scholarly journals Developing PspCas13b-based enhanced RESCUE system, eRESCUE, with efficient RNA base editing

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Guo Li ◽  
Yihan Wang ◽  
Xiangyang Li ◽  
Yuzhe Wang ◽  
Xingxu Huang ◽  
...  
Keyword(s):  
Genetic Code ◽  
Rna Editing ◽  
Genetic Diseases ◽  
Disease Treatment ◽  
Editing Efficiency ◽  
Base Editing ◽  
Rescue System ◽  
Adenine Deaminase ◽  
Deaminase Domain

AbstractRNA base editing is potential for cellular function research and genetic diseases treating. There are two main RNA base editors, REPAIR and RESCUE, for in vitro use. REPAIR was developed by fusing inactivated Cas13 (dCas13) with the adenine deaminase domain of ADAR2, which efficiently performs adenosine-to-inosine (A-to-I) RNA editing. RESCUE, which performs both cytidine-to-uridine (C-to-U) and A-to-I RNA editing, was developed by fusing inactivated Cas13 (dCas13) with the evolved ADAR2. However, the relatively low editing efficiency of the RESCUE system limits its broad application. Here, we constructed an enhanced RESCUE (eRESCUE) system; this dPspCas13b-RESCUE-NES system was generated by fusing inactivated PspCas13b with the evolved ADAR2. We determined the endogenous mRNA A-to-I and C-to-U editing efficiency mediated by the dPspCas13b-RESCUE-NES system in HEK-293T cells. This new RNA base editor was then used to induce 177Ser/Gly conversion of inhibitor kappa B kinase β (IKKβ) by changing the genetic code from AGU to GGU. The results showed that the eRESCUE editor mediates more efficient A-to-I and C-to-U RNA editing than the RESCUE RNA editor, as was previously reported. The 177Ser/Gly conversion of IKKβ, accomplished by converting the genetic code from AGU to GGU, resulted in a decrease in the phosphorylation of IKKβ and downregulation of downstream IKKβ-related genes. In summary, we developed a more efficient RNA base editor, eRESCUE, which may provide a useful tool for biomedical research and genetic disease treatment.

scholarly journals ecRESCUE: a novel ecDHFR-regulated RESCUE system with reduced RNA off-targeting activity

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Yihan Wang ◽  
Guo Li ◽  
Xiangyang Li ◽  
Yuzhe Wang ◽  
Xingxu Huang ◽  
...  
Keyword(s):  
Genetic Diseases ◽  
Transcriptional Level ◽  
In Vitro Experiments ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Considerable Potential ◽  
Base Editing ◽  
High Incidence ◽  
Rescue System

AbstractThe currently available RESCUE RNA base editing system demonstrates considerable potential for the treatment of genetic diseases at the transcriptional level. However, the relatively high incidence of off-target events hampers the precise RNA editing, thereby limiting its use in the clinical setting. This study describes a new RNA base editing method, named ecRESCUE, which utilizes inducible stabilization of the protein ecDHFR DD fused at the C-terminal of the original RESCUE system. In vitro experiments in 293T cells showed that the ecRESCUE editor markedly reduced the incidence of off-target single nucleotide polymorphisms without affecting the RNA A-to-I and C-to-U base editing efficiency. Altogether, these results demonstrate that the inducible ecRESCUE system represents an attractive approach to regulate and improve the outcome of the available RNA base editor with reduced off-targeting activity.

scholarly journals ecRESCUE: a novel ecDHFR-regulated RESCUE system with reduced RNA off-targeting activity

2021 ◽  
Author(s):  
Jianen Gao ◽  
Yihan Wang ◽  
Guo Li ◽  
Xiangyang Li ◽  
Yuzhe Wang ◽  
...  
Keyword(s):  
Genetic Diseases ◽  
Transcriptional Level ◽  
In Vitro Experiments ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Considerable Potential ◽  
Base Editing ◽  
High Incidence ◽  
Rescue System

