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Weinberg CE, Olzog VJ, Eckert I, Weinberg Z. Identification of over 200-fold more hairpin ribozymes than previously known in diverse circular RNAs. Nucleic Acids Res 2021; 49:6375-6388. [PMID: 34096583 PMCID: PMC8216279 DOI: 10.1093/nar/gkab454] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 05/12/2021] [Indexed: 11/18/2022] Open
Abstract
Self-cleaving ribozymes are catalytic RNAs that cut themselves at a specific inter-nucleotide linkage. They serve as a model of RNA catalysis, and as an important tool in biotechnology. For most of the nine known structural classes of self-cleaving ribozymes, at least hundreds of examples are known, and some are present in multiple domains of life. By contrast, only four unique examples of the hairpin ribozyme class are known, despite its discovery in 1986. We bioinformatically predicted 941 unique hairpin ribozymes of a different permuted form from the four previously known hairpin ribozymes, and experimentally confirmed several diverse predictions. These results profoundly expand the number of natural hairpin ribozymes, enabling biochemical analysis based on natural sequences, and suggest that a distinct permuted form is more biologically relevant. Moreover, all novel hairpins were discovered in metatranscriptomes. They apparently reside in RNA molecules that vary both in size—from 381 to 5170 nucleotides—and in protein content. The RNA molecules likely replicate as circular single-stranded RNAs, and potentially provide a dramatic increase in diversity of such RNAs. Moreover, these organisms have eluded previous attempts to isolate RNA viruses from metatranscriptomes—suggesting a significant untapped universe of viruses or other organisms hidden within metatranscriptome sequences.
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Affiliation(s)
- Christina E Weinberg
- Institute for Biochemistry, Leipzig University, Brüderstraße 34, 04103 Leipzig, Germany
| | - V Janett Olzog
- Institute for Biochemistry, Leipzig University, Brüderstraße 34, 04103 Leipzig, Germany
| | - Iris Eckert
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Centre for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107 Leipzig, Germany
| | - Zasha Weinberg
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Centre for Bioinformatics, Leipzig University, Härtelstraße 16-18, 04107 Leipzig, Germany
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2
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Catalytic RNA, ribozyme, and its applications in synthetic biology. Biotechnol Adv 2019; 37:107452. [DOI: 10.1016/j.biotechadv.2019.107452] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 09/16/2019] [Accepted: 09/17/2019] [Indexed: 12/21/2022]
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3
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Studying Parasite Gene Function and Interaction Through Ribozymes and Riboswitches Design Mechanism. Synth Biol (Oxf) 2018. [DOI: 10.1007/978-981-10-8693-9_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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4
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Kitamura Y. Synthesis of Nucleic Acid Mimics and Their Application in Nucleic Acid-based Medicine. YAKUGAKU ZASSHI 2017; 136:1491-1499. [PMID: 27803480 DOI: 10.1248/yakushi.16-00180] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nucleic acid-based drugs (NABDs) have recently attracted considerable attention as next-generation medicines, following the development of low molecular-weight and antibody drugs, because it is likely that they will have fewer side effects and greater target specificity than conventional medicines. Short double-stranded RNAs contain a 2-nucleotide overhang at the 3'-end of each strand. Small interfering RNAs (siRNAs) and microRNAs (miRNAs) inhibit gene expression by RNA interference (RNAi) and thus have great potential as NABDs. However, naked RNA strands have many problems that hinder their application as therapeutics, such as their rapid degradation in biological fluids, poor cellular uptake, and off-target effects. Therefore, artificially modified siRNAs and miRNAs have been studied extensively in an effort to overcome these problems. In this review, I summarize my recent studies on the synthesis of nucleic acid mimics and their application in RNAi-based medicine. The following two topics are specifically discussed: 1) the design and synthesis of chemically modified functional RNAs bearing nucleic acid mimics at their 3'-overhang region, which plays a key role in RNAi; and 2) the practical, reliable synthesis of nucleic acid mimics containing ethynyl groups.
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Affiliation(s)
- Yoshiaki Kitamura
- Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University
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5
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Crystal structure of Pistol, a class of self-cleaving ribozyme. Proc Natl Acad Sci U S A 2017; 114:1021-1026. [PMID: 28096403 DOI: 10.1073/pnas.1611191114] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Small self-cleaving ribozymes have been discovered in all evolutionary domains of life. They can catalyze site-specific RNA cleavage, and as a result, they have relevance in gene regulation. Comparative genomic analysis has led to the discovery of a new class of small self-cleaving ribozymes named Pistol. We report the crystal structure of Pistol at 2.97-Å resolution. Our results suggest that the Pistol ribozyme self-cleavage mechanism likely uses a guanine base in the active site pocket to carry out the phosphoester transfer reaction. The guanine G40 is in close proximity to serve as the general base for activating the nucleophile by deprotonating the 2'-hydroxyl to initiate the reaction (phosphoester transfer). Furthermore, G40 can also establish hydrogen bonding interactions with the nonbridging oxygen of the scissile phosphate. The proximity of G32 to the O5' leaving group suggests that G32 may putatively serve as the general acid. The RNA structure of Pistol also contains A-minor interactions, which seem to be important to maintain its tertiary structure and compact fold. Our findings expand the repertoire of ribozyme structures and highlight the conserved evolutionary mechanism used by ribozymes for catalysis.
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6
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Wawrzyniak-Turek K, Höbartner C. Enzymatic combinatorial nucleoside deletion scanning mutagenesis of functional RNA. Chem Commun (Camb) 2014; 50:10937-40. [PMID: 25097037 DOI: 10.1039/c4cc04719b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We describe a general and simple method to identify catalytically and structurally important nucleotides in functional RNAs. Our approach is based on statistical replacement of each nucleoside with a non-nucleosidic spacer (C3 linker, Δ), followed by separation of active library variants and readout of interference effects by analysis of enzymatic primer extension reactions.
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Affiliation(s)
- Katarzyna Wawrzyniak-Turek
- Research Group Nucleic Acid Chemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
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7
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Taniho K, Nakashima R, Kandeel M, Kitamura Y, Kitade Y. Synthesis and biological properties of chemically modified siRNAs bearing 1-deoxy-D-ribofuranose in their 3'-overhang region. Bioorg Med Chem Lett 2012; 22:2518-21. [PMID: 22377516 DOI: 10.1016/j.bmcl.2012.01.132] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 01/26/2012] [Accepted: 01/31/2012] [Indexed: 12/14/2022]
Abstract
To elucidate the role of the sugar moiety in the two natural nucleotides of the 3'-overhang region of small interfering RNA (siRNA), we synthesized siRNAs that incorporated two abasic nucleosides, 1-deoxy-D-ribofuranose (R(H)). We improved the method for preparing an O-protected abasic nucleoside, 1-deoxy-2,3,5-tri-O-benzoyl-β-D-ribofuranose, via the reductive cleavage of the anomeric position of 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose. To incorporate R(H) into oligonucleotides by the standard phosphoramidite solid phase method, R(H) was converted into its phosphoramidite derivative and the solid support linked to a controlled pore glass resin. Chemically modified RNAs possessing R(H) at the 3'-overhang region were easily prepared in good yields. siRNAs containing R(H) showed moderate nuclease-resistance and a desirable knockdown effect.
