The lexA::GAD(TP) entry in FlyBase represents an artificial transcriptional activator ('driver') that includes the DNA-binding domain from the Escherichia coli lexA gene (ECOGENE:EG10533) and the C-terminal transcriptional activation domain II from the Saccharomyces cerevisiae GAL4 gene ( SGDID:S000006169 ) (PMID:3028647). In addition, it carries a mutation in the GAL4 activation domain (T860P) that abolishes suppression by GAL80 (PMID:9811836). In Escherichia coli the lexA protein acts as a transcriptional repressor, binding specifically to the lexAop DNA sequence via its DNA-binding domain (reviewed in PMID:18726173). By fusing the lexA DNA-binding domain to a transcriptional activation domain, the resulting lexA::GAD(TP) protein is converted into a transcriptional activator that specifically binds lexAop. lexAop and lexA::GAD(TP) thus form a binary expression system that can be used to control the spatial and temporal expression of a gene of interest: a transgene or modified endogenous locus carrying the target gene of interest downstream of lexAop sequences is combined with a second transgene or modified endogenous locus encoding the lexA::GAD(TP) driver. The exact sequence of the driver may differ depending on the particular transgene or modified endogenous locus being used. In particular, in addition to containing GAL4 transcriptional activation domain II, some lexA::GAD(TP) drivers may contain an extended GAL4 sequence that also includes activation domain I (PMID:3028647), resulting in a stronger driver (FBrf0211848).