CRISPR/Cas, the Immune System of Bacteria and Archaea

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Science  08 Jan 2010:
Vol. 327, Issue 5962, pp. 167-170
DOI: 10.1126/science.1179555

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  1. Fig. 1

    Overview of the four CRISPR/cas systems present in Streptococcus thermophilus DGCC7710. For each system, gene organization is depicted on the top, with cas genes in gray, and the repeat-spacer array in black. Below the gene scheme, the repeat and spacer (captured phage or plasmid nucleic acid) content is detailed as black diamonds (T, terminal repeat) and white rectangles, respectively. Bottom line, consensus repeat sequence. L1 to L4, leader sequences. The predicted secondary structure of the CRISPR3 repeat is shown on the right. S. thermophilus CRISPR2, CRISPR3, and CRISPR4 systems are homologous to the CRISPR systems of Staphylococcus epidermidis (20), Streptococcus mutans (19), and E. coli (28), respectively.

  2. Fig. 2

    Overview of the CRISPR/Cas mechanism of action. (A) Immunization process: After insertion of exogenous DNA from viruses or plasmids, a Cas complex recognizes foreign DNA and integrates a novel repeat-spacer unit at the leader end of the CRISPR locus. (B) Immunity process: The CRISPR repeat-spacer array is transcribed into a pre-crRNA that is processed into mature crRNAs, which are subsequently used as a guide by a Cas complex to interfere with the corresponding invading nucleic acid. Repeats are represented as diamonds, spacers as rectangles, and the CRISPR leader is labeled L.

  3. Fig. 3

    CRISPR interference. The CRISPR/Cas systems may target either DNA or RNA to interfere with viruses, plasmids, prophages, or other chromosomally encoded sequences.