Abstract The currently available RESCUE RNA base editing system demonstrates considerable potential for the treatment of genetic diseases at the transcriptional level. However, the relatively high incidence of off-target events hampers the precise RNA editing, thereby limiting its use in the clinical setting. This study describes a new RNA base editing method, named ecRESCUE, which utilizes inducible stabilization of the protein ecDHFR DD fused at the C-terminal of the original RESCUE system. In vitro experiments in 293T cells showed that the ecRESCUE editor markedly reduced the incidence of off-target single nucleotide polymorphisms without affecting the RNA A-to-I and C-to-U base editing efficiency. Altogether, these results demonstrate that the inducible ecRESCUE system represents an attractive approach to regulate and improve the outcome of the available RNA base editor with reduced off-targeting activity.

scholarly journals A cytosine deaminase for programmable single-base RNA editing

Science ◽  
2019 ◽  
Vol 365 (6451) ◽  
pp. 382-386 ◽  
Author(s):  
Omar O. Abudayyeh ◽  
Jonathan S. Gootenberg ◽  
Brian Franklin ◽  
Jeremy Koob ◽  
Max J. Kellner ◽  
...  
Keyword(s):  
Rna Editing ◽  
Cytidine Deaminase ◽  
Cytosine Deaminase ◽  
Cellular Growth ◽  
Disease Treatment ◽  
Guide Rnas ◽  
Rna Targeting ◽  
Editing Activity ◽  
Adenine Deaminase ◽  
Deaminase Domain

Programmable RNA editing enables reversible recoding of RNA information for research and disease treatment. Previously, we developed a programmable adenosine-to-inosine (A-to-I) RNA editing approach by fusing catalytically inactivate RNA-targeting CRISPR-Cas13 (dCas13) with the adenine deaminase domain of ADAR2. Here, we report a cytidine-to-uridine (C-to-U) RNA editor, referred to as RNA Editing for Specific C-to-U Exchange (RESCUE), by directly evolving ADAR2 into a cytidine deaminase. RESCUE doubles the number of mutations targetable by RNA editing and enables modulation of phosphosignaling-relevant residues. We apply RESCUE to drive β-catenin activation and cellular growth. Furthermore, RESCUE retains A-to-I editing activity, enabling multiplexed C-to-U and A-to-I editing through the use of tailored guide RNAs.

Artificial RNA Editing with ADAR for Gene Therapy

2020 ◽  
Vol 20 (1) ◽  
pp. 44-54 ◽  
Author(s):  
Sonali Bhakta ◽  
Toshifumi Tsukahara
Keyword(s):  
Gene Therapy ◽  
Genetic Code ◽  
Molecular Mechanism ◽  
Rna Editing ◽  
Comparative Studies ◽  
Genetic Diseases ◽  
Adenosine Deaminases ◽  
Family Protein ◽  
Hydrolytic Deamination

Editing mutated genes is a potential way for the treatment of genetic diseases. G-to-A mutations are common in mammals and can be treated by adenosine-to-inosine (A-to-I) editing, a type of substitutional RNA editing. The molecular mechanism of A-to-I editing involves the hydrolytic deamination of adenosine to an inosine base; this reaction is mediated by RNA-specific deaminases, adenosine deaminases acting on RNA (ADARs), family protein. Here, we review recent findings regarding the application of ADARs to restoring the genetic code along with different approaches involved in the process of artificial RNA editing by ADAR. We have also addressed comparative studies of various isoforms of ADARs. Therefore, we will try to provide a detailed overview of the artificial RNA editing and the role of ADAR with a focus on the enzymatic site directed A-to-I editing.

scholarly journals One-step multiple site-specific base editing by direct embryo injection for precision and pyramid pig breeding

2020 ◽  
Author(s):  
Ruigao Song ◽  
Yu Wang ◽  
Qiantao Zheng ◽  
Jing Yao ◽  
Chunwei Cao ◽  
...  
Keyword(s):  
Stop Codon ◽  
Point Mutations ◽  
Embryonic Cells ◽  
Site Specific ◽  
Editing Efficiency ◽  
Base Editing ◽  
One Step ◽  
Pig Performance ◽  
Novel Alleles

