eLife assessment
This important study uses an innovative set of reporter assays to probe the role of the TnpB protein in IS608 transposition. The work provides independent support for the recently reported homing activity of TnpB, where the transposon is restored following excision, and suggests an additional function for TnpB in enhancing the transposase activity of the TnpA transposase. The overall approach is solid, but the authors should consider how the activity of the TnpB protein used, or the levels of ωRNA, impact their model.