Reactivation of insertionally inactivated Shiga toxin 2 genes of Escherichia coli O157:H7 caused by nonreplicative transposition of the insertion sequence.
IS1203v is an insertion sequence which has been found in inactivated Shiga toxin 2 genes of Escherichia coli O157:H7. We analyzed the transpositional mechanism of IS1203v in order to investigate whether the Shiga toxin 2 genes inactivated by IS1203v could revert to the wild type. When the transposase activity of IS1203v was enhanced by artificial frameshifting, IS1203v was obviously excised from the Shiga toxin 2 gene in a circular form. The IS1203v circle consisted of the entire IS1203v, but an extra 3-bp sequence (ATC) intervened between the 5' and 3' ends of IS1203v. The extra 3-bp sequence was identical to a direct repeat which was probably generated upon insertion. Moreover, we detected the Shiga toxin 2 gene with a precise excision of IS1203v. In the wild-type situation, the transposition products of IS1203v could be observed by PCR amplification. These results show that IS1203v can transpose in a nonreplicative manner and that the Shiga toxin gene inactivated by this insertion sequence can revert to the wild type.
Kusumoto
M
M
Tsuruga Institute of Biotechnology, Toyobo Co., Ltd., Tsuruga, Fukui 914-0047, Japan. masahiro.kusumuto@bio.toyobo.co.jp
Nishiya
Y
Y
Kawamura
Y
Y
D001427:Bacterial Toxins / Q000096:biosynthesis / Q000235:genetics*; D004261:DNA Replication; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004270:DNA, Circular; D019453:Escherichia coli O157 / Q000235:genetics* / Q000472:pathogenicity; D018965:Frameshifting, Ribosomal; D005798:Genes, Bacterial; D016254:Mutagenesis, Insertional; D011995:Recombination, Genetic; D022603:Shiga Toxins; D019895:Transposases / Q000378:metabolism
D001427:Bacterial Toxins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004270:DNA, Circular; D022603:Shiga Toxins; D019895:Transposases