The lexA(XVE) driver encodes a ligand-inducible transcriptional activator designed for use in a binary expression system. It is composed of the DNA-binding domain from the Escherichia coli lexA gene (ECOGENE:EG10533) fused to the ligand-binding domain from the Homo sapiens estrogen receptor 1 (ESR1, HGNC:3467). The lexA DNA-binding domain of the lexA(XVE) driver can bind specifically to the lexAop DNA sequence, but the presence of the ESR1 ligand-binding domain means that this binding, and subsequent transcriptional activation, can only occur in the presence of estradiol (PMID:11069700).