Movatterモバイル変換

[0]ホーム
URL:

Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
Thehttps:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

NIH NLM Logo
Log inShow account info
Access keysNCBI HomepageMyNCBI HomepageMain ContentMain Navigation
pubmed logo
Advanced Clipboard
User Guide

Full text links

Nature Publishing Group full text link Nature Publishing Group Free PMC article
Full text links

Actions

Share

Review
.2010 Mar;11(3):181-90.
doi: 10.1038/nrg2749.

CRISPR interference: RNA-directed adaptive immunity in bacteria and archaea

Affiliations
Review

CRISPR interference: RNA-directed adaptive immunity in bacteria and archaea

Luciano A Marraffini et al. Nat Rev Genet.2010 Mar.

Abstract

Sequence-directed genetic interference pathways control gene expression and preserve genome integrity in all kingdoms of life. The importance of such pathways is highlighted by the extensive study of RNA interference (RNAi) and related processes in eukaryotes. In many bacteria and most archaea, clustered, regularly interspaced short palindromic repeats (CRISPRs) are involved in a more recently discovered interference pathway that protects cells from bacteriophages and conjugative plasmids. CRISPR sequences provide an adaptive, heritable record of past infections and express CRISPR RNAs - small RNAs that target invasive nucleic acids. Here, we review the mechanisms of CRISPR interference and its roles in microbial physiology and evolution. We also discuss potential applications of this novel interference pathway.

PubMed Disclaimer

Conflict of interest statement

Competing interests statement

The authors declare no competing financial interests.

Figures

Figure 1
Figure 1. Features of CRISPR loci
Typically, clustered, regularly interspaced short palindromic repeats (CRISPRs, white boxes) are preceded by a leader sequence (black box) that is AT-rich but otherwise not conserved. The number of repeats can vary substantially, from a minimum of two to a few hundred. Repeat length, however, is restricted to 23 to 50 nucleotides. Repeats are separated by similarly sized, non-repetitive spacers (coloured boxes) that share sequence identity with fragments of plasmids and bacteriophage genomes and specify the targets of CRISPR interference. A set of CRISPR-associated (cas) genes immediately precedes or follows the repeats. These genes are conserved, can be classified into different families and subtypes, and encode the protein machinery responsible for CRISPR activity.
Figure 2
Figure 2. Acquisition of new repeat-spacer units
During the adaptation phase of clustered, regularly interspaced short palindromic repeat (CRISPR) immunity, new spacers derived from the invading DNA are incorporated into CRISPR loci. The mechanism of spacer acquisition is unknown but possibly uses the nuclease activity of CRISPR-associated 1 (Cas1) to generate short fragments of invading DNA. How the CRISPR machinery recognizes phage or plasmid DNA as invasive and therefore suitable for CRISPR locus incorporation is also unknown. The addition of new spacers is thought to involve an integration or conversion event and occurs at the leader-proximal end of the cluster. CRISPRs are shown as white boxes, the leader sequence is shown as a black box, non-repetitive spacers are shown as coloured boxes andcas genes are shown as grey arrows.
Figure 3
Figure 3. CRISPR interference
a | In the interference or defence phase of clustered, regularly interspaced short palindromic repeat (CRISPR) immunity, repeats and spacers are transcribed into a long precursor that is processed by a complex called CRISPR-associated complex for antiviral defence (Cascade) inEscherichia coli or CRISPR-associated 6 (Cas6) inPyrococcus furiosus, which generates small CRISPR RNAs (crRNAs). Processing occurs near the 3′ end of the repeat sequence, leaving a short (~8 nucleotides) repeat sequence 5′ of the crRNA spacer. crRNAs have a more heterogeneous 3′ terminus that sometimes contains the palindromic sequence of the downstream repeat and has the potential to form a stem–loop structure. CRISPR loci transcription seems to be constitutive and the leader sequence may act as a promoter (arrow). CRISPRs are shown as white boxes, the leader sequence is shown as a black box, non-repetitive spacers are shown as coloured boxes andcas genes are shown as grey arrows.b | RNAs serve as guides for an effector complex, presumably composed of Cas proteins, that recognizes invading DNA and blocks infection (white cross) by an unknown mechanism.
Figure 4
Figure 4. self versus non-self discrimination during CRISPR immunity
The spacer sequences of clustered, regularly interspaced short palindromic repeat (CRISPR) RNAs (crRNAs) have perfect complementarity with the CRISPR locus from which they are transcribed, which confers the potential to target CRISPR DNA. InStaphylococcus epidermidis, this autoimmune response is prevented by differential base pairing of spacer/target 5′ flanking sequences. A similar role for 3′ flanking sequences in other organisms cannot be excluded. Whereas interference requires crRNA/target mismatches outside the spacer sequence, complementarity between crRNA and repeat sequences in the CRISPR DNA prevents autoimmunity. The figure is adapted, with permission, fromNature REF. © (2010) Macmillan Publishers Ltd. All rights reserved.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Nakamura Y, Itoh T, Matsuda H, Gojobori T. Biased biological functions of horizontally transferred genes in prokaryotic genomes. Nature Genet. 2004;36:760–766. - PubMed
    1. Thomas CM, Nielsen KM. Mechanisms of, and barriers to, horizontal gene transfer between bacteria. Nature Rev Microbiol. 2005;3:711–721. - PubMed
    1. Ishino Y, Shinagawa H, Makino K, Amemura M, Nakata A. Nucleotide sequence of the iap gene, responsible for alkaline phosphatase isozyme conversion in Escherichia coli, and identification of the gene product. J Bacteriol. 1987;169:5429–5433. - PMC - PubMed
    1. Nakata A, Amemura M, Makino K. Unusual nucleotide arrangement with repeated sequences in the Escherichia coli K-12 chromosome. J Bacteriol. 1989;171:3553–3556. - PMC - PubMed
    1. Hermans PW, et al. Insertion element IS987 from Mycobacterium bovis BCG is located in a hot-spot integration region for insertion elements in Mycobacterium tuberculosis complex strains. Infect Immun. 1991;59:2695–2705. - PMC - PubMed

Publication types

MeSH terms

Substances

Related information

Grants and funding

LinkOut - more resources

Full text links
Nature Publishing Group full text link Nature Publishing Group Free PMC article
Cite
Send To

NCBI Literature Resources

MeSHPMCBookshelfDisclaimer

The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). Unauthorized use of these marks is strictly prohibited.

[8]ページ先頭
©2009-2025 Movatter.jp