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Liu L, Luo D, Zhang Y, Liu D, Yin K, Tang Q, Chou SH, He J. Characterization of the dual regulation by a c-di-GMP riboswitch Bc1 with a long expression platform from Bacillus thuringiensis. Microbiol Spectr 2024; 12:e0045024. [PMID: 38819160 PMCID: PMC11218506 DOI: 10.1128/spectrum.00450-24] [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: 02/19/2024] [Accepted: 04/29/2024] [Indexed: 06/01/2024] Open
Abstract
A riboswitch generally regulates the expression of its downstream genes through conformational change in its expression platform (EP) upon ligand binding. The cyclic diguanosine monophosphate (c-di-GMP) class I riboswitch Bc1 is widespread and conserved among Bacillus cereus group species. In this study, we revealed that Bc1 has a long EP with two typical ρ-independent terminator sequences 28 bp apart. The upstream terminator T1 is dominant in vitro, while downstream terminator T2 is more efficient in vivo. Through mutation analysis, we elucidated that Bc1 exerts a rare and incoherent "transcription-translation" dual regulation with T2 playing a crucial role. However, we found that Bc1 did not respond to c-di-GMP under in vitro transcription conditions, and the expressions of downstream genes did not change with fluctuation in intracellular c-di-GMP concentration. To explore this puzzle, we conducted SHAPE-MaP and confirmed the interaction of Bc1 with c-di-GMP. This shows that as c-di-GMP concentration increases, T1 unfolds but T2 remains almost intact and functional. The presence of T2 masks the effect of T1 unwinding, resulting in no response of Bc1 to c-di-GMP. The high Shannon entropy values of EP region imply the potential alternative structures of Bc1. We also found that zinc uptake regulator can specifically bind to the dual terminator coding sequence and slightly trigger the response of Bc1 to c-di-GMP. This work will shed light on the dual-regulation riboswitch and enrich our understanding of the RNA world.IMPORTANCEIn nature, riboswitches are involved in a variety of metabolic regulation, most of which preferentially regulate transcription termination or translation initiation of downstream genes in specific ways. Alternatively, the same or different riboswitches can exist in tandem to enhance regulatory effects or respond to multiple ligands. However, many putative conserved riboswitches have not yet been experimentally validated. Here, we found that the c-di-GMP riboswitch Bc1 with a long EP could form a dual terminator and exhibit non-canonical and incoherent "transcription-translation" dual regulation. Besides, zinc uptake regulator specifically bound to the coding sequence of the Bc1 EP and slightly mediated the action of Bc1. The application of SHAPE-MaP to the dual regulation mechanism of Bc1 may establish the foundation for future studies of such complex untranslated regions in other bacterial genomes.
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Affiliation(s)
- Lu Liu
- National Key Laboratory of Agricultural Microbiology & Hubei Hongshan Laboratory, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Dehua Luo
- National Key Laboratory of Agricultural Microbiology & Hubei Hongshan Laboratory, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Yongji Zhang
- National Key Laboratory of Agricultural Microbiology & Hubei Hongshan Laboratory, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Dingqi Liu
- National Key Laboratory of Agricultural Microbiology & Hubei Hongshan Laboratory, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Kang Yin
- National Key Laboratory of Agricultural Microbiology & Hubei Hongshan Laboratory, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Qing Tang
- National Key Laboratory of Agricultural Microbiology & Hubei Hongshan Laboratory, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Shan-Ho Chou
- National Key Laboratory of Agricultural Microbiology & Hubei Hongshan Laboratory, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Jin He
- National Key Laboratory of Agricultural Microbiology & Hubei Hongshan Laboratory, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
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Hespanhol JT, Nóbrega-Silva L, Bayer-Santos E. Regulation of type VI secretion systems at the transcriptional, posttranscriptional and posttranslational level. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001376. [PMID: 37552221 PMCID: PMC10482370 DOI: 10.1099/mic.0.001376] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 07/25/2023] [Indexed: 08/09/2023]
Abstract
Bacteria live in complex polymicrobial communities and are constantly competing for resources. The type VI secretion system (T6SS) is a widespread antagonistic mechanism used by Gram-negative bacteria to gain an advantage over competitors. T6SSs translocate toxic effector proteins inside target prokaryotic cells in a contact-dependent manner. In addition, some T6SS effectors can be secreted extracellularly and contribute to the scavenging scarce metal ions. Bacteria deploy their T6SSs in different situations, categorizing these systems into offensive, defensive and exploitative. The great variety of bacterial species and environments occupied by such species reflect the complexity of regulatory signals and networks that control the expression and activation of the T6SSs. Such regulation is tightly controlled at the transcriptional, posttranscriptional and posttranslational level by abiotic (e.g. pH, iron) or biotic (e.g. quorum-sensing) cues. In this review, we provide an update on the current knowledge about the regulatory networks that modulate the expression and activity of T6SSs across several species, focusing on systems used for interbacterial competition.
