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Chen JL, Taghavi A, Frank AJ, Fountain MA, Choudhary S, Roy S, Childs-Disney JL, Disney MD. NMR structures of small molecules bound to a model of a CUG RNA repeat expansion. Bioorg Med Chem Lett 2024; 111:129888. [PMID: 39002937 DOI: 10.1016/j.bmcl.2024.129888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2024] [Accepted: 07/10/2024] [Indexed: 07/15/2024]
Abstract
Trinucleotide repeat expansions fold into long, stable hairpins and cause a variety of incurable RNA gain-of-function diseases such as Huntington's disease, the myotonic dystrophies, and spinocerebellar ataxias. One approach for treating these diseases is to bind small molecules to these structured RNAs. Both Huntington's disease-like 2 (HDL2) and myotonic dystrophy type 1 (DM1) are caused by a r(CUG) repeat expansion, or r(CUG)exp. The RNA folds into a hairpin structure with a periodic array of 1 × 1 nucleotide UU loops (5'CUG/3'GUC; where the underlined nucleotides indicate the Us in the internal loop) that sequester various RNA-binding proteins (RBPs) and hence the source of its gain-of-function. Here, we report nuclear magnetic resonance (NMR)-refined structures of single 5'CUG/3'GUC motifs in complex with three different small molecules, a di-guandinobenzoate (1), a derivative of 1 where the guanidino groups have been exchanged for imidazole (2), and a quinoline with improved drug-like properties (3). These structures were determined using NMR spectroscopy and simulated annealing with restrained molecular dynamics (MD). Compounds 1, 2, and 3 formed stacking and hydrogen bonding interactions with the 5'CUG/3'GUC motif. Compound 3 also formed van der Waals interactions with the internal loop. The global structure of each RNA-small molecule complexes retains an A-form conformation, while the internal loops are still dynamic but to a lesser extent compared to the unbound form. These results aid our understanding of ligand-RNA interactions and enable structure-based design of small molecules with improved binding affinity for and biological activity against r(CUG)exp. As the first ever reported structures of a r(CUG) repeat bound to ligands, these structures can enable virtual screening campaigns combined with machine learning assisted de novo design.
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Affiliation(s)
- Jonathan L Chen
- Department of Chemistry, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA; Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Amirhossein Taghavi
- Department of Chemistry, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Alexander J Frank
- Department of Chemistry and Biochemistry, State University of New York at Fredonia, Fredonia, NY 14063, USA
| | - Matthew A Fountain
- Department of Chemistry and Biochemistry, State University of New York at Fredonia, Fredonia, NY 14063, USA
| | - Shruti Choudhary
- Department of Chemistry, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Soma Roy
- Department of Chemistry, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Jessica L Childs-Disney
- Department of Chemistry, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Matthew D Disney
- Department of Chemistry, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA; Department of Chemistry, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, 130 Scripps Way, Jupiter, FL 33458, USA.
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Chen JL, Taghavi A, Frank AJ, Fountain MA, Choudhary S, Roy S, Childs-Disney JL, Disney MD. NMR structures of small molecules bound to a model of an RNA CUG repeat expansion. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.21.600119. [PMID: 38948793 PMCID: PMC11213127 DOI: 10.1101/2024.06.21.600119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Trinucleotide repeat expansions fold into long, stable hairpins and cause a variety of incurable RNA gain-of-function diseases such as Huntington's disease, the myotonic dystrophies, and spinocerebellar ataxias. One approach for treating these diseases is to bind small molecules to the structured RNAs. Both Huntington's disease-like 2 (HDL2) and myotonic dystrophy type 1 (DM1) are caused by a r(CUG) repeat expansion, or r(CUG)exp. The RNA folds into a hairpin structure with a periodic array of 1×1 nucleotide UU loops (5'CUG/3'GUC; where the underlined nucleotides indicate the Us in the internal loop) that sequester various RNA-binding proteins (RBP) and hence the source of its gain-of-function. Here, we report NMR-refined structures of single 5'CUG/3'GUC motifs in complex with three different small molecules, a di-guandinobenzoate (1), a derivative of 1 where the guanidino groups have been exchanged for imidazole (2), and a quinoline with improved drug-like properties (3). These structures were determined using nuclear magnetic resonance (NMR) spectroscopy and simulated annealing with restrained molecular dynamics (MD). Compounds 1, 2, and 3 formed stacking and hydrogen bonding interactions with the 5'CUG/3'GUC motif. Compound 3 also formed van der Waals interactions with the internal loop. The global structure of each RNA-small molecule complexes retains an A-form conformation, while the internal loops are still dynamic but to a lesser extent compared to the unbound form. These results aid our understanding of ligand-RNA interactions and enable structure-based design of small molecules with improved binding affinity for and biological activity against r(CUG)exp. As the first ever reported structures of RNA r(CUG) repeats bound to ligands, these structures can enable virtual screening campaigns combined with machine learning assisted de novo design.
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Affiliation(s)
- Jonathan L. Chen
- Department of Chemistry, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Amirhossein Taghavi
- Department of Chemistry, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Alexander J. Frank
- Department of Chemistry and Biochemistry, State University of New York at Fredonia, Fredonia, NY 14063, USA
| | - Matthew A. Fountain
- Department of Chemistry and Biochemistry, State University of New York at Fredonia, Fredonia, NY 14063, USA
| | - Shruti Choudhary
- Department of Chemistry, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Soma Roy
- Department of Chemistry, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Jessica L. Childs-Disney
- Department of Chemistry, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, 130 Scripps Way, Jupiter, FL 33458, USA
| | - Matthew D. Disney
- Department of Chemistry, The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458, USA
- Department of Chemistry, The Herbert Wertheim UF Scripps Institute for Biomedical Innovation & Technology, 130 Scripps Way, Jupiter, FL 33458, USA
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Liu D, Shao Y, Piccirilli JA, Weizmann Y. Structures of artificially designed discrete RNA nanoarchitectures at near-atomic resolution. SCIENCE ADVANCES 2021; 7:eabf4459. [PMID: 34550747 PMCID: PMC8457670 DOI: 10.1126/sciadv.abf4459] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 08/02/2021] [Indexed: 05/11/2023]
Abstract
Although advances in nanotechnology have enabled the construction of complex and functional synthetic nucleic acid–based nanoarchitectures, high-resolution discrete structures are lacking because of the difficulty in obtaining good diffracting crystals. Here, we report the design and construction of RNA nanostructures based on homooligomerizable one-stranded tiles for x-ray crystallographic determination. We solved three structures to near-atomic resolution: a 2D parallelogram, a 3D nanobracelet unexpectedly formed from an RNA designed for a nanocage, and, eventually, a bona fide 3D nanocage designed with the guidance of the two previous structures. Structural details of their constituent motifs, such as kissing loops, branched kissing loops, and T-junctions, that resemble natural RNA motifs and resisted x-ray determination are revealed, providing insights into those natural motifs. This work unveils the largely unexplored potential of crystallography in gaining high-resolution feedback for nanoarchitectural design and suggests a route to investigate RNA motif structures by configuring them into nanoarchitectures.
