Isolation and characterization of IS1 circles

Sekine, Yoshiaki; Eisaki, Naoki; Kobayashi, Kiyoaki; Ohtsubo, Eiichi

doi:10.1016/s0378-1119(97)00057-7

Cited by 21 publications

(32 citation statements)

References 33 publications

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“…An IS1 mutant (IS1-31) with a single adenine insertion at the frameshifting site efficiently produces transposase and therefore can frequently transpose and mediate cointegration (49). The plasmid with this IS1 mutant generates miniplasmids, the deletion products generated by intramolecular transposition (50,51), as well as IS1 circles consisting of the entire IS1 sequence and a sequence 6 to 9 bp long which appears as a spacer between the IRL and IRR of IS1 (45).…”

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confidence: 99%

Involvement of H-NS in Transpositional Recombination Mediated by IS 1

et al. 2001

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IS1, the smallest active transposable element in bacteria, encodes a transposase that promotes inter-and intramolecular transposition. Host-encoded factors, e.g., histone-like proteins HU and integration host factor (IHF), are involved in the transposition reactions of some bacterial transposable elements. Host factors involved in the IS1 transposition reaction, however, are not known. We show that a plasmid with an IS1 derivative that efficiently produces transposase did not generate miniplasmids, the products of intramolecular transposition, in mutants deficient in a nucleoid-associated DNA-binding protein, H-NS, but did generate them in mutants deficient in histone-like proteins HU, IHF, Fis, and StpA. Nor did IS1 transpose intermolecularly to the target plasmid in the H-NS-deficient mutant. The hns mutation did not affect transcription from the indigenous promoter of IS1 for the expression of the transposase gene. These findings show that transpositional recombination mediated by IS1 requires H-NS but does not require the HU, IHF, Fis, or StpA protein in vivo. Gel retardation assays of restriction fragments of IS1-carrying plasmid DNA showed that no sites were bound preferentially by H-NS within the IS1 sequence. The central domain of H-NS, which is involved in dimerization and/or oligomerization of the H-NS protein, was important for the intramolecular transposition of IS1, but the N-and C-terminal domains, which are involved in the repression of certain genes and DNA binding, respectively, were not. The SOS response induced by the IS1 transposase was absent in the H-NSdeficient mutant strain but was present in the wild-type strain. We discuss the possibility that H-NS promotes the formation of an active IS1 DNA-transposase complex in which the IS1 ends are cleaved to initiate transpositional recombination through interaction with IS1 transposase.IS1 is an insertion element present in chromosomes and plasmids of enteric bacteria (for a review, see reference 38). IS1 (768 bp long) carries imperfect terminal inverted repeats (IRL and IRR) that are about 30 bp long (17,40). IS1 mediates the formation of cointegrates between the IS1-carrying plasmid and a target plasmid in which two copies of IS1 are duplicated at the two junctions in direct orientation (10,39). This element encodes two open reading frames, insA and BЈ-insB (16,32,33). Transcription occurs from a promoter present in the left-terminal region (IRL) preceding insA (31). A translational frameshift occurs in the Ϫ1 direction at the AAAAAAC (A 6 C) sequence in the overlapping region between the two open reading frames, producing the InsA-BЈ-InsB transframe protein, IS1 transposase (7, 49). Unless frameshifting occurs, IS1 produces InsA protein from insA which can bind to the IRs (51, 74) and inhibits transposition (30,75). An IS1 mutant (IS1-31) with a single adenine insertion at the frameshifting site efficiently produces transposase and therefore can frequently transpose and mediate cointegration (49). The plasmid with this IS1 mutant generates min...

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Involvement of H-NS in Transpositional Recombination Mediated by IS 1

et al. 2001

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“…7c). The sequence of the SRs, where it was traceable, always derived from the flanking regions of one or the other IR taking part in dimerization, as has been reported for other elements [IS1 (Sekine et al, 1997a, Turlan & Chandler, 1995; IS3 (Sekine et al, 1994); IS30 (Olasz et al, 1993); IS911 (Polard et al, 1992)]. The C4-derived C5 dimers of all three ISs contained the same SRs that separated the truncated IRs rather than the bases flanking the intact element in C4, whereas C3-borne IRR-IRL junctions behaved differently.…”