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Affiliation(s)
- Kazumi Taniho
- Department of Biomolecular Science, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
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8
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Cottrell JW, Kuzmin YI, Fedor MJ. Functional Analysis of Hairpin Ribozyme Active Site Architecture. J Biol Chem 2007; 282:13498-507. [PMID: 17351263 DOI: 10.1074/jbc.m700451200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The hairpin ribozyme is a small catalytic motif found in plant satellite RNAs where it catalyzes a reversible self-cleavage reaction during processing of replication intermediates. Crystallographic studies of hairpin ribozymes have provided high resolution views of the RNA functional groups that comprise the active site and stimulated biochemical studies that probed the contributions of nucleobase functional groups to catalytic chemistry. The dramatic loss of activity that results from perturbation of active site architecture points to the importance of positioning and orientation in catalytic rate acceleration. The current study focuses on the network of noncovalent interactions that align nucleophilic and leaving group oxygens in the orientation required for the S(N)2-type reaction mechanism and orient the active site nucleobases near the reactive phosphate to facilitate catalytic chemistry. Nucleotide modifications that alter or eliminate individual hydrogen bonding partners had different effects on the activation barrier to catalysis, the stability of ribozyme complexes in the ground state, and the internal equilibrium between cleavage and ligation of bound products. Furthermore, substitution of hydrogen bond donors and acceptors with seemingly equivalent pairs sometimes had very different functional consequences. These biochemical analyses augment high resolution structural information to provide insights into the functional significance of active site architecture.
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Affiliation(s)
- Joseph W Cottrell
- Department of Molecular Biology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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9
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10
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Kuzmin YI, Da Costa CP, Cottrell JW, Fedor MJ. Role of an active site adenine in hairpin ribozyme catalysis. J Mol Biol 2005; 349:989-1010. [PMID: 15907933 DOI: 10.1016/j.jmb.2005.04.005] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Revised: 03/25/2005] [Accepted: 04/05/2005] [Indexed: 11/23/2022]
Abstract
The hairpin ribozyme is a small catalytic RNA that accelerates reversible cleavage of a phosphodiester bond. Structural and mechanistic studies suggest that divalent metals stabilize the functional structure but do not participate directly in catalysis. Instead, two active site nucleobases, G8 and A38, appear to participate in catalytic chemistry. The features of A38 that are important for active site structure and chemistry were investigated by comparing cleavage and ligation reactions of ribozyme variants with A38 modifications. An abasic substitution of A38 reduced cleavage and ligation activity by 14,000-fold and 370,000-fold, respectively, highlighting the critical role of this nucleobase in ribozyme function. Cleavage and ligation activity of unmodified ribozymes increased with increasing pH, evidence that deprotonation of some functional group with an apparent pK(a) value near 6 is important for activity. The pH-dependent transition in activity shifted by several pH units in the basic direction when A38 was substituted with an abasic residue, or with nucleobase analogs with very high or low pK(a) values that are expected to retain the same protonation state throughout the experimental pH range. Certain exogenous nucleobases that share the amidine group of adenine restored activity to abasic ribozyme variants that lack A38. The pH dependence of chemical rescue reactions also changed according to the intrinsic basicity of the rescuing nucleobase, providing further evidence that the protonation state of the N1 position of purine analogs is important for rescue activity. These results are consistent with models of the hairpin ribozyme catalytic mechanism in which interactions with A38 provide electrostatic stabilization to the transition state.
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Affiliation(s)
- Yaroslav I Kuzmin
- Department of Molecular Biology, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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11
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Marsh AJ, Williams DM, Grasby JA. The synthesis and properties of oligoribonucleotide-spermine conjugates. Org Biomol Chem 2004; 2:2103-12. [PMID: 15254639 DOI: 10.1039/b404150j] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Polyamines stabilise nucleic acids against chemical and enzymatic degradation, facilitate the formation of secondary and tertiary structures and enhance cellular uptake. Therefore methods for the syntheses of polyamine-nucleic acid conjugates are of interest. A route for the syntheses of RNA-spermine conjugates has been developed. The polyamine was introduced to the C-5 position of uridine via an ethyl tether and the molecule elaborated into a synthon suitable for oligoribonucleotide assembly. The resultant oligomers were components of the hairpin ribozyme. Characterisation of the spermine-conjugated catalytic RNA revealed that attachment of the polyamine was well tolerated in three of four positions, namely U41, U37 and U34, suggesting that conjugation to C-5 brings about minimal structural perturbation.
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Affiliation(s)
- Andrew J Marsh
- Centre for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield, Brook Hill, Sheffield, UKS3 7HF
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12
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Wilson TJ, Lilley DMJ. Metal ion binding and the folding of the hairpin ribozyme. RNA (NEW YORK, N.Y.) 2002; 8:587-600. [PMID: 12022226 PMCID: PMC1370280 DOI: 10.1017/s1355838202020514] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The hairpin ribozyme comprises two formally unpaired loops carried on two arms of a four-way helical RNA junction. Addition of divalent metal ions brings about a conformational transition into an antiparallel structure in which there is an intimate association between the loops to generate the active form of the ribozyme. In this study, we have used fluorescence resonance energy transfer to analyze the global folding of the complete ribozyme, and the simple four-way junction derived from it, over a wide concentration range of divalent and monovalent metal ions. The simple junction undergoes an ion-induced rotation into an antiparallel form. In the presence of a constant background concentration of sodium ions, the magnesium-ion-induced transition is characterized by noncooperative binding with a Hill coefficient n = 1. By contrast, the magnesium-ion-induced folding of the complete ribozyme is more complex, involving two distinct binding phases. The first phase occurs in the micromolar range, and involves the cooperative binding of at least three magnesium ions. This can also be achieved by high concentrations of sodium ions, and is therefore likely to be due to diffuse binding of cations at the junction and the interface of the loop-loop interaction. The second phase occurs in the millimolar range, and can only be induced by divalent metal ions. This transition occurs in response to the noncooperative, site-specific binding of magnesium ions. We observe a good correlation between the extent of ion-induced folding and cleavage activity.
