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Shine M, Gordon J, Schärfen L, Zigackova D, Herzel L, Neugebauer KM. Co-transcriptional gene regulation in eukaryotes and prokaryotes. Nat Rev Mol Cell Biol 2024:10.1038/s41580-024-00706-2. [PMID: 38509203 DOI: 10.1038/s41580-024-00706-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2024] [Indexed: 03/22/2024]
Abstract
Many steps of RNA processing occur during transcription by RNA polymerases. Co-transcriptional activities are deemed commonplace in prokaryotes, in which the lack of membrane barriers allows mixing of all gene expression steps, from transcription to translation. In the past decade, an extraordinary level of coordination between transcription and RNA processing has emerged in eukaryotes. In this Review, we discuss recent developments in our understanding of co-transcriptional gene regulation in both eukaryotes and prokaryotes, comparing methodologies and mechanisms, and highlight striking parallels in how RNA polymerases interact with the machineries that act on nascent RNA. The development of RNA sequencing and imaging techniques that detect transient transcription and RNA processing intermediates has facilitated discoveries of transcription coordination with splicing, 3'-end cleavage and dynamic RNA folding and revealed physical contacts between processing machineries and RNA polymerases. Such studies indicate that intron retention in a given nascent transcript can prevent 3'-end cleavage and cause transcriptional readthrough, which is a hallmark of eukaryotic cellular stress responses. We also discuss how coordination between nascent RNA biogenesis and transcription drives fundamental aspects of gene expression in both prokaryotes and eukaryotes.
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Affiliation(s)
- Morgan Shine
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Jackson Gordon
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Leonard Schärfen
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Dagmar Zigackova
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Lydia Herzel
- Department of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, Berlin, Germany.
| | - Karla M Neugebauer
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA.
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2
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T N, Govindarajan S, Munavar MH. trans-translation system is important for maintaining genome integrity during DNA damage in bacteria. Res Microbiol 2023; 174:104136. [PMID: 37690591 DOI: 10.1016/j.resmic.2023.104136] [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: 04/21/2023] [Revised: 08/29/2023] [Accepted: 08/31/2023] [Indexed: 09/12/2023]
Abstract
DNA integrity in bacteria is regulated by various factors that act on the DNA. trans-translation has previously been shown to be important for the survival of Escherichia coli cells exposed to certain DNA-damaging agents. However, the mechanisms underlying this sensitivity are poorly understood. In this study, we explored the involvement of the trans-translation system in the maintenance of genome integrity using various DNA-damaging agents and mutant backgrounds. Relative viability assays showed that SsrA-defective cells were sensitive to DNA-damaging agents, such as nalidixic acid (NA), ultraviolet radiation (UV), and methyl methanesulfonate (MMS). The viability of SsrA-defective cells was rescued by deleting sulA, although the expression of SulA was not more pronounced in SsrA-defective cells than in wild-type cells. Live cell imaging using a Gam-GFP fluorescent reporter showed increased double-strand breaks (DSBs) in SsrA-defective cells during DNA damage. We also showed that the ribosome rescue function of SsrA was sufficient for DNA damage tolerance. DNA damage sensitivity can be alleviated by partial uncoupling of transcription and translation by using sub-lethal concentrations of ribosome inhibiting antibiotic (tetracycline) or by mutating the gene coding for RNase H (rnhA). Taken together, our results highlight the importance of trans-translation system in maintaining genome integrity and bacterial survival during DNA damage.
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Affiliation(s)
- Nagarajan T
- Department of Molecular Biology, School of Biological Sciences, Madurai Kamaraj University, Madurai, India; Department of Biological Sciences, SRM University-AP, Amaravati, India
| | | | - M Hussain Munavar
- Department of Molecular Biology, School of Biological Sciences, Madurai Kamaraj University, Madurai, India.
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3
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Wee LM, Tong AB, Florez Ariza AJ, Cañari-Chumpitaz C, Grob P, Nogales E, Bustamante CJ. A trailing ribosome speeds up RNA polymerase at the expense of transcript fidelity via force and allostery. Cell 2023; 186:1244-1262.e34. [PMID: 36931247 PMCID: PMC10135430 DOI: 10.1016/j.cell.2023.02.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 11/14/2022] [Accepted: 02/06/2023] [Indexed: 03/18/2023]
Abstract
In prokaryotes, translation can occur on mRNA that is being transcribed in a process called coupling. How the ribosome affects the RNA polymerase (RNAP) during coupling is not well understood. Here, we reconstituted the E. coli coupling system and demonstrated that the ribosome can prevent pausing and termination of RNAP and double the overall transcription rate at the expense of fidelity. Moreover, we monitored single RNAPs coupled to ribosomes and show that coupling increases the pause-free velocity of the polymerase and that a mechanical assisting force is sufficient to explain the majority of the effects of coupling. Also, by cryo-EM, we observed that RNAPs with a terminal mismatch adopt a backtracked conformation, while a coupled ribosome allosterically induces these polymerases toward a catalytically active anti-swiveled state. Finally, we demonstrate that prolonged RNAP pausing is detrimental to cell viability, which could be prevented by polymerase reactivation through a coupled ribosome.
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Affiliation(s)
- Liang Meng Wee
- QB3-Berkeley, Berkeley, CA, USA; Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA, USA
| | - Alexander B Tong
- QB3-Berkeley, Berkeley, CA, USA; Department of Chemistry, University of California Berkeley, Berkeley, CA, USA
| | - Alfredo Jose Florez Ariza
- QB3-Berkeley, Berkeley, CA, USA; Biophysics Graduate Group, University of California Berkeley, Berkeley, CA, USA
| | - Cristhian Cañari-Chumpitaz
- QB3-Berkeley, Berkeley, CA, USA; Department of Chemistry, University of California Berkeley, Berkeley, CA, USA; Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA, USA
| | - Patricia Grob
- QB3-Berkeley, Berkeley, CA, USA; Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA, USA; Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, USA
| | - Eva Nogales
- QB3-Berkeley, Berkeley, CA, USA; Biophysics Graduate Group, University of California Berkeley, Berkeley, CA, USA; Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, USA; Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA, USA; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
| | - Carlos J Bustamante
- QB3-Berkeley, Berkeley, CA, USA; Biophysics Graduate Group, University of California Berkeley, Berkeley, CA, USA; Department of Chemistry, University of California Berkeley, Berkeley, CA, USA; Department of Physics, University of California Berkeley, Berkeley, CA, USA; Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, USA; Kavli Energy Nanoscience Institute, Berkeley, CA, USA; Howard Hughes Medical Institute, University of California Berkeley, Berkeley, CA, USA; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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4
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Koppenhöfer S, Lang AS. Patterns of abundance, chromosomal localization, and domain organization among c-di-GMP-metabolizing genes revealed by comparative genomics of five alphaproteobacterial orders. BMC Genomics 2022; 23:834. [PMID: 36522693 PMCID: PMC9756655 DOI: 10.1186/s12864-022-09072-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 10/17/2022] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) is a bacterial second messenger that affects diverse processes in different bacteria, including the cell cycle, motility, and biofilm formation. Its cellular levels are controlled by the opposing activities of two types of enzymes, with synthesis by diguanylate cyclases containing a GGDEF domain and degradation by phosphodiesterases containing either an HD-GYP or an EAL domain. These enzymes are ubiquitous in bacteria with up to 50 encoded in some genomes, the specific functions of which are mostly unknown. RESULTS We used comparative analyses to identify genomic patterns among genes encoding proteins with GGDEF, EAL, and HD-GYP domains in five orders of the class Alphaproteobacteria. GGDEF-containing sequences and GGDEF-EAL hybrids were the most abundant and had the highest diversity of co-occurring auxiliary domains while EAL and HD-GYP containing sequences were less abundant and less diverse with respect to auxiliary domains. There were striking patterns in the chromosomal localizations of the genes found in two of the orders. The Rhodobacterales' EAL-encoding genes and Rhizobiales' GGDEF-EAL-encoding genes showed opposing patterns of distribution compared to the GGDEF-encoding genes. In the Rhodobacterales, the GGDEF-encoding genes showed a tri-modal distribution with peaks mid-way between the origin (ori) and terminus (ter) of replication and at ter while the EAL-encoding genes peaked near ori. The patterns were more complex in the Rhizobiales, but the GGDEF-encoding genes were biased for localization near ter. CONCLUSIONS The observed patterns in the chromosomal localizations of these genes suggest a coupling of synthesis and hydrolysis of c-di-GMP with the cell cycle. Moreover, the higher proportions and diversities of auxiliary domains associated with GGDEF domains and GGDEF-EAL hybrids compared to EAL or HD-GYP domains could indicate that more stimuli affect synthesis compared to hydrolysis of c-di-GMP.
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Affiliation(s)
- Sonja Koppenhöfer
- grid.25055.370000 0000 9130 6822Department of Biology, Memorial University of Newfoundland, St. John’s, Newfoundland and Labrador Canada
| | - Andrew S. Lang
- grid.25055.370000 0000 9130 6822Department of Biology, Memorial University of Newfoundland, St. John’s, Newfoundland and Labrador Canada
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RNase HI Depletion Strongly Potentiates Cell Killing by Rifampicin in Mycobacteria. Antimicrob Agents Chemother 2022; 66:e0209121. [PMID: 36154174 DOI: 10.1128/aac.02091-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Multidrug-resistant (MDR) tuberculosis (TB) is defined by the resistance of Mycobacterium tuberculosis, the causative organism, to the first-line antibiotics rifampicin and isoniazid. Mitigating or reversing resistance to these drugs offers a means of preserving and extending their use in TB treatment. R-loops are RNA/DNA hybrids that are formed in the genome during transcription, and they can be lethal to the cell if not resolved. RNase HI is an enzyme that removes R-loops, and this activity is essential in M. tuberculosis: knockouts of rnhC, the gene encoding RNase HI, are nonviable. This essentiality makes it a candidate target for the development of new antibiotics. In the model organism Mycolicibacterium smegmatis, RNase HI activity is provided by two enzymes, RnhA and RnhC. We show that the partial depletion of RNase HI activity in M. smegmatis, by knocking out either of the genes encoding RnhA or RnhC, led to the accumulation of R-loops. The sensitivity of the knockout strains to the antibiotics moxifloxacin, streptomycin, and rifampicin was increased, the latter by a striking near 100-fold. We also show that R-loop accumulation accompanies partial transcriptional inhibition, suggesting a mechanistic basis for the synergy between RNase HI depletion and rifampicin. A model of how transcriptional inhibition can potentiate R-loop accumulation is presented. Finally, we identified four small molecules that inhibit recombinant RnhC activity and that also potentiated rifampicin activity in whole-cell assays against M. tuberculosis, supporting an on-target mode of action and providing the first step in developing a new class of antimycobacterial drug.
