51
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Kadyrova LY, Kadyrov FA. Endonuclease activities of MutLα and its homologs in DNA mismatch repair. DNA Repair (Amst) 2016; 38:42-49. [PMID: 26719141 PMCID: PMC4820397 DOI: 10.1016/j.dnarep.2015.11.023] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 08/26/2015] [Accepted: 11/30/2015] [Indexed: 12/28/2022]
Abstract
MutLα is a key component of the DNA mismatch repair system in eukaryotes. The DNA mismatch repair system has several genetic stabilization functions. Of these functions, DNA mismatch repair is the major one. The loss of MutLα abolishes DNA mismatch repair, thereby predisposing humans to cancer. MutLα has an endonuclease activity that is required for DNA mismatch repair. The endonuclease activity of MutLα depends on the DQHA(X)2E(X)4E motif which is a part of the active site of the nuclease. This motif is also present in many bacterial MutL and eukaryotic MutLγ proteins, DNA mismatch repair system factors that are homologous to MutLα. Recent studies have shown that yeast MutLγ and several MutL proteins containing the DQHA(X)2E(X)4E motif possess endonuclease activities. Here, we review the endonuclease activities of MutLα and its homologs in the context of DNA mismatch repair.
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Affiliation(s)
- Lyudmila Y Kadyrova
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, IL 62901, USA
| | - Farid A Kadyrov
- Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, IL 62901, USA.
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52
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Manhart CM, Alani E. Roles for mismatch repair family proteins in promoting meiotic crossing over. DNA Repair (Amst) 2016; 38:84-93. [PMID: 26686657 PMCID: PMC4740264 DOI: 10.1016/j.dnarep.2015.11.024] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 08/14/2015] [Accepted: 11/30/2015] [Indexed: 12/13/2022]
Abstract
The mismatch repair (MMR) family complexes Msh4-Msh5 and Mlh1-Mlh3 act with Exo1 and Sgs1-Top3-Rmi1 in a meiotic double strand break repair pathway that results in the asymmetric cleavage of double Holliday junctions (dHJ) to form crossovers. This review discusses how meiotic roles for Msh4-Msh5 and Mlh1-Mlh3 do not fit paradigms established for post-replicative MMR. We also outline models used to explain how these factors promote the formation of meiotic crossovers required for the accurate segregation of chromosome homologs during the Meiosis I division.
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Affiliation(s)
- Carol M Manhart
- Department of Molecular Biology and Genetics, Cornell University, 457 Biotechnology Building, Ithaca, NY 14853-2703, USA
| | - Eric Alani
- Department of Molecular Biology and Genetics, Cornell University, 457 Biotechnology Building, Ithaca, NY 14853-2703, USA.
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53
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Pillon MC, Babu VMP, Randall JR, Cai J, Simmons LA, Sutton MD, Guarné A. The sliding clamp tethers the endonuclease domain of MutL to DNA. Nucleic Acids Res 2015; 43:10746-59. [PMID: 26384423 PMCID: PMC4678855 DOI: 10.1093/nar/gkv918] [Citation(s) in RCA: 37] [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: 07/16/2014] [Revised: 08/04/2015] [Accepted: 09/06/2015] [Indexed: 01/05/2023] Open
Abstract
The sliding clamp enhances polymerase processivity and coordinates DNA replication with other critical DNA processing events including translesion synthesis, Okazaki fragment maturation and DNA repair. The relative binding affinity of the sliding clamp for its partners determines how these processes are orchestrated and is essential to ensure the correct processing of newly replicated DNA. However, while stable clamp interactions have been extensively studied; dynamic interactions mediated by the sliding clamp remain poorly understood. Here, we characterize the interaction between the bacterial sliding clamp (β-clamp) and one of its weak-binding partners, the DNA mismatch repair protein MutL. Disruption of this interaction causes a mild mutator phenotype in Escherichia coli, but completely abrogates mismatch repair activity in Bacillus subtilis. We stabilize the MutL-β interaction by engineering two cysteine residues at variable positions of the interface. Using disulfide bridge crosslinking, we have stabilized the E. coli and B. subtilis MutL-β complexes and have characterized their structures using small angle X-ray scattering. We find that the MutL-β interaction greatly stimulates the endonuclease activity of B. subtilis MutL and supports this activity even in the absence of the N-terminal region of the protein.
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Affiliation(s)
- Monica C Pillon
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Vignesh M P Babu
- Department of Biochemistry, The School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, 14214, USA Witebsky Center for Microbial Pathogenesis and Immunology, The School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, 14214, USA
| | - Justin R Randall
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor MI 48109, USA
| | - Jiudou Cai
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Lyle A Simmons
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor MI 48109, USA
| | - Mark D Sutton
- Department of Biochemistry, The School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, 14214, USA Witebsky Center for Microbial Pathogenesis and Immunology, The School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, 14214, USA Genetics, Genomics and Bioinformatics Program, The School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, 14214, USA
| | - Alba Guarné
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada
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54
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How MutS finds a needle in a haystack. Proc Natl Acad Sci U S A 2015; 112:15265-6. [PMID: 26631743 DOI: 10.1073/pnas.1521023112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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55
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Friedhoff P, Li P, Gotthardt J. Protein-protein interactions in DNA mismatch repair. DNA Repair (Amst) 2015; 38:50-57. [PMID: 26725162 DOI: 10.1016/j.dnarep.2015.11.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 11/11/2015] [Accepted: 11/30/2015] [Indexed: 11/25/2022]
Abstract
The principal DNA mismatch repair proteins MutS and MutL are versatile enzymes that couple DNA mismatch or damage recognition to other cellular processes. Besides interaction with their DNA substrates this involves transient interactions with other proteins which is triggered by the DNA mismatch or damage and controlled by conformational changes. Both MutS and MutL proteins have ATPase activity, which adds another level to control their activity and interactions with DNA substrates and other proteins. Here we focus on the protein-protein interactions, protein interaction sites and the different levels of structural knowledge about the protein complexes formed with MutS and MutL during the mismatch repair reaction.
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Affiliation(s)
- Peter Friedhoff
- Institute for Biochemistry FB 08, Justus Liebig University, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany.
| | - Pingping Li
- Institute for Biochemistry FB 08, Justus Liebig University, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany
| | - Julia Gotthardt
- Institute for Biochemistry FB 08, Justus Liebig University, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany
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56
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Evolution of the methyl directed mismatch repair system in Escherichia coli. DNA Repair (Amst) 2015; 38:32-41. [PMID: 26698649 DOI: 10.1016/j.dnarep.2015.11.016] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 08/26/2015] [Accepted: 11/30/2015] [Indexed: 11/24/2022]
Abstract
DNA mismatch repair (MMR) repairs mispaired bases in DNA generated by replication errors. MutS or MutS homologs recognize mispairs and coordinate with MutL or MutL homologs to direct excision of the newly synthesized DNA strand. In most organisms, the signal that discriminates between the newly synthesized and template DNA strands has not been definitively identified. In contrast, Escherichia coli and some related gammaproteobacteria use a highly elaborated methyl-directed MMR system that recognizes Dam methyltransferase modification sites that are transiently unmethylated on the newly synthesized strand after DNA replication. Evolution of methyl-directed MMR is characterized by the acquisition of Dam and the MutH nuclease and by the loss of the MutL endonuclease activity. Methyl-directed MMR is present in a subset of Gammaproteobacteria belonging to the orders Enterobacteriales, Pasteurellales, Vibrionales, Aeromonadales, and a subset of the Alteromonadales (the EPVAA group) as well as in gammaproteobacteria that have obtained these genes by horizontal gene transfer, including the medically relevant bacteria Fluoribacter, Legionella, and Tatlockia and the marine bacteria Methylophaga and Nitrosococcus.
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57
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Groothuizen FS, Sixma TK. The conserved molecular machinery in DNA mismatch repair enzyme structures. DNA Repair (Amst) 2015; 38:14-23. [PMID: 26796427 DOI: 10.1016/j.dnarep.2015.11.012] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 10/05/2015] [Accepted: 11/30/2015] [Indexed: 12/25/2022]
Abstract
The machinery of DNA mismatch repair enzymes is highly conserved in evolution. The process is initiated by recognition of a DNA mismatch, and validated by ATP and the presence of a processivity clamp or a methylation mark. Several events in MMR promote conformational changes that lead to progression of the repair process. Here we discuss functional conformational changes in the MMR proteins and we compare the enzymes to paralogs in other systems.
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Affiliation(s)
- Flora S Groothuizen
- Division of Biochemistry and CGC.nl, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Titia K Sixma
- Division of Biochemistry and CGC.nl, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
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58
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Single-molecule motions and interactions in live cells reveal target search dynamics in mismatch repair. Proc Natl Acad Sci U S A 2015; 112:E6898-906. [PMID: 26575623 DOI: 10.1073/pnas.1507386112] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
MutS is responsible for initiating the correction of DNA replication errors. To understand how MutS searches for and identifies rare base-pair mismatches, we characterized the dynamic movement of MutS and the replisome in real time using superresolution microscopy and single-molecule tracking in living cells. We report that MutS dynamics are heterogeneous in cells, with one MutS population exploring the nucleoid rapidly, while another MutS population moves to and transiently dwells at the replisome region, even in the absence of appreciable mismatch formation. Analysis of MutS motion shows that the speed of MutS is correlated with its separation distance from the replisome and that MutS motion slows when it enters the replisome region. We also show that mismatch detection increases MutS speed, supporting the model for MutS sliding clamp formation after mismatch recognition. Using variants of MutS and the replication processivity clamp to impair mismatch repair, we find that MutS dynamically moves to and from the replisome before mismatch binding to scan for errors. Furthermore, a block to DNA synthesis shows that MutS is only capable of binding mismatches near the replisome. It is well-established that MutS engages in an ATPase cycle, which is necessary for signaling downstream events. We show that a variant of MutS with a nucleotide binding defect is no longer capable of dynamic movement to and from the replisome, showing that proper nucleotide binding is critical for MutS to localize to the replisome in vivo. Our results provide mechanistic insight into the trafficking and movement of MutS in live cells as it searches for mismatches.
