1
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Benureau Y, Pouvelle C, Dupaigne P, Baconnais S, Moreira Tavares E, Mazón G, Despras E, Le Cam E, Kannouche P. Changes in the architecture and abundance of replication intermediates delineate the chronology of DNA damage tolerance pathways at UV-stalled replication forks in human cells. Nucleic Acids Res 2022; 50:9909-9929. [PMID: 36107774 PMCID: PMC9508826 DOI: 10.1093/nar/gkac746] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 08/09/2022] [Accepted: 08/23/2022] [Indexed: 11/21/2022] Open
Abstract
DNA lesions in S phase threaten genome stability. The DNA damage tolerance (DDT) pathways overcome these obstacles and allow completion of DNA synthesis by the use of specialised translesion (TLS) DNA polymerases or through recombination-related processes. However, how these mechanisms coordinate with each other and with bulk replication remains elusive. To address these issues, we monitored the variation of replication intermediate architecture in response to ultraviolet irradiation using transmission electron microscopy. We show that the TLS polymerase η, able to accurately bypass the major UV lesion and mutated in the skin cancer-prone xeroderma pigmentosum variant (XPV) syndrome, acts at the replication fork to resolve uncoupling and prevent post-replicative gap accumulation. Repriming occurs as a compensatory mechanism when this on-the-fly mechanism cannot operate, and is therefore predominant in XPV cells. Interestingly, our data support a recombination-independent function of RAD51 at the replication fork to sustain repriming. Finally, we provide evidence for the post-replicative commitment of recombination in gap repair and for pioneering observations of in vivo recombination intermediates. Altogether, we propose a chronology of UV damage tolerance in human cells that highlights the key role of polη in shaping this response and ensuring the continuity of DNA synthesis.
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Affiliation(s)
- Yann Benureau
- UMR9019 CNRS, Genome Integrity and Cancers, Laboratory Genome Integrity , Immune Response and Cancers, Equipe Labellisée La Ligue Contre Le Cancer, Gustave Roussy 94805 , Villejuif , France
- UMR9019 CNRS, Genome Integrity and Cancers, Laboratory DSB Repair , Replication stress and Genome Integrity, Gustave Roussy 94805 , Villejuif, France
- Université Paris-Saclay , France
| | - Caroline Pouvelle
- UMR9019 CNRS, Genome Integrity and Cancers, Laboratory Genome Integrity , Immune Response and Cancers, Equipe Labellisée La Ligue Contre Le Cancer, Gustave Roussy 94805 , Villejuif , France
- Université Paris-Saclay , France
| | - Pauline Dupaigne
- UMR9019 CNRS, Genome Integrity and Cancers, Laboratory DSB Repair , Replication stress and Genome Integrity, Gustave Roussy 94805 , Villejuif, France
- Université Paris-Saclay , France
| | - Sonia Baconnais
- UMR9019 CNRS, Genome Integrity and Cancers, Laboratory DSB Repair , Replication stress and Genome Integrity, Gustave Roussy 94805 , Villejuif, France
- Université Paris-Saclay , France
| | - Eliana Moreira Tavares
- UMR9019 CNRS, Genome Integrity and Cancers, Laboratory DSB Repair , Replication stress and Genome Integrity, Gustave Roussy 94805 , Villejuif, France
- Université Paris-Saclay , France
| | - Gerard Mazón
- UMR9019 CNRS, Genome Integrity and Cancers, Laboratory DSB Repair , Replication stress and Genome Integrity, Gustave Roussy 94805 , Villejuif, France
- Université Paris-Saclay , France
| | - Emmanuelle Despras
- UMR9019 CNRS, Genome Integrity and Cancers, Laboratory Genome Integrity , Immune Response and Cancers, Equipe Labellisée La Ligue Contre Le Cancer, Gustave Roussy 94805 , Villejuif , France
- Université Paris-Saclay , France
| | - Eric Le Cam
- UMR9019 CNRS, Genome Integrity and Cancers, Laboratory DSB Repair , Replication stress and Genome Integrity, Gustave Roussy 94805 , Villejuif, France
- Université Paris-Saclay , France
| | - Patricia L Kannouche
- UMR9019 CNRS, Genome Integrity and Cancers, Laboratory Genome Integrity , Immune Response and Cancers, Equipe Labellisée La Ligue Contre Le Cancer, Gustave Roussy 94805 , Villejuif , France
- Université Paris-Saclay , France
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2
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Thakur M, Parulekar RS, Barale SS, Sonawane KD, Muniyappa K. Interrogating the substrate specificity landscape of UvrC reveals novel insights into its non-canonical function. Biophys J 2022; 121:3103-3125. [PMID: 35810330 PMCID: PMC9463653 DOI: 10.1016/j.bpj.2022.07.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Revised: 05/23/2022] [Accepted: 07/07/2022] [Indexed: 11/29/2022] Open
Abstract
Although it is relatively unexplored, accumulating data highlight the importance of tripartite crosstalk between nucleotide excision repair (NER), DNA replication, and recombination in the maintenance of genome stability; however, elucidating the underlying mechanisms remains challenging. While Escherichia coli uvrA and uvrB can fully complement polAΔ cells in DNA replication, uvrC attenuates this alternative DNA replication pathway, but the exact mechanism by which uvrC suppresses DNA replication is unknown. Furthermore, the identity of bona fide canonical and non-canonical substrates for UvrCs are undefined. Here, we reveal that Mycobacterium tuberculosis UvrC (MtUvrC) strongly binds to, and robustly cleaves, key intermediates of DNA replication/recombination as compared with the model NER substrates. Notably, inactivation of MtUvrC ATPase activity significantly attenuated its endonuclease activity, thus suggesting a causal link between these two functions. We built an in silico model of the interaction of MtUvrC with the Holliday junction (HJ), using a combination of homology modeling, molecular docking, and molecular dynamic simulations. The model predicted residues that were potentially involved in HJ binding. Six of these residues were mutated either singly or in pairs, and the resulting MtUvrC variants were purified and characterized. Among them, residues Glu595 and Arg597 in the helix-hairpin-helix motif were found to be crucial for the interaction between MtUvrC and HJ; consequently, mutations in these residues, or inhibition of ATP hydrolysis, strongly abrogated its DNA-binding and endonuclease activities. Viewed together, these findings expand the substrate specificity landscape of UvrCs and provide crucial mechanistic insights into the interplay between NER and DNA replication/recombination.
