Inhibition of transpositional recombination by OrfA and OrfB proteins encoded by insertion sequence IS<i>3</i>

Sekine, Yoshiaki; Izumi, Ken‐ichiro; Mizuno, Takaaki; Ohtsubo, Eiichi

doi:10.1046/j.1365-2443.1997.1440342.x

Cited by 33 publications

(21 citation statements)

References 34 publications

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“…Similarly, the abutted IRs of IS3 separated by GAG must have derived from the IS3A element of E. coli. Numerous SRs of unidentified origin were found in the IRR-IRL junctions of IS3 and IS150, as was also reported for IS1 and IS3 circles (Sekine et al, 1994(Sekine et al, , 1997b. This indicates that at any time the bacterial population carries transpositional intermediates deriving from new insertions, which may be present only in subclones of the cells.…”

Section: Discussionsupporting

confidence: 69%

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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Section: Discussionsupporting

confidence: 69%

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

et al. 2003

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“…Only in the case of IS3 could a function be assigned to the gene product. In this case, the InsB homologue acted together with the InsA homologue as a coinhibitor of transposition (27). However, in this test all IS3 genes were highly overexpressed.…”

Section: Vol 184 2002 Is150 Transposition 5839mentioning

confidence: 77%

“…While the data obtained in this way provided important contributions to our understanding of the transpositional processes, they are difficult to compare. Indeed, quite different results were obtained for the relative transposition rates when the InsAB homologues were synthesized alone and when all IS genes were expressed; the values ranged from 10 5 -fold stimulation in the case of IS2 (13) to 160-fold stimulation in the case of IS3 (27) to 60-fold inhibition in the case of IS911 (28). It remains to be determined whether these huge differences reflect true differences between the elements studied.…”

Section: Vol 184 2002 Is150 Transposition 5839mentioning

confidence: 98%

Escherichia coliInsertion Sequence IS150: Transposition via Circular and Linear Intermediates

Haas

Rak

2002

J Bacteriol

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IS150, a member of the widespread IS3 family, contains two consecutive out-of-phase open reading frames, orfA and orfB, that partially overlap. These open reading frames encode three proteins, InsA, InsB, and the InsAB protein, which is jointly encoded by both open reading frames by means of programmed translational frameshifting. We demonstrate that the InsAB protein represents the IS150 element's transposase. In vivo, the wild-type IS150 element generates circular excision products and linear IS150 molecules. Circular and linear species have previously been detected with mutant derivatives of other members of the IS3 family. Our finding supports the assumption that these products represent true transposition intermediates of members of this family. Analysis of the molecular nature of these two species suggested that the circular forms are precursors of the linear molecules. Elimination of InsA synthesis within the otherwise intact element led to accumulation of large amounts of the linear species, indicating that the primary role of InsA may be to prevent abortive production of the linear species and to couple generation of these species to productive insertion events.

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“…Some IS elements, such as IS1 and IS3, have two ORFs, and the product from one of the two ORFs acts as the negative regulator, inhibiting transposition of each element (24,40,53). These IS elements produce transposases as a transframe protein by translational frameshifting between the two ORFs (10,37,38,41).…”

Section: Discussionmentioning

confidence: 99%

Presence of a Characteristic D-D-E Motif in IS1Transposase

et al. 2002

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IS1 is an insertion element first identified in Escherichia coli (for a review, see reference 28). IS1 is only 768 bp in length and has imperfect terminal inverted repeats (IR) of about 30 bp (19,30). IS1 transposes to a new site and generates a duplication of a target sequence of 9 bp (in most cases) or 8 bp (in some cases) (13,14,17,29). IS1 has two open reading frames (ORFs), insA and BЈ-insB, which are required for transposing itself (18,25,26). insB is in the Ϫ1 frame with respect to insA. The Ϫ1 frameshifting occurs during translation at the AAAAAAC (A 6 C) sequence in the overlapping region between insA and BЈ-insB. The resulting transframe protein, InsA-BЈ-B, is IS1 transposase (10, 37).IS1 generates the InsA protein from insA unless translational frameshifting occurs. The InsA protein, which has the ability to bind to terminal IR sequences (43, 52, 54), inhibits transposition of IS1 (24, 53). IS1 with a 1-bp insertion in the A 6 C sequence, causing the two frames insA and BЈ-insB to be in the same frame, produces transposase without frameshifting and can thus transpose at a very high frequency (37, 39). These facts suggest that the InsB segment in IS1 transposase forms a catalytic domain. Many elements with structural features similar to those seen in IS1 have been identified in various bacteria and their plasmids (for a review, see reference 28). Most of them are highly homologous to IS1 and to one another (more than 90% sequence identity), whereas a few, such as IS1(NuXi) from Shigella dysenteriae, have low homology, about 55% (31).Transposases encoded by IS3 family elements and retroviral integrases have been found to have three acidic amino acid residues, D, D, and E, constituting a motif called the D-D-E motif, at positions where a polypeptide segment 35 amino acids long is usually present between the second D and third E residues (11, 23). The D-D-E motif has also been found in transposases encoded by IS630, Tn7, Tn552, and others and in integrases encoded by retrotransposons (7,34). Transposases encoded by IS10 and phage Mu also have the D-D-E motif, but a longer polypeptide segment of 130 or 55 amino acids is present between the second D and the E (4, 5, 49). The polypeptide segment with the D-D-E motif forms a catalytic domain in which the three acidic amino acid residues have an essential role in capturing Mg 2ϩ and other divalent cations (4). Tertiary structures of the catalytic core domains of human immunodeficiency virus type 1 (HIV-1) integrase and phage Mu transposase (MuA) and full-length Tn5 transposase have been determined by X-ray crystallography (6, 9, 35). These proteins characteristically have three ␤ sheets in tandem in the segment with the D-D-E motif, such that the first D residue is present in the first ␤ sheet.The transposase encoded by IS1 has been thought not to belong to the family of proteins with the D-D-E motif but to the phage integrase (Int) family (44) because IS1 transposase has the H-R-Y motif, which is conserved in all the Int family proteins (1, 3). In this study,...

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Inhibition of transpositional recombination by OrfA and OrfB proteins encoded by insertion sequence IS3

Cited by 33 publications

References 34 publications

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

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

Escherichia coliInsertion Sequence IS150: Transposition via Circular and Linear Intermediates

Presence of a Characteristic D-D-E Motif in IS1Transposase

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