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Campos-Chavez E, Paul S, Zhou Z, Alonso D, Verma AR, Fei J, Mondragón A. Translational T-box riboswitches bind tRNA by modulating conformational flexibility. Nat Commun 2024; 15:6592. [PMID: 39097611 PMCID: PMC11297988 DOI: 10.1038/s41467-024-50885-x] [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: 01/22/2024] [Accepted: 07/22/2024] [Indexed: 08/05/2024] Open
Abstract
T-box riboswitches are noncoding RNA elements involved in genetic regulation of most Gram-positive bacteria. They regulate amino acid metabolism by assessing the aminoacylation status of tRNA, subsequently affecting the transcription or translation of downstream amino acid metabolism-related genes. Here we present single-molecule FRET studies of the Mycobacterium tuberculosis IleS T-box riboswitch, a paradigmatic translational T-box. Results support a two-step binding model, where the tRNA anticodon is recognized first, followed by interactions with the NCCA sequence. Furthermore, after anticodon recognition, tRNA can transiently dock into the discriminator domain even in the absence of the tRNA NCCA-discriminator interactions. Establishment of the NCCA-discriminator interactions significantly stabilizes the fully bound state. Collectively, the data suggest high conformational flexibility in translational T-box riboswitches; and supports a conformational selection model for NCCA recognition. These findings provide a kinetic framework to understand how specific RNA elements underpin the binding affinity and specificity required for gene regulation.
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Affiliation(s)
- Eduardo Campos-Chavez
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, 60208, USA
| | - Sneha Paul
- Department of Biochemistry and Molecular Biology and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA
- Institute of Molecular Sciences of Orsay, Paris-Saclay University, 91405, Orsay, France
| | - Zunwu Zhou
- Department of Biochemistry and Molecular Biology and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA
| | - Dulce Alonso
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, 60208, USA
| | - Anjali R Verma
- Department of Chemistry, Columbia University, New York, NY, 10027, USA
- Biophysics Program and Institute for Physical Sciences and Technology, University of Maryland, College Park, MD, 20742, USA
| | - Jingyi Fei
- Department of Biochemistry and Molecular Biology and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA.
| | - Alfonso Mondragón
- Department of Molecular Biosciences, Northwestern University, Evanston, IL, 60208, USA.
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2
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Jia X, Zhang C, Luo B, Frandsen JK, Watkins AM, Li K, Zhang M, Wei X, Yang Y, Henkin TM, Su Z. Cryo-EM-guided engineering of T-box-tRNA modules with enhanced selectivity and sensitivity in translational regulation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.28.530422. [PMID: 36909519 PMCID: PMC10002618 DOI: 10.1101/2023.02.28.530422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/06/2023]
Abstract
Riboswitches are non-coding RNA elements that play vital roles in regulating gene expression. Their specific ligand-dependent structural reorganization facilitates their use as templates for design of engineered RNA switches for therapeutics, nanotechnology and synthetic biology. T-box riboswitches bind tRNAs to sense aminoacylation and control gene expression via transcription attenuation or translation inhibition. Here we determine the cryo-EM structure of the wild-type Mycobacterium smegmatis ileS T-box in complex with its cognate tRNA Ile . This structure shows a very flexible antisequestrator region that tolerates both 3'-OH and 2',3'-cyclic phosphate modification at the 3' end of tRNA Ile . Elongation of one helical turn (11-base pair) in both the tRNA acceptor arm and T-box Stem III maintains T-box-tRNA complex formation and increases the selectivity for tRNA 3' end modification. Moreover, elongation of Stem III results in ∼6-fold tighter binding to tRNA, which leads to increased sensitivity of downstream translational regulation indicated by precedent translation. Our results demonstrate that cryo-EM can guide RNA engineering to design improved riboswitch modules for translational regulation, and potentially a variety of additional functions.
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3
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Giarimoglou N, Kouvela A, Maniatis A, Papakyriakou A, Zhang J, Stamatopoulou V, Stathopoulos C. A Riboswitch-Driven Era of New Antibacterials. Antibiotics (Basel) 2022; 11:antibiotics11091243. [PMID: 36140022 PMCID: PMC9495366 DOI: 10.3390/antibiotics11091243] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/01/2022] [Accepted: 09/08/2022] [Indexed: 11/26/2022] Open
Abstract
Riboswitches are structured non-coding RNAs found in the 5′ UTR of important genes for bacterial metabolism, virulence and survival. Upon the binding of specific ligands that can vary from simple ions to complex molecules such as nucleotides and tRNAs, riboswitches change their local and global mRNA conformations to affect downstream transcription or translation. Due to their dynamic nature and central regulatory role in bacterial metabolism, riboswitches have been exploited as novel RNA-based targets for the development of new generation antibacterials that can overcome drug-resistance problems. During recent years, several important riboswitch structures from many bacterial representatives, including several prominent human pathogens, have shown that riboswitches are ideal RNA targets for new compounds that can interfere with their structure and function, exhibiting much reduced resistance over time. Most interestingly, mainstream antibiotics that target the ribosome have been shown to effectively modulate the regulatory behavior and capacity of several riboswitches, both in vivo and in vitro, emphasizing the need for more in-depth studies and biological evaluation of new antibiotics. Herein, we summarize the currently known compounds that target several main riboswitches and discuss the role of mainstream antibiotics as modulators of T-box riboswitches, in the dawn of an era of novel inhibitors that target important bacterial regulatory RNAs.
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Affiliation(s)
- Nikoleta Giarimoglou
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Adamantia Kouvela
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Alexandros Maniatis
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Athanasios Papakyriakou
- Institute of Biosciences & Applications, National Centre for Scientific Research “Demokritos”, Ag. Paraskevi, 15341 Athens, Greece
| | - Jinwei Zhang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA
| | | | - Constantinos Stathopoulos
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
- Correspondence: ; Tel.: +30-2610-997932
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4
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Zhang J. Unboxing the T-box riboswitches-A glimpse into multivalent and multimodal RNA-RNA interactions. WILEY INTERDISCIPLINARY REVIEWS-RNA 2020; 11:e1600. [PMID: 32633085 PMCID: PMC7583486 DOI: 10.1002/wrna.1600] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 04/25/2020] [Accepted: 04/29/2020] [Indexed: 12/17/2022]
Abstract
The T-box riboswitches are widespread bacterial noncoding RNAs that directly bind specific tRNAs, sense aminoacylation on bound tRNAs, and switch conformations to control amino-acid metabolism and to maintain nutritional homeostasis. The core mechanisms of tRNA recognition, amino acid sensing, and conformational switching by the T-boxes have been recently elucidated, providing a wealth of new insights into multivalent and multimodal RNA-RNA interactions. This review dissects the structures and tRNA-recognition mechanisms by the Stem I, Stem II, and Discriminator domains, which collectively compose the T-box riboswitches. It further compares and contrasts the two classes of T-boxes that regulate transcription and translation, respectively, and integrates recent findings to derive general themes, trends, and insights into complex RNA-RNA interactions. Specifically, the T-box paradigm reveals that noncoding RNAs can interact with each other through multiple coordinated contacts, concatenation of stacked helices, and mutually induced fit. Numerous tertiary contacts, especially those emanating from strings of single-stranded purines, act in concert to reinforce long-range base-pairing and stacking interactions. These coordinated, mixed-mode contacts allow the T-box RNA to sterically sense aminoacylation on the tRNA using a bipartite steric sieve, and to couple this readout to a conformational switch mediated by tRNA-T-box stacking. Together, the insights gleaned from the T-box riboswitches inform investigations into other complex RNA structures and assemblies, development of T-box-targeted antimicrobials, and may inspire design and engineering of novel RNA sensors, regulators, and interfaces. This article is categorized under: RNA Structure and Dynamics > RNA Structure, Dynamics and Chemistry Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs Regulatory RNAs/RNAi/Riboswitches > Riboswitches.
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Affiliation(s)
- Jinwei Zhang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland, USA
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5
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Suddala KC, Zhang J. High-affinity recognition of specific tRNAs by an mRNA anticodon-binding groove. Nat Struct Mol Biol 2019; 26:1114-1122. [PMID: 31792448 PMCID: PMC6903423 DOI: 10.1038/s41594-019-0335-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 10/21/2019] [Indexed: 11/10/2022]
Abstract
T-box riboswitches are modular bacterial noncoding RNAs that sense and regulate amino acid availability through direct interactions with tRNAs. Between the 5' anticodon-binding stem I domain and the 3' amino acid sensing domains of most T-boxes lies the stem II domain of unknown structure and function. Here, we report a 2.8-Å cocrystal structure of the Nocardia farcinica ileS T-box in complex with its cognate tRNAIle. The structure reveals a perpendicularly arranged ultrashort stem I containing a K-turn and an elongated stem II bearing an S-turn. Both stems rest against a compact pseudoknot, dock via an extended ribose zipper and jointly create a binding groove specific to the anticodon of its cognate tRNA. Contrary to proposed distal contacts to the tRNA elbow region, stem II locally reinforces the codon-anticodon interactions between stem I and tRNA, achieving low-nanomolar affinity. This study illustrates how mRNA junctions can create specific binding sites for interacting RNAs of prescribed sequence and structure.
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Affiliation(s)
- Krishna C Suddala
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, USA
| | - Jinwei Zhang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, USA.
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6
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Battaglia RA, Grigg JC, Ke A. Structural basis for tRNA decoding and aminoacylation sensing by T-box riboregulators. Nat Struct Mol Biol 2019; 26:1106-1113. [PMID: 31740853 PMCID: PMC6953718 DOI: 10.1038/s41594-019-0327-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 10/07/2019] [Indexed: 01/31/2023]
Abstract
T-box riboregulators are a class of cis-regulatory RNAs that govern the bacterial response to amino acid starvation by binding, decoding and reading the aminoacylation status of specific transfer RNAs. Here we provide a high-resolution crystal structure of a full-length T-box from Mycobacterium tuberculosis that explains tRNA decoding and aminoacylation sensing by this riboregulator. Overall, the T-box consists of decoding and aminoacylation sensing modules bridged by a rigid pseudoknot structure formed by the mid-region domains. Stem-I and the Stem-II S-turn assemble a claw-like decoding module, while the antiterminator, Stem-III, and the adjacent linker form a tightly interwoven aminoacylation sensing module. The uncharged tRNA is selectively recognized by an unexpected set of favorable contacts from the linker region in the aminoacylation sensing module. A complex structure with a charged tRNA mimic shows that the extra moiety dislodges the linker, which is indicative of the possible chain of events that lead to alternative base-pairing and altered expression output.
