MOLECULAR CHARACTERIZATION OF IS1541 INSERTIONS IN THE GENOME OF YERSINIA-PESTIS

The genome of Yersinia pestis, the causative agent of plague, contains at leash 30 copies of an element, designated IS1541, which is structu rally related to IS200 (85% identity), One such element is inserted wi thin the chromosomal inp gene (M. Simonet, B. Riot, N. Fortineau, and P. Berche, Infect. Immun. 64:375-379, 1996). Wt characterized other IS 1541 insertions by cloning 14 different Y. pestis 6/69M loci carrying a single copy of this insertion sequence (IS) into Escherichia coli an d, for each element, sequencing 250 bp of both Banking regions, In no ease was this IS element inserted into large open reading frames; howe ver, in eight cases, it was detected downstream (17 to 139 bp) of gene s 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 st em-loop structures (Delta G, <-10 kcal) resembling rho-independent tra nscription terminators in 8 of the 14 insertion sites, These motifs mi ght constitute hot spots far insertion of this IS1541 element within t he Y. pestis genome.