RESUMEN
Epigenome editing has emerged as a powerful technique for targeted manipulation of the chromatin and transcriptional landscape, employing designer DNA binding domains fused with effector domains, known as epi-editors. However, the constitutive expression of dCas9-based epi-editors presents challenges, including off-target activity and lack of temporal resolution. Recent advancements of dCas9-based epi-editors have addressed these limitations by introducing innovative switch systems that enable temporal control of their activity. These systems allow precise modulation of gene expression over time and offer a means to deactivate epi-editors, thereby reducing off-target effects associated with prolonged expression. The development of novel dCas9 effectors regulated by exogenous chemical signals has revolutionized temporal control in epigenome editing, significantly expanding the researcher's toolbox. Here, we provide a comprehensive review of the current state of these cutting-edge systems and specifically discuss their advantages and limitations, offering context to better understand their capabilities.
Asunto(s)
Epigénesis Genética , Edición Génica , Edición Génica/métodos , Humanos , Epigénesis Genética/efectos de los fármacos , Epigenoma , Sistemas CRISPR-Cas , Cromatina/genética , Cromatina/metabolismo , Epigenómica/métodos , AnimalesRESUMEN
Gluconobacter oxydans is an important Gram-negative industrial microorganism that produces vitamin C and other products due to its efficient membrane-bound dehydrogenase system. Its incomplete oxidation system has many crucial industrial applications. However, it also leads to slow growth and low biomass, requiring further metabolic modification for balancing the cell growth and incomplete oxidation process. As a non-model strain, G. oxydans lacks efficient genome editing tools and cannot perform rapid multi-gene editing and complex metabolic network regulation. In the last 15 years, our laboratory attempted to deploy multiple CRISPR/Cas systems in different G. oxydans strains and found none of them as functional. In this study, Cpf1-based or dCpf1-based CRISPRi was constructed to explore the targeted binding ability of Cpf1, while Cpf1-FokI was deployed to study its nuclease activity. A study on Cpf1 found that the CRISPR/Cpf1 system could locate the target genes in G. oxydans but lacked the nuclease cleavage activity. Therefore, the CRISPR/Cpf1-FokI system based on FokI nuclease was constructed. Single-gene knockout with efficiency up to 100% and double-gene iterative editing were achieved in G. oxydans. Using this system, AcrVA6, the anti-CRISPR protein of G. oxydans was discovered for the first time, and efficient genome editing was realized.
RESUMEN
Proteins capable of switching between distinct active states in response to biochemical cues are ideal for sensing and controlling biological processes. Activatable CRISPR-Cas systems are significant in precise genetic manipulation and sensitive molecular diagnostics, yet directly controlling Cas protein function remains challenging. Herein, we explore anti-CRISPR (Acr) proteins as modules to create synthetic Cas protein switches (CasPSs) based on computational chemistry-directed rational protein interface engineering. Guided by molecular fingerprint analysis, electrostatic potential mapping, and binding free energy calculations, we rationally engineer the molecular interaction interface between Cas12a and its cognate Acr proteins (AcrVA4 and AcrVA5) to generate a series of orthogonal protease-responsive CasPSs. These CasPSs enable the conversion of specific proteolytic events into activation of Cas12a function with high switching ratios (up to 34.3-fold). These advancements enable specific proteolysis-inducible genome editing in mammalian cells and sensitive detection of viral protease activities during virus infection. This work provides a promising strategy for developing CRISPR-Cas tools for controllable gene manipulation and regulation and clinical diagnostics.
Asunto(s)
Proteínas Asociadas a CRISPR , Edición Génica , Animales , Sistemas CRISPR-Cas/genética , Péptido Hidrolasas/genética , Péptido Hidrolasas/metabolismo , Proteínas Asociadas a CRISPR/genética , Proteínas Asociadas a CRISPR/metabolismo , Endopeptidasas/metabolismo , Proteasas Virales/genética , Proteasas Virales/metabolismo , Mamíferos/metabolismoRESUMEN
Anti-CRISPR (Acr) proteins are encoded by phages and other mobile genetic elements and inhibit host CRISPR-Cas immunity using versatile strategies. AcrIIC4 is a broad-spectrum Acr that inhibits the type II-C CRISPR-Cas9 system in several species by an unknown mechanism. Here, we determined a series of structures of Haemophilus parainfluenzae Cas9 (HpaCas9)-sgRNA in complex with AcrIIC4 and/or target DNA, as well as the crystal structure of AcrIIC4 alone. We found that AcrIIC4 resides in the crevice between the REC1 and REC2 domains of HpaCas9, where its extensive interactions restrict the mobility of the REC2 domain and prevent the unwinding of target double-stranded (ds) DNA at the PAM-distal end. Therefore, the full-length guide RNA:target DNA heteroduplex fails to form in the presence of AcrIIC4, preventing Cas9 nuclease activation. Altogether, our structural and biochemical studies illuminate a unique Acr mechanism that allows DNA binding to the Cas9 effector complex but blocks its cleavage by preventing R-loop formation, a key step supporting DNA cleavage by Cas9.
