1
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Staedtke V, Anstett K, Bedwell D, Giovannini M, Keeling K, Kesterson R, Kim Y, Korf B, Leier A, McManus ML, Sarnoff H, Vitte J, Walker JA, Plotkin SR, Wallis D. Gene-targeted therapy for neurofibromatosis and schwannomatosis: The path to clinical trials. Clin Trials 2024; 21:51-66. [PMID: 37937606 DOI: 10.1177/17407745231207970] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2023]
Abstract
Numerous successful gene-targeted therapies are arising for the treatment of a variety of rare diseases. At the same time, current treatment options for neurofibromatosis 1 and schwannomatosis are limited and do not directly address loss of gene/protein function. In addition, treatments have mostly focused on symptomatic tumors, but have failed to address multisystem involvement in these conditions. Gene-targeted therapies hold promise to address these limitations. However, despite intense interest over decades, multiple preclinical and clinical issues need to be resolved before they become a reality. The optimal approaches to gene-, mRNA-, or protein restoration and to delivery to the appropriate cell types remain elusive. Preclinical models that recapitulate manifestations of neurofibromatosis 1 and schwannomatosis need to be refined. The development of validated assays for measuring neurofibromin and merlin activity in animal and human tissues will be critical for early-stage trials, as will the selection of appropriate patients, based on their individual genotypes and risk/benefit balance. Once the safety of gene-targeted therapy for symptomatic tumors has been established, the possibility of addressing a wide range of symptoms, including non-tumor manifestations, should be explored. As preclinical efforts are underway, it will be essential to educate both clinicians and those affected by neurofibromatosis 1/schwannomatosis about the risks and benefits of gene-targeted therapy for these conditions.
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Affiliation(s)
- Verena Staedtke
- Department of Neurology, Johns Hopkins University, Baltimore, MD, USA
| | - Kara Anstett
- Department of Neurology, NYU Grossman School of Medicine, New York, NY, USA
| | - David Bedwell
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Marco Giovannini
- Department of Head and Neck Surgery, David Geffen School of Medicine at UCLA and Jonsson Comprehensive Cancer Center (JCCC), University of California Los Angeles, Los Angeles, CA, USA
| | - Kim Keeling
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Robert Kesterson
- Department of Cancer Precision Medicine, Pennington Biomedical Research Center, Baton Rouge, LA, USA
| | - YooRi Kim
- Gilbert Family Foundation, Detroit, MI, USA
| | - Bruce Korf
- Department of Genetics, The University of Alabama at Birmingham, Birmingham, AL, USA
| | - André Leier
- Department of Genetics, The University of Alabama at Birmingham, Birmingham, AL, USA
| | | | | | - Jeremie Vitte
- Department of Head and Neck Surgery, David Geffen School of Medicine at UCLA and Jonsson Comprehensive Cancer Center (JCCC), University of California Los Angeles, Los Angeles, CA, USA
| | - James A Walker
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Scott R Plotkin
- Department of Neurology and Cancer Center, Massachusetts General Hospital, Boston, MA, USA
| | - Deeann Wallis
- Department of Genetics, The University of Alabama at Birmingham, Birmingham, AL, USA
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2
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Najeh S, Zandi K, Djerroud S, Kharma N, Perreault J. Computer-Aided Design of Active Pseudoknotted Hammerhead Ribozymes. Methods Mol Biol 2021; 2167:91-111. [PMID: 32712917 DOI: 10.1007/978-1-0716-0716-9_7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Pseudoknots are important motifs for stabilizing the structure of functional RNAs. As an example, pseudoknotted hammerhead ribozymes are highly active compared to minimal ribozymes. The design of new RNA sequences that retain the function of a model RNA structure includes taking in account pseudoknots presence in the structure, which is usually a challenge for bioinformatics tools. Our method includes using "Enzymer," a software for designing RNA sequences with desired secondary structures that may include pseudoknots. Enzymer implements an efficient stochastic search and optimization algorithm to sample RNA sequences from low ensemble defect mutational landscape of an initial design template to generate an RNA sequence that is predicted to fold into the desired target structure.
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Affiliation(s)
- Sabrine Najeh
- Centre Armand-Frappier Santé Biotechnologie, Institut National de la Recherche Scientifique (INRS), Laval, QC, Canada
| | - Kasra Zandi
- Software Engineering and Computer Science Department, Concordia University, Montreal, QC, Canada
| | - Samia Djerroud
- Centre Armand-Frappier Santé Biotechnologie, Institut National de la Recherche Scientifique (INRS), Laval, QC, Canada
| | - Nawwaf Kharma
- Electrical and Computer Engineering Department, Concordia University, Montreal, QC, Canada.
| | - Jonathan Perreault
- Centre Armand-Frappier Santé Biotechnologie, Institut National de la Recherche Scientifique (INRS), Laval, QC, Canada.
