Methods | CRISPR-Cas, A Prokaryotic Adaptive Immune System

Charbonneau, Alexander A.; Gauvin, Colin; Lawrence, C. Martin

doi:10.1016/b978-0-12-819460-7.00026-8

Cited by 2 publications

(2 citation statements)

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“…The basic tenets of CRISPR-Cas adaptive immunity are now well established [ 1 , 2 , 3 ]. This heritable, adaptive immune response is manifested in three distinct stages, (i) adaptation, (ii) crRNA maturation and (iii) interference.…”

Section: Introductionmentioning

confidence: 99%

“…Collectively, the work above suggests the cA 4 second message generated by type III systems may act through Csa3a to provide an integrated Class 1 response in organisms harboring both type 1-A and type III systems [ 3 ]. Specifically, production of the cA 4 second messenger may stimulate primed acquisition of new spacers by upregulating transcription of the acquisition cassette (cas1, cas2 and cas4), and expression of the new spacers by upregulating transcription of the CRISPR loci as well [ 3 , 6 , 25 ]. Here we show that S. solfataricus Csa3a does indeed recognize cA 4 .…”

Section: Introductionmentioning

confidence: 99%

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Cyclic Tetra-Adenylate (cA4) Recognition by Csa3; Implications for an Integrated Class 1 CRISPR-Cas Immune Response in Saccharolobus solfataricus

et al. 2021

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Csa3 family transcription factors are ancillary CRISPR-associated proteins composed of N-terminal CARF domains and C-terminal winged helix-turn-helix domains. The activity of Csa3 transcription factors is thought to be controlled by cyclic oligoadenyate (cOA) second messengers produced by type III CRISPR-Cas surveillance complexes. Here we show that Saccharolobus solfataricus Csa3a recognizes cyclic tetra-adenylate (cA4) and that Csa3a lacks self-regulating “ring nuclease” activity present in some other CARF domain proteins. The crystal structure of the Csa3a/cA4 complex was also determined and the structural and thermodynamic basis for cA4 recognition are described, as are conformational changes in Csa3a associated with cA4 binding. We also characterized the effect of cA4 on recognition of putative DNA binding sites. Csa3a binds to putative promoter sequences in a nonspecific, cooperative and cA4-independent manner, suggesting a more complex mode of transcriptional regulation. We conclude the Csa3a/cA4 interaction represents a nexus between the type I and type III CRISPR-Cas systems present in S. solfataricus, and discuss the role of the Csa3/cA4 interaction in coordinating different arms of this integrated class 1 immune system to mount a synergistic, highly orchestrated immune response.

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Section: Introductionmentioning

confidence: 99%