Integrative Genetic Element That Reverses the Usual Target Gene Orientation

A genetic element integrating site specifically into a prokaryotic gene usually carries a copy of the 3′ portion of that gene that restores the active gene even as the original is disrupted. A cryptic element in Mesorhizobium loti instead carries a copy of the 5′ end of the tRNA gene into which it integrated. This has implications for the evolution of new integrase-site combinations.