SOS DNA Repair Research Articles

Transcriptome and proteome analyses of adaptive responses to methyl methanesulfonate in Escherichia coli K-12 and ada mutant strains

BackgroundThe Ada-dependent adaptive response system in Escherichia coli is important for increasing resistance to alkylation damage. However, the global transcriptional and translational changes during this response have not been reported. Here we present time-dependent global gene and protein expression profiles following treatment with methyl methanesulfonate (MMS) in E. coli W3110 and its ada mutant strains.ResultsTranscriptome profiling showed that 1138 and 2177 genes were differentially expressed in response to MMS treatment in the wild-type and mutant strains, respectively. A total of 81 protein spots representing 76 nonredundant proteins differentially expressed were identified using 2-DE and LC-MS/MS. In the wild-type strain, many genes were differentially expressed upon long-exposure to MMS, due to both adaptive responses and stationary phase responses. In the ada mutant strain, the genes involved in DNA replication, recombination, modification and repair were up-regulated 0.5 h after MMS treatment, indicating its connection to the SOS and other DNA repair systems. Interestingly, expression of the genes involved in flagellar biosynthesis, chemotaxis, and two-component regulatory systems related to drug or antibiotic resistance, was found to be controlled by Ada.ConclusionThese results show in detail the regulatory components and pathways controlling adaptive response and how the related genes including the Ada regulon are expressed with this response.

Genetic network inference as a series of discrimination tasks

Genetic network inference methods based on sets of differential equations generally require a great deal of time, as the equations must be solved many times. To reduce the computational cost, researchers have proposed other methods for inferring genetic networks by solving sets of differential equations only a few times, or even without solving them at all. When we try to obtain reasonable network models using these methods, however, we must estimate the time derivatives of the gene expression levels with great precision. In this study, we propose a new method to overcome the drawbacks of inference methods based on sets of differential equations. Our method infers genetic networks by obtaining classifiers capable of predicting the signs of the derivatives of the gene expression levels. For this purpose, we defined a genetic network inference problem as a series of discrimination tasks, then solved the defined series of discrimination tasks with a linear programming machine. Our experimental results demonstrated that the proposed method is capable of correctly inferring genetic networks, and doing so more than 500 times faster than the other inference methods based on sets of differential equations. Next, we applied our method to actual expression data of the bacterial SOS DNA repair system. And finally, we demonstrated that our approach relates to the inference method based on the S-system model. Though our method provides no estimation of the kinetic parameters, it should be useful for researchers interested only in the network structure of a target system. Supplementary data are available at Bioinformatics online.

Network evaluation from the consistency of the graph structure with the measured data

BackgroundA knowledge-based network, which is constructed by extracting as many relationships identified by experimental studies as possible and then superimposing them, is one of the promising approaches to investigate the associations between biological molecules. However, the molecular relationships change dynamically, depending on the conditions in a living cell, which suggests implicitly that all of the relationships in the knowledge-based network do not always exist. Here, we propose a novel method to estimate the consistency of a given network with the measured data: i) the network is quantified into a log-likelihood from the measured data, based on the Gaussian network, and ii) the probability of the likelihood corresponding to the measured data, named the graph consistency probability (GCP), is estimated based on the generalized extreme value distribution.ResultsThe plausibility and the performance of the present procedure are illustrated by various graphs with simulated data, and with two types of actual gene regulatory networks in Escherichia coli: the SOS DNA repair system with the corresponding data measured by fluorescence, and a set of 29 networks with data measured under anaerobic conditions by microarray. In the simulation study, the procedure for estimating GCP is illustrated by a simple network, and the robustness of the method is scrutinized in terms of various aspects: dimensions of sampling data, parameters in the simulation study, magnitudes of data noise, and variations of network structures.In the actual networks, the former example revealed that our method operates well for an actual network with a size similar to those of the simulated networks, and the latter example illustrated that our method can select the activated network candidates consistent with the actual data measured under specific conditions, among the many network candidates.ConclusionThe present method shows the possibility of bridging between the static network from the literature and the corresponding measurements, and thus will shed light on the network structure variations in terms of the changes in molecular interaction mechanisms that occur in response to the environment in a living cell.

