51
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D'Arcy BM, Blount J, Prakash A. Biochemical and structural characterization of two variants of uncertain significance in the PMS2 gene. Hum Mutat 2019; 40:458-471. [PMID: 30653781 DOI: 10.1002/humu.23708] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Revised: 12/28/2018] [Accepted: 01/14/2019] [Indexed: 12/16/2022]
Abstract
Lynch syndrome (LS) is an autosomal dominant inherited disorder that is associated with an increased predisposition to certain cancers caused by loss-of-function mutations in one of four DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6, or PMS2). The diagnosis of LS is often challenged by the identification of missense mutations where the functional effects are not known. These are termed variants of uncertain significance (VUSs) and account for 20%-30% of noncoding and missense mutations. VUSs cause ambiguity during clinical diagnosis and hinder implementation of appropriate medical management. In the current study, we focus on the functional and biological consequences of two nonsynonymous VUSs in PMS2. These variants, c.620G>A and c.123_131delGTTAGTAGA, result in the alteration of glycine 207 to glutamate (p.Gly207Glu) and the deletion of amino acid residues 42-44 (p.Leu42_Glu44del), respectively. While the PMS2 p.Gly207Glu variant retains in vitro MMR and ATPase activities, PMS2 p.Leu42_Glu44del appears to lack such capabilities. Structural and biophysical characterization using circular dichroism, small-angle X-ray scattering, and X-ray crystallography of the N-terminal domain of the PMS2 variants indicate that the p.Gly207Glu variant is properly folded similar to the wild-type enzyme, whereas p.Leu42_Glu44del is disordered and prone to aggregation.
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Affiliation(s)
- Brandon M D'Arcy
- Mitchell Cancer Institute, The University of South Alabama, Mobile, Alabama
| | - Jessa Blount
- Mitchell Cancer Institute, The University of South Alabama, Mobile, Alabama
| | - Aishwarya Prakash
- Mitchell Cancer Institute, The University of South Alabama, Mobile, Alabama
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52
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Abstract
The mitochondrial genome encodes proteins essential for the oxidative phosphorylation and, consequently, for proper mitochondrial function. Its localization and, possibly, structural organization contribute to higher DNA damage accumulation, when compared to the nuclear genome. In addition, the mitochondrial genome mutates at rates several times higher than the nuclear, although the causal relationship between these events are not clearly established. Maintaining mitochondrial DNA stability is critical for cellular function and organismal fitness, and several pathways contribute to that, including damage tolerance and bypass, degradation of damaged genomes and DNA repair. Despite initial evidence suggesting that mitochondria lack DNA repair activities, most DNA repair pathways have been at least partially characterized in mitochondria from several model organisms, including humans. In this chapter, we review what is currently known about how the main DNA repair pathways operate in mitochondria and contribute to mitochondrial DNA stability, with focus on the enzymology of mitochondrial DNA repair.
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Affiliation(s)
- Rebeca R Alencar
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - Caio M P F Batalha
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - Thiago S Freire
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - Nadja C de Souza-Pinto
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
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53
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Barry J, Wong ML, Alberts B. In vitro reconstitution of DNA replication initiated by genetic recombination: a T4 bacteriophage model for a type of DNA synthesis important for all cells. Mol Biol Cell 2018; 30:146-159. [PMID: 30403545 PMCID: PMC6337909 DOI: 10.1091/mbc.e18-06-0386] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Using a mixture of 10 purified DNA replication and DNA recombination proteins encoded by the bacteriophage T4 genome, plus two homologous DNA molecules, we have reconstituted the genetic recombination–initiated pathway that initiates DNA replication forks at late times of T4 bacteriophage infection. Inside the cell, this recombination-dependent replication (RDR) is needed to produce the long concatemeric T4 DNA molecules that serve as substrates for packaging the shorter, genome-sized viral DNA into phage heads. The five T4 proteins that catalyze DNA synthesis on the leading strand, plus the proteins required for lagging-strand DNA synthesis, are essential for the reaction, as are a special mediator protein (gp59) and a Rad51/RecA analogue (the T4 UvsX strand-exchange protein). Related forms of RDR are widespread in living organisms—for example, they play critical roles in the homologous recombination events that can restore broken ends of the DNA double helix, restart broken DNA replication forks, and cross over chromatids during meiosis in eukaryotes. Those processes are considerably more complex, and the results presented here should be informative for dissecting their detailed mechanisms.