Asunto(s)
Bacteriófagos , Sistemas CRISPR-Cas , Estructuras R-Loop , ARN Guía de Sistemas CRISPR-Cas , ADN/metabolismo , Bacteriófagos/genética , Edición GénicaRESUMEN
Mobile genetic elements (MGEs) such as bacteriophages and their host prokaryotes are trapped in an eternal battle against each other. To cope with foreign infection, bacteria and archaea have evolved multiple immune strategies, out of which CRISPR-Cas system is up to now the only discovered adaptive system in prokaryotes. Despite the fact that CRISPR-Cas system provides powerful and delicate protection against MGEs, MGEs have also evolved anti-CRISPR proteins (Acrs) to counteract the CRISPR-Cas immune defenses. To date, 46 families of Acrs targeting type I CRISPR-Cas system have been characterized, out of which structure information of 21 families have provided insights on their inhibition strategies. Here, we review the non-canonical inhibition strategies adopted by Acrs targeting type I CRISPR-Cas systems based on their structure information by incorporating the most recent advances in this field, and discuss our current understanding and future perspectives. The delicate interplay between type I CRISPR-Cas systems and their Acrs provides us with important insights into the ongoing fierce arms race between prokaryotic hosts and their predators.
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Archaea , Bacterias , Bacteriófagos , Sistemas CRISPR-Cas , Secuencias Repetitivas Esparcidas , Proteínas Virales , Archaea/genética , Archaea/virología , Bacterias/genética , Bacterias/virología , Bacteriófagos/genética , Bacteriófagos/metabolismo , Sistemas CRISPR-Cas/genética , Evolución Molecular , Proteínas Virales/química , Proteínas Virales/genética , Conformación ProteicaRESUMEN
CRISPR-Cas, as a tool for gene editing, has received extensive attention in recent years. Anti-CRISPR (Acr) proteins can inactivate the CRISPR-Cas defense system during interference phase, and can be used as a potential tool for the regulation of gene editing. In-depth study of Anti-CRISPR proteins is of great significance for the implementation of gene editing. In this study, we developed a high-accuracy prediction model based on two-step model fusion strategy, called AcrPred, which could produce an AUC of 0.952 with independent dataset validation. To further validate the proposed model, we compared with published tools and correctly identified 9 of 10 new Acr proteins, indicating the strong generalization ability of our model. Finally, for the convenience of related wet-experimental researchers, a user-friendly web-server AcrPred (Anti-CRISPR proteins Prediction) was established at http://lin-group.cn/server/AcrPred, by which users can easily identify potential Anti-CRISPR proteins.
Asunto(s)
Sistemas CRISPR-Cas , Edición Génica , Sistemas CRISPR-Cas/genética , Algoritmos , Aprendizaje Automático , Proteínas Virales/genéticaRESUMEN
BACKGROUND: Anti-CRISPR proteins are potent modulators that inhibit the CRISPR-Cas immunity system and have huge potential in gene editing and gene therapy as a genome-editing tool. Extensive studies have shown that anti-CRISPR proteins are essential for modifying endogenous genes, promoting the RNA-guided binding and cleavage of DNA or RNA substrates. In recent years, identifying and characterizing anti-CRISPR proteins has become a hot and significant research topic in bioinformatics. However, as most anti-CRISPR proteins fall short in sharing similarities to those currently known, traditional screening methods are time-consuming and inefficient. Machine learning methods could fill this gap with powerful predictive capability and provide a new perspective for anti-CRISPR protein identification. RESULTS: Here, we present a novel machine learning ensemble predictor, called PreAcrs, to identify anti-CRISPR proteins from protein sequences directly. Three features and eight different machine learning algorithms were used to train PreAcrs. PreAcrs outperformed other existing methods and significantly improved the prediction accuracy for identifying anti-CRISPR proteins. CONCLUSIONS: In summary, the PreAcrs predictor achieved a competitive performance for predicting new anti-CRISPR proteins in terms of accuracy and robustness. We anticipate PreAcrs will be a valuable tool for researchers to speed up the research process. The source code is available at: https://github.com/Lyn-666/anti_CRISPR.git .