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Affiliation(s)
| | - Jason C Grigg
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Ailong Ke
- Department of Molecular Biology and Genetics, Ithaca, NY, USA.
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7
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Suddala KC, Zhang J. An evolving tale of two interacting RNAs-themes and variations of the T-box riboswitch mechanism. IUBMB Life 2019; 71:1167-1180. [PMID: 31206978 DOI: 10.1002/iub.2098] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 05/10/2019] [Indexed: 01/10/2023]
Abstract
T-box riboswitches are a widespread class of structured noncoding RNAs in Gram-positive bacteria that regulate the expression of amino acid-related genes. They form negative feedback loops to maintain steady supplies of aminoacyl-transfer RNAs (tRNAs) to the translating ribosomes. T-box riboswitches are located in the 5' leader regions of mRNAs that they regulate and directly bind to their cognate tRNA ligands. T-boxes further sense the aminoacylation state of the bound tRNAs and, based on this readout, regulate gene expression at the level of transcription or translation. T-box riboswitches consist of two conserved domains-a 5' Stem I domain that is involved in specific tRNA recognition and a 3' antiterminator/antisequestrator (or discriminator) domain that senses the amino acid on the 3' end of the bound tRNA. Interaction of the 3' end of an uncharged but not charged tRNA with a thermodynamically weak discriminator domain stabilizes it to promote transcription readthrough or translation initiation. Recent biochemical, biophysical, and structural studies have provided high-resolution insights into the mechanism of tRNA recognition by Stem I, several structural models of full-length T-box-tRNA complexes, mechanism of amino acid sensing by the antiterminator domain, as well as kinetic details of tRNA binding to the T-box riboswitches. In addition, translation-regulating T-box riboswitches have been recently characterized, which presented key differences from the canonical transcriptional T-boxes. Here, we review the recent developments in understanding the T-box riboswitch mechanism that have employed various complementary approaches. Further, the regulation of multiple essential genes by T-boxes makes them very attractive drug targets to combat drug resistance. The recent progress in understanding the biochemical, structural, and dynamic aspects of the T-box riboswitch mechanism will enable more precise and effective targeting with small molecules. © 2019 IUBMB Life, 2019 © 2019 IUBMB Life, 71(8):1167-1180, 2019.
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Affiliation(s)
- Krishna C Suddala
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Jinwei Zhang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
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8
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Abstract
The T-box riboswitch is a unique, RNA-based regulatory mechanism that modulates expression of a wide variety of amino acid-related genes, predominantly in Firmicutes. RNAs of this class selectively bind a specific cognate tRNA, utilizing recognition of the tRNA anticodon and other tRNA features. The riboswitch monitors the aminoacylation status of the tRNA to induce expression of the regulated downstream gene(s) at the level of transcription antitermination or derepression of translation initiation in response to reduced tRNA charging via stabilization of an antiterminator or antisequestrator. Recent biochemical and structural studies have revealed new features of tRNA recognition that extend beyond the initially identified Watson-Crick base-pairing of a codon-like sequence in the riboswitch with the tRNA anticodon, and residues in the antiterminator or antisequestrator with the tRNA acceptor end. These studies have revealed new tRNA contacts and new modes of riboswitch function and ligand recognition that expand our understanding of RNA-RNA recognition and the biological roles of tRNA.
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9
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Zhang J, Chetnani B, Cormack ED, Alonso D, Liu W, Mondragón A, Fei J. Specific structural elements of the T-box riboswitch drive the two-step binding of the tRNA ligand. eLife 2018; 7:39518. [PMID: 30251626 PMCID: PMC6197855 DOI: 10.7554/elife.39518] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 09/24/2018] [Indexed: 12/29/2022] Open
Abstract
T-box riboswitches are cis-regulatory RNA elements that regulate the expression of proteins involved in amino acid biosynthesis and transport by binding to specific tRNAs and sensing their aminoacylation state. While the T-box modular structural elements that recognize different parts of a tRNA have been identified, the kinetic trajectory describing how these interactions are established temporally remains unclear. Using smFRET, we demonstrate that tRNA binds to the riboswitch in two steps, first anticodon recognition followed by the sensing of the 3’ NCCA end, with the second step accompanied by a T-box riboswitch conformational change. Studies on site-specific mutants highlight that specific T-box structural elements drive the two-step binding process in a modular fashion. Our results set up a kinetic framework describing tRNA binding by T-box riboswitches, and suggest such binding mechanism is kinetically beneficial for efficient, co-transcriptional recognition of the cognate tRNA ligand. Living organisms depend upon a group of chemicals called amino acids to survive. Amino acids are the building blocks of proteins, and proteins have many important roles within and around cells. Bacteria regulate certain genes to ensure they have the right balance of different amino acids to survive. By controlling the availability of certain proteins that help them to make or collect certain amino acids, bacteria can control their overall amino acid balance. Before a protein is made, a molecular machine called RNA polymerase must first copy the information in a gene to make a molecule called a messenger RNA (mRNA). The mRNA is then translated to make the protein from individual amino acids. In this process, each amino acid needs to be first attached to another molecule called a transfer RNA (tRNA). In many bacteria species, the mRNAs involved in making or transporting amino acids contain structures called T-boxes. These structures guide the RNA polymerase to make more of the mRNAs when the levels of the amino acid become too low. A T-box, however, does not sense the level of the amino acid directly. Instead it senses the number of tRNA molecules that do not carry an amino acid. Zhang, Chetnani et al. examined a particular T-box interacting with tRNA using pairs of fluorescent dyes to detect distances between molecules. The T-box first recognizes a part of the tRNA called the anticodon to make sure it binds the correct type of tRNA. It then changes its shape to detect whether the tRNA is attached to an amino acid. This two-step process is driven by multiple structural elements within the T-box, and the flexibility of the T-box plays a critical role. A cell’s survival depends on it keeping amino acid levels under control. Understanding how bacteria do this could lead to new antibiotic drugs that target the T-box to kill cells. This study also provides insights into the workings of mRNA components like T-boxes – a type of riboswitch – which is an unusual means of controlling gene activity.
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Affiliation(s)
- Jiacheng Zhang
- Institute for Biophysical Dynamics, University of Chicago, Chicago, United States
| | - Bhaskar Chetnani
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
| | | | - Dulce Alonso
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
| | - Wei Liu
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, United States
| | - Alfonso Mondragón
- Department of Molecular Biosciences, Northwestern University, Evanston, United States
| | - Jingyi Fei
- Institute for Biophysical Dynamics, University of Chicago, Chicago, United States.,Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, United States
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10
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New tRNA contacts facilitate ligand binding in a Mycobacterium smegmatis T box riboswitch. Proc Natl Acad Sci U S A 2018; 115:3894-3899. [PMID: 29581302 DOI: 10.1073/pnas.1721254115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
T box riboswitches are RNA regulatory elements widely used by organisms in the phyla Firmicutes and Actinobacteria to regulate expression of amino acid-related genes. Expression of T box family genes is down-regulated by transcription attenuation or inhibition of translation initiation in response to increased charging of the cognate tRNA. Three direct contacts with tRNA have been described; however, one of these contacts is absent in a subclass of T box RNAs and the roles of several structural domains conserved in most T box RNAs are unknown. In this study, structural elements of a Mycobacterium smegmatis ileS T box riboswitch variant with an Ultrashort (US) Stem I were sequentially deleted, which resulted in a progressive decrease in binding affinity for the tRNAIle ligand. Selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) revealed structural changes in conserved riboswitch domains upon interaction with the tRNA ligand. Cross-linking and mutational analyses identified two interaction sites, one between the S-turn element in Stem II and the T arm of tRNAIle and the other between the Stem IIA/B pseudoknot and the D loop of tRNAIle These newly identified RNA contacts add information about tRNA recognition by the T box riboswitch and demonstrate a role for the S-turn and pseudoknot elements, which resemble structural elements that are common in many cellular RNAs.
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11
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Chetnani B, Mondragón A. Molecular envelope and atomic model of an anti-terminated glyQS T-box regulator in complex with tRNAGly. Nucleic Acids Res 2017; 45:8079-8090. [PMID: 28531275 PMCID: PMC5570125 DOI: 10.1093/nar/gkx451] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 05/03/2017] [Accepted: 05/08/2017] [Indexed: 11/26/2022] Open
Abstract
A T-box regulator or riboswitch actively monitors the levels of charged/uncharged tRNA and participates in amino acid homeostasis by regulating genes involved in their utilization or biosynthesis. It has an aptamer domain for cognate tRNA recognition and an expression platform to sense the charge state and modulate gene expression. These two conserved domains are connected by a variable linker that harbors additional secondary structural elements, such as Stem III. The structural basis for specific tRNA binding is known, but the structural basis for charge sensing and the role of other elements remains elusive. To gain new structural insights on the T-box mechanism, a molecular envelope was calculated from small angle X-ray scattering data for the Bacillus subtilis glyQS T-box riboswitch in complex with an uncharged tRNAGly. A structural model of an anti-terminated glyQS T-box in complex with its cognate tRNAGly was derived based on the molecular envelope. It shows the location and relative orientation of various secondary structural elements. The model was validated by comparing the envelopes of the wild-type complex and two variants. The structural model suggests that in addition to a possible regulatory role, Stem III could aid in preferential stabilization of the T-box anti-terminated state allowing read-through of regulated genes.
