101
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Erie DA, Weninger KR. Single molecule studies of DNA mismatch repair. DNA Repair (Amst) 2014; 20:71-81. [PMID: 24746644 DOI: 10.1016/j.dnarep.2014.03.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 03/21/2014] [Accepted: 03/22/2014] [Indexed: 11/30/2022]
Abstract
DNA mismatch repair, which involves is a widely conserved set of proteins, is essential to limit genetic drift in all organisms. The same system of proteins plays key roles in many cancer related cellular transactions in humans. Although the basic process has been reconstituted in vitro using purified components, many fundamental aspects of DNA mismatch repair remain hidden due in part to the complexity and transient nature of the interactions between the mismatch repair proteins and DNA substrates. Single molecule methods offer the capability to uncover these transient but complex interactions and allow novel insights into mechanisms that underlie DNA mismatch repair. In this review, we discuss applications of single molecule methodology including electron microscopy, atomic force microscopy, particle tracking, FRET, and optical trapping to studies of DNA mismatch repair. These studies have led to formulation of mechanistic models of how proteins identify single base mismatches in the vast background of matched DNA and signal for their repair.
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Affiliation(s)
- Dorothy A Erie
- Department of Chemistry and Curriculum in Applied Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States.
| | - Keith R Weninger
- Department of Physics, North Carolina State University, Raleigh, NC 27695, United States
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102
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Thomason LC, Sawitzke JA, Li X, Costantino N, Court DL. Recombineering: genetic engineering in bacteria using homologous recombination. CURRENT PROTOCOLS IN MOLECULAR BIOLOGY 2014; 106:1.16.1-1.16.39. [PMID: 24733238 DOI: 10.1002/0471142727.mb0116s106] [Citation(s) in RCA: 147] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The bacterial chromosome and bacterial plasmids can be engineered in vivo by homologous recombination using PCR products and synthetic oligonucleotides as substrates. This is possible because bacteriophage-encoded recombination proteins efficiently recombine sequences with homologies as short as 35 to 50 bases. Recombineering allows DNA sequences to be inserted or deleted without regard to location of restriction sites. This unit first describes preparation of electrocompetent cells expressing the recombineering functions and their transformation with dsDNA or ssDNA. It then presents support protocols that describe several two-step selection/counter-selection methods of making genetic alterations without leaving any unwanted changes in the targeted DNA, and a method for retrieving onto a plasmid a genetic marker (cloning by retrieval) from the Escherichia coli chromosome or a co-electroporated DNA fragment. Additional protocols describe methods to screen for unselected mutations, removal of the defective prophage from recombineering strains, and other useful techniques.
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Affiliation(s)
- Lynn C Thomason
- Basic Science Program, GRCBL-Molecular Control & Genetics Section, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc, Frederick, Maryland
| | - James A Sawitzke
- Molecular Control and Genetics Section, Gene Regulation and Chromosome Biology, National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland
| | - Xintian Li
- Molecular Control and Genetics Section, Gene Regulation and Chromosome Biology, National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland
| | - Nina Costantino
- Molecular Control and Genetics Section, Gene Regulation and Chromosome Biology, National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland
| | - Donald L Court
- Molecular Control and Genetics Section, Gene Regulation and Chromosome Biology, National Cancer Institute at Frederick, National Institutes of Health, Frederick, Maryland
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103
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Bennett GM, Moran NA. Small, smaller, smallest: the origins and evolution of ancient dual symbioses in a Phloem-feeding insect. Genome Biol Evol 2014; 5:1675-88. [PMID: 23918810 PMCID: PMC3787670 DOI: 10.1093/gbe/evt118] [Citation(s) in RCA: 206] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Many insects rely on bacterial symbionts with tiny genomes specialized for provisioning nutrients lacking in host diets. Xylem sap and phloem sap are both deficient as insect diets, but differ dramatically in nutrient content, potentially affecting symbiont genome evolution. For sap-feeding insects, sequenced symbiont genomes are available only for phloem-feeding examples from the suborder Sternorrhyncha and xylem-feeding examples from the suborder Auchenorrhyncha, confounding comparisons. We sequenced genomes of the obligate symbionts, Sulcia muelleri and Nasuia deltocephalinicola, of the phloem-feeding pest insect, Macrosteles quadrilineatus (Auchenorrhyncha: Cicadellidae). Our results reveal that Nasuia-ALF has the smallest bacterial genome yet sequenced (112 kb), and that the Sulcia-ALF genome (190 kb) is smaller than that of Sulcia in other insect lineages. Together, these symbionts retain the capability to synthesize the 10 essential amino acids, as observed for several symbiont pairs from xylem-feeding Auchenorrhyncha. Nasuia retains genes enabling synthesis of two amino acids, DNA replication, transcription, and translation. Both symbionts have lost genes underlying ATP synthesis through oxidative phosphorylation, possibly as a consequence of the enriched sugar content of phloem. Shared genomic features, including reassignment of the UGA codon from Stop to tryptophan, and phylogenetic results suggest that Nasuia-ALF is most closely related to Zinderia, the betaproteobacterial symbiont of spittlebugs. Thus, Nasuia/Zinderia and Sulcia likely represent ancient associates that have co-resided in hosts since the divergence of leafhoppers and spittlebugs >200 Ma, and possibly since the origin of the Auchenorrhyncha, >260 Ma.
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Affiliation(s)
- Gordon M Bennett
- Department of Ecology and Evolutionary Biology & Microbial Diversity Institute, Yale University
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104
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Avila J, Gómez-Ramos A, Soriano E. Variations in brain DNA. Front Aging Neurosci 2014; 6:323. [PMID: 25505410 PMCID: PMC4243573 DOI: 10.3389/fnagi.2014.00323] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 11/06/2014] [Indexed: 12/16/2022] Open
Abstract
It is assumed that DNA sequences are conserved in the diverse cell types present in a multicellular organism like the human being. Thus, in order to compare the sequences in the genome of DNA from different individuals, nucleic acid is commonly isolated from a single tissue. In this regard, blood cells are widely used for this purpose because of their availability. Thus blood DNA has been used to study genetic familiar diseases that affect other tissues and organs, such as the liver, heart, and brain. While this approach is valid for the identification of familial diseases in which mutations are present in parental germinal cells and, therefore, in all the cells of a given organism, it is not suitable to identify sporadic diseases in which mutations might occur in specific somatic cells. This review addresses somatic DNA variations in different tissues or cells (mainly in the brain) of single individuals and discusses whether the dogma of DNA invariance between cell types is indeed correct. We will also discuss how single nucleotide somatic variations arise, focusing on the presence of specific DNA mutations in the brain.
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Affiliation(s)
- Jesús Avila
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), ISCIIIMadrid, Spain
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Neurobiology LaboratoryMadrid, Spain
- *Correspondence: Jesús Avila, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Neurobiology Laboratory, 208, C/ Nicolás Cabrera no. 1, Madrid, 28049, Spain e-mail: ; Eduardo Soriano, Department of Cell Biology, Faculty of Biology, University of Barcelona, Developmental Neurobiology and Regeneration Lab, Parc Científic de Barcelona, Baldiri i Reixac, 10, Barcelona 08028, Spain e-mail:
| | - Alberto Gómez-Ramos
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), ISCIIIMadrid, Spain
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Neurobiology LaboratoryMadrid, Spain
| | - Eduardo Soriano
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), ISCIIIMadrid, Spain
- Department of Cell Biology, Faculty of Biology, University of Barcelona, Developmental Neurobiology and Regeneration Lab, Parc Científic de BarcelonaBarcelona, Spain
- Vall d’Hebrón Institut de Recerca (VHIR)Barcelona, Spain
- *Correspondence: Jesús Avila, Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Neurobiology Laboratory, 208, C/ Nicolás Cabrera no. 1, Madrid, 28049, Spain e-mail: ; Eduardo Soriano, Department of Cell Biology, Faculty of Biology, University of Barcelona, Developmental Neurobiology and Regeneration Lab, Parc Científic de Barcelona, Baldiri i Reixac, 10, Barcelona 08028, Spain e-mail:
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105
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Bacterial endosymbiosis in a chordate host: long-term co-evolution and conservation of secondary metabolism. PLoS One 2013; 8:e80822. [PMID: 24324632 PMCID: PMC3851785 DOI: 10.1371/journal.pone.0080822] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 10/16/2013] [Indexed: 11/19/2022] Open
Abstract
Intracellular symbiosis is known to be widespread in insects, but there are few described examples in other types of host. These symbionts carry out useful activities such as synthesizing nutrients and conferring resistance against adverse events such as parasitism. Such symbionts persist through host speciation events, being passed down through vertical transmission. Due to various evolutionary forces, symbionts go through a process of genome reduction, eventually resulting in tiny genomes where only those genes essential to immediate survival and those beneficial to the host remain. In the marine environment, invertebrates such as tunicates are known to harbor complex microbiomes implicated in the production of natural products that are toxic and probably serve a defensive function. Here, we show that the intracellular symbiont Candidatus Endolissoclinum faulkneri is a long-standing symbiont of the tunicate Lissoclinum patella, that has persisted through cryptic speciation of the host. In contrast to the known examples of insect symbionts, which tend to be either relatively recent or ancient relationships, the genome of Ca. E. faulkneri has a very low coding density but very few recognizable pseudogenes. The almost complete degradation of intergenic regions and stable gene inventory of extant strains of Ca. E. faulkneri show that further degradation and deletion is happening very slowly. This is a novel stage of genome reduction and provides insight into how tiny genomes are formed. The ptz pathway, which produces the defensive patellazoles, is shown to date to before the divergence of Ca. E. faulkneri strains, reinforcing its importance in this symbiotic relationship. Lastly, as in insects we show that stable symbionts can be lost, as we describe an L. patella animal where Ca. E. faulkneri is displaced by a likely intracellular pathogen. Our results suggest that intracellular symbionts may be an important source of ecologically significant natural products in animals.
