The P{UAS.RMCE.w+} 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. P{UAS.RMCE.w+} also contains UASt regulatory sequences; these are outside of the attP-flanked RMCE target cassette.