Practice question

Location of SECIS diverges between domains reflecting distinct recoding strategies. Eukaryotic SECIS lies in 3' untranslated region often 500 to 2500 nucleotides downstream of UGA, acting at distance via mRNA looping facilitated by SBP2 binding ribosome and eS31 protein. Multiple isoforms share conserved secondary structure but variable primary sequence. Bacterial SECIS immediately follows UGA within open reading frame, directly contacted by SelB C-terminal domain. Distant 3' UTR placement allows single SECIS to recode multiple UGAs and integrates selenium availability regulation effectively.