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Kiran K, Patil KN. Characterization of Staphylococcus aureus RecX protein: Molecular insights into negative regulation of RecA protein and implications in HR processes. J Biochem 2023; 174:227-237. [PMID: 37115499 DOI: 10.1093/jb/mvad039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 04/11/2023] [Accepted: 04/17/2023] [Indexed: 04/29/2023] Open
Abstract
Homologous recombination (HR) is essential for genome stability and for maintaining genetic diversity. In eubacteria, RecA protein plays a key role during DNA repair, transcription, and HR. RecA is regulated at multiple levels, but majorly by RecX protein. Moreover, studies have shown RecX is a potent inhibitor of RecA and thus acts as an antirecombinase. Staphylococcus aureus is a major food-borne pathogen that causes skin, bone joint, and bloodstream infections. To date, RecX's role in S. aureus has remained enigmatic. Here, we show that S. aureus RecX (SaRecX) is expressed during exposure to DNA-damaging agents, and purified RecX protein directly interacts physically with RecA protein. The SaRecX is competent to bind with single-stranded DNA preferentially and double-stranded DNA feebly. Significantly, SaRecX impedes the RecA-driven displacement loop and inhibits formation of the strand exchange. Notably, SaRecX also abrogates adenosine triphosphate hydrolysis and abolishes the LexA coprotease activity. These findings highlight the role of the RecX protein as an antirecombinase during HR and play a pivotal role in regulation of RecA during the DNA transactions.
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Affiliation(s)
- Kajal Kiran
- Department of Microbiology and Fermentation Technology, Council of Scientific and Industrial Research-Central Food Technological Research Institute (CSIR-CFTRI), Mysuru 570 020, Karnataka, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, Uttar Pradesh, India
| | - K Neelakanteshwar Patil
- Department of Microbiology and Fermentation Technology, Council of Scientific and Industrial Research-Central Food Technological Research Institute (CSIR-CFTRI), Mysuru 570 020, Karnataka, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, Uttar Pradesh, India
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2
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Piccinini L, Iacopino S, Cazzaniga S, Ballottari M, Giuntoli B, Licausi F. A synthetic switch based on orange carotenoid protein to control blue-green light responses in chloroplasts. PLANT PHYSIOLOGY 2022. [PMID: 35289909 DOI: 10.1101/2021.01.27.428448] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Synthetic biology approaches to engineer light-responsive systems are widely used, but their applications in plants are still limited due to the interference with endogenous photoreceptors and the intrinsic requirement of light for photosynthesis. Cyanobacteria possess a family of soluble carotenoid-associated proteins named orange carotenoid proteins (OCPs) that, when activated by blue-green light, undergo a reversible conformational change that enables the photoprotection mechanism that occurs on the phycobilisome. Exploiting this system, we developed a chloroplast-localized synthetic photoswitch based on a protein complementation assay where two nanoluciferase fragments were fused to separate polypeptides corresponding to the OCP2 domains. Since Arabidopsis (Arabidopsis thaliana) does not possess the prosthetic group needed for the assembly of the OCP2 complex, we first implemented the carotenoid biosynthetic pathway with a bacterial β-carotene ketolase enzyme (crtW) to generate keto-carotenoid-producing plants. The photoswitch was tested and characterized in Arabidopsis protoplasts and stably transformed plants with experiments aimed to uncover its regulation by a range of light intensities, wavelengths, and its conversion dynamics. Finally, we applied the OCP-based photoswitch to control transcriptional responses in chloroplasts in response to green light illumination by fusing the two OCP fragments with the plastidial SIGMA FACTOR 2 and bacteriophage T4 anti-sigma factor AsiA. This pioneering study establishes the basis for future implementation of plastid optogenetics to regulate organelle responses upon exposure to specific light spectra.
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Affiliation(s)
- Luca Piccinini
- Plantlab, Institute of Life Sciences, Scuola Superiore Sant'Anna, Pisa 56127, Italy
| | - Sergio Iacopino
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
| | - Stefano Cazzaniga
- Department of Biotechnology, University of Verona, Verona 37134, Italy
| | - Matteo Ballottari
- Department of Biotechnology, University of Verona, Verona 37134, Italy
| | - Beatrice Giuntoli
- Plantlab, Institute of Life Sciences, Scuola Superiore Sant'Anna, Pisa 56127, Italy
- Department of Biology, University of Pisa, Pisa 56126, Italy
| | - Francesco Licausi
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
- Department of Biology, University of Pisa, Pisa 56126, Italy
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3
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Piccinini L, Iacopino S, Cazzaniga S, Ballottari M, Giuntoli B, Licausi F. A synthetic switch based on orange carotenoid protein to control blue-green light responses in chloroplasts. PLANT PHYSIOLOGY 2022; 189:1153-1168. [PMID: 35289909 PMCID: PMC9157063 DOI: 10.1093/plphys/kiac122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 02/20/2022] [Indexed: 05/11/2023]
Abstract
Synthetic biology approaches to engineer light-responsive systems are widely used, but their applications in plants are still limited due to the interference with endogenous photoreceptors and the intrinsic requirement of light for photosynthesis. Cyanobacteria possess a family of soluble carotenoid-associated proteins named orange carotenoid proteins (OCPs) that, when activated by blue-green light, undergo a reversible conformational change that enables the photoprotection mechanism that occurs on the phycobilisome. Exploiting this system, we developed a chloroplast-localized synthetic photoswitch based on a protein complementation assay where two nanoluciferase fragments were fused to separate polypeptides corresponding to the OCP2 domains. Since Arabidopsis (Arabidopsis thaliana) does not possess the prosthetic group needed for the assembly of the OCP2 complex, we first implemented the carotenoid biosynthetic pathway with a bacterial β-carotene ketolase enzyme (crtW) to generate keto-carotenoid-producing plants. The photoswitch was tested and characterized in Arabidopsis protoplasts and stably transformed plants with experiments aimed to uncover its regulation by a range of light intensities, wavelengths, and its conversion dynamics. Finally, we applied the OCP-based photoswitch to control transcriptional responses in chloroplasts in response to green light illumination by fusing the two OCP fragments with the plastidial SIGMA FACTOR 2 and bacteriophage T4 anti-sigma factor AsiA. This pioneering study establishes the basis for future implementation of plastid optogenetics to regulate organelle responses upon exposure to specific light spectra.
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Affiliation(s)
- Luca Piccinini
- Plantlab, Institute of Life Sciences, Scuola Superiore Sant’Anna, Pisa 56127, Italy
| | - Sergio Iacopino
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
| | - Stefano Cazzaniga
- Department of Biotechnology, University of Verona, Verona 37134, Italy
| | - Matteo Ballottari
- Department of Biotechnology, University of Verona, Verona 37134, Italy
| | - Beatrice Giuntoli
- Plantlab, Institute of Life Sciences, Scuola Superiore Sant’Anna, Pisa 56127, Italy
- Department of Biology, University of Pisa, Pisa 56126, Italy
| | - Francesco Licausi
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
- Department of Biology, University of Pisa, Pisa 56126, Italy
- Author for correspondence:
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4
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Liu Y, Wang B. A Novel Eukaryote-Like CRISPR Activation Tool in Bacteria: Features and Capabilities. Bioessays 2020; 42:e1900252. [PMID: 32310310 DOI: 10.1002/bies.201900252] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 03/03/2020] [Indexed: 11/09/2022]
Abstract
CRISPR (clustered regularly interspaced short palindromic repeats) activation (CRISPRa) in bacteria is an attractive method for programmable gene activation. Recently, a eukaryote-like, σ54 -dependent CRISPRa system has been reported. It exhibits high dynamic ranges and permits flexible target site selection. Here, an overview of the existing strategies of CRISPRa in bacteria is presented, and the characteristics and design principles of the CRISPRa system are introduced. Possible scenarios for applying the eukaryote-like CRISPRa system is discussed with corresponding suggestions for performance optimization and future functional expansion. The authors envision the new eukaryote-like CRISPRa system enabling novel designs in multiplexed gene regulation and promoting research in the σ54 -dependent gene regulatory networks among a variety of biotechnology relevant or disease-associated bacterial species.
