Cellular effects of SNP −1639 G>A. (A) Vector construction. VKORC1 promoter with the SNP −1639 G>A is placed before the VKORC1 cDNA in the pBudCE4.1 vector for carboxylation assay. The vector carries a luciferase gene to control for transfection efficiency. (B) Warfarin inhibition of the SNPs. Inhibition curves (left) relative IC₅₀ level (right). (C) Cellular mRNA level of the SNPs. (D) Cellular protein level of the SNPs. The western blots use the anti-VKORC1 (left) and anti-flag (right) antibodies, with β-actin level (bottom) as controls. (E) Protein level comparison by in-cell ELISA. All error bars represent 3 repeats. **P < .01 by Student t test.