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Chung WH. Signification and Application of Mutator and Antimutator Phenotype-Induced Genetic Variations in Evolutionary Adaptation and Cancer Therapeutics. J Microbiol 2023; 61:1013-1024. [PMID: 38100001 DOI: 10.1007/s12275-023-00091-z] [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: 10/09/2023] [Revised: 10/30/2023] [Accepted: 11/01/2023] [Indexed: 01/11/2024]
Abstract
Mutations present a dichotomy in their implications for cellular processes. They primarily arise from DNA replication errors or damage repair processes induced by environmental challenges. Cumulative mutations underlie genetic variations and drive evolution, yet also contribute to degenerative diseases such as cancer and aging. The mutator phenotype elucidates the heightened mutation rates observed in malignant tumors. Evolutionary adaptation, analogous to bacterial and eukaryotic systems, manifests through mutator phenotypes during changing environmental conditions, highlighting the delicate balance between advantageous mutations and their potentially detrimental consequences. Leveraging the genetic tractability of Saccharomyces cerevisiae offers unique insights into mutator phenotypes and genome instability akin to human cancers. Innovative reporter assays in yeast model organisms enable the detection of diverse genome alterations, aiding a comprehensive analysis of mutator phenotypes. Despite significant advancements, our understanding of the intricate mechanisms governing spontaneous mutation rates and preserving genetic integrity remains incomplete. This review outlines various cellular pathways affecting mutation rates and explores the role of mutator genes and mutation-derived phenotypes, particularly prevalent in malignant tumor cells. An in-depth comprehension of mutator and antimutator activities in yeast and higher eukaryotes holds promise for effective cancer control strategies.
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Affiliation(s)
- Woo-Hyun Chung
- College of Pharmacy, Duksung Women's University, Seoul, 01369, Republic of Korea.
- Innovative Drug Center, Duksung Women's University, Seoul, 01369, Republic of Korea.
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2
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Fatemi N, Tu SJ, Chung CC, Moghadam PK, Mojarad EN, Sadeghi A, Totonchi M, Aghdaei HA, Chang JG. Whole exome sequencing identifies MAP3K1, MSH2, and MLH1 as potential cancer-predisposing genes in familial early-onset colorectal cancer. Kaohsiung J Med Sci 2023; 39:896-903. [PMID: 37314251 DOI: 10.1002/kjm2.12715] [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: 01/20/2023] [Revised: 05/01/2023] [Accepted: 05/21/2023] [Indexed: 06/15/2023] Open
Abstract
The incidence of early-onset colorectal cancer (CRC), which affects people under 50, is increasing for unknown reasons. Additionally, no underlying genetic cause is found in 20%-30% of patients suspected of having familial CRC syndrome. Whole exome sequencing (WES) has generated evidence for new genes associated with CRC susceptibility, but many patients remain undiagnosed. This study applied WES in five early-onset CRC patients from three unrelated families to identify novel genetic variants that could be linked to rapid disease development. Furthermore, the candidate variants were validated using Sanger sequencing. Two heterozygote variations, c.1077-2A>G and c.199G>A, were found in the MSH2 and the MLH1 genes, respectively. Sanger sequencing analysis confirmed that these (likely) pathogenic mutations segregated in all the affected families' members. In addition, we identified a rare heterozygote variant (c.175C>T) with suspected pathogenic potential in the MAP3K1 gene; formally the variant is of uncertain significance (VUS). Our findings support the hypothesis that CRC onset may be oligogenic and molecularly heterogeneous. Larger and more robust studies are needed to understand the genetic basis of early-onset CRC development, combined with novel functional analyses and omics approaches.
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Affiliation(s)
- Nayeralsadat Fatemi
- Basic and Molecular Epidemiology of Gastrointestinal Disorders Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Siang-Jyun Tu
- Center for Precision Medicine, China Medical University Hospital, Taichung, Taiwan
| | - Chin-Chun Chung
- Center for Precision Medicine, China Medical University Hospital, Taichung, Taiwan
| | - Pardis Ketabi Moghadam
- Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Ehsan Nazemalhosseini Mojarad
- Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Amir Sadeghi
- Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mehdi Totonchi
- Basic and Molecular Epidemiology of Gastrointestinal Disorders Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
- Department of Genetics, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran
| | - Hamid Asadzadeh Aghdaei
- Basic and Molecular Epidemiology of Gastrointestinal Disorders Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Jan-Gowth Chang
- Center for Precision Medicine, China Medical University Hospital, Taichung, Taiwan
- Department of Bioinformatics and Medical Engineering, Asia University, Taichung, Taiwan
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3
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Saini PK, Dawitz H, Aufschnaiter A, Bondarev S, Thomas J, Amblard A, Stewart J, Thierry-Mieg N, Ott M, Pierrel F. The [PSI +] prion modulates cytochrome c oxidase deficiency caused by deletion of COX12. Mol Biol Cell 2022; 33:ar130. [PMID: 36129767 PMCID: PMC9727813 DOI: 10.1091/mbc.e21-10-0499] [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: 10/18/2021] [Revised: 09/09/2022] [Accepted: 09/13/2022] [Indexed: 02/04/2023] Open
Abstract
Cytochrome c oxidase (CcO) is a pivotal enzyme of the mitochondrial respiratory chain, which sustains bioenergetics of eukaryotic cells. Cox12, a peripheral subunit of CcO oxidase, is required for full activity of the enzyme, but its exact function is unknown. Here experimental evolution of a Saccharomyces cerevisiae Δcox12 strain for ∼300 generations allowed to restore the activity of CcO oxidase. In one population, the enhanced bioenergetics was caused by a A375V mutation in the cytosolic AAA+ disaggregase Hsp104. Deletion or overexpression of HSP104 also increased respiration of the Δcox12 ancestor strain. This beneficial effect of Hsp104 was related to the loss of the [PSI+] prion, which forms cytosolic amyloid aggregates of the Sup35 protein. Overall, our data demonstrate that cytosolic aggregation of a prion impairs the mitochondrial metabolism of cells defective for Cox12. These findings identify a new functional connection between cytosolic proteostasis and biogenesis of the mitochondrial respiratory chain.
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Affiliation(s)
- Pawan Kumar Saini
- Univ. Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, 38000 Grenoble, France
| | - Hannah Dawitz
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
| | - Andreas Aufschnaiter
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
| | - Stanislav Bondarev
- Department of Genetics and Biotechnology, St. Petersburg State University, St. Petersburg, Russia
| | - Jinsu Thomas
- Univ. Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, 38000 Grenoble, France
| | - Amélie Amblard
- Univ. Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, 38000 Grenoble, France
| | - James Stewart
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, 50931 Cologne, Germany
- Wellcome Centre for Mitochondrial Research, Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom
| | - Nicolas Thierry-Mieg
- Univ. Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, 38000 Grenoble, France
| | - Martin Ott
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
- Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Gothenburg 40530, Sweden
| | - Fabien Pierrel
- Univ. Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, 38000 Grenoble, France
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Evolutionary Significance of Fungal Hypermutators: Lessons Learned from Clinical Strains and Implications for Fungal Plant Pathogens. mSphere 2022; 7:e0008722. [PMID: 35638358 PMCID: PMC9241500 DOI: 10.1128/msphere.00087-22] [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: 11/20/2022] Open
Abstract
Rapid evolution of fungal pathogens poses a serious threat to medicine and agriculture. The mutation rate determines the pace of evolution of a fungal pathogen. Hypermutator fungal strains have an elevated mutation rate owing to certain defects such as those in the DNA mismatch repair system. Studies in Saccharomyces cerevisiae show that hypermutators expedite evolution by generating beneficial alleles at a faster pace than the wild-type strains. However, an accumulation of deleterious alleles in a hypermutator may reduce its fitness. The balance between fitness cost and mutation benefit determines the prevalence of hypermutators in a population. This balance is affected by a complex interaction of ploidy, mode of reproduction, population size, and recent population history. Studies in human fungal pathogens like Aspergillus fumigatus, Candida albicans, Candida glabrata, Cryptococcus deuterogattii, and Cryptococcus neoformans have highlighted the importance of hypermutators in host adaptation and development of antifungal resistance. However, a critical examination of hypermutator biology, experimental evolution studies, and epidemiological studies suggests that hypermutators may impact evolutionary investigations. This review aims to integrate the knowledge about biology, experimental evolution, and dynamics of fungal hypermutators to critically examine the evolutionary role of hypermutators in fungal pathogen populations and project implications of hypermutators in the evolution of fungal plant pathogen populations. Understanding the factors determining the emergence and evolution of fungal hypermutators can open a novel avenue of managing rapidly evolving fungal pathogens in medicine and agriculture.
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5
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Harder A. Do non-pathogenic variants of DNA mismatch repair genes modify neurofibroma load in neurofibromatosis type 1? Childs Nerv Syst 2022; 38:705-713. [PMID: 34997843 PMCID: PMC8940751 DOI: 10.1007/s00381-021-05436-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 12/13/2021] [Indexed: 01/07/2023]
Abstract
Non-pathogenic mismatch repair (MMR) gene variants can be associated with decreased MMR capacity in several settings. Due to an increased mutation rate, reduced MMR capacity leads to accumulation of somatic sequence changes in tumour suppressor genes such as in the neurofibromatosis type 1 (NF1) gene. Patients with autosomal dominant NF1 typically develop neurofibromas ranging from single to thousands. Concerning the number of neurofibromas NF1 patients face a situation that is still not predictable. A few studies suggested that germline non-pathogenic MMR gene variants modify the number of neurofibromas in NF1 and by this mechanism may promote the extent of neurofibroma manifestation. This review represents first evidence that specific non-pathogenic single nucleotide variants of MMR genes act as a modifier of neurofibroma manifestation in NF1, highlighting MSH2 re4987188 as the best analysed non-pathogenic variant so far. In summary, besides MSH2 promotor methylation, specific non-pathogenic germline MSH2 variants are associated with the extent of neurofibroma manifestation. Those variants can serve as a biomarker to facilitate better mentoring of NF1 patients at risk.
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Affiliation(s)
- Anja Harder
- Institute of Pathology, Medical Faculty, Martin Luther University Halle-Wittenberg, Halle (Saale), 06120, Germany.
- Institute of Neuropathology, University Hospital Münster, Münster, Germany.
- Faculty of Health Sciences, Joint Faculty, Potsdam, Germany.
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6
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Ollodart AR, Yeh CLC, Miller AW, Shirts BH, Gordon AS, Dunham MJ. Multiplexing mutation rate assessment: determining pathogenicity of Msh2 variants in Saccharomyces cerevisiae. Genetics 2021; 218:iyab058. [PMID: 33848333 PMCID: PMC8225350 DOI: 10.1093/genetics/iyab058] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 04/02/2021] [Indexed: 01/01/2023] Open
Abstract
Despite the fundamental importance of mutation rate as a driving force in evolution and disease risk, common methods to assay mutation rate are time-consuming and tedious. Established methods such as fluctuation tests and mutation accumulation experiments are low-throughput and often require significant optimization to ensure accuracy. We established a new method to determine the mutation rate of many strains simultaneously by tracking mutation events in a chemostat continuous culture device and applying deep sequencing to link mutations to alleles of a DNA-repair gene. We applied this method to assay the mutation rate of hundreds of Saccharomyces cerevisiae strains carrying mutations in the gene encoding Msh2, a DNA repair enzyme in the mismatch repair pathway. Loss-of-function mutations in MSH2 are associated with hereditary nonpolyposis colorectal cancer, an inherited disorder that increases risk for many different cancers. However, the vast majority of MSH2 variants found in human populations have insufficient evidence to be classified as either pathogenic or benign. We first benchmarked our method against Luria-Delbrück fluctuation tests using a collection of published MSH2 missense variants. Our pooled screen successfully identified previously characterized nonfunctional alleles as high mutators. We then created an additional 185 human missense variants in the yeast ortholog, including both characterized and uncharacterized alleles curated from ClinVar and other clinical testing data. In a set of alleles of known pathogenicity, our assay recapitulated ClinVar's classification; we then estimated pathogenicity for 157 variants classified as uncertain or conflicting reports of significance. This method is capable of studying the mutation rate of many microbial species and can be applied to problems ranging from the generation of high-fidelity polymerases to measuring the frequency of antibiotic resistance emergence.