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Bharti R, Siebert D, Blombach B, Grimm DG. Systematic analysis of the underlying genomic architecture for transcriptional-translational coupling in prokaryotes. NAR Genom Bioinform 2022; 4:lqac074. [PMID: 36186922 PMCID: PMC9514032 DOI: 10.1093/nargab/lqac074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 09/05/2022] [Accepted: 09/15/2022] [Indexed: 11/12/2022] Open
Abstract
Transcriptional-translational coupling is accepted to be a fundamental mechanism of gene expression in prokaryotes and therefore has been analyzed in detail. However, the underlying genomic architecture of the expression machinery has not been well investigated so far. In this study, we established a bioinformatics pipeline to systematically investigated >1800 bacterial genomes for the abundance of transcriptional and translational associated genes clustered in distinct gene cassettes. We identified three highly frequent cassettes containing transcriptional and translational genes, i.e. rplk-nusG (gene cassette 1; in 553 genomes), rpoA-rplQ-rpsD-rpsK-rpsM (gene cassette 2; in 656 genomes) and nusA-infB (gene cassette 3; in 877 genomes). Interestingly, each of the three cassettes harbors a gene (nusG, rpsD and nusA) encoding a protein which links transcription and translation in bacteria. The analyses suggest an enrichment of these cassettes in pathogenic bacterial phyla with >70% for cassette 3 (i.e. Neisseria, Salmonella and Escherichia) and >50% for cassette 1 (i.e. Treponema, Prevotella, Leptospira and Fusobacterium) and cassette 2 (i.e. Helicobacter, Campylobacter, Treponema and Prevotella). These insights form the basis to analyze the transcriptional regulatory mechanisms orchestrating transcriptional-translational coupling and might open novel avenues for future biotechnological approaches.
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Affiliation(s)
- Richa Bharti
- Technical University of Munich, Campus Straubing for Biotechnology and Sustainability, Bioinformatics, Petersgasse 18, 94315 Straubing, Germany
- Weihenstephan-Triesdorf University of Applied Sciences, Petersgasse 18, 94315 Straubing, Germany
- SynBiofoundry@TUM, Technical University of Munich, Schulgasse 22, 94315 Straubing, Germany
| | - Daniel Siebert
- SynBiofoundry@TUM, Technical University of Munich, Schulgasse 22, 94315 Straubing, Germany
- Technical University of Munich, Campus Straubing for Biotechnology and Sustainability, Microbial Biotechnology, Uferstraße 53, 94315 Straubing, Germany
| | - Bastian Blombach
- SynBiofoundry@TUM, Technical University of Munich, Schulgasse 22, 94315 Straubing, Germany
- Technical University of Munich, Campus Straubing for Biotechnology and Sustainability, Microbial Biotechnology, Uferstraße 53, 94315 Straubing, Germany
| | - Dominik G Grimm
- Technical University of Munich, Campus Straubing for Biotechnology and Sustainability, Bioinformatics, Petersgasse 18, 94315 Straubing, Germany
- Weihenstephan-Triesdorf University of Applied Sciences, Petersgasse 18, 94315 Straubing, Germany
- SynBiofoundry@TUM, Technical University of Munich, Schulgasse 22, 94315 Straubing, Germany
- Technical University of Munich, Department of Informatics, Boltzmannstr. 3, 85748 Garching, Germany
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Modulation of RecFORQ- and RecA-Mediated Homologous Recombination in Escherichia coli by Isoforms of Translation Initiation Factor IF2. J Bacteriol 2022; 204:e0056921. [PMID: 35343793 DOI: 10.1128/jb.00569-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Homologous recombination (HR) is critically important for chromosomal replication, as well as DNA damage repair in all life forms. In Escherichia coli, the process of HR comprises (i) two parallel presynaptic pathways that are mediated, respectively, by proteins RecB/C/D and RecF/O/R/Q; (ii) a synaptic step mediated by RecA that leads to generation of Holliday junctions (HJs); and (iii) postsynaptic steps mediated sequentially by HJ-acting proteins RuvA/B/C followed by proteins PriA/B/C of replication restart. Combined loss of RuvA/B/C and a DNA helicase UvrD is synthetically lethal, which is attributed to toxicity caused by accumulated HJs since viability in these double mutant strains is restored by removal of the presynaptic or synaptic proteins RecF/O/R/Q or RecA, respectively. Here we show that, as in ΔuvrD strains, ruv mutations confer synthetic lethality in cells deficient for transcription termination factor Rho, and that loss of RecFORQ presynaptic pathway proteins or of RecA suppresses this lethality. Furthermore, loss of IF2-1 (which is one of three isoforms [IF2-1, IF2-2, and IF2-3] of the essential translation initiation factor IF2 that are synthesized from three in-frame initiation codons in infB) also suppressed uvrD-ruv and rho-ruv lethalities, whereas deficiency of IF2-2 and IF2-3 exacerbated the synthetic defects. Our results suggest that Rho deficiency is associated with an increased frequency of HR that is mediated by the RecFORQ pathway along with RecA. They also lend support to earlier reports that IF2 isoforms participate in DNA transactions, and we propose that they do so by modulation of HR functions. IMPORTANCE The process of homologous recombination (HR) is important for maintenance of genome integrity in all cells. In Escherichia coli, the RecA protein is a critical participant in HR, which acts at a step common to and downstream of two HR pathways mediated by the RecBCD and RecFOR proteins, respectively. In this study, an isoform (IF2-1) of the translation initiation factor IF2 has been identified as a novel facilitator of RecA's function in vivo during HR.
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Cai X, Wang Q, Fang Y, Yao D, Zhan Y, An B, Yan B, Cai J. Attenuator LRR - a regulatory tool for modulating gene expression in Gram-positive bacteria. Microb Biotechnol 2021; 14:2538-2551. [PMID: 33720523 PMCID: PMC8601186 DOI: 10.1111/1751-7915.13797] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 02/24/2021] [Accepted: 02/24/2021] [Indexed: 11/28/2022] Open
Abstract
With the rapid development of synthetic biology in recent years, particular attention has been paid to RNA devices, especially riboswitches, because of their significant and diverse regulatory roles in prokaryotic and eukaryotic cells. Due to the limited performance and context-dependence of riboswitches, only a few of them (such as theophylline, tetracycline and ciprofloxacin riboswitches) have been utilized as regulatory tools in biotechnology. In the present study, we demonstrated that a ribosome-dependent ribo-regulator, LRR, discovered in our previous work, exhibits an attractive regulatory performance. Specifically, it offers a 60-fold change in expression in the presence of retapamulin and a low level of leaky expression of about 1-2% without antibiotics. Moreover, LRR can be combined with different promoters and performs well in Bacillus thuringiensis, B. cereus, B. amyloliquefaciens, and B. subtilis. Additionally, LRR also functions in the Gram-negative bacterium Escherichia coli. Furthermore, we demonstrate its ability to control melanin metabolism in B. thuringiensis BMB171. Our results show that LRR can be applied to regulate gene expression, construct genetic circuits and tune metabolic pathways, and has great potential for many applications in synthetic biology.
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Affiliation(s)
- Xia Cai
- Department of MicrobiologyCollege of Life SciencesNankai UniversityTianjin300071China
| | - Qian Wang
- Department of MicrobiologyCollege of Life SciencesNankai UniversityTianjin300071China
| | - Yu Fang
- Department of MicrobiologyCollege of Life SciencesNankai UniversityTianjin300071China
| | - Die Yao
- Department of MicrobiologyCollege of Life SciencesNankai UniversityTianjin300071China
| | - Yunda Zhan
- Department of MicrobiologyCollege of Life SciencesNankai UniversityTianjin300071China
| | - Baoju An
- Department of MicrobiologyCollege of Life SciencesNankai UniversityTianjin300071China
| | - Bing Yan
- Department of MicrobiologyCollege of Life SciencesNankai UniversityTianjin300071China
| | - Jun Cai
- Department of MicrobiologyCollege of Life SciencesNankai UniversityTianjin300071China
- Key Laboratory of Molecular Microbiology and TechnologyMinistry of EducationTianjin300071China
- Tianjin Key Laboratory of Microbial Functional GenomicsTianjin300071China
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9
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Zheleva A, Camino LP, Fernández-Fernández N, García-Rubio M, Askjaer P, García-Muse T, Aguilera A. THSC/TREX-2 deficiency causes replication stress and genome instability in Caenorhabditis elegans. J Cell Sci 2021; 134:jcs258435. [PMID: 34553761 PMCID: PMC10658913 DOI: 10.1242/jcs.258435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 09/11/2021] [Indexed: 11/20/2022] Open
Abstract
Transcription is an essential process of DNA metabolism, yet it makes DNA more susceptible to DNA damage. THSC/TREX-2 is a conserved eukaryotic protein complex with a key role in mRNP biogenesis and maturation that prevents genome instability. One source of such instability is linked to transcription, as shown in yeast and human cells, but the underlying mechanism and whether this link is universal is still unclear. To obtain further insight into the putative role of the THSC/TREX-2 complex in genome integrity, we have used Caenorhabditis elegans mutants of the thp-1 and dss-1 components of THSC/TREX-2. These mutants show similar defective meiosis, DNA damage accumulation and activation of the DNA damage checkpoint. However, they differ from each other regarding replication defects, as determined by measuring dUTP incorporation in the germline. Interestingly, this specific thp-1 mutant phenotype can be partially rescued by overexpression of RNase H. Furthermore, both mutants show a mild increase in phosphorylation of histone H3 at Ser10 (H3S10P), a mark previously shown to be linked to DNA-RNA hybrid-mediated genome instability. These data support the view that both THSC/TREX-2 factors prevent transcription-associated DNA damage derived from DNA-RNA hybrid accumulation by separate means.
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Affiliation(s)
- Angelina Zheleva
- Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas-Universidad Pablo de Olavide, 41092 Seville, Spain
| | - Lola P. Camino
- Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas-Universidad Pablo de Olavide, 41092 Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - Nuria Fernández-Fernández
- Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas-Universidad Pablo de Olavide, 41092 Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - María García-Rubio
- Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas-Universidad Pablo de Olavide, 41092 Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - Peter Askjaer
- Centro Andaluz de Biología del Desarrollo (CABD), Consejo Superior de Investigaciones Científicas-Universidad Pablo de Olavide, 41013 Seville, Spain
| | - Tatiana García-Muse
- Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas-Universidad Pablo de Olavide, 41092 Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas-Universidad Pablo de Olavide, 41092 Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
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10
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Topoisomerase I Essentiality, DnaA-Independent Chromosomal Replication, and Transcription-Replication Conflict in Escherichia coli. J Bacteriol 2021; 203:e0019521. [PMID: 34124945 DOI: 10.1128/jb.00195-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Topoisomerase I (Topo I) of Escherichia coli, encoded by topA, acts to relax negative supercoils in DNA. Topo I deficiency results in hypernegative supercoiling, formation of transcription-associated RNA-DNA hybrids (R-loops), and DnaA- and oriC-independent constitutive stable DNA replication (cSDR), but some uncertainty persists as to whether topA is essential for viability in E. coli and related enterobacteria. Here, we show that several topA alleles, including ΔtopA, confer lethality in derivatives of wild-type E. coli strain MG1655. Viability in the absence of Topo I was restored with two perturbations, neither of which reversed the hypernegative supercoiling phenotype: (i) in a reduced-genome strain (MDS42) or (ii) by an RNA polymerase (RNAP) mutation, rpoB*35, that has been reported to alleviate the deleterious consequences of RNAP backtracking and transcription-replication conflicts. Four phenotypes related to cSDR were identified for topA mutants: (i) one of the topA alleles rescued ΔdnaA lethality; (ii) in dnaA+ derivatives, Topo I deficiency generated a characteristic copy number peak in the terminus region of the chromosome; (iii) topA was synthetically lethal with rnhA (encoding RNase HI, whose deficiency also confers cSDR); and (iv) topA rnhA synthetic lethality was itself rescued by ΔdnaA. We propose that the terminal lethal consequence of hypernegative DNA supercoiling in E. coli topA mutants is RNAP backtracking during transcription elongation and associated R-loop formation, which in turn leads to transcription-replication conflicts and to cSDR. IMPORTANCE In all life forms, double-helical DNA exists in a topologically supercoiled state. The enzymes DNA gyrase and topoisomerase I act, respectively, to introduce and to relax negative DNA supercoils in Escherichia coli. That gyrase deficiency leads to bacterial death is well established, but the essentiality of topoisomerase I for viability has been less certain. This study confirms that topoisomerase I is essential for E. coli viability and suggests that in its absence, aberrant chromosomal DNA replication and excessive transcription-replication conflicts occur that are responsible for lethality.
