The P{attP.w+.attP} element acts as a target for recombination-mediated cassette exchange (RMCE). It contains a w+mC marker flanked by a pair of inverted attP sites. The entire attP-flanked cassette can be replaced with DNA from a compatible donor plasmid (where the sequence to be inserted is flanked by inverted attB sites) through RMCE driven by the phiC31:int integrase.