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MESH Headings
- Bacillus subtilis/genetics
- Bacillus subtilis/metabolism
- Base Sequence
- Models, Molecular
- Nucleic Acid Conformation
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Transfer, Gly/chemistry
- RNA, Transfer, Gly/genetics
- RNA, Transfer, Gly/metabolism
- Riboswitch/genetics
- Scattering, Small Angle
- X-Ray Diffraction
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Affiliation(s)
- Bhaskar Chetnani
- Department of Molecular Biosciences, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
| | - Alfonso Mondragón
- Department of Molecular Biosciences, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
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12
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Fang X, Michnicka M, Zhang Y, Wang YX, Nikonowicz EP. Capture and Release of tRNA by the T-Loop Receptor in the Function of the T-Box Riboswitch. Biochemistry 2017; 56:3549-3558. [PMID: 28621923 PMCID: PMC5813812 DOI: 10.1021/acs.biochem.7b00284] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In Gram-positive bacteria, the tRNA-dependent T-box riboswitch system regulates expression of amino acid biosynthetic and aminoacyl-tRNA synthetase genes through a transcription attenuation mechanism. Binding of uncharged tRNA "closes" the switch, allowing transcription read-through. Structural studies of the 100-nucleotide stem I domain reveal tRNA utilizes base pairing and stacking interactions to bind the stem, but little is known structurally about the 180-nucleotide riboswitch core (stem I, stem III, and antiterminator stem) in complex with tRNA or the mechanism of coupling of the intermolecular binding domains crucial to T-box function. Here we utilize solution structural and biophysical methods to characterize the interplay of the different riboswitch-tRNA contact points using Bacillus subtilis and Oceanobacillus iheyensis glycyl T-box and T-box:tRNA constructs. The data reveal that tRNA:riboswitch core binding at equilibrium involves only Specifier-anticodon and antiterminator-acceptor stem pairing. The elbow:platform stacking interaction observed in studies of the T-box stem I domain is released after pairing between the acceptor stem and the bulge in the antiterminator helix. The results are consistent with the model of T-box riboswitch:tRNA function in which tRNA is captured by stem I of the nascent mRNA followed by stabilization of the antiterminator helix and the paused transcription complex.
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Affiliation(s)
- Xianyang Fang
- Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China, 100084
- Structural Biophysics Laboratory, National Cancer Institute, Frederick, MD 21702
| | | | - Yikan Zhang
- Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China, 100084
| | - Yun-Xing Wang
- Structural Biophysics Laboratory, National Cancer Institute, Frederick, MD 21702
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13
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Apostolidi M, Saad NY, Drainas D, Pournaras S, Becker HD, Stathopoulos C. A glyS T-box riboswitch with species-specific structural features responding to both proteinogenic and nonproteinogenic tRNAGly isoacceptors. RNA (NEW YORK, N.Y.) 2015; 21:1790-806. [PMID: 26276802 PMCID: PMC4574755 DOI: 10.1261/rna.052712.115] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 07/13/2015] [Indexed: 06/04/2023]
Abstract
In Staphylococcus aureus, a T-box riboswitch exists upstream of the glyS gene to regulate transcription of the sole glycyl-tRNA synthetase, which aminoacylates five tRNA(Gly) isoacceptors bearing GCC or UCC anticodons. Subsequently, the glycylated tRNAs serve as substrates for decoding glycine codons during translation, and also as glycine donors for exoribosomal synthesis of pentaglycine peptides during cell wall formation. Probing of the predicted T-box structure revealed a long stem I, lacking features previously described for similar T-boxes. Moreover, the antiterminator stem includes a 42-nt long intervening sequence, which is staphylococci-specific. Finally, the terminator conformation adopts a rigid two-stem structure, where the intervening sequence forms the first stem followed by the second stem, which includes the more conserved residues. Interestingly, all five tRNA(Gly) isoacceptors interact with S. aureus glyS T-box with different binding affinities and they all induce transcription readthrough at different levels. The ability of both GCC and UCC anticodons to interact with the specifier loop indicates ambiguity during the specifier triplet reading, similar to the unconventional reading of glycine codons during protein synthesis. The S. aureus glyS T-box structure is consistent with the recent crystallographic and NMR studies, despite apparent differences, and highlights the phylogenetic variability of T-boxes when studied in a genome-dependent context. Our data suggest that the S. aureus glyS T-box exhibits differential tRNA selectivity, which possibly contributes toward the regulation and synchronization of ribosomal and exoribosomal peptide synthesis, two essential but metabolically unrelated pathways.
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Affiliation(s)
- Maria Apostolidi
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Nizar Y Saad
- Unité Mixte de Recherche 7156 Génétique Moléculaire, Génomique, Microbiologie, CNRS, Université de Strasbourg, F-67084 Strasbourg, France
| | - Denis Drainas
- Department of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
| | - Spyros Pournaras
- Department of Microbiology, School of Medicine, University of Athens, 11527 Athens, Greece
| | - Hubert D Becker
- Unité Mixte de Recherche 7156 Génétique Moléculaire, Génomique, Microbiologie, CNRS, Université de Strasbourg, F-67084 Strasbourg, France
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14
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Liu LC, Grundy FJ, Henkin TM. Non-Conserved Residues in Clostridium acetobutylicum tRNA(Ala) Contribute to tRNA Tuning for Efficient Antitermination of the alaS T Box Riboswitch. Life (Basel) 2015; 5:1567-82. [PMID: 26426057 PMCID: PMC4695836 DOI: 10.3390/life5041567] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 09/16/2015] [Accepted: 09/18/2015] [Indexed: 11/16/2022] Open
Abstract
The T box riboswitch regulates expression of amino acid-related genes in Gram-positive bacteria by monitoring the aminoacylation status of a specific tRNA, the binding of which affects the folding of the riboswitch into mutually exclusive terminator or antiterminator structures. Two main pairing interactions between the tRNA and the leader RNA have been demonstrated to be necessary, but not sufficient, for efficient antitermination. In this study, we used the Clostridium acetobutylicum alaS gene, which encodes alanyl-tRNA synthetase, to investigate the specificity of the tRNA response. We show that the homologous C. acetobutylicum tRNAAla directs antitermination of the C. acetobutylicum alaS gene in vitro, but the heterologous Bacillus subtilis tRNAAla (with the same anticodon and acceptor end) does not. Base substitutions at positions that vary between these two tRNAs revealed synergistic and antagonistic effects. Variation occurs primarily at positions that are not conserved in tRNAAla species, which indicates that these non-conserved residues contribute to optimal antitermination of the homologous alaS gene. This study suggests that elements in tRNAAla may have coevolved with the homologous alaS T box leader RNA for efficient antitermination.
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Affiliation(s)
- Liang-Chun Liu
- Department of Microbiology and Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA.
| | - Frank J Grundy
- Department of Microbiology and Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA.
| | - Tina M Henkin
- Department of Microbiology and Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA.
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15
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Caserta E, Liu LC, Grundy FJ, Henkin TM. Codon-Anticodon Recognition in the Bacillus subtilis glyQS T Box Riboswitch: RNA-DEPENDENT CODON SELECTION OUTSIDE THE RIBOSOME. J Biol Chem 2015; 290:23336-47. [PMID: 26229106 DOI: 10.1074/jbc.m115.673236] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Indexed: 12/28/2022] Open
Abstract
Many amino acid-related genes in Gram-positive bacteria are regulated by the T box riboswitch. The leader RNA of genes in the T box family controls the expression of downstream genes by monitoring the aminoacylation status of the cognate tRNA. Previous studies identified a three-nucleotide codon, termed the "Specifier Sequence," in the riboswitch that corresponds to the amino acid identity of the downstream genes. Pairing of the Specifier Sequence with the anticodon of the cognate tRNA is the primary determinant of specific tRNA recognition. This interaction mimics codon-anticodon pairing in translation but occurs in the absence of the ribosome. The goal of the current study was to determine the effect of a full range of mismatches for comparison with codon recognition in translation. Mutations were individually introduced into the Specifier Sequence of the glyQS leader RNA and tRNA(Gly) anticodon to test the effect of all possible pairing combinations on tRNA binding affinity and antitermination efficiency. The functional role of the conserved purine 3' of the Specifier Sequence was also verifiedin this study. We found that substitutions at the Specifier Sequence resulted in reduced binding, the magnitude of which correlates well with the predicted stability of the RNA-RNA pairing. However, the tolerance for specific mismatches in antitermination was generally different from that during decoding, which reveals a unique tRNA recognition pattern in the T box antitermination system.
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Affiliation(s)
- Enrico Caserta
- From the Department of Microbiology and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210
| | - Liang-Chun Liu
- From the Department of Microbiology and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210
| | - Frank J Grundy
- From the Department of Microbiology and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210
| | - Tina M Henkin
- From the Department of Microbiology and Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210
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16
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T box riboswitches in Actinobacteria: translational regulation via novel tRNA interactions. Proc Natl Acad Sci U S A 2015; 112:1113-8. [PMID: 25583497 DOI: 10.1073/pnas.1424175112] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The T box riboswitch regulates many amino acid-related genes in Gram-positive bacteria. T box riboswitch-mediated gene regulation was shown previously to occur at the level of transcription attenuation via structural rearrangements in the 5' untranslated (leader) region of the mRNA in response to binding of a specific uncharged tRNA. In this study, a novel group of isoleucyl-tRNA synthetase gene (ileS) T box leader sequences found in organisms of the phylum Actinobacteria was investigated. The Stem I domains of these RNAs lack several highly conserved elements that are essential for interaction with the tRNA ligand in other T box RNAs. Many of these RNAs were predicted to regulate gene expression at the level of translation initiation through tRNA-dependent stabilization of a helix that sequesters a sequence complementary to the Shine-Dalgarno (SD) sequence, thus freeing the SD sequence for ribosome binding and translation initiation. We demonstrated specific binding to the cognate tRNA(Ile) and tRNA(Ile)-dependent structural rearrangements consistent with regulation at the level of translation initiation, providing the first biochemical demonstration, to our knowledge, of translational regulation in a T box riboswitch.
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17
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18
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Henkin TM. The T box riboswitch: A novel regulatory RNA that utilizes tRNA as its ligand. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1839:959-963. [PMID: 24816551 DOI: 10.1016/j.bbagrm.2014.04.022] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 04/25/2014] [Accepted: 04/28/2014] [Indexed: 12/23/2022]
Abstract
The T box riboswitch is a cis-acting regulatory RNA that controls expression of amino acid-related genes in response to the aminoacylation state of a specific tRNA. Multiple genes in the same organism can utilize this mechanism, with each gene responding independently to its cognate tRNA. The uncharged tRNA interacts directly with the regulatory RNA element, and this interaction promotes readthrough of an intrinsic transcriptional termination site upstream of the regulated coding sequence. A second class of T box elements uses a similar tRNA-dependent response to regulate translation initiation. This review will describe the current state of our knowledge about this regulatory system. This article is part of a Special Issue entitled: Riboswitches.