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Affiliation(s)
- Di Liu
- Department of Chemistry, The University of Chicago, Chicago, IL 60637, USA
| | - Yaming Shao
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Joseph A. Piccirilli
- Department of Chemistry, The University of Chicago, Chicago, IL 60637, USA
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Yossi Weizmann
- Department of Chemistry, The University of Chicago, Chicago, IL 60637, USA
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel
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Pujari N, Saundh SL, Acquah FA, Mooers BHM, Ferré-D’Amaré AR, Leung AKW. Engineering Crystal Packing in RNA Structures I: Past and Future Strategies for Engineering RNA Packing in Crystals. CRYSTALS 2021; 11:952. [PMID: 34745656 PMCID: PMC8570644 DOI: 10.3390/cryst11080952] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
X-ray crystallography remains a powerful method to gain atomistic insights into the catalytic and regulatory functions of RNA molecules. However, the technique requires the preparation of diffraction-quality crystals. This is often a resource- and time-consuming venture because RNA crystallization is hindered by the conformational heterogeneity of RNA, as well as the limited opportunities for stereospecific intermolecular interactions between RNA molecules. The limited success at crystallization explains in part the smaller number of RNA-only structures in the Protein Data Bank. Several approaches have been developed to aid the formation of well-ordered RNA crystals. The majority of these are construct-engineering techniques that aim to introduce crystal contacts to favor the formation of well-diffracting crystals. A typical example is the insertion of tetraloop-tetraloop receptor pairs into non-essential RNA segments to promote intermolecular association. Other methods of promoting crystallization involve chaperones and crystallization-friendly molecules that increase RNA stability and improve crystal packing. In this review, we discuss the various techniques that have been successfully used to facilitate crystal packing of RNA molecules, recent advances in construct engineering, and directions for future research in this vital aspect of RNA crystallography.
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Affiliation(s)
- Narsimha Pujari
- Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
| | - Stephanie L. Saundh
- Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
| | - Francis A. Acquah
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Blaine H. M. Mooers
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
- Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Adrian R. Ferré-D’Amaré
- Biochemistry and Biophysics Center, National Heart, Lung and Blood Institute, Bethesda, MD 20892, USA
| | - Adelaine Kwun-Wai Leung
- Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
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Robinson GC, Kaufmann M, Roux C, Martinez-Font J, Hothorn M, Thore S, Fitzpatrick TB. Crystal structure of the pseudoenzyme PDX1.2 in complex with its cognate enzyme PDX1.3: a total eclipse. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2019; 75:400-415. [PMID: 30988257 DOI: 10.1107/s2059798319002912] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 02/25/2019] [Indexed: 11/10/2022]
Abstract
Pseudoenzymes have burst into the limelight recently as they provide another dimension to regulation of cellular protein activity. In the eudicot plant lineage, the pseudoenzyme PDX1.2 and its cognate enzyme PDX1.3 interact to regulate vitamin B6 biosynthesis. This partnership is important for plant fitness during environmental stress, in particular heat stress. PDX1.2 increases the catalytic activity of PDX1.3, with an overall increase in vitamin B6 biosynthesis. However, the mechanism by which this is achieved is not known. In this study, the Arabidopsis thaliana PDX1.2-PDX1.3 complex was crystallized in the absence and presence of ligands, and attempts were made to solve the X-ray structures. Three PDX1.2-PDX1.3 complex structures are presented: the PDX1.2-PDX1.3 complex as isolated, PDX1.2-PDX1.3-intermediate (in the presence of substrates) and a catalytically inactive complex, PDX1.2-PDX1.3-K97A. Data were also collected from a crystal of a selenomethionine-substituted complex, PDX1.2-PDX1.3-SeMet. In all cases the protein complexes assemble as dodecamers, similar to the recently reported individual PDX1.3 homomer. Intriguingly, the crystals of the protein complex are statistically disordered owing to the high degree of structural similarity of the individual PDX1 proteins, such that the resulting configuration is a composite of both proteins. Despite the differential methionine content, selenomethionine substitution of the PDX1.2-PDX1.3 complex did not resolve the problem. Furthermore, a comparison of the catalytically competent complex with a noncatalytic complex did not facilitate the resolution of the individual proteins. Interestingly, another catalytic lysine in PDX1.3 (Lys165) that pivots between the two active sites in PDX1 (P1 and P2), and the corresponding glutamine (Gln169) in PDX1.2, point towards P1, which is distinctive to the initial priming for catalytic action. This state was previously only observed upon trapping PDX1.3 in a catalytically operational state, as Lys165 points towards P2 in the resting state. Overall, the study shows that the integration of PDX1.2 into a heteromeric dodecamer assembly with PDX1.3 does not cause a major structural deviation from the overall architecture of the homomeric complex. Nonetheless, the structure of the PDX1.2-PDX1.3 complex highlights enhanced flexibility in key catalytic regions for the initial steps of vitamin B6 biosynthesis. This report highlights what may be an intrinsic limitation of X-ray crystallography in the structural investigation of pseudoenzymes.
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Affiliation(s)
- Graham C Robinson
- Department of Botany and Plant Biology, University of Geneva, 30 Quai E. Ansermet, 1211 Geneva, Switzerland
| | - Markus Kaufmann
- Department of Botany and Plant Biology, University of Geneva, 30 Quai E. Ansermet, 1211 Geneva, Switzerland
| | - Céline Roux
- Department of Botany and Plant Biology, University of Geneva, 30 Quai E. Ansermet, 1211 Geneva, Switzerland
| | - Jacobo Martinez-Font
- Department of Botany and Plant Biology, University of Geneva, 30 Quai E. Ansermet, 1211 Geneva, Switzerland
| | - Michael Hothorn
- Department of Botany and Plant Biology, University of Geneva, 30 Quai E. Ansermet, 1211 Geneva, Switzerland
| | - Stéphane Thore
- Department of Molecular Biology, University of Geneva, 30 Quai E. Ansermet, 1211 Geneva, Switzerland
| | - Teresa B Fitzpatrick
- Department of Botany and Plant Biology, University of Geneva, 30 Quai E. Ansermet, 1211 Geneva, Switzerland
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Using two-fluid nozzle for spray freeze drying to produce porous powder formulation of naked siRNA for inhalation. Int J Pharm 2018; 552:67-75. [PMID: 30244146 DOI: 10.1016/j.ijpharm.2018.09.045] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 09/01/2018] [Accepted: 09/18/2018] [Indexed: 01/05/2023]
Abstract
Spray freeze drying is an attractive technology to produce powder formulation for inhalation. It can be used to generate large porous particles which tend to aerosolize efficiently and do not aggregate readily. It also avoids material to be exposed to elevated temperature. In this study, we reported the use of two-fluid nozzle to produce spray freeze dried powder of small interfering RNA (siRNA). The effect of atomization gas flow rate and liquid feed rate were inspected initially using herring sperm DNA (hsDNA) as nucleic acid model. The atomization gas flow rate was found to have a major impact on the aerosol properties. The higher the atomization gas flow rate, the smaller the particle size, the higher the fine particle fraction (FPF). In contrast, the liquid feed rate had very minor effect. Subsequently, spray freeze dried siRNA powder was produced at various atomization gas flow rates. The particles produced were highly porous as examined with the scanning electron microscopy, and the structural integrity of the siRNA was demonstrated with gel electrophoresis. The gene-silencing effect of the siRNA was also successfully preserved in vitro. The best performing siRNA formulation was prepared at the highest atomization gas flow rate investigated with a moderate FPF of 30%. However, this was significantly lower than that obtained with the corresponding hsDNA counterparts (FPF ∼57%). A direct comparison between the hsDNA and siRNA formulations revealed that the former exhibited a lower density, hence a smaller aerodynamic diameter despite similar geometric size.