Conservation of the LexA repressor binding site in Deinococcus radiodurans

Summary The LexA protein is a transcriptional repressor of the bacterial SOS DNA repair system, which comprises a set of DNA repair and cellular survival genes that are induced in response to DNA damage. Its varied DNA binding motifs have been characterized and reported in the Escherichia coli, Bacillus subtilis, rhizobia family members, marine magnetotactic bacterium, Salmonella typhimurium and recently in Mycobacterium tuberculosis and this motifs information has been used in our theoretical analysis to detect its novel regulated genes in radio-resistant Deinococcus radiodurans genome. This bacterium showed presence of SOS-box like consensus sequence in the upstream sequences of 3166 genes with >60% motif score similarity percentage (MSSP) on both strands. Attempts to identify LexA-binding sites and the composition of the putative SOS regulon in D. radiodurans have been unsuccessful so far. To resolve the problem we performed theoretical analysis with modifications on reported data set of genes related to DNA repair (61 genes), stress response (145 genes) and some unusual predicted operons (21 clusters). Expression of some of the predicted SOS-box regulated operon members then was examined through the previously reported microarray data which confirm the expression of only single predicted operon i.e. DRB0143 (AAA superfamily NTPase related to 5-methylcytosine specific restriction enzyme subunit McrB) and DRB0144 (homolog of the McrC subunit of the McrBC restriction modification system). The methodology involved weight matrix construction through CONSENSUS algorithm using information of conserved upstream sequences of eight known genes including dinB, tagC, lexA, recA, uvrB, yneA of B. subtilis while lexA and recA of D. radiodurans through phylogenetic footprinting method and later detection of similar conserved SOS-box like LexA binding motifs through both RSAT & PoSSuMsearch programs. The resultant DNA consensus sequence had highly conserved 14 bp SOS-box like binding site.

Dynamical pathway analysis

BackgroundAlthough a great deal is known about one gene or protein and its functions under different environmental conditions, little information is available about the complex behaviour of biological networks subject to different environmental perturbations. Observing differential expressions of one or more genes between normal and abnormal cells has been a mainstream method of discovering pertinent genes in diseases and therefore valuable drug targets. However, to date, no such method exists for elucidating and quantifying the differential dynamical behaviour of genetic regulatory networks, which can have greater impact on phenotypes than individual genes.ResultsWe propose to redress the deficiency by formulating the functional study of biological networks as a control problem of dynamical systems. We developed mathematical methods to study the stability, the controllability, and the steady-state behaviour, as well as the transient responses of biological networks under different environmental perturbations. We applied our framework to three real-world datasets: the SOS DNA repair network in E. coli under different dosages of radiation, the GSH redox cycle in mice lung exposed to either poisonous air or normal air, and the MAPK pathway in mammalian cell lines exposed to three types of HIV type I Vpr, a wild type and two mutant types; and we found that the three genetic networks exhibited fundamentally different dynamical properties in normal and abnormal cells.ConclusionDifference in stability, relative stability, degrees of controllability, and transient responses between normal and abnormal cells means considerable difference in dynamical behaviours and different functioning of cells. Therefore differential dynamical properties can be a valuable tool in biomedical research.

Conservation of the LexA repressor binding site in Deinococcus radiodurans.