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Affiliation(s)
- Manoj Thakur
- Department of Biochemistry, Indian Institute of Science, Bengaluru, India.
| | | | - Sagar S Barale
- Structural Bioinformatics Unit, Shivaji University, Kolhapur, India
| | - Kailas D Sonawane
- Department of Microbiology, Shivaji University, Kolhapur, India; Structural Bioinformatics Unit, Shivaji University, Kolhapur, India
| | - Kalappa Muniyappa
- Department of Biochemistry, Indian Institute of Science, Bengaluru, India.
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3
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Del Val E, Nasser W, Abaibou H, Reverchon S. Design and comparative characterization of RecA variants. Sci Rep 2021; 11:21106. [PMID: 34702889 PMCID: PMC8548320 DOI: 10.1038/s41598-021-00589-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 10/14/2021] [Indexed: 11/08/2022] Open
Abstract
RecA plays a central role in DNA repair and is a main actor involved in recombination and activation of the SOS response. It is also used in the context of biotechnological applications in recombinase polymerase isothermal amplification (RPA). In this work, we studied the biological properties of seven RecA variants, in particular their recombinogenic activity and their ability to induce the SOS response, to better understand the structure-function relationship of RecA and the effect of combined mutations. We also investigated the biochemical properties of RecA variants that may be useful for the development of biotechnological applications. We showed that Dickeya dadantii RecA (DdRecA) had an optimum strand exchange activity at 30 °C and in the presence of a dNTP mixture that inhibited Escherichia coli RecA (EcRecA). The differences between the CTD and C-tail of the EcRecA and DdRecA domains could explain the altered behaviour of DdRecA. D. radiodurans RecA (DrRecA) was unable to perform recombination and activation of the SOS response in an E. coli context, probably due to its inability to interact with E. coli recombination accessory proteins and SOS LexA repressor. DrRecA strand exchange activity was totally inhibited in the presence of chloride ions but worked well in acetate buffer. The overproduction of Pseudomonas aeruginosa RecA (PaRecA) in an E. coli context was responsible for a higher SOS response and defects in cellular growth. PaRecA was less inhibited by the dNTP mixture than EcRecA. Finally, the study of three variants, namely, EcPa, EcRecAV1 and EcRecAV2, that contained a combination of mutations that, taken independently, are described as improving recombination, led us to raise new hypotheses on the structure-function relationship and on the monomer-monomer interactions that perturb the activity of the protein as a whole.
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Affiliation(s)
- Elsa Del Val
- UMR5240, Microbiologie, Adaptation et Pathogénie, University of Lyon, Université Claude Bernard Lyon 1, INSA-Lyon, CNRS, 11 Avenue Jean Capelle, 69621, Villeurbanne, France
- Molecular Innovation Unit, Centre Christophe Mérieux, bioMérieux, 5 Rue des Berges, 38024, Grenoble Cedex 01, France
| | - William Nasser
- UMR5240, Microbiologie, Adaptation et Pathogénie, University of Lyon, Université Claude Bernard Lyon 1, INSA-Lyon, CNRS, 11 Avenue Jean Capelle, 69621, Villeurbanne, France
| | - Hafid Abaibou
- Molecular Innovation Unit, Centre Christophe Mérieux, bioMérieux, 5 Rue des Berges, 38024, Grenoble Cedex 01, France.
| | - Sylvie Reverchon
- UMR5240, Microbiologie, Adaptation et Pathogénie, University of Lyon, Université Claude Bernard Lyon 1, INSA-Lyon, CNRS, 11 Avenue Jean Capelle, 69621, Villeurbanne, France.
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A Comprehensive View of Translesion Synthesis in Escherichia coli. Microbiol Mol Biol Rev 2020; 84:84/3/e00002-20. [PMID: 32554755 DOI: 10.1128/mmbr.00002-20] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The lesion bypass pathway, translesion synthesis (TLS), exists in essentially all organisms and is considered a pathway for postreplicative gap repair and, at the same time, for lesion tolerance. As with the saying "a trip is not over until you get back home," studying TLS only at the site of the lesion is not enough to understand the whole process of TLS. Recently, a genetic study uncovered that polymerase V (Pol V), a poorly expressed Escherichia coli TLS polymerase, is not only involved in the TLS step per se but also participates in the gap-filling reaction over several hundred nucleotides. The same study revealed that in contrast, Pol IV, another highly expressed TLS polymerase, essentially stays away from the gap-filling reaction. These observations imply fundamentally different ways these polymerases are recruited to DNA in cells. While access of Pol IV appears to be governed by mass action, efficient recruitment of Pol V involves a chaperone-like action of the RecA filament. We present a model of Pol V activation: the 3' tip of the RecA filament initially stabilizes Pol V to allow stable complex formation with a sliding β-clamp, followed by the capture of the terminal RecA monomer by Pol V, thus forming a functional Pol V complex. This activation process likely determines higher accessibility of Pol V than of Pol IV to normal DNA. Finally, we discuss the biological significance of TLS polymerases during gap-filling reactions: error-prone gap-filling synthesis may contribute as a driving force for genetic diversity, adaptive mutation, and evolution.
