title: The xbp-1 gene is essential for development in Drosophila.
abstract: We report in this paper the characterization of Dxbp-1, the Drosophila homologue of the xpb-1 gene that encodes a "bZIP"-containing transcription factor that plays a key role in the unfolded protein response (UPR), an evolutionarily conserved signalling pathway activated by an overload of misfolded proteins in the endoplasmic reticulum (ER). Dxbp-1 is ubiquitously transcribed, and high levels are found in embryonic salivary glands and in the ovarian follicle cells committed to the synthesis of the respiratory appendages. Loss of function of Dxbp-1 induced a recessive larval lethality, thus, revealing an essential requirement for this gene. The Dxbp-1 transcript was submitted to an "unconventional" splicing that generated a processed Dxbp-1s transcript encoding a DXbp-1 protein isoform, as is the case for yeast, Caenorhabditis elegans and vertebrate hac1/xbp-1 transcripts after UPR activation. However, in the absence of exogenously induced ER stress, the Dxbp-1s transcript was also detectable not only throughout embryonic and larval development but also in adults with a high level of accumulation in the male sexual apparatus and, to a lesser extent, in the salivary glands of the third-instar larvae. Using a Dxbp-1:GFP transgene as an in vivo reporter for Dxbp-1 mRNA unconventional splicing, we confirmed that Dxbp-1 processing took place in the salivary glands of the third-instar larvae. The Dxbp-1 gene appears, thus, to play an essential role during the development of Drosophila, hypothetically by stimulating the folding capacities of the ER in cells committed to intense secretory activities.
authors.affiliation: Institut Jacques Monod, UMR 7592, CNRS, Université Denis-Diderot Paris 7 and Université Paris 6 Pierre et Marie Curie, 2, Place Jussieu, 75251, Paris Cedex 05, France.
authors.forename: Sami
authors.initials: S
authors.lastname: Souid
authors.forename: Jean-Antoine
authors.initials: JA
authors.lastname: Lepesant
authors.forename: Constantin
authors.initials: C
authors.lastname: Yanicostas
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D004330:Drosophila / Q000196:embryology / Q000235:genetics* / Q000254:growth & development*; D029721:Drosophila Proteins / Q000235:genetics*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D017344:Genes, Insect; D049452:Green Fluorescent Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D009866:Oogenesis / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C517798:Xbp1 protein, Drosophila; D049452:Green Fluorescent Proteins