88 results found
McQuail J, Carpousis AJ, Wigneshweraraj S, 2021, The association between Hfq and RNase E in long-term nitrogen-starved Escherichia coli, MOLECULAR MICROBIOLOGY, ISSN: 0950-382X
Bakovic J, Yu BYK, Silva D, et al., 2021, Redox Regulation of the Quorum-sensing Transcription Factor AgrA by Coenzyme A, ANTIOXIDANTS, Vol: 10
Zhyvoloup A, Yu BYK, Bakovic J, et al., 2020, Analysis of disulphide bond linkage between CoA and protein cysteine thiols during sporulation and in spores of Bacillus species, FEMS MICROBIOLOGY LETTERS, Vol: 367, ISSN: 0378-1097
Switzer A, Burchell L, McQuail J, et al., 2020, The adaptive response to long-term nitrogen starvation in Escherichia coli requires the breakdown of allantoin., Journal of Bacteriology, Vol: 202, Pages: 1-11, ISSN: 0021-9193
Bacteria initially respond to nutrient starvation by eliciting large-scale transcriptional changes. The accompanying changes in gene expression and metabolism allow the bacterial cells to effectively adapt to the nutrient starved state. How the transcriptome subsequently changes as nutrient starvation ensues is not well understood. We used nitrogen (N) starvation as a model nutrient starvation condition to study the transcriptional changes in Escherichia coli experiencing long-term N starvation. The results reveal that the transcriptome of N starved E. coli undergoes changes that are required to maximise chances of viability and to effectively recover growth when N starvation conditions become alleviated. We further reveal that, over time, N starved E. coli cells rely on the degradation of allantoin for optimal growth recovery when N becomes replenished. This study provides insights into the temporally coordinated adaptive responses that occur in E. coli experiencing sustained N starvation.IMPORTANCE Bacteria in their natural environments seldom encounter conditions that support continuous growth. Hence, many bacteria spend the majority of their time in states of little or no growth due to starvation of essential nutrients. To cope with prolonged periods of nutrient starvation, bacteria have evolved several strategies, primarily manifesting themselves through changes in how the information in their genes is accessed. How these coping strategies change over time under nutrient starvation is not well understood and this knowledge is not only important to broaden our understanding of bacterial cell function, but also to potentially find ways to manage harmful bacteria. This study provides insights into how nitrogen starved Escherichia coli bacteria rely on different genes during long term nitrogen starvation.
McQuail J, Switzer A, Burchell L, et al., 2020, The RNA-binding protein Hfq assembles into foci-like structures in nitrogen starved Escherichia coli, Journal of Biological Chemistry, Vol: 295, Pages: 12355-12367, ISSN: 0021-9258
The initial adaptive responses to nutrient depletion in bacteria often occur at the level of gene expression. Hfq is an RNA-binding protein present in diverse bacterial lineages and contributes to many different aspects of RNA metabolism during gene expression. Using photoactivated localization microscopy (PALM) and single molecule tracking, we demonstrate that Hfq forms a distinct and reversible focus-like structure in Escherichia coli specifically experiencing long-term nitrogen (N) starvation. Using the ability of T7 phage to replicate in N-starved bacteria as a biological probe of E. coli cell function during N starvation, we demonstrate that Hfq foci have a role in the adaptive response of E. coli to long-term N starvation. We further show that Hfq foci formation does not depend on gene expression once N starvation has set in and occurs independently of the transcription factor N-regulatory protein C (NtrC), that activates the initial adaptive response to N starvation in E. coli These results serve as a paradigm to demonstrate that bacterial adaptation to long-term nutrient starvation can be spatiotemporally coordinated and can occur independently of de novo gene expression during starvation.
Krishna A, Liu B, Peacock SJ, et al., 2020, The prevalence and implications of single-nucleotide polymorphisms in genes encoding 3 the RNA polymerase of clinical isolates of Staphylococcus aureus, MicrobiologyOpen, Vol: 9, Pages: 1-8, ISSN: 2045-8827
Central to the regulation of bacterial gene expression is the multisubunit enzyme RNA polymerase (RNAP), which is responsible for catalyzing transcription. As all adaptive processes are underpinned by changes in gene expression, the RNAP can be considered the major mediator of any adaptive response in the bacterial cell. In bacterial pathogens, theoretically, single nucleotide polymorphisms (SNPs) in genes that encode subunits of the RNAP and associated factors could mediate adaptation and confer a selective advantage to cope with biotic and abiotic stresses. We investigated this possibility by undertaking a systematic survey of SNPs in genes encoding the RNAP and associated factors in a collection of 1,429 methicillin‐resistant Staphylococcus aureus (MRSA) clinical isolates. We present evidence for the existence of several, hitherto unreported, nonsynonymous SNPs in genes encoding the RNAP and associated factors of MRSA ST22 clinical isolates and propose that the acquisition of amino acid substitutions in the RNAP could represent an adaptive strategy that contributes to the pathogenic success of MRSA.