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106
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Zhu L, Cai Z, Zhang Y, Li Y. Engineering stress tolerance ofEscherichia coliby stress-induced mutagenesis (SIM)-based adaptive evolution. Biotechnol J 2013; 9:120-7. [DOI: 10.1002/biot.201300277] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 09/02/2013] [Accepted: 09/15/2013] [Indexed: 01/02/2023]
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107
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Gualberto JM, Mileshina D, Wallet C, Niazi AK, Weber-Lotfi F, Dietrich A. The plant mitochondrial genome: dynamics and maintenance. Biochimie 2013; 100:107-20. [PMID: 24075874 DOI: 10.1016/j.biochi.2013.09.016] [Citation(s) in RCA: 189] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 09/17/2013] [Indexed: 12/21/2022]
Abstract
Plant mitochondria have a complex and peculiar genetic system. They have the largest genomes, as compared to organelles from other eukaryotic organisms. These can expand tremendously in some species, reaching the megabase range. Nevertheless, whichever the size, the gene content remains modest and restricted to a few polypeptides required for the biogenesis of the oxidative phosphorylation chain complexes, ribosomal proteins, transfer RNAs and ribosomal RNAs. The presence of autonomous plasmids of essentially unknown function further enhances the level of complexity. The physical organization of the plant mitochondrial DNA includes a set of sub-genomic forms resulting from homologous recombination between repeats, with a mixture of linear, circular and branched structures. This material is compacted into membrane-bound nucleoids, which are the inheritance units but also the centers of genome maintenance and expression. Recombination appears to be an essential characteristic of plant mitochondrial genetic processes, both in shaping and maintaining the genome. Under nuclear surveillance, recombination is also the basis for the generation of new mitotypes and is involved in the evolution of the mitochondrial DNA. In line with, or as a consequence of its complex physical organization, replication of the plant mitochondrial DNA is likely to occur through multiple mechanisms, potentially involving recombination processes. We give here a synthetic view of these aspects.
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Affiliation(s)
- José M Gualberto
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France.
| | - Daria Mileshina
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France.
| | - Clémentine Wallet
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France.
| | - Adnan Khan Niazi
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France.
| | - Frédérique Weber-Lotfi
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France.
| | - André Dietrich
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France.
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108
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Lenhart JS, Pillon MC, Guarné A, Simmons LA. Trapping and visualizing intermediate steps in the mismatch repair pathwayin vivo. Mol Microbiol 2013; 90:680-98. [DOI: 10.1111/mmi.12389] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/29/2013] [Indexed: 01/08/2023]
Affiliation(s)
- Justin S. Lenhart
- Department of Molecular, Cellular, and Developmental Biology; University of Michigan; 830 North University Ave Ann Arbor MI 48109-1048 USA
| | - Monica C. Pillon
- Department of Biochemistry and Biomedical Sciences; McMaster University; 1280 Main Street West Hamilton Ontario L8S 4K1 Canada
| | - Alba Guarné
- Department of Biochemistry and Biomedical Sciences; McMaster University; 1280 Main Street West Hamilton Ontario L8S 4K1 Canada
| | - Lyle A. Simmons
- Department of Molecular, Cellular, and Developmental Biology; University of Michigan; 830 North University Ave Ann Arbor MI 48109-1048 USA
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109
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McCullough LE, Santella RM, Cleveland RJ, Millikan RC, Olshan AF, North KE, Bradshaw PT, Eng SM, Terry MB, Shen J, Crew KD, Rossner P, Teitelbaum SL, Neugut AI, Gammon MD. Polymorphisms in DNA repair genes, recreational physical activity and breast cancer risk. Int J Cancer 2013; 134:654-63. [PMID: 23852586 DOI: 10.1002/ijc.28383] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 06/19/2013] [Indexed: 12/29/2022]
Abstract
The mechanisms driving the inverse association between recreational physical activity (RPA) and breast cancer risk are complex. While exercise is associated with increased reactive oxygen species production it may also improve damage repair systems, particularly those that operate on single-strand breaks including base excision repair (BER), nucleotide excision repair (NER) and mismatch repair (MMR). Of these repair pathways, the role of MMR in breast carcinogenesis is least investigated. Polymorphisms in MMR or other DNA repair gene variants may modify the association between RPA and breast cancer incidence. We investigated the individual and joint effects of variants in three MMR pathway genes (MSH3, MLH1 and MSH2) on breast cancer occurrence using resources from the Long Island Breast Cancer Study Project. We additionally characterized interactions between RPA and genetic polymorphisms in MMR, BER and NER pathways. We found statistically significant multiplicative interactions (p < 0.05) between MSH2 and MLH1, as well as between postmenopausal RPA and four variants in DNA repair (XPC-Ala499Val, XPF-Arg415Gln, XPG-Asp1104His and MLH1-lle219Val). Significant risk reductions were observed among highly active women with the common genotype for XPC (OR = 0.54; 95% CI, 0.36-0.81) and XPF (OR = 0.62; 95% CI, 0.44-0.87), as well as among active women who carried at least one variant allele in XPG (OR = 0.46; 95% CI, 0.29-0.77) and MLH1 (OR = 0.46; 95% CI, 0.30-0.71). Our data show that women with minor alleles in both MSH2 and MLH1 could be at increased breast cancer risk. RPA may be modified by genes in the DNA repair pathway, and merit further investigation.
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Affiliation(s)
- Lauren E McCullough
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA
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110
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Sahu PK, Srinivasadesikan V, Jhong ML, Lee SL. Model calculations for the base-pairing specificity of mutagenic exocyclic DNA adduct 1,N 6-ethenoadenine. Struct Chem 2013. [DOI: 10.1007/s11224-013-0318-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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111
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Sequence-specific and DNA structure-dependent interactions of Escherichia coli MutS and human p53 with DNA. Anal Biochem 2013; 442:51-61. [PMID: 23928048 DOI: 10.1016/j.ab.2013.07.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2013] [Revised: 07/19/2013] [Accepted: 07/23/2013] [Indexed: 11/20/2022]
Abstract
Many proteins involved in DNA repair systems interact with DNA that has structure altered from the typical B-form helix. Using magnetic beads to immobilize DNAs containing various types of structures, we evaluated the in vitro binding activities of two well-characterized DNA repair proteins, Escherichia coli MutS and human p53. E. coli MutS bound to double-stranded DNAs, with higher affinity for a G/T mismatch compared to a G/A mismatch and highest affinity for larger non-B-DNA structures. E. coli MutS bound best to DNA between pH 6 and 9. Experiments discriminated between modes of p53-DNA binding, and increasing ionic strength reduced p53 binding to nonspecific double-stranded DNA, but had minor effects on binding to consensus response sequences or single-stranded DNA. Compared to nonspecific DNA sequences, p53 bound with a higher affinity to mismatches and base insertions, while binding to various hairpin structures was similar to that observed to its consensus DNA sequence. For hairpins containing CTG repeats, the extent of p53 binding was proportional to the size of the repeat. In summary, using the flexibility of the magnetic bead separation assay we demonstrate that pH and ionic strength influence the binding of two DNA repair proteins to a variety of DNA structures.
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112
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Zeller A, Koenig J, Schmitt G, Singer T, Guérard M. Genotoxicity profile of azidothymidine in vitro. Toxicol Sci 2013; 135:317-27. [PMID: 23811827 DOI: 10.1093/toxsci/kft149] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Azidothymidine (Zidovudine, AZT) is part of the standard care of treatment for acquired immunodeficiency syndrome since many years. A great number of studies on the genotoxic potential of AZT have been published, but no comprehensive hypothesis yet explains all observations. We investigated a multitude of genotoxic endpoints, both in vitro and in vivo, with the goal to complete the picture. The mutagenic potential of AZT in bacteria was found to be restricted to strains with an "ochre" target sequence and could be abrogated both by thymidine supplementation and rat liver S9 mix. Single-strand breaks in mammalian cells were detected in the comet assay after short-term treatment (3h) with AZT, which did not induce micronuclei. The latter were mainly seen after prolonged exposure (24 and 48h) and are probably not directly related to AZT incorporation into DNA. Our data demonstrate that short-term exposure to low AZT concentrations does not induce biologically relevant micronucleation. Only treatment with high concentrations of AZT for prolonged time periods manifests in substantial micronucleus induction. Furthermore, we found that high concentrations of thymidine have no effect in the comet assay but increase micronucleus frequency in a manner very similar to AZT. These results lead us to the following hypothesis: AZT is triphosphorylated and then incorporated into DNA strands, leading to mutations and cytotoxicity. Cellular attempts to repair these DNA lesions as well as stalled replication forks due to chain termination are detectable with the comet assay. Increased micronucleus frequency is likely related to nucleotide pool imbalance.
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Affiliation(s)
- Andreas Zeller
- * F. Hoffmann-La Roche AG, Non-Clinical Safety, 4070 Basel, Switzerland
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113
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Shimada A, Kawasoe Y, Hata Y, Takahashi TS, Masui R, Kuramitsu S, Fukui K. MutS stimulates the endonuclease activity of MutL in an ATP-hydrolysis-dependent manner. FEBS J 2013; 280:3467-79. [PMID: 23679952 DOI: 10.1111/febs.12344] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 05/02/2013] [Accepted: 05/07/2013] [Indexed: 11/30/2022]
Abstract
In the initial steps of DNA mismatch repair, MutS recognizes a mismatched base and recruits the latent endonuclease MutL onto the mismatch-containing DNA in concert with other proteins. MutL then cleaves the error-containing strand to introduce an entry point for the downstream excision reaction. Because MutL has no intrinsic ability to recognize a mismatch and discriminate between newly synthesized and template strands, the endonuclease activity of MutL is strictly regulated by ATP-binding in order to avoid nonspecific degradation of the genomic DNA. However, the activation mechanism for its endonuclease activity remains unclear. In this study, we found that the coexistence of a mismatch, ATP and MutS unlocks the ATP-binding-dependent suppression of MutL endonuclease activity. Interestingly, ATPase-deficient mutants of MutS were unable to activate MutL. Furthermore, wild-type MutS activated ATPase-deficient mutants of MutL less efficiently than wild-type MutL. We concluded that ATP hydrolysis by MutS and MutL is involved in the mismatch-dependent activation of MutL endonuclease activity.
