1
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Mala P, Saraogi I. Enhanced Codon-Anticodon Interaction at In-Frame UAG Stop Codon Improves the Efficiency of Non-Natural Amino Acid Mutagenesis. ACS Chem Biol 2022; 17:1051-1060. [PMID: 35532803 DOI: 10.1021/acschembio.1c00782] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The introduction of non-natural amino acids into proteins through the stop codon readthrough methodology has been used to design proteins for diverse applications. However, this method suffers from low yields of the modified protein, as the suppressor tRNA that recognizes the stop codon is unable to compete effectively with release factor 1 (RF1), which terminates translation. We reasoned that a suppressor tRNA with improved interaction with the UAG stop codon on the mRNA will be able to compete more effectively with RF1. To test this idea, we inserted two 2,6-diaminopurine (D) units in the tRNA anticodon stem loop, including one at the third position of the tRNA anticodon. The modified suppressor tRNA could potentially form additional H-bonds between the N2-exocyclic amine of D and the C2 carbonyl group of uracil, thereby enhancing mRNA-tRNA interaction and/or altering tRNA conformation. The stronger interaction at the codon-anticodon interface resulted in improved UAG decoding efficiency and a higher yield of the modified protein containing a non-natural amino acid at multiple sites. Our findings are consistent with the importance of hydrogen bonding and tRNA conformation at the tRNA-mRNA duplex interface during in-frame UAG suppression, which improves protein translation at multiple UAG stop sites. This work provides valuable inputs toward improved non-natural amino acid mutagenesis for creating designer proteins.
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Affiliation(s)
- Purnima Mala
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal 462066, India
| | - Ishu Saraogi
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal 462066, India
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal 462066, India
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2
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Li NS, Koo SC, Piccirilli JA. Synthesis of Oligoribonucleotides Containing a 2'-Amino-5'- S-phosphorothiolate Linkage. J Org Chem 2021; 86:13231-13244. [PMID: 34533968 PMCID: PMC8491167 DOI: 10.1021/acs.joc.1c01059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
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Oligoribonucleotides
containing a photocaged 2′-amino-5′-S-phophorothiolate linkage have potential applications as
therapeutic agents and biological probes to investigate the RNA structure
and function. We envisioned that oligoribonucleotides containing a
2′-amino-5′-S-phosphorothiolate linkage
could provide an approach to identify the general base within catalytic
RNAs by chemogenetic suppression. To enable preliminary tests of this
idea, we developed synthetic approaches to a dinucleotide, trinucleotide,
and oligoribonucleotide containing a photocaged 2′-amino-5′-S-phosphorothiolate linkage. We incorporated the photocaged
2′-amino-5′-S-phosphorothiolate linkage
into an oligoribonucleotide substrate for the hepatitis delta virus
(HDV) ribozyme and investigated the pH dependence of its cleavage
following UV irradiation both in the presence and absence of the ribozyme.
The substrate exhibited a pH-rate profile characteristic of the modified
linkage but reacted slower when bound to the ribozyme. Cleavage inhibition
by the HDV ribozyme could reflect a non-productive ground-state interaction
with the modified substrate’s nucleophilic 2′-NH2 or a poor fit of the modified transition state at the ribozyme’s
active site.
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Affiliation(s)
- Nan-Sheng Li
- Department of Biochemistry & Molecular Biology, University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, Unites States
| | - Selene C Koo
- Department of Biochemistry & Molecular Biology, University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, Unites States
| | - Joseph A Piccirilli
- Department of Biochemistry & Molecular Biology, University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, Unites States.,Department of Chemistry, University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, Unites States
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3
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Hiller DA, Dunican BF, Nallur S, Li NS, Piccirilli JA, Strobel SA. The Positively Charged Active Site of the Bacterial Toxin RelE Causes a Large Shift in the General Base p Ka. Biochemistry 2020; 59:1665-1671. [PMID: 32320214 DOI: 10.1021/acs.biochem.9b01047] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The bacterial toxin RelE cleaves mRNA in the ribosomal A site. Although it shares a global fold with other microbial RNases, the active site contains several positively charged residues instead of histidines and glutamates that are typical of ribonucleases. The pH dependences of wild-type and mutant RelE indicate it uses general acid-base catalysis, but either the general acid (proposed to be R81) or the general base must have a substantially downshifted pKa. However, which group is shifted cannot be determined using available structural and biochemical data. Here, we use a phosphorothiolate at the scissile phosphate to remove the need for a general acid. We show this modification rescues nearly all of the defect of the R81A mutation, supporting R81 as the general acid. We also find that the observed pKa of the general base is dependent on the charge of the side chain at position 81. This indicates that positive charge in the active site contributes to a general base pKa downshifted by more than 5 units. Although this modestly reduces the effectiveness of general acid-base catalysis, it is strongly supplemented by the role of the positive charge in stabilizing the transition state for cleavage. Furthermore, we show that the ribosome is required for cleavage but not binding of mRNA by RelE. Ribosome functional groups do not directly contact the scissile phosphate, indicating that positioning and charge interactions dominate RelE catalysis. The unusual RelE active site catalyzes phosphoryl transfer at a rate comparable to those of similar enzymes, but in a ribosome-dependent fashion.
