilitates repair of DNA double-strand breaks, but is not essential for DNA double-strand break repair during meiotic recombination. The DNA damage signaling function of GEN-1 is separable from its role in DNA repair. Unexpectedly, GEN-1 defines a DNA damage-signaling pathway that acts in parallel to the canonical pathway mediated by CHK-1 phosphorylation and CEP-1/p53. Thus, an enzyme that can resolve Holliday junctions may directly couple a late step in DNA repair to a pathway that regulates cell cycle progression in response to DNA damage.
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Affiliation(s)
- Aymeric P. Bailly
- Wellcome Trust Centre for Gene Regulation and Expression, University of Dundee, Dundee, United Kingdom
| | - Alasdair Freeman
- Cancer Research United Kingdom Nucleic Acid Structure Research Group, University of Dundee, Dundee, United Kingdom
| | - Julie Hall
- Department of Genetics and Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Anne-Cécile Déclais
- Cancer Research United Kingdom Nucleic Acid Structure Research Group, University of Dundee, Dundee, United Kingdom
| | - Arno Alpi
- Wellcome Trust Centre for Gene Regulation and Expression, University of Dundee, Dundee, United Kingdom
| | - David M. J. Lilley
- Cancer Research United Kingdom Nucleic Acid Structure Research Group, University of Dundee, Dundee, United Kingdom
| | - Shawn Ahmed
- Department of Genetics and Department of Biology, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Anton Gartner
- Wellcome Trust Centre for Gene Regulation and Expression, University of Dundee, Dundee, United Kingdom
- * E-mail:
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14
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Substrate recognition and catalysis by flap endonucleases and related enzymes. Biochem Soc Trans 2010; 38:433-7. [DOI: 10.1042/bst0380433] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
FENs (flap endonucleases) and related FEN-like enzymes [EXO-1 (exonuclease-1), GEN-1 (gap endonuclease 1) and XPG (xeroderma pigmentosum complementation group G)] are a family of bivalent-metal-ion-dependent nucleases that catalyse structure-specific hydrolysis of DNA duplex-containing nucleic acid structures during DNA replication, repair and recombination. In the case of FENs, the ability to catalyse reactions on a variety of substrates has been rationalized as a result of combined functional and structural studies. Analyses of FENs also exemplify controversies regarding the two-metal-ion mechanism. However, kinetic studies of T5FEN (bacteriophage T5 FEN) reveal that a two-metal-ion-like mechanism for chemical catalysis is plausible. Consideration of the metallobiochemistry and the positioning of substrate in metal-free structures has led to the proposal that the duplex termini of substrates are unpaired in the catalytically active form and that FENs and related enzymes may recognize breathing duplex termini within more complex structures. An outstanding issue in FEN catalysis is the role played by the intermediate (I) domain arch or clamp. It has been proposed that FENs thread the 5′-portion of their substrates through this arch, which is wide enough to accommodate single-stranded, but not double-stranded, DNA. However, FENs exhibit gap endonuclease activity acting upon substrates that have a region of 5′-duplex. Moreover, the action of other FEN family members such as GEN-1, proposed to target Holliday junctions without termini, appears incompatible with a threading mechanism. An alterative is that the I domain is used as a clamp. A future challenge is to clarify the role of this domain in FENs and related enzymes.
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Sakaguchi K, Ishibashi T, Uchiyama Y, Iwabata K. The multi-replication protein A (RPA) system--a new perspective. FEBS J 2009; 276:943-63. [PMID: 19154342 DOI: 10.1111/j.1742-4658.2008.06841.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Replication protein A (RPA) complex has been shown, using both in vivo and in vitro approaches, to be required for most aspects of eukaryotic DNA metabolism: replication, repair, telomere maintenance and homologous recombination. Here, we review recent data concerning the function and biological importance of the multi-RPA complex. There are distinct complexes of RPA found in the biological kingdoms, although for a long time only one type of RPA complex was believed to be present in eukaryotes. Each complex probably serves a different role. In higher plants, three distinct large and medium subunits are present, but only one species of the smallest subunit. Each of these protein subunits forms stable complexes with their respective partners. They are paralogs as complex. Humans possess two paralogs and one analog of RPA. The multi-RPA system can be regarded as universal in eukaryotes. Among eukaryotic kingdoms, paralogs, orthologs, analogs and heterologs of many DNA synthesis-related factors, including RPA, are ubiquitous. Convergent evolution seems to be ubiquitous in these processes. Using recent findings, we review the composition and biological functions of RPA complexes.
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Affiliation(s)
- Kengo Sakaguchi
- Department of Applied Biological Science, Tokyo University of Science, Chiba, Japan.
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Identification of Holliday junction resolvases from humans and yeast. Nature 2008; 456:357-61. [PMID: 19020614 DOI: 10.1038/nature07470] [Citation(s) in RCA: 290] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2008] [Accepted: 09/26/2008] [Indexed: 11/09/2022]
Abstract
Four-way DNA intermediates, also known as Holliday junctions, are formed during homologous recombination and DNA repair, and their resolution is necessary for proper chromosome segregation. Here we identify nucleases from Saccharomyces cerevisiae and human cells that promote Holliday junction resolution, in a manner analogous to that shown by the Escherichia coli Holliday junction resolvase RuvC. The human Holliday junction resolvase, GEN1, and its yeast orthologue, Yen1, were independently identified using two distinct experimental approaches: GEN1 was identified by mass spectrometry following extensive fractionation of HeLa cell-free extracts, whereas Yen1 was detected by screening a yeast gene fusion library for nucleases capable of Holliday junction resolution. The eukaryotic Holliday junction resolvases represent a new subclass of the Rad2/XPG family of nucleases. Recombinant GEN1 and Yen1 resolve Holliday junctions by the introduction of symmetrically related cuts across the junction point, to produce nicked duplex products in which the nicks can be readily ligated.
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