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Seminar July 2022


Published on 4 July 2022

Start Monday July 4th at 4pm (CET, Berlin/Paris) **cancelled** Posponed later on (probably in September), stay tuned ** Please accept our apologizes

(3 pm London/Lisbon, 10am New-York, 7am San Francisco, 5pm Tel Aviv)


Main Speaker: Cynthia Sharma, Professor, Institute of Molecular Infection Biology (IMIB), University of Würzburg, Germany (Link)


Title: Regulatory RNAs in pathogenic Epsilonproteobacteria

Abstract:

Non-coding RNAs and RNA-protein (RNP) complexes play central roles in diverse physiological processes in all kingdoms of life. Research in our lab focuses on RNA-based processes in the two pathogenic Epsilonproteobacteria Helicobacter pylori, the cuasative agent of gastric cancer, and the related food-borne pathogen Campylobacter jejuni. We are especially interested in the roles of small, regulatory RNAs (sRNAs) and RNPs in virulence control as well as novel mechanisms of gene regulation. For example, we have discovered new connections between so-called phase-variation at length variable DNA repeats and post-transcriptional regulation. I will present our work on sRNAs from H. pylori and C. jejuni that target variable G-repeats and regulate genes involved in host colonization as well as antibiotic sensitivity. Moreover, we recently identified a sRNA that is itself regulated by a phase-variable repeat and acts as a central regulator of the major virulence factors of H. pylori.

Short session speaker (8 minutes long): Fabian König

Title: A 3´UTR-derived, processed small RNA modulates flagellar biogenesis by repression of the anti-sigma factor FlgM in Campylobacter jejuni

Abstract:

In Campylobacter jejuni, as for many pathogens, flagella are a crucial virulence factor, enabling traversal through the viscous mucus layer of the human intestine. Flagellar biogenesis is known to involve hierarchical transcriptional control of each component, with class I genes transcribed from sigma-70-dependent promoters, and class II and class III genes transcribed with the help of alternative sigma factors, RpoN and FliA, respectively. In contrast to transcriptional control, less is known about post-transcriptional regulation of flagellar biosynthesis cascades by small regulatory RNAs (sRNAs). Here, we have characterized a conserved Campylobacter sRNA, CJnc230, encoded downstream of the RpoN-dependent flagellar hook structural protein FlgE, and found that three ribonucleases are involved in sRNA maturation. RNase III cleaves off the sRNA from the flgE mRNA, while RNase Y and PNPase process CJnc230 at its 3´ end. We identified a regulator of flagella-flagella interactions as well as the anti-sigma-28 factor FlgM as targets of CJnc230 repression. CJnc230 overexpression led to de-repression of FliA and subsequent upregulation of class III flagellar genes such as the major flagellin flaA, culminating in an increase in motility and flagellar length. Overexpression of the FliA-dependent sRNA CJnc170 instead led to reduced motility suggesting sRNA-mediated regulation of C. jejuni flagellar biosynthesis through balancing of the hierarchically expressed components.

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