scholarly journals Quantification of Cas9 binding and cleavage across diverse guide sequences maps landscapes of target engagement

2021 ◽  
Vol 7 (8) ◽  
pp. eabe5496
Author(s):  
Evan A. Boyle ◽  
Winston R. Becker ◽  
Hua B. Bai ◽  
Janice S. Chen ◽  
Jennifer A. Doudna ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Dna Cleavage ◽  
High Specificity ◽  
Biophysical Model ◽  
Target Sequence ◽  
Sequence Context ◽  
Guide Rnas ◽  
Target Dna ◽  
Target Binding ◽  
Model Sequence

The RNA-guided nuclease Cas9 has unlocked powerful methods for perturbing both the genome through targeted DNA cleavage and the regulome through targeted DNA binding, but limited biochemical data have hampered efforts to quantitatively model sequence perturbation of target binding and cleavage across diverse guide sequences. We present scalable, sequencing-based platforms for high-throughput filter binding and cleavage and then perform 62,444 quantitative binding and cleavage assays on 35,047 on- and off-target DNA sequences across 90 Cas9 ribonucleoproteins (RNPs) loaded with distinct guide RNAs. We observe that binding and cleavage efficacy, as well as specificity, vary substantially across RNPs; canonically studied guides often have atypically high specificity; sequence context surrounding the target modulates Cas9 on-rate; and Cas9 RNPs may sequester targets in nonproductive states that contribute to “proofreading” capability. Lastly, we distill our findings into an interpretable biophysical model that predicts changes in binding and cleavage for diverse target sequence perturbations.

scholarly journals Quantification of Cas9 binding and cleavage across diverse guide sequences maps landscapes of target engagement

2020 ◽  
Author(s):  
Evan A Boyle ◽  
Winston R Becker ◽  
Hua B Bai ◽  
Janice S Chen ◽  
Jennifer A Doudna ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Dna Cleavage ◽  
High Specificity ◽  
Biophysical Model ◽  
Target Sequence ◽  
Sequence Context ◽  
Guide Rnas ◽  
Target Dna ◽  
Target Binding ◽  
Model Sequence

AbstractThe RNA-guided nuclease Cas9 has unlocked powerful methods for perturbing both the genome through targeted DNA cleavage and the regulome through targeted DNA binding, but limited biochemical data has hampered efforts to quantitatively model sequence perturbation of target binding and cleavage across diverse guide sequences. We present scalable, sequencing-based platforms for high-throughput filter binding and cleavage, then perform 62,444 quantitative binding and cleavage assays on 35,047 on- and off-target DNA sequences across 90 Cas9 ribonucleoproteins (RNPs) loaded with distinct guide RNAs. We observe that binding and cleavage efficacy, as well as specificity, vary substantially across RNPs; canonically studied guides often have atypically high specificity; sequence context surrounding the target significantly influences Cas9 on-rate; and Cas9 RNPs may sequester targets in nonproductive states that contribute to “proofreading” capability. Finally, we distill our findings into an interpretable biophysical model that predicts changes in binding and cleavage for diverse target sequence perturbations.

scholarly journals Enhancement of target specificity of CRISPR–Cas12a by using a chimeric DNA–RNA guide

2020 ◽  
Vol 48 (15) ◽  
pp. 8601-8616 ◽  
Author(s):  
Hanseop Kim ◽  
Wi-jae Lee ◽  
Yeounsun Oh ◽  
Seung-Hun Kang ◽  
Junho K Hur ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Genome Engineering ◽  
Target Genes ◽  
Target Sequence ◽  
Energy Potential ◽  
Guide Rna ◽  
Sequence Recognition ◽  
Protospacer Adjacent Motif ◽  
Effective Manner ◽  
Target Dna

