title: A short motif in Drosophila SECIS Binding Protein 2 provides differential binding affinity to SECIS RNA hairpins.
abstract: Selenoproteins contain the amino acid selenocysteine which is encoded by a UGA Sec codon. Recoding UGA Sec requires a complex mechanism, comprising the cis-acting SECIS RNA hairpin in the 3'UTR of selenoprotein mRNAs, and trans-acting factors. Among these, the SECIS Binding Protein 2 (SBP2) is central to the mechanism. SBP2 has been so far functionally characterized only in rats and humans. In this work, we report the characterization of the Drosophila melanogaster SBP2 (dSBP2). Despite its shorter length, it retained the same selenoprotein synthesis-promoting capabilities as the mammalian counterpart. However, a major difference resides in the SECIS recognition pattern: while human SBP2 (hSBP2) binds the distinct form 1 and 2 SECIS RNAs with similar affinities, dSBP2 exhibits high affinity toward form 2 only. In addition, we report the identification of a K (lysine)-rich domain in all SBP2s, essential for SECIS and 60S ribosomal subunit binding, differing from the well-characterized L7Ae RNA-binding domain. Swapping only five amino acids between dSBP2 and hSBP2 in the K-rich domain conferred reversed SECIS-binding properties to the proteins, thus unveiling an important sequence for form 1 binding.
authors.affiliation: Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC, Strasbourg, France.
authors.forename: Akiko
authors.initials: A
authors.lastname: Takeuchi
authors.forename: David
authors.initials: D
authors.lastname: Schmitt
authors.forename: Charles
authors.initials: C
authors.lastname: Chapple
authors.forename: Elena
authors.initials: E
authors.lastname: Babaylova
authors.forename: Galina
authors.initials: G
authors.lastname: Karpova
authors.forename: Roderic
authors.initials: R
authors.lastname: Guigo
authors.forename: Alain
authors.initials: A
authors.lastname: Krol
authors.forename: Christine
authors.initials: C
authors.lastname: Allmang
mesh_terms: D020413:3' Untranslated Regions / Q000737:chemistry*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D029721:Drosophila Proteins / Q000737:chemistry* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics*; D008969:Molecular Sequence Data; D017354:Point Mutation; D011485:Protein Binding; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D054683:Ribosome Subunits, Large, Eukaryotic / Q000378:metabolism; D051140:Selenoproteins / Q000235:genetics*
chemical_list: D020413:3' Untranslated Regions; D029721:Drosophila Proteins; D016601:RNA-Binding Proteins; C541025:SECIS binding protein 2, Drosophila; C121530:SECISBP2 protein, human; D051140:Selenoproteins