The mechanisms for transcriptional regulation of porcine cytochrome P450 3A46

• 1、Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou 510642

Abstract：Studying the function, structure, catalytic mechanism, and regulational mechanism of a porcine cytochrome P450 (CYP) isoform, which is involved in the metabolism of important endogenous or exogenous compounds, is important not only for veterinary pharmacology and toxicology but also for new drug development and human health. Our previous research indicated that porcine CYP3A46 is a critical metabolic enzyme in porcine liver, which can metabolize nifedipine, T-2 toxin, and HT-2 toxin. Additionally, the proximal GC box, DR4, and distal HNF1 binding site are the important cis-regulatory elements involved in the basal and rifampicin (RIF) induced transcriptional regulation of porcine CYP3A46, which are recognized by Sp1, PXR, and HNF1α, respectively. In this paper, we further studied the regulatory mechanisms for both the basal and RIF-mediated transcriptional activation of CYP3A46 in porcine liver through mutagenesis, overexpression, and so on. We further confirmed that the proximal GC box and the DR4 motif is involved in regulating the constitutive and RIF induced transcriptional activation of CYP3A46 respectively, while the distal HNF1 binding site is responsible for both the constitutive and RIF induced transcriptional activation of CYP3A46. The results of overexpressing PXR and HNF1α in culture cells further confirmed that both PXR and HNF1α contribute significantly to sustaining a high level of CYP3A46 transcription by binding to the proximal DR4 motif and the distal HNF1 binding site, respectively.

Keywords： Animal physiology and biochemistry Cytochrome P450 3A46 Transcriptional regulation Sp1 HNF1α PXR