A 1.3kb genomic fragment containing Bap170 regulatory sequences (this fragment extends from within exon 1 of the neighbouring Trap1 gene to the BamHI site in exon 2 of Bap170) is fused upstream of Ecol\lacZ. The protein produced contains the first 194 N-terminal amino acid residues of Bap170 fused to the complete Ecol\lacZ coding sequence.