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Affiliation(s)
- David A Hiller
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States.,Department of Chemistry and Chemical Biology Institute, Yale University, West Haven, Connecticut 06516, United States
| | - Brian F Dunican
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Sunitha Nallur
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States.,Department of Chemistry and Chemical Biology Institute, Yale University, West Haven, Connecticut 06516, United States
| | - Nan-Sheng Li
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Joseph A Piccirilli
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Scott A Strobel
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States.,Department of Chemistry and Chemical Biology Institute, Yale University, West Haven, Connecticut 06516, United States
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4
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Li NS, Lu J, Piccirilli JA. Synthesis of 5'-Thio-3'-O-ribonucleoside Phosphoramidites. J Org Chem 2017; 82:12003-12013. [PMID: 29049877 DOI: 10.1021/acs.joc.7b01484] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The chemical synthesis of phosphoramidite derivatives of all four 5'-deoxy-5'-thioribonucleosides is described. These phosphoramidites contained trityl (A, G, C, and U), dimethoxytrityl (A and G), or tert-butyldisulfanyl (G) as the 5'-S-protecting group. The application of several of these phosphoramidites for solid-phase synthesis of oligoribonucleotides containing a 2'-O-photocaged 5'-S-phosphorothiolate linkage or 5'-thiol-labeled RNAs is also further investigated.
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Affiliation(s)
- Nan-Sheng Li
- Department of Biochemistry & Molecular Biology and Department of Chemistry, University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States
| | - Jun Lu
- Department of Biochemistry & Molecular Biology and Department of Chemistry, University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States
| | - Joseph A Piccirilli
- Department of Biochemistry & Molecular Biology and Department of Chemistry, University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States
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5
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Eguaogie O, Cooke LA, Martin PML, Ravalico F, Conway LP, Hodgson DRW, Law CJ, Vyle JS. Synthesis of novel pyrophosphorothiolate-linked dinucleoside cap analogues in a ball mill. Org Biomol Chem 2015; 14:1201-5. [PMID: 26565694 DOI: 10.1039/c5ob02061a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Michaelis-Arbuzov reactions of S-aryl disulfide derivatives of 3'-thiothymidine or 5'-thioadenosine with tris(trimethylsilyl) phosphite proceeded in high yields to the corresponding phosphorothiolate monoesters. Subsequent hydrolytic desilylation and phosphate coupling were effected in one-pot using liquid-assisted grinding in a vibration ball mill. Novel 3',5'- and 5',5'-pyrophosphorothiolate-linked dinucleoside cap analogues were thereby prepared.
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Affiliation(s)
- Olga Eguaogie
- School of Chemistry and Chemical Engineering, Queen's University Belfast, David Keir Building, Stranmillis Road, Belfast BT9 5AG, UK.
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6
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Lu J, Koo SC, Li NS, Piccirilli JA. Synthesis of 2'-O-photocaged ribonucleoside phosphoramidites. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2015; 34:114-29. [PMID: 25621705 DOI: 10.1080/15257770.2014.965256] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The chemical synthesis and incorporation of the phosphoramidite derivatives of 2 '-O-photocaged ribonucleosides (A, C, G and U) with o-nitrobenzyl, α-methyl-o-nitrobenzyl or 4,5-dimethoxy-2-nitrobenzyl group into oligoribonucleotides are described. The efficiency of UV irradiated uncaging of these 2'-O-photocaged oligoribonucleotides was found in the order of α-methyl-o-nitrobenzyl < 4,5-dimethoxy-2-nitrobenzyl < 2'-O-o-nitrobenzyl.