Section: Discussionmentioning

confidence: 79%

“…Similar to the dimer structures, the covalently joined IRs are also separated by a few base pairs in the circular form of the IS elements. These minicircles can be considered as intermediates of simple insertion, as reported for IS1 (Sekine et al, 1997a;Turlan & Chandler, 1995), IS2 (Lewis & Grindley, 1997), IS3 (Sekine et al, 1994), IS150 (Welz, 1993;Haas & Rak, 2002), IS256 (Prudhomme et al, 2002) and IS911 (Ton-Hoang et al, 1997. The synthetic IS dimer model seems to be applicable for the elements that form both minicircles and dimers (IS2, IS21, IS30, IS256 and IS911); however, its validity might also be extended to additional elements (e.g.…”

Section: Introductionmentioning

confidence: 77%

“…However, additional experimental evidence is required to determine the overall occurrence of this intermediate in other IS elements, and further potential members may be found among the elements for which minicircle formation has already been reported [e.g. IS1 (Sekine et al, 1997a;Turlan & Chandler, 1995)]. It has been suggested that covalently closed IS circles and dimers could be alternative representations of the same transpositional pathway (Lewis & Grindley, 1997;Kiss & Olasz, 1999).…”

Section: Discussionmentioning

confidence: 99%

“…Such junctions have been identified in IS dimers consisting of two directly repeated elements and in minicircles formed by circularization of a single element. IS dimers have been isolated from IS2 (Szeverényi et al, 1996a), IS21 (Reimmann & Haas, 1987, 1990Reimmann et al, 1989), IS30 (Dalrymple, 1987;Olasz et al, 1993Olasz et al, , 1997, IS256 (Prudhomme et al, 2002) and IS911 (Turlan et al, 2000), and covalently closed circular IS elements have been described for IS1 (Sekine et al, 1997a, Turlan & Chandler, 1995, IS2 (Lewis & Grindley, 1997), IS3 (Sekine et al, 1994), IS30 (Kiss & Olasz, 1999), IS117 (Smokvina et al, 1994), IS150 (Welz, 1993;Haas & Rak, 2002), IS256 (Prudhomme et al, 2002) and IS911 (Polard et al, 1992(Polard et al, , 1996. For some of these elements both circular and dimeric forms have been reported, suggesting a possible connection between the formation and transposition of these structures, as described for IS30 (Kiss & Olasz, 1999).…”

Section: Introductionmentioning

confidence: 99%

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Detection and analysis of transpositionally active head-to-tail dimers in three additional Escherichia coli IS elements

et al. 2003

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This study demonstrates that Escherichia coli insertion elements IS3, IS150 and IS186 are able to form transpositionally active head-to-tail dimers which show similar structure and transpositional activity to the dimers of IS2, IS21 and IS30. These structures arise by joining of the left and right inverted repeats (IRs) of two elements. The resulting junction includes a spacer region (SR) of a few base pairs derived from the flanking sequence of one of the reacting IRs. Head-to-tail dimers of IS3, IS150 and IS186 are unstable due to their transpositional activity. They can be resolved in two ways that seem to form a general rule for those elements reported to form dimers. One way is a sitespecific process (dimer dissolution) which is accompanied by the loss of one IS copy along with the SR. The other is 'classical' transposition where the joined ends integrate into the target DNA. In intramolecular transposition this often gives rise to deletion formation, whereas in intermolecular transposition it gives rise to replicon fusion. The results presented for IS3, IS150 and IS186 are in accordance with the IS dimer model, which is in turn consistent with models based on covalently closed minicircles.

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Transposase and cointegrase: specialized transposition proteins of the bacterial insertion sequence IS21 and related elements

Berger

Haas

2001

CMLS, Cell. Mol. Life Sci.

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The bacterial insertion sequence IS21 shares with many insertion sequences a two-step, reactive junction transposition pathway, for which a model is presented in this review: a reactive junction with abutted inverted repeats is first formed and subsequently integrated into the target DNA. The reactive junction occurs in IS21-IS21 tandems and IS21 minicircles. In addition, IS21 shows a unique specialization of transposition functions. By alternative translation initiation, the transposase gene codes for two products: the transposase, capable of promoting both steps of the reactive junction pathway, and the cointegrase, which only promotes the integration of reactive junctions but with higher efficiency. This review also includes a survey of the IS21 family and speculates on the possibility that other members present a similar transpositional specialization.

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Isolation and characterization of IS1 circles

Cited by 21 publications

References 33 publications

Involvement of H-NS in Transpositional Recombination Mediated by IS 1

Involvement of H-NS in Transpositional Recombination Mediated by IS 1

Detection and analysis of transpositionally active head-to-tail dimers in three additional Escherichia coli IS elements

Transposase and cointegrase: specialized transposition proteins of the bacterial insertion sequence IS21 and related elements

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