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CRISPR-Cas Adaptive Immune Systems of the Sulfolobales: Unravelling Their Complexity and Diversity.

Garrett RA, Shah SA, Erdmann S, Liu G, Mousaei M, León-Sobrino C, Peng W, Gudbergsdottir S, Deng L, Vestergaard G, Peng X, She Q - Life (Basel) (2015)

Bottom Line: Recent work also supports critical roles for non-core Cas proteins, especially during Type III-directed interference, and this is consistent with these proteins tending to coevolve with core Cas proteins.Various novel aspects of CRISPR-Cas systems of the Sulfolobales are considered including an alternative spacer acquisition mechanism, reversible spacer acquisition, the formation and significance of antisense CRISPR RNAs, and a novel mechanism for avoidance of CRISPR-Cas defense.Finally, questions regarding the basis for the complexity, diversity, and apparent redundancy, of the intracellular CRISPR-Cas systems are discussed.

View Article: PubMed Central - PubMed

Affiliation: Archaea Centre, Department of Biology, Copenhagen University, Ole Maaløes Vej 5, DK2200 Copenhagen N, Denmark. garrett@bio.ku.dk.

ABSTRACT
The Sulfolobales have provided good model organisms for studying CRISPR-Cas systems of the crenarchaeal kingdom of the archaea. These organisms are infected by a wide range of exceptional archaea-specific viruses and conjugative plasmids, and their CRISPR-Cas systems generally exhibit extensive structural and functional diversity. They carry large and multiple CRISPR loci and often multiple copies of diverse Type I and Type III interference modules as well as more homogeneous adaptation modules. These acidothermophilic organisms have recently provided seminal insights into both the adaptation process, the diverse modes of interference, and their modes of regulation. The functions of the adaptation and interference modules tend to be loosely coupled and the stringency of the crRNA-DNA sequence matching during DNA interference is relatively low, in contrast to some more streamlined CRISPR-Cas systems of bacteria. Despite this, there is evidence for a complex and differential regulation of expression of the diverse functional modules in response to viral infection. Recent work also supports critical roles for non-core Cas proteins, especially during Type III-directed interference, and this is consistent with these proteins tending to coevolve with core Cas proteins. Various novel aspects of CRISPR-Cas systems of the Sulfolobales are considered including an alternative spacer acquisition mechanism, reversible spacer acquisition, the formation and significance of antisense CRISPR RNAs, and a novel mechanism for avoidance of CRISPR-Cas defense. Finally, questions regarding the basis for the complexity, diversity, and apparent redundancy, of the intracellular CRISPR-Cas systems are discussed.

No MeSH data available.


Related in: MedlinePlus

Adaptation cas gene cassette of S. islandicus M.16.4 where the csa3 gene encoding a putative transcriptional regulator is interrupted by an integrated plasmid or virus via the predicted integration att sites that are shown (modified from [56]). The closely related strain M.16.27 lacks the integrated element [87].
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life-05-00783-f007: Adaptation cas gene cassette of S. islandicus M.16.4 where the csa3 gene encoding a putative transcriptional regulator is interrupted by an integrated plasmid or virus via the predicted integration att sites that are shown (modified from [56]). The closely related strain M.16.27 lacks the integrated element [87].

Mentions: The genome of S. islandicus M.16.4 isolated from the Mutnovsky Volcano, Kamchatka, Russia carries a csa3 gene physically linked to an adaptation gene cassette [87] and the Csa3 protein is likely to regulate transcription from the gene cassette [38]. However, in this strain the csa3 gene carries an integrated genetic element of viral or plasmid origin that had apparently integrated at the indicated att site (Figure 7) [56]. The sequence of the interrupted csa3 gene is highly conserved, relative to those of related strains, suggesting that the integration event is reversible [56]. Another strain M.16.27, from the same solfataric field, exhibits an intact csa3 gene and, unlike strain M.16.4, it carries a CRISPR spacer with a perfect sequence match to the integrated element [56,87]. Thus, the integrated genetic element in strain M.16.4 can potentially inhibit expression of the adaptation Cas proteins and, as demonstrated for another S.islandicus strain [109], this will prevent expression of Csa3 and thereby inhibit spacer acquisition. Consequently, other copies of the genetic element will be able to propagate in strain M.16.4, whereas for strain M.16.27, the CRISPR Type I-A interference system could eliminate the invading genetic element.