The LexA protein is a transcriptional repressor of the bacterial SOS DNA repair system, which comprises a set of DNA repair and cellular survival genes that are induced in response to DNA damage. Its varied DNA binding motifs have been characterized and reported in the Escherichia coli, Bacillus subtilis, rhizobia family members, marine magnetotactic bacterium, Salmonella typhimurium and recently in Mycobacterium tuberculosis and this motifs information has been used in our theoretical analysis to detect its novel regulated genes in radio-resistant Deinococcus radiodurans genome. This bacterium showed presence of SOS-box like consensus sequence in the upstream sequences of 3166 genes with >60% motif score similarity percentage (MSSP) on both strands. Attempts to identify LexA-binding sites and the composition of the putative SOS regulon in D. radiodurans have been unsuccessful so far. To resolve the problem we performed theoretical analysis with modifications on reported data set of genes related to DNA repair (61 genes), stress response (145 genes) and some unusual predicted operons (21 clusters). Expression of some of the predicted SOS-box regulated operon members then was examined through the previously reported microarray data which confirm the expression of only single predicted operon i.e. DRB0143 (AAA superfamily NTPase related to 5-methylcytosine specific restriction enzyme subunit McrB) and DRB0144 (homolog of the McrC subunit of the McrBC restriction modification system). The methodology involved weight matrix construction through CONSENSUS algorithm using information of conserved upstream sequences of eight known genes including dinB, tagC, lexA, recA, uvrB, yneA of B. subtilis while lexA and recA of D. radiodurans through phylogenetic footprinting method and later detection of similar conserved SOS-box like LexA binding motifs through both RSAT & PoSSuMsearch programs. The resultant DNA consensus sequence had highly conserved 14 bp SOS-box like binding site.

Incarnation of classical pro- and eukaryotic mechanisms of mutagenesis in hypermutagenesis and immunity of vertebrates

M.E. Lobashev has brilliantly postulated in 1947 that error-prone repair contribute to mutations in cells. This was shown to be true once the mechanisms of UV mutagenesis in Escherichia coli were deciphered. Induced mutations are generated during error-prone SOS DNA repair with the involvement of inaccurate DNA polymerases belonging to the Y family. Currently, several distinct mutator enzymes participating in spontaneous and induced mutagenesis have been identified. Upon induction of these proteins, mutation rates increase by several orders of magnitude. These proteins regulate the mutation rates in evolution and in ontogeny during immune response. In jawed vertebrates, somatic hypermutagenesis occurs in the variable regions of immunoglobulin genes, leading to affinity maturation of antibodies. The process is initiated by cytidine deamination in DNA to uracil by AID (Activation-Induced Deaminase). Further repair of uracil-containing DNA through proteins that include the Y family DNA polymerases causes mutations, induce gene conversion, and class switch recombination. In jawless vertebrates, the variable lymphocyte receptors (VLR) serve as the primary molecules for adaptive immunity. Generation of mature VLRs most likely depends on agnathan AID-like deaminases. AID and its orthologs in lamprey (PmCDA1 and PMCDA2) belong to the AID/APOBEC family of RNA/DNA editing cytidine deaminases. This family includes enzymes with different functions: APOBEC1 edits RNA, APOBEC3 restricts retroviruses. The functions of APOBEC2 and APOBEC4 have not been yet determined. Here, we report a new member of the AID/APOBEC family, APOBEC5, in the bacterium Xanthomonas oryzae. The widespread presence of RNA/DNA editing deaminases suggests that they are an ancient means of generating genetic diversity.

Development of Signature-Tagged Mutagenesis in Burkholderia pseudomallei To Identify Genes Important in Survival and Pathogenesis

Burkholderia pseudomallei, the causative agent of melioidosis, is an important human pathogen in Southeast Asia and northern Australia for which a vaccine is unavailable. A panel of 892 double signature-tagged mutants was screened for virulence using an intranasal BALB/c mouse model of infection. A novel DNA tag microarray identified 33 mutants as being attenuated in spleens, while 6 were attenuated in both lungs and spleens. The transposon insertion sites in spleen-attenuated mutants revealed genes involved in several stages of capsular polysaccharide biosynthesis and DNA replication and repair, a putative oxidoreductase, ABC transporters, and a lipoprotein that may be important in intercellular spreading. The six mutants identified as missing in both lungs and spleens were found to have insertions in recA involved in the SOS response and DNA repair; putative auxotrophs of leucine, threonine, p-aminobenzoic acid, and a mutant with an insertion in aroB causing auxotrophy for aromatic compounds were also found. Murine challenge studies revealed partial protection in BALB/c mice vaccinated with the aroB mutant. The refined signature-tagged mutagenesis approach developed in this study was used to efficiently identify attenuating mutants from this highly pathogenic species and could be applied to other organisms.

