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Kuszczynska A, Bors M, Podskoczyj K, Leszczynska G. Chemistry of installing epitranscriptomic 5-modified cytidines in RNA oligomers. Org Biomol Chem 2024; 22:7271-7286. [PMID: 39177469 DOI: 10.1039/d4ob01098a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/24/2024]
Abstract
Studies of 5-hydroxymethylcytidine (hm5C), 5-formylcytidine (f5C) and 5-carboxycytidine (ca5C) modifications as products of the 5-methylcytidine (m5C) oxidative demethylation pathway in cellular mRNAs constitute an important element of the new epitranscriptomic field of research. The dynamic process of m5C conversion and final turnover to the parent cytidine is considered a post-transcriptional layer of gene-expression regulation. However, the regulatory mechanism associated with epitranscriptomic cytidine modifications remains largely unknown. Therefore, oligonucleotides containing m5C oxidation products are of great value for the next generation of biochemical, biophysical, and structural studies on their function, metabolism, and contribution to human diseases. Herein, we summarize the synthetic strategies developed for the incorporation of hm5C, f5C and ca5C into RNA oligomers by phosphoramidite chemistry, including post-synthetic C5-cytidine functionalization and enzymatic methods.
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Affiliation(s)
- Anna Kuszczynska
- Institute of Organic Chemistry, Faculty of Chemistry, University of Technology, 90-924 Lodz, Zeromskiego 116, Poland.
| | - Milena Bors
- Institute of Organic Chemistry, Faculty of Chemistry, University of Technology, 90-924 Lodz, Zeromskiego 116, Poland.
| | - Karolina Podskoczyj
- Institute of Organic Chemistry, Faculty of Chemistry, University of Technology, 90-924 Lodz, Zeromskiego 116, Poland.
| | - Grazyna Leszczynska
- Institute of Organic Chemistry, Faculty of Chemistry, University of Technology, 90-924 Lodz, Zeromskiego 116, Poland.
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Flemmich L, Bereiter R, Micura R. Chemical Synthesis of Modified RNA. Angew Chem Int Ed Engl 2024; 63:e202403063. [PMID: 38529723 DOI: 10.1002/anie.202403063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 03/16/2024] [Accepted: 03/26/2024] [Indexed: 03/27/2024]
Abstract
Ribonucleic acids (RNAs) play a vital role in living organisms. Many of their cellular functions depend critically on chemical modification. Methods to modify RNA in a controlled manner-both in vitro and in vivo-are thus essential to evaluate and understand RNA biology at the molecular and mechanistic levels. The diversity of modifications, combined with the size and uniformity of RNA (made up of only 4 nucleotides) makes its site-specific modification a challenging task that needs to be addressed by complementary approaches. One such approach is solid-phase RNA synthesis. We discuss recent developments in this field, starting with new protection concepts in the ongoing effort to overcome current size limitations. We continue with selected modifications that have posed significant challenges for their incorporation into RNA. These include deazapurine bases required for atomic mutagenesis to elucidate mechanistic aspects of catalytic RNAs, and RNA containing xanthosine, N4-acetylcytidine, 5-hydroxymethylcytidine, 3-methylcytidine, 2'-OCF3, and 2'-N3 ribose modifications. We also discuss the all-chemical synthesis of 5'-capped mRNAs and the enzymatic ligation of chemically synthesized oligoribonucleotides to obtain long RNA with multiple distinct modifications, such as those needed for single-molecule FRET studies. Finally, we highlight promising developments in RNA-catalyzed RNA modification using cofactors that transfer bioorthogonal functionalities.
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Affiliation(s)
- Laurin Flemmich
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80-82, 6020, Innsbruck, Austria
| | - Raphael Bereiter
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80-82, 6020, Innsbruck, Austria
| | - Ronald Micura
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80-82, 6020, Innsbruck, Austria
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Tanpure AA, Balasubramanian S. Synthesis and Multiple Incorporations of 2'-O-Methyl-5-hydroxymethylcytidine, 5-Hydroxymethylcytidine and 5-Formylcytidine Monomers into RNA Oligonucleotides. Chembiochem 2017; 18:2236-2241. [PMID: 28901692 PMCID: PMC5779611 DOI: 10.1002/cbic.201700492] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Indexed: 01/09/2023]
Abstract
The synthesis of 2'-O-methyl-5-hydroxymethylcytidine (hm5 Cm), 5-hydroxymethylcytidine (hm5 C) and 5-formylcytidine (f5 C) phosphoramidite monomers has been developed. Optimisation of mild post-synthetic deprotection conditions enabled the synthesis of RNA containing all four naturally occurring cytosine modifications (hm5 Cm, hm5 C, f5 C plus 5-methylcytosine). Given the considerable interest in RNA modifications and epitranscriptomics, the availability of synthetic monomers and RNAs containing these modifications will be valuable for elucidating their biological function(s).