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11
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Simon I, Delaleau M, Schwartz A, Boudvillain M. A Large Insertion Domain in the Rho Factor From a Low G + C, Gram-negative Bacterium is Critical for RNA Binding and Transcription Termination Activity. J Mol Biol 2021; 433:167060. [PMID: 34023400 DOI: 10.1016/j.jmb.2021.167060] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/30/2021] [Accepted: 05/16/2021] [Indexed: 10/21/2022]
Abstract
Rho-dependent termination of transcription (RDTT) is a critical regulatory mechanism specific to bacteria. In a subset of species including most Actinobacteria and Bacteroidetes, the Rho factor contains a large, poorly conserved N-terminal insertion domain (NID) of cryptic function. To date, only two NID-bearing Rho factors from high G + C Actinobacteria have been thoroughly characterized. Both can trigger RDTT at promoter-proximal sites or with structurally constrained transcripts that are unsuitable for the archetypal, NID-less Rho factor of Escherichia coli (EcRho). Here, we provide the first biochemical characterization of a NID-bearing Rho factor from a low G + C bacterium. We show that Bacteroides fragilis Rho (BfRho) is a bona fide RNA-dependent NTPase motor able to unwind long RNA:DNA duplexes and to disrupt transcription complexes. The large NID (~40% of total mass) strongly increases BfRho affinity for RNA, is strictly required for RDTT, but does not promote RDTT at promoter-proximal sites or with a structurally constrained transcript. Furthermore, the NID does not preclude modulation of RDTT by transcription factors NusA and NusG or by the Rho inhibitor bicyclomycin. Although the NID contains a prion-like Q/N-rich motif, it does not spontaneously trigger formation of β-amyloids. Thus, despite its unusually large RNA binding domain, BfRho behaves more like the NID-less EcRho than NID-bearing counterparts from high G + C Actinobacteria. Our data highlight the evolutionary plasticity of Rho's N-terminal region and illustrate how RDTT is adapted to distinct genomic contents.
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Affiliation(s)
- Isabelle Simon
- Centre de Biophysique Moléculaire, CNRS UPR4301, Rue Charles Sadron, 45071 Orléans cedex 2, France; ED 549, Santé, Sciences Biologiques & Chimie du Vivant, Université d'Orléans, France
| | - Mildred Delaleau
- Centre de Biophysique Moléculaire, CNRS UPR4301, Rue Charles Sadron, 45071 Orléans cedex 2, France
| | - Annie Schwartz
- Centre de Biophysique Moléculaire, CNRS UPR4301, Rue Charles Sadron, 45071 Orléans cedex 2, France
| | - Marc Boudvillain
- Centre de Biophysique Moléculaire, CNRS UPR4301, Rue Charles Sadron, 45071 Orléans cedex 2, France.
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12
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Irastortza-Olaziregi M, Amster-Choder O. Coupled Transcription-Translation in Prokaryotes: An Old Couple With New Surprises. Front Microbiol 2021; 11:624830. [PMID: 33552035 PMCID: PMC7858274 DOI: 10.3389/fmicb.2020.624830] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 12/18/2020] [Indexed: 01/17/2023] Open
Abstract
Coupled transcription-translation (CTT) is a hallmark of prokaryotic gene expression. CTT occurs when ribosomes associate with and initiate translation of mRNAs whose transcription has not yet concluded, therefore forming "RNAP.mRNA.ribosome" complexes. CTT is a well-documented phenomenon that is involved in important gene regulation processes, such as attenuation and operon polarity. Despite the progress in our understanding of the cellular signals that coordinate CTT, certain aspects of its molecular architecture remain controversial. Additionally, new information on the spatial segregation between the transcriptional and the translational machineries in certain species, and on the capability of certain mRNAs to localize translation-independently, questions the unanimous occurrence of CTT. Furthermore, studies where transcription and translation were artificially uncoupled showed that transcription elongation can proceed in a translation-independent manner. Here, we review studies supporting the occurrence of CTT and findings questioning its extent, as well as discuss mechanisms that may explain both coupling and uncoupling, e.g., chromosome relocation and the involvement of cis- or trans-acting elements, such as small RNAs and RNA-binding proteins. These mechanisms impact RNA localization, stability, and translation. Understanding the two options by which genes can be expressed and their consequences should shed light on a new layer of control of bacterial transcripts fate.
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Affiliation(s)
- Mikel Irastortza-Olaziregi
- Department of Microbiology and Molecular Genetics, Faculty of Medicine, IMRIC, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Orna Amster-Choder
- Department of Microbiology and Molecular Genetics, Faculty of Medicine, IMRIC, The Hebrew University of Jerusalem, Jerusalem, Israel
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13
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Wang B, Artsimovitch I. NusG, an Ancient Yet Rapidly Evolving Transcription Factor. Front Microbiol 2021; 11:619618. [PMID: 33488562 PMCID: PMC7819879 DOI: 10.3389/fmicb.2020.619618] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 12/07/2020] [Indexed: 12/19/2022] Open
Abstract
Timely and accurate RNA synthesis depends on accessory proteins that instruct RNA polymerase (RNAP) where and when to start and stop transcription. Among thousands of transcription factors, NusG/Spt5 stand out as the only universally conserved family of regulators. These proteins interact with RNAP to promote uninterrupted RNA synthesis and with diverse cellular partners to couple transcription to RNA processing, modification or translation, or to trigger premature termination of aberrant transcription. NusG homologs are present in all cells that utilize bacterial-type RNAP, from endosymbionts to plants, underscoring their ancient and essential function. Yet, in stark contrast to other core RNAP components, NusG family is actively evolving: horizontal gene transfer and sub-functionalization drive emergence of NusG paralogs, such as bacterial LoaP, RfaH, and UpxY. These specialized regulators activate a few (or just one) operons required for expression of antibiotics, capsules, secretion systems, toxins, and other niche-specific macromolecules. Despite their common origin and binding site on the RNAP, NusG homologs differ in their target selection, interacting partners and effects on RNA synthesis. Even among housekeeping NusGs from diverse bacteria, some factors promote pause-free transcription while others slow the RNAP down. Here, we discuss structure, function, and evolution of NusG proteins, focusing on unique mechanisms that determine their effects on gene expression and enable bacterial adaptation to diverse ecological niches.
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Affiliation(s)
- Bing Wang
- Department of Microbiology and the Center for RNA Biology, The Ohio State University, Columbus, OH, United States
| | - Irina Artsimovitch
- Department of Microbiology and the Center for RNA Biology, The Ohio State University, Columbus, OH, United States
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14
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Abstract
Exposure of bacteria to sublethal concentrations of antibiotics can lead to bacterial adaptation and survival at higher doses of inhibitors, which in turn can lead to the emergence of antibiotic resistance. The presence of sublethal concentrations of antibiotics targeting translation results in an increase in the amount of ribosomes per cell but nonetheless a decrease in the cells’ growth rate. In this work, we have found that inhibition of ribosome activity can result in a decrease in the amount of free RNA polymerase available for transcription, thus limiting the protein expression rate via a different pathway than what was expected. This result can be explained by our observation that long genes, such as those coding for RNA polymerase subunits, have a higher probability of premature translation termination in the presence of ribosome inhibitors, while expression of short ribosomal genes is affected less, consistent with their increased concentration. In bacterial cells, inhibition of ribosomes by sublethal concentrations of antibiotics leads to a decrease in the growth rate despite an increase in ribosome content. The limitation of ribosomal activity results in an increase in the level of expression from ribosomal promoters; this can deplete the pool of RNA polymerase (RNAP) that is available for the expression of nonribosomal genes. However, the magnitude of this effect remains to be quantified. Here, we use the change in the activity of constitutive promoters with different affinities for RNAP to quantify the change in the concentration of free RNAP. The data are consistent with a significant decrease in the amount of RNAP available for transcription of both ribosomal and nonribosomal genes. Results obtained with different reporter genes reveal an mRNA length dependence on the amount of full-length translated protein, consistent with the decrease in ribosome processivity affecting more strongly the translation of longer genes. The genes coding for the β and β' subunits of RNAP are among the longest genes in the Escherichia coli genome, while the genes coding for ribosomal proteins are among the shortest genes. This can explain the observed decrease in transcription capacity that favors the expression of genes whose promoters have a high affinity for RNAP, such as ribosomal promoters. IMPORTANCE Exposure of bacteria to sublethal concentrations of antibiotics can lead to bacterial adaptation and survival at higher doses of inhibitors, which in turn can lead to the emergence of antibiotic resistance. The presence of sublethal concentrations of antibiotics targeting translation results in an increase in the amount of ribosomes per cell but nonetheless a decrease in the cells’ growth rate. In this work, we have found that inhibition of ribosome activity can result in a decrease in the amount of free RNA polymerase available for transcription, thus limiting the protein expression rate via a different pathway than what was expected. This result can be explained by our observation that long genes, such as those coding for RNA polymerase subunits, have a higher probability of premature translation termination in the presence of ribosome inhibitors, while expression of short ribosomal genes is affected less, consistent with their increased concentration.
