1
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Arbel-Groissman M, Liefshitz B, Kupiec M. Effects of PCNA Stability on the Formation of Mutations. Int J Mol Sci 2024; 25:8646. [PMID: 39201337 PMCID: PMC11354803 DOI: 10.3390/ijms25168646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2024] [Revised: 08/06/2024] [Accepted: 08/07/2024] [Indexed: 09/02/2024] Open
Abstract
The fidelity of replication, especially in the presence of DNA damage, is essential for the proper function of cells. Mutations that inactivate genes involved in DNA damage repair or bypass are enriched in several types of cancer cells. Thus, it is important to further our understanding of the mechanisms governing replication fidelity. PCNA is a ring-shaped complex that encircles DNA at the front of the replication fork, at the double-stranded/single-stranded DNA junction. It serves as a processivity factor for the different DNA replication polymerases, allowing them to replicate longer stretches of DNA by physically tethering them to the DNA and preventing their detachment. In addition, PCNA also regulates and coordinates different DNA damage bypass pathways meant to allow DNA replication in the presence of DNA damage. Due to its essentiality and the numerous functions it has in the cell, much is still unclear about PCNA. Here, we utilize PCNA mutants that lower the stability of the PCNA complex on the chromatin, and thus tend to disassociate and fall from the DNA. Using these mutants, we show that PCNA's physical presence on the DNA can prevent DNA misalignment at repetitive sequences, leading to increased mutation formation. We also show that PCNA-interacting proteins play an important role in strengthening the ring's stability on the chromatin. Such repetitive sequence-induced mutations are common in several human diseases and it is important to study their formation and the mechanisms guarding against them.
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Affiliation(s)
| | | | - Martin Kupiec
- The Shmunis School of Biomedicine & Cancer Research, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel
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2
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Trost H, Lopezcolorado FW, Merkell A, Stark JM. Functions of PMS2 and MLH1 important for regulation of divergent repeat-mediated deletions. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.05.606388. [PMID: 39149360 PMCID: PMC11326157 DOI: 10.1101/2024.08.05.606388] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
Repeat-mediated deletions (RMDs) are a type of deletion rearrangement that utilizes two repetitive elements to bridge a DNA double-strand break (DSB) that leads to loss of the intervening sequence and one of the repeats. Sequence divergence between repeats causes RMD suppression and indeed this divergence must be resolved in the RMD products. The mismatch repair factor, MLH1, was shown to be critical for both RMD suppression and a polarity of sequence divergence resolution in RMDs. Here, we sought to study the interrelationship between these two aspects of RMD regulation (i.e., RMD suppression and polar divergence resolution), by examining several mutants of MLH1 and its binding partner PMS2. To begin with, we show that PMS2 is also critical for both RMD suppression and polar resolution of sequence divergence in RMD products. Then, with six mutants of the MLH1-PMS2 heterodimer, we found several different patterns: three mutants showed defects in both functions, one mutant showed loss of RMD suppression but not polar divergence resolution, whereas another mutant showed the opposite, and finally one mutant showed loss of RMD suppression but had a complex effect on polar divergence resolution. These findings indicate that RMD suppression vs. polar resolution of sequence divergence are distinct functions of MLH1-PMS2.
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Affiliation(s)
- Hannah Trost
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of the City of Hope, Duarte, California 91010, USA
- Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, California 91010, USA
| | - Felicia Wednesday Lopezcolorado
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of the City of Hope, Duarte, California 91010, USA
| | - Arianna Merkell
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of the City of Hope, Duarte, California 91010, USA
| | - Jeremy M. Stark
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of the City of Hope, Duarte, California 91010, USA
- Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, California 91010, USA
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3
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Piscitelli JM, Witte SJ, Sakinejad YS, Manhart CM. The Mlh1-Pms1 endonuclease uses ATP to preserve DNA discontinuities as strand discrimination signals to facilitate mismatch repair. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.13.598860. [PMID: 38915520 PMCID: PMC11195183 DOI: 10.1101/2024.06.13.598860] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/26/2024]
Abstract
In eukaryotic post-replicative mismatch repair, MutS homologs (MSH) detect mismatches and recruit MLH complexes to nick the newly replicated DNA strand upon activation by the replication processivity clamp, PCNA. This incision enables mismatch removal and DNA repair. Biasing MLH endonuclease activity to the newly replicated DNA strand is crucial for repair. In reconstituted in vitro assays, PCNA is loaded at pre-existing discontinuities and orients the major MLH endonuclease Mlh1-Pms1/MLH1-PMS2 (yeast/human) to nick the discontinuous strand. In vivo, newly replicated DNA transiently contains discontinuities which are critical for efficient mismatch repair. How these discontinuities are preserved as strand discrimination signals during the window of time where mismatch repair occurs is unknown. Here, we demonstrate that yeast Mlh1-Pms1 uses ATP binding to recognize DNA discontinuities. This complex does not efficiently interact with PCNA, which partially suppresses ATPase activity, and prevents dissociation from the discontinuity. These data suggest that in addition to initiating mismatch repair by nicking newly replicated DNA, Mlh1-Pms1 protects strand discrimination signals, aiding in maintaining its own strand discrimination signposts. Our findings also highlight the significance of Mlh1-Pms1's ATPase activity for inducing DNA dissociation, as mutant proteins deficient in this function become immobilized on DNA post-incision, explaining in vivo phenotypes.
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Affiliation(s)
| | - Scott J. Witte
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania, 19122, USA
| | - Yasmine S. Sakinejad
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania, 19122, USA
| | - Carol M. Manhart
- Department of Chemistry, Temple University, Philadelphia, Pennsylvania, 19122, USA
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4
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Storozhuk O, Bruekner SR, Paul A, Lebbink JHG, Sixma TK, Friedhoff P. MutL Activates UvrD by Interaction Between the MutL C-terminal Domain and the UvrD 2B Domain. J Mol Biol 2024; 436:168589. [PMID: 38677494 DOI: 10.1016/j.jmb.2024.168589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 04/14/2024] [Accepted: 04/19/2024] [Indexed: 04/29/2024]
Abstract
UvrD is a helicase vital for DNA replication and quality control processes. In its monomeric state, UvrD exhibits limited helicase activity, necessitating either dimerization or assistance from an accessory protein to efficiently unwind DNA. Within the DNA mismatch repair pathway, MutL plays a pivotal role in relaying the repair signal, enabling UvrD to unwind DNA from the strand incision site up to and beyond the mismatch. Although this interdependence is well-established, the precise mechanism of activation and the specific MutL-UvrD interactions that trigger helicase activity remain elusive. To address these questions, we employed site-specific crosslinking techniques using single-cysteine variants of MutL and UvrD followed by functional assays. Our investigation unveils that the C-terminal domain of MutL not only engages with UvrD but also acts as a self-sufficient activator of UvrD helicase activity on DNA substrates with 3'-single-stranded tails. Especially when MutL is covalently attached to the 2B or 1B domain the tail length can be reduced to a minimal substrate of 5 nucleotides without affecting unwinding efficiency.
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Affiliation(s)
- Olha Storozhuk
- Institute for Biochemistry, FB 08, Justus Liebig University, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany
| | - Susanne R Bruekner
- Division of Biochemistry, Netherlands Cancer Institute and Oncode Institute, Amsterdam, the Netherlands
| | - Ankon Paul
- Department of Molecular Genetics, Oncode Institute, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, the Netherlands
| | - Joyce H G Lebbink
- Department of Molecular Genetics, Oncode Institute, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, the Netherlands; Department of Radiotherapy, Erasmus University Medical Center, Rotterdam, the Netherlands
| | - Titia K Sixma
- Division of Biochemistry, Netherlands Cancer Institute and Oncode Institute, Amsterdam, the Netherlands
| | - Peter Friedhoff
- Institute for Biochemistry, FB 08, Justus Liebig University, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany.
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5
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Kawasoe Y, Shimokawa S, Gillespie PJ, Blow JJ, Tsurimoto T, Takahashi TS. The Atad5 RFC-like complex is the major unloader of proliferating cell nuclear antigen in Xenopus egg extracts. J Biol Chem 2024; 300:105588. [PMID: 38141767 PMCID: PMC10827553 DOI: 10.1016/j.jbc.2023.105588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 12/04/2023] [Accepted: 12/11/2023] [Indexed: 12/25/2023] Open
Abstract
Proliferating cell nuclear antigen (PCNA) is a homo-trimeric clamp complex that serves as the molecular hub for various DNA transactions, including DNA synthesis and post-replicative mismatch repair. Its timely loading and unloading are critical for genome stability. PCNA loading is catalyzed by Replication factor C (RFC) and the Ctf18 RFC-like complex (Ctf18-RLC), and its unloading is catalyzed by Atad5/Elg1-RLC. However, RFC, Ctf18-RLC, and even some subcomplexes of their shared subunits are capable of unloading PCNA in vitro, leaving an ambiguity in the division of labor in eukaryotic clamp dynamics. By using a system that specifically detects PCNA unloading, we show here that Atad5-RLC, which accounts for only approximately 3% of RFC/RLCs, nevertheless provides the major PCNA unloading activity in Xenopus egg extracts. RFC and Ctf18-RLC each account for approximately 40% of RFC/RLCs, while immunodepletion of neither Rfc1 nor Ctf18 detectably affects the rate of PCNA unloading in our system. PCNA unloading is dependent on the ATP-binding motif of Atad5, independent of nicks on DNA and chromatin assembly, and inhibited effectively by PCNA-interacting peptides. These results support a model in which Atad5-RLC preferentially unloads DNA-bound PCNA molecules that are free from their interactors.
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Affiliation(s)
| | - Sakiko Shimokawa
- Graduate School of Systems Life Sciences, Kyushu University, Fukuoka, Japan
| | - Peter J Gillespie
- Division of Molecular, Cell & Developmental Biology, School of Life Sciences, University of Dundee, Dundee, UK
| | - J Julian Blow
- Division of Molecular, Cell & Developmental Biology, School of Life Sciences, University of Dundee, Dundee, UK
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6
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Steele EJ, Franklin A, Lindley RA. Somatic mutation patterns at Ig and Non-Ig Loci. DNA Repair (Amst) 2024; 133:103607. [PMID: 38056368 DOI: 10.1016/j.dnarep.2023.103607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 11/17/2023] [Accepted: 11/21/2023] [Indexed: 12/08/2023]
Abstract
The reverse transcriptase (RT) model of immunoglobulin (Ig) somatic hypermutation (SHM) has received insufficient scientific attention. This is understandable given that DNA deamination mediated by activation-induced deaminase (AID), the initiating step of Ig SHM, has dominated experiments since 2002. We summarise some key history of the RT Ig SHM model dating to 1987. For example, it is now established that DNA polymerase η, the sole DNA repair polymerase involved in post-replication short-patch repair, is an efficient cellular RT. This implies that it is potentially able to initiate target site reverse transcription by RNA-directed DNA repair at AID-induced lesions. Recently, DNA polymerase θ has also been shown to be an efficient cellular RT. Since DNA polymerase θ plays no significant role in Ig SHM, it could serve a similar RNA-dependent DNA polymerase role as DNA polymerase η at non-Ig loci in the putative RNA-templated nucleotide excision repair of bulky adducts and other mutagenic lesions on the transcribed strand. A major yet still poorly recognised consequence of the proposed RT process in Ig SHM is the generation of significant and characteristic strand-biased mutation signatures at both deoxyadenosine/deoxythymidine and deoxyguanosine/deoxycytidine base pairs. In this historical perspective, we highlight how diagnostic strand-biased mutation signatures are detected in vivo during SHM at both Ig loci in germinal centre B lymphocytes and non-Ig loci in cancer genomes. These strand-biased signatures have been significantly obscured by technical issues created by improper use of the polymerase chain reaction technique. A heightened awareness of this fact should contribute to better data interpretation and somatic mutation pattern recognition both at Ig and non-Ig loci.
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Affiliation(s)
- Edward J Steele
- Melville Analytics Pty Ltd, 2/102 Duke St, Kangaroo Point, Brisbane 4169, Qld, Australia.
| | - Andrew Franklin
- Novartis Pharmaceuticals UK Limited, The WestWorks Building, White City Place, 195 Wood Lane, W12 7FQ London, United Kingdom
| | - Robyn A Lindley
- GMDxgenomics, Suite 201, 697 Burke Rd, Camberwell, Melbourne 3124, Vic, Australia; Department of Clinical Pathology, Faculty of Medicine, Dentistry & Health Sciences, University of Melbourne, Vic, Australia
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7
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Medina-Rivera M, Phelps S, Sridharan M, Becker J, Lamb N, Kumar C, Sutton M, Bielinsky A, Balakrishnan L, Surtees J. Elevated MSH2 MSH3 expression interferes with DNA metabolism in vivo. Nucleic Acids Res 2023; 51:12185-12206. [PMID: 37930834 PMCID: PMC10711559 DOI: 10.1093/nar/gkad934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/30/2023] [Accepted: 10/10/2023] [Indexed: 11/08/2023] Open
Abstract
The Msh2-Msh3 mismatch repair (MMR) complex in Saccharomyces cerevisiae recognizes and directs repair of insertion/deletion loops (IDLs) up to ∼17 nucleotides. Msh2-Msh3 also recognizes and binds distinct looped and branched DNA structures with varying affinities, thereby contributing to genome stability outside post-replicative MMR through homologous recombination, double-strand break repair (DSBR) and the DNA damage response. In contrast, Msh2-Msh3 promotes genome instability through trinucleotide repeat (TNR) expansions, presumably by binding structures that form from single-stranded (ss) TNR sequences. We previously demonstrated that Msh2-Msh3 binding to 5' ssDNA flap structures interfered with Rad27 (Fen1 in humans)-mediated Okazaki fragment maturation (OFM) in vitro. Here we demonstrate that elevated Msh2-Msh3 levels interfere with DNA replication and base excision repair in vivo. Elevated Msh2-Msh3 also induced a cell cycle arrest that was dependent on RAD9 and ELG1 and led to PCNA modification. These phenotypes also required Msh2-Msh3 ATPase activity and downstream MMR proteins, indicating an active mechanism that is not simply a result of Msh2-Msh3 DNA-binding activity. This study provides new mechanistic details regarding how excess Msh2-Msh3 can disrupt DNA replication and repair and highlights the role of Msh2-Msh3 protein abundance in Msh2-Msh3-mediated genomic instability.
