Near-cognate tRNAs increase the efficiency and precision of pseudouridine-mediated readthrough of premature termination codons
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ABSTRACT:
ORGANISM(S): Mus musculus Homo sapiens
PROVIDER: GSE237633 | GEO | 2024/01/29
REPOSITORIES: GEO
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Project description:Nonsense mutations, responsible for ~11% of genetic diseases, create premature stop codons (PTCs) and lead to truncated and often non-functional proteins. Recently, programmable RNA pseudouridylation has emerged as a new type of RNA base editor to suppress PTCs. However, current methods suffer from low efficiency and limited precision. Here, we develop RESTART v3, an updated version of RESTART, which utilizes near-cognate tRNAs to improve the readthrough efficiency of pseudouridine-modified PTCs. We show an average of ~5-fold higher editing efficiency than RESTART v2 in cultured cells, currently the most active RNA pseudouridylation tool to mediate PTC readthrough. Moreover, RESTART v3 achieves functional PTC readthrough in disease cell models of cystic fibrosis and Hurler syndrome. Furthermore, RESTART v3 enables accurate incorporation of the original amino acid for nearly half of the PTC sites, considering the naturally occurring frequencies of sense to nonsense codons. In line with the benign off-target effect of RESTART, RESTART v3 does not change the coding information nor the expression level of transcripts with off-target editing; except for the specifically overexpressed tRNA molecule, it does not alter the expression level of endogenous tRNA pool. Overall, RESTART v3 represents an enhanced RNA base editor with increased efficiency and accuracy.
2024-01-29 | GSE237632 | GEO
Project description:Nonsense mutations, responsible for ~11% of genetic diseases, create premature stop codons (PTCs) and lead to truncated and often non-functional proteins. Recently, programmable RNA pseudouridylation has emerged as a new type of RNA base editor to suppress PTCs. However, current methods suffer from low efficiency and limited precision. Here, we develop RESTART v3, an updated version of RESTART, which utilizes near-cognate tRNAs to improve the readthrough efficiency of pseudouridine-modified PTCs. We show an average of ~5-fold higher editing efficiency than RESTART v2 in cultured cells, currently the most active RNA pseudouridylation tool to mediate PTC readthrough. Moreover, RESTART v3 achieves functional PTC readthrough in disease cell models of cystic fibrosis and Hurler syndrome. Furthermore, RESTART v3 enables accurate incorporation of the original amino acid for nearly half of the PTC sites, considering the naturally occurring frequencies of sense to nonsense codons. In line with the benign off-target effect of RESTART, RESTART v3 does not change the coding information nor the expression level of transcripts with off-target editing; except for the specifically overexpressed tRNA molecule, it does not alter the expression level of endogenous tRNA pool. Overall, RESTART v3 represents an enhanced RNA base editor with increased efficiency and accuracy.
2024-01-29 | GSE237631 | GEO
Project description:Nonsense mutations, responsible for ~11% of genetic diseases, create premature stop codons (PTCs) and lead to truncated and often non-functional proteins. Recently, programmable RNA pseudouridylation has emerged as a new type of RNA base editor to suppress PTCs. However, current methods suffer from low efficiency and limited precision. Here, we develop RESTART v3, an updated version of RESTART, which utilizes near-cognate tRNAs to improve the readthrough efficiency of pseudouridine-modified PTCs. We show an average of ~5-fold higher editing efficiency than RESTART v2 in cultured cells, currently the most active RNA pseudouridylation tool to mediate PTC readthrough. Moreover, RESTART v3 achieves functional PTC readthrough in disease cell models of cystic fibrosis and Hurler syndrome. Furthermore, RESTART v3 enables accurate incorporation of the original amino acid for nearly half of the PTC sites, considering the naturally occurring frequencies of sense to nonsense codons. In line with the benign off-target effect of RESTART, RESTART v3 does not change the coding information nor the expression level of transcripts with off-target editing; except for the specifically overexpressed tRNA molecule, it does not alter the expression level of endogenous tRNA pool. Overall, RESTART v3 represents an enhanced RNA base editor with increased efficiency and accuracy.
