Nucleotide sequence of the ends of the conjugative shuttle transposon Tn1545

Abstract

The conjugative shuttle transposon Tn1545 from Streptococcus pneumoniae transposes in various gram-positive bacterial genera following self-transfer and in Escherichia coli after cloning. Analysis of the junction fragments and of the targets before insertion and after excision of the element by DNA hybridization and sequencing indicated that Tn1545 (1) is not flanked by terminal repeated sequences in either direct or opposite orientation, (2) is flanked, in an asymmetric fashion, by terminal variable base pairs, one at the left and three at the right of the element, (3) inserts in a target DNA consensus sequence, (4) does not generate duplication of the target DNA upon insertion, and (5) excises precisely.

Genetic analysis of a tetracycline resistance element from Clostridium difficile and its conjugal transfer to and from Bacillus subtilis

“…The fact that the C. dzficile element shows no hybridization to oligonucleotides homologous to both ends of Tn916 shows further differences between the two elements. The nucleotide sequence of the extremities of Tn916 and the only other conjugative transposon (from a Gram-positive host) for which data are available, Tn1545, is almost identical for at least 250 bp (Caillaud & Courvalin, 1987;Clewell et al, 1988). Our results suggest that the C. d@cile element is likely to be a conjugative transposon related to but distinct from Tn916 and Tn1545.…”

Specific DNA cleavage mediated by the integrase of conjugative transposon Tn916

“…The int genes of these two transposons differ by a single nucleotide which causes a conservative amino acid substitution (38,53). The ends of the two transposons are identical for at least 186 bp at the left end and 108 bp at the right end (10,15), and the int genes complement each other genetically (8,31). The int gene encodes a protein that shares local sequence homology with members of the integrase family of site-specific recombinases, including those encoded by bacteriophage lambda (INT ) and the yeast 2m plasmid (FLP) (3,38,39).…”

Evidence that coupling sequences play a frequency-determining role in conjugative transposition of Tn916 in Enterococcus faecalis

“…Tn916 (16.4 kb; encodes resistance to tetracycline), which was originally identified in Enterococcus faecalis DS16 (13), and Tn1545 (25.3 kb; encodes resistance to tetracycline, erythromycin, and kanamycin) from Streptococcus pneumoniae BM4200 (10), are two such elements that have been studied in some detail. These transposons exhibit significant homology, have imperfect terminal inverted repeats (20 of 26 nucleotides), and, unlike many other transposons, do not generate duplications of the target DNA upon insertion (2,6). Movement is via an excision-insertion mechanism somewhat analogous to that of the lambdoid phages (24,25), with the intermediate in the process being a nonreplicative circular molecule (5,29).…”