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3
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Leier A, Bedwell DM, Chen AT, Dickson G, Keeling KM, Kesterson RA, Korf BR, Marquez Lago TT, Müller UF, Popplewell L, Zhou J, Wallis D. Mutation-Directed Therapeutics for Neurofibromatosis Type I. MOLECULAR THERAPY. NUCLEIC ACIDS 2020; 20:739-753. [PMID: 32408052 PMCID: PMC7225739 DOI: 10.1016/j.omtn.2020.04.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 04/20/2020] [Accepted: 04/23/2020] [Indexed: 02/07/2023]
Abstract
Significant advances in biotechnology have led to the development of a number of different mutation-directed therapies. Some of these techniques have matured to a level that has allowed testing in clinical trials, but few have made it to approval by drug-regulatory bodies for the treatment of specific diseases. While there are still various hurdles to be overcome, recent success stories have proven the potential power of mutation-directed therapies and have fueled the hope of finding therapeutics for other genetic disorders. In this review, we summarize the state-of-the-art of various therapeutic approaches and assess their applicability to the genetic disorder neurofibromatosis type I (NF1). NF1 is caused by the loss of function of neurofibromin, a tumor suppressor and downregulator of the Ras signaling pathway. The condition is characterized by a variety of phenotypes and includes symptoms such as skin spots, nervous system tumors, skeletal dysplasia, and others. Hence, depending on the patient, therapeutics may need to target different tissues and cell types. While we also discuss the delivery of therapeutics, in particular via viral vectors and nanoparticles, our main focus is on therapeutic techniques that reconstitute functional neurofibromin, most notably cDNA replacement, CRISPR-based DNA repair, RNA repair, antisense oligonucleotide therapeutics including exon skipping, and nonsense suppression.
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Affiliation(s)
- Andre Leier
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - David M Bedwell
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Ann T Chen
- Department of Neurosurgery, Yale University, New Haven, CT 06510, USA
| | - George Dickson
- Centre of Biomedical Sciences, Department of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
| | - Kim M Keeling
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Robert A Kesterson
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Bruce R Korf
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | | | - Ulrich F Müller
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093, USA
| | - Linda Popplewell
- Centre of Biomedical Sciences, Department of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
| | - Jiangbing Zhou
- Department of Neurosurgery, Yale University, New Haven, CT 06510, USA
| | - Deeann Wallis
- Department of Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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4
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Chi SI, Dahl M, Emblem Å, Johansen SD. Giant group I intron in a mitochondrial genome is removed by RNA back-splicing. BMC Mol Biol 2019; 20:16. [PMID: 31153363 PMCID: PMC6545197 DOI: 10.1186/s12867-019-0134-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 05/23/2019] [Indexed: 01/29/2023] Open
Abstract
Background The mitochondrial genomes of mushroom corals (Corallimorpharia) are remarkable for harboring two complex group I introns; ND5-717 and COI-884. How these autocatalytic RNA elements interfere with mitochondrial RNA processing is currently not known. Here, we report experimental support for unconventional processing events of ND5-717 containing RNA. Results We obtained the complete mitochondrial genome sequences and corresponding mitochondrial transcriptomes of the two distantly related corallimorpharian species Ricordea yuma and Amplexidiscus fenestrafer. All mitochondrial genes were found to be expressed at the RNA-level. Both introns were perfectly removed by autocatalytic splicing, but COI-884 excision appeared more efficient than ND5-717. ND5-717 was organized into giant group I intron elements of 18.1 kb and 19.3 kb in A. fenestrafer and R. yuma, respectively. The intron harbored almost the entire mitochondrial genome embedded within the P8 peripheral segment. Conclusion ND5-717 was removed by group I intron splicing from a small primary transcript that contained a permutated intron–exon arrangement. The splicing pathway involved a circular exon-containing RNA intermediate, which is a hallmark of RNA back-splicing. ND5-717 represents the first reported natural group I intron that becomes excised by back-splicing from a permuted precursor RNA. Back-splicing may explain why Corallimorpharia mitochondrial genomes tolerate giant group I introns. Electronic supplementary material The online version of this article (10.1186/s12867-019-0134-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sylvia Ighem Chi
- Department of Medical Biology, Faculty of Health Sciences, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Mikael Dahl
- Department of Medical Biology, Faculty of Health Sciences, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Åse Emblem
- Department of Medical Biology, Faculty of Health Sciences, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Steinar D Johansen
- Department of Medical Biology, Faculty of Health Sciences, UiT-The Arctic University of Norway, Tromsø, Norway. .,Genomics Group, Faculty of Biosciences and Aquaculture, Nord University, Bodø, Norway.