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15
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Johnson GE, Lalanne JB, Peters ML, Li GW. Functionally uncoupled transcription-translation in Bacillus subtilis. Nature 2020; 585:124-128. [PMID: 32848247 PMCID: PMC7483943 DOI: 10.1038/s41586-020-2638-5] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 05/22/2020] [Indexed: 11/10/2022]
Abstract
Tight coupling of transcription and translation is considered a defining feature of bacterial gene expression1,2. The pioneering ribosome can both physically associate and kinetically coordinate with RNA polymerase (RNAP)3-11, forming a signal-integration hub for co-transcriptional regulation that includes translation-based attenuation12,13 and RNA quality control2. However, it remains unclear whether transcription-translation coupling-together with its broad functional consequences-is indeed a fundamental characteristic of bacteria other than Escherichia coli. Here we show that RNAPs outpace pioneering ribosomes in the Gram-positive model bacterium Bacillus subtilis, and that this 'runaway transcription' creates alternative rules for both global RNA surveillance and translational control of nascent RNA. In particular, uncoupled RNAPs in B. subtilis explain the diminished role of Rho-dependent transcription termination, as well as the prevalence of mRNA leaders that use riboswitches and RNA-binding proteins. More broadly, we identified widespread genomic signatures of runaway transcription in distinct phyla across the bacterial domain. Our results show that coupled RNAP-ribosome movement is not a general hallmark of bacteria. Instead, translation-coupled transcription and runaway transcription constitute two principal modes of gene expression that determine genome-specific regulatory mechanisms in prokaryotes.
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Affiliation(s)
- Grace E Johnson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jean-Benoît Lalanne
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Michelle L Peters
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Gene-Wei Li
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA.
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16
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Huang YH, Hilal T, Loll B, Bürger J, Mielke T, Böttcher C, Said N, Wahl MC. Structure-Based Mechanisms of a Molecular RNA Polymerase/Chaperone Machine Required for Ribosome Biosynthesis. Mol Cell 2020; 79:1024-1036.e5. [DOI: 10.1016/j.molcel.2020.08.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 06/29/2020] [Accepted: 08/11/2020] [Indexed: 01/18/2023]
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17
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Interplay between Position-Dependent Codon Usage Bias and Hydrogen Bonding at the 5' End of ORFeomes. mSystems 2020; 5:5/4/e00613-20. [PMID: 32788408 PMCID: PMC7426154 DOI: 10.1128/msystems.00613-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Codon usage bias exerts control over a wide variety of molecular processes. The positioning of synonymous codons within coding sequences (CDSs) dictates protein expression by mechanisms such as local translation efficiency, mRNA Gibbs free energy, and protein cotranslational folding. In this work, we explore how codon usage affects the position-dependent content of hydrogen bonding, which in turn influences energy requirements for unwinding double-stranded DNA (dsDNA). We categorized codons according to their hydrogen bond content and found differential effects on hydrogen bonding encoded by codon variants. The specific positional disposition of codon variants within CDSs creates a ramp of hydrogen bonding at the 5' end of the ORFeome in Escherichia coli CDSs occupying the first position of operons are subjected to selective pressure that reduces their hydrogen bonding compared to internal CDSs, and highly transcribed CDSs demand a lower maximum capacity of hydrogen bonds per codon, suggesting that the energetic requirement for unwinding the dsDNA in highly transcribed CDSs has evolved to be minimized in E. coli Subsequent analysis of over 14,000 ORFeomes showed a pervasive ramp of hydrogen bonding at the 5' end in Bacteria and Archaea that positively correlates with the probability of mRNA secondary structure formation. Both the ramp and the correlation were not found in Fungi The position-dependent hydrogen bonding might be part of the mechanism that contributes to the coordination between transcription and translation in Bacteria and Archaea A Web-based application to analyze the position-dependent hydrogen bonding of ORFeomes has been developed and is publicly available (https://juanvillada.shinyapps.io/hbonds/).IMPORTANCE Redundancy of the genetic code creates a vast space of alternatives to encode a protein. Synonymous codons exert control over a variety of molecular and physiological processes of cells mainly through influencing protein biosynthesis. Recent findings have shown that synonymous codon choice affects transcription by controlling mRNA abundance, mRNA stability, transcription termination, and transcript biosynthesis cost. In this work, by analyzing thousands of Bacteria, Archaea, and Fungi genomes, we extend recent findings by showing that synonymous codon choice, corresponding to the number of hydrogen bonds in a codon, can also have an effect on the energetic requirements for unwinding double-stranded DNA in a position-dependent fashion. This report offers new perspectives on the mechanism behind the transcription-translation coordination and complements previous hypotheses on the resource allocation strategies used by Bacteria and Archaea to manage energy efficiency in gene expression.
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18
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Dai X, Zhu M. Coupling of Ribosome Synthesis and Translational Capacity with Cell Growth. Trends Biochem Sci 2020; 45:681-692. [DOI: 10.1016/j.tibs.2020.04.010] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 04/11/2020] [Accepted: 04/27/2020] [Indexed: 12/31/2022]
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19
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Chen M, Fredrick K. RNA Polymerase's Relationship with the Ribosome: Not So Physical, Most of the Time. J Mol Biol 2020; 432:3981-3986. [PMID: 32198117 DOI: 10.1016/j.jmb.2020.03.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 03/03/2020] [Accepted: 03/11/2020] [Indexed: 01/19/2023]
Abstract
In bacteria, the rates of transcription elongation and translation elongation are coordinated, changing together in response to growth conditions. It has been proposed that this is due to physical coupling of RNA polymerase and the lead ribosome on nascent mRNA, an interaction important for preventing premature transcription termination by Rho factor. Recent studies challenge this view and provide evidence that coordination is indirect, mediated in Escherichia coli by the alarmone (p)ppGpp. Here, we discuss these new findings and how they shape our understanding of the functional relationship between RNA polymerase and the ribosome as well as the basis of transcriptional polarity.
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Affiliation(s)
- Menglin Chen
- Department of Microbiology, Ohio State Biochemistry Program, and Center for RNA Biology, The Ohio State University, 484 W. 12(th) Ave, Columbus, OH, 43210, USA
| | - Kurt Fredrick
- Department of Microbiology, Ohio State Biochemistry Program, and Center for RNA Biology, The Ohio State University, 484 W. 12(th) Ave, Columbus, OH, 43210, USA.
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20
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Veetil RT, Malhotra N, Dubey A, Seshasayee ASN. Laboratory Evolution Experiments Help Identify a Predominant Region of Constitutive Stable DNA Replication Initiation. mSphere 2020; 5:e00939-19. [PMID: 32102945 PMCID: PMC7045392 DOI: 10.1128/msphere.00939-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 02/06/2020] [Indexed: 01/06/2023] Open
Abstract
The bacterium Escherichia coli can initiate replication in the absence of the replication initiator protein DnaA and/or the canonical origin of replication oriC in a ΔrnhA background. This phenomenon, which can be primed by R-loops, is called constitutive stable DNA replication (cSDR). Whether DNA replication during cSDR initiates in a stochastic manner through the length of the chromosome or at specific sites and how E. coli can find adaptations to loss of fitness caused by cSDR remain inadequately answered. We use laboratory evolution experiments of ΔrnhA-ΔdnaA strains followed by deep sequencing to show that DNA replication preferentially initiates within a broad region located ∼0.4 to 0.7 Mb clockwise of oriC. This region includes many bisulfite-sensitive sites, which have been previously defined as R-loop-forming regions, and includes a site containing sequence motifs that favor R-loop formation. Initiation from this region would result in head-on replication-transcription conflicts at rRNA loci. Inversions of these rRNA loci, which can partly resolve these conflicts, help the bacterium suppress the fitness defects of cSDR. These inversions partially restore the gene expression changes brought about by cSDR. The inversion, however, increases the possibility of conflicts at essential mRNA genes, which would utilize only a minuscule fraction of RNA polymerase molecules, most of which transcribe rRNA genes. Whether subsequent adaptive strategies would attempt to resolve these conflicts remains an open question.IMPORTANCE The bacterium E. coli can replicate its DNA even in the absence of the molecules that are required for canonical replication initiation. This often requires the formation of RNA-DNA hybrid structures and is referred to as constitutive stable DNA replication (cSDR). Where on the chromosome does cSDR initiate? We answer this question using laboratory evolution experiments and genomics and show that selection favors cSDR initiation predominantly at a region ∼0.6 Mb clockwise of oriC. Initiation from this site will result in more head-on collisions of DNA polymerase with RNA polymerase operating on rRNA loci. The bacterium adapts to this problem by inverting a region of the genome including several rRNA loci such that head-on collisions between the two polymerases are minimized. Understanding such evolutionary strategies in the context of cSDR can provide insights into the potential causes of resistance to antibiotics that target initiation of DNA replication.
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Affiliation(s)
- Reshma T Veetil
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Gandhi Krishi Vigyan Kendra, Bengaluru, Karnataka, India
- School of Life Science, The University of Trans-Disciplinary Health Sciences & Technology (TDU), Bengaluru, Karnataka, India
| | - Nitish Malhotra
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Gandhi Krishi Vigyan Kendra, Bengaluru, Karnataka, India
| | - Akshara Dubey
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Gandhi Krishi Vigyan Kendra, Bengaluru, Karnataka, India
| | - Aswin Sai Narain Seshasayee
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Gandhi Krishi Vigyan Kendra, Bengaluru, Karnataka, India
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21
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Huang YH, Said N, Loll B, Wahl MC. Structural basis for the function of SuhB as a transcription factor in ribosomal RNA synthesis. Nucleic Acids Res 2020; 47:6488-6503. [PMID: 31020314 PMCID: PMC6614801 DOI: 10.1093/nar/gkz290] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 03/29/2019] [Accepted: 04/10/2019] [Indexed: 11/28/2022] Open
Abstract
Ribosomal RNA synthesis in Escherichia coli involves a transcription complex, in which RNA polymerase is modified by a signal element on the transcript, Nus factors A, B, E and G, ribosomal protein S4 and inositol mono-phosphatase SuhB. This complex is resistant to ρ-dependent termination and facilitates ribosomal RNA folding, maturation and subunit assembly. The functional contributions of SuhB and their structural bases are presently unclear. We show that SuhB directly binds the RNA signal element and the C-terminal AR2 domain of NusA, and we delineate the atomic basis of the latter interaction by macromolecular crystallography. SuhB recruitment to a ribosomal RNA transcription complex depends on the RNA signal element but not on the NusA AR2 domain. SuhB in turn is required for stable integration of the NusB/E dimer into the complex. In vitro transcription assays revealed that SuhB is crucial for delaying or suppressing ρ-dependent termination, that SuhB also can reduce intrinsic termination, and that SuhB-AR2 contacts contribute to these effects. Together, our results reveal functions of SuhB during ribosomal RNA synthesis and delineate some of the underlying molecular interactions.