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59
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Lenhart JS, Pillon MC, Guarné A, Biteen JS, Simmons LA. Mismatch repair in Gram-positive bacteria. Res Microbiol 2015; 167:4-12. [PMID: 26343983 DOI: 10.1016/j.resmic.2015.08.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 08/14/2015] [Accepted: 08/26/2015] [Indexed: 12/31/2022]
Abstract
DNA mismatch repair (MMR) is responsible for correcting errors formed during DNA replication. DNA polymerase errors include base mismatches and extra helical nucleotides referred to as insertion and deletion loops. In bacteria, MMR increases the fidelity of the chromosomal DNA replication pathway approximately 100-fold. MMR defects in bacteria reduce replication fidelity and have the potential to affect fitness. In mammals, MMR defects are characterized by an increase in mutation rate and by microsatellite instability. In this review, we discuss current advances in understanding how MMR functions in bacteria lacking the MutH and Dam methylase-dependent MMR pathway.
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Affiliation(s)
- Justin S Lenhart
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, United States; Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, United States
| | - Monica C Pillon
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada
| | - Alba Guarné
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
| | - Julie S Biteen
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, United States.
| | - Lyle A Simmons
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, United States.
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60
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Abstract
DNA mismatch repair (MMR) identifies and corrects errors made during replication. In all organisms except those expressing MutH, interactions between a DNA mismatch, MutS, MutL, and the replication processivity factor (β-clamp or PCNA) activate the latent MutL endonuclease to nick the error-containing daughter strand. This nick provides an entry point for downstream repair proteins. Despite the well-established significance of strand-specific nicking in MMR, the mechanism(s) by which MutS and MutL assemble on mismatch DNA to allow the subsequent activation of MutL's endonuclease activity by β-clamp/PCNA remains elusive. In both prokaryotes and eukaryotes, MutS homologs undergo conformational changes to a mobile clamp state that can move away from the mismatch. However, the function of this MutS mobile clamp is unknown. Furthermore, whether the interaction with MutL leads to a mobile MutS-MutL complex or a mismatch-localized complex is hotly debated. We used single molecule FRET to determine that Thermus aquaticus MutL traps MutS at a DNA mismatch after recognition but before its conversion to a sliding clamp. Rather than a clamp, a conformationally dynamic protein assembly typically containing more MutL than MutS is formed at the mismatch. This complex provides a local marker where interaction with β-clamp/PCNA could distinguish parent/daughter strand identity. Our finding that MutL fundamentally changes MutS actions following mismatch detection reframes current thinking on MMR signaling processes critical for genomic stability.
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61
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Kadyrova LY, Dahal BK, Kadyrov FA. Evidence that the DNA mismatch repair system removes 1-nucleotide Okazaki fragment flaps. J Biol Chem 2015. [PMID: 26224637 DOI: 10.1074/jbc.m115.660357] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The DNA mismatch repair (MMR) system plays a major role in promoting genome stability and suppressing carcinogenesis. In this work, we investigated whether the MMR system is involved in Okazaki fragment maturation. We found that in the yeast Saccharomyces cerevisiae, the MMR system and the flap endonuclease Rad27 act in overlapping pathways that protect the nuclear genome from 1-bp insertions. In addition, we determined that purified yeast and human MutSα proteins recognize 1-nucleotide DNA and RNA flaps. In reconstituted human systems, MutSα, proliferating cell nuclear antigen, and replication factor C activate MutLα endonuclease to remove the flaps. ATPase and endonuclease mutants of MutLα are defective in the flap removal. These results suggest that the MMR system contributes to the removal of 1-nucleotide Okazaki fragment flaps.
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Affiliation(s)
- Lyudmila Y Kadyrova
- From the Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901
| | - Basanta K Dahal
- From the Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901
| | - Farid A Kadyrov
- From the Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901
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62
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Jing R, Sun J, Wang Y, Li M. Domain position prediction based on sequence information by using fuzzy mean operator. Proteins 2015; 83:1462-9. [PMID: 26009844 DOI: 10.1002/prot.24833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 04/23/2015] [Accepted: 05/17/2015] [Indexed: 11/09/2022]
Abstract
The prediction of protein domain region is an advantageous process on the study of protein structure and function. In this study, we proposed a new method, which is composed of fuzzy mean operator and region division, to predict the particular positions of domains in a target protein based on its sequence. The whole sequence is aligned and scored by using fuzzy mean operator, and the final determination of domain region position is realized by region division. A published benchmark is used for the comparison with previous researches. In addition, we generate two extra datasets to examine the stability of this method. Finally, the prediction accuracy of independent test dataset achieved by our method was up to 84.13%. We wish that this method could be useful for related researches.
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Affiliation(s)
- Runyu Jing
- Chemical Information Center (CIC), College of Chemistry, Sichuan University, Chengdu, 610064, China
| | - Jing Sun
- Chemical Information Center (CIC), College of Chemistry, Sichuan University, Chengdu, 610064, China
| | - Yuelong Wang
- Chemical Information Center (CIC), College of Chemistry, Sichuan University, Chengdu, 610064, China
| | - Menglong Li
- Chemical Information Center (CIC), College of Chemistry, Sichuan University, Chengdu, 610064, China
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63
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Kokes M, Dunn JD, Granek JA, Nguyen BD, Barker JR, Valdivia RH, Bastidas RJ. Integrating chemical mutagenesis and whole-genome sequencing as a platform for forward and reverse genetic analysis of Chlamydia. Cell Host Microbe 2015; 17:716-25. [PMID: 25920978 DOI: 10.1016/j.chom.2015.03.014] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 02/11/2015] [Accepted: 03/17/2015] [Indexed: 11/18/2022]
Abstract
Gene inactivation by transposon insertion or allelic exchange is a powerful approach to probe gene function. Unfortunately, many microbes, including Chlamydia, are not amenable to routine molecular genetic manipulations. Here we describe an arrayed library of chemically induced mutants of the genetically intransigent pathogen Chlamydia trachomatis, in which all mutations have been identified by whole-genome sequencing, providing a platform for reverse genetic applications. An analysis of possible loss-of-function mutations in the collection uncovered plasticity in the central metabolic properties of this obligate intracellular pathogen. We also describe the use of the library in a forward genetic screen that identified InaC as a bacterial factor that binds host ARF and 14-3-3 proteins and modulates F-actin assembly and Golgi redistribution around the pathogenic vacuole. This work provides a robust platform for reverse and forward genetic approaches in Chlamydia and should serve as a valuable resource to the community.
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Affiliation(s)
- Marcela Kokes
- Department of Molecular Genetics and Microbiology and Center for the Genomics of Microbial Systems, Duke University Medical Center, 268 CARL Building, Box 3054, Durham, NC 27710, USA
| | - Joe Dan Dunn
- Department of Molecular Genetics and Microbiology and Center for the Genomics of Microbial Systems, Duke University Medical Center, 268 CARL Building, Box 3054, Durham, NC 27710, USA
| | - Joshua A Granek
- Department of Molecular Genetics and Microbiology and Center for the Genomics of Microbial Systems, Duke University Medical Center, 268 CARL Building, Box 3054, Durham, NC 27710, USA; Department of Biostatistics and Bioinformatics, Duke University Medical Center, 2424 Erwin Road, Suite 1102 Hock Plaza, Box 2721, Durham, NC 27710, USA
| | - Bidong D Nguyen
- Department of Molecular Genetics and Microbiology and Center for the Genomics of Microbial Systems, Duke University Medical Center, 268 CARL Building, Box 3054, Durham, NC 27710, USA
| | - Jeffrey R Barker
- Department of Molecular Genetics and Microbiology and Center for the Genomics of Microbial Systems, Duke University Medical Center, 268 CARL Building, Box 3054, Durham, NC 27710, USA
| | - Raphael H Valdivia
- Department of Molecular Genetics and Microbiology and Center for the Genomics of Microbial Systems, Duke University Medical Center, 268 CARL Building, Box 3054, Durham, NC 27710, USA.
| | - Robert J Bastidas
- Department of Molecular Genetics and Microbiology and Center for the Genomics of Microbial Systems, Duke University Medical Center, 268 CARL Building, Box 3054, Durham, NC 27710, USA.
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64
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Small-angle X-ray scattering analysis reveals the ATP-bound monomeric state of the ATPase domain from the homodimeric MutL endonuclease, a GHKL phosphotransferase superfamily protein. Extremophiles 2015; 19:643-56. [PMID: 25809295 DOI: 10.1007/s00792-015-0745-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 03/14/2015] [Indexed: 11/27/2022]
Abstract
DNA mismatch repair is an excision system that removes mismatched bases chiefly generated by replication errors. In this system, MutL endonucleases direct the excision reaction to the error-containing strand of the duplex by specifically incising the newly synthesized strand. Both bacterial homodimeric and eukaryotic heterodimeric MutL proteins belong to the GHKL ATPase/kinase superfamily that comprises the N-terminal ATPase and C-terminal dimerization regions. Generally, the GHKL proteins show large ATPase cycle-dependent conformational changes, including dimerization-coupled ATP binding of the N-terminal domain. Interestingly, the ATPase domain of human PMS2, a subunit of the MutL heterodimer, binds ATP without dimerization. The monomeric ATP-bound state of the domain has been thought to be characteristic of heterodimeric GHKL proteins. In this study, we characterized the ATP-bound state of the ATPase domain from the Aquifex aeolicus MutL endonuclease, which is a homodimeric GHKL protein unlike the eukaryotic MutL. Gel filtration, dynamic light scattering, and small-angle X-ray scattering analyses clearly showed that the domain binds ATP in a monomeric form despite its homodimeric nature. This indicates that the uncoupling of dimerization and ATP binding is a common feature among bacterial and eukaryotic MutL endonucleases, which we suggest is closely related to the molecular mechanisms underlying mismatch repair.