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Affiliation(s)
- Atsuhiro Shimada
- Department of Biological Sciences, Graduate School of Science, Osaka University, Suita, Osaka, Japan
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114
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Taira K, Kaneto S, Nakano K, Watanabe S, Takahashi E, Arimoto S, Okamoto K, Schaaper RM, Negishi K, Negishi T. Distinct pathways for repairing mutagenic lesions induced by methylating and ethylating agents. Mutagenesis 2013; 28:341-50. [PMID: 23446177 PMCID: PMC3630523 DOI: 10.1093/mutage/get010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
DNA alkylation damage can be repaired by nucleotide excision repair (NER), base excision repair (BER) or by direct removal of alkyl groups from modified bases by O(6)-alkylguanine DNA alkyltransferase (AGT; E.C. 2.1.1.63). DNA mismatch repair (MMR) is also likely involved in this repair. We have investigated alkylation-induced mutagenesis in a series of NER- or AGT-deficient Escherichia coli strains, alone or in combination with defects in the MutS, MutL or MutH components of MMR. All strains used contained the F'prolac from strain CC102 (F'CC102) episome capable of detecting specifically lac GC to AT reverse mutations resulting from O(6)-alkylguanine. The results showed the repair of O(6)-methylguanine to be performed by AGT ≫ MMR > NER in order of importance, whereas the repair of O(6)-ethylguanine followed the order NER > AGT > MMR. Studies with double mutants showed that in the absence of AGT or NER repair pathways, the lack of MutS protein generally increased mutant frequencies for both methylating and ethylating agents, suggesting a repair or mutation avoidance role for this protein. However, lack of MutL or MutH protein did not increase alkylation-induced mutagenesis under these conditions and, in fact, reduced mutagenesis by the N-alkyl-N-nitrosoureas MNU and ENU. The combined results suggest that little or no alkylation damage is actually corrected by the mutHLS MMR system; instead, an as yet unspecified interaction of MutS protein with alkylated DNA may promote the involvement of a repair system other than MMR to avoid a mutagenic outcome. Furthermore, both mutagenic and antimutagenic effects of MMR were detected, revealing a dual function of the MMR system in alkylation-exposed cells.
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Affiliation(s)
- Kentaro Taira
- Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Tsushima, Okayama 700-8530, Japan
- NIEHS, Research Triangle Park, NC 27709, USA and
- Nihon Pharmaceutical University, Ina, Kita-Adachi-Gun, Saitama 362-0806, Japan
| | - Satomi Kaneto
- Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Tsushima, Okayama 700-8530, Japan
- NIEHS, Research Triangle Park, NC 27709, USA and
- Nihon Pharmaceutical University, Ina, Kita-Adachi-Gun, Saitama 362-0806, Japan
| | - Kota Nakano
- Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Tsushima, Okayama 700-8530, Japan
- NIEHS, Research Triangle Park, NC 27709, USA and
- Nihon Pharmaceutical University, Ina, Kita-Adachi-Gun, Saitama 362-0806, Japan
| | - Shinji Watanabe
- Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Tsushima, Okayama 700-8530, Japan
- NIEHS, Research Triangle Park, NC 27709, USA and
- Nihon Pharmaceutical University, Ina, Kita-Adachi-Gun, Saitama 362-0806, Japan
| | - Eizo Takahashi
- Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Tsushima, Okayama 700-8530, Japan
- NIEHS, Research Triangle Park, NC 27709, USA and
- Nihon Pharmaceutical University, Ina, Kita-Adachi-Gun, Saitama 362-0806, Japan
| | - Sakae Arimoto
- Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Tsushima, Okayama 700-8530, Japan
- NIEHS, Research Triangle Park, NC 27709, USA and
- Nihon Pharmaceutical University, Ina, Kita-Adachi-Gun, Saitama 362-0806, Japan
| | - Keinosuke Okamoto
- Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Tsushima, Okayama 700-8530, Japan
- NIEHS, Research Triangle Park, NC 27709, USA and
- Nihon Pharmaceutical University, Ina, Kita-Adachi-Gun, Saitama 362-0806, Japan
| | | | - Kazuo Negishi
- Nihon Pharmaceutical University, Ina, Kita-Adachi-Gun, Saitama 362-0806, Japan
| | - Tomoe Negishi
- *To whom correspondence should be addressed. Tel: +81 86 251 7946; Fax: +81 86 251 7926; E-mail:
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115
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Dong Z, Wang H, Dong Y, Wang Y, Liu W, Miao G, Lin X, Wang D, Liu B. Extensive microsatellite variation in rice induced by introgression from wild rice (Zizania latifolia Griseb.). PLoS One 2013; 8:e62317. [PMID: 23638037 PMCID: PMC3634730 DOI: 10.1371/journal.pone.0062317] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 03/20/2013] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND It is widely accepted that interspecific hybridization may induce genomic instability in the resultant hybrids. However, few studies have been performed on the genomic analysis of homoploid hybrids and introgression lines. We have reported previously that by introgressive hybridization, a set of introgression lines between rice (Oryza sativa L.) and wild rice (Zizania latifolia Griseb.) was successfully generated, and which have led to the release of several cultivars. METHODOLOGY Using 96 microsatellite markers located in the nuclear and organelle genomes of rice, we investigated microsatellite stability in three typical introgression lines. Expression of a set of mismatch repair (MMR) genes and microsatellite-containing genes was also analyzed. RESULTS/CONCLUSIONS Compared with the recipient rice cultivar (Matsumae), 55 of the 96 microsatellite loci revealed variation in one or more of the introgression lines, and 58.2% of the altered alleles were shared by at least two lines, indicating that most of the alterations had occurred in the early stages of introgression before their further differentiation. 73.9% of the non-shared variations were detected only in one introgression line, i.e. RZ2. Sequence alignment showed that the variations included substitutions and indels that occurred both within the repeat tracts and in the flanking regions. Interestingly, expression of a set of MMR genes altered dramatically in the introgression lines relative to their rice parent, suggesting participation of the MMR system in the generation of microsatellite variants. Some of the altered microsatellite loci are concordant with changed expression of the genes harboring them, suggesting their possible cis-regulatory roles in controlling gene expression. Because these genes bear meaningful homology to known-functional proteins, we conclude that the introgression-induced extensive variation of microsatellites may have contributed to the novel phenotypes in the introgression lines.
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Affiliation(s)
- Zhenying Dong
- Key Laboratory of Molecular Epigenetics of MOE and Institute of Genetics and Cytology, Northeast Normal University, Changchun, China
- The State Key Laboratory of Plant Cell and Chromosomal Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Hongyan Wang
- Faculty of Life Science, Liaoning University, Shenyang, China
| | - Yuzhu Dong
- School of Life Sciences, Changchun Normal University, Changchun, China
| | - Yongming Wang
- Key Laboratory of Molecular Epigenetics of MOE and Institute of Genetics and Cytology, Northeast Normal University, Changchun, China
| | - Wei Liu
- Key Laboratory of Molecular Epigenetics of MOE and Institute of Genetics and Cytology, Northeast Normal University, Changchun, China
| | - Gaojian Miao
- Key Laboratory of Molecular Epigenetics of MOE and Institute of Genetics and Cytology, Northeast Normal University, Changchun, China
| | - Xiuyun Lin
- Key Laboratory of Molecular Epigenetics of MOE and Institute of Genetics and Cytology, Northeast Normal University, Changchun, China
| | - Daqing Wang
- Key Laboratory of Molecular Epigenetics of MOE and Institute of Genetics and Cytology, Northeast Normal University, Changchun, China
| | - Bao Liu
- Key Laboratory of Molecular Epigenetics of MOE and Institute of Genetics and Cytology, Northeast Normal University, Changchun, China
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116
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Chen X, Zhang J. No gene-specific optimization of mutation rate in Escherichia coli. Mol Biol Evol 2013; 30:1559-62. [PMID: 23533222 DOI: 10.1093/molbev/mst060] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Mutation rate is one of the most fundamental parameters in genetics and evolutionary biology because mutation rate has major impacts on the incidence of disease, the amount of genetic variation, and the rate and trajectory of evolution. Based on estimates of synonymous nucleotide diversity in Escherichia coli, a recent study claimed that the per-nucleotide mutation rate in a gene decreases with the rise of its expression level or the intensity of purifying selection and that this trend reflects adaptive risk management. Here, we demonstrate that this argument is theoretically untenable, especially in the lack of mechanisms that simultaneously tune the mutabilities of multiple genes with similar fractions of deleterious mutations. Analyzing published genome sequences of E. coli mutation accumulation lines, we show that mutation rates are actually higher in more highly expressed genes, similar to previous genome-wide observations in Salmonella typhimurium, Saccharomyces cerevisiae, and the human germline. These general patterns likely arise from transcription-associated mutagenesis that exceeds transcription-coupled repair.
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Affiliation(s)
- Xiaoshu Chen
- Department of Ecology and Evolutionary Biology, University of Michigan, USA
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117
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Abstract
From microbes to multicellular eukaryotic organisms, all cells contain pathways responsible for genome maintenance. DNA replication allows for the faithful duplication of the genome, whereas DNA repair pathways preserve DNA integrity in response to damage originating from endogenous and exogenous sources. The basic pathways important for DNA replication and repair are often conserved throughout biology. In bacteria, high-fidelity repair is balanced with low-fidelity repair and mutagenesis. Such a balance is important for maintaining viability while providing an opportunity for the advantageous selection of mutations when faced with a changing environment. Over the last decade, studies of DNA repair pathways in bacteria have demonstrated considerable differences between Gram-positive and Gram-negative organisms. Here we review and discuss the DNA repair, genome maintenance, and DNA damage checkpoint pathways of the Gram-positive bacterium Bacillus subtilis. We present their molecular mechanisms and compare the functions and regulation of several pathways with known information on other organisms. We also discuss DNA repair during different growth phases and the developmental program of sporulation. In summary, we present a review of the function, regulation, and molecular mechanisms of DNA repair and mutagenesis in Gram-positive bacteria, with a strong emphasis on B. subtilis.