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Affiliation(s)
- Anja R Ollodart
- Molecular Cellular Biology Program, University of Washington, Seattle, WA 98195, USA
- Genome Sciences Department, University of Washington, Seattle, WA 98195, USA
| | - Chiann-Ling C Yeh
- Genome Sciences Department, University of Washington, Seattle, WA 98195, USA
| | - Aaron W Miller
- Genome Sciences Department, University of Washington, Seattle, WA 98195, USA
| | - Brian H Shirts
- Department of Laboratory Medicine, University of Washington, Seattle, WA 98195, USA
| | - Adam S Gordon
- Department of Pharmacology, Northwestern University, Chicago, IL 60208, USA
| | - Maitreya J Dunham
- Genome Sciences Department, University of Washington, Seattle, WA 98195, USA
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7
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Harris C, Savas J, Ray S, Shanle EK. Yeast-based screening of cancer mutations in the DNA damage response protein Mre11 demonstrates importance of conserved capping domain residues. Mol Biol Rep 2021; 48:4107-4119. [PMID: 34075539 DOI: 10.1007/s11033-021-06424-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 05/20/2021] [Indexed: 10/21/2022]
Abstract
DNA damage response (DDR) pathways are initiated to prevent mutations from being passed on in the event of DNA damage. Mutations in DDR proteins can contribute to the development and maintenance of cancer cells, but many mutations observed in human tumors have not been functionally characterized. Because a proper response to DNA damage is fundamental to living organisms, DDR proteins and processes are often highly conserved. The goal of this project was to use Saccharomyces cerevisiae as a model for functional screening of human cancer mutations in conserved DDR proteins. After comparing the cancer mutation frequency and conservation of DDR proteins, Mre11 was selected for functional screening. A subset of mutations in conserved residues was analyzed by structural modeling and screened for functional effects in yeast Mre11. Yeast expressing wild type or mutant Mre11 were then assessed for DNA damage sensitivity using hydroxyurea (HU) and methyl methanesulfonate (MMS). The results were further validated in human cancer cells. The N-terminal point mutations tested in yeast Mre11 do not confer sensitivity to DNA damage sensitivity, suggesting that these residues are dispensable for yeast Mre11 function and may have conserved sequence without conserved function. However, a mutation near the capping domain associated with breast and colorectal cancers compromises Mre11 function in both yeast and human cells. These results provide novel insight into the function of this conserved capping domain residue and demonstrate a framework for yeast-based screening of cancer mutations.
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Affiliation(s)
- Caitlin Harris
- Department of Biological and Environmental Sciences, Longwood University, Farmville, VA, 23901, USA
| | - Jessica Savas
- Department of Biological and Environmental Sciences, Longwood University, Farmville, VA, 23901, USA
| | - Sreerupa Ray
- Department of Biology, Linfield University, McMinnville, OR, 97128, USA
| | - Erin K Shanle
- Department of Biological and Environmental Sciences, Longwood University, Farmville, VA, 23901, USA.
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8
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Setting molecular traps in yeast for identification of anticancer drug targets. Proc Natl Acad Sci U S A 2021; 118:2105547118. [PMID: 33853860 PMCID: PMC8106309 DOI: 10.1073/pnas.2105547118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Arlow T, Kim J, Haye-Bertolozzi JE, Martínez CB, Fay C, Zorensky E, Rose MD, Gammie AE. MutSα mismatch repair protein stability is governed by subunit interaction, acetylation, and ubiquitination. G3 (BETHESDA, MD.) 2021; 11:jkaa065. [PMID: 33793773 PMCID: PMC8063085 DOI: 10.1093/g3journal/jkaa065] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 12/14/2020] [Indexed: 11/13/2022]
Abstract
In eukaryotes, DNA mismatch recognition is accomplished by the highly conserved MutSα (Msh2/Msh6) and MutSβ (Msh2/Msh3) complexes. Previously, in the yeast Saccharomyces cerevisiae, we determined that deleting MSH6 caused wild-type Msh2 levels to drop by ∼50%. In this work, we determined that Msh6 steady-state levels are coupled to increasing or decreasing levels of Msh2. Although Msh6 and Msh2 are reciprocally regulated, Msh3 and Msh2 are not. Msh2 missense variants that are able to interact with Msh6 were destabilized when Msh6 was deleted; in contrast, variants that fail to dimerize were not further destabilized in cells lacking Msh6. In the absence of Msh6, Msh2 is turned over at a faster rate and degradation is mediated by the ubiquitin-proteasome pathway. Mutagenesis of certain conserved lysines near the dimer interface restored the levels of Msh2 in the absence of Msh6, further supporting a dimer stabilization mechanism. We identified two alternative forms of regulation both with the potential to act via lysine residues, including acetylation by Gcn5 and ubiquitination by the Not4 ligase. In the absence of Gcn5, Msh2 levels were significantly decreased; in contrast, deleting Not4 stabilized Msh2 and Msh2 missense variants with partial function. The stabilizing effect on Msh2 by either the presence of Msh6 or the absence of Not4 are dependent on Gcn5. Taken together, the results suggest that the wild-type MutSα mismatch repair protein stability is governed by subunit interaction, acetylation, and ubiquitination.
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Affiliation(s)
- Tim Arlow
- Ophthalmic Associates, Johnstown, PA
| | | | | | | | | | | | - Mark D. Rose
- Georgetown University, Georgetown, Washington D.C
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Jia X, Burugula BB, Chen V, Lemons RM, Jayakody S, Maksutova M, Kitzman JO. Massively parallel functional testing of MSH2 missense variants conferring Lynch syndrome risk. Am J Hum Genet 2021; 108:163-175. [PMID: 33357406 PMCID: PMC7820803 DOI: 10.1016/j.ajhg.2020.12.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 12/03/2020] [Indexed: 12/20/2022] Open
Abstract
The lack of functional evidence for the majority of missense variants limits their clinical interpretability and poses a key barrier to the broad utility of carrier screening. In Lynch syndrome (LS), one of the most highly prevalent cancer syndromes, nearly 90% of clinically observed missense variants are deemed “variants of uncertain significance” (VUS). To systematically resolve their functional status, we performed a massively parallel screen in human cells to identify loss-of-function missense variants in the key DNA mismatch repair factor MSH2. The resulting functional effect map is substantially complete, covering 94% of the 17,746 possible variants, and is highly concordant (96%) with existing functional data and expert clinicians’ interpretations. The large majority (89%) of missense variants were functionally neutral, perhaps unexpectedly in light of its evolutionary conservation. These data provide ready-to-use functional evidence to resolve the ∼1,300 extant missense VUSs in MSH2 and may facilitate the prospective classification of newly discovered variants in the clinic.
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Djursby M, Madsen MB, Frederiksen JH, Berchtold LA, Therkildsen C, Willemoe GL, Hasselby JP, Wikman F, Okkels H, Skytte AB, Nilbert M, Wadt K, Gerdes AM, van Overeem Hansen T. New Pathogenic Germline Variants in Very Early Onset and Familial Colorectal Cancer Patients. Front Genet 2020; 11:566266. [PMID: 33193653 PMCID: PMC7541943 DOI: 10.3389/fgene.2020.566266] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 08/24/2020] [Indexed: 12/30/2022] Open
Abstract
A genetic diagnosis facilitates personalized cancer treatment and clinical care of relatives at risk, however, although 25% of colorectal cancer cases are familial, around 95% of the families are genetically unresolved. In this study, we performed gene panel analysis on germline DNA of 32 established or candidate colorectal cancer predisposing genes in 149 individuals from either families with an accumulation of colorectal cancers or families with only one sporadic case of very early onset colorectal cancer (≤40 years at diagnosis). We identified pathogenic or likely pathogenic genetic variants in 10.1% of the participants in genes such as APC, POLE, MSH2 or PMS2. The MSH2 variant, c.2168C>T, p.(Ser723Phe) was previously described as a variant of unknown significance, but we have now reclassified it to be likely pathogenic. The POLE variant, c.1089C>A, p.(Asn363Lys) was identified in a patient with three metachronous colorectal cancers from age 28 and turned out to be de novo. One pathogenic PMS2 variant was novel. We also identified a number of highly interesting variants of unknown significance in APC, BUB1, TP53 and RPS20. The RPS20 variant is novel and was found in a large Amsterdam I positive family with a multi tumor phenotype including 12 cases of CRC from as early as age 24. This variant was found to segregate with cancer in the family and multiple in silico tools predict it to be pathogenic. Our data further support the shift from phenotypic-based cancer panels to large panels including all established genes involved in hereditary cancer syndromes or (targeted) whole genome sequencing. Additionally, identification of a likely disease-predisposing variant in RPS20 expands the phenotypic spectrum of RPS20-related cancers and emphasize that this gene is relevant to include in colorectal cancer gene panels.
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Affiliation(s)
- Malene Djursby
- Department of Clinical Genetics, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Majbritt B Madsen
- Center for Genomic Medicine, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Jane H Frederiksen
- Department of Clinical Genetics, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Lukas A Berchtold
- Center for Genomic Medicine, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Christina Therkildsen
- The Danish HNPCC Register, Clinical Research Centre, Copenhagen University Hospital, Hvidovre, Denmark
| | - Gro L Willemoe
- Department of Pathology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Jane P Hasselby
- Department of Pathology, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Friedrik Wikman
- Department of Molecular Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Henrik Okkels
- Section of Molecular Diagnostics, Department of Clinical Chemistry, Aalborg University Hospital, Aalborg, Denmark
| | - Anne-Bine Skytte
- Department of Clinical Genetics, Aarhus University Hospital, Aarhus, Denmark
| | - Mef Nilbert
- The Danish HNPCC Register, Clinical Research Centre, Copenhagen University Hospital, Hvidovre, Denmark
| | - Karin Wadt
- Department of Clinical Genetics, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Anne-Marie Gerdes
- Department of Clinical Genetics, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
| | - Thomas van Overeem Hansen
- Department of Clinical Genetics, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
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Mirzaei R, Mohammadzadeh R, Mirzaei H, Sholeh M, Karampoor S, Abdi M, Alikhani MY, Kazemi S, Ahmadyousefi Y, Jalalifar S, Yousefimashouf R. Role of
microRNAs
in
Staphylococcus aureus
infection: Potential biomarkers and mechanism. IUBMB Life 2020; 72:1856-1869. [DOI: 10.1002/iub.2325] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 05/15/2020] [Indexed: 01/27/2023]
Affiliation(s)
- Rasoul Mirzaei
- Department of Microbiology, School of MedicineHamadan University of Medical Sciences Hamadan Iran
| | - Rokhsareh Mohammadzadeh
- Department of Microbiology, School of MedicineIran University of Medical Sciences Tehran Iran
| | - Hamed Mirzaei
- Research Center for Biochemistry and Nutrition in Metabolic Diseases, Institute for Basic SciencesKashan University of Medical Sciences Kashan Iran
| | - Mohammad Sholeh
- Department of Microbiology, School of MedicineIran University of Medical Sciences Tehran Iran
| | - Sajad Karampoor
- Department of Virology, School of MedicineIran University of Medical Sciences Tehran Iran
| | - Milad Abdi
- Department of Microbiology, School of MedicineIran University of Medical Sciences Tehran Iran
- Student Research Committee, Faculty of MedicineIran University of Medical Sciences Tehran Iran
| | - Mohammad Yousef Alikhani
- Department of Microbiology, School of MedicineHamadan University of Medical Sciences Hamadan Iran
| | - Sima Kazemi
- Department of Microbiology, School of MedicineHamadan University of Medical Sciences Hamadan Iran
| | - Yaghoub Ahmadyousefi
- Department of Medical Biotechnology, School of Advanced Medical Sciences and TechnologiesHamadan University of Medical Sciences Hamadan Iran
- Research Center for Molecular MedicineHamadan University of Medical Sciences Hamadan Iran
| | - Saba Jalalifar
- Department of Microbiology, School of MedicineIran University of Medical Sciences Tehran Iran
| | - Rasoul Yousefimashouf
- Department of Microbiology, School of MedicineHamadan University of Medical Sciences Hamadan Iran
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Cervelli T, Lodovichi S, Bellè F, Galli A. Yeast-based assays for the functional characterization of cancer-associated variants of human DNA repair genes. MICROBIAL CELL 2020; 7:162-174. [PMID: 32656256 PMCID: PMC7328678 DOI: 10.15698/mic2020.07.721] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Technological advances are continuously revealing new genetic variants that are often difficult to interpret. As one of the most genetically tractable model organisms, yeast can have a central role in determining the consequences of human genetic variation. DNA repair gene mutations are associated with many types of cancers, therefore the evaluation of the functional impact of these mutations is crucial for risk assessment and for determining therapeutic strategies. Owing to the evolutionary conservation of DNA repair pathways between human cells and the yeast Saccharomyces cerevisiae, several functional assays have been developed. Here, we describe assays for variants of human genes belonging to the major DNA repair pathways divided in functional assays for human genes with yeast orthologues and human genes lacking a yeast orthologue. Human genes with orthologues can be studied by introducing the correspondent human mutations directly in the yeast gene or expressing the human gene carrying the mutations; while the only possible approach for human genes without a yeast orthologue is the heterologous expression. The common principle of these approaches is that the mutated gene determines a phenotypic alteration that can vary according to the gene studied and the domain of the protein. Here, we show how the versatility of yeast can help in classifying cancer-associated variants.
