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Wolf K, Kosinski J, Gibson TJ, Wesch N, Dötsch V, Genuardi M, Cordisco EL, Zeuzem S, Brieger A, Plotz G. A conserved motif in the disordered linker of human MLH1 is vital for DNA mismatch repair and its function is diminished by a cancer family mutation. Nucleic Acids Res 2023; 51:6307-6320. [PMID: 37224528 PMCID: PMC10325900 DOI: 10.1093/nar/gkad418] [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: 12/12/2022] [Revised: 04/26/2023] [Accepted: 05/17/2023] [Indexed: 05/26/2023] Open
Abstract
DNA mismatch repair (MMR) is essential for correction of DNA replication errors. Germline mutations of the human MMR gene MLH1 are the major cause of Lynch syndrome, a heritable cancer predisposition. In the MLH1 protein, a non-conserved, intrinsically disordered region connects two conserved, catalytically active structured domains of MLH1. This region has as yet been regarded as a flexible spacer, and missense alterations in this region have been considered non-pathogenic. However, we have identified and investigated a small motif (ConMot) in this linker which is conserved in eukaryotes. Deletion of the ConMot or scrambling of the motif abolished mismatch repair activity. A mutation from a cancer family within the motif (p.Arg385Pro) also inactivated MMR, suggesting that ConMot alterations can be causative for Lynch syndrome. Intriguingly, the mismatch repair defect of the ConMot variants could be restored by addition of a ConMot peptide containing the deleted sequence. This is the first instance of a DNA mismatch repair defect conferred by a mutation that can be overcome by addition of a small molecule. Based on the experimental data and AlphaFold2 predictions, we suggest that the ConMot may bind close to the C-terminal MLH1-PMS2 endonuclease and modulate its activation during the MMR process.
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Affiliation(s)
- Karla Wolf
- Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, 60590, Germany
| | - Jan Kosinski
- European Molecular Biology Laboratory (EMBL), Centre for Structural Systems Biology (CSSB), Hamburg, 22607, Germany
| | - Toby J Gibson
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Heidelberg, 69117, Germany
| | - Nicole Wesch
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt am Main, 60438, Germany
| | - Volker Dötsch
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt am Main, 60438, Germany
| | - Maurizio Genuardi
- UOC Genetica Medica, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome00168, Italy
| | - Emanuela Lucci Cordisco
- Dipartimento di Scienze della Vita e di Sanità Pubblica, Università Cattolica del Sacro Cuore, Rome00168, Italy
| | - Stefan Zeuzem
- Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, 60590, Germany
| | - Angela Brieger
- Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, 60590, Germany
| | - Guido Plotz
- Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, 60590, Germany
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2
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Abstract
DNA mismatch repair (MMR) is a highly conserved genome stabilizing pathway that corrects DNA replication errors, limits chromosomal rearrangements, and mediates the cellular response to many types of DNA damage. Counterintuitively, MMR is also involved in the generation of mutations, as evidenced by its role in causing somatic triplet repeat expansion in Huntington’s disease (HD) and other neurodegenerative disorders. In this review, we discuss the current state of mechanistic knowledge of MMR and review the roles of key enzymes in this pathway. We also present the evidence for mutagenic function of MMR in CAG repeat expansion and consider mechanistic hypotheses that have been proposed. Understanding the role of MMR in CAG expansion may shed light on potential avenues for therapeutic intervention in HD.
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Affiliation(s)
- Ravi R Iyer
- CHDI Management/CHDI Foundation, Princeton, NJ, USA
| | - Anna Pluciennik
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA, USA
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3
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Risdon EN, Chau CH, Price DK, Sartor O, Figg WD. PARP Inhibitors and Prostate Cancer: To Infinity and Beyond BRCA. Oncologist 2021; 26:e115-e129. [PMID: 32790034 PMCID: PMC7794174 DOI: 10.1634/theoncologist.2020-0697] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Accepted: 08/04/2020] [Indexed: 12/18/2022] Open
Abstract
The U.S. Food and Drug Administration recently approved two poly-adenosine diphosphate-ribose polymerase (PARP) inhibitors, olaparib and rucaparib, for treatment of biomarker-positive metastatic castrate resistant prostate cancer. The benefits of PARP inhibition have been well characterized in patients who have BRCA1 and BRCA2 mutations in several forms of cancer. BRCA1 and BRCA2 occupy key roles in DNA damage repair, which is comprised of several different pathways with numerous participants. Patients with mutations in other key genes within the DNA damage repair pathway may also respond to treatment with PARP inhibitors, and identification of these alterations could significantly increase the percentage of patients that may benefit from PARP inhibition. This review focuses on the potential for synthetically lethal interactions between PARP inhibitors and non-BRCA DNA damage repair genes. IMPLICATIONS FOR PRACTICE: The treatment potential of PARP inhibition has been well characterized in patients with BRCA1 and BRCA2 mutations, but there is compelling evidence for expanding the use of PARP inhibitors to mutations of other non-BRCA DNA damage repair (DDR) genes. This could increase the percentage of patients that may benefit from treatment with PARP inhibitors alone or in combination with other therapies. Understanding the significance of PARP inhibitor-sensitizing alterations in other common non-BRCA DDR genes will help guide clinical decisions to provide targeted treatment options to a wider population of patients.