Autogenous and nonautogenous control of response in a genetic network

Feedback-based control methods determine the behavior of cellular systems, an example being autogenous control, the regulation of production of a protein by itself. This control strategy was theoretically shown to be superior to an equivalent but nonautogenously regulated system when based on a repressor. Although some of its advantages were later confirmed with isolated synthetic circuits, the superiority of autogenous control in natural networks remains untested. Here, we use the SOS DNA repair system of Escherichia coli, where autogenous control is part of a single-input module, as a valid model to evaluate the functional advantages and biological implications of this mechanism. We redesign the control of its master regulator, the protein LexA, so that it becomes nonautogenously controlled. We compare both systems by combining high-resolution expression measurements with mathematical modeling. We show that the stronger stability associated with the autogenous regulation prevents false triggering of the response due to transient fluctuations in the inducing signal and that this control also reduces the system recovery time at low DNA damage. Likewise, autoregulation produces responses proportional to the damage signal level. In contrast, bacteria with LexA constitutively expressed induce maximal action even for very low damage levels. This excess in response comes at a cost, because it reduces comparatively the growth rate of these cells. Our results suggest that autogenous control evolved as a strategy to optimally respond to multiple levels of input signal minimizing the costs of the response and highlights reasons why master regulators of single-input modules are mostly autorepressed.

Global Regulatory Impact of ClpP Protease ofStaphylococcus aureuson Regulons Involved in Virulence, Oxidative Stress Response, Autolysis, and DNA Repair

Staphylococcus aureus is an important pathogen, causing a wide range of infections including sepsis, wound infections, pneumonia, and catheter-related infections. In several pathogens ClpP proteases were identified by in vivo expression technologies to be important for virulence. Clp proteolytic complexes are responsible for adaptation to multiple stresses by degrading accumulated and misfolded proteins. In this report clpP, encoding the proteolytic subunit of the ATP-dependent Clp protease, was deleted, and gene expression of DeltaclpP was determined by global transcriptional analysis using DNA-microarray technology. The transcriptional profile reveals a strong regulatory impact of ClpP on the expression of genes encoding proteins that are involved in the pathogenicity of S. aureus and adaptation of the pathogen to several stresses. Expression of the agr system and agr-dependent extracellular virulence factors was diminished. Moreover, the loss of clpP leads to a complete transcriptional derepression of genes of the CtsR- and HrcA-controlled heat shock regulon and a partial derepression of genes involved in oxidative stress response, metal homeostasis, and SOS DNA repair controlled by PerR, Fur, MntR, and LexA. The levels of transcription of genes encoding proteins involved in adaptation to anaerobic conditions potentially regulated by an Fnr-like regulator were decreased. Furthermore, the expression of genes whose products are involved in autolysis was deregulated, leading to enhanced autolysis in the mutant. Our results indicate a strong impact of ClpP proteolytic activity on virulence, stress response, and physiology in S. aureus.

Random Gene Dissection: A Tool for the Investigation of Protein Structural Organization

To investigate the domain structure of proteins and the function of individual domains, proteins are usually subjected to limited proteolysis, followed by isolation of protein fragments and determination of their functions. We have developed an approach we call random gene dissection (RGD) for the identification of functional protein domains and their interdomain regions as well as their in vivo complementing fragments. The approach was tested on a two-domain protein, the type IIS restriction endonuclease BfiI. The collection of BfiI insertional mutants was screened for those that are endonucleolytically active and thus induce the SOS DNA repair response. Sixteen isolated mutants of the wild-type specificity contained insertions that were dispersed in a relatively large region of the target recognition domain. They split the gene into two complementing parts that separately were unable to induce the SOS DNA repair response. In contrast, all 19 mutants of relaxed specificity contained the cassette inserted into a very narrow interdomain region that connects BfiI domains responsible for DNA recognition and for cleavage. As expected, only the N-terminal fragment of BfiI was required to induce SOS response. Our results demonstrate that RGD can be used as a general method to identify complementing fragments and functional domains in enzymes.

