Feedback control of Campylobacter jejuni flagellin levels through reciprocal binding of FliW to flagellin and the global regulator CsrA

• Published in: Molecular microbiology Vol. 102; no. 2; pp. 207 - 220
• Main Authors: Radomska, Katarzyna A., Ordoñez, Soledad R., Wösten, Marc M. S. M., Wagenaar, Jaap A., van Putten, Jos P. M.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.10.2016
• Subjects: Bacterial Proteins - metabolism; Biosynthesis; Campylobacter jejuni; Campylobacter jejuni - genetics; Campylobacter jejuni - metabolism; CVI Infectiebiologie; CVI Infection Biology; Feedback, Physiological; Flagella - metabolism; Flagellin - biosynthesis; Flagellin - metabolism; Gene Expression Regulation, Bacterial - genetics; Genes; Infectiebiologie; Infection Biology; Proteins; Repressor Proteins - metabolism; RNA-Binding Proteins - metabolism; Sigma Factor - metabolism
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.13455

Summary Bacterial flagella assembly is tightly regulated to ensure a timely and sequential production of the various flagellum constituents. In the pathogen Campylobacter jejuni the hierarchy in flagella biosynthesis is largely determined at the transcriptional level through the activity of the alternative sigma factors sigma54 and sigma28. Here, we report that C. jejuni flagellin levels are also controlled at the post‐transcriptional level via the thus far poorly‐characterized flagellar assembly factor FliW. Analysis of flagellin synthesis in C. jejuni 81116 and a ΔfliW knock‐out mutant showed reduced flagellin protein levels in the mutant strain while ectopic expression of FliW resulted in enhanced levels. Real‐time RT‐PCR revealed relatively minor changes in flaA and flaB mRNA levels for the recombinant and parent strain consistent with post‐transcriptional regulation. Purified FliW was found to bind to FlaA and FlaB flagellin as well as to the global post‐transcriptional regulator CsrA. Inactivation of CsrA resulted in increased levels of flagellin translation. An in vitro translation assay confirmed the regulatory role of CsrA in flagellin biosynthesis. We propose that competitive reciprocal binding of FliW to flagellins and the RNA binding protein CsrA serves as a feedback mechanism to control the number of cytosolic flagellin copies at the protein level. We discovered a novel mechanism of regulation of flagellin biosynthesis in the bacterial pathogen Campylobacter jejuni. This mechanism controls flagellin levels through interaction of the flagellin assembly factor FliW with flagellin and the global post‐transcriptional regulator CsrA.