P{(-FRT)lacZ.HP} is an enhancer trap construct generated in vivo by excision of the FRT cassette from the P{HomingPigeon.FRT} element. The enhancer trap sequence consists of sequence including the weak P\T promoter and coding sequence for the first 125 P\T amino acids fused upstream of the lacZ coding sequence. A single FRT site is present downstream of the enhancer trap sequence.

The lacZ reporter encoded by the P{(-FRT)lacZ.HP} construct is expected to be localized to the nucleus, because it is fused to the N-terminal 125 amino acid residues of P\T (which have been shown to be sufficient for nuclear localization).