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7
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Chen JL, VanEtten DM, Fountain MA, Yildirim I, Disney MD. Structure and Dynamics of RNA Repeat Expansions That Cause Huntington's Disease and Myotonic Dystrophy Type 1. Biochemistry 2017; 56:3463-3474. [PMID: 28617590 PMCID: PMC5810133 DOI: 10.1021/acs.biochem.7b00252] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
RNA repeat expansions cause a host of incurable, genetically defined diseases. The most common class of RNA repeats consists of trinucleotide repeats. These long, repeating transcripts fold into hairpins containing 1 × 1 internal loops that can mediate disease via a variety of mechanism(s) in which RNA is the central player. Two of these disorders are Huntington's disease and myotonic dystrophy type 1, which are caused by r(CAG) and r(CUG) repeats, respectively. We report the structures of two RNA constructs containing three copies of a r(CAG) [r(3×CAG)] or r(CUG) [r(3×CUG)] motif that were modeled with nuclear magnetic resonance spectroscopy and simulated annealing with restrained molecular dynamics. The 1 × 1 internal loops of r(3×CAG) are stabilized by one-hydrogen bond (cis Watson-Crick/Watson-Crick) AA pairs, while those of r(3×CUG) prefer one- or two-hydrogen bond (cis Watson-Crick/Watson-Crick) UU pairs. Assigned chemical shifts for the residues depended on the identity of neighbors or next nearest neighbors. Additional insights into the dynamics of these RNA constructs were gained by molecular dynamics simulations and a discrete path sampling method. Results indicate that the global structures of the RNA are A-form and that the loop regions are dynamic. The results will be useful for understanding the dynamic trajectory of these RNA repeats but also may aid in the development of therapeutics.
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Affiliation(s)
- Jonathan L. Chen
- Department of Chemistry, The Scripps Research Institute, Jupiter, Florida 33458, United States
| | - Damian M. VanEtten
- Department of Chemistry and Biochemistry, State University of New York at Fredonia, Fredonia, New York 14063, United States
| | - Matthew A. Fountain
- Department of Chemistry and Biochemistry, State University of New York at Fredonia, Fredonia, New York 14063, United States
| | - Ilyas Yildirim
- Department of Chemistry, The Scripps Research Institute, Jupiter, Florida 33458, United States
- Department of Chemistry and Biochemistry, Florida Atlantic University, Jupiter, Florida 33458, United States
| | - Matthew D. Disney
- Department of Chemistry, The Scripps Research Institute, Jupiter, Florida 33458, United States
- Department of Chemistry and Biochemistry, Florida Atlantic University, Jupiter, Florida 33458, United States
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8
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Jeong EH, Kim H, Jang B, Cho H, Ryu J, Kim B, Park Y, Kim J, Lee JB, Lee H. Technological development of structural DNA/RNA-based RNAi systems and their applications. Adv Drug Deliv Rev 2016; 104:29-43. [PMID: 26494399 DOI: 10.1016/j.addr.2015.10.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 09/01/2015] [Accepted: 10/12/2015] [Indexed: 01/04/2023]
Abstract
RNA interference (RNAi)-based gene therapy has drawn tremendous attention due to its highly specific gene regulation by selective degradation of any target mRNA. There have been multiple reports regarding the development of various cationic materials for efficient siRNA delivery, however, many studies still suffer from the conventional delivery problems such as suboptimal transfection performance, a lack of tissue specificity, and potential cytotoxicity. Despite the huge therapeutic potential of siRNAs, conventional gene carriers have failed to guarantee successful gene silencing in vivo, thus not warranting clinical trials. The relatively short double-stranded structure of siRNAs has resulted in uncompromising delivery formulations, as well as low transfection efficiency, compared with the conventional nucleic acid drugs such as plasmid DNAs. Recent developments in structural siRNA and RNAi nanotechnology have enabled more refined and reliable in vivo gene silencing with multiple advantages over naked siRNAs. This review focuses on recent progress in the development of structural DNA/RNA-based RNAi systems and their potential therapeutic applications. In addition, an extensive list of prior reports on various RNAi systems is provided and categorized by their distinctive molecular characters.
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The X-ray Structures of Six Octameric RNA Duplexes in the Presence of Different Di- and Trivalent Cations. Int J Mol Sci 2016; 17:ijms17070988. [PMID: 27355942 PMCID: PMC4964368 DOI: 10.3390/ijms17070988] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 06/10/2016] [Accepted: 06/15/2016] [Indexed: 12/15/2022] Open
Abstract
Due to the polyanionic nature of RNA, the principles of charge neutralization and electrostatic condensation require that cations help to overcome the repulsive forces in order for RNA to adopt a three-dimensional structure. A precise structural knowledge of RNA-metal ion interactions is crucial to understand the mechanism of metal ions in the catalytic or regulatory activity of RNA. We solved the crystal structure of an octameric RNA duplex in the presence of the di- and trivalent metal ions Ca(2+), Mn(2+), Co(2+), Cu(2+), Sr(2+), and Tb(3+). The detailed investigation reveals a unique innersphere interaction to uracil and extends the knowledge of the influence of metal ions for conformational changes in RNA structure. Furthermore, we could demonstrate that an accurate localization of the metal ions in the X-ray structures require the consideration of several crystallographic and geometrical parameters as well as the anomalous difference map.
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Symersky J, Guo Y, Wang J, Lu M. Crystallographic study of a MATE transporter presents a difficult case in structure determination with low-resolution, anisotropic data and crystal twinning. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2015; 71:2287-96. [PMID: 26527145 PMCID: PMC4631480 DOI: 10.1107/s1399004715016995] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 09/10/2015] [Indexed: 11/10/2022]
Abstract
NorM from Neisseria gonorrhoeae (NorM-NG) belongs to the multidrug and toxic compound extrusion (MATE) family of membrane-transport proteins, which can extrude cytotoxic chemicals across cell membranes and confer multidrug resistance. Here, the structure determination of NorM-NG is described, which had been hampered by low resolution (∼ 4 Å), data anisotropy and pseudo-merohedral twinning. The crystal structure was solved using molecular replacement and was corroborated by conducting a difference Fourier analysis. The NorM-NG structure displays an extracellular-facing conformation, similar to that of NorM-NG bound to a crystallization chaperone. The approaches taken to determine the NorM-NG structure and the lessons learned from this study are discussed, which may be useful for analyzing X-ray diffraction data with similar shortcomings.
