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Andrew Varble, Luciano Marraffini
Here we review how the Cas9 nuclease mediates anti-phage immunity and how it can be repurposed for the genetic engineering of human cells and other eukaryotic organisms.
Pascal Maguin, Andrew Varble, Joshua W Modell, Luciano A Marraffini
We found that restriction endonucleases provide a short-term defense, which is rapidly overcome through methylation of the phage genome. In a small fraction of the cells, however, restriction results in the acquisition of spacer sequences from the cleavage site, which mediates a robust type II-A CRISPR-Cas immune response against the methylated phage
Andrew Varble, Edmondo Campisi, Chad W Euler, Pascal Maguin, Albina Kozlova, Jessica Fyodorova, Jakob T Rostøl, Vincent A Fischetti, Luciano A Marraffini
Here we demonstrate that the ΦAP1.1 temperate phage utilizes an alternative approach to antagonize the type II-A CRISPR response in Streptococcus pyogenes. Immediately after infection, this phage expresses a small anti-CRISPR protein, AcrIIA23, that prevents Cas9 function, allowing ΦAP1.1 to integrate into the direct repeats of the CRISPR locus, neutralizing immunity.
Victor Chen, Matthew E Griffin, Pascal Maguin, Andrew Varble, Howard C Hang
The dissection of E. faecium functions and mechanisms has been restricted by inefficient gene-editing methods. To address these limitations, here, we report that the expression of E. faecium RecT recombinase significantly improves the efficiency of recombineering technologies in both commensal and antibiotic-resistant strains of E. faecium and other Enterococcus species such as E. durans and E. hirae.
Charlie Y Mo, Jacob Mathai, Jakob T Rostøl, Andrew Varble,, Dalton V Banh, Luciano A Marraffini
Here we show that the non-specific DNase activity of the staphylococcal type III-A CRISPR-Cas system increases mutations in the host and accelerates the generation of antibiotic resistance in Staphylococcus aureus and Staphylococcus epidermidis.
Andrew Varble, Luciano A Marraffini
Recent work in the field has revealed unexpected features of the CRISPR-Cas mechanism: (i) collateral, nonspecific, cleavage of host nucleic acids; (ii) secondary messengers that amplify the immune response; and (iii) immunosuppression of CRISPR targeting by phage-encoded inhibitors. Here, we review these new and exciting findings.
Andrew Varble, Sean Meaden, Rodolphe Barrangou, Edze R Westra, Luciano A Marraffini
Although CRISPR-cas loci are widely distributed throughout microbial genomes and often display hallmarks of horizontal gene transfer10-12, the drivers of CRISPR dissemination remain unclear. Here, we show that spacers can recombine with phage target sequences to mediate a form of specialized transduction of CRISPR elements
Gregory W Goldberg, Elizabeth A McMillan, Andrew Varble, Joshua W Modell, Poulami Samai, Wenyan Jiang, Luciano A Marraffini
Here we show that maintenance of conditionally tolerant type III-A systems can produce fitness costs within populations of Staphylococcus aureus lysogens.
Nora C Pyenson, Kaitlyn Gayvert, Andrew Varble, Olivier Elemento, Luciano A Marraffini
Here we show that targeting by the Staphylococcus epidermidis type III-A CRISPR-Cas system does not require PAM or seed sequences, and thus prevents viral escape via single-nucleotide substitutions. Instead, viral escapers can only arise through complete target deletion.