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Affiliation(s)
- Yang Liu
- School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3FF, UK.,Centre for Synthetic and Systems Biology, University of Edinburgh, Edinburgh, EH9 3FF, UK
| | - Baojun Wang
- School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3FF, UK.,Centre for Synthetic and Systems Biology, University of Edinburgh, Edinburgh, EH9 3FF, UK
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5
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Shi J, Wen A, Zhao M, You L, Zhang Y, Feng Y. Structural basis of σ appropriation. Nucleic Acids Res 2019; 47:9423-9432. [PMID: 31392983 PMCID: PMC6755090 DOI: 10.1093/nar/gkz682] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/23/2019] [Accepted: 07/26/2019] [Indexed: 01/25/2023] Open
Abstract
Bacteriophage T4 middle promoters are activated through a process called σ appropriation, which requires the concerted effort of two T4-encoded transcription factors: AsiA and MotA. Despite extensive biochemical and genetic analyses, puzzle remains, in part, because of a lack of precise structural information for σ appropriation complex. Here, we report a single-particle cryo-electron microscopy (cryo-EM) structure of an intact σ appropriation complex, comprising AsiA, MotA, Escherichia coli RNA polymerase (RNAP), σ70 and a T4 middle promoter. As expected, AsiA binds to and remodels σ region 4 to prevent its contact with host promoters. Unexpectedly, AsiA undergoes a large conformational change, takes over the job of σ region 4 and provides an anchor point for the upstream double-stranded DNA. Because σ region 4 is conserved among bacteria, other transcription factors may use the same strategy to alter the landscape of transcription immediately. Together, the structure provides a foundation for understanding σ appropriation and transcription activation.
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Affiliation(s)
- Jing Shi
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Aijia Wen
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
| | - Minxing Zhao
- Department of Emergency Medicine of the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China
| | - Linlin You
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yu Zhang
- Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China
| | - Yu Feng
- Department of Biophysics, and Department of Pathology of Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China
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6
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Zhu K, Shao M, Zhou D, Xing YX, Yang LT, Li YR. Functional analysis of Leifsonia xyli subsp. xyli membrane protein gene Lxx18460 (anti-sigma K). BMC Microbiol 2019; 19:2. [PMID: 30616519 PMCID: PMC6323826 DOI: 10.1186/s12866-018-1378-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 12/19/2018] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Sugarcane is an important sugar and economic crop in the world. Ratoon stunting Disease (RSD) of sugarcane, caused by Leifsonia xyli subsp. xyli, is widespread in countries and regions where sugarcane is grown and also limited to sugarcane productivity. Although the whole genome sequencing of Leifsonia xyli subsp. xyli was completed, progress in understanding the molecular mechanism of the disease has been slow because it is difficult to grow in culture. RESULTS The Leifsonia xyli subsp. xyli membrane protein gene Lxx18460 (anti-sigma K) was cloned from the Lxx-infected sugarcane cultivar GT11 at the mature stage using RT-PCR technique, and the gene structure and expression in infected sugarcane were analyzed. The Lxx18460 gene was transformed into Nicotiana tabacum by Agrobacterium tumefaciens-mediation. The transgenic tobacco plants overexpressing Lxx18460 had lower levels in plant height, leaf area, net photosynthetic rate and endogenous hormones of IAA, ABA and GA3, as well as lower activities of three antioxidant enzymes, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) than the wild type (WT) tobacco. With the plant growth, the expression of Lxx18460 gene and protein was increased. To better understand the regulation of Lxx18460 expression, transcriptome analysis of leaves from transgenic and wild type tobacco was performed. A total of 60,222 all-unigenes were obtained through BGISEQ-500 sequencing. Compared the transgenic plants with the WT plants, 11,696 upregulated and 5949 downregulated genes were identified. These differentially expressed genes involved in many metabolic pathways including signal transduction, biosynthesis of other secondary metabolism, carbohydrate metabolism and so on. Though the data presented here are from a heterologous system, Lxx 18460 has an adverse impact on the growth of tobacco; it reduces the photosynthesis of tobacco, destroys the activity of defense enzymes, and affects the levels of endogenous hormones, which indicate that Lxx18460 may act important roles in the course of infection in sugarcane. CONCLUSIONS This is the first study on analyzing the function of the membrane protein gene Lxx18460 of anti-sigma K (σK) factor in Leifsonia xyli subsp. xyli. Our findings will improve the understanding of the interaction between the RSD pathogen Leifsonia xyli subsp. xyli and sugarcane. The output of this study will also be helpful to explore the pathogenesis of RSD.
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Affiliation(s)
- Kai Zhu
- College of Agriculture, State Key Laboratory of Conservation and Utilization of Subtropical Agro-bio resources, Guangxi University, Nanning, 530005 China
| | - Min Shao
- College of Agriculture, State Key Laboratory of Conservation and Utilization of Subtropical Agro-bio resources, Guangxi University, Nanning, 530005 China
| | - Dan Zhou
- College of Agriculture, State Key Laboratory of Conservation and Utilization of Subtropical Agro-bio resources, Guangxi University, Nanning, 530005 China
| | - Yong-Xiu Xing
- College of Agriculture, State Key Laboratory of Conservation and Utilization of Subtropical Agro-bio resources, Guangxi University, Nanning, 530005 China
| | - Li-Tao Yang
- College of Agriculture, State Key Laboratory of Conservation and Utilization of Subtropical Agro-bio resources, Guangxi University, Nanning, 530005 China
- Ministry of Agriculture Key Laboratory of Sugarcane Biotechnology and Genetic Improvement (Guangxi), Guangxi Key Laboratory of Sugarcane Genetic Improvement, Sugarcane Research Center, Chinese Academy of Agricultural Sciences-Guangxi Academy of Agricultural Sciences, Nanning, 530007 China
| | - Yang-Rui Li
- College of Agriculture, State Key Laboratory of Conservation and Utilization of Subtropical Agro-bio resources, Guangxi University, Nanning, 530005 China
- Ministry of Agriculture Key Laboratory of Sugarcane Biotechnology and Genetic Improvement (Guangxi), Guangxi Key Laboratory of Sugarcane Genetic Improvement, Sugarcane Research Center, Chinese Academy of Agricultural Sciences-Guangxi Academy of Agricultural Sciences, Nanning, 530007 China
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7
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The E. coli anti-sigma factor Rsd: studies on the specificity and regulation of its expression. PLoS One 2011; 6:e19235. [PMID: 21573101 PMCID: PMC3089606 DOI: 10.1371/journal.pone.0019235] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Accepted: 03/23/2011] [Indexed: 12/31/2022] Open
Abstract
Background Among the seven different sigma factors in E. coli σ70 has the highest concentration and affinity for the core RNA polymerase. The E. coli protein Rsd is regarded as an anti-sigma factor, inhibiting σ70-dependent transcription at the onset of stationary growth. Although binding of Rsd to σ70 has been shown and numerous structural studies on Rsd have been performed the detailed mechanism of action is still unknown. Methodology/Principal Findings We have performed studies to unravel the function and regulation of Rsd expression in vitro and in vivo. Cross-linking and affinity binding revealed that Rsd is able to interact with σ70, with the core enzyme of RNA polymerase and is able to form dimers in solution. Unexpectedly, we find that Rsd does also interact with σ38, the stationary phase-specific sigma factor. This interaction was further corroborated by gel retardation and footprinting studies with different promoter fragments and σ38- or σ70-containing RNA polymerase in presence of Rsd. Under competitive in vitro transcription conditions, in presence of both sigma factors, a selective inhibition of σ70-dependent transcription was prevailing, however. Analysis of rsd expression revealed that the nucleoid-associated proteins H-NS and FIS, StpA and LRP bind to the regulatory region of the rsd promoters. Furthermore, the major promoter P2 was shown to be down-regulated in vivo by RpoS, the stationary phase-specific sigma factor and the transcription factor DksA, while induction of the stringent control enhanced rsd promoter activity. Most notably, the dam-dependent methylation of a cluster of GATC sites turned out to be important for efficient rsd transcription. Conclusions/Significance The results contribute to a better understanding of the intricate mechanism of Rsd-mediated sigma factor specificity changes during stationary phase.
