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Molecular Cell Jun 2024In Saccharomyces cerevisiae (S. cerevisiae), Mre11-Rad50-Xrs2 (MRX)-Sae2 nuclease activity is required for the resection of DNA breaks with secondary structures or...
In Saccharomyces cerevisiae (S. cerevisiae), Mre11-Rad50-Xrs2 (MRX)-Sae2 nuclease activity is required for the resection of DNA breaks with secondary structures or protein blocks, while in humans, the MRE11-RAD50-NBS1 (MRN) homolog with CtIP is needed to initiate DNA end resection of all breaks. Phosphorylated Sae2/CtIP stimulates the endonuclease activity of MRX/N. Structural insights into the activation of the Mre11 nuclease are available only for organisms lacking Sae2/CtIP, so little is known about how Sae2/CtIP activates the nuclease ensemble. Here, we uncover the mechanism of Mre11 activation by Sae2 using a combination of AlphaFold2 structural modeling of biochemical and genetic assays. We show that Sae2 stabilizes the Mre11 nuclease in a conformation poised to cleave substrate DNA. Several designs of compensatory mutations establish how Sae2 activates MRX in vitro and in vivo, supporting the structural model. Finally, our study uncovers how human CtIP, despite considerable sequence divergence, employs a similar mechanism to activate MRN.
Topics: Saccharomyces cerevisiae Proteins; Saccharomyces cerevisiae; Endonucleases; DNA-Binding Proteins; Endodeoxyribonucleases; Humans; Exodeoxyribonucleases; Models, Molecular; Phosphorylation; DNA Repair Enzymes; DNA Breaks, Double-Stranded; Acid Anhydride Hydrolases; Mutation; MRE11 Homologue Protein; DNA Repair; Enzyme Activation
PubMed: 38870937
DOI: 10.1016/j.molcel.2024.05.019 -
Methods in Molecular Biology (Clifton,... 2024Nucleosome occupancy plays an important role in chromatin compaction, affecting biological processes by hampering the binding of cis-acting elements such as...
Nucleosome occupancy plays an important role in chromatin compaction, affecting biological processes by hampering the binding of cis-acting elements such as transcription factors, RNA polymerase machinery, and coregulatory. Accessible regions allow for cis-acting elements to bind DNA and regulate transcription. Here, we detail our protocol to profile nucleosome occupancy and chromatin structure dynamics under drought stress at the genome-wide scale using micrococcal nuclease (MNase) digestion. Combining variable MNase concentration treatments and high-throughput sequencing, we investigate the changes in the overall chromatin state using bread wheat samples from an exemplary drought experiment.
Topics: Nucleosomes; Micrococcal Nuclease; High-Throughput Nucleotide Sequencing; Stress, Physiological; Triticum; Droughts; Gene Expression Regulation, Plant; Chromatin; Plants
PubMed: 38869785
DOI: 10.1007/978-1-0716-3973-3_2 -
Mikrochimica Acta Jun 2024The combination of CRISPR/Cas12a and functional DNA provides the possibility of constructing biosensors for detecting non-nucleic-acid targets. In the current study, the...
The combination of CRISPR/Cas12a and functional DNA provides the possibility of constructing biosensors for detecting non-nucleic-acid targets. In the current study, the duplex protospacer adjacent motif (PAM) in the activator of CRISPR/Cas12a was used as a molecular switch, and a sensitive adenosine triphosphate (ATP) detection biosensor was constructed using an allosteric probe-conjugated PAM site formation in hybridization chain reaction (HCR) integrated with the CRISPR/Cas12a system (APF-CRISPR). In the absence of ATP, an aptamer-containing probe (AP) is in a stem-loop structure, which blocks the initiation of HCR. In the presence of ATP, the structure of AP is changed upon ATP binding, resulting in the release of the HCR trigger strand and the production of long duplex DNA with many PAM sites. Since the presence of a duplex PAM site is crucial for triggering the cleavage activity of CRISPR/Cas12a, the ATP-dependent formation of the PAM site in HCR products can initiate the FQ-reporter cleavage, allowing ATP quantification by measuring the fluorescent signals. By optimizing the sequence elements and detection conditions, the aptasensor demonstrated superior detection performance. The limit of detection (LOD) of the assay was estimated to be 1.16 nM, where the standard deviation of the blank was calculated based on six repeated measurements. The dynamic range of the detection was 25-750 nM, and the whole workflow of the assay was approximately 60 min. In addition, the reliability and practicability of the aptasensor were validated by comparing it with a commercially available chemiluminescence kit for ATP detection in serum. Due to its high sensitivity, specificity, and reliable performance, the APF-CRISPR holds great potential in bioanalytical studies for ATP detection. In addition, we have provided a proof-of-principle for constructing a CRISPR/Cas12a-based aptasensor, in which the PAM is utilized to regulate Cas12a cleavage activity.
