title: Function and regulation of clustered regularly interspaced short palindromic repeats (CRISPR) / CRISPR associated (Cas) systems.
abstract: Phages are the most abundant biological entities on earth and pose a constant challenge to their bacterial hosts. Thus, bacteria have evolved numerous 'innate' mechanisms of defense against phage, such as abortive infection or restriction/modification systems. In contrast, the clustered regularly interspaced short palindromic repeats (CRISPR) systems provide acquired, yet heritable, sequence-specific 'adaptive' immunity against phage and other horizontally-acquired elements, such as plasmids. Resistance is acquired following viral infection or plasmid uptake when a short sequence of the foreign genome is added to the CRISPR array. CRISPRs are then transcribed and processed, generally by CRISPR associated (Cas) proteins, into short interfering RNAs (crRNAs), which form part of a ribonucleoprotein complex. This complex guides the crRNA to the complementary invading nucleic acid and targets this for degradation. Recently, there have been rapid advances in our understanding of CRISPR/Cas systems. In this review, we will present the current model(s) of the molecular events involved in both the acquisition of immunity and interference stages and will also address recent progress in our knowledge of the regulation of CRISPR/Cas systems.
authors.affiliation: Department of Microbiology and Immunology, University of Otago, Dunedin 9054, New Zealand. ricco896@student.otago.ac.nz
authors.forename: Corinna
authors.initials: C
authors.lastname: Richter
authors.forename: James T
authors.initials: JT
authors.lastname: Chang
authors.forename: Peter C
authors.initials: PC
authors.lastname: Fineran
mesh_terms: D000220:Adaptation, Biological; D001435:Bacteriophages / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D064130:CRISPR-Associated Proteins; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000821:virology*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D055029:Inverted Repeat Sequences; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D025941:Protein Interaction Mapping; D034622:RNA Interference; D012323:RNA Processing, Post-Transcriptional; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity
chemical_list: D064130:CRISPR-Associated Proteins; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D034741:RNA, Small Interfering; D004706:Endodeoxyribonucleases; C557650:YgbT protein, E coli