7tr9
Cascade complex from type I-A CRISPR-Cas systemCascade complex from type I-A CRISPR-Cas system
Structural highlights
Publication Abstract from PubMedType I CRISPR-Cas systems typically rely on a two-step process to degrade DNA. First, an RNA-guided complex named Cascade identifies the complementary DNA target. The helicase-nuclease fusion enzyme Cas3 is then recruited in trans for processive DNA degradation. Contrary to this model, here, we show that type I-A Cascade and Cas3 function as an integral effector complex. We provide four cryoelectron microscopy (cryo-EM) snapshots of the Pyrococcus furiosus (Pfu) type I-A effector complex in different stages of DNA recognition and degradation. The HD nuclease of Cas3 is autoinhibited inside the effector complex. It is only allosterically activated upon full R-loop formation, when the entire targeted region has been validated by the RNA guide. The mechanistic insights inspired us to convert Pfu Cascade-Cas3 into a high-sensitivity, low-background, and temperature-activated nucleic acid detection tool. Moreover, Pfu CRISPR-Cas3 shows robust bi-directional deletion-editing activity in human cells, which could find usage in allele-specific inactivation of disease-causing mutations. Allosteric control of type I-A CRISPR-Cas3 complexes and establishment as effective nucleic acid detection and human genome editing tools.,Hu C, Ni D, Nam KH, Majumdar S, McLean J, Stahlberg H, Terns MP, Ke A Mol Cell. 2022 Aug 4;82(15):2754-2768.e5. doi: 10.1016/j.molcel.2022.06.007. Epub , 2022 Jul 13. PMID:35835111[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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