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5
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Jain R, Dhiman S, Grogan DW. Genetic Control of Oxidative Mutagenesis in Sulfolobus acidocaldarius. J Bacteriol 2020; 202:JB.00756-19. [PMID: 32482723 PMCID: PMC8404708 DOI: 10.1128/jb.00756-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 05/26/2020] [Indexed: 02/01/2023] Open
Abstract
To identify DNA-oxidation defenses of hyperthermophilic archaea, we deleted genes encoding the putative 7,8-dihydro-8-oxoguanine (oxoG)-targeted N-glycosylase of S. acidocaldarius (ogg; Saci_01367), the Y-family DNA polymerase (dbh; Saci_0554), or both, and measured the effects on cellular survival, replication accuracy, and oxoG bypass in vivo Spontaneous G:C to T:A transversions were elevated in all Δogg and Δdbh constructs, and the Δogg Δdbh double mutant lost viability at a faster rate than isogenic WT and ogg strains. The distribution of G:C to T:A transversions within mutation-detector genes suggested that reactivity of G toward oxidation and the effect on translation contribute heavily to the pattern of mutations that are recovered. An impact of the Ogg protein on overall efficiency of bypassing oxoG in transforming DNA was evident only in the absence of Dbh, and Ogg status did not affect the accuracy of bypass. Dbh function, in contrast, dramatically influenced both the efficiency and accuracy of oxoG bypass. Thus, Ogg and Dbh were found to work independently to avoid mutagenesis by oxoG, and inactivating this simple but effective defense system by deleting both genes imposed a severe mutational burden on S. acidocaldarius cells.IMPORTANCE Hyperthermophilic archaea are expected to have effective (and perhaps atypical) mechanisms to limit the genetic consequences of DNA damage, but few gene products have been demonstrated to have genome-preserving functions in vivo This study confirmed by genetic criteria that the S. acidocaldarius Ogg protein avoids the characteristic mutagenesis of G oxidation. This enzyme and the bypass polymerase Dbh have similar impacts on genome stability but work independently, and may comprise most of the DNA-oxidation defense of S. acidocaldarius The critical dependence of accurate oxoG bypass on the accessory DNA polymerase Dbh further argues that some form of polymerase exchange is important for accurate genome replication in Sulfolobus, and perhaps in related hyperthermophilic archaea.
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Affiliation(s)
- Rupal Jain
- Department of Biological Sciences, 614 Rieveschl Hall, ML0006, University of Cincinnati 513-556-9748
| | - Samuel Dhiman
- Department of Biological Sciences, 614 Rieveschl Hall, ML0006, University of Cincinnati 513-556-9748
| | - Dennis W Grogan
- Department of Biological Sciences, 614 Rieveschl Hall, ML0006, University of Cincinnati 513-556-9748
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6
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Maslowska KH, Makiela‐Dzbenska K, Fijalkowska IJ. The SOS system: A complex and tightly regulated response to DNA damage. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2019; 60:368-384. [PMID: 30447030 PMCID: PMC6590174 DOI: 10.1002/em.22267] [Citation(s) in RCA: 201] [Impact Index Per Article: 40.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 10/29/2018] [Accepted: 11/13/2018] [Indexed: 05/10/2023]
Abstract
Genomes of all living organisms are constantly threatened by endogenous and exogenous agents that challenge the chemical integrity of DNA. Most bacteria have evolved a coordinated response to DNA damage. In Escherichia coli, this inducible system is termed the SOS response. The SOS global regulatory network consists of multiple factors promoting the integrity of DNA as well as error-prone factors allowing for survival and continuous replication upon extensive DNA damage at the cost of elevated mutagenesis. Due to its mutagenic potential, the SOS response is subject to elaborate regulatory control involving not only transcriptional derepression, but also post-translational activation, and inhibition. This review summarizes current knowledge about the molecular mechanism of the SOS response induction and progression and its consequences for genome stability. Environ. Mol. Mutagen. 60:368-384, 2019. © 2018 The Authors. Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.
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Affiliation(s)
- Katarzyna H. Maslowska
- Cancer Research Center of Marseille, CNRS, UMR7258Inserm, U1068; Institut Paoli‐Calmettes, Aix‐Marseille UniversityMarseilleFrance
- Institute of Biochemistry and Biophysics, Polish Academy of SciencesWarsawPoland
| | | | - Iwona J. Fijalkowska
- Institute of Biochemistry and Biophysics, Polish Academy of SciencesWarsawPoland
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7
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Patoli AA, Patoli BB. The N-Terminal 6×His Tag on β-Clamp Processivity Factor Occludes Gly66 and Affects the Growth of Escherichia coli B834 (DE3) Cells. Mol Biol 2019. [DOI: 10.1134/s0026893319010126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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8
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The SOS and RpoS Regulons Contribute to Bacterial Cell Robustness to Genotoxic Stress by Synergistically Regulating DNA Polymerase Pol II. Genetics 2017; 206:1349-1360. [PMID: 28468910 PMCID: PMC5500135 DOI: 10.1534/genetics.116.199471] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 04/25/2017] [Indexed: 11/18/2022] Open
Abstract
Mitomycin C (MMC) is a genotoxic agent that induces DNA cross-links, DNA alkylation, and the production of reactive oxygen species (ROS). MMC induces the SOS response and RpoS regulons in Escherichia coli SOS-encoded functions are required for DNA repair, whereas the RpoS regulon is typically induced by metabolic stresses that slow growth. Thus, induction of the RpoS regulon by MMC may be coincidental, because DNA damage slows growth; alternatively, the RpoS regulon may be an adaptive response contributing to cell survival. In this study, we show that the RpoS regulon is primarily induced by MMC-induced ROS production. We also show that RpoS regulon induction is required for the survival of MMC-treated growing cells. The major contributor to RpoS-dependent resistance to MMC treatment is DNA polymerase Pol II, which is encoded by the polB gene belonging to the SOS regulon. The observation that polB gene expression is controlled by the two major stress response regulons that are required to maximize survival and fitness further emphasizes the key role of this DNA polymerase as an important factor in genome stability.
