Functional characterization of an active Rag-like transposase.

The formation of diverse immunoglobulin genes results in part from Rag protein-mediated DNA double-strand breaks at the edges of immunoglobulin gene segments, followed by combinatorial reassembly of these segments. We report that a Transib transposase from the insect Helicoverpa zea is active in vitro and that its breakage and joining activities mimic those of Rag, providing strong evidence that Rag and Transib transposases were derived from a common progenitor.