Direct interaction between the TnsA and TnsB subunits controls the heteromeric
            <i>Tn7</i>
            transposase

Choi, Ki Young; Liu, Ying; Sarnovsky, Robert; Craig, Nancy L.

doi:10.1073/pnas.1305716110

Cited by 27 publications

(21 citation statements)

References 38 publications

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“…The TnsA protein is the most highly conserved gene of the Tn7-like elements and is responsible for the unique behavior of the elements with heteromeric transposases (46)(47)(48)(49). We collected and annotated 10,349 loci containing at least tniQ/tnsD or tnsA (Dataset S2) and reconstructed a tree for both protein families ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…6A) (56,63). The TnsABC proteins are normally insufficient for Tn7 transposition in vivo or in vitro (64); however, certain gainof-function mutations in the regulator protein TnsC (TnsC*) allow untargeted transposition in the absence of TnsD or TnsE (47,65,66). Notably, transposition in this case is attracted to a specific location adjacent to a short segment of triplex-forming DNAs (58,67).…”

Section: Chromosomal Insertions Of the I-f Crispr-cas-associated Elemmentioning

confidence: 99%

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Recruitment of CRISPR-Cas systems by Tn7-like transposons

Peters

Makarova

Shmakov

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

245

267

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A survey of bacterial and archaeal genomes shows that many Tn7-like transposons contain minimal type I-F CRISPR-Cas systems that consist of fused cas8f and cas5f, cas7f, and cas6f genes and a short CRISPR array. Several small groups of Tn7-like transposons encompass similarly truncated type I-B CRISPR-Cas. This minimal gene complement of the transposon-associated CRISPR-Cas systems implies that they are competent for pre-CRISPR RNA (precrRNA) processing yielding mature crRNAs and target binding but not target cleavage that is required for interference. Phylogenetic analysis demonstrates that evolution of the CRISPR-Cas-containing transposons included a single, ancestral capture of a type I-F locus and two independent instances of type I-B loci capture. We show that the transposon-associated CRISPR arrays contain spacers homologous to plasmid and temperate phage sequences and, in some cases, chromosomal sequences adjacent to the transposon. We hypothesize that the transposon-encoded CRISPR-Cas systems generate displacement (R-loops) in the cognate DNA sites, targeting the transposon to these sites and thus facilitating their spread via plasmids and phages. These findings suggest the existence of RNAguided transposition and fit the guns-for-hire concept whereby mobile genetic elements capture host defense systems and repurpose them for different stages in the life cycle of the element.CRISPR-Cas systems | Tn7 transposon | transposition strategy | crRNA guide | target-site selection

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Section: Resultsmentioning

confidence: 99%

Section: Chromosomal Insertions Of the I-f Crispr-cas-associated Elemmentioning

confidence: 99%

Recruitment of CRISPR-Cas systems by Tn7-like transposons

Peters

Makarova

Shmakov

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

245

267

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“…Tn7 encodes five transposition-related proteins (TnsA, B, C, D and E) with TnsA/TnsB forming the heteromeric transposase (85,86). TnsB, which contains a predicted RNase H-like catalytic domain, cuts the transferred strand generating the 3′-OH but the non-transferred strand cut is by TnsA, which is a restriction endonuclease-like nuclease (87).…”

