Transcription of the target is required for IS102 mediated deletions.

We have constructed several plasmids to test the specificity of target selection for IS102 associated deletions. We had previously shown that the cIII region of phage lambda is a target for IS102 mediated deletions and this region was therefore introduced in pSC101, where IS102 resides, in such a way that it was silent, transcribed or fully expressed. The deletion selection was provided by the galactokinase system. The results we have obtained show that transcription of the target region is required for deletion formation. The frequency of deletions in this target depends on its position along the transcript and is also influenced by translation. Implications of these results on the regional specificity of transposition are discussed.