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Affiliation(s)
- Jun Lu
- a Department of Biochemistry & Molecular Biology and Department of Chemistry , University of Chicago , Chicago , Illinois , United States
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7
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Recent advances in H-phosphonate chemistry. Part 1. H-phosphonate esters: synthesis and basic reactions. Top Curr Chem (Cham) 2015; 361:137-77. [PMID: 25370520 DOI: 10.1007/128_2014_562] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
This review covers recent progress in the preparation of H-phosphonate mono- and diesters, basic studies on mechanistic and stereochemical aspects of this class of phosphorus compounds, and their fundamental chemistry in terms of transformation of P-H bonds into P-heteroatom bonds. Selected recent applications of H-phosphonate derivatives in basic organic phosphorus chemistry and in the synthesis of biologically important phosphorus compounds are also discussed.
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8
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Korhonen HJ, Conway LP, Hodgson DRW. Phosphate analogues in the dissection of mechanism. Curr Opin Chem Biol 2014; 21:63-72. [PMID: 24879389 DOI: 10.1016/j.cbpa.2014.05.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 05/01/2014] [Accepted: 05/02/2014] [Indexed: 11/16/2022]
Abstract
Phosphoryl group transfer is central to genetic replication, cellular signalling and many metabolic processes. Understanding the mechanisms of phosphorylation and phosphate ester and anhydride cleavage is key to efforts towards biotechnological and biomedical exploitation of phosphate-handling enzymes. Analogues of phosphate esters and anhydrides are indispensable tools, alongside protein mutagenesis and computational methods, for the dissection of phosphoryl transfer mechanisms. Hydrolysable and non-hydrolysable phosphate analogues have provided insight into the nature and sites of phosphoryl transfer processes. Kinetic isotope effects and crystallography using transition state analogues have painted more detailed pictures of transition states and how enzymes work to stabilise them.
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Affiliation(s)
- Heidi J Korhonen
- Department of Chemistry, Durham University Mountjoy Site, South Road, Durham DH1 3LE, UK; Department of Chemistry, University of Turku, Vatselankatu 2, 20014 Turku, Finland
| | - Louis P Conway
- Department of Chemistry, Durham University Mountjoy Site, South Road, Durham DH1 3LE, UK
| | - David R W Hodgson
- Department of Chemistry, Durham University Mountjoy Site, South Road, Durham DH1 3LE, UK.
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9
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Li NS, Tuttle N, Staley J, Piccirilli JA. Synthesis and incorporation of the phosphoramidite derivative of 2'-O-photocaged 3'-s-thioguanosine into oligoribonucleotides: substrate for probing the mechanism of RNA catalysis. J Org Chem 2014; 79:3647-52. [PMID: 24635216 PMCID: PMC4203407 DOI: 10.1021/jo4028374] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Indexed: 11/30/2022]
Abstract
Oligoribonucleotides containing 3'-S-phosphorothiolate linkages possess properties that can reveal deep mechanistic insights into ribozyme-catalyzed reactions. "Photocaged" 3'-S- RNAs could provide a strategy to stall reactions at the chemical stage and release them after assembly steps have occurred. Toward this end, we describe here an approach for the synthesis of 2'-O-(o-nitrobenzyl)-3'-thioguanosine phosphoramidite starting from N(2)-isobutyrylguanosine in nine steps with 10.2% overall yield. Oligonucleotides containing the 2'-O-(o-nitrobenzyl)-3'-S-guanosine nucleotide were then constructed, characterized, and used in a nuclear pre-mRNA splicing reaction.
