IS Dra 2 transposition in D einococcus radiodurans is downregulated by TnpB

Summary Transposable elements belonging to the recently identified IS 200 / IS 605 family radically differ from classical insertion sequences in their transposition mechanism by strictly requiring single‐stranded DNA substrates. This IS family includes elements encoding only the transposase ( TnpA ), and others, like IS Dra 2 from D einococcus radiodurans , which contain a second gene, tnpB , dispensable for transposition and of unknown function to date. Here, we show that TnpB has an inhibitory effect on the excision and insertion steps of IS Dra 2 transposition. This inhibitory action of TnpB was maintained when IS Dra 2 transposition was induced by γ‐irradiation of the host cells and required the integrity of its putative zinc finger motif. We also demonstrate the negative role of TnpB when IS Dra 2 transposition was monitored in a heterologous E scherichia coli host, indicating that TnpB ‐mediated inhibition does not involve D einococcus ‐specific factors. TnpB therefore appears to play a regulatory role in IS Dra 2 transposition.