AbstractPrecise and simultaneous acquisition of multiple beneficial alleles in the genome to improve pig performance are pivotal for making elite breeders. Cytidine base editors (CBEs) have emerged as powerful tools for site-specific single nucleotide replacement. Here, we compare the editing efficiency of four CBEs in porcine embryonic cells and embryos to show that hA3A-BE3-Y130F and hA3A-eBE3-Y130F consistently results in higher base-editing efficiency and lower toxic effects to in vitro embryo development. We also show that zygote microinjection of hA3A-BE3-Y130F results in one-step generation of pigs (3BE pigs) harboring C-to-T point mutations, including a stop codon in CD163 and in MSTN and induce beneficial allele in IGF2. The 3BE pigs showed improved growth performance, hip circumference, food conversion rate. Our results demonstrate that CBEs can mediate high throughput genome editing by direct embryo microinjection. Our approach allows immediate introduction of novel alleles for beneficial traits in transgene-free animals for pyramid breeding.

scholarly journals A qPCR method for genome editing efficiency determination and single-cell clone screening in human cells

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Bo Li ◽  
Naixia Ren ◽  
Lele Yang ◽  
Junhao Liu ◽  
Qilai Huang
Keyword(s):  
Single Cell ◽  
Genome Editing ◽  
Cell Clone ◽  
Editing Efficiency ◽  
Base Editing ◽  
Single Cell Clone ◽  
Cell Clones ◽  
Nucleotide Mismatch

AbstractCRISPR/Cas9 technology has been widely used for targeted genome modification both in vivo and in vitro. However, an effective method for evaluating genome editing efficiency and screening single-cell clones for desired modification is still lacking. Here, we developed this real time PCR method based on the sensitivity of Taq DNA polymerase to nucleotide mismatch at primer 3′ end during initiating DNA replication. Applications to CRISPR gRNAs targeting EMX1, DYRK1A and HOXB13 genes in Lenti-X 293 T cells exhibited comprehensive advantages. Just in one-round qPCR analysis using genomic DNA from cells underwent CRISPR/Cas9 or BE4 treatments, the genome editing efficiency could be determined accurately and quickly, for indel, HDR as well as base editing. When applied to single-cell clone screening, the genotype of each cell colony could also be determined accurately. This method defined a rigorous and practical way in quantify genome editing events.

scholarly journals Programmable RNA base editing with a single gRNA-free enzyme

2021 ◽  
Author(s):  
Wenjian Han ◽  
Wendi Huang ◽  
Miaowei Mao ◽  
Tong Wei ◽  
Yanwen Ye ◽  
...  
Keyword(s):  
Rna Editing ◽  
Rna Binding ◽  
Artificial Enzyme ◽  
Free System ◽  
Editing Efficiency ◽  
Base Editing ◽  
Guide Rna ◽  
Human Proteins ◽  
Target Effect ◽  
Puf Domain

ABSTRACTProgrammable RNA editing enables rewriting gene expression without changing genome sequences. Current tools for specific RNA editing dependent on the assembly of guide RNA into an RNA/protein complex, causing delivery barrier and low editing efficiency. We report a new gRNA-free system, RNA editing with individual RNA-binding enzyme (REWIRE), to perform precise base editing with a single engineered protein. This artificial enzyme contains a human-originated programmable PUF domain to specifically recognize RNAs and different deaminase domains to achieve efficient A-to-I or C-to-U editing, which achieved 60-80% editing rate in human cells, with a few non-specific editing sites in the targeted region and a low level off-target effect globally. The RNA-binding domain in REWIREs was further optimized to improve editing efficiency and minimize off-target effects. We applied the REWIREs to correct disease-associated mutations and achieve both types of base editing in mice. As a single-component system originated from human proteins, REWIRE presents a precise and efficient RNA editing platform with broad applicability.

scholarly journals Distinct in vivo roles for double-stranded RNA-binding domains of the Xenopus RNA-editing enzyme ADAR1 in chromosomal targeting

2003 ◽  
Vol 161 (2) ◽  
pp. 309-319 ◽  
Author(s):  
Michael Doyle ◽  
Michael F. Jantsch
Keyword(s):  
Rna Editing ◽  
Rna Binding ◽  
Double Stranded Rna ◽  
Binding Domains ◽  
Initial Substrate ◽  
Rna Binding Domains ◽  
Editing Enzyme ◽  
Deaminase Domain

