title: CRISPR-Cas immunity in prokaryotes.
abstract: Prokaryotic organisms are threatened by a large array of viruses and have developed numerous defence strategies. Among these, only clustered, regularly interspaced short palindromic repeat (CRISPR)-Cas systems provide adaptive immunity against foreign elements. Upon viral injection, a small sequence of the viral genome, known as a spacer, is integrated into the CRISPR locus to immunize the host cell. Spacers are transcribed into small RNA guides that direct the cleavage of the viral DNA by Cas nucleases. Immunization through spacer acquisition enables a unique form of evolution whereby a population not only rapidly acquires resistance to its predators but also passes this resistance mechanism vertically to its progeny.
authors.affiliation: Laboratory of Bacteriology, The Rockefeller University, 1230 York Avenue, New York, New York 10065, USA.
authors.forename: Luciano A
authors.initials: LA
authors.lastname: Marraffini
mesh_terms: D064130:CRISPR-Associated Proteins / Q000378:metabolism; D064113:CRISPR-Cas Systems / Q000235:genetics / Q000276:immunology*; D004926:Escherichia coli / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000821:virology; D011387:Prokaryotic Cells / Q000276:immunology* / Q000821:virology
chemical_list: D064130:CRISPR-Associated Proteins