Nucleotide sequence of the transposon Tn7 gene encoding an aminoglycoside-modifying enzyme, 3″(9)-<i>O</i>-nucleotidyltransferase

Fling, Mary E.; Kopf, Jan; Richards, Cynthia A.

doi:10.1093/nar/13.19.7095

Cited by 85 publications

(57 citation statements)

References 30 publications

(36 reference statements)

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“…A variation of the cassette content in Tn7 was previously observed among related elements such as Tn1825 and Tn1826 (42) and Tn4132 (49). Since two cassettes in Tn7, dfrA1 and aadA1, have also been observed in class 1 integrons (14,40), some cassettes appear to have been transferred among integron classes. Part of the integrase gene on Tn7 was included in a sequence by Simonsen et al (36).…”

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confidence: 74%

“…In this work we have sequenced the complete intI2 gene, and all areas of Tn7 beyond those that have previously been analyzed, i.e., dfrA1 (15,36), sat (42), aadA1 (14), and tnsA-tnsE (15a). The new data cover regions on either side of the cassettes, as indicated by horizontal lines in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The third cassette in Tn7 contains the aadA1 gene encoding an adenylyltransferase, which inactivates streptomycin and spectinomycin (14) (Fig. 1).…”

Section: Resultsmentioning

confidence: 99%

“…The three previously defined cassettes borne on Tn7 mediate resistance to trimethoprim (dfrA1 [15,40]), streptothricin (sat [39,42]) and spectinomycin (aadA1 [14]). We checked for further excisable units and found a fourth cassette downstream of those described previously.…”

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confidence: 99%

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IntI2 Integron Integrase in Tn7

et al. 2002

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Integrons can insert and excise antibiotic resistance genes on plasmids in bacteria by site-specific recombination. Class 1 integrons code for an integrase, IntI1 (337 amino acids in length), and are generally borne on elements derived from Tn5090, such as that found in the central part of Tn21. A second class of integron is found on transposon Tn7 and its relatives. We have completed the sequence of the Tn7 integrase gene, intI2, which contains an internal stop codon. This codon was found to be conserved among intI2 genes on three other Tn7-like transposons harboring different cassettes. The predicted peptide sequence (IntI2*) is 325 amino acids long and is 46% identical to IntI1. In order to detect recombination activity, the internal stop codon at position 179 in the parental allele was changed to a triplet coding for glutamic acid. The sequences flanking the cassette arrays in the class 1 and 2 integrons are not closely related, but a common pool of mobile cassettes is used by the different integron classes; two of the three antibiotic resistance cassettes on Tn7 and its close relatives are also found in various class 1 integrons. We also observed a fourth excisable cassette downstream of those described previously in Tn7. The fourth cassette encodes a 165-amino-acid protein of unknown function with 6.5 contiguous repeats of a sequence coding for 7 amino acids. IntI2*179E promoted site-specific excision of each of the cassettes in Tn7 at different frequencies. The integrases from Tn21 and Tn7 showed limited cross-specificity in that IntI1 could excise all cassettes from both Tn21 and Tn7. However, we did not observe a corresponding excision of the aadA1 cassette from Tn21 by IntI2*179E.

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confidence: 74%

Section: Resultsmentioning

confidence: 99%

“…The third cassette in Tn7 contains the aadA1 gene encoding an adenylyltransferase, which inactivates streptomycin and spectinomycin (14) (Fig. 1).…”

Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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IntI2 Integron Integrase in Tn7

et al. 2002

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“…The M and R-end sequences, on the other hand, are direct repeats containing intrinsic inverted repeats. Such a structure surrounding ORF2 is reminiscent of the aadA and sat genes in Tn7 and related Tn1825, which were suggested to have inserted into the transposons via integrase-mediated site-specific recombinations (10,37). Downstream from the M sequence is another stem-loop structure which is immediately preceded by the dam methylation site (Fig.…”

Section: Methodsmentioning

confidence: 99%

Characterization of insertion sequence IS892 and related elements from the cyanobacterium Anabaena sp. strain PCC 7120

Cai

1991

J Bacteriol

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IS892, one of the several insertion sequence (IS) elements discovered in Anabaena sp. strain PCC 7120 (Y. Cai and C. P. Wolk, J. Bacteriol. 172:3138-3145, 1990), is 1,675 bp with 24-bp near-perfect inverted terminal repeats and has two open reading frames (ORFs) that could code for proteins of 233 and 137 amino acids. Upon insertion into target sites, this IS generates an 8-bp directly repeated target duplication. A 32-bp sequence in the region between ORF1 and ORF2 is similar to the sequence of the inverted ternmini. Similar inverted repeats are found within each of those three segments, and the sequences of these repeats bear some similarity to the 11-bp direct repeats flanking the 11-kb insertion interrupting the nifD gene of this strain (J. W. Golden, S. J. Robinson, and R. Haselkorn, Nature [London] 314:419-423, 1985). A sequence similar to that of a binding site for the Escherichia coli integration host factor is found about 120 bp from the left end of IS892. Partial nucleotide sequences of active IS elements IS892N and IS892T, members of the IS892 family from the same Anabaena strain, were shown to be very similar to the sequence of IS892.Insertion sequences (IS) are transposable elements that are generally smaller than transposons and normally bear only genes related to transposition (for a review, see reference 12). Because IS elements lack selectable markers, they are usually identified by their ability to introduce insertional mutations in marker genes and operons (9, 14). Most IS elements from a variety of prokaryotes are 0.8 to 2.5 kb in size and have a pair of near-perfect inverted terminal repeats ranging from 8 to 41 bp. Almost all bacterial IS elements characterized to date generate directly repeated duplications of their target DNA sequences upon insertion. Many elements make a duplication of a fixed number of base pairs, ranging from 2 to 13 bp, as a characteristic of the element (12).Cyanobacteria (blue-green algae) are prokaryotes that differ physiologically and phylogenetically (43) from other eubacteria. Two active IS elements have been isolated and sequenced from cyanobacteria: IS701 from Calothrix sp. strain PCC 7601 (12, 27) and IS891 from Anabaena sp. strain M-131 (4). IS701 appears to be a typical IS element with inverted terminal repeats and the generation of target duplications (27). By contrast, IS891 lacks inverted terminal repeats and fails to generate a target duplication upon insertion (4). In addition, genetic elements, collectively denoted the mys family, from the cyanobacterium Anabaena sp. strain PCC 7120 were suggested to be IS on the basis of the structural similarity of their nucleotide sequence to that of typical IS elements (1).In a study of spontaneous mutation of the conditionally lethal gene sacB in Anabaena sp. strain PCC 7120, 10 IS elements of five different sizes were detected and one of them, IS892, was restriction mapped (7). I report here a more detailed study of IS892 and of related IS elements in this Anabaena strain. MATERIALS AND METHODSBacterial strains,...

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