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5
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Advances in engineered trans-acting regulatory RNAs and their application in bacterial genome engineering. J Ind Microbiol Biotechnol 2019; 46:819-830. [PMID: 30887255 DOI: 10.1007/s10295-019-02160-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 03/05/2019] [Indexed: 12/15/2022]
Abstract
Small noncoding RNAs, a large class of ancient posttranscriptional regulators, are increasingly recognized and utilized as key modulators of gene expression in a broad range of microorganisms. Owing to their small molecular size and the central role of Watson-Crick base pairing in defining their interactions, structure and function, numerous diverse types of trans-acting RNA regulators that are functional at the DNA, mRNA and protein levels have been experimentally characterized. It has become increasingly clear that most small RNAs play critical regulatory roles in many processes and are, therefore, considered to be powerful tools for genetic engineering and synthetic biology. The trans-acting regulatory RNAs accelerate this ability to establish potential framework for genetic engineering and genome-scale engineering, which allows RNA structure characterization, easier to design and model compared to DNA or protein-based systems. In this review, we summarize recent advances in engineered trans-acting regulatory RNAs that are used in bacterial genome-scale engineering and in novel cellular capabilities as well as their implementation in wide range of biotechnological, biological and medical applications.
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6
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Abstract
Recent advances in RNA engineering during the last two decades have supported the development of RNA-based therapeutics targeting a variety of human diseases. The broad scope of these emerging drugs clearly demonstrates the versatility of RNA. Ribozymes have been seen as promising candidates in this area. However, efficient intracellular application of ribozymes remains challenging, and other strategies appear to have outperformed ribozymes as molecular drugs. Nevertheless, trans-cleaving ribozymes have been applied for specific cleavage of target mRNAs in order to inhibit undesired gene expression. Furthermore, ribozymes have been engineered to allow site-directed RNA sequence alterations, enabling the correction of genetic misinformation at the RNA level. This chapter provides an overview of ribozyme-based strategies, highlighting the promises and pitfalls for potential therapeutic applications.
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Affiliation(s)
- Darko Balke
- University of Greifswald, Institute of Biochemistry Felix-Hausdorff-Str. 4 17487 Greifswald Germany
| | - Sabine Müller
- University of Greifswald, Institute of Biochemistry Felix-Hausdorff-Str. 4 17487 Greifswald Germany
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7
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Lee CH, Han SR, Lee SW. Group I Intron-Based Therapeutics Through Trans-Splicing Reaction. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2018; 159:79-100. [PMID: 30340790 DOI: 10.1016/bs.pmbts.2018.07.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In 1982, the Cech group discovered that an intron structure in an rRNA precursor of Tetrahymena thermophila is sufficient to complete splicing without assistance from proteins. This was the first moment that scientists recognized RNAs can have catalytic activities derived from their own unique three-dimensional structures and thus play more various roles in biological processes than thought before. Several additional catalytic RNAs, called ribozymes, were subsequently identified in nature followed by intense studies to reveal their mechanisms of action and to engineer them for use in fields such as molecular cell biology, therapeutics, imaging, etc. Naturally occurring RNA-targeting ribozymes can be broadly classified into two categories by their abilities: Self-cleavage and self-splicing. Since ribozymes use base-pairing to recognize cleavage sites, identification of the catalytic center of naturally occurring ribozymes enables to engineer from "self" to "trans" acting ones which has accelerated to design and use ribozyme as valuable tools in gene therapy fields. Especially, group I intron-based trans-splicing ribozyme has unique property to use as a gene therapeutic agent. It can destroy and simultaneously repair (and/or reprogram) target RNAs to yield the desired therapeutic RNAs, maintaining endogenous spatial and temporal gene regulation of target RNAs. There have been progressive improvements in trans-splicing ribozymes and successful applications of these elements in gene therapy and molecular imaging approaches for various pathogenic conditions. In this chapter, current status of trans-splicing ribozyme therapeutics, focusing on Tetrahymena group I intron-based ribozymes, and their future prospects will be discussed.
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Affiliation(s)
- Chang Ho Lee
- Department of Integrated Life Sciences, Dankook University, Yongin, Republic of Korea
| | | | - Seong-Wook Lee
- Department of Integrated Life Sciences, Dankook University, Yongin, Republic of Korea; Rznomics Inc., Gwangju, Republic of Korea.
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8
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Balke D, Becker A, Müller S. In vitro repair of a defective EGFP transcript and translation into a functional protein. Org Biomol Chem 2018; 14:6729-37. [PMID: 27314882 DOI: 10.1039/c6ob01043a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Twin ribozymes mediate the exchange of a short patch of RNA against an exogenous oligonucleotide within a suitable RNA substrate. Thus, twin ribozymes are promising tools for RNA repair, i.e. for the treatment of genetic disorders at the mRNA level. A number of twin ribozyme-mediated RNA fragment exchange reactions have been successfully demonstrated using short model substrates. Herein we show for the first time a twin ribozyme-mediated in vitro repair of a full-length transcript and translation into a functional protein. The system is based on the repair of a designed mutant EGFP mRNA containing the four-base deletion ΔACTC (190-193). Upon twin ribozyme-mediated replacement of a patch of 15 nucleotides with an externally added repair oligonucleotide (19 mer) the wild type sequence of the EGFP transcript could be restored with 32% yield. This is the first time that such a high twin ribozyme-mediated repair yield, so far observed only for short model substrates, has been obtained for a full-length mRNA. Translation of the repaired EGFP-ΔACTC mRNA produces functional EGFP, as detected by the restored fluorescence.