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Affiliation(s)
- Emily N. Risdon
- Genitourinary Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of HealthBethesdaMarylandUSA
| | - Cindy H. Chau
- Genitourinary Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of HealthBethesdaMarylandUSA
| | - Douglas K. Price
- Genitourinary Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of HealthBethesdaMarylandUSA
| | | | - William D. Figg
- Genitourinary Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of HealthBethesdaMarylandUSA
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4
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Tamura K, Kaneda M, Futagawa M, Takeshita M, Kim S, Nakama M, Kawashita N, Tatsumi-Miyajima J. Genetic and genomic basis of the mismatch repair system involved in Lynch syndrome. Int J Clin Oncol 2019; 24:999-1011. [PMID: 31273487 DOI: 10.1007/s10147-019-01494-y] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 06/17/2019] [Indexed: 12/11/2022]
Abstract
Lynch syndrome is a cancer-predisposing syndrome inherited in an autosomal-dominant manner, wherein colon cancer and endometrial cancer develop frequently in the family, it results from a loss-of-function mutation in one of four different genes (MLH1, MSH2, MSH6, and PMS2) encoding mismatch repair proteins. Being located immediately upstream of the MSH2 gene, EPCAM abnormalities can affect MSH2 and cause Lynch syndrome. Mismatch repair proteins are involved in repairing of incorrect pairing (point mutations and deletion/insertion of simple repetitive sequences, so-called microsatellites) that can arise during DNA replication. MSH2 forms heterodimers with MSH6 or MSH3 (MutSα, MutSβ, respectively) and is involved in mismatch-pair recognition and initiation of repair. MLH1 forms a complex with PMS2, and functions as an endonuclease. If the mismatch repair system is thoroughly working, genome integrity is maintained completely. Lynch syndrome is a state of mismatch repair deficiency due to a monoallelic abnormality of any mismatch repair genes. The phenotype indicating the mismatch repair deficiency can be frequently shown as a microsatellite instability in tumors. Children with germline biallelic mismatch repair gene abnormalities were reported to develop conditions such as gastrointestinal polyposis, colorectal cancer, brain cancer, leukemia, etc., and so on, demonstrating the need to respond with new concepts in genetic counseling. In promoting cancer genome medicine in a new era, such as by utilizing immune checkpoints, it is important to understand the genetic and genomic molecular background, including the status of mismatch repair deficiency.
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Affiliation(s)
- Kazuo Tamura
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan.
| | - Motohide Kaneda
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan
| | - Mashu Futagawa
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan
| | - Miho Takeshita
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan
| | - Sanghyuk Kim
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan
| | - Mina Nakama
- Division of Clinical Genetics, Gifu University Hospital, Gifu, Japan
| | - Norihito Kawashita
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan
| | - Junko Tatsumi-Miyajima
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan
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5
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Determination of Mismatch Repair Status in Human Cancer and Its Clinical Significance: Does One Size Fit All? Adv Anat Pathol 2019; 26:270-279. [PMID: 30932972 DOI: 10.1097/pap.0000000000000234] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The clinical management of cancers has progressed rapidly into the immunopathology era, with the unprecedented histology-agnostic approval of pembrolizumab in mismatch repair (MMR) deficient tumors. Despite the significant recent achievements in the treatment of these patients, however, the identification of clinically relevant subclasses of cancers based on the MMR status remains a major challenge. Many investigations have assessed the role of different diagnostic tools, including immunohistochemistry, microsatellite instability, and tumor mutational burden in both prognostic and therapeutic settings, with heterogenous results. To date, there are no tumor-specific guidelines or companion diagnostic tests for MMR assessment, and this analysis is often performed with locally developed methods. In this review, we provide a comprehensive overview of the current state-of-knowledge of MMR alterations in syndromic and sporadic tumors and discuss the available armamentarium for MMR pathologic characterization, from morphology to high-throughput molecular tools.
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Gupta D, Heinen CD. The mismatch repair-dependent DNA damage response: Mechanisms and implications. DNA Repair (Amst) 2019; 78:60-69. [PMID: 30959407 DOI: 10.1016/j.dnarep.2019.03.009] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 02/25/2019] [Accepted: 03/16/2019] [Indexed: 12/22/2022]
Abstract
An important role for the DNA mismatch repair (MMR) pathway in maintaining genomic stability is embodied in its conservation through evolution and the link between loss of MMR function and tumorigenesis. The latter is evident as inheritance of mutations within the major MMR genes give rise to the cancer predisposition condition, Lynch syndrome. Nonetheless, how MMR loss contributes to tumorigenesis is not completely understood. In addition to preventing the accumulation of mutations, MMR also directs cellular responses, such as cell cycle checkpoint or apoptosis activation, to different forms of DNA damage. Understanding this MMR-dependent DNA damage response may provide insight into the full tumor suppressing capabilities of the MMR pathway. Here, we delve into the proposed mechanisms for the MMR-dependent response to DNA damaging agents. We discuss how these pre-clinical findings extend to the clinical treatment of cancers, emphasizing MMR status as a crucial variable in selection of chemotherapeutic regimens. Also, we discuss how loss of the MMR-dependent damage response could promote tumorigenesis via the establishment of a survival advantage to endogenous levels of stress in MMR-deficient cells.
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Affiliation(s)
- Dipika Gupta
- Center for Molecular Oncology, UConn Health, Farmington, CT 06030, USA
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7
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Proteome Stability as a Key Factor of Genome Integrity. Int J Mol Sci 2017; 18:ijms18102036. [PMID: 28937603 PMCID: PMC5666718 DOI: 10.3390/ijms18102036] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 09/11/2017] [Accepted: 09/19/2017] [Indexed: 12/11/2022] Open
Abstract
DNA damage is constantly produced by both endogenous and exogenous factors; DNA lesions then trigger the so-called DNA damaged response (DDR). This is a highly synchronized pathway that involves recognition, signaling and repair of the damage. Failure to eliminate DNA lesions is associated with genome instability, a driving force in tumorigenesis. Proteins carry out the vast majority of cellular functions and thus proteome quality control (PQC) is critical for the maintenance of cellular functionality. PQC is assured by the proteostasis network (PN), which under conditions of proteome instability address the triage decision of protein fold, hold, or degrade. Key components of the PN are the protein synthesis modules, the molecular chaperones and the two main degradation machineries, namely the autophagy-lysosome and the ubiquitin-proteasome pathways; also, part of the PN are a number of stress-responsive cellular sensors including (among others) heat shock factor 1 (Hsf1) and the nuclear factor erythroid 2-related factor 2 (Nrf2). Nevertheless, the lifestyle- and/or ageing-associated gradual accumulation of stressors results in increasingly damaged and unstable proteome due to accumulation of misfolded proteins and/or protein aggregates. This outcome may then increase genomic instability due to reduced fidelity in processes like DNA replication or repair leading to various age-related diseases including cancer. Herein, we review the role of proteostatic machineries in nuclear genome integrity and stability, as well as on DDR responses.
