The Mi{Hto} element contains UAS regulatory sequences and basal promoter (derived from the P{EP} element), an artificial first exon that encodes two tags (3xTag:FLAG and mCherry) and a 5' splice site downstream of this exon. The artificial exon includes a 5'UTR from the strongly expressed sqh gene. The artificial exon can act as an inducible protein trap cassette upon insertion into the genome either upstream of an endogenous gene or in an intron. When expression is driven from the UAS sequences via a GAL4 driver, the artificial exon can splice out into the genome, forming a fusion transcript with the next available downstream ('target') exon. This may result in tagging of the coding sequence of the targeted exon if the Mi{Hto} insertion is in the correct splice frame. If the insertion is in a coding intron intron, any fusion protein produced may be defective, since it will lack the normal coding sequence from exons that are N-terminal to the Mi{Hto} insertion. Two natural polyA sites in the Minos right inverted repeat have been mutated to prevent the formation of unfused mCherry protein. The entire inducible protein trap cassette is flanked by inverted attP sites, which allows for the replacement of this entire sequence with DNA from a compatible donor plasmid (where the sequence to be inserted is flanked by inverted attB sites) through recombination-mediated cassette exchange (RMCE) driven by the phiC31:int integrase.