Personne : Hynes, Alexander
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Widespread anti-CRISPR proteins in virulent bacteriophages inhibit a range of Cas9 proteins
2018-07-25, Moineau, Sylvain, Hynes, Alexander, Loehr, Jérémy, Goulet, Adeline, Agudelo, Daniel, Amigues, Béatrice, Doyon, Yannick, Rousseau, Geneviève M., Romero, Dennis A., Fremaux, Christophe, Horvath, Philippe, Cambillau, Christian
CRISPR-Cas systems are bacterial anti-viral systems, and bacterial viruses (bacteriophages, phages) can carry anti-CRISPR (Acr) proteins to evade that immunity. Acrs can also fine-tune the activity of CRISPR-based genome-editing tools. While Acrs are prevalent in phages capable of lying dormant in a CRISPR-carrying host, their orthologs have been observed only infrequently in virulent phages. Here we identify AcrIIA6, an Acr encoded in 33% of virulent Streptococcus thermophilus phage genomes. The X-ray structure of AcrIIA6 displays some features unique to this Acr family. We compare the activity of AcrIIA6 to those of other Acrs, including AcrIIA5 (also from S. thermophilus phages), and characterize their effectiveness against a range of CRISPR-Cas systems. Finally, we demonstrate that both Acr families from S. thermophilus phages inhibit Cas9-mediated genome editing of human cells.
Adaptation in bacterial CRISPR-Cas immunity can be driven by defective phages
2014-07-24, Moineau, Sylvain, Hynes, Alexander, Villion, Manuela
Clustered regularly interspaced short palindromic repeats (CRISPRs) and their associated cas genes serve as a prokaryotic ‘adaptive’ immune system, protecting against foreign DNA elements such as bacteriophages. CRISPR-Cas systems function by incorporating short DNA ‘spacers’, homologous to invading DNA sequences, into a CRISPR array (adaptation). The array is then transcribed and matured into RNA molecules (maturation) that target homologous DNA for cleavage (interference). It is unclear how these three stages could occur quickly enough in a naive phage-infected cell to interfere with phage replication before this cell would be irrevocably damaged by the infection. Here we demonstrate that cells can acquire spacers from defective phages at a rate directly proportional to the quantity of replication-deficient phages to which the cells are exposed. This process is reminiscent of immunization in humans by vaccination with inactivated viruses.
Programming native CRISPR arrays for the generation of targeted immunity
2016-05-03, Moineau, Sylvain, Hynes, Alexander, Labrie, Simon
ABSTRACT : The adaptive immune system of prokaryotes, called CRISPR-Cas (clustered regularly interspaced short palindromic repeats and CRISPR-associated genes), results in specific cleavage of invading nucleic acid sequences recognized by the cell’s “memory” of past encounters. Here, we exploited the properties of native CRISPR-Cas systems to program the natural “memorization” process, efficiently generating immunity not only to a bacteriophage or plasmid but to any specifically chosen DNA sequence. IMPORTANCE : CRISPR-Cas systems have entered the public consciousness as genome editing tools due to their readily programmable nature. In industrial settings, natural CRISPR-Cas immunity is already exploited to generate strains resistant to potentially disruptive viruses. However, the natural process by which bacteria acquire new target specificities (adaptation) is difficult to study and manipulate. The target against which immunity is conferred is selected stochastically. By biasing the immunization process, we offer a means to generate customized immunity, as well as provide a new tool to study adaptation.
Phagebook : the social network
2017-03-16, Moineau, Sylvain, Hynes, Alexander
Much like social networks are used to connect with friends or relatives, bacteria communicate with relatives through quorum sensing. Viruses, though, were thought to be asocial—until now. Erez et al. (2017) reveal that viruses are also sharing information with relatives.
Applications of CRISPR-Cas in its natural habitat
2016-06-07, Lemay, Marie-Laurence, Moineau, Sylvain, Hynes, Alexander
Key components of CRISPR-Cas systems have been adapted into a powerful genome-editing tool that has caught the headlines and the attention of the public. Canonically, a customized RNA serves to guide an endonuclease (e.g. Cas9) to its DNA target, resulting in precise genomic lesions that can be repaired in a personalized fashion by cellular machinery. Here, we turn to the microbes that are the source of this system to explore many of its other notable applications. These include mining the CRISPR 'memory' arrays for functional genomic data, generation of customized virus-resistant or plasmid-refractory bacterial cells, editing of previously intractable viral genomes, and exploiting the unique properties of a catalytically inactive Cas9, dCas9, to serve as a highly customizable anti-nucleic acid 'antibody'.