2024-01-29 | GSE237630 | GEO
Project description:Nonsense mutations, responsible for ~11% of genetic diseases, create premature stop codons (PTCs) and lead to truncated and often non-functional proteins. Recently, programmable RNA pseudouridylation has emerged as a new type of RNA base editor to suppress PTCs. However, current methods suffer from low efficiency and limited precision. Here, we develop RESTART v3, an updated version of RESTART, which utilizes near-cognate tRNAs to improve the readthrough efficiency of pseudouridine-modified PTCs. We show an average of ~5-fold higher editing efficiency than RESTART v2 in cultured cells, currently the most active RNA pseudouridylation tool to mediate PTC readthrough. Moreover, RESTART v3 achieves functional PTC readthrough in disease cell models of cystic fibrosis and Hurler syndrome. Furthermore, RESTART v3 enables accurate incorporation of the original amino acid for nearly half of the PTC sites, considering the naturally occurring frequencies of sense to nonsense codons. In line with the benign off-target effect of RESTART, RESTART v3 does not change the coding information nor the expression level of transcripts with off-target editing; except for the specifically overexpressed tRNA molecule, it does not alter the expression level of endogenous tRNA pool. Overall, RESTART v3 represents an enhanced RNA base editor with increased efficiency and accuracy.
2024-01-29 | GSE237629 | GEO
Project description:The molecular mechanism of stop codon recognition by the release factor eRF1 in complex with eRF3 has been described in great detail; however, our understanding of what determines the difference in termination efficiencies among various stop codon tetranucleotides and how near-cognate (nc) tRNAs recode stop codons during programmed readthrough in Saccharomyces cerevisiae is still poor. Here, we show that UGA-C as the only tetranucleotide of all four possible combinations dramatically exacerbated the readthrough phenotype of the stop codon recognition-deficient mutants in eRF1. Since the same is true also for UAA-C and UAG-C, we propose that the exceptionally high readthrough levels that all three stop codons display when followed by cytosine are partially caused by the compromised sampling ability of eRF1, which specifically senses cytosine at the +4 position. The difference in termination efficiencies among the remaining three UGA-N tetranucleotides is then given by their varying preferences for nc-tRNAs. In particular, UGA-A allows increased incorporation of Trp-tRNA whereas UGA-G and UGA-C favor Cys-tRNA. Our findings thus expand the repertoire of general decoding rules by showing that the +4 base determines the preferred selection of nc-tRNAs and, in the case of cytosine, it also genetically interacts with eRF1. Finally, using an example of the GCN4 translational control governed by four short uORFs, we also show how the evolution of this mechanism dealt with undesirable readthrough on those uORFs that serve as the key translation reinitiation promoting features of the GCN4 regulation, as both of these otherwise counteracting activities, readthrough versus reinitiation, are mediated by eIF3.
| S-EPMC4748822 | biostudies-literature
Project description:One-third of monogenic inherited diseases result from premature termination codons (PTCs). Readthrough of in-frame PTCs enables synthesis of full-length functional proteins. However, extended variability in the response to readthrough treatment is found among patients, which correlates with the level of nonsense transcripts. Here, we aimed to reveal cellular pathways affecting this inter-patient variability. We show that activation of the unfolded protein response (UPR) governs the response to readthrough treatment by regulating the levels of transcripts carrying PTCs. Quantitative proteomic analyses showed substantial differences in UPR activation between patients carrying PTCs, correlating with their response. We further found a significant inverse correlation between the UPR and nonsense-mediated mRNA decay (NMD), suggesting a feedback loop between these homeostatic pathways. We uncovered and characterized the mechanism underlying this NMD-UPR feedback loop, which augments both UPR activation and NMD attenuation. Importantly, this feedback loop enhances the response to readthrough treatment, highlighting its clinical importance. Altogether, our study demonstrates the importance of the UPR and its regulatory network for genetic diseases caused by PTCs and for cell homeostasis under normal conditions.
| S-EPMC4023889 | biostudies-literature
Project description:Premature termination codons (PTCs) are generally associated with severe forms of genetic diseases. Readthrough of in-frame PTCs using small molecules is a promising therapeutic approach. Nonetheless, the outcome of preclinical studies has been low and variable. Treatment efficacy depends on: 1) the level of drug-induced readthrough, 2) the amount of target transcripts, and 3) the activity of the recoded protein. The aim of the present study was to identify, in the cystic fibrosis transmembrane conductance regulator (CFTR) model, recoded channels from readthrough therapy that may be enhanced using CFTR modulators. First, drug-induced readthrough of 15 PTCs was measured using a dual reporter system under basal conditions and in response to gentamicin and negamycin. Secondly, exon skipping associated with these PTCs was evaluated with a minigene system. Finally, incorporated amino acids were identified by mass spectrometry and the function of the predicted recoded CFTR channels corresponding to these 15 PTCs was measured. Nonfunctional channels were subjected to CFTR-directed ivacaftor-lumacaftor treatments. The results demonstrated that CFTR modulators increased activity of recoded channels, which could also be confirmed in cells derived from a patient. In conclusion, this work will provide a framework to adapt treatments to the patient's genotype by identifying the most efficient molecule for each PTC and the recoded channels needing co-therapies to rescue channel function.
