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PubMed2001

Transposition of IS10 from the host Escherichia coli genome to a plasmid may lead to cloning artefacts.

During recloning of Nicotiana tabacum L. repetitive sequence R8.3 in Escherichia coli, a modified clone that differed from the original by the insertion of an IS10 sequence was unintentionally produced. The insert was flanked by a 9-bp direct repeat derived from the R8.3 sequence, the 9-bp duplication of acceptor DNA in the site of insertion being a characteristic of IS10 transposition events. A database search using the FASTA program showed IS10 and other prokaryotic IS elements inserted into numerous eukaryotic clones. Unexpectedly, the IS10, which is not a natural component of the E. coli genome, appeared to be by far the most frequent contaminant of DNA databases among several IS sequences tested. In the GenEMBL database, the IS10 query sequence yielded positive scores with more than 500 eukaryotic clones. Insertions of shortened IS10 sequences having only one intact terminal inverted repeat were commonly found. Most full-length IS10 insertions (32 out of 40 analyzed) were flanked by 9-bp direct repeats having the consensus 5'-NPuCNN-NGPyN-3' with a strong preference for 5'-TGCTNA-GNN-3'. One insertion was flanked by an inverted repeat of more than 400 bp in length. PCR amplification and Southern analysis revealed the presence of IS10 sequences in E. coli strains commonly used for DNA cloning, including some reported to be Tn10-free. No IS10-specific PCR product was obtained with N. tabacum or human DNA. Our data suggest that transposition of IS10 elements may accompany cloning steps, particularly into large BAC vectors. This might lead to the relatively frequent contamination of DNA databases by this bacterial sequence. It is estimated that one in approximately every thousand eukaryotic clone in the databases is contaminated by IS-derived sequences. We recommend checking submitted sequences for the presence of IS10 and other IS elements. In addition, DNA databases should be corrected by removing contaminating IS sequences.

Animals↗
PubMed1992

The linear mitochondrial plasmid pAL2-1 of a long-lived Podospora anserina mutant is an invertron encoding a DNA and RNA polymerase.

The molecular characterization of an additional DNA species (pAL2-1) which was identified previously in a long-lived extrachromosomal mutant (AL2) of Podospora anserina revealed that this element is a mitochondrial linear plasmid. pAL2-1 is absent from the corresponding wild-type strain, has a size of 8395 bp and contains perfect long terminal inverted repeats (TIRs) of 975 bp. Exonuclease digestion experiments indicated that proteins are covalently bound at the 5' termini of the plasmid. Two long, non-overlapping open reading frames, ORF1 (3,594 bp) and ORF2 (2847 bp), have been identified, which are located on opposite strands and potentially encode a DNA and an RNA polymerase, respectively. The ORF1-encoded polypeptide contains three conserved regions which may be responsible for a 3'-5' exonuclease activity and the typical consensus sequences for DNA polymerases of the D type. In addition, an amino-acid sequence motif (YSRLRT), recently shown to be conserved in terminal proteins from various bacteriophages, has been identified in the amino-terminal part of the putative protein. According to these properties, this first linear plasmid identified in P. anserina shares all characteristics with invertrons, a group of linear mobile genetic elements.

Amino Acid Sequence↗
PubMed1995

Characterization of transposon Tn5469 from the cyanobacterium Fremyella diplosiphon.

A transposon, designated Tn5469, was isolated from mutant strain FdR1 of the filamentous cyanobacterium Fremyella diplosiphon following its insertion into the rcaC gene. Tn5469 is a 4,904-bp noncomposite transposon with 25-bp near-perfect terminal inverted repeats and has three tandemly arranged, slightly overlapping potential open reading frames (ORFs) encoding proteins of 104.6 kDa (909 residues), 42.5 kDa (375 residues), and 31.9 kDa (272 residues). Insertion of Tn5469 into the rcaC gene in strain FdR1 generated a duplicate 5-bp target sequence. On the basis of amino acid sequence identifies, the largest ORF, designated tnpA, is predicted to encode a composite transposase protein. A 230-residue domain near the amino terminus of the TnpA protein has 15.4% amino acid sequence identity with a corresponding domain for the putative transposase encoded by Lactococcus lactis insertion sequence S1 (ISS1). In addition, the sequence for the carboxyl-terminal 600 residues of the TnpA protein is 20.0% identical to that for the TniA transposase encoded by Tn5090 on Klebsiella aerogenes plasmid R751. The TnpA and TniA proteins contain the D,D(35)E motif characteristic of a recently defined superfamily consisting of bacterial transposases and integrase proteins of eukaryotic retroelements and retrotransposons. The two remaining ORFs on Tn5469 encode proteins of unknown function. Southern blot analysis showed that wild-type F. diplosiphon harbors five genomic copies of Tn5469. In comparison, mutant strain FdR1 harbors an extra genomic copy of Tn5469 which was localized to the inactivated rcaC gene. Among five morphologically distinct cyanobacterial strains examined, none was found to contain genomic sequences homologous to Tn5469.