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65
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Abstract
Homologous recombination (HR) and mismatch repair (MMR) are inextricably linked. HR pairs homologous chromosomes before meiosis I and is ultimately responsible for generating genetic diversity during sexual reproduction. HR is initiated in meiosis by numerous programmed DNA double-strand breaks (DSBs; several hundred in mammals). A characteristic feature of HR is the exchange of DNA strands, which results in the formation of heteroduplex DNA. Mismatched nucleotides arise in heteroduplex DNA because the participating parental chromosomes contain nonidentical sequences. These mismatched nucleotides may be processed by MMR, resulting in nonreciprocal exchange of genetic information (gene conversion). MMR and HR also play prominent roles in mitotic cells during genome duplication; MMR rectifies polymerase misincorporation errors, whereas HR contributes to replication fork maintenance, as well as the repair of spontaneous DSBs and genotoxic lesions that affect both DNA strands. MMR suppresses HR when the heteroduplex DNA contains excessive mismatched nucleotides, termed homeologous recombination. The regulation of homeologous recombination by MMR ensures the accuracy of DSB repair and significantly contributes to species barriers during sexual reproduction. This review discusses the history, genetics, biochemistry, biophysics, and the current state of studies on the role of MMR in homologous and homeologous recombination from bacteria to humans.
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Affiliation(s)
- Maria Spies
- Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242
| | - Richard Fishel
- Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University Medical Center and Comprehensive Cancer Center, Columbus, Ohio 43210 Human Genetics Institute, The Ohio State University Medical Center, Columbus, Ohio 43210 Physics Department, The Ohio State University, Columbus, Ohio 43210
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66
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Guarné A, Charbonnier JB. Insights from a decade of biophysical studies on MutL: Roles in strand discrimination and mismatch removal. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2015; 117:149-156. [PMID: 25701376 DOI: 10.1016/j.pbiomolbio.2015.02.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Revised: 01/31/2015] [Accepted: 02/09/2015] [Indexed: 11/18/2022]
Abstract
DNA mismatch repair (MMR) is a conserved pathway that safeguards genome integrity by correcting replication errors. The coordinated actions of two proteins (MutS and MutL) initiate the mismatch repair response and defects in the genes encoding for these proteins have been linked to sporadic and hereditary cancers. The basic steps to repair a mismatch include recognizing the mismatch, discriminating the newly synthesized from the parental strand, removing and re-synthesizing the erroneous strand. Although the DNA mismatch repair pathway has been extensively studied over the last four decades, the strand discrimination mechanism has remained elusive in most organisms. Work over the last decade has brought significant progress onto this step of the pathway, in turn ascribing new and critical roles to the MutL protein. In this review, we describe biochemical, biophysical and structural analyses that have clarified how MutL aids at discriminating the newly synthesized strand from its template and marking it for removal.
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Affiliation(s)
- Alba Guarné
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
| | - Jean-Baptiste Charbonnier
- CEA, IBITECS, Laboratoire de Biologie Structurale et Radiobiologie, CE-Saclay, F-91191 Gif sur Yvette, France; CNRS, URA 2096, F-91191 Gif sur Yvette, France.
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67
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68
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Thermoadaptation-directed enzyme evolution in an error-prone thermophile derived from Geobacillus kaustophilus HTA426. Appl Environ Microbiol 2014; 81:149-58. [PMID: 25326311 DOI: 10.1128/aem.02577-14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Thermostability is an important property of enzymes utilized for practical applications because it allows long-term storage and use as catalysts. In this study, we constructed an error-prone strain of the thermophile Geobacillus kaustophilus HTA426 and investigated thermoadaptation-directed enzyme evolution using the strain. A mutation frequency assay using the antibiotics rifampin and streptomycin revealed that G. kaustophilus had substantially higher mutability than Escherichia coli and Bacillus subtilis. The predominant mutations in G. kaustophilus were A · T→G · C and C · G→T · A transitions, implying that the high mutability of G. kaustophilus was attributable in part to high-temperature-associated DNA damage during growth. Among the genes that may be involved in DNA repair in G. kaustophilus, deletions of the mutSL, mutY, ung, and mfd genes markedly enhanced mutability. These genes were subsequently deleted to construct an error-prone thermophile that showed much higher (700- to 9,000-fold) mutability than the parent strain. The error-prone strain was auxotrophic for uracil owing to the fact that the strain was deficient in the intrinsic pyrF gene. Although the strain harboring Bacillus subtilis pyrF was also essentially auxotrophic, cells became prototrophic after 2 days of culture under uracil starvation, generating B. subtilis PyrF variants with an enhanced half-denaturation temperature of >10°C. These data suggest that this error-prone strain is a promising host for thermoadaptation-directed evolution to generate thermostable variants from thermolabile enzymes.
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69
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Banasik M, Sachadyn P. Conserved motifs of MutL proteins. Mutat Res 2014; 769:69-79. [PMID: 25771726 DOI: 10.1016/j.mrfmmm.2014.07.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 07/16/2014] [Accepted: 07/22/2014] [Indexed: 02/02/2023]
Abstract
The MutL protein is best known for its function in DNA mismatch repair (MMR). However, there is evidence to suggest that MutL is not only the linker connecting the functions of MutS and MutH in MMR, but that it also participates in other repair systems, such as Very Short Patch (VSP), Base Excision (BER) and Nucleotide Excision Repair (NER). This study set out to identify the most highly conserved amino acid sequence motifs in MutL proteins. We analyzed 208 MutL amino acid sequences of 199 representative prokaryotic species belonging to 28 classes of bacteria and archaea. The analysis revealed 16 conserved motifs situated in the ATPase and endonuclease domains, as well as within the disordered loop, and in the MutL regions interacting with the β clamp of DNA polymerase III. The conserved sequence motifs thus determined constitute a structural definition of MutL and they may be used in site-directed mutagenesis studies. We found conserved residues within the potential regions where binding with MutS occurs. However, the existing data does not provide clues as to the possible sites of MutL interactions with the proteins involved in other DNA repair systems such as NER, BER and VSP. We determined the 57 most highly conserved amino acid residues, including 43 which were identical in all the sequences analyzed. The greater part of the most predominantly conserved amino acid residues identified in MutL are identical to the corresponding residues reported as mutational hot-spots in one of its human homologues, MLH1, but not in the other, PMS2. This is the first study to present the conserved sequence motifs of MutL widespread in bacteria and archaea and the classification of MutLs into five groups distinguished on the basis of differences in the C-terminal region. Our analysis is of use in better understanding MutL functions.
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Affiliation(s)
- Michał Banasik
- Gdańsk University of Technology, Microbiology Department, Gdańsk, Poland
| | - Paweł Sachadyn
- Gdańsk University of Technology, Microbiology Department, Gdańsk, Poland.
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70
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Lee JB, Cho WK, Park J, Jeon Y, Kim D, Lee SH, Fishel R. Single-molecule views of MutS on mismatched DNA. DNA Repair (Amst) 2014; 20:82-93. [PMID: 24629484 PMCID: PMC4245035 DOI: 10.1016/j.dnarep.2014.02.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 02/11/2014] [Accepted: 02/14/2014] [Indexed: 01/09/2023]
Abstract
Base-pair mismatches that occur during DNA replication or recombination can reduce genetic stability or conversely increase genetic diversity. The genetics and biophysical mechanism of mismatch repair (MMR) has been extensively studied since its discovery nearly 50 years ago. MMR is a strand-specific excision-resynthesis reaction that is initiated by MutS homolog (MSH) binding to the mismatched nucleotides. The MSH mismatch-binding signal is then transmitted to the immediate downstream MutL homolog (MLH/PMS) MMR components and ultimately to a distant strand scission site where excision begins. The mechanism of signal transmission has been controversial for decades. We have utilized single molecule Forster Resonance Energy Transfer (smFRET), Fluorescence Tracking (smFT) and Polarization Total Internal Reflection Fluorescence (smP-TIRF) to examine the interactions and dynamic behaviors of single Thermus aquaticus MutS (TaqMutS) particles on mismatched DNA. We determined that TaqMutS forms an incipient clamp to search for a mismatch in ~1 s intervals by 1-dimensional (1D) thermal fluctuation-driven rotational diffusion while in continuous contact with the helical duplex DNA. When MutS encounters a mismatch it lingers for ~3 s to exchange bound ADP for ATP (ADP→ATP exchange). ATP binding by TaqMutS induces an extremely stable clamp conformation (~10 min) that slides off the mismatch and moves along the adjacent duplex DNA driven simply by 1D thermal diffusion. The ATP-bound sliding clamps rotate freely while in discontinuous contact with the DNA. The visualization of a train of MSH proteins suggests that dissociation of ATP-bound sliding clamps from the mismatch permits multiple mismatch-dependent loading events. These direct observations have provided critical clues into understanding the molecular mechanism of MSH proteins during MMR.