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Affiliation(s)
- Timothy J Wilson
- Cancer Research-UK Nucleic Acid Structure Research Group, Department of Biochemistry, MSI/WTB Complex, The University of Dundee
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13
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Ryder SP, Strobel SA. Comparative analysis of hairpin ribozyme structures and interference data. Nucleic Acids Res 2002; 30:1287-91. [PMID: 11884625 PMCID: PMC101345 DOI: 10.1093/nar/30.6.1287] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Great strides in understanding the molecular underpinnings of RNA catalysis have been achieved with advances in RNA structure determination by NMR spectroscopy and X-ray crystallography. Despite these successes the functional relevance of a given structure can only be assessed upon comparison with biochemical studies performed on functioning RNA molecules. The hairpin ribozyme presents an excellent case study for such a comparison. The active site is comprised of two stems each with an internal loop that forms a series of non-canonical base pairs. These loops dock into each other to create an active site for catalysis. Recently, three independent structures have been determined for this catalytic RNA, including two NMR structures of the isolated loop A and loop B stems and a high-resolution crystal structure of both loops in a docked conformation. These structures differ significantly both in their tertiary fold and the nature of the non-canonical base pairs formed within each loop. Several of the chemical groups required to achieve a functioning hairpin ribozyme have been determined by nucleotide analog interference mapping (NAIM). Here we compare the three hairpin structures with previously published NAIM data to assess the convergence between the structural and functional data. While there is significant disparity between the interference data and the individual NMR loop structures, there is almost complete congruity with the X-ray structure. The only significant differences cluster around an occluded pocket adjacent to the scissile phosphate. These local differences may suggest a role for these atoms in the transition state, either directly in chemistry or via a local structural rearrangement.
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Affiliation(s)
- Sean P Ryder
- Yale University, Department of Molecular Biophysics and Biochemistry, 260 Whitney Avenue, New Haven, CT 06520-8114, USA
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14
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Affiliation(s)
- K J Hampel
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont 05405, USA
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15
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Pinard R, Hampel KJ, Heckman JE, Lambert D, Chan PA, Major F, Burke JM. Functional involvement of G8 in the hairpin ribozyme cleavage mechanism. EMBO J 2001; 20:6434-42. [PMID: 11707414 PMCID: PMC125305 DOI: 10.1093/emboj/20.22.6434] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The catalytic determinants for the cleavage and ligation reactions mediated by the hairpin ribozyme are integral to the polyribonucleotide chain. We describe experiments that place G8, a critical guanosine, at the active site, and point to an essential role in catalysis. Cross-linking and modeling show that formation of a catalytic complex is accompanied by a conformational change in which N1 and O6 of G8 become closely apposed to the scissile phosphodiester. UV cross-linking, hydroxyl-radical footprinting and native gel electrophoresis indicate that G8 variants inhibit the reaction at a step following domain association, and that the tertiary structure of the inactive complex is not measurably altered. Rate-pH profiles and fluorescence spectroscopy show that protonation at the N1 position of G8 is required for catalysis, and that modification of O6 can inhibit the reaction. Kinetic solvent isotope analysis suggests that two protons are transferred during the rate-limiting step, consistent with rate-limiting cleavage chemistry involving concerted deprotonation of the attacking 2'-OH and protonation of the 5'-O leaving group. We propose mechanistic models that are consistent with these data, including some that invoke a novel keto-enol tautomerization.
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Affiliation(s)
| | | | | | - Dominic Lambert
- Department of Microbiology and Molecular Genetics, The University of Vermont, 306 Stafford Hall, Burlington, VT 05405, USA and
Département d’Informatique et Recherche Opérationelle, Université de Montréal, 2920 Chemin de la Tour, C.P.6128, Succ. Centre-ville, Montréal, Québec H3C 3J7, Canada Corresponding author e-mail:
K.J.Hampel and R.Pinard contributed equally to this work
| | | | - Francois Major
- Department of Microbiology and Molecular Genetics, The University of Vermont, 306 Stafford Hall, Burlington, VT 05405, USA and
Département d’Informatique et Recherche Opérationelle, Université de Montréal, 2920 Chemin de la Tour, C.P.6128, Succ. Centre-ville, Montréal, Québec H3C 3J7, Canada Corresponding author e-mail:
K.J.Hampel and R.Pinard contributed equally to this work
| | - John M. Burke
- Department of Microbiology and Molecular Genetics, The University of Vermont, 306 Stafford Hall, Burlington, VT 05405, USA and
Département d’Informatique et Recherche Opérationelle, Université de Montréal, 2920 Chemin de la Tour, C.P.6128, Succ. Centre-ville, Montréal, Québec H3C 3J7, Canada Corresponding author e-mail:
K.J.Hampel and R.Pinard contributed equally to this work
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16
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Ryder SP, Oyelere AK, Padilla JL, Klostermeier D, Millar DP, Strobel SA. Investigation of adenosine base ionization in the hairpin ribozyme by nucleotide analog interference mapping. RNA (NEW YORK, N.Y.) 2001; 7:1454-1463. [PMID: 11680850 PMCID: PMC1370189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Tertiary structure in globular RNA folds can create local environments that lead to pKa perturbation of specific nucleotide functional groups. To assess the prevalence of functionally relevant adenosine-specific pKa perturbation in RNA structure, we have altered the nucleotide analog interference mapping (NAIM) approach to include a series of a phosphorothioate-tagged adenosine analogs with shifted N1 pKa values. We have used these analogs to analyze the hairpin ribozyme, a small self-cleaving/ligating RNA catalyst that is proposed to employ a general acid-base reaction mechanism. A single adenosine (A10) within the ribozyme active site displayed an interference pattern consistent with a functionally significant base ionization. The exocyclic amino group of a second adenosine (A38) contributes substantially to hairpin catalysis, but ionization of the nucleotide does not appear to be important for activity. Within the hairpin ribozyme crystal structure, A10 and A38 line opposite edges of a solvent-excluded cavity adjacent to the 5'-OH nucleophile. The results are inconsistent with the model of ribozyme chemistry in which A38 acts as a general acid-base catalyst, and suggest that the hairpin ribozyme uses an alternative mechanism to achieve catalytic rate enhancement that utilizes functional groups within a solvent-excluded cleft in the ribozyme active site.
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Affiliation(s)
- S P Ryder
- Yale University, Department of Molecular Biophysics and Biochemistry, New Haven, Connecticut 06520-8114, USA
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17
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Rupert PB, Ferré-D'Amaré AR. Crystal structure of a hairpin ribozyme-inhibitor complex with implications for catalysis. Nature 2001; 410:780-6. [PMID: 11298439 DOI: 10.1038/35071009] [Citation(s) in RCA: 358] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The hairpin ribozyme catalyses sequence-specific cleavage of RNA. The active site of this natural RNA results from the docking of two irregular helices: stems A and B. One strand of stem A harbours the scissile bond. The 2.4 A resolution structure of a hairpin ribozyme-inhibitor complex reveals that the ribozyme aligns the 2'-OH nucleophile and the 5'-oxo leaving group by twisting apart the nucleotides that flank the scissile phosphate. The base of the nucleotide preceding the cleavage site is stacked within stem A; the next nucleotide, a conserved guanine, is extruded from stem A and accommodated by a highly complementary pocket in the minor groove of stem B. Metal ions are absent from the active site. The bases of four conserved purines are positioned potentially to serve as acid-base catalysts. This is the first structure determination of a fully assembled ribozyme active site that catalyses a phosphodiester cleavage without recourse to metal ions.
