Notes: These authors describe use of firefly and NanoLuc® luciferases in a coincidence reporter system to screen compounds for their ability to activate transcription of the Parkin gene (PARK2), a potential target for treatment of Parkinson's disease. In a coincidence reporter system, a single transcript containing two luciferase genes is generated. Inclusion of a 2A “ribosomal skipping” sequence between the two luciferase genes enables translation of two reporter proteins. This approach is useful in drug screening because the use of two independent reporters to monitor a single transcriptional event provides a way to distinguish true “hits” from experimental artifacts caused by interaction between library compounds and reporter proteins. True “hits” (compounds that affect transcription of the gene being monitored) cause a signal from both reporters; false positives caused by interaction of compounds with the reporter protein cause a signal from only one reporter. This paper describes the first use of firefly and NanoLuc® luciferases, and the Nano-Glo® Dual-Luciferase® Reporter Assay, in a coincidence reporter system to screen a compound library in an HTS assay. (4565)