Tabib-Salazar A, Mulvenna N, Severinov K, et al., 2019, Xenogeneic regulation of the bacterial transcription machinery, Journal of Molecular Biology, Vol: 431, Pages: 4078-4092, ISSN: 0022-2836
The parasitic life cycle of viruses involves the obligatory subversion of the host's macromolecular processes for efficient viral progeny production. Viruses that infect bacteria, bacteriophages (phages), are no exception and have evolved sophisticated ways to control essential biosynthetic machineries of their bacterial prey to benefit phage development. The xenogeneic regulation of bacterial cell function is a poorly understood area of bacteriology. The activity of the bacterial transcription machinery, the RNA polymerase (RNAP), is often regulated by a variety of mechanisms involving small phage-encoded proteins. In this review, we provide a brief overview of known phage proteins that interact with the bacterial RNAP and compare how two prototypical phages of Escherichia coli, T4 and T7, use small proteins to 'puppeteer' the bacterial RNAP to ensure a successful infection.
Mulvenna N, Hantke I, Burchell L, et al., 2019, Xenogeneic modulation of the ClpCP protease of Bacillus subtilis by a phage-encoded adaptor-like protein., Journal of Biological Chemistry, Vol: 294, Pages: 17501-17511, ISSN: 0021-9258
Like eukaryotic and archaeal viruses, which coopt the host's cellular pathways for their replication, bacteriophages have evolved strategies to alter the metabolism of their bacterial host. SPO1 bacteriophage infection of Bacillus subtilis results in a comprehensive remodelling of cellular processes leading to conversion of the bacterial cell into a factory for phage progeny production. A cluster of 26 genes in the SPO1 genome, called the host takeover module, encodes for potentially cytotoxic proteins that specifically shut down various processes in the bacterial host, including transcription, DNA synthesis, and cell division. However, the properties and bacterial targets of many genes of the SPO1 host takeover module remain elusive. Through a systematic analysis of gene products encoded by the SPO1 host takeover module, here we identified eight gene products that attenuated B. subtilis growth. Of the eight phage gene products that attenuated bacterial growth, a 25 kDa protein, called Gp53, was shown to interact with the AAA+ chaperone protein ClpC of the ClpCP protease of B. subtilis. Our results further reveal that Gp53 is a phage encoded adaptor-like protein, which modulates the activity of the ClpCP protease to enable efficient SPO1 phage progeny development. In summary, our findings indicate that the bacterial ClpCP protease is the target of xenogeneic (dys)regulation by a SPO1 phage-derived factor and add Gp53 to the list of antibacterial products that target bacterial protein degradation, which therefore may have utility for the development of novel antibacterial agents.
Switzer A, Brown D, Wigneshweraraj S, 2018, New insights into the adaptive transcriptional response to nitrogen starvation in Escherichia coli, Biochemical Society Transactions, Vol: 46, Pages: 1721-1728, ISSN: 0300-5127
Bacterial adaptive responses to biotic and abiotic stresses often involve large-scale reprogramming of the transcriptome. Since nitrogen is an essential component of the bacterial cell, the transcriptional basis of the adaptive response to nitrogen starvation has been well studied. The adaptive response to N starvation in Escherichia coli is primarily a ‘scavenging response’, which results in the transcription of genes required for the transport and catabolism of nitrogenous compounds. However, recent genome-scale studies have begun to uncover and expand some of the intricate regulatory complexities that underpin the adaptive transcriptional response to nitrogen starvation in E. coli. The purpose of this review is to highlight some of these new developments.