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Sistemas CRISPR-Cas , Edición Génica , Edición Génica/métodos , Aprendizaje Automático , Algoritmos , ARNRESUMEN
As the most abundant biological entities on earth, bacteriophages (phages) were considered as the antagonists of bacteria. With the rapid development of genomics and molecular biology technologies, a subtle and complex relationship between phages and their host bacteria has been uncovered. Prophage refers to an intracellular form of a bacteriophage, which is usually integrated into the hereditary material of the host. Prophage is ubiquitously distributed in bacterial genomes. It reproduces when the host does and can affect important biological properties of their bacterial hosts, such as virulence, biofilm formation and host immunity. Interestingly, prophages were also involved in regulating the lysogeny-lytic state by "monitoring" the quorum sensing of bacteria. Recently, anti-CRISPR proteins encoded by prophages were found, which attracts a lot of attention. In this review, we summarized the prediction, distribution, classification and functions of prophages to lay a foundation for further studying interactions between phages and bacteria.
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Bacteriófagos , Profagos , Bacterias/genética , Bacteriófagos/genética , Genoma Bacteriano , Lisogenia/genética , Profagos/genéticaRESUMEN
CRISPR-Cas systems are bacterial anti-viral systems, and phages use anti-CRISPR proteins (Acrs) to inactivate these systems. Here, we report a novel mechanism by which AcrIF11 inhibits the type I-F CRISPR system. Our structural and biochemical studies demonstrate that AcrIF11 functions as a novel mono-ADP-ribosyltransferase (mART) to modify N250 of the Cas8f subunit, a residue required for recognition of the protospacer-adjacent motif, within the crRNA-guided surveillance (Csy) complex from Pseudomonas aeruginosa. The AcrIF11-mediated ADP-ribosylation of the Csy complex results in complete loss of its double-stranded DNA (dsDNA) binding activity. Biochemical studies show that AcrIF11 requires, besides Cas8f, the Cas7.6f subunit for binding to and modifying the Csy complex. Our study not only reveals an unprecedented mechanism of type I CRISPR-Cas inhibition and the evolutionary arms race between phages and bacteria but also suggests an approach for designing highly potent regulatory tools in the future applications of type I CRISPR-Cas systems.
Asunto(s)
Proteínas Asociadas a CRISPR/antagonistas & inhibidores , Sistemas CRISPR-Cas/fisiología , Proteínas Virales/metabolismo , ADP-Ribosilación/fisiología , Proteínas Bacterianas/genética , Bacteriófagos/genética , Proteínas Asociadas a CRISPR/genética , Proteínas Asociadas a CRISPR/metabolismo , Sistemas CRISPR-Cas/genética , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas/genética , Microscopía por Crioelectrón/métodos , ADN/metabolismo , Modelos Moleculares , ARN Bacteriano/metabolismo , Proteínas Virales/genéticaRESUMEN
Gene editing is a genetic engineering technology that can modify, delete, or insert a small piece of DNA at a specific point in the genome of cells and organisms. Gene editing technology holds great promises in the fields of disease treatment, gene function regulation, gene detection, drug research and development, and crop breeding. However, side effects, such as off-target editing, genotoxicity and other issues, have gradually emerged in the application. In the CRISPR (clustered regularly interspaced short palindromic repeats) system, the Cas9 nuclease can specifically recognize the target DNA by the base pairing of a guide RNA (gRNA) with the target DNA. Upon target recognition, the two DNA strands are cleaved by distinct domains of the Cas9 nuclease. Since both Cas9 nuclease and gRNA possess different characteristics in their own activities, recognition sites and binding ability to specific target, it is essential to precisely regulate the activity of Cas9 nuclease and gRNA in both time and space manners, thus preventing the risk of side effects and enhancing the precise regulation of the CRISPR/Cas9 gene editing technology. In this review, we summarize the advances in the precise control of gene editing, especially CRISPR/cas9 over several dimensions using fusion Cas9 proteins regulated by light, temperature and drugs, exploiting and screening anti-CRISPRs proteins, synthesizing and identifying small molecules- inhibitors, and developing other therapeutic agents, thereby providing a reference and research ideas for human disease treatment, crop and livestock improvement and prevention of biotechnology misuse.
