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Ding D, Fang Z, Kim SC, O’Flaherty DK, Jia X, Stone TB, Zhou L, Szostak JW. Unusual Base Pair between Two 2-Thiouridines and Its Implication for Nonenzymatic RNA Copying. J Am Chem Soc 2024; 146:3861-3871. [PMID: 38293747 PMCID: PMC10870715 DOI: 10.1021/jacs.3c11158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 01/05/2024] [Accepted: 01/08/2024] [Indexed: 02/01/2024]
Abstract
2-Thiouridine (s2U) is a nucleobase modification that confers enhanced efficiency and fidelity both on modern tRNA codon translation and on nonenzymatic and ribozyme-catalyzed RNA copying. We have discovered an unusual base pair between two 2-thiouridines that stabilizes an RNA duplex to a degree that is comparable to that of a native A:U base pair. High-resolution crystal structures indicate similar base-pairing geometry and stacking interactions in duplexes containing s2U:s2U compared to those with U:U pairs. Notably, the C═O···H-N hydrogen bond in the U:U pair is replaced with a C═S···H-N hydrogen bond in the s2U:s2U base pair. The thermodynamic stability of the s2U:s2U base pair suggested that this self-pairing might lead to an increased error frequency during nonenzymatic RNA copying. However, competition experiments show that s2U:s2U base-pairing induces only a low level of misincorporation during nonenzymatic RNA template copying because the correct A:s2U base pair outcompetes the slightly weaker s2U:s2U base pair. In addition, even if an s2U is incorrectly incorporated, the addition of the next base is greatly hindered. This strong stalling effect would further increase the effective fidelity of nonenzymatic RNA copying with s2U. Our findings suggest that s2U may enhance the rate and extent of nonenzymatic copying with only a minimal cost in fidelity.
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Affiliation(s)
- Dian Ding
- Department
of Chemistry and Chemical Biology, Harvard
University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
- Department
of Molecular Biology and Center for Computational and Integrative
Biology, Massachusetts General Hospital, 185 Cambridge Street, Boston, Massachusetts 02114, United States
| | - Ziyuan Fang
- Howard
Hughes Medical Institute, Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Seohyun Chris Kim
- Department
of Chemistry and Chemical Biology, Harvard
University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
- Department
of Molecular Biology and Center for Computational and Integrative
Biology, Massachusetts General Hospital, 185 Cambridge Street, Boston, Massachusetts 02114, United States
- Department
of Genetics, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, Massachusetts 02115, United States
| | - Derek K. O’Flaherty
- Department
of Chemistry, College of Engineering and Physical Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Xiwen Jia
- Department
of Chemistry and Chemical Biology, Harvard
University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
- Department
of Molecular Biology and Center for Computational and Integrative
Biology, Massachusetts General Hospital, 185 Cambridge Street, Boston, Massachusetts 02114, United States
| | - Talbot B. Stone
- Department
of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
- Penn
Institute for RNA Innovation, University
of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Lijun Zhou
- Department
of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
- Penn
Institute for RNA Innovation, University
of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Jack W. Szostak
- Howard
Hughes Medical Institute, Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
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Whitaker D, Powner MW. Prebiotic synthesis and triphosphorylation of 3'-amino-TNA nucleosides. Nat Chem 2022; 14:766-774. [PMID: 35778563 DOI: 10.1038/s41557-022-00982-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 05/23/2022] [Indexed: 12/22/2022]
Abstract
Nucleosides are essential to the emergence of life, and so their synthesis is a key challenge for prebiotic chemistry. Although amino-nucleosides have enhanced reactivity in water compared with ribonucleosides, they are assumed to be prebiotically irrelevant due to perceived difficulties with their selective formation. Here we demonstrate that 3'-amino-TNA nucleosides (TNA, threose nucleic acid) are formed diastereoselectively and regiospecifically from prebiotic feedstocks in four high-yielding steps. Phosphate provides an unexpected resolution, leading to spontaneous purification of the genetically relevant threo-isomer. Furthermore, 3'-amino-TNA nucleosides are shown to be phosphorylated directly in water, under mild conditions with cyclic trimetaphosphate, forming a nucleoside triphosphate (NTP) in a manner not feasible for canonical nucleosides. Our results suggest 3'-amino-TNA nucleosides may have been present on the early Earth, and the ease with which these NTPs form, alongside the inherent selectivity for the Watson-Crick base-pairing threo-monomer, warrants further study of the role they could play during the emergence of life.
