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Cryo-EM structure of anti-CRISPR AcrIF9, bound to the type I-F crRNA-guided CRISPR surveillance complexCryo-EM structure of anti-CRISPR AcrIF9, bound to the type I-F crRNA-guided CRISPR surveillance complex
Structural highlights
Function[CSY1_PSEAB] CRISPR (clustered regularly interspaced short palindromic repeat) is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain sequences complementary to antecedent mobile elements and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). Cas3 and Cascade participate in CRISPR interference, the third stage of CRISPR immunity (Potential). Involved in crRNA production or stability. The Csy ribonucleoprotein complex binds target ssDNA with high affinity but target dsDNA with much lower affinity.[1] [2] [CAS6_PSEAB] CRISPR (clustered regularly interspaced short palindromic repeat) is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain sequences complementary to antecedent mobile elements and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA). Processes pre-crRNA into individual crRNA units. Absolutely required for crRNA production or stability. Upon expression in E.coli endonucleolytically processes pre-crRNA, although disruption and reconstitution experiments indicate that in situ other genes are also required for processing. Yields 5'-hydroxy and 3'-phosphate groups. The Csy ribonucleoprotein complex binds target ssDNA with high affinity but target dsDNA with much lower affinity.[3] [4] [5] Publication Abstract from PubMedBacteria have evolved sophisticated adaptive immune systems, called CRISPR-Cas, that provide sequence-specific protection against phage infection. In turn, phages have evolved a broad spectrum of anti-CRISPRs that suppress these immune systems. Here we report structures of anti-CRISPR protein IF9 (AcrIF9) in complex with the type I-F CRISPR RNA-guided surveillance complex (Csy). In addition to sterically blocking the hybridization of complementary dsDNA to the CRISPR RNA, our results show that AcrIF9 binding also promotes non-sequence-specific engagement with dsDNA, potentially sequestering the complex from target DNA. These findings highlight the versatility of anti-CRISPR mechanisms utilized by phages to suppress CRISPR-mediated immune systems. AcrIF9 tethers non-sequence specific dsDNA to the CRISPR RNA-guided surveillance complex.,Hirschi M, Lu WT, Santiago-Frangos A, Wilkinson R, Golden SM, Davidson AR, Lander GC, Wiedenheft B Nat Commun. 2020 Jun 1;11(1):2730. doi: 10.1038/s41467-020-16512-1. PMID:32483187[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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