Group II introns collaborate with their hosts to promote genome plasticity by retrotransposition

Group II introns, like other retrotransposons, require host factors to mobilize1. Bacteria are hospitable hosts for group II introns, providing cellular polymerases, nucleases and DNA ligase to complete the retromobility process. In a genetic screen, we identified additional host factors involved in RNA processing, DNA replication, energy metabolism and global regulation that impact retromobility2. RNase E, which is the central component of the RNA degradosome, depresses retrohoming levels in response to cellular physiology, whereas global regulators cAMP and ppGpp elevate group II intron mobility during starvation3. The effect of RNaseE is mediated by retroelement expression levels, while the global regulators exert their effect on the DNA target. Actions on the DNA target can be via altering the nucleoid, introducing nicks or stalling replication forks. Thereby, the cell's global circuitry modulates group II intron movement and can stimulate genetic diversity.