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The Adaptive Immune System of Haloferax volcanii.

Maier LK, Dyall-Smith M, Marchfelder A - Life (Basel) (2015)

Bottom Line: To fight off invading genetic elements, prokaryotes have developed an elaborate defence system that is both adaptable and heritable-the CRISPR-Cas system (CRISPR is short for: clustered regularly interspaced short palindromic repeats and Cas: CRISPR associated).A systematic search revealed that six protospacer adjacent motif (PAM) sequences are recognised by the Haloferax defence system.For successful invader recognition, a non-contiguous seed sequence of 10 base-pairs between the crRNA and the invader is required.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology II, Ulm University, 89069 Ulm, Germany. lisa-katharina.maier@uni-ulm.de.

ABSTRACT
To fight off invading genetic elements, prokaryotes have developed an elaborate defence system that is both adaptable and heritable-the CRISPR-Cas system (CRISPR is short for: clustered regularly interspaced short palindromic repeats and Cas: CRISPR associated). Comprised of proteins and multiple small RNAs, this prokaryotic defence system is present in 90% of archaeal and 40% of bacterial species, and enables foreign intruders to be eliminated in a sequence-specific manner. There are three major types (I-III) and at least 14 subtypes of this system, with only some of the subtypes having been analysed in detail, and many aspects of the defence reaction remaining to be elucidated. Few archaeal examples have so far been analysed. Here we summarize the characteristics of the CRISPR-Cas system of Haloferax volcanii, an extremely halophilic archaeon originally isolated from the Dead Sea. It carries a single CRISPR-Cas system of type I-B, with a Cascade like complex composed of Cas proteins Cas5, Cas6b and Cas7. Cas6b is essential for CRISPR RNA (crRNA) maturation but is otherwise not required for the defence reaction. A systematic search revealed that six protospacer adjacent motif (PAM) sequences are recognised by the Haloferax defence system. For successful invader recognition, a non-contiguous seed sequence of 10 base-pairs between the crRNA and the invader is required.

No MeSH data available.


Related in: MedlinePlus

The CRISPR-Cas type I-B system of Haloferax volcanii. (A) The system consists of eight Cas proteins and three CRISPR arrays. Specific for class I systems is the presence of the Cas3 protein. The presence of a Cas8b protein defines this system as type I-B. The cas gene cluster is flanked by two of the CRISPR loci while the third locus is encoded on the main chromosome. In comparison to the published genome sequence of Haloferax strain DS2 [22] the H119 strain has a deletion in CRISPR locus P1 (23 spacers and repeats deleted) [20]. Gene locations on pHV4 and the main chromosome are indicated (in kb) but their sizes are not to scale. (B) The repeat sequences of the three CRISPR loci are identical except for one nucleotide at position 23 (shown in red). Processing of the CRISPR RNA by Cas6b takes place between nucleotides 22 and 23 in the repeat sequence (indicated by an arrow) leaving an 8 nucleotide repeat sequence upstream of the spacer and the remaining 22 nucleotides of the repeat downstream of the spacer.
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life-05-00521-f002: The CRISPR-Cas type I-B system of Haloferax volcanii. (A) The system consists of eight Cas proteins and three CRISPR arrays. Specific for class I systems is the presence of the Cas3 protein. The presence of a Cas8b protein defines this system as type I-B. The cas gene cluster is flanked by two of the CRISPR loci while the third locus is encoded on the main chromosome. In comparison to the published genome sequence of Haloferax strain DS2 [22] the H119 strain has a deletion in CRISPR locus P1 (23 spacers and repeats deleted) [20]. Gene locations on pHV4 and the main chromosome are indicated (in kb) but their sizes are not to scale. (B) The repeat sequences of the three CRISPR loci are identical except for one nucleotide at position 23 (shown in red). Processing of the CRISPR RNA by Cas6b takes place between nucleotides 22 and 23 in the repeat sequence (indicated by an arrow) leaving an 8 nucleotide repeat sequence upstream of the spacer and the remaining 22 nucleotides of the repeat downstream of the spacer.

Mentions: Hfx. volcanii is a halophilic euryarchaeon first isolated from the shores of the Dead Sea [18]. It grows best at around 45 °C, requires a salinity of approximately 2.5 M NaCl and maintains an equally high intracellular salt concentration [18,19]. Haloferax possesses a single CRISPR-Cas system of subtype I-B, with three different CRISPR loci; one on the main chromosome (locus C) and two on the large (636 kb) chromosomal plasmid pHV4 (locus P1, P2) (Figure 2) [20,21]. The P1 and P2 loci flank the single cas gene cassette that carries genes for eight Cas proteins (Cas1-8b). The repeat sequences of all three CRISPR loci are 30 nt in length and identical in sequence (in all but one nucleotide), whereas spacer sequences vary in length from 34 to 39 nucleotides.