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Affiliation(s)
- Jindrich Symersky
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA
| | - Yi Guo
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA
| | - Jimin Wang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA
| | - Min Lu
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA
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11
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MicroRNA delivery for regenerative medicine. Adv Drug Deliv Rev 2015; 88:108-22. [PMID: 26024978 DOI: 10.1016/j.addr.2015.05.014] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 05/13/2015] [Accepted: 05/21/2015] [Indexed: 12/26/2022]
Abstract
MicroRNA (miRNA) directs post-transcriptional regulation of a network of genes by targeting mRNA. Although relatively recent in development, many miRNAs direct differentiation of various stem cells including induced pluripotent stem cells (iPSCs), a major player in regenerative medicine. An effective and safe delivery of miRNA holds the key to translating miRNA technologies. Both viral and nonviral delivery systems have seen success in miRNA delivery, and each approach possesses advantages and disadvantages. A number of studies have demonstrated success in augmenting osteogenesis, improving cardiogenesis, and reducing fibrosis among many other tissue engineering applications. A scaffold-based approach with the possibility of local and sustained delivery of miRNA is particularly attractive since the physical cues provided by the scaffold may synergize with the biochemical cues induced by miRNA therapy. Herein, we first briefly cover the application of miRNA to direct stem cell fate via replacement and inhibition therapies, followed by the discussion of the promising viral and nonviral delivery systems. Next we present the unique advantages of a scaffold-based delivery in achieving lineage-specific differentiation and tissue development.
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12
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Gully BS, Shah KR, Lee M, Shearston K, Smith NM, Sadowska A, Blythe AJ, Bernath-Levin K, Stanley WA, Small ID, Bond CS. The design and structural characterization of a synthetic pentatricopeptide repeat protein. ACTA ACUST UNITED AC 2015; 71:196-208. [PMID: 25664731 DOI: 10.1107/s1399004714024869] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 11/12/2014] [Indexed: 11/10/2022]
Abstract
Proteins of the pentatricopeptide repeat (PPR) superfamily are characterized by tandem arrays of a degenerate 35-amino-acid α-hairpin motif. PPR proteins are typically single-stranded RNA-binding proteins with essential roles in organelle biogenesis, RNA editing and mRNA maturation. A modular, predictable code for sequence-specific binding of RNA by PPR proteins has recently been revealed, which opens the door to the de novo design of bespoke proteins with specific RNA targets, with widespread biotechnological potential. Here, the design and production of a synthetic PPR protein based on a consensus sequence and the determination of its crystal structure to 2.2 Å resolution are described. The crystal structure displays helical disorder, resulting in electron density representing an infinite superhelical PPR protein. A structural comparison with related tetratricopeptide repeat (TPR) proteins, and with native PPR proteins, reveals key roles for conserved residues in directing the structure and function of PPR proteins. The designed proteins have high solubility and thermal stability, and can form long tracts of PPR repeats. Thus, consensus-sequence synthetic PPR proteins could provide a suitable backbone for the design of bespoke RNA-binding proteins with the potential for high specificity.
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Affiliation(s)
- Benjamin S Gully
- School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia, Australia
| | - Kunal R Shah
- School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia, Australia
| | - Mihwa Lee
- School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia, Australia
| | - Kate Shearston
- School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia, Australia
| | - Nicole M Smith
- School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia, Australia
| | - Agata Sadowska
- School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia, Australia
| | - Amanda J Blythe
- School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia, Australia
| | - Kalia Bernath-Levin
- School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia, Australia
| | - Will A Stanley
- School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia, Australia
| | - Ian D Small
- Australian Research Council Centre of Excellence in Plant Energy Biology, The University of Western Australia, Crawley, Western Australia, Australia
| | - Charles S Bond
- School of Chemistry and Biochemistry, The University of Western Australia, Crawley, Western Australia, Australia
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13
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Dendrimers for siRNA Delivery. Pharmaceuticals (Basel) 2013; 6:161-83. [PMID: 24275946 PMCID: PMC3816686 DOI: 10.3390/ph6020161] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 01/17/2013] [Accepted: 01/29/2013] [Indexed: 01/18/2023] Open
Abstract
Since the discovery of the “starburst polymer”, later renamed as dendrimer, this class of polymers has gained considerable attention for numerous biomedical applications, due mainly to the unique characteristics of this macromolecule, including its monodispersity, uniformity, and the presence of numerous functionalizable terminal groups. In recent years, dendrimers have been studied extensively for their potential application as carriers for nucleic acid therapeutics, which utilize the cationic charge of the dendrimers for effective dendrimer-nucleic acid condensation. siRNA is considered a promising, versatile tool among various RNAi-based therapeutics, which can effectively regulate gene expression if delivered successfully inside the cells. This review reports on the advancements in the development of dendrimers as siRNA carriers.
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Protein-resistant, reductively dissociable polyplexes for in vivo systemic delivery and tumor-targeting of siRNA. Biomaterials 2013; 34:2370-9. [PMID: 23294546 DOI: 10.1016/j.biomaterials.2012.12.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 12/09/2012] [Indexed: 01/19/2023]
Abstract
Small interfering RNA (siRNA) has been considered as a very attractive therapeutic alternative to chemical drugs; however, the chemical and biological instability and poor delivery efficiency of siRNA limit its success in clinical applications. Here we report a protein-resistant, reductively dissociable siRNA delivery system based on self-assembled polyelectrolyte complexes of dextran-siRNA conjugates linked by disulfide bonds. The prepared polyplexes exhibit excellent dispersion stability in the presence of serum because of the anti-fouling property of dextran exposed onto the complex surface. The enzymatic degradation of siRNA is also effectively suppressed within the complex. Folates are introduced as an active tumor-targeting moiety via the conjugation of folates to the hydroxyl groups of dextran. An in vivo investigation with a xenograft tumor mouse model shows that the folate-decorated dextran-siRNA conjugates are very efficiently targeted to cancer cells and induce sequence-specific gene silencing.
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15
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Lee SH, Chung BH, Park TG, Nam YS, Mok H. Small-interfering RNA (siRNA)-based functional micro- and nanostructures for efficient and selective gene silencing. Acc Chem Res 2012; 45:1014-25. [PMID: 22413937 DOI: 10.1021/ar2002254] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Because of RNA's ability to encode structure and functional information, researchers have fabricated diverse geometric structures from this polymer at the micro- and nanoscale. With their tunable structures, rigidity, and biocompatibility, novel two-dimensional and three-dimensional RNA structures can serve as a fundamental platform for biomedical applications, including engineered tissues, biosensors, and drug delivery vehicles. The discovery of the potential of small-interfering RNA (siRNA) has underscored the applications of RNA-based micro- and nanostructures in medicine. Small-interfering RNA (siRNA), synthetic double-stranded RNA consisting of approximately 21 base pairs, suppresses problematic target genes in a sequence-specific manner via inherent RNA interference (RNAi) processing. As a result, siRNA offers a potential strategy for treatment of many human diseases. However, due to inefficient delivery to cells and off-target effects, the clinical application of therapeutic siRNA has been very challenging. To address these issues, researchers have studied a variety of nanocarrier systems for siRNA delivery. In this Account, we describe several strategies for efficient siRNA delivery and selective gene silencing. We took advantage of facile chemical conjugation and complementary hybridization to design novel siRNA-based micro- and nanostructures. Using chemical crosslinkers and hydrophobic/hydrophilic polymers at the end of siRNA, we produced various RNA-based structures, including siRNA block copolymers, micelles, linear siRNA homopolymers, and microhydrogels. Because of their increased charge density and flexibility compared with conventional siRNA, these micro- and nanostructures can form polyelectrolyte complexes with poorly charged and biocompatible cationic carriers that are both more condensed and more homogenous than the complexes formed in other carrier systems. In addition, the fabricated siRNA-based structures are linked by cleavable disulfide bonds for facile generation of original siRNA in the cytosol and for target-specific gene silencing. These newly developed siRNA-based structures greatly enhance intracellular uptake and gene silencing both in vitro and in vivo, making them promising biomaterials for siRNA therapeutics.