Abstract The CRISPR–Cas9 system is widely used for target-specific genome engineering. CRISPR–Cas12a (Cpf1) is one of the CRISPR effectors that controls target genes by recognizing thymine-rich protospacer adjacent motif (PAM) sequences. Cas12a has a higher sensitivity to mismatches in the guide RNA than does Cas9; therefore, off-target sequence recognition and cleavage are lower. However, it tolerates mismatches in regions distant from the PAM sequence (TTTN or TTN) in the protospacer, and off-target cleavage issues may become more problematic when Cas12a activity is improved for therapeutic purposes. Therefore, we investigated off-target cleavage by Cas12a and modified the Cas12a (cr)RNA to address the off-target cleavage issue. We developed a CRISPR–Cas12a that can induce mutations in target DNA sequences in a highly specific and effective manner by partially substituting the (cr)RNA with DNA to change the energy potential of base pairing to the target DNA. A model to explain how chimeric (cr)RNA guided CRISPR–Cas12a and SpCas9 nickase effectively work in the intracellular genome is suggested. Chimeric guide-based CRISPR- Cas12a genome editing with reduced off-target cleavage, and the resultant, increased safety has potential for therapeutic applications in incurable diseases caused by genetic mutations.

scholarly journals The stepwise endonuclease activity of a thermophilic Argonaute protein

2019 ◽  
Author(s):  
Guanhua Xun ◽  
Qian Liu ◽  
Yuesheng Chong ◽  
Zhonglei Li ◽  
Xiang Guo ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Dna Cleavage ◽  
Pyrococcus Furiosus ◽  
Dna Amplification ◽  
Endonuclease Activity ◽  
Gene Detection ◽  
Complementary Sequences ◽  
Argonaute Proteins ◽  
Target Dna ◽  
Single Reaction

AbstractThermophilic Argonaute proteins (Agos) can function as endonucleases via specific guide-target base-pairing cleavage for host defense. The ability to cleave target DNA sequences at any arbitrary sites endows them with reprogramed DNA capacity. Here, we identify that an Ago from the hyperthermophilic archaeon Pyrococcus furiosus (PfAgo) shows a stepwise endonuclease activity, which is demonstrated by the double strand DNA cleavage directed by a single guide DNA rather than canonical one pair of guide DNAs. We reveal that the cleavage products with 5’-phosphorylated ends can used as the renewed guide which is capable to induce next round of cleavage to complementary sequences of target DNA. By combining the PfAgo stepwise endonuclease activity followed by target DNA amplification, we establish a rapid and specific platform for the unambiguously multiplex gene detection, termed RADAR (Renewed-gDNA Assisted DNA-cleavage by Argonaute). In the end, RADAR was applied to distinguish of human papillomavirus of serotypes in patient samples in a single reaction, suggesting that our technique would be adopted for diagnosing application.

scholarly journals Enhancement of Target Specificity of CRISPR-Cas12a by Using a Chimeric DNA-RNA Guide

2020 ◽  
Author(s):  
Hanseop Kim ◽  
Wi-jae Lee ◽  
Seung-Hun Kang ◽  
Junho K. Hur ◽  
Hyomin Lee ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Genome Engineering ◽  
Target Genes ◽  
Genetic Mutation ◽  
Target Sequence ◽  
Energy Potential ◽  
Guide Rna ◽  
Sequence Recognition ◽  
Effective Manner ◽  
Target Dna

AbstractThe CRISPR-Cas9 system is widely used for target-specific genome engineering. Cpf1 is one of the CRISPR effectors that controls target genes by recognizing thymine-rich protospacer adjacent motif (PAM) sequences. Cpf1 has a higher sensitivity to mismatches in the guide RNA than does Cas9; therefore, off-target sequence recognition and cleavage are lower. However, it tolerates mismatches in regions distant from the PAM sequence (TTTN or TTN) in the protospacer, and off-target cleavage issues may become more problematic when Cpf1 activity is improved for therapeutic purposes. In our study, we investigated off-target cleavage by Cpf1 and modified the Cpf1 (cr)RNA to address the off-target cleavage issue. We developed a CRISPR-Cpf1 that can induce mutations in target DNA sequences in a highly specific and effective manner by partially substituting the (cr)RNA with DNA to change the energy potential of base pairing to the target DNA. A model to explain how chimeric (cr)RNA guided CRISPR-Cpf1 and SpCas9 nickase effectively work in the intracellular genome is suggested. In our results, CRISPR-Cpf1 induces less off-target mutations at the cell level, when chimeric DNA-RNA guide was used for genome editing. This study has a potential for therapeutic applications in incurable diseases caused by genetic mutation.