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Affiliation(s)
- Jack Barry
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158-2517
| | - Mei Lie Wong
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158-2517
| | - Bruce Alberts
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158-2517
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54
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Lahiri S, Li Y, Hingorani MM, Mukerji I. MutSγ-Induced DNA Conformational Changes Provide Insights into Its Role in Meiotic Recombination. Biophys J 2018; 115:2087-2101. [PMID: 30467025 DOI: 10.1016/j.bpj.2018.10.029] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 10/16/2018] [Accepted: 10/22/2018] [Indexed: 01/11/2023] Open
Abstract
In many organisms, MutSγ plays a role in meiotic recombination, facilitating crossover formation between homologous chromosomes. Failure to form crossovers leads to improper segregation of chromosomes and aneuploidy, which in humans result in infertility and birth defects. To improve current understanding of MutSγ function, this study investigates the binding affinities and structures of MutSγ in complex with DNA substrates that model homologous recombination intermediates. For these studies, we overexpressed and isolated from Escherichia coli the yeast MutSγ protein Saccharomyces cerevisiae (Sc) Msh4-Msh5. Sc Msh4-Msh5 binds Holliday junction (HJ)-like substrates, 3' overhangs, single-stranded (ss) forks, and the displacement loop with nanomolar affinity. The weakest binding affinities are detected for an intact duplex and open-junction construct. Similar to the human protein, Sc Msh4-Msh5 exhibits the highest affinity for the HJ with a Kd < 0.4 nM in solution. Energy-transfer experiments further demonstrate that DNA structure is modulated by the binding interaction with the largest changes associated with substrates containing an ss end. Upon binding, Sc Msh4-Msh5 displaces the ss away from the duplex in most of the ss-containing intermediates, potentially enabling the binding of RPA and other proteins. In the case of the junction-like intermediates, Msh4-Msh5 binding either stabilizes the existing stacked structure or induces formation of the stacked X conformation. Significantly, we find that upon binding, Msh4-Msh5 stacks an open-junction construct to the same extent as the standard junction. Stabilization of the junction in the stacked conformation is generally refractory to branch migration, which is consistent with a potential role for MutSγ to stabilize HJs and prevent branch migration until resolution by MutLγ. The different binding modalities observed suggest that Msh4-Msh5 not only binds to and stabilizes stacked junctions but also participates in meiotic recombination before junction formation through the stabilization of single-end invasion intermediates.
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Affiliation(s)
- Sudipta Lahiri
- Department of Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut
| | - Yan Li
- Department of Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut
| | - Manju M Hingorani
- Department of Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut
| | - Ishita Mukerji
- Department of Molecular Biology and Biochemistry, Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut.
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55
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Wang Z, Wang W, Cui YC, Pan Q, Zhu W, Gendron P, Guo F, Cen S, Witcher M, Liang C. HIV-1 Employs Multiple Mechanisms To Resist Cas9/Single Guide RNA Targeting the Viral Primer Binding Site. J Virol 2018; 92:e01135-18. [PMID: 30068653 PMCID: PMC6158435 DOI: 10.1128/jvi.01135-18] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 07/26/2018] [Indexed: 12/23/2022] Open
Abstract
The clustered regularly interspaced short palindromic repeat (CRISPR)-CRISPR-associated protein 9 (Cas9) gene-editing technology has been used to inactivate viral DNA as a new strategy to eliminate chronic viral infections, including HIV-1. This utility of CRISPR-Cas9 is challenged by the high heterogeneity of HIV-1 sequences, which requires the design of the single guide RNA (sgRNA; utilized by the CRISPR-Cas9 system to recognize the target DNA) to match a specific HIV-1 strain in an HIV patient. One solution to this challenge is to target the viral primer binding site (PBS), which HIV-1 copies from cellular tRNA3 Lys in each round of reverse transcription and is thus conserved in almost all HIV-1 strains. In this study, we demonstrate that PBS-targeting sgRNA directs Cas9 to cleave the PBS DNA, which evokes deletions or insertions (indels) and strongly diminishes the production of infectious HIV-1. While HIV-1 escapes from PBS-targeting Cas9/sgRNA, unique resistance mechanisms are observed that are dependent on whether the plus or the minus strand of the PBS DNA is bound by sgRNA. Characterization of these viral escape mechanisms will inform future engineering of Cas9 variants that can more potently and persistently inhibit HIV-1 infection.IMPORTANCE The results of this study demonstrate that the gene-editing complex Cas9/sgRNA can be programmed to target and cleave HIV-1 PBS DNA, and thus, inhibit HIV-1 infection. Given that almost all HIV-1 strains have the same PBS, which is copied from the cellular tRNA3 Lys during reverse transcription, PBS-targeting sgRNA can be used to inactivate HIV-1 DNA of different strains. We also discovered that HIV-1 uses different mechanisms to resist Cas9/sgRNAs, depending on whether they target the plus or the minus strand of PBS DNA. These findings allow us to predict that a Cas9 variant that uses the CCA sequence as the protospacer adjacent motif (PAM) should more strongly and persistently suppress HIV-1 replication. Together, these data have identified the PBS as the target DNA of Cas9/sgRNA and have predicted how to improve Cas9/sgRNA to achieve more efficient and sustainable suppression of HIV-1 infection, therefore improving the capacity of Cas9/sgRNA in curing HIV-1 infection.