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Affiliation(s)
- Soo Hyeon Lee
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea
| | - Bong Hyun Chung
- BioNanotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 125 Gwahak-ro, Yuseong-gu, Daejeon 305-806, Republic of Korea
| | - Tae Gwan Park
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea
| | - Yoon Sung Nam
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea
| | - Hyejung Mok
- Department of Bioscience and Biotechnology, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 143-701, Republic of Korea
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Tamjar J, Katorcha E, Popov A, Malinina L. Structural dynamics of double-helical RNAs composed of CUG/CUG- and CUG/CGG-repeats. J Biomol Struct Dyn 2012; 30:505-23. [PMID: 22731704 DOI: 10.1080/07391102.2012.687517] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Human genetic trinucleotide repeat expansion diseases (TREDs) are characterized by triplet repeat expansions, most frequently found as CNG-tracts in genome. At RNA level, such expansions suggestively result in formation of double-helical hairpins that become a potential source for small RNAs involved in RNA interference (RNAi). Here, we present three crystal structures of RNA fragments composed of triplet repeats CUG and CGG/CUG, as well as two crystal structures of same triplets in a protein-bound state. We show that both 20mer pG(CUG)(6)C and 19mer pGG(CGG)(3)(CUG)(2)CC form A-RNA duplexes, in which U·U or G·U mismatches are flanked/stabilized by two consecutive Watson-Crick G·C base pairs resulting in high-stacking GpC steps in every third position of the duplex. Despite interruption of this regularity in another 19mer, p(CGG)(3)C(CUG)(3), the oligonucleotide still forms regular double-helical structure, characterized, however, by 12 bp (rather than 11 bp) per turn. Analysis of newly determined molecular structures reveals the dynamic aspects of U·U and G·U mismatching within CNG-repetitive A-RNA and in a protein-bound state, as well as identifies an additional mode of U·U pairing essential for its dynamics and sheds the light on possible role of regularity of trinucleotide repeats for double-helical RNA structure. Findings are important for understanding the structural behavior of CNG-repetitive RNA double helices implicated in TREDs.
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Affiliation(s)
- Jevgenia Tamjar
- Structural Biology Unit, CIC bioGUNE, Technology Park of Bizkaia, Derio-Bilbao 48160, Spain
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17
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Motooka D, Kawahara K, Nakamura S, Doi M, Nishi Y, Nishiuchi Y, Kang YK, Nakazawa T, Uchiyama S, Yoshida T, Ohkubo T, Kobayashi Y. The triple helical structure and stability of collagen model peptide with 4(s)-hydroxyprolyl-pro-gly units. Biopolymers 2011; 98:111-21. [DOI: 10.1002/bip.21730] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 10/09/2011] [Accepted: 10/13/2011] [Indexed: 12/22/2022]
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18
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Lee SH, Mok H, Lee Y, Park TG. Self-assembled siRNA–PLGA conjugate micelles for gene silencing. J Control Release 2011; 152:152-8. [DOI: 10.1016/j.jconrel.2010.12.007] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 12/09/2010] [Accepted: 12/17/2010] [Indexed: 12/14/2022]
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19
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Monaghan M, Pandit A. RNA interference therapy via functionalized scaffolds. Adv Drug Deliv Rev 2011; 63:197-208. [PMID: 21241760 DOI: 10.1016/j.addr.2011.01.006] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Revised: 12/16/2010] [Accepted: 01/05/2011] [Indexed: 12/27/2022]
Abstract
Tissue engineering aims to provide structural and biomolecular cues to compromised tissues through scaffolds. An emerging biomolecular cue is that of RNA interference by which the expression of genes can be silenced through a potent endogenous pathway. Recombinant viral-based approaches in RNAi delivery exist; however non-viral strategies offer many opportunities to exploit this mechanism of regulation in a safer way. Current RNAi therapies in clinical trials are without a vector (naked) or have slightly modified structures. Modification of these molecules with efficient backbone moieties for improved stability and potency, protecting and buffering them with delivery vehicles, and using scaffolds as reservoirs of delivery is at the frontier of current research. However, to enable an efficient sustained therapeutic effect scaffolds have a potentially significant role to play. This review presents non-viral delivery of RNAi that have been attempted via tissue engineered scaffolds. For RNAi to have a clinical impact, it is imperative to evaluate optimal delivery systems to ensure that the efficacy of this promising technology can be maximized.
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Affiliation(s)
- Michael Monaghan
- Network of Excellence for Functional Biomaterials, National University of Ireland-Galway, Ireland
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20
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Jeong JH, Park TG, Kim SH. Self-assembled and nanostructured siRNA delivery systems. Pharm Res 2011; 28:2072-85. [PMID: 21424157 DOI: 10.1007/s11095-011-0412-y] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Accepted: 02/25/2011] [Indexed: 12/21/2022]
Abstract
A wide range of organic and inorganic materials have been used in the development of nano-scale self-assembling gene delivery systems to improve the therapeutic efficacy of nucleic acid drugs. Small interfering RNA (siRNA) has recently been recognized as a promising and potent nucleic acid medicine for the treatment of incurable genetic disorders including cancer; however, siRNA-based therapeutics suffer from the same delivery problems as conventional nucleic acid drugs such as plasmid DNA and antisense oligonucleotides. Many of the delivery strategies developed for nucleic acid drugs have been applied to siRNA therapeutics, but they have not produced satisfactory in vivo gene silencing efficiencies to warrant clinical trials. This review discusses recent progress in the development of self-assembled and nanostructured delivery systems for efficient siRNA-induced gene silencing and their potential application in clinical settings.