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Liu H, Jiang X, Wang T, Yu F, Wang X, Chen J, Xie X, Fan H. Myeloid zinc finger 1 protein is a key transcription stimulating factor of PYROXD2 promoter. Oncol Rep 2017; 38:3245-3253. [DOI: 10.3892/or.2017.5990] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 07/31/2017] [Indexed: 11/05/2022] Open
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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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10
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Groothuizen FS, Sixma TK. The conserved molecular machinery in DNA mismatch repair enzyme structures. DNA Repair (Amst) 2015; 38:14-23. [PMID: 26796427 DOI: 10.1016/j.dnarep.2015.11.012] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 10/05/2015] [Accepted: 11/30/2015] [Indexed: 12/25/2022]
Abstract
The machinery of DNA mismatch repair enzymes is highly conserved in evolution. The process is initiated by recognition of a DNA mismatch, and validated by ATP and the presence of a processivity clamp or a methylation mark. Several events in MMR promote conformational changes that lead to progression of the repair process. Here we discuss functional conformational changes in the MMR proteins and we compare the enzymes to paralogs in other systems.
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Affiliation(s)
- Flora S Groothuizen
- Division of Biochemistry and CGC.nl, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Titia K Sixma
- Division of Biochemistry and CGC.nl, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
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11
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Bridge G, Rashid S, Martin SA. DNA mismatch repair and oxidative DNA damage: implications for cancer biology and treatment. Cancers (Basel) 2014; 6:1597-614. [PMID: 25099886 PMCID: PMC4190558 DOI: 10.3390/cancers6031597] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 07/02/2014] [Accepted: 07/18/2014] [Indexed: 11/26/2022] Open
Abstract
Many components of the cell, including lipids, proteins and both nuclear and mitochondrial DNA, are vulnerable to deleterious modifications caused by reactive oxygen species. If not repaired, oxidative DNA damage can lead to disease-causing mutations, such as in cancer. Base excision repair and nucleotide excision repair are the two DNA repair pathways believed to orchestrate the removal of oxidative lesions. However, recent findings suggest that the mismatch repair pathway may also be important for the response to oxidative DNA damage. This is particularly relevant in cancer where mismatch repair genes are frequently mutated or epigenetically silenced. In this review we explore how the regulation of oxidative DNA damage by mismatch repair proteins may impact on carcinogenesis. We discuss recent studies that identify potential new treatments for mismatch repair deficient tumours, which exploit this non-canonical role of mismatch repair using synthetic lethal targeting.
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Affiliation(s)
- Gemma Bridge
- Centre for Molecular Oncology, Barts Cancer Institute, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK.
| | - Sukaina Rashid
- Centre for Molecular Oncology, Barts Cancer Institute, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK.
| | - Sarah A Martin
- Centre for Molecular Oncology, Barts Cancer Institute, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK.
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12
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Sequence-specific and DNA structure-dependent interactions of Escherichia coli MutS and human p53 with DNA. Anal Biochem 2013; 442:51-61. [PMID: 23928048 DOI: 10.1016/j.ab.2013.07.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2013] [Revised: 07/19/2013] [Accepted: 07/23/2013] [Indexed: 11/20/2022]
Abstract
Many proteins involved in DNA repair systems interact with DNA that has structure altered from the typical B-form helix. Using magnetic beads to immobilize DNAs containing various types of structures, we evaluated the in vitro binding activities of two well-characterized DNA repair proteins, Escherichia coli MutS and human p53. E. coli MutS bound to double-stranded DNAs, with higher affinity for a G/T mismatch compared to a G/A mismatch and highest affinity for larger non-B-DNA structures. E. coli MutS bound best to DNA between pH 6 and 9. Experiments discriminated between modes of p53-DNA binding, and increasing ionic strength reduced p53 binding to nonspecific double-stranded DNA, but had minor effects on binding to consensus response sequences or single-stranded DNA. Compared to nonspecific DNA sequences, p53 bound with a higher affinity to mismatches and base insertions, while binding to various hairpin structures was similar to that observed to its consensus DNA sequence. For hairpins containing CTG repeats, the extent of p53 binding was proportional to the size of the repeat. In summary, using the flexibility of the magnetic bead separation assay we demonstrate that pH and ionic strength influence the binding of two DNA repair proteins to a variety of DNA structures.