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Affiliation(s)
- Tina M Henkin
- Department of Microbiology and Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA.
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19
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Grigg JC, Ke A. Structural determinants for geometry and information decoding of tRNA by T box leader RNA. Structure 2013; 21:2025-32. [PMID: 24095061 PMCID: PMC3879790 DOI: 10.1016/j.str.2013.09.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 09/01/2013] [Accepted: 09/03/2013] [Indexed: 01/07/2023]
Abstract
T box riboswitches are cis-acting RNA elements that bind to tRNA and sense its aminoacylation state to influence gene expression. Here, we present the 3.2 Å resolution X-ray crystal structures of the T box Stem I-tRNA complex and tRNA, in isolation. T box Stem I forms an arched conformation with extensive intermolecular contacts to two key points of tRNA, the anticodon and D/T-loops. Free and complexed tRNA exist in significantly different conformations, with the contacts stabilizing flexible D/T-loops and a rearrangement of the D-loop. Using a designed T box RNA/tRNA system, we demonstrate that the T box riboswitch monitors the length and orientation of two essential contacts. Length or orientation mismatches engineered into the T box riboswitch and tRNA disrupt the complex, whereas simultaneous insertion of full helical turns realigns the interfaces and restores interaction between artificially elongated T box riboswitch and tRNA molecules.
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Affiliation(s)
- Jason C. Grigg
- Department of Molecular Biology and Genetics, Cornell University, 253 Biotechnology Building, Ithaca, NY 14850, USA
| | - Ailong Ke
- Department of Molecular Biology and Genetics, Cornell University, 253 Biotechnology Building, Ithaca, NY 14850, USA,Correspondence:
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20
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Grigg JC, Ke A. Sequence, structure, and stacking: specifics of tRNA anchoring to the T box riboswitch. RNA Biol 2013; 10:1761-4. [PMID: 24356646 DOI: 10.4161/rna.26996] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The term riboswitch usually refers to small molecule sensing regulatory modules in the 5' untranslated regions of a mRNA. They are typically comprised of separate ligand binding and regulatory domains. The T box riboswitch is unique from other identified riboswitches because its effector is an essential macromolecule, tRNA. It senses the aminoacylation state of tRNA to regulate genes involved in a variety of functions relating to amino acid metabolism and tRNA aminoacylation. T box riboswitches performs an intuitively simple process using a complex structured RNA element and, until recently, the underlying mechanisms were poorly understood. Only two sequence-specific contacts had been previously identified: (1) between the specifier sequence (codon) and the tRNA anticodon and (2) between an anti-terminator stem loop and the tRNA acceptor arm CCA tail. tRNA aminoacylation blocks the latter interaction and therefore serves as the switch between termination and anti-termination. Outside of these two contacts, the structure and functions of T box riboswitches have come to light in some recent studies. We recently described the X-ray crystal structure of the highly conserved T box riboswitch distal Stem I region and demonstrated that this region interacts with the tRNA elbow to anchor it to the riboswitch. Independently, Lehmann et al. used sequence homology search to arrive at a similar model for Stem I-tRNA interactions. The model was further supported by two recent structures of the Stem I-tRNA complex, determined independently by our group and by Zhang and Ferré-D'Amaré. This article highlights some of these contributions to synthesize an updated model for tRNA recognition by the T box riboswitch.
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Affiliation(s)
- Jason C Grigg
- The Department of Molecular Biology and Genetics; Cornell University; Ithaca, NY USA
| | - Ailong Ke
- The Department of Molecular Biology and Genetics; Cornell University; Ithaca, NY USA
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21
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Chang AT, Nikonowicz EP. Solution NMR determination of hydrogen bonding and base pairing between the glyQS T box riboswitch Specifier domain and the anticodon loop of tRNA(Gly). FEBS Lett 2013; 587:3495-9. [PMID: 24036450 DOI: 10.1016/j.febslet.2013.09.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 08/30/2013] [Accepted: 09/02/2013] [Indexed: 10/26/2022]
Abstract
In Gram-positive bacteria the tRNA-dependent T box riboswitch regulates the expression of many amino acid biosynthetic and aminoacyl-tRNA synthetase genes through a transcription attenuation mechanism. The Specifier domain of the T box riboswitch contains the Specifier sequence that is complementary to the tRNA anticodon and is flanked by a highly conserved purine nucleotide that could result in a fourth base pair involving the invariant U33 of tRNA. We show that the interaction between the T box Specifier domain and tRNA consists of three Watson-Crick base pairs and that U33 confers stability to the complex through intramolecular hydrogen bonding. Enhanced packing within the Specifier domain loop E motif may stabilize the complex and contribute to cognate tRNA selection.
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Affiliation(s)
- Andrew T Chang
- Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005-1892, United States
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22
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T box RNA decodes both the information content and geometry of tRNA to affect gene expression. Proc Natl Acad Sci U S A 2013; 110:7240-5. [PMID: 23589841 PMCID: PMC3645572 DOI: 10.1073/pnas.1222214110] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The T box leader sequence is an RNA element that controls gene expression by binding directly to a specific tRNA and sensing its aminoacylation state. This interaction controls expression of amino acid-related genes in a negative feedback loop. The T box RNA structure is highly conserved, but its tRNA binding mechanism is only partially understood. Known sequence elements are the specifier sequence, which recognizes the tRNA anticodon, and the antiterminator bulge, which base pairs with the tRNA acceptor end. Here, we reveal the crucial function of the highly conserved stem I distal region in tRNA recognition and report its 2.65-Å crystal structure. The apex of this region contains an intricately woven loop-loop interaction between two conserved motifs, the Adenine-guanine (AG) bulge and the distal loop. This loop-loop structure presents a base triple on its surface that is optimally positioned for base-stacking interactions. Mutagenesis, cross-linking, and small-angle X-ray scattering data demonstrate that the apical base triple serves as a binding platform to dock the tRNA D- and T-loops. Strikingly, the binding platform strongly resembles the D- and T-loop binding elements from RNase P and the ribosome exit site, suggesting that this loop-loop structure may represent a widespread tRNA recognition platform. We propose a two-checkpoint molecular ruler model for tRNA decoding in which the information content of tRNA is first examined through specifier sequence-anticodon interaction, and the length of the tRNA anticodon arm is then measured by the distal loop-loop platform. When both conditions are met, tRNA is secured, and its aminoacylation state is sensed.
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23
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Lehmann J, Jossinet F, Gautheret D. A universal RNA structural motif docking the elbow of tRNA in the ribosome, RNAse P and T-box leaders. Nucleic Acids Res 2013; 41:5494-502. [PMID: 23580544 PMCID: PMC3664808 DOI: 10.1093/nar/gkt219] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The structure and function of conserved motifs constituting the apex of Stem I in T-box mRNA leaders are investigated. We point out that this apex shares striking similarities with the L1 stalk (helices 76–78) of the ribosome. A sequence and structure analysis of both elements shows that, similarly to the head of the L1 stalk, the function of the apex of Stem I lies in the docking of tRNA through a stacking interaction with the conserved G19:C56 base pair platform. The inferred structure in the apex of Stem I consists of a module of two T-loops bound together head to tail, a module that is also present in the head of the L1 stalk, but went unnoticed. Supporting the analysis, we show that a highly conserved structure in RNAse P formerly described as the J11/12–J12/11 module, which is precisely known to bind the elbow of tRNA, constitutes a third instance of this T-loop module. A structural analysis explains why six nucleotides constituting the core of this module are highly invariant among all three types of RNA. Our finding that major RNA partners of tRNA bind the elbow with a same RNA structure suggests an explanation for the origin of the tRNA L-shape.
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Affiliation(s)
- Jean Lehmann
- Université Paris-Sud, Institut de Génétique et Microbiologie, CNRS UMR 8621, Orsay F-91405, France.
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24
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Solution structure of the K-turn and Specifier Loop domains from the Bacillus subtilis tyrS T-box leader RNA. J Mol Biol 2011; 408:99-117. [PMID: 21333656 DOI: 10.1016/j.jmb.2011.02.014] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Revised: 02/03/2011] [Accepted: 02/04/2011] [Indexed: 01/28/2023]
Abstract
In Gram-positive bacteria, the RNA transcripts of many amino acid biosynthetic and aminoacyl tRNA synthetase genes contain 5' untranslated regions, or leader RNAs, that function as riboswitches. These T-box riboswitches bind cognate tRNA molecules and regulate gene expression by a transcription attenuation mechanism. The Specifier Loop domain of the leader RNA contains nucleotides that pair with nucleotides in the tRNA anticodon loop and is flanked on one side by a kink-turn (K-turn), or GA, sequence motif. We have determined the solution NMR structure of the K-turn sequence element within the context of the Specifier Loop domain. The K-turn sequence motif has several noncanonical base pairs typical of K-turn structures but adopts an extended conformation. The Specifier Loop domain contains a loop E structural motif, and the single-strand Specifier nucleotides stack with their Watson-Crick edges displaced toward the minor groove. Mg(2+) leads to a significant bending of the helix axis at the base of the Specifier Loop domain, but does not alter the K-turn. Isothermal titration calorimetry indicates that the K-turn sequence causes a small enhancement of the interaction between the tRNA anticodon arm and the Specifier Loop domain. One possibility is that the K-turn structure is formed and stabilized when tRNA binds the T-box riboswitch and interacts with Stem I and the antiterminator helix. This motif in turn anchors the orientation of Stem I relative to the 3' half of the leader RNA, further stabilizing the tRNA-T box complex.
