A Brief History of Genetic Therapy: Gene Therapy, Antisense Technology, and Genomics
Eric Wickstrom in Clinical Trials of Genetic Therapy with Antisense DNA and DNA Vectors, 2020
Catalytic RNAs are RNA structures capable of cleaving covalent bonds in an RNA molecule. Catalytic RNAs were first described by Cech's laboratory (Zaug et al., 1980; Cech et al., 1981; Kruger et al., 1982) and Altman etal. (Guerrier-Takada et al., 1983). Cech described the catalytic removal of introns in the pre-rRNA of the ciliated protozoan, Tetrahymena thermophila. The term "ribozyme" describes RNA (ribonucleic acid) molecules with catalytic properties analogous to enzymes, as explained by Kruger et al. (1982), Because the IVS RNA is not an enzyme but has some enzyme-like characteristics, we call it a ribozyme, an RNA molecule that has the intrinsic ability to break and form covalent bonds.
The science of biotechnology
Ronald P. Evens in Biotechnology, 2020
Ribozymes are RNA molecules comprising sequences of nucleic acids that possess enzymatic catalytic properties and bind to specific sites in DNA or RNA and cleave the chain. A ribozyme will have subunits responsible for the binding function and subunits responsible for enzyme function. They generally have the following desirable traits: specificity in targeting, cleavage of target RNA, small size amenable to formulation and dosing, and multiple turnover (one molecule binds and acts and then moves on to next molecule and repeats its function). However, challenges are manifold; for example, the need for cell insertion (transfection), nuclease protection in the blood, and chaperone proteins for movement in cell cytoplasm. No products have yet been approved. Aptamers are small oligonucleotide molecules that bind to proteins to disrupt disease pathogenesis. Their benefits are small molecular size, specificity toward target protein, and low immunogenicity; however, limitations are nuclease susceptibility, short systemic half-lives, and possibly limited affinity to targets. Proof of principle has been achieved as one aptamer has been approved for use, a pegylated conjugate of an oligonucleotide for wet acute macular degeneration, pegaptanib (Macugen®). The pegylation protects the molecule from lysis from nucleases, and offers a longer serum half-life and a measure of immunity.
Therapies to Prevent or Inhibit Chemokine Receptor Expression
Thomas R. O’Brien in Chemokine Receptors and AIDS, 2019
Ribozymes are enzymatic RNA molecules that can be designed to specifically recognize and cleave other RNAs. By disrupting the normal coding sequence of the RNA molecule, ribozymes can prevent or diminish the translation of proteins encoded by the targeted sequence. The first studies to target HIV were directed at inhibition of HIV gag expression (110) and to sequences in the 5’ LTR of the HIV genome (111). Several groups have developed ribozymes targeted to CCR5 (112,113 and J Rossi, personal communication). Where reported (112), ribozyme effects on CCR5 expression have not been dramatic (a 60% reduction in a cell line co-transfected with CCR5 and a 20-fold molar excess of plasmid encoding the ribozyme) and have not yet been analyzed for effects on HIV infectivity. Attempts to improve ribozyme expression or intracellular localization, or to pair ribozyme and other HIV-inhibitory strategies, may be required to advance this concept.
Challenges with the discovery of RNA-based therapeutics for flaviviruses
Published in Expert Opinion on Drug Discovery, 2023
Mei-Yue Wang, Rong Zhao, Yu-Lan Wang, De-Ping Wang, Ji-Min Cao
In addition, there are some ribozyme-based strategies against flaviviruses. Ribozymes are small RNA molecules with catalytic activity and can target the particular site of RNA to cleave it. For instance, Nawtaisong et al. [36] constructed 14 hammerhead ribozymes and tested the effectiveness of these ribozymes in the suppression of DENV-2 replication in lentivirus-transduced mosquito cells. The ribozymes were expressed using pan retroviral vectors and controlled by Aedes aegypti tRNAval promoter. In lentivirus-transduced C6/36 mosquito cells, 100-fold suppression of virus replication could be observed. Another study designed the group I trans-splicing introns (a type of ribozyme) to target the conserved 5’-3’ cyclization sequence (CS) region which is common to all four DENV serotypes (DENV-1–4) [37]. The examples are presented in Table 1.
The discovery and development of RNA-based therapies for treatment of HIV-1 infection
Published in Expert Opinion on Drug Discovery, 2023
Michelle J Chen, Anne Gatignol, Robert J. Scarborough
Ribozymes are RNAs that catalyze biochemical reactions. The first ribozyme was identified in self-splicing introns, where the RNA catalyzes both cleavage and ligation reactions that result in the excision of the intron from the transcript [38]. Subsequently, it was shown that RNA is the catalytic moiety in RNase P complexes that cleave pre-transfer (t)RNAs [39] and in ribosomes, where ribosomal RNA is responsible for catalyzing the linkage of amino acids to form proteins [40]. The most diverse group of ribozymes are the small, naturally occurring, self-cleaving ribozymes from which most ribozyme therapies have been derived [29,41]. Although these ribozymes catalyze self-cleavage reactions, they can be easily modified to cleave in trans and designed to target an RNA through complementary base pairing. An advantage of small self-cleaving ribozyme motifs is that they do not require cellular proteins to catalyze target cleavage, limiting their ability to disturb cellular physiology. Examples of trans-cleaving ribozymes based on these motifs are shown in Figure 1.
Virus-associated ribozymes and nano carriers against COVID-19
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2021
Beyza Dönmüş, Sinan Ünal, Fatma Ceren Kirmizitaş, Nelisa Türkoğlu Laçin
Although the ribozymes in this group appear to be the same as many other proteinase enzymes, ribozymes only affect specific phosphodiester bonds using their base mapping and other interactions to determine the cut site within their active region [64]. Several hundred nucleotides length group I and II introns and RNase P are larger, structurally more complex ribozymes. These two groups can be distinguished according to their class of introns, splicing mechanisms and secondary structures [65]. Group I introns are part of the precursor rRNA transcripts and do not require a separate component to be removed from the construct. The source of the catalytic activity is in the intron itself. Group II introns are part of the precursor mRNA and tRNA transcripts produced in mitochondria and chloroplasts, and unlike group I introns, they do not require a guanosine cofactor for catalytic activity [66]. We have summarized the types of ribozymes below.
Related Knowledge Centers
- Catalysis
- DNA
- Enzyme
- Gene Expression
- Ribosome
- Rna
- Rna Splicing
- Rna
- Rna Splicing
- DNA
- Rna World
- Directed Evolution
- Translation