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Edelbrock MA, Kaliyaperumal S, Williams KJ. Structural, molecular and cellular functions of MSH2 and MSH6 during DNA mismatch repair, damage signaling and other noncanonical activities. Mutat Res 2013; 743-744:53-66. [PMID: 23391514 DOI: 10.1016/j.mrfmmm.2012.12.008] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 12/28/2012] [Accepted: 12/31/2012] [Indexed: 11/18/2022]
Abstract
The field of DNA mismatch repair (MMR) has rapidly expanded after the discovery of the MutHLS repair system in bacteria. By the mid 1990s yeast and human homologues to bacterial MutL and MutS had been identified and their contribution to hereditary non-polyposis colorectal cancer (HNPCC; Lynch syndrome) was under intense investigation. The human MutS homologue 6 protein (hMSH6), was first reported in 1995 as a G:T binding partner (GTBP) of hMSH2, forming the hMutSα mismatch-binding complex. Signal transduction from each DNA-bound hMutSα complex is accomplished by the hMutLα heterodimer (hMLH1 and hPMS2). Molecular mechanisms and cellular regulation of individual MMR proteins are now areas of intensive research. This review will focus on molecular mechanisms associated with mismatch binding, as well as emerging evidence that MutSα, and in particular, MSH6, is a key protein in MMR-dependent DNA damage response and communication with other DNA repair pathways within the cell. MSH6 is unstable in the absence of MSH2, however it is the DNA lesion-binding partner of this heterodimer. MSH6, but not MSH2, has a conserved Phe-X-Glu motif that recognizes and binds several different DNA structural distortions, initiating different cellular responses. hMSH6 also contains the nuclear localization sequences required to shuttle hMutSα into the nucleus. For example, upon binding to O(6)meG:T, MSH6 triggers a DNA damage response that involves altered phosphorylation within the N-terminal disordered domain of this unique protein. While many investigations have focused on MMR as a post-replication DNA repair mechanism, MMR proteins are expressed and active in all phases of the cell cycle. There is much more to be discovered about regulatory cellular roles that require the presence of MutSα and, in particular, MSH6.
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Affiliation(s)
| | - Saravanan Kaliyaperumal
- Division of Comparative Medicine and Pathology, New England Primate Research Center, One Pine Hill Drive, Southborough, MA 01772, USA.
| | - Kandace J Williams
- University of Toledo College of Medicine and Life Sciences, Department of Biochemistry & Cancer Biology, 3000 Transverse Dr., Toledo, OH 43614, USA.
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14
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Halabi A, Ditch S, Wang J, Grabczyk E. DNA mismatch repair complex MutSβ promotes GAA·TTC repeat expansion in human cells. J Biol Chem 2012; 287:29958-67. [PMID: 22787155 DOI: 10.1074/jbc.m112.356758] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
While DNA repair has been implicated in CAG·CTG repeat expansion, its role in the GAA·TTC expansion of Friedreich ataxia (FRDA) is less clear. We have developed a human cellular model that recapitulates the DNA repeat expansion found in FRDA patient tissues. In this model, GAA·TTC repeats expand incrementally and continuously. We have previously shown that the expansion rate is linked to transcription within the repeats. Our working hypothesis is that structures formed within the GAA·TTC repeat during transcription attract DNA repair enzymes that then facilitate the expansion process. MutSβ, a heterodimer of MSH2 and MSH3, is known to have a role in CAG·CTG repeat expansion. We now show that shRNA knockdown of either MSH2 or MSH3 slowed GAA·TTC expansion in our system. We further characterized the role of MutSβ in GAA·TTC expansion using a functional assay in primary FRDA patient-derived fibroblasts. These fibroblasts have no known propensity for instability in their native state. Ectopic expression of MSH2 and MSH3 induced GAA·TTC repeat expansion in the native FXN gene. MSH2 is central to mismatch repair and its absence or reduction causes a predisposition to cancer. Thus, despite its essential role in GAA·TTC expansion, MSH2 is not an attractive therapeutic target. The absence or reduction of MSH3 is not strongly associated with cancer predisposition. Accordingly, MSH3 has been suggested as a therapeutic target for CAG·CTG repeat expansion disorders. Our results suggest that MSH3 may also serve as a therapeutic target to slow the expansion of GAA·TTC repeats in the future.
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Affiliation(s)
- Anasheh Halabi
- Department of Genetics, Health Sciences Center, Louisiana State University, New Orleans, LA 70112, USA
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15
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Qi Y, Schoene NW, Lartey FM, Cheng WH. Selenium compounds activate ATM-dependent DNA damage response via the mismatch repair protein hMLH1 in colorectal cancer cells. J Biol Chem 2010; 285:33010-33017. [PMID: 20709753 DOI: 10.1074/jbc.m110.137406] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Epidemiological and animal studies indicate that selenium supplementation suppresses risk of colorectal and other cancers. The majority of colorectal cancers are characterized by a defective DNA mismatch repair (MMR). Here, we have employed the MMR-deficient HCT 116 colorectal cancer cells and the MMR-proficient HCT 116 cells with hMLH1 complementation to investigate the role of hMLH1 in selenium-induced DNA damage response, a tumorigenesis barrier. The ATM (ataxia telangiectasia mutated) protein responds to clastogens and initiates DNA damage response. We show that hMLH1 complementation sensitizes HCT 116 cells to methylseleninic acid, methylselenocysteine, and sodium selenite via reactive oxygen species and facilitates the selenium-induced oxidative 8-oxoguanine damage, DNA breaks, G(2)/M checkpoint response, and ATM pathway activation. Pretreatment of the hMLH1-complemented HCT 116 cells with the antioxidant N-acetylcysteine or 2,2,6,6-tetramethylpiperidine-1-oxyl or the ATM kinase inhibitor KU55933 suppresses hMLH1-dependent DNA damage response to selenium exposure. Selenium treatment stimulates the association between hMLH1 and hPMS2 proteins, a heterodimer critical for functional MMR, in a manner dependent on ATM and reactive oxygen species. Taken together, the results suggest a new role of selenium in mitigating tumorigenesis by targeting the MMR pathway, whereby the lack of hMLH1 renders the HCT 116 colorectal cancer cells resistant to selenium-induced DNA damage response.