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Affiliation(s)
- Arun A. Tanpure
- Department of ChemistryUniversity of CambridgeLensfield RoadCambridgeCB2 1EWUK
| | - Shankar Balasubramanian
- Department of ChemistryUniversity of CambridgeLensfield RoadCambridgeCB2 1EWUK
- Cancer Research (UK)Cambridge InstituteLi Ka Shing Centre University of CambridgeRobinson WayCambridgeCB2 0REUK
- School of Clinical MedicineUniversity of CambridgeCambridgeCB2 0SPUK
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Michaelides IN, Tago N, Viverge B, Carell T. Synthesis of RNA Containing 5-Hydroxymethyl-, 5-Formyl-, and 5-Carboxycytidine. Chemistry 2017; 23:15894-15898. [PMID: 28906048 DOI: 10.1002/chem.201704216] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Indexed: 12/17/2022]
Abstract
5-Hydroxymethyl-, 5-formyl-, and 5-carboxy-2'-deoxycytidine are new epigenetic bases (hmdC, fdC, cadC) that were recently discovered in the DNA of higher eukaryotes. The same bases (5-hydroxymethyl-, 5-formyl-, and 5-carboxycytidine; hmC, fC, and caC) have now also been detected in mammalian RNA with a high abundance in mRNA. While DNA phosphoramidites (PAs) that allow the synthesis of xdC-containing oligonucleotides for deeper biological studies are available, the corresponding silyl-protected RNA PAs for fC and caC have not yet been disclosed. Here, we report novel RNA PAs for hmC, fC, and caC that can be used in routine RNA synthesis. The new building blocks are compatible with the canonical PAs and also with themselves, which enables even the synthesis of RNA strands containing all three of these bases. The study will pave the way for detailed physical, biochemical, and biological studies to unravel the function of these non-canonical modifications in RNA.
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Affiliation(s)
- Iacovos N Michaelides
- Center for Integrated Protein Science at the Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, Munich, Germany.,Current address: AstraZeneca, 310 Cambridge Science Park, Milton Road, Cambridge, CB4 0FZ, UK
| | - Nobuhiro Tago
- Center for Integrated Protein Science at the Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, Munich, Germany
| | - Bastien Viverge
- Center for Integrated Protein Science at the Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, Munich, Germany
| | - Thomas Carell
- Center for Integrated Protein Science at the Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, Munich, Germany
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Francis AJ, Resendiz MJE. Protocol for the Solid-phase Synthesis of Oligomers of RNA Containing a 2'-O-thiophenylmethyl Modification and Characterization via Circular Dichroism. J Vis Exp 2017. [PMID: 28784951 DOI: 10.3791/56189] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Solid-phase synthesis has been used to obtain canonical and modified polymers of nucleic acids, specifically of DNA or RNA, which has made it a popular methodology for applications in various fields and for different research purposes. The procedure described herein focuses on the synthesis, purification, and characterization of dodecamers of RNA 5'-[CUA CGG AAU CAU]-3' containing zero, one, or two modifications located at the C2'-O-position. The probes are based on 2-thiophenylmethyl groups, incorporated into RNA nucleotides via standard organic synthesis and introduced into the corresponding oligonucleotides via their respective phosphoramidites. This report makes use of phosphoramidite chemistry via the four canonical nucleobases (Uridine (U), Cytosine (C), Guanosine (G), Adenosine (A)), as well as 2-thiophenylmethyl functionalized nucleotides modified at the 2'-O-position; however, the methodology is amenable for a large variety of modifications that have been developed over the years. The oligonucleotides were synthesized on a controlled-pore glass (CPG) support followed by cleavage from the resin and deprotection under standard conditions, i.e., a mixture of ammonia and methylamine (AMA) followed by hydrogen fluoride/triethylamine/N-methylpyrrolidinone. The corresponding oligonucleotides were purified via polyacrylamide electrophoresis (20% denaturing) followed by elution, desalting, and isolation via reversed-phase chromatography (Sep-pak, C18-column). Quantification and structural parameters were assessed via ultraviolet-visible (UV-vis) and circular dichroism (CD) photometric analysis, respectively. This report aims to serve as a resource and guide for beginner and expert researchers interested in embarking in this field. It is expected to serve as a work-in-progress as new technologies and methodologies are developed. The description of the methodologies and techniques within this document correspond to a DNA/RNA synthesizer (refurbished and purchased in 2013) that uses phosphoramidite chemistry.