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8
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Hinton DM. Transcriptional control in the prereplicative phase of T4 development. Virol J 2010; 7:289. [PMID: 21029433 PMCID: PMC2988021 DOI: 10.1186/1743-422x-7-289] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Accepted: 10/28/2010] [Indexed: 12/18/2022] Open
Abstract
Control of transcription is crucial for correct gene expression and orderly development. For many years, bacteriophage T4 has provided a simple model system to investigate mechanisms that regulate this process. Development of T4 requires the transcription of early, middle and late RNAs. Because T4 does not encode its own RNA polymerase, it must redirect the polymerase of its host, E. coli, to the correct class of genes at the correct time. T4 accomplishes this through the action of phage-encoded factors. Here I review recent studies investigating the transcription of T4 prereplicative genes, which are expressed as early and middle transcripts. Early RNAs are generated immediately after infection from T4 promoters that contain excellent recognition sequences for host polymerase. Consequently, the early promoters compete extremely well with host promoters for the available polymerase. T4 early promoter activity is further enhanced by the action of the T4 Alt protein, a component of the phage head that is injected into E. coli along with the phage DNA. Alt modifies Arg265 on one of the two α subunits of RNA polymerase. Although work with host promoters predicts that this modification should decrease promoter activity, transcription from some T4 early promoters increases when RNA polymerase is modified by Alt. Transcription of T4 middle genes begins about 1 minute after infection and proceeds by two pathways: 1) extension of early transcripts into downstream middle genes and 2) activation of T4 middle promoters through a process called sigma appropriation. In this activation, the T4 co-activator AsiA binds to Region 4 of σ⁷⁰, the specificity subunit of RNA polymerase. This binding dramatically remodels this portion of σ⁷⁰, which then allows the T4 activator MotA to also interact with σ⁷⁰. In addition, AsiA restructuring of σ⁷⁰ prevents Region 4 from forming its normal contacts with the -35 region of promoter DNA, which in turn allows MotA to interact with its DNA binding site, a MotA box, centered at the -30 region of middle promoter DNA. T4 sigma appropriation reveals how a specific domain within RNA polymerase can be remolded and then exploited to alter promoter specificity.
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Affiliation(s)
- Deborah M Hinton
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Building 8, Room 2A-13, Bethesda, MD 20892-0830, USA.
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9
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Gilmore JM, Bieber Urbauer RJ, Minakhin L, Akoyev V, Zolkiewski M, Severinov K, Urbauer JL. Determinants of affinity and activity of the anti-sigma factor AsiA. Biochemistry 2010; 49:6143-54. [PMID: 20545305 DOI: 10.1021/bi1002635] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The AsiA protein is a T4 bacteriophage early gene product that regulates transcription of host and viral genes. Monomeric AsiA binds tightly to the sigma(70) subunit of Escherichia coli RNA polymerase, thereby inhibiting transcription from bacterial promoters and phage early promoters and coactivating transcription from phage middle promoters. Results of structural studies have identified amino acids at the protomer-protomer interface in dimeric AsiA and at the monomeric AsiA-sigma(70) interface and demonstrated substantial overlap in the sets of residues that comprise each. Here we evaluate the contributions of individual interfacial amino acid side chains to protomer-protomer affinity in AsiA homodimers, to monomeric AsiA affinity for sigma(70), and to AsiA function in transcription. Sedimentation equilibrium, dynamic light scattering, electrophoretic mobility shift, and transcription activity measurements were used to assess affinity and function of site-specific AsiA mutants. Alanine substitutions for solvent-inaccessible residues positioned centrally in the protomer-protomer interface of the AsiA homodimer, V14, I17, and I40, resulted in the largest changes in free energy of dimer association, whereas alanine substitutions at other interfacial positions had little effect. These residues also contribute significantly to AsiA-dependent regulation of RNA polymerase activity, as do additional residues positioned at the periphery of the interface (K20 and F21). Notably, the relative contributions of a given amino acid side chain to RNA polymerase inhibition and activation (MotA-independent) by AsiA are very similar in most cases. The mainstay for intermolecular affinity and AsiA function appears to be I17. Our results define the core interfacial residues of AsiA, establish roles for many of the interfacial amino acids, are in agreement with the tenets underlying protein-protein interactions and interfaces, and will be beneficial for a general, comprehensive understanding of the mechanistic underpinnings of bacterial RNA polymerase regulation.
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Affiliation(s)
- Joshua M Gilmore
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, USA
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10
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Greenstein AE, Hammel M, Cavazos A, Alber T. Interdomain communication in the Mycobacterium tuberculosis environmental phosphatase Rv1364c. J Biol Chem 2009; 284:29828-35. [PMID: 19700407 DOI: 10.1074/jbc.m109.056168] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
An "environmental phosphatase" controls bacterial transcriptional responses through alternative sigma factor subunits of RNA polymerase and a partner switching mechanism has been proposed to mediate phosphatase regulation. In many bacteria, the environmental phosphatase and multiple regulators are encoded in separate genes whose products form transient complexes. In contrast, in the Mycobacterium tuberculosis homolog, Rv1364c, the phosphatase is fused to two characteristic regulatory modules with sequence similarities to anti-sigma factor kinases and anti-anti-sigma factor proteins. Here we exploit this fusion to explore interactions between the phosphatase and the regulatory domains. We show quantitatively that the anti-sigma factor kinase domain activates the phosphatase domain, the kinase-phosphatase fusion protein autophosphorylates in Escherichia coli, and phosphorylation is antagonized by the phosphatase activity. Small angle x-ray scattering defines solution structures consistent with the interdomain communication observed biochemically. Taken together, these data indicate that Rv1364c provides a single chain framework to understand the structure, function, and regulation of environmental phosphatases throughout the bacterial kingdom.
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Affiliation(s)
- Andrew E Greenstein
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3220, USA
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11
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Patikoglou GA, Westblade LF, Campbell EA, Lamour V, Lane WJ, Darst SA. Crystal structure of the Escherichia coli regulator of sigma70, Rsd, in complex with sigma70 domain 4. J Mol Biol 2007; 372:649-59. [PMID: 17681541 PMCID: PMC2083641 DOI: 10.1016/j.jmb.2007.06.081] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2007] [Revised: 06/19/2007] [Accepted: 06/28/2007] [Indexed: 10/23/2022]
Abstract
The Escherichia coli Rsd protein binds tightly and specifically to the RNA polymerase (RNAP) sigma(70) factor. Rsd plays a role in alternative sigma factor-dependent transcription by biasing the competition between sigma(70) and alternative sigma factors for the available core RNAP. Here, we determined the 2.6 A-resolution X-ray crystal structure of Rsd bound to sigma(70) domain 4 (sigma(70)(4)), the primary determinant for Rsd binding within sigma(70). The structure reveals that Rsd binding interferes with the two primary functions of sigma(70)(4), core RNAP binding and promoter -35 element binding. Interestingly, the most highly conserved Rsd residues form a network of interactions through the middle of the Rsd structure that connect the sigma(70)(4)-binding surface with three cavities exposed on distant surfaces of Rsd, suggesting functional coupling between sigma(70)(4) binding and other binding surfaces of Rsd, either for other proteins or for as yet unknown small molecule effectors. These results provide a structural basis for understanding the role of Rsd, as well as its ortholog, AlgQ, a positive regulator of Pseudomonas aeruginosa virulence, in transcription regulation.
