The Yersinia pseudotuberculosis Cpx envelope stress system contributes to transcriptional activation of rovM

Edvin J Thanikkal,Dharmender K Gahlot,Junfa Liu,Marcus Fredriksson Sundbom,Jyoti M Gurung,Kristina Ruuth,Monika K Francis,Ikenna R Obi,Karl M Thompson,Shiyun Chen,Petra Dersch,Matthew S Francis

doi:10.1080/21505594.2018.1556151

Abstract

ABSTRACTThe Gram-negative enteropathogen Yersinia pseudotuberculosis possesses a number of regulatory systems that detect cell envelope damage caused by noxious extracytoplasmic stresses. The CpxA sensor kinase and CpxR response regulator two-component regulatory system is one such pathway. Active Cpx signalling upregulates various factors designed to repair and restore cell envelope integrity. Concomitantly, this pathway also down-regulates key determinants of virulence. In Yersinia, cpxA deletion accumulates high levels of phosphorylated CpxR (CpxR~P). Accumulated CpxR~P directly repressed rovA expression and this limited expression of virulence-associated processes. A second transcriptional regulator, RovM, also negatively regulates rovA expression in response to nutrient stress. Hence, this study aimed to determine if CpxR~P can influence rovA expression through control of RovM levels. We determined that the active CpxR~P isoform bound to the promoter of rovM and directly induced its expression, which naturally associated with a concurrent reduction in rovA expression. Site-directed mutagenesis of the CpxR~P binding sequence in the rovM promoter region desensitised rovM expression to CpxR~P. These data suggest that accumulated CpxR~P inversely manipulates the levels of two global transcriptional regulators, RovA and RovM, and this would be expected to have considerable influence on Yersinia pathophysiology and metabolism.

Highlights

All bacteria contain a cell envelope or cell wall, and its preservation is essential for cell viability
We found that accumulated CpxR exists as a phosphorylated isoform (CpxR~P) in Y. pseudotuberculosis can directly bind to the rovM regulatory region to enhance its transcriptional output leading to accumulated RovM levels, which in turn limits RovA accumulation
We have previously shown that in Y. pseudotuberculosis ΔcpxA, accumulated CpxR~P binds to the promoter regions of rovA leading to a lowered transcriptional output [60]

Summary

Introduction

All bacteria contain a cell envelope or cell wall, and its preservation is essential for cell viability. Based upon available genome-wide transcriptome data, phosphorylated CpxR (CpxR~P) acts as a transcription factor to activate or repress ~100 gene targets in bacteria [8,9,10,11]. Among these are a number of small regulatory RNAs [9], including the newly described regulatory RNA, CpxQ, which works together with the Hfq protein to repress mRNAs of envelope proteins [12,13]

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