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Affiliation(s)
- Zhen Wang
- Lady Davis Institute, Jewish General Hospital, Montreal, Canada
- Department of Medicine, McGill University, Montreal, Canada
| | - Wenzhou Wang
- Lady Davis Institute, Jewish General Hospital, Montreal, Canada
- Department of Microbiology & Immunology, McGill University, Montreal, Canada
| | - Ya Cheng Cui
- Department of Medicine, McGill University, Montreal, Canada
| | - Qinghua Pan
- Lady Davis Institute, Jewish General Hospital, Montreal, Canada
| | - Weijun Zhu
- Institute of Pathogen Biology, Chinese Academy of Medical Science, Beijing, China
| | - Patrick Gendron
- Institute for Research in Immunology and Cancer, University of Montreal, Montreal, Canada
| | - Fei Guo
- Institute of Pathogen Biology, Chinese Academy of Medical Science, Beijing, China
| | - Shan Cen
- Institute of Medicinal Biotechnology, Chinese Academy of Medical Science, Beijing, China
| | - Michael Witcher
- Lady Davis Institute, Jewish General Hospital, Montreal, Canada
- Department of Oncology, McGill University, Montreal, Canada
| | - Chen Liang
- Lady Davis Institute, Jewish General Hospital, Montreal, Canada
- Department of Medicine, McGill University, Montreal, Canada
- Department of Microbiology & Immunology, McGill University, Montreal, Canada
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56
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Ito S, Shiraishi M, Tsuchihashi K, Takatsuka R, Yamamoto J, Kuraoka I, Iwai S. Fluorescence detection of DNA mismatch repair in human cells. Sci Rep 2018; 8:12181. [PMID: 30111891 PMCID: PMC6093906 DOI: 10.1038/s41598-018-30733-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 08/06/2018] [Indexed: 01/23/2023] Open
Abstract
Mismatched base pairs, produced by nucleotide misincorporation by DNA polymerase, are repaired by the mismatch repair (MMR) pathway to maintain genetic integrity. We have developed a method for the fluorescence detection of the cellular MMR ability. A mismatch, which would generate a stop codon in the mRNA transcript unless it was repaired, was introduced into the gene encoding the enhanced green fluorescent protein (EGFP) in an expression plasmid. When MMR-proficient HeLa cells were transformed with this plasmid, the production of active EGFP was observed by fluorescence microscopy. It was assumed that the nick required to initiate the MMR pathway was produced non-specifically in the cells. In contrast, fluorescence was not detected for three types of MMR-deficient cells, LoVo, HCT116, and DLD-1, transformed with the same plasmid. In addition, the expression of a red fluorescent protein gene was utilized to avoid false-negative results. This simple fluorescence method may improve the detection of repair defects, as a biomarker for cancer diagnosis and therapy.
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Affiliation(s)
- Shunsuke Ito
- Division of Chemistry, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan
| | - Miyako Shiraishi
- Division of Chemistry, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan
| | - Kazuki Tsuchihashi
- Division of Chemistry, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan
| | - Reine Takatsuka
- Division of Chemistry, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan
| | - Junpei Yamamoto
- Division of Chemistry, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan
| | - Isao Kuraoka
- Division of Chemistry, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.,Department of Chemistry, Faculty of Science, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka, 814-0180, Japan
| | - Shigenori Iwai
- Division of Chemistry, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka, 560-8531, Japan.