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Affiliation(s)
- Melisa Medina-Rivera
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Samantha Phelps
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Madhumita Sridharan
- Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN, 46202, USA
| | - Jordan Becker
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Natalie A Lamb
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Charanya Kumar
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Mark D Sutton
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
| | - Anja Bielinsky
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Lata Balakrishnan
- Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN, 46202, USA
| | - Jennifer A Surtees
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo NY, 14203, USA
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8
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Psakhye I, Kawasumi R, Abe T, Hirota K, Branzei D. PCNA recruits cohesin loader Scc2 to ensure sister chromatid cohesion. Nat Struct Mol Biol 2023; 30:1286-1294. [PMID: 37592094 PMCID: PMC10497406 DOI: 10.1038/s41594-023-01064-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 07/12/2023] [Indexed: 08/19/2023]
Abstract
Sister chromatid cohesion, established during replication by the ring-shaped multiprotein complex cohesin, is essential for faithful chromosome segregation. Replisome-associated proteins are required to generate cohesion by two independent pathways. One mediates conversion of cohesins bound to unreplicated DNA ahead of replication forks into cohesive entities behind them, while the second promotes cohesin de novo loading onto newly replicated DNA. The latter process depends on the cohesin loader Scc2 (NIPBL in vertebrates) and the alternative PCNA loader CTF18-RFC. However, the mechanism of de novo cohesin loading during replication is unknown. Here we show that PCNA physically recruits the yeast cohesin loader Scc2 via its C-terminal PCNA-interacting protein motif. Binding to PCNA is crucial, as the scc2-pip mutant deficient in Scc2-PCNA interaction is defective in cohesion when combined with replisome mutants of the cohesin conversion pathway. Importantly, the role of NIPBL recruitment to PCNA for cohesion generation is conserved in vertebrate cells.
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Affiliation(s)
- Ivan Psakhye
- IFOM ETS, the AIRC Institute of Molecular Oncology, Milan, Italy.
| | - Ryotaro Kawasumi
- IFOM ETS, the AIRC Institute of Molecular Oncology, Milan, Italy
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji-shi, Japan
| | - Takuya Abe
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji-shi, Japan
| | - Kouji Hirota
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji-shi, Japan
| | - Dana Branzei
- IFOM ETS, the AIRC Institute of Molecular Oncology, Milan, Italy.
- Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche, Pavia, Italy.
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9
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Putnam CD, Kolodner RD. Insights into DNA cleavage by MutL homologs from analysis of conserved motifs in eukaryotic Mlh1. Bioessays 2023; 45:e2300031. [PMID: 37424007 PMCID: PMC10530380 DOI: 10.1002/bies.202300031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Revised: 06/02/2023] [Accepted: 06/15/2023] [Indexed: 07/11/2023]
Abstract
MutL family proteins contain an N-terminal ATPase domain (NTD), an unstructured interdomain linker, and a C-terminal domain (CTD), which mediates constitutive dimerization between subunits and often contains an endonuclease active site. Most MutL homologs direct strand-specific DNA mismatch repair by cleaving the error-containing daughter DNA strand. The strand cleavage reaction is poorly understood; however, the structure of the endonuclease active site is consistent with a two- or three-metal ion cleavage mechanism. A motif required for this endonuclease activity is present in the unstructured linker of Mlh1 and is conserved in all eukaryotic Mlh1 proteins, except those from metamonads, which also lack the almost absolutely conserved Mlh1 C-terminal phenylalanine-glutamate-arginine-cysteine (FERC) sequence. We hypothesize that the cysteine in the FERC sequence is autoinhibitory, as it sequesters the active site. We further hypothesize that the evolutionary co-occurrence of the conserved linker motif with the FERC sequence indicates a functional interaction, possibly by linker motif-mediated displacement of the inhibitory cysteine. This role is consistent with available data for interactions between the linker motif with DNA and the CTDs in the vicinity of the active site.
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Affiliation(s)
- Christopher D. Putnam
- Ludwig Institute for Cancer Research San Diego Branch, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660
- Departments of Medicine, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660
- Moores Cancer Center, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660
| | - Richard D. Kolodner
- Ludwig Institute for Cancer Research San Diego Branch, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660
- Cellular and Molecular Medicine, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660
- Moores Cancer Center, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660
- Institute of Genomic Medicine, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660
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10
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Trost H, Merkell A, Lopezcolorado FW, Stark J. Resolution of sequence divergence for repeat-mediated deletions shows a polarity that is mediated by MLH1. Nucleic Acids Res 2023; 51:650-667. [PMID: 36620890 PMCID: PMC9881173 DOI: 10.1093/nar/gkac1240] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 11/07/2022] [Accepted: 01/04/2023] [Indexed: 01/10/2023] Open
Abstract
Repeat-mediated deletions (RMDs) are a type of chromosomal rearrangement between two homologous sequences that causes loss of the sequence between the repeats, along with one of the repeats. Sequence divergence between repeats suppresses RMDs; the mechanisms of such suppression and of resolution of the sequence divergence remains poorly understood. We identified RMD regulators using a set of reporter assays in mouse cells that test two key parameters: repeat sequence divergence and the distances between one repeat and the initiating chromosomal break. We found that the mismatch repair factor MLH1 suppresses RMDs with sequence divergence in the same pathway as MSH2 and MSH6, and which is dependent on residues in MLH1 and its binding partner PMS2 that are important for nuclease activity. Additionally, we found that the resolution of sequence divergence in the RMD product has a specific polarity, where divergent bases that are proximal to the chromosomal break end are preferentially removed. Moreover, we found that the domain of MLH1 that forms part of the MLH1-PMS2 endonuclease is important for polarity of resolution of sequence divergence. We also identified distinctions between MLH1 versus TOP3α in regulation of RMDs. We suggest that MLH1 suppresses RMDs with sequence divergence, while also promoting directional resolution of sequence divergence in the RMD product.
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Affiliation(s)
- Hannah Trost
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA
- Irell and Manella Graduate School of Biological Sciences, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA
| | - Arianna Merkell
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA
| | | | - Jeremy M Stark
- To whom correspondence should be addressed. Tel: +1 626 218-6346; Fax: +1 626 218 8892;
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11
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Effects of Defective Unloading and Recycling of PCNA Revealed by the Analysis of ELG1 Mutants. Int J Mol Sci 2023; 24:ijms24021568. [PMID: 36675081 PMCID: PMC9863317 DOI: 10.3390/ijms24021568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 01/10/2023] [Accepted: 01/11/2023] [Indexed: 01/15/2023] Open
Abstract
Timely and complete replication of the genome is essential for life. The PCNA ring plays an essential role in DNA replication and repair by contributing to the processivity of DNA polymerases and by recruiting proteins that act in DNA replication-associated processes. The ELG1 gene encodes a protein that works, together with the Rfc2-5 subunits (shared by the replication factor C complex), to unload PCNA from chromatin. While ELG1 is not essential for life, deletion of the gene has strong consequences for the stability of the genome, and elg1 mutants exhibit sensitivity to DNA damaging agents, defects in genomic silencing, high mutation rates, and other striking phenotypes. Here, we sought to understand whether all the roles attributed to Elg1 in genome stability maintenance are due to its effects on PCNA unloading, or whether they are due to additional functions of the protein. By using a battery of mutants that affect PCNA accumulation at various degrees, we show that all the phenotypes measured correlate with the amount of PCNA left at the chromatin. Our results thus demonstrate the importance of Elg1 and of PCNA unloading in promoting proper chromatin structure and in maintaining a stable genome.
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12
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Daniels HG, Knicely BG, Miller AK, Thompson A, Plattner R, Goellner EM. Inhibition of ABL1 by tyrosine kinase inhibitors leads to a downregulation of MLH1 by Hsp70-mediated lysosomal protein degradation. Front Genet 2022; 13:940073. [PMID: 36338985 PMCID: PMC9631443 DOI: 10.3389/fgene.2022.940073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 10/03/2022] [Indexed: 01/07/2023] Open
Abstract
The DNA mismatch repair (MMR) pathway and its regulation are critical for genomic stability. Mismatch repair (MMR) follows replication and repairs misincorporated bases and small insertions or deletions that are not recognized and removed by the proofreading polymerase. Cells deficient in MMR exhibit an increased overall mutation rate and increased expansion and contraction of short repeat sequences in the genome termed microsatellite instability (MSI). MSI is often a clinical measure of genome stability in tumors and is used to determine the course of treatment. MMR is also critical for inducing apoptosis after alkylation damage from environmental agents or DNA-damaging chemotherapy. MLH1 is essential for MMR, and loss or mutation of MLH1 leads to defective MMR, increased mutation frequency, and MSI. In this study, we report that tyrosine kinase inhibitors, imatinib and nilotinib, lead to decreased MLH1 protein expression but not decreased MLH1 mRNA levels. Of the seven cellular targets of Imatinib and nilotinib, we show that silencing of ABL1 also reduces MLH1 protein expression. Treatment with tyrosine kinase inhibitors or silencing of ABL1 results in decreased apoptosis after treatment with alkylating agents, suggesting the level of MLH1 reduction is sufficient to disrupt MMR function. We also report MLH1 is tyrosine phosphorylated by ABL1. We demonstrate that MLH1 downregulation by ABL1 knockdown or inhibition requires chaperone protein Hsp70 and that MLH1 degradation can be abolished with the lysosomal inhibitor bafilomycin. Taken together, we propose that ABL1 prevents MLH1 from being targeted for degradation by the chaperone Hsp70 and that in the absence of ABL1 activity at least a portion of MLH1 is degraded through the lysosome. This study represents an advance in understanding MMR pathway regulation and has important clinical implications as MMR status is used in the clinic to inform patient treatment, including the use of immunotherapy.
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Affiliation(s)
- Hannah G. Daniels
- University of Kentucky, College of Medicine Department of Toxicology and Cancer Biology, Lexington, KY, United States
| | - Breanna G. Knicely
- University of Kentucky, College of Medicine Department of Toxicology and Cancer Biology, Lexington, KY, United States
| | - Anna Kristin Miller
- University of Kentucky, College of Medicine Department of Toxicology and Cancer Biology, Lexington, KY, United States
| | - Ana Thompson
- Berea College, Berea, KY, United States,University of Kentucky Markey Cancer Center, Lexington, KY, United States
| | - Rina Plattner
- University of Kentucky Markey Cancer Center, Lexington, KY, United States,University of Kentucky, College of Medicine Department of Pharmacology and Nutritional Sciences, Lexington, KY, United States
| | - Eva M. Goellner
- University of Kentucky, College of Medicine Department of Toxicology and Cancer Biology, Lexington, KY, United States,University of Kentucky Markey Cancer Center, Lexington, KY, United States,*Correspondence: Eva M. Goellner,
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13
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The unstructured linker of Mlh1 contains a motif required for endonuclease function which is mutated in cancers. Proc Natl Acad Sci U S A 2022; 119:e2212870119. [PMID: 36215471 PMCID: PMC9586283 DOI: 10.1073/pnas.2212870119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
DNA mismatch repair (MMR) prevents mutations caused by DNA-replication errors and suppresses multiple types of cancers. During MMR, the Mlh1-Pms1 complex is recruited to mispair-containing DNA and nicks the newly replicated DNA strand, targeting it for degradation and resynthesis. Here, we identified an amino acid sequence within the unstructured linker of Mlh1 required for endonuclease activity. This sequence functioned when moved within the Mlh1 linker or when moved to the Pms1 linker. These results reveal a functional role for the intrinsically disordered region, which is conserved from yeast to humans and is mutated in cancer, suggesting that it organizes the catalytically active complex even though the required sequence can be distant from the active site. Eukaryotic DNA mismatch repair (MMR) depends on recruitment of the Mlh1-Pms1 endonuclease (human MLH1-PMS2) to mispaired DNA. Both Mlh1 and Pms1 contain a long unstructured linker that connects the N- and carboxyl-terminal domains. Here, we demonstrated the Mlh1 linker contains a conserved motif (Saccharomyces cerevisiae residues 391–415) required for MMR. The Mlh1-R401A,D403A-Pms1 linker motif mutant protein was defective for MMR and endonuclease activity in vitro, even though the conserved motif could be >750 Å from the carboxyl-terminal endonuclease active site or the N-terminal adenosine triphosphate (ATP)-binding site. Peptides encoding this motif inhibited wild-type Mlh1-Pms1 endonuclease activity. The motif functioned in vivo at different sites within the Mlh1 linker and within the Pms1 linker. Motif mutations in human cancers caused a loss-of-function phenotype when modeled in S. cerevisiae. These results suggest that the Mlh1 motif promotes the PCNA-activated endonuclease activity of Mlh1-Pms1 via interactions with DNA, PCNA, RFC, or other domains of the Mlh1-Pms1 complex.
