title: Ire1 mediated mRNA splicing in a C-terminus deletion mutant of Drosophila Xbp1.
abstract: The Unfolded Protein Response is a homeostatic mechanism that permits eukaryotic cells to cope with Endoplasmic Reticulum (ER) stress caused by excessive accumulation of misfolded proteins in the ER lumen. The more conserved branch of the UPR relies on an ER transmembrane enzyme, Ire1, which, upon ER stress, promotes the unconventional splicing of a small intron from the mRNA encoding the transcription factor Xbp1. In mammals, two specific regions (the hydrophobic region 2--HR2--and the C-terminal translational pausing site) present in the Xbp1unspliced protein mediate the recruitment of the Xbp1 mRNA-ribosome-nascent chain complex to the ER membrane, so that Xbp1 mRNA can be spliced by Ire1. Here, we generated a Drosophila Xbp1 deletion mutant (Excision101) lacking both HR2 and C-terminal region, but not the Ire1 splicing site. We show that Ire1-dependent splicing of Xbp1 mRNA is reduced, but not abolished in Excision101. Our results suggest the existence of additional mechanisms for ER membrane targeting of Xbp1 mRNA that are independent of the C-terminal domain of Drosophila Xbp1unspliced.
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal.
authors.forename: Dina S
authors.initials: DS
authors.lastname: Coelho
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal.
authors.forename: Catarina J
authors.initials: CJ
authors.lastname: Gaspar
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal.
authors.forename: Pedro M
authors.initials: PM
authors.lastname: Domingos
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics*; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics*; D004721:Endoplasmic Reticulum / Q000235:genetics; D059865:Endoplasmic Reticulum Stress / Q000235:genetics; D004722:Endoribonucleases / Q000235:genetics*; D012326:RNA Splicing / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D017384:Sequence Deletion / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics; D056811:Unfolded Protein Response / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C517798:Xbp1 protein, Drosophila; D004722:Endoribonucleases; C511918:inositol requiring enzyme-1, Drosophila