The Adaptive Immune System of Haloferax volcanii.

Maier LK, Dyall-Smith M, Marchfelder A - Life (Basel) (2015)

The CRISPR-Cas type I-B system of Haloferax volcanii. (A) The system consists of eight Cas proteins and three CRISPR arrays. Specific for class I systems is the presence of the Cas3 protein. The presence of a Cas8b protein defines this system as type I-B. The cas gene cluster is flanked by two of the CRISPR loci while the third locus is encoded on the main chromosome. In comparison to the published genome sequence of Haloferax strain DS2 [22] the H119 strain has a deletion in CRISPR locus P1 (23 spacers and repeats deleted) [20]. Gene locations on pHV4 and the main chromosome are indicated (in kb) but their sizes are not to scale. (B) The repeat sequences of the three CRISPR loci are identical except for one nucleotide at position 23 (shown in red). Processing of the CRISPR RNA by Cas6b takes place between nucleotides 22 and 23 in the repeat sequence (indicated by an arrow) leaving an 8 nucleotide repeat sequence upstream of the spacer and the remaining 22 nucleotides of the repeat downstream of the spacer.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4390866&req=5

life-05-00521-f002: The CRISPR-Cas type I-B system of Haloferax volcanii. (A) The system consists of eight Cas proteins and three CRISPR arrays. Specific for class I systems is the presence of the Cas3 protein. The presence of a Cas8b protein defines this system as type I-B. The cas gene cluster is flanked by two of the CRISPR loci while the third locus is encoded on the main chromosome. In comparison to the published genome sequence of Haloferax strain DS2 [22] the H119 strain has a deletion in CRISPR locus P1 (23 spacers and repeats deleted) [20]. Gene locations on pHV4 and the main chromosome are indicated (in kb) but their sizes are not to scale. (B) The repeat sequences of the three CRISPR loci are identical except for one nucleotide at position 23 (shown in red). Processing of the CRISPR RNA by Cas6b takes place between nucleotides 22 and 23 in the repeat sequence (indicated by an arrow) leaving an 8 nucleotide repeat sequence upstream of the spacer and the remaining 22 nucleotides of the repeat downstream of the spacer.
Mentions: Hfx. volcanii is a halophilic euryarchaeon first isolated from the shores of the Dead Sea [18]. It grows best at around 45 °C, requires a salinity of approximately 2.5 M NaCl and maintains an equally high intracellular salt concentration [18,19]. Haloferax possesses a single CRISPR-Cas system of subtype I-B, with three different CRISPR loci; one on the main chromosome (locus C) and two on the large (636 kb) chromosomal plasmid pHV4 (locus P1, P2) (Figure 2) [20,21]. The P1 and P2 loci flank the single cas gene cassette that carries genes for eight Cas proteins (Cas1-8b). The repeat sequences of all three CRISPR loci are 30 nt in length and identical in sequence (in all but one nucleotide), whereas spacer sequences vary in length from 34 to 39 nucleotides.

Bottom Line: To fight off invading genetic elements, prokaryotes have developed an elaborate defence system that is both adaptable and heritable-the CRISPR-Cas system (CRISPR is short for: clustered regularly interspaced short palindromic repeats and Cas: CRISPR associated).A systematic search revealed that six protospacer adjacent motif (PAM) sequences are recognised by the Haloferax defence system.For successful invader recognition, a non-contiguous seed sequence of 10 base-pairs between the crRNA and the invader is required.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology II, Ulm University, 89069 Ulm, Germany. lisa-katharina.maier@uni-ulm.de.

ABSTRACT
To fight off invading genetic elements, prokaryotes have developed an elaborate defence system that is both adaptable and heritable-the CRISPR-Cas system (CRISPR is short for: clustered regularly interspaced short palindromic repeats and Cas: CRISPR associated). Comprised of proteins and multiple small RNAs, this prokaryotic defence system is present in 90% of archaeal and 40% of bacterial species, and enables foreign intruders to be eliminated in a sequence-specific manner. There are three major types (I-III) and at least 14 subtypes of this system, with only some of the subtypes having been analysed in detail, and many aspects of the defence reaction remaining to be elucidated. Few archaeal examples have so far been analysed. Here we summarize the characteristics of the CRISPR-Cas system of Haloferax volcanii, an extremely halophilic archaeon originally isolated from the Dead Sea. It carries a single CRISPR-Cas system of type I-B, with a Cascade like complex composed of Cas proteins Cas5, Cas6b and Cas7. Cas6b is essential for CRISPR RNA (crRNA) maturation but is otherwise not required for the defence reaction. A systematic search revealed that six protospacer adjacent motif (PAM) sequences are recognised by the Haloferax defence system. For successful invader recognition, a non-contiguous seed sequence of 10 base-pairs between the crRNA and the invader is required.

No MeSH data available.


Related in: MedlinePlus