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Affiliation(s)
- Yongmei Qi
- From the Department of Nutrition and Food Science, University of Maryland, College Park, Maryland 20742; School of Life Science, Lanzhou University, Lanzhou, Gansu 730000, China
| | - Norberta W Schoene
- Diet, Genomics, and Immunology Laboratory, Beltsville Human Nutrition Research Center, United States Department of Agriculture, Beltsville, Maryland 20705
| | - Frederick M Lartey
- From the Department of Nutrition and Food Science, University of Maryland, College Park, Maryland 20742
| | - Wen-Hsing Cheng
- From the Department of Nutrition and Food Science, University of Maryland, College Park, Maryland 20742.
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16
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Brieger A, Adryan B, Wolpert F, Passmann S, Zeuzem S, Trojan J. Cytoskeletal scaffolding proteins interact with Lynch-Syndrome associated mismatch repair protein MLH1. Proteomics 2010; 10:3343-55. [DOI: 10.1002/pmic.200900672] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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17
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Mastrocola AS, Heinen CD. Nuclear reorganization of DNA mismatch repair proteins in response to DNA damage. DNA Repair (Amst) 2010; 9:120-33. [PMID: 20004149 PMCID: PMC2819642 DOI: 10.1016/j.dnarep.2009.11.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Revised: 10/16/2009] [Accepted: 11/04/2009] [Indexed: 12/16/2022]
Abstract
The DNA mismatch repair (MMR) system is highly conserved and vital for preserving genomic integrity. Current mechanistic models for MMR are mainly derived from in vitro assays including reconstitution of strand-specific MMR and DNA binding assays using short oligonucleotides. However, fundamental questions regarding the mechanism and regulation in the context of cellular DNA replication remain. Using synchronized populations of HeLa cells we demonstrated that hMSH2, hMLH1 and PCNA localize to the chromatin during S-phase, and accumulate to a greater extent in cells treated with a DNA alkylating agent. In addition, using small interfering RNA to deplete hMSH2, we demonstrated that hMLH1 localization to the chromatin is hMSH2-dependent. hMSH2/hMLH1/PCNA proteins, when associated with the chromatin, form a complex that is greatly enhanced by DNA damage. The DNA damage caused by high doses of alkylating agents leads to a G(2) arrest after only one round of replication. In these G(2)-arrested cells, an hMSH2/hMLH1 complex persists on chromatin, however, PCNA is no longer in the complex. Cells treated with a lower dose of alkylating agent require two rounds of replication before cells arrest in G(2). In the first S-phase, the MMR proteins form a complex with PCNA, however, during the second S-phase PCNA is missing from that complex. The distinction between these complexes may suggest separate functions for the MMR proteins in damage repair and signaling. Additionally, using confocal immunofluorescence, we observed a population of hMSH6 that localized to the nucleolus. This population is significantly reduced after DNA damage suggesting that the protein is shuttled out of the nucleolus in response to damage. In contrast, hMLH1 is excluded from the nucleolus at all times. Thus, the nucleolus may act to segregate a population of hMSH2-hMSH6 from hMLH1-hPMS2 such that, in the absence of DNA damage, an inappropriate response is not invoked.
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Affiliation(s)
- Adam S. Mastrocola
- Neag Comprehensive Cancer Center and Center for Molecular Medicine, University of Connecticut Health Center, Farmington, Connecticut 06030, USA
| | - Christopher D. Heinen
- Neag Comprehensive Cancer Center and Center for Molecular Medicine, University of Connecticut Health Center, Farmington, Connecticut 06030, USA
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Hsieh P, Yamane K. DNA mismatch repair: molecular mechanism, cancer, and ageing. Mech Ageing Dev 2008; 129:391-407. [PMID: 18406444 PMCID: PMC2574955 DOI: 10.1016/j.mad.2008.02.012] [Citation(s) in RCA: 291] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2007] [Revised: 02/22/2008] [Accepted: 02/28/2008] [Indexed: 02/09/2023]
Abstract
DNA mismatch repair (MMR) proteins are ubiquitous players in a diverse array of important cellular functions. In its role in post-replication repair, MMR safeguards the genome correcting base mispairs arising as a result of replication errors. Loss of MMR results in greatly increased rates of spontaneous mutation in organisms ranging from bacteria to humans. Mutations in MMR genes cause hereditary nonpolyposis colorectal cancer, and loss of MMR is associated with a significant fraction of sporadic cancers. Given its prominence in mutation avoidance and its ability to target a range of DNA lesions, MMR has been under investigation in studies of ageing mechanisms. This review summarizes what is known about the molecular details of the MMR pathway and the role of MMR proteins in cancer susceptibility and ageing.
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Affiliation(s)
- Peggy Hsieh
- Genetics & Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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Slean MM, Panigrahi GB, Ranum LP, Pearson CE. Mutagenic roles of DNA "repair" proteins in antibody diversity and disease-associated trinucleotide repeat instability. DNA Repair (Amst) 2008; 7:1135-54. [PMID: 18485833 DOI: 10.1016/j.dnarep.2008.03.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
While DNA repair proteins are generally thought to maintain the integrity of the whole genome by correctly repairing mutagenic DNA intermediates, there are cases where DNA "repair" proteins are involved in causing mutations instead. For instance, somatic hypermutation (SHM) and class switch recombination (CSR) require the contribution of various DNA repair proteins, including UNG, MSH2 and MSH6 to mutate certain regions of immunoglobulin genes in order to generate antibodies of increased antigen affinity and altered effector functions. Another instance where "repair" proteins drive mutations is the instability of gene-specific trinucleotide repeats (TNR), the causative mutations of numerous diseases including Fragile X mental retardation syndrome (FRAXA), Huntington's disease (HD), myotonic dystrophy (DM1) and several spinocerebellar ataxias (SCAs) all of which arise via various modes of pathogenesis. These healthy and deleterious mutations that are induced by repair proteins are distinct from the genome-wide mutations that arise in the absence of repair proteins: they occur at specific loci, are sensitive to cis-elements (sequence context and/or epigenetic marks) and transcription, occur in specific tissues during distinct developmental windows, and are age-dependent. Here we review and compare the mutagenic role of DNA "repair" proteins in the processes of SHM, CSR and TNR instability.
