Non-identity-mediated CRISPR-bacteriophage interaction mediated via the Csy and Cas3 proteins.
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Cas3 acts downstream of crRNA production and requires both its HD and its DEXD/H domains
"the core Cas protein Cas3 functions downstream of small crRNA production and that this protein requires functional HD (predicted phosphohydrolase) and DEXD/H (predicted helicase) domains to suppress biofilm formation in DMS3 lysogens"
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The PA14 Yersinia-subtype locus was reported not to confer resistance to phage DMS3, acting instead on biofilm formation
"the Yersinia-subtype CRISPR region of Pseudomonas aeruginosa strain UCBPP-PA14 plays no detectable role in viral immunity but instead is required for bacteriophage DMS3-dependent inhibition of biofilm formation"
Bacteriophage genes that inactivate the CRISPR/Cas bacterial immune system.
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The PA14 type I-F locus restricts replication of CRISPR-sensitive phages
"The CRISPR-sensitive phages fail to replicate on PA14 due to the action of the CRISPR/Cas system14, but are able to replicate on PA14"
Multiple mechanisms for CRISPR-Cas inhibition by anti-CRISPR proteins.
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An anti-CRISPR protein inhibits the system by binding Cas3 and blocking its recruitment to the DNA-bound surveillance complex
"The third anti-CRISPR protein operates by binding to the Cas3 helicase-nuclease and preventing its recruitment to the DNA-bound CRISPR-Cas complex"
Foreign DNA acquisition by the I-F CRISPR-Cas system requires all components of the interference machinery.
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Truncating the fused protein after the Cas2 module abolishes spacer acquisition
"A D124Oc mutation in the cas2+cas3 gene that introduced an ochre stop codon instead of aspartate codon at position 124, after the cas2 portion of the fused gene, abolished spacer acquisition"
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Point mutants of the nuclease and helicase catalytic centres each abolish spacer acquisition
"Point mutations introducing single amino acid substitutions in the endonuclease (D124A) and helicase (D576N) domains of the Cas3 protein also prevented spacer acquisition"
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Type I-F systems encode Cas2 and Cas3 as a single fused protein
"A specific feature of type I-F systems is a fusion of cas2 and cas3 homologs, which are encoded on separate genes in other CRISPR"
Structural basis of Cas3 inhibition by the bacteriophage protein AcrF3.
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Crystal structure of the anti-CRISPR AcrF3 bound to Pseudomonas aeruginosa Cas3
"we report the crystal structure of the anti-CRISPR protein AcrF3 in complex with Pseudomonas aeruginosa Cas3 (PaCas3)"
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Inhibition works by trapping a nucleotide-bound state, plugging the helicase DNA-binding tunnel and masking the Cascade-recruitment surface
"locks PaCas3 in an ADP-bound form, blocks the entrance of the DNA-binding tunnel in the helicase domain, and masks the linker region and C-terminal domain of PaCas3, thereby preventing recruitment by Cascade and inhibiting the type I-F CRISPR-Cas system"
Cryo-EM Structures Reveal Mechanism and Inhibition of DNA Targeting by a CRISPR-Cas Surveillance Complex.
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R-loop formation by the Csy complex triggers recruitment of Cas3, which degrades the target DNA
"Formation of the R-loop in both Csy and the related Type I-E Cse complexes triggers recruitment of the endonuclease Cas3, which degrades the target dsDNA"
Inhibition mechanisms of AcrF9, AcrF8, and AcrF6 against type I-F CRISPR-Cas complex revealed by cryo-EM.
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In vitro DNA cleavage by the reconstituted type I-F system is strictly Cas3-dependent
"WT AcrF9 inhibits the DNA binding and subsequent Cas3 recruitment of the Csy complex, suppressing DNA degradation"
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Relieving anti-CRISPR inhibition increases Cas3-mediated DNA cleavage
"We found that these mutations result in much stronger DNA cleavage activities of Cas3 compared to the WT AcrF6"
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Cas3 docks on the C-terminal helical bundle of the Csy large subunit Cas8f
"The Cas3 protein (P. aeruginosa) was proposed to interact with the C-terminal helical bundle of Cas8f"