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Affiliation(s)
- Darko Balke
- Ernst-Moritz-Arndt-Universität Greifswald, Institut für Biochemie, Felix-Hausdorff-Str. 4, 17487 Greifswald, Germany.
| | - Aileen Becker
- Ernst-Moritz-Arndt-Universität Greifswald, Institut für Biochemie, Felix-Hausdorff-Str. 4, 17487 Greifswald, Germany.
| | - Sabine Müller
- Ernst-Moritz-Arndt-Universität Greifswald, Institut für Biochemie, Felix-Hausdorff-Str. 4, 17487 Greifswald, Germany.
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9
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Lee CH, Han SR, Lee SW. Therapeutic applications of group I intron-based trans-splicing ribozymes. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 9:e1466. [PMID: 29383855 DOI: 10.1002/wrna.1466] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2017] [Revised: 12/10/2017] [Accepted: 12/14/2017] [Indexed: 12/21/2022]
Abstract
Since the breakthrough discovery of catalytic RNAs (ribozymes) in the early 1980s, valuable ribozyme-based gene therapies have been developed for incurable diseases ranging from genetic disorders to viral infections and cancers. Ribozymes can be engineered and used to downregulate or repair pathogenic genes via RNA cleavage mediated by trans-cleaving ribozymes or repair and reprograming mediated by trans-splicing ribozymes, respectively. Uniquely, trans-splicing ribozymes can edit target RNAs via simultaneous destruction and repair (and/or reprograming) to yield the desired therapeutic RNAs, thus selectively inducing therapeutic gene activity in cells expressing the target RNAs. In contrast to traditional gene therapy approaches, such as simple addition of therapeutic transgenes or inhibition of disease-causing genes, the selective repair and/or reprograming abilities of trans-splicing ribozymes in target RNA-expressing cells facilitates the maintenance of endogenous spatial and temporal gene regulation and reduction of disease-associated transcript expression. In molecular imaging technologies, trans-splicing ribozymes can be used to reprogram specific RNAs in living cells and organisms by the 3'-tagging of reporter RNAs. The past two decades have seen progressive improvements in trans-splicing ribozymes and the successful application of these elements in gene therapy and molecular imaging approaches for various pathogenic conditions, such as genetic, infectious, and malignant disease. This review provides an overview of the current status of trans-splicing ribozyme therapeutics, focusing on Tetrahymena group I intron-based ribozymes, and their future prospects. This article is categorized under: RNA in Disease and Development > RNA in Disease.
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Affiliation(s)
- Chang Ho Lee
- Department of Integrated Life Sciences, Dankook University, Yongin, Republic of Korea
| | - Seung Ryul Han
- Department of Integrated Life Sciences, Dankook University, Yongin, Republic of Korea
| | - Seong-Wook Lee
- Department of Integrated Life Sciences, Dankook University, Yongin, Republic of Korea
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10
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Petree JR, Yehl K, Galior K, Glazier R, Deal B, Salaita K. Site-Selective RNA Splicing Nanozyme: DNAzyme and RtcB Conjugates on a Gold Nanoparticle. ACS Chem Biol 2018; 13:215-224. [PMID: 29155548 PMCID: PMC6085866 DOI: 10.1021/acschembio.7b00437] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Modifying RNA through either splicing or editing is a fundamental biological process for creating protein diversity from the same genetic code. Developing novel chemical biology tools for RNA editing has potential to transiently edit genes and to provide a better understanding of RNA biochemistry. Current techniques used to modify RNA include the use of ribozymes, adenosine deaminase, and tRNA endonucleases. Herein, we report a nanozyme that is capable of splicing virtually any RNA stem-loop. This nanozyme is comprised of a gold nanoparticle functionalized with three enzymes: two catalytic DNA strands with ribonuclease function and an RNA ligase. The nanozyme cleaves and then ligates RNA targets, performing a splicing reaction that is akin to the function of the spliceosome. Our results show that the three-enzyme reaction can remove a 19 nt segment from a 67 nt RNA loop with up to 66% efficiency. The complete nanozyme can perform the same splice reaction at 10% efficiency. These splicing nanozymes represent a new promising approach for gene manipulation that has potential for applications in living cells.
