The BAC clone RP11-89H19 containing the entire human VDR gene and its surrounding intergenic segments (82 kb of the 5'-intergenic region and 48 kb of the 3'-intergenic region) was engineered by BAC recombineering techniques to contain a hemagglutinin tag (HA) at the translation start site of the human VDR gene and a cassette containing an IRES-driven luciferase reporter and a TK promoter-driven neomycin resistance gene selection mechanism in the 3' untranslated region of the human VDR gene. The leucine to serine (L233S) mutation was introduced through nucleotide mutagenesis (CTG to TCG) at codon 233. This mutation compromises the 1,25(OH)2D3-binding capacity of the VDR. Three lines were generated; T805, T806, and T807. T807 is the high expressing line.