Making the cut(s): how Cas12a cleaves target and non-target DNA

2019 ◽  
Vol 47 (5) ◽  
pp. 1499-1510 ◽  
Author(s):  
Daan C. Swarts
Keyword(s):  
Conformational Changes ◽  
Dna Sequences ◽  
Dna Cleavage ◽  
Transcriptional Control ◽  
Molecular Mechanisms ◽  
Nucleic Acid Detection ◽  
Target Dna ◽  
Activated State ◽  
Dna Strand ◽  
Cis And Trans

Abstract CRISPR–Cas12a (previously named Cpf1) is a prokaryotic deoxyribonuclease that can be programmed with an RNA guide to target complementary DNA sequences. Upon binding of the target DNA, Cas12a induces a nick in each of the target DNA strands, yielding a double-stranded DNA break. In addition to inducing cis-cleavage of the targeted DNA, target DNA binding induces trans-cleavage of non-target DNA. As such, Cas12a–RNA guide complexes can provide sequence-specific immunity against invading nucleic acids such as bacteriophages and plasmids. Akin to CRISPR–Cas9, Cas12a has been repurposed as a genetic tool for programmable genome editing and transcriptional control in both prokaryotic and eukaryotic cells. In addition, its trans-cleavage activity has been applied for high-sensitivity nucleic acid detection. Despite the demonstrated value of Cas12a for these applications, the exact molecular mechanisms of both cis- and trans-cleavage of DNA were not completely understood. Recent studies have revealed mechanistic details of Cas12a-mediates DNA cleavage: base pairing of the RNA guide and the target DNA induces major conformational changes in Cas12a. These conformational changes render Cas12a in a catalytically activated state in which it acts as deoxyribonuclease. This deoxyribonuclease activity mediates cis-cleavage of the displaced target DNA strand first, and the RNA guide-bound target DNA strand second. As Cas12a remains in the catalytically activated state after cis-cleavage, it subsequently demonstrates trans-cleavage of non-target DNA. Here, I review the mechanistic details of Cas12a-mediated cis- and trans-cleavage of DNA. In addition, I discuss how bacteriophage-derived anti-CRISPR proteins can inhibit Cas12a activity.

scholarly journals Quantification of the affinities of CRISPR–Cas9 nucleases for cognate protospacer adjacent motif (PAM) sequences

2020 ◽  
Vol 295 (19) ◽  
pp. 6509-6517 ◽  
Author(s):  
Vladimir Mekler ◽  
Konstantin Kuznedelov ◽  
Konstantin Severinov
Keyword(s):  
Genome Editing ◽  
Target Location ◽  
Dna Probes ◽  
Target Sequence ◽  
Francisella Novicida ◽  
Guide Rna ◽  
Guide Rnas ◽  
Cas9 Nuclease ◽  
Protospacer Adjacent Motif ◽  
Target Dna