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Affiliation(s)
- Jessica R. Petree
- Department of Chemistry, Emory University, Atlanta, GA 30322, United States
| | - Kevin Yehl
- Department of Chemistry, Emory University, Atlanta, GA 30322, United States
| | - Kornelia Galior
- Department of Chemistry, Emory University, Atlanta, GA 30322, United States
| | - Roxanne Glazier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia 30322, United States
| | - Brendan Deal
- Department of Chemistry, Emory University, Atlanta, GA 30322, United States
| | - Khalid Salaita
- Department of Chemistry, Emory University, Atlanta, GA 30322, United States
- Winship Cancer Institute, Emory University, Atlanta, GA 30322, United States
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia 30322, United States
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11
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Guha TK, Wai A, Mullineux ST, Hausner G. The intron landscape of the mtDNA cytb gene among the Ascomycota: introns and intron-encoded open reading frames. Mitochondrial DNA A DNA Mapp Seq Anal 2017; 29:1015-1024. [DOI: 10.1080/24701394.2017.1404042] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Tuhin K. Guha
- Department of Microbiology, University of Manitoba, Winnipeg, Canada
| | - Alvan Wai
- Department of Microbiology, University of Manitoba, Winnipeg, Canada
| | | | - Georg Hausner
- Department of Microbiology, University of Manitoba, Winnipeg, Canada
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12
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Design and Experimental Evolution of trans-Splicing Group I Intron Ribozymes. Molecules 2017; 22:molecules22010075. [PMID: 28045452 PMCID: PMC6155759 DOI: 10.3390/molecules22010075] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 12/27/2016] [Accepted: 12/29/2016] [Indexed: 12/31/2022] Open
Abstract
Group I intron ribozymes occur naturally as cis-splicing ribozymes, in the form of introns that do not require the spliceosome for their removal. Instead, they catalyze two consecutive trans-phosphorylation reactions to remove themselves from a primary transcript, and join the two flanking exons. Designed, trans-splicing variants of these ribozymes replace the 3′-portion of a substrate with the ribozyme’s 3′-exon, replace the 5′-portion with the ribozyme’s 5′-exon, or insert/remove an internal sequence of the substrate. Two of these designs have been evolved experimentally in cells, leading to variants of group I intron ribozymes that splice more efficiently, recruit a cellular protein to modify the substrate’s gene expression, or elucidate evolutionary pathways of ribozymes in cells. Some of the artificial, trans-splicing ribozymes are promising as tools in therapy, and as model systems for RNA evolution in cells. This review provides an overview of the different types of trans-splicing group I intron ribozymes that have been generated, and the experimental evolution systems that have been used to improve them.
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13
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Abstract
Introns inserted within introns are commonly referred to as twintrons, however the original definition for twintron implied that splicing of the external member of the twintron could only proceed upon splicing of the internal member. This review examines the various types of twintron-like arrangements that have been reported and assigns them to either nested or twintron categories that are subdivided further into subtypes based on differences of their mode of splicing. Twintron-like arrangements evolved independently by fortuitous events among different types of introns but once formed they offer opportunities for the evolution of new regulatory strategies and/or novel genetic elements.
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Affiliation(s)
- Mohamed Hafez
- a Department of Biochemistry ; Faculty of Medicine; University of Montreal ; Montréal , QC Canada.,b Department of Botany and Microbiology ; Faculty of Science; Suez University ; Suez , Egypt
| | - Georg Hausner
- c Department of Microbiology ; University of Manitoba ; Winnipeg , MB Canada
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14
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Kushwaha M, Rostain W, Prakash S, Duncan JN, Jaramillo A. Using RNA as Molecular Code for Programming Cellular Function. ACS Synth Biol 2016; 5:795-809. [PMID: 26999422 DOI: 10.1021/acssynbio.5b00297] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
RNA is involved in a wide-range of important molecular processes in the cell, serving diverse functions: regulatory, enzymatic, and structural. Together with its ease and predictability of design, these properties can lead RNA to become a useful handle for biological engineers with which to control the cellular machinery. By modifying the many RNA links in cellular processes, it is possible to reprogram cells toward specific design goals. We propose that RNA can be viewed as a molecular programming language that, together with protein-based execution platforms, can be used to rewrite wide ranging aspects of cellular function. In this review, we catalogue developments in the use of RNA parts, methods, and associated computational models that have contributed to the programmability of biology. We discuss how RNA part repertoires have been combined to build complex genetic circuits, and review recent applications of RNA-based parts and circuitry. We explore the future potential of RNA engineering and posit that RNA programmability is an important resource for firmly establishing an era of rationally designed synthetic biology.
