Search Results (51)

Thermophilic prokaryotic Argonaute proteins (pAgos) have emerged as powerful tools for nucleic acid manipulation, with applications in nucleic acid detection, and DNA assembly. However, their strong dependence on high-temperature catalytic activity limits their utility under moderate conditions. TcAgo, a thermophilic Argonaute nuclease from Thermogladius calderae, exhibits efficient DNA-guided target DNA cleavage above 80 °C, yet its structural basis and catalytic mechanism remain unclear. In this study, we attempted to analyze the structure of the TcAgo ternary complex and performed rational engineering based on its structure and characteristics of cold-adapted enzymes. A mutant, mTcAgo (K574G, D577G), was obtained with enhanced activity at moderate temperatures. Compared with the wild type, mTcAgo exhibited significantly improved cleavage activity toward both DNA and RNA targets at 37 °C. It utilized multiple guide types, including 5′OH- and 5′P-modified DNA and RNA guides, with a preference for 5′P-gDNA. mTcAgo displayed optimal activity at pH 7–8, broad salt tolerance, and an extended catalytic temperature range from 37 °C to 95 °C. Notably, it retained high activity after incubation at 90 °C, with a melting temperature of ~88 °C, and efficiently cleaved GC-rich targets under low Mg²⁺ conditions. These results demonstrate that rational cold-adaptation engineering can expand the functional temperature range of thermophilic pAgos, providing a promising strategy for developing versatile nucleic acid tools. Full article

The CRISPR-Cas systems, identified initially as adaptive immune mechanisms in bacteria and archaea against viral threats, have rapidly evolved into transformative tools in genetic engineering and biotechnology. These RNA-guided systems are broadly classified into Class 1, comprising multi-subunit complexes, and Class 2, characterized by compact single-effector protein, such as Cas9, Cas12, and Cas13. Their remarkable structural and functional diversity enables microorganisms to adapt to diverse ecological niches, offering a vast repertoire of genome-editing strategies. Beyond their natural role in maintaining genome integrity and defense, CRISPR-Cas systems have been extensively repurposed for precise genome modification, transcriptional regulation, epigenetic editing, and nucleic acid detection. Recent advances in computational mining of microbial genomes and metagenomes have uncovered a broad range of novel CRISPR effectors with unique properties, distinct protospacer adjacent motif (PAM) requirements, RNA-targeting capabilities, miniature architectures, and promiscuous cleavage activities that significantly expand the molecular biology toolkit. The development of CRISPR-based technologies such as base editing, prime editing, gene knock-in/out, and live-cell DNA/RNA imaging exemplifies the versatility of these systems. Despite the challenges associated with delivering complex Class 1 systems, both classes are now being actively harnessed across diverse microbial platforms. Concurrently, the CRISPR-Cas research, particularly for guide RNA (gRNA) design and activity prediction, has revolutionized target specificity and editing efficiency. This review presents a comprehensive overview of CRISPR-Cas system diversity, their genomic landscape in microorganisms, and their cutting-edge biotechnological applications. It also emphasizes the transformative potential of CRISPR in synthetic biology, therapeutics, diagnostics, environmental remediation, and agriculture, while also addressing the ethical and biosafety considerations surrounding its deployment. As CRISPR-Cas systems continue to evolve, they stand at the forefront of innovations that bridge natural microbial immunity with engineered precision tools for next-generation biotechnology. Full article

Conventional Escherichia coli (E. coli) detection methods are often time-consuming, while molecular diagnostics typically rely on expensive thermocycling equipment. To address these limitations, this study developed a rapid nucleic acid detection method for E. coli by integrating multienzyme isothermal rapid amplification (MIRA) with Pyrococcus furiosus Argonaute (PfAgo)-mediated targeted cleavage. The conserved housekeeping gene phoA was selected as the target, and specific MIRA primers and 5′-phosphorylated guide DNAs (gDNAs) were designed accordingly. After exponential amplification at 39 °C, the amplicons were specifically recognized by PfAgo at 95 °C, leading to molecular beacon cleavage and generation of a detectable FAM fluorescence signal. Among the tested guides, gDNA6 showed the highest cleavage efficiency. Optimal performance was achieved with 1 μM PfAgo, 0.5 μM gDNA, and 5 mM MnCl₂. The optimized MIRA-PfAgo assay demonstrated a limit of detection of 10⁰ copies/μL, comparable to qPCR, and exhibited high specificity with no cross-reactivity against common enteric pathogens. In 28 clinical and environmental samples, the assay results were fully consistent with those of qPCR. Overall, the MIRA-PfAgo platform provides a rapid, sensitive, and specific approach for E. coli detection, demonstrating strong potential to reduce reliance on precision thermal cyclers for resource-limited applications. Full article

