Molecular Mechanisms of CRISPR-Cas Immunity in Bacteria.

Publication Type	Review
Authors	Nussenzweig P, Marraffini L
Journal	Annu Rev Genet
Volume	54
Pagination	93-120
Date Published	08/28/2020
ISSN	1545-2948
Keywords	Bacteria, CRISPR-Cas Systems, Immunity
Abstract	Prokaryotes have developed numerous defense strategies to combat the constant threat posed by the diverse genetic parasites that endanger them. Clustered regularly interspaced short palindromic repeat (CRISPR)-Cas loci guard their hosts with an adaptive immune system against foreign nucleic acids. Protection starts with an immunization phase, in which short pieces of the invader's genome, known as spacers, are captured and integrated into the CRISPR locus after infection. Next, during the targeting phase, spacers are transcribed into CRISPR RNAs (crRNAs) that guide CRISPR-associated (Cas) nucleases to destroy the invader's DNA or RNA. Here we describe the many different molecular mechanisms of CRISPR targeting and how they are interconnected with the immunization phase through a third phase of the CRISPR-Cas immune response: primed spacer acquisition. In this phase, Cas proteins direct the crRNA-guided acquisition of additional spacers to achieve a more rapid and robust immunization of the population.
DOI	10.1146/annurev-genet-022120-112523
PubMed ID	32857635