The induction of hepatic selenium-binding protein by aryl hydrocarbon (Ah)-receptor ligands in rats

Selenium-binding protein (SeBP) is one of the cytosolic proteins which is believed to bind to selenium without containing selenocysteine. Although its physiological role remains to be identified, it has recently attracted interest due to its participation in the late stages of intra-Golgi protein transport. In a previous study, we found that SeBP in rat liver is significantly increased following administration of aryl hydrocarbon (Ah)-receptor ligands, 3,3',4,4',5-pentachlorobiphenyl (PCB 126) and 3-methylcholanthrene (MC). Little research has been carried out to examine the properties of the inducibility of SeBP by xenobiotics. The objectives of this study were to analyze the control of transcription of the message by Ah-receptor ligands. In this report, we cloned an inducible rat SeBP. The resulting PCR product consisted of the full coding sequence for the 472 amino acids. The deduced amino acid sequence exhibited homologies with mouse SeBP, mouse acetaminophen-binding protein and human SeBP of 92%, 93% and 87%, respectively. We also measured the mRNA level by quantitative reverse transcriptional (RT)-PCR. Treatment of rats with PCB126 resulted in significant induction of the mRNA of this protein in the liver compared with the control level. Our data represent the first report showing that SeBP is induced by an Ah-receptor ligand at the mRNA level.