Section: Transposition Pathways 1 Rnase H-like Transposases (I) Replmentioning

confidence: 99%

Mechanisms of DNA Transposition

Hickman

Dyda

2015

Microbiol Spectr

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DNA transposases use a limited repertoire of structurally and mechanistically distinct nuclease domains to catalyze the DNA strand breaking and rejoining reactions that comprise DNA transposition. Here, we review the mechanisms of the four known types of transposition reactions catalyzed by (1) RNase H-like transposases (also known as DD(E/D) enzymes); (2) HUH single-stranded DNA transposases; (3) serine transposases; and (4) tyrosine transposases. The large body of accumulated biochemical and structural data, particularly for the RNase H-like transposases, has revealed not only the distinguishing features of each transposon family, but also some emerging themes that appear conserved across all families. The more-recently characterized single-stranded DNA transposases provide insight into how an ancient HUH domain fold has been adapted for transposition to accomplish excision and then site-specific integration. The serine and tyrosine transposases are structurally and mechanistically related to their cousins, the serine and tyrosine site-specific recombinases, but have to date been less intensively studied. These types of enzymes are particularly intriguing as in the context of site-specific recombination they require strict homology between recombining sites, yet for transposition can catalyze the joining of transposon ends to form an excised circle and then integration into a genomic site with much relaxed sequence specificity.In this chapter, we provide an overview of the fundamental concepts of DNA transposition mechanisms. Our aim is to emphasize basic themes and, in this effort, we will focus on specific illustrative cases rather than attempt an exhaustive review of the literature. We hope that the selected references will point the curious reader towards the landmark studies in the field as well as some of the most exciting recent results. We also direct the reader to other recent reviews (1-3).DNA transposases are enyzmes that move discrete segments of DNA called transposons from one location in the genome (often called the donor site) to a new site without using RNA intermediates. DNA transposases are usually encoded by the mobile element itself (in which case they are "autonomous" transposons). However, some transposons are missing a self-encoded transposase yet have ends that can be recognized by a transposase encoded somewhere else in the genome, and thus are "non-autonomous" (Siguier et al., this volume). Although logic suggests that all DNA transposons are moved by transposases, the term was originally reserved for those enzymes that do not require significant regions of homology between any part of the transposon and the sites to which they are moved, the so-called target (or insertion or integration) sites. As biology is not always neat and tidy, transposases can exhibit a spectrum of homology requirements and vagaries of terminology have arisen such that certain transposases are sometimes referred to as "resolvases" or by the generic term "recombinases".From a mechanistic perspective, t...

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“…TnsA is a nuclease that mediates cleavage at the 5′ ends of the transposon (27,28). Although TnsA lacks specific DNA-binding activity, it is positioned at the transposon ends by interaction with TnsB (29). Thus, TnsA and TnsB collaborate to excise Tn7 from the donor site and insert it into a target site.…”

mentioning

confidence: 99%

The Tn7 transposition regulator TnsC interacts with the transposase subunit TnsB and target selector TnsD

Choi

Spencer

Craig

2014

Proc. Natl. Acad. Sci. U.S.A.

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The excision of transposon Tn7 from a donor site and its insertion into its preferred target site, attachment site attTn7, is mediated by four Tn7-encoded transposition proteins: TnsA, TnsB, TnsC, and TnsD. Transposition requires the assembly of a nucleoprotein complex containing all four Tns proteins and the DNA substrates, the donor site containing Tn7, and the preferred target site attTn7. TnsA and TnsB together form the heteromeric Tn7 transposase, and TnsD is a target-selecting protein that binds specifically to attTn7. TnsC is the key regulator of transposition, interacting with both the TnsAB transposase and TnsD-attTn7. We show here that TnsC interacts directly with TnsB, and identify the specific region of TnsC involved in the TnsB-TnsC interaction during transposition. We also show that a TnsC mutant defective in interaction with TnsB is defective for Tn7 transposition both in vitro and in vivo. Tn7 displays cis-acting target immunity, which blocks Tn7 insertion into a target DNA that already contains Tn7. We provide evidence that the direct TnsB-TnsC interaction that we have identified also mediates cis-acting Tn7 target immunity. We also show that TnsC interacts directly with the target selector protein TnsD.photocrosslinking | protein-protein interaction | transpososome | transposable element

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Direct interaction between the TnsA and TnsB subunits controls the heteromeric Tn7 transposase

Cited by 27 publications

References 38 publications

Recruitment of CRISPR-Cas systems by Tn7-like transposons

Recruitment of CRISPR-Cas systems by Tn7-like transposons

Mechanisms of DNA Transposition

The Tn7 transposition regulator TnsC interacts with the transposase subunit TnsB and target selector TnsD

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