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12
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Pons T, González B, Ceciliani F, Galizzi A. FlgM anti-sigma factors: identification of novel members of the family, evolutionary analysis, homology modeling, and analysis of sequence-structure-function relationships. J Mol Model 2006; 12:973-83. [PMID: 16673084 DOI: 10.1007/s00894-005-0096-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2005] [Accepted: 12/02/2005] [Indexed: 10/24/2022]
Abstract
FlgM proteins, also known as Anti-sigma-28 factor (sigma28), are negative regulators of flagellin synthesis. Recently, a three-dimensional structure of the Aquifex aeolicus sigma28/FlgM complex (PDB code: 1rp3) was determined by X-ray crystallography at 2.3 A resolution. Furthermore, experimental data on bacterial FlgM, including site-directed mutagenesis and structural characterization by NMR are also available. However, an interpretation of the sequence-structure-function relationships combining X-ray and NMR data with the evolutionary information extracted from the increasing number of FlgM-related sequences annotated in databases is not available. In the present study, we combined database sequence searches and sequence-analysis tools to update the multiple sequence alignment of a previously characterized cluster of orthologs (COG2747) and the PFAM classification of protein domains (PF04316) for the FlgM family. A phylogenetic analysis of 77 protein sequences revealed the presence of at least three major sequence clades within the FlgM family. Besides, we predicted functional residues using a SequenceSpace method. We also generated homology models for Bacillus subtilis and Salmonella typhimurium FlgM proteins, for which sequence-structure-function relationship data are available, and used the docking program ClusPro to hypothesize about the dimer association between FlgM proteins. In conclusion, the analysis presented in this work will be useful in designing new experiments to understand better protein-protein interactions between FglM, sigma factors, and putative molecules from the flagellar export apparatus. Electronic Supplementary Material is available in the online version of this article at http://link.springer.de/
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Affiliation(s)
- T Pons
- Centro de Ingeniería Genética y Biotecnología, Havana, 10600, Cuba.
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13
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Nabuurs SB, Spronk CAEM, Vuister GW, Vriend G. Traditional biomolecular structure determination by NMR spectroscopy allows for major errors. PLoS Comput Biol 2006; 2:e9. [PMID: 16462939 PMCID: PMC1359070 DOI: 10.1371/journal.pcbi.0020009] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2005] [Accepted: 12/29/2005] [Indexed: 12/04/2022] Open
Abstract
One of the major goals of structural genomics projects is to determine the three-dimensional structure of representative members of as many different fold families as possible. Comparative modeling is expected to fill the remaining gaps by providing structural models of homologs of the experimentally determined proteins. However, for such an approach to be successful it is essential that the quality of the experimentally determined structures is adequate. In an attempt to build a homology model for the protein dynein light chain 2A (DLC2A) we found two potential templates, both experimentally determined nuclear magnetic resonance (NMR) structures originating from structural genomics efforts. Despite their high sequence identity (96%), the folds of the two structures are markedly different. This urged us to perform in-depth analyses of both structure ensembles and the deposited experimental data, the results of which clearly identify one of the two models as largely incorrect. Next, we analyzed the quality of a large set of recent NMR-derived structure ensembles originating from both structural genomics projects and individual structure determination groups. Unfortunately, a visual inspection of structures exhibiting lower quality scores than DLC2A reveals that the seriously flawed DLC2A structure is not an isolated incident. Overall, our results illustrate that the quality of NMR structures cannot be reliably evaluated using only traditional experimental input data and overall quality indicators as a reference and clearly demonstrate the urgent need for a tight integration of more sophisticated structure validation tools in NMR structure determination projects. In contrast to common methodologies where structures are typically evaluated as a whole, such tools should preferentially operate on a per-residue basis. Three-dimensional biomolecular structures provide an invaluable source of biologically relevant information. To be able to learn the most of the wealth of information that these structures can provide us, it is of great importance that the quality and accuracy of the protein structure models deposited in the Protein Data Bank are as high as possible. In this work, the authors describe an analysis that illustrates that this is unfortunately not the case for many protein structures solved using nuclear magnetic resonance spectroscopy. They present an example in which two strikingly different models describing the same protein are analyzed using commonly available structure validation tools, and the results of this analysis show one of the two models to be incorrect. Subsequently, using a large set of recently determined structures, the authors demonstrate that unfortunately this example does not stand on its own. The analyses and examples clearly illustrate that relying solely on the experimental data to evaluate structural quality can provide a false sense of correctness and the combination of multiple sophisticated structure validation tools is required to detect the presence of errors in protein nuclear magnetic resonance structures.
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Affiliation(s)
- Sander B Nabuurs
- Center for Molecular and Biomolecular Informatics, Nijmegen Center for Molecular Life Sciences, Radboud University, Nijmegen, Netherlands
| | - Chris A. E. M Spronk
- Center for Molecular and Biomolecular Informatics, Nijmegen Center for Molecular Life Sciences, Radboud University, Nijmegen, Netherlands
| | - Geerten W Vuister
- Department of Biophysical Chemistry, Institute for Molecules and Materials, Radboud University, Nijmegen, Netherlands
- * To whom correspondence should be addressed. E-mail: (GWV); (GV)
| | - Gert Vriend
- Center for Molecular and Biomolecular Informatics, Nijmegen Center for Molecular Life Sciences, Radboud University, Nijmegen, Netherlands
- * To whom correspondence should be addressed. E-mail: (GWV); (GV)
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14
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Bieber Urbauer RJ, Gilmore JM, Rosasco SE, Hattle JM, Cowley AB, Urbauer JL. Cloning, high yield overexpression, purification, and characterization of AlgH, a regulator of alginate biosynthesis in Pseudomonas aeruginosa. Protein Expr Purif 2005; 43:57-64. [PMID: 16084397 DOI: 10.1016/j.pep.2005.02.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2005] [Revised: 02/20/2005] [Accepted: 02/24/2005] [Indexed: 10/25/2022]
Abstract
The most common cause of mortality among cystic fibrosis sufferers is infection by antibiotic resistant strains of Pseudomonas aeruginosa. Means to control these strains continue to be an important goal. An integral component of the ability of many of these strains to defy antibiotic therapies is the protection afforded by the mucoexopolysaccharide alginate. Production of alginate by P. aeruginosa is tightly regulated at the transcriptional level. AlgH, a putative transcriptional regulator, is involved in regulating alginate biosynthesis as well as nucleoside diphosphate kinase activity and succinyl coenzyme A synthetase activity in P. aeruginosa. Sequence homologues are found in many bacterial species. Here, we describe a method for high level overexpression and high yield/high purity production of AlgH for biophysical and functional studies. The algH gene was cloned and AlgH was overexpressed in Escherichia coli using a commercially available vector with an inducible T7 promoter. We purified the recombinantly produced protein using a rapid classical purification scheme. The yield of purified protein, either isotopically labeled for NMR studies or unlabeled, is excellent (30-37 mg of purified protein per liter of minimal media culture), as is the purity (>95% pure). Analysis of the secondary structure using circular dichroism and NMR indicates that the protein is comprised of both beta-sheet and alpha-helical secondary structural elements. Heteronuclear NMR spectra indicate that AlgH is a monodisperse, folded globular protein. This rapid, high yield, and high purity method for AlgH production will permit further biophysical characterization of this protein including high resolution structural studies.