Krishna A, Holden M, Peacock S, et al., 2018, Naturally occurring polymorphisms in the virulence regulator Rsp modulate Staphylococcus aureus survival in blood and antibiotic susceptibility, Microbiology, Vol: 164, Pages: 1189-1195, ISSN: 1350-0872
Nasal colonization by the pathogen Staphylococcus aureus is a risk factor for subsequent infection. Loss of function mutations in the gene encoding the virulence regulator Rsp are associated with the transition of S. aureus from a colonizing isolate to one that causes bacteraemia. Here, we report the identification of several novel activity-altering mutations in rsp detected in clinical isolates, including for the first time, mutations that enhance agr operon activity. We assessed how these mutations affected infection-relevant phenotypes and found loss and enhancement of function mutations to have contrasting effects on S. aureus survival in blood and antibiotic susceptibility. These findings add to the growing body of evidence that suggests S. aureus ‘trades off’ virulence for the acquisition of traits that benefit survival in the host, and indicates that infection severity and treatment options can be significantly affected by mutations in the virulence regulator rsp.
Switzer A, Evangelopoulos D, Figueira R, et al., 2018, A novel regulatory factor affecting the transcription of methionine biosynthesis genes in Escherichia coli experiencing sustained nitrogen starvation, Microbiology, Vol: 164, Pages: 1457-1470, ISSN: 1350-0872
The initial adaptive transcriptional response to nitrogen (N) starvation in Escherichia coli involves large-scale alterations to the transcriptome mediated by the transcriptional activator, NtrC. One of these NtrC-activated genes is yeaG, which encodes a conserved bacterial kinase. Although it is known that YeaG is required for optimal survival under sustained N starvation, the molecular basis by which YeaG benefits N starved E. coli remains elusive. By combining transcriptomics with targeted metabolomics analyses, we demonstrate that the methionine biosynthesis pathway becomes transcriptionally dysregulated in ΔyeaG bacteria experiencing sustained N starvation. It appears the ability of MetJ, the master transcriptional repressor of methionine biosynthesis genes, to effectively repress transcription of genes under its control is compromised in ΔyeaG bacteria under sustained N starvation, resulting in transcriptional derepression of MetJ-regulated genes. Although the aberrant biosynthesis does not appear to be a contributing factor for the compromised viability of ΔyeaG bacteria experiencing sustained N starvation, this study identifies YeaG as a novel regulatory factor in E. coli affecting the transcription of methionine biosynthesis genes under sustained N starvation.
Liu B, Wang Z, Lan L, et al., 2018, A rapid colorimetric method to visualize protein interactions, Chemistry - A European Journal, Vol: 24, Pages: 6727-6731, ISSN: 0947-6539
As key molecules in most biological pathways, proteins physically contact one or more biomolecules in a highly specific manner. Several driving forces (i.e., electrostatic and hydrophobic) facilitate such interactions and a variety of methods have been developed to monitor these processes both in vivo and in vitro. In this work, a new method is reported for the detection of protein interactions by visualizing a color change of a cyanine compound, a supramolecule complex of 3,3-di-(3-sulfopropyl)-4,5,4',5'-dibenzo-9-methyl-thiacarbocyanine triethylammonium salt (MTC). Nuclear magnetic resonance (NMR) studies suggest that the hydrophobic nature of the protein surfaces drives MTC into different types of aggregates with distinct colors. When proteins interact with other biomolecules, the hydrophobic surface of the complex differs, resulting in a shift in the form of MTC aggregation, which results in a color change. As a result, this in vitro method has the potential to become a rapid tool for the confirmation of protein-biomolecule interactions, without the requirements for sophisticated instrumentation or approaches.
Tabib-Salazar A, Liu B, Declan B, et al., 2018, T7 phage factor required for managing RpoS in Escherichia coli, Proceedings of the National Academy of Sciences, Vol: 115, Pages: E5353-E5362, ISSN: 0027-8424
T7 development in Escherichia coli requires the inhibition of the housekeepingform of the bacterial RNA polymerase (RNAP), Eσ70, by two T7 proteins: Gp2and Gp5.7. While the biological role of Gp2 is well understood, that of Gp5.7remains to be fully deciphered. Here, we present results from functional andstructural analyses to reveal that Gp5.7 primarily serves to inhibit EσS, thepredominant form of the RNAP in the stationary phase of growth, whichaccumulates in exponentially growing E. coli as a consequence of buildup ofguanosine pentaphosphate ((p)ppGpp) during T7 development. We furtherdemonstrate a requirement of Gp5.7 for T7 development in E. coli cells in thestationary phase of growth. Our finding represents a paradigm for how somelytic phages have evolved distinct mechanisms to inhibit the bacterialtranscription machinery to facilitate phage development in bacteria in theexponential and stationary phases of growth.