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Affiliation(s)
- Ji Hoon Jeong
- School of Pharmacy, Sungkyunkwan University, Suwon 440-746, South Korea
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21
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Lee SH, Mok H, Park TG. Di- and Triblock siRNA-PEG Copolymers: PEG Density Effect of Polyelectrolyte Complexes on Cellular Uptake and Gene Silencing Efficiency. Macromol Biosci 2010; 11:410-8. [DOI: 10.1002/mabi.201000347] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Indexed: 12/11/2022]
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22
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Tolbert BS, Miyazaki Y, Barton S, Kinde B, Starck P, Singh R, Bax A, Case DA, Summers MF. Major groove width variations in RNA structures determined by NMR and impact of 13C residual chemical shift anisotropy and 1H-13C residual dipolar coupling on refinement. JOURNAL OF BIOMOLECULAR NMR 2010; 47:205-19. [PMID: 20549304 PMCID: PMC2929647 DOI: 10.1007/s10858-010-9424-x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Accepted: 04/20/2010] [Indexed: 05/22/2023]
Abstract
Ribonucleic acid structure determination by NMR spectroscopy relies primarily on local structural restraints provided by (1)H- (1)H NOEs and J-couplings. When employed loosely, these restraints are broadly compatible with A- and B-like helical geometries and give rise to calculated structures that are highly sensitive to the force fields employed during refinement. A survey of recently reported NMR structures reveals significant variations in helical parameters, particularly the major groove width. Although helical parameters observed in high-resolution X-ray crystal structures of isolated A-form RNA helices are sensitive to crystal packing effects, variations among the published X-ray structures are significantly smaller than those observed in NMR structures. Here we show that restraints derived from aromatic (1)H- (13)C residual dipolar couplings (RDCs) and residual chemical shift anisotropies (RCSAs) can overcome NMR restraint and force field deficiencies and afford structures with helical properties similar to those observed in high-resolution X-ray structures.
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Affiliation(s)
- Blanton S Tolbert
- Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250
| | - Yasuyuki Miyazaki
- Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250
| | - Shawn Barton
- Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250
| | - Benyam Kinde
- Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250
| | - Patrice Starck
- Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250
| | - Rashmi Singh
- Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250
| | - Ad Bax
- Laboratory of Chemical Physics, NIDDK, National Institutes of Health, Bethesda, MD 208992
| | - David A. Case
- Dept. of Chemistry & Chemical Biology and BioMaPS Institute, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854-8087, Phone: (732)-445-5885; Fax: (732)-445-5958;
| | - Michael F Summers
- Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, phone: (410)-455-2527; fax: (410)-455-1174;
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23
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Mok H, Lee SH, Park JW, Park TG. Multimeric small interfering ribonucleic acid for highly efficient sequence-specific gene silencing. NATURE MATERIALS 2010; 9:272-278. [PMID: 20098433 DOI: 10.1038/nmat2626] [Citation(s) in RCA: 193] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Accepted: 12/21/2009] [Indexed: 05/28/2023]
Abstract
Small interfering RNA (siRNA) with 19-21 base pairs has been recently recognized as a new therapeutic agent for effectively silencing a specific gene on a post-transcription level. For siRNA therapeutics, safe and efficient delivery issues are significant hurdles to clinical applications. Here we present a new class of biologically active siRNA structure based on chemically self-crosslinked and multimerized siRNA through cleavable disulphide linkages. The multimerized siRNA can produce more stable and compact polyelectrolyte complexes with less cytotoxic cationic carriers than naked siRNA because of substantially increased charge densities and the presence of flexible chemical linkers in the backbone. The cleavable and multimerized siRNA shows greatly enhanced gene-silencing efficiencies in vitro and in vivo through a target-messenger-RNA-specific RNA interference processing without significantly eliciting immune induction. This study demonstrates that the multimerized siRNA structure complexed with selected cationic condensing agents can serve as potential gene-silencing therapeutics for treating various diseases.
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Affiliation(s)
- Hyejung Mok
- Department of Biological Sciences and Graduate School of Nanoscience and Technology, Korea Advanced Institute of Science and Technology, Daejeon, 305-701, South Korea
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24
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Lu K, Miyazaki Y, Summers MF. Isotope labeling strategies for NMR studies of RNA. JOURNAL OF BIOMOLECULAR NMR 2010; 46:113-25. [PMID: 19789981 PMCID: PMC2797625 DOI: 10.1007/s10858-009-9375-2] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Accepted: 08/20/2009] [Indexed: 05/04/2023]
Abstract
The known biological functions of RNA have expanded in recent years and now include gene regulation, maintenance of sub-cellular structure, and catalysis, in addition to propagation of genetic information. As for proteins, RNA function is tightly correlated with structure. Unlike proteins, structural information for larger, biologically functional RNAs is relatively limited. NMR signal degeneracy, relaxation problems, and a paucity of long-range (1)H-(1)H dipolar contacts have limited the utility of traditional NMR approaches. Selective isotope labeling, including nucleotide-specific and segmental labeling strategies, may provide the best opportunities for obtaining structural information by NMR. Here we review methods that have been developed for preparing and purifying isotopically labeled RNAs, as well as NMR strategies that have been employed for signal assignment and structure determination.
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Affiliation(s)
- Kun Lu
- Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 USA
| | - Yasuyuki Miyazaki
- Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 USA
| | - Michael F. Summers
- Howard Hughes Medical Institute and Department of Chemistry and Biochemistry, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 USA
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25
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Surface-engineered targeted PPI dendrimer for efficient intracellular and intratumoral siRNA delivery. J Control Release 2009; 140:284-93. [PMID: 19567257 DOI: 10.1016/j.jconrel.2009.06.019] [Citation(s) in RCA: 218] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 06/19/2009] [Accepted: 06/20/2009] [Indexed: 01/17/2023]
Abstract
Low penetration ability of Small Interfering RNA (siRNA) through the cellular plasma membrane combined with its limited stability in blood, limits the effectiveness of the systemic delivery of siRNA. In order to overcome such difficulties, we constructed a nanocarrier-based delivery system by taking advantage of the lessons learned from the problems in the delivery of DNA. In the present study, siRNA nanoparticles were first formulated with Poly(Propyleneimine) (PPI) dendrimers. To provide lateral and steric stability to withstand the aggressive environment in the blood stream, the formed siRNA nanoparticles were caged with a dithiol containing cross-linker molecules followed by coating them with Poly(Ethylene Glycol) (PEG) polymer. A synthetic analog of Luteinizing Hormone-Releasing Hormone (LHRH) peptide was conjugated to the distal end of PEG polymer to direct the siRNA nanoparticles specifically to the cancer cells. Our results demonstrated that this layer-by-layer modification and targeting approach confers the siRNA nanoparticles stability in plasma and intracellular bioavailability, provides for their specific uptake by tumor cells, accumulation of siRNA in the cytoplasm of cancer cells, and efficient gene silencing. In addition, in vivo body distribution data confirmed high specificity of the proposed targeting delivery approach which created the basis for the prevention of adverse side effects of the treatment on healthy organs.
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26
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Crystallographic studies of DNA and RNA. Methods 2009; 47:168-76. [DOI: 10.1016/j.ymeth.2008.09.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Accepted: 09/10/2008] [Indexed: 11/23/2022] Open
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Abstract
Preparation of suitably large and well-ordered single crystals is usually the rate-limiting step in the determination of the three-dimensional structure of RNAs and their complexes with proteins by X-ray crystallography. This unit discusses a variety of experimental considerations for obtaining crystals of RNAs and RNA-protein complexes. Topics include design of crystallizable constructs, screening, and optimization of crystallization conditions.
