Functional characterization of promoter region polymorphisms of human CYP2C19 gene.

CYP2C19 is an enzyme involved in the metabolism of several clinically important drugs. The variations in the CYP2C19 promoter region may alter the transcription of the gene by altering the interaction between the trans and cis-acting elements. In the present study, CYP2C19 promoter region with different variant alleles were cloned into a pGL-3 basic luciferase reporter vector and transfected into HepG2 cell lines. Subsequently, dual luciferase activity was measured to evaluate the activity of the promoter region. Gel shift assays with predicted binding sites for CCAAT displacement protein, activating transcription factor-2 and glucocorticoid receptor were performed. Results from this study indicate that few variations present in the putative cis-acting elements of the CYP2C19 promoter region such as -1442T>C, -779A>C and -98T>C -1498T>G and -828del>T alter the transcription of the gene. Specific binding with nuclear proteins was also observed in gel shift assays. This may account for the interindividual variations in gene expression and genotype dependant differences in gene transcription. The results also suggest the role of activating transcription factor-2 and CCAAT displacement repressor protein on CYP2C19 gene transcription.