title: Adjustments, extinction, and remains of selenocysteine incorporation machinery in the nematode lineage.
abstract: Selenocysteine (Sec) is encoded by an UGA codon with the help of a SECIS element present in selenoprotein mRNAs. SECIS-binding protein (SBP2/SCBP-2) mediates Sec insertion, but the roles of its domains and the impact of its deficiency on Sec insertion are not fully understood. We used Caenorhabditis elegans to examine SBP2 function since it possesses a single selenoprotein, thioredoxin reductase-1 (TRXR-1). All SBP2 described so far have an RNA-binding domain (RBD) and a Sec-incorporation domain (SID). Surprisingly, C. elegans SBP2 lacks SID and consists only of an RBD. An sbp2 deletion mutant strain ablated Sec incorporation demonstrating SBP2 essentiality for Sec incorporation. Further in silico analyses of nematode genomes revealed conservation of SBP2 lacking SID and maintenance of Sec incorporation linked to TRXR-1. Remarkably, parasitic plant nematodes lost the ability to incorporate Sec, but retained SecP43, a gene associated with Sec incorporation. Interestingly, both selenophosphate synthetase (SPS) genes are absent in plant parasitic nematodes, while only Cys-containing SPS2 is present in Sec-incorporating nematodes. Our results indicate that C. elegans and the nematode lineage provide key insights into Sec incorporation and the evolution of Sec utilization trait, selenoproteomes, selenoproteins, and Sec residues. Finally, our study provides evidence of noncanonical translation initiation in C. elegans, not previously known for this well-established animal model.
authors.affiliation: Cátedra de Inmunología, Facultad de Química, Instituto de Higiene, Universidad de la República, Montevideo 11600, Uruguay.
authors.forename: Lucía
authors.initials: L
authors.lastname: Otero
authors.affiliation: Cátedra de Inmunología, Facultad de Química, Instituto de Higiene, Universidad de la República, Montevideo 11600, Uruguay.
authors.forename: Laura
authors.initials: L
authors.lastname: Romanelli-Cedrez
authors.affiliation: Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Anton A
authors.initials: AA
authors.lastname: Turanov
authors.affiliation: Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Vadim N
authors.initials: VN
authors.lastname: Gladyshev
authors.affiliation: Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41013 Sevilla, Spain Departamento de Fisiología, Anatomía y Biología Celular, Centro Andaluz de Biología del Desarrollo (CABD-CSIC), Universidad Pablo de Olavide, 41013 Sevilla, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Miranda-Vizuete
authors.affiliation: Cátedra de Inmunología, Facultad de Química, Instituto de Higiene, Universidad de la República, Montevideo 11600, Uruguay.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Salinas
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D020029:Base Pairing; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D018388:Codon, Terminator; D019143:Evolution, Molecular; D020868:Gene Silencing; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism; D017279:Selenocysteine / Q000235:genetics / Q000378:metabolism*; D051140:Selenoproteins / Q000235:genetics
chemical_list: D018388:Codon, Terminator; D051140:Selenoproteins; D017279:Selenocysteine; D012343:RNA, Transfer
keywords: Caenorhabditis elegans; SBP2; SECIS-binding protein; selenocysteine; selenoprotein; translation initiation