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25
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Wang J, Henkin TM, Nikonowicz EP. NMR structure and dynamics of the Specifier Loop domain from the Bacillus subtilis tyrS T box leader RNA. Nucleic Acids Res 2010; 38:3388-98. [PMID: 20110252 PMCID: PMC2879506 DOI: 10.1093/nar/gkq020] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Gram-positive bacteria utilize a tRNA-responsive transcription antitermination mechanism, designated the T box system, to regulate expression of many amino acid biosynthetic and aminoacyl-tRNA synthetase genes. The RNA transcripts of genes controlled by this mechanism contain 5′ untranslated regions, or leader RNAs, that specifically bind cognate tRNA molecules through pairing of nucleotides in the tRNA anticodon loop with nucleotides in the Specifier Loop domain of the leader RNA. We have determined the solution structure of the Specifier Loop domain of the tyrS leader RNA from Bacillus subtilis. Fifty percent of the nucleotides in the Specifier Loop domain adopt a loop E motif. The Specifier Sequence nucleotides, which pair with the tRNA anticodon, stack with their Watson–Crick edges rotated toward the minor groove and exhibit only modest flexibility. We also show that a Specifier Loop domain mutation that impairs the function of the B. subtilis glyQS T box RNA disrupts the tyrS loop E motif. Our results suggest a mechanism for tRNA–Specifier Loop binding in which the phosphate backbone kink created by the loop E motif causes the Specifier Sequence bases to rotate toward the minor groove, which increases accessibility for pairing with bases in the anticodon loop of tRNA.
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Affiliation(s)
- Jiachen Wang
- Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77251-1892, USA
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26
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Green NJ, Grundy FJ, Henkin TM. The T box mechanism: tRNA as a regulatory molecule. FEBS Lett 2009; 584:318-24. [PMID: 19932103 DOI: 10.1016/j.febslet.2009.11.056] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 11/13/2009] [Accepted: 11/16/2009] [Indexed: 11/18/2022]
Abstract
The T box mechanism is widely used in Gram-positive bacteria to regulate expression of aminoacyl-tRNA synthetase genes and genes involved in amino acid biosynthesis and uptake. Binding of a specific uncharged tRNA to a riboswitch element in the nascent transcript causes a structural change in the transcript that promotes expression of the downstream coding sequence. In most cases, this occurs by stabilization of an antiterminator element that competes with formation of a terminator helix. Specific tRNA recognition by the nascent transcript results in increased expression of genes important for tRNA aminoacylation in response to decreased pools of charged tRNA.
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Affiliation(s)
- Nicholas J Green
- Department of Microbiology, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
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27
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Means JA, Simson CM, Zhou S, Rachford AA, Rack JJ, Hines JV. Fluorescence probing of T box antiterminator RNA: insights into riboswitch discernment of the tRNA discriminator base. Biochem Biophys Res Commun 2009; 389:616-21. [PMID: 19755116 DOI: 10.1016/j.bbrc.2009.09.037] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Accepted: 09/10/2009] [Indexed: 11/28/2022]
Abstract
The T box transcription antitermination riboswitch is one of the main regulatory mechanisms utilized by Gram-positive bacteria to regulate genes that are involved in amino acid metabolism. The details of the antitermination event, including the role that Mg(2+) plays, in this riboswitch have not been completely elucidated. In these studies, details of the antitermination event were investigated utilizing 2-aminopurine to monitor structural changes of a model antiterminator RNA when it was bound to model tRNA. Based on the results of these fluorescence studies, the model tRNA binds the model antiterminator RNA via an induced-fit. This binding is enhanced by the presence of Mg(2+), facilitating the complete base pairing of the model tRNA acceptor end with the complementary bases in the model antiterminator bulge.
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Affiliation(s)
- John A Means
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701, USA
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28
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Abstract
Regulation of gene expression in bacteria by cis-acting RNA elements can be investigated both in vivo and in vitro. Analyses in vivo can focus on changes in mRNA transcript levels or in protein production. Systems that are regulated at the level of premature termination of transcription are best analyzed by monitoring expression of a fusion to an easily assayable reporter gene construct or by direct measurement of the terminated and readthrough transcripts. These experimental approaches are described in the context of the Bacillus subtilis T box mechanism, which responds to uncharged tRNA as the effector, and are readily adaptable to other regulatory systems that respond to other signal molecules, and other experimental systems.
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29
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Biochemical features and functional implications of the RNA-based T-box regulatory mechanism. Microbiol Mol Biol Rev 2009; 73:36-61. [PMID: 19258532 DOI: 10.1128/mmbr.00026-08] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The T-box mechanism is a common regulatory strategy used for modulating the expression of genes of amino acid metabolism-related operons in gram-positive bacteria, especially members of the Firmicutes. T-box regulation is usually based on a transcription attenuation mechanism in which an interaction between a specific uncharged tRNA and the 5' region of the transcript stabilizes an antiterminator structure in preference to a terminator structure, thereby preventing transcription termination. Although single T-box regulatory elements are common, double or triple T-box arrangements are also observed, expanding the regulatory range of these elements. In the present study, we predict the functional implications of T-box regulation in genes encoding aminoacyl-tRNA synthetases, proteins of amino acid biosynthetic pathways, transporters, and regulatory proteins. We also consider the global impact of the use of this regulatory mechanism on cell physiology. Novel biochemical relationships between regulated genes and their corresponding metabolic pathways were revealed. Some of the genes identified, such as the quorum-sensing gene luxS, in members of the Lactobacillaceae were not previously predicted to be regulated by the T-box mechanism. Our analyses also predict an imbalance in tRNA sensing during the regulation of operons containing multiple aminoacyl-tRNA synthetase genes or biosynthetic genes involved in pathways common to more than one amino acid. Based on the distribution of T-box regulatory elements, we propose that this regulatory mechanism originated in a common ancestor of members of the Firmicutes, Chloroflexi, Deinococcus-Thermus group, and Actinobacteria and was transferred into the Deltaproteobacteria by horizontal gene transfer.
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30
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Fauzi H, Agyeman A, Hines JV. T box transcription antitermination riboswitch: influence of nucleotide sequence and orientation on tRNA binding by the antiterminator element. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1789:185-91. [PMID: 19152843 PMCID: PMC2656570 DOI: 10.1016/j.bbagrm.2008.12.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 12/09/2008] [Accepted: 12/09/2008] [Indexed: 11/18/2022]
Abstract
Many bacteria utilize riboswitch transcription regulation to monitor and appropriately respond to cellular levels of important metabolites or effector molecules. The T box transcription antitermination riboswitch responds to cognate uncharged tRNA by specifically stabilizing an antiterminator element in the 5'-untranslated mRNA leader region and precluding formation of a thermodynamically more stable terminator element. Stabilization occurs when the tRNA acceptor end base pairs with the first four nucleotides in the seven nucleotide bulge of the highly conserved antiterminator element. The significance of the conservation of the antiterminator bulge nucleotides that do not base pair with the tRNA is unknown, but they are required for optimal function. In vitro selection was used to determine if the isolated antiterminator bulge context alone dictates the mode in which the tRNA acceptor end binds the bulge nucleotides. No sequence conservation beyond complementarity was observed and the location was not constrained to the first four bases of the bulge. The results indicate that formation of a structure that recognizes the tRNA acceptor end in isolation is not the determinant driving force for the high phylogenetic sequence conservation observed within the antiterminator bulge. Additional factors or T box leader features more likely influenced the phylogenetic sequence conservation.
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Affiliation(s)
- Hamid Fauzi
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
| | - Akwasi Agyeman
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
- Molecular and Cellular Biology Program, Ohio University, Athens, OH, 45701, USA
| | - Jennifer V. Hines
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
- Molecular and Cellular Biology Program, Ohio University, Athens, OH, 45701, USA
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31
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Jack K, Means JA, Hines JV. Characterizing riboswitch function: identification of Mg2+ binding site in T box antiterminator RNA. Biochem Biophys Res Commun 2008; 370:306-10. [PMID: 18371302 PMCID: PMC2526249 DOI: 10.1016/j.bbrc.2008.03.079] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Accepted: 03/19/2008] [Indexed: 11/19/2022]
Abstract
T box bacterial genes utilize a riboswitch mechanism to regulate gene expression at the transcriptional level. Complementary base pairing of the 5'-untranslated mRNA with uncharged cognate tRNA stabilizes formation of an antiterminator element and permits complete transcription. In the absence of tRNA, a mutually exclusive RNA terminator element forms and results in transcription termination. This regulatory mechanism requires divalent metal ions at the antitermination event. The structural effects of Mg(2+) binding to antiterminator model RNA were investigated to ascertain if this requirement is due to the presence of a specific metal ion binding site in the antiterminator. Spectroscopic analysis identified the presence of a hydrated, diffuse Mg(2+) binding site. The results indicate that the mechanistic requirement for divalent metal ions is not due to Mg(2+)-induced pre-formation of a functional antiterminator receptor; rather, Mg(2+) binds in a helical region of high phylogenetic sequence conservation adjacent to the tRNA binding site.
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Affiliation(s)
- K.D. Jack
- Department of Chemistry & Biochemistry, Ohio University, Athens, OH 45701
| | - J. A. Means
- Department of Chemistry & Biochemistry, Ohio University, Athens, OH 45701
| | - J. V. Hines
- Department of Chemistry & Biochemistry, Ohio University, Athens, OH 45701
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32
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Anupam R, Nayek A, Green NJ, Grundy FJ, Henkin TM, Means JA, Bergmeier SC, Hines JV. 4,5-Disubstituted oxazolidinones: High affinity molecular effectors of RNA function. Bioorg Med Chem Lett 2008; 18:3541-4. [PMID: 18502126 DOI: 10.1016/j.bmcl.2008.05.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Revised: 04/24/2008] [Accepted: 05/02/2008] [Indexed: 10/22/2022]
Abstract
The T box transcription antitermination system is a riboswitch found primarily in Gram-positive bacteria which monitors the aminoacylation of the cognate tRNA and regulates a variety of amino acid-related genes. Novel 4,5-disubstituted oxazolidinones were identified as high affinity RNA molecular effectors that modulate the transcription antitermination function of the T box riboswitch.
