Intramolecular transposition of IS102.

It has been postulated that deletions mediated by transposable elements are intramolecular transposition events. An implication of this hypothesis is that the deleted fragment may be recovered if it is capable of autonomous replication. We report here the characterization of the products of intramolecular transposition of the element IS102 in bireplicons. We show that when two origins (ori's) (of pSC101 and R6-5) generate the same copy numbers, two dissociated replicons are recovered as well as the inversions. On the contrary, when two ori's (of pSC101 and pBR322) have different copy numbers, intramolecular transposition results essentially in inversions. However, the very low frequency (5 X 10(-8)) at which intramolecular transpositions in the bireplicons occurs, as compared to the single replicon (10(-4)), suggests that a complete transposition reaction may not be necessary to generate deletions.