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Affiliation(s)
- P B Rupert
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA
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18
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Pinard R, Lambert D, Heckman JE, Esteban JA, Gundlach CW, Hampel KJ, Glick GD, Walter NG, Major F, Burke JM. The hairpin ribozyme substrate binding-domain: a highly constrained D-shaped conformation. J Mol Biol 2001; 307:51-65. [PMID: 11243803 DOI: 10.1006/jmbi.2000.4472] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The two domains of the hairpin ribozyme-substrate complex, usually depicted as straight structural elements, must interact with one another in order to form an active conformation. Little is known about the internal geometry of the individual domains in an active docked complex. Using various crosslinking and structural approaches in conjunction with molecular modeling (constraint-satisfaction program MC-SYM), we have investigated the conformation of the substrate-binding domain in the context of the active docked ribozyme-substrate complex. The model generated by MC-SYM showed that the domain is not straight but adopts a bent conformation (D-shaped) in the docked state of the ribozyme, indicating that the two helices bounding the internal loop are closer than was previously assumed. This arrangement rationalizes the observed ability of hairpin ribozymes with a circularized substrate-binding strand to cleave a circular substrate, and provides essential information concerning the organization of the substrate in the active conformation. The internal geometry of the substrate-binding strand places G8 of the substrate-binding strand near the cleavage site, which has allowed us to predict the crucial role played by this nucleotide in the reaction chemistry.
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Affiliation(s)
- R Pinard
- Markey Center for Molecular Genetics, Department of Microbiology and Molecular Genetics, The University of Vermont, Burlington, VT 05405, USA
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Abstract
The global structures of branched RNA species are important to their function. Branched RNA species are defined as molecules in which double-helical segments are interrupted by abrupt discontinuities. These include helical junctions of different orders, and base bulges and loops. Common helical junctions are three- and four-way junctions, often interrupted by mispairs or additional nucleotides. There are many interesting examples of functional RNA junctions, including the hammerhead and hairpin ribozymes, and junctions that serve as binding sites for proteins. The junctions display some common structural properties. These include a tendency to undergo pairwise helical stacking and ion-induced conformational transitions. Helical branchpoints can act as key architectural components and as important sites for interactions with proteins. Copyright 1999 John Wiley & Sons, Inc.
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Affiliation(s)
- David M. J. Lilley
- CRC Nucleic Acid Structure Research Group, Department of Biochemistry, The University of Dundee, Dundee DD1 4HN, UK
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20
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Zhao ZY, Wilson TJ, Maxwell K, Lilley DM. The folding of the hairpin ribozyme: dependence on the loops and the junction. RNA (NEW YORK, N.Y.) 2000; 6:1833-46. [PMID: 11142382 PMCID: PMC1370052 DOI: 10.1017/s1355838200001230] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
In its natural context, the hairpin ribozyme is constructed around a four-way helical junction. This presents the two loops that interact to form the active site on adjacent arms, requiring rotation into an antiparallel structure to bring them into proximity. In the present study we have compared the folding of this form of the ribozyme and subspecies lacking either the loops or the helical junction using fluorescence resonance energy transfer. The complete ribozyme as a four-way junction folds into an antiparallel structure by the cooperative binding of magnesium ions, requiring 20-40 microM for half-maximal extent of folding ([Mg2+]1/2) and a Hill coefficient n = 2. The isolated junction (lacking the loops) also folds into a corresponding antiparallel structure, but does so noncooperatively (n = 1) at a higher magnesium ion concentration ([Mg2+]1/2 = 3 mM). Introduction of a G + 1A mutation into loop A of the ribozyme results in a species with very similar folding to the simple junction, and complete loss of ribozyme activity. Removal of the junction from the ribozyme, replacing it either with a strand break (serving as a hinge) or a GC5 bulge, results in greatly impaired folding, with [Mg2+]1/2 > 20 mM. The results indicate that the natural form of the ribozyme undergoes ion-induced folding by the cooperative formation of an antiparallel junction and loop-loop interaction to generate the active form of the ribozyme. The four-way junction thus provides a scaffold in the natural RNA that facilitates the folding of the ribozyme into the active form.
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Affiliation(s)
- Z Y Zhao
- Department of Biochemistry, The University of Dundee, United Kingdom
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21
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Sargueil B, McKenna J, Burke JM. Analysis of the functional role of a G.A sheared base pair by in vitro genetics. J Biol Chem 2000; 275:32157-66. [PMID: 10906144 DOI: 10.1074/jbc.m005591200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A classical genetic strategy has been combined with an in vitro selection method to search for functional interactions between the two domains of the hairpin ribozyme. G(21) is located within internal loop B; it is proposed to form a sheared base pair with A(43) across loop B and to bind a Mg(2+) ion. Both nucleotides are important for ribozyme function, and G.A sheared base pairs are a very widespread motif in structured RNA. We took advantage of its presence in the hairpin ribozyme to study its functional role. Pseudorevertants, in which the loss of G(21) was compensated by mutations at other positions, were isolated by in vitro selection. The vast majority of G(21) revertants contained substitutions within domain A, pointing to functional communication between specific sites within the two domains of the hairpin ribozyme. The possibility of a direct or redundant contacts is supported by electrophoretic mobility shift studies showing that a complex formed between domain B of the ribozyme and the substrate was disrupted and restored by base substitutions that have analogous effects on catalytic activity. The functional significance of this complex, the role of the nucleotides involved, and the basis for magnesium ion requirement is discussed.
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Affiliation(s)
- B Sargueil
- Centre de Génétique Moléculaire, CNRS, Avenue de la Terrasse, 91190 Gif sur Yvette, France.
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22
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Beigelman L, Matulic-Adamic J, Karpeisky A, Haeberli P, Sweedler D. Base-modified phosphoramidite analogs of pyrimidine ribonucleosides for RNA structure-activity studies. Methods Enzymol 2000; 317:39-65. [PMID: 10829271 DOI: 10.1016/s0076-6879(00)17005-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Affiliation(s)
- L Beigelman
- Ribozyme Pharmaceuticals, Inc., Boulder, Colorado 80301, USA
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23
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Abstract
The hairpin ribozyme belongs to the family of small catalytic RNAs that cleave RNA substrates in a reversible reaction that generates 2',3'-cyclic phosphate and 5'-hydroxyl termini. The hairpin catalytic motif was discovered in the negative strand of the tobacco ringspot virus satellite RNA, where hairpin ribozyme-mediated self-cleavage and ligation reactions participate in processing RNA replication intermediates. The self-cleaving hairpin, hammerhead, hepatitis delta and Neurospora VS RNAs each adopt unique structures and exploit distinct kinetic and catalytic mechanisms despite catalyzing the same chemical reactions. Mechanistic studies of hairpin ribozyme reactions provided early evidence that, like protein enzymes, RNA enzymes are able to exploit a variety of catalytic strategies. In contrast to the hammerhead and Tetrahymena ribozyme reactions, hairpin-mediated cleavage and ligation proceed through a catalytic mechanism that does not require direct coordination of metal cations to phosphate or water oxygens. The hairpin ribozyme is a better ligase than it is a nuclease while the hammerhead reaction favors cleavage over ligation of bound products by nearly 200-fold. Recent structure-function studies have begun to yield insights into the molecular bases of these unique features of the hairpin ribozyme.