CRISPR-Cas Adaptive Immune Systems of the Sulfolobales: Unravelling Their Complexity and Diversity.

Garrett RA, Shah SA, Erdmann S, Liu G, Mousaei M, León-Sobrino C, Peng W, Gudbergsdottir S, Deng L, Vestergaard G, Peng X, She Q - Life (Basel) (2015)

Adaptation cas gene cassette of S. islandicus M.16.4 where the csa3 gene encoding a putative transcriptional regulator is interrupted by an integrated plasmid or virus via the predicted integration att sites that are shown (modified from [56]). The closely related strain M.16.27 lacks the integrated element [87].
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390879&req=5

life-05-00783-f007: Adaptation cas gene cassette of S. islandicus M.16.4 where the csa3 gene encoding a putative transcriptional regulator is interrupted by an integrated plasmid or virus via the predicted integration att sites that are shown (modified from [56]). The closely related strain M.16.27 lacks the integrated element [87].
Mentions: The genome of S. islandicus M.16.4 isolated from the Mutnovsky Volcano, Kamchatka, Russia carries a csa3 gene physically linked to an adaptation gene cassette [87] and the Csa3 protein is likely to regulate transcription from the gene cassette [38]. However, in this strain the csa3 gene carries an integrated genetic element of viral or plasmid origin that had apparently integrated at the indicated att site (Figure 7) [56]. The sequence of the interrupted csa3 gene is highly conserved, relative to those of related strains, suggesting that the integration event is reversible [56]. Another strain M.16.27, from the same solfataric field, exhibits an intact csa3 gene and, unlike strain M.16.4, it carries a CRISPR spacer with a perfect sequence match to the integrated element [56,87]. Thus, the integrated genetic element in strain M.16.4 can potentially inhibit expression of the adaptation Cas proteins and, as demonstrated for another S.islandicus strain [109], this will prevent expression of Csa3 and thereby inhibit spacer acquisition. Consequently, other copies of the genetic element will be able to propagate in strain M.16.4, whereas for strain M.16.27, the CRISPR Type I-A interference system could eliminate the invading genetic element.

Bottom Line: Recent work also supports critical roles for non-core Cas proteins, especially during Type III-directed interference, and this is consistent with these proteins tending to coevolve with core Cas proteins.Various novel aspects of CRISPR-Cas systems of the Sulfolobales are considered including an alternative spacer acquisition mechanism, reversible spacer acquisition, the formation and significance of antisense CRISPR RNAs, and a novel mechanism for avoidance of CRISPR-Cas defense.Finally, questions regarding the basis for the complexity, diversity, and apparent redundancy, of the intracellular CRISPR-Cas systems are discussed.

View Article: PubMed Central - PubMed

Affiliation: Archaea Centre, Department of Biology, Copenhagen University, Ole Maaløes Vej 5, DK2200 Copenhagen N, Denmark. garrett@bio.ku.dk.

ABSTRACT
The Sulfolobales have provided good model organisms for studying CRISPR-Cas systems of the crenarchaeal kingdom of the archaea. These organisms are infected by a wide range of exceptional archaea-specific viruses and conjugative plasmids, and their CRISPR-Cas systems generally exhibit extensive structural and functional diversity. They carry large and multiple CRISPR loci and often multiple copies of diverse Type I and Type III interference modules as well as more homogeneous adaptation modules. These acidothermophilic organisms have recently provided seminal insights into both the adaptation process, the diverse modes of interference, and their modes of regulation. The functions of the adaptation and interference modules tend to be loosely coupled and the stringency of the crRNA-DNA sequence matching during DNA interference is relatively low, in contrast to some more streamlined CRISPR-Cas systems of bacteria. Despite this, there is evidence for a complex and differential regulation of expression of the diverse functional modules in response to viral infection. Recent work also supports critical roles for non-core Cas proteins, especially during Type III-directed interference, and this is consistent with these proteins tending to coevolve with core Cas proteins. Various novel aspects of CRISPR-Cas systems of the Sulfolobales are considered including an alternative spacer acquisition mechanism, reversible spacer acquisition, the formation and significance of antisense CRISPR RNAs, and a novel mechanism for avoidance of CRISPR-Cas defense. Finally, questions regarding the basis for the complexity, diversity, and apparent redundancy, of the intracellular CRISPR-Cas systems are discussed.

No MeSH data available.


Related in: MedlinePlus