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Identification and characterization of int (integrase), xis (excisionase) and chromosomal attachment sites of the integrative and conjugative element ICE Bs1 of Bacillus subtilis
Author(s) -
Lee Catherine A.,
Auchtung Jennifer M.,
Monson Rita E.,
Grossman Alan D.
Publication year - 2007
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2007.06000.x
Subject(s) - biology , integrases , genetics , bacillus subtilis , integrase , transposable element , locus (genetics) , gene , microbiology and biotechnology , genome , bacteria
Summary ICE Bs1 is an integrative and conjugative element (conjugative transposon) integrated into trnS‐leu2 in Bacillus subtilis . In response to DNA damage or high concentrations of potential mating partners, ICE Bs1 can excise and transfer to various recipients, including other species. We found that excision of ICE Bs1 occurs by site‐specific recombination within 60 bp direct repeats that mark the junctions between ICE Bs1 and chromosomal DNA. Excision required two ICE Bs1 genes, int (integrase, ydcL ), predicted to encode a tyrosine recombinase similar to that of phage lambda, and xis (excisionase, sacV ). Ectopic expression of xis was sufficient to induce excision of ICE Bs1 , indicating that regulation of xis transcription by DNA damage and peptide signalling normally controls excision. Int, but not Xis, was needed for site‐specific integration. We found that in the absence of the primary bacterial attachment site ( attB ) in trnS‐leu2 , ICE Bs1 integrated in secondary attachment sites that are similar to a 17 bp sequence in attB . In the absence of int , ICE Bs1 could recombine into the chromosome by RecA‐dependent homologous recombination, provided ICE Bs1 contained a region of sequence identity to a chromosomal locus.