Small regulatory RNAs in Streptococcus pneumoniae: discovery and biological functions.

Joana Wilton,Mónica Amblar,Cristina Herranz,Alicia Gómez,Paloma Acebo

doi:10.3389/fgene.2015.00126

Abstract

Streptococcus pneumoniae is a prominent human pathogen responsible for many severe diseases and the leading cause of childhood mortality worldwide. The pneumococcus is remarkably adept at colonizing and infecting different niches in the human body, and its adaptation to dynamic host environment is a central aspect of its pathogenesis. In the last decade, increasing findings have evidenced small RNAs (sRNAs) as vital regulators in a number of important processes in bacteria. In S. pneumoniae, a small antisense RNA was first discovered in the pMV158 plasmid as a copy number regulator. More recently, genome-wide screens revealed that the pneumococcal genome also encodes multiple sRNAs, many of which have important roles in virulence while some are implicated in competence control. The knowledge of the sRNA-mediated regulation in pneumococcus remains very limited, and future research is needed for better understanding of functions and mechanisms. Here, we provide a comprehensive summary of the current knowledge on sRNAs from S. pneumoniae, focusing mainly on the trans-encoded sRNAs.

Highlights

Streptococcus pneumoniae, the pneumococcus, is an opportunistic pathogen responsible for a wide spectrum of human diseases, ranging from mild otitis media to more severe infections such as meningitis, sepsis, or endocarditis
The first regulatory RNA discovered in pneumococcus was a plasmid-encoded bona-fide antisense RNA described by del Solar and Espinosa (1992), and its role in establishment, replication, and copy number regulation has been deeply investigated
The tmRNA has been associated with deficiencies in stress-response and pathogenicity in other bacteria (Withey and Friedman, 2003; Okan et al, 2006, 2010; Keiler, 2008) and has a central role in the trans-translation mechanism, a RNA and protein quality control system that resolves challenges associated with stalled ribosomes on non-stop mRNAs (Giudice et al, 2014; Shimizu, 2014)

Summary

Introduction

Streptococcus pneumoniae, the pneumococcus, is an opportunistic pathogen responsible for a wide spectrum of human diseases, ranging from mild otitis media to more severe infections such as meningitis, sepsis, or endocarditis. It is the main etiological agent of community-acquired pneumonia, causing more deaths in young children than any other infectious disease (O’Brien et al, 2009). S. pneumoniae is a normal component of the human commensal flora, asymptomatically colonizing the upper respiratory tracts of children and healthy adults. Transition to opportunistic pathogen often occurs after a respiratory tract infection and is triggered by unknown host and bacterial factors. Disease progression exposes S. pneumoniae to numerous environmental changes and stress conditions, and rapid adaptation is a key factor for survival and replication

Regulatory RNAs in pneumococci

RNAs Encoded in Extrachromosomal Elements

Pathogenesis profilea

Competence modulation and autolysisf Competence modulationd

Findings

Concluding Remarks and Perspectives