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Affiliation(s)
- Nan-Sheng Li
- Department of Biochemistry &
Molecular Biology, Department of Chemistry, and Department of
Molecular Genetics & Cell Biology, University
of Chicago, Chicago, Illinois 60637, United
States
| | - Nicole Tuttle
- Department of Biochemistry &
Molecular Biology, Department of Chemistry, and Department of
Molecular Genetics & Cell Biology, University
of Chicago, Chicago, Illinois 60637, United
States
| | - Jonathan
P. Staley
- Department of Biochemistry &
Molecular Biology, Department of Chemistry, and Department of
Molecular Genetics & Cell Biology, University
of Chicago, Chicago, Illinois 60637, United
States
| | - Joseph A. Piccirilli
- Department of Biochemistry &
Molecular Biology, Department of Chemistry, and Department of
Molecular Genetics & Cell Biology, University
of Chicago, Chicago, Illinois 60637, United
States
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10
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Sharma P, Lait LA, Wetmore SD. yDNA versus yyDNA pyrimidines: computational analysis of the effects of unidirectional ring expansion on the preferred sugar-base orientation, hydrogen-bonding interactions and stacking abilities. Phys Chem Chem Phys 2013; 15:2435-48. [PMID: 23303174 DOI: 10.1039/c2cp43910g] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The properties of natural, y- and yy-pyrimidines are compared using computational (B3LYP, MP2) methods. Ring expansion upon incorporation of benzene or naphthalene into the natural pyrimidines affects the preferred orientation of the base about the glycosidic bond in the corresponding nucleoside to a similar extent. Specifically, although the natural pyrimidines preferentially adopt the anti orientation with respect to the 2'-deoxyribose moiety, the expanded analogues will likely display (anti/syn) conformational heterogeneity, which may lead to alternate hydrogen-bonding modes in double-stranded duplexes. Nevertheless, the A:T Watson-Crick hydrogen-bond strengths do not significantly change upon base expansion, while the G:C interaction energy is slightly strengthened upon incorporation of either expanded pyrimidine. The largest effect of base expansion occurs in the stacking energies. Specifically, the maximum (most negative) stacking energies in isolated dimers formed by aligning the nucleobase centers of mass can be increased up to 45% by inclusion of a single y-pyrimidine and up to 55% by consideration of a yy-pyrimidine. Similar increases in the stacking interactions are found when a simplified duplex model composed of two stacked (hydrogen-bonded) base pairs is considered, where both the intrastrand and interstrand stacking interactions can be increased and the effects are more pronounced for the yy-pyrimidines. Moreover, the total stability (sum of all hydrogen-bonding and stacking interactions) is greater for duplexes containing expanded yy-pyrimidines compared to y-pyrimidines, which is mainly due to enhanced stacking interactions. Thus, our calculations suggest that multiple unidirectional increases in the size of the nucleobase spacer can continuously enhance the stability of expanded duplexes.
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Affiliation(s)
- Purshotam Sharma
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta, Canada T1K 3M4
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11
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Kath-Schorr S, Wilson TJ, Li NS, Lu J, Piccirilli JA, Lilley DMJ. General acid-base catalysis mediated by nucleobases in the hairpin ribozyme. J Am Chem Soc 2012; 134:16717-24. [PMID: 22958171 DOI: 10.1021/ja3067429] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The catalytic mechanism by which the hairpin ribozyme accelerates cleavage or ligation of the phosphodiester backbone of RNA has been incompletely understood. There is experimental evidence for an important role for an adenine (A38) and a guanine (G8), and it has been proposed that these act in general acid-base catalysis. In this work we show that a large reduction in cleavage rate on substitution of A38 by purine (A38P) can be reversed by replacement of the 5'-oxygen atom at the scissile phosphate by sulfur (5'-PS), which is a much better leaving group. This is consistent with A38 acting as the general acid in the unmodified ribozyme. The rate of cleavage of the 5'-PS substrate by the A38P ribozyme increases with pH log-linearly, indicative of a requirement for a deprotonated base with a relatively high pK(a). On substitution of G8 by diaminopurine, the 5'-PS substrate cleavage rate at first increases with pH and then remains at a plateau, exhibiting an apparent pK(a) consistent with this nucleotide acting in general base catalysis. Alternative explanations for the pH dependence of hairpin ribozyme reactivity are discussed, from which we conclude that general acid-base catalysis by A38 and G8 is the simplest and most probable explanation consistent with all the experimental data.