Switzer A, Evangelopoulos D, Figueira R, et al., 2018, A role for a conserved kinase in the transcriptional control of methionine biosynthesis inEscherichia coliexperiencing sustained nitrogen starvation, Publisher: Cold Spring Harbor Laboratory
<jats:title>ABSTRACT</jats:title><jats:p>The initial adaptive transcriptional response to nitrogen (N) starvation in<jats:italic>Escherichia coli</jats:italic>involves large-scale alterations to the transcriptome mediated by the transcription activator, NtrC. One of the NtrC-activated genes is<jats:italic>yeaG</jats:italic>, which encodes a conserved bacterial kinase. Although it is known that YeaG is required for optimal survival under sustained N starvation, the molecular basis by which YeaG benefits N starved<jats:italic>E. coli</jats:italic>remains elusive. By combining transcriptomics with targeted metabolomics analyses, we demonstrate that the methionine biosynthesis pathway becomes transcriptionally dysregulated in<jats:italic>ΔyeaG</jats:italic>bacteria experiencing sustained N starvation. This results in the aberrant and energetically costly biosynthesis of methionine and associated metabolites under sustained N starvation with detrimental consequences to cell viability. It appears the activity of the master transcriptional repressor of methionine biosynthesis genes, MetJ, is compromised in<jats:italic>ΔyeaG</jats:italic>bacteria under sustained N starvation, resulting in transcriptional derepression of MetJ-regulated genes. The results suggest that YeaG is a novel regulatory factor and functions as a molecular brake in the transcriptional control of both the NtrC-regulon and methionine biosynthesis genes in<jats:italic>E. coli</jats:italic>experiencing sustained N starvation.</jats:p>
Duchi D, Gryte K, Robb NC, et al., 2017, Conformational heterogeneity and bubble dynamics in single bacterial transcription initiation complexes., Nucleic Acids Research, Vol: 46, Pages: 677-688, ISSN: 0305-1048
Transcription initiation is a major step in gene regulation for all organisms. In bacteria, the promoter DNA is first recognized by RNA polymerase (RNAP) to yield an initial closed complex. This complex subsequently undergoes conformational changes resulting in DNA strand separation to form a transcription bubble and an RNAP-promoter open complex; however, the series and sequence of conformational changes, and the factors that influence them are unclear. To address the conformational landscape and transitions in transcription initiation, we applied single-molecule Förster resonance energy transfer (smFRET) on immobilized Escherichia coli transcription open complexes. Our results revealed the existence of two stable states within RNAP-DNA complexes in which the promoter DNA appears to adopt closed and partially open conformations, and we observed large-scale transitions in which the transcription bubble fluctuated between open and closed states; these transitions, which occur roughly on the 0.1 s timescale, are distinct from the millisecond-timescale dynamics previously observed within diffusing open complexes. Mutational studies indicated that the σ70 region 3.2 of the RNAP significantly affected the bubble dynamics. Our results have implications for many steps of transcription initiation, and support a bend-load-open model for the sequence of transitions leading to bubble opening during open complex formation.
Sarkar P, Switzer A, Peters C, et al., 2017, Phenotypic consequences of RNA polymerase dysregulation in Escherichiacoli, Nucleic Acids Research, Vol: 45, Pages: 11131-11143, ISSN: 1362-4962
Many bacterial adaptive responses to changes in growth conditions due to biotic and abiotic factors involve reprogramming of gene expression at the transcription level. The bacterial RNA polymerase (RNAP), which catalyzes transcription, can thus be considered as the major mediator of cellular adaptive strategies. But how do bacteria respond if a stress factor directly compromises the activity of the RNAP? We used a phage-derived small protein to specifically perturb bacterial RNAP activity in exponentially growing Escherichia coli. Using cytological profiling, tracking RNAP behavior at single-molecule level and transcriptome analysis, we reveal that adaptation to conditions that directly perturb bacterial RNAP performance can result in a biphasic growth behavior and thereby confer the ‘adapted’ bacterial cells an enhanced ability to tolerate diverse antibacterial stresses. The results imply that while synthetic transcriptional rewiring may confer bacteria with the intended desirable properties, such approaches may also collaterally allow them to acquire undesirable traits.