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118
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Lenhart JS, Sharma A, Hingorani MM, Simmons LA. DnaN clamp zones provide a platform for spatiotemporal coupling of mismatch detection to DNA replication. Mol Microbiol 2012; 87:553-68. [PMID: 23228104 DOI: 10.1111/mmi.12115] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/21/2012] [Indexed: 11/30/2022]
Abstract
Mismatch repair (MMR) increases the fidelity of DNA replication by identifying and correcting replication errors. Processivity clamps are vital components of DNA replication and MMR, yet the mechanism and extent to which they participate in MMR remains unclear. We investigated the role of the Bacillus subtilis processivity clamp DnaN, and found that it serves as a platform for mismatch detection and coupling of repair to DNA replication. By visualizing functional MutS fluorescent fusions in vivo, we find that MutS forms foci independent of mismatch detection at sites of replication (i.e. the replisome). These MutS foci are directed to the replisome by DnaN clamp zones that aid mismatch detection by targeting the search to nascent DNA. Following mismatch detection, MutS disengages from the replisome, facilitating repair. We tested the functional importance of DnaN-mediated mismatch detection for MMR, and found that it accounts for 90% of repair. This high dependence on DnaN can be bypassed by increasing MutS concentration within the cell, indicating a secondary mode of detection in vivo whereby MutS directly finds mismatches without associating with the replisome. Overall, our results provide new insight into the mechanism by which DnaN couples mismatch recognition to DNA replication in living cells.
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Affiliation(s)
- Justin S Lenhart
- Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
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119
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Hughes RA, Miklos AE, Ellington AD. Enrichment of error-free synthetic DNA sequences by CEL I nuclease. ACTA ACUST UNITED AC 2012; Chapter 3:Unit3.24. [PMID: 22870859 DOI: 10.1002/0471142727.mb0324s99] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
As the availability of DNA sequence information has grown, so has the need to replicate DNA sequences synthetically. Synthetically produced DNA sequences allow the researcher to exert greater control over model systems and allow for the combinatorial design and construction of novel metabolic and regulatory pathways, as well as optimized protein-coding sequences for biotechnological applications. This utility has made synthetically produced DNA a hallmark of the molecular biosciences and a mainstay of synthetic biology. However, synthetically produced DNA has a significant shortcoming in that it typically has an error rate that is orders of magnitude higher when compared to DNA sequences derived directly from a biological source. This relatively high error rate adds to the cost and labor necessary to obtain sequence-verified clones from synthetically produced DNA sequences. This unit describes a protocol to enrich error-free sequences from a population of error-rich DNA via treatment with CEL I (Surveyor) endonuclease. This method is a straightforward and quick way of reducing the error content of synthetic DNA pools and reliably reduces the error rates by >6-fold per round of treatment.
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Affiliation(s)
- Randall A Hughes
- The University of Texas at Austin, Applied Research Laboratories, Department of Chemistry and Biochemistry, Center for Systems and Synthetic Biology, Austin, Texas, USA
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120
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Zhou K, Michiels CW, Aertsen A. Variation of intragenic tandem repeat tract of tolA modulates Escherichia coli stress tolerance. PLoS One 2012; 7:e47766. [PMID: 23094082 PMCID: PMC3477136 DOI: 10.1371/journal.pone.0047766] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 09/20/2012] [Indexed: 11/18/2022] Open
Abstract
In recent work we discovered that the intragenic tandem repeat (TR) region of the tolA gene is highly variable among different Escherichia coli strains. The aim of this study was therefore to investigate the biological function and dynamics of TR variation in E. coli tolA. The biological impact of TR variation was examined by comparing the ability of a set of synthetic tolA variants with in frame repeat copies varying from 2 to 39 to rescue the altered susceptibility of an E. coli ΔtolA mutant to deoxycholic acid, sodium dodecyl sulfate, hyperosmolarity, and infection with filamentous bacteriophage. Interestingly, although each of the TolA variants was able to at least partly rescue the ΔtolA mutant, the extent was clearly dependent on both the repeat number and the type of stress imposed, indicating the existence of opposing selective forces with regard to the optimal TR copy number. Subsequently, TR dynamics in a clonal population were assayed, and we could demonstrate that TR contractions are RecA dependent and enhanced in a DNA repair deficient uvrD background, and can occur at a frequency of 6.9×10−5.
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Affiliation(s)
- Kai Zhou
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, KU Leuven, Leuven, Belgium
| | - Chris W. Michiels
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, KU Leuven, Leuven, Belgium
| | - Abram Aertsen
- Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, KU Leuven, Leuven, Belgium
- * E-mail:
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121
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Hargreaves VV, Putnam CD, Kolodner RD. Engineered disulfide-forming amino acid substitutions interfere with a conformational change in the mismatch recognition complex Msh2-Msh6 required for mismatch repair. J Biol Chem 2012; 287:41232-44. [PMID: 23045530 DOI: 10.1074/jbc.m112.402495] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ATP binding causes the mispair-bound Msh2-Msh6 mismatch recognition complex to slide along the DNA away from the mismatch, and ATP is required for the mispair-dependent interaction between Msh2-Msh6 and Mlh1-Pms1. It has been inferred from these observations that ATP induces conformational changes in Msh2-Msh6; however, the nature of these conformational changes and their requirement in mismatch repair are poorly understood. Here we show that ATP induces a conformational change within the C-terminal region of Msh6 that protects the trypsin cleavage site after Msh6 residue Arg(1124). An engineered disulfide bond within this region prevented the ATP-driven conformational change and resulted in an Msh2-Msh6 complex that bound mispaired bases but could not form sliding clamps or bind Mlh1-Pms1. The engineered disulfide bond also reduced mismatch repair efficiency in vivo, indicating that this ATP-driven conformational change plays a role in mismatch repair.
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Affiliation(s)
- Victoria V Hargreaves
- Ludwig Institute for Cancer Research, Department of Medicine, Moores-University of California San Diego Cancer Center, and Institute of Genomic Medicine, University of California School of Medicine, San Diego, La Jolla, California 92093-0669, USA
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122
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Coelho AC, Leprohon P, Ouellette M. Generation of Leishmania hybrids by whole genomic DNA transformation. PLoS Negl Trop Dis 2012; 6:e1817. [PMID: 23029579 PMCID: PMC3447969 DOI: 10.1371/journal.pntd.0001817] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 08/01/2012] [Indexed: 11/19/2022] Open
Abstract
Genetic exchange is a powerful tool to study gene function in microorganisms. Here, we tested the feasibility of generating Leishmania hybrids by electroporating genomic DNA of donor cells into recipient Leishmania parasites. The donor DNA was marked with a drug resistance marker facilitating the selection of DNA transfer into the recipient cells. The transferred DNA was integrated exclusively at homologous locus and was as large as 45 kb. The independent generation of L. infantum hybrids with L. major sequences was possible for several chromosomal regions. Interfering with the mismatch repair machinery by inactivating the MSH2 gene enabled an increased efficiency of recombination between divergent sequences, hence favouring the selection of hybrids between species. Hybrids were shown to acquire the phenotype derived from the donor cells, as demonstrated for the transfer of drug resistance genes from L. major into L. infantum. The described method is a first step allowing the generation of in vitro hybrids for testing gene functions in a natural genomic context in the parasite Leishmania.
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Affiliation(s)
| | | | - Marc Ouellette
- Centre de Recherche en Infectiologie, Université Laval, Québec, Canada
- * E-mail:
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124
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Aguilar C, Escalante A, Flores N, de Anda R, Riveros-McKay F, Gosset G, Morett E, Bolívar F. Genetic changes during a laboratory adaptive evolution process that allowed fast growth in glucose to an Escherichia coli strain lacking the major glucose transport system. BMC Genomics 2012; 13:385. [PMID: 22884033 PMCID: PMC3469383 DOI: 10.1186/1471-2164-13-385] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 08/02/2012] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND Escherichia coli strains lacking the phosphoenolpyruvate: carbohydrate phosphotransferase system (PTS), which is the major bacterial component involved in glucose transport and its phosphorylation, accumulate high amounts of phosphoenolpyruvate that can be diverted to the synthesis of commercially relevant products. However, these strains grow slowly in glucose as sole carbon source due to its inefficient transport and metabolism. Strain PB12, with 400% increased growth rate, was isolated after a 120 hours adaptive laboratory evolution process for the selection of faster growing derivatives in glucose. Analysis of the genetic changes that occurred in the PB12 strain that lacks PTS will allow a better understanding of the basis of its growth adaptation and, therefore, in the design of improved metabolic engineering strategies for enhancing carbon diversion into the aromatic pathways. RESULTS Whole genome analyses using two different sequencing methodologies: the Roche NimbleGen Inc. comparative genome sequencing technique, and high throughput sequencing with Illumina Inc. GAIIx, allowed the identification of the genetic changes that occurred in the PB12 strain. Both methods detected 23 non-synonymous and 22 synonymous point mutations. Several non-synonymous mutations mapped in regulatory genes (arcB, barA, rpoD, rna) and in other putative regulatory loci (yjjU, rssA and ypdA). In addition, a chromosomal deletion of 10,328 bp was detected that removed 12 genes, among them, the rppH, mutH and galR genes. Characterization of some of these mutated and deleted genes with their functions and possible functions, are presented. CONCLUSIONS The deletion of the contiguous rppH, mutH and galR genes that occurred simultaneously, is apparently the main reason for the faster growth of the evolved PB12 strain. In support of this interpretation is the fact that inactivation of the rppH gene in the parental PB11 strain substantially increased its growth rate, very likely by increasing glycolytic mRNA genes stability. Furthermore, galR inactivation allowed glucose transport by GalP into the cell. The deletion of mutH in an already stressed strain that lacks PTS is apparently responsible for the very high mutation rate observed.
