The PBac{brp(FRT.Stop)GFP} construct contains brp regulatory and coding sequences (genomic fragment of ~50kb) in which the stop codon has been replaced by an FRT cassette containing transcriptional and translational stop sequences, followed by a T:Avic\GFP tag, the 2A peptide and a lexA::VP16 fusion. The lexA::VP16 fusion contains a mutation in lexA that renders it non-functional. Sequences downstream of the stop cassette are not translated, and thus the brp protein produced is not tagged and no lexA::VP16 protein is produced. In the presence of FLPase, the FRT cassette is excised. The brp protein produced is now tagged with T:Avic\GFP. Although the presence of the 2A peptide allows the lexA::VP16 fusion to be cotranslated as a separate protein, this protein is non-functional due to the mutation in lexA.