du Plessis J, Cloete R, Burchell L, et al., 2017, Exploring the potential of T7 bacteriophage protein Gp2 as a novel inhibitor of mycobacterial RNA polymerase, Tuberculosis, Vol: 106, Pages: 82-90, ISSN: 1472-9792
Over the past six decades, there has been a decline in novel therapies to treat tuberculosis, while the causative agent of this disease has become increasingly resistant to current treatment regimens. Bacteriophages (phages) are able to kill bacterial cells and understanding this process could lead to novel insights for the treatment of mycobacterial infections. Phages inhibit bacterial gene transcription through phage-encoded proteins which bind to RNA polymerase (RNAP), thereby preventing bacterial transcription. Gp2, a T7 phage protein which binds to the beta prime (β′) subunit of RNAP in Escherichia coli, has been well characterized in this regard. Here, we aimed to determine whether Gp2 is able to inhibit RNAP in Mycobacterium tuberculosis as this may provide new possibilities for inhibiting the growth of this deadly pathogen. Results from an electrophoretic mobility shift assay and in vitro transcription assay revealed that Gp2 binds to mycobacterial RNAP and inhibits transcription; however to a much lesser degree than in E. coli. To further understand the molecular basis of these results, a series of in silico techniques were used to assess the interaction between mycobacterial RNAP and Gp2, providing valuable insight into the characteristics of this protein-protein interaction.
Sarkar P, Switzer A, Peters C, et al., 2017, Phenotypic consequences of RNA polymerase dysregulation in Escherichia coli, Publisher: Cold Spring Harbor Laboratory
<jats:title>ABSTRACT</jats:title><jats:p>Many bacterial adaptive responses to changes in growth conditions due to biotic and abiotic factors involve reprogramming of gene expression at the transcription level. The bacterial RNA polymerase (RNAP), which catalyzes transcription, can thus be considered as the major mediator of cellular adaptive strategies. But how do bacteria respond if a stress factor directly compromises the activity of the RNAP? We used a phage-derived small protein to specifically perturb bacterial RNAP activity in exponentially growing <jats:italic>Escherichia coli</jats:italic>. Using cytological profiling, tracking RNAP behavior at single-molecule level and transcriptome analysis, we reveal that adaptation to conditions that directly perturb bacterial RNAP performance can result in a biphasic growth behavior and thereby confer the ‘adapted’ bacterial cells an enhanced ability to tolerate diverse antibacterial stresses. The results imply that while synthetic transcriptional rewiring may confer bacteria with the intended desirable properties, such approaches may also collaterally allow them to acquire undesirable traits.</jats:p>
Tabib-Salazar A, Liu B, Shadrin A, et al., 2017, Full shut-off of Escherichia coli RNA-polymerase by T7 phage requires a small phage-encoded DNA-binding protein, Nucleic Acids Research, Vol: 45, Pages: 7697-7707, ISSN: 1362-4962
Infection of Escherichia coli by the T7 phage leads to rapid and selective inhibition of the bacterial RNA polymerase (RNAP) by the 7 kDa T7 protein Gp2. We describe the identification and functional and structural characterisation of a novel 7 kDa T7 protein, Gp5.7, which adopts a winged helix-turn-helix-like structure and specifically represses transcription initiation from host RNAP-dependent promoters on the phage genome via a mechanism that involves interaction with DNA and the bacterial RNAP. Whereas Gp2 is indispensable for T7 growth in E. coli, we show that Gp5.7 is required for optimal infection outcome. Our findings provide novel insights into how phages fine-tune the activity of the host transcription machinery to ensure both successful and efficient phage progeny development.
Pader V, Hakim S, Painter KL, et al., 2016, Staphylococcus aureus inactivates daptomycin by releasing membrane phospholipids, Nature Microbiology, Vol: 2, Pages: 1-8, ISSN: 2058-5276
Daptomycin is a bactericidal antibiotic of last resort for serious infections caused by methicillin-resistant Staphylococcus aureus (MRSA)1,2. Although resistance is rare, treatment failure can occur in more than 20% of cases3,4 and so there is a pressing need to identify and mitigate factors that contribute to poor therapeutic outcomes. Here, we show that loss of the Agr quorum-sensing system, which frequently occurs in clinical isolates, enhances S. aureus survival during daptomycin treatment. Wild-type S. aureus was killed rapidly by daptomycin, but Agr-defective mutants survived antibiotic exposure by releasing membrane phospholipids, which bound and inactivated the antibiotic. Although wild-type bacteria also released phospholipid in response to daptomycin, Agr-triggered secretion of small cytolytic toxins, known as phenol soluble modulins, prevented antibiotic inactivation. Phospholipid shedding by S. aureus occurred via an active process and was inhibited by the β-lactam antibiotic oxacillin, which slowed inactivation of daptomycin and enhanced bacterial killing. In conclusion, S. aureus possesses a transient defence mechanism that protects against daptomycin, which can be compromised by Agr-triggered toxin production or an existing therapeutic antibiotic.
