title: Regulation of selenocysteine incorporation into the selenium transport protein, selenoprotein P.
abstract: Selenoproteins are unique as they contain selenium in their active site in the form of the 21st amino acid selenocysteine (Sec), which is encoded by an in-frame UGA stop codon. Sec incorporation requires both cis- and trans-acting factors, which are known to be sufficient for Sec incorporation in vitro, albeit with low efficiency. However, the abundance of the naturally occurring selenoprotein that contains 10 Sec residues (SEPP1) suggests that processive and efficient Sec incorporation occurs in vivo. Here, we set out to study native SEPP1 synthesis in vitro to identify factors that regulate processivity and efficiency. Deletion analysis of the long and conserved 3'-UTR has revealed that the incorporation of multiple Sec residues is inherently processive requiring only the SECIS elements but surprisingly responsive to the selenium concentration. We provide evidence that processive Sec incorporation is linked to selenium utilization and that reconstitution of known Sec incorporation factors in a wheat germ lysate does not permit multiple Sec incorporation events, thus suggesting a role for yet unidentified mammalian-specific processes or factors. The relationship between our findings and the channeling theory of translational efficiency is discussed.
authors: From the Department of Biochemistry and Molecular Biology, Rutgers Robert Wood Johnson Medical School, Piscataway, New Jersey 08854.
authors: Sumangala P
authors: SP
authors: Shetty
authors: From the Department of Biochemistry and Molecular Biology, Rutgers Robert Wood Johnson Medical School, Piscataway, New Jersey 08854.
authors: Ravi
authors: R
authors: Shah
authors: From the Department of Biochemistry and Molecular Biology, Rutgers Robert Wood Johnson Medical School, Piscataway, New Jersey 08854 paul.copeland@rutgers.edu.
authors: Paul R
authors: PR
authors: Copeland
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D000818:Animals; D002474:Cell-Free System; D056945:Hep G2 Cells; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008957:Models, Genetic; D009154:Mutation; D014176:Protein Biosynthesis / Q000187:drug effects / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000235:genetics* / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D012643:Selenium / Q000378:metabolism / Q000494:pharmacology; D017279:Selenocysteine / Q000235:genetics* / Q000378:metabolism; D051149:Selenoprotein P / Q000235:genetics* / Q000378:metabolism
chemical_list: D020413:3' Untranslated Regions; D012333:RNA, Messenger; D012346:RNA, Transfer, Amino Acyl; D051149:Selenoprotein P; C112705:selenocysteinyl-tRNA; D017279:Selenocysteine; D008156:Luciferases; D012643:Selenium
keywords: Channeling; SEPP1; Selenium; Selenocysteine; Selenocysteine Insertion Sequence (SECIS); Selenoprotein; Translation