Bacillus and Paenibacillus species are common and widely distributed microorganisms in food systems, often implicated in food spoilage and quality issues. Bacillus subtilis, in particular, has been associated with gas production and package bulging in seasoned foods. In this study, we developed a rapid and visual detection method for Bacillus subtilis by integrating (Recombinase Polymerase Amplification) RPA with (Clustered Regularly Interspaced Short Palindromic Repeats) CRISPR/Cas12a technology (designated as RPA-CRISPR/Cas12a). Specific RPA primers and probes were designed based on the conserved gyrB gene of Bacillus subtilis. Two sets of crRNA were designed according to the number of T-rich PAM sites on the RPA-amplified target sequence, and the reaction conditions were optimized in combination with the CRISPR/Cas12a trans-cleavage detection technology. Under optimized conditions, the crRNA3 guide (with a TT-rich PAM site) demonstrated superior cleavage efficiency compared to crRNA2 (TTT-rich PAM), while crRNA1 (TTTT-rich PAM) showed no activity. The assay achieved a detection limit of 150 pg/μL for genomic DNA and 5.5 CFU/mL for bacterial suspensions within 10 min at 37 °C. The method exhibited high specificity and sensitivity, providing a robust tool for early and on-site detection of Bacillus subtilis in food products. Full article

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9, a genome-editing technology pioneered in 2012, enables the precise correction of deleterious mutations or disruption of disease-causing genes through targeted double-strand breaks (DSBs), offering potential for treating genetic diseases. However, CRISPR/Cas9 can cause off-target cleavage at non-specific DNA sites, leading to unintended insertions or deletions (indels), which limit its safety and applicability despite ongoing improvements in specificity. Recently, prime editing (PE), an advanced CRISPR-derived technology, has been employed with a Cas9 nickase (Cas9n) fused with a reverse transcriptase and a prime editing guide RNA (pegRNA) to enable precise insertions, deletions, and transversions without inducing DSBs, thus reducing risks of indels and chromosomal aberrations. Furthermore, ongoing optimizations, such as improved pegRNA design and enhanced editing efficiency, have expanded the applications of PE in medical therapeutics, agriculture, and fundamental research. This review summarizes recent advancements in the PE system, including optimized pegRNA designs and enzyme engineering for enhanced efficiency and specificity, alongside novel delivery methods. It also evaluates cutting-edge delivery strategies, such as adeno-associated virus (AAV) vectors, lipid nanoparticles (LNPs) and novel extracellular vesicle (EV)-based systems, and explores PE applications in vitro and in vivo, including disease modeling and therapeutic gene correction. Full article

Argonaute (Ago) proteins are ubiquitous across all domains of life. Some prokaryotic Agos (pAgos) function as endonucleases that utilize short nucleic acid guides to recognize and cleave complementary targets. Yet, considerable diversity within pAgos leaves many of their biochemical and functional features insufficiently understood. This study characterizes CalAgo, an pAgo from the mesophilic bacterium Cohnella algarum, which demonstrates DNA-guided DNA endonuclease and RNA endonuclease activities at physiological temperatures. CalAgo’s cleavage activity depends on Mn²⁺ and Mg²⁺ ions and remains effective across a wide range of temperatures and pH levels. CalAgo utilizes only short guides ranging from 15 to 21 nucleotides (nt) in length, in contrast to other reported pAgos that target both DNA and RNA, which often exhibit broad guide selectivity. CalAgo preferentially loads 5′-phosphorylated guides and shows no significant preference among guides with different 5′-end nucleotides. CalAgo is sensitive to guide–target mismatches, and introducing a single mismatch at positions 12 or 15 of the guide strand abolished detectable activity. Structural modeling suggests that this unique guide specificity may originate from structural features in its PAZ domain involved in 3′-guide binding. In summary, this study deepens insight into mesophilic pAgos and supports their potential utility in nucleic acid-based applications. Full article

CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPR-associated protein) nucleases enable precise genome editing, but off-target cleavage remains a critical challenge. Here, we report the development of MAD7_HF, a high-fidelity variant of the MAD7 nuclease engineered through a bacterial screening system leveraging the DNA gyrase-targeting toxic gene ccdB. This system couples survival to efficient on-target cleavage and minimal off-target activity, mimicking the transient action required for high-precision editing. Through iterative selection and sequencing validation, we identified MAD7_HF, harboring three substitutions (R187C, S350T, K1019N) that enhanced discrimination between on- and off-target sites. In Escherichia coli assays, MAD7_HF exhibited a >20-fold reduction in off-target cleavage across multiple mismatch contexts while maintaining on-target efficiency comparable to wild-type MAD7. Structural modeling revealed that these mutations stabilize the guide RNA-DNA hybrid at on-target sites and weaken interactions with mismatched sequences. This work establishes a high-throughput bacterial screening strategy that allows the identification of Cas12a variants with improved specificity at a given target site, providing a useful framework for future efforts to develop precision genome-editing tools. Full article

Pest management is undergoing a transformative shift with the development of the cutting-edge antisense technologies: RNA interference (RNAi), contact unmodified antisense DNA biotechnology (CUADb), and the CRISPR-associated proteins (CRISPR/Cas). These approaches function by facilitating sequence-specific pairing of nucleic acids followed by nuclease-mediated cleavage, offering exceptional precision for targeted pest control. While RNA-guided mechanisms such as RNAi and CRISPR/Cas were initially characterized in non-insect systems, primarily as innate defenses against viral infections, the DNA-guided CUADb pathway was first identified in insect pests as a functional pest control strategy. Its broader role in ribosomal RNA (rRNA) biogenesis was recognized later. Together, these discoveries have revealed an entirely new dimension of gene regulation, with profound implications for sustainable pest management. Despite sharing a common principle of sequence-specific targeting RNAi, CUADb, and CRISPR/Cas differ in several key aspects, including their mechanisms of action, target specificity, and applicability. Rather than serving as universal solutions, each technology is likely to be optimally effective against specific pest groups. Moreover, these technologies allow for rapid adaptation of control strategies to overcome target-site resistance, ensuring long-term efficacy. This review summarizes the core functional characteristics, potential applications, and current limitations of each antisense technology, emphasizing their complementary roles in advancing environmentally sustainable pest control. By integrating foundational biological discoveries with applied innovations, this work provides a new perspectives on incorporating antisense-based strategies into next-generation integrated pest management systems. Full article

Clostridium butyricum Argonaute (CbAgo) can achieve DNA-guided DNA recognition and cleavage at physiological temperatures (~37 °C), making it a promising tool for gene editing. However, its significant off-target effects, particularly associated with the seed region (sites 2–8), pose challenges for precise gene therapy. This study focuses on enhancing the specificity of the seed region recognition to mitigate these off-target effects. We investigated the molecular recognition process between the CbAgo-gDNA complex and the seed region of the target DNA using molecular dynamics simulations and automated path searching. Our findings reveal that positively charged residues located in an α-helix domain at the DNA–protein interface (R279, H285, K287, K288, K291, K298) facilitate rapid binding to the DNA phosphate backbone. Such interaction enhances the pre-formation of the DNA double helix, reducing the reliance on base complementarity during duplex pairing. Further simulations showed that alanine replacement of these positively charged residues led to significantly improved sequence specificity for the target DNA seed region. Collectively, these results offered critical insights into the origin of off-target recognition by CbAgo in its seed region, shedding lights on its fidelity enhancement. Full article

