Regulation of Tn5 transposition in Salmonella typhimurium

The drug-resistance element Tn5 transposes with high frequency immediately after entry into a cell. Establishment of Tn5 within a cell results in a decrease in this transposition frequency. This phenomenon resembles "zygotic induction" of repressible operons and prophages. Evidence is presented that Tn5 transposition is under negative control by a factor encoded within the element itself. Established Tn5 elements (that contain point mutations inactivating the resistance gene) are able to inhibit transposition of an incoming Tn5 element by a factor of 12- to 70-fold. Several deletion derivatives of Tn5 lack the ability to inhibit transposition.