Characterization of the SECIS binding protein 2 complex required for the co-translational insertion of selenocysteine in mammals

Nucleic Acids Res. 2005 Sep 9;33(16):5172-80. doi: 10.1093/nar/gki826. Print 2005.

Abstract

Selenocysteine is incorporated into at least 25 human proteins by a complex mechanism that is a unique modification of canonical translation elongation. Selenocysteine incorporation requires the concerted action of a kink-turn structural RNA (SECIS) element in the 3' untranslated region of each selenoprotein mRNA, a selenocysteine-specific translation elongation factor (eEFSec) and a SECIS binding protein (SBP2). Here, we analyze the molecular context in which SBP2 functions. Contrary to previous findings, a combination of gel filtration chromatography and co-purification studies demonstrates that SBP2 does not self-associate. However, SBP2 is found to be quantitatively associated with ribosomes. Interestingly, a wild-type but not mutant SECIS element is able to effectively compete with the SBP2 ribosome interaction, indicating that SBP2 cannot simultaneously interact with the ribosome and the SECIS element. This data also supports the hypothesis that SBP2 interacts with one or more kink turns on 28S rRNA. Based on these results, we propose a revised model for selenocysteine incorporation where SBP2 remains ribosome bound except during selenocysteine delivery to the ribosomal A-site.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3' Untranslated Regions*
  • Animals
  • Binding, Competitive
  • Cell Line
  • Chromatography, Gel
  • Dimerization
  • Models, Genetic
  • Protein Biosynthesis*
  • Proteins / genetics*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / isolation & purification
  • RNA-Binding Proteins / metabolism*
  • Rats
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Ribosomes / metabolism*
  • Selenocysteine / metabolism*
  • Selenoproteins

Substances

  • 3' Untranslated Regions
  • Proteins
  • RNA-Binding Proteins
  • Recombinant Proteins
  • Secisbp2 protein, rat
  • Selenoproteins
  • Selenocysteine