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Schultz SK, Kothe U. Fluorescent labeling of tRNA for rapid kinetic interaction studies with tRNA-binding proteins. Methods Enzymol 2023; 692:103-126. [PMID: 37925176 DOI: 10.1016/bs.mie.2023.05.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2023]
Abstract
Transfer RNA (tRNA) plays a critical role during translation and interacts with numerous proteins during its biogenesis, functional cycle and degradation. In particular, tRNA is extensively post-transcriptionally modified by various tRNA modifying enzymes which each target a specific nucleotide at different positions within tRNAs to introduce different chemical modifications. Fluorescent assays can be used to study the interaction between a protein and tRNA. Moreover, rapid mixing fluorescence stopped-flow assays provide insights into the kinetics of the tRNA-protein interaction in order to elucidate the tRNA binding mechanism for the given protein. A prerequisite for these studies is a fluorescently labeled molecule, such as fluorescent tRNA, wherein a change in fluorescence occurs upon protein binding. In this chapter, we discuss the utilization of tRNA modifications in order to introduce fluorophores at particular positions within tRNAs. Particularly, we focus on in vitro thiolation of a uridine at position 8 within tRNAs using the tRNA modification enzyme ThiI, followed by labeling of the thiol group with fluorescein. As such, this fluorescently labeled tRNA is primarily unmodified, with the exception of the thiolation modification to which the fluorophore is attached, and can be used as a substrate to study the binding of different tRNA-interacting factors. Herein, we discuss the example of studying the tRNA binding mechanism of the tRNA modifying enzymes TrmB and DusA using internally fluorescein-labeled tRNA.
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Affiliation(s)
- Sarah K Schultz
- Alberta RNA Research and Training Institute (ARRTI), Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, AB, Canada; Department of Chemistry, University of Manitoba, Winnipeg, MB, Canada
| | - Ute Kothe
- Alberta RNA Research and Training Institute (ARRTI), Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, AB, Canada; Department of Chemistry, University of Manitoba, Winnipeg, MB, Canada.
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Schultz SK, Meadows K, Kothe U. Molecular mechanism of tRNA binding by the Escherichia coli N7 guanosine methyltransferase TrmB. J Biol Chem 2023; 299:104612. [PMID: 36933808 PMCID: PMC10130221 DOI: 10.1016/j.jbc.2023.104612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 03/11/2023] [Accepted: 03/12/2023] [Indexed: 03/18/2023] Open
Abstract
Among the large and diverse collection of tRNA modifications, 7-methylguanosine (m7G) is frequently found in the tRNA variable loop at position 46. This modification is introduced by the TrmB enzyme, which is conserved in bacteria and eukaryotes. However, the molecular determinants and the mechanism for tRNA recognition by TrmB are not well understood. Complementing the report of various phenotypes for different organisms lacking TrmB homologs, we report here hydrogen peroxide sensitivity for the Escherichia coli ΔtrmB knockout strain. To gain insight into the molecular mechanism of tRNA binding by E. coli TrmB in real-time, we developed a new assay based on introducing a 4-thiouridine modification at position 8 of in vitro transcribed tRNAPhe enabling us to fluorescently label this unmodified tRNA. Using rapid kinetic stopped-flow measurements with this fluorescent tRNA, we examined the interaction of wildtype and single substitution variants of TrmB with tRNA. Our results reveal the role of SAM for rapid and stable tRNA binding, the rate-limiting nature of m7G46 catalysis for tRNA release, and the importance of residues R26, T127 and R155 across the entire surface of TrmB for tRNA binding.
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Affiliation(s)
- Sarah K Schultz
- Alberta RNA Research and Training Institute (ARRTI), Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada; Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Kieran Meadows
- Alberta RNA Research and Training Institute (ARRTI), Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada
| | - Ute Kothe
- Alberta RNA Research and Training Institute (ARRTI), Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada; Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada.
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Site-Specific Fluorescent Labeling of RNA Interior Positions. Molecules 2021; 26:molecules26051341. [PMID: 33802273 PMCID: PMC7959133 DOI: 10.3390/molecules26051341] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 02/26/2021] [Accepted: 03/01/2021] [Indexed: 02/08/2023] Open
Abstract
The introduction of fluorophores into RNA for both in vitro and in cellulo studies of RNA function and cellular distribution is a subject of great current interest. Here I briefly review methods, some well-established and others newly developed, which have been successfully exploited to site-specifically fluorescently label interior positions of RNAs, as a guide to investigators seeking to apply this approach to their studies. Most of these methods can be applied directly to intact RNAs, including (1) the exploitation of natural posttranslational modifications, (2) the repurposing of enzymatic transferase reactions, and (3) the nucleic acid-assisted labeling of intact RNAs. In addition, several methods are described in which specifically labeled RNAs are prepared de novo.