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9
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Abstract
All living organisms are continually exposed to agents that damage their DNA, which threatens the integrity of their genome. As a consequence, cells are equipped with a plethora of DNA repair enzymes to remove the damaged DNA. Unfortunately, situations nevertheless arise where lesions persist, and these lesions block the progression of the cell's replicase. In these situations, cells are forced to choose between recombination-mediated "damage avoidance" pathways or a specialized DNA polymerase (pol) to traverse the blocking lesion. The latter process is referred to as Translesion DNA Synthesis (TLS). As inferred by its name, TLS not only results in bases being (mis)incorporated opposite DNA lesions but also bases being (mis)incorporated downstream of the replicase-blocking lesion, so as to ensure continued genome duplication and cell survival. Escherichia coli and Salmonella typhimurium possess five DNA polymerases, and while all have been shown to facilitate TLS under certain experimental conditions, it is clear that the LexA-regulated and damage-inducible pols II, IV, and V perform the vast majority of TLS under physiological conditions. Pol V can traverse a wide range of DNA lesions and performs the bulk of mutagenic TLS, whereas pol II and pol IV appear to be more specialized TLS polymerases.
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10
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Gruber AJ, Erdem AL, Sabat G, Karata K, Jaszczur MM, Vo DD, Olsen TM, Woodgate R, Goodman MF, Cox MM. A RecA protein surface required for activation of DNA polymerase V. PLoS Genet 2015; 11:e1005066. [PMID: 25811184 PMCID: PMC4374754 DOI: 10.1371/journal.pgen.1005066] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 02/11/2015] [Indexed: 11/25/2022] Open
Abstract
DNA polymerase V (pol V) of Escherichia coli is a translesion DNA polymerase responsible for most of the mutagenesis observed during the SOS response. Pol V is activated by transfer of a RecA subunit from the 3'-proximal end of a RecA nucleoprotein filament to form a functional complex called DNA polymerase V Mutasome (pol V Mut). We identify a RecA surface, defined by residues 112-117, that either directly interacts with or is in very close proximity to amino acid residues on two distinct surfaces of the UmuC subunit of pol V. One of these surfaces is uniquely prominent in the active pol V Mut. Several conformational states are populated in the inactive and active complexes of RecA with pol V. The RecA D112R and RecA D112R N113R double mutant proteins exhibit successively reduced capacity for pol V activation. The double mutant RecA is specifically defective in the ATP binding step of the activation pathway. Unlike the classic non-mutable RecA S117F (recA1730), the RecA D112R N113R variant exhibits no defect in filament formation on DNA and promotes all other RecA activities efficiently. An important pol V activation surface of RecA protein is thus centered in a region encompassing amino acid residues 112, 113, and 117, a surface exposed at the 3'-proximal end of a RecA filament. The same RecA surface is not utilized in the RecA activation of the homologous and highly mutagenic RumA'2B polymerase encoded by the integrating-conjugative element (ICE) R391, indicating a lack of structural conservation between the two systems. The RecA D112R N113R protein represents a new separation of function mutant, proficient in all RecA functions except SOS mutagenesis.
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Affiliation(s)
- Angela J Gruber
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Aysen L Erdem
- Departments of Biological Sciences and Chemistry, University of Southern California, Los Angeles, California, United States of America
| | - Grzegorz Sabat
- Biotechnology Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Kiyonobu Karata
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Malgorzata M Jaszczur
- Departments of Biological Sciences and Chemistry, University of Southern California, Los Angeles, California, United States of America
| | - Dan D Vo
- Departments of Biological Sciences and Chemistry, University of Southern California, Los Angeles, California, United States of America
| | - Tayla M Olsen
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Roger Woodgate
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Myron F Goodman
- Departments of Biological Sciences and Chemistry, University of Southern California, Los Angeles, California, United States of America
| | - Michael M Cox
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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11
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Repair on the go: E. coli maintains a high proliferation rate while repairing a chronic DNA double-strand break. PLoS One 2014; 9:e110784. [PMID: 25353327 PMCID: PMC4213011 DOI: 10.1371/journal.pone.0110784] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 09/16/2014] [Indexed: 11/19/2022] Open
Abstract
DNA damage checkpoints exist to promote cell survival and the faithful inheritance of genetic information. It is thought that one function of such checkpoints is to ensure that cell division does not occur before DNA damage is repaired. However, in unicellular organisms, rapid cell multiplication confers a powerful selective advantage, leading to a dilemma. Is the activation of a DNA damage checkpoint compatible with rapid cell multiplication? By uncoupling the initiation of DNA replication from cell division, the Escherichia coli cell cycle offers a solution to this dilemma. Here, we show that a DNA double-strand break, which occurs once per replication cycle, induces the SOS response. This SOS induction is needed for cell survival due to a requirement for an elevated level of expression of the RecA protein. Cell division is delayed, leading to an increase in average cell length but with no detectable consequence on mutagenesis and little effect on growth rate and viability. The increase in cell length caused by chronic DNA double-strand break repair comprises three components: two types of increase in the unit cell size, one independent of SfiA and SlmA, the other dependent of the presence of SfiA and the absence of SlmA, and a filamentation component that is dependent on the presence of either SfiA or SlmA. These results imply that chronic checkpoint induction in E. coli is compatible with rapid cell multiplication. Therefore, under conditions of chronic low-level DNA damage, the SOS checkpoint operates seamlessly in a cell cycle where the initiation of DNA replication is uncoupled from cell division.