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Affiliation(s)
- Yong-Heng Huang
- Freie Universität Berlin, Laboratory of Structural Biochemistry, Takustraβe 6, D-14195 Berlin, Germany
| | - Nelly Said
- Freie Universität Berlin, Laboratory of Structural Biochemistry, Takustraβe 6, D-14195 Berlin, Germany
| | - Bernhard Loll
- Freie Universität Berlin, Laboratory of Structural Biochemistry, Takustraβe 6, D-14195 Berlin, Germany
| | - Markus C Wahl
- Freie Universität Berlin, Laboratory of Structural Biochemistry, Takustraβe 6, D-14195 Berlin, Germany.,Helmholtz-Zentrum Berlin für Materialien und Energie, Macromolecular Crystallography, Albert-Einstein-Straße 15, D-12489 Berlin, Germany
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22
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Zhu M, Mori M, Hwa T, Dai X. Disruption of transcription-translation coordination in Escherichia coli leads to premature transcriptional termination. Nat Microbiol 2019; 4:2347-2356. [PMID: 31451774 PMCID: PMC6903697 DOI: 10.1038/s41564-019-0543-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2019] [Accepted: 07/18/2019] [Indexed: 11/09/2022]
Abstract
Tight coordination between transcription and translation is crucial to maintaining the integrity of gene expression in bacteria, yet how bacteria manage to coordinate these two processes remains unclear. Possible direct physical coupling between the RNA polymerase and ribosome has been thoroughly investigated in recent years. Here, we quantitatively characterize the transcriptional kinetics of Escherichia coli under different growth conditions. Transcriptional and translational elongation remain coordinated under various nutrient conditions, as previously reported. However, transcriptional elongation was not affected under antibiotics that slowed down translational elongation. This result was also found by introducing nonsense mutation that completely dissociated transcription from translation. Our data thus provide direct evidence that translation is not required to maintain the speed of transcriptional elongation. In cases where transcription and translation are dissociated, our study provides quantitative characterization of the resulting process of premature transcriptional termination (PTT). PTT-mediated polarity caused by translation-targeting antibiotics substantially affected the coordinated expression of genes in several long operons, contributing to the key physiological effects of these antibiotics. Our results also suggest a model in which the coordination between transcriptional and translational elongation under normal growth conditions is implemented by guanosine tetraphosphate.
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Affiliation(s)
- Manlu Zhu
- School of Life Sciences, Central China Normal University, Wuhan, China
| | - Matteo Mori
- Department of Physics, University of California at San Diego, La Jolla, CA, USA
| | - Terence Hwa
- Department of Physics, University of California at San Diego, La Jolla, CA, USA.
| | - Xiongfeng Dai
- School of Life Sciences, Central China Normal University, Wuhan, China.
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23
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Stoof R, Wood A, Goñi-Moreno Á. A Model for the Spatiotemporal Design of Gene Regulatory Circuits †. ACS Synth Biol 2019; 8:2007-2016. [PMID: 31429541 DOI: 10.1021/acssynbio.9b00022] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Mathematical modeling assists the design of synthetic regulatory networks by providing a detailed mechanistic understanding of biological systems. Models that can predict the performance of a design are fundamental for synthetic biology since they minimize iterations along the design-build-test lifecycle. Such predictability depends crucially on what assumptions (i.e., biological simplifications) the model considers. Here, we challenge a common assumption when it comes to the modeling of bacterial-based gene regulation: considering negligible the effects of intracellular physical space. It is commonly assumed that molecules, such as transcription factors (TF), are homogeneously distributed inside a cell, so there is no need to model their diffusion. We describe a mathematical model that accounts for molecular diffusion and show how simulations of network performance are decisively affected by the distance between its components. Specifically, the model focuses on the search by a TF for its target promoter. The combination of local searches, via one-dimensional sliding along the chromosome, and global searches, via three-dimensional diffusion through the cytoplasm, determine TF-promoter interplay. Previous experimental results with engineered bacteria in which the distance between TF source and target was minimized or enlarged were successfully reproduced by the spatially resolved model we introduce here. This suggests that the spatial specification of the circuit alone can be exploited as a design parameter in synthetic biology to select programmable output levels.
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Affiliation(s)
- Ruud Stoof
- School of Computing, Newcastle University, Newcastle upon Tyne NE4 5TG, U.K
| | - Alexander Wood
- School of Computing, Newcastle University, Newcastle upon Tyne NE4 5TG, U.K
| | - Ángel Goñi-Moreno
- School of Computing, Newcastle University, Newcastle upon Tyne NE4 5TG, U.K
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24
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Carrier MC, Lalaouna D, Massé E. Broadening the Definition of Bacterial Small RNAs: Characteristics and Mechanisms of Action. Annu Rev Microbiol 2019; 72:141-161. [PMID: 30200848 DOI: 10.1146/annurev-micro-090817-062607] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The first report of trans-acting RNA-based regulation in bacterial cells dates back to 1984. Subsequent studies in diverse bacteria unraveled shared properties of trans-acting small regulatory RNAs, forming a clear definition of these molecules. These shared characteristics have been used extensively to identify new small RNAs (sRNAs) and their interactomes. Recently however, emerging technologies able to resolve RNA-RNA interactions have identified new types of regulatory RNAs. In this review, we present a broader definition of trans-acting sRNA regulators and discuss their newly discovered intrinsic characteristics.
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Affiliation(s)
- Marie-Claude Carrier
- RNA Group, Department of Biochemistry, University of Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada; , ,
| | - David Lalaouna
- RNA Group, Department of Biochemistry, University of Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada; , ,
| | - Eric Massé
- RNA Group, Department of Biochemistry, University of Sherbrooke, Sherbrooke, Quebec J1H 5N4, Canada; , ,
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25
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Kovacs-Simon A, Hemsley CM, Scott AE, Prior JL, Titball RW. Burkholderia thailandensis strain E555 is a surrogate for the investigation of Burkholderia pseudomallei replication and survival in macrophages. BMC Microbiol 2019; 19:97. [PMID: 31092204 PMCID: PMC6521459 DOI: 10.1186/s12866-019-1469-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 04/30/2019] [Indexed: 02/02/2023] Open
Abstract
Background Burkholderia pseudomallei is a human pathogen causing severe infections in tropical and subtropical regions and is classified as a bio-threat agent. B. thailandensis strain E264 has been proposed as less pathogenic surrogate for understanding the interactions of B. pseudomallei with host cells. Results We show that, unlike B. thailandensis strain E264, the pattern of growth of B. thailandensis strain E555 in macrophages is similar to that of B. pseudomallei. We have genome sequenced B. thailandensis strain E555 and using the annotated sequence identified genes and proteins up-regulated during infection. Changes in gene expression identified more of the known B. pseudomallei virulence factors than changes in protein levels and used together we identified 16% of the currently known B. pseudomallei virulence factors. These findings demonstrate the utility of B. thailandensis strain E555 to study virulence of B. pseudomallei. Conclusions A weakness of studies using B. thailandensis as a surrogate for B. pseudomallei is that the strains used replicate at a slower rate in infected cells. We show that the pattern of growth of B. thailandensis strain E555 in macrophages closely mirrors that of B. pseudomallei. Using this infection model we have shown that virulence factors of B. pseudomallei can be identified as genes or proteins whose expression is elevated on the infection of macrophages. This finding confirms the utility of B. thailandensis strain E555 as a surrogate for B. pseudomallei and this strain should be used for future studies on virulence mechanisms. Electronic supplementary material The online version of this article (10.1186/s12866-019-1469-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- A Kovacs-Simon
- College of Life and Environmental Sciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter, EX4 4QD, UK.
| | - C M Hemsley
- College of Life and Environmental Sciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter, EX4 4QD, UK
| | - A E Scott
- CBR Division, Defence Science and Technology Laboratory, Porton Down, Salisbury, SP4 0JQ, UK
| | - J L Prior
- College of Life and Environmental Sciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter, EX4 4QD, UK.,CBR Division, Defence Science and Technology Laboratory, Porton Down, Salisbury, SP4 0JQ, UK
| | - R W Titball
- College of Life and Environmental Sciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter, EX4 4QD, UK
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26
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Mathieu K, Javed W, Vallet S, Lesterlin C, Candusso MP, Ding F, Xu XN, Ebel C, Jault JM, Orelle C. Functionality of membrane proteins overexpressed and purified from E. coli is highly dependent upon the strain. Sci Rep 2019; 9:2654. [PMID: 30804404 PMCID: PMC6390180 DOI: 10.1038/s41598-019-39382-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 01/22/2019] [Indexed: 11/24/2022] Open
Abstract
Overexpression of correctly folded membrane proteins is a fundamental prerequisite for functional and structural studies. One of the most commonly used expression systems for the production of membrane proteins is Escherichia coli. While misfolded proteins typically aggregate and form inclusions bodies, membrane proteins that are addressed to the membrane and extractable by detergents are generally assumed to be properly folded. Accordingly, GFP fusion strategy is often used as a fluorescent proxy to monitor their expression and folding quality. Here we investigated the functionality of two different multidrug ABC transporters, the homodimer BmrA from Bacillus subtilis and the heterodimer PatA/PatB from Streptococcus pneumoniae, when produced in several E. coli strains with T7 expression system. Strikingly, while strong expression in the membrane of several strains could be achieved, we observed drastic differences in the functionality of these proteins. Moreover, we observed a general trend in which mild detergents mainly extract the population of active transporters, whereas a harsher detergent like Fos-choline 12 could solubilize transporters irrespective of their functionality. Our results suggest that the amount of T7 RNA polymerase transcripts may indirectly but notably impact the structure and activity of overexpressed membrane proteins, and advise caution when using GFP fusion strategy.
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Affiliation(s)
- Khadija Mathieu
- Université de Lyon, CNRS, UMR 5086 "Molecular Microbiology and Structural Biochemistry", IBCP, 69367, Lyon, France
| | - Waqas Javed
- Université de Lyon, CNRS, UMR 5086 "Molecular Microbiology and Structural Biochemistry", IBCP, 69367, Lyon, France.,Université Grenoble Alpes, CNRS, CEA, IBS, 38000, Grenoble, France
| | - Sylvain Vallet
- Université de Lyon, CNRS, UMR 5086 "Molecular Microbiology and Structural Biochemistry", IBCP, 69367, Lyon, France
| | - Christian Lesterlin
- Université de Lyon, CNRS, UMR 5086 "Molecular Microbiology and Structural Biochemistry", IBCP, 69367, Lyon, France
| | - Marie-Pierre Candusso
- Université de Lyon, CNRS, UMR 5086 "Molecular Microbiology and Structural Biochemistry", IBCP, 69367, Lyon, France
| | - Feng Ding
- Department of Chemistry & Biochemistry, Old Dominion University, Norfolk, VA, 23529, USA
| | - Xiaohong Nancy Xu
- Department of Chemistry & Biochemistry, Old Dominion University, Norfolk, VA, 23529, USA
| | - Christine Ebel
- Université Grenoble Alpes, CNRS, CEA, IBS, 38000, Grenoble, France
| | - Jean-Michel Jault
- Université de Lyon, CNRS, UMR 5086 "Molecular Microbiology and Structural Biochemistry", IBCP, 69367, Lyon, France.
| | - Cédric Orelle
- Université de Lyon, CNRS, UMR 5086 "Molecular Microbiology and Structural Biochemistry", IBCP, 69367, Lyon, France.