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Affiliation(s)
- M J Fedor
- Department of Molecular Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, MB35, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA.
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24
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Schmidt C, Welz R, Müller S. RNA double cleavage by a hairpin-derived twin ribozyme. Nucleic Acids Res 2000; 28:886-94. [PMID: 10648779 PMCID: PMC102578 DOI: 10.1093/nar/28.4.886] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/1999] [Revised: 12/15/1999] [Accepted: 12/15/1999] [Indexed: 11/12/2022] Open
Abstract
The hairpin ribozyme is a small catalytic RNA that catalyses reversible sequence-specific RNA hydrolysis in trans. It consists of two domains, which interact with each other by docking in an antiparallel fashion. There is a region between the two domains acting as a flexible hinge for interdomain interactions to occur. Hairpin ribozymes with reverse-joined domains have been constructed by dissecting the domains at the hinge and rejoining them in reverse order. We have used both the conventional and reverse-joined hairpin ribozymes for the design of a hairpin-derived twin ribozyme. We show that this twin ribozyme cleaves a suitable RNA substrate at two specific sites while maintaining the target specificity of the individual monoribozymes. For characterisation of the studied ribozymes we have evaluated a quantitative assay of sequence-specific ribozyme activity using fluorescently labelled RNA substrates in conjunction with an automated DNA sequencer. This assay was found to be applicable with hairpin and hairpin-derived ribozymes. The results demonstrate the potential of hairpin ribozymes for multi-target strategies of RNA cleavage and suggest the possibility for employing hairpin-derived twin ribozymes as powerful tools for RNA manipulation in vitro and in vivo.
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Affiliation(s)
- C Schmidt
- Humboldt-Universität zu Berlin, Institut für Chemie, Fachinstitut für Organische und Bioorganische Chemie, Hessische Strasse 1-2, 10115 Berlin, Germany
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25
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Komatsu Y, Kumagai I, Ohtsuka E. Investigation of the recognition of an important uridine in an internal loop of a hairpin ribozyme prepared using post-synthetically modified oligonucleotides. Nucleic Acids Res 1999; 27:4314-23. [PMID: 10536137 PMCID: PMC148711 DOI: 10.1093/nar/27.22.4314] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We introduced 4-thio- ((4S)U), 2-thio- ((2S)U), 4- O -methyluridine ((4Me)U) and cytidine substitutions for U+2, which is an important base for cleavage in a substrate RNA. Oligonucleotides containing 4-thio- and 4- O -methyluridine were prepared by a new convenient post-synthetic modification method using a 4- O - p -nitrophenyl-uridine derivative. A hairpin ribozyme cleaved the substrate RNA with either C+2, (4S)U+2 or (4Me)U+2 at approximately 14-, 6- and 4-fold lower rates, respectively, than that of the natural substrate. In contrast, the substrate with a (2S)U+2 was cleaved with the same activity as the natural substrate. These results suggest that the O4 of U+2 is involved in hydrogen bonding at loop A, but the O2 of U+2 is not recognized by the active residues. Circular dichroism data of the ribozymes containing (4S)U+2 and (2S)U+2, as well as the susceptibility of the thiocarbonyl group to hydrogen peroxide, suggest that a conformational change of U+2 occurs during the domain docking in the cleavage reaction. We propose here the conformational change of U+2 from the ground state to the active molecule during the reaction.
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Affiliation(s)
- Y Komatsu
- Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
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26
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Barroso-delJesus A, Tabler M, Berzal-Herranz A. Comparative kinetic analysis of structural variants of the hairpin ribozyme reveals further potential to optimize its catalytic performance. ANTISENSE & NUCLEIC ACID DRUG DEVELOPMENT 1999; 9:433-40. [PMID: 10555150 DOI: 10.1089/oli.1.1999.9.433] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The hairpin ribozyme derived from the minus strand of the satellite RNA associated with the tobacco ringspot virus is one of the small catalytic RNAs that has been shown to catalyze trans-cleavage reactions. There is much interest in designing hairpin ribozymes with improved catalytic activity for the development of new therapeutic agents. Extensive mutagenesis studies as well as in vitro selection experiments have been performed to define the structure and optimize its catalytic activity. This communication describes a comparative kinetic analysis of four structural variants, introduced, either alone, or in combination, into the hairpin ribozyme. We have shown that extension of the helix 2 from 4 to 6 bp resulted in a significant decrease in K(M). Furthermore, the combination of this extension with the simultaneous stabilization of helix 4, led to a more than two-fold increase in the catalytic efficiency. This variant showed a 15-fold reduction in the K(M) value in respect to the wild-type ribozyme. This could be of great interest for the in vivo application of this catalytic motif. The 9-bp enlargement of helix 4 implied about a three-fold improvement in the catalytic activity. Similarly, the U39C substitution brought up the efficiency of the ribozyme slightly. However, introduction of nucleotides at the hinge region between A and B domains reduced the catalytic activity. This reduction was gradually increased with the number of nucleotides. Results obtained with variants carrying more than one modification always agreed with the ones obtained from each single variant.
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Affiliation(s)
- A Barroso-delJesus
- Instituto de Parasitología y Biomedicina López-Neyra CSIC, Granada, Spain
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27
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Ryder SP, Strobel SA. Nucleotide analog interference mapping of the hairpin ribozyme: implications for secondary and tertiary structure formation. J Mol Biol 1999; 291:295-311. [PMID: 10438622 DOI: 10.1006/jmbi.1999.2959] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The hairpin ribozyme is a small, naturally occurring RNA capable of folding into a distinct three-dimensional structure and catalyzing a specific phosphodiester transfer reaction. We have adapted a high throughput screening procedure entitled nucleotide analog interference mapping (NAIM) to identify functional groups important for proper folding and catalysis of this ribozyme. A total of 18 phosphorothioate-tagged nucleotide analogs were used to determine the contribution made by individual ribose 2'-OH and purine functional groups to the hairpin ribozyme ligation reaction. Substitution with 2'-deoxy-nucleotide analogs disrupted activity at six sites within the ribozyme, and a unique interference pattern was observed at each of the 11 conserved purine nucleotides. In most cases where such information is available, the NAIM data agree with the previously reported single-site substitution results. The interference patterns are interpreted in comparison to the isolated loop A and loop B NMR structures and a model of the intact ribozyme. These data provide biochemical evidence in support of many, but not all, of the non-canonical base-pairs observed by NMR in each loop, and identify the functional groups most likely to participate in the tertiary interface between loop A and loop B. These groups include the 2'-OH groups of A10, G11, U12, C25, and A38, the exocyclic amine of G11, and the minor groove edge of A9 and A24. The data also predict non-A form sugar pucker geometry at U39 and U41. Based upon these results, a revised model for the loop A tertiary interaction with loop B is proposed. This work defines the chemical basis of purine nucleotide conservation in the hairpin ribozyme, and provides a basis for the design and interpretation of interference suppression experiments.