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Affiliation(s)
- Rajaneesh Anupam
- Department of Chemistry & Biochemistry, Ohio University, Athens, OH 45701, USA
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33
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Henkin TM, Grundy FJ. Sensing metabolic signals with nascent RNA transcripts: the T box and S box riboswitches as paradigms. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2007; 71:231-7. [PMID: 17381302 DOI: 10.1101/sqb.2006.71.020] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Recent studies in a variety of bacterial systems have revealed a number of regulatory systems in which the 5' region of a gene plays a key role in regulation of the downstream coding sequences. These RNA regions act in cis to determine if the full-length transcript will be synthesized or if the coding sequence(s) will be translated. Each class of system includes an RNA element whose structure is modulated in response to a specific regulatory signal, and the signals measured can include small molecules, small RNAs (including tRNA), and physical parameters such as temperature. Multiple sets of genes can be regulated by a particular mechanism, and multiple systems of this type, each of which responds to a specific signal, can be present in a single organism. In addition, different classes of RNA elements can be found that respond to a particular signal, indicating the existence of multiple alternate solutions to the same regulatory problem. The T box and S box systems, which respond to uncharged tRNA and S-adenosylmethionine (SAM), respectively, provide paradigms of two systems of this type.
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Affiliation(s)
- T M Henkin
- Department of Microbiology and The RNA Group, The Ohio State University, Columbus, Ohio 43210, USA
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34
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Means JA, Wolf S, Agyeman A, Burton JS, Simson CM, Hines JV. T box riboswitch antiterminator affinity modulated by tRNA structural elements. Chem Biol Drug Des 2007; 69:139-45. [PMID: 17381728 DOI: 10.1111/j.1747-0285.2007.00476.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A unique RNA-RNA interaction occurs between uncharged tRNA and the untranslated mRNA leader region of bacterial T box genes. The interaction results in activation of a transcriptional antitermination molecular switch (riboswitch) by stabilizing an antiterminator RNA element and precluding formation of a competing transcriptional terminator RNA element. The stabilization requires the base pairing of cognate tRNA acceptor end nucleotides with the antiterminator. To develop an appropriate model system for detailed structural studies and to screen for small molecule disruption of this important RNA-RNA interaction, steady-state fluorescence measurements of antiterminator model RNAs were used to determine the dissociation constant for model tRNA binding. The antiterminator-binding affinity for the full, minihelix, microhelix, and tetramer tRNA models differed by orders of magnitude. In addition, not all of the tRNA models exhibited functionally relevant binding specificity. The results from these experiments highlight the importance of looking beyond the level of known base pairing interactions when designing functionally relevant models of riboswitch systems.
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Affiliation(s)
- John A Means
- Department of Chemistry & Biochemistry, Ohio University, Athens, OH 45701, USA
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35
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Means J, Katz S, Nayek A, Anupam R, Hines JV, Bergmeier SC. Structure–activity studies of oxazolidinone analogs as RNA-binding agents. Bioorg Med Chem Lett 2006; 16:3600-4. [PMID: 16603349 DOI: 10.1016/j.bmcl.2006.03.068] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Revised: 03/20/2006] [Accepted: 03/21/2006] [Indexed: 11/26/2022]
Abstract
We have synthesized and tested a series of novel 3,4,5-tri- and 4,5-disubstituted oxazolidinones for their ability to bind two structurally related T box antiterminator model RNAs. We have found that optimal binding selectivity is found in a small group of 4,5-disubstituted oxazolidinones.
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Affiliation(s)
- John Means
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701, USA
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36
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Nelson AR, Henkin TM, Agris PF. tRNA regulation of gene expression: interactions of an mRNA 5'-UTR with a regulatory tRNA. RNA (NEW YORK, N.Y.) 2006; 12:1254-61. [PMID: 16741230 PMCID: PMC1484421 DOI: 10.1261/rna.29906] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Many genes encoding aminoacyl-tRNA synthetases and other amino acid-related products in Gram-positive bacteria, including important pathogens, are regulated through interaction of unacylated tRNA with the 5'-untranslated region (5'-UTR) of the mRNA. Each gene regulated by this mechanism responds specifically to the cognate tRNA, and specificity is determined by pairing of the anticodon of the tRNA with a codon sequence in the "Specifier Loop" of the 5'-UTR. For the 5'-UTR to function in gene regulation, the mRNA folding interactions must be sufficiently stable to present the codon sequence for productive binding to the anticodon of the matching tRNA. A model bimolecular system was developed in which the interaction between two half molecules ("Common" and "Specifier") would reconstitute the Specifier Loop region of the 5'-UTR of the Bacillus subtilis glyQS gene, encoding GlyRS mRNA. Gel mobility shift analysis and fluorescence spectroscopy yielded experimental Kds of 27.6 +/- 1.0 microM and 10.5 +/- 0.7 microM, respectively, for complex formation between Common and Specifier half molecules. The reconstituted 5'-UTR of the glyQS mRNA bound the anticodon stem and loop of tRNA(Gly) (ASL(Gly)(GCC)) specifically and with a significant affinity (Kd = 20.2 +/- 1.4 microM). Thus, the bimolecular 5'-UTR and ASL(Gly)(GCC) models mimic the RNA-RNA interaction required for T box gene regulation in vivo.
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MESH Headings
- 5' Untranslated Regions/genetics
- Bacillus subtilis/genetics
- Base Sequence
- Electrophoresis, Polyacrylamide Gel
- Gene Expression Regulation
- Models, Molecular
- Nucleic Acid Conformation
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Transfer/chemistry
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- Spectrometry, Fluorescence
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Affiliation(s)
- Audrey R Nelson
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695-7622, USA
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37
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Gutierrez-Preciado A, Jensen RA, Yanofsky C, Merino E. New insights into regulation of the tryptophan biosynthetic operon in Gram-positive bacteria. Trends Genet 2005; 21:432-6. [PMID: 15953653 DOI: 10.1016/j.tig.2005.06.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2005] [Accepted: 06/02/2005] [Indexed: 10/25/2022]
Abstract
The tryptophan operon of Bacillus subtilis serves as an excellent model for investigating transcription regulation in Gram-positive bacteria. In this article, we extend this knowledge by analyzing the predicted regulatory regions in the trp operons of other fully sequenced Gram-positive bacteria. Interestingly, it appears that in eight of the organisms examined, transcription of the trp operon appears to be regulated by tandem T-box elements. These regulatory elements have recently been described in the trp operons of two bacterial species. Single T-box elements are commonly found in Gram-positive bacteria in operons encoding aminoacyl tRNA synthetases and proteins performing other functions. Different regulatory mechanisms appear to be associated with variations of trp gene organization within the trp operon.
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Affiliation(s)
- A Gutierrez-Preciado
- Department of Molecular Microbiology, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Cuernavaca, Morelos 62271, Mexico
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38
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Fauzi H, Jack KD, Hines JV. In vitro selection to identify determinants in tRNA for Bacillus subtilis tyrS T box antiterminator mRNA binding. Nucleic Acids Res 2005; 33:2595-602. [PMID: 15879350 PMCID: PMC1090546 DOI: 10.1093/nar/gki546] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The T box transcription antitermination regulatory system, found in Gram-positive bacteria, is dependent on a complex set of interactions between uncharged tRNA and the 5'-untranslated mRNA leader region of the regulated gene. One of these interactions involves the base pairing of the acceptor end of cognate tRNA with four bases in a 7 nt bulge of the antiterminator RNA. In vitro selection of randomized tRNA binding to Bacillus subtilis tyrS antiterminator model RNAs was used to determine what, if any, sequence trends there are for binding beyond the known base pair complementarity. The model antiterminator RNAs were selected for the wild-type tertiary fold of tRNA. While there were no obvious sequence correlations between the selected tRNAs, there were correlations between certain tertiary structural elements and binding efficiency to different antiterminator model RNAs. In addition, one antiterminator model selected primarily for a kissing tRNA T loop-antiterminator bulge interaction, while another antiterminator model resulted in no such selection. The selection results indicate that, at the level of tertiary structure, there are ideal matches between tRNAs and antiterminator model RNAs consistent with in vivo observations and that additional recognition features, beyond base pair complementarity, may play a role in the formation of the complex.
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Affiliation(s)
| | | | - Jennifer V. Hines
- To whom correspondence should be addressed. Tel: +1 740 517 8482; Fax: +1 740 593 0148;
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39
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Even S, Pellegrini O, Zig L, Labas V, Vinh J, Bréchemmier-Baey D, Putzer H. Ribonucleases J1 and J2: two novel endoribonucleases in B.subtilis with functional homology to E.coli RNase E. Nucleic Acids Res 2005; 33:2141-52. [PMID: 15831787 PMCID: PMC1079966 DOI: 10.1093/nar/gki505] [Citation(s) in RCA: 243] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Many prokaryotic organisms lack an equivalent of RNase E, which plays a key role in mRNA degradation in Escherichia coli. In this paper, we report the purification and identification by mass spectrometry in Bacillus subtilis of two paralogous endoribonucleases, here named RNases J1 and J2, which share functional homologies with RNase E but no sequence similarity. Both enzymes are able to cleave the B.subtilis thrS leader at a site that can also be cleaved by E.coli RNase E. We have previously shown that cleavage at this site increases the stability of the downstream messenger. Moreover, RNases J1/J2 are sensitive to the 5′ phosphorylation state of the substrate in a site-specific manner. Orthologues of RNases J1/J2, which belong to the metallo-β-lactamase family, are evolutionarily conserved in many prokaryotic organisms, representing a new family of endoribonucleases. RNases J1/J2 appear to be implicated in regulatory processing/maturation of specific mRNAs, such as the T-box family members thrS and thrZ, but may also contribute to global mRNA degradation.