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Affiliation(s)
- Tiziana Cervelli
- Yeast Genetics and Genomics Group, Laboratory of Functional Genetics and Genomics, Institute of Clinical Physiology CNR, Via Moruzzi 1, 56125 Pisa, Italy
| | - Samuele Lodovichi
- Yeast Genetics and Genomics Group, Laboratory of Functional Genetics and Genomics, Institute of Clinical Physiology CNR, Via Moruzzi 1, 56125 Pisa, Italy
| | - Francesca Bellè
- Yeast Genetics and Genomics Group, Laboratory of Functional Genetics and Genomics, Institute of Clinical Physiology CNR, Via Moruzzi 1, 56125 Pisa, Italy
| | - Alvaro Galli
- Yeast Genetics and Genomics Group, Laboratory of Functional Genetics and Genomics, Institute of Clinical Physiology CNR, Via Moruzzi 1, 56125 Pisa, Italy
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15
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Abstract
Antifungal resistance is an inevitable phenomenon when fungal pathogens are exposed to antifungal drugs. These drugs can be grouped in four distinct classes (azoles, candins, polyenes, and pyrimidine analogs) and are used in different clinical settings. Failures in therapy implicate the sequential or combined use of these different drug classes, which can result in some cases in the development of multidrug resistance (MDR). MDR is particularly challenging in the clinic since it drastically reduces possible treatment alternatives. In this study, we report the rapid development of MDR in Candida lusitaniae in a patient, which became resistant to all known antifungal agents used until now in medicine. To understand how MDR developed in C. lusitaniae, whole-genome sequencing followed by comparative genome analysis was undertaken in sequential MDR isolates. This helped to detect all specific mutations linked to drug resistance and explained the different MDR patterns exhibited by the clinical isolates. Multidrug resistance (MDR) has emerged in hospitals due to the use of several agents administered in combination or sequentially to the same individual. We reported earlier MDR in Candida lusitaniae during therapy with amphotericin B (AmB), azoles, and candins. Here, we used comparative genomic approaches between the initial susceptible isolate and 4 other isolates with different MDR profiles. From a total of 18 nonsynonymous single nucleotide polymorphisms (NSS) in genome comparisons with the initial isolate, six could be associated with MDR. One of the single nucleotide polymorphisms (SNPs) occurred in a putative transcriptional activator (MRR1) resulting in a V668G substitution in isolates resistant to azoles and 5-fluorocytosine (5-FC). We demonstrated by genome editing that MRR1 acted by upregulation of MFS7 (a multidrug transporter) in the presence of the V668G substitution. MFS7 itself mediated not only azole resistance but also 5-FC resistance, which represents a novel resistance mechanism for this drug class. Three other distinct NSS occurred in FKS1 (a glucan synthase gene that is targeted by candins) in three candin-resistant isolates. Last, two other NSS in ERG3 and ERG4 (ergosterol biosynthesis) resulting in nonsense mutations were revealed in AmB-resistant isolates, one of which accumulated the two ERG NSS. AmB-resistant isolates lacked ergosterol and exhibited sterol profiles, consistent with ERG3 and ERG4 defects. In conclusion, this genome analysis combined with genetics and metabolomics helped decipher the resistance profiles identified in this clinical case. MDR isolates accumulated six different mutations conferring resistance to all antifungal agents used in medicine. This case study illustrates the capacity of C. lusitaniae to rapidly adapt under drug pressure within the host.
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16
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Abildgaard AB, Stein A, Nielsen SV, Schultz-Knudsen K, Papaleo E, Shrikhande A, Hoffmann ER, Bernstein I, Gerdes AM, Takahashi M, Ishioka C, Lindorff-Larsen K, Hartmann-Petersen R. Computational and cellular studies reveal structural destabilization and degradation of MLH1 variants in Lynch syndrome. eLife 2019; 8:e49138. [PMID: 31697235 PMCID: PMC6837844 DOI: 10.7554/elife.49138] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 10/23/2019] [Indexed: 12/13/2022] Open
Abstract
Defective mismatch repair leads to increased mutation rates, and germline loss-of-function variants in the repair component MLH1 cause the hereditary cancer predisposition disorder known as Lynch syndrome. Early diagnosis is important, but complicated by many variants being of unknown significance. Here we show that a majority of the disease-linked MLH1 variants we studied are present at reduced cellular levels. We show that destabilized MLH1 variants are targeted for chaperone-assisted proteasomal degradation, resulting also in degradation of co-factors PMS1 and PMS2. In silico saturation mutagenesis and computational predictions of thermodynamic stability of MLH1 missense variants revealed a correlation between structural destabilization, reduced steady-state levels and loss-of-function. Thus, we suggest that loss of stability and cellular degradation is an important mechanism underlying many MLH1 variants in Lynch syndrome. Combined with analyses of conservation, the thermodynamic stability predictions separate disease-linked from benign MLH1 variants, and therefore hold potential for Lynch syndrome diagnostics.
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Affiliation(s)
- Amanda B Abildgaard
- Department of Biology, The Linderstrøm-Lang Centre for Protein ScienceUniversity of CopenhagenCopenhagenDenmark
| | - Amelie Stein
- Department of Biology, The Linderstrøm-Lang Centre for Protein ScienceUniversity of CopenhagenCopenhagenDenmark
| | - Sofie V Nielsen
- Department of Biology, The Linderstrøm-Lang Centre for Protein ScienceUniversity of CopenhagenCopenhagenDenmark
| | - Katrine Schultz-Knudsen
- Department of Biology, The Linderstrøm-Lang Centre for Protein ScienceUniversity of CopenhagenCopenhagenDenmark
| | - Elena Papaleo
- Department of Biology, The Linderstrøm-Lang Centre for Protein ScienceUniversity of CopenhagenCopenhagenDenmark
| | - Amruta Shrikhande
- DNRF Center for Chromosome Stability, Department of Cellular and Molecular MedicineUniversity of CopenhagenCopenhagenDenmark
| | - Eva R Hoffmann
- DNRF Center for Chromosome Stability, Department of Cellular and Molecular MedicineUniversity of CopenhagenCopenhagenDenmark
| | - Inge Bernstein
- Department of Surgical GastroenterologyAalborg University HospitalAalborgDenmark
| | | | - Masanobu Takahashi
- Department of Medical OncologyTohoku University Hospital, Tohoku UniversitySendaiJapan
| | - Chikashi Ishioka
- Department of Medical OncologyTohoku University Hospital, Tohoku UniversitySendaiJapan
| | - Kresten Lindorff-Larsen
- Department of Biology, The Linderstrøm-Lang Centre for Protein ScienceUniversity of CopenhagenCopenhagenDenmark
| | - Rasmus Hartmann-Petersen
- Department of Biology, The Linderstrøm-Lang Centre for Protein ScienceUniversity of CopenhagenCopenhagenDenmark
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17
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Rath A, Mishra A, Ferreira VD, Hu C, Omerza G, Kelly K, Hesse A, Reddi HV, Grady JP, Heinen CD. Functional interrogation of Lynch syndrome-associated MSH2 missense variants via CRISPR-Cas9 gene editing in human embryonic stem cells. Hum Mutat 2019; 40:2044-2056. [PMID: 31237724 DOI: 10.1002/humu.23848] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 05/08/2019] [Accepted: 06/19/2019] [Indexed: 12/18/2022]
Abstract
Lynch syndrome (LS) predisposes patients to cancer and is caused by germline mutations in the DNA mismatch repair (MMR) genes. Identifying the deleterious mutation, such as a frameshift or nonsense mutation, is important for confirming an LS diagnosis. However, discovery of a missense variant is often inconclusive. The effects of these variants of uncertain significance (VUS) on disease pathogenesis are unclear, though understanding their impact on protein function can help determine their significance. Laboratory functional studies performed to date have been limited by their artificial nature. We report here an in-cellulo functional assay in which we engineered site-specific MSH2 VUS using clustered regularly interspaced short palindromic repeats-Cas9 gene editing in human embryonic stem cells. This approach introduces the variant into the endogenous MSH2 loci, while simultaneously eliminating the wild-type gene. We characterized the impact of the variants on cellular MMR functions including DNA damage response signaling and the repair of DNA microsatellites. We classified the MMR functional capability of eight of 10 VUS providing valuable information for determining their likelihood of being bona fide pathogenic LS variants. This human cell-based assay system for functional testing of MMR gene VUS will facilitate the identification of high-risk LS patients.
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Affiliation(s)
- Abhijit Rath
- Center for Molecular Oncology and Institute for Systems Genomics, UConn Health, Farmington, Connecticut
| | - Akriti Mishra
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut
| | | | - Chaoran Hu
- Department of Statistics, University of Connecticut, Storrs, Connecticut.,Connecticut Institute for Clinical and Translational Science, UConn Health, Farmington, Connecticut
| | - Gregory Omerza
- Clinical Genomics Laboratory, The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut
| | - Kevin Kelly
- Clinical Genomics Laboratory, The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut
| | - Andrew Hesse
- Clinical Genomics Laboratory, The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut
| | - Honey V Reddi
- Clinical Genomics Laboratory, The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut
| | - James P Grady
- Connecticut Institute for Clinical and Translational Science, UConn Health, Farmington, Connecticut
| | - Christopher D Heinen
- Center for Molecular Oncology and Institute for Systems Genomics, UConn Health, Farmington, Connecticut
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18
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Natali F, Rancati G. The Mutator Phenotype: Adapting Microbial Evolution to Cancer Biology. Front Genet 2019; 10:713. [PMID: 31447882 PMCID: PMC6691094 DOI: 10.3389/fgene.2019.00713] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 07/05/2019] [Indexed: 01/07/2023] Open
Abstract
The mutator phenotype hypothesis was postulated almost 40 years ago to reconcile the observation that while cancer cells display widespread mutational burden, acquisition of mutations in non-transformed cells is a rare event. Moreover, it also suggested that cancer evolution could be fostered by increased genome instability. Given the evolutionary conservation throughout the tree of life and the genetic tractability of model organisms, yeast and bacterial species pioneered studies to dissect the functions of genes required for genome maintenance (caretaker genes) or for cell growth control (gatekeeper genes). In this review, we first provide an overview of what we learned from model organisms about the roles of these genes and the genome instability that arises as a consequence of their dysregulation. We then discuss our current understanding of how mutator phenotypes shape the evolution of bacteria and yeast species. We end by bringing clinical evidence that lessons learned from single-cell organisms can be applied to tumor evolution.
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Affiliation(s)
- Federica Natali
- Institute of Medical Biology (IMB), Agency for Science, Technology and Research (ASTAR), Singapore, Singapore.,School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Giulia Rancati
- Institute of Medical Biology (IMB), Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
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19
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Bouvet D, Bodo S, Munier A, Guillerm E, Bertrand R, Colas C, Duval A, Coulet F, Muleris M. Methylation Tolerance-Based Functional Assay to Assess Variants of Unknown Significance in the MLH1 and MSH2 Genes and Identify Patients With Lynch Syndrome. Gastroenterology 2019; 157:421-431. [PMID: 30998989 DOI: 10.1053/j.gastro.2019.03.071] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 03/07/2019] [Accepted: 03/29/2019] [Indexed: 12/12/2022]
Abstract
BACKGROUND & AIMS Approximately 75% of patients with suspected Lynch syndrome carry variants in MLH1 or MSH2, proteins encoded by these genes are required for DNA mismatch repair (MMR). However, 30% of these are variants of unknown significance (VUS). A assay that measures cell response to the cytotoxic effects of a methylating agent can determine the effects of VUS in MMR genes and identify patients with constitutional MMR-deficiency syndrome. We adapted this method to test the effects of VUS in MLH1 and MSH2 genes found in patients with suspected Lynch syndrome. METHODS We transiently expressed MLH1 or MSH2 variants in MLH1- or MSH2-null human colorectal cancer cell lines (HCT116 or LoVo), respectively. The MMR process causes death of cells with methylation-damaged DNA bases, so we measured proportions of cells that undergo death following exposure to the methylating agent; cells that escaped its toxicity were considered to have variants that affect function of the gene product. Using this assay, we analyzed 88 variants (mainly missense variants), comprising a validation set of 40 previously classified variants (19 in MLH1 and 21 in MSH2) and a prospective set of 48 VUS (25 in MLH1 and 23 in MSH2). Prediction scores were calculated for all VUS according to the recommendations of the American College of Medical Genetics and Genomics, based on clinical, somatic, in silico, population, and functional data. RESULTS The assay correctly classified 39 of 40 variants in the validation set. The assay identified 12 VUS that did alter function of the gene product and 28 VUS that did not; the remaining 8 VUS had intermediate effects on MMR capacity and could not be classified. Comparison of assay results with prediction scores confirmed the ability of the assay to discriminate VUS that affected the function of the gene products from those that did not. CONCLUSIONS Using an assay that measures the ability of the cells to undergo death following DNA damage induction by a methylating agent, we were able to assess whether variants in MLH1 and MSH2 cause defects in DNA MMR. This assay might be used to help assessing the pathogenicity of VUS in MLH1 and MSH2 found in patients with suspected Lynch syndrome.
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Affiliation(s)
- Delphine Bouvet
- Sorbonne Université, Inserm, Centre de Recherche Saint-Antoine, CRSA, Paris, France; Equipe labellisée par la Ligue Nationale contre le Cancer, Paris, France
| | - Sahra Bodo
- Sorbonne Université, Inserm, Centre de Recherche Saint-Antoine, CRSA, Paris, France; Equipe labellisée par la Ligue Nationale contre le Cancer, Paris, France
| | - Annie Munier
- Sorbonne Université, Inserm, Centre de recherche Saint-Antoine, UMS30-LUMIC, Plateforme de Cytométrie en Flux CISA, site Saint-Antoine, Paris, France
| | - Erell Guillerm
- Sorbonne Université, Inserm, Centre de Recherche Saint-Antoine, CRSA, Paris, France; Equipe labellisée par la Ligue Nationale contre le Cancer, Paris, France; Genetics Department, AP-HP, Hôpital Universitaire Pitié-Salpétrière, Paris, France
| | - Romane Bertrand
- Sorbonne Université, Inserm, Centre de Recherche Saint-Antoine, CRSA, Paris, France; Equipe labellisée par la Ligue Nationale contre le Cancer, Paris, France
| | - Chrystelle Colas
- Sorbonne Université, Inserm, Centre de Recherche Saint-Antoine, CRSA, Paris, France; Equipe labellisée par la Ligue Nationale contre le Cancer, Paris, France; Institut Curie, Paris Sciences Lettres Research University, Department of Genetics, Paris, France
| | - Alex Duval
- Equipe labellisée par la Ligue Nationale contre le Cancer, Paris, France; Sorbonne Université, Inserm, Centre de Recherche Saint-Antoine, CRSA, AP-HP, Biochimie, biologie moléculaire, Paris, France
| | - Florence Coulet
- Sorbonne Université, Inserm, Centre de Recherche Saint-Antoine, CRSA, Paris, France; Equipe labellisée par la Ligue Nationale contre le Cancer, Paris, France; Genetics Department, AP-HP, Hôpital Universitaire Pitié-Salpétrière, Paris, France
| | - Martine Muleris
- Sorbonne Université, Inserm, Centre de Recherche Saint-Antoine, CRSA, Paris, France; Equipe labellisée par la Ligue Nationale contre le Cancer, Paris, France.