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Riml C, Lusser A, Ennifar E, Micura R. Synthesis, Thermodynamic Properties, and Crystal Structure of RNA Oligonucleotides Containing 5-Hydroxymethylcytosine. J Org Chem 2017; 82:7939-7945. [PMID: 28707898 DOI: 10.1021/acs.joc.7b01171] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
5-Hydroxymethylcytosine (hm5C) is an RNA modification that has attracted significant interest because of the finding that RNA hydroxymethylation can favor mRNA translation. For insight into the mechanistic details of hm5C function to be obtained, the availability of RNAs containing this modification at defined positions that can be used for in vitro studies is highly desirable. In this work, we present an eight-step route to 5-hydroxymethylcytidine (hm5rC) phosphoramidite for solid-phase synthesis of modified RNA oligonucleotides. Furthermore, we examined the effects of hm5rC on RNA duplex stability and its impact on structure formation using the sarcin-ricin loop (SRL) motif. Thermal denaturation experiments revealed that hm5rC increases RNA duplex stability. By contrast, when cytosine within an UNCG tetraloop motif was replaced by hm5rC, the thermodynamic stability of the corresponding hairpin fold was attenuated. Importantly, incorporation of hm5rC into the SRL motif resulted in an RNA crystal structure at 0.85 Å resolution. Besides changes in the hydration pattern at the site of modification, a slight opening of the hm5rC-G pair compared to the unmodified C-G in the native structure was revealed.
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Affiliation(s)
- Christian Riml
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck , 6020 Innsbruck, Austria
| | - Alexandra Lusser
- Division of Molecular Biology, Biocenter, Medical University of Innsbruck , 6020 Innsbruck, Austria
| | - Eric Ennifar
- Université de Strasbourg, CNRS , Architecture et Réactivité des ARN, UPR 9002, 67000 Strasbourg, France
| | - Ronald Micura
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck , 6020 Innsbruck, Austria
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Schmid K, Adobes-Vidal M, Helm M. Alkyne-Functionalized Coumarin Compound for Analytic and Preparative 4-Thiouridine Labeling. Bioconjug Chem 2017; 28:1123-1134. [PMID: 28263563 DOI: 10.1021/acs.bioconjchem.7b00035] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Bioconjugation of RNA is a dynamic field recently reinvigorated by a surge in research on post-transcriptional modification. This work focuses on the bioconjugation of 4-thiouridine, a nucleoside that occurs as a post-transcriptional modification in bacterial RNA and is used as a metabolic label and for cross-linking purposes in eukaryotic RNA. A newly designed coumarin compound named 4-bromomethyl-7-propargyloxycoumarin (PBC) is introduced, which exhibits remarkable selectivity for 4-thiouridine. Bearing a terminal alkyne group, it is conductive to secondary bioconjugation via "click chemistry", thereby offering a wide range of preparative and analytical options. We applied PBC to quantitatively monitor the metabolic incorporation of s4U as a label into RNA and for site-specific introduction of a fluorophore into bacterial tRNA at position 8, allowing the determination of its binding constant to an RNA-modification enzyme.
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Affiliation(s)
- Katharina Schmid
- Institute of Pharmacy and Biochemistry, Johannes-Gutenberg University Mainz , Staudingerweg 5, D-55128 Mainz, Germany
| | - Maria Adobes-Vidal
- Electrochemistry & Interfaces Group, Department of Chemistry, University of Warwick , Coventry, CV4 7AL United Kingdom
| | - Mark Helm
- Institute of Pharmacy and Biochemistry, Johannes-Gutenberg University Mainz , Staudingerweg 5, D-55128 Mainz, Germany
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Jud L, Micura R. An Unconventional Acid-Labile Nucleobase Protection Concept for Guanosine Phosphoramidites in RNA Solid-Phase Synthesis. Chemistry 2017; 23:3406-3413. [PMID: 27943429 DOI: 10.1002/chem.201605056] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Indexed: 12/14/2022]
Abstract
We present an innovative O6 -tert-butyl/N2 -tert-butyloxycarbonyl protection concept for guanosine (G) phosphoramidites. This concept is advantageous for 2'-modified G building blocks because of very efficient synthetic access when compared with existing routes that usually employ O6 -(4-nitrophenyl)ethyl/N2 -acyl protection or that start from 2-aminoadenosine involving enzymatic transformation into guanosine later on in the synthetic path. The new phosphoramidites are fully compatible with 2'-O-tBDMS or TOM phosphoramidites in standard RNA solid-phase synthesis and deprotection, and provide excellent quality of tailored RNAs for the growing range of applications in RNA biophysics, biochemistry, and biology.