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Affiliation(s)
| | | | | | - Valerie Labas
- CNRS UMR7637, ESPCI10 rue Vauquelin 75005 Paris, France
| | - Joelle Vinh
- CNRS UMR7637, ESPCI10 rue Vauquelin 75005 Paris, France
| | | | - Harald Putzer
- To whom correspondence should be addressed. Tel: +33 1 58 41 51 27; Fax: +33 1 58 41 50 20;
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40
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Yousef MR, Grundy FJ, Henkin TM. Structural transitions induced by the interaction between tRNA(Gly) and the Bacillus subtilis glyQS T box leader RNA. J Mol Biol 2005; 349:273-87. [PMID: 15890195 DOI: 10.1016/j.jmb.2005.03.061] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2005] [Revised: 03/18/2005] [Accepted: 03/22/2005] [Indexed: 10/25/2022]
Abstract
The T box system regulates expression of amino acid-related genes in Gram-positive bacteria through premature termination of transcription. Synthesis of the full-length mRNA requires stabilization of an antiterminator element in the 5' untranslated leader RNA by the cognate uncharged tRNA. tRNA(Gly)-dependent antitermination of the Bacillus subtilis glyQS gene (encoding glycyl-tRNA synthetase) can be reproduced in a purified in vitro transcription system, indicating that the nascent transcript is sufficient for interaction with the tRNA. Genetic analyses previously demonstrated base pairing of a single codon in the leader RNA with the tRNA anticodon, and between the antiterminator and the tRNA acceptor end. In this study, we established conditions for specific binding of tRNA(Gly) to glyQS leader RNA generated by phage T7 RNA polymerase. Structural mapping studies revealed tRNA(Gly)-induced protection in the glyQS leader RNA at the two known sites of interaction with the tRNA, as well as at other regions between these sites. The proposed tRNA-dependent structural switch between the competing terminator and antiterminator forms of the leader RNA was demonstrated directly. Changes in tRNA(Gly) upon binding to glyQS leader RNA were detected in the anticodon loop, consistent with pairing with the specifier sequence, and in the highly conserved G19 in the D-loop, similar to effects induced by codon-anticodon interaction in the ribosome. This study provides biochemical evidence for direct interaction of tRNA(Gly) with full-length in vitro transcribed glyQS leader RNA, and an initial view of structural modulations of both RNA partners within the complex.
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MESH Headings
- 5' Untranslated Regions/chemistry
- 5' Untranslated Regions/genetics
- 5' Untranslated Regions/metabolism
- Bacillus subtilis/genetics
- Glycine-tRNA Ligase/genetics
- Magnesium/pharmacology
- Nucleic Acid Conformation
- Peptide Chain Termination, Translational/genetics
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Transfer, Gly/chemistry
- RNA, Transfer, Gly/genetics
- RNA, Transfer, Gly/metabolism
- Ribonuclease H/metabolism
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Affiliation(s)
- Mary R Yousef
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
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41
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Grundy FJ, Yousef MR, Henkin TM. Monitoring uncharged tRNA during transcription of the Bacillus subtilis glyQS gene. J Mol Biol 2004; 346:73-81. [PMID: 15663928 DOI: 10.1016/j.jmb.2004.11.051] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2004] [Revised: 11/19/2004] [Accepted: 11/19/2004] [Indexed: 10/26/2022]
Abstract
Expression of the Bacillus subtilis glyQS gene, encoding glycyl-tRNA synthetase, depends on stabilization of an antiterminator element during transcription of the 5' region of the mRNA by binding of uncharged tRNA(Gly). The glyQS gene is a member of the T box family of genes, all of which are involved in generation of charged tRNA. Each gene in this family exhibits an increase in readthrough of a termination signal located upstream of the start of the coding sequence in response to a decrease in the ratio of charged to uncharged tRNA. Many structural features of T box RNAs that are necessary for tRNA-dependent antitermination have been defined, but little is known about the timing or sequence of events that lead to a productive interaction with uncharged tRNA and discrimination against charged tRNA. To investigate these issues, transcription complexes were blocked artificially at specific positions along the leader sequence and tested for the ability to recognize tRNA. Although the sequence element that binds the tRNA anticodon is located more than 100 nt before the termination signal, complexes with nascent transcripts extending to just upstream of the termination site were still competent for antitermination. This result indicates that the transcript can fold into a receptive structure in the absence of the tRNA, and that tRNA is not necessary prior to this point. A mimic of charged tRNA(Gly) inhibited antitermination by uncharged tRNA unless the leader RNA-tRNA(Gly) complexes contained the complete antiterminator. These results suggest that the transcription complex can interact with either uncharged or charged tRNA until it approaches the termination point, allowing maximal flexibility in monitoring the ratio of charged to uncharged tRNA.
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Affiliation(s)
- Frank J Grundy
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
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42
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Grundy FJ, Henkin TM. Kinetic analysis of tRNA-directed transcription antitermination of the Bacillus subtilis glyQS gene in vitro. J Bacteriol 2004; 186:5392-9. [PMID: 15292140 PMCID: PMC490933 DOI: 10.1128/jb.186.16.5392-5399.2004] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Binding of uncharged tRNA to the nascent transcript promotes readthrough of a leader region transcription termination signal in genes regulated by the T box transcription antitermination mechanism. Each gene in the T box family responds independently to its cognate tRNA, with specificity determined by base pairing of the tRNA to the leader at the anticodon and acceptor ends of the tRNA. tRNA binding stabilizes an antiterminator element in the transcript that sequesters sequences that participate in formation of the terminator helix. tRNA(Gly)-dependent antitermination of the Bacillus subtilis glyQS leader was previously demonstrated in a purified in vitro assay system. This assay system was used to investigate the kinetics of transcription through the glyQS leader and the effect of tRNA and transcription elongation factors NusA and NusG on transcriptional pausing and antitermination. Several pause sites, including a major site in the loop of stem III of the leader, were identified, and the effect of modulation of pausing on antitermination efficiency was analyzed. We found that addition of tRNA(Gly) can promote antitermination as long as the tRNA is added before the majority of the transcription complexes reach the termination site, and variations in pausing affect the requirements for timing of tRNA addition.
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MESH Headings
- 5' Untranslated Regions
- Anticodon
- Bacillus subtilis/genetics
- Bacillus subtilis/metabolism
- Base Pairing
- Base Sequence
- DNA-Directed RNA Polymerases/metabolism
- Escherichia coli Proteins/metabolism
- Gene Expression Regulation, Bacterial
- Genes, Bacterial
- Kinetics
- Models, Molecular
- Molecular Sequence Data
- Nucleic Acid Conformation
- Peptide Elongation Factors/metabolism
- RNA, Bacterial/chemistry
- RNA, Bacterial/metabolism
- RNA, Messenger/metabolism
- RNA, Transfer, Gly/metabolism
- RNA-Binding Proteins/metabolism
- Regulatory Sequences, Nucleic Acid
- Terminator Regions, Genetic
- Transcription Factors/metabolism
- Transcription, Genetic
- Transcriptional Elongation Factors
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Affiliation(s)
- Frank J Grundy
- Department of Microbiology, The Ohio State University, Columbus, 43210, USA
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43
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Yousef MR, Grundy FJ, Henkin TM. tRNA requirements for glyQS antitermination: a new twist on tRNA. RNA (NEW YORK, N.Y.) 2003; 9:1148-1156. [PMID: 12923262 PMCID: PMC1370478 DOI: 10.1261/rna.5540203] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2003] [Accepted: 05/30/2003] [Indexed: 05/24/2023]
Abstract
Transcription antitermination of the Bacillus subtilis glyQS gene, a member of the T box gene regulation family, can be induced during in vitro transcription in a minimal system using purified B. subtilis RNA polymerase by the addition of unmodified T7 RNA polymerase-transcribed tRNA(Gly). Antitermination was previously shown to depend on base-pairing between the glyQS leader and the tRNA at the anticodon and acceptor ends. In this study, variants of tRNA(Gly) were generated to identify additional tRNA elements required for antitermination activity, and to determine the effect of structural changes in the tRNA. We find that additions to the 3' end of the tRNA blocked antitermination, in agreement with the prediction that uncharged tRNA is the effector in vivo, whereas insertion of 1 nucleotide between the acceptor stem and the 3' UCCA residues had no effect. Disruption of the D-loop/T-loop tertiary interaction inhibited antitermination function, as was previously demonstrated for tRNA(Tyr)-directed antitermination of the B. subtilis tyrS gene in vivo. Insertion of a single base pair in the anticodon stem was tolerated, whereas further insertions abolished antitermination. However, we find that major alterations in the length of the acceptor stem are tolerated, and the insertions exhibited a pattern of periodicity suggesting that there is face-of-the-helix dependence in the positioning of the unpaired UCCA residues at the 3' end of the tRNA for interaction with the antiterminator bulge and antitermination.
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Affiliation(s)
- Mary R Yousef
- Department of Microbiology, The Ohio State University, Columbus, Ohio 43210, USA
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44
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Gerdeman MS, Henkin TM, Hines JV. Solution structure of the Bacillus subtilis T-box antiterminator RNA: seven nucleotide bulge characterized by stacking and flexibility. J Mol Biol 2003; 326:189-201. [PMID: 12547201 DOI: 10.1016/s0022-2836(02)01339-6] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The T-box transcription antitermination regulatory system is an important mechanism for regulation of expression of aminoacyl-tRNA synthetase, amino acid biosynthesis and transporter gene expression in Gram-positive bacteria. Antitermination is dependent on a complex set of interactions between uncharged tRNA and the leader region of the mRNA of the regulated gene. Here, we report the solution structure of a model RNA, based on the Bacillus subtilis tyrS antiterminator, determined to an rmsd of 3.47A for all nine converged structures and 2.66A for the seven structures representing the consensus family. The antiterminator is comprised of two short helices with an intervening 7nt bulge. The bulge region of the antiterminator, which ultimately interacts with the acceptor end of tRNA, exhibits extensive stacking at the 3' end (encompassing the highly conserved ACC residues) and is the site of a pronounced kink between the two flanking helices. The 5' end of the bulge exhibits evidence of conformational flexibility. On the basis of the structural studies, there is no indication that the bases at the 5' end of the bulge that ultimately base-pair with tRNA are pre-organized for binding. Instead, the data are consistent with a model in which the stacking-induced structure at the 3' end of the bulge may facilitate the pre-selection of a set of conformations for the tRNA to sample during binding.