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Gholamalipour Y, Johnson WC, Martin CT. Efficient inhibition of RNA self-primed extension by addition of competing 3'-capture DNA-improved RNA synthesis by T7 RNA polymerase. Nucleic Acids Res 2019; 47:e118. [PMID: 31392994 PMCID: PMC6821179 DOI: 10.1093/nar/gkz700] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 07/23/2019] [Accepted: 08/01/2019] [Indexed: 12/18/2022] Open
Abstract
In vitro synthesized RNA is used widely in studies of RNA biology, biotechnology and RNA therapeutics. However, in vitro synthesized RNA often contains impurities, such as RNAs with lengths shorter and longer than the expected runoff RNA. We have recently confirmed that longer RNA products are formed predominantly via cis self-primed extension, in which released runoff RNA folds back on itself to prime its own RNA-templated extension. In the current work, we demonstrate that addition of a DNA oligonucleotide (capture DNA) that is complementary to the 3′ end of the expected runoff RNA effectively prevents self-primed extension, even under conditions commonly used for high RNA yields. Moreover, the presence of this competing capture DNA during ‘high yield’ transcription, leads to an increase in the yield of expected runoff RNA by suppressing the formation of undesired longer RNA byproducts.
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Affiliation(s)
- Yasaman Gholamalipour
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - William C Johnson
- Department of Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Craig T Martin
- Department of Chemistry, University of Massachusetts Amherst, Amherst, MA 01003, USA
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Masuda I, Igarashi T, Sakaguchi R, Nitharwal RG, Takase R, Han KY, Leslie BJ, Liu C, Gamper H, Ha T, Sanyal S, Hou YM. A genetically encoded fluorescent tRNA is active in live-cell protein synthesis. Nucleic Acids Res 2017; 45:4081-4093. [PMID: 27956502 PMCID: PMC5397188 DOI: 10.1093/nar/gkw1229] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 12/06/2016] [Indexed: 11/14/2022] Open
Abstract
Transfer RNAs (tRNAs) perform essential tasks for all living cells. They are major components of the ribosomal machinery for protein synthesis and they also serve in non-ribosomal pathways for regulation and signaling metabolism. We describe the development of a genetically encoded fluorescent tRNA fusion with the potential for imaging in live Escherichia coli cells. This tRNA fusion carries a Spinach aptamer that becomes fluorescent upon binding of a cell-permeable and non-toxic fluorophore. We show that, despite having a structural framework significantly larger than any natural tRNA species, this fusion is a viable probe for monitoring tRNA stability in a cellular quality control mechanism that degrades structurally damaged tRNA. Importantly, this fusion is active in E. coli live-cell protein synthesis allowing peptidyl transfer at a rate sufficient to support cell growth, indicating that it is accommodated by translating ribosomes. Imaging analysis shows that this fusion and ribosomes are both excluded from the nucleoid, indicating that the fusion and ribosomes are in the cytosol together possibly engaged in protein synthesis. This fusion methodology has the potential for developing new tools for live-cell imaging of tRNA with the unique advantage of both stoichiometric labeling and broader application to all cells amenable to genetic engineering.
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Affiliation(s)
- Isao Masuda
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | - Takao Igarashi
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | - Reiko Sakaguchi
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | - Ram G Nitharwal
- Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC 75124, Uppsala, Sweden
| | - Ryuichi Takase
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | - Kyu Young Han
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.,CREOL, College of Optics & Photonics, University of Central Florida, 4304 Scorpius St., Orlando, FL 32816, USA
| | - Benjamin J Leslie
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.,Howard Hughes Medical Institute, Baltimore, MD 21205, USA
| | - Cuiping Liu
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | - Howard Gamper
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | - Taekjip Ha
- Department of Physics and Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.,Howard Hughes Medical Institute, Baltimore, MD 21205, USA.,Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA.,Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA.,Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Suparna Sanyal
- Department of Cell and Molecular Biology, Uppsala University, Box-596, BMC 75124, Uppsala, Sweden
| | - Ya-Ming Hou
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
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Liu C, Stonestrom AJ, Christian T, Yong J, Takase R, Hou YM, Yang X. Molecular Basis and Consequences of the Cytochrome c-tRNA Interaction. J Biol Chem 2016; 291:10426-36. [PMID: 26961879 DOI: 10.1074/jbc.m115.697789] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Indexed: 11/06/2022] Open
Abstract
The intrinsic apoptosis pathway occurs through the release of mitochondrial cytochrome c to the cytosol, where it promotes activation of the caspase family of proteases. The observation that tRNA binds to cytochrome c revealed a previously unexpected mode of apoptotic regulation. However, the molecular characteristics of this interaction, and its impact on each interaction partner, are not well understood. Using a novel fluorescence assay, we show here that cytochrome c binds to tRNA with an affinity comparable with other tRNA-protein binding interactions and with a molecular ratio of ∼3:1. Cytochrome c recognizes the tertiary structural features of tRNA, particularly in the core region. This binding is independent of the charging state of tRNA but is regulated by the redox state of cytochrome c. Compared with reduced cytochrome c, oxidized cytochrome c binds to tRNA with a weaker affinity, which correlates with its stronger pro-apoptotic activity. tRNA binding both facilitates cytochrome c reduction and inhibits the peroxidase activity of cytochrome c, which is involved in its release from mitochondria. Together, these findings provide new insights into the cytochrome c-tRNA interaction and apoptotic regulation.
