Transcriptional Regulation of UDP-Glucuronosyltransferases

Recent evidence has been provided that five nuclear receptors (NRs), (pregnane X receptor [PXR], constitutive androstane receptor [CAR], farnesoid X receptor [FXR] and peroxisome proliferator-activated receptor [PPARα and γ]) regulate the expression of UGT1A loci. This chapter presents an overview of the most recent developments in our understanding of transcriptional regulation of UDP-glucuronosyltransferase (UGT) genes, and specifically focuses on the regulation of UGTs via NRs, with a strong emphasis on the biochemical and molecular techniques applied to this area of investigation. Procedures are described for the isolation and analysis of UGT proximal and distal promoters. The use of transgenic animals in the study of the mechanism of regulation of UGT expression is described, as is the assessment of the effects of various gene inducers on expression of UGTs in HepG2 and Caco-2 cell culture. Techniques for transient transfection of HepG2 and Caco-2 cells with NRs and UGT promoter constructs are presented. In addition, general methods are provided for various molecular and biochemical methods used in the isolation and characterization of UGT promoters.