The UASp entry in FlyBase represents an engineered regulatory region that includes UAS 'upstream activation' sequences plus a promoter fragment derived from the P-element transposase gene (P\T), where the P\T fragment includes the 5'UTR in addition to the promoter. The UASp regulatory region was originally constructed as part of the pP{UASp} cloning vector (FBrf0105917). The UAS regulatory sequence present in UASp is specifically bound by the DNA-binding domain of the Saccharomyces cerevisiae GAL4 gene ( SGDID:S000006169 ) (PMID:3886158). 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 the UASp regulatory region can be combined with a transgene or modified endogenous locus encoding any 'driver' that includes the GAL4 DNA-binding domain plus a transcriptional activation sequence (FBrf0064375, also reviewed in FBrf0233764, FBrf0216478). Transgenes that contain the UASp regulatory region are expressed in the female germline (FBrf0105917) in the presence of an appropriate driver, but are often less well expressed in somatic tissues.