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27
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Abstract
Organisms display astonishing levels of cell and molecular diversity, including genome size, shape, and architecture. In this chapter, we review how the genome can be viewed as both a structural and an informational unit of biological diversity and explicitly define our intended meaning of genetic information. A brief overview of the characteristic features of bacterial, archaeal, and eukaryotic cell types and viruses sets the stage for a review of the differences in organization, size, and packaging strategies of their genomes. We include a detailed review of genetic elements found outside the primary chromosomal structures, as these provide insights into how genomes are sometimes viewed as incomplete informational entities. Lastly, we reassess the definition of the genome in light of recent advancements in our understanding of the diversity of genomic structures and the mechanisms by which genetic information is expressed within the cell. Collectively, these topics comprise a good introduction to genome biology for the newcomer to the field and provide a valuable reference for those developing new statistical or computation methods in genomics. This review also prepares the reader for anticipated transformations in thinking as the field of genome biology progresses.
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28
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Raghunathan N, Kapshikar RM, Leela JK, Mallikarjun J, Bouloc P, Gowrishankar J. Genome-wide relationship between R-loop formation and antisense transcription in Escherichia coli. Nucleic Acids Res 2018; 46:3400-3411. [PMID: 29474582 PMCID: PMC5909445 DOI: 10.1093/nar/gky118] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 01/30/2018] [Accepted: 02/09/2018] [Indexed: 12/22/2022] Open
Abstract
Transcription termination by Rho is essential for viability in various bacteria, including some major pathogens. Since Rho acts by targeting nascent RNAs that are not simultaneously translated, it also regulates antisense transcription. Here we show that RNase H-deficient mutants of Escherichia coli exhibit heightened sensitivity to the Rho inhibitor bicyclomycin, and that Rho deficiency provokes increased formation of RNA-DNA hybrids (R-loops) which is ameliorated by expression of the phage T4-derived R-loop helicase UvsW. We also provide evidence that in Rho-deficient cells, R-loop formation blocks subsequent rounds of antisense transcription at more than 500 chromosomal loci. Hence these antisense transcripts, which can extend beyond 10 kb in their length, are only detected when Rho function is absent or compromised and the UvsW helicase is concurrently expressed. Thus the potential for antisense transcription in bacteria is much greater than hitherto recognized; and the cells are able to retain viability even when nearly one-quarter of their total non-rRNA abundance is accounted for by antisense transcripts, provided that R-loop formation from them is curtailed.
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Affiliation(s)
- Nalini Raghunathan
- Laboratory of Bacterial Genetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana 500039, India
- Graduate Studies, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India
| | - Rajvardhan M Kapshikar
- Laboratory of Bacterial Genetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana 500039, India
- Graduate Studies, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India
| | - Jakku K Leela
- Laboratory of Bacterial Genetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana 500039, India
| | - Jillella Mallikarjun
- Laboratory of Bacterial Genetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana 500039, India
- Graduate Studies, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India
| | - Philippe Bouloc
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, F-91198, Gif-sur-Yvette cedex, France
| | - Jayaraman Gowrishankar
- Laboratory of Bacterial Genetics, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana 500039, India
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29
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Logic of two antagonizing intra-species quorum sensing systems in bacteria. Biosystems 2018; 165:88-98. [PMID: 29407383 DOI: 10.1016/j.biosystems.2018.01.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 12/08/2017] [Accepted: 01/10/2018] [Indexed: 12/24/2022]
Abstract
Bacteria release signaling molecules into the surrounding environment and sense them when present in their proximity. Using this strategy, a cell estimates the number of neighbors in its surrounding. Upon sensing a critical number of individuals, bacteria coordinate a number of cellular processes. This density-dependent control of gene expression and physiology is called quorum sensing (QS). Quorum sensing controls a wide variety of functions in bacteria, including those related to motility, growth, virulence etc. Quorum sensing has been widely observed in bacteria while the individuals of the same species or different species compete and cooperate each other. Interestingly, many species possess more than one QS system (intra-species) and these QS systems interact each other to perform quorum sensing. Thus, several logical arrangements can be possible based on the interaction among intra-species QS systems - parallel, series, antagonizing, and agonizing. In this work, we perform simulations to understand the logic of interaction between two antagonizing intra-species QS systems. In such an interaction, one QS system gets fully expressed and the other only gets partially expressed. This is found to be dictated by the interplay between autoinducer's diffusivity and antagonizing strength. In addition, we speculate an important role of the intracellular regulators (eg. LuxR) in maintaining the uniform response among the individual cells from the different localities. We also expect the interplay between the autoinducer's diffusivity and distribution of cells in fine tuning the collective response. Interestingly, in a localized niche with a heterogeneous cell distribution, the cells are expected to perform a global quorum sensing via fully expressed QS system and a local quorum sensing via partially expressed QS system.
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30
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Abstract
The central dogma processes of DNA replication, transcription, and translation are responsible for the maintenance and expression of every gene in an organism. An orthogonal central dogma may insulate genetic programs from host regulation and allow expansion in the roles of these processes within the cell.
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Affiliation(s)
- Chang C. Liu
- Department of Biomedical Engineering, University of California, Irvine, California, USA
- Department of Chemistry, University of California, Irvine, California, USA
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California, USA
| | - Michael C. Jewett
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois, USA
| | - Jason W. Chin
- Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
- Department of Chemistry, Cambridge University, Cambridge, UK
| | - Chris A. Voigt
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Synthetic Biology Center, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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31
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Abstract
Topoisomerase I (Top1) resolves torsional stress that accumulates during transcription, replication and chromatin remodeling by introducing a transient single-strand break in DNA. The cleavage activity of Top1 has opposing roles, either promoting or destabilizing genome integrity depending on the context. Resolution of transcription-associated negative supercoils, for example, prevents pairing of the nascent RNA with the DNA template (R-loops) as well as DNA secondary structure formation. Reduced Top1 levels thus enhance CAG repeat contraction, somatic hypermutation, and class switch recombination. Actively transcribed ribosomal DNA is also destabilized in the absence of Top1, reflecting the importance of Top1 in ensuring efficient transcription. In terms of promoting genome instability, an aborted Top1 catalytic cycle stimulates deletions at short tandem repeats and the enzyme's transesterification activity supports illegitimate recombination. Finally, Top1 incision at ribonucleotides embedded in DNA generates deletions in tandem repeats, and induces gross chromosomal rearrangements and mitotic recombination.
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Affiliation(s)
- Jang-Eun Cho
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, 213 Research Drive, CARL 384, Durham, NC, 27710, USA
| | - Sue Jinks-Robertson
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, 213 Research Drive, CARL 384, Durham, NC, 27710, USA.
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32
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Peterson BF, Scharf ME. Metatranscriptomic Techniques for Identifying Cellulases in Termites and their Symbionts. Methods Mol Biol 2018; 1796:85-101. [PMID: 29856048 DOI: 10.1007/978-1-4939-7877-9_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Characterizing symbiotic communities, like that of the termite hindgut, is essential for understanding their functionality and capabilities. However, the same complexity that allows termites to digest wood so efficiently also makes them difficult to study. With the expansion in technology and sequencing strategies the feasibility of sequencing entire consortiums or microecosystems is now possible. Here we present an adapted library preparation strategy which allows for the detection and measurement of expressed genes from all three domains of life in a single sample simultaneously. This technique effectively captures the transcriptome contributions by the various members of the consortium regardless of their taxonomic identity, which can then be annotated using custom-built databases and reciprocal BLASTing. Joining the universality of this library prep strategy with the power of bioinformatics allows for the identification of cellulases and other genes encoding carbohydrate active enzymes from complex communities using metatranscriptomics.
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33
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Modulation of Global Transcriptional Regulatory Networks as a Strategy for Increasing Kanamycin Resistance of the Translational Elongation Factor-G Mutants in Escherichia coli. G3-GENES GENOMES GENETICS 2017; 7:3955-3966. [PMID: 29046437 PMCID: PMC5714492 DOI: 10.1534/g3.117.300284] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Evolve and resequence experiments have provided us a tool to understand bacterial adaptation to antibiotics. In our previous work, we used short-term evolution to isolate mutants resistant to the ribosome targeting antibiotic kanamycin, and reported that Escherichia coli develops low cost resistance to kanamycin via different point mutations in the translation Elongation Factor-G (EF-G). Furthermore, we had shown that the resistance of EF-G mutants could be increased by second site mutations in the genes rpoD/cpxA/topA/cyaA Mutations in three of these genes had been discovered in earlier screens for aminoglycoside resistance. In this work, we expand our understanding of these second site mutations, the goal being to understand how these mutations affect the activities of the mutated gene products to confer resistance. We show that the mutation in cpxA most likely results in an active Cpx stress response. Further evolution of an EF-G mutant in a higher concentration of kanamycin than what was used in our previous experiments identified the cpxA locus as a primary target for a significant increase in resistance. The mutation in cyaA results in a loss of catalytic activity and probably results in resistance via altered CRP function. Despite a reduction in cAMP levels, the CyaAN600Y mutant has a transcriptome indicative of increased CRP activity, pointing to an unknown role for CyaA and / or cAMP in gene expression. From the transcriptomes of double and single mutants, we describe the epistasis between the mutation in EF-G and these second site mutations. We show that the large scale transcriptomic changes in the topoisomerase I (FusAA608E-TopAS180L) mutant likely result from increased negative supercoiling in the cell. Finally, genes with known roles in aminoglycoside resistance were present among the misregulated genes in the mutants.
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34
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Kuzminov A. When DNA Topology Turns Deadly - RNA Polymerases Dig in Their R-Loops to Stand Their Ground: New Positive and Negative (Super)Twists in the Replication-Transcription Conflict. Trends Genet 2017; 34:111-120. [PMID: 29179918 DOI: 10.1016/j.tig.2017.10.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2017] [Revised: 10/20/2017] [Accepted: 10/30/2017] [Indexed: 12/19/2022]
Abstract
Head-on replication-transcription conflict is especially bitter in bacterial chromosomes, explaining why actively transcribed genes are always co-oriented with replication. The mechanism of this conflict remains unclear, besides the anticipated accumulation of positive supercoils between head-on-conflicting polymerases. Unexpectedly, experiments in bacterial and human cells reveal that head-on replication-transcription conflict induces R-loops, indicating hypernegative supercoiling [(-)sc] in the region - precisely the opposite of that assumed. Further, as a result of these R-loops, both replication and transcription in the affected region permanently stall, so the failure of R-loop removal in RNase H-deficient bacteria becomes lethal. How hyper(-)sc emerges in the middle of a positively supercoiled chromosomal domain is a mystery that requires rethinking of topoisomerase action around polymerases.
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Affiliation(s)
- Andrei Kuzminov
- Department of Microbiology, University of Illinois at Urbana-Champaign, B103 CLSL, 601 South Goodwin Avenue, Urbana, IL 61801-3709, USA.