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Affiliation(s)
- Meghan M Slean
- Program of Genetics & Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1L7
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Brieger A, Plotz G, Zeuzem S, Trojan J. Thymosin beta 4 expression and nuclear transport are regulated by hMLH1. Biochem Biophys Res Commun 2007; 364:731-6. [DOI: 10.1016/j.bbrc.2007.10.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2007] [Accepted: 10/03/2007] [Indexed: 10/22/2022]
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Plotz G, Welsch C, Giron-Monzon L, Friedhoff P, Albrecht M, Piiper A, Biondi RM, Lengauer T, Zeuzem S, Raedle J. Mutations in the MutSalpha interaction interface of MLH1 can abolish DNA mismatch repair. Nucleic Acids Res 2006; 34:6574-86. [PMID: 17135187 PMCID: PMC1747184 DOI: 10.1093/nar/gkl944] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
MutLα, a heterodimer of MLH1 and PMS2, plays a central role in human DNA mismatch repair. It interacts ATP-dependently with the mismatch detector MutSα and assembles and controls further repair enzymes. We tested if the interaction of MutLα with DNA-bound MutSα is impaired by cancer-associated mutations in MLH1, and identified one mutation (Ala128Pro) which abolished interaction as well as mismatch repair activity. Further examinations revealed three more residues whose mutation interfered with interaction. Homology modelling of MLH1 showed that all residues clustered in a small accessible surface patch, suggesting that the major interaction interface of MutLα for MutSα is located on the edge of an extensive β-sheet that backs the MLH1 ATP binding pocket. Bioinformatic analysis confirmed that this patch corresponds to a conserved potential protein–protein interaction interface which is present in both human MLH1 and its E.coli homologue MutL. MutL could be site-specifically crosslinked to MutS from this patch, confirming that the bacterial MutL–MutS complex is established by the corresponding interface in MutL. This is the first study that identifies the conserved major MutLα–MutSα interaction interface in MLH1 and demonstrates that mutations in this interface can affect interaction and mismatch repair, and thereby can also contribute to cancer development.
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Affiliation(s)
- Guido Plotz
- Klinik für Innere Medizin II, Gebäude 41Kirrberger Straße, Universität des Saarlandes, D-66421 Homburg/Saar, Germany
- To whom correspondence should be addressed. Tel: +49 6841 16 23253; Fax: +49 6841 16 23570;
| | - Christoph Welsch
- Klinik für Innere Medizin II, Gebäude 41Kirrberger Straße, Universität des Saarlandes, D-66421 Homburg/Saar, Germany
- Max Planck Institut für Informatik, Stuhlsatzenhausweg 85D-66123 Saarbrücken, Germany
| | - Luis Giron-Monzon
- Institut für Biochemie (FB 08), Justus-Liebig-Universität GiessenD-35392 Giessen, Germany
| | - Peter Friedhoff
- Institut für Biochemie (FB 08), Justus-Liebig-Universität GiessenD-35392 Giessen, Germany
| | - Mario Albrecht
- Max Planck Institut für Informatik, Stuhlsatzenhausweg 85D-66123 Saarbrücken, Germany
| | - Albrecht Piiper
- Klinik für Innere Medizin II, Gebäude 41Kirrberger Straße, Universität des Saarlandes, D-66421 Homburg/Saar, Germany
| | - Ricardo M. Biondi
- Klinik für Innere Medizin II, Gebäude 41Kirrberger Straße, Universität des Saarlandes, D-66421 Homburg/Saar, Germany
| | - Thomas Lengauer
- Max Planck Institut für Informatik, Stuhlsatzenhausweg 85D-66123 Saarbrücken, Germany
| | - Stefan Zeuzem
- Klinik für Innere Medizin II, Gebäude 41Kirrberger Straße, Universität des Saarlandes, D-66421 Homburg/Saar, Germany
| | - Jochen Raedle
- Klinik für Innere Medizin II, Gebäude 41Kirrberger Straße, Universität des Saarlandes, D-66421 Homburg/Saar, Germany
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22
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Plotz G, Zeuzem S, Raedle J. DNA mismatch repair and Lynch syndrome. J Mol Histol 2006; 37:271-83. [PMID: 16821093 DOI: 10.1007/s10735-006-9038-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2006] [Accepted: 06/06/2006] [Indexed: 01/31/2023]
Abstract
The evolutionary conserved mismatch repair proteins correct a wide range of DNA replication errors. Their importance as guardians of genetic integrity is reflected by the tremendous decrease of replication fidelity (two to three orders of magnitude) conferred by their loss. Germline mutations in mismatch repair genes, predominantly MSH2 and MLH1, have been found to underlie the Lynch syndrome (also called hereditary non-polyposis colorectal cancer, HNPCC), a hereditary predisposition for cancer. Lynch syndrome affects predominantly the colon and accounts for 2-5% of all colon cancer cases. During more than 30 years of biochemical, crystallographic and clinical research, deep insight has been achieved in the function of mismatch repair and the diseases that are associated with its loss. We review the biochemistry of mismatch repair and also introduce the clinical, diagnostic and genetic aspects of Lynch syndrome.
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Affiliation(s)
- Guido Plotz
- Klinik für Innere Medizin II, Universitätsklinikum des Saarlandes, Kirrberger Strasse, Gebäude 41, D-66421 Homburg, Germany.
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Abstract
By removing biosynthetic errors from newly synthesized DNA, mismatch repair (MMR) improves the fidelity of DNA replication by several orders of magnitude. Loss of MMR brings about a mutator phenotype, which causes a predisposition to cancer. But MMR status also affects meiotic and mitotic recombination, DNA-damage signalling, apoptosis and cell-type-specific processes such as class-switch recombination, somatic hypermutation and triplet-repeat expansion. This article reviews our current understanding of this multifaceted DNA-repair system in human cells.