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57
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Single-cell mutagenic responses and cell death revealed in real time. Proc Natl Acad Sci U S A 2018; 115:7168-7170. [PMID: 29946022 DOI: 10.1073/pnas.1808986115] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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58
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Abstract
A large number of chemicals and several physical agents, such as UV light and γ-radiation, have been associated with the etiology of human cancer. Generation of DNA damage (also known as DNA adducts or lesions) induced by these agents is an important first step in the process of carcinogenesis. Evolutionary processes gave rise to DNA repair tools that are efficient in repairing damaged DNA; yet replication of damaged DNA may take place prior to repair, particularly when they are induced at a high frequency. Damaged DNA replication may lead to gene mutations, which in turn may give rise to altered proteins. Mutations in an oncogene, a tumor-suppressor gene, or a gene that controls the cell cycle can generate a clonal cell population with a distinct advantage in proliferation. Many such events, broadly divided into the stages of initiation, promotion, and progression, which may occur over a long period of time and transpire in the context of chronic exposure to carcinogens, can lead to the induction of human cancer. This is exemplified in the long-term use of tobacco being responsible for an increased risk of lung cancer. This mini-review attempts to summarize this wide area that centers on DNA damage as it relates to the development of human cancer.
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Affiliation(s)
- Ashis K Basu
- Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060, USA.
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59
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de Barros AC, Takeda AAS, Dreyer TR, Velazquez-Campoy A, Kobe B, Fontes MRM. DNA mismatch repair proteins MLH1 and PMS2 can be imported to the nucleus by a classical nuclear import pathway. Biochimie 2017; 146:87-96. [PMID: 29175432 DOI: 10.1016/j.biochi.2017.11.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 11/22/2017] [Indexed: 01/11/2023]
Abstract
MLH1 and PMS2 proteins form the MutLα heterodimer, which plays a major role in DNA mismatch repair (MMR) in humans. Mutations in MMR-related proteins are associated with cancer, especially with colon cancer. The N-terminal region of MutLα comprises the N-termini of PMS2 and MLH1 and, similarly, the C-terminal region of MutLα is composed by the C-termini of PMS2 and MLH1, and the two are connected by linker region. The nuclear localization sequences (NLSs) necessary for the nuclear transport of the two proteins are found in this linker region. However, the exact NLS sequences have been controversial, with different sequences reported, particularly for MLH1. The individual components are not imported efficiently, presumably due to their C-termini masking their NLSs. In order to gain insights into the nuclear transport of these proteins, we solved the crystal structures of importin-α bound to peptides corresponding to the supposed NLSs of MLH1 and PMS2 and performed isothermal titration calorimetry to study their binding affinities. Both putative MLH1 and PMS2 NLSs can bind to importin-α as monopartite NLSs, which is in agreement with some previous studies. However, MLH1-NLS has the highest affinity measured by a natural NLS peptide, suggesting a major role of MLH1 protein in nuclear import compared to PMS2. Finally, the role of MLH1 and PMS2 in the nuclear transport of the MutLα heterodimer is discussed.
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Affiliation(s)
- Andrea C de Barros
- Departamento de Física e Biofísica, Instituto de Biociências, Universidade Estadual Paulista, Botucatu, SP, Brazil
| | - Agnes A S Takeda
- Departamento de Física e Biofísica, Instituto de Biociências, Universidade Estadual Paulista, Botucatu, SP, Brazil
| | - Thiago R Dreyer
- Departamento de Física e Biofísica, Instituto de Biociências, Universidade Estadual Paulista, Botucatu, SP, Brazil
| | - Adrian Velazquez-Campoy
- Institute of Biocomputation and Physics of Complex Systems (BIFI), Joint-Unit IQFR-CSIC-BIFI, University of Zaragoza, Zaragoza, Spain; Dep. of Biochemistry and Molecular and Cell Biology, University of Zaragoza, Zaragoza, Spain; Fundacion ARAID, Government of Aragon, Zaragoza, Spain
| | - Boštjan Kobe
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, Queensland 4072, Australia
| | - Marcos R M Fontes
- Departamento de Física e Biofísica, Instituto de Biociências, Universidade Estadual Paulista, Botucatu, SP, Brazil.
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60
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Hu J, Selby CP, Adar S, Adebali O, Sancar A. Molecular mechanisms and genomic maps of DNA excision repair in Escherichia coli and humans. J Biol Chem 2017; 292:15588-15597. [PMID: 28798238 DOI: 10.1074/jbc.r117.807453] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Nucleotide excision repair is a major DNA repair mechanism in all cellular organisms. In this repair system, the DNA damage is removed by concerted dual incisions bracketing the damage and at a precise distance from the damage. Here, we review the basic mechanisms of excision repair in Escherichia coli and humans and the recent genome-wide mapping of DNA damage and repair in these organisms at single-nucleotide resolution.