Precise Temporal Modulation in the Response of the SOS DNA Repair Network in Individual Bacteria

The SOS genetic network is responsible for the repair/bypass of DNA damage in bacterial cells. While the initial stages of the response have been well characterized, less is known about the dynamics of the response after induction and its shutoff. To address this, we followed the response of the SOS network in living individual Escherichia coli cells. The promoter activity (PA) of SOS genes was monitored using fluorescent protein-promoter fusions, with high temporal resolution, after ultraviolet irradiation activation. We find a temporal pattern of discrete activity peaks masked in studies of cell populations. The number of peaks increases, while their amplitude reaches saturation, as the damage level is increased. Peak timing is highly precise from cell to cell and is independent of the stage in the cell cycle at the time of damage. Evidence is presented for the involvement of the umuDC operon in maintaining the pattern of PA and its temporal precision, providing further evidence for the role UmuD cleavage plays in effecting a timed pause during the SOS response, as previously proposed. The modulations in PA we observe share many features in common with the oscillatory behavior recently observed in a mammalian DNA damage response. Our results, which reveal a hitherto unknown modulation of the SOS response, underscore the importance of carrying out dynamic measurements at the level of individual living cells in order to unravel how a natural genetic network operates at the systems level.

Bacterial Persistence and Antibiotic Resistance

The inherent persistence of bacterial populations after exposure to antibiotics or other stress is well known but little understood. Such persistence is distinct from acquired antibiotic resistance and, on regrowth, such bacteria are still antibiotic sensitive (see the Perspective by Levin). Balaban et al. investigated the growth dynamics of various mutant and wild-type Escherichia coli using a microfluidic device to track individual organisms. At least three different phenotypes were revealed. Those with a normal growth rate were killed. Type I persisters exited stationary phase very slowly--hours rather than minutes after nutrients were restored. Type II persisters arose by a spontaneous switch from the normal growth rate to grow consistently more slowly, regardless of growth conditions, and, rarely, could switch back to the normal growth rate. Many pathogens have become resistant to the β-lactam antibiotics, like penicillin, by a variety of mechanisms, including mutation of penicillin-binding protein genes, destruction of the antibiotic by β-lactamases, or inhibition of uptake by the bacterial cells. Miller et al. (see the Perspective by Levin) describe another mechanism for avoiding the lethal effects of antibiotics. Damage to penicillin binding protein 3 activates the DpiBA two-component signal transduction cascade and eventually triggers the SOS DNA repair response. When SOS kicks in, cell division pauses, and the bacteria escape lethal damage, at least from short-term antibiotic exposure, because synthesis of new cell walls shuts down. N. Q. Balaban, J. Merrin, R. Chait, L. Kowalik, S. Leibler, Bacterial persistence as a phenotypic switch. Science 305 , 1622-1625 (2004). [Abstract] [Full Text] B. R. Levin, Noninherited resistance to antibiotics. Science 305 , 1578-1579 (2004). [Summary] [Full Text] C. Miller, L. E. Thomsen, C. Gaggero, R. Mosseri, H. Ingmer, S. N. Cohen, SOS response induction by ß-lactams and bacterial defense against antibiotic lethality. Science 305 , 1629-1631 (2004). [Abstract] [Full Text]

Genotoxicity monitoring using a 2D-spectroscopic GFP whole cell biosensing system

A 2D-spectroscopic genotoxicity biosensing system is presented. This optical sensing system monitors the genotoxicant-induced expression of green fluorescent protein (GFP) in a recombinant Escherichia coli strain. In this organism, GFP synthesis is driven by the recA gene promoter of the bacterial SOS DNA repair system. Using nalidixic acid as a model genotoxicant, we have demonstrated a response range that varies as a function of the excitation wavelength. When GFP fluorescence was monitored at 510 nm, the linear working range to nalidixic acid was within the range of 0.03–0.3 ppm at 390 nm excitation and 0.05–0.3 ppm at 480 nm excitation.

Assigning numbers to the arrows: parameterizing a gene regulation network by using accurate expression kinetics.

