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Signal-dependent degradation of the Oct/POU protein Nubbin in response to infection
Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
(English)Manuscript (preprint) (Other academic)
National Category
Biological Sciences
Research subject
Molecular Biology
Identifiers
URN: urn:nbn:se:su:diva-106561OAI: oai:DiVA.org:su-106561DiVA: diva2:737265
Available from: 2014-08-12 Created: 2014-08-12 Last updated: 2014-08-13
In thesis
1. Role of POU/Oct transcription factors in Drosophila immunity
Open this publication in new window or tab >>Role of POU/Oct transcription factors in Drosophila immunity
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In response to infection, Drosophila melanogaster relies on the ability to mount a robust and potent innate immune response, characterized by induction of cellular and humoral processes. While rapid immune induction is of utmost importance, it is equally important to restrict and repress immune gene expression, where and when it is not needed. The aim of my studies was to elucidate the in vivo role of the Oct1/POU2F1 homolog Nubbin (Nub), an evolutionarily conserved transcription factor, in innate immunity.

The transcription factor Nub-PD, a product of the nub gene, was studied in wild type and mutant (nub1) flies, as well as in transgenic flies that either overexpress or down-regulate Nub-PD. Infection-studies were conducted after both oral and septic infection. Expression analysis of target genes using quantitative mRNA measurements and microarray analysis of wild type and nub1, reveal that Nub-PD acts as a bona fide repressor of NF-κB/Relish-dependent expression of immune defense genes, e.g. antimicrobial peptides. I show that Nub-PD represses transcription in uninfected flies by binding to oct DNA sequence motifs located upstream of a number of immune genes. In the event of infection, repression by Nub-PD is alleviated through rapid signal-dependent degradation, in a proteasome- and Imd-dependent manner, allowing initiation of antimicrobial peptide gene expression in both fat body and intestine. Lastly, we show that nub1 mutants also exhibit a shortened lifespan as well as elevated loads of gut bacteria with altered composition. We suggest that the aberrant immune gene activation, elevated bacterial loads, and altered bacterial composition in nub1 can collectively explain the shortened lifespan.

In conclusion, this work reveals a novel function of Nub-PD as a negative regulator of immune and stress response genes in vivo. Furthermore, my work sheds light on the importance of Nub-PD in host survival and in supporting a balanced composition of the gut microbiota.

Place, publisher, year, edition, pages
Stockholm: Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 2014. 68 p.
Keyword
Antimicrobial peptides, Drosophila, host-pathogen interaction, immune gene expression, immune signaling, NF-kB, microbiota, POU/Oct transcription factors, protein degradation, stress response, transcriptional regulation
National Category
Biochemistry and Molecular Biology
Research subject
Molecular Biology
Identifiers
urn:nbn:se:su:diva-106562 (URN)978-91-7447-959-1 (ISBN)
Public defence
2014-09-12, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript.

Available from: 2014-08-21 Created: 2014-08-12 Last updated: 2014-08-29Bibliographically approved

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