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14
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Yang XW, Han XP, Han C, London J, Fishel R, Liu J. MutS functions as a clamp loader by positioning MutL on the DNA during mismatch repair. Nat Commun 2022; 13:5808. [PMID: 36192430 PMCID: PMC9530208 DOI: 10.1038/s41467-022-33479-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 09/20/2022] [Indexed: 11/20/2022] Open
Abstract
Highly conserved MutS and MutL homologs operate as protein dimers in mismatch repair (MMR). MutS recognizes mismatched nucleotides forming ATP-bound sliding clamps, which subsequently load MutL sliding clamps that coordinate MMR excision. Several MMR models envision static MutS-MutL complexes bound to mismatched DNA via a positively charged cleft (PCC) located on the MutL N-terminal domains (NTD). We show MutL-DNA binding is undetectable in physiological conditions. Instead, MutS sliding clamps exploit the PCC to position a MutL NTD on the DNA backbone, likely enabling diffusion-mediated wrapping of the remaining MutL domains around the DNA. The resulting MutL sliding clamp enhances MutH endonuclease and UvrD helicase activities on the DNA, which also engage the PCC during strand-specific incision/excision. These MutS clamp-loader progressions are significantly different from the replication clamp-loaders that attach the polymerase processivity factors β-clamp/PCNA to DNA, highlighting the breadth of mechanisms for stably linking crucial genome maintenance proteins onto DNA.
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Affiliation(s)
- Xiao-Wen Yang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai, 200031, China
| | - Xiao-Peng Han
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai, 200031, China
| | - Chong Han
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai, 200031, China
| | - James London
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Richard Fishel
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA.
- The Molecular Carcinogenesis and Chemoprevention Program, The James Comprehensive Cancer Center, Columbus, OH, 43210, USA.
| | - Jiaquan Liu
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai, 200031, China.
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15
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DuPrie ML, Palacio T, Calil FA, Kolodner RD, Putnam CD. Mlh1 interacts with both Msh2 and Msh6 for recruitment during mismatch repair. DNA Repair (Amst) 2022; 119:103405. [PMID: 36122480 PMCID: PMC9639671 DOI: 10.1016/j.dnarep.2022.103405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Revised: 08/30/2022] [Accepted: 09/10/2022] [Indexed: 11/29/2022]
Abstract
Eukaryotic DNA mismatch repair (MMR) initiates through mispair recognition by the MutS homologs Msh2-Msh6 and Msh2-Msh3 and subsequent recruitment of the MutL homologs Mlh1-Pms1 (human MLH1-PMS2). In bacteria, MutL is recruited by interactions with the connector domain of one MutS subunit and the ATPase and core domains of the other MutS subunit. Analysis of the S. cerevisiae and human homologs have only identified an interaction between the Msh2 connector domain and Mlh1. Here we investigated whether a conserved Msh6 ATPase/core domain-Mlh1 interaction and an Msh2-Msh6 interaction with Pms1 also act in MMR. Mutations in MLH1 affecting interactions with both the Msh2 and Msh6 interfaces caused MMR defects, whereas equivalent pms1 mutations did not cause MMR defects. Mutant Mlh1-Pms1 complexes containing Mlh1 amino acid substitutions were defective for recruitment to mispaired DNA by Msh2-Msh6, did not support MMR in reconstituted Mlh1-Pms1-dependent MMR reactions in vitro, but were proficient in Msh2-Msh6-independent Mlh1-Pms1 endonuclease activity. These results indicate that Mlh1, the common subunit of the Mlh1-Pms1, Mlh1-Mlh2, and Mlh1-Mlh3 complexes, but not Pms1, is recruited by Msh2-Msh6 through interactions with both of its subunits.
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Affiliation(s)
- Matthew L DuPrie
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660, USA
| | - Tatiana Palacio
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660, USA
| | - Felipe A Calil
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660, USA
| | - Richard D Kolodner
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660, USA; Department of Cellular and Molecular Medicine University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660, USA; Moores-UCSD Cancer Center University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660, USA; Institute of Genomic Medicine University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660, USA
| | - Christopher D Putnam
- Ludwig Institute for Cancer Research, University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660, USA; Department of Medicine University of California School of Medicine, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0660, USA.
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16
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Thakar T, Dhoonmoon A, Straka J, Schleicher EM, Nicolae CM, Moldovan GL. Lagging strand gap suppression connects BRCA-mediated fork protection to nucleosome assembly through PCNA-dependent CAF-1 recycling. Nat Commun 2022; 13:5323. [PMID: 36085347 PMCID: PMC9463168 DOI: 10.1038/s41467-022-33028-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 08/29/2022] [Indexed: 11/17/2022] Open
Abstract
The inability to protect stalled replication forks from nucleolytic degradation drives genome instability and underlies chemosensitivity in BRCA-deficient tumors. An emerging hallmark of BRCA-deficiency is the inability to suppress replication-associated single-stranded DNA (ssDNA) gaps. Here, we report that lagging strand ssDNA gaps interfere with the ASF1-CAF-1 nucleosome assembly pathway, and drive fork degradation in BRCA-deficient cells. We show that CAF-1 function at replication forks is lost in BRCA-deficient cells, due to defects in its recycling during replication stress. This CAF-1 recycling defect is caused by lagging strand gaps which preclude PCNA unloading, causing sequestration of PCNA-CAF-1 complexes on chromatin. Importantly, correcting PCNA unloading defects in BRCA-deficient cells restores CAF-1-dependent fork stability. We further show that the activation of a HIRA-dependent compensatory histone deposition pathway restores fork stability to BRCA-deficient cells. We thus define lagging strand gap suppression and nucleosome assembly as critical enablers of BRCA-mediated fork stability. Efficient DNA replication is crucial for genome stability. Here, Thakar et al. report that accumulation of lagging strand ssDNA gaps during replication interferes with nucleosome assembly and drives replication fork degradation in BRCA-deficient cells.
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Affiliation(s)
- Tanay Thakar
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - Ashna Dhoonmoon
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - Joshua Straka
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - Emily M Schleicher
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - Claudia M Nicolae
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - George-Lucian Moldovan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA.
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17
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Meas R, Nititham J, Taylor KE, Maher S, Clairmont K, Carufe KEW, Kashgarian M, Nottoli T, Cheong A, Nagel ZD, Gaffney PM, Criswell LA, Sweasy JB. A Human MSH6 Germline Variant Associated With Systemic Lupus Erythematosus Induces Lupus-like Disease in Mice. ACR Open Rheumatol 2022; 4:760-770. [PMID: 35708944 PMCID: PMC9469486 DOI: 10.1002/acr2.11471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 02/09/2022] [Accepted: 02/22/2022] [Indexed: 01/28/2023] Open
Abstract
OBJECTIVE To determine if single-nucleotide polymorphisms (SNPs) in DNA repair genes are enriched in individuals with systemic lupus erythematosus (SLE) and if they are sufficient to confer a disease phenotype in a mouse model. METHODS Human exome chip data of 2499 patients with SLE and 1230 healthy controls were analyzed to determine if variants in 10 different mismatch repair genes (MSH4, EXO1, MSH2, MSH6, MLH1, MSH3, POLH, PMS2, ML3, and APEX2) were enriched in individuals with SLE. A mouse model of the MSH6 SNP, which was found to be enriched in individuals with SLE, was created using CRISPR/Cas9 gene targeting. Wildtype mice and mice heterozygous and homozygous for the MSH6 variant were then monitored for 2 years for the development of autoimmune phenotypes, including the presence of high levels of antinuclear antibodies (ANA). Additionally, somatic hypermutation frequencies and spectra of the intronic region downstream of the VH J558-rearranged JH4 immunoglobulin gene was characterized from Peyer's patches. RESULTS Based on the human exome chip data, the MSH6 variant (rs63750897, p.Ser503Cys) is enriched among patients with SLE versus controls after we corrected for ancestry (odds ratio = 8.39, P = 0.0398). Mice homozygous for the MSH6 variant (Msh6S502C/S502C ) harbor significantly increased levels of ANA. Additionally, the Msh6S502C/S502C mice display a significant increase in the infiltration of CD68+ cells (a marker for monocytes and macrophages) into the lung alveolar space as well as apoptotic cells. Furthermore, characterization of somatic hypermutation in these mice reveals an increase in the DNA polymerase η mutational signature. CONCLUSION An MSH6 mutation that is enriched in humans diagnosed with lupus was identified. Mice harboring this Msh6 mutation develop increased autoantibodies and an inflammatory lung disease. These results suggest that the human MSH6 variant is linked to the development of SLE.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Ana Cheong
- Harvard School of Public HealthBostonMassachusettsUSA
| | | | | | - Lindsey A. Criswell
- National Institute of Arthritis and Musculoskeletal and Skin DiseasesBethesdaMarylandUSA
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18
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Wang S, Lee K, Gray S, Zhang Y, Tang C, Morrish R, Tosti E, van Oers J, Amin MR, Cohen P, MacCarthy T, Roa S, Scharff M, Edelmann W, Chahwan R. Role of EXO1 nuclease activity in genome maintenance, the immune response and tumor suppression in Exo1D173A mice. Nucleic Acids Res 2022; 50:8093-8106. [PMID: 35849338 PMCID: PMC9371890 DOI: 10.1093/nar/gkac616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Revised: 05/30/2022] [Accepted: 06/30/2022] [Indexed: 11/14/2022] Open
Abstract
DNA damage response pathways rely extensively on nuclease activity to process DNA intermediates. Exonuclease 1 (EXO1) is a pleiotropic evolutionary conserved DNA exonuclease involved in various DNA repair pathways, replication, antibody diversification, and meiosis. But, whether EXO1 facilitates these DNA metabolic processes through its enzymatic or scaffolding functions remains unclear. Here, we dissect the contribution of EXO1 enzymatic versus scaffolding activity by comparing Exo1DA/DA mice expressing a proven nuclease-dead mutant form of EXO1 to entirely EXO1-deficient Exo1-/- and EXO1 wild type Exo1+/+ mice. We show that Exo1DA/DA and Exo1-/- mice are compromised in canonical DNA repair processing, suggesting that the EXO1 enzymatic role is important for error-free DNA mismatch and double-strand break repair pathways. However, in non-canonical repair pathways, EXO1 appears to have a more nuanced function. Next-generation sequencing of heavy chain V region in B cells showed the mutation spectra of Exo1DA/DA mice to be intermediate between Exo1+/+ and Exo1-/- mice, suggesting that both catalytic and scaffolding roles of EXO1 are important for somatic hypermutation. Similarly, while overall class switch recombination in Exo1DA/DA and Exo1-/- mice was comparably defective, switch junction analysis suggests that EXO1 might fulfill an additional scaffolding function downstream of class switching. In contrast to Exo1-/- mice that are infertile, meiosis progressed normally in Exo1DA/DA and Exo1+/+ cohorts, indicating that a structural but not the nuclease function of EXO1 is critical for meiosis. However, both Exo1DA/DA and Exo1-/- mice displayed similar mortality and cancer predisposition profiles. Taken together, these data demonstrate that EXO1 has both scaffolding and enzymatic functions in distinct DNA repair processes and suggest a more composite and intricate role for EXO1 in DNA metabolic processes and disease.