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35
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Auboeuf D. Genome evolution is driven by gene expression-generated biophysical constraints through RNA-directed genetic variation: A hypothesis. Bioessays 2017; 39. [DOI: 10.1002/bies.201700069] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Didier Auboeuf
- Univ Lyon, ENS de Lyon, Univ Claude Bernard, CNRS UMR 5239, INSERM U1210; Laboratory of Biology and Modelling of the Cell; Site Jacques Monod; Lyon France
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36
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Goñi-Moreno Á, Benedetti I, Kim J, de Lorenzo V. Deconvolution of Gene Expression Noise into Spatial Dynamics of Transcription Factor-Promoter Interplay. ACS Synth Biol 2017; 6:1359-1369. [PMID: 28355056 DOI: 10.1021/acssynbio.6b00397] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Gene expression noise is not only the mere consequence of stochasticity, but also a signal that reflects the upstream physical dynamics of the cognate molecular machinery. Soil bacteria facing recalcitrant pollutants exploit noise of catabolic promoters to deploy beneficial phenotypes such as metabolic bet-hedging and/or division of biochemical labor. Although the role of upstream promoter-regulator interplay in the origin of this noise is little understood, its specifications are probably ciphered in flow cytometry data patterns. We studied Pm promoter activity of the environmental bacterium Pseudomonas putida and its cognate regulator XylS by following expression of Pm-gfp fusions in single cells. Using mathematical modeling and computational simulations, we determined the kinetic properties of the system and used them as a baseline code to interpret promoter activity in terms of upstream regulator dynamics. Transcriptional noise was predicted to depend on the intracellular physical distance between regulator source (where XylS is produced) and the target promoter. Experiments with engineered bacteria in which this distance is minimized or enlarged confirmed the predicted effects of source/target proximity on noise patterns. This approach allowed deconvolution of cytometry data into mechanistic information on gene expression flow. It also provided a basis for selecting programmable noise levels in synthetic regulatory circuits.
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Affiliation(s)
- Ángel Goñi-Moreno
- Systems Biology Program, Centro Nacional de Biotecnología CSIC, Campus de Cantoblanco, Madrid 28049, Spain
| | - Ilaria Benedetti
- Systems Biology Program, Centro Nacional de Biotecnología CSIC, Campus de Cantoblanco, Madrid 28049, Spain
| | - Juhyun Kim
- Systems Biology Program, Centro Nacional de Biotecnología CSIC, Campus de Cantoblanco, Madrid 28049, Spain
| | - Víctor de Lorenzo
- Systems Biology Program, Centro Nacional de Biotecnología CSIC, Campus de Cantoblanco, Madrid 28049, Spain
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37
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Abstract
At the end of the multistep transcription process, the elongating RNA polymerase (RNAP) is dislodged from the DNA template either at specific DNA sequences, called the terminators, or by a nascent RNA-dependent helicase, Rho. In Escherichia coli, about half of the transcription events are terminated by the Rho protein. Rho utilizes its RNA-dependent ATPase activities to translocate along the mRNA and eventually dislodges the RNAP via an unknown mechanism. The transcription elongation factor NusG facilitates this termination process by directly interacting with Rho. In this review, we discuss current models describing the mechanism of action of this hexameric transcription terminator, its regulation by different cis and trans factors, and the effects of the termination process on physiological processes in bacterial cells, particularly E. coli and Salmonella enterica Typhimurium.
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Affiliation(s)
- Pallabi Mitra
- Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Nampally, Hyderabad-500001, India; , , ,
| | - Gairika Ghosh
- Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Nampally, Hyderabad-500001, India; , , , .,Department of Graduate Studies, Manipal University, Manipal, Karnataka-576104, India
| | - Md Hafeezunnisa
- Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Nampally, Hyderabad-500001, India; , , , .,Department of Graduate Studies, Manipal University, Manipal, Karnataka-576104, India
| | - Ranjan Sen
- Laboratory of Transcription, Center for DNA Fingerprinting and Diagnostics, Nampally, Hyderabad-500001, India; , , ,
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38
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Hansen MMK, Ventosa Rosquelles M, Yelleswarapu M, Maas RJM, van Vugt-Jonker AJ, Heus HA, Huck WTS. Protein Synthesis in Coupled and Uncoupled Cell-Free Prokaryotic Gene Expression Systems. ACS Synth Biol 2016; 5:1433-1440. [PMID: 27306580 DOI: 10.1021/acssynbio.6b00010] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Secondary structure formation of mRNA, caused by desynchronization of transcription and translation, is known to impact gene expression in vivo. Yet, inactivation of mRNA by secondary structures in cell-free protein expression is frequently overlooked. Transcription and translation rates are often not highly synchronized in cell-free expression systems, leading to a temporal mismatch between the processes and a drop in efficiency of protein production. By devising a cell-free gene expression platform in which transcriptional and translational elongation are successfully performed independently, we determine that sequence-dependent mRNA secondary structures are the main cause of mRNA inactivation in in vitro gene expression.
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Affiliation(s)
- Maike M. K. Hansen
- Radboud University, Institute for Molecules
and Materials, Heyendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
| | - Marta Ventosa Rosquelles
- Radboud University, Institute for Molecules
and Materials, Heyendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
| | - Maaruthy Yelleswarapu
- Radboud University, Institute for Molecules
and Materials, Heyendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
| | - Roel J. M. Maas
- Radboud University, Institute for Molecules
and Materials, Heyendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
| | - Aafke J. van Vugt-Jonker
- Radboud University, Institute for Molecules
and Materials, Heyendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
| | - Hans A. Heus
- Radboud University, Institute for Molecules
and Materials, Heyendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
| | - Wilhelm T. S. Huck
- Radboud University, Institute for Molecules
and Materials, Heyendaalseweg
135, 6525 AJ Nijmegen, The Netherlands
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39
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Abstract
Plasmids are autonomously replicating pieces of DNA. This article discusses theta plasmid replication, which is a class of circular plasmid replication that includes ColE1-like origins of replication popular with expression vectors. All modalities of theta plasmid replication initiate synthesis with the leading strand at a predetermined site and complete replication through recruitment of the host's replisome, which extends the leading strand continuously while synthesizing the lagging strand discontinuously. There are clear differences between different modalities of theta plasmid replication in mechanisms of DNA duplex melting and in priming of leading- and lagging-strand synthesis. In some replicons duplex melting depends on transcription, while other replicons rely on plasmid-encoded trans-acting proteins (Reps); primers for leading-strand synthesis can be generated through processing of a transcript or in other replicons by the action of host- or plasmid-encoded primases. None of these processes require DNA breaks. The frequency of replication initiation is tightly regulated to facilitate establishment in permissive hosts and to achieve a steady state. The last section of the article reviews how plasmid copy number is sensed and how this feedback modulates the frequency of replication.
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40
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Grylak-Mielnicka A, Bidnenko V, Bardowski J, Bidnenko E. Transcription termination factor Rho: a hub linking diverse physiological processes in bacteria. Microbiology (Reading) 2016; 162:433-447. [DOI: 10.1099/mic.0.000244] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- Aleksandra Grylak-Mielnicka
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
- Institute of Biochemistry and Biophysics PAS, 02-106 Warsaw, Poland
| | - Vladimir Bidnenko
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
| | - Jacek Bardowski
- Institute of Biochemistry and Biophysics PAS, 02-106 Warsaw, Poland
| | - Elena Bidnenko
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France
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41
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Wells JN, Bergendahl LT, Marsh JA. Operon Gene Order Is Optimized for Ordered Protein Complex Assembly. Cell Rep 2016; 14:679-685. [PMID: 26804901 PMCID: PMC4742563 DOI: 10.1016/j.celrep.2015.12.085] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 11/07/2015] [Accepted: 12/17/2015] [Indexed: 01/07/2023] Open
Abstract
The assembly of heteromeric protein complexes is an inherently stochastic process in which multiple genes are expressed separately into proteins, which must then somehow find each other within the cell. Here, we considered one of the ways by which prokaryotic organisms have attempted to maximize the efficiency of protein complex assembly: the organization of subunit-encoding genes into operons. Using structure-based assembly predictions, we show that operon gene order has been optimized to match the order in which protein subunits assemble. Exceptions to this are almost entirely highly expressed proteins for which assembly is less stochastic and for which precisely ordered translation offers less benefit. Overall, these results show that ordered protein complex assembly pathways are of significant biological importance and represent a major evolutionary constraint on operon gene organization. Operon-encoded subunits tend to be encoded by neighboring genes and form large interfaces Operon gene order is often optimized for the order of protein complex assembly Exceptions are mostly highly expressed proteins for which assembly is less stochastic
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Affiliation(s)
- Jonathan N Wells
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, United Kingdom
| | - L Therese Bergendahl
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, United Kingdom
| | - Joseph A Marsh
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, United Kingdom.
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42
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Skoneczna A, Kaniak A, Skoneczny M. Genetic instability in budding and fission yeast-sources and mechanisms. FEMS Microbiol Rev 2015; 39:917-67. [PMID: 26109598 PMCID: PMC4608483 DOI: 10.1093/femsre/fuv028] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/26/2015] [Indexed: 12/17/2022] Open
Abstract
Cells are constantly confronted with endogenous and exogenous factors that affect their genomes. Eons of evolution have allowed the cellular mechanisms responsible for preserving the genome to adjust for achieving contradictory objectives: to maintain the genome unchanged and to acquire mutations that allow adaptation to environmental changes. One evolutionary mechanism that has been refined for survival is genetic variation. In this review, we describe the mechanisms responsible for two biological processes: genome maintenance and mutation tolerance involved in generations of genetic variations in mitotic cells of both Saccharomyces cerevisiae and Schizosaccharomyces pombe. These processes encompass mechanisms that ensure the fidelity of replication, DNA lesion sensing and DNA damage response pathways, as well as mechanisms that ensure precision in chromosome segregation during cell division. We discuss various factors that may influence genome stability, such as cellular ploidy, the phase of the cell cycle, transcriptional activity of a particular region of DNA, the proficiency of DNA quality control systems, the metabolic stage of the cell and its respiratory potential, and finally potential exposure to endogenous or environmental stress. The stability of budding and fission yeast genomes is influenced by two contradictory factors: (1) the need to be fully functional, which is ensured through the replication fidelity pathways of nuclear and mitochondrial genomes through sensing and repairing DNA damage, through precise chromosome segregation during cell division; and (2) the need to acquire changes for adaptation to environmental challenges.
