The SECIS element is typically located in the 3' untranslated region (UTR) of mRNA in eukaryotes and within the coding region in prokaryotes. It forms a stem-loop structure that is recognized by specific proteins and the ribosome, enabling the recoding of the UGA stop codon to insert selenocysteine instead. This process is mediated by several factors, including the SECIS-binding protein 2 (SBP2), elongation factor eEFSec, and the specialized selenocysteine tRNA (tRNASec).