Amino Acid Sequence↗
PubMed2002

Genome analysis and strain comparison of correia repeats and correia repeat-enclosed elements in pathogenic Neisseria.

Whole genome sequences of Neisseria meningitidis strains Z2491 and MC58 and Neisseria gonorrhoeae FA1090 were analyzed for Correia repeats (CR) and CR-enclosed elements (CREE). A total of 533, 516, and 256 copies of CR and 270, 261, and 102 copies of CREE were found in these three genomes, respectively. The lengths of CREE range from 28 to 348 bp, and the lengths of multicopy CREE appear mainly in the ranges of 154 to 156 bp and 105 to 107 bp. The distribution of CREE lengths is similar between the two N. meningitidis genomes, with a greater number of 154- to 156-bp CREE (163 and 152 copies in N. meningitidis strain Z2491 and N. meningitidis strain MC58, respectively) than 105- to 107-bp CREE (72 and 77 copies). In the N. gonorrhoeae strain FA1090 genome there are relatively more 105- to 107-bp CREE (51 copies) than 154- to 156-bp CREE (36 copies). The genomic distribution of 107-bp CREE also shows similarity between the two N. meningitidis strains (15 copies share the same loci) and differences between N. meningitidis strains and N. gonorrhoeae FA1090 (only one copy is located in the same locus). Detailed sequence analysis showed that both the terminal inverted repeats and the core regions of CREE are composed of distinct basic sequence blocks. Direct TA dinucleotide repeats exist at the termini of all CREE. A survey of DNA sequence upstream of the sialyltransferase gene, lst, in several Neisseria isolates showed that 5 N. meningitidis strains contain a 107-bp CREE in this region but 25 N. gonorrhoeae strains show an exact absence of a 105-bp sequence block (i.e., the 107-bp CREE without a 5' TA dinucleotide) in the same region. Whole-genome sequence analysis confirmed that this 105-bp indel exists in many homologous 107-bp CREE loci. Thus, we postulate that all CREE are made of target TA with indels of various lengths. Analysis of 107-bp CREE revealed that they exist predominantly in intergenic regions and are often near virulence, metabolic, and transporter genes. The abundance of CREE in Neisseria genomes suggests that they may have played a role in genome organization, function, and evolution. Their differential distribution in different pathogenic Neisseria strains may contribute to the distinct behaviors of each Neisseria species.

Base Sequence↗
PubMed1989

The avian retroviral integration protein cleaves the terminal sequences of linear viral DNA at the in vivo sites of integration.

The purified integration protein (IN) of avian myeloblastosis virus is shown to nick double-stranded oligodeoxynucleotide substrates that mimic the ends of the linear form of viral DNA. In the presence of Mg2+, nicks are created 2 nucleotides from the 3' OH ends of both the U5 plus strand and the U3 minus strand. Similar cleavage is observed in the presence of Mn2+ but only when the extent of the reaction is limited. Neither the complementary strands nor sequences representing the termini of human immunodeficiency virus type 1 DNA were cleaved at analogous positions. Analysis of a series of substrates containing U5 base substitutions has defined the sequence requirements for site-selective nicking; nucleotides near the cleavage site are most critical for activity. The minimum substrate size required to demonstrate significant activity corresponds to the nearly perfect 15-base terminal inverted repeat. This in vitro activity of IN thus produces viral DNA ends that are joined to host DNA in vivo and corresponds to an expected early step in the integrative recombination reaction. These results provide the first enzymatic support using purified retroviral proteins for a linear DNA precursor to the integrated provirus.

Avian Leukosis Virus↗
PubMed1999

Genetic instability associated with insertion of IS6100 into one end of the Streptomyces lividans chromosome.