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20
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A Novel, Drug Resistance-Independent, Fluorescence-Based Approach To Measure Mutation Rates in Microbial Pathogens. mBio 2019; 10:mBio.00120-19. [PMID: 30808701 PMCID: PMC6391916 DOI: 10.1128/mbio.00120-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Measurements of mutation rates—i.e., how often proliferating cells acquire mutations in their DNA—are essential for understanding cellular processes that maintain genome stability. Many traditional mutation rate measurement assays are based on detecting mutations that cause resistance to a particular drug. Such assays typically work well for laboratory strains but have significant limitations when comparing clinical or environmental isolates that have various intrinsic levels of drug tolerance, which confounds the interpretation of results. Here we report the development and validation of a novel method of measuring mutation rates, which detects mutations that cause loss of fluorescence rather than acquisition of drug resistance. Using this method, we measured the mutation rates of clinical isolates of fungal pathogen Candida glabrata. This assay can be adapted to other organisms and used to compare mutation rates in contexts where unequal drug sensitivity is anticipated. All evolutionary processes are underpinned by a cellular capacity to mutate DNA. To identify factors affecting mutagenesis, it is necessary to compare mutation rates between different strains and conditions. Drug resistance-based mutation reporters are used extensively to measure mutation rates, but they are suitable only when the compared strains have identical drug tolerance levels—a condition that is not satisfied under many “real-world” circumstances, e.g., when comparing mutation rates among a series of environmental or clinical isolates. Candida glabrata is a fungal pathogen that shows a high degree of genetic diversity and fast emergence of antifungal drug resistance. To enable meaningful comparisons of mutation rates among C. glabrata clinical isolates, we developed a novel fluorescence-activated cell sorting-based approach to measure the mutation rate of a chromosomally integrated GFP gene. We found that in Saccharomyces cerevisiae this approach recapitulated the reported mutation rate of a wild-type strain and the mutator phenotype of a shu1Δ mutant. In C. glabrata, the GFP reporter captured the mutation rate increases caused either by a genotoxic agent or by deletion of DNA mismatch repair gene MSH2, as well as the specific mutational signature associated with msh2Δ. Finally, the reporter was used to measure the mutation rates of C. glabrata clinical isolates carrying different alleles of MSH2. Together, these results show that fluorescence-based mutation reporters can be used to measure mutation rates in microbes under conditions of unequal drug susceptibility to reveal new insights about drivers of mutagenesis.
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21
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Hayashida G, Shioi S, Hidaka K, Fujikane R, Hidaka M, Tsurimoto T, Tsuzuki T, Oda S, Nakatsu Y. Differential genomic destabilisation in human cells with pathogenic MSH2 mutations introduced by genome editing. Exp Cell Res 2019; 377:24-35. [PMID: 30802454 DOI: 10.1016/j.yexcr.2019.02.020] [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: 11/29/2018] [Accepted: 02/20/2019] [Indexed: 12/12/2022]
Abstract
Repeat destabilisation is variously associated with human disease. In neoplastic diseases, microsatellite instability (MSI) has been regarded as simply reflecting DNA mismatch repair (MMR) deficiency. However, several discrepancies have been pointed out. Firstly, the MSI+ phenotype is not uniform in human neoplasms. Established classification utilises the frequency of microsatellite changes, i.e. MSI-H (high) and -L (low), the former regarded as an authentic MMR-defective phenotype. In addition, we have observed the qualitatively distinct modes of MSI, i.e. Type A and Type B. One discrepancy we previously pointed out is that tumours occurring in MMR gene knockout mice exhibited not drastic microsatellite changes typical in MSI-H tumours (i.e. Type B mode) but minor and more subtle alterations (i.e. Type A mode). In the present study, MSH2 mutations reported in Lynch syndrome (LS) kindred have been introduced into HeLa cells using the CRISPR/Cas9 system. The established mutant clones clearly exhibited MMR-defective phenotypes with alkylating agent-tolerance and elevated mutation frequencies. Nevertheless, microsatellites were not markedly destabilised as in MSI-H tumours occurring in LS patients, and all the observed alterations were uniformly Type A, which confirms the results in mice. Our findings suggest added complexities to the molecular mechanisms underlying repeat destabilisation in human genome.
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Affiliation(s)
- Genki Hayashida
- Department of Medical Biophysics and Radiation Biology, Faculty of Medical Sciences, Kyushu University, Japan; Department of Biology, School of Sciences, Kyushu University, Fukuoka, Japan
| | - Seijiro Shioi
- Clinical Research Institute, Cancer Genetics Laboratory, National Kyushu Cancer Center, Fukuoka, Japan
| | - Kyoko Hidaka
- Centre for Fundamental Education, University of Kitakyushu, Kitakyushu, Japan
| | - Ryosuke Fujikane
- Department of Odontology and Fukuoka Dental College, Fukuoka, Japan
| | - Masumi Hidaka
- Department of Odontology and Fukuoka Dental College, Fukuoka, Japan
| | - Toshiki Tsurimoto
- Department of Biology, School of Sciences, Kyushu University, Fukuoka, Japan
| | - Teruhisa Tsuzuki
- Department of Medical Biophysics and Radiation Biology, Faculty of Medical Sciences, Kyushu University, Japan; Advanced Science Research Center, Fukuoka Dental College, Fukuoka, Japan
| | - Shinya Oda
- Clinical Research Institute, Cancer Genetics Laboratory, National Kyushu Cancer Center, Fukuoka, Japan.
| | - Yoshimichi Nakatsu
- Department of Medical Biophysics and Radiation Biology, Faculty of Medical Sciences, Kyushu University, Japan.
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22
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Mercatanti A, Lodovichi S, Cervelli T, Galli A. CRIMEtoYHU: a new web tool to develop yeast-based functional assays for characterizing cancer-associated missense variants. FEMS Yeast Res 2018; 17:4562592. [PMID: 29069390 DOI: 10.1093/femsyr/fox078] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 09/25/2017] [Indexed: 12/13/2022] Open
Abstract
Evaluation of the functional impact of cancer-associated missense variants is more difficult than for protein-truncating mutations and consequently standard guidelines for the interpretation of sequence variants have been recently proposed. A number of algorithms and software products were developed to predict the impact of cancer-associated missense mutations on protein structure and function. Importantly, direct assessment of the variants using high-throughput functional assays using simple genetic systems can help in speeding up the functional evaluation of newly identified cancer-associated variants. We developed the web tool CRIMEtoYHU (CTY) to help geneticists in the evaluation of the functional impact of cancer-associated missense variants. Humans and the yeast Saccharomyces cerevisiae share thousands of protein-coding genes although they have diverged for a billion years. Therefore, yeast humanization can be helpful in deciphering the functional consequences of human genetic variants found in cancer and give information on the pathogenicity of missense variants. To humanize specific positions within yeast genes, human and yeast genes have to share functional homology. If a mutation in a specific residue is associated with a particular phenotype in humans, a similar substitution in the yeast counterpart may reveal its effect at the organism level. CTY simultaneously finds yeast homologous genes, identifies the corresponding variants and determines the transferability of human variants to yeast counterparts by assigning a reliability score (RS) that may be predictive for the validity of a functional assay. CTY analyzes newly identified mutations or retrieves mutations reported in the COSMIC database, provides information about the functional conservation between yeast and human and shows the mutation distribution in human genes. CTY analyzes also newly found mutations and aborts when no yeast homologue is found. Then, on the basis of the protein domain localization and functional conservation between yeast and human, the selected variants are ranked by the RS. The RS is assigned by an algorithm that computes functional data, type of mutation, chemistry of amino acid substitution and the degree of mutation transferability between human and yeast protein. Mutations giving a positive RS are highly transferable to yeast and, therefore, yeast functional assays will be more predictable. To validate the web application, we have analyzed 8078 cancer-associated variants located in 31 genes that have a yeast homologue. More than 50% of variants are transferable to yeast. Incidentally, 88% of all transferable mutations have a reliability score >0. Moreover, we analyzed by CTY 72 functionally validated missense variants located in yeast genes at positions corresponding to the human cancer-associated variants. All these variants gave a positive RS. To further validate CTY, we analyzed 3949 protein variants (with positive RS) by the predictive algorithm PROVEAN. This analysis shows that yeast-based functional assays will be more predictable for the variants with positive RS. We believe that CTY could be an important resource for the cancer research community by providing information concerning the functional impact of specific mutations, as well as for the design of functional assays useful for decision support in precision medicine.
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Affiliation(s)
- Alberto Mercatanti
- Yeast Genetics and Genomics Group, Laboratory of Functional Genetics and Genomics, Institute of Clinical Physiology CNR, via G. Moruzzi 1, 56124 Pisa, Italy
| | - Samuele Lodovichi
- Yeast Genetics and Genomics Group, Laboratory of Functional Genetics and Genomics, Institute of Clinical Physiology CNR, via G. Moruzzi 1, 56124 Pisa, Italy
- PhD program in Clinical and Translational Science, University of Pisa, Pisa, Italy
| | - Tiziana Cervelli
- Yeast Genetics and Genomics Group, Laboratory of Functional Genetics and Genomics, Institute of Clinical Physiology CNR, via G. Moruzzi 1, 56124 Pisa, Italy
| | - Alvaro Galli
- Yeast Genetics and Genomics Group, Laboratory of Functional Genetics and Genomics, Institute of Clinical Physiology CNR, via G. Moruzzi 1, 56124 Pisa, Italy
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23
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Gibney PA, Schieler A, Chen JC, Bacha-Hummel JM, Botstein M, Volpe M, Silverman SJ, Xu Y, Bennett BD, Rabinowitz JD, Botstein D. Common and divergent features of galactose-1-phosphate and fructose-1-phosphate toxicity in yeast. Mol Biol Cell 2018; 29:897-910. [PMID: 29444955 PMCID: PMC5896929 DOI: 10.1091/mbc.e17-11-0666] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Metabolic dysregulation leading to sugar-phosphate accumulation is toxic in organisms ranging from bacteria to humans. By comparing two models of sugar-phosphate toxicity in Saccharomyces cerevisiae, we demonstrate that toxicity occurs, at least in part, through multiple, isomer-specific mechanisms, rather than a single general mechanism.
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Affiliation(s)
- Patrick A Gibney
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544.,Calico Life Sciences LLC, South San Francisco, CA 94080.,Department of Food Science, Cornell University, Ithaca, NY 14853
| | - Ariel Schieler
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544
| | - Jonathan C Chen
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544.,Department of Chemistry, Princeton University, Princeton, NJ 08544
| | | | - Maxim Botstein
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544
| | - Matthew Volpe
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544
| | - Sanford J Silverman
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544
| | - Yifan Xu
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544.,Department of Chemistry, Princeton University, Princeton, NJ 08544
| | | | - Joshua D Rabinowitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544.,Department of Chemistry, Princeton University, Princeton, NJ 08544
| | - David Botstein
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544.,Calico Life Sciences LLC, South San Francisco, CA 94080.,Department of Food Science, Cornell University, Ithaca, NY 14853
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24
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Miyashita K, Fujii K, Suehiro Y, Taguchi K, Uike N, Yoshida MA, Oda S. Heterochronous occurrence of microsatellite instability in multiple myeloma - an implication for a role of defective DNA mismatch repair in myelomagenesis. Leuk Lymphoma 2018; 59:2454-2459. [PMID: 29384409 DOI: 10.1080/10428194.2018.1427862] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Kaname Miyashita
- a Department of Hematology , National Kyushu Cancer Center , Fukuoka , Japan.,b Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences , Kyushu University , Fukuoka , Japan
| | - Kei Fujii
- c Department of Surgery and Oncology, Graduate School of Medical Sciences , Kyushu University , Fukuoka , Japan
| | - Youko Suehiro
- a Department of Hematology , National Kyushu Cancer Center , Fukuoka , Japan
| | - Kenichi Taguchi
- d Clinical Research Institute, Cancer Genetics Laboratory , National Kyushu Cancer Center , Fukuoka , Japan
| | - Naokuni Uike
- a Department of Hematology , National Kyushu Cancer Center , Fukuoka , Japan
| | - Mitsuaki A Yoshida
- e Department of Radiation Biology, Institute of Radiation Emergency Medicine , Hirosaki University , Aomori , Japan
| | - Shinya Oda
- d Clinical Research Institute, Cancer Genetics Laboratory , National Kyushu Cancer Center , Fukuoka , Japan
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25
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Kampmeyer C, Nielsen SV, Clausen L, Stein A, Gerdes AM, Lindorff-Larsen K, Hartmann-Petersen R. Blocking protein quality control to counter hereditary cancers. Genes Chromosomes Cancer 2017; 56:823-831. [PMID: 28779490 DOI: 10.1002/gcc.22487] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2017] [Revised: 07/29/2017] [Accepted: 08/01/2017] [Indexed: 12/28/2022] Open
Abstract
Inhibitors of molecular chaperones and the ubiquitin-proteasome system have already been clinically implemented to counter certain cancers, including multiple myeloma and mantle cell lymphoma. The efficacy of this treatment relies on genomic alterations in cancer cells causing a proteostatic imbalance, which makes them more dependent on protein quality control (PQC) mechanisms than normal cells. Accordingly, blocking PQC, e.g. by proteasome inhibitors, may cause a lethal proteotoxic crisis in cancer cells, while leaving normal cells unaffected. Evidence, however, suggests that the PQC system operates by following a better-safe-than-sorry principle and is thus prone to target proteins that are only slightly structurally perturbed, but still functional. Accordingly, implementing PQC inhibitors may also, through an entirely different mechanism, hold potential for other cancers. Several inherited cancer susceptibility syndromes, such as Lynch syndrome and von Hippel-Lindau disease, are caused by missense mutations in tumor suppressor genes, and in some cases, the resulting amino acid substitutions in the encoded proteins cause the cellular PQC system to target them for degradation, although they may still retain function. As a consequence of this over-meticulous PQC mechanism, the cell may end up with an insufficient amount of the abnormal, but functional, protein, which in turn leads to a loss-of-function phenotype and manifestation of the disease. Increasing the amounts of such proteins by stabilizing with chemical chaperones, or by targeting molecular chaperones or the ubiquitin-proteasome system, may thus avert or delay the disease onset. Here, we review the potential of targeting the PQC system in hereditary cancer susceptibility syndromes.