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Affiliation(s)
- Jong-Bong Lee
- Department of Physics, POSTECH, Pohang 790-784, Republic of Korea; School of Interdisciplinary Bioscience & Bioengineering, POSTECH, Pohang 790-784, Republic of Korea.
| | - Won-Ki Cho
- Department of Physics, POSTECH, Pohang 790-784, Republic of Korea
| | - Jonghyun Park
- Department of Physics, POSTECH, Pohang 790-784, Republic of Korea
| | - Yongmoon Jeon
- Department of Physics, POSTECH, Pohang 790-784, Republic of Korea
| | - Daehyung Kim
- Department of Physics, POSTECH, Pohang 790-784, Republic of Korea
| | - Seung Hwan Lee
- School of Interdisciplinary Bioscience & Bioengineering, POSTECH, Pohang 790-784, Republic of Korea
| | - Richard Fishel
- Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University, Columbus, OH 43210, United States; Physics Department, The Ohio State University, Columbus, OH 43210, United States.
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71
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NMR characterization of the interaction of the endonuclease domain of MutL with divalent metal ions and ATP. PLoS One 2014; 9:e98554. [PMID: 24901533 PMCID: PMC4047009 DOI: 10.1371/journal.pone.0098554] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Accepted: 05/05/2014] [Indexed: 12/26/2022] Open
Abstract
MutL is a multi-domain protein comprising an N-terminal ATPase domain (NTD) and C-terminal dimerization domain (CTD), connected with flexible linker regions, that plays a key role in DNA mismatch repair. To expand understanding of the regulation mechanism underlying MutL endonuclease activity, our NMR-based study investigated interactions between the CTD of MutL, derived from the hyperthermophilic bacterium Aquifex aeolicus (aqMutL-CTD), and putative binding molecules. Chemical shift perturbation analysis with the model structure of aqMutL-CTD and circular dichroism results revealed that tight Zn2+ binding increased thermal stability without changing secondary structures to function at high temperatures. Peak intensity analysis exploiting the paramagnetic relaxation enhancement effect indicated the binding site for Mn2+, which shared binding sites for Zn2+. The coexistence of these two metal ions appears to be important for the function of MutL. Chemical shift perturbation analysis revealed a novel ATP binding site in aqMutL-CTD. A docking simulation incorporating the chemical shift perturbation data provided a putative scheme for the intermolecular interactions between aqMutL-CTD and ATP. We proposed a simple and understandable mechanical model for the regulation of MutL endonuclease activity in MMR based on the relative concentrations of ATP and CTD through ATP binding-regulated interdomain interactions between CTD and NTD.
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72
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Campbell CS, Hombauer H, Srivatsan A, Bowen N, Gries K, Desai A, Putnam CD, Kolodner RD. Mlh2 is an accessory factor for DNA mismatch repair in Saccharomyces cerevisiae. PLoS Genet 2014; 10:e1004327. [PMID: 24811092 PMCID: PMC4014439 DOI: 10.1371/journal.pgen.1004327] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 03/10/2014] [Indexed: 12/30/2022] Open
Abstract
In Saccharomyces cerevisiae, the essential mismatch repair (MMR) endonuclease Mlh1-Pms1 forms foci promoted by Msh2-Msh6 or Msh2-Msh3 in response to mispaired bases. Here we analyzed the Mlh1-Mlh2 complex, whose role in MMR has been unclear. Mlh1-Mlh2 formed foci that often colocalized with and had a longer lifetime than Mlh1-Pms1 foci. Mlh1-Mlh2 foci were similar to Mlh1-Pms1 foci: they required mispair recognition by Msh2-Msh6, increased in response to increased mispairs or downstream defects in MMR, and formed after induction of DNA damage by phleomycin but not double-stranded breaks by I-SceI. Mlh1-Mlh2 could be recruited to mispair-containing DNA in vitro by either Msh2-Msh6 or Msh2-Msh3. Deletion of MLH2 caused a synergistic increase in mutation rate in combination with deletion of MSH6 or reduced expression of Pms1. Phylogenetic analysis demonstrated that the S. cerevisiae Mlh2 protein and the mammalian PMS1 protein are homologs. These results support a hypothesis that Mlh1-Mlh2 is a non-essential accessory factor that acts to enhance the activity of Mlh1-Pms1. Lynch syndrome (hereditary nonpolyposis colorectal cancer or HNPCC) is a common cancer predisposition syndrome. In this syndrome, predisposition to cancer results from increased accumulation of mutations due to defective mismatch repair (MMR) caused by a mutation in one of the human mismatch repair genes MLH1, MSH2, MSH6 or PMS2. In addition to these genes, various DNA replication factors and the excision factor EXO1 function in the repair of damaged DNA by the MMR pathway. In Saccharomyces cerevisiae, the MLH2 gene encodes a MutL homolog protein whose role in DNA mismatch repair has been unclear. Here, we used phylogenetic analysis to demonstrate that the S. cerevisiae Mlh2 protein and the mammalian Pms1 protein are homologs. A combination of genetics, biochemistry and imaging studies were used to demonstrate that the Mlh1-Mlh2 complex is recruited to mispair-containing DNA by the Msh2-Msh6 and Msh2-Msh3 mispair recognition complexes where it forms foci that colocalize with Mlh1-Pms1 foci (note that scPms1 is the homolog of hPms2) and augments the function of the Mlh1-Pms1 complex. Thus, this work establishes the Mlh1-Mlh2 complex as a non-essential accessory factor that functions in MMR.
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Affiliation(s)
- Christopher S. Campbell
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, La Jolla, California, United States of America
| | - Hans Hombauer
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, La Jolla, California, United States of America
- German Cancer Research Center (DKFZ), Im Neuenheimer Feld 581, Heidelberg, Germany
| | - Anjana Srivatsan
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, La Jolla, California, United States of America
| | - Nikki Bowen
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, La Jolla, California, United States of America
| | - Kerstin Gries
- German Cancer Research Center (DKFZ), Im Neuenheimer Feld 581, Heidelberg, Germany
| | - Arshad Desai
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, La Jolla, California, United States of America
- Department of Cellular and Molecular Medicine, University of California School of Medicine, San Diego, La Jolla, California, United States of America
- Moores-UCSD Cancer Center, University of California School of Medicine, San Diego, La Jolla, California, United States of America
| | - Christopher D. Putnam
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, La Jolla, California, United States of America
- Department of Medicine, University of California School of Medicine, San Diego, La Jolla, California, United States of America
| | - Richard D. Kolodner
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, La Jolla, California, United States of America
- Department of Cellular and Molecular Medicine, University of California School of Medicine, San Diego, La Jolla, California, United States of America
- Moores-UCSD Cancer Center, University of California School of Medicine, San Diego, La Jolla, California, United States of America
- Department of Medicine, University of California School of Medicine, San Diego, La Jolla, California, United States of America
- * E-mail:
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73
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Erie DA, Weninger KR. Single molecule studies of DNA mismatch repair. DNA Repair (Amst) 2014; 20:71-81. [PMID: 24746644 DOI: 10.1016/j.dnarep.2014.03.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 03/21/2014] [Accepted: 03/22/2014] [Indexed: 11/30/2022]
Abstract
DNA mismatch repair, which involves is a widely conserved set of proteins, is essential to limit genetic drift in all organisms. The same system of proteins plays key roles in many cancer related cellular transactions in humans. Although the basic process has been reconstituted in vitro using purified components, many fundamental aspects of DNA mismatch repair remain hidden due in part to the complexity and transient nature of the interactions between the mismatch repair proteins and DNA substrates. Single molecule methods offer the capability to uncover these transient but complex interactions and allow novel insights into mechanisms that underlie DNA mismatch repair. In this review, we discuss applications of single molecule methodology including electron microscopy, atomic force microscopy, particle tracking, FRET, and optical trapping to studies of DNA mismatch repair. These studies have led to formulation of mechanistic models of how proteins identify single base mismatches in the vast background of matched DNA and signal for their repair.
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Affiliation(s)
- Dorothy A Erie
- Department of Chemistry and Curriculum in Applied Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States.
| | - Keith R Weninger
- Department of Physics, North Carolina State University, Raleigh, NC 27695, United States
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74
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Martín-López JV, Fishel R. The mechanism of mismatch repair and the functional analysis of mismatch repair defects in Lynch syndrome. Fam Cancer 2014; 12:159-68. [PMID: 23572416 DOI: 10.1007/s10689-013-9635-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The majority of Lynch syndrome (LS), also known as hereditary non-polyposis colorectal cancer (HNPCC), has been linked to heterozygous defects in DNA mismatch repair (MMR). MMR is a highly conserved pathway that recognizes and repairs polymerase misincorporation errors and nucleotide damage as well as functioning as a damage sensor that signals apoptosis. Loss-of-heterozygosity (LOH) that retains the mutant MMR allele and epigenetic silencing of MMR genes are associated with an increased mutation rate that drives carcinogenesis as well as microsatellite instability that is a hallmark of LS/HNPCC. Understanding the biophysical functions of the MMR components is crucial to elucidating the role of MMR in human tumorigenesis and determining the pathogenetic consequences of patients that present in the clinic with an uncharacterized variant of the MMR genes. We summarize the historical association between LS/HNPCC and MMR, discuss the mechanism of the MMR and finally examine the functional analysis of MMR defects found in LS/HNPCC patients and their relationship with the severity of the disease.
