IS861, a group B streptococcal insertion sequence related to IS150 and IS3 of Escherichia coli

Abstract

A 1,442-base-pair (bp) insertion sequence (IS861) was identified in the type Ill group B streptococcal (GBS) strain COH-1. It is flanked by 26-bp imperfect inverted repeats and contains two open reading frames, 1 and 2, encoding 141-and 277-amino-acid proteins, respectively. A 3-bp target sequence, ACA, is duplicated and flanks each inverted repeat. IS861 shares greater than 30% homology with IS3 and IS150 of Escherichia coli, primarily in the region of their putative transposases. Northern (RNA) analysis revealed that RNA is actively transcribed in vivo by IS861 and 17-and 36-kilodalton proteins were synthesized in E. coli maxicell assays. Multiple copies of IS861 were observed throughout the chromosome of COH-1, and one of the copies is located near genes involved in GBS capsule synthesis. IS861 is the first insertion sequence identified in GBS. Its role in GBS and the significance of its relationship to the phylogenetically similar insertion sequences typified by IS150 and IS3 of E. coli are unknown.

Transposition in Shigella dysenteriae: isolation and analysis of IS911, a new member of the IS3 group of insertion sequences

“…Sequence analysis of IS911 indicates that it is a member of the IS3 group of elements (32,33). This analysis also revealed that IS3411 (12), IS476 (14), and ISRJ (29) belong to this group.…”

“…Detailed comparisons were performed within a group (the IS3 family) comprising IS911 and nine other insertion sequences which, on the basis of similarities in their primary structure (DNA and translated open reading frames [ORFs]) and overall organization, appear to be related (see Results) (32,33). They all contain two consecutive and partly overlapping ORFs which cover most of the length of one strand.…”

Physiological impact of transposable elements encoding DDE transposases in the environmental adaptation of Streptococcus agalactiae

“…IS861 is flanked by 26 bp imperfect inverted repeats and contains two overlapping ORFs encoding 141 and 277 aa proteins. These ORFs were found to be actively transcribed in vivo but in larger transcripts, suggesting that adjacent genes are also transcribed in a polycistronic message (Rubens et al, 1989). In strain COH-1, one of the nine IS861 copies is located near genes involved in capsular synthesis.…”

“…The capsule of S. agalactiae is a major virulence factor involved in the inhibition of the activation of the complement alternative pathway, the impairment of the bactericidal function of neutrophils, the selective internalization of the bacteria into dendritic cells via caveolae-independent but lipid raftdependent pathways, and the intracellular survival of the bacteria (Lemire et al, 2012). It has been proposed that IS861 could have a regulatory function on S. agalactiae capsule expression, although no differences in copy number or locations of IS861 between differently encapsulated strains could be found (Rubens et al, 1989;Sellin et al, 1995). Nevertheless, in one non-typable strain isolated from the blood of a patient, IS861 was found to be inserted within the capsular cpsD gene (Sellin et al, 2000).…”

“…This 1442 bp IS was first identified in strain COH-1 (Rubens et al, 1989; Table 1). In S. agalactiae strains, the number of IS861 copies varies between zero and nine (Dmitriev et al, 2003;Rubens et al, 1989). IS861 is flanked by 26 bp imperfect inverted repeats and contains two overlapping ORFs encoding 141 and 277 aa proteins.…”