Topics: Adenosine Triphosphate; Biosensing Techniques; Aptamers, Nucleotide; CRISPR-Cas Systems; CRISPR-Associated Proteins; Limit of Detection; Bacterial Proteins; Nucleic Acid Hybridization; Endodeoxyribonucleases
PubMed: 38867016
DOI: 10.1007/s00604-024-06477-z -
Nature Communications Jun 2024Genetic testing is crucial for precision cancer medicine. However, detecting multiple same-site insertions or deletions (indels) is challenging. Here, we introduce CoHIT...
Genetic testing is crucial for precision cancer medicine. However, detecting multiple same-site insertions or deletions (indels) is challenging. Here, we introduce CoHIT (Cas12a-based One-for-all High-speed Isothermal Test), a one-pot CRISPR-based assay for indel detection. Leveraging an engineered AsCas12a protein variant with high mismatch tolerance and broad PAM scope, CoHIT can use a single crRNA to detect multiple NPM1 gene c.863_864 4-bp insertions in acute myeloid leukemia (AML). After optimizing multiple parameters, CoHIT achieves a detection limit of 0.01% and rapid results within 30 minutes, without wild-type cross-reactivity. It successfully identifies NPM1 mutations in 30 out of 108 AML patients and demonstrates potential in monitoring minimal residual disease (MRD) through continuous sample analysis from three patients. The CoHIT method is also competent for detecting indels of KIT, BRAF, and EGFR genes. Integration with lateral flow test strips and microfluidic chips highlights CoHIT's adaptability and multiplexing capability, promising significant advancements in clinical cancer diagnostics.
Topics: Humans; Leukemia, Myeloid, Acute; INDEL Mutation; CRISPR-Cas Systems; Nucleophosmin; Neoplasm, Residual; Nuclear Proteins; Proto-Oncogene Proteins B-raf; Genetic Testing; ErbB Receptors; Bacterial Proteins; Endodeoxyribonucleases; CRISPR-Associated Proteins
PubMed: 38866774
DOI: 10.1038/s41467-024-49414-7 -
PLoS Biology Jun 2024CRISPR-Cas12a, often regarded as a precise genome editor, still requires improvements in specificity. In this study, we used a GFP-activation assay to screen 14 new...
CRISPR-Cas12a, often regarded as a precise genome editor, still requires improvements in specificity. In this study, we used a GFP-activation assay to screen 14 new Cas12a nucleases for mammalian genome editing, successfully identifying 9 active ones. Notably, these Cas12a nucleases prefer pyrimidine-rich PAMs. Among these nucleases, we extensively characterized Mb4Cas12a obtained from Moraxella bovis CCUG 2133, which recognizes a YYN PAM (Y = C or T). Our biochemical analysis demonstrates that Mb4Cas12a can cleave double-strand DNA across a wide temperature range. To improve specificity, we constructed a SWISS-MODEL of Mb4Cas12a based on the FnCas12a crystal structure and identified 8 amino acids potentially forming hydrogen bonds at the target DNA-crRNA interface. By replacing these amino acids with alanine to disrupt the hydrogen bond, we tested the influence of each mutation on Mb4Cas12a specificity. Interestingly, the F370A mutation improved specificity with minimal influence on activity. Further study showed that Mb4Cas12a-F370A is capable of discriminating single-nucleotide polymorphisms. These new Cas12a orthologs and high-fidelity variants hold substantial promise for therapeutic applications.
Topics: Gene Editing; CRISPR-Cas Systems; CRISPR-Associated Proteins; Alleles; Humans; Endodeoxyribonucleases; Animals; Protein Engineering; Bacterial Proteins; Polymorphism, Single Nucleotide; Mutation; DNA; HEK293 Cells
PubMed: 38865309
DOI: 10.1371/journal.pbio.3002680 -
Analytical Chemistry Jun 2024Due to their ability to selectively target pathogen-specific nucleic acids, CRISPR-Cas systems are increasingly being employed as diagnostic tools. "One-pot" assays that...