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Affiliation(s)
- Juana V Martín-López
- Department of Molecular Virology, Immunology and Medical Genetics, Human Cancer Genetics, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA
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75
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Roesner LM, Mielke C, Fähnrich S, Merkhoffer Y, Dittmar KEJ, Drexler HG, Dirks WG. Stable expression of MutLγ in human cells reveals no specific response to mismatched DNA, but distinct recruitment to damage sites. J Cell Biochem 2014; 114:2405-14. [PMID: 23696135 DOI: 10.1002/jcb.24591] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Accepted: 05/01/2013] [Indexed: 12/21/2022]
Abstract
The human DNA mismatch repair (MMR) gene family comprises four MutL paralogues capable of forming heterodimeric MutLα (MLH1-PMS2), MutLβ (MLH1-PMS1), and MutLγ (MLH1-MLH3) protein complexes. Human MutL subunits PMS2 and MLH3 contain an evolutionarily conserved amino acid motif DQHA(X)2E(X)4E identified as an endonucleolytic domain capable of incising a defective DNA strand. PMS2 of MutLα is generally accepted to be the sole executor of endonucleolytic activity, but since MLH3 was shown to be able to perform DNA repair at low levels in vitro, our aim was to investigate whether or not MLH3 is activated as a backup under MutLα-deficient conditions. Here, we report stable expression of GFP-tagged MLH3 in the isogenic cell lines 293 and 293T which are functional or defective for MLH1 expression, respectively. As expected, MLH3 formed dimeric complexes with endogenous and recombinant MLH1. MutLγ dimers were recruited to sites of DNA damage induced by UVA micro-irradiation as shown for MutLα. Surprisingly, splicing variant MLH3Δ7 lacking the endonucleolytic motif displayed congruent foci formation, implying that recruitment is not necessarily representing active DNA repair. As an alternative test for repair enzyme activity, we combined alkylation-directed DNA damage with comet formation assays. While recombinant MutLα led to full recovery of DNA damage response in MMR deficient cells, expression of MutLγ or single MLH3 failed to do so. These experiments show recruitment and persistence of MutLγ-heterodimers at UVA-induced DNA lesions. However, we demonstrate that in a MutLα-deficient background no DNA repair-specific function carried out by MutLγ can be detected in living cells.
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Affiliation(s)
- Lennart M Roesner
- Department of Human and Animal Cell Lines, Leibniz-Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany.
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76
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Ranjha L, Anand R, Cejka P. The Saccharomyces cerevisiae Mlh1-Mlh3 heterodimer is an endonuclease that preferentially binds to Holliday junctions. J Biol Chem 2014; 289:5674-86. [PMID: 24443562 DOI: 10.1074/jbc.m113.533810] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MutLγ, a heterodimer of the MutL homologues Mlh1 and Mlh3, plays a critical role during meiotic homologous recombination. The meiotic function of Mlh3 is fully dependent on the integrity of a putative nuclease motif DQHAX2EX4E, inferring that the anticipated nuclease activity of Mlh1-Mlh3 is involved in the processing of joint molecules to generate crossover recombination products. Although a vast body of genetic and cell biological data regarding Mlh1-Mlh3 is available, mechanistic insights into its function have been lacking due to the unavailability of the recombinant protein complex. Here we expressed the yeast Mlh1-Mlh3 heterodimer and purified it into near homogeneity. We show that recombinant MutLγ is a nuclease that nicks double-stranded DNA. We demonstrate that MutLγ binds DNA with a high affinity and shows a marked preference for Holliday junctions. We also expressed the human MLH1-MLH3 complex and show that preferential binding to Holliday junctions is a conserved capacity of eukaryotic MutLγ complexes. Specific DNA recognition has never been observed with any other eukaryotic MutL homologue. MutLγ thus represents a new paradigm for the function of the eukaryotic MutL protein family. We provide insights into the mode of Holliday junction recognition and show that Mlh1-Mlh3 prefers to bind the open unstacked Holliday junction form. This further supports the model where MutLγ is part of a complex acting on joint molecules to generate crossovers in meiosis.
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Affiliation(s)
- Lepakshi Ranjha
- From the Institute of Molecular Cancer Research, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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77
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Rogacheva MV, Manhart CM, Chen C, Guarne A, Surtees J, Alani E. Mlh1-Mlh3, a meiotic crossover and DNA mismatch repair factor, is a Msh2-Msh3-stimulated endonuclease. J Biol Chem 2014; 289:5664-73. [PMID: 24403070 DOI: 10.1074/jbc.m113.534644] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Crossing over between homologous chromosomes is initiated in meiotic prophase in most sexually reproducing organisms by the appearance of programmed double strand breaks throughout the genome. In Saccharomyces cerevisiae the double-strand breaks are resected to form three prime single-strand tails that primarily invade complementary sequences in unbroken homologs. These invasion intermediates are converted into double Holliday junctions and then resolved into crossovers that facilitate homolog segregation during Meiosis I. Work in yeast suggests that Msh4-Msh5 stabilizes invasion intermediates and double Holliday junctions, which are resolved into crossovers in steps requiring Sgs1 helicase, Exo1, and a putative endonuclease activity encoded by the DNA mismatch repair factor Mlh1-Mlh3. We purified Mlh1-Mlh3 and showed that it is a metal-dependent and Msh2-Msh3-stimulated endonuclease that makes single-strand breaks in supercoiled DNA. These observations support a direct role for an Mlh1-Mlh3 endonuclease activity in resolving recombination intermediates and in DNA mismatch repair.
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Affiliation(s)
- Maria V Rogacheva
- From the Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853-2703
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78
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Smith CE, Mendillo ML, Bowen N, Hombauer H, Campbell CS, Desai A, Putnam CD, Kolodner RD. Dominant mutations in S. cerevisiae PMS1 identify the Mlh1-Pms1 endonuclease active site and an exonuclease 1-independent mismatch repair pathway. PLoS Genet 2013; 9:e1003869. [PMID: 24204293 PMCID: PMC3814310 DOI: 10.1371/journal.pgen.1003869] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 08/25/2013] [Indexed: 12/28/2022] Open
Abstract
Lynch syndrome (hereditary nonpolypsis colorectal cancer or HNPCC) is a common cancer predisposition syndrome. Predisposition to cancer in this syndrome results from increased accumulation of mutations due to defective mismatch repair (MMR) caused by a mutation in one of the mismatch repair genes MLH1, MSH2, MSH6 or PMS2/scPMS1. To better understand the function of Mlh1-Pms1 in MMR, we used Saccharomyces cerevisiae to identify six pms1 mutations (pms1-G683E, pms1-C817R, pms1-C848S, pms1-H850R, pms1-H703A and pms1-E707A) that were weakly dominant in wild-type cells, which surprisingly caused a strong MMR defect when present on low copy plasmids in an exo1Δ mutant. Molecular modeling showed these mutations caused amino acid substitutions in the metal coordination pocket of the Pms1 endonuclease active site and biochemical studies showed that they inactivated the endonuclease activity. This model of Mlh1-Pms1 suggested that the Mlh1-FERC motif contributes to the endonuclease active site. Consistent with this, the mlh1-E767stp mutation caused both MMR and endonuclease defects similar to those caused by the dominant pms1 mutations whereas mutations affecting the predicted metal coordinating residue Mlh1-C769 had no effect. These studies establish that the Mlh1-Pms1 endonuclease is required for MMR in a previously uncharacterized Exo1-independent MMR pathway. Lynch syndrome (hereditary nonpolypsis colorectal cancer or HNPCC) is a common cancer predisposition syndrome. Predisposition to cancer in this syndrome results from increased accumulation of mutations due to defective mismatch repair (MMR) caused by a mutation in one of the mismatch repair genes MLH1, MSH2, MSH6 or PMS2/scPMS1. In addition to these genes, various DNA replication factors and the excision factor EXO1 function in the repair of damaged DNA by the MMR pathway. Although EXO1 is considered to be the major repair nuclease functioning in mismatch repair, the relatively low mutation rates caused by an exo1 deletion suggest otherwise. Here we used genetics, microscopy and protein biochemistry to analyze the model organism Saccharomyces cerevisiae to further characterize a poorly understood mismatch repair pathway that functions in the absence of EXO1 that is highly dependent on the Mlh1-Pms1 complex. Surprisingly, we found that the highly conserved metal binding site that is critical for the endonuclease activity of the Mlh1-Pms1 heterodimer is required for MMR in the absence of Exo1 to a much greater extent than in the presence of Exo1. Thus, this work establishes that there are at least two different polynucleotide excision pathways that function in MMR.
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Affiliation(s)
- Catherine E Smith
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, La Jolla, California, United States of America
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79
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Lenhart JS, Pillon MC, Guarné A, Simmons LA. Trapping and visualizing intermediate steps in the mismatch repair pathwayin vivo. Mol Microbiol 2013; 90:680-98. [DOI: 10.1111/mmi.12389] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/29/2013] [Indexed: 01/08/2023]
Affiliation(s)
- Justin S. Lenhart
- Department of Molecular, Cellular, and Developmental Biology; University of Michigan; 830 North University Ave Ann Arbor MI 48109-1048 USA
| | - Monica C. Pillon
- Department of Biochemistry and Biomedical Sciences; McMaster University; 1280 Main Street West Hamilton Ontario L8S 4K1 Canada
| | - Alba Guarné
- Department of Biochemistry and Biomedical Sciences; McMaster University; 1280 Main Street West Hamilton Ontario L8S 4K1 Canada
| | - Lyle A. Simmons
- Department of Molecular, Cellular, and Developmental Biology; University of Michigan; 830 North University Ave Ann Arbor MI 48109-1048 USA
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80
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Correa EME, De Tullio L, Vélez PS, Martina MA, Argaraña CE, Barra JL. Analysis of DNA structure and sequence requirements for Pseudomonas aeruginosa MutL endonuclease activity. J Biochem 2013; 154:505-11. [PMID: 23969026 DOI: 10.1093/jb/mvt080] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The hallmark of the mismatch repair system in bacterial and eukaryotic organisms devoid of MutH is the presence of a MutL homologue with endonuclease activity. The aim of this study was to analyse whether different DNA structures affect Pseudomonas aeruginosa MutL (PaMutL) endonuclease activity and to determine if a specific nucleotide sequence is required for this activity. Our results showed that PaMutL was able to nick covalently closed circular plasmids but not linear DNA at high ionic strengths, while the activity on linear DNA was only found below 60 mM salt. In addition, single strand DNA, ss/ds DNA boundaries and negatively supercoiling degree were not required for PaMutL nicking activity. Finally, the analysis of the incision sites revealed that PaMutL, as well as Bacillus thuringiensis MutL homologue, did not show DNA sequence specificity.
