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. 2009 Dec 1:1:95.
doi: 10.3410/B1-95.

CRISPR-Cas: an adaptive immunity system in prokaryotes

Eugene V Koonin  1 , Kira S Makarova
Affiliations

CRISPR-Cas: an adaptive immunity system in prokaryotes

Eugene V Koonin et al. F1000 Biol Rep. .

Abstract

Most of the archaea and numerous bacteria possess an elaborate system of adaptive immunity to mobile genetic elements known as the CRISPR (clustered regularly interspaced short palindromic repeats)-associated system (CRISPR-Cas), which consists of arrays of short repeats interspersed with unique DNA spacers and adjacent operons encompassing CRISPR-associated (cas) genes with predicted and, in some cases, experimentally validated nuclease, helicase, and polymerase activities. The system functions by integrating fragments of alien DNA between the repeats and employing their transcripts to degrade the DNA of the respective invading elements via an RNA interference-like mechanism. The CRISPR-Cas system is a case of apparent Lamarckian inheritance.

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Figures

Figure 1.
Figure 1.. Representation of the CRISPR (clustered regularly interspaced short palindromic repeats)-Cas system in archaeal and bacterial lineages
The bars show the fractions of sequenced genomes in each group that possess CRISPR-Cas (red) and lack CRISPR-Cas (blue). The actual numbers of available genomes are also indicated for both parts of each bar. The figure is based on the results of screening of the proteins encoded in 774 archaeal and bacterial genomes for statistically significant sequence similarity to Cas1 sequences using BLASTP [32].
See this image and copyright information in PMC

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