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28
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Gary DJ, Puri N, Won YY. Polymer-based siRNA delivery: Perspectives on the fundamental and phenomenological distinctions from polymer-based DNA delivery. J Control Release 2007; 121:64-73. [PMID: 17588702 DOI: 10.1016/j.jconrel.2007.05.021] [Citation(s) in RCA: 388] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2007] [Accepted: 05/15/2007] [Indexed: 12/24/2022]
Abstract
Gene therapy holds tremendous promise in the treatment of many genetic and acquired diseases. The future of gene therapy in humans, however, is contingent upon the discovery of safe and effective carriers of genetic material. Polymers represent a class of materials that can be extensively modified to meet the needs of a particular gene delivery system. A variety of polymer formulations have been proposed in the literature as potential carriers, most of which facilitate gene delivery by encapsulating, and in some cases, condensing nucleic acids into nano-sized particles which can then be taken up by cells. Crucial to successful delivery of the gene to a cell is the polymer's ability to protect its contents from degradation in the extracellular environment. A well-designed carrier will also promote cellular uptake and intracellular release of the nucleic acid. In the past, a common approach to gene therapy has been to transfect cells with a polymer-encapsulated DNA plasmid designed to replace a defective gene in the target-cell genome. Within the last few years, however, RNA interference (RNAi) has emerged as a novel therapeutic pathway by which harmful genes can be "silenced" by delivering complementary short interfering RNA (siRNA) to target cells. siRNA delivery facilitated by polymers, although very promising, suffers from many of the same limitations as DNA delivery. This review will (1) highlight the similarities and differences between these two methods of gene therapy and (2) discuss how some of the remaining challenges in siRNA delivery facilitated by polymers can be addressed by applying knowledge from the longer-studied problem of DNA delivery.
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Affiliation(s)
- Dana J Gary
- School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907, USA
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29
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Bernacchi S, Ennifar E, Tóth K, Walter P, Langowski J, Dumas P. Mechanism of Hairpin-Duplex Conversion for the HIV-1 Dimerization Initiation Site. J Biol Chem 2005; 280:40112-21. [PMID: 16169845 DOI: 10.1074/jbc.m503230200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have used the dimerization initiation site of HIV-1 genomic RNA as a model to investigate hairpin-duplex interconversion with a combination of fluorescence, UV melting, gel electrophoresis, and x-ray crystallographic techniques. Fluorescence studies with molecular beacons and crystallization experiments with 23-nucleotide dimerization initiation site fragments showed that the ratio of hairpin to duplex formed after annealing in water essentially depends on RNA concentration and not on cooling kinetics. With natural sequences allowing to form the most stable duplex, and thus also the loop-loop complex (or "kissing complex"), concentrations as low as 3 mum in strands are necessary to obtain a majority of the hairpin form. With a mutated sequence preventing kissing complex formation, a majority of hairpins was even obtained at 80 mum in strands. However, this did not prevent an efficient conversion from hairpin to duplex in the presence of salts. Kinetic considerations are in favor of duplex formation from intermediates involving hairpins engaged in cruciform dimers rather than from free strands. The very first step of formation of such a cruciform intermediate could be trapped in a crystal structure. This mechanism might be significant for the dynamics of small RNAs beyond the strict field of HIV-1.
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Affiliation(s)
- Serena Bernacchi
- Institut de Biologie Moléculaire et Cellulaire, UPR 9002 du CNRS Conventionnée à l'Université Louis Pasteur Strasbourg, F-67084 Strasbourg Cedex, France
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30
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MacElrevey C, Wedekind JE. Crystallization and X-ray diffraction analysis of the Trp/amber editing site of hepatitis delta virus (+)RNA: a case of rational design. Acta Crystallogr Sect F Struct Biol Cryst Commun 2005; 61:1049-53. [PMID: 16511232 PMCID: PMC1978144 DOI: 10.1107/s1744309105035888] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2005] [Accepted: 11/02/2005] [Indexed: 11/10/2022]
Abstract
RNA editing by mammalian ADAR1 (Adenosine Deaminase Acting on RNA) is required for the life cycle of the hepatitis delta virus (HDV). Editing extends the single viral open reading frame to yield two protein products of alternate length. ADARs are believed to recognize double-stranded RNA substrates via a ;structure-based' readout mechanism. Crystals of 10-mer duplexes representing the HDV RNA-editing site diffracted to 1.35 A resolution, but suffered from merohedral twinning and averaging of the base registry. Expansion of the construct to include two flanking 3 x 1 internal loops yielded crystals in the primitive tetragonal space group P4(1)2(1)2 or P4(3)2(1)2. X-ray diffraction data were collected to 2.8 A resolution, revealing a unit cell with parameters a = 62.5, c = 63.5 A. The crystallization and X-ray analysis of multiple forms of the HDV RNA-editing substrate, encounters with common RNA crystal-growth defects and a strategy to overcome these problems are reported.
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Affiliation(s)
- Celeste MacElrevey
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
| | - Joseph E. Wedekind
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
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Mooers BHM, Logue JS, Berglund JA. The structural basis of myotonic dystrophy from the crystal structure of CUG repeats. Proc Natl Acad Sci U S A 2005; 102:16626-31. [PMID: 16269545 PMCID: PMC1283809 DOI: 10.1073/pnas.0505873102] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Myotonic dystrophy (DM) type 1 is associated with an expansion of (>50) CTG repeats within the 3' untranslated region (UTR) of the dystrophin myotonin protein kinase gene (dmpk). In the corresponding mRNA transcript, the CUG repeats form an extended stem-loop structure. The double-stranded RNA of the stem sequesters RNA binding proteins away from their normal cellular targets resulting in aberrant transcription, alternative splicing patterns, or both, thereby leading to DM. To better understand the structural basis of DM type 1, we determined to 1.58-A resolution the x-ray crystal structure of an 18-bp RNA containing six CUG repeats. The CUG repeats form antiparallel double-stranded helices that stack end-on-end in the crystal to form infinite, pseudocontinuous helices similar to the long CUG stem loops formed by the expanded CUG repeats in DM type 1. The CUG helix is very similar in structure to A-form RNA with the exception of the unique U-U mismatches. This structure provides a high-resolution view of a toxic, trinucleotide repeat RNA.
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Affiliation(s)
- Blaine H M Mooers
- Department of Chemistry, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403-1229, USA
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32
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Abstract
Solution NMR spectroscopy of nucleic acids has been limited by the short-range nature of the nuclear Overhauser effect and scalar coupling restraints normally used in structure determination. The addition of residual dipolar couplings, obtained from slightly oriented mixtures, provides bond vector angles relative to a universal alignment tensor. The accurate determination of helix curvature, domain orientation and the stoichiometry of homomultimeric nucleic acid complexes is now possible.
