Investigation of the role of RNA-binding proteins in bacterial gene regulation

Sammanfattning: Salmonella is a common food-borne, intracellular pathogen that causes infections in animals and humans. During infection of the host, flagella serve as important virulence factors that enable the bacterium to reach the site of infection and adhere to the host-cell. Flagella are complex organelles, and their expression is organized by an intricate, regulatory network, governed by the transcription factor FlhDC. While the transcriptional regulation of flagellar genes in Salmonellais well described, there is little known about post-transcriptional mechanisms. The RNA binding protein ProQ was found to promote motility, but the molecular mode of action remained unclear. Recently, the small RNA FlgO was found to be a contributing genetic factor for ProQ-dependent flagellar gene expression. FlgO was hypothesized to base-pair with the 5’untranslated region of the flhDC mRNA and thereby promote translation of the mRNA. As ProQ was positively affecting FlgO steady-state levels, I hypothesized that ProQ stabilizes or aids in processing of FlgO. Further, I investigated the effect of FlgO on translation of the flhDC mRNA. The results of this work showed that the stability and processing of FlgO is independent of ProQ, and in vitro binding assays showed no binding of ProQ to FlgO. However, the RNA binding protein Hfq was found to bind and stabilize FlgO. Further, I found that overexpression of FlgO increases flhDC mRNA translation and that this effect is independent of the small RNAs ArcZ, OmrA/B and OxyS, all of which are known to repress flhDC translation. The precise molecular mechanism of how FlgO stimulates translation of flhDCremains subject for future work.