Binding of the RNA chaperone Hfq to the type IV pilus base is crucial for its function in S ynechocystis sp. PCC 6803

• Published in: Molecular microbiology 2014-05, Vol.92 (4), p.840-852
• Main Authors: Schuergers, Nils, Ruppert, Ulrike, Watanabe, Satoru, Nürnberg, Dennis J., Lochnit, Günter, Dienst, Dennis, Mullineaux, Conrad W., Wilde, Annegret
• Format: Article
• Language: English
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.12595

The bacterial RNA ‐binding protein Hfq functions in post‐transcriptional regulation of gene expression. There is evidence in a range of bacteria for specific subcellular localization of Hfq ; however, the mechanism and role of Hfq localization remain unclear. Cyanobacteria harbour a subfamily of Hfq that is structurally conserved but exhibits divergent RNA binding sites. Mutational analysis in the cyanobacterium S ynechocystis sp. PCC 6803 revealed that several conserved amino acids on the proximal side of the Hfq hexamer are crucial not only for Hfq ‐dependent RNA accumulation but also for phototaxis, the latter of which depends on type IV pili. Co‐immunoprecipitation and yeast two‐hybrid analysis show that the secretion ATPase PilB 1 (a component of the type IV pilus base) is an interaction partner of Hfq . Fluorescence microscopy revealed that Hfq is localized to the cytoplasmic membrane in a PilB 1‐dependent manner. Concomitantly, Hfq ‐dependent RNA accumulation is abrogated in a Δ pilB1 mutant, indicating that localization to the pilus base via interaction with PilB1 is essential for Hfq function in cyanobacteria.