Recognition of triple-helical DNA structures by transposon Tn7

We have found that the bacterial transposon Tn7 can recognize and preferent ially insert adjacent to triple-helical nucleic acid structures. Both synth etic intermolecular triplexes, formed through the pairing of a short triple r-forming oligonucleotide on a plasmid DNA, and naturally occurring mirror repeat sequences known to form intramolecular triplexes or H-form DNA are p referential targets for Tn7 insertion in vitro. This target site selectivit y depends upon the recognition of the tripler region by a Tn7-encoded ATP-u sing protein, TnsC, which controls Tn7 target site selection: the interacti on of TnsC with the tripler region results in recruitment and activation of the Tn7 transposase, Recognition of a nucleic acid structural motif provid es both new information into the factors that influence Tn7's target site s election and broadens its targeting capabilities.