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Affiliation(s)
- César Aguilar
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos 62210, México
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125
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Robertson AB, Matson SW. Reconstitution of the very short patch repair pathway from Escherichia coli. J Biol Chem 2012; 287:32953-66. [PMID: 22846989 DOI: 10.1074/jbc.m112.384321] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Escherichia coli very short patch (VSP) repair pathway corrects thymidine-guanine mismatches that result from spontaneous hydrolytic deamination damage of 5-methyl cytosine. The VSP repair pathway requires the Vsr endonuclease, DNA polymerase I, a DNA ligase, MutS, and MutL to function at peak efficiency. The biochemical roles of most of these proteins in the VSP repair pathway have been studied extensively. However, these proteins have not been studied together in the context of VSP repair in an in vitro system. Using purified components of the VSP repair system in a reconstitution reaction, we have begun to develop an understanding of the role played by each of these proteins in the VSP repair pathway and have gained insights into their interactions. In this report we demonstrate an in vitro reconstitution of the VSP repair pathway using a plasmid DNA substrate. Surprisingly, the repair track length can be modulated by the concentration of DNA ligase. We propose roles for MutL and MutS in coordination of this repair pathway.
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Affiliation(s)
- Adam B Robertson
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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126
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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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127
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Monument MJ, Lessnick SL, Schiffman JD, Randall RT. Microsatellite instability in sarcoma: fact or fiction? ISRN ONCOLOGY 2012; 2012:473146. [PMID: 23401795 PMCID: PMC3564276 DOI: 10.5402/2012/473146] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Accepted: 05/02/2012] [Indexed: 01/03/2023]
Abstract
Microsatellite instability (MSI) is a unique molecular abnormality, indicative of a deficient DNA mismatch repair (MMR) system. Described and characterized in the colorectal cancer literature, the MSI-positive phenotype is predictive of disease susceptibility, pathogenesis, and prognosis. The clinical relevance of MSI in colorectal cancer has inspired similar inquisition within the sarcoma literature, although unfortunately, with very heterogeneous results. Evolving detection techniques, ill-defined sarcoma-specific microsatellite loci and small study numbers have hampered succinct conclusions. The literature does suggest that MSI in sarcoma is observed at a frequency similar to that of sporadic colorectal cancers, although there is little evidence to suggest that MSI-positive tumors share distinct biological attributes. Emerging evidence in Ewing sarcoma has demonstrated an intriguing mechanistic role of microsatellite DNA in the activation of key EWS/FLI-target genes. These findings provide an alternative perspective to the biological implications of microsatellite instability in sarcoma and warrant further investigation using sophisticated detection techniques, sensitive microsatellite loci, and appropriately powered study designs.
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Affiliation(s)
- Michael J Monument
- Sarcoma Services, Department of Orthopaedics, Huntsman Cancer Institute, University of Utah School of Medicine, 2000 Circle of Hope, Salt Lake City, UT 84112, USA
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128
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LIN CHUYIN, LIN WENWEN, KAO HSIAOWEI. The complete mitochondrial genome of the mackerel icefish, Champsocephalus gunnari (Actinopterygii: Channichthyidae), with reference to the evolution of mitochondrial genomes in Antarctic notothenioids. Zool J Linn Soc 2012. [DOI: 10.1111/j.1096-3642.2012.00820.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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129
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Poleszak K, Kaminska KH, Dunin-Horkawicz S, Lupas A, Skowronek KJ, Bujnicki JM. Delineation of structural domains and identification of functionally important residues in DNA repair enzyme exonuclease VII. Nucleic Acids Res 2012; 40:8163-74. [PMID: 22718974 PMCID: PMC3439923 DOI: 10.1093/nar/gks547] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Exonuclease VII (ExoVII) is a bacterial nuclease involved in DNA repair and recombination that hydrolyses single-stranded DNA. ExoVII is composed of two subunits: large XseA and small XseB. Thus far, little was known about the molecular structure of ExoVII, the interactions between XseA and XseB, the architecture of the nuclease active site or its mechanism of action. We used bioinformatics methods to predict the structure of XseA, which revealed four domains: an N-terminal OB-fold domain, a middle putatively catalytic domain, a coiled-coil domain and a short C-terminal segment. By series of deletion and site-directed mutagenesis experiments on XseA from Escherichia coli, we determined that the OB-fold domain is responsible for DNA binding, the coiled-coil domain is involved in binding multiple copies of the XseB subunit and residues D155, R205, H238 and D241 of the middle domain are important for the catalytic activity but not for DNA binding. Altogether, we propose a model of sequence–structure–function relationships in ExoVII.
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Affiliation(s)
- Katarzyna Poleszak
- Laboratory of Bioinformatics and Protein Engineering, International Institute of Molecular and Cell Biology, ks. Trojdena 4, PL-02-109 Warsaw, Poland
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130
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Cooper LA, Simmons LA, Mobley HLT. Involvement of mismatch repair in the reciprocal control of motility and adherence of uropathogenic Escherichia coli. Infect Immun 2012; 80:1969-79. [PMID: 22473602 PMCID: PMC3370570 DOI: 10.1128/iai.00043-12] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 03/22/2012] [Indexed: 11/20/2022] Open
Abstract
Type 1 fimbriae and flagella, two surface organelles critical for colonization of the urinary tract by uropathogenic Escherichia coli (UPEC), mediate opposing virulence objectives. Type 1 fimbriae facilitate adhesion to mucosal cells and promote bacterial persistence in the urinary tract, while flagella propel bacteria through urine and along mucous layers during ascension to the upper urinary tract. Using a transposon screen of the E. coli CFT073 fim locked-ON (L-ON) mutant, a construct that constitutively expresses type 1 fimbriae and represses motility, we identified six mutants that exhibited a partial restoration of motility. Among these six mutated genes was mutS, which encodes a component of the methyl-directed mismatch repair (MMR) system. When complemented with mutS in trans, motility was again repressed. To determine whether the MMR system, in general, is involved in this reciprocal control, we characterized the effects of gene deletions of other MMR components on UPEC motility. Isogenic deletions of mutS, mutH, and mutL were constructed in both wild-type CFT073 and fim L-ON backgrounds. All MMR mutants showed an increase in motility in the wild-type background, and ΔmutH and ΔmutS mutations increased motility in the fim L-ON background. Cochallenge of the wild-type strain with an MMR-defective strain showed a subtle but significant competitive advantage in the bladder and spleen for the MMR mutant using the murine model of ascending urinary tract infection after 48 h. Our findings demonstrate that the MMR system generally affects the reciprocal regulation of motility and adherence and thus could contribute to UPEC pathogenesis during urinary tract infections.
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Affiliation(s)
- Lauren A. Cooper
- Department of Epidemiology, University of Michigan School of Public Health
| | - Lyle A. Simmons
- Department of Molecular, Cellular, and Developmental Biology, College of Literature, Science, and the Arts, University of Michigan
| | - Harry L. T. Mobley
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
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131
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Research on plants for the understanding of diseases of nuclear and mitochondrial origin. J Biomed Biotechnol 2012; 2012:836196. [PMID: 22690124 PMCID: PMC3368588 DOI: 10.1155/2012/836196] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 03/28/2012] [Indexed: 11/17/2022] Open
Abstract
Different model organisms, such as Escherichia coli, Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, mouse, cultured human cell lines, among others, were used to study the mechanisms of several human diseases. Since human genes and proteins have been structurally and functionally conserved in plant organisms, the use of plants, especially Arabidopsis thaliana, as a model system to relate molecular defects to clinical disorders has recently increased. Here, we briefly review our current knowledge of human diseases of nuclear and mitochondrial origin and summarize the experimental findings of plant homologs implicated in each process.
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132
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Kumar P, Nagarajaram HA. A study on mutational dynamics of simple sequence repeats in relation to mismatch repair system in prokaryotic genomes. J Mol Evol 2012; 74:127-39. [PMID: 22415400 DOI: 10.1007/s00239-012-9491-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Accepted: 02/15/2012] [Indexed: 11/30/2022]
Abstract
Mutational bias toward expansion or contraction of simple sequence repeats (SSRs) is referred to as directionality of SSR evolution. In this communication, we report the mutational bias exhibited by mononucleotide SSRs occurring in the non-coding regions of several prokaryotic genomes. Our investigations revealed that the strains or species lacking mismatch repair (MMR) system generally show higher number of polymorphic SSRs than those species/strains having MMR system. An exception to this observation was seen in the mycobacterial genomes that are MMR deficient where only a few SSR tracts were seen with mutations. This low incidence of SSR mutations even in the MMR-deficient background could be attributed to the high fidelity of the DNA polymerases as a consequence of high generation time of the mycobacteria. MMR system-deficient species generally did not show any bias toward mononucleotide SSR expansions or contractions indicating a neutral evolution of SSRs in these species. The MMR-proficient species in which the observed mutations correspond to secondary mutations showed bias toward contraction of polymononucleotide tracts, perhaps, indicating low efficiency of MMR system to repair SSR-induced slippage errors on template strands. This bias toward deletion in the mononucleotide SSR tracts might be a probable reason behind scarcity for long poly A|T and G|C tracts in prokaryotic systems which are mostly MMR proficient. In conclusion, our study clearly demonstrates mutational dynamics of SSRs in relation to the presence/absence of MMR system in the prokaryotic system.
