UAS regulatory sequences are fused upstream of Rab6, including its native stop codon and extension 3'UTR. The Rab6 coding sequence is tagged at the N-terminal end with EGFP. In addition, the coding sequence for NanoLuc (missing a start codon) has been inserted immediately upstream of the second in-frame stop codon in the extension 3'UTR. If translation terminates at the native Rab6 stop codon, the NanoLuc reporter is not translated. If translational readthrough occurs past the stop codon, the Rab6 protein produced is tagged with the NanoLuc reporter.