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Affiliation(s)
- Josef Jiricny
- Institute of Molecular Cancer Research, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
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Plotz G, Piiper A, Wormek M, Zeuzem S, Raedle J. Analysis of the human MutLalpha.MutSalpha complex. Biochem Biophys Res Commun 2005; 340:852-9. [PMID: 16403449 DOI: 10.1016/j.bbrc.2005.12.096] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Accepted: 12/14/2005] [Indexed: 11/23/2022]
Abstract
Human DNA mismatch repair is initiated by MutSalpha which ATP-dependently recruits MutLalpha. Analysis of this complex is difficult due to its transient and dynamic nature. We have optimized conditions for investigation of MutLalpha.MutSalpha complexes using a DNA pulldown assay. Non-specific DNA end-binding, which frequently interfered with analysis of the interaction, did not occur under the applied conditions. MutSalpha had significantly higher affinity to DNA mispairs, but its interaction with MutLalpha did not require a mismatch. Complex formation was best supported by low magnesium concentration and low temperature at physiological pH and salt concentration. Complex formation was delayed by the slowly hydrolyzable ATP analog ATPgammaS, undetectable with the non-hydrolyzable analog AMP-PNP, and occurred weakly with a combination of AMP-PNP and ADP, confirming that hydrolysis was required. The described conditions likely capture an intermediate of the repair reaction which has bound ATP and ADP in the two nucleotide-binding sites of MutSalpha.
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Affiliation(s)
- Guido Plotz
- University of the Saarland, Klinik für Innere Medizin II, Homburg/Saar, Germany.
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25
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Pearson CE, Nichol Edamura K, Cleary JD. Repeat instability: mechanisms of dynamic mutations. Nat Rev Genet 2005; 6:729-42. [PMID: 16205713 DOI: 10.1038/nrg1689] [Citation(s) in RCA: 645] [Impact Index Per Article: 33.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Disease-causing repeat instability is an important and unique form of mutation that is linked to more than 40 neurological, neurodegenerative and neuromuscular disorders. DNA repeat expansion mutations are dynamic and ongoing within tissues and across generations. The patterns of inherited and tissue-specific instability are determined by both gene-specific cis-elements and trans-acting DNA metabolic proteins. Repeat instability probably involves the formation of unusual DNA structures during DNA replication, repair and recombination. Experimental advances towards explaining the mechanisms of repeat instability have broadened our understanding of this mutational process. They have revealed surprising ways in which metabolic pathways can drive or protect from repeat instability.
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Affiliation(s)
- Christopher E Pearson
- Program of Genetics and Genomic Biology, The Hospital for Sick Children, 15-312, TMDT, 101 College Street, East Tower, Toronto, Ontario M5G 1L7, Canada.
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Brieger A, Plotz G, Raedle J, Weber N, Baum W, Caspary WF, Zeuzem S, Trojan J. Characterization of the nuclear import of human MutLalpha. Mol Carcinog 2005; 43:51-8. [PMID: 15754314 DOI: 10.1002/mc.20081] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
DNA mismatch repair (MMR) is essential for the maintenance of replication fidelity. Its major task is to recognize mismatches as well as insertion/deletion loops of newly synthesized DNA strands. Although different players of human MMR have been identified, the regulation of essential steps of MMR is poorly understood. Because MMR is initiated in the nucleus, nuclear import might be a mechanism to regulate MMR. Nuclear targeting is accomplished by conserved signal sequences called nuclear localization signals (NLS), which represent clusters of positively charged amino acids (aa). hMLH1 contains two clusters of positively charged amino acids, which are candidate NLS sequences (aa 469-472 and 496-499), while hPMS2 contains one (aa 574-580). To study the effect of these clusters on nuclear import, NLS mutants of hMLH1 and hPMS2 were generated and expressed in 293T cells. The subcellular localization of the mutant constructs was monitored by confocal laser microscopy. We demonstrated that missense mutations of two signal sequences, one in hMLH1 and one in hPMS2, lead to impaired nuclear import, which was especially prominent for mutants of the hMLH1 residues K471 and R472; and hPMS2 residues K577 and R578.
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Affiliation(s)
- A Brieger
- Medizinische Klinik I, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt a.M., Germany
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27
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Mendillo ML, Mazur DJ, Kolodner RD. Analysis of the interaction between the Saccharomyces cerevisiae MSH2-MSH6 and MLH1-PMS1 complexes with DNA using a reversible DNA end-blocking system. J Biol Chem 2005; 280:22245-57. [PMID: 15811858 DOI: 10.1074/jbc.m407545200] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Lac repressor-operator interaction was used as a reversible DNA end-blocking system in conjunction with an IAsys biosensor instrument (Thermo Affinity Sensors), which detects total internal reflectance and allows monitoring of binding and dissociation in real time, in order to develop a system for studying the ability of mismatch repair proteins to move along the DNA. The MSH2-MSH6 complex bound to a mispaired base was found to be converted by ATP binding to a form that showed rapid sliding along the DNA and dissociation via the DNA ends and also showed slow, direct dissociation from the DNA. In contrast, the MSH2-MSH6 complex bound to a base pair containing DNA only showed direct dissociation from the DNA. The MLH1-PMS1 complex formed both mispair-dependent and mispair-independent ternary complexes with the MSH2-MSH6 complex on DNA. The mispair-independent ternary complexes were formed most efficiently on DNA molecules with free ends under conditions where ATP hydrolysis did not occur, and only exhibited direct dissociation from the DNA. The mispair-dependent ternary complexes were formed in the highest yield on DNA molecules with blocked ends, required ATP and magnesium for formation, and showed both dissociation via the DNA ends and direct dissociation from the DNA.
