Event date : Wednesday, 15 Dec 2021
Time: from 16:00 to 17:00
Mechanisms of CRISPR-mediated immunity and applications beyond editing
Andrew Santiago-Frangos, Ph.D.
Postdoctoral Scientist, Department of Microbiology and Immunology, Montana State University, USA.
Wednesday, 15th December 2021
16:00 – 17:00 h (Cypriot time)
A mechanistic understanding of CRISPR (clustered regularly interspaced short palindromic repeat) adaptive immune systems has led to creative new applications transforming science and medicine. However, we still know relatively little about the diverse mechanisms that govern CRISPR adaptation to phages and the diversity of effector proteins responsible for viral clearance. CRISPR-associated proteins (Cas1 and Cas2) integrate foreign DNA fragments at the "leader" end of CRISPR loci, where these DNA fragments act as "molecular vaccination cards" against phage genomes. Such polarized integration is crucial because spacers at the leader end of the CRISPR provide greater immunity against recently encountered phages. We have identified DNA motifs in CRISPR leaders that are necessary for efficient integration of foreign DNA into the subtype I-F CRISPR loci in Pseudomonas aeruginosa. Further, DNA helical phase is critical to the 3D organization of DNA motifs and DNA binding proteins during integration. Collectively, these studies shed light on the "grammatical rules" of sequence motifs that regulate the storage of genetic information in CRISPR loci. This past year, to address an urgent need for new rapid and reliable viral diagnostics, we repurposed the type III CRISPR-Cas system for sensitive and sequence specific detection of SARS-CoV-2 RNA. RNA recognition by type III systems triggers Cas10-mediated polymerase activity, which simultaneously generates pyrophosphates, protons, and cyclic oligonucleotides. This CRISPR-based diagnostic yields colorimetric or fluorometric readouts in less than 30 minutes. Ongoing work will increase the sensitivity and decrease the time to result of this diagnostic.