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Affiliation(s)
- Shanzhi Wang
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, NY 10461, USA
- Current position: Department of Chemistry, University of Arkansas at Little Rock, Little Rock, AR 72204, USA
| | - Kyeryoung Lee
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, NY 10461, USA
| | - Stephen Gray
- Department of Biomedical Sciences, Cornell University, NY 14853, USA
- Current position: School of Life Sciences, University of Nottingham, Nottingham NG7 2UH, UK
| | - Yongwei Zhang
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, NY 10461, USA
| | - Catherine Tang
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY, USA
| | - Rikke B Morrish
- Current position: School of Physics and Astronomy, University of Exeter, Exeter EX4 4QD, UK
| | - Elena Tosti
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, NY 10461, USA
| | - Johanna van Oers
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, NY 10461, USA
| | - Mohammad Ruhul Amin
- Department of Computer and Information Science, Fordham University, Bronx, NY, USA
| | - Paula E Cohen
- Department of Biomedical Sciences, Cornell University, NY 14853, USA
| | - Thomas MacCarthy
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY, USA
| | - Sergio Roa
- Department of Biochemistry and Genetics, University of Navarra, 31008Pamplona, Spain
- Centro de Investigacion Biomedica en Red de Cancer (CIBERONC), Instituto de Salud Carlos III, Madrid, Spain
- Navarra Institute for Health Research (IdiSNA), Pamplona, Spain
| | - Matthew D Scharff
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, NY 10461, USA
| | - Winfried Edelmann
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, NY 10461, USA
| | - Richard Chahwan
- Institute of Experimental Immunology, University of Zurich, Zurich 8057, Switzerland
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19
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Fukushima R, Suzuki T, Komatsu Y, Kamiya H. Biased distribution of action-at-a-distance mutations by 8-oxo-7,8-dihydroguanine. Mutat Res 2022; 825:111794. [PMID: 36027647 DOI: 10.1016/j.mrfmmm.2022.111794] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 07/22/2022] [Accepted: 08/08/2022] [Indexed: 06/15/2023]
Abstract
8-Oxo-7,8-dihydroguanine (8-hydroxyguanine, G°) is a major oxidized base that is considered to play pivotal roles in the pathogenesis of various diseases, including cancer. G° induces G:C → T:A transversions at the damage site and untargeted (action-at-a-distance) mutations of G bases at 5'-GpA sequences. In this study, we examined the distribution of the action-at-a-distance mutations and the effects of the replication origin position relative to G° on the untargeted mutagenesis. The G° base was introduced into two shuttle plasmids, each with the SV40 replication origin at a different position with respect to the supF gene. The oxidized base was located at an upstream or downstream site (outside of the gene), or the center of the region encoding the pre-tRNA sequence of the gene, in the sense strand. These shuttle plasmids were introduced into human U2OS cells. The action-at-a-distance mutations were more frequently induced when the G° base was located downstream of the supF gene than upstream of the gene. In addition, more action-at-a-distance mutations were observed when the SV40 origin was present on the 5'-side of the G° base. These results indicated that the action-at-a-distance mutations are predominantly induced on the 5'-side of the lesion and occurred more frequently when the damaged base was located on the lagging strand template.
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Affiliation(s)
- Ruriko Fukushima
- Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan
| | - Tetsuya Suzuki
- Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
| | - Yasuo Komatsu
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 2-17-2-1 Tsukisamu-Higashi, Toyohira-ku, Sapporo 062-8517, Japan
| | - Hiroyuki Kamiya
- Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
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20
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Xie H, Wang W, Qi W, Jin W, Xia B. Targeting DNA Repair Response Promotes Immunotherapy in Ovarian Cancer: Rationale and Clinical Application. Front Immunol 2021; 12:661115. [PMID: 34712221 PMCID: PMC8546337 DOI: 10.3389/fimmu.2021.661115] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 09/22/2021] [Indexed: 01/21/2023] Open
Abstract
Immune checkpoint inhibitors (ICI) have emerged as a powerful oncologic treatment modality for patients with different solid tumors. Unfortunately, the efficacy of ICI monotherapy in ovarian cancer is limited, and combination therapy provides a new opportunity for immunotherapy in ovarian cancer. DNA damage repair (DDR) pathways play central roles in the maintenance of genomic integrity and promote the progression of cancer. A deficiency in DDR genes can cause different degrees of DNA damage that enhance local antigen release, resulting in systemic antitumor immune responses. Thus, the combination of DDR inhibitors with ICI represents an attractive therapeutic strategy with the potential to improve the clinical outcomes of patients with ovarian cancer. In this review, we provide an overview of the interconnectivity between DDR pathway deficiency and immune response, summarize available clinical trials on the combination therapy in ovarian cancer, and discuss the potential predictive biomarkers that can be utilized to guide the use of combination therapy.
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Affiliation(s)
- Hongyu Xie
- Clinical Research Center, Women’s Hospital School of Medicine Zhejiang University, Hangzhou, China
- Department of Gynecology Oncology, Harbin Medical University Cancer Hospital, Harbin, China
| | - Wenjie Wang
- Department of Epidemiology and Biostatistics, School of Public Health, Harbin Medical University, Harbin, China
| | - Wencai Qi
- Department of Gynecology Oncology, Division of Life Sciences and Medicine, The First Affiliated Hospital of University of Science and Technology, Hefei, China
| | - Weilin Jin
- Institute of Cancer Neuroscience, Medical Frontier Innovation Research Center, The First Hospital of Lanzhou University, The First Clinical Medical College of Lanzhou University, Lanzhou, China
| | - Bairong Xia
- Department of Gynecology Oncology, Division of Life Sciences and Medicine, The First Affiliated Hospital of University of Science and Technology, Hefei, China
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21
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Rad27 and Exo1 function in different excision pathways for mismatch repair in Saccharomyces cerevisiae. Nat Commun 2021; 12:5568. [PMID: 34552065 PMCID: PMC8458276 DOI: 10.1038/s41467-021-25866-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 08/31/2021] [Indexed: 11/20/2022] Open
Abstract
Eukaryotic DNA Mismatch Repair (MMR) involves redundant exonuclease 1 (Exo1)-dependent and Exo1-independent pathways, of which the Exo1-independent pathway(s) is not well understood. The exo1Δ440-702 mutation, which deletes the MutS Homolog 2 (Msh2) and MutL Homolog 1 (Mlh1) interacting peptides (SHIP and MIP boxes, respectively), eliminates the Exo1 MMR functions but is not lethal in combination with rad27Δ mutations. Analyzing the effect of different combinations of the exo1Δ440-702 mutation, a rad27Δ mutation and the pms1-A99V mutation, which inactivates an Exo1-independent MMR pathway, demonstrated that each of these mutations inactivates a different MMR pathway. Furthermore, it was possible to reconstitute a Rad27- and Msh2-Msh6-dependent MMR reaction in vitro using a mispaired DNA substrate and other MMR proteins. Our results demonstrate Rad27 defines an Exo1-independent eukaryotic MMR pathway that is redundant with at least two other MMR pathways. Defects in DNA mismatch repair (MMR) have been linked to inherited and sporadic cancers. Here the authors demonstrate that the DNA repair protein Rad27 (human FEN1) functions in one of three redundant mispair excision pathways, where its flap endonuclease activity catalyzes mispair excision.
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22
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Furman CM, Wang TY, Zhao Q, Yugandhar K, Yu H, Alani E. Handcuffing intrinsically disordered regions in Mlh1-Pms1 disrupts mismatch repair. Nucleic Acids Res 2021; 49:9327-9341. [PMID: 34390347 PMCID: PMC8450099 DOI: 10.1093/nar/gkab694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 07/19/2021] [Accepted: 07/28/2021] [Indexed: 12/02/2022] Open
Abstract
The DNA mismatch repair (MMR) factor Mlh1–Pms1 contains long intrinsically disordered regions (IDRs) whose exact functions remain elusive. We performed cross-linking mass spectrometry to identify interactions within Mlh1–Pms1 and used this information to insert FRB and FKBP dimerization domains into their IDRs. Baker's yeast strains bearing these constructs were grown with rapamycin to induce dimerization. A strain containing FRB and FKBP domains in the Mlh1 IDR displayed a complete defect in MMR when grown with rapamycin. but removing rapamycin restored MMR functions. Strains in which FRB was inserted into the IDR of one MLH subunit and FKBP into the other subunit were also MMR defective. The MLH complex containing FRB and FKBP domains in the Mlh1 IDR displayed a rapamycin-dependent defect in Mlh1–Pms1 endonuclease activity. In contrast, linking the Mlh1 and Pms1 IDRs through FRB-FKBP dimerization inappropriately activated Mlh1–Pms1 endonuclease activity. We conclude that dynamic and coordinated rearrangements of the MLH IDRs both positively and negatively regulate how the MLH complex acts in MMR. The application of the FRB-FKBP dimerization system to interrogate in vivo functions of a critical repair complex will be useful for probing IDRs in diverse enzymes and to probe transient loss of MMR on demand.
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Affiliation(s)
- Christopher M Furman
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Ting-Yi Wang
- Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
| | - Qiuye Zhao
- Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
| | - Kumar Yugandhar
- Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
| | - Haiyuan Yu
- Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
| | - Eric Alani
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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23
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Su J, Xu R, Mongia P, Toyofuku N, Nakagawa T. Fission yeast Rad8/HLTF facilitates Rad52-dependent chromosomal rearrangements through PCNA lysine 107 ubiquitination. PLoS Genet 2021; 17:e1009671. [PMID: 34292936 PMCID: PMC8297803 DOI: 10.1371/journal.pgen.1009671] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 06/18/2021] [Indexed: 11/19/2022] Open
Abstract
Gross chromosomal rearrangements (GCRs), including translocation, deletion, and inversion, can cause cell death and genetic diseases such as cancer in multicellular organisms. Rad51, a DNA strand exchange protein, suppresses GCRs by repairing spontaneous DNA damage through a conservative way of homologous recombination, gene conversion. On the other hand, Rad52 that catalyzes single-strand annealing (SSA) causes GCRs using homologous sequences. However, the detailed mechanism of Rad52-dependent GCRs remains unclear. Here, we provide genetic evidence that fission yeast Rad8/HLTF facilitates Rad52-dependent GCRs through the ubiquitination of lysine 107 (K107) of PCNA, a DNA sliding clamp. In rad51Δ cells, loss of Rad8 eliminated 75% of the isochromosomes resulting from centromere inverted repeat recombination, showing that Rad8 is essential for the formation of the majority of isochromosomes in rad51Δ cells. Rad8 HIRAN and RING finger mutations reduced GCRs, suggesting that Rad8 facilitates GCRs through 3’ DNA-end binding and ubiquitin ligase activity. Mms2 and Ubc4 but not Ubc13 ubiquitin-conjugating enzymes were required for GCRs. Consistent with this, mutating PCNA K107 rather than the well-studied PCNA K164 reduced GCRs. Rad8-dependent PCNA K107 ubiquitination facilitates Rad52-dependent GCRs, as PCNA K107R, rad8, and rad52 mutations epistatically reduced GCRs. In contrast to GCRs, PCNA K107R did not significantly change gene conversion rates, suggesting a specific role of PCNA K107 ubiquitination in GCRs. PCNA K107R enhanced temperature-sensitive growth defects of DNA ligase I cdc17-K42 mutant, implying that PCNA K107 ubiquitination occurs when Okazaki fragment maturation fails. Remarkably, K107 is located at the interface between PCNA subunits, and an interface mutation D150E bypassed the requirement of PCNA K107 and Rad8 ubiquitin ligase for GCRs. These data suggest that Rad8-dependent PCNA K107 ubiquitination facilitates Rad52-dependent GCRs by changing the PCNA clamp structure. Gross chromosomal rearrangements (GCRs), including translocation, can alter gene dosage and activity, resulting in genetic diseases such as cancer. However, GCRs can occur by some enzymes, including Rad52 recombinase, and result in chromosomal evolution. Therefore, GCRs are not only pathological but also physiological phenomena from an evolutionary point of view. However, the detailed mechanism of GCRs remains unclear. Here, using fission yeast, we show that the homolog of human HLTF, Rad8 causes GCRs through noncanonical ubiquitination of proliferating cellular nuclear antigen (PCNA) at a lysine 107 (K107). Rad51, a DNA strand exchange protein, suppresses the formation of isochromosomes whose arms mirror each another and chromosomal truncation. We found that, like Rad52, Rad8 is required for isochromosome formation but not chromosomal truncation in rad51Δ cells, showing a specific role of Rad8 in homology-mediated GCRs. Mutations in Rad8 ubiquitin E3 ligase RING finger domain, Mms2-Ubc4 ubiquitin-conjugating enzymes, and PCNA K107 reduced GCRs in rad51Δ cells, suggesting that Rad8-Mms2-Ubc4-dependent PCNA K107 ubiquitination facilitates GCRs. PCNA trimers form a DNA sliding clamp. The K107 residue is located at the PCNA-PCNA interface, and an interface mutation D150E restored GCRs in PCNA K107R mutant cells. This study provides genetic evidence that Rad8-dependent PCNA K107 ubiquitination facilitates GCRs by changing the PCNA clamp structure.
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Affiliation(s)
- Jie Su
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Japan
| | - Ran Xu
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Japan
| | - Piyusha Mongia
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Japan
| | - Naoko Toyofuku
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Japan
| | - Takuro Nakagawa
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Japan
- * E-mail:
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24
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Strand discrimination in DNA mismatch repair. DNA Repair (Amst) 2021; 105:103161. [PMID: 34171627 DOI: 10.1016/j.dnarep.2021.103161] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 06/15/2021] [Accepted: 06/16/2021] [Indexed: 11/24/2022]
Abstract
DNA mismatch repair (MMR) corrects non-Watson-Crick basepairs generated by replication errors, recombination intermediates, and some forms of chemical damage to DNA. In MutS and MutL homolog-dependent MMR, damaged bases do not identify the error-containing daughter strand that must be excised and resynthesized. In organisms like Escherichia coli that use methyl-directed MMR, transient undermethylation identifies the daughter strand. For other organisms, growing in vitro and in vivo evidence suggest that strand discrimination is mediated by DNA replication-associated daughter strand nicks that direct asymmetric loading of the replicative clamp (the β-clamp in bacteria and the proliferating cell nuclear antigen, PCNA, in eukaryotes). Structural modeling suggests that replicative clamps mediate strand specificity either through the ability of MutL homologs to recognize the fixed orientation of the daughter strand relative to one face of the replicative clamps or through parental strand-specific diffusion of replicative clamps on DNA, which places the daughter strand in the MutL homolog endonuclease active site. Finally, identification of bacteria that appear to lack strand discrimination mediated by a replicative clamp and a pre-existing nick suggest that other strand discrimination mechanisms exist or that these organisms perform MMR by generating a double-stranded DNA break intermediate, which may be analogous to NucS-mediated MMR.