A basic challenge in systems biology is to understand the dynamical behavior of gene regulation networks. Current approaches aim at determining the network structure based on genomic-scale data. However, the network connectivity alone is not sufficient to define its dynamics; one needs to also specify the kinetic parameters for the regulation reactions. Here, we ask whether effective kinetic parameters can be assigned to a transcriptional network based on expression data. We present a combined experimental and theoretical approach based on accurate high temporal-resolution measurement of promoter activities from living cells by using green fluorescent protein (GFP) reporter plasmids. We present algorithms that use these data to assign effective kinetic parameters within a mathematical model of the network. To demonstrate this, we employ a well defined network, the SOS DNA repair system of Escherichia coli. We find a strikingly detailed temporal program of expression that correlates with the functional role of the SOS genes and is driven by a hierarchy of effective kinetic parameter strengths for the various promoters. The calculated parameters can be used to determine the kinetics of all SOS genes given the expression profile of just one representative, allowing a significant reduction in complexity. The concentration profile of the master SOS transcriptional repressor can be calculated, demonstrating that relative protein levels may be determined from purely transcriptional data. This finding opens the possibility of assigning kinetic parameters to transcriptional networks on a genomic scale.

Para-aminobenzoic acid inhibits a set of SOS functions in Escherichia coli K12

PABA — Vitamin H1 of group B, has obtained increasing fundamental interest as a very potent natural antimutagen after a series of our publications since 1979. In the first set of our experiments, we studied PABA in the assays with the alkylating agent N-methyl- N-nitrosourea (MNU). Mutagenic efficiency of this agent was suppressed up to 10-fold when PABA was administered into Escherichia coli cells concurrently with the mutagen or prior to the mutagenic treatment. NMR spectrometric and UV-spectrophotometric measurements did not reveal an interaction between the direct acting MNU and PABA, typical for some N-nitroso compounds and phenolics. PABA suppressed the error-prone DNA repair pathway induced by UV-irradiation. PABA decreased MNU-induced phage λ lysogenic induction more than two orders of magnitude. PABA inhibited the thermal shift up to 400-fold in phage λ from the permissive to non-permissive temperature in E. coli mutant tif-1 and decreased about two-fold W-reactivation of UV-damaged phage λ. Chloramphenicol treatment of the cells just after the mutagenic treatment prevented the occurrence of PABA specific activity. The results suggest that PABA affects the SOS DNA repair pathway and the mutagenic response of E. coli. PABA appears to be an effective bioantimutagen reducing mutagenesis by modulating the error-prone DNA repair (SOS) response.

Role of iron ions in the SOS DNA repair response induced in E.coli by nitric oxide donors

Conference Abstract| October 01 2000 Role of iron ions in the SOS DNA repair response induced in E.coli by nitric oxide donors I. I. Lobysheva; I. I. Lobysheva 14 Kosygin St., Moscow 117977, Russia Search for other works by this author on: This Site PubMed Google Scholar M. V. Stupakova; M. V. Stupakova 14 Kosygin St., Moscow 117977, Russia Search for other works by this author on: This Site PubMed Google Scholar V. D. Mikoyan; V. D. Mikoyan 14 Kosygin St., Moscow 117977, Russia Search for other works by this author on: This Site PubMed Google Scholar A. F. Vanin; A. F. Vanin 14 Kosygin St., Moscow 117977, Russia Search for other works by this author on: This Site PubMed Google Scholar S. V. Vasilieva S. V. Vasilieva 14 Kosygin St., Moscow 117977, Russia Search for other works by this author on: This Site PubMed Google Scholar Biochem Soc Trans (2000) 28 (5): A165. https://doi.org/10.1042/bst028a165c Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter LinkedIn Cite Icon Cite Get Permissions Citation I. I. Lobysheva, M. V. Stupakova, V. D. Mikoyan, A. F. Vanin, S. V. Vasilieva; Role of iron ions in the SOS DNA repair response induced in E.coli by nitric oxide donors. Biochem Soc Trans 1 October 2000; 28 (5): A165. doi: https://doi.org/10.1042/bst028a165c Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Society Transactions Search Advanced Search This content is only available as a PDF. © 2000 Biochemical Society2000 Article PDF first page preview Close Modal You do not currently have access to this content.