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Affiliation(s)
- Pankaj Kumar
- Laboratory of Computational Biology, Centre for DNA Fingerprinting and Diagnostics (CDFD), Tuljaguda Complex, 4-1-714, Mozamjahi Rd, Nampally, Hyderabad, 500 001, India
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The mismatch repair system protects against intergenerational GAA repeat instability in a Friedreich ataxia mouse model. Neurobiol Dis 2012; 46:165-71. [PMID: 22289650 DOI: 10.1016/j.nbd.2012.01.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Revised: 12/21/2011] [Accepted: 01/09/2012] [Indexed: 11/21/2022] Open
Abstract
Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by a dynamic GAA repeat expansion mutation within intron 1 of the FXN gene. Studies of mouse models for other trinucleotide repeat (TNR) disorders have revealed an important role of mismatch repair (MMR) proteins in TNR instability. To explore the potential role of MMR proteins on intergenerational GAA repeat instability in FRDA, we have analyzed the transmission of unstable GAA repeat expansions from FXN transgenic mice which have been crossed with mice that are deficient for Msh2, Msh3, Msh6 or Pms2. We find in all cases that absence of parental MMR protein not only maintains transmission of GAA expansions and contractions, but also increases GAA repeat mutability (expansions and/or contractions) in the offspring. This indicates that Msh2, Msh3, Msh6 and Pms2 proteins are not the cause of intergenerational GAA expansions or contractions, but act in their canonical MMR capacity to protect against GAA repeat instability. We further identified differential modes of action for the four MMR proteins. Thus, Msh2 and Msh3 protect against GAA repeat contractions, while Msh6 protects against both GAA repeat expansions and contractions, and Pms2 protects against GAA repeat expansions and also promotes contractions. Furthermore, we detected enhanced occupancy of Msh2 and Msh3 proteins downstream of the FXN expanded GAA repeat, suggesting a model in which Msh2/3 dimers are recruited to this region to repair mismatches that would otherwise produce intergenerational GAA contractions. These findings reveal substantial differences in the intergenerational dynamics of expanded GAA repeat sequences compared with expanded CAG/CTG repeats, where Msh2 and Msh3 are thought to actively promote repeat expansions.
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The functions of MutL in mismatch repair: the power of multitasking. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 110:41-70. [PMID: 22749142 DOI: 10.1016/b978-0-12-387665-2.00003-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
DNA mismatch repair enhances genomic stability by correcting errors that have escaped polymerase proofreading. One of the critical steps in DNA mismatch repair is discriminating the new from the parental DNA strand as only the former needs repair. In Escherichia coli, the latent endonuclease MutH carries out this function. However, most prokaryotes and all eukaryotes lack a mutH gene. MutL is a key component of this system that mediates protein-protein interactions during mismatch recognition, strand discrimination, and strand removal. Hence, it had long been thought that the primary function of MutL was coordinating sequential mismatch repair steps. However, recent studies have revealed that most MutL homologs from organisms lacking MutH encode a conserved metal-binding motif associated with a weak endonuclease activity. As MutL homologs bearing this activity are found only in organisms relying on MutH-independent DNA mismatch repair, this finding unveils yet another crucial function of the MutL protein at the strand discrimination step. In this chapter, we review recent functional and structural work aimed at characterizing the multiple functions of MutL and discuss how the endonuclease activity of MutL is regulated by other repair factors.
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135
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Abstract
Mismatch repair corrects biosynthetic errors generated during DNA replication. Mismatch repair deficiency causes a mutator phenotype and directly underlies hereditary nonpolyposis colorectal cancer and some sporadic cancers. Because of remarkably high conservation of the mismatch repair machinery between the budding yeast (Saccharomyces cerevisiae) and humans, the study of mismatch repair in yeast has provided tremendous insights into the mechanisms of this repair pathway in humans. Here we describe a set of practical protocols for how to prepare the yeast and HeLa cell-free nuclear extracts and site-specific DNA mismatch substrates, and how to carry out the in vitro mismatch repair assay. We validated the yeast cell-free system by the mismatch repair deficient strain (Δmsh2) and the complementation assay with purified yeast MutSα.
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Affiliation(s)
- Fenghua Yuan
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, Miami, FL, USA.
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136
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Ma S, Saaem I, Tian J. Error correction in gene synthesis technology. Trends Biotechnol 2011; 30:147-54. [PMID: 22209624 DOI: 10.1016/j.tibtech.2011.10.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2011] [Revised: 10/21/2011] [Accepted: 10/21/2011] [Indexed: 11/15/2022]
Abstract
Accurate, economical and high-throughput gene and genome synthesis is essential to the development of synthetic biology and biotechnology. New large-scale gene synthesis methods harnessing the power of DNA microchips have recently been demonstrated. Yet, the technology is still compromised by a high occurrence of errors in the synthesized products. These errors still require substantial effort to correct. To solve this bottleneck, novel approaches based on new chemistry, enzymology or next generation sequencing have emerged. This review discusses these new trends and promising strategies of error filtration, correction and prevention in de novo gene and genome synthesis. Continued innovation in error correction technologies will enable affordable and large-scale gene and genome synthesis in the near future.
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Affiliation(s)
- Siying Ma
- Department of Biomedical Engineering and the Institute for Genome Sciences and Policy, Duke University, Durham, NC 27708, USA
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137
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Giannouli M, Di Popolo A, Durante-Mangoni E, Bernardo M, Cuccurullo S, Amato G, Tripodi MF, Triassi M, Utili R, Zarrilli R. Molecular epidemiology and mechanisms of rifampicin resistance in Acinetobacter baumannii isolates from Italy. Int J Antimicrob Agents 2011; 39:58-63. [PMID: 22055530 DOI: 10.1016/j.ijantimicag.2011.09.016] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 09/07/2011] [Accepted: 09/20/2011] [Indexed: 02/06/2023]
Abstract
Use of rifampicin (RIF) in combination with colistin (COL) has been proposed for the treatment of multidrug-resistant Acinetobacter baumannii infections owing to in vitro synergism. The aim of the present study was to evaluate the molecular epidemiology and mechanisms of RIF resistance in 57 clinical isolates of A. baumannii in two tertiary care hospitals in Naples (Italy) from 2006 to 2010. Amongst the collection, 36 isolates showed high RIF minimum inhibitory concentrations (MICs) (256 mg/L to ≥512 mg/L), 16 showed intermediate MICs (8-16 mg/L) and 5 had low MICs (4 mg/L). Of the 36 isolates with elevated RIF MICs, 35 were assigned to sequence type ST2 and 1 to ST78. Amongst the 57 isolates, 35 carried at least one mutation in rpoB, including H535L in 9 isolates and double mutations D525N and P544L in 7 isolates, whilst 22 showed no rpoB mutations. Treatment with the efflux pump inhibitor phenyl-arginine-β-naphthylamide (PAβN) of resistant isolates with no mutations in rpoB and different RIF MICs reduced the MIC by >10-fold and restored the synergism between RIF and COL in time-kill studies, whilst it had no effect on strains carrying rpoB mutations. In conclusion, the emergence of elevated RIF MICs in A. baumannii isolates from our geographical area was mostly caused by mutations in rpoB; low to intermediate RIF MICs were also caused by altered membrane permeability to the drug. The phenomenon was contributed by the selection of two prevalent clones both assigned to ST2 genotype. These data may have implications for the correct identification of cases with A. baumannii infection that would not benefit from addition of RIF to COL.
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Affiliation(s)
- Maria Giannouli
- Dipartimento di Scienze Mediche Preventive, Università di Napoli Federico II, Via Pansini 5, Naples, Italy
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138
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Lang WH, Coats JE, Majka J, Hura GL, Lin Y, Rasnik I, McMurray CT. Conformational trapping of mismatch recognition complex MSH2/MSH3 on repair-resistant DNA loops. Proc Natl Acad Sci U S A 2011; 108:E837-44. [PMID: 21960445 PMCID: PMC3198364 DOI: 10.1073/pnas.1105461108] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Insertion and deletion of small heteroduplex loops are common mutations in DNA, but why some loops are prone to mutation and others are efficiently repaired is unknown. Here we report that the mismatch recognition complex, MSH2/MSH3, discriminates between a repair-competent and a repair-resistant loop by sensing the conformational dynamics of their junctions. MSH2/MSH3 binds, bends, and dissociates from repair-competent loops to signal downstream repair. Repair-resistant Cytosine-Adenine-Guanine (CAG) loops adopt a unique DNA junction that traps nucleotide-bound MSH2/MSH3, and inhibits its dissociation from the DNA. We envision that junction dynamics is an active participant and a conformational regulator of repair signaling, and governs whether a loop is removed by MSH2/MSH3 or escapes to become a precursor for mutation.
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Affiliation(s)
- Walter H. Lang
- Lawrence Berkeley National Laboratory, Life Sciences Division, 1 Cyclotron Road, Berkeley, CA 94720
| | - Julie E. Coats
- Department of Physics, Emory University, 400 Dowman Drive, MSC N214, Atlanta, GA 30322
| | - Jerzy Majka
- Lawrence Berkeley National Laboratory, Life Sciences Division, 1 Cyclotron Road, Berkeley, CA 94720
| | - Greg L. Hura
- Lawrence Berkeley National Laboratory, Life Sciences Division, 1 Cyclotron Road, Berkeley, CA 94720
| | - Yuyen Lin
- Department of Physics, Emory University, 400 Dowman Drive, MSC N214, Atlanta, GA 30322
| | - Ivan Rasnik
- Department of Physics, Emory University, 400 Dowman Drive, MSC N214, Atlanta, GA 30322
| | - Cynthia T. McMurray
- Lawrence Berkeley National Laboratory, Life Sciences Division, 1 Cyclotron Road, Berkeley, CA 94720
- Department of Molecular Pharmacology and Experimental Therapeutics
- Department of Biochemistry and Molecular Biology, Mayo Foundation, 200 First Street, Rochester, MN 55905; and
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139
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Klocko AD, Schroeder JW, Walsh BW, Lenhart JS, Evans ML, Simmons LA. Mismatch repair causes the dynamic release of an essential DNA polymerase from the replication fork. Mol Microbiol 2011; 82:648-63. [PMID: 21958350 DOI: 10.1111/j.1365-2958.2011.07841.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Mismatch repair (MMR) corrects DNA polymerase errors occurring during genome replication. MMR is critical for genome maintenance, and its loss increases mutation rates several hundred fold. Recent work has shown that the interaction between the mismatch recognition protein MutS and the replication processivity clamp is important for MMR in Bacillus subtilis. To further understand how MMR is coupled to DNA replication, we examined the subcellular localization of MMR and DNA replication proteins fused to green fluorescent protein (GFP) in live cells, following an increase in DNA replication errors. We demonstrate that foci of the essential DNA polymerase DnaE-GFP decrease following mismatch incorporation and that loss of DnaE-GFP foci requires MutS. Furthermore, we show that MutS and MutL bind DnaE in vitro, suggesting that DnaE is coupled to repair. We also found that DnaE-GFP foci decrease in vivo following a DNA damage-independent arrest of DNA synthesis showing that loss of DnaE-GFP foci is caused by perturbations to DNA replication. We propose that MutS directly contacts the DNA replication machinery, causing a dynamic change in the organization of DnaE at the replication fork during MMR. Our results establish a striking and intimate connection between MMR and the replicating DNA polymerase complex in vivo.