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Affiliation(s)
- Ramona J Bieber Urbauer
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602-7229, USA
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15
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Hinton DM, Pande S, Wais N, Johnson XB, Vuthoori M, Makela A, Hook-Barnard I. Transcriptional takeover by σ appropriation: remodelling of the σ 70 subunit of Escherichia coli RNA polymerase by the bacteriophage T4 activator MotA and co-activator AsiA. Microbiology (Reading) 2005; 151:1729-1740. [PMID: 15941982 DOI: 10.1099/mic.0.27972-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Activation of bacteriophage T4 middle promoters, which occurs about 1 min after infection, uses two phage-encoded factors that change the promoter specificity of the host RNA polymerase. These phage factors, the MotA activator and the AsiA co-activator, interact with theσ70specificity subunit ofEscherichia coliRNA polymerase, which normally contacts the −10 and −35 regions of host promoter DNA. Like host promoters, T4 middle promoters have a good match to the canonicalσ70DNA element located in the −10 region. However, instead of theσ70DNA recognition element in the promoter's −35 region, they have a 9 bp sequence (a MotA box) centred at −30, which is bound by MotA. Recent work has begun to provide information about the MotA/AsiA system at a detailed molecular level. Accumulated evidence suggests that the presence of MotA and AsiA reconfigures protein–DNA contacts in the upstream promoter sequences, without significantly affecting the contacts ofσ70with the −10 region. This type of activation, which is called ‘σappropriation’, is fundamentally different from other well-characterized models of prokaryotic activation in which an activator frequently serves to forceσ70to contact a less than ideal −35 DNA element. This review summarizes the interactions of AsiA and MotA withσ70, and discusses how these interactions accomplish the switch to T4 middle promoters by inhibiting the typical contacts of the C-terminal region ofσ70, region 4, with the host −35 DNA element and with other subunits of polymerase.
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Affiliation(s)
- Deborah M Hinton
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Suchira Pande
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Neelowfar Wais
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Xanthia B Johnson
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Madhavi Vuthoori
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Anna Makela
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - India Hook-Barnard
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
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16
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Minakhin L, Severinov K. Transcription regulation by bacteriophage T4 AsiA. Protein Expr Purif 2005; 41:1-8. [PMID: 15802215 DOI: 10.1016/j.pep.2004.09.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2004] [Revised: 09/29/2004] [Indexed: 10/25/2022]
Abstract
Bacteriophage T4 AsiA, a strong inhibitor of bacterial RNA polymerase, was the first antisigma protein to be discovered. Recent advances that made it possible to purify large amounts of this highly toxic protein led to an increased understanding of AsiA function and structure. In this review, we discuss how the small 10-KDa AsiA protein plays a key role in T4 development through its ability to both inhibit and activate bacterial RNA polymerase transcription.
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Affiliation(s)
- Leonid Minakhin
- Waksman Institute for Microbiology, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ 08854, United States
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17
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Abstract
A recent structure obtained by nuclear magnetic resonance (NMR) spectroscopy shows that the binding of a small phage factor to the sigma(70) subunit of Escherichia coli RNA polymerase induces an unprecedented remodeling of a region of sigma(70), converting a DNA-binding helix-turn-helix into a continuous pseudohelix. This conformational change suggests how the phage factor can function both as an inhibitor and co-activator of transcription.
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Affiliation(s)
- Deborah M Hinton
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, MD 20892-0830, USA.
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18
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Qin Y, Smyth AJ, Su S, Farrand SK. Dimerization properties of TraM, the antiactivator that modulates TraR-mediated quorum-dependent expression of the Ti plasmid tra genes. Mol Microbiol 2005; 53:1471-85. [PMID: 15387823 DOI: 10.1111/j.1365-2958.2004.04216.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
TraM, an 11.2 kDa antiactivator, modulates the acyl-homoserine lactone-mediated autoinduction of Ti plasmid conjugative transfer by interacting directly with TraR, the quorum-sensing transcriptional activator. Most antiactivators and antisigma factors examined to date act in dimer form. However, whether, and if so, how TraM dimerizes is unknown. Analyses based on a genetic assay using fusions of TraM to the lambda cI DNA binding domain, and biochemical assays using chemical crosslinking and gel filtration chromatography showed that TraM forms homodimers. Although SDS-PAGE studies suggested that the lone cysteine residue at position 71 was involved in interprotomer disulfide-bridging in TraM, altering Cys-71 to a serine did not significantly affect dimerization or the antiactivator activity of this mutant protein when expressed at wild-type levels in vivo. Analysis of N-terminal, C-terminal, and internal deletion mutants of TraM identified two regions of the protein involved in dimerization; one located within a segment between residues 20 and 50, and the other located to a segment between residues 67 and 96. Both regions are required for formation of fully stable dimers. Analysis of the activity of these deletion mutants in vivo, and their ability to bind TraR and to disrupt TraR-DNA complexes in vitro, suggests that while the internal segment of the protein is required for dimerization, determinants located at the far C-terminus and beginning at between residues 10 and 20 at the N-terminus play a role in TraR binding and antiactivator function. When co-expressed with lambda cI'::TraR fusions, wild-type TraM mediated quormone-independent dimerization of the transcriptional activator, suggesting that dimers of TraM can multimerize TraR.
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Affiliation(s)
- Yinping Qin
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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19
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Pineda M, Gregory BD, Szczypinski B, Baxter KR, Hochschild A, Miller ES, Hinton DM. A family of anti-sigma70 proteins in T4-type phages and bacteria that are similar to AsiA, a Transcription inhibitor and co-activator of bacteriophage T4. J Mol Biol 2005; 344:1183-97. [PMID: 15561138 DOI: 10.1016/j.jmb.2004.10.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2004] [Revised: 09/30/2004] [Accepted: 10/05/2004] [Indexed: 11/24/2022]
Abstract
Anti-sigma70 factors interact with sigma70 proteins, the specificity subunits of prokaryotic RNA polymerase. The bacteriophage T4 anti-sigma70 protein, AsiA, binds tightly to regions 4.1 and 4.2 of the sigma70 subunit of Escherichia coli RNA polymerase and inhibits transcription from sigma70 promoters that require recognition of the canonical sigma70 -35 DNA sequence. In the presence of the T4 transcription activator MotA, AsiA also functions as a co-activator of transcription from T4 middle promoters, which retain the canonical sigma70 -10 consensus sequence but have a MotA box sequence centered at -30 rather than the sigma70 -35 sequence. The E.coli anti-sigma70 protein Rsd also interacts with region 4.2 of sigma70 and inhibits transcription from sigma70 promoters. Our sequence comparisons of T4 AsiA with Rsd, with the predicted AsiA orthologs of the T4-type phages RB69, 44RR, KVP40, and Aeh1, and with AlgQ, a regulator of alginate production in Pseudomonas aeruginosa indicate that these proteins share conserved amino acid residues at positions known to be important for the binding of T4 AsiA to sigma70 region 4. We show that, like T4 AsiA, Rsd binds to sigma70 in a native protein gel and, as with T4 AsiA, a L18S substitution in Rsd disrupts this complex. Previous work has assigned sigma70 amino acid F563, within region 4.1, as a critical determinant for AsiA binding. This residue is also involved in the binding of sigma70 to the beta-flap of core, suggesting that AsiA inhibits transcription by disrupting the interaction between sigma70 region 4.1 and the beta-flap. We find that as with T4 AsiA, the interaction of KVP40 AsiA, Rsd, or AlgQ with sigma70 region 4 is diminished by the substitution F563Y. We also demonstrate that like T4 AsiA and Rsd, KVP40 AsiA inhibits transcription from sigma70-dependent promoters. We speculate that the phage AsiA orthologs, Rsd, and AlgQ are members of a related family in T4-type phage and bacteria, which interact similarly with primary sigma factors. In addition, we show that even though a clear MotA ortholog has not been identified in the KVP40 genome and the phage genome appears to lack typical middle promoter sequences, KVP40 AsiA activates transcription from T4 middle promoters in the presence of T4 MotA. We speculate that KVP40 encodes a protein that is dissimilar in sequence, but functionally equivalent, to T4 MotA.