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Affiliation(s)
- Stephanie Kath-Schorr
- Cancer Research UK, Nucleic Acid Structure Research Group, MSI/WTB Complex, The University of Dundee, Dow Street, Dundee DD1 5EH, UK
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12
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Li NS, Frederiksen JK, Piccirilli JA. Synthesis, properties, and applications of oligonucleotides containing an RNA dinucleotide phosphorothiolate linkage. Acc Chem Res 2011; 44:1257-69. [PMID: 21882874 DOI: 10.1021/ar200131t] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
RNA represents a prominent class of biomolecules. Present in all living systems, RNA plays many essential roles in gene expression, regulation, and development. Accordingly, many biological processes depend on the accurate enzymatic processing, modification, and cleavage of RNA. Understanding the catalytic mechanisms of these enzymes therefore represents an important goal in defining living systems at the molecular level. In this context, RNA molecules bearing 3'- or 5'-S-phosphorothiolate linkages comprise what are arguably among the most incisive mechanistic probes available. They have been instrumental in showing that RNA splicing systems are metalloenzymes and in mapping the ligands that reside within RNA active sites. The resulting models have in turn verified the functional relevance of crystal structures. In other cases, phosphorothiolates have offered an experimental strategy to circumvent the classic problem of kinetic ambiguity; mechanistic enzymologists have used this tool to assign precise roles to catalytic groups as general acids or bases. These insights into macromolecular function are enabled by the synthesis of nucleic acids bearing phosphorothiolate linkages and the unique chemical properties they impart. In this Account, we review the synthesis, properties, and applications of oligonucleotides and oligodeoxynucleotides containing an RNA dinucleotide phosphorothiolate linkage. Phosphorothioate linkages are structurally very similar to phosphorothiolate linkages, as reflected in the single letter of difference in nomenclature. Phosphorothioate substitutions, in which sulfur replaces one or both nonbridging oxygens within a phosphodiester linkage, are now widely available and are used routinely in numerous biochemical and medicinal applications. Indeed, synthetic phosphorothioate linkages can be introduced readily via a sulfurization step programmed into automated solid-phase oligonucleotide synthesizers. In contrast, phosphorothiolate oligonucleotides, in which sulfur replaces a specific 3'- or 5'-bridging oxygen, have presented a more difficult synthetic challenge, requiring chemical alterations to the attached sugar moiety. Here we begin by outlining the synthetic strategies used to access these phosphorothiolate RNA analogues. The Arbuzov reaction and phosphoramidite chemistry are often brought to bear in creating either 3'- or 5'-S-phosphorothiolate dinucleotides. We then summarize the responses of the phosphorothiolate derivatives to chemical and enzymatic cleavage agents, as well as mechanistic insights their use has engendered. They demonstrate particular utility as probes of metal-ion-dependent phosphotransesterification, general acid-base-catalyzed phosphotransesterification, and rate-limiting chemistry. The 3'- and 5'-S-phosphorothiolates have proven invaluable in elucidating the mechanisms of enzymatic and nonenzymatic phosphoryl transfer reactions. Considering that RNA cleavage represents a fundamental step in the maturation, degradation, and regulation of this important macromolecule, the significant synthetic challenges that remain offer rich research opportunities.
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Affiliation(s)
- Nan-Sheng Li
- Department of Biochemistry and Molecular Biology and ‡Department of Chemistry, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States
| | - John K. Frederiksen
- Department of Biochemistry and Molecular Biology and ‡Department of Chemistry, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States
| | - Joseph A. Piccirilli
- Department of Biochemistry and Molecular Biology and ‡Department of Chemistry, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States
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13
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Base ionization and ligand binding: how small ribozymes and riboswitches gain a foothold in a protein world. Curr Opin Struct Biol 2011; 21:327-34. [PMID: 21530235 DOI: 10.1016/j.sbi.2011.03.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 03/30/2011] [Accepted: 03/31/2011] [Indexed: 11/21/2022]
Abstract
Genome sequencing has produced thousands of nonprotein coding (nc)RNA sequences including new ribozymes and riboswitches. Such RNAs are notable for their extraordinary functionality, which entails exquisite folding that culminates in biocatalytic or ligand-binding capabilities. Here we discuss advances in relating ncRNA form to function with an emphasis on base pK(a) shifting by the hairpin and hepatitis delta virus ribozymes. We then describe ligand binding by the two smallest riboswitches, which target preQ(1) and S-adenosyl-(l)-homocysteine, followed by an analysis of a second-messenger riboswitch that binds cyclic-di-GMP. Each riboswitch is then compared to a protein that binds the same ligand to contrast binding properties. The results showcase the breadth of functionality attainable from ncRNAs, as well as molecular features notable for antibacterial design.
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