Dataset Information

Targeted transposition with Tn7 elements: safe sites, mobile plasmids, CRISPR/Cas and beyond.

ABSTRACT: Transposon Tn7 is notable for the control it exercises over where transposition events are directed. One Tn7 integration pathways recognizes a highly conserved attachment (att) site in the chromosome, while a second pathway specifically recognizes mobile plasmids that facilitate transfer of the element to new hosts. In this review, I discuss newly discovered families of Tn7-like elements with different targeting pathways. Perhaps the most exciting examples are multiple instances where Tn7-like elements have repurposed CRISPR/Cas systems. In these cases, the CRISPR/Cas systems have lost their canonical defensive function to destroy incoming mobile elements; instead, the systems have been naturally adapted to use guide RNAs to specifically direct transposition into these mobile elements. The new families of Tn7-like elements also include a variety of novel att sites in bacterial chromosomes where genome islands can form. Interesting families have also been revealed where proteins described in the prototypic Tn7 element are fused or otherwise repurposed for the new dual activities. This expanded understanding of Tn7-like elements broadens our view of how genetic systems are repurposed and provides potentially exciting new tools for genome modification and genomics. Future opportunities and challenges to understanding the impact of the new families of Tn7-like elements are discussed.

SUBMITTER: Peters JE

PROVIDER: S-EPMC6904524 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Targeted transposition with Tn7 elements: safe sites, mobile plasmids, CRISPR/Cas and beyond.

Peters Joseph E JE

Molecular microbiology 20190918 6

Transposon Tn7 is notable for the control it exercises over where transposition events are directed. One Tn7 integration pathways recognizes a highly conserved attachment (att) site in the chromosome, while a second pathway specifically recognizes mobile plasmids that facilitate transfer of the element to new hosts. In this review, I discuss newly discovered families of Tn7-like elements with different targeting pathways. Perhaps the most exciting examples are multiple instances where Tn7-like e ...[more]

PMID: 31502713

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Project description:BackgroundBacteria are prey for many viruses that hijack the bacterial cell in order to propagate, which can result in bacterial cell lysis and death. Bacteria have developed diverse strategies to counteract virus predation, one of which is the clustered regularly interspaced short palindromic repeat (CRISPR) and CRISPR associated (Cas) proteins immune defense system. Species within the bacterial family Vibrionaceae are marine organisms that encounter large numbers of phages. Our goal was to determine the significance of CRISPR-Cas systems as a mechanism of defense in this group by investigating their prevalence, phylogenetic distribution, and genome context.ResultsHerein, we describe all the CRISPR-Cas system types and their distribution within the family Vibrionaceae. In Vibrio cholerae genomes, we identified multiple variant type I-F systems, which were also present in 41 additional species. In a large number of Vibrio species, we identified a mini type I-F system comprised of tniQcas5cas7cas6f, which was always associated with Tn7-like transposons. The Tn7-like elements, in addition to the CRISPR-Cas system, also contained additional cargo genes such as restriction modification systems and type three secretion systems. A putative hybrid CRISPR-Cas system was identified containing type III-B genes followed by a type I-F cas6f and a type I-F CRISPR that was associated with a prophage in V. cholerae and V. metoecus strains. Our analysis identified CRISPR-Cas types I-C, I-E, I-F, II-B, III-A, III-B, III-D, and the rare type IV systems as well as cas loci architectural variants among 70 species. All systems described contained a CRISPR array that ranged in size from 3 to 179 spacers. The systems identified were present predominantly within mobile genetic elements (MGEs) such as genomic islands, plasmids, and transposon-like elements. Phylogenetic analysis of Cas proteins indicated that the CRISPR-Cas systems were acquired by horizontal gene transfer.ConclusionsOur data show that CRISPR-Cas systems are phylogenetically widespread but sporadic in occurrence, actively evolving, and present on MGEs within Vibrionaceae.

Dataset Information

Targeted transposition with Tn7 elements: safe sites, mobile plasmids, CRISPR/Cas and beyond.

Publications

Targeted transposition with Tn7 elements: safe sites, mobile plasmids, CRISPR/Cas and beyond.

Similar Datasets

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