Structural highlights
Function
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.[1] [2] [3]
Publication Abstract from PubMed
CRISPR-Cas systems are bacterial adaptive immune systems, and phages counteract these systems using many approaches such as producing anti-CRISPR (Acr) proteins. Here, we report the structures of both AcrIF14 and its complex with the crRNA-guided surveillance (Csy) complex. Our study demonstrates that apart from interacting with the Csy complex to block the hybridization of target DNA to the crRNA, AcrIF14 also endows the Csy complex with the ability to interact with non-sequence-specific dsDNA as AcrIF9 does. Further structural studies of the Csy-AcrIF14-dsDNA complex and biochemical studies uncover that the PAM recognition loop of the Cas8f subunit of the Csy complex and electropositive patches within the N-terminal domain of AcrIF14 are essential for the non-sequence-specific dsDNA binding to the Csy-AcrIF14 complex, which is different from the mechanism of AcrIF9. Our findings highlight the prevalence of Acr-induced non-specific DNA binding and shed light on future studies into the mechanisms of such Acr proteins.
Insights into the dual functions of AcrIF14 during the inhibition of type I-F CRISPR-Cas surveillance complex.,Liu X, Zhang L, Xiu Y, Gao T, Huang L, Xie Y, Yang L, Wang W, Wang P, Zhang Y, Yang M, Feng Y Nucleic Acids Res. 2021 Sep 27;49(17):10178-10191. doi: 10.1093/nar/gkab738. PMID:34432044[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Haurwitz RE, Jinek M, Wiedenheft B, Zhou K, Doudna JA. Sequence- and structure-specific RNA processing by a CRISPR endonuclease. Science. 2010 Sep 10;329(5997):1355-8. PMID:20829488 doi:10.1126/science.1192272
- ↑ Cady KC, O'Toole GA. Non-identity-mediated CRISPR-bacteriophage interaction mediated via the Csy and Cas3 proteins. J Bacteriol. 2011 Jul;193(14):3433-45. doi: 10.1128/JB.01411-10. Epub 2011 Mar, 11. PMID:21398535 doi:http://dx.doi.org/10.1128/JB.01411-10
- ↑ Haurwitz RE, Sternberg SH, Doudna JA. Csy4 relies on an unusual catalytic dyad to position and cleave CRISPR RNA. EMBO J. 2012 Apr 20. doi: 10.1038/emboj.2012.107. PMID:22522703 doi:10.1038/emboj.2012.107
- ↑ Liu X, Zhang L, Xiu Y, Gao T, Huang L, Xie Y, Yang L, Wang W, Wang P, Zhang Y, Yang M, Feng Y. Insights into the dual functions of AcrIF14 during the inhibition of type I-F CRISPR-Cas surveillance complex. Nucleic Acids Res. 2021 Sep 27;49(17):10178-10191. PMID:34432044 doi:10.1093/nar/gkab738
