Preferential cis action of IS10 transposase depends upon its mode of synthesis

A number of bacterial DNA-binding proteins, including IS element transposases, act preferentially in cis. We show below that the degree of preferential cis action by IS10 transposase depends upon its mode of synthesis at steps subsequent to transcription initiation. Cis preference is increased several fold by mutations that decrease translation initiation, by the presence of IS10-specific antisense RNA and by plasmids that increase the level of cellular RNases. Conversely, cis preference is decreased by mutations that increase translation initiation; in some cases, cis preference is nearly abolished. Mutations that alter the rate of transcription initiation have no effect. In light of other observations, we suggest that cis preference is strongly dependent upon the rate at which transcripts are released from their templates and/or the half-life of the transposase message. These observations provide further evidence that inefficient translation plays multiple roles in the biology of IS10.