The Saccharomyces cerevisiae GAL4 gene ( SGDID:S000006169 ) encodes a transcriptional activator that contains both a sequence-specific DNA-binding domain and a transcriptional activation domain. GAL4 protein binds as a dimer to the UAS regulatory sequence, resulting in transcriptional activation of a downstream gene (reviewed in FBrf0233764). This property can be utilized to form a binary expression system to control the spatial and temporal expression of a gene of interest: a transgene or modified endogenous locus in which the target gene of interest is downstream of UAS sequences is combined with a transgene or modified endogenous locus encoding the GAL4 'driver' (FBrf0064375, also reviewed in FBrf0233764, FBrf0216478). The GAL4 entry in FlyBase represents the basic binary expression driver in which both DNA-binding domain and transcriptional activation sequences are derived from the Saccharomyces cerevisiae GAL4 gene, though the exact sequence of the driver may differ depending on the particular transgene or modified endogenous locus being used. The expression pattern of a gene of interest can be further refined by adding the GAL80 suppressor, which binds to GAL4 such that although it can still bind the UAS sequence it can no longer activate transcription (adapted from FBrf0233764).