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Affiliation(s)
- Elisa M E Correa
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC, UNC-CONICET), Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA Córdoba, Argentina and Centro de Excelencia en Productos, Procesos e Innovación Tecnológica de la Provincia de Córdoba (CEPROCOR), Pabellón CEPROCOR (X5164), Santa María de Punilla, Córdoba, Argentina
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81
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Slow conformational changes in MutS and DNA direct ordered transitions between mismatch search, recognition and signaling of DNA repair. J Mol Biol 2013; 425:4192-205. [PMID: 23973435 DOI: 10.1016/j.jmb.2013.08.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 08/12/2013] [Accepted: 08/13/2013] [Indexed: 01/04/2023]
Abstract
MutS functions in mismatch repair (MMR) to scan DNA for errors, identify a target site and trigger subsequent events in the pathway leading to error removal and DNA re-synthesis. These actions, enabled by the ATPase activity of MutS, are now beginning to be analyzed from the perspective of the protein itself. This study provides the first ensemble transient kinetic data on MutS conformational dynamics as it works with DNA and ATP in MMR. Using a combination of fluorescence probes (on Thermus aquaticus MutS and DNA) and signals (intensity, anisotropy and resonance energy transfer), we have monitored the timing of key conformational changes in MutS that are coupled to mismatch binding and recognition, ATP binding and hydrolysis, as well as sliding clamp formation and signaling of repair. Significant findings include (a) a slow step that follows weak initial interaction between MutS and DNA, in which concerted conformational changes in both macromolecules control mismatch recognition, and (b) rapid, binary switching of MutS conformations that is concerted with ATP binding and hydrolysis and (c) is stalled after mismatch recognition to control formation of the ATP-bound MutS sliding clamp. These rate-limiting pre- and post-mismatch recognition events outline the mechanism of action of MutS on DNA during initiation of MMR.
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82
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Pillon MC, Dubinsky M, Johnston RN, Liu SL, Guarné A. Characterization of the defects in the ATP lid of E. coli MutL that cause transient hypermutability. DNA Repair (Amst) 2013; 12:864-9. [PMID: 23916559 DOI: 10.1016/j.dnarep.2013.07.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 07/05/2013] [Accepted: 07/07/2013] [Indexed: 12/12/2022]
Abstract
Mutator strains spontaneously arise in bacterial populations under stress in an attempt to increase evolutionary adaptation. Inactivation of the ubiquitous DNA mismatch repair pathway, whose normal function is to correct replication errors and hence increase replication fidelity, is often the cause of the mutator phenotype. One of the essential genes in this pathway, mutL, includes a short tandem repeat that is prone to polymerase slippage during replication. While extensive work has established that this repetitive sequence is a genuine genetic switch, the mechanism of MutL inactivation remains unclear. This short tandem repeat is translated into a LALALA motif that resides near the ATPase active site of MutL. Therefore, changes in the length of this motif are presumed to alter the ATPase activity of MutL. We have engineered variants of Escherichia coli MutL with shorter/longer LALALA motifs and characterized their ATPase and DNA binding functions. We have found that the deletion or insertion of a single LA repeat did not compromise the structural integrity of the protein, nor did it affect MutS- or DNA-binding activity. However, it severely compromised ATP binding and, consequently, engagement of the N-terminal domains; both essential activities for proper DNA mismatch repair. These results are discussed in the context of the structure of MutL.
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Affiliation(s)
- Monica C Pillon
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
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83
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Miguel V, Correa EME, De Tullio L, Barra JL, Argaraña CE, Villarreal MA. Analysis of the interaction interfaces of the N-terminal domain from Pseudomonas aeruginosa MutL. PLoS One 2013; 8:e69907. [PMID: 23922851 PMCID: PMC3724809 DOI: 10.1371/journal.pone.0069907] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Accepted: 06/13/2013] [Indexed: 12/02/2022] Open
Abstract
Mismatch Repair System corrects mutations arising from DNA replication that escape from DNA polymerase proofreading activity. This system consists of three main proteins, MutS-L-H, responsible for lesion recognition and repair. MutL is a member of GHKL ATPase family and its ATPase cycle has been proposed to modulate MutL activity during the repair process. Pseudomonas aeruginosa MutL (PaMutL) contains an N-terminal (NTD) ATPase domain connected by a linker to a C-terminal (CTD) dimerization domain that possesses metal ion-dependent endonuclease activity. With the aim to identify characteristics that allow the PaMutL NTD allosteric control of CTD endonuclease activity, we used an in silico and experimental approach to determine the interaction surfaces of P. aeruginosa NTD (PaNTD), and compared it with the well characterized Escherichia coli MutL NTD (EcNTD). Molecular dynamics simulations of PaNTD and EcNTD bound to or free of adenosine nucleotides showed that a significant difference exists between the behavior of the EcNTD and PaNTD dimerization interface, particularly in the ATP lid. Structure based simulations of MutL homologues with endonuclease activity were performed that allowed an insight of the dimerization interface behavior in this family of proteins. Our experimental results show that, unlike EcNTD, PaNTD is dimeric in presence of ADP. Simulations in mixed solvent allowed us to identify the PaNTD putative DNA binding patch and a putative interaction patch located opposite to the dimerization face. Structure based simulations of PaNTD dimer in presence of ADP or ATP suggest that nucleotide binding could differentially modulate PaNTD protein-protein interactions. Far western assays performed in presence of ADP or ATP are in agreement with our in silico analysis.
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Affiliation(s)
- Virginia Miguel
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina
| | - Elisa M. E. Correa
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina
| | - Luisina De Tullio
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina
| | - José L. Barra
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina
| | - Carlos E. Argaraña
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina
| | - Marcos A. Villarreal
- Instituto de Investigaciones en Físico-Química de Córdoba (INFIQC), CONICET, Departamento de Matemática y Física, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina
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84
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Abstract
The concentration of ribonucleoside triphosphates (rNTPs) in cells is far greater than the concentration of deoxyribonucleoside triphosphates (dNTPs), and this pool imbalance presents a challenge for DNA polymerases (Pols) to select their proper substrate. This report examines the effect of nucleotide pool imbalance on the rate and fidelity of the Escherichia coli replisome. We find that rNTPs decrease replication fork rate by competing with dNTPs at the active site of the C-family Pol III replicase at a step that does not require correct base-pairing. The effect of rNTPs on Pol rate generalizes to B-family eukaryotic replicases, Pols δ and ε. Imbalance of the dNTP pool also slows the replisome and thus is not specific to rNTPs. We observe a measurable frequency of rNMP incorporation that predicts one rNTP incorporated every 2.3 kb during chromosome replication. Given the frequency of rNMP incorporation, the repair of rNMPs is likely rapid. RNase HII nicks DNA at single rNMP residues to initiate replacement with dNMP. Considering that rNMPs will mark the new strand, RNase HII may direct strand-specificity for mismatch repair (MMR). How the newly synthesized strand is recognized for MMR is uncertain in eukaryotes and most bacteria, which lack a methyl-directed nicking system. Here we demonstrate that Bacillus subtilis incorporates rNMPs in vivo, that RNase HII plays a role in their removal, and the RNase HII gene deletion enhances mutagenesis, suggesting a possible role of incorporated rNMPs in MMR.
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85
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Perevoztchikova SA, Romanova EA, Oretskaya TS, Friedhoff P, Kubareva EA. Modern aspects of the structural and functional organization of the DNA mismatch repair system. Acta Naturae 2013; 5:17-34. [PMID: 24303200 PMCID: PMC3848065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This review is focused on the general aspects of the DNA mismatch repair (MMR) process. The key proteins of the DNA mismatch repair system are MutS and MutL. To date, their main structural and functional characteristics have been thoroughly studied. However, different opinions exist about the initial stages of the mismatch repair process with the participation of these proteins. This review aims to summarize the data on the relationship between the two MutS functions, ATPase and DNA-binding, and to systematize various models of coordination between the mismatch site and the strand discrimination site in DNA. To test these models, novel techniques for the trapping of short-living complexes that appear at different MMR stages are to be developed.
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Affiliation(s)
- S. A. Perevoztchikova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, 1, bld. 40, Moscow, Russia, 119991
| | - E. A. Romanova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, 1, bld. 40, Moscow, Russia, 119991
| | - T. S. Oretskaya
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, 1, bld. 40, Moscow, Russia, 119991
- Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1, bld. 3, Moscow, Russia, 119991
| | - P. Friedhoff
- Institute of Biochemistry, FB 08, Justus Liebig University, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany
| | - E. A. Kubareva
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, 1, bld. 40, Moscow, Russia, 119991
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86
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Shimada A, Kawasoe Y, Hata Y, Takahashi TS, Masui R, Kuramitsu S, Fukui K. MutS stimulates the endonuclease activity of MutL in an ATP-hydrolysis-dependent manner. FEBS J 2013; 280:3467-79. [PMID: 23679952 DOI: 10.1111/febs.12344] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 05/02/2013] [Accepted: 05/07/2013] [Indexed: 11/30/2022]
Abstract
In the initial steps of DNA mismatch repair, MutS recognizes a mismatched base and recruits the latent endonuclease MutL onto the mismatch-containing DNA in concert with other proteins. MutL then cleaves the error-containing strand to introduce an entry point for the downstream excision reaction. Because MutL has no intrinsic ability to recognize a mismatch and discriminate between newly synthesized and template strands, the endonuclease activity of MutL is strictly regulated by ATP-binding in order to avoid nonspecific degradation of the genomic DNA. However, the activation mechanism for its endonuclease activity remains unclear. In this study, we found that the coexistence of a mismatch, ATP and MutS unlocks the ATP-binding-dependent suppression of MutL endonuclease activity. Interestingly, ATPase-deficient mutants of MutS were unable to activate MutL. Furthermore, wild-type MutS activated ATPase-deficient mutants of MutL less efficiently than wild-type MutL. We concluded that ATP hydrolysis by MutS and MutL is involved in the mismatch-dependent activation of MutL endonuclease activity.