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Affiliation(s)
- Jinchuan Hu
- From the Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7260 and
| | - Christopher P Selby
- From the Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7260 and
| | - Sheera Adar
- From the Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7260 and.,the Department of Microbiology and Molecular Genetics, Hebrew University-Hadassah Medical School, Ein Kerem 71120, Jerusalem, Israel
| | - Ogun Adebali
- From the Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7260 and
| | - Aziz Sancar
- From the Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7260 and
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61
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Pećina-Šlaus N, Kafka A, Bukovac A, Vladušić T, Tomas D, Hrašćan R. Genetic changes of MLH1 and MSH2 genes could explain constant findings on microsatellite instability in intracranial meningioma. Tumour Biol 2017; 39:1010428317705791. [PMID: 28705114 DOI: 10.1177/1010428317705791] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Postreplicative mismatch repair safeguards the stability of our genome. The defects in its functioning will give rise to microsatellite instability. In this study, 50 meningiomas were investigated for microsatellite instability. Two major mismatch repair genes, MLH1 and MSH2, were analyzed using microsatellite markers D1S1611 and BAT26 amplified by polymerase chain reaction and visualized by gel electrophoresis on high-resolution gels. Furthermore, genes DVL3 (D3S1262), AXIN1 (D16S3399), and CDH1 (D16S752) were also investigated for microsatellite instability. Our study revealed constant presence of microsatellite instability in meningioma patients when compared to their autologous blood DNA. Altogether 38% of meningiomas showed microsatellite instability at one microsatellite locus, 16% on two, and 13.3% on three loci. The percent of detected microsatellite instability for MSH2 gene was 14%, and for MLH1, it was 26%, for DVL3 22.9%, for AXIN1 17.8%, and for CDH1 8.3%. Since markers also allowed for the detection of loss of heterozygosity, gross deletions of MLH1 gene were found in 24% of meningiomas. Genetic changes between MLH1 and MSH2 were significantly positively correlated (p = 0.032). We also noted a positive correlation between genetic changes of MSH2 and DVL3 genes (p = 0.034). No significant associations were observed when MLH1 or MSH2 was tested against specific histopathological meningioma subtype or World Health Organization grade. However, genetic changes in DVL3 were strongly associated with anaplastic histology of meningioma (χ2 = 9.14; p = 0.01). Our study contributes to better understanding of the genetic profile of human intracranial meningiomas and suggests that meningiomas harbor defective cellular DNA mismatch repair mechanisms.
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Affiliation(s)
- Nives Pećina-Šlaus
- 1 Laboratory of Neurooncology, Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia.,2 Department of Biology, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Anja Kafka
- 1 Laboratory of Neurooncology, Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia.,2 Department of Biology, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Anja Bukovac
- 1 Laboratory of Neurooncology, Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia.,2 Department of Biology, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Tomislav Vladušić
- 3 Department of Biochemical Engineering, Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia
| | - Davor Tomas
- 4 Department of Pathology, School of Medicine, University of Zagreb, Zagreb, Croatia.,5 University Hospital "Sisters of Charity," Zagreb, Croatia
| | - Reno Hrašćan
- 3 Department of Biochemical Engineering, Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia
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62
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Abstract
This introductory article should be viewed as a prologue to the Free Radical Biology & Medicine Special Issue devoted to the important topic of Oxidatively Damaged DNA and its Repair. This special issue is dedicated to Professor Tomas Lindahl, co-winner of the 2015 Nobel Prize in Chemistry for his seminal discoveries in the area repair of oxidatively damaged DNA. In the past several years it has become abundantly clear that DNA oxidation is a major consequence of life in an oxygen-rich environment. Concomitantly, survival in the presence of oxygen, with the constant threat of deleterious DNA mutations and deletions, has largely been made possible through the evolution of a vast array of DNA repair enzymes. The articles in this Oxidatively Damaged DNA & Repair special issue detail the reactions by which intracellular DNA is oxidatively damaged, and the enzymatic reactions and pathways by which living organisms survive such assaults by repair processes.
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Affiliation(s)
- Jean Cadet
- Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine de des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4
| | - Kelvin J A Davies
- Leonard Davis School of Gerontology of the Ethel Percy Andrus Gerontology Center, the University of Southern California, Los Angeles, CA 90089-0191, USA; Division of Molecular & Computational Biology, Department of Biological Sciences of the Dornsife College of Letters, Arts, and Sciences, the University of Southern California, Los Angeles, CA 90089-0191, USA.