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Affiliation(s)
- Caroline Kampmeyer
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, DK-2200, Denmark
| | - Sofie V Nielsen
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, DK-2200, Denmark
| | - Lene Clausen
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, DK-2200, Denmark
| | - Amelie Stein
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, DK-2200, Denmark
| | - Anne-Marie Gerdes
- Department of Clinical Genetics, Rigshospitalet, Blegdamsvej 9, Copenhagen, DK-2100, Denmark
| | - Kresten Lindorff-Larsen
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, DK-2200, Denmark
| | - Rasmus Hartmann-Petersen
- Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen, DK-2200, Denmark
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Predicting the impact of Lynch syndrome-causing missense mutations from structural calculations. PLoS Genet 2017; 13:e1006739. [PMID: 28422960 PMCID: PMC5415204 DOI: 10.1371/journal.pgen.1006739] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 05/03/2017] [Accepted: 04/05/2017] [Indexed: 12/02/2022] Open
Abstract
Accurate methods to assess the pathogenicity of mutations are needed to fully leverage the possibilities of genome sequencing in diagnosis. Current data-driven and bioinformatics approaches are, however, limited by the large number of new variations found in each newly sequenced genome, and often do not provide direct mechanistic insight. Here we demonstrate, for the first time, that saturation mutagenesis, biophysical modeling and co-variation analysis, performed in silico, can predict the abundance, metabolic stability, and function of proteins inside living cells. As a model system, we selected the human mismatch repair protein, MSH2, where missense variants are known to cause the hereditary cancer predisposition disease, known as Lynch syndrome. We show that the majority of disease-causing MSH2 mutations give rise to folding defects and proteasome-dependent degradation rather than inherent loss of function, and accordingly our in silico modeling data accurately identifies disease-causing mutations and outperforms the traditionally used genetic disease predictors. Thus, in conclusion, in silico biophysical modeling should be considered for making genotype-phenotype predictions and for diagnosis of Lynch syndrome, and perhaps other hereditary diseases. The protein quality control system targets misfolded proteins for degradation. So far it has not been possible from sequence or structural data to predict the biological stability of a misfolded protein, or the effect of mutations on intracellular protein levels. Here we demonstrate that in silico saturation mutagenesis and biophysical calculations of the structural stability of the human mismatch repair protein MSH2 correlate with cellular protein levels, turnover and function. Of 24 different MSH2 variants, some of which are linked to Lynch syndrome, a destabilization of as little as 3 kcal/mol is sufficient to cause rapid degradation via the ubiquitin-proteasome pathway. Thus, biophysical modeling can, to a large extent, predict the metabolic stability of proteins. We also show that the same biophysical calculations can be used to distinguish with high accuracy neutral sequence variation from pathogenic variants, and that the calculations outperform several traditionally used disease predictors. We therefore suggest the method to be of potential value for patient stratification in Lynch syndrome, and perhaps other hereditary diseases.
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27
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Lodovichi S, Vitello M, Cervelli T, Galli A. Expression of cancer related BRCA1 missense variants decreases MMS-induced recombination in Saccharomyces cerevisiae without altering its nuclear localization. Cell Cycle 2016; 15:2723-31. [PMID: 27484786 DOI: 10.1080/15384101.2016.1215389] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
BRCA1 tumor suppressor gene is found mutated in familial breast and ovarian cancer. Most cancer related mutations were found located at the RING (Really Interesting New Gene) and at the BRCT (BRca1 C-Terminal) domain. However, 20 y after its identification, the biological role of BRCA1 and which domains are more relevant for tumor suppression are still being elucidated. We previously reported that expression of BRCA1 cancer related variants in the RING and BRCT domain increases spontaneous homologous recombination in yeast indicating that BRCA1 may interact with yeast DNA repair/recombination. To finally demonstrate whether BRCA1 interacts with yeast DNA repair, we exposed yeast cells expressing BRCA1wt, the cancer-related variants C-61G and M1775R to different doses of the alkylating agent methyl methane-sulfonate (MMS) and then evaluated the effect on survival and homologous recombination. Cells expressing BRCA1 cancer variants were more sensitive to MMS and less inducible to recombination as compared to cell expressing BRCA1wt. Moreover, BRCA1-C61G and -M1775R did not change their nuclear localization form as compared to the BRCA1wt or the neutral variant R1751Q indicating a difference in the DNA damage processing. We propose a model where BRCA1 cancer variants interact with the DNA double strand break repair pathways producing DNA recombination intermediates, that maybe less repairable and decrease MMS-induced recombination and survival. Again, this study strengthens the use of yeast as model system to characterize the mechanisms leading to cancer in humans carrying the BRCA1 missense variant.
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Affiliation(s)
- Samuele Lodovichi
- a Yeast Genetics and Genomics, Institute of Clinical Physiology , CNR, Pisa , Italy
| | - Martina Vitello
- a Yeast Genetics and Genomics, Institute of Clinical Physiology , CNR, Pisa , Italy
| | - Tiziana Cervelli
- a Yeast Genetics and Genomics, Institute of Clinical Physiology , CNR, Pisa , Italy
| | - Alvaro Galli
- a Yeast Genetics and Genomics, Institute of Clinical Physiology , CNR, Pisa , Italy
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Hinkle KL, Anderson CC, Forkey B, Griffin J, Cone K, Vitzthum C, Olsen D. Exposure to the lampricide 3-trifluoromethyl-4-nitrophenol results in increased expression of carbohydrate transporters in Saccharomyces cerevisiae. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2016; 35:1727-1732. [PMID: 26606276 PMCID: PMC5076018 DOI: 10.1002/etc.3314] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 09/10/2015] [Accepted: 11/24/2015] [Indexed: 06/05/2023]
Abstract
The lampricide 3-trifluoromethyl-4-nitrophenol (TFM) is used to control sea lamprey (Petromyzon marinus) populations in freshwater lakes. Although TFM can have sublethal and lethal effects, little is known about gene expression changes with TFM exposure. Microarray analysis was used to determine differential gene expression over 4 h of exposure in Saccharomyces cerevisiae. Among the most significantly up-regulated genes were regulators of carbohydrate transport, including HXT1, HXT3, HXT4, IMA5, MIG2, and YKR075C. Environ Toxicol Chem 2016;35:1727-1732. © 2015 SETAC.
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Affiliation(s)
- Karen L. Hinkle
- Department of Biology and Physical Education, Norwich University, Northfield, VT USA
| | - Chad C. Anderson
- Department of Biology and Physical Education, Norwich University, Northfield, VT USA
| | - Blake Forkey
- Department of Biology and Physical Education, Norwich University, Northfield, VT USA
| | - Jacob Griffin
- Department of Biology and Physical Education, Norwich University, Northfield, VT USA
- Department of Mathematics, Norwich University, Northfield, VT USA
| | - Kelsey Cone
- Department of Biology and Physical Education, Norwich University, Northfield, VT USA
| | - Carl Vitzthum
- Department of Biology and Physical Education, Norwich University, Northfield, VT USA
| | - Darlene Olsen
- Department of Mathematics, Norwich University, Northfield, VT USA
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Oligonucleotide-directed mutagenesis screen to identify pathogenic Lynch syndrome-associated MSH2 DNA mismatch repair gene variants. Proc Natl Acad Sci U S A 2016; 113:4128-33. [PMID: 26951660 DOI: 10.1073/pnas.1520813113] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Single-stranded DNA oligonucleotides can achieve targeted base-pair substitution with modest efficiency but high precision. We show that "oligo targeting" can be used effectively to study missense mutations in DNA mismatch repair (MMR) genes. Inherited inactivating mutations in DNA MMR genes are causative for the cancer predisposition Lynch syndrome (LS). Although overtly deleterious mutations in MMR genes can clearly be ascribed as the cause of LS, the functional implications of missense mutations are often unclear. We developed a genetic screen to determine the pathogenicity of these variants of uncertain significance (VUS), focusing on mutator S homolog 2 (MSH2). VUS were introduced into the endogenous Msh2 gene of mouse embryonic stem cells by oligo targeting. Subsequent selection for MMR-deficient cells using the guanine analog 6-thioguanine allowed the detection of MMR-abrogating VUS. The screen was able to distinguish weak and strong pathogenic variants from polymorphisms and was used to investigate 59 Msh2 VUS. Nineteen of the 59 VUS were identified as pathogenic. Functional assays revealed that 14 of the 19 detected variants fully abrogated MMR activity and that five of the detected variants attenuated MMR activity. Implementation of the screen in clinical practice allows proper counseling of mutation carriers and treatment of their tumors.
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The Eukaryotic Mismatch Recognition Complexes Track with the Replisome during DNA Synthesis. PLoS Genet 2015; 11:e1005719. [PMID: 26684201 PMCID: PMC4684283 DOI: 10.1371/journal.pgen.1005719] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 11/10/2015] [Indexed: 01/06/2023] Open
Abstract
During replication, mismatch repair proteins recognize and repair mispaired bases that escape the proofreading activity of DNA polymerase. In this work, we tested the model that the eukaryotic mismatch recognition complex tracks with the advancing replisome. Using yeast, we examined the dynamics during replication of the leading strand polymerase Polε using Pol2 and the eukaryotic mismatch recognition complex using Msh2, the invariant protein involved in mismatch recognition. Specifically, we synchronized cells and processed samples using chromatin immunoprecipitation combined with custom DNA tiling arrays (ChIP-chip). The Polε signal was not detectable in G1, but was observed at active origins and replicating DNA throughout S-phase. The Polε signal provided the resolution to track origin firing timing and efficiencies as well as replisome progression rates. By detecting Polε and Msh2 dynamics within the same strain, we established that the mismatch recognition complex binds origins and spreads to adjacent regions with the replisome. In mismatch repair defective PCNA mutants, we observed that Msh2 binds to regions of replicating DNA, but the distribution and dynamics are altered, suggesting that PCNA is not the sole determinant for the mismatch recognition complex association with replicating regions, but may influence the dynamics of movement. Using biochemical and genomic methods, we provide evidence that both MutS complexes are in the vicinity of the replisome to efficiently repair the entire spectrum of mutations during replication. Our data supports the model that the proximity of MutSα/β to the replisome for the efficient repair of the newly synthesized strand before chromatin reassembles. During replication, errors that escape the replication machinery are identified and repaired by DNA mismatch repair proteins. A mismatch in the helix is recognized by MutS homologs and subsequent events include excision of the error-containing strand followed by re-synthesis. A critical step in this process is directing repair to the newly synthesized strand. Current data suggest that transient discontinuities in the DNA backbone, known as nicks, generated during replication serve as the strand discrimination signals. Additionally, proteins that package DNA have the capacity to block mismatch recognition and are known to rapidly assemble behind the replication fork. Thus, there must be a short window of opportunity for the mismatch recognition complexes to scan for mismatches and access the strand discrimination signals. To address these issues, we tested the model that the mismatch recognition complexes track with the replisome. We employed high resolution genomic methods to determine that during replication, the mismatch recognition complexes bind origins of replication and advances with the replisome. The findings support the hypothesis that the mismatch recognition proteins track with the DNA replication machinery to accurately survey and repair the newly synthesized strands while the DNA is unpackaged and strand specificity signals are accessible.