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Affiliation(s)
- Atsuhiro Shimada
- Department of Biological Sciences, Graduate School of Science, Osaka University, Suita, Osaka, Japan
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87
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Yang H, Yung M, Li L, Hoch JA, Ryan CM, Kar UK, Souda P, Whitelegge JP, Miller JH. Evidence that YycJ is a novel 5′–3′ double-stranded DNA exonuclease acting in Bacillus anthracis mismatch repair. DNA Repair (Amst) 2013; 12:334-46. [DOI: 10.1016/j.dnarep.2013.02.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 01/27/2013] [Accepted: 02/05/2013] [Indexed: 11/29/2022]
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88
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Phillips D, Wnetrzak J, Nibau C, Barakate A, Ramsay L, Wright F, Higgins JD, Perry RM, Jenkins G. Quantitative high resolution mapping of HvMLH3 foci in barley pachytene nuclei reveals a strong distal bias and weak interference. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:2139-54. [PMID: 23554258 PMCID: PMC3654414 DOI: 10.1093/jxb/ert079] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
In barley (Hordeum vulgare L.), chiasmata (the physical sites of genetic crossovers) are skewed towards the distal ends of chromosomes, effectively consigning a large proportion of genes to recombination coldspots. This has the effect of limiting potential genetic variability, and of reducing the efficiency of map-based cloning and breeding approaches for this crop. Shifting the sites of recombination to more proximal chromosome regions by forward and reverse genetic means may be profitable in terms of realizing the genetic potential of the species, but is predicated upon a better understanding of the mechanisms governing the sites of these events, and upon the ability to recognize real changes in recombination patterns. The barley MutL Homologue (HvMLH3), a marker for class I interfering crossovers, has been isolated and a specific antibody has been raised. Immunolocalization of HvMLH3 along with the synaptonemal complex transverse filament protein ZYP1, used in conjunction with fluorescence in situ hybridization (FISH) tagging of specific barley chromosomes, has enabled access to the physical recombination landscape of the barley cultivars Morex and Bowman. Consistent distal localization of HvMLH3 foci throughout the genome, and similar patterns of HvMLH3 foci within bivalents 2H and 3H have been observed. A difference in total numbers of HvMLH3 foci between these two cultivars has been quantified, which is interpreted as representing genotypic variation in class I crossover frequency. Discrepancies between the frequencies of HvMLH3 foci and crossover frequencies derived from linkage analysis point to the existence of at least two crossover pathways in barley. It is also shown that interference of HvMLH3 foci is relatively weak compared with other plant species.
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Affiliation(s)
- Dylan Phillips
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Penglais, Aberystwyth, Ceredigion SY23 3DA, UK
| | - Joanna Wnetrzak
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Penglais, Aberystwyth, Ceredigion SY23 3DA, UK
| | - Candida Nibau
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Penglais, Aberystwyth, Ceredigion SY23 3DA, UK
| | | | | | - Frank Wright
- Biomathematics and Statistics Scotland, Invergowrie, Dundee DD2 5DA, UK
| | | | - Ruth M. Perry
- School of Biosciences, University of Birmingham, Birmingham, UK
| | - Glyn Jenkins
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Penglais, Aberystwyth, Ceredigion SY23 3DA, UK
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89
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Abstract
The mismatch repair (MMR) system detects non-Watson-Crick base pairs and strand misalignments arising during DNA replication and mediates their removal by catalyzing excision of the mispair-containing tract of nascent DNA and its error-free resynthesis. In this way, MMR improves the fidelity of replication by several orders of magnitude. It also addresses mispairs and strand misalignments arising during recombination and prevents synapses between nonidentical DNA sequences. Unsurprisingly, MMR malfunction brings about genomic instability that leads to cancer in mammals. But MMR proteins have recently been implicated also in other processes of DNA metabolism, such as DNA damage signaling, antibody diversification, and repair of interstrand cross-links and oxidative DNA damage, in which their functions remain to be elucidated. This article reviews the progress in our understanding of the mechanism of replication error repair made during the past decade.
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Affiliation(s)
- Josef Jiricny
- Institute of Molecular Cancer Research, University of Zurich and ETH Zurich, 8057 Zurich, Switzerland.
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90
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Structure of the MutLα C-terminal domain reveals how Mlh1 contributes to Pms1 endonuclease site. Nat Struct Mol Biol 2013; 20:461-8. [PMID: 23435383 DOI: 10.1038/nsmb.2511] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 01/04/2013] [Indexed: 01/30/2023]
Abstract
Mismatch-repair factors have a prominent role in surveying eukaryotic DNA-replication fidelity and in ensuring correct meiotic recombination. These functions depend on MutL-homolog heterodimers with Mlh1. In humans, MLH1 mutations underlie half of hereditary nonpolyposis colorectal cancers (HNPCCs). Here we report crystal structures of the MutLα (Mlh1-Pms1 heterodimer) C-terminal domain (CTD) from Saccharomyces cerevisiae, alone and in complex with fragments derived from Mlh1 partners. These structures reveal structural rearrangements and additional domains in MutLα as compared to the bacterial MutL counterparts and show that the strictly conserved C terminus of Mlh1 forms part of the Pms1 endonuclease site. The structures of the ternary complexes between MutLα(CTD) and Exo1 or Ntg2 fragments reveal the binding mode of the MIP-box motif shared by several Mlh1 partners. Finally, the structures provide a rationale for the deleterious impact of MLH1 mutations in HNPCCs.
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91
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Abstract
From microbes to multicellular eukaryotic organisms, all cells contain pathways responsible for genome maintenance. DNA replication allows for the faithful duplication of the genome, whereas DNA repair pathways preserve DNA integrity in response to damage originating from endogenous and exogenous sources. The basic pathways important for DNA replication and repair are often conserved throughout biology. In bacteria, high-fidelity repair is balanced with low-fidelity repair and mutagenesis. Such a balance is important for maintaining viability while providing an opportunity for the advantageous selection of mutations when faced with a changing environment. Over the last decade, studies of DNA repair pathways in bacteria have demonstrated considerable differences between Gram-positive and Gram-negative organisms. Here we review and discuss the DNA repair, genome maintenance, and DNA damage checkpoint pathways of the Gram-positive bacterium Bacillus subtilis. We present their molecular mechanisms and compare the functions and regulation of several pathways with known information on other organisms. We also discuss DNA repair during different growth phases and the developmental program of sporulation. In summary, we present a review of the function, regulation, and molecular mechanisms of DNA repair and mutagenesis in Gram-positive bacteria, with a strong emphasis on B. subtilis.
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92
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Lenhart JS, Sharma A, Hingorani MM, Simmons LA. DnaN clamp zones provide a platform for spatiotemporal coupling of mismatch detection to DNA replication. Mol Microbiol 2012; 87:553-68. [PMID: 23228104 DOI: 10.1111/mmi.12115] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/21/2012] [Indexed: 11/30/2022]
Abstract
Mismatch repair (MMR) increases the fidelity of DNA replication by identifying and correcting replication errors. Processivity clamps are vital components of DNA replication and MMR, yet the mechanism and extent to which they participate in MMR remains unclear. We investigated the role of the Bacillus subtilis processivity clamp DnaN, and found that it serves as a platform for mismatch detection and coupling of repair to DNA replication. By visualizing functional MutS fluorescent fusions in vivo, we find that MutS forms foci independent of mismatch detection at sites of replication (i.e. the replisome). These MutS foci are directed to the replisome by DnaN clamp zones that aid mismatch detection by targeting the search to nascent DNA. Following mismatch detection, MutS disengages from the replisome, facilitating repair. We tested the functional importance of DnaN-mediated mismatch detection for MMR, and found that it accounts for 90% of repair. This high dependence on DnaN can be bypassed by increasing MutS concentration within the cell, indicating a secondary mode of detection in vivo whereby MutS directly finds mismatches without associating with the replisome. Overall, our results provide new insight into the mechanism by which DnaN couples mismatch recognition to DNA replication in living cells.
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Affiliation(s)
- Justin S Lenhart
- Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
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93
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Abstract
The DNA mismatch repair (MMR) system is a major DNA repair pathway whose function is critical for the correction of DNA biosynthetic errors. MMR is initiated by the binding of MutS proteins to mismatches and unpaired nucleotides followed by the recruitment of MutL proteins. The major MutL activity in eukaryotes is performed by MutLα, the heterocomplex of MLH1-PMS1 in yeast and plants and MLH1-PMS2 in humans. We here report the effect the expression of Arabidopsis PMS1 protein exerts on Saccharomyces cerevisiae genomic stability. A strain carrying specific microsatellite instability reporter systems was chosen for the study. The plant protein failed to complement the hypermutator phenotype of a pms1 deficient strain but increased approximately 14-fold and 2,000-fold the mutation rates of his7-2 and lys2::InsE-A 14 loci of MMR proficient strains when compared to wild-type strains, respectively. Overexpressing AtMLH1 in the AtPMS1-overproducing strain generated an increase in mutation rate comparable to that of AtPMS1 expression alone. Deletion of the C-terminal residues implicated in protein-protein interaction and including the putative endonuclease sequence of AtPMS1 completely eliminated the mutator phenotype. Taken together, these results indicate that the plant proteins affect yeast genomic stability, very possibly altering protein-protein interactions that are necessary to complete repair.
