Genetic analysis of Tn7 transposition.

The purpose of this work was to localize the DNA regions necessary for the transposition of Tn7. Several deletions of Tn7 were constructed by the excision of DNA fragments between restriction sites. The ability of these deleted Tn7s to transpose onto the recipient plasmid RP4 was examined. All the deleted Tn7s isolated in this work had lost their transposing capability. The possibility of complementing them was studied using plasmids containing all or part of Tn7. Two deleted Tn7s could not be complemented by an entire Tn7 indicating that a DNA sequence greater than the 42 bp terminal sequence is needed for recognition of the transposon by a transposition function. Four other deleted Tn7s could be complemented by Tn7. One of these was studied intensively in complementation experiments using different parts of Tn7 to obtain transposition. The results obtained allow us to propose that all genes needed for transposition of Tn7 onto plasmids are contained in a DNA segment of between 6.0 and 7.4 kb. Furthermore, one essential function must be contained in a DNA fragment longer than 2.5 kb on the right-hand end of Tn7. The classification of Tn7 with regard to the other transposable elements is discussed.