The effects of promoter SNP on VKORC1 mRNA expression. (A) Transcriptional activity of promoter fragments containing −1639 G or −1639 A, measured by luciferase reporter gene assays in 4 different cell lines. (B) Effects of 5′ upstream fragments F1 and F2 on transcription activity of proximate promoter fragment F3. (C) Allelic mRNA expression of VKORC1 in HepG2 cells after cotransfection with VKORC1 gene constructs. The constructs combine −1639 G or −1639 A alleles with either haplotype A or B of the transcribed region. Data are means plus or minus SD.