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Sistemas CRISPR-Cas , Edición Génica , ARN Guía de Kinetoplastida/genética , Animales , Biotecnología , Productos Agrícolas , Humanos , GanadoRESUMEN
In the arms race against bacteria, bacteriophages have evolved diverse anti-CRISPR proteins (Acrs) that block CRISPR-Cas immunity. Acrs play key roles in the molecular coevolution of bacteria with their predators, use a variety of mechanisms of action, and provide tools to regulate Cas-based genome manipulation. Here, we present structural and functional analyses of AcrIIA6, an Acr from virulent phages, exploring its unique anti-CRISPR action. Our cryo-EM structures and functional data of AcrIIA6 binding to Streptococcus thermophilus Cas9 (St1Cas9) show that AcrIIA6 acts as an allosteric inhibitor and induces St1Cas9 dimerization. AcrIIA6 reduces St1Cas9 binding affinity for DNA and prevents DNA binding within cells. The PAM and AcrIIA6 recognition sites are structurally close and allosterically linked. Mechanistically, AcrIIA6 affects the St1Cas9 conformational dynamics associated with PAM binding. Finally, we identify a natural St1Cas9 variant resistant to AcrIIA6 illustrating Acr-driven mutational escape and molecular diversification of Cas9 proteins.
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Bacteriófagos/metabolismo , Proteína 9 Asociada a CRISPR/metabolismo , Sistemas CRISPR-Cas , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas , ADN/metabolismo , Streptococcus thermophilus/enzimología , Proteínas Virales/metabolismo , Regulación Alostérica , Bacteriófagos/genética , Sitios de Unión , Proteína 9 Asociada a CRISPR/genética , Proteína 9 Asociada a CRISPR/ultraestructura , ADN/genética , ADN/ultraestructura , Escherichia coli/enzimología , Escherichia coli/genética , Humanos , Células K562 , Cinética , Mutación , Unión Proteica , Conformación Proteica , Streptococcus thermophilus/genética , Relación Estructura-Actividad , Proteínas Virales/genética , Proteínas Virales/ultraestructuraRESUMEN
The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) ribonucleoprotein (RNP) complex is an RNA-guided DNA-nuclease that is part of the bacterial adaptive immune system. CRISPR/Cas9 RNP has been adapted for targeted genome editing within cells and whole organisms with new applications vastly outpacing detection and quantification of gene-editing reagents. Detection of the CRISPR/Cas9 RNP within biological samples is critical for assessing gene-editing reagent delivery efficiency, retention, persistence, and distribution within living organisms. Conventional detection methods are effective, yet the expense and lack of scalability for antibody-based affinity reagents limit these techniques for clinical and/or field settings. This necessitates the development of low cost, scalable CRISPR/Cas9 RNP affinity reagents as alternatives or augments to antibodies. Herein, we report the development of the Streptococcus pyogenes anti-CRISPR/Cas9 protein, AcrIIA4, as a novel affinity reagent. An engineered cysteine linker enables covalent immobilization of AcrIIA4 onto glassy carbon electrodes functionalized via aryl diazonium chemistry for detection of CRISPR/Cas9 RNP by electrochemical, fluorescent, and colorimetric methods. Electrochemical measurements achieve a detection of 280 pM RNP in reaction buffer and 8â¯nM RNP in biologically representative conditions. Our results demonstrate the ability of anti-CRISPR proteins to serve as robust, specific, flexible, and economical recognition elements in biosensing/quantification devices for CRISPR/Cas9 RNP.