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12
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Babu M, Arnold R, Bundalovic-Torma C, Gagarinova A, Wong KS, Kumar A, Stewart G, Samanfar B, Aoki H, Wagih O, Vlasblom J, Phanse S, Lad K, Yeou Hsiung Yu A, Graham C, Jin K, Brown E, Golshani A, Kim P, Moreno-Hagelsieb G, Greenblatt J, Houry WA, Parkinson J, Emili A. Quantitative genome-wide genetic interaction screens reveal global epistatic relationships of protein complexes in Escherichia coli. PLoS Genet 2014; 10:e1004120. [PMID: 24586182 PMCID: PMC3930520 DOI: 10.1371/journal.pgen.1004120] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 12/03/2013] [Indexed: 02/02/2023] Open
Abstract
Large-scale proteomic analyses in Escherichia coli have documented the composition and physical relationships of multiprotein complexes, but not their functional organization into biological pathways and processes. Conversely, genetic interaction (GI) screens can provide insights into the biological role(s) of individual gene and higher order associations. Combining the information from both approaches should elucidate how complexes and pathways intersect functionally at a systems level. However, such integrative analysis has been hindered due to the lack of relevant GI data. Here we present a systematic, unbiased, and quantitative synthetic genetic array screen in E. coli describing the genetic dependencies and functional cross-talk among over 600,000 digenic mutant combinations. Combining this epistasis information with putative functional modules derived from previous proteomic data and genomic context-based methods revealed unexpected associations, including new components required for the biogenesis of iron-sulphur and ribosome integrity, and the interplay between molecular chaperones and proteases. We find that functionally-linked genes co-conserved among γ-proteobacteria are far more likely to have correlated GI profiles than genes with divergent patterns of evolution. Overall, examining bacterial GIs in the context of protein complexes provides avenues for a deeper mechanistic understanding of core microbial systems. Genome-wide genetic interaction (GI) screens have been performed in yeast, but no analogous large-scale studies have yet been reported for bacteria. Here, we have used E. coli synthetic genetic array (eSGA) technology developed by our group to quantitatively map GIs to reveal epistatic dependencies and functional cross-talk among ∼600,000 digenic mutant combinations. By combining this epistasis information with functional modules derived by our group's earlier efforts from proteomic and genomic context (GC)-based methods, we identify several unexpected pathway-level dependencies, functional links between protein complexes, and biological roles of uncharacterized bacterial gene products. As part of the study, two of our pathway predictions from GI screens were validated experimentally, where we confirmed the role of these new components in iron-sulphur biogenesis and ribosome integrity. We also extrapolated the epistatic connectivity diagram of E. coli to 233 distantly related γ-proteobacterial species lacking GI information, and identified co-conserved genes and functional modules important for bacterial pathogenesis. Overall, this study describes the first genome-scale map of GIs in gram-negative bacterium, and through integrative analysis with previously derived protein-protein and GC-based interaction networks presents a number of novel insights into the architecture of bacterial pathways that could not have been discerned through either network alone.
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Affiliation(s)
- Mohan Babu
- Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan, Canada
- * E-mail: (MB); (AE)
| | - Roland Arnold
- Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
| | - Cedoljub Bundalovic-Torma
- Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Alla Gagarinova
- Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Keith S. Wong
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Ashwani Kumar
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan, Canada
| | - Geordie Stewart
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Bahram Samanfar
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University, Ottawa, Ontario, Canada
| | - Hiroyuki Aoki
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan, Canada
| | - Omar Wagih
- Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
| | - James Vlasblom
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan, Canada
| | - Sadhna Phanse
- Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan, Canada
| | - Krunal Lad
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan, Canada
| | | | - Christopher Graham
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan, Canada
| | - Ke Jin
- Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, Saskatchewan, Canada
| | - Eric Brown
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
| | - Ashkan Golshani
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University, Ottawa, Ontario, Canada
| | - Philip Kim
- Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
| | | | - Jack Greenblatt
- Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Walid A. Houry
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - John Parkinson
- Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Andrew Emili
- Banting and Best Department of Medical Research, Donnelly Centre, University of Toronto, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- * E-mail: (MB); (AE)
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13
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Competitive fitness during feast and famine: how SOS DNA polymerases influence physiology and evolution in Escherichia coli. Genetics 2013; 194:409-20. [PMID: 23589461 DOI: 10.1534/genetics.113.151837] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Escherichia coli DNA polymerases (Pol) II, IV, and V serve dual roles by facilitating efficient translesion DNA synthesis while simultaneously introducing genetic variation that can promote adaptive evolution. Here we show that these alternative polymerases are induced as cells transition from exponential to long-term stationary-phase growth in the absence of induction of the SOS regulon by external agents that damage DNA. By monitoring the relative fitness of isogenic mutant strains expressing only one alternative polymerase over time, spanning hours to weeks, we establish distinct growth phase-dependent hierarchies of polymerase mutant strain competitiveness. Pol II confers a significant physiological advantage by facilitating efficient replication and creating genetic diversity during periods of rapid growth. Pol IV and Pol V make the largest contributions to evolutionary fitness during long-term stationary phase. Consistent with their roles providing both a physiological and an adaptive advantage during stationary phase, the expression patterns of all three SOS polymerases change during the transition from log phase to long-term stationary phase. Compared to the alternative polymerases, Pol III transcription dominates during mid-exponential phase; however, its abundance decreases to <20% during long-term stationary phase. Pol IV transcription dominates as cells transition out of exponential phase into stationary phase and a burst of Pol V transcription is observed as cells transition from death phase to long-term stationary phase. These changes in alternative DNA polymerase transcription occur in the absence of SOS induction by exogenous agents and indicate that cell populations require appropriate expression of all three alternative DNA polymerases during exponential, stationary, and long-term stationary phases to attain optimal fitness and undergo adaptive evolution.