Due to their ability to selectively target pathogen-specific nucleic acids, CRISPR-Cas systems are increasingly being employed as diagnostic tools. "One-pot" assays that combine nucleic acid amplification and CRISPR-Cas systems (NAAT-CRISPR-Cas) in a single step have emerged as one of the most popular CRISPR-Cas biosensing formats. However, operational simplicity comes at a cost, with one-pot assays typically being less sensitive than corresponding two-step NAAT-CRISPR-Cas assays and often failing to detect targets at low concentrations. It is thought that these performance reductions result from the competition between the two enzymatic processes driving the assay, namely, Cas-mediated -cleavage and polymerase-mediated amplification of the target DNA. Herein, we describe a novel one-pot RPA-Cas12a assay that circumvents this issue by leveraging complexation of the target-specific sgRNA and Cas12a to purposefully limit the concentration of active Cas12a during the early stages of the assay. Using a clinically relevant assay against a DNA target for HPV-16, we show how this format reduces competition between target cleavage and amplification and engenders significant improvements in detection limit when compared to the traditional one-pot assay format, even in patient-derived samples. Finally, to gain further insight into the assay, we use experimental data to formulate a mechanistic model describing the competition between the Cas enzyme and nucleic acid amplification. These findings suggest that purposefully limiting -cleavage rates of Cas proteins is a viable strategy for improving the performance of one-pot NAAT-CRISPR-Cas assays.
Topics: CRISPR-Cas Systems; CRISPR-Associated Proteins; RNA, Guide, CRISPR-Cas Systems; Humans; Endodeoxyribonucleases; Bacterial Proteins; Nucleic Acid Amplification Techniques; Replication Protein A; Biosensing Techniques
PubMed: 38864271
DOI: 10.1021/acs.analchem.4c01777 -
Nature Communications Jun 2024Sickle cell disease is a devastating blood disorder that originates from a single point mutation in the HBB gene coding for hemoglobin. Here, we develop a GMP-compatible...
Sickle cell disease is a devastating blood disorder that originates from a single point mutation in the HBB gene coding for hemoglobin. Here, we develop a GMP-compatible TALEN-mediated gene editing process enabling efficient HBB correction via a DNA repair template while minimizing risks associated with HBB inactivation. Comparing viral versus non-viral DNA repair template delivery in hematopoietic stem and progenitor cells in vitro, both strategies achieve comparable HBB correction and result in over 50% expression of normal adult hemoglobin in red blood cells without inducing β-thalassemic phenotype. In an immunodeficient female mouse model, transplanted cells edited with the non-viral strategy exhibit higher engraftment and gene correction levels compared to those edited with the viral strategy. Transcriptomic analysis reveals that non-viral DNA repair template delivery mitigates P53-mediated toxicity and preserves high levels of long-term hematopoietic stem cells. This work paves the way for TALEN-based autologous gene therapy for sickle cell disease.
Topics: Anemia, Sickle Cell; Gene Editing; Animals; Hematopoietic Stem Cells; Humans; Female; Mice; Genetic Therapy; Transcription Activator-Like Effector Nucleases; Hematopoietic Stem Cell Transplantation; beta-Globins; Tumor Suppressor Protein p53; DNA Repair; Mutation; beta-Thalassemia; Disease Models, Animal; Gene Transfer Techniques
PubMed: 38862518
DOI: 10.1038/s41467-024-49353-3 -
Biosensors & Bioelectronics Oct 2024Recent findings on CRISPR-Cas enzymes with collateral DNAse/RNAse activity have led to new and innovative methods for pathogen detection. However, many CRISPR-Cas assays...