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Peña-Diaz J, Rasmussen LJ. Approaches to diagnose DNA mismatch repair gene defects in cancer. DNA Repair (Amst) 2015; 38:147-154. [PMID: 26708048 DOI: 10.1016/j.dnarep.2015.11.022] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 08/12/2015] [Accepted: 11/30/2015] [Indexed: 12/12/2022]
Abstract
The DNA repair pathway mismatch repair (MMR) is responsible for the recognition and correction of DNA biosynthetic errors caused by inaccurate nucleotide incorporation during replication. Faulty MMR leads to failure to address the mispairs or insertion deletion loops (IDLs) left behind by the replicative polymerases and results in increased mutation load at the genome. The realization that defective MMR leads to a hypermutation phenotype and increased risk of tumorigenesis highlights the relevance of this pathway for human disease. The association of MMR defects with increased risk of cancer development was first observed in colorectal cancer patients that carried inactivating germline mutations in MMR genes and the disease was named as hereditary non-polyposis colorectal cancer (HNPCC). Currently, a growing list of cancers is found to be MMR defective and HNPCC has been renamed Lynch syndrome (LS) partly to include the associated risk of developing extra-colonic cancers. In addition, a number of non-hereditary, mostly epigenetic, alterations of MMR genes have been described in sporadic tumors. Besides conferring a strong cancer predisposition, genetic or epigenetic inactivation of MMR genes also renders cells resistant to some chemotherapeutic agents. Therefore, diagnosis of MMR deficiency has important implications for the management of the patients, the surveillance of their relatives in the case of LS and for the choice of treatment. Some of the alterations found in MMR genes have already been well defined and their pathogenicity assessed. Despite this substantial wealth of knowledge, the effects of a large number of alterations remain uncharacterized (variants of uncertain significance, VUSs). The advent of personalized genomics is likely to increase the list of VUSs found in MMR genes and anticipates the need of diagnostic tools for rapid assessment of their pathogenicity. This review describes current tools and future strategies for addressing the relevance of MMR gene alterations in human disease.
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Affiliation(s)
- Javier Peña-Diaz
- Center for Healthy Aging, Department of Neuroscience and Pharmacology, University of Copenhagen, DK-2200 Copenhagen, Denmark.
| | - Lene Juel Rasmussen
- Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, DK-2200 Copenhagen, Denmark.
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32
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Abstract
Despite a billion years of divergent evolution, the baker’s yeast Saccharomyces cerevisiae has long proven to be an invaluable model organism for studying human biology. Given its tractability and ease of genetic manipulation, along with extensive genetic conservation with humans, it is perhaps no surprise that researchers have been able to expand its utility by expressing human proteins in yeast, or by humanizing specific yeast amino acids, proteins or even entire pathways. These methods are increasingly being scaled in throughput, further enabling the detailed investigation of human biology and disease-specific variations of human genes in a simplified model organism.
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33
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Yazdi PG, Pedersen BA, Taylor JF, Khattab OS, Chen YH, Chen Y, Jacobsen SE, Wang PH. Increasing Nucleosome Occupancy Is Correlated with an Increasing Mutation Rate so Long as DNA Repair Machinery Is Intact. PLoS One 2015; 10:e0136574. [PMID: 26308346 PMCID: PMC4550472 DOI: 10.1371/journal.pone.0136574] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 08/04/2015] [Indexed: 12/30/2022] Open
Abstract
Deciphering the multitude of epigenomic and genomic factors that influence the mutation rate is an area of great interest in modern biology. Recently, chromatin has been shown to play a part in this process. To elucidate this relationship further, we integrated our own ultra-deep sequenced human nucleosomal DNA data set with a host of published human genomic and cancer genomic data sets. Our results revealed, that differences in nucleosome occupancy are associated with changes in base-specific mutation rates. Increasing nucleosome occupancy is associated with an increasing transition to transversion ratio and an increased germline mutation rate within the human genome. Additionally, cancer single nucleotide variants and microindels are enriched within nucleosomes and both the coding and non-coding cancer mutation rate increases with increasing nucleosome occupancy. There is an enrichment of cancer indels at the theoretical start (74 bp) and end (115 bp) of linker DNA between two nucleosomes. We then hypothesized that increasing nucleosome occupancy decreases access to DNA by DNA repair machinery and could account for the increasing mutation rate. Such a relationship should not exist in DNA repair knockouts, and we thus repeated our analysis in DNA repair machinery knockouts to test our hypothesis. Indeed, our results revealed no correlation between increasing nucleosome occupancy and increasing mutation rate in DNA repair knockouts. Our findings emphasize the linkage of the genome and epigenome through the nucleosome whose properties can affect genome evolution and genetic aberrations such as cancer.
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Affiliation(s)
- Puya G. Yazdi
- UC Irvine Diabetes Center, University of California at Irvine, Irvine, California, United States of America
- Sue and Bill Gross Stem Cell Research Center, University of California at Irvine, Irvine, California, United States of America
- Department of Medicine, University of California at Irvine, Irvine, California, United States of America
| | - Brian A. Pedersen
- UC Irvine Diabetes Center, University of California at Irvine, Irvine, California, United States of America
- Sue and Bill Gross Stem Cell Research Center, University of California at Irvine, Irvine, California, United States of America
- Department of Medicine, University of California at Irvine, Irvine, California, United States of America
| | - Jared F. Taylor
- UC Irvine Diabetes Center, University of California at Irvine, Irvine, California, United States of America
- Sue and Bill Gross Stem Cell Research Center, University of California at Irvine, Irvine, California, United States of America
- Department of Medicine, University of California at Irvine, Irvine, California, United States of America
| | - Omar S. Khattab
- UC Irvine Diabetes Center, University of California at Irvine, Irvine, California, United States of America
- Sue and Bill Gross Stem Cell Research Center, University of California at Irvine, Irvine, California, United States of America
| | - Yu-Han Chen
- UC Irvine Diabetes Center, University of California at Irvine, Irvine, California, United States of America
- Sue and Bill Gross Stem Cell Research Center, University of California at Irvine, Irvine, California, United States of America
- Department of Medicine, University of California at Irvine, Irvine, California, United States of America
| | - Yumay Chen
- UC Irvine Diabetes Center, University of California at Irvine, Irvine, California, United States of America
- Sue and Bill Gross Stem Cell Research Center, University of California at Irvine, Irvine, California, United States of America
- Department of Medicine, University of California at Irvine, Irvine, California, United States of America
| | - Steven E. Jacobsen
- Department of Molecular, Cell and Developmental Biology, University of California at Los Angeles, Los Angeles, California, United States of America
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California at Los Angeles, Los Angeles, California, United States of America
- Howard Hughes Medical Institute, University of California at Los Angeles, Los Angeles, California, United States of America
| | - Ping H. Wang
- UC Irvine Diabetes Center, University of California at Irvine, Irvine, California, United States of America
- Sue and Bill Gross Stem Cell Research Center, University of California at Irvine, Irvine, California, United States of America
- Department of Medicine, University of California at Irvine, Irvine, California, United States of America
- Department of Biological Chemistry, University of California at Irvine, Irvine, California, United States of America
- Department of Physiology & Biophysics, University of California at Irvine, Irvine, California, United States of America
- * E-mail:
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34
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Whole-genome mutational landscape of liver cancers displaying biliary phenotype reveals hepatitis impact and molecular diversity. Nat Commun 2015; 6:6120. [PMID: 25636086 DOI: 10.1038/ncomms7120] [Citation(s) in RCA: 156] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 12/17/2015] [Indexed: 02/06/2023] Open
Abstract
Intrahepatic cholangiocarcinoma and combined hepatocellular cholangiocarcinoma show varying degrees of biliary epithelial differentiation, which can be defined as liver cancer displaying biliary phenotype (LCB). LCB is second in the incidence for liver cancers with and without chronic hepatitis background and more aggressive than hepatocellular carcinoma (HCC). To gain insight into its molecular alterations, we performed whole-genome sequencing analysis on 30 LCBs. Here we show, the genome-wide substitution patterns of LCBs developed in chronic hepatitis livers overlapped with those of 60 HCCs, whereas those of hepatitis-negative LCBs diverged. The subsequent validation study on 68 LCBs identified recurrent mutations in TERT promoter, chromatin regulators (BAP1, PBRM1 and ARID2), a synapse organization gene (PCLO), IDH genes and KRAS. The frequencies of KRAS and IDHs mutations, which are associated with poor disease-free survival, were significantly higher in hepatitis-negative LCBs. This study reveals the strong impact of chronic hepatitis on the mutational landscape in liver cancer and the genetic diversity among LCBs.
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35
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Loconte DC, Patruno M, Lastella P, Di Gregorio C, Grossi V, Forte G, Ingravallo G, Varvara D, Bagnulo R, Simone C, Resta N, Stella A. A rare MSH2 mutation causes defective binding to hMSH6, normal hMSH2 staining, and loss of hMSH6 at advanced cancer stage. Hum Pathol 2014; 45:2162-7. [PMID: 25106712 DOI: 10.1016/j.humpath.2014.05.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Revised: 05/22/2014] [Accepted: 05/28/2014] [Indexed: 01/13/2023]
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36
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Challenges in assessing pathogenicity based on frequency of variants in mismatch repair genes: an extreme case of a MSH2 variant and a meta-analysis. Gene 2014; 546:421-4. [PMID: 24933000 DOI: 10.1016/j.gene.2014.06.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 04/30/2014] [Accepted: 06/13/2014] [Indexed: 11/21/2022]
Abstract
The clinical interpretation of variants in mismatch repair (MMR) genes associated with Lynch syndrome can be confusing when the functional nature of the variant is not clearly defined. We report an extreme case where a polymorphism in the MSH2 gene which had a low minor allele frequency, was misclassified as a mutation based on low evidential methods in the database and previous publications. We expanded this experience to perform a systematic meta-analysis in order to investigate other variants that have potentially been misclassified. Our results suggested that the interpretation of pathogenicity should be more cautious and emphasized the need for solid validation through multiple analyses including functional analysis for variants in MMR genes.
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37
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Zhang M, Xiang S, Joo HY, Wang L, Williams KA, Liu W, Hu C, Tong D, Haakenson J, Wang C, Zhang S, Pavlovicz RE, Jones A, Schmidt KH, Tang J, Dong H, Shan B, Fang B, Radhakrishnan R, Glazer PM, Matthias P, Koomen J, Seto E, Bepler G, Nicosia SV, Chen J, Li C, Gu L, Li GM, Bai W, Wang H, Zhang X. HDAC6 deacetylates and ubiquitinates MSH2 to maintain proper levels of MutSα. Mol Cell 2014; 55:31-46. [PMID: 24882211 DOI: 10.1016/j.molcel.2014.04.028] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 01/21/2014] [Accepted: 04/16/2014] [Indexed: 11/28/2022]
Abstract
MutS protein homolog 2 (MSH2) is a key DNA mismatch repair protein. It forms the MSH2-MSH6 (MutSα) and MSH2-MSH3 (MutSβ) heterodimers, which help to ensure genomic integrity. MutSα not only recognizes and repairs mismatched nucleotides but also recognizes DNA adducts induced by DNA-damaging agents, and triggers cell-cycle arrest and apoptosis. Loss or depletion of MutSα from cells leads to microsatellite instability (MSI) and resistance to DNA damage. Although the level of MutSα can be reduced by the ubiquitin-proteasome pathway, the detailed mechanisms of this regulation remain elusive. Here we report that histone deacetylase 6 (HDAC6) sequentially deacetylates and ubiquitinates MSH2, leading to MSH2 degradation. In addition, HDAC6 significantly reduces cellular sensitivity to DNA-damaging agents and decreases cellular DNA mismatch repair activities by downregulation of MSH2. Overall, these findings reveal a mechanism by which proper levels of MutSα are maintained.
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Affiliation(s)
- Mu Zhang
- Department of Pathology and Cell Biology, USF Morsani College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA
| | - Shengyan Xiang
- Department of Pathology and Cell Biology, USF Morsani College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA
| | - Heui-Yun Joo
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Kaul Human Genetics Building 402A, 720 South 20th Street, Birmingham, AL 35294, USA
| | - Lei Wang
- Department of Pathology and Cell Biology, USF Morsani College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA
| | - Kendra A Williams
- Department of Pathology and Cell Biology, USF Morsani College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA
| | - Wei Liu
- Department of Pathology and Cell Biology, USF Morsani College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA
| | - Chen Hu
- Department of Pathology and Cell Biology, USF Morsani College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA
| | - Dan Tong
- Graduate Center for Toxicology, Markey Cancer Center, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Joshua Haakenson
- Department of Pathology and Cell Biology, USF Morsani College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA
| | - Chuangui Wang
- Key Laboratory of Medical Cell Biology, Institute for Translational Medicine, China Medical University, Shengyang 110000, China
| | - Shengping Zhang
- Key Laboratory of Medical Cell Biology, Institute for Translational Medicine, China Medical University, Shengyang 110000, China
| | - Ryan E Pavlovicz
- Biophysics Program, The Ohio State University, Columbus, OH 43210, USA
| | - Amanda Jones
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Kaul Human Genetics Building 402A, 720 South 20th Street, Birmingham, AL 35294, USA
| | - Kristina H Schmidt
- Department of Cell Biology, Microbiology, and Molecular Biology, University of South Florida, Tampa, FL 33620, USA; Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA
| | - Jinfu Tang
- Department of Pathology and Cell Biology, USF Morsani College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA
| | - Huiqin Dong
- Department of Pathology and Cell Biology, USF Morsani College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA
| | - Bin Shan
- Medical Sciences, Washington State University at Spokane, 412E Spokane Falls Boulevard, Spokane, WA 99201, USA
| | - Bin Fang
- Proteomics, SRB-3, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA
| | - Rangasudhagar Radhakrishnan
- Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA
| | - Peter M Glazer
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Patrick Matthias
- Friedrich Miescher Institute for Biomedical Research, Novartis Research Foundation, 4058 Basel, Switzerland
| | - John Koomen
- Proteomics, SRB-3, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA
| | - Edward Seto
- Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA
| | - Gerold Bepler
- Molecular Therapeutics Program, Karmanos Cancer Institute, 4100 John R, Detroit, MI 48201, USA
| | - Santo V Nicosia
- Department of Pathology and Cell Biology, USF Morsani College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA; Chemical Biology and Molecular Medicine Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA
| | - Jiandong Chen
- Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA
| | - Chenglong Li
- Biophysics Program, The Ohio State University, Columbus, OH 43210, USA; Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA
| | - Liya Gu
- Graduate Center for Toxicology, Markey Cancer Center, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Guo-Min Li
- Graduate Center for Toxicology, Markey Cancer Center, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Wenlong Bai
- Department of Pathology and Cell Biology, USF Morsani College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA; Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA
| | - Hengbin Wang
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Kaul Human Genetics Building 402A, 720 South 20th Street, Birmingham, AL 35294, USA
| | - Xiaohong Zhang
- Department of Pathology and Cell Biology, USF Morsani College of Medicine, 12901 Bruce B. Downs Boulevard, Tampa, FL 33612, USA; Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA.