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Affiliation(s)
- Manish Kushwaha
- Warwick
Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Coventry, CV4 7AL, U.K
| | - William Rostain
- Warwick
Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Coventry, CV4 7AL, U.K
- iSSB, Genopole,
CNRS, UEVE, Université Paris-Saclay, Évry, France
| | - Satya Prakash
- Warwick
Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Coventry, CV4 7AL, U.K
| | - John N. Duncan
- Warwick
Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Coventry, CV4 7AL, U.K
| | - Alfonso Jaramillo
- Warwick
Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Coventry, CV4 7AL, U.K
- iSSB, Genopole,
CNRS, UEVE, Université Paris-Saclay, Évry, France
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15
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Dolan GF, Müller UF. Trans-splicing with the group I intron ribozyme from Azoarcus. RNA (NEW YORK, N.Y.) 2014; 20:202-213. [PMID: 24344321 PMCID: PMC3895272 DOI: 10.1261/rna.041012.113] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 11/02/2013] [Indexed: 06/02/2023]
Abstract
Group I introns are ribozymes (catalytic RNAs) that excise themselves from RNA primary transcripts by catalyzing two successive transesterification reactions. These cis-splicing ribozymes can be converted into trans-splicing ribozymes, which can modify the sequence of a separate substrate RNA, both in vitro and in vivo. Previous work on trans-splicing ribozymes has mostly focused on the 16S rRNA group I intron ribozyme from Tetrahymena thermophila. Here, we test the trans-splicing potential of the tRNA(Ile) group I intron ribozyme from the bacterium Azoarcus. This ribozyme is only half the size of the Tetrahymena ribozyme and folds faster into its active conformation in vitro. Our results showed that in vitro, the Azoarcus and Tetrahymena ribozymes favored the same set of splice sites on a substrate RNA. Both ribozymes showed the same trans-splicing efficiency when containing their individually optimized 5' terminus. In contrast to the previously optimized 5'-terminal design of the Tetrahymena ribozyme, the Azoarcus ribozyme was most efficient with a trans-splicing design that resembled the secondary structure context of the natural cis-splicing Azoarcus ribozyme, which includes base-pairing between the substrate 5' portion and the ribozyme 3' exon. These results suggested preferred trans-splicing interactions for the Azoarcus ribozyme under near-physiological in vitro conditions. Despite the high activity in vitro, however, the splicing efficiency of the Azoarcus ribozyme in Escherichia coli cells was significantly below that of the Tetrahymena ribozyme.
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MESH Headings
- Azoarcus/enzymology
- Azoarcus/genetics
- Base Sequence
- Chloramphenicol O-Acetyltransferase/genetics
- Escherichia coli
- Inverted Repeat Sequences
- Molecular Sequence Data
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Catalytic/chemistry
- RNA, Catalytic/genetics
- RNA, Catalytic/metabolism
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Protozoan/chemistry
- RNA, Protozoan/genetics
- RNA, Protozoan/metabolism
- Substrate Specificity
- Tetrahymena thermophila/enzymology
- Trans-Splicing
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16
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Vazquez-Anderson J, Contreras LM. Regulatory RNAs: charming gene management styles for synthetic biology applications. RNA Biol 2013; 10:1778-97. [PMID: 24356572 DOI: 10.4161/rna.27102] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
RNAs have many important functional properties, including that they are independently controllable and highly tunable. As a result of these advantageous properties, their use in a myriad of sophisticated devices has been widely explored. Yet, the exploitation of RNAs for synthetic applications is highly dependent on the ability to characterize the many new molecules that continue to be discovered by large-scale sequencing and high-throughput screening techniques. In this review, we present an exhaustive survey of the most recent synthetic bacterial riboswitches and small RNAs while emphasizing their virtues in gene expression management. We also explore the use of these RNA components as building blocks in the RNA synthetic biology toolbox and discuss examples of synthetic RNA components used to rewire bacterial regulatory circuitry. We anticipate that this field will expand its catalog of smart devices by mimicking and manipulating natural RNA mechanisms and functions.
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Affiliation(s)
- Jorge Vazquez-Anderson
- McKetta Department of Chemical Engineering; University of Texas at Austin; Austin, TX USA
| | - Lydia M Contreras
- McKetta Department of Chemical Engineering; University of Texas at Austin; Austin, TX USA
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17
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Amini ZN, Müller UF. Low selection pressure aids the evolution of cooperative ribozyme mutations in cells. J Biol Chem 2013; 288:33096-106. [PMID: 24089519 DOI: 10.1074/jbc.m113.511469] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Understanding the evolution of functional RNA molecules is important for our molecular understanding of biology. Here we tested experimentally how two evolutionary parameters, selection pressure and recombination, influenced the evolution of an evolving RNA population. This was done using four parallel evolution experiments that employed low or gradually increasing selection pressure, and recombination events either at the end or dispersed throughout the evolution. As model system, a trans-splicing group I intron ribozyme was evolved in Escherichia coli cells over 12 rounds of selection and amplification, including mutagenesis and recombination. The low selection pressure resulted in higher efficiency of the evolved ribozyme populations, whereas differences in recombination did not have a strong effect. Five mutations were responsible for the highest efficiency. The first mutation swept quickly through all four evolving populations, whereas the remaining four mutations accumulated later and more efficiently under low selection pressure. To determine why low selection pressure aided this evolution, all evolutionary intermediates between the wild type and the 5-mutation variant were constructed, and their activities at three different selection pressures were determined. The resulting fitness profiles showed a high cooperativity among the four late mutations, which can explain why high selection pressure led to inefficient evolution. These results show experimentally how low selection pressure can benefit the evolution of cooperative mutations in functional RNAs.
