P{ET.lexAop.lacZ} is an enhancer trap construct that encodes the lacZ reporter. The enhancer trap sequence is at the 3' end of the construct and consists of the minimal Hsp70 promoter (-45 to +207 relative to the transcription start site, does not contain Trl binding sites) fused in-frame upstream of the lacZ coding sequence. Eight copies of the lexAop binding site are present upstream of the Hsp70 promoter; this results in P{ET.lexAop.lacZ} showing conditional enhancer trapping that is dependent on a PBAP subunit (Bap170 and e(y)3 have been tested) being tethered to the minimal Hsp70 promoter by being fused to lexA, which binds the lexAop sequence.