The CRISPR/Cas9 nucleases have been widely applied for genome editing in various organisms. Cas9 nucleases complexed with a guide RNA (Cas9–gRNA) find their targets by scanning and interrogating the genomic DNA for sequences complementary to the gRNA. Recognition of the DNA target sequence requires a short protospacer adjacent motif (PAM) located outside this sequence. Given that the efficiency of target location may depend on the strength of interactions that promote target recognition, here we sought to compare affinities of different Cas9 nucleases for their cognate PAM sequences. To this end, we measured affinities of Cas9 nucleases from Streptococcus pyogenes, Staphylococcus aureus, and Francisella novicida complexed with guide RNAs (gRNAs) (SpCas9–gRNA, SaCas9–gRNA, and FnCas9–gRNA, respectively) and of three engineered SpCas9–gRNA variants with altered PAM specificities for short, PAM-containing DNA probes. We used a “beacon” assay that measures the relative affinities of DNA probes by determining their ability to competitively affect the rate of Cas9–gRNA binding to fluorescently labeled target DNA derivatives called “Cas9 beacons.” We observed significant differences in the affinities for cognate PAM sequences among the studied Cas9 enzymes. The relative affinities of SpCas9–gRNA and its engineered variants for canonical and suboptimal PAMs correlated with previous findings on the efficiency of these PAM sequences in genome editing. These findings suggest that high affinity of a Cas9 nuclease for its cognate PAM promotes higher genome-editing efficiency.

scholarly journals Massively parallel kinetic profiling of natural and engineered CRISPR nucleases

2019 ◽  
Author(s):  
Stephen K. Jones ◽  
John A. Hawkins ◽  
Nicole V. Johnson ◽  
Cheulhee Jung ◽  
Kuang Hu ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Massively Parallel ◽  
Biophysical Model ◽  
Rna Sequences ◽  
Time Resolved ◽  
Guide Rna ◽  
Dna Library ◽  
Cleavage Specificity ◽  
Target Binding

AbstractEngineered Streptococcus pyogenes (Sp) Cas9s and Acidaminococcus sp. (As) Cas12a (formerly Cpf1) improve cleavage specificity in human cells. However, the fidelity, enzymatic mechanisms, and cleavage products of emerging CRISPR nucleases have not been profiled systematically across partially mispaired off-target DNA sequences. Here, we describe NucleaSeq— nuclease digestion and deep sequencing—a massively parallel platform that measures cleavage kinetics and captures the time-resolved identities of cleaved products for more than ten thousand DNA targets that include mismatches, insertions, and deletions relative to the guide RNA. The binding specificity of each enzyme is measured on the same DNA library via the chip-hybridized association mapping platform (CHAMP). Using this integrated cleavage and binding platform, we profile four SpCas9 variants and AsCas12a. Engineered Cas9s retain wtCas9-like off-target binding but increase cleavage specificity; Cas9-HF1 shows the most dramatic increase in cleavage specificity. Surprisingly, wtCas12a—reported as a more specific nuclease in cells—has cleavage specificity similar to wtCas9 in vitro. Initial cleavage position and subsequent end-trimming vary across nucleases, guide RNA sequences, and position and base identity of mispairs in target DNAs. Using these large datasets, we develop a biophysical model that reveals mechanistic insights into off-target cleavage activities by these nucleases. More broadly, NucleaSeq enables rapid, quantitative, and systematic comparison of the specificities and cleavage products of engineered and natural nucleases.

scholarly journals Cas12a trans-cleavage can be modulated in vitro and is active on ssDNA, dsDNA, and RNA

2019 ◽  
Author(s):  
Ryan T. Fuchs ◽  
Jennifer Curcuru ◽  
Megumu Mabuchi ◽  
Paul Yourik ◽  
G. Brett Robb
Keyword(s):  
Dna Sequences ◽  
Nuclease Activity ◽  
Target Sequence ◽  
Sequence Composition ◽  
Guide Rna ◽  
Dna Targeting ◽  
Single Turnover ◽  
Target Dna ◽  
Buffer Composition

