Transposition of IS<i>1</i> circles

Shiga, Yasuyuki; Sekine, Yoshiaki; Ohtsubo, Eiichi

doi:10.1046/j.1365-2443.1999.00281.x

Cited by 18 publications

(14 citation statements)

References 52 publications

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“…An IS1 circle with a spacer sequence of 6 to 9 bp has been shown to transpose to target plasmids at a very high frequency because of transposase (53). This transposition was accompanied by removal of the spacer sequence in the IS1 circle and by duplication of a sequence at the target site.…”

Section: Discussionmentioning

confidence: 99%

“…In the H-NS-deficient strain, however, IS1 circles transpose even to non-AT-rich regions (53). These observations led us to assume that H-NS participates in the step involving the target DNA molecule.…”

Section: Discussionmentioning

confidence: 99%

“…CSH26 and CU211 were transformed by pMC1403 (a derivative of pBR322 with a lacZ gene lacking its promoter) or pCM101 (a pMC1403 derivative having the 5Ј portion of IS1 [the 1-to-208 region based on the coordinates given to IS1] cloned in frame with the promoter-less lacZ gene). Promoter activities were measured as described previously (53).…”

Section: Enzymes and H-ns Proteinmentioning

confidence: 99%

“…IS1 transposase induction of the SOS response is dependent on the IS1 ends, indicating that SOS induction is caused by transposase-mediated DNA cleavages at the IS1 ends (26). IS1 circles are transposed to target plasmids at a very high frequency owing to the presence of transposase, and the SOS response is induced in cells containing IS1 circles (53). These IS1 circles appear to act as intermediates leading to simple insertion into the target DNA via the cleavage of the circles, thereby inducing the SOS response.…”

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confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Enzymes and H-ns Proteinmentioning

confidence: 99%

mentioning

confidence: 99%

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

et al. 2001

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“…Transpositionally active junctions have been reported experimentally for several other IS families, e.g. IS21 (Reimmann & Haas, 1990), IS30 (Kiss & Olasz, 1999;Olasz et al, 1993) and IS1 (Shiga et al, 1999;Ton-Hoang et al, 1997).…”

Section: Introductionmentioning

confidence: 90%

Formation of an inverted repeat junction in the transposition of insertion sequence ISLC3 isolated from Lactobacillus casei

Chen

Tsai

et al. 2008

Microbiology

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An insertion sequence, ISLC3, of 1351 bp has been isolated from Lactobacillus casei. Formation of IS circles containing a 3 bp spacer (complete junction) or deletion of 25 bp at the left inverted repeat (IRL) between the abutted IS ends of the ISLC3 junction region (deleted junction) was also discovered in the lactobacilli and Escherichia coli system studied. We found that the promoter formed by the complete junction P jun was more active than that formed by the 25 bp deleted junction P djun or the indigenous promoter P IRL . The corresponding transcription start sites for both promoter P jun and P IRL as well as P djun were subsequently determined using a primer extension assay. The activity of transposase OrfAB of ISLC3 was also assayed using an in vitro system. It was found that this transposase preferred to cleave a single DNA strand at the IRR over the IRL end in the transposition process, suggesting that attack of one end by the other was oriented from IRR to IRL.

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