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Affiliation(s)
- Julia Takuno Hespanhol
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| | - Luize Nóbrega-Silva
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| | - Ethel Bayer-Santos
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
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Ryan C, Rahman MM, Kumar V, Rozners E. Triplex-Forming Peptide Nucleic Acid Controls Dynamic Conformations of RNA Bulges. J Am Chem Soc 2023; 145:10497-10504. [PMID: 37155726 PMCID: PMC10198159 DOI: 10.1021/jacs.2c12488] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Indexed: 05/10/2023]
Abstract
RNA folding is driven by the formation of double-helical segments interspaced by loops of unpaired nucleotides. Among the latter, bulges formed by one or several unpaired nucleotides are one of the most common structural motifs that play an important role in stabilizing RNA-RNA, RNA-protein, and RNA-small molecule interactions. Single-nucleotide bulges can fold in alternative structures where the unpaired nucleobase is either looped-out (flexible) in a solvent or stacked-in (intercalated) between the base pairs. In the present study, we discovered that triplex-forming peptide nucleic acids (PNAs) had unusually high affinity for single-purine-nucleotide bulges in double-helical RNA. Depending on the PNA's sequence, the triplex formation shifted the equilibrium between looped-out and stacked-in conformations. The ability to control the dynamic equilibria of RNA's structure will be an important tool for studying structure-function relationships in RNA biology and may have potential in novel therapeutic approaches targeting disease-related RNAs.
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Affiliation(s)
- Christopher
A. Ryan
- Department of Chemistry, The State
University of New York, Binghamton University, Binghamton, New York 13902, United States
| | - Md Motiar Rahman
- Department of Chemistry, The State
University of New York, Binghamton University, Binghamton, New York 13902, United States
| | - Vipin Kumar
- Department of Chemistry, The State
University of New York, Binghamton University, Binghamton, New York 13902, United States
| | - Eriks Rozners
- Department of Chemistry, The State
University of New York, Binghamton University, Binghamton, New York 13902, United States
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Ueda T, Nishimura KI, Nishiyama Y, Tominaga Y, Miyazaki K, Furuta H, Matsumura S, Ikawa Y. Pairwise Engineering of Tandemly Aligned Self-Splicing Group I Introns for Analysis and Control of Their Alternative Splicing. Biomolecules 2023; 13:biom13040654. [PMID: 37189401 DOI: 10.3390/biom13040654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Revised: 04/03/2023] [Accepted: 04/03/2023] [Indexed: 04/08/2023] Open
Abstract
Alternative splicing is an important mechanism in the process of eukaryotic nuclear mRNA precursors producing multiple protein products from a single gene. Although group I self-splicing introns usually perform regular splicing, limited examples of alternative splicing have also been reported. The exon-skipping type of splicing has been observed in genes containing two group I introns. To characterize splicing patterns (exon-skipping/exon-inclusion) of tandemly aligned group I introns, we constructed a reporter gene containing two Tetrahymena introns flanking a short exon. To control splicing patterns, we engineered the two introns in a pairwise manner to design pairs of introns that selectively perform either exon-skipping or exon-inclusion splicing. Through pairwise engineering and biochemical characterization, the structural elements important for the induction of exon-skipping splicing were elucidated.