Mesophilic microbial sources of prokaryotic Argonaute (pAgo) programmable nucleases have garnered considerable attention for their potential applications in genome editing and molecular diagnostics. In this study, we characterized a novel pAgo from the mesophilic bacterium Chroococcidiopsis sp. (ChAgo), which can cleave single-stranded DNA (ssDNA) using both 5′-phosphorylated guide DNA (5′P-gDNA) and 5′-hydroxylated guide DNA (5′OH-gDNA). Efficient cleavage occurs using 14–25 nt 5′P-gDNA and 13–20 nt 5′OH-gDNA in the presence of Mn²⁺ ions at temperatures ranging from 25 to 75 °C, with optimal activity at 55 °C. ChAgo demonstrates low tolerance for single-base mismatches, similar to other pAgo proteins. The cleavage efficiency varies based on the guide/target pair, with mismatches at specific positions significantly reducing activity. For instance, mismatches at positions 4, 5, or 12 in T-gDNA/target pairs and at positions 5 or 8–10 in g38NT-gDNA/target pairs notably decrease efficiency. ChAgo’s sensitivity to mismatches makes it a promising tool for nucleic acid manipulation and detection, requiring initial screening for high cleavage efficiency sites and subsequent identification of mismatch positions. Full article

DNA gyrase is a bacterial type IIA topoisomerase that can create temporary double-stranded DNA breaks to regulate DNA topology and an archetypical target of antibiotics. The widely used quinolone class of drugs use a water–metal ion bridge in interacting with the GyrA subunit of DNA gyrase. Zoliflodacin sits in the same pocket as quinolones but interacts with the GyrB subunit and also stabilizes lethal double-stranded DNA breaks. Gepotidacin has been observed to sit on the twofold axis of the complex, midway between the two four-base-pair separated DNA-cleavage sites and has been observed to stabilize singe-stranded DNA breaks. Here, we use information from three crystal structures of complexes of Staphlococcus aureus DNA gyrase (one with a precursor of gepotidacin and one with the progenitor of zoliflodacin) to propose a simple single moving metal-ion-catalyzed DNA-cleavage mechanism. Our model explains why the catalytic tyrosine is in the tyrosinate (negatively charged) form for DNA cleavage. Movement of a single catalytic metal-ion (Mg²⁺ or Mn²⁺) guides water-mediated protonation and cleavage of the scissile phosphate, which is then accepted by the catalytic tyrosinate. Type IIA topoisomerases need to be able to rapidly cut the DNA when it becomes positively supercoiled (in front of replication forks and transcription bubbles) and we propose that the original purpose of the small Greek Key domain, common to all type IIA topoisomerases, was to allow access of the catalytic metal to the DNA-cleavage site. Although the proposed mechanism is consistent with published data, it is not proven and other mechanisms have been proposed. Finally, how such mechanisms can be experimentally distinguished is considered. Full article

Piglet diarrhea poses significant economic losses to the pig industry, posing a worldwide challenge that urgently needs to be addressed in pig breeding practices. Porcine rotavirus (PoRV) is an important viral diarrhea pathogen in piglets, with a high incidence rate and a tendency to cause growth retardation. To enhance the sensitivity and specificity of PoRV detection, we sequenced the NSP3 gene of G5 and G9 genotypes of rotavirus A (RVA), enabling simultaneous detection of the two serotypes. Subsequently, we developed a rapid PoRV detection method using a combination of recombinase-aided amplification (RAA) and CRISPR/Cas12a. In this method, Cas12a binds to RAA amplification products, guided by CRISPR-derived RNA (crRNA), which activates its cleavage activity and releases fluorescence by cutting FAM-BHQ-labeled single-stranded DNA (ssDNA). In the optimized reaction system, the recombinant plasmid PoRV can achieve a highly sensitive reaction within 30 min at 37 °C, with a detection limit as low as 2.43 copies/μL, which is ten times higher in sensitivity compared to the qPCR method. Results from specificity testing indicate that no cross-reactivity was observed between the RAA-CRISPR/Cas12a analysis of PoRV and other viral pathogens, including PoRV G3, PoRV G4, porcine epidemic diarrhea virus (PEDV), porcine epidemic diarrhea (PDCoV), and porcine reproductive and respiratory syndrome virus (PRRSV). In the clinical sample detection using the RAA-CRISPR/Cas12a method and qPCR, Cohen’s Kappa value reached as high as 0.952. Furthermore, this approach eliminates the need for large-scale instrumentation, offering a visual result under an ultraviolet lamp through fluorescence signal output. Full article