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Affiliation(s)
- Zhaleh N Amini
- From the Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093
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18
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Hedberg A, Johansen SD. Nuclear group I introns in self-splicing and beyond. Mob DNA 2013; 4:17. [PMID: 23738941 PMCID: PMC3679873 DOI: 10.1186/1759-8753-4-17] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Accepted: 05/14/2013] [Indexed: 01/09/2023] Open
Abstract
Group I introns are a distinct class of RNA self-splicing introns with an ancient origin. All known group I introns present in eukaryote nuclei interrupt functional ribosomal RNA genes located in ribosomal DNA loci. The discovery of the Tetrahymena intron more than 30 years ago has been essential to our understanding of group I intron catalysis, higher-order RNA structure, and RNA folding, but other intron models have provided information about the biological role. Nuclear group I introns appear widespread among eukaryotic microorganisms, and the plasmodial slime molds (myxomycetes) contain an abundance of self-splicing introns. Here, we summarize the main conclusions from previous work on the Tetrahymena intron on RNA self-splicing catalysis as well as more recent work on myxomycete intron biology. Group I introns in myxomycetes that represent different evolutionary stages, biological roles, and functional settings are discussed.
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Affiliation(s)
- Annica Hedberg
- RNA lab-RAMP, Department of Medical Biology, Faculty of Health Sciences, University of Tromsø, Tromsø N-9037, Norway.
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19
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Abstract
Group I intron ribozymes constitute one of the main classes of ribozymes and have been a particularly important model in the discovery of key concepts in RNA biology as well as in the development of new methods. Compared to other ribozyme classes, group I intron ribozymes display considerable variation both in their structure and the reactions they catalyze. The best described pathway is the splicing pathway that results in a spliced out intron and ligated exons. This is paralleled by the circularization pathway that leads to full-length circular intron and un-ligated exons. In addition, the intronic products of these pathways have the potential to integrate into targets and to form various types of circular RNA molecules. Thus, group I intron ribozymes and associated elements found within group I introns is a rich source of biological phenomena. This chapter provides a strategy and protocols for initial characterization of new group I intron ribozymes.
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Affiliation(s)
- Henrik Nielsen
- Department of Cellular and Molecular Medicine, The Panum Institute, University of Copenhagen, Copenhagen, Denmark.
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20
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Abstract
Spliceosome-mediated RNA trans-splicing (SMaRT) is an RNA-based technology to reprogram genes for diagnostic and therapeutic purposes. For the correction of genetic diseases, SMaRT offers several advantages over traditional gene-replacement strategies. SMaRT protocols have recently been used for in vitro phenotypic correction of a variety of genetic disorders, ranging from epidermolysis bullosa to neurodegenerative diseases. In vivo studies are currently bringing trans-splicing RNA therapy toward clinical application. In this review, we summarize the progress made toward the medical use of SMaRT and provide an outlook on its upcoming applications.
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21
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Meluzzi D, Olson KE, Dolan GF, Arya G, Müller UF. Computational prediction of efficient splice sites for trans-splicing ribozymes. RNA (NEW YORK, N.Y.) 2012; 18:590-602. [PMID: 22274956 PMCID: PMC3285945 DOI: 10.1261/rna.029884.111] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 12/02/2011] [Indexed: 05/31/2023]
Abstract
Group I introns have been engineered into trans-splicing ribozymes capable of replacing the 3'-terminal portion of an external mRNA with their own 3'-exon. Although this design makes trans-splicing ribozymes potentially useful for therapeutic application, their trans-splicing efficiency is usually too low for medical use. One factor that strongly influences trans-splicing efficiency is the position of the target splice site on the mRNA substrate. Viable splice sites are currently determined using a biochemical trans-tagging assay. Here, we propose a rapid and inexpensive alternative approach to identify efficient splice sites. This approach involves the computation of the binding free energies between ribozyme and mRNA substrate. We found that the computed binding free energies correlate well with the trans-splicing efficiency experimentally determined at 18 different splice sites on the mRNA of chloramphenicol acetyl transferase. In contrast, our results from the trans-tagging assay correlate less well with measured trans-splicing efficiency. The computed free energy components suggest that splice site efficiency depends on the following secondary structure rearrangements: hybridization of the ribozyme's internal guide sequence (IGS) with mRNA substrate (most important), unfolding of substrate proximal to the splice site, and release of the IGS from the 3'-exon (least important). The proposed computational approach can also be extended to fulfill additional design requirements of efficient trans-splicing ribozymes, such as the optimization of 3'-exon and extended guide sequences.