Brown DR, Sheppard CM, Matthews S, et al., 2016, The Xp10 bacteriophage protein P7 inhibits transcription by the major and major variant forms of the host RNA polymerase via a common mechanism, Journal of Molecular Biology, Vol: 428, Pages: 3911-3919, ISSN: 1089-8638
The σ factor is a functionally obligatory subunit of the bacterial transcription machinery, the RNA polymerase. Bacteriophage-encoded small proteins that either modulate or inhibit the bacterial RNAP to allow the temporal regulation of bacteriophage gene expression often target the activity of the major bacterial σ factor, σ70. Previously, we showed that during Xanthomonas oryzae phage Xp10 infection, the phage protein P7 inhibits the host RNAP by preventing the productive engagement with the promoter and simultaneously displaces the σ70 factor from the RNAP. In this study, we demonstrate that P7 also inhibits the productive engagement of the bacterial RNAP containing the major variant bacterial σ factor, σ54, with its cognate promoter. The results suggest for the first time that the major variant form of the host RNAP can also be targeted by bacteriophage-encoded transcription regulatory proteins. Since the major and major variant σ factor interacting surfaces in the RNAP substantially overlap, but different regions of σ70 and σ54 are used for binding to the RNAP, our results further underscore the importance of the σ–RNAP interface in bacterial RNAP function and regulation and potentially for intervention by antibacterials.
Figueira R, Brown DR, Ferreira D, et al., 2015, Adaptation to sustained nitrogen starvation by Escherichia coli requires the eukaryote-like serine/ threonine kinase YeaG, Scientific Reports, Vol: 5, ISSN: 2045-2322
Thompson CC, Griffiths C, Nicod SS, et al., 2015, The Rsb phosphoregulatory network controls availability of the primary sigma factor in Chlamydia trachomatis and influences the kinetics of growth and development, PLOS Pathogens, Vol: 11, Pages: 1-22, ISSN: 1553-7366
Chlamydia trachomatis is the leading cause of both bacterial sexually transmitted infection and infection-derived blindness world-wide. No vaccine has proven protective to date in humans. C. trachomatis only replicates from inside a host cell, and has evolved to acquire a variety of nutrients directly from its host. However, a typical human immune response will normally limit the availability of a variety of essential nutrients. Thus, it is thought that the success of C. trachomatis as a human pathogen may lie in its ability to survive these immunological stress situations by slowing growth and development until conditions in the cell have improved. This mode of growth is known as persistence and how C. trachomatis senses stress and responds in this manner is an important area of research. Our report characterizes a complete signaling module, the Rsb network, that is capable of controlling the growth rate or infectivity of Chlamydia. By manipulating the levels of different pathway components, we were able to accelerate and restrict the growth and development of this pathogen. Our results suggest a mechanism by which Chlamydia can tailor its growth rate to the conditions within the host cell. The disruption of this pathway could generate a strain incapable of surviving a typical human immune response and would represent an attractive candidate as an attenuated growth vaccine.
Thomas MS, Wigneshweraraj S, 2014, Regulation of virulence gene expression, VIRULENCE, Vol: 5, Pages: 832-834, ISSN: 2150-5594
Nicod SS, Weinzierl RO, Burchell L, et al., 2014, Systematic mutational analysis of the LytTR DNA binding domain of Staphylococcus aureus virulence gene transcription factor AgrA, Nucleic Acids Research, Vol: 42, Pages: 12523-12536, ISSN: 1362-4962
Most DNA-binding bacterial transcription factors contact DNA through a recognition α-helix in their DNA-binding domains. An emerging class of DNA-binding transcription factors, predominantly found in pathogenic bacteria interact with the DNA via a relatively novel type of DNA-binding domain, called the LytTR domain, which mainly comprises β strands. Even though the crystal structure of the LytTR domain of the virulence gene transcription factor AgrA from Staphylococcus aureus bound to its cognate DNA sequence is available, the contribution of specific amino acid residues in the LytTR domain of AgrA to transcription activation remains elusive. Here, for the first time, we have systematically investigated the role of amino acid residues in transcription activation in a LytTR domain-containing transcription factor. Our analysis, which involves in vivo and in vitro analyses and molecular dynamics simulations of S. aureus AgrA identifies a highly conserved tyrosine residue, Y229, as a major amino acid determinant for maximal activation of transcription by AgrA and provides novel insights into structure-function relationships in S. aureus AgrA.