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Affiliation(s)
- Douglas MacDonald
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA
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33
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Littlefield O, Nelson HC. Crystal packing interaction that blocks crystallization of a site-specific DNA binding protein-DNA complex. Proteins 2001; 45:219-28. [PMID: 11599025 DOI: 10.1002/prot.1142] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We present here three high-resolution crystal structures of complexes between the DNA-binding domain of the heat-shock transcription factor (HSF) and DNA oligomers. Although the DNA oligomers contain HSF's specific binding sequence, called a heat-shock element, the crystal structures do not contain the specific protein-DNA complex. In one crystal structure, the 10 base pair DNA oligomer is statically disordered. In the other two related structures, the 12 base pair DNA oligomers are in unique positions, but the protein-DNA contacts in these two crystals are not sequence specific. In all three structures, the DNA appears to act as a rigid, polyanion scaffold to support columns of proteins in a crystalline lattice. A robust crystal packing interface between protein monomers obscures the true DNA-binding surface, known from previous genetic and biochemical studies. By redesigning the protein to interfere with the crystal lattice contacts, we were able to obtain physiologically relevant crystals in a specific protein-DNA complex. Thus, a crystal-packing interface was able to prevent the weak, but physiological relevant interactions between a protein and DNA.
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Affiliation(s)
- O Littlefield
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
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Wyszko E, Barciszewska MZ, Bald R, Erdmann VA, Barciszewski J. The specific hydrolysis of HIV-1 TAR RNA element with the anti-TAR hammerhead ribozyme: structural and functional implications. Int J Biol Macromol 2001; 28:373-80. [PMID: 11325424 DOI: 10.1016/s0141-8130(01)00138-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The main transcriptional regulator of the human immunodeficiency virus is the Tat protein, which recognises and binds to a fragment RNA at the 5' end of viral mRNA, named transactivation response element (TAR) RNA. Extensive mutagenesis studies have shown that a region of TAR RNA important for Tat binding involves a set of nucleotides surrounding a characteristic UCU nucleotide bulge. The specific Tat-TAR complex formation enhances the rate of transcription elongation but inhibition of that interaction prevents the human immunodeficiency virus type 1 (HIV-1) replication. If so, a possibility of virus inactivation would be a site specific degradation of the TAR RNA element. To break down and inactivate TAR RNA, we designated the anti-hammerhead (HH) ribozyme to cleave nucleosides within the bulge. We showed for the first time the new type of the AUC hammerhead ribozyme, which hydrolyses specifically the TAR RNA element at C8 nucleotide in the bulge (C24 in the standard TAR RNA numbering). The cleavage reaction has broad magnesium requirements. Mn and particularly Ca are less efficient. Argininamide interferes with the cleavage of TAR RNA induced by the ribozyme. These results have two implications; (i) structural, where the HIV-1 TAR RNA element in solution occurs in equilibrium of only two forms, one of which, a double stranded RNA, meets structural requirements for ribozyme pairing and cleavage, and (ii) functional, the HH ribozyme can be explored for an inactivation of HIV-1 through the TAR RNA element deintegration.
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Affiliation(s)
- E Wyszko
- Institute of Bioorganic Chemistry of the Polish Academy of Sciences, Noskowskiego 12, 61794, Poznan, Poland
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Abstract
Several crystal structures of RNA fragments, alone or in complex with a specific protein, have been recently solved. In addition, the structures of an artificial ribozyme, the leadzyme, and the cleavage product of a human pathogen ribozyme, have extended the structural diversity of ribozyme architectures. The attained set of folding rules and motifs expand the repertoire seen previously in tRNA structures.
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Affiliation(s)
- E Westhof
- UPR9002, Institut de Biologie Moléculaire et Cellulaire du CNRS, Strasbourg-Cedex, F-67084, France.
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Sharma N, Furter R, Kast P, Tirrell DA. Efficient introduction of aryl bromide functionality into proteins in vivo. FEBS Lett 2000; 467:37-40. [PMID: 10664452 DOI: 10.1016/s0014-5793(00)01120-0] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Artificial proteins can be engineered to exhibit interesting solid state, liquid crystal or interfacial properties and may ultimately serve as important alternatives to conventional polymeric materials. The utility of protein-based materials is limited, however, by the availability of just the 20 amino acids that are normally recognized and utilized by biological systems; many desirable functional groups cannot be incorporated directly into proteins by biosynthetic means. In this study, we incorporate para-bromophenylalanine (p-Br-phe) into a model target protein, mouse dihydrofolate reductase (DHFR), by using a bacterial phenylalanyl-tRNA synthetase (PheRS) variant with relaxed substrate specificity. Coexpression of the mutant PheRS and DHFR in a phenylalanine auxotrophic Escherichia coli host strain grown in p-Br-phe-supplemented minimal medium resulted in 88% replacement of phenylalanine residues by p-Br-phe; variation in the relative amounts of phe and p-Br-phe in the medium allows control of the degree of substitution by the analog. Protein expression yields of 20-25 mg/l were obtained from cultures supplemented with p-Br-phe; this corresponds to about two-thirds of the expression levels characteristic of cultures supplemented with phe. The aryl bromide function is stable under the conditions used to purify DHFR and creates new opportunities for post-translational derivatization of brominated proteins via metal-catalyzed coupling reactions. In addition, bromination may be useful in X-ray studies of proteins via the multiwavelength anomalous diffraction (MAD) technique.
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Affiliation(s)
- N Sharma
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA 01003, USA
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Wild K, Weichenrieder O, Leonard GA, Cusack S. The 2 A structure of helix 6 of the human signal recognition particle RNA. Structure 1999; 7:1345-52. [PMID: 10574798 DOI: 10.1016/s0969-2126(00)80024-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
BACKGROUND The mammalian signal recognition particle (SRP) is an essential cytoplasmic ribonucleoprotein complex involved in targeting signal-peptide-containing proteins to the endoplasmic reticulum. Assembly of the SRP requires protein SRP19 to bind first to helix 6 of the SRP RNA before the signal-peptide-recognizing protein, SRP54, can bind to helix 8 of the RNA. Helix 6 is closed by a GGAG tetraloop, which has been shown to form part of the SRP19-binding site. RESULTS The high-resolution (2.0 A) structure of a fragment of human SRP RNA comprising 29 nucleotides of helix 6 has been determined using the multiple anomalous dispersion (MAD) method and bromine-labelled RNA. In the crystal the molecule forms 28-mer duplexes rather than the native monomeric hairpin structure, although two chemically equivalent 11 base pair stretches of the duplex represent the presumed native structure. The duplex has highly distorted A-RNA geometry caused by the occurrence of several non-Watson-Crick base pairs. These include a 5'-GGAG-3'/3'-GAGG-5' purine bulge (which replaces the tetraloop) and a 5'-AC-3'/3'-CA-5' tandem mismatch that, depending on the protonation state of the adenine bases, adopts a different conformation in the two native-like parts of the structure. The structure also shows the 2'3'-cyclic phosphate reaction product of the hammerhead ribozyme cleavage reaction. CONCLUSIONS The 29-mer RNA is the first RNA structure of the human SRP and provides some insight into the binding mode of SRP19. The observed strong irregularities of the RNA helix make the major groove wide enough and flat enough to possibly accommodate an alpha helix of SRP19. The variety of non-canonical base pairs observed enlarges the limited repertoire of irregular RNA folds known to date and the observed conformation of the 2'3'-cyclic phosphate containing Ade29 is consistent with the current understanding of the hammerhead ribozyme reaction mechanism.
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Affiliation(s)
- K Wild
- EMBL Grenoble Outstation, Grenoble, F-38042, France
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