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Affiliation(s)
- Tomoki Ueda
- Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
| | - Kei-ichiro Nishimura
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Moto-oka 744, Nishi-ku, Fukuoka 819-0395, Japan
| | - Yuka Nishiyama
- Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
| | - Yuto Tominaga
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Moto-oka 744, Nishi-ku, Fukuoka 819-0395, Japan
| | - Katsushi Miyazaki
- Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
| | - Hiroyuki Furuta
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Moto-oka 744, Nishi-ku, Fukuoka 819-0395, Japan
| | - Shigeyoshi Matsumura
- Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
- Graduate School of Innovative Life Science, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
| | - Yoshiya Ikawa
- Department of Chemistry, Graduate School of Science and Engineering, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
- Graduate School of Innovative Life Science, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
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Landgraf T, Völklein AE, Fürtig B, Schwalbe H. The cotranscriptional folding landscape for two cyclic di-nucleotide-sensing riboswitches with highly homologous aptamer domains acting either as ON- or OFF-switches. Nucleic Acids Res 2022; 50:6639-6655. [PMID: 35736222 PMCID: PMC9262584 DOI: 10.1093/nar/gkac514] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 05/03/2022] [Accepted: 06/07/2022] [Indexed: 12/24/2022] Open
Abstract
Riboswitches are gene regulatory elements located in untranslated mRNA regions. They bind inducer molecules with high affinity and specificity. Cyclic-di-nucleotide-sensing riboswitches are major regulators of genes for the environment, membranes and motility (GEMM) of bacteria. Up to now, structural probing assays or crystal structures have provided insight into the interaction between cyclic-di-nucleotides and their corresponding riboswitches. ITC analysis, NMR analysis and computational modeling allowed us to gain a detailed understanding of the gene regulation mechanisms for the Cd1 (Clostridium difficile) and for the pilM (Geobacter metallireducens) riboswitches and their respective di-nucleotides c-di-GMP and c-GAMP. Binding capability showed a 25 nucleotide (nt) long window for pilM and a 61 nt window for Cd1. Within this window, binding affinities ranged from 35 μM to 0.25 μM spanning two orders of magnitude for Cd1 and pilM showing a strong dependence on competing riboswitch folds. Experimental results were incorporated into a Markov simulation to further our understanding of the transcriptional folding pathways of riboswitches. Our model showed the ability to predict riboswitch gene regulation and its dependence on transcription speed, pausing and ligand concentration.
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Affiliation(s)
| | | | - Boris Fürtig
- Correspondence may also be addressed to Boris Fürtig.
| | - Harald Schwalbe
- To whom correspondence should be addressed. Tel: +49 69 798 29737; Fax: +49 69 798 29515;
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Ariza-Mateos A, Nuthanakanti A, Serganov A. Riboswitch Mechanisms: New Tricks for an Old Dog. BIOCHEMISTRY (MOSCOW) 2021; 86:962-975. [PMID: 34488573 DOI: 10.1134/s0006297921080071] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Discovered almost twenty years ago, riboswitches turned out to be one of the most common regulatory systems in bacteria, with representatives found in eukaryotes and archaea. Unlike many other regulatory elements, riboswitches are entirely composed of RNA and capable of modulating expression of genes by direct binding of small cellular molecules. While bacterial riboswitches had been initially thought to control production of enzymes and transporters associated with small organic molecules via feedback regulatory circuits, later findings identified riboswitches directing expression of a wide range of genes and responding to various classes of molecules, including ions, signaling molecules, and others. The 5'-untranslated mRNA regions host a vast majority of riboswitches, which modulate transcription or translation of downstream genes through conformational rearrangements in the ligand-sensing domains and adjacent expression-controlling platforms. Over years, the repertoire of regulatory mechanisms employed by riboswitches has greatly expanded; most recent studies have highlighted the importance of alternative mechanisms, such as RNA degradation, for the riboswitch-mediated genetic circuits. This review discusses the plethora of bacterial riboswitch mechanisms and illustrates how riboswitches utilize different features and approaches to elicit various regulatory responses.
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Affiliation(s)
- Ascensión Ariza-Mateos
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Ashok Nuthanakanti
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Alexander Serganov
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY 10016, USA.