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Affiliation(s)
- Lukas Jud
- Institute of Organic Chemistry, Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80-82, 6020, Innsbruck, Austria
| | - Ronald Micura
- Institute of Organic Chemistry, Center for Molecular Biosciences Innsbruck (CMBI), University of Innsbruck, Innrain 80-82, 6020, Innsbruck, Austria
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Amort T, Rieder D, Wille A, Khokhlova-Cubberley D, Riml C, Trixl L, Jia XY, Micura R, Lusser A. Distinct 5-methylcytosine profiles in poly(A) RNA from mouse embryonic stem cells and brain. Genome Biol 2017; 18:1. [PMID: 28077169 PMCID: PMC5225599 DOI: 10.1186/s13059-016-1139-1] [Citation(s) in RCA: 313] [Impact Index Per Article: 44.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 12/16/2016] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Recent work has identified and mapped a range of posttranscriptional modifications in mRNA, including methylation of the N6 and N1 positions in adenine, pseudouridylation, and methylation of carbon 5 in cytosine (m5C). However, knowledge about the prevalence and transcriptome-wide distribution of m5C is still extremely limited; thus, studies in different cell types, tissues, and organisms are needed to gain insight into possible functions of this modification and implications for other regulatory processes. RESULTS We have carried out an unbiased global analysis of m5C in total and nuclear poly(A) RNA of mouse embryonic stem cells and murine brain. We show that there are intriguing differences in these samples and cell compartments with respect to the degree of methylation, functional classification of methylated transcripts, and position bias within the transcript. Specifically, we observe a pronounced accumulation of m5C sites in the vicinity of the translational start codon, depletion in coding sequences, and mixed patterns of enrichment in the 3' UTR. Degree and pattern of methylation distinguish transcripts modified in both embryonic stem cells and brain from those methylated in either one of the samples. We also analyze potential correlations between m5C and micro RNA target sites, binding sites of RNA binding proteins, and N6-methyladenosine. CONCLUSION Our study presents the first comprehensive picture of cytosine methylation in the epitranscriptome of pluripotent and differentiated stages in the mouse. These data provide an invaluable resource for future studies of function and biological significance of m5C in mRNA in mammals.
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Affiliation(s)
- Thomas Amort
- Division of Molecular Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Dietmar Rieder
- Division of Bioinformatics, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Alexandra Wille
- Division of Molecular Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | | | - Christian Riml
- Department of Organic Chemistry and Center for Molecular Biosciences (CMBI), Leopold-Franzens University, 6020 Innsbruck, Austria
| | - Lukas Trixl
- Division of Molecular Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria
| | | | - Ronald Micura
- Department of Organic Chemistry and Center for Molecular Biosciences (CMBI), Leopold-Franzens University, 6020 Innsbruck, Austria
| | - Alexandra Lusser
- Division of Molecular Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria
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Riml C, Micura R. Automated Chemical Solid-Phase Synthesis and Deprotection of 5-Hydroxymethylcytosine-Containing RNA. Methods Mol Biol 2017; 1562:295-302. [PMID: 28349469 DOI: 10.1007/978-1-4939-6807-7_20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
5-Hydroxymethylcytosine is an epigenetic base modification that is part of the demethylation pathway of 5-methylcytosine in DNA. 5-Methylcytosine is iteratively oxidized to 5-hydroxymethylcytosine, 5-formylcytosine, and 5-carboxycytosine by enzymes of the TET protein family. Since the discovery of 5-hydroxymethylcytosine also in RNA its role in regulatory processes and metabolism remains elusive. To gain more insight into the function of RNA containing 5-hydroxymethylcytidine, innovative and interdisciplinary approaches are required. In this context, synthetic oligoribonucleotides containing 5-hyroxymethylcytidine are an inevitable tool. Therefore, in this chapter, we present the efficient synthesis of RNA oligonucleotides containing 5-hydroxymethylcytosine by solid-phase synthesis. The incorporation of the modified cytosine derivative into RNA is compatible with standard phosphoramidite-based synthesis procedures of oligoribonucleotides.
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Affiliation(s)
- Christian Riml
- Institute of Organic Chemistry and Center for Molecular Biosciences, CMBI, Leopold-Franzens University, Innrain 80-82, 6020, Innbruck, Austria
| | - Ronald Micura
- Institute of Organic Chemistry and Center for Molecular Biosciences, CMBI, Leopold-Franzens University, Innrain 80-82, 6020, Innbruck, Austria.
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