SpoVG Is a Conserved RNA-Binding Protein That Regulates Listeria monocytogenes Lysozyme Resistance, Virulence, and Swarming Motility.

Thomas P Burke,Daniel A Portnoy,John J Mekalanos

doi:10.1128/mbio.00240-16

Abstract

ABSTRACTIn this study, we sought to characterize the targets of the abundant Listeria monocytogenes noncoding RNA Rli31, which is required for L. monocytogenes lysozyme resistance and pathogenesis. Whole-genome sequencing of lysozyme-resistant suppressor strains identified loss-of-expression mutations in the promoter of spoVG, and deletion of spoVG rescued lysozyme sensitivity and attenuation in vivo of the rli31 mutant. SpoVG was demonstrated to be an RNA-binding protein that interacted with Rli31 in vitro. The relationship between Rli31 and SpoVG is multifaceted, as both the spoVG-encoded protein and the spoVG 5′-untranslated region interacted with Rli31. In addition, we observed that spoVG-deficient bacteria were nonmotile in soft agar and suppressor mutations that restored swarming motility were identified in the gene encoding a major RNase in Gram-positive bacteria, RNase J1. Collectively, these findings suggest that SpoVG is similar to global posttranscriptional regulators, a class of RNA-binding proteins that interact with noncoding RNA, regulate genes in concert with RNases, and control pleiotropic aspects of bacterial physiology.

Highlights

In this study, we sought to characterize the targets of the abundant Listeria monocytogenes noncoding RNA Rli31, which is required for L. monocytogenes lysozyme resistance and pathogenesis
Three mutations mapped to the response regulator walR, one mapped to the histidine kinase walK, and one mapped to walI, a negative regulator of walRK that we previously characterized as a lysozyme-sensitive mutant in L. monocytogenes [7]
SpoVG mutations were identified as suppressors of L. monocytogenes lysozyme sensitivity. spoVG is broadly conserved among bacteria [12] and has been extensively characterized for nearly 4 decades in Gram-positive bacteria [13, 14, 16, 17, 20, 32]. spoVG mutations cause diverse phenotypes in B. subtilis and S. aureus related to capsule formation [15], sporulation [16, 17], enzyme secretion [14], antibiotic resistance [13], and cell division [17]

Summary

Introduction

We sought to characterize the targets of the abundant Listeria monocytogenes noncoding RNA Rli, which is required for L. monocytogenes lysozyme resistance and pathogenesis. We observed that spoVG-deficient bacteria were nonmotile in soft agar and suppressor mutations that restored swarming motility were identified in the gene encoding a major RNase in Gram-positive bacteria, RNase J1 These findings suggest that SpoVG is similar to global posttranscriptional regulators, a class of RNA-binding proteins that interact with noncoding RNA, regulate genes in concert with RNases, and control pleiotropic aspects of bacterial physiology. We determined that SpoVG is an RNA-binding protein that interacts with noncoding RNAs, regulates genes in cooperation with RNases, and controls pleiotropic aspects of bacterial physiology, including motility, carbon metabolism, and virulence Together, these characteristics are similar to those of posttranscriptional gene regulators such as CsrA, a class of RNA-binding molecules that are fundamental for synchronizing environmental cues with gene regulation in order to adapt bacteria to their diverse ecological domains [11]. Considering that these proteins have been primarily characterized in Gram-negative bacteria, we hypothesize that SpoVG may act as a functionally conserved counterpart to these molecules in Gram-positive organisms

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Conclusion