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Joshi A, Mahmoud SA, Kim SK, Ogdahl JL, Lee VT, Chien P, Yildiz FH. c-di-GMP inhibits LonA-dependent proteolysis of TfoY in Vibrio cholerae. PLoS Genet 2020; 16:e1008897. [PMID: 32589664 PMCID: PMC7371385 DOI: 10.1371/journal.pgen.1008897] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 07/20/2020] [Accepted: 05/30/2020] [Indexed: 02/06/2023] Open
Abstract
The LonA (or Lon) protease is a central post-translational regulator in diverse bacterial species. In Vibrio cholerae, LonA regulates a broad range of behaviors including cell division, biofilm formation, flagellar motility, c-di-GMP levels, the type VI secretion system (T6SS), virulence gene expression, and host colonization. Despite LonA’s role in cellular processes critical for V. cholerae’s aquatic and infectious life cycles, relatively few LonA substrates have been identified. LonA protease substrates were therefore identified through comparison of the proteomes of wild-type and ΔlonA strains following translational inhibition. The most significantly enriched LonA-dependent protein was TfoY, a known regulator of motility and the T6SS in V. cholerae. Experiments showed that TfoY was required for LonA-mediated repression of motility and T6SS-dependent killing. In addition, TfoY was stabilized under high c-di-GMP conditions and biochemical analysis determined direct binding of c-di-GMP to LonA results in inhibition of its protease activity. The work presented here adds to the list of LonA substrates, identifies LonA as a c-di-GMP receptor, demonstrates that c-di-GMP regulates LonA activity and TfoY protein stability, and helps elucidate the mechanisms by which LonA controls important V. cholerae behaviors. This study provides insights into the mechanisms and consequences of LonA-mediated regulated proteolysis in Vibrio cholerae, the causal organism of the acute diarrheal disease cholera that is endemic in more than 47 countries across the globe. Lon is broadly conserved in bacterial systems; uncovering the molecular connection between c-di-GMP signaling and LonA-mediated proteolysis of V. cholerae will provide conceptual frameworks for the development of intervention strategies to combat virulence by bacterial pathogens.
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Affiliation(s)
- Avatar Joshi
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Samar A. Mahmoud
- Department of Biochemistry and Molecular Biology, Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Soo-Kyoung Kim
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
| | - Justyne L. Ogdahl
- Department of Biochemistry and Molecular Biology, Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Vincent T. Lee
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, United States of America
| | - Peter Chien
- Department of Biochemistry and Molecular Biology, Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, Massachusetts, United States of America
| | - Fitnat H. Yildiz
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, California, United States of America
- * E-mail:
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The Vc2 Cyclic di-GMP-Dependent Riboswitch of Vibrio cholerae Regulates Expression of an Upstream Putative Small RNA by Controlling RNA Stability. J Bacteriol 2019; 201:JB.00293-19. [PMID: 31405916 DOI: 10.1128/jb.00293-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 07/17/2019] [Indexed: 11/20/2022] Open
Abstract
Cyclic di-GMP (c-di-GMP) is a bacterial second messenger molecule that is important in the biology of Vibrio cholerae, but the molecular mechanisms by which this molecule regulates downstream phenotypes have not been fully characterized. We have previously shown that the Vc2 c-di-GMP-binding riboswitch, encoded upstream of the gene tfoY, functions as an off switch in response to c-di-GMP. However, the mechanism by which c-di-GMP controls expression of tfoY has not been fully elucidated. During our studies of this mechanism, we determined that c-di-GMP binding to Vc2 also controls the abundance and stability of upstream noncoding RNAs with 3' ends located immediately downstream of the Vc2 riboswitch. Our results suggest these putative small RNAs (sRNAs) are not generated by transcriptional termination but rather by preventing degradation of the upstream untranslated RNA when c-di-GMP is bound to Vc2.IMPORTANCE Riboswitches are typically RNA elements located in the 5' untranslated region of mRNAs. They are highly structured and specifically recognize and respond to a given chemical cue to alter transcription termination or translation initiation. In this work, we report a novel mechanism of riboswitch-mediated gene regulation in Vibrio cholerae whereby a 3' riboswitch, named Vc2, controls the stability of upstream untranslated RNA upon binding to its cognate ligand, the second messenger cyclic di-GMP, leading to the accumulation of previously undescribed putative sRNAs. We further demonstrate that binding of the ligand to the riboswitch prevents RNA degradation. As binding of riboswitches to their ligands often produces compactly structured RNA, we hypothesize this mechanism of gene regulation is widespread.
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