Molecular Characterization of IS 1541 Insertions in the Genome of Yersinia pestis

Abstract

The genome of Yersinia pestis, the causative agent of plague, contains at least 30 copies of an element, designated IS1541, which is structurally related to IS200(85% identity). One such element is inserted within the chromosomalinv gene (M. Simonet, B. Riot, N. Fortineau, and P. Berche, Infect. Immun. 64:375–379, 1996). We characterized other IS1541 insertions by cloning 14 different Y. pestis 6/69M loci carrying a single copy of this insertion sequence (IS) into Escherichia coli and, for each element, sequencing 250 bp of both flanking regions. In no case was this IS element inserted into large open reading frames; however, in eight cases, it was detected downstream (17 to 139 bp) of genes thought to be transcribed monocistronically or which constituted the last gene of an operon, and in only one case was it detected upstream (37 bp) of the first gene of an operon. Sequence analysis revealed stem-loop structures (ΔG, <−10 kcal) resembling rho-independent transcription terminators in 8 of the 14 insertion sites. These motifs might constitute hot spots for insertion of this IS1541element within the Y. pestis genome.

Characterization of IS1541-like elements in Yersinia enterocolitica and Yersinia pseudotuberculosis

“…As expected from previous studies [3,6,7], IS1541A, IS1541B, IS1541C and IS1541D were inserted in an AT-rich region but none of these four elements were located within an ORF. Sequence analysis of the IS £anking regions revealed that (i) IS1541A was present downstream of an ORF highly homologous (90% sequence identity) with the Serratia marcescens gene himA encoding the integration host factor K subunit [8], (ii) IS1541C was found 4 bp downstream of a DNA segment displaying 86% identity with IS1328, an element previously described in another O:8 strain, WA [9].…”

“…Asterisks within the box indicate identical nucleotides. Left and right extremities were de¢ned as in[3].…”

A novel class of small repetitive DNA sequences inEnterococcus faecalis

“…This type of SLS is overrepresented in the genomes of low-GC firmicutes, and may serve multiple functions (Petrillo et al, 2006). Several ISs tend to insert into regions of dyad symmetry (Odaert et al, 1998;Calcutt et al, 1999;Hu et al, 2001;Choi et al, 2003), and rhoindependent transcriptional terminator-like sequences are privileged sites of integration for the small (130-170 bp) YPAL repeats in Yersiniae (De Gregorio et al, 2006). Interestingly, YPAL induce the duplication of 8-25 bp of target sequences, and this results in the formation of long complementary terminal regions (De Gregorio et al, 2006).…”

Transposition of ISHp608, member of an unusual family of bacterial insertion sequences

“…Some, such as IS605, carry two open reading frames (orfs), tnpA and tnpB. Using IS1541 from Yersinia pestis (Odaert et al, 1998) as an enquiry sequence confirmed that tnpA from IS605, isolated from H. pylori, was a member of this group. A more recent search of the public databases using tnpA and tnpB from IS605 as query sequences revealed a large number of related elements in over 65 bacterial species (B Ton-Hoang and M Chandler, unpublished results).…”