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Affiliation(s)
- S P Ryder
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
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28
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Shippy R, Lockner R, Farnsworth M, Hampel A. The hairpin ribozyme. Discovery, mechanism, and development for gene therapy. Mol Biotechnol 1999; 12:117-29. [PMID: 10554775 DOI: 10.1385/mb:12:1:117] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The hairpin ribozyme is a member of a family of small RNA endonucleases, which includes hammer-head, human hepatitis delta virus, Neurospora VS, and the lead-dependent catalytic RNAs. All these catalytic RNAs reversibly cleave the phosphodiester bond of substrate RNA to generate 5'-hydroxyl and 2',3'-cyclic phosphate termini. Whereas the reaction products from family members are similar, large structural and mechanistic differences exist. Structurally the hairpin ribozyme has two principal domains that interact to facilitate catalysis. The hairpin ribozyme uses a catalytic mechanism that does not require metals for cleavage or ligation of substrate RNA. In this regard it is presently unique among RNA catalysts. Targeting rules for cleavage of substrate have been determined and required bases for catalysis have been identified. The hairpin ribozyme has been developed and used for gene therapy and was the first ribozyme to be approved for human clinical trials.
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Affiliation(s)
- R Shippy
- Department of Biological Sciences, Northern Illinois University, DeKalb 60115, USA
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29
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Young KJ, Vyle JS, Pickering TJ, Cohen MA, Holmes SC, Merkel O, Grasby JA. The role of essential pyrimidines in the hairpin ribozyme-catalysed reaction. J Mol Biol 1999; 288:853-66. [PMID: 10329184 DOI: 10.1006/jmbi.1999.2748] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The hairpin ribozyme is an example of a small catalytic RNA that catalyses the endonucleolytic transesterification of RNA in a highly sequence-specific manner. We have utilised chemical synthesis of RNA to create mutants of the hairpin ribozyme in which a nucleoside analogue replaces one of the essential pyrimidines in the ribozyme. Individual pyrimidine nucleosides were substituted by 4-thiouridine, O4-methyluridine, O2-methyluridine or 2-pyrimidinone-1-beta-d-riboside. To facilitate the synthesis of oligoribonucleotides containing 4-thiouridine, we have devised a new synthetic route to the key intermediate 5'-O-(4, 4'-dimethoxytrityl)-2'-O-tert-butyldimethylsilyl-S-cyanoethyl-4-thiou ridine. The ability of the modified ribozymes to support catalysis was studied and the steady-state kinetic parameters were determined for each mutant. The range of analogues used in this study allows the important functional groups of the essential pyrimidines to be identified. The results demonstrate that each pyrimidine (U41, U42 and C25) plays an important role in hairpin ribozyme catalysis. The findings are discussed in terms of the various models that have been proposed for loop B of the hairpin ribozyme.
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Affiliation(s)
- K J Young
- Krebs Institute, University of Sheffield, Sheffield, S3 7HF, UK
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30
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Pinard R, Heckman JE, Burke JM. Alignment of the two domains of the hairpin ribozyme-substrate complex defined by interdomain photoaffinity crosslinking. J Mol Biol 1999; 287:239-51. [PMID: 10080888 DOI: 10.1006/jmbi.1999.2626] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The hairpin ribozyme-substrate complex contains two independently folding domains that interact with one another to form a catalytic complex. However, little is known about the key structural elements involved in these tertiary interactions. Here, we report the use of a photochemical crosslinking method to investigate the relative proximity and orientation of the two domains of the hairpin ribozyme. This method allows the incorporation of a photochemical azidophenacyl group at specified positions within synthetic oligoribonucleotides. Photocrosslinking was performed following the assembly of four RNA oligonucleotides into active ribozyme-substrate complexes. Two photoagent attachment sites in the substrate binding strand within domain A (between positions A7-G8 and A10-G11) and three in the 5' strand of domain B (A20-G21, A22-A23 and A24-C25) were studied. Several crosslinks between the substrate binding strand and the 5' segment of domain B were detected. All of the photo agent-specific crosslinked species were dependent upon proper assembly and folding of the ribozyme-substrate complex. In addition, a substrate base mutation (G+1 to A+1) that prevents the docking of the two domains, blocks the crosslink formation. Four interdomain crosslinks (A7-G8/C25-A26 (two species); A10-G11/A22 and A24-C25/C12-G13) have been shown to retain catalytic activity. Taken together, these results indicate that the characterized crosslinks provide important information concerning the alignment of the two domains and accurately reflect the active docked conformation of the molecule.
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Affiliation(s)
- R Pinard
- Department of Microbiology and Molecular Genetics, University of Vermont, 306 Stafford Hall, Burlington, VT, 05405, USA
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31
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Thomson JB, Lilley DM. The influence of junction conformation on RNA cleavage by the hairpin ribozyme in its natural junction form. RNA (NEW YORK, N.Y.) 1999; 5:180-7. [PMID: 10024170 PMCID: PMC1369750 DOI: 10.1017/s1355838299981670] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
In the natural form of the hairpin ribozyme the two loop-carrying duplexes that comprise the majority of essential bases for activity form two adjacent helical arms of a four-way RNA junction. In the present work we have manipulated the sequence around the junction in a way known to perturb the global folding properties. We find that replacement of the junction by a different sequence that has the same conformational properties as the natural sequence gives closely similar reaction rate and Arrhenius activation energy for the substrate cleavage reaction. By comparison, rotation of the natural sequence in order to alter the three-dimensional folding of the ribozyme leads to a tenfold reduction in the kinetics of cleavage. Replacement with the U1 four-way junction that is resistant to rotation into the antiparallel structure required to allow interaction between the loops also gives a tenfold reduction in cleavage rate. The results indicate that the conformation of the junction has a major influence on the catalytic activity of the ribozyme. The results are all consistent with a role for the junction in the provision of a framework by which the loops are presented for interaction in order to create the active form of the ribozyme.