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Affiliation(s)
- Marc L Mendillo
- Ludwig Institute for Cancer Research, Department of Medicine and Cancer Center, School of Medicine, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0669, USA
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Antony E, Hingorani MM. Mismatch recognition-coupled stabilization of Msh2-Msh6 in an ATP-bound state at the initiation of DNA repair. Biochemistry 2003; 42:7682-93. [PMID: 12820877 PMCID: PMC2839877 DOI: 10.1021/bi034602h] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mismatch repair proteins correct errors in DNA via an ATP-driven process. In eukaryotes, the Msh2-Msh6 complex recognizes base pair mismatches and small insertion/deletions in DNA and initiates repair. Both Msh2 and Msh6 proteins contain Walker ATP-binding motifs that are necessary for repair activity. To understand how these proteins couple ATP binding and hydrolysis to DNA binding/mismatch recognition, the ATPase activity of Saccharomyces cerevisiae Msh2-Msh6 was examined under pre-steady-state conditions. Acid-quench experiments revealed that in the absence of DNA, Msh2-Msh6 hydrolyzes ATP rapidly (burst rate = 3 s(-1) at 20 degrees C) and then undergoes a slow step in the pathway that limits catalytic turnover (k(cat) = 0.1 s(-1)). ATP is hydrolyzed similarly in the presence of fully matched duplex DNA; however, in the presence of a G:T mismatch or +T insertion-containing DNA, ATP hydrolysis is severely suppressed (rate = 0.1 s(-1)). Pulse-chase experiments revealed that Msh2-Msh6 binds ATP rapidly in the absence or in the presence of DNA (rate = 0.1 microM(-1) s(-1)), indicating that for the Msh2-Msh6.mismatched DNA complex, a step after ATP binding but before or at ATP hydrolysis is the rate-limiting step in the pathway. Thus, mismatch recognition is coupled to a dramatic increase in the residence time of ATP on Msh2-Msh6. This mismatch-induced, stable ATP-bound state of Msh2-Msh6 likely signals downstream events in the repair pathway.
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Affiliation(s)
- Edwin Antony
- Wesleyan University, Molecular Biology and Biochemistry Department, 205 Hall-Atwater Laboratories, Middletown, Connecticut 06459, USA
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Acharya S, Foster PL, Brooks P, Fishel R. The coordinated functions of the E. coli MutS and MutL proteins in mismatch repair. Mol Cell 2003; 12:233-46. [PMID: 12887908 DOI: 10.1016/s1097-2765(03)00219-3] [Citation(s) in RCA: 228] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The Escherichia coli MutS and MutL proteins have been conserved throughout evolution, although their combined functions in mismatch repair (MMR) are poorly understood. We have used biochemical and genetic studies to ascertain a physiologically relevant mechanism for MMR. The MutS protein functions as a regional lesion sensor. ADP-bound MutS specifically recognizes a mismatch. Repetitive rounds of mismatch-provoked ADP-->ATP exchange results in the loading of multiple MutS hydrolysis-independent sliding clamps onto the adjoining duplex DNA. MutL can only associate with ATP-bound MutS sliding clamps. Interaction of the MutS-MutL sliding clamp complex with MutH triggers ATP binding by MutL that enhances the endonuclease activity of MutH. Additionally, MutL promotes ATP binding-independent turnover of idle MutS sliding clamps. These results support a model of MMR that relies on two dynamic and redundant ATP-regulated molecular switches.
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Affiliation(s)
- Samir Acharya
- Genetics and Molecular Biology Program, Kimmel Cancer Center - BLSB 933, 233 S. 10th Street, Philadelphia, PA 19107, USA.
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Plotz G, Raedle J, Brieger A, Trojan J, Zeuzem S. N-terminus of hMLH1 confers interaction of hMutLalpha and hMutLbeta with hMutSalpha. Nucleic Acids Res 2003; 31:3217-26. [PMID: 12799449 PMCID: PMC162253 DOI: 10.1093/nar/gkg420] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Mismatch repair is a highly conserved system that ensures replication fidelity by repairing mispairs after DNA synthesis. In humans, the two protein heterodimers hMutSalpha (hMSH2-hMSH6) and hMutLalpha (hMLH1-hPMS2) constitute the centre of the repair reaction. After recognising a DNA replication error, hMutSalpha recruits hMutLalpha, which then is thought to transduce the repair signal to the excision machinery. We have expressed an ATPase mutant of hMutLalpha as well as its individual subunits hMLH1 and hPMS2 and fragments of hMLH1, followed by examination of their interaction properties with hMutSalpha using a novel interaction assay. We show that, although the interaction requires ATP, hMutLalpha does not need to hydrolyse this nucleotide to join hMutSalpha on DNA, suggesting that ATP hydrolysis by hMutLalpha happens downstream of complex formation. The analysis of the individual subunits of hMutLalpha demonstrated that the hMutSalpha-hMutLalpha interaction is predominantly conferred by hMLH1. Further experiments revealed that only the N-terminus of hMLH1 confers this interaction. In contrast, only the C-terminus stabilised and co-immunoprecipitated hPMS2 when both proteins were co-expressed in 293T cells, indicating that dimerisation and stabilisation are mediated by the C-terminal part of hMLH1. We also examined another human homologue of bacterial MutL, hMutLbeta (hMLH1-hPMS1). We show that hMutLbeta interacts as efficiently with hMutSalpha as hMutLalpha, and that it predominantly binds to hMutSalpha via hMLH1 as well.
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Affiliation(s)
- Guido Plotz
- 2nd Department of Medicine, University of the Saarland, Kirrberger Strasse, D-66421 Homburg/Saar, Germany
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