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Affiliation(s)
- Andrew D Klocko
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
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140
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Wu S, Chen J, Ji Y, Liu Y, Gao L, Chen G, Shen K, Huang B. Association between the hMSH2 IVS12-6 T>C polymorphism and cancer risk: A meta-analysis. Exp Ther Med 2011; 2:1193-1198. [PMID: 22977643 DOI: 10.3892/etm.2011.336] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Accepted: 08/08/2011] [Indexed: 12/16/2022] Open
Abstract
The hMSH2 gene, a member of the mismatch repair (MMR) pathway, plays a key role in the maintenance of genomic integrity. The common sequence variation in hMSH2, IVS12-6 T>C, has been implicated in cancer risk. However, the results of published studies on this polymorphism remain conflicting. Hence, we conducted a meta-analysis to clarify the role of the hMSH2 IVS12-6 T>C polymorphism in cancer. We performed a comprehensive literature search updated to March 2011 of studies on the associations between the hMSH2 IVS12-6 T>C polymorphism and cancer risk. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the associations. Thirteen studies involving 7,527 patients and 8,762 control subjects were included in this meta-analysis. The overall results indicated no major influence of the polymorphism on cancer risk. However, stratified analysis by cancer types showed that the hMSH2 IVS12-6 polymorphism increased the risk for non-Hodgkin's lymphomas (heterozygote comparison: OR=1.62; 95% CI 1.06-2.47). When stratified by the source of controls, significant associations were observed in hospital-based populations (heterozygote comparison: OR=1.28; 95% CI 1.02-1.61). These results indicate that the polymorphism of hMSH2, IVS12-6, may cause a different effect in different types of cancers. To draw more comprehensive conclusions, further prospective studies with larger numbers of participants worldwide are required to examine the associations between this polymorphism and cancer risk.
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Affiliation(s)
- Song Wu
- Department of Cardiothoracic Surgery, The Affiliated Jiangyin People's Hospital of Southeast University Medical College, Jiangyin
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141
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Romeo F, Falbo L, Di Sanzo M, Misaggi R, Faniello MC, Viglietto G, Cuda G, Costanzo F, Quaresima B. BRCA1 is required for hMLH1 stabilization following doxorubicin-induced DNA damage. Int J Biochem Cell Biol 2011; 43:1754-63. [PMID: 21864706 DOI: 10.1016/j.biocel.2011.08.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Revised: 07/29/2011] [Accepted: 08/09/2011] [Indexed: 10/17/2022]
Abstract
Human DNA mismatch repair (MMR) is involved in the removal of DNA base mismatches that arise either during DNA replication or are caused by DNA damage. In this study, we show that the activation of the MMR component hMLH1 in response to doxorubicin (DOX) treatment requires the presence of BRCA1 and that this phenomenon is mediated by an ATM/ATR dependent phosphorylation of the hMLH1 Ser-406 residue. BRCA1 is an oncosuppressor protein with a central role in the DNA damage response and it is a critical component of the ATM/ATR mediated checkpoint signaling. Starting from a previous finding in which we demonstrated that hMLH1 is able to bind to BRCA1, in this study we asked whether BRCA1 might be the bridge for ATM/ATR dependent phosphorylation of the hMLH1 molecular partner. We found that: (i) the negative modulation of BRCA1 expression is able to produce a remarkable reversal of hMLH1 stabilization, (ii) BRCA1 is required for post-translational modification produced by DOX treatment on hMLH1 which is, in turn, attributed to the ATM/ATR activity, (iii) the serine 406 phosphorylatable residue is critical for hMLH1 activation by ATM/ATR via BRCA1. Taken together, our data lend support to the hypothesis suggesting an important role of this oncosuppressor as a scaffold or bridging protein in DNA-damage response signaling via downstream phosphorylation of the ATM/ATR substrate hMLH1.
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Affiliation(s)
- Francesco Romeo
- Department of Experimental and Clinical Medicine, Magna Græcia University of Catanzaro, Salvatore Venuta Campus, Viale Europa, 88100 Catanzaro, Italy
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142
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Srinivasadesikan V, Sahu PK, Lee SL. Model calculations for the misincorporation of nucleotides opposite five-membered exocyclic DNA adduct: N(2),3-ethenoguanine. J Phys Chem B 2011; 115:10537-46. [PMID: 21776999 DOI: 10.1021/jp202738v] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Five-membered exocyclic DNA adducts are biologically very significant because of their potential to block DNA replication and transcription. N(2),3-Ethenoguanine (N(2,3)-εG) has been identified in the liver DNA of vinyl chloride-exposed rats as a five-membered DNA adduct. Singer et al. ( Carcinogenesis 1987 , 8 , 745 - 747 ) reported that the misincorporation of thymine (T), with two hydrogen bonds to N(2,3)-εG, represents the mutagenic event. Although the base-pairing specificity and mode of misincorporation have been studied experimentally for the N(2),3-ethenoguanine adduct, molecular-level information is not yet clear. In this study, we have considered all four different DNA nucleotides paired with the N(2),3-ethenoguanine adduct for model calculations toward the determination of base-pairing specificity. To provide insight into the mutagenic process of DNA damage based on geometric characteristics and electronic properties, the B3LYP and M06 methods were employed for these model calculations. Single-point energy calculations at the MP2/6-311++G** level on the corresponding optimized geometries were also carried out to better estimate the hydrogen-bonding strengths. The polarizable conductor calculation model (CPCM), which accounts for the overall polarizability of the solvent, was also employed. The computed reaction enthalpy values lie in the order εG-G(2) (10.3 kcal/mol) > εG-G(4) (9.6 kcal/mol) > εG-T(4) (9.2 kcal/mol) > εG-G(1) (9.1 kcal/mol) > εG-A(5) (8.2 kcal/mol) > εG-C(2) (7.9 kcal/mol) at the M06 level, which indicates that guanine and thymine are most favorable for mispairing with the N(2),3-ethenoguanine adduct.
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143
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Tseng Q, Orans J, Hast MA, Iyer RR, Changela A, Modrich PL, Beese LS. Purification, crystallization and preliminary X-ray diffraction analysis of the human mismatch repair protein MutSβ. Acta Crystallogr Sect F Struct Biol Cryst Commun 2011; 67:947-52. [PMID: 21821902 PMCID: PMC3151135 DOI: 10.1107/s1744309111019300] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Accepted: 05/21/2011] [Indexed: 11/10/2022]
Abstract
MutSβ is a eukaryotic mismatch repair protein that preferentially targets extrahelical unpaired nucleotides and shares partial functional redundancy with MutSα (MSH2-MSH6). Although mismatch recognition by MutSα has been shown to involve a conserved Phe-X-Glu motif, little is known about the lesion-binding mechanism of MutSβ. Combined MSH3/MSH6 deficiency triggers a strong predisposition to cancer in mice and defects in msh2 and msh6 account for roughly half of hereditary nonpolyposis colorectal cancer mutations. These three MutS homologs are also believed to play a role in trinucleotide repeat instability, which is a hallmark of many neurodegenerative disorders. The baculovirus overexpression and purification of recombinant human MutSβ and three truncation mutants are presented here. Binding assays with heteroduplex DNA were carried out for biochemical characterization. Crystallization and preliminary X-ray diffraction analysis of the protein bound to a heteroduplex DNA substrate are also reported.