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25
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Elez M. Mismatch Repair: From Preserving Genome Stability to Enabling Mutation Studies in Real-Time Single Cells. Cells 2021; 10:cells10061535. [PMID: 34207040 PMCID: PMC8235422 DOI: 10.3390/cells10061535] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 06/11/2021] [Accepted: 06/15/2021] [Indexed: 12/18/2022] Open
Abstract
Mismatch Repair (MMR) is an important and conserved keeper of the maintenance of genetic information. Miroslav Radman's contributions to the field of MMR are multiple and tremendous. One of the most notable was to provide, along with Bob Wagner and Matthew Meselson, the first direct evidence for the existence of the methyl-directed MMR. The purpose of this review is to outline several aspects and biological implications of MMR that his work has helped unveil, including the role of MMR during replication and recombination editing, and the current understanding of its mechanism. The review also summarizes recent discoveries related to the visualization of MMR components and discusses how it has helped shape our understanding of the coupling of mismatch recognition to replication. Finally, the author explains how visualization of MMR components has paved the way to the study of spontaneous mutations in living cells in real time.
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Affiliation(s)
- Marina Elez
- Micalis Institute, INRAE, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France;
- Laboratoire Jean Perrin (LJP), Institut de Biologie Paris-Seine (IBPS), CNRS, Sorbonne Université, F-75005 Paris, France
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26
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Ortega J, Lee GS, Gu L, Yang W, Li GM. Mispair-bound human MutS-MutL complex triggers DNA incisions and activates mismatch repair. Cell Res 2021; 31:542-553. [PMID: 33510387 PMCID: PMC8089094 DOI: 10.1038/s41422-021-00468-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 12/17/2020] [Indexed: 01/30/2023] Open
Abstract
DNA mismatch repair (MMR) relies on MutS and MutL ATPases for mismatch recognition and strand-specific nuclease recruitment to remove mispaired bases in daughter strands. However, whether the MutS-MutL complex coordinates MMR by ATP-dependent sliding on DNA or protein-protein interactions between the mismatch and strand discrimination signal is ambiguous. Using functional MMR assays and systems preventing proteins from sliding, we show that sliding of human MutSα is required not for MMR initiation, but for final mismatch removal. MutSα recruits MutLα to form a mismatch-bound complex, which initiates MMR by nicking the daughter strand 5' to the mismatch. Exonuclease 1 (Exo1) is then recruited to the nick and conducts 5' → 3' excision. ATP-dependent MutSα dissociation from the mismatch is necessary for Exo1 to remove the mispaired base when the excision reaches the mismatch. Therefore, our study has resolved a long-standing puzzle, and provided new insights into the mechanism of MMR initiation and mispair removal.
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Affiliation(s)
- Janice Ortega
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Grace Sanghee Lee
- Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, KY USA ,Present Address: Division of Viral Hepatitis, National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Liya Gu
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Wei Yang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD USA
| | - Guo-Min Li
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX USA ,Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, KY USA
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27
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Zhou CS, Feng MT, Chen X, Gao Y, Chen L, Li LD, Li DH, Cao YQ. Exonuclease 1 (EXO1) is a Potential Prognostic Biomarker and Correlates with Immune Infiltrates in Lung Adenocarcinoma. Onco Targets Ther 2021; 14:1033-1048. [PMID: 33623391 PMCID: PMC7894803 DOI: 10.2147/ott.s286274] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 01/16/2021] [Indexed: 12/16/2022] Open
Abstract
Background Exonuclease 1 (EXO1) has been identified to be highly expressed in different human malignancies, but its expression and prognostic role in lung adenocarcinoma (LUAD) remain unknown. Materials and Methods Two independent cohorts extracted from public databases and one cohort from our center were analyzed in this study. Expression levels of EXO1 in LUAD tissues and paired para-cancer tissues were detected. The prognostic value of EXO1 in LUAD patients was evaluated in the three cohorts. Enrichment analyses were performed to explore the possible underlying biological pathways. Moreover, we also explored the correlations between EXO1 and tumor-infiltrating immune cells and evaluated the impact of EXO1 knock-down on the migration of lung cancer cells. Results In this study, we found that EXO1 was highly expressed in LUAD tissues compared with para-cancerous tissues in public databases (p < 0.01), which was consistent with our data (p < 0.01). Survival analysis indicated that high expression of EXO1 was associated with poor prognosis in LUAD (p < 0.01). Enrichment analyses indicated that biological pathways like cell cycle regulation, DNA damage and repair, immune response, neuroactive ligand-receptor interaction, may be associated with EXO1 aberrant expression. Moreover, high expression of EXO1 was correlated with decreased infiltrating B cells (p < 0.01) and CD4+ T cells (p < 0.01) levels, and low infiltrating levels of B cells (p < 0.01) and dendritic cells (DCs) (p < 0.05) indicated poor overall survival (OS) in LUAD. Additionally, in vitro experiments suggested that knockdown of EXO1 may inhibit the migratory ability of lung cancer cells. Conclusion In conclusion, EXO1 is a potential prognostic biomarker in LUAD, and correlates with infiltrating levels of immune cells in the tumor microenvironment. Further prospective validation of EXO1 in lung cancer is warranted.
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Affiliation(s)
- Chang-Shuai Zhou
- Department of Neurosurgery, Fudan University Shanghai Cancer Center, Shanghai, People's Republic of China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China
| | - Ming-Tao Feng
- Department of Neurosurgery, Fudan University Shanghai Cancer Center, Shanghai, People's Republic of China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China
| | - Xin Chen
- Department of Neurosurgery, Fudan University Shanghai Cancer Center, Shanghai, People's Republic of China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China
| | - Yang Gao
- Department of Neurosurgery, Fudan University Shanghai Cancer Center, Shanghai, People's Republic of China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China
| | - Lei Chen
- Department of Neurosurgery, Fudan University Shanghai Cancer Center, Shanghai, People's Republic of China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China
| | - Liang-Dong Li
- Department of Neurosurgery, Fudan University Shanghai Cancer Center, Shanghai, People's Republic of China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China
| | - De-Heng Li
- Department of Neurosurgery, Fudan University Shanghai Cancer Center, Shanghai, People's Republic of China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China
| | - Yi-Qun Cao
- Department of Neurosurgery, Fudan University Shanghai Cancer Center, Shanghai, People's Republic of China.,Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China
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28
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Reyes GX, Kolodziejczak A, Devakumar LJPS, Kubota T, Kolodner RD, Putnam CD, Hombauer H. Ligation of newly replicated DNA controls the timing of DNA mismatch repair. Curr Biol 2021; 31:1268-1276.e6. [PMID: 33417883 PMCID: PMC8281387 DOI: 10.1016/j.cub.2020.12.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 11/10/2020] [Accepted: 12/14/2020] [Indexed: 11/23/2022]
Abstract
Mismatch repair (MMR) safeguards genome stability through recognition and excision of DNA replication errors.1–4 How eukaryotic MMR targets the newly replicated strand in vivo has not been established. MMR reactions reconstituted in vitro are directed to the strand containing a preexisting nick or gap,5–8 suggesting that strand discontinuities could act as discrimination signals. Another candidate is the proliferating cell nuclear antigen (PCNA) that is loaded at replication forks and is required for the activation of Mlh1-Pms1 endonuclease.7–9 Here, we discovered that overexpression of DNA ligase I (Cdc9) in Saccharomyces cerevisiae causes elevated mutation rates and increased chromatin-bound PCNA levels and accumulation of Pms1 foci that are MMR intermediates, suggesting that premature ligation of replication-associated nicks interferes with MMR. We showed that yeast Pms1 expression is mainly restricted to S phase, in agreement with the temporal coupling between MMR and DNA replication.10 Restricting Pms1 expression to the G2/M phase caused a mutator phenotype that was exacerbated in the absence of the exonuclease Exo1. This mutator phenotype was largely suppressed by increasing the lifetime of replication-associated DNA nicks, either by reducing or delaying Cdc9 ligase activity in vivo. Therefore, Cdc9 dictates a window of time for MMR determined by transient DNA nicks that direct the Mlh1-Pms1 in a strand-specific manner. Because DNA nicks occur on both newly synthesized leading and lagging strands,11 these results establish a general mechanism for targeting MMR to the newly synthesized DNA, thus preventing the accumulation of mutations that underlie the development of human cancer. The correction of DNA replication errors by the mismatch repair (MMR) machinery requires the discrimination between parental and daughter DNA strands. Reyes et al. provide evidence that DNA replication-associated nicks are used as MMR strand discrimination signals and that DNA ligase I (Cdc9) activity dictates a window of time for MMR.
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Affiliation(s)
- Gloria X Reyes
- DNA Repair Mechanisms and Cancer, German Cancer Research Center (DKFZ), Heidelberg 69120, Germany
| | - Anna Kolodziejczak
- DNA Repair Mechanisms and Cancer, German Cancer Research Center (DKFZ), Heidelberg 69120, Germany; Faculty of Bioscience, Heidelberg University, Heidelberg 69120, Germany
| | - Lovely Jael Paul Solomon Devakumar
- Institute of Medical Sciences, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Foresterhill, Aberdeen, Scotland AB25 2ZD, UK
| | - Takashi Kubota
- Institute of Medical Sciences, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Foresterhill, Aberdeen, Scotland AB25 2ZD, UK
| | - Richard D Kolodner
- Ludwig Institute for Cancer Research, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0669, USA; Department of Cellular and Molecular Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0669, USA; Moores Cancer Center at UC San Diego Health, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0669, USA; Institute of Genomic Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0669, USA
| | - Christopher D Putnam
- Ludwig Institute for Cancer Research, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0669, USA; Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093-0669, USA
| | - Hans Hombauer
- DNA Repair Mechanisms and Cancer, German Cancer Research Center (DKFZ), Heidelberg 69120, Germany; Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Heidelberg 69120, Germany.
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29
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Identification of MLH2/hPMS1 dominant mutations that prevent DNA mismatch repair function. Commun Biol 2020; 3:751. [PMID: 33303966 PMCID: PMC7730388 DOI: 10.1038/s42003-020-01481-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 11/11/2020] [Indexed: 12/27/2022] Open
Abstract
Inactivating mutations affecting key mismatch repair (MMR) components lead to microsatellite instability (MSI) and cancer. However, a number of patients with MSI-tumors do not present alterations in classical MMR genes. Here we discovered that specific missense mutations in the MutL homolog MLH2, which is dispensable for MMR, confer a dominant mutator phenotype in S. cerevisiae. MLH2 mutations elevated frameshift mutation rates, and caused accumulation of long-lasting nuclear MMR foci. Both aspects of this phenotype were suppressed by mutations predicted to prevent the binding of Mlh2 to DNA. Genetic analysis revealed that mlh2 dominant mutations interfere with both Exonuclease 1 (Exo1)-dependent and Exo1-independent MMR. Lastly, we demonstrate that a homolog mutation in human hPMS1 results in a dominant mutator phenotype. Our data support a model in which yeast Mlh1-Mlh2 or hMLH1-hPMS1 mutant complexes act as roadblocks on DNA preventing MMR, unraveling a novel mechanism that can account for MSI in human cancer.
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30
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Liu Q, Zhu X, Lindström M, Shi Y, Zheng J, Hao X, Gustafsson CM, Liu B. Yeast mismatch repair components are required for stable inheritance of gene silencing. PLoS Genet 2020; 16:e1008798. [PMID: 32469861 PMCID: PMC7286534 DOI: 10.1371/journal.pgen.1008798] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 06/10/2020] [Accepted: 04/26/2020] [Indexed: 11/19/2022] Open
Abstract
Alterations in epigenetic silencing have been associated with ageing and tumour formation. Although substantial efforts have been made towards understanding the mechanisms of gene silencing, novel regulators in this process remain to be identified. To systematically search for components governing epigenetic silencing, we developed a genome-wide silencing screen for yeast (Saccharomyces cerevisiae) silent mating type locus HMR. Unexpectedly, the screen identified the mismatch repair (MMR) components Pms1, Mlh1, and Msh2 as being required for silencing at this locus. We further found that the identified genes were also required for proper silencing in telomeres. More intriguingly, the MMR mutants caused a redistribution of Sir2 deacetylase, from silent mating type loci and telomeres to rDNA regions. As a consequence, acetylation levels at histone positions H3K14, H3K56, and H4K16 were increased at silent mating type loci and telomeres but were decreased in rDNA regions. Moreover, knockdown of MMR components in human HEK293T cells increased subtelomeric DUX4 gene expression. Our work reveals that MMR components are required for stable inheritance of gene silencing patterns and establishes a link between the MMR machinery and the control of epigenetic silencing.