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Affiliation(s)
- Daniel Whitaker
- Department of Chemistry, University College London, London, UK
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3
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Duzdevich D, Carr CE, Ding D, Zhang SJ, Walton TS, Szostak JW. Competition between bridged dinucleotides and activated mononucleotides determines the error frequency of nonenzymatic RNA primer extension. Nucleic Acids Res 2021; 49:3681-3691. [PMID: 33744957 PMCID: PMC8053118 DOI: 10.1093/nar/gkab173] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Revised: 02/12/2021] [Accepted: 03/05/2021] [Indexed: 12/15/2022] Open
Abstract
Nonenzymatic copying of RNA templates with activated nucleotides is a useful model for studying the emergence of heredity at the origin of life. Previous experiments with defined-sequence templates have pointed to the poor fidelity of primer extension as a major problem. Here we examine the origin of mismatches during primer extension on random templates in the simultaneous presence of all four 2-aminoimidazole-activated nucleotides. Using a deep sequencing approach that reports on millions of individual template-product pairs, we are able to examine correct and incorrect polymerization as a function of sequence context. We have previously shown that the predominant pathway for primer extension involves reaction with imidazolium-bridged dinucleotides, which form spontaneously by the reaction of two mononucleotides with each other. We now show that the sequences of correctly paired products reveal patterns that are expected from the bridged dinucleotide mechanism, whereas those associated with mismatches are consistent with direct reaction of the primer with activated mononucleotides. Increasing the ratio of bridged dinucleotides to activated mononucleotides, either by using purified components or by using isocyanide-based activation chemistry, reduces the error frequency. Our results point to testable strategies for the accurate nonenzymatic copying of arbitrary RNA sequences.
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Affiliation(s)
- Daniel Duzdevich
- To whom correspondence should be addressed. Tel: +1 617 726 5102; Fax: +1 617 643 332;
| | - Christopher E Carr
- Department of Molecular Biology, Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Dian Ding
- Department of Molecular Biology, Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
| | - Stephanie J Zhang
- Department of Molecular Biology, Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
| | - Travis S Walton
- Department of Molecular Biology, Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Jack W Szostak
- Department of Molecular Biology, Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
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Duzdevich D, Carr CE, Szostak JW. Deep sequencing of non-enzymatic RNA primer extension. Nucleic Acids Res 2020; 48:e70. [PMID: 32427335 PMCID: PMC7337528 DOI: 10.1093/nar/gkaa400] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 04/02/2020] [Accepted: 05/05/2020] [Indexed: 12/02/2022] Open
Abstract
Life emerging in an RNA world is expected to propagate RNA as hereditary information, requiring some form of primitive replication without enzymes. Non-enzymatic template-directed RNA primer extension is a model of the copying step in this posited form of replication. The sequence space accessed by primer extension dictates potential pathways to self-replication and, eventually, ribozymes. Which sequences can be accessed? What is the fidelity of the reaction? Does the recently illuminated mechanism of primer extension affect the distribution of sequences that can be copied? How do sequence features respond to experimental conditions and prebiotically relevant contexts? To help answer these and related questions, we here introduce a deep-sequencing methodology for studying RNA primer extension. We have designed and vetted special RNA constructs for this purpose, honed a protocol for sample preparation and developed custom software that analyzes sequencing data. We apply this new methodology to proof-of-concept controls, and demonstrate that it works as expected and reports on key features of the sequences accessed by primer extension.
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Affiliation(s)
- Daniel Duzdevich
- Department of Molecular Biology, Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Christopher E Carr
- Department of Molecular Biology, Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jack W Szostak
- Department of Molecular Biology, Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Howard Hughes Medical Institute, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
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Abstract
The emergence of functional cooperation between the three main classes of biomolecules - nucleic acids, peptides and lipids - defines life at the molecular level. However, how such mutually interdependent molecular systems emerged from prebiotic chemistry remains a mystery. A key hypothesis, formulated by Crick, Orgel and Woese over 40 year ago, posits that early life must have been simpler. Specifically, it proposed that an early primordial biology lacked proteins and DNA but instead relied on RNA as the key biopolymer responsible not just for genetic information storage and propagation, but also for catalysis, i.e. metabolism. Indeed, there is compelling evidence for such an 'RNA world', notably in the structure of the ribosome as a likely molecular fossil from that time. Nevertheless, one might justifiably ask whether RNA alone would be up to the task. From a purely chemical perspective, RNA is a molecule of rather uniform composition with all four bases comprising organic heterocycles of similar size and comparable polarity and pK a values. Thus, RNA molecules cover a much narrower range of steric, electronic and physicochemical properties than, e.g. the 20 amino acid side-chains of proteins. Herein we will examine the functional potential of RNA (and other nucleic acids) with respect to self-replication, catalysis and assembly into simple protocellular entities.
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