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A target specificity switch in IS 911 transposition: the role of the OrfA protein
Author(s) -
Loot C.,
Turlan C.,
Rousseau P.,
TonHoang B.,
Chandler M.
Publication year - 2002
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/cdf403
Subject(s) - transposable element , biology , transposition (logic) , insertion sequence , transposase , inverted repeat , dna , dna transposable elements , genetics , microbiology and biotechnology , mutant , gene , genome , linguistics , philosophy
The role played by insertion sequence IS 911 proteins, OrfA and OrfAB, in the choice of a target for insertion was studied. IS 911 transposition occurs in several steps: synapsis of the two transposon ends (IRR and IRL); formation of a figure‐of‐eight intermediate where both ends are joined by a single‐strand bridge; resolution into a circular form carrying an IRR–IRL junction; and insertion into a DNA target. In vivo , with OrfAB alone, an IS 911 ‐based transposon integrated with high probability next to an IS 911 end located on the target plasmid. OrfA greatly reduced the proportion of these events. This was confirmed in vitro using a transposon with a preformed IRR–IRL junction to examine the final insertion step. Addition of OrfA resulted in a large increase in insertion frequency and greatly increased the proportion of non‐targeted insertions. The intermolecular reaction leading to targeted insertion may resemble the intramolecular reaction involving figure‐of‐eight molecules, which leads to the formation of circles. OrfA could, therefore, be considered as a molecular switch modulating the site‐specific recombination activity of OrfAB and facilitating dispersion of the insertion sequence (IS) to ‘non‐homologous’ target sites.