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Affiliation(s)
- Quincy Tseng
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
| | - Jillian Orans
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
| | - Michael A. Hast
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
| | - Ravi R. Iyer
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
| | - Anita Changela
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
| | - Paul L. Modrich
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
- Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA
| | - Lorena S. Beese
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
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144
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Bilewitch JP, Degnan SM. A unique horizontal gene transfer event has provided the octocoral mitochondrial genome with an active mismatch repair gene that has potential for an unusual self-contained function. BMC Evol Biol 2011; 11:228. [PMID: 21801381 PMCID: PMC3166940 DOI: 10.1186/1471-2148-11-228] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Accepted: 07/29/2011] [Indexed: 11/22/2022] Open
Abstract
Background The mitochondrial genome of the Octocorallia has several characteristics atypical for metazoans, including a novel gene suggested to function in DNA repair. This mtMutS gene is favored for octocoral molecular systematics, due to its high information content. Several hypotheses concerning the origins of mtMutS have been proposed, and remain equivocal, although current weight of support is for a horizontal gene transfer from either an epsilonproteobacterium or a large DNA virus. Here we present new and compelling evidence on the evolutionary origin of mtMutS, and provide the very first data on its activity, functional capacity and stability within the octocoral mitochondrial genome. Results The mtMutS gene has the expected conserved amino acids, protein domains and predicted tertiary protein structure. Phylogenetic analysis indicates that mtMutS is not a member of the MSH family and therefore not of eukaryotic origin. MtMutS clusters closely with representatives of the MutS7 lineage; further support for this relationship derives from the sharing of a C-terminal endonuclease domain that confers a self-contained mismatch repair function. Gene expression analyses confirm that mtMutS is actively transcribed in octocorals. Rates of mitochondrial gene evolution in mtMutS-containing octocorals are lower than in their hexacoral sister-group, which lacks the gene, although paradoxically the mtMutS gene itself has higher rates of mutation than other octocoral mitochondrial genes. Conclusions The octocoral mtMutS gene is active and codes for a protein with all the necessary components for DNA mismatch repair. A lower rate of mitochondrial evolution, and the presence of a nicking endonuclease domain, both indirectly support a theory of self-sufficient DNA mismatch repair within the octocoral mitochondrion. The ancestral affinity of mtMutS to non-eukaryotic MutS7 provides compelling support for an origin by horizontal gene transfer. The immediate vector of transmission into octocorals can be attributed to either an epsilonproteobacterium in an endosymbiotic association or to a viral infection, although DNA viruses are not currently known to infect both bacteria and eukaryotes, nor mitochondria in particular. In consolidating the first known case of HGT into an animal mitochondrial genome, these findings suggest the need for reconsideration of the means by which metazoan mitochondrial genomes evolve.
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Affiliation(s)
- Jaret P Bilewitch
- School of Biological Sciences, University of Queensland, St, Lucia, Brisbane, Queensland, Australia
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145
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Karpinets T, Greenwood D, Pogribny I, Samatova N. Bacterial stationary-state mutagenesis and Mammalian tumorigenesis as stress-induced cellular adaptations and the role of epigenetics. Curr Genomics 2011; 7:481-96. [PMID: 18369407 DOI: 10.2174/138920206779315764] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Revised: 11/11/2006] [Accepted: 11/23/2006] [Indexed: 01/16/2023] Open
Abstract
Mechanisms of cellular adaptation may have some commonalities across different organisms. Revealing these common mechanisms may provide insight in the organismal level of adaptation and suggest solutions to important problems related to the adaptation. An increased rate of mutations, referred as the mutator phenotype, and beneficial nature of these mutations are common features of the bacterial stationary-state mutagenesis and of the tumorigenic transformations in mammalian cells. We argue that these commonalities of mammalian and bacterial cells result from their stress-induced adaptation that may be described in terms of a common model. Specifically, in both organisms the mutator phenotype is activated in a subpopulation of proliferating stressed cells as a strategy to survival. This strategy is an alternative to other survival strategies, such as senescence and programmed cell death, which are also activated in the stressed cells by different subpopulations. Sustained stress-related proliferative signalling and epigenetic mechanisms play a decisive role in the choice of the mutator phenotype survival strategy in the cells. They reprogram cellular functions by epigenetic silencing of cell-cycle inhibitors, DNA repair, programmed cell death, and by activation of repetitive DNA elements. This reprogramming leads to the mutator phenotype that is implemented by error-prone cell divisions with the involvement of Y family polymerases. Studies supporting the proposed model of stress-induced cellular adaptation are discussed. Cellular mechanisms involved in the bacterial stress-induced adaptation are considered in more detail.
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Affiliation(s)
- Tv Karpinets
- Computational Biology Institute, Computer Science and Mathematics Division, Oak Ridge National Laboratory, P.O. Box 2008, MS6164, Oak Ridge, TN 37831, USA
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146
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Aparicio JM. The paradox of the resolution of the lek paradox based on mate choice for heterozygosity. Anim Behav 2011. [DOI: 10.1016/j.anbehav.2011.03.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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147
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Schorzman AN, Perera L, Cutalo-Patterson JM, Pedersen LC, Pedersen LG, Kunkel TA, Tomer KB. Modeling of the DNA-binding site of yeast Pms1 by mass spectrometry. DNA Repair (Amst) 2011; 10:454-65. [PMID: 21354867 PMCID: PMC3084373 DOI: 10.1016/j.dnarep.2011.01.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 01/07/2011] [Accepted: 01/24/2011] [Indexed: 11/26/2022]
Abstract
Mismatch repair (MMR) corrects replication errors that would otherwise lead to mutations and, potentially, various forms of cancer. Among several proteins required for eukaryotic MMR, MutLα is a heterodimer comprised of Mlh1 and Pms1. The two proteins dimerize along their C-terminal domains (CTDs), and the CTD of Pms1 houses a latent endonuclease that is required for MMR. The highly conserved N-terminal domains (NTDs) independently bind DNA and possess ATPase active sites. Here we use two protein footprinting techniques, limited proteolysis and oxidative surface mapping, coupled with mass spectrometry to identify amino acids involved along the DNA-binding surface of the Pms1-NTD. Limited proteolysis experiments elucidated several basic residues that were protected in the presence of DNA, while oxidative surface mapping revealed one residue that is uniquely protected from oxidation. Furthermore, additional amino acids distributed throughout the Pms1-NTD were protected from oxidation either in the presence of a non-hydrolyzable analog of ATP or DNA, indicating that each ligand stabilizes the protein in a similar conformation. Based on the recently published X-ray crystal structure of yeast Pms1-NTD, a model of the Pms1-NTD/DNA complex was generated using the mass spectrometric data as constraints. The proposed model defines the DNA-binding interface along a positively charged groove of the Pms1-NTD and complements prior mutagenesis studies of Escherichia coli and eukaryotic MutL.
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Affiliation(s)
- Allison N. Schorzman
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Lalith Perera
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Jenny M. Cutalo-Patterson
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Lars C. Pedersen
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Lee G. Pedersen
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Thomas A. Kunkel
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Kenneth B. Tomer
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709
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Soni A, Bansal A, Singh L, Mishra AK, Majumdar M, Regina T, Mohanty N, Saxena S. Gene Expression Profile and Mutational Analysis of DNA Mismatch Repair Genes in Carcinoma Prostate in Indian Population. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2011; 15:319-24. [DOI: 10.1089/omi.2010.0110] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Abha Soni
- Institute of Pathology, Indian Council of Medical Research, Tumour Biology, New Delhi, India
| | - Anju Bansal
- Institute of Pathology, Indian Council of Medical Research, Tumour Biology, New Delhi, India
| | - L.C. Singh
- Institute of Pathology, Indian Council of Medical Research, Tumour Biology, New Delhi, India
| | - Ashwani K. Mishra
- Institute of Pathology, Indian Council of Medical Research, Tumour Biology, New Delhi, India
| | | | - Thoudam Regina
- Institute of Pathology, Indian Council of Medical Research, Tumour Biology, New Delhi, India
| | - N.K. Mohanty
- Safdarjung Hospital and VMMC, Department of Urology, New Delhi, India
| | - Sunita Saxena
- Institute of Pathology, Indian Council of Medical Research, Tumour Biology, New Delhi, India
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149
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Lario LD, Ramirez-Parra E, Gutierrez C, Casati P, Spampinato CP. Regulation of plant MSH2 and MSH6 genes in the UV-B-induced DNA damage response. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:2925-37. [PMID: 21307385 DOI: 10.1093/jxb/err001] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Deleterious effects of UV-B radiation on DNA include the formation of cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts (6-4PPs). These lesions must be repaired to maintain the integrity of DNA and provide genetic stability. Of the several repair systems involved in the recognition and removal of UV-B-induced lesions in DNA, the focus in the present study was on the mismatch repair system (MMR). The contribution of MutSα (MSH2-MSH6) to UV-induced DNA lesion repair and cell cycle regulation was investigated. MSH2 and MSH6 genes in Arabidopsis and maize are up-regulated by UV-B, indicating that MMR may have a role in UV-B-induced DNA damage responses. Analysis of promoter sequences identified MSH6 as a target of the E2F transcription factors. Using electrophoretic mobility shift assays, MSH6 was experimentally validated as an E2F target gene, suggesting an interaction between MMR genes and the cell cycle control. Mutations in MSH2 or MSH6 caused an increased accumulation of CPDs relative to wild-type plants. In addition, msh2 mutant plants showed a different expression pattern of cell cycle marker genes after the UV-B treatment when compared with wild-type plants. Taken together, these data provide evidence that plant MutSα is involved in a UV-B-induced DNA damage response pathway.
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Affiliation(s)
- Luciana D Lario
- Centro de Estudios Fotosintéticos y Bioquímicos, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina
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150
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Otero-Navas I, Seminario JM. Molecular electrostatic potentials of DNA base-base pairing and mispairing. J Mol Model 2011; 18:91-101. [PMID: 21625905 DOI: 10.1007/s00894-011-1028-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Accepted: 02/14/2011] [Indexed: 11/28/2022]
Abstract
An understanding of why adenine (A) pairs with thymine (T) and cytosine (C) with guanine (G) in DNA is very useful in the design of sensors and other related devices. We report the use of dissociation energies, geometries and molecular electrostatic potentials (MEPs) to justify the canonical (AT and CG) Watson-Crick pairs. We also analyze all mismatches in both configurations-cis and trans-with respect to their glycoside bonds. As expected, we found that the most stable pair configuration corresponds to CG, providing an energy criterion for that preferred configuration. The reason why A gets together with T is much more difficult to explain as the energy of this pair is smaller than the energy of some other mismatched pairs. We tested MEPs to see if they could shed light on this problem. Interestingly, MEPs yield a unique pattern (shape) for the two canonical cases but different shapes for the mismatches. A tunnel of positive potential surrounded by a negative one is found interconnecting the three H-bonds of CG and the two of AT. This MEP tunnel, assisted partially by energetics and geometrical criteria, unambiguously determine a distinctive feature of the affinity between A and T as well as that between G and C.
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Affiliation(s)
- Ivonne Otero-Navas
- Department of Chemical Engineering, Texas A&M University, College Station, Texas, USA
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