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Affiliation(s)
- Qian Liu
- Department of Chemistry and Molecular Biology, University of Gothenburg, Medicinaregatan, Goteborg, Sweden
| | - Xuefeng Zhu
- Institute of Biomedicine, University of Gothenburg, Goteborg, Sweden
- * E-mail: (XZ); (BL)
| | - Michelle Lindström
- Department of Chemistry and Molecular Biology, University of Gothenburg, Medicinaregatan, Goteborg, Sweden
| | - Yonghong Shi
- Institute of Biomedicine, University of Gothenburg, Goteborg, Sweden
| | - Ju Zheng
- Department of Chemistry and Molecular Biology, University of Gothenburg, Medicinaregatan, Goteborg, Sweden
- Department of Biology, Functional Biology, KU Leuven, Heverlee, Belgium
| | - Xinxin Hao
- Department of Chemistry and Molecular Biology, University of Gothenburg, Medicinaregatan, Goteborg, Sweden
| | | | - Beidong Liu
- Department of Chemistry and Molecular Biology, University of Gothenburg, Medicinaregatan, Goteborg, Sweden
- Center for Large-scale cell-based screening, Faculty of Science, University of Gothenburg, Medicinaregatan, Goteborg, Sweden
- * E-mail: (XZ); (BL)
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31
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Paul Solomon Devakumar LJ, Gaubitz C, Lundblad V, Kelch BA, Kubota T. Effective mismatch repair depends on timely control of PCNA retention on DNA by the Elg1 complex. Nucleic Acids Res 2020; 47:6826-6841. [PMID: 31114918 PMCID: PMC6648347 DOI: 10.1093/nar/gkz441] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 05/06/2019] [Accepted: 05/09/2019] [Indexed: 11/14/2022] Open
Abstract
Proliferating cell nuclear antigen (PCNA) is a sliding clamp that acts as a central co-ordinator for mismatch repair (MMR) as well as DNA replication. Loss of Elg1, the major subunit of the PCNA unloader complex, causes over-accumulation of PCNA on DNA and also increases mutation rate, but it has been unclear if the two effects are linked. Here we show that timely removal of PCNA from DNA by the Elg1 complex is important to prevent mutations. Although premature unloading of PCNA generally increases mutation rate, the mutator phenotype of elg1Δ is attenuated by PCNA mutants PCNA-R14E and PCNA-D150E that spontaneously fall off DNA. In contrast, the elg1Δ mutator phenotype is exacerbated by PCNA mutants that accumulate on DNA due to enhanced electrostatic PCNA–DNA interactions. Epistasis analysis suggests that PCNA over-accumulation on DNA interferes with both MMR and MMR-independent process(es). In elg1Δ, over-retained PCNA hyper-recruits the Msh2–Msh6 mismatch recognition complex through its PCNA-interacting peptide motif, causing accumulation of MMR intermediates. Our results suggest that PCNA retention controlled by the Elg1 complex is critical for efficient MMR: PCNA needs to be on DNA long enough to enable MMR, but if it is retained too long it interferes with downstream repair steps.
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Affiliation(s)
- Lovely Jael Paul Solomon Devakumar
- Institute of Medical Sciences, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
| | - Christl Gaubitz
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | | | - Brian A Kelch
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Takashi Kubota
- Institute of Medical Sciences, School of Medicine, Medical Sciences & Nutrition, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, Scotland, UK
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32
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Hum YF, Jinks-Robertson S. Mismatch recognition and subsequent processing have distinct effects on mitotic recombination intermediates and outcomes in yeast. Nucleic Acids Res 2019; 47:4554-4568. [PMID: 30809658 PMCID: PMC6511840 DOI: 10.1093/nar/gkz126] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 02/12/2019] [Accepted: 02/23/2019] [Indexed: 01/25/2023] Open
Abstract
The post-replicative mismatch repair (MMR) system has anti-recombination activity that limits interactions between diverged sequences by recognizing mismatches in strand-exchange intermediates. In contrast to their equivalent roles during replication-error repair, mismatch recognition is more important for anti-recombination than subsequent mismatch processing. To obtain insight into this difference, ectopic substrates with 2% sequence divergence were used to examine mitotic recombination outcome (crossover or noncrossover; CO and NCO, respectively) and to infer molecular intermediates formed during double-strand break repair in Saccharomyces cerevisiae. Experiments were performed in an MMR-proficient strain, a strain with compromised mismatch-recognition activity (msh6Δ) and a strain that retained mismatch-recognition activity but was unable to process mismatches (mlh1Δ). While the loss of either mismatch binding or processing elevated the NCO frequency to a similar extent, CO events increased only when mismatch binding was compromised. The molecular features of NCOs, however, were altered in fundamentally different ways depending on whether mismatch binding or processing was eliminated. These data suggest a model in which mismatch recognition reverses strand-exchange intermediates prior to the initiation of end extension, while subsequent mismatch processing that is linked to end extension specifically destroys NCO intermediates that contain conflicting strand-discrimination signals for mismatch removal.
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Affiliation(s)
- Yee Fang Hum
- University Program in Genetics and Genomics, Duke University, Durham, NC, USA
| | - Sue Jinks-Robertson
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA
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33
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Liu J, Lee R, Britton BM, London JA, Yang K, Hanne J, Lee JB, Fishel R. MutL sliding clamps coordinate exonuclease-independent Escherichia coli mismatch repair. Nat Commun 2019; 10:5294. [PMID: 31757945 PMCID: PMC6876574 DOI: 10.1038/s41467-019-13191-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Accepted: 10/22/2019] [Indexed: 01/09/2023] Open
Abstract
A shared paradigm of mismatch repair (MMR) across biology depicts extensive exonuclease-driven strand-specific excision that begins at a distant single-stranded DNA (ssDNA) break and proceeds back past the mismatched nucleotides. Historical reconstitution studies concluded that Escherichia coli (Ec) MMR employed EcMutS, EcMutL, EcMutH, EcUvrD, EcSSB and one of four ssDNA exonucleases to accomplish excision. Recent single-molecule images demonstrated that EcMutS and EcMutL formed cascading sliding clamps on a mismatched DNA that together assisted EcMutH in introducing ssDNA breaks at distant newly replicated GATC sites. Here we visualize the complete strand-specific excision process and find that long-lived EcMutL sliding clamps capture EcUvrD helicase near the ssDNA break, significantly increasing its unwinding processivity. EcSSB modulates the EcMutL–EcUvrD unwinding dynamics, which is rarely accompanied by extensive ssDNA exonuclease digestion. Together these observations are consistent with an exonuclease-independent MMR strand excision mechanism that relies on EcMutL–EcUvrD helicase-driven displacement of ssDNA segments between adjacent EcMutH–GATC incisions. The mechanics of MMR strand specific excision that begins at a distant ssDNA break are not yet clear. Here the authors have used multiple single molecule imaging techniques to visualize the behavior of MMR components on mismatched DNA substrates and reveal an exonuclease-independent mechanism for E.coli MMR.
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Affiliation(s)
- Jiaquan Liu
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Ryanggeun Lee
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, 37673, Korea
| | - Brooke M Britton
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - James A London
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Keunsang Yang
- School of Interdisciplinary Bioscience and Bioengineering, POSTECH, Pohang, Gyeongbuk, 37673, Korea
| | - Jeungphill Hanne
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Jong-Bong Lee
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk, 37673, Korea. .,School of Interdisciplinary Bioscience and Bioengineering, POSTECH, Pohang, Gyeongbuk, 37673, Korea.
| | - Richard Fishel
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA.
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34
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Goellner EM. Chromatin remodeling and mismatch repair: Access and excision. DNA Repair (Amst) 2019; 85:102733. [PMID: 31698199 DOI: 10.1016/j.dnarep.2019.102733] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 09/06/2019] [Accepted: 10/09/2019] [Indexed: 01/03/2023]
Abstract
DNA mismatch repair (MMR) increases replication fidelity and genome stability by correcting DNA polymerase errors that remain after replication. Defects in MMR result in the accumulation of mutations and lead to human tumor development. Germline mutations in MMR cause the hereditary cancer syndrome, Lynch syndrome. After replication, DNA is reorganized into its chromatin structure and wrapped around histone octamers. DNA MMR is thought to be less efficient in recognizing and repairing mispairs packaged in chromatin, in which case MMR must either compete for access to naked DNA before histone deposition or actively move nucleosomes to access the mispair. This article reviews studies into the mechanistic and physical interactions between MMR and various chromatin-associated factors, including the histone deposition complex CAF1. Recent Xenopus and Saccharomyces cerevisiae studies describe a physical interaction between Msh2 and chromatin-remodeling ATPase Fun30/SMARCAD1, with potential mechanistic roles for SMARCAD1 in moving histones for both mispair access and excision tract elongation. The RSC complex, another histone remodeling complex, also potentially influences excision tract length. Deletion mutations of RSC2 point to mechanistic interactions with the MMR pathways. Together, these studies paint a picture of complex interactions between MMR and the chromatin environment that will require numerous additional genetic, biochemical, and cell biology experiments to fully understand. Understanding how these pathways interconnect is essential in fully understanding eukaryotic MMR and has numerous implications in human tumor formation and treatment.
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Affiliation(s)
- Eva M Goellner
- Department of Toxicology and Cancer Biology, Markey Cancer Center, University of Kentucky College of Medicine, Lexington, KY, 40536, USA.
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35
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Schmidt TT, Sharma S, Reyes GX, Gries K, Gross M, Zhao B, Yuan JH, Wade R, Chabes A, Hombauer H. A genetic screen pinpoints ribonucleotide reductase residues that sustain dNTP homeostasis and specifies a highly mutagenic type of dNTP imbalance. Nucleic Acids Res 2019; 47:237-252. [PMID: 30462295 PMCID: PMC6326808 DOI: 10.1093/nar/gky1154] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 10/29/2018] [Indexed: 12/12/2022] Open
Abstract
The balance and the overall concentration of intracellular deoxyribonucleoside triphosphates (dNTPs) are important determinants of faithful DNA replication. Despite the established fact that changes in dNTP pools negatively influence DNA replication fidelity, it is not clear why certain dNTP pool alterations are more mutagenic than others. As intracellular dNTP pools are mainly controlled by ribonucleotide reductase (RNR), and given the limited number of eukaryotic RNR mutations characterized so far, we screened for RNR1 mutations causing mutator phenotypes in Saccharomyces cerevisiae. We identified 24 rnr1 mutant alleles resulting in diverse mutator phenotypes linked in most cases to imbalanced dNTPs. Among the identified rnr1 alleles the strongest mutators presented a dNTP imbalance in which three out of the four dNTPs were elevated (dCTP, dTTP and dGTP), particularly if dGTP levels were highly increased. These rnr1 alleles caused growth defects/lethality in DNA replication fidelity-compromised backgrounds, and caused strong mutator phenotypes even in the presence of functional DNA polymerases and mismatch repair. In summary, this study pinpoints key residues that contribute to allosteric regulation of RNR’s overall activity or substrate specificity. We propose a model that distinguishes between different dNTP pool alterations and provides a mechanistic explanation why certain dNTP imbalances are particularly detrimental.
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Affiliation(s)
- Tobias T Schmidt
- DNA Repair Mechanisms and Cancer, German Cancer Research Center (DKFZ), Heidelberg D-69120, Germany.,Faculty of Bioscience, Heidelberg University, Heidelberg D-69120, Germany
| | - Sushma Sharma
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå SE-901 87 Sweden
| | - Gloria X Reyes
- DNA Repair Mechanisms and Cancer, German Cancer Research Center (DKFZ), Heidelberg D-69120, Germany
| | - Kerstin Gries
- DNA Repair Mechanisms and Cancer, German Cancer Research Center (DKFZ), Heidelberg D-69120, Germany
| | - Maike Gross
- DNA Repair Mechanisms and Cancer, German Cancer Research Center (DKFZ), Heidelberg D-69120, Germany
| | - Boyu Zhao
- DNA Repair Mechanisms and Cancer, German Cancer Research Center (DKFZ), Heidelberg D-69120, Germany.,Faculty of Bioscience, Heidelberg University, Heidelberg D-69120, Germany
| | - Jui-Hung Yuan
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), Heidelberg D-69118, Germany
| | - Rebecca Wade
- Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), Heidelberg D-69118, Germany.,Interdisciplinary Center for Scientific Computing (IWR), Heidelberg D-69120, Germany.,Center for Molecular Biology of the University of Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Heidelberg D-69120, Germany
| | - Andrei Chabes
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå SE-901 87 Sweden.,Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå SE-901 87, Sweden
| | - Hans Hombauer
- DNA Repair Mechanisms and Cancer, German Cancer Research Center (DKFZ), Heidelberg D-69120, Germany
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36
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Tiwari V, Wilson DM. DNA Damage and Associated DNA Repair Defects in Disease and Premature Aging. Am J Hum Genet 2019; 105:237-257. [PMID: 31374202 PMCID: PMC6693886 DOI: 10.1016/j.ajhg.2019.06.005] [Citation(s) in RCA: 125] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 06/05/2019] [Indexed: 12/14/2022] Open
Abstract
Genetic information is constantly being attacked by intrinsic and extrinsic damaging agents, such as reactive oxygen species, atmospheric radiation, environmental chemicals, and chemotherapeutics. If DNA modifications persist, they can adversely affect the polymerization of DNA or RNA, leading to replication fork collapse or transcription arrest, or can serve as mutagenic templates during nucleic acid synthesis reactions. To combat the deleterious consequences of DNA damage, organisms have developed complex repair networks that remove chemical modifications or aberrant base arrangements and restore the genome to its original state. Not surprisingly, inherited or sporadic defects in DNA repair mechanisms can give rise to cellular outcomes that underlie disease and aging, such as transformation, apoptosis, and senescence. In the review here, we discuss several genetic disorders linked to DNA repair defects, attempting to draw correlations between the nature of the accumulating DNA damage and the pathological endpoints, namely cancer, neurological disease, and premature aging.