Analysis of 548 recombinant strains of Streptomyces lividans carrying chromosomal insertions of IS6100 revealed that six mutants contained DNA amplifications. The amplifications differed in size but included IS6100 sequences. Hybridization with representative cosmid clones containing sequences from the unstable regions of the chromosome indicated that, in each mutant, DNA rearrangements affected just one of the chromosome ends. The amplifications were derived either from a region immediately proximal to the terminal inverted repeat (TIR) or further distal, from a previously characterized type I amplifiable unit of DNA. There was no evidence for extensive deletions accompanying the amplifications and chromosome linearity was maintained with, at least in five mutants, clear evidence for no loss of either TIR. The nature of the rearrangements provides evidence that insertions affecting the integrity of a chromosome end can contribute to genetic instability in Streptomyces.

Chromosomes, Bacterial↗
PubMed1999

Linearization and transposition of circular molecules of insertion sequence IS3.

IS3 transposase has been shown to promote production of characteristic circular and linear IS3 molecules from the IS3-carrying plasmid; IS3 circles have the entire IS3 sequence with terminal inverted repeats, IRL and IRR, which are separated by a three base-pair sequence originally flanking either end in the parental plasmid, whereas linear IS3 molecules have three nucleotide overhangs at their 5' ends. Here, we showed that a plasmid carrying an IS3 derivative, which is flanked by different sequences at both ends, generated IS3 circles and linear IS3 molecules owing to the action of transposase. Cloning and sequencing analyses of the linear molecules showed that each had the same 5'-protruding three nucleotide overhanging sequences at both ends, suggesting that the linear molecules were not generated from the parental plasmid by the two double-strand breaks at both end regions of IS3. The plasmid carrying IS3 with a two base-pair mutation in the terminal dinucleotide, which would be required for transposase to cleave the 3' end of IS3, could still generate linear molecules as well as circles. Plasmids bearing an IS3 circle were cleaved by transposase and gave linear molecules with the same 5'-protruding three nucleotide overhanging sequences. These show that the linear molecules are generated from IS3 circles via a double-strand break at the three base-pair intervening sequence. Plasmids carrying an IS3 circle with the two base-pair end mutation still were cleaved by transposase, though with reduced efficiencies, suggesting that IS3 transposase has the ability to cleave not only the 3' end of IS3, but a site three nucleotides from the 5' end of IS3. IS3 circles also were shown to transpose to the target plasmids. The end mutation almost completely inhibited this transposition, showing that the terminal dinucleotides are important for the transfer of the 3' end of IS3 to the target as well as for the end cleavage.

Base Pairing↗
PubMed1980

Nucleotide sequence analysis of the transforming region and large terminal redundancies of Moloney murine sarcoma virus.

The sequence of the transforming region of the Moloney murine sarcoma virus genome has been determined by using molecularly cloned viral DNA. This region, 3.6 to 5.8 kilobase pairs from the left end of the molecule, contains the entire cellular insertion (src) sequence as well as helper viral sequences including the large terminal repeat (LTR). On the viral RNA strand, a long (1224 bases) open reading frame commenced to the left of the src-helper virus junction and terminated at a point 58 nucleotides into helper viral sequences to the right of src. Possible promoter and acceptor splice signals were detected in helper viral sequences upstream from this open reading frame. On the antiviral RNA strand, several promoter-like sequences, including one within the src region itself, were identified. However, no open reading frame downstream from these promoters was detected in the antiviral RNA strand. The LTR was found to contain promoter-like sequences as well as LTR was found to contain promoter-like sequences as well as mRNA capping and polyadenylylation signals. In addition, it possessed an 11-base inverted terminal repeat at each end. Thus, the structure of the Moloney murine sarcoma virus genome with an LTR at each end resembles that of prokaryotic transposable elements.

Bacteriophage lambda↗
PubMed1990

Nucleotide sequence of the promoter-distal region of the tra operon of plasmid R100, including traI (DNA helicase I) and traD genes.