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De Lellis L, Aceto GM, Curia MC, Catalano T, Mammarella S, Veschi S, Fantini F, Battista P, Stigliano V, Messerini L, Mareni C, Sala P, Bertario L, Radice P, Cama A. Integrative analysis of hereditary nonpolyposis colorectal cancer: the contribution of allele-specific expression and other assays to diagnostic algorithms. PLoS One 2013; 8:e81194. [PMID: 24278394 PMCID: PMC3835792 DOI: 10.1371/journal.pone.0081194] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 10/09/2013] [Indexed: 01/27/2023] Open
Abstract
The identification of germline variants predisposing to hereditary nonpolyposis colorectal cancer (HNPCC) is crucial for clinical management of carriers, but several probands remain negative for such variants or bear variants of uncertain significance (VUS). Here we describe the results of integrative molecular analyses in 132 HNPCC patients providing evidences for improved genetic testing of HNPCC with traditional or next generation methods. Patients were screened for: germline allele-specific expression (ASE), nucleotide variants, rearrangements and promoter methylation of mismatch repair (MMR) genes; germline EPCAM rearrangements; tumor microsatellite instability (MSI) and immunohistochemical (IHC) MMR protein expression. Probands negative for pathogenic variants of MMR genes were screened for germline APC and MUTYH sequence variants. Most germline defects identified were sequence variants and rearrangements of MMR genes. Remarkably, altered germline ASE of MMR genes was detected in 8/22 (36.5%) probands analyzed, including 3 cases negative at other screenings. Moreover, ASE provided evidence for the pathogenic role and guided the characterization of a VUS shared by 2 additional probands. No germline MMR gene promoter methylation was observed and only one EPCAM rearrangement was detected. In several cases, tumor IHC and MSI diverged from germline screening results. Notably, APC or biallelic MUTYH germline defects were identified in 2/19 probands negative for pathogenic variants of MMR genes. Our results show that ASE complements gDNA-based analyses in the identification of MMR defects and in the characterization of VUS affecting gene expression, increasing the number of germline alterations detected. An appreciable fraction of probands negative for MMR gene variants harbors APC or MUTYH variants. These results indicate that germline ASE analysis and screening for APC and MUTYH defects should be included in HNPCC diagnostic algorithms.
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Affiliation(s)
- Laura De Lellis
- Department of Pharmacy, “G. d’Annunzio” University, Chieti, Italy
| | - Gitana Maria Aceto
- Department of Experimental and Clinical Sciences, “G. d’Annunzio” University, Chieti, Italy
- Unit of Molecular Pathology and Genomics, Aging Research Center, “G. d’Annunzio” University Foundation, Chieti, Italy
| | - Maria Cristina Curia
- Department of Medical, Oral and Biotechnological Sciences, “G. d’Annunzio” University, Chieti, Italy
- Unit of Molecular Pathology and Genomics, Aging Research Center, “G. d’Annunzio” University Foundation, Chieti, Italy
| | - Teresa Catalano
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | | | - Serena Veschi
- Unit of Molecular Pathology and Genomics, Aging Research Center, “G. d’Annunzio” University Foundation, Chieti, Italy
| | - Fabiana Fantini
- Department of Experimental and Clinical Sciences, “G. d’Annunzio” University, Chieti, Italy
| | - Pasquale Battista
- Department of Experimental and Clinical Sciences, “G. d’Annunzio” University, Chieti, Italy
| | - Vittoria Stigliano
- Department of Gastroenterology, Unit of Hereditary Colorectal Cancer, National Cancer Institute, Regina Elena (IRE), Rome, Italy
| | - Luca Messerini
- Section of Pathological Anatomy, Department of Medical and Surgical Critical Care, University of Florence, Florence, Italy
| | - Cristina Mareni
- Department of Internal Medicine, University of Genova, Genova, Italy
| | - Paola Sala
- Unit of Hereditary Digestive Tract Tumors, Department of Preventive and Predictive Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Lucio Bertario
- Unit of Hereditary Digestive Tract Tumors, Department of Preventive and Predictive Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Paolo Radice
- Unit of Molecular bases of genetic risk and genetic testing, Department of Preventive and Predictive Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Alessandro Cama
- Department of Pharmacy, “G. d’Annunzio” University, Chieti, Italy
- * E-mail:
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39
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Dunham MJ, Fowler DM. Contemporary, yeast-based approaches to understanding human genetic variation. Curr Opin Genet Dev 2013; 23:658-64. [PMID: 24252429 DOI: 10.1016/j.gde.2013.10.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2013] [Revised: 10/01/2013] [Accepted: 10/02/2013] [Indexed: 01/11/2023]
Abstract
Determining how genetic variation contributes to human health and disease is a critical challenge. As one of the most genetically tractable model organisms, yeast has played a central role in meeting this challenge. The advent of new technologies, including high-throughput DNA sequencing and synthesis, proteomics, and computational methods, has vastly increased the power of yeast-based approaches to determine the consequences of human genetic variation. Recent successes include systematic exploration of the effects of gene dosage, large-scale analysis of the effect of coding variation on gene function, and the use of humanized yeast to model disease. By virtue of its manipulability, small genome size, and genetic tractability, yeast is poised to help us understand human genetic variation.
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Affiliation(s)
- Maitreya J Dunham
- Department of Genome Sciences, University of Washington, Foege Building, Box 355065, 3720 15th Avenue NE, Seattle, WA 98195-5065, USA.
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Mismatch repair genes Mlh1 and Mlh3 modify CAG instability in Huntington's disease mice: genome-wide and candidate approaches. PLoS Genet 2013; 9:e1003930. [PMID: 24204323 PMCID: PMC3814320 DOI: 10.1371/journal.pgen.1003930] [Citation(s) in RCA: 156] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 09/15/2013] [Indexed: 11/19/2022] Open
Abstract
The Huntington's disease gene (HTT) CAG repeat mutation undergoes somatic expansion that correlates with pathogenesis. Modifiers of somatic expansion may therefore provide routes for therapies targeting the underlying mutation, an approach that is likely applicable to other trinucleotide repeat diseases. Huntington's disease HdhQ111 mice exhibit higher levels of somatic HTT CAG expansion on a C57BL/6 genetic background (B6.HdhQ111) than on a 129 background (129.HdhQ111). Linkage mapping in (B6x129).HdhQ111 F2 intercross animals identified a single quantitative trait locus underlying the strain-specific difference in expansion in the striatum, implicating mismatch repair (MMR) gene Mlh1 as the most likely candidate modifier. Crossing B6.HdhQ111 mice onto an Mlh1 null background demonstrated that Mlh1 is essential for somatic CAG expansions and that it is an enhancer of nuclear huntingtin accumulation in striatal neurons. HdhQ111 somatic expansion was also abolished in mice deficient in the Mlh3 gene, implicating MutLγ (MLH1–MLH3) complex as a key driver of somatic expansion. Strikingly, Mlh1 and Mlh3 genes encoding MMR effector proteins were as critical to somatic expansion as Msh2 and Msh3 genes encoding DNA mismatch recognition complex MutSβ (MSH2–MSH3). The Mlh1 locus is highly polymorphic between B6 and 129 strains. While we were unable to detect any difference in base-base mismatch or short slipped-repeat repair activity between B6 and 129 MLH1 variants, repair efficiency was MLH1 dose-dependent. MLH1 mRNA and protein levels were significantly decreased in 129 mice compared to B6 mice, consistent with a dose-sensitive MLH1-dependent DNA repair mechanism underlying the somatic expansion difference between these strains. Together, these data identify Mlh1 and Mlh3 as novel critical genetic modifiers of HTT CAG instability, point to Mlh1 genetic variation as the likely source of the instability difference in B6 and 129 strains and suggest that MLH1 protein levels play an important role in driving of the efficiency of somatic expansions. The expansion of a CAG repeat underlies Huntington's disease (HD), with longer CAG tracts giving rise to earlier onset and more severe disease. In individuals harboring a CAG expansion the repeat undergoes further somatic expansion over time, particularly in brain cells most susceptible to disease pathogenesis. Preventing this repeat lengthening may delay disease onset and/or slow progression. We are using mouse models of HD to identify the factors that modify the somatic expansion of the HD CAG repeat, as these may provide novel targets for therapeutic intervention. To identify genetic modifiers of somatic expansion in HD mouse models we have used both an unbiased genetic mapping approach in inbred mouse strains that exhibit different levels of somatic expansion, as well as targeted gene knockout approaches. Our results demonstrate that: 1) Mlh1 and Mlh3 genes, encoding components of the DNA mismatch repair pathway, are critical for somatic CAG expansion; 2) in the absence of somatic expansion the pathogenic process in the mouse is slowed; 3) MLH1 protein levels are likely to be a driver of the efficiency of somatic expansion. Together, our data provide new insight into the factors underlying the process of somatic expansion of the HD CAG repeat.
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Terui H, Tachikawa T, Kakuta M, Nishimura Y, Yatsuoka T, Yamaguchi K, Yura K, Akagi K. Molecular and clinical characteristics of MSH6 germline variants detected in colorectal cancer patients. Oncol Rep 2013; 30:2909-16. [PMID: 24100870 DOI: 10.3892/or.2013.2781] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 08/16/2013] [Indexed: 11/06/2022] Open
Abstract
The MSH6 gene is one of the mismatch repair genes involved in Lynch syndrome and its mutations account for 10-20% of Lynch syndrome. Although previous studies suggested that the difference of the geographical region affects the clinical phenotype of Lynch syndrome, there has been no report on the detailed features of Japanese Lynch syndrome patients carrying an MSH6 mutation. The aim of the present study was to investigate the clinical and molecular features of MSH6 mutation carriers in Japan. Surgically resected 1720 colorectal carcinoma specimens were screened by microsatellite instability (MSI) testing and the MSI-high cases were subjected to a germline mutation analysis of the mismatch repair genes MLH1, MSH2 and MSH6. We investigated the clinical and molecular features of the MSH6 variants, such as the family cancer history, pathological findings, immunohistochemistry, methylation status of the MLH1 promoter and BRAF mutation in the colorectal tumor. Furthermore, the impact of the missense variants on MSH6 protein was predicted by using in silico tools. We identified nine novel pathogenic mutations and eight unclassified missense variants. Among the eight missense variants, three were suspected pathogenic by in silico analysis. We also found that most colorectal cancers in the MSH6 mutation carrier were diagnosed after the age of 50 and were localized distally. Furthermore, the mean age at diagnosis of endometrial cancer in Japanese MSH6 mutation carriers (49.2 years) was earlier than previous reports from Western countries (56.5 years). These results may improve the surveillance program for Japanese MSH6 mutation carriers.
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Affiliation(s)
- Hiroko Terui
- Division of Molecular Diagnosis and Cancer Prevention, Saitama Cancer Center, Saitama 362-0806, Japan
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42
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Mutation rates, spectra, and genome-wide distribution of spontaneous mutations in mismatch repair deficient yeast. G3-GENES GENOMES GENETICS 2013; 3:1453-65. [PMID: 23821616 PMCID: PMC3755907 DOI: 10.1534/g3.113.006429] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
DNA mismatch repair is a highly conserved DNA repair pathway. In humans, germline mutations in hMSH2 or hMLH1, key components of mismatch repair, have been associated with Lynch syndrome, a leading cause of inherited cancer mortality. Current estimates of the mutation rate and the mutational spectra in mismatch repair defective cells are primarily limited to a small number of individual reporter loci. Here we use the yeast Saccharomyces cerevisiae to generate a genome-wide view of the rates, spectra, and distribution of mutation in the absence of mismatch repair. We performed mutation accumulation assays and next generation sequencing on 19 strains, including 16 msh2 missense variants implicated in Lynch cancer syndrome. The mutation rate for DNA mismatch repair null strains was approximately 1 mutation per genome per generation, 225-fold greater than the wild-type rate. The mutations were distributed randomly throughout the genome, independent of replication timing. The mutation spectra included insertions/deletions at homopolymeric runs (87.7%) and at larger microsatellites (5.9%), as well as transitions (4.5%) and transversions (1.9%). Additionally, repeat regions with proximal repeats are more likely to be mutated. A bias toward deletions at homopolymers and insertions at (AT)n microsatellites suggests a different mechanism for mismatch generation at these sites. Interestingly, 5% of the single base pair substitutions might represent double-slippage events that occurred at the junction of immediately adjacent repeats, resulting in a shift in the repeat boundary. These data suggest a closer scrutiny of tumor suppressors with homopolymeric runs with proximal repeats as the potential drivers of oncogenesis in mismatch repair defective cells.
