Coordinated Transcriptional Regulation of Cytochrome P450 3As by Nuclear Transcription Factor Y and Specificity Protein 1.

The cytochrome P450 3A subfamily plays vital roles in the metabolism of endogenous chemicals and xenobiotics. Understanding the basal expression of CYP3A in humans and pigs is crucial for drug evaluation. In this study, we demonstrated that the basal transcriptional regulation of genes in hepatocytes is evolutionarily conserved between humans and pigs. The basal expression of genes is transactivated by two -acting elements, the CCAAT and GC boxes, located a constant distance apart in the proximal promoter region of six genes. Mutation analysis of these two -acting elements suggested that they play important roles in mediating basal expression, but to different extents because of the nucleotide variations in the elements. Two transcription factors, nuclear transcription factor Y (NF-Y) and specificity protein 1 (Sp1), directly bind to these -acting elements in proximal promoters in HepG2 cells and porcine hepatocytes. Furthermore, changing the distance between the NF-Y and Sp1 binding sites resulted in decreases in the promoter activity of genes. Conclusively, our results show that human and porcine genes are regulated by NF-Y and Sp1 in a coordinated manner, and that the distance between these two -acting elements is crucial for constitutive expression.