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14
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Abstract
Homologous recombination is an ubiquitous process that shapes genomes and repairs DNA damage. The reaction is classically divided into three phases: presynaptic, synaptic, and postsynaptic. In Escherichia coli, the presynaptic phase involves either RecBCD or RecFOR proteins, which act on DNA double-stranded ends and DNA single-stranded gaps, respectively; the central synaptic steps are catalyzed by the ubiquitous DNA-binding protein RecA; and the postsynaptic phase involves either RuvABC or RecG proteins, which catalyze branch-migration and, in the case of RuvABC, the cleavage of Holliday junctions. Here, we review the biochemical properties of these molecular machines and analyze how, in light of these properties, the phenotypes of null mutants allow us to define their biological function(s). The consequences of point mutations on the biochemical properties of recombination enzymes and on cell phenotypes help refine the molecular mechanisms of action and the biological roles of recombination proteins. Given the high level of conservation of key proteins like RecA and the conservation of the principles of action of all recombination proteins, the deep knowledge acquired during decades of studies of homologous recombination in bacteria is the foundation of our present understanding of the processes that govern genome stability and evolution in all living organisms.
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15
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Rosenberg SM, Shee C, Frisch RL, Hastings PJ. Stress-induced mutation via DNA breaks in Escherichia coli: a molecular mechanism with implications for evolution and medicine. Bioessays 2012; 34:885-92. [PMID: 22911060 PMCID: PMC3533179 DOI: 10.1002/bies.201200050] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Evolutionary theory assumed that mutations occur constantly, gradually, and randomly over time. This formulation from the "modern synthesis" of the 1930s was embraced decades before molecular understanding of genes or mutations. Since then, our labs and others have elucidated mutation mechanisms activated by stress responses. Stress-induced mutation mechanisms produce mutations, potentially accelerating evolution, specifically when cells are maladapted to their environment, that is, when they are stressed. The mechanisms of stress-induced mutation that are being revealed experimentally in laboratory settings provide compelling models for mutagenesis that propels pathogen-host adaptation, antibiotic resistance, cancer progression and resistance, and perhaps much of evolution generally. We discuss double-strand-break-dependent stress-induced mutation in Escherichia coli. Recent results illustrate how a stress response activates mutagenesis and demonstrate this mechanism's generality and importance to spontaneous mutation. New data also suggest a possible harmony between previous, apparently opposed, models for the molecular mechanism. They additionally strengthen the case for anti-evolvability therapeutics for infectious disease and cancer.
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Affiliation(s)
- Susan M Rosenberg
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
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16
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Belov OV, Krasavin EA, Parkhomenko AY. Mathematical model of induced mutagenesis in bacteria Escherichia coli under ultraviolet irradiation. Biophysics (Nagoya-shi) 2010. [DOI: 10.1134/s0006350910040287] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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17
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Morita R, Nakane S, Shimada A, Inoue M, Iino H, Wakamatsu T, Fukui K, Nakagawa N, Masui R, Kuramitsu S. Molecular mechanisms of the whole DNA repair system: a comparison of bacterial and eukaryotic systems. J Nucleic Acids 2010; 2010:179594. [PMID: 20981145 PMCID: PMC2957137 DOI: 10.4061/2010/179594] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 07/27/2010] [Indexed: 11/20/2022] Open
Abstract
DNA is subjected to many endogenous and exogenous damages. All organisms have developed a complex network of DNA repair mechanisms. A variety of different DNA repair pathways have been reported: direct reversal, base excision repair, nucleotide excision repair, mismatch repair, and recombination repair pathways. Recent studies of the fundamental mechanisms for DNA repair processes have revealed a complexity beyond that initially expected, with inter- and intrapathway complementation as well as functional interactions between proteins involved in repair pathways. In this paper we give a broad overview of the whole DNA repair system and focus on the molecular basis of the repair machineries, particularly in Thermus thermophilus HB8.
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Affiliation(s)
- Rihito Morita
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
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18
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Chandani S, Jacobs C, Loechler EL. Architecture of y-family DNA polymerases relevant to translesion DNA synthesis as revealed in structural and molecular modeling studies. J Nucleic Acids 2010; 2010. [PMID: 20936174 PMCID: PMC2945684 DOI: 10.4061/2010/784081] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 07/26/2010] [Indexed: 12/22/2022] Open
Abstract
DNA adducts, which block replicative DNA polymerases (DNAPs), are often bypassed by lesion-bypass DNAPs, which are mostly in the Y-Family. Y-Family DNAPs can do non-mutagenic or mutagenic dNTP insertion, and understanding this difference is important, because mutations transform normal into tumorigenic cells. Y-Family DNAP architecture that dictates mechanism, as revealed in structural and modeling studies, is considered. Steps from adduct blockage of replicative DNAPs, to bypass by a lesion-bypass DNAP, to resumption of synthesis by a replicative DNAP are described. Catalytic steps and protein conformational changes are considered. One adduct is analyzed in greater detail: the major benzo[a]pyrene adduct (B[a]P-N2-dG), which is bypassed non-mutagenically (dCTP insertion) by Y-family DNAPs in the IV/κ-class and mutagenically (dATP insertion) by V/η-class Y-Family DNAPs. Important architectural differences between IV/κ-class versus V/η-class DNAPs are discussed, including insights gained by analyzing ~400 sequences each for bacterial DNAPs IV and V, along with sequences from eukaryotic DNAPs kappa, eta and iota. The little finger domains of Y-Family DNAPs do not show sequence conservation; however, their structures are remarkably similar due to the presence of a core of hydrophobic amino acids, whose exact identity is less important than the hydrophobic amino acid spacing.