The RNA-editing enzyme adenosine deaminase that acts on RNA (ADAR1) deaminates adenosines to inosines in double-stranded RNA substrates. Currently, it is not clear how the enzyme targets and discriminates different substrates in vivo. However, it has been shown that the deaminase domain plays an important role in distinguishing various adenosines within a given substrate RNA in vitro. Previously, we could show that Xenopus ADAR1 is associated with nascent transcripts on transcriptionally active lampbrush chromosomes, indicating that initial substrate binding and possibly editing itself occurs cotranscriptionally. Here, we demonstrate that chromosomal association depends solely on the three double-stranded RNA-binding domains (dsRBDs) found in the central part of ADAR1, but not on the Z-DNA–binding domain in the NH2 terminus nor the catalytic deaminase domain in the COOH terminus of the protein. Most importantly, we show that individual dsRBDs are capable of recognizing different chromosomal sites in an apparently specific manner. Thus, our results not only prove the requirement of dsRBDs for chromosomal targeting, but also show that individual dsRBDs have distinct in vivo localization capabilities that may be important for initial substrate recognition and subsequent editing specificity.

scholarly journals Comprehensive interrogation of the ADAR2 deaminase domain for engineering enhanced RNA base-editing activity, functionality and specificity

2020 ◽  
Author(s):  
Dhruva Katrekar ◽  
Nathan Palmer ◽  
Yichen Xiang ◽  
Anushka Saha ◽  
Dario Meluzzi ◽  
...  
Keyword(s):  
Rna Editing ◽  
Rna Motifs ◽  
Mutagenesis Screen ◽  
Base Editing ◽  
Adenosine Deaminases ◽  
Editing Activity ◽  
Exogenous Delivery ◽  
Deaminase Domain ◽  
The Impact ◽  
Increased Activity

ABSTRACTAdenosine deaminases acting on RNA (ADARs) can be repurposed to enable programmable RNA editing, however their exogenous delivery leads to transcriptome-wide off-targeting, and additionally, enzymatic activity on certain RNA motifs, especially those flanked by a 5’ guanosine is very low thus limiting their utility as a transcriptome engineering toolset. To address this, we explored comprehensive ADAR2 protein engineering via three approaches: First, we performed a novel deep mutational scan of the deaminase domain that enabled direct coupling of variants to corresponding RNA editing activity. Experimentally measuring the impact of every amino acid substitution across 261 residues, i.e. ~5000 variants, on RNA editing, revealed intrinsic domain properties, and also several mutations that greatly enhanced RNA editing. Second, we performed a domain-wide mutagenesis screen to identify variants that increased activity at 5’-GA-3’ motifs, and discovered novel mutants that enabled robust RNA editing. Third, we engineered the domain at the fragment level to create split deaminases. Notably, compared to full-length deaminase overexpression, split-deaminases resulted in >1000 fold more specific RNA editing. Taken together, we anticipate this comprehensive deaminase engineering will enable broader utility of the ADAR toolset for RNA biotechnology and therapeutic applications.

scholarly journals RNA Sequence and Base Pairing Effects on Insertion Editing in Trypanosoma brucei

2002 ◽  
Vol 22 (5) ◽  
pp. 1567-1576 ◽  
Author(s):  
Robert P. Igo ◽  
Sobomabo D. Lawson ◽  
Kenneth Stuart
Keyword(s):  
Trypanosoma Brucei ◽  
Rna Editing ◽  
Base Pair ◽  
Editing Site ◽  
Base Pairing ◽  
Editing Efficiency ◽  
Rna Sequence ◽  
Guide Rnas

ABSTRACT RNA editing inserts and deletes uridylates (U's) in kinetoplastid mitochondrial pre-mRNAs by a series of enzymatic steps. Small guide RNAs (gRNAs) specify the edited sequence. Editing, though sometimes extensive, is precise. The effects of mutating pre-mRNA and gRNA sequences in, around, and upstream of the editing site on the specificity and efficiency of in vitro insertion editing were examined. U's could be added opposite guiding pyrimidines, but guiding purines, particularly A's, were required for efficient ligation. A base pair between mRNA and gRNA immediately upstream of the editing site was not required for insertion editing, although it greatly enhanced its efficiency and accuracy. In addition, a gRNA/mRNA duplex upstream of the editing site enhanced insertion editing when it was close to the editing site, but prevented cleavage, and hence editing, when immediately adjacent to the editing site. Thus, several aspects of mRNA-gRNA interaction, as well as gRNA base pairing with added U's, optimize editing efficiency, although they are not required for insertion editing.

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