Painter KL, Krishna A, Wigneshweraraj S, et al., 2014, What role does the quorum-sensing accessory gene regulator system play during Staphylococcus aureus bacteremia?, Trends in Microbiology, Vol: In Press, ISSN: 0966-842X
Brown DR, Barton G, Pan Z, et al., 2014, Combinatorial stress responses: direct coupling of two major stress responses in Escherichia coli, Microbial Cell, Vol: 1, Pages: 315-317, ISSN: 2311-2638
Nitrogen is an essential element for all life, and this isno different for the bacterial cell. Numerous cellularmacromolecules contain nitrogen, including proteins,nucleic acids and cell wall components. In Escherichiacoli and related bacteria, the nitrogen stress (Ntr) responseallows cells to rapidly sense and adapt to nitrogenlimitation by scavenging for alternative nitrogensources through the transcriptional activation oftransport systems and catabolic and biosynthetic operonsby the global transcriptional regulator NtrC. Nitrogen-starvedbacterial cells also synthesize the(p)ppGpp effector molecules of a second global bacterialstress response - the stringent response. Recently,we showed that the transcription of relA, the genewhich encodes the major (p)ppGpp synthetase in E.coli, is activated by NtrC during nitrogen starvation.Our results revealed that in E. coli and related bacteria,NtrC functions in combinatorial stress and serves tocouple two major stress responses, the Ntr responseand stringent response.
Brown DR, Barton G, Pan Z, et al., 2014, Nitrogen stress response and stringent response are coupled in Escherichia coli, Nature Communications, Vol: 5, ISSN: 2041-1723
Assimilation of nitrogen is an essential process in bacteria. The nitrogen regulation stress response is an adaptive mechanism used by nitrogen-starved Escherichia coli to scavenge for alternative nitrogen sources and requires the global transcriptional regulator NtrC. In addition, nitrogen-starved E. coli cells synthesize a signal molecule, guanosine tetraphosphate (ppGpp), which serves as an effector molecule of many processes including transcription to initiate global physiological changes, collectively termed the stringent response. The regulatory mechanisms leading to elevated ppGpp levels during nutritional stresses remain elusive. Here, we show that transcription of relA, a key gene responsible for the synthesis of ppGpp, is activated by NtrC during nitrogen starvation. The results reveal that NtrC couples these two major bacterial stress responses to manage conditions of nitrogen limitation, and provide novel mechanistic insights into how a specific nutritional stress leads to elevating ppGpp levels in bacteria.
Sharma A, Leach RN, Gell C, et al., 2014, Domain movements of the enhancer-dependent sigma factor drive DNA delivery into the RNA polymerase active site: insights from single molecule studies, NUCLEIC ACIDS RESEARCH, Vol: 42, Pages: 5177-5190, ISSN: 0305-1048
Liu B, Shadrin A, Sheppard C, et al., 2014, A bacteriophage transcription regulator inhibits bacterial transcription initiation by Sigma-factor displacement, Nucleic Acids Research, Vol: 42, Pages: 4294-4305, ISSN: 0305-1048
Bacteriophages (phages) appropriate essential processes of bacterial hosts to benefit their own development. The multisubunit bacterial RNA polymerase (RNAp) enzyme, which catalyses DNA transcription, is targeted by phage-encoded transcription regulators that selectively modulate its activity. Here, we describe the structural and mechanistic basis for the inhibition of bacterial RNAp by the transcription regulator P7 encoded by Xanthomonas oryzae phage Xp10. We reveal that P7 uses a two-step mechanism to simultaneously interact with the catalytic β and β’ subunits of the bacterial RNAp and inhibits transcription initiation by inducing the displacement of the σ70-factor on initial engagement of RNAp with promoter DNA. The new mode of interaction with and inhibition mechanism of bacterial RNAp by P7 underscore the remarkable variety of mechanisms evolved by phages to interfere with host transcription.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.