The nucleotide sequence of the promoter-distal region of the tra operon of R100 was determined. There are five open reading frames in the region between traT and finO, and their protein products were identified. Nucleotide sequences of plasmid F corresponding to the junction regions among the open reading frames seen in R100 were also determined. Comparison of these nucleotide sequences revealed strong homology in the regions containing traD, traI and an open reading frame (named orfD). The TraD protein (83,899 Da) contains three hydrophobic regions, of which two are located near the amino-terminal region. This protein also contains a possible ATP-binding consensus sequence at the amino-terminal region and a characteristic repeated peptide sequence (Gln-Gln-Pro)10 at the carboxy-terminal region. The TraI protein (191,679 Da) contains the sequence motif conserved in an ATP-dependent DNA helicase superfamily in its carboxy-terminal region. The protein product of orfD, which is probably a new tra gene (named traX), contains 65% hydrophobic amino acids, especially rich in alanine and leucine. There exist non-homologous regions between R100 and F that could be represented as four I-D (insertion or deletion) loops in heteroduplex molecules. Assignment of each loop to the strand of R100 or F was , however, found to be the reverse from that previously assumed. The three I-D loops that were located between traT and traD, between traD and traI, and between traI and finO had no terminal inverted repeat sequences nor had they any homology with known insertion sequences, while the fourth was IS3, located within the finO gene of F. The sequences in the I-D loops, except IS3, may also code for proteins that are, however, likely to be nonessential for transfer of plasmids.

Amino Acid Sequence↗
PubMed1991

The kalilo linear senescence-inducing plasmid of Neurospora is an invertron and encodes DNA and RNA polymerases.

The nucleotide sequence of kalilo, a linear plasmid that induces senescence in Neurospora by integrating into the mitochondrial chromosome, reveals structural and genetic features germane to the unique properties of this element. Prominent features include: (1) very long perfect terminal inverted repeats of nucleotide sequences which are devoid of obvious genetic functions, but are unusually GC-rich near both ends of the linear DNA; (2) small imperfect palindromes that are situated at the termini of the plasmid and are cognate with the active sites for plasmid integration into mtDNA; (3) two large, non-overlapping open-reading frames, ORF-1 and ORF-2, which are located on opposite strands of the plasmid and potentially encode RNA and DNA polymerases, respectively, and (4) a set of imperfect palindromes that coincide with similar structures that have been detected at more or less identical locations in the nucleotide sequences of other linear mitochondrial plasmids. The nucleotide sequence does not reveal a distinct gene that codes for the protein that is attached to the ends of the plasmid. However, a 335-amino acid, cryptic, N-terminal domain of the putative DNA polymerase might function as the terminal protein. Although the plasmid has been co-purified with nuclei and mitochondria, its nucleotide composition and codon usage indicate that it is a mitochondrial genetic element.

Amino Acid Sequence↗
PubMed2000

The terminal protein of a linear mitochondrial plasmid is encoded in the N-terminus of the DNA polymerase gene in white-rot fungus Pleurotus ostreatus.

The gene structure and expression of the linear mitochondrial plasmids of the white-rot fungus Pleurotus ostreatus, pMLP1 and pMLP2, were analyzed. Cleavage by proteinase K and exonucleases indicated that the 5' ends of pMLP1 and pMLP2 DNAs were associated with terminal proteins. Nucleotide sequencing of the entire pMLP1 DNA revealed that it consists of 9,879 bp with terminal inverted repeat (TIR) sequences of 381 bp. The end sequence of TIR in pMLP1 is 3'-CCCCC-5', similar to those of Escherichia coli phage PRDI. The pMLP1 plasmid harbors two long open reading frames (ORFI and ORF2) and at least one minor ORF (mORF1). The deduced product of ORF1 is homologous to RNA polymerases of yeast mitochondria and several bacteriophages, whereas that of ORF2 is homologous to the protein-primed DNA polymerases of family B type. The mORF1 encodes a highly basic protein, most likely a TIR-binding protein, with no apparent sequence homology in the database. Expression of the predicted gene products from pMLP1 in mitochondria was demonstrated by Western blot analysis using antibodies against various expressed regions of pMLP1 ORFs. A plasmid-free strain, generated by curing with ethidium bromide, did not express any of these gene products. Terminal proteins of 70 kDa (TP1) and 73 kDa (TP2) were identified from pMLP1 and pMLP2, respectively. Western blot analysis indicated that TP1 was generated from the N-terminal half of the full-length product of ORF2 encoding a putative DNA polymerase.

Amino Acid Sequence↗
PubMed1985

Cointegration and resolution mediated by IS101 present in plasmid pSC101.