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Affiliation(s)
- J B Thomson
- Department of Biochemistry, The University of Dundee, United Kingdom
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32
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Peracchi A, Matulic-Adamic J, Wang S, Beigelman L, Herschlag D. Structure-function relationships in the hammerhead ribozyme probed by base rescue. RNA (NEW YORK, N.Y.) 1998; 4:1332-46. [PMID: 9814755 PMCID: PMC1369707 DOI: 10.1017/s1355838298980979] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
We previously showed that the deleterious effects from introducing abasic nucleotides in the hammerhead ribozyme core can, in some instances, be relieved by exogenous addition of the ablated base and that the relative ability of different bases to rescue catalysis can be used to probe functional aspects of the ribozyme structure [Peracchi et al., Proc NatAcad Sci USA 93:11522]. Here we examine rescue at four additional positions, 3, 9, 12 and 13, to probe transition state interactions and to demonstrate the strengths and weaknesses of base rescue as a tool for structure-function studies. The results confirm functional roles for groups previously probed by mutagenesis, provide evidence that specific interactions observed in the ground-state X-ray structure are maintained in the transition state, and suggest formation in the transition state of other interactions that are absent in the ground state. In addition, the results suggest transition state roles for some groups that did not emerge as important in previous mutagenesis studies, presumably because base rescue has the ability to reveal interactions that are obscured by local structural redundancy in traditional mutagenesis. The base rescue results are complemented by comparing the effects of the abasic and phenyl nucleotide substitutions. The results together suggest that stacking of the bases at positions 9, 13 and 14 observed in the ground state is important for orienting other groups in the transition state. These findings add to our understanding of structure-function relationships in the hammerhead ribozyme and help delineate positions that may undergo rearrangements in the active hammerhead structure relative to the ground-state structure. Finally, the particularly efficient rescue by 2-methyladenine at position 13 relative to adenine and other bases suggests that natural base modifications may, in some instance, provide additional stability by taking advantage of hydrophobic interactions in folded RNAs.
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Affiliation(s)
- A Peracchi
- Department of Biochemistry, Stanford University, California 94305-5307, USA
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33
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Abstract
Synthetic oligonucleotide analogs have greatly aided our understanding of several biochemical processes. Efficient solid-phase and enzyme-assisted synthetic methods and the availability of modified base analogs have added to the utility of such oligonucleotides. In this review, we discuss the applications of synthetic oligonucleotides that contain backbone, base, and sugar modifications to investigate the mechanism and stereochemical aspects of biochemical reactions. We also discuss interference mapping of nucleic acid-protein interactions; spectroscopic analysis of biochemical reactions and nucleic acid structures; and nucleic acid cross-linking studies. The automation of oligonucleotide synthesis, the development of versatile phosphoramidite reagents, and efficient scale-up have expanded the application of modified oligonucleotides to diverse areas of fundamental and applied biological research. Numerous reports have covered oligonucleotides for which modifications have been made of the phosphodiester backbone, of the purine and pyrimidine heterocyclic bases, and of the sugar moiety; these modifications serve as structural and mechanistic probes. In this chapter, we review the range, scope, and practical utility of such chemically modified oligonucleotides. Because of space limitations, we discuss only those oligonucleotides that contain phosphate and phosphate analogs as internucleotidic linkages.
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Affiliation(s)
- S Verma
- Max-Planck-Institut für Experimentelle Medizin, Göttingen, Germany
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34
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Cepero E, Hnatyszyn HJ, Kraus G, Lichtenheld MG. Potent inhibition of CTLA-4 expression by an anti-CTLA-4 ribozyme. Biochem Biophys Res Commun 1998; 247:838-43. [PMID: 9647780 DOI: 10.1006/bbrc.1998.8889] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Blockading the negative-regulatory CTLA-4 receptor has emerged as a powerful strategy with clinical potential to enhance T-cell responses. Some experimental tumors, for example, are rejected when anti-CTLA-4 antibodies are administered in vivo. The concise target cells and downstream events, however, remain to be defined. The development of gene transfer reagents that inhibit CTLA-4 may facilitate such investigations and may expand the therapeutic range. This communication describes an anti-CTLA-4 hairpin ribozyme that specifically abrogates CTLA-4 expression after gene transfer into a murine T-cell model. The analysis of multiple and independently derived clones and bulk cultures showed that CTLA-4 induction was inhibited > 90% at the RNA level and that it was undetectable at the protein level, with and without selective pressure. This potent inhibition required the catalytic function of the ribozyme. The anti-CTLA-4 ribozyme may be an alternative tool with which to continue the functional and therapeutical exploration of CTLA-4.
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Affiliation(s)
- E Cepero
- Department of Microbiology and Immunology, University of Miami, School of Medicine, Florida 33101, USA
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35
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Murchie AI, Thomson JB, Walter F, Lilley DM. Folding of the hairpin ribozyme in its natural conformation achieves close physical proximity of the loops. Mol Cell 1998; 1:873-81. [PMID: 9660970 DOI: 10.1016/s1097-2765(00)80086-6] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The hairpin ribozyme is a self-cleaving motif found in the negatives strand of the satellite RNA of some plant viruses. In its natural context, the ribozyme comprises four helices, two of which contain conserved formally unpaired loops, that are adjacent arms of a four-way RNA junction. We show that the arms that would carry these loops are brought close together in the global conformation of the isolated junction. Using fluorescence resonance energy transfer, we demonstrate a two-magnesium ion-dependent conformational transition of the complete ribozyme that brings the loopbearing arms into close physical proximity. The ribozyme is active as a four-way junction, and the rate of cleavage may be modulated by the conformation of the four-way junction.
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Affiliation(s)
- A I Murchie
- Department of Biochemistry, University of Dundee, United Kingdom
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36
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Liu YH, Symons RH. Specific RNA self-cleavage in coconut cadang cadang viroid: potential for a role in rolling circle replication. RNA (NEW YORK, N.Y.) 1998; 4:418-429. [PMID: 9630248 PMCID: PMC1369628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The rolling circle replication of the small, single-stranded viroid RNAs requires a specific processing reaction to produce monomeric RNAs that are ligated into the final circular form. For avocado sunblotch viroid, peach latent mosaic viroid, and chrysanthemum chlorotic mottle viroid, the hammerhead self-cleavage reaction is considered to provide this processing reaction. We have searched for a similar type of reaction in the 246-nt coconut cadang cadang viroid, the smallest viroid of the 24-member potato spindle tuber viroid (PSTV) group. RNA transcripts prepared from the cloned central or C domain of this viroid self-cleaved specifically after denaturation with methylmercuric hydroxide followed by incubation in the presence of spermidine but in the absence of added magnesium ions. The unique cleavage site was located in the bottom strand of the C domain within a potential hairpin structure that is conserved within members of all three subgroups of the PSTV group of viroids.
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Affiliation(s)
- Y H Liu
- Department of Plant Science, University of Adelaide, Waite Campus, SA, Australia
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37
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Abstract
Recent studies of the hairpin ribozyme have revealed a distinct catalytic mechanism for this small RNA motif. Inner-sphere coordinated metal ions are not required, as the inert metal ion complex cobalt hexammine promotes catalysis. Detailed kinetic analyses have defined rates of individual steps in the catalytic cycle. Functional group modification, NMR studies of subdomains and cross-linking experiments, in combination with computer modeling, have led to a proposal for domain interactions in the substrate-ribozyme complex.
