Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Replacing the SpCas9 HNH domain by deaminases generates compact base editors with an alternative targeting scope

ABSTRACT: Base editors are RNA-guided deaminases that enable site-specific nucleotide transitions. The targeting scope of these Cas-deaminase fusion proteins critically depends on the availability of a protospacer adjacent motif (PAM) at the selected genomic locus, and is limited to a window within the CRISPR-Cas R-loop where single stranded (ss)DNA is accessible to the deaminase. Here, we reason that the Cas9-HNH nuclease domain sterically constrains ssDNA accessibility, and demonstrate that omission of this domain expands the editing window. By exchanging the HNH nuclease domain with an adenosine deaminase, we furthermore engineer adenine base editor variants (HNHx-ABE) with PAM-proximally shifted editing windows. HNHx-ABEs are substantially reduced in size, and expand the targeting scope of base editors. Our finding that the HNH domain is replaceable could moreover benefit future protein engineering efforts, where Cas9 operates together with other enzyme domains.

ORGANISM(S): Homo sapiens

PROVIDER: GSE161293 | GEO | 2020/11/12

REPOSITORIES: GEO

ACCESS DATA

Json Xml

Dataset's files

Source:

			Action	DRS
		Other

Items per page:

1 - 1 of 1

Similar Datasets

Replacing the SpCas9 HNH domain by deaminases generates compact base editors with an alternative targeting scope [DNA-seq]

Project description:Base editors are RNA-guided deaminases that enable site-specific nucleotide transitions. The targeting scope of these Cas-deaminase fusion proteins critically depends on the availability of a protospacer adjacent motif (PAM) at the selected genomic locus, and is limited to a window within the CRISPR-Cas R-loop where single stranded (ss)DNA is accessible to the deaminase. Here, we reason that the Cas9-HNH nuclease domain sterically constrains ssDNA accessibility, and demonstrate that omission of this domain expands the editing window. By exchanging the HNH nuclease domain with an adenosine deaminase, we furthermore engineer adenine base editor variants (HNHx-ABE) with PAM-proximally shifted editing windows. HNHx-ABEs are substantially reduced in size, and expand the targeting scope of base editors. Our finding that the HNH domain is replaceable could moreover benefit future protein engineering efforts, where Cas9 operates together with other enzyme domains.

2020-11-12 | GSE161380 | GEO

Replacing the SpCas9 HNH domain by deaminases generates compact base editors with an alternative targeting scope [RNA-seq]

2020-11-12 | GSE161379 | GEO

Base editing with a Cpf1–cytidine deaminase fusion

Project description:The targeting range of CRISPR-Cas9 base editors (BEs) is limited by their G/C-rich PAM sequences. To overcome this limitation, we developed a CRISPR/Cpf1-based BE by fusing the rat cytosine deaminase APOBEC1 to a catalytically inactive version of Lachnospiraceae bacterium Cpf1. The base editor recognizes a T-rich PAM sequence and converts C to T in human cells with low levels of indels, non-C-to-T substitutions and off-target editing.

2018-03-18 | GSE110136 | GEO

CRISPR adenine and cytosine base editors with reduced RNA off-target activities [ABE]

Project description:CRISPR-guided DNA base editors enable the efficient installation of targeted single-nucleotide changes. Cytosine or adenine base editors (CBEs or ABEs), which are fusions of cytidine or adenosine deaminases to CRISPR-Cas nickases, can efficiently induce DNA C-to-T or A-to-G alterations in DNA, respectively. We recently demonstrated that both the widely used CBE BE3 (harboring a rat APOBEC1 cytidine deaminase) and the optimized ABEmax editor can induce tens of thousands of guide RNA-independent, transcriptome-wide RNA base edits in human cells with high efficiencies. In addition, we showed the feasibility of creating SElective Curbing of Unwanted RNA Editing (SECURE)-BE3 variants that exhibit substantially reduced unwanted RNA editing activities while retaining robust and more precise on-target DNA editing. Here we describe structure-guided engineering of SECURE-ABE variants that not only possess reduced off-target RNA editing with comparable on-target DNA activities but are also the smallest Streptococcus pyogenes Cas9 (SpCas9) base editors described to date. In addition, we tested CBEs composed of cytidine deaminases other than APOBEC1 and found that human APOBEC3A (hA3A) cytidine deaminase CBE induces substantial transcriptome-wide RNA base edits with high efficiencies. By contrast, a previously described “enhanced” A3A (eA3A) cytidine deaminase CBE or a human activation-induced cytidine deaminase (hAID) CBE induce substantially reduced or near background levels of RNA edits. In sum, our work describes broadly useful SECURE-ABE and -CBE base editors and reinforces the importance of minimizing RNA editing activities of DNA base editors for research and therapeutic applications.