The design of controllable and precise RNA-targeted CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats) systems is an important problem of modern molecular biology and genetic technology. Herein, we have designed a series of photocleavable guide CRISPR RNAs (crRNA) and their 2′-modified (2′-fluoro and locked nucleic acid) analogs containing one or two 1-(2-nitrophenyl)-1,2-ethanediol photolabile linkers (PL). We have demonstrated that these crRNAs can be destroyed by relatively mild UVA irradiation with the rate constants 0.24–0.77 min⁻¹ and that the photocleavage markedly slows down the action of Cas9 nuclease in the model in vitro system. Two PLs provide more rapid crRNA destruction than a single linker. PLs in the crRNA structure improve the specificity of DNA cleavage by Cas9 nuclease for the fully complementary target. The application of photocleavable crRNA in CRISPR/Cas9 genome editing permits the system to be switched off in a spatiotemporally controlled manner, thus alleviating its off-target effects. Full article

Infection by retroviruses and the mobilization of transposable elements cause DNA damage that can be catastrophic for a cell. If the cell survives, the mutations generated by retrotransposition may confer a selective advantage, although, more commonly, the effect of new integrants is neutral or detrimental. If retrotransposition occurs in gametes or in the early embryo, it introduces genetic modifications that can be transmitted to the progeny and may become fixed in the germline of that species. PIWI-interacting RNAs (piRNAs) are single-stranded, 21–35 nucleotide RNAs generated by the PIWI clade of Argonaute proteins that maintain the integrity of the animal germline by silencing transposons. The sequence specific manner by which piRNAs and germline-encoded PIWI proteins repress transposons is reminiscent of CRISPR, which retains memory for invading pathogen sequences. piRNAs are processed preferentially from the unspliced transcripts of piRNA clusters. Via complementary base pairing, mature antisense piRNAs guide the PIWI clade of Argonaute proteins to transposon RNAs for degradation. Moreover, these piRNA-loaded PIWI proteins are imported into the nucleus to modulate the co-transcriptional repression of transposons by initiating histone and DNA methylation. How retroviruses that invade germ cells are first recognized as foreign by the piRNA machinery, as well as how endogenous piRNA clusters targeting the sequences of invasive genetic elements are acquired, is not known. Currently, koalas (Phascolarctos cinereus) are going through an epidemic due to the horizontal and vertical transmission of the KoRV-A gammaretrovirus. This provides an unprecedented opportunity to study how an exogenous retrovirus becomes fixed in the genome of its host, and how piRNAs targeting this retrovirus are generated in germ cells of the infected animal. Initial experiments have shown that the unspliced transcript from KoRV-A proviruses in koala testes, but not the spliced KoRV-A transcript, is directly processed into sense-strand piRNAs. The cleavage of unspliced sense-strand transcripts is thought to serve as an initial innate defense until antisense piRNAs are generated and an adaptive KoRV-A-specific genome immune response is established. Further research is expected to determine how the piRNA machinery recognizes a new foreign genetic invader, how it distinguishes between spliced and unspliced transcripts, and how a mature genome immune response is established, with both sense and antisense piRNAs and the methylation of histones and DNA at the provirus promoter. Full article

CRISPR-Cas12e is a recently identified gene-editing tool mainly known because its relatively small size benefits cell delivery. Drastically different from Cas9, it creates a blunt-end double-strand breakage of the DNA via two cleavage sites; Cas12e produces a sticky-end double-strand breakage of the DNA through only one cleavage site in its RuvC domain, meaning two consecutive cleavage events first on the non-target strand (ntsDNA) and then the target strand (tsDNA). Though crucial for Cas12e’s cleavage efficiency, the mechanism by which Cas12e loads tsDNA for the second cleavage remains elusive. Through molecular dynamics simulations and our recently matured traveling-salesman-based automated path-searching (TAPS) algorithm, we identified a series of positively charged residues (Arg856^TSL, Arg768^RuvC, Lys898^TSL, Arg904^TSL, Arg764^RuvC) that guide the tsDNA backbone toward the cleavage site of wild-type PlmCas12e. Further simulations of the R856L and R904L mutants supported such observations. More interestingly, we found the key role of Glu662^RuvC in coordinating Arg764^RuvC, preventing its occupation of the cleavage site, and facilitating tsDNA cleavage. Additional simulations confirmed that mutating Glu662^RuvC to valine disabled such coordination and created a stable intermediate state with Arg764^RuvC occupying the cleavage site before tsDNA loading. These insights, revealing an elaborate mechanism of cleavage facilitation, offer essential guiding principles for future rational engineering of Cas12e into more efficient gene-editing tools. Full article