背景
This gene encodes a selenoprotein that is predominantly expressed in the liver and secreted
into the plasma. This selenoprotein is unique in that it contains multiple selenocysteine (Sec)
residues per polypeptide (10 in human), and accounts for most of the selenium in plasma. It
has been implicated as an extracellular antioxidant, and in the transport of selenium to
extra-hepatic tissues via apolipoprotein E receptor-2 (apoER2). Mice lacking this gene exhibit
neurological dysfunction, suggesting its importance in normal brain function. Sec is encoded
by the UGA codon, which normally signals translation termination. The 3' UTRs of
selenoprotein mRNAs contain a conserved stem-loop structure, designated the Sec insertion
sequence (SECIS) element, that is necessary for the recognition of UGA as a Sec codon,
rather than as a stop signal. The mRNA for this selenoprotein contains two SECIS elements.
The use of alternative polyadenylation sites, one located in between the two SECIS
elements, results in two populations of mRNAs containing either both (predominant) or just
the upstream SECIS element (PMID:27881738). Alternatively spliced transcript variants have
also been found for this gene
