In trans adaptation and RNA-guided silencing by a Klebsiella plasmid-encoded type IV-A3 CRISPR-Cas system
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ABSTRACT:
PROVIDER: PRJEB61733 | ENA |
REPOSITORIES: ENA
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Project description:CRISPR-Cas mediated DNA-interference typically relies on sequence-specific binding and nucleolytic degradation of foreign genetic material. Type IV-A CRISPR-Cas systems diverge from this general mechanism, using a nuclease-independent interference pathway to suppress gene expression for gene regulation and plasmid competition. To understand how the type IV-A system associated effector complex achieves this interference, we determined cryo-EM structures of two evolutionarily distinct type IV-A complexes (types IV-38 A1 and IV-A3) bound to cognate DNA-targets in the presence and absence of the type IV-A signature DinG effector helicase. The structures reveal how the effector complexes recognize the protospacer adjacent motif and target-strand DNA to form an R-loop structure. Additionally, we reveal differences between types IV-A1 and IV-A3 in DNA interactions and structural motifs that allow for in trans recruitment of DinG. Our study provides a detailed view of type IV-A mediated DNA-interference and presents a structural foundation for engineering type IV-A-based genome editing tools.
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Project description:Anti-CRISPRs (Acrs) are diverse proteins or RNAs that protect invading phages and plasmids from host CRISPR-Cas immunity. Most Acrs neutralize their cognate Cas proteins via direct physical interaction. Here we describe CasPRs, a particularly widespread family of DNA-binding Acrs that recognize specific sequence motifs within cas gene coding regions, thereby blocking RNA polymerase and silencing transcription. We demonstrate that eight diverse CasPRs bind to the cas8b gene to repress the type I-B CRISPR-Cas system in its native host, Listeria seeligeri. Meanwhile, a CasPR from Streptococcus dysgalactiae silences type II-A CRISPR-Cas immunity by binding to the cas9 coding sequence. We found that one CasPR is required to inhibit CRISPR immunity during lysogeny by its host prophage. Taken together, our results indicate that members of the CasPR family have diverged to silence completely unrelated CRISPR types, and suggest transcriptional repression is a common mode of phage-mediated immune antagonism.
2026-03-10 | GSE324000 | GEO
Project description:Anti-CRISPRs (Acrs) are diverse proteins or RNAs that protect invading phages and plasmids from host CRISPR-Cas immunity. Most Acrs neutralize their cognate Cas proteins via direct physical interaction. Here we describe CasPRs, a particularly widespread family of DNA-binding Acrs that recognize specific sequence motifs within cas gene coding regions, thereby blocking RNA polymerase and silencing transcription. We demonstrate that eight diverse CasPRs bind to the cas8b gene to repress the type I-B CRISPR-Cas system in its native host, Listeria seeligeri. Meanwhile, a CasPR from Streptococcus dysgalactiae silences type II-A CRISPR-Cas immunity by binding to the cas9 coding sequence. We found that one CasPR is required to inhibit CRISPR immunity during lysogeny by its host prophage. Taken together, our results indicate that members of the CasPR family have diverged to silence completely unrelated CRISPR types, and suggest transcriptional repression is a common mode of phage-mediated immune antagonism.
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Project description:Bacteria and archaea use CRISPR-Cas adaptive immune systems to destroy complementary nucleic acids using RNAs derived from CRISPR loci. Here, we provide the first functional evidence for type IV CRISPR-Cas, demonstrating that the system from Pseudomonas aeruginosa strain PA83 mediates RNA-guided interference against a plasmid in vivo, both clearing the plasmid and inhibiting its uptake. This interference depends on the putative NTP-dependent helicase activity of Csf4/DinG.
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Project description:Transient elimination of RNAs by CRISPR-Cas13 systems has been widely used in basic and applied sciences over the last years. However, the efficiency of the system can be enhanced in vivo, and its application has generated controversy due to the recently described collateral activity in mammalian cells and mouse models. Here, we have optimized the CRISPR-RfxCas13d (CasRx) system for an optimized RNA targeting in vivo in zebrafish embryos, by different and compatible approaches. These strategies include the use of chemically modified guide RNAs to increase and sustain mRNA knockdown, an improved nuclear targeting, and the evaluation of ex vivo computational models for predicting gRNA efficiency in vivo. Furthermore, our study demonstrated that transient CRISPR-RfxCas13d approaches can effectively deplete endogenous mRNAs in zebrafish embryos without inducing collateral effects, except for targeting extremely abundant RNAs. For that, we have implemented alternative RNA-targeting CRISPR-Cas systems with reduced or absent collateral activity in zebrafish embryos. Altogether, these findings contribute to optimize CRISPR-Cas technology for RNA targeting in zebrafish through transient approaches and assist the progress of potential implications for knockdown therapies in vivo.
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Project description:In this work the favorable PAM sequences for a type IV-A CRISPR-Cas system were determined
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Project description:CRISPR/Cas loci commonly encode both proteins and small guide RNAs (crRNAs) to assemble ribonucleoproteins particles (RNPs) that confer a sequence-based, adaptive immunity against viruses and plasmids in prokaryotes. However, it has not been established whether this conserved synteny of RNA and protein genes is needed for the efficient RNP production in vivo. We show that the pathogenic bacterium Salmonella Typhimurium harbours two physically unlinked loci, CRISPR01 and CRISPR02, both of which produce mature crRNAs, although CRISPR02 lacks the protein genes for the type I-specific Cascade complex. Utilizing these coexisting complete and orphan CRISPR loci, we provide the first in vivo evidence for a crRNA-dependent assembly of Cascade. Strikingly, the full RNP assembles identically on crRNAs from either CRISPR cassette, i.e. regardless of their expression in cis or trans. Deep sequencing of Cas-bound transcripts identifies crRNAs derived from both loci as the sole bona fide targets of Cascade, although individual Cas proteins may interact with other cellular RNAs outside of the Cascade context. Altogether, our data demonstrate that CRISPR RNAs, independently of their origin, serve as the organizing centre of Cascade in vivo and are the main reason-to-be for its protein components in Salmonella.
2017-04-24 | GSE58602 | GEO