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Affiliation(s)
- Vinod Tiwari
- Laboratory of Molecular Gerontology, National Institute on Aging, Intramural Research Program, National Institutes of Health, 251 Bayview Boulevard, Suite 100, Baltimore, MD 21224, USA.
| | - David M Wilson
- Laboratory of Molecular Gerontology, National Institute on Aging, Intramural Research Program, National Institutes of Health, 251 Bayview Boulevard, Suite 100, Baltimore, MD 21224, USA.
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37
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Jiang Q, Zhang W, Liu C, Lin Y, Wu Q, Dai J. Dissecting PCNA function with a systematically designed mutant library in yeast. J Genet Genomics 2019; 46:301-313. [PMID: 31281030 DOI: 10.1016/j.jgg.2019.03.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Revised: 02/27/2019] [Accepted: 03/07/2019] [Indexed: 11/26/2022]
Abstract
Proliferating cell nuclear antigen (PCNA), encoded by POL30 in Saccharomyces cerevisiae, is a key component of DNA metabolism. Here, a library consisting of 304 PCNA mutants was designed and constructed to probe the contribution of each residue to the biological function of PCNA. Five regions with elevated sensitivity to DNA damaging reagents were identified using high-throughput phenotype screening. Using a series of genetic and biochemical analyses, we demonstrated that one particular mutant, K168A, has defects in the DNA damage tolerance (DDT) pathway by disrupting the interaction between PCNA and Rad5. Subsequent domain analysis showed that the PCNA-Rad5 interaction is a prerequisite for the function of Rad5 in DDT. Our study not only provides a resource in the form of a library of versatile mutants to study the functions of PCNA, but also reveals a key residue on PCNA (K168) which highlights the importance of the PCNA-Rad5 interaction in the template switching (TS) pathway.
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Affiliation(s)
- Qingwen Jiang
- Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China; Shenzhen Key Laboratory of Synthetic Genomics and Center for Synthetic Genomics, Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Weimin Zhang
- Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China; Shenzhen Key Laboratory of Synthetic Genomics and Center for Synthetic Genomics, Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Chenghao Liu
- Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Yicong Lin
- Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China; Shenzhen Key Laboratory of Synthetic Genomics and Center for Synthetic Genomics, Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Qingyu Wu
- Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Junbiao Dai
- Center for Synthetic and Systems Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China; Shenzhen Key Laboratory of Synthetic Genomics and Center for Synthetic Genomics, Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.
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38
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Wu R, Amin A, Wang Z, Huang Y, Man-Hei Cheung M, Yu Z, Yang W, Liang C. The interaction networks of the budding yeast and human DNA replication-initiation proteins. Cell Cycle 2019; 18:723-741. [PMID: 30890025 DOI: 10.1080/15384101.2019.1586509] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
DNA replication is a stringently regulated cellular process. In proliferating cells, DNA replication-initiation proteins (RIPs) are sequentially loaded onto replication origins during the M-to-G1 transition to form the pre-replicative complex (pre-RC), a process known as replication licensing. Subsequently, additional RIPs are recruited to form the pre-initiation complex (pre-IC). RIPs and their regulators ensure that chromosomal DNA is replicated exactly once per cell cycle. Origin recognition complex (ORC) binds to, and marks replication origins throughout the cell cycle and recruits other RIPs including Noc3p, Ipi1-3p, Cdt1p, Cdc6p and Mcm2-7p to form the pre-RC. The detailed mechanisms and regulation of the pre-RC and its exact architecture still remain unclear. In this study, pairwise protein-protein interactions among 23 budding yeast and 16 human RIPs were systematically and comprehensively examined by yeast two-hybrid analysis. This study tested 470 pairs of yeast and 196 pairs of human RIPs, from which 113 and 96 positive interactions, respectively, were identified. While many of these interactions were previously reported, some were novel, including various ORC and MCM subunit interactions, ORC self-interactions, and the interactions of IPI3 and NOC3 with several pre-RC and pre-IC proteins. Ten of the novel interactions were further confirmed by co-immunoprecipitation assays. Furthermore, we identified the conserved interaction networks between the yeast and human RIPs. This study provides a foundation and framework for further understanding the architectures, interactions and functions of the yeast and human pre-RC and pre-IC.
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Affiliation(s)
- Rentian Wu
- a Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience , Hong Kong University of Science and Technology , Hong Kong , China.,b Guangzhou HKUST Fok Ying Tung Research Institute , Guangzhou , China
| | - Aftab Amin
- a Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience , Hong Kong University of Science and Technology , Hong Kong , China.,b Guangzhou HKUST Fok Ying Tung Research Institute , Guangzhou , China.,c School of Chinese Medicine , Hong Kong Baptist University , Guangzhou , China
| | - Ziyi Wang
- a Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience , Hong Kong University of Science and Technology , Hong Kong , China
| | - Yining Huang
- a Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience , Hong Kong University of Science and Technology , Hong Kong , China
| | - Marco Man-Hei Cheung
- a Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience , Hong Kong University of Science and Technology , Hong Kong , China.,b Guangzhou HKUST Fok Ying Tung Research Institute , Guangzhou , China
| | - Zhiling Yu
- c School of Chinese Medicine , Hong Kong Baptist University , Guangzhou , China
| | - Wei Yang
- a Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience , Hong Kong University of Science and Technology , Hong Kong , China.,d Guangdong Lewwin Pharmaceutical Research Institute Co., Ltd , Hong Kong , China
| | - Chun Liang
- a Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience , Hong Kong University of Science and Technology , Hong Kong , China.,b Guangzhou HKUST Fok Ying Tung Research Institute , Guangzhou , China.,e ntelgen Limited , Hong Kong-Guangzhou-Foshan , China
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39
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Kim Y, Furman CM, Manhart CM, Alani E, Finkelstein I. Intrinsically disordered regions regulate both catalytic and non-catalytic activities of the MutLα mismatch repair complex. Nucleic Acids Res 2019; 47:1823-1835. [PMID: 30541127 PMCID: PMC6393296 DOI: 10.1093/nar/gky1244] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 11/27/2018] [Accepted: 12/05/2018] [Indexed: 12/12/2022] Open
Abstract
Intrinsically disordered regions (IDRs) are present in at least 30% of the eukaryotic proteome and are enriched in chromatin-associated proteins. Using a combination of genetics, biochemistry and single-molecule biophysics, we characterize how IDRs regulate the functions of the yeast MutLα (Mlh1-Pms1) mismatch repair (MMR) complex. Shortening or scrambling the IDRs in both subunits ablates MMR in vivo. Mlh1-Pms1 complexes with shorter IDRs that disrupt MMR retain wild-type DNA binding affinity but are impaired for diffusion on both naked and nucleosome-coated DNA. Moreover, the IDRs also regulate the adenosine triphosphate hydrolysis and nuclease activities that are encoded in the structured N- and C-terminal domains of the complex. This combination of phenotypes underlies the catastrophic MMR defect seen with the mutant MutLα in vivo. More broadly, this work highlights an unanticipated multi-functional role for IDRs in regulating both facilitated diffusion on chromatin and nucleolytic processing of a DNA substrate.
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Affiliation(s)
- Yoori Kim
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | - Christopher M Furman
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Carol M Manhart
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Eric Alani
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Ilya J Finkelstein
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
- Center for Systems and Synthetic Biology, University of Texas at Austin, Austin, TX 78712, USA
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40
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Human Exonuclease 1 (EXO1) Regulatory Functions in DNA Replication with Putative Roles in Cancer. Int J Mol Sci 2018; 20:ijms20010074. [PMID: 30585186 PMCID: PMC6337416 DOI: 10.3390/ijms20010074] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 12/12/2018] [Accepted: 12/19/2018] [Indexed: 12/11/2022] Open
Abstract
Human exonuclease 1 (EXO1), a 5'→3' exonuclease, contributes to the regulation of the cell cycle checkpoints, replication fork maintenance, and post replicative DNA repair pathways. These processes are required for the resolution of stalled or blocked DNA replication that can lead to replication stress and potential collapse of the replication fork. Failure to restart the DNA replication process can result in double-strand breaks, cell-cycle arrest, cell death, or cellular transformation. In this review, we summarize the involvement of EXO1 in the replication, DNA repair pathways, cell cycle checkpoints, and the link between EXO1 and cancer.
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41
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Kim D, Fishel R, Lee JB. Coordinating Multi-Protein Mismatch Repair by Managing Diffusion Mechanics on the DNA. J Mol Biol 2018; 430:4469-4480. [PMID: 29792877 PMCID: PMC6388638 DOI: 10.1016/j.jmb.2018.05.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 05/01/2018] [Accepted: 05/16/2018] [Indexed: 12/15/2022]
Abstract
DNA mismatch repair (MMR) corrects DNA base-pairing errors that occur during DNA replication. MMR catalyzes strand-specific DNA degradation and resynthesis by dynamic molecular coordination of sequential downstream pathways. The temporal and mechanistic order of molecular events is essential to insure interactions in MMR that occur over long distances on the DNA. Biophysical real-time studies of highly conserved components on mismatched DNA have shed light on the mechanics of MMR. Single-molecule imaging has visualized stochastically coordinated MMR interactions that are based on thermal fluctuation-driven motions. In this review, we describe the role of diffusivity and stochasticity in MMR beginning with mismatch recognition through strand-specific excision. We conclude with a perspective of the possible research directions that should solve the remaining questions in MMR.
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Affiliation(s)
- Daehyung Kim
- Department of Physics, Pohang University of Science & Technology (POSTECH), Pohang 37673, Korea
| | - Richard Fishel
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA.
| | - Jong-Bong Lee
- Department of Physics, Pohang University of Science & Technology (POSTECH), Pohang 37673, Korea; Interdisciplinary Bioscience & Bioengineering, POSTECH, Pohang 37673, Korea.
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42
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Identification of Exo1-Msh2 interaction motifs in DNA mismatch repair and new Msh2-binding partners. Nat Struct Mol Biol 2018; 25:650-659. [PMID: 30061603 DOI: 10.1038/s41594-018-0092-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 06/14/2018] [Indexed: 02/07/2023]
Abstract
Eukaryotic DNA mismatch repair (MMR) involves both exonuclease 1 (Exo1)-dependent and Exo1-independent pathways. We found that the unstructured C-terminal domain of Saccharomyces cerevisiae Exo1 contains two MutS homolog 2 (Msh2)-interacting peptide (SHIP) boxes downstream from the MutL homolog 1 (Mlh1)-interacting peptide (MIP) box. These three sites were redundant in Exo1-dependent MMR in vivo and could be replaced by a fusion protein between an N-terminal fragment of Exo1 and Msh6. The SHIP-Msh2 interactions were eliminated by the msh2M470I mutation, and wild-type but not mutant SHIP peptides eliminated Exo1-dependent MMR in vitro. We identified two S. cerevisiae SHIP-box-containing proteins and three candidate human SHIP-box-containing proteins. One of these, Fun30, had a small role in Exo1-dependent MMR in vivo. The Remodeling of the Structure of Chromatin (Rsc) complex also functioned in both Exo1-dependent and Exo1-independent MMR in vivo. Our results identified two modes of Exo1 recruitment and a peptide module that mediates interactions between Msh2 and other proteins, and they support a model in which Exo1 functions in MMR by being tethered to the Msh2-Msh6 complex.
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43
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Ohashi E, Tsurimoto T. Functions of Multiple Clamp and Clamp-Loader Complexes in Eukaryotic DNA Replication. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1042:135-162. [PMID: 29357057 DOI: 10.1007/978-981-10-6955-0_7] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Proliferating cell nuclear antigen (PCNA) and replication factor C (RFC) were identified in the late 1980s as essential factors for replication of simian virus 40 DNA in human cells, by reconstitution of the reaction in vitro. Initially, they were only thought to be involved in the elongation stage of DNA replication. Subsequent studies have demonstrated that PCNA functions as more than a replication factor, through its involvement in multiple protein-protein interactions. PCNA appears as a functional hub on replicating and replicated chromosomal DNA and has an essential role in the maintenance genome integrity in proliferating cells.Eukaryotes have multiple paralogues of sliding clamp, PCNA and its loader, RFC. The PCNA paralogues, RAD9, HUS1, and RAD1 form the heterotrimeric 9-1-1 ring that is similar to the PCNA homotrimeric ring, and the 9-1-1 clamp complex is loaded onto sites of DNA damage by its specific loader RAD17-RFC. This alternative clamp-loader system transmits DNA-damage signals in genomic DNA to the checkpoint-activation network and the DNA-repair apparatus.Another two alternative loader complexes, CTF18-RFC and ELG1-RFC, have roles that are distinguishable from the role of the canonical loader, RFC. CTF18-RFC interacts with one of the replicative DNA polymerases, Polε, and loads PCNA onto leading-strand DNA, and ELG1-RFC unloads PCNA after ligation of lagging-strand DNA. In the progression of S phase, these alternative PCNA loaders maintain appropriate amounts of PCNA on the replicating sister DNAs to ensure that specific enzymes are tethered at specific chromosomal locations.
