Regulation of CRISPR–Cas adaptive immune systems

Patterson, Adrian G; Yevstigneyeva, Mariya S; Fineran, Peter C.

doi:10.1016/j.mib.2017.02.004

Cited by 74 publications

(75 citation statements)

References 63 publications

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“…The absence of this mechanism is possibly because this strategy would be unable to interfere with CRISPR nucleases that were assembled prior to infection. Nonetheless, many CRISPR systems are tightly regulated and are often activated in response to cell density and other factors (Høyland-Kroghsbo et al, 2016; Patterson et al, 2016, 2017). Inhibition of crRNA binding could be an effective Acr method to inhibit those systems where RNP assembly coincides with phage infection, and such inhibitors may yet be discovered.…”

Section: Discussionmentioning

confidence: 99%

A Broad-Spectrum Inhibitor of CRISPR-Cas9

Harrington¹,

Doxzen²,

Ma³

et al. 2017

Cell

226

317

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SUMMARY CRISPR-Cas9 proteins function within bacterial immune systems to target and destroy invasive DNA and have been harnessed as a robust technology for genome editing. Small bacteriophage-encoded anti-CRISPR proteins (Acrs) can inactivate Cas9, providing an efficient off-switch for Cas9-based applications. Here we show that two Acrs, AcrIIC1 and AcrIIC3, inhibit Cas9 by distinct strategies. AcrIIC1 is a broad-spectrum Cas9 inhibitor that prevents DNA cutting by multiple divergent Cas9 orthologs through direct binding to the conserved HNH catalytic domain of Cas9. A crystal structure of an AcrIIC1-Cas9 HNH domain complex shows how AcrIIC1 traps Cas9 in a DNA-bound but catalytically inactive state. By contrast, AcrIIC3 blocks activity of a single Cas9 ortholog and induces Cas9 dimerization while preventing binding to the target DNA. These two orthogonal mechanisms allow for separate control of Cas9 target binding and cleavage and suggest applications to allow DNA binding while preventing DNA cutting by Cas9.

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Section: Discussionmentioning

confidence: 99%

A Broad-Spectrum Inhibitor of CRISPR-Cas9

Harrington¹,

Doxzen²,

Ma³

et al. 2017

Cell

226

317

View full text Add to dashboard Cite

show abstract

“…Our results provide the first example of an intrinsic CRISPR-Cas regulator within a bacterial host. The emerging literature on CRISPR-Cas regulation in bacteria focuses on transcription factors or chaperones encoded in the genomes of hosts with type I CRISPRsystems 20 . In these cases, CRISPR-Cas promoters likely evolved to join existing regulons, enabling CRISPR activities to be tied to a variety of internal and environmental stimuli.…”

Section: Discussionmentioning

confidence: 99%

“…How are CRISPR systems regulated within their bacterial hosts to prevent autoimmunity and enhance targeting of foreign agents? Several studies have demonstrated transcriptional and post-transcriptional CRISPR-Cas regulation in response to extracellular and intracellular cues 20 , including phage infection [21][22][23][24][25] , quorum sensing 26,27 , membrane stress [28][29][30][31] , metabolic status 21,32,33 and surface association 34 . In many cases where the regulatory mechanisms are known, host-encoded transcription factors interact with CRISPR-Cas promoters 32,33,35,36 , although several studies have shown that archaeal type I-A systems can be intrinsically controlled by dedicated Cas-encoded transcription factors 25,[37][38][39][40] .…”

Section: Introductionmentioning

confidence: 99%

A natural single-guide RNA repurposes Cas9 to autoregulate CRISPR-Cas expression

Workman

Pammi

Nguyen

et al. 2020

Preprint

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CRISPR-Cas systems provide their prokaryotic hosts with acquired immunity against viruses and other foreign genetic elements, but how these systems are regulated to prevent auto-immunity is poorly understood. In type II CRISPR-Cas systems, a transactivating CRISPR RNA (tracrRNA) scaffold functions together with a CRISPR RNA (crRNA) guide to program Cas9 for the recognition and cleavage of foreign DNA targets. Here, we show that a long-form tracrRNA performs an unexpected second function by folding into a natural single guide that directs Cas9 to transcriptionally repress its own promoter. Further, we demonstrate that Pcas9 serves as a critical regulatory node; de-repression causes a dramatic induction of Cas genes, crRNAs and tracrRNAs resulting in a 3,000-fold increase in immunization rates against unrecognized viruses. Heightened immunity comes at the cost of increased auto-immune toxicity, demonstrating the critical importance of the controller. Using a bioinformatic analysis, we provide evidence that tracrRNA-mediated autoregulation is widespread in type II CRISPR-Cas systems. Collectively, we unveil a new paradigm for the intrinsic regulation of CRISPR-Cas systems by natural single guides, which may facilitate the frequent horizontal transfer of these systems into new hosts that have not yet evolved their own regulatory strategies.

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“…Diversity of CRISPR-Cas systems is mirrored in emerging knowledge of networks for transcriptional regulation of CRISPR-Cas systems in different organisms, reviewed recently [54]. H-NS is a consistent performer across species for regulating CRISPR-Cas systems, acting as a transcriptional repressor, but there are many more unique or specialized effects of other transcriptional regulators.…”

Section: Examples Of Non-cas Host Proteins In Crispr-cas Immunitymentioning

confidence: 99%

CRISPR-Cas adaptive immunity and the three Rs

Killelea

Bolt

2017

Bioscience Reports

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In this summary, we focus on fundamental biology of Clustered Regularly Interspersed Short Palindromic Repeats (CRISPR)-Cas (CRISPR-associated proteins) adaptive immunity in bacteria. Emphasis is placed on emerging information about functional interplay between Cas proteins and proteins that remodel DNA during homologous recombination (HR), DNA replication or DNA repair. We highlight how replication forks may act as ‘trigger points’ for CRISPR adaptation events, and the potential for cascade-interference complexes to act as precise roadblocks in DNA replication by an invader MGE (mobile genetic element), without the need for DNA double-strand breaks.

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Regulation of CRISPR–Cas adaptive immune systems

Cited by 74 publications

References 63 publications

A Broad-Spectrum Inhibitor of CRISPR-Cas9

A Broad-Spectrum Inhibitor of CRISPR-Cas9

A natural single-guide RNA repurposes Cas9 to autoregulate CRISPR-Cas expression

CRISPR-Cas adaptive immunity and the three Rs

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