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Affiliation(s)
- Dario Meluzzi
- Department of Chemistry and Biochemistry, University of California, San Diego, California 92093, USA
- Department of NanoEngineering, University of California, San Diego, California 92093, USA
| | - Karen E. Olson
- Department of Chemistry and Biochemistry, University of California, San Diego, California 92093, USA
| | - Gregory F. Dolan
- Department of Chemistry and Biochemistry, University of California, San Diego, California 92093, USA
| | - Gaurav Arya
- Department of NanoEngineering, University of California, San Diego, California 92093, USA
| | - Ulrich F. Müller
- Department of Chemistry and Biochemistry, University of California, San Diego, California 92093, USA
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22
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Olson KE, Müller UF. An in vivo selection method to optimize trans-splicing ribozymes. RNA (NEW YORK, N.Y.) 2012; 18:581-589. [PMID: 22274958 PMCID: PMC3285944 DOI: 10.1261/rna.028472.111] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Accepted: 12/01/2011] [Indexed: 05/31/2023]
Abstract
Group I intron ribozymes can repair mutated mRNAs by replacing the 3'-terminal portion of the mRNA with their own 3'-exon. This trans-splicing reaction has the potential to treat genetic disorders and to selectively kill cancer cells or virus-infected cells. However, these ribozymes have not yet been used in therapy, partially due to a low in vivo trans-splicing efficiency. Previous strategies to improve the trans-splicing efficiencies focused on designing and testing individual ribozyme constructs. Here we describe a method that selects the most efficient ribozymes from millions of ribozyme variants. This method uses an in vivo rescue assay where the mRNA of an inactivated antibiotic resistance gene is repaired by trans-splicing group I intron ribozymes. Bacterial cells that express efficient trans-splicing ribozymes are able to grow on medium containing the antibiotic chloramphenicol. We randomized a 5'-terminal sequence of the Tetrahymena thermophila group I intron and screened a library with 9 × 10⁶ ribozyme variants for the best trans-splicing activity. The resulting ribozymes showed increased trans-splicing efficiency and help the design of efficient trans-splicing ribozymes for different sequence contexts. This in vivo selection method can now be used to optimize any sequence in trans-splicing ribozymes.
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Affiliation(s)
- Karen E. Olson
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA
| | - Ulrich F. Müller
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA
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23
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Noguchi K, Ishitu Y, Takaku H. Evaluating target silencing by short hairpin RNA mediated by the group I intron in cultured mammalian cells. BMC Biotechnol 2011; 11:79. [PMID: 21781346 PMCID: PMC3151216 DOI: 10.1186/1472-6750-11-79] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Accepted: 07/25/2011] [Indexed: 02/07/2023] Open
Abstract
Background The group I intron, a ribozyme that catalyzes its own splicing reactions in the absence of proteins in vitro, is a potential target for rational engineering and attracted our interest due to its potential utility in gene repair using trans-splicing. However, the ribozyme activity of a group I intron appears to be facilitated by RNA chaperones in vivo; therefore, the efficiency of self-splicing could be dependent on the structure around the insert site or the length of the sequence to be inserted. To better understand how ribozyme activity could be modulated in cultured mammalian cells, a group I intron was inserted into a short hairpin RNA (shRNA), and silencing of a reporter gene by the shRNA was estimated to reflect self-splicing activity in vivo. In addition, we appended a theophylline-binding aptamer to the ribozyme to investigate any potential effects caused by a trans-effector. Results shRNA-expression vectors in which the loop region of the shRNA was interrupted by an intron were constructed to target firefly luciferase mRNA. There was no remarkable toxicity of the shRNA-expression vectors in Cos cells, and the decrease in luciferase activity was measured as an index of the ribozyme splicing activity. In contrast, the expression of the shRNA through intron splicing was completely abolished in 293T cells, although the silencing induced by the shRNA-expressing vector alone was no different from that in the Cos cells. The splicing efficiency of the aptamer-appended intron also had implications for the potential of trans-factors to differentially promote self-splicing among cultured mammalian cells. Conclusions Silencing by shRNAs interrupted by a group I intron could be used to monitor self-splicing activity in cultured mammalian cells, and the efficiency of self-splicing appears to be affected by cell-type specific factors, demonstrating the potential effectiveness of a trans-effector.
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Affiliation(s)
- Kousei Noguchi
- Department of Life and Environmental Science, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan
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24
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The application of ribozymes and DNAzymes in muscle and brain. Molecules 2010; 15:5460-72. [PMID: 20714308 PMCID: PMC6257783 DOI: 10.3390/molecules15085460] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 08/03/2010] [Accepted: 08/05/2010] [Indexed: 12/04/2022] Open
Abstract
The discovery of catalytic nucleic acids (CNAs) has provided scientists with valuable tools for the identification of new therapies for several untreated diseases through down regulation or modulation of endogenous gene expression involved in these ailments. These CNAs aim either towards the elimination or repair of pathological gene expression. Ribozymes, a class of CNAs, can be mostly used to down-regulate (by RNA cleavage) or repair (by RNA trans-splicing) unwanted gene expression involved in disease. DNAzymes, derived by in vitro selection processes are also able to bind and cleave RNA targets and therefore down-regulate gene expression. The purpose of this review is to present and discuss several applications of ribozymes and DNAzymes in muscle and brain. There are several diseases which affect muscle and brain and catalytic nucleic acids have been used as tools to target specific cellular transcripts involved in these groups of diseases.
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