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43
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Goldberg Y, Kedar I, Kariiv R, Halpern N, Plesser M, Hubert A, Kaduri L, Sagi M, Lerer I, Abeliovich D, Hamburger T, Nissan A, Goldshmidt H, Solar I, Geva R, Strul H, Rosner G, Baris H, Levi Z, Peretz T. Lynch Syndrome in high risk Ashkenazi Jews in Israel. Fam Cancer 2013; 13:65-73. [DOI: 10.1007/s10689-013-9675-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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44
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Distinct requirements within the Msh3 nucleotide binding pocket for mismatch and double-strand break repair. J Mol Biol 2013; 425:1881-1898. [PMID: 23458407 DOI: 10.1016/j.jmb.2013.02.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Revised: 02/21/2013] [Accepted: 02/22/2013] [Indexed: 11/20/2022]
Abstract
In Saccharomyces cerevisiae, repair of insertion/deletion loops is carried out by Msh2-Msh3-mediated mismatch repair (MMR). Msh2-Msh3 is also required for 3' non-homologous tail removal (3' NHTR) in double-strand break repair. In both pathways, Msh2-Msh3 binds double-strand/single-strand junctions and initiates repair in an ATP-dependent manner. However, the kinetics of the two processes appear different; MMR is likely rapid in order to coordinate with the replication fork, whereas 3' NHTR has been shown to be a slower process. To understand the molecular requirements in both repair pathways, we performed an in vivo analysis of well-conserved residues in Msh3 that are hypothesized to be required for MMR and/or 3' NHTR. These residues are predicted to be involved in either communication between the DNA-binding and ATPase domains within the complex or nucleotide binding and/or exchange within Msh2-Msh3. We identified a set of aromatic residues within the FLY motif of the predicted Msh3 nucleotide binding pocket that are essential for Msh2-Msh3-mediated MMR but are largely dispensable for 3' NHTR. In contrast, mutations in other regions gave similar phenotypes in both assays. Based on these results, we suggest that the two pathways have distinct requirements with respect to the position of the bound ATP within Msh3. We propose that the differences are related, at least in part, to the kinetics of each pathway. Proper binding and positioning of ATP is required to induce rapid conformational changes at the replication fork, but is less important when more time is available for repair, as in 3' NHTR.
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45
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Tennen RI, Haye JE, Wijayatilake HD, Arlow T, Ponzio D, Gammie AE. Cell-cycle and DNA damage regulation of the DNA mismatch repair protein Msh2 occurs at the transcriptional and post-transcriptional level. DNA Repair (Amst) 2013; 12:97-109. [PMID: 23261051 PMCID: PMC3749301 DOI: 10.1016/j.dnarep.2012.11.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Revised: 10/03/2012] [Accepted: 11/06/2012] [Indexed: 12/13/2022]
Abstract
DNA mismatch repair during replication is a conserved process essential for maintaining genomic stability. Mismatch repair is also implicated in cell-cycle arrest and apoptosis after DNA damage. Because yeast and human mismatch repair systems are well conserved, we have employed the budding yeast Saccharomyces cerevisiae to understand the regulation and function of the mismatch repair gene MSH2. Using a luciferase-based transcriptional reporter, we defined a 218-bp region upstream of MSH2 that contains cell-cycle and DNA damage responsive elements. The 5' end of the MSH2 transcript was mapped by primer extension and was found to encode a small upstream open reading frame (uORF). Mutagenesis of the uORF start codon or of the uORF stop codon, which creates a continuous reading frame with MSH2, increased Msh2 steady-state protein levels ∼2-fold. Furthermore, we found that the cell-cycle transcription factors Swi6, Swi4, and Mbp1-along with SCB/MCB cell-cycle binding sites upstream of MSH2-are all required for full basal expression of MSH2. Mutagenesis of the cell-cycle boxes resulted in a minor reduction in basal Msh2 levels and a 3-fold defect in mismatch repair. Disruption of the cell-cycle boxes also affected growth in a DNA polymerase-defective strain background where mismatch repair is essential, particularly in the presence of the DNA damaging agent methyl methane sulfonate (MMS). Promoter replacements conferring constitutive expression of MSH2 revealed that the transcriptional induction in response to MMS is required to maintain induced levels of Msh2. Turnover experiments confirmed an elevated rate of degradation in the presence of MMS. Taken together, the data show that the DNA damage regulation of Msh2 occurs at the transcriptional and post-transcriptional levels. The transcriptional and translational control elements identified are conserved in mammalian cells, underscoring the use of yeast as a model system to examine the regulation of MSH2.
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Affiliation(s)
- Ruth I. Tennen
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544-1014, United States
| | - Joanna E. Haye
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544-1014, United States
| | | | - Tim Arlow
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544-1014, United States
| | - Danielle Ponzio
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544-1014, United States
| | - Alison E. Gammie
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544-1014, United States
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46
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Arlow T, Scott K, Wagenseller A, Gammie A. Proteasome inhibition rescues clinically significant unstable variants of the mismatch repair protein Msh2. Proc Natl Acad Sci U S A 2013; 110:246-51. [PMID: 23248292 PMCID: PMC3538226 DOI: 10.1073/pnas.1215510110] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
MSH2 is required for DNA mismatch repair recognition in eukaryotes. Deleterious mutations in human MSH2 account for approximately half of the alleles associated with a common hereditary cancer syndrome. Previously, we characterized clinically identified MSH2 missense mutations, using yeast as a model system, and found that the most common cause of defective DNA mismatch repair was low levels of the variant Msh2 proteins. Here, we show that increased protein turnover is responsible for the reduced cellular levels. Increasing gene dosage of more than half of the missense alleles fully restored function. A titration experiment revealed that raising the expression level of one variant to less than wild-type levels restored mismatch repair, suggesting that overexpression is not always required to regain function. We found that the ubiquitin-mediated proteasome degradation pathway is the major mechanism for increased turnover of the Msh2 variants and identified the primary ubiquitin ligase as San1. Deletion of San1 restored protein levels for all but one variant, but did not elevate wild-type Msh2 levels. The unstable variants interacted with San1, whereas wild-type Msh2 did not. Additionally, san1Δ suppressed the mismatch repair defect of unstable variants. Of medical significance, the clinically approved drug Bortezomib partially restored protein levels and mismatch repair function for low-level variants and reversed the resistance to cisplatin, a common chemotherapeutic. Our results provide the foundation for an innovative therapeutic regime for certain mismatch-repair-defective cancers that are refractory to conventional chemotherapies.
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Affiliation(s)
- Tim Arlow
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Kristan Scott
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Aubrey Wagenseller
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Alison Gammie
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
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47
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Rasmussen LJ, Heinen CD, Royer-Pokora B, Drost M, Tavtigian S, Hofstra RMW, de Wind N. Pathological assessment of mismatch repair gene variants in Lynch syndrome: past, present, and future. Hum Mutat 2012; 33:1617-25. [PMID: 22833534 DOI: 10.1002/humu.22168] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2012] [Accepted: 07/11/2012] [Indexed: 12/12/2022]
Abstract
Lynch syndrome (LS) is caused by germline mutations in DNA mismatch repair (MMR) genes and is the most prevalent hereditary colorectal cancer syndrome. A significant proportion of variants identified in MMR and other common cancer susceptibility genes are missense or noncoding changes whose consequences for pathogenicity cannot be easily interpreted. Such variants are designated as "variants of uncertain significance" (VUS). Management of LS can be significantly improved by identifying individuals who carry a pathogenic variant and thus benefit from screening, preventive, and therapeutic measures. Also, identifying family members that do not carry the variant is important so they can be released from the intensive surveillance. Determining which genetic variants are pathogenic and which are neutral is a major challenge in clinical genetics. The profound mechanistic knowledge on the genetics and biochemistry of MMR enables the development and use of targeted assays to evaluate the pathogenicity of variants found in suspected patients with LS. We describe different approaches for the functional analysis of MMR gene VUS and propose development of a validated diagnostic framework. Furthermore, we call attention to common misconceptions about functional assays and endorse development of an integrated approach comprising validated assays for diagnosis of VUS in patients suspected of LS.
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Affiliation(s)
- Lene Juel Rasmussen
- Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Denmark.
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48
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Residues in the N-terminal domain of MutL required for mismatch repair in Bacillus subtilis. J Bacteriol 2012; 194:5361-7. [PMID: 22843852 DOI: 10.1128/jb.01142-12] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Mismatch repair is a highly conserved pathway responsible for correcting DNA polymerase errors incorporated during genome replication. MutL is a mismatch repair protein known to coordinate several steps in repair that ultimately results in strand removal following mismatch identification by MutS. MutL homologs from bacteria to humans contain well-conserved N-terminal and C-terminal domains. To understand the contribution of the MutL N-terminal domain to mismatch repair, we analyzed 14 different missense mutations in Bacillus subtilis MutL that were conserved with missense mutations identified in the human MutL homolog MLH1 from patients with hereditary nonpolyposis colorectal cancer (HNPCC). We characterized missense mutations in or near motifs important for ATP binding, ATPase activity, and DNA binding. We found that 13 of the 14 missense mutations conferred a substantial defect to mismatch repair in vivo, while three mutant alleles showed a dominant negative increase in mutation frequency to wild-type mutL. We performed immunoblot analysis to determine the relative stability of each mutant protein in vivo and found that, although most accumulated, several mutant proteins failed to maintain wild-type levels, suggesting defects in protein stability. The remaining missense mutations located in areas of the protein important for DNA binding, ATP binding, and ATPase activities of MutL compromised repair in vivo. Our results define functional residues in the N-terminal domain of B. subtilis MutL that are critical for mismatch repair in vivo.
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49
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Heinen CD, Juel Rasmussen L. Determining the functional significance of mismatch repair gene missense variants using biochemical and cellular assays. Hered Cancer Clin Pract 2012; 10:9. [PMID: 22824075 PMCID: PMC3434035 DOI: 10.1186/1897-4287-10-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 06/28/2012] [Indexed: 12/15/2022] Open
Abstract
With the discovery that the hereditary cancer susceptibility disease Lynch syndrome (LS) is caused by deleterious germline mutations in the DNA mismatch repair (MMR) genes nearly 20 years ago, genetic testing can now be used to diagnose this disorder in patients. A definitive diagnosis of LS can direct how clinicians manage the disease as well as prevent future cancers for the patient and their families. A challenge emerges, however, when a germline missense variant is identified in a MMR gene in a suspected LS patient. The significance of a single amino acid change in these large repair proteins is not immediately obvious resulting in them being designated variants of uncertain significance (VUS). One important strategy for resolving this uncertainty is to determine whether the variant results in a non-functional protein. The ability to reconstitute the MMR reaction in vitro has provided an important experimental tool for studying the functional consequences of VUS. However, beyond this repair assay, a number of other experimental methods have been developed that allow us to test the effect of a VUS on discrete biochemical steps or other aspects of MMR function. Here, we describe some of these assays along with the challenges of using such assays to determine the functional consequences of MMR VUS which, in turn, can provide valuable insight into their clinical significance. With increased gene sequencing in patients, the number of identified VUS has expanded dramatically exacerbating this problem for clinicians. However, basic science research laboratories around the world continue to expand our knowledge of the overall MMR molecular mechanism providing new opportunities to understand the functional significance, and therefore pathogenic significance, of VUS.
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Affiliation(s)
- Christopher D Heinen
- Neag Comprehensive Cancer Center and Center for Molecular Medicine, University of Connecticut Health Center, 233 Farmington Avenue, ML3101 Farmington, CT, USA.
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50
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Colas C, Coulet F, Svrcek M, Collura A, Fléjou JF, Duval A, Hamelin R. Lynch or not Lynch? Is that always a question? Adv Cancer Res 2012; 113:121-66. [PMID: 22429854 DOI: 10.1016/b978-0-12-394280-7.00004-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The familial cancer syndrome referred to as Lynch I and II was renamed hereditary nonpolyposis colorectal cancer (HNPCC) only to revert later to Lynch syndrome (LS). LS is the most frequent human predisposition for the development of colorectal cancer (CRC), and probably also for endometrial and gastric cancers, although it has yet to acquire a consensus name. Its estimated prevalence ranges widely from 2% to 7% of all CRCs due to the fact that tumors from patients with LS are difficult to recognize at both the clinical and molecular level. This review is based on two assumptions. First, all LS patients inherit a predisposition to develop CRC (without polyposis) and/or other tumors from the Lynch spectrum. Second, all LS patients have a germline defect in one of the DNA mismatch repair (MMR) genes. When a somatic second hit inactivates the relevant MMR gene, the consequence is instability of DNA repeat sequences such as microsatellites and the tumors are referred to as having the microsatellite instability (MSI) phenotype. However, some of the inherited predisposition to develop CRC without concurrent polyposis, termed HNPCC, is found in non-LS patients, while not all MSI tumors are from LS cases. LS tumors are therefore at the junction of inherited and MSI cases. We describe here the defining characteristics of LS tumors that differentiate them from inherited non-MSI tumors and from non-inherited MSI tumors.
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Affiliation(s)
- Chrystelle Colas
- INSERM, UMRS 938, Centre de Recherche Saint-Antoine, Equipe Instabilité des Microsatellites et Cancers, Paris, France
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