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Intramolecular transposition of insertion sequence IS 91 results in second‐site simple insertions
Author(s) -
Bernales Irantzu,
Mendiola M. Victoria,
De La Cruz Fernando
Publication year - 1999
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 - 10.1046/j.1365-2958.1999.01432.x
Subject(s) - transposase , transposable element , insertion sequence , transposition (logic) , biology , plasmid , tn10 , inverted repeat , genetics , open reading frame , gene , insertion , microbiology and biotechnology , mutant , peptide sequence , genome , linguistics , philosophy
A series of plasmids carrying an IR L ‐ kan ‐IR R transposable cassette, in which IR L and IR R are the left‐ and right‐terminal sequences of IS 91 , have been constructed. These cassettes could be complemented for transposition with similar efficiency when IS 91 transposase was provided either in cis or in trans . A total of 87% of IS 91 transposition products were simple insertions of the element, while the remaining 13% were plasmid fusions and co‐integrates. When transposase expression was induced from an upstream lac promoter, transposition frequency increased approximately 100‐fold. An open reading frame (ORF) present upstream of the transposase gene, ORF121, could be involved in target selection, as mutations affecting this ORF were altered in their insertion specificity. Intramolecular rearrangements were analysed by looking at transposition events disrupting a chloramphenicol resistance gene ( cat ) located outside the transposable cassette. Plasmid instability resulting from insertion of an extra copy of IR L ‐ kan ‐IR R within the cat gene was observed; transposition products contained a second copy of the cassette inserted either as a direct or as an inverted repeat. No deletion or inversion of the intervening DNA was observed. These results could be explained as a consequence of intramolecular transposition of IS 91 according to a model of rolling‐circle transposition.