Molecular cloning of the gene encoding pregnane X receptor (PXR; NR1I2) and the constitutive androstane receptor (CAR; NR1I3) in pigs

摘要

The pregnane X receptor (PXR; NR1I2) and the constitutive androstane receptor (CAR; NR1I3) are members of the nuclear receptor superfamily that act as transcription factors. They regulate the expression of several important genes that encode enzymes responsible for the metabolism of endogenous hormones and exogenous substances. We determined the nucleotide sequences of porcine CAR and PXR genes by using cDNA clones derived from porcine cDNA libraries. The porcine CAR gene has a 1407 bp mRNA, which contains a 216 bp 5'-untranslated region (UTR), a 144 bp 3'-UTR, and a 1047 bp coding region that encodes 348 amino acids. The mRNA sequence of porcine PXR is composed of 2567 bp that contains a 273 bp 5'-UTR, a 1266 bp putative coding region encoding 421amino acids, and a 1028 bp 3'-UTR. The porcine CAR and porcine PXR proteins showed a high degree of sequence identity in their DNA-binding domain (DBD) and ligand-binding domain (LBD) with 80 %-90 % amino acid identity in comparison with those of humans.However, the A/B domain of the porcine CAR and PXR proteins is considerably different in comparison with that of humans. Eighty six percentage and 43 % sequence identity is found between porcine and human CAR proteins and porcine and human PXR proteins,respectively. The mRNA expression of both porcine CAR and PXR was detected in liver, small intestine, and kidney by using reverse-transcription (RT)-PCR.