Recent findings on CRISPR-Cas enzymes with collateral DNAse/RNAse activity have led to new and innovative methods for pathogen detection. However, many CRISPR-Cas assays necessitate DNA pre-amplification to boost sensitivity, restricting their utility for point-of-care applications. Achieving higher sensitivity without DNA pre-amplification presents a significant challenge. In this study, we introduce a Terminal deoxynucleotidyl Transferase (TdT)-based amplification loop, creating a positive feedback mechanism within the CRISPR-Cas12a pathogen detection system. Upon recognizing pathogenic target DNA, Cas12a triggers trans-cleavage of a FRET reporter and a specific enhancer molecule oligonucleotide, indicated by the acronym POISER (Partial Or Incomplete Sites for crRNA recognition). POISER comprises half of a CRISPR-RNA recognition site, which is subsequently elongated by TdT enzymatic activity. This process, involving pathogen recognition-induced Cas12a cleavage and TdT elongation, results in a novel single-stranded DNA target. This target can subsequently be recognized by a POISER-specific crRNA, activating more Cas12a enzymes. Our study demonstrates that these POISER-cycles enhance the signal strength in fluorescent-based CRISPR-Cas12a assays. Although further refinement is desirable, POISER holds promise as a valuable tool for the detection of pathogens in point-of-care testing, surveillance, and environmental monitoring.
Topics: CRISPR-Cas Systems; Biosensing Techniques; CRISPR-Associated Proteins; DNA, Bacterial; DNA Nucleotidylexotransferase; Endodeoxyribonucleases; Nucleic Acid Amplification Techniques; Bacterial Proteins; Humans
PubMed: 38861812
DOI: 10.1016/j.bios.2024.116464 -
Analytical Chemistry Jun 2024Rapid and sensitive RNA detection is of great value in diverse areas, ranging from biomedical research to clinical diagnostics. Existing methods for RNA detection often...
Rapid and sensitive RNA detection is of great value in diverse areas, ranging from biomedical research to clinical diagnostics. Existing methods for RNA detection often rely on reverse transcription (RT) and DNA amplification or involve a time-consuming procedure and poor sensitivity. Herein, we proposed a CRISPR/Cas12a-enabled amplification-free assay for rapid, specific, and sensitive RNA diagnostics. This assay, which we termed T7/G4-CRISPR, involved the use of a T7-powered nucleic acid circuit to convert a single RNA target into numerous DNA activators via toehold-mediated strand displacement reaction and T7 exonuclease-mediated target recycling amplification, followed by activating Cas12a -cleavage of the linker strands inhibiting split G-Quadruplex (G4) assembly, thereby inducing fluorescence attenuation proportion to the input RNA target. We first performed step-by-step validation of the entire assay process and optimized the reaction parameters. Using the optimal conditions, T7/G4-CRISPR was capable of detecting as low as 3.6 pM target RNA, obtaining ∼100-fold improvement in sensitivity compared with the most direct Cas12a assays. Meanwhile, its excellent specificity could discriminate single nucleotide variants adjacent to the toehold region and allow species-specific pathogen identification. Furthermore, we applied it for analyzing bacterial 16S rRNA in 40 clinical urine samples, exhibiting a sensitivity of 90% and a specificity of 100% when validated by RT-quantitative PCR. Therefore, we envision that T7/G4-CRISPR will serve as a promising RNA sensing approach to expand the toolbox of CRISPR-based diagnostics.
Topics: CRISPR-Cas Systems; G-Quadruplexes; Humans; Exodeoxyribonucleases; RNA; Nucleic Acid Amplification Techniques; CRISPR-Associated Proteins; Bacterial Proteins; Endodeoxyribonucleases
PubMed: 38860917
DOI: 10.1021/acs.analchem.4c01800 -
Chemical Communications (Cambridge,... Jun 2024Herein, a universal nucleic acid analysis platform was constructed for sensitive and accurate detection of miRNA-155 and ctDNA using isothermal amplification-assisted...
Herein, a universal nucleic acid analysis platform was constructed for sensitive and accurate detection of miRNA-155 and ctDNA using isothermal amplification-assisted CRISPR/Cas12a and a tetrahedral DNA nanostructure (TDN) supported sensing interface. Under the optimal experimental conditions, the prepared sensor achieved specific detection of miRNA-155 and ctDNA at as low as aM levels in 2.6 h. Furthermore, the platform was also successfully applied to human serum sample recovery experiments and cancer cell lysates, demonstrating outstanding reliability and accuracy. We firmly believe that this work provides a universal, sensitive, and practical tool for early clinical diagnosis.
Topics: Biosensing Techniques; Humans; CRISPR-Cas Systems; Electrochemical Techniques; MicroRNAs; DNA; Nucleic Acid Amplification Techniques; Circulating Tumor DNA; Nanostructures; Limit of Detection; Bacterial Proteins; Endodeoxyribonucleases; CRISPR-Associated Proteins
PubMed: 38860504
DOI: 10.1039/d4cc01646g