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63
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64
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Lakhani B, Thayer KM, Hingorani MM, Beveridge DL. Evolutionary Covariance Combined with Molecular Dynamics Predicts a Framework for Allostery in the MutS DNA Mismatch Repair Protein. J Phys Chem B 2017; 121:2049-2061. [PMID: 28135092 PMCID: PMC5346969 DOI: 10.1021/acs.jpcb.6b11976] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
![]()
Mismatch
repair (MMR) is an essential, evolutionarily conserved
pathway that maintains genome stability by correcting base-pairing
errors in DNA. Here we examine the sequence and structure of MutS
MMR protein to decipher the amino acid framework underlying its two
key activities—recognizing mismatches in DNA and using ATP
to initiate repair. Statistical coupling analysis (SCA) identified
a network (sector) of coevolved amino acids in the MutS protein family.
The potential functional significance of this SCA sector was assessed
by performing molecular dynamics (MD) simulations for alanine mutants
of the top 5% of 160 residues in the distribution, and control nonsector
residues. The effects on three independent metrics were monitored:
(i) MutS domain conformational dynamics, (ii) hydrogen bonding between
MutS and DNA/ATP, and (iii) relative ATP binding free energy. Each
measure revealed that sector residues contribute more substantively
to MutS structure–function than nonsector residues. Notably,
sector mutations disrupted MutS contacts with DNA and/or ATP from
a distance via contiguous pathways and correlated motions, supporting
the idea that SCA can identify amino acid networks underlying allosteric
communication. The combined SCA/MD approach yielded novel, experimentally
testable hypotheses for unknown roles of many residues distributed
across MutS, including some implicated in Lynch cancer syndrome.
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Affiliation(s)
- Bharat Lakhani
- Molecular Biology and Biochemistry Department, ‡Molecular Biophysics Program, §Chemistry Department, and ∥Computer Science Department, Wesleyan University , Middletown, Connecticut 06459, United States
| | - Kelly M Thayer
- Molecular Biology and Biochemistry Department, ‡Molecular Biophysics Program, §Chemistry Department, and ∥Computer Science Department, Wesleyan University , Middletown, Connecticut 06459, United States
| | - Manju M Hingorani
- Molecular Biology and Biochemistry Department, ‡Molecular Biophysics Program, §Chemistry Department, and ∥Computer Science Department, Wesleyan University , Middletown, Connecticut 06459, United States
| | - David L Beveridge
- Molecular Biology and Biochemistry Department, ‡Molecular Biophysics Program, §Chemistry Department, and ∥Computer Science Department, Wesleyan University , Middletown, Connecticut 06459, United States
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65
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Affiliation(s)
- Neil M Kad
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK
| | - Bennett Van Houten
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, Pennsylvania 15213, USA
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Identification of β Clamp-DNA Interaction Regions That Impair the Ability of E. coli to Tolerate Specific Classes of DNA Damage. PLoS One 2016; 11:e0163643. [PMID: 27685804 PMCID: PMC5042465 DOI: 10.1371/journal.pone.0163643] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 09/12/2016] [Indexed: 12/13/2022] Open
Abstract
The E. coli dnaN-encoded β sliding clamp protein plays a pivotal role in managing the actions on DNA of the 5 bacterial DNA polymerases, proteins involved in mismatch repair, as well as several additional proteins involved in DNA replication. Results of in vitro experiments indicate that the loading of β clamp onto DNA relies on both the DnaX clamp loader complex as well as several discrete sliding clamp-DNA interactions. However, the importance of these DNA interactions to E. coli viability, as well as the ability of the β clamp to support the actions of its numerous partner proteins, have not yet been examined. To determine the contribution of β clamp-DNA interactions to the ability of E. coli to cope with different classes of DNA damage, we used alanine scanning to mutate 22 separate residues mapping to 3 distinct β clamp surfaces known or nearby those known to contact the DNA template, including residues P20-L27 (referred to here as loop I), H148-Y154 (loop II) and 7 different residues lining the central pore of the β clamp through which the DNA template threads. Twenty of these 22 dnaN mutants supported bacterial growth. While none of these 20 conferred sensitivity to hydrogen peroxide or ultra violet light, 12 were sensitized to NFZ, 5 were sensitized to MMS, 8 displayed modestly altered frequencies of DNA damage-induced mutagenesis, and 2 may be impaired for supporting hda function. Taken together, these results demonstrate that discrete β clamp-DNA interaction regions contribute to the ability of E. coli to tolerate specific classes of DNA damage.
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