Figure 1: Comparisons of the mechanisms of integration for Sleeping Beauty transposon and phiC31 integrase. A. Transposition of Sleeping Beauty requires flanking inverted repeat/direct repeat sequences (IR/DR elements). Transposase proteins bind to the IR/DR elements and generate a synaptic complex that targets TAdinucleotides within the genome using a cut and paste mechanism. The remaining plasmid sequence is lost during integration. B. The phiC31 integrase is a member of the serine-recombinase family of site-specific recombinases. The minimal sequences required for integrase activity are a 39 bp attP site and a 34 bp attB site [51]. The entire plasmid integrates into the genome with flanking attR and attL sites.