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Affiliation(s)
- Adrianna Skoneczna
- Laboratory of Mutagenesis and DNA Repair, Institute of Biochemistry and Biophysics, Polish Academy of Science, 02-106 Warsaw, Poland
| | - Aneta Kaniak
- Laboratory of Mutagenesis and DNA Repair, Institute of Biochemistry and Biophysics, Polish Academy of Science, 02-106 Warsaw, Poland
| | - Marek Skoneczny
- Department of Genetics, Institute of Biochemistry and Biophysics, Polish Academy of Science, 02-106 Warsaw, Poland
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43
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End of the beginning: elongation and termination features of alternative modes of chromosomal replication initiation in bacteria. PLoS Genet 2015; 11:e1004909. [PMID: 25569209 PMCID: PMC4287441 DOI: 10.1371/journal.pgen.1004909] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
In bacterial cells, bidirectional replication of the circular chromosome is initiated from a single origin (oriC) and terminates in an antipodal terminus region such that movement of the pair of replication forks is largely codirectional with transcription. The terminus region is flanked by discrete Ter sequences that act as polar, or direction-dependent, arrest sites for fork progression. Alternative oriC-independent modes of replication initiation are possible, one of which is constitutive stable DNA replication (cSDR) from transcription-associated RNA–DNA hybrids or R-loops. Here, I discuss the distinctive attributes of fork progression and termination associated with different modes of bacterial replication initiation. Two hypothetical models are proposed: that head-on collisions between pairs of replication forks, which are a feature of replication termination in all kingdoms of life, provoke bilateral fork reversal reactions; and that cSDR is characterized by existence of distinct subpopulations in bacterial cultures and a widespread distribution of origins in the genome, each with a small firing potential. Since R-loops are known to exist in eukaryotic cells and to inflict genome damage in G1 phase, it is possible that cSDR-like events promote aberrant replication initiation even in eukaryotes.
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Afonina ZA, Myasnikov AG, Shirokov VA, Klaholz BP, Spirin AS. Conformation transitions of eukaryotic polyribosomes during multi-round translation. Nucleic Acids Res 2014; 43:618-28. [PMID: 25520190 PMCID: PMC4288168 DOI: 10.1093/nar/gku1270] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Using sedimentation and cryo electron tomography techniques, the conformations of eukaryotic polyribosomes formed in a long-term cell-free translation system were analyzed over all the active system lifetime (20–30 translation rounds during 6–8 h in wheat germ extract at 25°C). Three distinct types of the conformations were observed: (i) circular polyribosomes, varying from ring-shaped forms to circles collapsed into double rows, (ii) linear polyribosomes, tending to acquire planar zigzag-like forms and (iii) densely packed 3D helices. At the start, during the first two rounds of translation mostly the circular (ring-shaped and double-row) polyribosomes and the linear (free-shaped and zigzag-like) polyribosomes were formed (‘juvenile phase’). The progressive loading of the polyribosomes with translating ribosomes induced the opening of the circular polyribosomes and the transformation of a major part of the linear polyribosomes into the dense 3D helices (‘transitional phase’). After 2 h from the beginning (about 8–10 rounds of translation) this compact form of polyribosomes became predominant, whereas the circular and linear polyribosome fractions together contained less than half of polysomal ribosomes (‘steady-state phase’). The latter proportions did not change for several hours. Functional tests showed a reduced translational activity in the fraction of the 3D helical polyribosomes.
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Affiliation(s)
- Zhanna A Afonina
- Institute of Protein Research, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
| | - Alexander G Myasnikov
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), Centre National de la Recherche Scientifique (CNRS) UMR 7104; Institut National de la Santé de la Recherche Médicale (INSERM) U964; Université de Strasbourg, 1 rue Laurent Fries, 67404 Illkirch, France
| | - Vladimir A Shirokov
- Institute of Protein Research, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
| | - Bruno P Klaholz
- Centre for Integrative Biology (CBI), Department of Integrated Structural Biology, IGBMC (Institute of Genetics and of Molecular and Cellular Biology), Centre National de la Recherche Scientifique (CNRS) UMR 7104; Institut National de la Santé de la Recherche Médicale (INSERM) U964; Université de Strasbourg, 1 rue Laurent Fries, 67404 Illkirch, France
| | - Alexander S Spirin
- Institute of Protein Research, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
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Abstract
One of the most important discoveries in the field of microbiology in the last two decades is that bacterial cells have intricate subcellular organization. This understanding has emerged mainly from the depiction of spatial and temporal organization of proteins in specific domains within bacterial cells, e.g., midcell, cell poles, membrane and periplasm. Because translation of bacterial RNA molecules was considered to be strictly coupled to their synthesis, they were not thought to specifically localize to regions outside the nucleoid. However, the increasing interest in RNAs, including non-coding RNAs, encouraged researchers to explore the spatial and temporal localization of RNAs in bacteria. The recent technological improvements in the field of fluorescence microscopy allowed subcellular imaging of RNAs even in the tiny bacterial cells. It has been reported by several groups, including ours that transcripts may specifically localize in such cells. Here we review what is known about localization of RNA and of the pathways that determine RNA fate in bacteria, and discuss the possible cues and mechanisms underlying these distribution patterns.
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Affiliation(s)
- Avi-ad Avraam Buskila
- a Department of Microbiology and Molecular Genetics; IMRIC ; The Hebrew University Faculty of Medicine ; Israel
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Abstract
Transcription requires unwinding complementary DNA strands, generating torsional stress, and sensitizing the exposed single strands to chemical reactions and endogenous damaging agents. In addition, transcription can occur concomitantly with the other major DNA metabolic processes (replication, repair, and recombination), creating opportunities for either cooperation or conflict. Genetic modifications associated with transcription are a global issue in the small genomes of microorganisms in which noncoding sequences are rare. Transcription likewise becomes significant when one considers that most of the human genome is transcriptionally active. In this review, we focus specifically on the mutagenic consequences of transcription. Mechanisms of transcription-associated mutagenesis in microorganisms are discussed, as is the role of transcription in somatic instability of the vertebrate immune system.
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Affiliation(s)
- Sue Jinks-Robertson
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710;
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Kumar S, Balamurali MM, Sankaran K. Bacterial lipid modification of proteins requires appropriate secretory signals even for expression - implications for biogenesis and protein engineering. Mol Membr Biol 2014; 31:183-94. [PMID: 25156679 DOI: 10.3109/09687688.2014.943819] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Sec- and Tat-mediated bacterial lipid modification of proteins are important posttranslational processes owing to their vital roles in cellular functions, membrane targeting and biotechnological applications like ELISA, biosensor, adjuvant-free vaccines, liposomal drug delivery etc. However a better understanding of the tight coupling of secretory and lipid modification machineries and the processes associated will help unravel this essential biological event and utilize it for engineering applications. Further, there is a need for a systematic and convincing investigation into membrane targeting, solubilization and ease-of-purification of engineered lipoproteins to facilitate scientists in readily applying this new protein engineering tool. Therefore, in this study, we have investigated systematically recombinant expression, translocation, solubilization and purification of three White Spot Syndrome Viral (WSSV) proteins, ICP11, VP28 and VP281. Our study shows that the lipid modification and secretion processes are tightly coupled to the extent that mismatch between folding kinetics and signal sequence of target proteins could lead to transcriptional-translational uncoupling or aborted translation. The proteins expressed as lipoproteins through Tat-pathway were targeted to the inner membrane achieving considerable enrichment. These His-tagged proteins were then purified to apparent homogeneity in detergent-free form using single-step Immobilized Metal Affinity Chromatography. This study has interesting findings in lipoprotein biogenesis enhancing the scope of this unique post-translational protein engineering tool for obtaining pure detergent-free, membrane or hydrophobic surface-associating diagnostic targets and vaccine candidates for WSSV.
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48
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Evidence against translational repression by the carboxyltransferase component of Escherichia coli acetyl coenzyme A carboxylase. J Bacteriol 2014; 196:3768-75. [PMID: 25157077 DOI: 10.1128/jb.02091-14] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
In Escherichia coli, synthesis of the malonyl coenzyme A (malonyl-CoA) required for membrane lipid synthesis is catalyzed by acetyl-CoA carboxylase, a large complex composed of four subunits. The subunit proteins are needed in a defined stoichiometry, and it remains unclear how such production is achieved since the proteins are encoded at three different loci. Meades and coworkers (G. Meades, Jr., B. K. Benson, A. Grove, and G. L. Waldrop, Nucleic Acids Res. 38:1217-1227, 2010, doi:http://dx.doi.org/10.1093/nar/gkp1079) reported that coordinated production of the AccA and AccD subunits is due to a translational repression mechanism exerted by the proteins themselves. The AccA and AccD subunits form the carboxyltransferase (CT) heterotetramer that catalyzes the second partial reaction of acetyl-CoA carboxylase. Meades et al. reported that CT tetramers bind the central portions of the accA and accD mRNAs and block their translation in vitro. However, long mRNA molecules (500 to 600 bases) were required for CT binding, but such long mRNA molecules devoid of ribosomes seemed unlikely to exist in vivo. This, plus problematical aspects of the data reported by Meades and coworkers, led us to perform in vivo experiments to test CT tetramer-mediated translational repression of the accA and accD mRNAs. We report that increased levels of CT tetramer have no detectable effect on translation of the CT subunit mRNAs.
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Aguilera A, Gaillard H. Transcription and recombination: when RNA meets DNA. Cold Spring Harb Perspect Biol 2014; 6:6/8/a016543. [PMID: 25085910 DOI: 10.1101/cshperspect.a016543] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A particularly relevant phenomenon in cell physiology and proliferation is the fact that spontaneous mitotic recombination is strongly enhanced by transcription. The most accepted view is that transcription increases the occurrence of double-strand breaks and/or single-stranded DNA gaps that are repaired by recombination. Most breaks would arise as a consequence of the impact that transcription has on replication fork progression, provoking its stalling and/or breakage. Here, we discuss the mechanisms responsible for the cross talk between transcription and recombination, with emphasis on (1) the transcription-replication conflicts as the main source of recombinogenic DNA breaks, and (2) the formation of cotranscriptional R-loops as a major cause of such breaks. The new emerging questions and perspectives are discussed on the basis of the interference between transcription and replication, as well as the way RNA influences genome dynamics.
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Affiliation(s)
- Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Universidad de Sevilla, 41092 Seville, Spain
| | - Hélène Gaillard
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Universidad de Sevilla, 41092 Seville, Spain
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Spatially segregated transcription and translation in cells of the endomembrane-containing bacterium Gemmata obscuriglobus. Proc Natl Acad Sci U S A 2014; 111:11067-72. [PMID: 25024214 DOI: 10.1073/pnas.1409187111] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The dogma of coupled transcription and translation in bacteria has been challenged by recent reports of spatial segregation of these processes within the relatively simple cellular organization of the model organisms Escherichia coli and Bacillus subtilis. The bacterial species Gemmata obscuriglobus possesses an extensive endomembrane system. The membranes generate a very convoluted intracellular architecture in which some of the cell's ribosomes appear to have less direct access to the cell's nucleoid(s) than others. This observation prompted us to test the hypothesis that a substantial proportion of G. obscuriglobus translation may be spatially segregated from transcription. Using immunofluorescence and immunoelectron microscopy, we showed that translating ribosomes are localized throughout the cell, with a quantitatively greater proportion found in regions distal to nucleoid(s). Our results extend information about the phylogenetic and morphological diversity of bacteria in which the spatial organization of transcription and translation has been studied. These findings also suggest that endomembranes may provide an obstacle to colocated transcription and translation, a role for endomembranes that has not been reported previously for a prokaryotic organism. Our studies of G. obscuriglobus may provide a useful background for consideration of the evolutionary development of eukaryotic cellular complexity and how it led to decoupled processes of gene expression in eukaryotes.
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