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94
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Abstract
DNA mismatch repair (MMR) corrects replication errors in newly synthesized DNA. It also has an antirecombination action on heteroduplexes that contain similar but not identical sequences. This review focuses on the genetics and development of MMR and not on the latest biochemical mechanisms. The main focus is on MMR in Escherichia coli, but examples from Streptococcuspneumoniae and Bacillussubtilis have also been included. In most organisms, only MutS (detects mismatches) and MutL (an endonuclease) and a single exonucleaseare present. How this system discriminates between newlysynthesized and parental DNA strands is not clear. In E. coli and its relatives, however, Dam methylation is an integral part of MMR and is the basis for strand discrimination. A dedicated site-specific endonuclease, MutH, is present, andMutL has no endonuclease activity; four exonucleases can participate in MMR. Although it might seem that the accumulated wealth of genetic and biochemical data has given us a detailed picture of the mechanism of MMR in E. coli, the existence of three competing models to explain the initiation phase indicates the complexity of the system. The mechanism of the antirecombination action of MMR is largely unknown, but only MutS and MutL appear to be necessary. A primary site of action appears to be on RecA, although subsequent steps of the recombination process can also be inhibited. In this review, the genetics of Very Short Patch (VSP) repair of T/G mismatches arising from deamination of 5-methylcytosineresidues is also discussed.
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95
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Residues in the N-terminal domain of MutL required for mismatch repair in Bacillus subtilis. J Bacteriol 2012; 194:5361-7. [PMID: 22843852 DOI: 10.1128/jb.01142-12] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Mismatch repair is a highly conserved pathway responsible for correcting DNA polymerase errors incorporated during genome replication. MutL is a mismatch repair protein known to coordinate several steps in repair that ultimately results in strand removal following mismatch identification by MutS. MutL homologs from bacteria to humans contain well-conserved N-terminal and C-terminal domains. To understand the contribution of the MutL N-terminal domain to mismatch repair, we analyzed 14 different missense mutations in Bacillus subtilis MutL that were conserved with missense mutations identified in the human MutL homolog MLH1 from patients with hereditary nonpolyposis colorectal cancer (HNPCC). We characterized missense mutations in or near motifs important for ATP binding, ATPase activity, and DNA binding. We found that 13 of the 14 missense mutations conferred a substantial defect to mismatch repair in vivo, while three mutant alleles showed a dominant negative increase in mutation frequency to wild-type mutL. We performed immunoblot analysis to determine the relative stability of each mutant protein in vivo and found that, although most accumulated, several mutant proteins failed to maintain wild-type levels, suggesting defects in protein stability. The remaining missense mutations located in areas of the protein important for DNA binding, ATP binding, and ATPase activities of MutL compromised repair in vivo. Our results define functional residues in the N-terminal domain of B. subtilis MutL that are critical for mismatch repair in vivo.
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96
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Plys AJ, Rogacheva MV, Greene EC, Alani E. The unstructured linker arms of Mlh1-Pms1 are important for interactions with DNA during mismatch repair. J Mol Biol 2012; 422:192-203. [PMID: 22659005 DOI: 10.1016/j.jmb.2012.05.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 05/17/2012] [Accepted: 05/22/2012] [Indexed: 02/07/2023]
Abstract
DNA mismatch repair (MMR) models have proposed that MSH (MutS homolog) proteins identify DNA polymerase errors while interacting with the DNA replication fork. MLH (MutL homolog) proteins (primarily Mlh1-Pms1 in baker's yeast) then survey the genome for lesion-bound MSH proteins. The resulting MSH-MLH complex formed at a DNA lesion initiates downstream steps in repair. MLH proteins act as dimers and contain long (20-30 nm) unstructured arms that connect two terminal globular domains. These arms can vary between 100 and 300 amino acids in length, are highly divergent between organisms, and are resistant to amino acid substitutions. To test the roles of the linker arms in MMR, we engineered a protease cleavage site into the Mlh1 linker arm domain of baker's yeast Mlh1-Pms1. Cleavage of the Mlh1 linker arm in vitro resulted in a defect in Mlh1-Pms1 DNA binding activity, and in vivo proteolytic cleavage resulted in a complete defect in MMR. We then generated a series of truncation mutants bearing Mlh1 and Pms1 linker arms of varying lengths. This work revealed that MMR is greatly compromised when portions of the Mlh1 linker are removed, whereas repair is less sensitive to truncation of the Pms1 linker arm. Purified complexes containing truncations in Mlh1 and Pms1 linker arms were analyzed and found to have differential defects in DNA binding that also correlated with the ability to form a ternary complex with Msh2-Msh6 and mismatch DNA. These observations are consistent with the unstructured linker domains of MLH proteins providing distinct interactions with DNA during MMR.
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Affiliation(s)
- Aaron J Plys
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853-2073, USA
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97
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Characterization of C- and N-terminal domains of Aquifex aeolicus MutL endonuclease: N-terminal domain stimulates the endonuclease activity of C-terminal domain in a zinc-dependent manner. Biosci Rep 2012; 31:309-22. [PMID: 20961292 DOI: 10.1042/bsr20100116] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
DNA MMR (mismatch repair) is an excision repair system that removes mismatched bases generated primarily by failure of the 3'-5' proofreading activity associated with replicative DNA polymerases. MutL proteins homologous to human PMS2 are the endonucleases that introduce the entry point of the excision reaction. Deficiency in PMS2 function is one of the major etiologies of hereditary non-polyposis colorectal cancers in humans. Although recent studies revealed that the CTD (C-terminal domain) of MutL harbours weak endonuclease activity, the regulatory mechanism of this activity remains unknown. In this paper, we characterize in detail the CTD and NTD (N-terminal domain) of aqMutL (Aquifex aeolicus MutL). On the one hand, CTD existed as a dimer in solution and showed weak DNA-binding and Mn2+-dependent endonuclease activities. On the other hand, NTD was monomeric and exhibited a relatively strong DNA-binding activity. It was also clarified that NTD promotes the endonuclease activity of CTD. NTD-mediated activation of CTD was abolished by depletion of the zinc-ion from the reaction mixture or by the substitution of the zinc-binding cysteine residue in CTD with an alanine. On the basis of these results, we propose a model for the intramolecular regulatory mechanism of MutL endonuclease activity.
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98
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Chahwan R, van Oers JMM, Avdievich E, Zhao C, Edelmann W, Scharff MD, Roa S. The ATPase activity of MLH1 is required to orchestrate DNA double-strand breaks and end processing during class switch recombination. ACTA ACUST UNITED AC 2012; 209:671-8. [PMID: 22451719 PMCID: PMC3328365 DOI: 10.1084/jem.20111531] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
MLH1 ATPase activity is essential for class switch recombination but not for somatic hypermutation. Antibody diversification through somatic hypermutation (SHM) and class switch recombination (CSR) are similarly initiated in B cells with the generation of U:G mismatches by activation-induced cytidine deaminase but differ in their subsequent mutagenic consequences. Although SHM relies on the generation of nondeleterious point mutations, CSR depends on the production of DNA double-strand breaks (DSBs) and their adequate recombination through nonhomologous end joining (NHEJ). MLH1, an ATPase member of the mismatch repair (MMR) machinery, is emerging as a likely regulator of whether a U:G mismatch progresses toward mutation or DSB formation. We conducted experiments on cancer modeled ATPase-deficient MLH1G67R knockin mice to determine the function that the ATPase domain of MLH1 mediates in SHM and CSR. Mlh1GR/GR mice displayed a significant decrease in CSR, mainly attributed to a reduction in the generation of DSBs and diminished accumulation of 53BP1 at the immunoglobulin switch regions. However, SHM was normal in these mice, which distinguishes MLH1 from upstream members of the MMR pathway and suggests a very specific role of its ATPase-dependent functions during CSR. In addition, we show that the residual switching events still taking place in Mlh1GR/GR mice display unique features, suggesting a role for the ATPase activity of MLH1 beyond the activation of the endonuclease functions of its MMR partner PMS2. A preference for switch junctions with longer microhomologies in Mlh1GR/GR mice suggests that through its ATPase activity, MLH1 also has an impact in DNA end processing, favoring canonical NHEJ downstream of the DSB. Collectively, our study shows that the ATPase domain of MLH1 is important to transmit the CSR signaling cascade both upstream and downstream of the generation of DSBs.
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Affiliation(s)
- Richard Chahwan
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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The functions of MutL in mismatch repair: the power of multitasking. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 110:41-70. [PMID: 22749142 DOI: 10.1016/b978-0-12-387665-2.00003-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
DNA mismatch repair enhances genomic stability by correcting errors that have escaped polymerase proofreading. One of the critical steps in DNA mismatch repair is discriminating the new from the parental DNA strand as only the former needs repair. In Escherichia coli, the latent endonuclease MutH carries out this function. However, most prokaryotes and all eukaryotes lack a mutH gene. MutL is a key component of this system that mediates protein-protein interactions during mismatch recognition, strand discrimination, and strand removal. Hence, it had long been thought that the primary function of MutL was coordinating sequential mismatch repair steps. However, recent studies have revealed that most MutL homologs from organisms lacking MutH encode a conserved metal-binding motif associated with a weak endonuclease activity. As MutL homologs bearing this activity are found only in organisms relying on MutH-independent DNA mismatch repair, this finding unveils yet another crucial function of the MutL protein at the strand discrimination step. In this chapter, we review recent functional and structural work aimed at characterizing the multiple functions of MutL and discuss how the endonuclease activity of MutL is regulated by other repair factors.
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Yang H, Yung M, Sikavi C, Miller JH. The role of Bacillus anthracis RecD2 helicase in DNA mismatch repair. DNA Repair (Amst) 2011; 10:1121-30. [DOI: 10.1016/j.dnarep.2011.08.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 08/17/2011] [Accepted: 08/18/2011] [Indexed: 02/07/2023]
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