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Affiliation(s)
- Sushil Chandani
- Biology Department, Boston University, Boston, MA 02215, USA
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19
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Effect of translesion DNA polymerases, endonucleases and RpoS on mutation rates in Salmonella typhimurium. Genetics 2010; 185:783-95. [PMID: 20421601 DOI: 10.1534/genetics.110.116376] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It has been suggested that bacteria have evolved mechanisms to increase their mutation rate in response to various stresses and that the translesion DNA polymerase Pol IV under control of the LexA regulon and the alternative sigma factor RpoS are involved in regulating this mutagenesis. Here we examined in Salmonella enterica serovar Typhimurium LT2 the rates for four different types of mutations (rifampicin, nalidixic acid, and chlorate resistance and Lac(+) reversion) during various growth conditions and with different levels of four translesion DNA polymerases (Pol II, Pol IV, Pol V, and SamAB) and RpoS. Constitutive derepression of the LexA regulon by a lexA(def) mutation had no effect on Lac(+) reversion rates but increased the other three mutation rates up to 11-fold, and the contribution of the translesion DNA polymerases to this mutagenesis varied with the type of mutation examined. The increase in mutation rates in the lexA(def) mutant required the presence of the LexA-controlled UvrB protein and endonucleases UvrC and Cho. With regard to the potential involvement of RpoS in mutagenesis, neither an increase in RpoS levels conferred by artificial overexpression from a plasmid nor long-term stationary phase incubation or slow growth caused an increase in any of the four mutation rates measured, alone or in combination with overexpression of the translesion DNA polymerases. In conclusion, mutation rates are remarkably robust and no combination of growth conditions, induction of translesion DNA polymerases by inactivation of LexA, or increased RpoS expression could confer an increase in mutation rates higher than the moderate increase caused by derepression of the LexA regulon alone.
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20
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Koskiniemi S, Andersson DI. Translesion DNA polymerases are required for spontaneous deletion formation in Salmonella typhimurium. Proc Natl Acad Sci U S A 2009; 106:10248-53. [PMID: 19525399 PMCID: PMC2700912 DOI: 10.1073/pnas.0904389106] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2008] [Indexed: 01/12/2023] Open
Abstract
How spontaneous deletions form in bacteria is still a partly unresolved problem. Here, we show that deletion formation in Salmonella typhimurium requires the presence of functional translesion polymerases. First, in wild-type bacteria, removal of the known translesion DNA polymerases, PolII (polB), PolIV (dinB), PolV (umuDC), and SamAB (samAB), resulted in a 10-fold decrease in the deletion rate, indicating that 90% of all spontaneous deletions require these polymerases for their formation. Second, overexpression of these polymerases by derepression of the DNA damage-inducible LexA regulon caused a 25-fold increase in deletion rate that depended on the presence of functional translesion polymerases. Third, overexpression of the polymerases PolII and PolIV from a plasmid increased the deletion rate 12- to 30-fold, respectively. Last, in a recBC(-) mutant where dsDNA ends are stabilized due to the lack of the end-processing nuclease RecBC, the deletion rate was increased 20-fold. This increase depended on the translesion polymerases. In lexA(def) mutant cells with constitutive SOS expression, a 10-fold increase in DNA breaks was observed. Inactivation of all 4 translesion polymerases in the lexA(def) mutant reduced the deletion rate 250-fold without any concomitant reduction in the amount of DNA breaks. Mutational inactivation of 3 endonucleases under LexA control reduced the number of DNA breaks to the wild-type level in a lexA(def) mutant with a concomitant 50-fold reduction in deletion rate. These findings suggest that the translesion polymerases are not involved in forming the DNA breaks, but that they require them to stimulate deletion formation.
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Affiliation(s)
- Sanna Koskiniemi
- Department of Medical Biochemistry and Microbiology, Uppsala University, S-751 23 Uppsala, Sweden
| | - Dan I. Andersson
- Department of Medical Biochemistry and Microbiology, Uppsala University, S-751 23 Uppsala, Sweden
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21
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Babic A, Lindner AB, Vulic M, Stewart EJ, Radman M. Direct visualization of horizontal gene transfer. Science 2008; 319:1533-6. [PMID: 18339941 DOI: 10.1126/science.1153498] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Conjugation allows bacteria to acquire genes for antibiotic resistance, novel virulence attributes, and alternative metabolic pathways. Using a fluorescent protein fusion, SeqA-YFP, we have visualized this process in real time and in single cells of Escherichia coli. We found that the F pilus mediates DNA transfer at considerable cell-to-cell distances. Integration of transferred DNA by recombination occurred in up to 96% of recipients; in the remaining cells, the transferred DNA was fully degraded by the RecBCD helicase/nuclease. The acquired integrated DNA was tracked through successive replication rounds and was found to occasionally split and segregate with different chromosomes, leading to the inheritance of different gene clusters within the cell lineage. The incidence of DNA splitting corresponds to about one crossover per cell generation.
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22
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Silverman AP, Jiang Q, Goodman MF, Kool ET. Steric and electrostatic effects in DNA synthesis by the SOS-induced DNA polymerases II and IV of Escherichia coli. Biochemistry 2007; 46:13874-81. [PMID: 17988102 DOI: 10.1021/bi700851z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The SOS-induced DNA polymerases II and IV (pol II and pol IV, respectively) of Escherichia coli play important roles in processing lesions that occur in genomic DNA. Here we study how electrostatic and steric effects play different roles in influencing the efficiency and fidelity of DNA synthesis by these two enzymes. These effects were probed by the use of nonpolar shape analogues of thymidine, in which substituted toluenes replace the polar thymine base. We compared thymine with nonpolar analogues to evaluate the importance of hydrogen bonding in the polymerase active sites, while we used comparisons among a set of variably sized thymine analogues to measure the role of steric effects in the two enzymes. Steady-state kinetics measurements were carried out to evaluate activities for nucleotide insertion and extension. The results showed that both enzymes inserted nucleotides opposite nonpolar template bases with moderate to low efficiency, suggesting that both polymerases benefit from hydrogen bonding or other electrostatic effects involving the template base. Surprisingly, however, pol II inserted nonpolar nucleotide (dNTP) analogues into a primer strand with high (wild-type) efficiency, while pol IV handled them with an extremely low efficiency. Base pair extension studies showed that both enzymes bypass non-hydrogen-bonding template bases with moderately low efficiency, suggesting a possible beneficial role of minor groove hydrogen bonding interactions at the N-1 position. Measurement of the two polymerases' sensitivity to steric size changes showed that both enzymes were relatively flexible, yielding only small kinetic differences with increases or decreases in nucleotide size. Comparisons are made to recent data for DNA pol I (Klenow fragment), the archaeal polymerase Dpo4, and human pol kappa.
