title: Generation and analysis of an ICE R391 deletion library identifies genes involved in the element encoded UV-inducible cell-sensitising function.
abstract: ICE R391, a prototype member of the SXT/R391 family of site-specific integrative conjugative elements (ICEs), frequently isolated from enterobacterial pathogens, exhibits an unusual, recA-dependent, UV-inducible, cell-sensitising function. This significantly decreases postirradiation cell survival rates in Escherichia coli host cells, a trait that would at first appear to be counterproductive in terms of adaptation to stress conditions. Construction and screening of a complete ICE R391 deletion library in E. coli identified three ICE R391 genes, orfs90/91, encoding a putative transcriptional enhancer, and orf43, encoding a putative type IV secretion system outer membrane-associated conjugative transfer protein, in the cell-sensitising function. Cloning and complementation of these genes confirmed their involvement in UV sensitising. Expression of both orfs90/91 and orf43 in wild-type E. coli indicated that orf43 encodes a cytotoxic gene product upon up-regulation. Deletion of the orf43 homologue in SXT, s050, also abolished its associated UV sensitisation. We hypothesise that ICE R391 and other members of the SXT/R391 family display decreased survival rates upon exposure to UV irradiation through the induction of orf43.
authors: Department of Chemical and Environmental Sciences, Molecular and Structural Biochemistry Laboratory, University of Limerick, Limerick, Ireland.
authors: Patricia
authors: P
authors: Armshaw
authors: J Tony
authors: JT
authors: Pembroke
mesh_terms: D004926:Escherichia coli / Q000235:genetics* / Q000528:radiation effects*; D017353:Gene Deletion; D015723:Gene Library; D005816:Genetic Complementation Test; D020071:Interspersed Repetitive Sequences; D050296:Microbial Viability / Q000528:radiation effects*; D014466:Ultraviolet Rays