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Affiliation(s)
- Melissa Pineda
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Building 8, Room 2A-13, National Institutes of Health, Bethesda, MD 20892-0830, USA
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20
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Tiemann B, Depping R, Gineikiene E, Kaliniene L, Nivinskas R, Rüger W. ModA and ModB, two ADP-ribosyltransferases encoded by bacteriophage T4: catalytic properties and mutation analysis. J Bacteriol 2004; 186:7262-72. [PMID: 15489438 PMCID: PMC523198 DOI: 10.1128/jb.186.21.7262-7272.2004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacteriophage T4 encodes three ADP-ribosyltransferases, Alt, ModA, and ModB. These enzymes participate in the regulation of the T4 replication cycle by ADP-ribosylating a defined set of host proteins. In order to obtain a better understanding of the phage-host interactions and their consequences for regulating the T4 replication cycle, we studied cloning, overexpression, and characterization of purified ModA and ModB enzymes. Site-directed mutagenesis confirmed that amino acids, as deduced from secondary structure alignments, are indeed decisive for the activity of the enzymes, implying that the transfer reaction follows the Sn1-type reaction scheme proposed for this class of enzymes. In vitro transcription assays performed with Alt- and ModA-modified RNA polymerases demonstrated that the Alt-ribosylated polymerase enhances transcription from T4 early promoters on a T4 DNA template, whereas the transcriptional activity of ModA-modified polymerase, without the participation of T4-encoded auxiliary proteins for middle mode or late transcription, is reduced. The results presented here support the conclusion that ADP-ribosylation of RNA polymerase and of other host proteins allows initial phage-directed mRNA synthesis reactions to escape from host control. In contrast, subsequent modification of the other cellular target proteins limits transcription from phage early genes and participates in redirecting transcription to phage middle and late genes.
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Affiliation(s)
- Bernd Tiemann
- Ruhr Universität Bochum, Fakultät für Biologie, Arbeitsgruppe Molekulare Genetik, 44780 Bochum, Germany.
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21
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22
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Lambert LJ, Wei Y, Schirf V, Demeler B, Werner MH. T4 AsiA blocks DNA recognition by remodeling sigma70 region 4. EMBO J 2004; 23:2952-62. [PMID: 15257291 PMCID: PMC514929 DOI: 10.1038/sj.emboj.7600312] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2004] [Accepted: 06/16/2004] [Indexed: 11/09/2022] Open
Abstract
Bacteriophage T4 AsiA is a versatile transcription factor capable of inhibiting host gene expression as an 'anti-sigma' factor while simultaneously promoting gene-specific expression of T4 middle genes in conjunction with T4 MotA. To accomplish this task, AsiA engages conserved region 4 of Eschericia coli sigma70, blocking recognition of most host promoters by sequestering the DNA-binding surface at the AsiA/sigma70 interface. The three-dimensional structure of an AsiA/region 4 complex reveals that the C-terminal alpha helix of region 4 is unstructured, while four other helices adopt a completely different conformation relative to the canonical structure of unbound region 4. That AsiA induces, rather than merely stabilizes, this rearrangement can be realized by comparison to the homologous structures of region 4 solved in a variety of contexts, including the structure of Thermotoga maritima sigmaA region 4 described herein. AsiA simultaneously occupies the surface of region 4 that ordinarily contacts core RNA polymerase (RNAP), suggesting that an AsiA-bound sigma70 may also undergo conformational changes in the context of the RNAP holoenzyme.
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Affiliation(s)
- Lester J Lambert
- Laboratory of Molecular Biophysics, Rockefeller University, New York, NY, USA
| | - Yufeng Wei
- Laboratory of Molecular Biophysics, Rockefeller University, New York, NY, USA
| | - Virgil Schirf
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX, USA
| | - Borries Demeler
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX, USA
| | - Milton H Werner
- Laboratory of Molecular Biophysics, Rockefeller University, New York, NY, USA
- Laboratory of Molecular Biophysics, The Rockefeller University, 1230 York Avenue, Box 42, New York, NY 10021, USA. Tel.: +1 212 327 7221; Fax: +1 212 327 7222; E-mail:
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23
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Abstract
Bacteriophages have developed an impressive array of ingenious mechanisms to modify bacterial host RNA polymerase to make it serve viral needs. In this review we summarize the current knowledge about two types of host RNA polymerase modifications induced by double-stranded DNA phages: covalent modifications and modifications through RNA polymerase-binding proteins. We interpret the biochemical and genetic data within the framework of a structure-function model of bacterial RNA polymerase and viral biology.
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Affiliation(s)
- Sergei Nechaev
- Center for Molecular Genetics, University of California, San Diego, 9500 Gilman Dr., La Jolla, California 92093-0634, USA.
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24
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Kamali-Moghaddam M, Geiduschek EP. Thermoirreversible and thermoreversible promoter opening by two Escherichia coli RNA polymerase holoenzymes. J Biol Chem 2003; 278:29701-9. [PMID: 12754208 DOI: 10.1074/jbc.m304604200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Promoter opening, in which the complementary DNA strands separate around the transcriptional start site, is generally thermoreversible. An exceptional case of thermoirreversible opening of the T4 late promoter has been analyzed by KMnO4 footprinting and transcription. T4 late promoters, which consist of an 8-base pair (bp) TATA box "-10" element, are recognized by the small, phage-encoded, highly diverged sigma-family initiation subunit gp55. The T4 late promoter only opens above 15-20 degrees C, but once it has been formed remains open and transcriptionally active for days at -0.5 degrees C. The low temperature-trapped open complex and its isothermally formed state are shown to be structurally distinctive. Two "extended -10" sigma 70 promoters, which, like the T4 late promoter, lack "-35" sites, have been subjected to a comparative analysis: the T4 middle promoter PrIIB2 opens and closes thermoreversibly under conditions of basal and MotA- and AsiA-activated transcription. The open galP1 promoter complex, whose transcription bubble is very AT-rich, also closes reversibly upon shift to -0.5 degrees C, but more slowly than does the rIIB2 promoter. Formation of a trapped-open low temperature state of the promoter complex appears to be a singular property of gp55-RNA polymerase holoenzyme.
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Affiliation(s)
- Masood Kamali-Moghaddam
- Division of Biological Sciences and Center for Molecular Genetics, University of California, San Diego, La Jolla, California 92093-0634, USA.
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25
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Minakhin L, Severinov K. On the role of the Escherichia coli RNA polymerase sigma 70 region 4.2 and alpha-subunit C-terminal domains in promoter complex formation on the extended -10 galP1 promoter. J Biol Chem 2003; 278:29710-8. [PMID: 12801925 DOI: 10.1074/jbc.m304906200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bacterial promoters of the extended -10 class contain a single consensus element, and the DNA sequence upstream of this element is not critical for promoter activity. Open promoter complexes can be formed on an extended -10 Escherichia coli galP1 promoter at temperatures as low as 6 degrees C, when complexes on most promoters are closed. Here, we studied the contribution of upstream contacts to promoter complex formation using galP1 and its derivatives lacking the extended -10 motif and/or containing the -35 promoter consensus element. A panel of E. coli RNA polymerase holoenzymes containing two, one, or no alpha-subunit C-terminal domains (alpha CTD) and either wild-type sigma 70 subunit or sigma 70 lacking region 4.2 was assembled and tested for promoter complex formation. At 37 degrees C, alpha CTD and sigma 70 region 4.2 were individually dispensable for promoter complex formation on galP1 derivatives with extended -10 motif. However, no promoter complexes formed when both alpha CTD and sigma 70 region 4.2 were absent. Thus, in the context of an extended -10 promoter, alpha CTD and sigma 70 region 4.2 interactions with upstream DNA can functionally substitute for each other. In contrast, at low temperature, alpha CTD and sigma 70 region 4.2 interactions with upstream DNA were found to be functionally distinct, for sigma 70 region 4.2 but not alpha CTD was required for open promoter complex formation on galP1 derivatives with extended -10 motif. We propose a model involving sigma 70 region 4.2 interaction with the beta flap domain that explains these observations.
