The vanTA entry in FlyBase represents an artificial transcriptional activator ('driver') that includes the DNA-binding domain from the vanR gene of Caulobacter vibrioides and a transcriptional activation domain from the Herpes simplex virus Type 1 VP16 gene. The vanR DNA-binding domain binds specifically to the vanO DNA sequence, and thus vanO and vanTA 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 vanO sequences is combined with a second transgene or modified endogenous locus encoding the vanTA driver. The activity of the vanTA driver can potentially be suppressed by vanillic acid (a specific ligand of vanR): upon binding to vanillic acid it is expected that vanTA will undergo a conformational change preventing it from binding the vanO sequence, thus reducing or preventing its ability to induce transcription (PMID:22187155). The exact sequence of the driver may differ depending on the particular transgene or modified endogenous locus being used. In particular, the number of VP16 activation domains present may vary, and/or the VP16 activation domains may contain mutations that alter the strength of transcriptional activation.