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MESH Headings
- Bacillus subtilis/genetics
- Base Pairing
- Base Sequence
- Conserved Sequence
- Gene Expression Regulation, Bacterial
- Models, Molecular
- Nuclear Magnetic Resonance, Biomolecular
- Nucleic Acid Conformation
- Nucleotides/chemistry
- Nucleotides/genetics
- Pliability
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Transfer/chemistry
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- Solutions
- Terminator Regions, Genetic/genetics
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Affiliation(s)
- Melinda S Gerdeman
- Division of Medicinal Chemistry, College of Pharmacy, Ohio State University, Columbus, OH 43210, USA
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45
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Grundy FJ, Winkler WC, Henkin TM. tRNA-mediated transcription antitermination in vitro: codon-anticodon pairing independent of the ribosome. Proc Natl Acad Sci U S A 2002; 99:11121-6. [PMID: 12165569 PMCID: PMC123220 DOI: 10.1073/pnas.162366799] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Uncharged tRNA acts as the effector for transcription antitermination of genes in the T box family in Bacillus subtilis and other Gram-positive bacteria. Genetic studies suggested that expression of these genes is induced by stabilization of an antiterminator element in the leader RNA of each target gene by the cognate uncharged tRNA. The specificity of the tRNA response is dependent on a single codon in the leader, which was postulated to pair with the anticodon of the corresponding tRNA. It was not known whether the leader RNA-tRNA interaction requires additional factors. We show here that tRNA-dependent antitermination occurs in vitro in a purified transcription system, in the absence of ribosomes or accessory factors, demonstrating that the RNA-RNA interaction is sufficient to control gene expression by antitermination. The tRNA response exhibits similar specificity in vivo and in vitro, and the antitermination reaction in vitro is independent of NusA and functions with either B. subtilis or Escherichia coli RNA polymerase.
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MESH Headings
- Anticodon/genetics
- Bacillus subtilis/genetics
- Base Sequence
- Chromosomes, Bacterial/genetics
- Codon/genetics
- Gene Expression Regulation, Enzymologic
- Gram-Positive Bacteria/genetics
- Models, Genetic
- Molecular Sequence Data
- Nucleic Acid Conformation
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Spliced Leader/chemistry
- RNA, Spliced Leader/genetics
- RNA, Transfer/metabolism
- RNA, Transfer, Gly/genetics
- RNA, Transfer, Tyr/genetics
- Terminator Regions, Genetic/genetics
- Transcription, Genetic
- beta-Galactosidase/genetics
- beta-Galactosidase/metabolism
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Affiliation(s)
- Frank J Grundy
- Department of Microbiology, Ohio State University, Columbus, OH 43210, USA
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46
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Putzer H, Condon C, Brechemier-Baey D, Brito R, Grunberg-Manago M. Transfer RNA-mediated antitermination in vitro. Nucleic Acids Res 2002; 30:3026-33. [PMID: 12136084 PMCID: PMC135736 DOI: 10.1093/nar/gkf415] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The threonyl-tRNA synthetase gene (thrS) is a member of the T-box family of approximately 250 genes, found essentially in Gram-positive bacteria, regulated by a tRNA-dependent antitermination mechanism in response to starvation for the cognate amino acid. While interaction between uncharged tRNA and the untranslated leader region of these genes has been firmly established by genetic means, attempts to show this interaction or to reconstitute the antitermination mechanism in vitro using purified tRNAs have so far failed. In addition, a number of conserved sequences have been identified in the T-box leaders, for which no function has yet been assigned. This suggests that factors other than the tRNA are important for this type of control. Here we demonstrate tRNA-mediated antitermination for the first time in vitro, using the regulatory tRNA(Thr) isoacceptor isolated from Bacillus subtilis and a partially purified protein fraction. As predicted by the model, aminoacylation of tRNA(Thr(GGU)) with threonine completely abolishes its ability to act as an effector. The role of the partially purified protein fraction can be functionally substituted by high concentrations of spermidine. However, this polyamine does not play a significant role in the induction of thrS expression in vivo, suggesting that it is specific protein co-factors that promote T-box gene regulation in conjunction with uncharged tRNA.
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MESH Headings
- Anticodon/genetics
- Bacillus subtilis/genetics
- Bacillus subtilis/metabolism
- Bacterial Proteins/genetics
- Exotoxins
- Membrane Proteins/genetics
- Mutation
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- RNA, Transfer, Thr/genetics
- RNA, Transfer, Thr/metabolism
- Terminator Regions, Genetic/genetics
- Threonine-tRNA Ligase/genetics
- Threonine-tRNA Ligase/metabolism
- Transcription, Genetic/genetics
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Affiliation(s)
- Harald Putzer
- CNRS-UPR 9073, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France.
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47
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Grundy FJ, Moir TR, Haldeman MT, Henkin TM. Sequence requirements for terminators and antiterminators in the T box transcription antitermination system: disparity between conservation and functional requirements. Nucleic Acids Res 2002; 30:1646-55. [PMID: 11917026 PMCID: PMC101844 DOI: 10.1093/nar/30.7.1646] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The T box transcription termination control system is used in Gram-positive bacteria to regulate expression of aminoacyl-tRNA synthetase and other amino acid-related genes. Readthrough of a transcriptional terminator located in the leader region of the target gene is dependent on a specific interaction between the nascent leader transcript and the cognate uncharged tRNA. This interaction is required for formation of an antiterminator structure in the leader, which prevents formation of a competing transcriptional terminator stem-loop. The antiterminators and terminators of genes in this family are highly conserved in both secondary structure and primary sequence; the antiterminator contains the T box sequence, which is the most highly conserved leader element. These conserved features were investigated by phylogenetic and mutational analysis. Changes at highly conserved positions in the bulge and in the helix above the bulge reduced function, while alteration of other positions that were as much as 96% conserved did not have a major effect. The disparity between sequence conservation and function may be due to the requirement for maintaining base pairing in both the antiterminator and terminator structures.
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Affiliation(s)
- Frank J Grundy
- Department of Microbiology, The Ohio State University, 484 West 12th Avenue, Columbus, OH 43210, USA
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48
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Gerdeman MS, Henkin TM, Hines JV. In vitro structure-function studies of the Bacillus subtilis tyrS mRNA antiterminator: evidence for factor-independent tRNA acceptor stem binding specificity. Nucleic Acids Res 2002; 30:1065-72. [PMID: 11842119 PMCID: PMC100339 DOI: 10.1093/nar/30.4.1065] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2001] [Revised: 12/04/2001] [Accepted: 12/04/2001] [Indexed: 11/14/2022] Open
Abstract
Expression of many aminoacyl-tRNA synthetase, amino acid biosynthesis and transport genes in Bacillus subtilis is controlled at the level of transcription termination using the T box system and requires the formation of specific secondary structures in the mRNA leader region. One structure functions as a transcriptional terminator, while an alternate form, the antiterminator, is necessary for transcription of the downstream coding regions. We have investigated the interaction of antiterminator model RNAs, based on the B.subtilis tyrS antiterminator with tRNA(Tyr) and tRNA acceptor stem models, using a gel shift assay. Binding of the antiterminator RNA to tRNA(Tyr) was dependent on complimentarity with the acceptor end of the tRNA or microhelix; affinity for the microhelix RNA was reduced relative to the tRNA. Alteration of a conserved position in the non-base pairing region of the bulge greatly reduced tRNA binding, consistent with in vivo studies. Therefore, it appears that some of the antiterminator-tRNA binding specificity is dependent on the structure of the antiterminator bulge alone and the complex it forms with tRNA in the absence of additional trans-acting factors. During the course of these studies we also discovered that the antiterminator can form a 'kissing' bulge complex, a unique RNA motif. The ease of formation of this RNA homodimer illustrates the propensity for the bulge of the antiterminator to bind RNA.
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MESH Headings
- 5' Untranslated Regions
- Bacillus subtilis/genetics
- Base Pairing
- Base Sequence
- Binding Sites
- Dimerization
- Electrophoretic Mobility Shift Assay
- Molecular Sequence Data
- Nucleic Acid Conformation
- RNA, Bacterial/chemistry
- RNA, Bacterial/metabolism
- RNA, Bacterial/physiology
- RNA, Messenger/chemistry
- RNA, Messenger/metabolism
- RNA, Messenger/physiology
- RNA, Transfer, Tyr/chemistry
- RNA, Transfer, Tyr/metabolism
- Structure-Activity Relationship
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Affiliation(s)
- Melinda S Gerdeman
- Division of Medicinal Chemistry, College of Pharmacy and Department of Microbiology, Ohio State University, Columbus, OH 43210, USA
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van de Guchte M, Ehrlich SD, Chopin A. Identity elements in tRNA-mediated transcription antitermination: implication of tRNA D- and T-arms in mRNA recognition. MICROBIOLOGY (READING, ENGLAND) 2001; 147:1223-1233. [PMID: 11320125 DOI: 10.1099/00221287-147-5-1223] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
tRNA-mediated transcription antitermination has been shown to control the expression of several amino acid biosynthesis operons and aminoacyl-tRNA-synthetase-encoding genes in Gram-positive bacteria. A model originally put forward by Grundy & Henkin describes the conserved structural features of the leader sequences of these operons and genes. Two sequences of 3 and 4 nt, respectively, take a central position in this model and are thought to be responsible for the binding of the system-specific uncharged tRNA, an interaction which would stabilize the antiterminator conformation of the leader. Here a further evolution of this model is presented based on an analysis of trp regulation in Lactococcus lactis in which a function is assigned to hitherto unexplained conserved structures in the leader sequence. It is postulated that the mRNA-tRNA interaction involves various parts of the tRNA in addition to the anticodon and the acceptor in the original model and that these additional interactions contribute to the recognition of a specific tRNA, and hence to the specificity and efficacy of the regulatory response.
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Affiliation(s)
- Maarten van de Guchte
- Laboratoire de Génétique Microbienne, Institut National de la Recherche Agronomique, 78352Jouy-en-Josas Cedex, France1
| | - S Dusko Ehrlich
- Laboratoire de Génétique Microbienne, Institut National de la Recherche Agronomique, 78352Jouy-en-Josas Cedex, France1
| | - Alain Chopin
- Laboratoire de Génétique Microbienne, Institut National de la Recherche Agronomique, 78352Jouy-en-Josas Cedex, France1
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Abstract
Transcription termination is a dynamic process and is subject to control at a number of levels. New information about the molecular mechanisms of transcription elongation and termination, as well as new insights into protein-RNA interactions, are providing a framework for increased understanding of the molecular details of transcription termination control.
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Affiliation(s)
- T M Henkin
- Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA.
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