DNA nicks inflicted by restriction endonucleases are repaired by a RecA- and RecB-dependent pathway in Escherichia coli.

Two mutants of the EcoRI endonuclease (R200K and E144C) predominantly nick only one strand of the DNA substrate. Temperature sensitivity of the mutant enzymes allowed us to study the consequences of inflicting DNA nicks at EcoRI sites in vivo. Expression of the EcoRI endonuclease mutants in the absence of the EcoRI methyltransferase induces the SOS DNA repair response and greatly reduces viability of recA56, recB21 and lexA3 mutant strains of Escherichia coli. In parallel studies, overexpression of the EcoRV endonuclease in cells also expressing the EcoRV methyltransferase was used to introduce nicks at non-cognate EcoRV sites in the bacterial genome. EcoRV overproduction was lethal in recA56 and recB21 mutant strains and moderately toxic in a lexA3 mutant strain. The toxic effect of EcoRV overproduction could be partially alleviated by introduction into the cells of multiple copies of the E. coli DNA ligase gene. These observations suggest that an increased number of DNA nicks can overwhelm the repair capacity of DNA ligase, resulting in the conversion of a proportion of DNA nicks into DNA lesions that require recombination for repair.

Induction of the SOS DNA repair response in Escherichia coli by nitric oxide donating agents: dinitrosyl iron complexes with thiol-containing ligands and S-nitrosothiols

The ability of nitric oxide (NO) donor compounds to induce the SOS DNA repair response in Escherichia coli is reported. Dinitrosyl iron complexes with glutathione and cysteine (DNIC) are the most potent SOS-inducers. S-Nitrosothiols (RSNO) mediate a similar response at 10–100 μM, but the response decreases sharply at concentrations above 0.5 mM. Pretreatment of the cells with the chelating agent o-phenanthroline (OP) prevents induction of the SOS response by all agents used. On the other hand, the toxicity of S-nitrosothiols is higher than that of DNIC. The EPR study showsthe appearance of an EPR DNIC-type signal after incubation of the cells with S-nitrosoglutathione because of mutual transformation between RSNO and DNIC in the presence of accessible iron inside the cells. Pretreatment of the cells with OP leads to a decrease in this signal. Analysis of NO donor effects reveals a dual role of the iron ions in reactivity and toxicity of the compounds studied, i.e. (i) stabilization of the cytotoxic RSNO and (ii) generation of the SOS signal.

The expression of recombinant genes from bacteriophage lambda strong promoters triggers the SOS response in escherichia coli

Biotechnology and BioengineeringVolume 64, Issue 1 p. 127-127 AddendumFree Access The expression of recombinant genes from bacteriophage lambda strong promoters triggers the SOS response in Escherichia coli A. Arís, A. Arís Institut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainSearch for more papers by this authorJ.L. Corchero, J.L. Corchero Institut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainSearch for more papers by this authorA. Benito, A. Benito Institut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainSearch for more papers by this authorX. Carbonell, X. Carbonell Institut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainSearch for more papers by this authorE. Viaplana, E. Viaplana Institut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainSearch for more papers by this authorA. Villaverde, Corresponding Author A. Villaverde a.villaverde@cc.uab.es Institut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainInstitut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainSearch for more papers by this author A. Arís, A. Arís Institut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainSearch for more papers by this authorJ.L. Corchero, J.L. Corchero Institut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainSearch for more papers by this authorA. Benito, A. Benito Institut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainSearch for more papers by this authorX. Carbonell, X. Carbonell Institut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainSearch for more papers by this authorE. Viaplana, E. Viaplana Institut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainSearch for more papers by this authorA. Villaverde, Corresponding Author A. Villaverde a.villaverde@cc.uab.es Institut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainInstitut de Biologia Fonamental and Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, SpainSearch for more papers by this author First published: 26 March 2000 https://doi.org/10.1002/(SICI)1097-0290(19990705)64:1<127::AID-BIT14>3.0.CO;2-0Citations: 3AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume64, Issue15 July 1999Pages 127-127 RelatedInformation