IS10 TN10 TRANSPOSITION EFFICIENTLY ACCOMMODATES DIVERSE TRANSPOSON END CONFIGURATIONS

Transposon Tn10 and its component insertion sequence IS10 move by non- replicative transposition, We have studied the array of reaction inter mediates and products in a high efficiency in vitro IS10/Tn10 transpos ition reaction, Synapsis of two transposon ends, followed by cleavage and strand transfer, can occur very efficiently irrespective of the re lative locations and orientations of the two ends, The two participati ng ends can occur in inverted or direct orientation on the same molecu le or, most importantly, on two different molecules, This behavior con trasts sharply with that of Mu, in which transposition is strongly bia sed in favor of inverted repeat synapsis, Mechanistically, the absence of discrimination amongst various end configurations implies that the architecture within the IS10/Tn10 synaptic complex is relatively simp le, i.e. lacking any significant intertwining of component DNA strands , Biologically these observations are important because they suggest t hat the IS10 insertion sequence module has considerable flexibility in the types of DNA rearrangements that it can promote, Most importantly , it now seems highly probable that a single non-replicative IS10 elem ent can promote DNA rearrangements usually attributed to replicative t ransposition, i.e. adjacent deletions and cointegrates, by utilizing t ransposon ends on two sister chromosomes, Other events which probably also contribute to the diversity of IS10/Tn10-promoted rearrangements are discussed.