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Affiliation(s)
- Adam P Silverman
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA
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23
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Bjedov I, Dasgupta CN, Slade D, Le Blastier S, Selva M, Matic I. Involvement of Escherichia coli DNA polymerase IV in tolerance of cytotoxic alkylating DNA lesions in vivo. Genetics 2007; 176:1431-40. [PMID: 17483416 PMCID: PMC1931539 DOI: 10.1534/genetics.107.072405] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Accepted: 05/03/2007] [Indexed: 11/18/2022] Open
Abstract
Escherichia coli PolIV, a DNA polymerase capable of catalyzing synthesis past replication-blocking DNA lesions, belongs to the most ubiquitous branch of Y-family DNA polymerases. The goal of this study is to identify spontaneous DNA damage that is bypassed specifically and accurately by PolIV in vivo. We increased the amount of spontaneous DNA lesions using mutants deficient for different DNA repair pathways and measured mutation frequency in PolIV-proficient and -deficient backgrounds. We found that PolIV performs an error-free bypass of DNA damage that accumulates in the alkA tag genetic background. This result indicates that PolIV is involved in the error-free bypass of cytotoxic alkylating DNA lesions. When the amount of cytotoxic alkylating DNA lesions is increased by the treatment with chemical alkylating agents, PolIV is required for survival in an alkA tag-proficient genetic background as well. Our study, together with the reported involvement of the mammalian PolIV homolog, Polkappa, in similar activity, indicates that Y-family DNA polymerases from the DinB branch can be added to the list of evolutionarily conserved molecular mechanisms that counteract cytotoxic effects of DNA alkylation. This activity is of major biological relevance because alkylating agents are continuously produced endogenously in all living cells and are also present in the environment.
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Affiliation(s)
- Ivana Bjedov
- INSERM U571, Faculté de Médecine, Université Paris 5, 75730 Paris Cedex 15, France
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24
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Jarosz DF, Beuning PJ, Cohen SE, Walker GC. Y-family DNA polymerases in Escherichia coli. Trends Microbiol 2007; 15:70-7. [PMID: 17207624 DOI: 10.1016/j.tim.2006.12.004] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2006] [Revised: 11/13/2006] [Accepted: 12/14/2006] [Indexed: 10/23/2022]
Abstract
The observation that mutations in the Escherichia coli genes umuC+ and umuD+ abolish mutagenesis induced by UV light strongly supported the counterintuitive notion that such mutagenesis is an active rather than passive process. Genetic and biochemical studies have revealed that umuC+ and its homolog dinB+ encode novel DNA polymerases with the ability to catalyze synthesis past DNA lesions that otherwise stall replication--a process termed translesion synthesis (TLS). Similar polymerases have been identified in nearly all organisms, constituting a new enzyme superfamily. Although typically viewed as unfaithful copiers of DNA, recent studies suggest that certain TLS polymerases can perform proficient and moderately accurate bypass of particular types of DNA damage. Moreover, various cellular factors can modulate their activity and mutagenic potential.
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Affiliation(s)
- Daniel F Jarosz
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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25
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Abstract
In nature, microbes live under a variety of harsh conditions, such as excess DNA damage, starvation, pH shift, or high temperatures. Microbial cells respond to such stressful conditions mostly by switching global patterns of gene expression to relieve the environmental stress. The SOS response, which is induced by DNA damage, is one such global network of gene expression that plays a crucial role in balancing the genomic stability and flexibility that are necessary to adapt to harsh environments. Here, I review the roles of SOS-inducible and noninducible lesion-bypass DNA polymerases in mutagenesis induced by environmental stress, and discuss how these polymerases are coordinated for the replication of damaged chromosomes. Possible contributions of lesion-bypass DNA polymerase in hyperthermophilic archaea, e.g., Sulfolobus solfataricus, to genome maintenance are also discussed.
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Affiliation(s)
- Takehiko Nohmi
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan.
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26
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Pavlov YI, Shcherbakova PV, Rogozin IB. Roles of DNA Polymerases in Replication, Repair, and Recombination in Eukaryotes. INTERNATIONAL REVIEW OF CYTOLOGY 2006; 255:41-132. [PMID: 17178465 DOI: 10.1016/s0074-7696(06)55002-8] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The functioning of the eukaryotic genome depends on efficient and accurate DNA replication and repair. The process of replication is complicated by the ongoing decomposition of DNA and damage of the genome by endogenous and exogenous factors. DNA damage can alter base coding potential resulting in mutations, or block DNA replication, which can lead to double-strand breaks (DSB) and to subsequent chromosome loss. Replication is coordinated with DNA repair systems that operate in cells to remove or tolerate DNA lesions. DNA polymerases can serve as sensors in the cell cycle checkpoint pathways that delay cell division until damaged DNA is repaired and replication is completed. Eukaryotic DNA template-dependent DNA polymerases have different properties adapted to perform an amazingly wide spectrum of DNA transactions. In this review, we discuss the structure, the mechanism, and the evolutionary relationships of DNA polymerases and their possible functions in the replication of intact and damaged chromosomes, DNA damage repair, and recombination.
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Affiliation(s)
- Youri I Pavlov
- Eppley Institute for Research in Cancer and Allied Diseases, Departments of Biochemistry and Molecular Biology, and Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA
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