ABSTRACTCRISPR-Cas12a (Cpf1) are RNA-guided nuclease effectors of acquired immune response that act in their native organisms by cleaving targeted DNA sequences. Like CRISPR-Cas9 RNA-guided DNA targeting enzymes, Cas12a orthologs have been repurposed for genome editing in non-native organisms and for DNA manipulationin vitro. Recent studies have shown that activation of Cas12a via guide RNA-target DNA pairing causes multiple turnover, non-specific ssDNA degradation intrans, after single turnover on-target cleavage incis. We find that the non-specifictransnuclease activity affects RNA and dsDNA in addition to ssDNA, an activity made more evident by adjustment of reaction buffer composition. The magnitude of thetransnuclease activity varies depending on features of the guide RNA being used, specifically target sequence composition and length. We also find that the magnitude oftransnuclease activity varies between the three most well-studied Cas12a orthologs and that the Cas12a fromLachnospiraceaebacterium ND2006 appears to be the most active.

scholarly journals Predicting primer and panel off-target rate in QIAseq targeted DNA panels using convolutional neural networks

2020 ◽  
Author(s):  
Chang Xu ◽  
Raghavendra Padmanabhan ◽  
Frank Reinecke ◽  
John DiCarlo ◽  
Yexun Wang
Keyword(s):  
Neural Network ◽  
Dna Sequences ◽  
Test Panel ◽  
True Value ◽  
The Neural Network ◽  
Target Template ◽  
Common Task ◽  
Target Dna ◽  
Target Binding ◽  
Target Rates

AbstractIn QIAseq targeted DNA panels, synthetic primers (short single-strand DNA sequences) are used for target enrichment via complementary DNA binding. Off-target priming could occur in this process when a primer binds to some loci where the DNA sequences are identical or very similar to the target template. These off-target DNA segments go through the rest of the workflow, wasting sequencing resources in unwanted regions. Off-target cannot be avoided if some segments of the target region are repetitive throughout the genome, nor can it be quantified until after sequencing. But if off-target rates can be prospectively predicted, scientists can make informed decisions about investment on high off-target panels.We developed pordle (predicting off-target rate with deep learning and epcr07), a convolutional neural network (CNN) model to predict off-target binding events of a given primer. The neural network was trained using 10 QIAseq DNA panels with 29,274 unique primers and then tested on an independent QIAseq panel with 7,576 primers. The model predicted a 10.5% off-target rate for the test panel, a -0.1% bias from the true value of 10.6%. The model successfully selected the better primer (in terms of off-target rate) for 89.2% of 3,835 pairs of close-by primers in the test panel whose off-target rates differ by at least 10%. The order-preserving property may help panel developers select the optimal primer from a group of candidates, which is a common task in panel design.

scholarly journals Structural basis for Cas9 off-target activity

2021 ◽  
Author(s):  
Martin Pacesa ◽  
Chun-Han Lin ◽  
Antoine Clery ◽  
Katja Bargsten ◽  
Matthew J. Irby ◽  
...  
Keyword(s):  
Rational Design ◽  
Target Prediction ◽  
Structural Basis ◽  
Guide Rna ◽  
Guide Rnas ◽  
Target Dna ◽  
Bona Fide ◽  
Dna Specificity ◽  
Target Binding ◽  
Target Activity

The target DNA specificity of the CRISPR-associated genome editor nuclease Cas9 is determined by complementarity to a 20-nucleotide segment in its guide RNA. However, Cas9 can bind and cleave partially complementary off-target sequences, which raises safety concerns for its use in clinical applications. Here we report crystallographic structures of Cas9 bound to bona fide off-target substrates, revealing that off-target binding is enabled by a range of non- canonical base pairing interactions and preservation of base stacking within the guide-off-target heteroduplex. Off-target sites containing single-nucleotide deletions relative to the guide RNA are accommodated by base skipping rather than RNA bulge formation. Additionally, PAM-distal mismatches result in duplex unpairing and induce a conformational change of the Cas9 REC lobe that perturbs its conformational activation. Together, these insights provide a structural rationale for the off-target activity of Cas9 and contribute to the improved rational design of guide RNAs and off-target prediction algorithms.

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