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Affiliation(s)
- Leonid Minakhin
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
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26
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Campbell EA, Tupy JL, Gruber TM, Wang S, Sharp MM, Gross CA, Darst SA. Crystal structure of Escherichia coli sigmaE with the cytoplasmic domain of its anti-sigma RseA. Mol Cell 2003; 11:1067-78. [PMID: 12718891 DOI: 10.1016/s1097-2765(03)00148-5] [Citation(s) in RCA: 209] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The sigma factors are the key regulators of bacterial transcription. ECF (extracytoplasmic function) sigma's are the largest and most divergent group of sigma(70) family members. ECF sigma's are normally sequestered in an inactive complex by their specific anti-sigma factor, which often spans the inner membrane. Here, we determined the 2 A resolution crystal structure of the Escherichia coli ECF sigma factor sigma(E) in an inhibitory complex with the cytoplasmic domain of its anti-sigma, RseA. Despite extensive sequence variability, the two major domains of sigma(E) are virtually identical in structure to the corresponding domains of other sigma(70) family members. In combination with a model of the sigma(E) holoenzyme and biochemical data, the structure reveals that RseA functions by sterically occluding the two primary binding determinants on sigma(E) for core RNA polymerase.
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Affiliation(s)
- Elizabeth A Campbell
- Laboratory of Molecular Biophysics, The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA
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27
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Abstract
Bacterial sigma factors play a key role in promoter recognition, making direct contact with conserved promoter elements. Most sigma factors belong to the sigma70 family, named for the primary sigma factor in Escherichia coli. Members of the sigma70 family typically share four conserved regions and, here, we focus on region 4, which is directly involved in promoter recognition and serves as a target for a variety of regulators of transcription initiation. We review recent advances in the understanding of the mechanism of action of regulators that target region 4 of sigma.
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Affiliation(s)
- Simon L Dove
- Division of Infectious Diseases, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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28
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Truncaite L, Piesiniene L, Kolesinskiene G, Zajanckauskaite A, Driukas A, Klausa V, Nivinskas R. Twelve new MotA-dependent middle promoters of bacteriophage T4: consensus sequence revised. J Mol Biol 2003; 327:335-46. [PMID: 12628241 DOI: 10.1016/s0022-2836(03)00125-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Bacteriophage T4 middle-mode transcription requires Escherichia coli RNA polymerase, phage-encoded transcriptional activator MotA and co-activator AsiA that form a complex at a middle promoter DNA. T4 middle promoters have been defined by a consensus sequence deduced from the list of 14 middle promoters identified in earlier studies. To date, 33 middle promoters have been mapped on the T4 genome. Of these, 12 contain differences even at the highly conserved positions of the consensus sequence. In the T4 prereplicative gene cluster between genes e and rpbA, we have identified 12 new middle promoters, most of which contain differences from the consensus sequence deduced previously. Analysis of base conservation in the different sequence positions of new middle promoters, as well as those identified previously, revealed some new features of middle T4 promoters. We propose to define these promoters by a MotA box (a/t)(a/t)(a/t)TGCTTtA centred at the position -30, the sequence TAtaAT centred at -10 relative to the transcriptional start site, and the spacer region of 12(+/-1) base-pairs between them.
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Affiliation(s)
- Lidija Truncaite
- Department of Gene Engineering, Institute of Biochemistry, Mokslininku 12, 2600 Vilnius, Lithuania
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29
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Miller ES, Kutter E, Mosig G, Arisaka F, Kunisawa T, Rüger W. Bacteriophage T4 genome. Microbiol Mol Biol Rev 2003; 67:86-156, table of contents. [PMID: 12626685 PMCID: PMC150520 DOI: 10.1128/mmbr.67.1.86-156.2003] [Citation(s) in RCA: 551] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Phage T4 has provided countless contributions to the paradigms of genetics and biochemistry. Its complete genome sequence of 168,903 bp encodes about 300 gene products. T4 biology and its genomic sequence provide the best-understood model for modern functional genomics and proteomics. Variations on gene expression, including overlapping genes, internal translation initiation, spliced genes, translational bypassing, and RNA processing, alert us to the caveats of purely computational methods. The T4 transcriptional pattern reflects its dependence on the host RNA polymerase and the use of phage-encoded proteins that sequentially modify RNA polymerase; transcriptional activator proteins, a phage sigma factor, anti-sigma, and sigma decoy proteins also act to specify early, middle, and late promoter recognition. Posttranscriptional controls by T4 provide excellent systems for the study of RNA-dependent processes, particularly at the structural level. The redundancy of DNA replication and recombination systems of T4 reveals how phage and other genomes are stably replicated and repaired in different environments, providing insight into genome evolution and adaptations to new hosts and growth environments. Moreover, genomic sequence analysis has provided new insights into tail fiber variation, lysis, gene duplications, and membrane localization of proteins, while high-resolution structural determination of the "cell-puncturing device," combined with the three-dimensional image reconstruction of the baseplate, has revealed the mechanism of penetration during infection. Despite these advances, nearly 130 potential T4 genes remain uncharacterized. Current phage-sequencing initiatives are now revealing the similarities and differences among members of the T4 family, including those that infect bacteria other than Escherichia coli. T4 functional genomics will aid in the interpretation of these newly sequenced T4-related genomes and in broadening our understanding of the complex evolution and ecology of phages-the most abundant and among the most ancient biological entities on Earth.
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Affiliation(s)
- Eric S Miller
- Department of Microbiology, North Carolina State University, Raleigh, North Carolina 27695-7615, USA.
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Minakhin L, Niedziela-Majka A, Kuznedelov K, Adelman K, Urbauer JL, Heyduk T, Severinov K. Interaction of T4 AsiA with its target sites in the RNA polymerase sigma70 subunit leads to distinct and opposite effects on transcription. J Mol Biol 2003; 326:679-90. [PMID: 12581632 DOI: 10.1016/s0022-2836(02)01442-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Bacteriophage T4 AsiA is a homodimeric protein that orchestrates a switch from the host and early viral transcription to middle viral transcription by binding to the sigma(70) subunit of Escherichia coli RNA polymerase holoenzyme (Esigma(70)) and preventing promoter complex formation on most E.coli and early T4 promoters. In addition, Esigma(70)AsiA, but not Esigma(70), is a substrate of transcription activation by T4-encoded DNA-binding protein MotA, a co-activator of transcription from middle viral promoters. The molecular determinants of sigma(70)-AsiA interaction necessary for transcription inhibition reside in the sigma(70) conserved region 4.2, which recognizes the -35 promoter consensus element. The molecular determinants of sigma(70)-AsiA interaction necessary for MotA-dependent transcription activation have not been identified. Here, we show that in the absence of sigma(70) region 4.2, AsiA interacts with sigma(70) conserved region 4.1 and activates transcription in a MotA-independent manner. Further, we show that the AsiA dimer must dissociate to interact with either region 4.2 or region 4.1 of sigma(70). We propose that MotA may co-activate transcription by restricting AsiA binding to sigma(70) region 4.1.
