The xbp-1 gene is essential for development in Drosophila.
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.
Souid
Sami
S
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.
Lepesant
Jean-Antoine
JA
Yanicostas
Constantin
C
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
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