A certain class of cointegrate plasmids was found to occur between a pSC101 derivative and a second plasmid pBV320 in E. coli F- cells. Cleavage analysis and DNA sequencing showed that the cointegrate plasmid contained direct repeats of an insertion sequence IS101 at the recombination junctions, indicating that formation of cointegrates was mediated by IS101, which is a natural constituent of pSC101. These cointegrates were formed only in cells which contained the transposon gamma-delta, suggesting that the gamma-delta sequence, which provides transposase, is responsible for cointegration. Whenever the cointegrate plasmids were present in cells containing gamma-delta or its related transposon Tn3, the cointegrates were dissolved to give pBV320::IS101 due to recombination at duplicated IS101 sequences in the cointegrates, suggesting that both gamma-delta and Tn3, which provide a resolvase, are responsible for the resolution of the cointegrates. Comparison between the nucleotide sequence of IS101 and those of gamma-delta and Tn3 shows a high degree of homology in the regions that have been shown to be the binding sites of resolvases, as well as in the terminal inverted repeats. However, there is no homology between IS101 and the other element, gamma-delta or Tn3, in the internal resolution site, at which the resolution event may occur.

Ampicillin↗
PubMed1999

A novel pseudoautosomal human gene encodes a putative protein similar to Ac-like transposases.

We report the cloning of a novel gene, called Tramp, in the Xp/Yp PAR region that has a functional homologue on the Y chromosome and escapes X-inactivation. This gene encodes, within a single exon, a putative protein that has amino acid similarity with transposases of the Ac family. Flanking this gene we have identified putative terminal inverted repeats (TIRs) and a duplicate target site, suggesting that it may be an ancient transposable element. The nucleotide differences in these sites and the TIR-binding inactivity of the putative Tramp protein suggest that this element is not an autonomous transposon. In the human genome, the Tramp protein may be involved in the transposition of other transposable elements, like medium reiterated frequency repeats, or it could be specialized in the acquisition of a new cellular function.

Amino Acid Sequence↗
PubMed2003

Ribonuclease III-mediated processing of specific Neisseria meningitidis mRNAs.

Approx. 2% of the Neisseria meningitidis genome consists of small DNA insertion sequences known as Correia or nemis elements, which feature TIRs (terminal inverted repeats) of 26-27 bp in length. Elements interspersed with coding regions are co-transcribed with flanking genes into mRNAs, processed at double-stranded RNA structures formed by TIRs. N. meningitidis RNase III (endoribonuclease III) is sufficient to process nemis+ RNAs. RNA hairpins formed by nemis with the same termini (26/26 and 27/27 repeats) are cleaved. By contrast, bulged hairpins formed by 26/27 repeats inhibit cleavage, both in vitro and in vivo. In electrophoretic mobility shift assays, all hairpin types formed similar retarded complexes upon incubation with RNase III. The levels of corresponding nemis+ and nemis- mRNAs, and the relative stabilities of RNA segments processed from nemis+ transcripts in vitro, may both vary significantly.

Base Sequence↗
PubMed2001

Sequences and replication of genomes of the archaeal rudiviruses SIRV1 and SIRV2: relationships to the archaeal lipothrixvirus SIFV and some eukaryal viruses.

The double-stranded DNA genomes of the viruses SIRV1 and SIRV2, which infect the extremely thermophilic archaeon Sulfolobus and belong to the family Rudiviridae, were sequenced. They are linear, covalently closed at the ends, and 32,312 and 35,502 bp long, respectively, with an A+T content of 75%. The genomes of SIRV1 and SIRV2 carry inverted terminal repeats of 2029 and 1628 bp, respectively, which contain multiple direct repeats. SIRV1 and SIRV2 genomes contain 45 and 54 ORFs, respectively, of which 44 are homologous to one another. Their predicted functions include a DNA polymerase, a Holliday junction resolvase, and a dUTPase. The genomes consist of blocks with well-conserved sequences separated by nonconserved sequences. Recombination, gene duplication, horizontal gene transfer, and substitution of viral genes by homologous host genes have contributed to their evolution. The finding of head-to-head and tail-to-tail linked replicative intermediates suggests that the linear genomes replicate by the same mechanism as the similarly organized linear genomes of the eukaryal poxviruses, African swine fever virus and Chlorella viruses. SIRV1 and SIRV2 both contain motifs that resemble the binding sites for Holliday junction resolvases of eukaryal viruses and may use common mechanisms for resolution of replicative intermediates. The results suggest a common origin of the replication machineries of the archaeal rudiviruses and the above-mentioned eukaryal viruses. About 1/3 of the ORFs of each rudivirus have homologs in the Sulfolobus virus SIFV of the family Lipothrixviridae, indicating that the two viral families form a superfamily. The finding of inverted repeats of at least 0.8 kb at the termini of the linear genome of SIFV supports this inference.