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Affiliation(s)
- Leonid Minakhin
- Department of Genetics, Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
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Pal D, Vuthoori M, Pande S, Wheeler D, Hinton DM. Analysis of regions within the bacteriophage T4 AsiA protein involved in its binding to the sigma70 subunit of E. coli RNA polymerase and its role as a transcriptional inhibitor and co-activator. J Mol Biol 2003; 325:827-41. [PMID: 12527294 DOI: 10.1016/s0022-2836(02)01307-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Bacteriophage T4 AsiA, a protein of 90 amino acid residues, binds to the sigma(70) subunit of Escherichia coli RNA polymerase and inhibits host or T4 early transcription or, together with the T4 MotA protein, activates T4 middle transcription. To investigate which regions within AsiA are involved in forming a complex with sigma(70) and in providing transcriptional functions we generated random mutations throughout AsiA and targeted mutations within the C-terminal region. We tested mutant proteins for their ability to complement the growth of T4 asiA am phage under non-suppressing conditions, to inhibit E. coli growth, to interact with sigma(70) region 4 in a two-hybrid assay, to bind to sigma(70) in a native protein gel, and to inhibit or activate transcription in vitro using a T4 middle promoter that is active with RNA polymerase alone, is inhibited by AsiA, and is activated by MotA/AsiA. We find that substitutions within the N-terminal half of AsiA, at amino acid residues V14, L18, and I40, rendered the protein defective for binding to sigma(70). These residues reside at the monomer-monomer interface in recent NMR structures of the AsiA dimer. In contrast, AsiA missing the C-terminal 44 amino acid residues interacted well with sigma(70) region 4 in the two-hybrid assay, and AsiA missing the C-terminal 17 amino acid residues (Delta74-90) bound to sigma(70) and was fully competent in standard in vitro transcription assays. However, the presence of the C-terminal region delayed formation of transcriptionally competent species when the AsiA/polymerase complex was pre-incubated with the promoter in the absence of MotA. Our results suggest that amino acid residues within the N-terminal half of AsiA are involved in forming or maintaining the AsiA/sigma(70) complex. The C-terminal region of AsiA, while not absolutely required for inhibition or co-activation, aids inhibition by slowing the formation of transcription complexes between a promoter and the AsiA/polymerase complex.
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Affiliation(s)
- Debashis Pal
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, USA
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32
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Li W, Stevenson CEM, Burton N, Jakimowicz P, Paget MSB, Buttner MJ, Lawson DM, Kleanthous C. Identification and structure of the anti-sigma factor-binding domain of the disulphide-stress regulated sigma factor sigma(R) from Streptomyces coelicolor. J Mol Biol 2002; 323:225-36. [PMID: 12381317 DOI: 10.1016/s0022-2836(02)00948-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The extracytoplasmic function (ECF) sigma factor sigma(R) is a global regulator of redox homeostasis in the antibiotic-producing bacterium Streptomyces coelicolor, with a similar role in other actinomycetes such as Mycobacterium tuberculosis. Normally maintained in an inactive state by its bound anti-sigma factor RsrA, sigma(R) dissociates in response to intracellular disulphide-stress to direct core RNA polymerase to transcribe genes, such as trxBA and trxC that encode the enzymes of the thioredoxin disulphide reductase pathway, that re-establish redox homeostasis. Little is known about where RsrA binds on sigma(R) or how it suppresses sigma(R)-dependent transcriptional activity. Using a combination of proteolysis, surface-enhanced laser desorption ionisation mass spectrometry and pull-down assays we identify an N-terminal, approximately 10kDa domain (sigma(RN)) that encompasses region 2 of sigma(R) that represents the major RsrA binding site. We show that sigma(RN) inhibits transcription by an unrelated sigma factor and that this inhibition is relieved by RsrA binding, reaffirming that region 2 is involved in binding to core RNA polymerase but also demonstrating that the likely mechanism by which RsrA inhibits sigma(R) activity is by blocking this association. We also report the 2.4A resolution crystal structure of sigma(RN) that reveals extensive structural conservation with the equivalent region of sigma(70) from Escherichia coli as well as with the cyclin-box, a domain-fold found in the eukaryotic proteins TFIIB and cyclin A. sigma(RN) has a propensity to aggregate, due to steric complementarity of oppositely charged surfaces on the domain, but this is inhibited by RsrA, an observation that suggests a possible mode of action for RsrA which we compare to other well-studied sigma factor-anti-sigma factor systems.
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Affiliation(s)
- Wei Li
- School of Biological Sciences, University of East Anglia, NR4 7TJ, Norwich, UK
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Venkatesh R, Ganesh N, Guhan N, Reddy MS, Chandrasekhar T, Muniyappa K. RecX protein abrogates ATP hydrolysis and strand exchange promoted by RecA: insights into negative regulation of homologous recombination. Proc Natl Acad Sci U S A 2002; 99:12091-6. [PMID: 12218174 PMCID: PMC129403 DOI: 10.1073/pnas.192178999] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In many eubacteria, coexpression of recX with recA is essential for attenuation of the deleterious effects of recA overexpression; however, the molecular mechanism has remained enigmatic. Here, we show that Mycobacterium tuberculosis RecX binds directly to M. tuberculosis RecA as well as M. smegmatis and E. coli RecA proteins in vivo and in vitro, but not single-stranded DNA binding protein. The direct association of RecX with RecA failed to regulate the specificity or extent of binding of RecA either to DNA or ATP, ligands that are central to activation of its functions. Significantly, RecX severely impeded ATP hydrolysis and the generation of heteroduplex DNA promoted by homologous, as well as heterologous, RecA proteins. These findings reveal a mode of negative regulation of RecA, and imply that RecX might act as an anti-recombinase to quell inappropriate recombinational repair during normal DNA metabolism.
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Affiliation(s)
- R Venkatesh
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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Pande S, Makela A, Dove SL, Nickels BE, Hochschild A, Hinton DM. The bacteriophage T4 transcription activator MotA interacts with the far-C-terminal region of the sigma70 subunit of Escherichia coli RNA polymerase. J Bacteriol 2002; 184:3957-64. [PMID: 12081968 PMCID: PMC135182 DOI: 10.1128/jb.184.14.3957-3964.2002] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2001] [Accepted: 04/24/2002] [Indexed: 11/20/2022] Open
Abstract
Transcription from bacteriophage T4 middle promoters uses Escherichia coli RNA polymerase together with the T4 transcriptional activator MotA and the T4 coactivator AsiA. AsiA binds tightly within the C-terminal portion of the sigma70 subunit of RNA polymerase, while MotA binds to the 9-bp MotA box motif, which is centered at -30, and also interacts with sigma70. We show here that the N-terminal half of MotA (MotA(NTD)), which is thought to include the activation domain, interacts with the C-terminal region of sigma70 in an E. coli two-hybrid assay. Replacement of the C-terminal 17 residues of sigma70 with comparable sigma38 residues abolishes the interaction with MotA(NTD) in this assay, as does the introduction of the amino acid substitution R608C. Furthermore, in vitro transcription experiments indicate that a polymerase reconstituted with a sigma70 that lacks C-terminal amino acids 604 to 613 or 608 to 613 is defective for MotA-dependent activation. We also show that a proteolyzed fragment of MotA that contains the C-terminal half (MotA(CTD)) binds DNA with a K(D(app)) that is similar to that of full-length MotA. Our results support a model for MotA-dependent activation in which protein-protein contact between DNA-bound MotA and the far-C-terminal region of sigma70 helps to substitute functionally for an interaction between sigma70 and a promoter -35 element.
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Affiliation(s)
- Suchira Pande
- Laboratory of Molecular and Cellular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0830, USA
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