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Selenocysteine incorporation in metazoa: the peculiar case of the nematode lineage

AutorOtero, Lucía; Romanelli-Cedrez, Laura; Gladyshev, Vadim N.; Miranda-Vizuete, Antonio ; Salinas, Gustavo
Fecha de publicaciónjun-2013
Citación19th International C. elegans Meeting (2013)
ResumenSelenocysteine (Sec) incorporation into proteins occurs through a non-canonical mechanism: a Sec incorporation sequence (SECIS) present in the selenoprotein mRNA binds to a SECIS-binding protein allowing a UGA codon to be reprogrammed for Sec. Using Caenorhabditis elegans to study Sec incorporation, we found that its SECIS-binding protein (K04G2.11) is significantly shorter than any known SECIS-binding protein and lacks the putative Sec incorporation domain (SID). We amplified the full-length mRNA and confirmed the annotated sequence. A comparative analysis with other SECIS-binding proteins showed extended amino acid homology in the annotated 5'UTR, upstream the first in-frame AUG codon. This suggests that K04G2.11 would have a non-AUG translation initiation. Moreover, the extension of the ORF completes the functional L7Ae domain. Initiation of translation would occur at an AUU codon in an adequate context for translation initiation (GAAAAUU). We generated transgenic strains that overexpress K04G2.11 fused to a polyHis tail. By sequential metal and SECIS affinity chromatography, we isolated from transgenic strains, but not from N2, a 20kDa protein, which corresponds to the expected mass from the proposed AUU start codon. By 75Se metabolic incorporation we demonstrated that this gene is functional and essential for Sec incorporation. The absence of the SID domain in the genome is remarkable and suggests that Sec incorporation mechanism in C. elegans is peculiar. We investigate Sec incorporation in the nematode lineage. The analysis of nematode genomes indicates: i) the SID domain is absent, ii) SECIS-binding proteins consist of the L7Ae domain only, iii) the existence of non-AUG initiation of translation in nematodes SECIS-binding proteins, and iv) the absence of Sec incorporation in plant nematode parasites. Our results indicate that nematoda is an interesting lineage to study the dynamics of the evolution of Sec incorporation. They also point out the occurrence of non-AUG translation initiation in C. elegans, not described before, a finding that needs to be further investigated.
DescripciónPóster presentado en la 19th International Caenorhabditis elegans Meeting, celebrada en Los Ángeles del 26 al 30 de junio de 2013.
Aparece en las colecciones: (IBIS) Comunicaciones congresos
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