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Proteínas Bacterianas/análisis , Bacteriófagos/química , Técnicas Biosensibles/métodos , Proteína 9 Asociada a CRISPR/análisis , Streptococcus pyogenes/química , Proteínas Virales/química , Sistemas CRISPR-Cas , Proteínas Inmovilizadas/química , Ligandos , Modelos MolecularesRESUMEN
CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR-associated proteins) systems provide prokaryotic cells with adaptive immunity against invading bacteriophages. Bacteriophages counteract bacterial responses by encoding anti-CRISPR inhibitor proteins (Acr). However, the structural basis for their inhibitory actions remains largely unknown. Here, we report the crystal structure of the AcrIIA2-SpyCas9-sgRNA (single-guide RNA) complex at 3.3 Å resolution. We show that AcrIIA2 binds SpyCas9 at a position similar to the target DNA binding region. More specifically, AcrIIA2 interacts with the protospacer adjacent motif (PAM) recognition residues of Cas9, preventing target double-stranded DNA (dsDNA) detection. Thus, phage-encoded AcrIIA2 appears to act as a DNA mimic that blocks subsequent dsDNA binding by virtue of its highly acidic residues, disabling bacterial Cas9 by competing with target dsDNA binding with a binding motif distinct from AcrIIA4. Our study provides a more detailed mechanistic understanding of AcrIIA2-mediated inhibition of SpyCas9, the most widely used genome-editing tool, opening new avenues for improved regulatory precision during genome editing.
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Bacteriófagos/metabolismo , Proteína 9 Asociada a CRISPR/metabolismo , Sistemas CRISPR-Cas , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas , Escherichia coli/enzimología , Edición Génica/métodos , Imitación Molecular , Proteínas Virales/metabolismo , Bacteriófagos/genética , Sitios de Unión , Unión Competitiva , Proteína 9 Asociada a CRISPR/antagonistas & inhibidores , Proteína 9 Asociada a CRISPR/química , Proteína 9 Asociada a CRISPR/genética , ADN/química , ADN/genética , ADN/metabolismo , Escherichia coli/genética , Escherichia coli/virología , Modelos Moleculares , Conformación de Ácido Nucleico , Unión Proteica , Conformación Proteica , Dominios y Motivos de Interacción de Proteínas , ARN Guía de Kinetoplastida/química , ARN Guía de Kinetoplastida/genética , ARN Guía de Kinetoplastida/metabolismo , Relación Estructura-Actividad , Proteínas Virales/química , Proteínas Virales/genéticaRESUMEN
Virus capsids are protein shells that protect the viral genome from environmental assaults, while maintaining the high internal pressure of the tightly packaged genome. To elucidate how capsids maintain stability under harsh conditions, we investigated the capsid components of the hyperthermophilic phage P74-26. We determined the structure of capsid protein gp87 and show that it has the same fold as decoration proteins in many other phages, despite lacking significant sequence homology. We also find that gp87 is significantly more stable than mesophilic homologs. Our analysis of the gp87 structure reveals that the core "ß tulip" domain is conserved in trimeric capsid components across numerous double-stranded DNA viruses, including Herpesviruses. Moreover, this ß barrel domain is found in anti-CRISPR protein AcrIIC1, suggesting a mechanism for the evolution of this Cas9 inhibitor. Our work illustrates the principles for increased stability of gp87, and extends the evolutionary reach of the ß tulip domain.
Asunto(s)
Bacteriófagos/metabolismo , Proteínas de la Cápside/química , Herpesviridae/metabolismo , Bacteriófagos/química , Proteína 9 Asociada a CRISPR/antagonistas & inhibidores , Evolución Molecular , Herpesviridae/química , Modelos Moleculares , Dominios Proteicos , Pliegue de Proteína , Estabilidad Proteica , Estructura Secundaria de ProteínaRESUMEN
Prokaryotic CRISPR-Cas adaptive immune systems utilize sequence-specific RNA-guided endonucleases to defend against infection by viruses, bacteriophages, and mobile elements, while these foreign genetic elements evolve diverse anti-CRISPR proteins to overcome the CRISPR-Cas-mediated defense of the host. Recently, AcrIIA2 and AcrIIA4, encoded by Listeria monocytogene prophages, were shown to block the endonuclease activity of type II-A Streptococcus pyogene Cas9 (SpyCas9). We now report the crystal structure of AcrIIA4 in complex with single-guide RNA-bound SpyCas9, thereby establishing that AcrIIA4 preferentially targets critical residues essential for PAM duplex recognition, as well as blocks target DNA access to key catalytic residues lining the RuvC pocket. These structural insights, validated by biochemical assays on key mutants, demonstrate that AcrIIA4 competitively occupies both PAM-interacting and non-target DNA strand cleavage catalytic pockets. Our studies provide insights into anti-CRISPR-mediated suppression mechanisms for inactivating SpyCas9, thereby broadening the applicability of CRISPR-Cas regulatory tools for genome editing.