| S-EPMC5827411 | biostudies-literature
Project description:Nonsense mutations introduce a premature termination codon (PTC) and are the underlying cause of multiple rare genetic diseases and cancers. Although certain aminoglycosides bind to eukaryotic ribosomes enabling incorporation of an amino acid at the PTC and formation of full-length protein, they are inefficient and toxic at therapeutic doses. Library screening in assays that measure readthrough at a PTC in the TP53 gene in human HDQ-P1 cells identified six novel 2-aminothiazole-4-carboxamide derivatives that potentiate the PTC readthrough (PTCR) efficiency of G418 when used in combination. The two most potent compounds incorporated a 4-indazole motif on the 2-aminothiazole nitrogen and a hydrophobic aryl substituent on the carboxamide nitrogen. These compounds are valuable tools to further investigate the therapeutic potential of aminoglycoside-induced PTCR.
| S-EPMC6511968 | biostudies-literature
Project description:BackgroundDecoding of mRNAs is performed by aminoacyl tRNAs (aa-tRNAs). This process is highly accurate, however, at low frequencies (10(-3) - 10(-4)) the wrong aa-tRNA can be selected, leading to incorporation of aberrant amino acids. Although our understanding of what constitutes the correct or cognate aa-tRNA:mRNA interaction is well defined, a functional distinction between near-cognate or single mismatched, and unpaired or non-cognate interactions is lacking.Methodology/principal findingsMisreading of several synonymous codon substitutions at the catalytic site of firefly luciferase was assayed in Saccharomyces cerevisiae. Analysis of the results in the context of current kinetic and biophysical models of aa-tRNA selection suggests that the defining feature of near-cognate aa-tRNAs is their potential to form mini-helical structures with A-site codons, enabling stimulation of GTPase activity of eukaryotic Elongation Factor 1A (eEF1A). Paromomycin specifically stimulated misreading of near-cognate but not of non-cognate aa-tRNAs, providing a functional probe to distinguish between these two classes. Deletion of the accessory elongation factor eEF1Bgamma promoted increased misreading of near-cognate, but hyperaccurate reading of non-cognate codons, suggesting that this factor also has a role in tRNA discrimination. A mutant of eEF1Balpha, the nucleotide exchange factor for eEF1A, promoted a general increase in fidelity, suggesting that the decreased rates of elongation may provide more time for discrimination between aa-tRNAs. A mutant form of ribosomal protein L5 promoted hyperaccurate decoding of both types of codons, even though it is topologically distant from the decoding center.Conclusions/significanceIt is important to distinguish between near-cognate and non-cognate mRNA:tRNA interactions, because such a definition may be important for informing therapeutic strategies for suppressing these two different categories of mutations underlying many human diseases. This study suggests that the defining feature of near-cognate aa-tRNAs is their potential to form mini-helical structures with A-site codons in the ribosomal decoding center. An aminoglycoside and a ribosomal factor can be used to distinguish between near-cognate and non-cognate interactions.
| S-EPMC1885216 | biostudies-literature
Project description:Cystic fibrosis (CF) is caused by a mutation of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene, which disrupts an ion channel involved in hydration maintenance via anion homeostasis. Nearly 5% of CF patients possess one or more copies of the G542X allele, which results in a stop codon at residue 542, preventing full-length CFTR protein synthesis. Identifying small-molecule modulators of mutant CFTR biosynthesis that affect the readthrough of this and other premature termination codons to synthesize a fully functional CFTR protein represents a novel target area of drug discovery. We describe the implementation and integration for large-scale screening of a homogeneous, 1536-well functional G542X-CFTR readthrough assay. The assay uses HEK 293 cells engineered to overexpress the G542X-CFTR mutant, whose functional activity is monitored with a membrane potential dye. Cells are co-incubated with a CFTR amplifier and CFTR corrector to maximize mRNA levels and trafficking of CFTR to the cell surface. Compounds that allow translational readthrough and synthesis of functional CFTR chloride channels are reflected by changes in membrane potential in response to cAMP stimulation with forskolin and CFTR channel potentiation with genistein. Assay statistics yielded Z' values of 0.69 ± 0.06. As further evidence of its suitability for high-throughput screening, we completed automated screening of approximately 666,000 compounds, identifying 7761 initial hits. Following secondary and tertiary assays, we identified 188 confirmed hit compounds with low and submicromolar potencies. Thus, this approach takes advantage of a phenotypic screen with high-throughput scalability to identify new small-molecule G542X-CFTR readthrough modulators.
| S-EPMC7838340 | biostudies-literature