Mechanism of Insertion and Cointegration Mediated by IS1 and Tn3

Abstract

Insertion sequence (IS) and transposable (Tn) elements are discrete segments of DNA that move from one site to another on a different or the same genome and cause structural rearrangements of the genomes (Bukhari et al. 1977). IS1 is a typical insertion element. It was found originally as an inserted sequence about 700–800 bp in length in various bacterial operons, resulting in strong polar effects on these operons (Fiandt et al, 1972; Hirsch et al. 1972; Jaskunas and Nomura 1977). IS1 also appears as repeated DNA sequences in a group of resistance plasmids, such as R100 and R1, in phage P1, and in various bacterial chromosomes (Hu et al. 1975b; Arber et al. 1979; Nyman et al. 1981). It is involved in rearrangements of plasmid genomes such that it promotes deletion mutations (Reif and Saedler 1975; Mickel et al. 1977), transposition of antibiotic-resistance and enterotoxin genes (MacHattie et al. 1977;...