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Affiliation(s)
- N G Walter
- Department of Microbiology and Molecular Genetics, Markey Center for Molecular Genetics, 306 Stafford Hall, University of Vermont, Burlington, VT 05405, USA
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38
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39
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Earnshaw DJ, Masquida B, Müller S, Sigurdsson ST, Eckstein F, Westhof E, Gait MJ. Inter-domain cross-linking and molecular modelling of the hairpin ribozyme. J Mol Biol 1997; 274:197-212. [PMID: 9398527 DOI: 10.1006/jmbi.1997.1405] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The hairpin ribozyme is a small catalytic RNA composed of two helical domains containing a small and a large internal loop and, thus, constitutes a valuable paradigm for the study of RNA structure and catalysis. We have carried out molecular modelling of the hairpin ribozyme to learn how the two domains (A and B) might fold and approach each other. To help distinguish alternative inter-domain orientations, we have chemically synthesized hairpin ribozymes containing 2'-2' disulphide linkages of known spacing (12 or 16 A) between defined ribose residues in the internal loop regions of each domain. The abilities of cross-linked ribozymes to carry out RNA cleavage under single turnover conditions were compared to the corresponding disulphide-reduced, untethered ribozymes. Ribozymes were classed in three categories according to whether their cleavage rates were marginally, moderately, or strongly affected by cross-linking. This rank order of activity guided the docking of the two domains in the molecular modelling process. The proposed three-dimensional model of the hairpin ribozyme incorporates three different crystallographically determined structural motifs: in domain A, the 5'-GAR-3'-motif of the hammerhead ribozyme, in domain B, the J4/5 motif of group I ribozymes, and connecting the two domains, a "ribose zipper", another group I ribozyme feature, formed between the hydroxyl groups of residues A10, G11 of domain A and C25, A24 of domain B. This latter feature might be key to the selection and precise orientation of the inter-domain docking necessary for the specific phosphodiester cleavage. The model provides an important basis for further studies of hairpin ribozyme structure and function.
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Affiliation(s)
- D J Earnshaw
- Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
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40
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Hampel A. The hairpin ribozyme: discovery, two-dimensional model, and development for gene therapy. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1997; 58:1-39. [PMID: 9308362 DOI: 10.1016/s0079-6603(08)60032-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
This review chronicles the discovery of the hairpin ribozyme, its characterization, and determination of the two-dimensional structure, culminating with its use for human gene therapy as an AIDS therapeutic. The minimal sequence constituting the hairpin ribozyme catalytic domain was identified from a small plant viral satellite RNA. Biochemical characterization showed it to be among the most efficient of all known ribozymes. Mutagenesis determined that the two-dimensional structure had four helices, consisting of 17 Watson-Crick base pairs and one A:G pair for a total of 18 bp. The helices were interspersed with five single-stranded loops. Helices 1 and 2 were located between the ribozyme and substrate, allowing the ribozyme to recognize the substrate. The substrate had a sequence preference of BN*GUC where * is the site of cleavage and N*GUC the substrate loop between these two helices. By using sequences of this type, it was possible to design the ribozyme to base pair with the substrate and cleave heterologous RNA substrates-leading to design of the hairpin ribozyme for gene therapy. The HIV-1 sequence was searched for suitable target sites, and ribozymes were designed, optimized, catalytically characterized, and tested in vivo against HIV-1 targets. Two ribozymes had excellent in vitro catalytic parameters and inhibited in vivo expression of viral proteins by 3-4 logs in tissue culture cells. Viral replication was inhibited as well. They have been developed as human AIDS therapeutics, and will likely be the first ribozymes to be tested as human drugs in clinical trials.
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Affiliation(s)
- A Hampel
- Department of Biological Sciences, Northern Illinois University, DeKalb 60115, USA
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Duckett DR, Murchie AI, Clegg RM, Bassi GS, Giraud-Panis MJ, Lilley DM. Nucleic acid structure and recognition. Biophys Chem 1997; 68:53-62. [PMID: 17029905 DOI: 10.1016/s0301-4622(97)00007-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/1995] [Accepted: 01/16/1997] [Indexed: 11/19/2022]
Abstract
We review the global structures adopted by branched nucleic acids, including three- and four-way helical junctions in DNA and RNA. We find that some general folding principles emerge. First, all the structures exhibit a tendency to undergo pairwise coaxial helical stacking when permitted by the local stereochemistry of strand exchange. Second, metal ions generally play an important role in facilitating folding of branched nucleic acids. These principles can be applied to functionally important branched nucleic acids, such as the Holliday DNA junction of genetic recombination, and the hammerhead ribozyme in RNA.
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Affiliation(s)
- D R Duckett
- CRC Nucleic Acid Structure Research Group, Department of Biochemistry, The University, Dundee, DD1 4HN UK
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Earnshaw DJ, Gait MJ. Progress toward the structure and therapeutic use of the hairpin ribozyme. ANTISENSE & NUCLEIC ACID DRUG DEVELOPMENT 1997; 7:403-11. [PMID: 9303192 DOI: 10.1089/oli.1.1997.7.403] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The hairpin ribozyme is one of a number of small catalytic RNAs that are excellent paradigms for RNA structure-function analysis and have potential also as therapeutic agents. This review outlines current understanding of the structure of the hairpin ribozyme and its basis for catalytic activity. Included also is a discussion of the functional group requirements for cleavage and the first steps being taken to understanding its folding. Finally, recent developments are highlighted in engineering the hairpin ribozyme for intracellular use as a potential gene therapy agent.
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Affiliation(s)
- D J Earnshaw
- Medical Research Council, Laboratory of Molecular Biology, Cambridge, UK
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Shin C, Choi JN, Song SI, Song JT, Ahn JH, Lee JS, Choi YD. The loop B domain is physically separable from the loop A domain in the hairpin ribozyme. Nucleic Acids Res 1996; 24:2685-9. [PMID: 8758996 PMCID: PMC146020 DOI: 10.1093/nar/24.14.2685] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
In order to understand the catalysis mechanism of the hairpin ribozyme, mutant ribozymes were constructed. The distance between the loop A domain and the loop B domain was extended by inserting various lengths of nucleotide linkers at the hinge region in cis mutants, or the domains were separated physically in a trans mutant. All the mutant ribozymes, including the trans mutant, could cleave substrate RNA at the predicted site. A cis mutant with a single nucleotide insertion exhibited cleavage activity about twice as high as that of the wild-type (wt) ribozyme. The insertion of 2-5 nucleotides (nt) gradually reduced the activity to the level of the wt ribozyme. Insertion of a longer linker, up to 11 nt, resulted in the reduction of activity to one half of that of the wt ribozyme. The ribozyme with a single nucleotide insertion at the hinge region seems to form a more suitable conformation for catalysis by three-dimensional fold-back of the loop B to loop A containing the cleavage site. The trans mutant, in which the A and B domains were physically separated, maintained a significant level of activity, suggesting that both domains are necessary for catalysis, but separable. These results demonstrate that interaction between the A and B domains results in catalysis.
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Affiliation(s)
- C Shin
- Research Center for New BioMaterials in Agriculture, Seoul National University, Suwon, Korea
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