2019-07-11 | GSE129889 | GEO

CRISPR adenine and cytosine base editors with reduced RNA off-target activities [CBE]

2019-07-11 | GSE129893 | GEO

Compact zinc finger architecture utilizing toxin-derived cytidine deaminases for highly efficient base editing in human cells -T cells

Project description:Nucleobase editors represent an emerging technology that enables precise single-base edits to the genomes of eukaryotic cells. Most nucleobase editors use deaminase domains that act upon single-stranded DNA and require RNA-guided proteins such as Cas9 to unwind the DNA prior to editing. However, the most recent class of base editors utilizes a deaminase domain, DddAtox, that can act upon double-stranded DNA. Here, we target DddAtox fragments and a FokI-based nickase to the human CIITA gene by fusing these domains to arrays of engineered zinc fingers (ZFs). We also identify a broad variety of Toxin-Derived Deaminases (TDDs) orthologous to DddAtox that allow us to fine-tune properties such as targeting density and specificity. TDD-derived ZF base editors enable up to 73% base editing in T cells with good cell viability and favorable specificity.

2024-01-12 | GSE253182 | GEO

Compact zinc finger architecture utilizing toxin-derived cytidine deaminases for highly efficient base editing in human cells-K562 cells

2024-01-12 | GSE253184 | GEO

High-fidelity base editing mediated by Cpf1-cytidine deaminase fusion

Project description:C-to-T base editing mediated by CRISPR/Cas9 base editors (BEs) needs a G/C-rich PAM and the editing fidelity is compromised by unwanted indels and non-C-to-T substitutions. We developed CRISPR/Cpf1-based BEs to recognize a T-rich PAM and induce efficient C-to-T editing with few indels and/or non-C-to-T substitutions. The requirement of editing fidelity in therapeutic-related trials necessitates the development of CRISPR/Cpf1-based BEs, which also facilitates base editing in A/T-rich regions.

2018-10-16 | GSE105002 | GEO

Transcriptome-wide off-target RNA editing induced by CRISPR-guided DNA base editors [ABE-max]

Project description:CRISPR-Cas base editor technology enables targeted nucleotide alterations and is being rapidly deployed for research and potential therapeutic applications. The most widely used base editors induce DNA cytosine (C) deamination with rat APOBEC1 (rAPOBEC1) enzyme, which is targeted by a linked Cas protein-guide RNA (gRNA) complex. Previous studies of cytosine base editor (CBE) specificity have identified off-target DNA edits in human cells. Here we show that a CBE with rAPOBEC1 can cause extensive transcriptome-wide RNA cytosine deamination in human cells, inducing tens of thousands of C-to-uracil (U) edits with frequencies ranging from 0.07% to 100% in 38% - 58% of expressed genes. CBE-induced RNA edits occur in both protein-coding and non-protein-coding sequences and generate missense, nonsense, splice site, 5’ UTR, and 3’ UTR mutations. We engineered two CBE variants bearing rAPOBEC1 mutations that substantially decrease the numbers of RNA edits (reductions of >390-fold and >3,800-fold) in human cells. These variants also showed more precise on-target DNA editing and, with the majority of gRNAs tested, editing efficiencies comparable to those observed with wild-type CBE. Finally, we show that recently described adenine base editors (ABEs) can also induce transcriptome-wide RNA edits. These results have important implications for the research and therapeutic uses of base editors, illustrate the feasibility of engineering improved variants with reduced RNA editing activities, and suggest the need to more fully define and characterize the RNA off-target effects of deaminase enzymes in base editor platforms.

2019-03-31 | GSE126502 | GEO

Transcriptome-wide off-target RNA editing induced by CRISPR-guided DNA base editors

2019-03-31 | GSE121668 | GEO