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Affiliation(s)
- Cuiping Liu
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Aaron J Stonestrom
- the Department of Cancer Biology and Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, and
| | - Thomas Christian
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Jeongsik Yong
- the Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455
| | - Ryuichi Takase
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Ya-Ming Hou
- From the Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107,
| | - Xiaolu Yang
- the Department of Cancer Biology and Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, and
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Abstract
Transfer RNA (tRNA) molecules contain many chemical modifications that are introduced after transcription. A major form of these modifications is methyl transfer to bases and backbone groups, using S-adenosyl methionine (AdoMet) as the methyl donor. Each methylation confers a specific advantage to tRNA in structure or in function. A remarkable methylation is to the G37 base on the 3'-side of the anticodon to generate m(1)G37-tRNA, which suppresses frameshift errors during protein synthesis and is therefore essential for cell growth in all three domains of life. This methylation is catalyzed by TrmD in bacteria and by Trm5 in eukaryotes and archaea. Although TrmD and Trm5 catalyze the same methylation reaction, kinetic analysis reveals that these two enzymes are unrelated to each other and are distinct in their reaction mechanism. This chapter summarizes the kinetic assays that are used to reveal the distinction between TrmD and Trm5. Three types of assays are described, the steady-state, the pre-steady-state, and the single-turnover assays, which collectively provide the basis for mechanistic investigation of AdoMet-dependent methyl transfer reactions.
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Affiliation(s)
- Ya-Ming Hou
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania USA.
| | - Isao Masuda
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania USA
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Wetzel C, Li S, Limbach PA. Metabolic de-isotoping for improved LC-MS characterization of modified RNAs. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:1114-1123. [PMID: 24760295 DOI: 10.1007/s13361-014-0889-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 03/15/2014] [Accepted: 03/17/2014] [Indexed: 06/03/2023]
Abstract
Mapping, sequencing, and quantifying individual noncoding ribonucleic acids (ncRNAs), including post-transcriptionally modified nucleosides, by mass spectrometry is a challenge that often requires rigorous sample preparation prior to analysis. Previously, we have described a simplified method for the comparative analysis of RNA digests (CARD) that is applicable to relatively complex mixtures of ncRNAs. In the CARD approach for transfer RNA (tRNA) analysis, two complete sets of digestion products from total tRNA are compared using the enzymatic incorporation of (16)O/(18)O isotopic labels. This approach allows one to rapidly screen total tRNAs from gene deletion mutants or comparatively sequence total tRNA from two related bacterial organisms. However, data analysis can be challenging because of convoluted mass spectra arising from the natural (13)C and (15) N isotopes present in the ribonuclease-digested tRNA samples. Here, we demonstrate that culturing in (12)C-enriched/(13)C-depleted media significantly reduces the isotope patterns that must be interpreted during the CARD experiment. Improvements in data quality yield a 35 % improvement in detection of tRNA digestion products that can be uniquely assigned to particular tRNAs. These mass spectral improvements lead to a significant reduction in data processing attributable to the ease of spectral identification of labeled digestion products and will enable improvements in the relative quantification of modified RNAs by the (16)O/(18)O differential labeling approach.
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Affiliation(s)
- Collin Wetzel
- Rieveschl Laboratories for Mass Spectrometry, Department of Chemistry, University of Cincinnati, Cincinnati, OH, 45221-0172, USA
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Ishizuka T, Kimoto M, Sato A, Hirao I. Site-specific functionalization of RNA molecules by an unnatural base pair transcription system via click chemistry. Chem Commun (Camb) 2012; 48:10835-7. [DOI: 10.1039/c2cc36293g] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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