ABSTRACT

The dramatic impact of selenium (Se) status on selenoprotein gene expression and the differential responses of various selenoproteins to Se depletion or repletion are fascinating, although the mechanism of Se regulation and the physiological implication remain largely unclear. A dozen of Se-dependent proteins identified in mammals share at least two distinct features. First, Se in the polypeptide is covalently bound in a moiety of selenocysteine encoded by thymine-guanine-adenine, normally a stop codon. Second, Se availability regulates expression of not only their protein and activity, but also their mRNA levels in cells or tissues. Differences in Se regulation of the Selenoprotein W protein from that of the glutathione peroxidase activities in several tissues have been illustrated in rats fed diets containing Se ranged from 0.004 to 4.0 mg/kg. Many factors other than Se can influence expression of selenoproteins.