African Swine Fever Virus↗
PubMed2003

IS Rm31, a new insertion sequence of the IS 66 family in Sinorhizobium meliloti.

Sinorhizobium meliloti natural populations show a high level of genetic polymorphism possibly due to the presence of mobile genetic elements such as insertion sequences (IS), transposons, and bacterial mobile introns. The analysis of the DNA sequence polymorphism of the nod region of S. meliloti p SymA megaplasmid in an Italian isolate led to the discovery of a new insertion sequence, IS Rm31. IS Rm31 is 2,803 bp long and has 22-bp-long terminal inverted repeat sequences, 8-bp direct repeat sequences generated by transposition, and three ORFs (A, B, C) coding for proteins of 124, 115, and 541 amino acids, respectively. ORF A and ORF C are significantly similar to members of the transposase family. Amino acid and nucleotide sequences indicate that IS Rm31 is a member of the IS 66 family. IS Rm31 sequences were found in 30.5% of the Italian strains analyzed, and were also present in several collection strains of the Rhizobiaceae family, including S. meliloti strain 1021. Alignment of targets sites in the genome of strains carrying IS Rm31 suggested that IS Rm31 inserts randomly into S. meliloti genomes. Moreover, analysis of IS Rm31 insertion sites revealed DNA sequences not present in the recently sequenced S. meliloti strain 1021 genome. In fact, IS Rm31 was in some cases linked to DNA fragments homologous to sequences found in other rhizobia species.

Base Composition↗
PubMed2005

Anaconda, a new class of transposon belonging to the Mu superfamily, has diversified by acquiring host genes during rice evolution.

A new type of transposon, named Anaconda (Anac) has been found in rice (Oryza sativa). In this paper, we demonstrate that Anaconda elements have diversified by acquisition of host cellular genes, amplification of the elements, and substitution and deletion of short segments. We identified four Anaconda elements in studies of rice alternative oxidase (AOX) genes, and subsequently isolated an additional 23 elements based on the identity of their terminal inverted repeats (TIRs). The Anaconda elements have long TIRs (114-458 bp). They also have direct repeats of 9 or 10 bp in their flanking regions that are thought to have been generated upon transposition. These structural features reveal that the Anaconda elements belong to the Mu superfamily. The most prominent feature of the Anaconda elements is the high frequency with which they have acquired host cellular genes. Of the 27 elements found here, 19 appear to have sequences presumably derived from rice genes, for example, the genes for AOX1c (four elements), cytochrome P450 (five elements), L: -asparaginase (five elements), and PCF8 (two elements). Four elements, AnacA1-A4, have both the AOX1c and P450 genes. One element, AnacB14, involves a gene similar to mudrA of maize MuDR. Database analyses revealed that the loci of 26 of the 27 Anaconda elements in the subspecies japonica are the same as those in the subspecies indica. This suggests that these elements were incorporated before the divergence of these two subspecies.

Amino Acid Sequence↗
PubMed2006

Functional analysis of unique class II insertion sequence IS1071.

Various xenobiotic-degrading genes on many catabolic plasmids are often flanked by two copies of an insertion sequence, IS1071. This 3.2-kb IS element has long (110-bp) terminal inverted repeats (IRs) and a transposase gene that are phylogenetically related to those of the class II transposons. However, the transposition mechanism of IS1071 has remained unclear. Our study revealed that IS1071 was only able to transpose at high frequencies in two environmental beta-proteobacterial strains, Comamonas testosteroni and Delftia acidovorans, and not in any of the bacteria examined which belong to the alpha- and gamma-proteobacteria. IS1071 was found to have the functional features of the class II transposons in that (i) the final product of the IS1071 transposition was a cointegrate of its donor and target DNA molecules connected by two directly repeated copies of IS1071, one at each junction; (ii) a 5-bp duplication of the target sequence was observed at the insertion site; and (iii) a tnpA mutation of IS1071 was efficiently complemented by supplying the wild-type tnpA gene in trans. Deletion analysis of the IS1071 IR sequences indicated that nearly the entire region of the IRs was required for its transposition, suggesting that the interaction between the transposase and IRs of IS1071 might be different from that of the other well-characterized class II transposons.

Base Sequence↗