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Affiliation(s)
- Eiji Ohashi
- Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan
| | - Toshiki Tsurimoto
- Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.
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44
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Kondratick CM, Litman JM, Shaffer KV, Washington MT, Dieckman LM. Crystal structures of PCNA mutant proteins defective in gene silencing suggest a novel interaction site on the front face of the PCNA ring. PLoS One 2018; 13:e0193333. [PMID: 29499038 PMCID: PMC5834165 DOI: 10.1371/journal.pone.0193333] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 02/08/2018] [Indexed: 11/19/2022] Open
Abstract
Proliferating cell nuclear antigen (PCNA), a homotrimeric protein, is the eukaryotic sliding clamp that functions as a processivity factor for polymerases during DNA replication. Chromatin association factor 1 (CAF-1) is a heterotrimeric histone chaperone protein that is required for coupling chromatin assembly with DNA replication in eukaryotes. CAF-1 association with replicating DNA, and the targeting of newly synthesized histones to sites of DNA replication and repair requires its interaction with PCNA. Genetic studies have identified three mutant forms of PCNA in yeast that cause defects in gene silencing and exhibit altered association of CAF-1 to chromatin in vivo, as well as inhibit binding to CAF-1 in vitro. Three of these mutant forms of PCNA, encoded by the pol30-6, pol30-8, and the pol30-79 alleles, direct the synthesis of PCNA proteins with the amino acid substitutions D41A/D42A, R61A/D63A, and L126A/I128A, respectively. Interestingly, these double alanine substitutions are located far away from each other within the PCNA protein. To understand the structural basis of the interaction between PCNA and CAF-1 and how disruption of this interaction leads to reduced gene silencing, we determined the X-ray crystal structures of each of these mutant PCNA proteins. All three of the substitutions caused disruptions of a surface cavity on the front face of the PCNA ring, which is formed in part by three loops comprised of residues 21–24, 41–44, and 118–134. We suggest that this cavity is a novel binding pocket required for the interaction between PCNA and CAF-1, and that this region in PCNA also represents a potential binding site for other PCNA-binding proteins.
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Affiliation(s)
- Christine M. Kondratick
- Department of Biochemistry, University of Iowa College of Medicine, Iowa City, IA, United States of America
| | - Jacob M. Litman
- Department of Biochemistry, University of Iowa College of Medicine, Iowa City, IA, United States of America
| | - Kurt V. Shaffer
- Department of Chemistry, Creighton University, Omaha, NE, United States of America
| | - M. Todd Washington
- Department of Biochemistry, University of Iowa College of Medicine, Iowa City, IA, United States of America
| | - Lynne M. Dieckman
- Department of Chemistry, Creighton University, Omaha, NE, United States of America
- * E-mail:
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Pivotal roles of PCNA loading and unloading in heterochromatin function. Proc Natl Acad Sci U S A 2018; 115:E2030-E2039. [PMID: 29440488 DOI: 10.1073/pnas.1721573115] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In Saccharomyces cerevisiae, heterochromatin structures required for transcriptional silencing of the HML and HMR loci are duplicated in coordination with passing DNA replication forks. Despite major reorganization of chromatin structure, the heterochromatic, transcriptionally silent states of HML and HMR are successfully maintained throughout S-phase. Mutations of specific components of the replisome diminish the capacity to maintain silencing of HML and HMR through replication. Similarly, mutations in histone chaperones involved in replication-coupled nucleosome assembly reduce gene silencing. Bridging these observations, we determined that the proliferating cell nuclear antigen (PCNA) unloading activity of Elg1 was important for coordinating DNA replication forks with the process of replication-coupled nucleosome assembly to maintain silencing of HML and HMR through S-phase. Collectively, these data identified a mechanism by which chromatin reassembly is coordinated with DNA replication to maintain silencing through S-phase.
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46
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Choe KN, Moldovan GL. Forging Ahead through Darkness: PCNA, Still the Principal Conductor at the Replication Fork. Mol Cell 2017; 65:380-392. [PMID: 28157503 DOI: 10.1016/j.molcel.2016.12.020] [Citation(s) in RCA: 203] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 11/28/2016] [Accepted: 12/21/2016] [Indexed: 10/20/2022]
Abstract
Proliferating cell nuclear antigen (PCNA) lies at the center of the faithful duplication of eukaryotic genomes. With its distinctive doughnut-shaped molecular structure, PCNA was originally studied for its role in stimulating DNA polymerases. However, we now know that PCNA does much more than promote processive DNA synthesis. Because of the complexity of the events involved, cellular DNA replication poses major threats to genomic integrity. Whatever predicament lies ahead for the replication fork, PCNA is there to orchestrate the events necessary to handle it. Through its many protein interactions and various post-translational modifications, PCNA has far-reaching impacts on a myriad of cellular functions.
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Affiliation(s)
- Katherine N Choe
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - George-Lucian Moldovan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
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47
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DNA mismatch repair and its many roles in eukaryotic cells. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2017; 773:174-187. [PMID: 28927527 DOI: 10.1016/j.mrrev.2017.07.001] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 07/01/2017] [Accepted: 07/06/2017] [Indexed: 02/06/2023]
Abstract
DNA mismatch repair (MMR) is an important DNA repair pathway that plays critical roles in DNA replication fidelity, mutation avoidance and genome stability, all of which contribute significantly to the viability of cells and organisms. MMR is widely-used as a diagnostic biomarker for human cancers in the clinic, and as a biomarker of cancer susceptibility in animal model systems. Prokaryotic MMR is well-characterized at the molecular and mechanistic level; however, MMR is considerably more complex in eukaryotic cells than in prokaryotic cells, and in recent years, it has become evident that MMR plays novel roles in eukaryotic cells, several of which are not yet well-defined or understood. Many MMR-deficient human cancer cells lack mutations in known human MMR genes, which strongly suggests that essential eukaryotic MMR components/cofactors remain unidentified and uncharacterized. Furthermore, the mechanism by which the eukaryotic MMR machinery discriminates between the parental (template) and the daughter (nascent) DNA strand is incompletely understood and how cells choose between the EXO1-dependent and the EXO1-independent subpathways of MMR is not known. This review summarizes recent literature on eukaryotic MMR, with emphasis on the diverse cellular roles of eukaryotic MMR proteins, the mechanism of strand discrimination and cross-talk/interactions between and co-regulation of MMR and other DNA repair pathways in eukaryotic cells. The main conclusion of the review is that MMR proteins contribute to genome stability through their ability to recognize and promote an appropriate cellular response to aberrant DNA structures, especially when they arise during DNA replication. Although the molecular mechanism of MMR in the eukaryotic cell is still not completely understood, increased used of single-molecule analyses in the future may yield new insight into these unsolved questions.
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Schizosaccharomyces pombe MutSα and MutLα Maintain Stability of Tetra-Nucleotide Repeats and Msh3 of Hepta-Nucleotide Repeats. G3-GENES GENOMES GENETICS 2017; 7:1463-1473. [PMID: 28341698 PMCID: PMC5427490 DOI: 10.1534/g3.117.040816] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Defective mismatch repair (MMR) in humans is associated with colon cancer and instability of microsatellites, that is, DNA sequences with one or several nucleotides repeated. Key factors of eukaryotic MMR are the heterodimers MutSα (Msh2-Msh6), which recognizes base-base mismatches and unpaired nucleotides in DNA, and MutLα (Mlh1-Pms1), which facilitates downstream steps. In addition, MutSβ (Msh2-Msh3) recognizes DNA loops of various sizes, although our previous data and the data presented here suggest that Msh3 of Schizosaccharomyces pombe does not play a role in MMR. To test microsatellite stability in S. pombe and hence DNA loop repair, we have inserted tetra-, penta-, and hepta-nucleotide repeats in the ade6 gene and determined their Ade+ reversion rates and spectra in wild type and various mutants. Our data indicate that loops with four unpaired nucleotides in the nascent and the template strand are the upper limit of MutSα- and MutLα-mediated MMR in S. pombe Stability of hepta-nucleotide repeats requires Msh3 and Exo1 in MMR-independent processes as well as the DNA repair proteins Rad50, Rad51, and Rad2FEN1 Most strikingly, mutation rates in the double mutants msh3 exo1 and msh3 rad51 were decreased when compared to respective single mutants, indicating that Msh3 prevents error prone processes carried out by Exo1 and Rad51. We conclude that Msh3 has no obvious function in MMR in S. pombe, but contributes to DNA repeat stability in MMR-independent processes.
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Alterations in cellular metabolism triggered by URA7 or GLN3 inactivation cause imbalanced dNTP pools and increased mutagenesis. Proc Natl Acad Sci U S A 2017; 114:E4442-E4451. [PMID: 28416670 DOI: 10.1073/pnas.1618714114] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Eukaryotic DNA replication fidelity relies on the concerted action of DNA polymerase nucleotide selectivity, proofreading activity, and DNA mismatch repair (MMR). Nucleotide selectivity and proofreading are affected by the balance and concentration of deoxyribonucleotide (dNTP) pools, which are strictly regulated by ribonucleotide reductase (RNR). Mutations preventing DNA polymerase proofreading activity or MMR function cause mutator phenotypes and consequently increased cancer susceptibility. To identify genes not previously linked to high-fidelity DNA replication, we conducted a genome-wide screen in Saccharomyces cerevisiae using DNA polymerase active-site mutants as a "sensitized mutator background." Among the genes identified in our screen, three metabolism-related genes (GLN3, URA7, and SHM2) have not been previously associated to the suppression of mutations. Loss of either the transcription factor Gln3 or inactivation of the CTP synthetase Ura7 both resulted in the activation of the DNA damage response and imbalanced dNTP pools. Importantly, these dNTP imbalances are strongly mutagenic in genetic backgrounds where DNA polymerase function or MMR activity is partially compromised. Previous reports have shown that dNTP pool imbalances can be caused by mutations altering the allosteric regulation of enzymes involved in dNTP biosynthesis (e.g., RNR or dCMP deaminase). Here, we provide evidence that mutations affecting genes involved in RNR substrate production can cause dNTP imbalances, which cannot be compensated by RNR or other enzymatic activities. Moreover, Gln3 inactivation links nutrient deprivation to increased mutagenesis. Our results suggest that similar genetic interactions could drive mutator phenotypes in cancer cells.
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Bowen N, Kolodner RD. Reconstitution of Saccharomyces cerevisiae DNA polymerase ε-dependent mismatch repair with purified proteins. Proc Natl Acad Sci U S A 2017; 114:3607-3612. [PMID: 28265089 PMCID: PMC5389320 DOI: 10.1073/pnas.1701753114] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Mammalian and Saccharomyces cerevisiae mismatch repair (MMR) proteins catalyze two MMR reactions in vitro. In one, mispair binding by either the MutS homolog 2 (Msh2)-MutS homolog 6 (Msh6) or the Msh2-MutS homolog 3 (Msh3) stimulates 5' to 3' excision by exonuclease 1 (Exo1) from a single-strand break 5' to the mispair, excising the mispair. In the other, Msh2-Msh6 or Msh2-Msh3 activate the MutL homolog 1 (Mlh1)-postmeiotic segregation 1 (Pms1) endonuclease in the presence of a mispair and a nick 3' to the mispair, to make nicks 5' to the mispair, allowing Exo1 to excise the mispair. DNA polymerase δ (Pol δ) is thought to catalyze DNA synthesis to fill in the gaps resulting from mispair excision. However, colocalization of the S. cerevisiae mispair recognition proteins with the replicative DNA polymerases during DNA replication has suggested that DNA polymerase ε (Pol ε) may also play a role in MMR. Here we describe the reconstitution of Pol ε-dependent MMR using S. cerevisiae proteins. A mixture of Msh2-Msh6 (or Msh2-Msh3), Exo1, RPA, RFC-Δ1N, PCNA, and Pol ε was found to catalyze both short-patch and long-patch 5' nick-directed MMR of a substrate containing a +1 (+T) mispair. When the substrate contained a nick 3' to the mispair, a mixture of Msh2-Msh6 (or Msh2-Msh3), Exo1, RPA, RFC-Δ1N, PCNA, and Pol ε was found to catalyze an MMR reaction that required Mlh1-Pms1. These results demonstrate that Pol ε can act in eukaryotic MMR in vitro.
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Affiliation(s)
- Nikki Bowen
- Ludwig Institute for Cancer Research, University of California School of Medicine, La Jolla, CA 92093-0669
| | - Richard D Kolodner
- Ludwig Institute for Cancer Research, University of California School of Medicine, La Jolla, CA 92093-0669;
- Department of Cellular and Molecular Medicine, University of California School of Medicine, La Jolla, CA 92093-0669
- Moores-University of California San Diego Cancer Center, University of California School of Medicine, La Jolla, CA 92093-0669
- Institute of Genomic Medicine, University of California School of Medicine, La Jolla, CA 92093-0669
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