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Pivotal Roles for Ribonucleases in Streptococcus pneumoniae Pathogenesis

ABSTRACT: RNases perform indispensable functions in regulating gene expression in many bacterial pathogens by processing and/or degrading RNAs. Despite the pivotal role of RNases in regulating bacterial virulence factors, the functions of RNases have not yet been studied in the major human respiratory pathogen Streptococcus pneumoniae (pneumococcus). Here, we sought to determine the impact of two conserved RNases, the endoribonuclease RNase Y and exoribonuclease polynucleotide phosphorylase (PNPase), on the physiology and virulence of S. pneumoniae serotype 2 strain D39. We report that RNase Y and PNPase are essential for pneumococcal pathogenesis as both deletion mutants showed strong attenuation of virulence in murine models of invasive pneumonia. Genome-wide transcriptomic analysis revealed that nearly 200 mRNA transcripts were significantly up-regulated, whereas the abundance of several pneumococcal sRNAs, including the Ccn (CiaR Controlled Noncoding RNA) sRNAs, were altered in the ∆rny mutant relative to the wild-type strain. Additionally, lack of RNase Y resulted in pleiotropic phenotypes that included defects in pneumococcal cell morphology and growth in vitro. In contrast, Dpnp mutants showed no growth defect in vitro, but differentially expressed a total of 40 transcripts including the tryptophan biosynthesis operon genes and numerous 5’-cis-acting regulatory RNAs, a majority of which were previously shown to impact pneumococcal disease progression in mice using the serotype 4 strain TIGR4. Altogether our data suggest that RNase Y exerts a global impact on pneumococcal physiology, while PNPase-mediates virulence phenotypes, likely through sRNA regulation.

ORGANISM(S): Streptococcus pneumoniae D39

PROVIDER: GSE173392 | GEO | 2021/09/02

REPOSITORIES: GEO

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Project description:The polynucleotide phosphorylase (PNPase) is conserved among both Gram-positive and Gram-negative bacteria. As a core part of the degradosome, the PNPase is involved in maintaining proper RNA levels within the bacterial cell. It plays a major role in RNA homeostasis and decay since it acts as a 3’- to 5’-exoribonuclease. Furthermore PNPase can catalyze the reverse reaction by elongating RNA molecules in 5’- to 3’-end direction which finally has a destabilizing effect on the prolonged RNA molecule. RNA degradation can be initiated by an endonucleolytic cleavage and then by further promoted by exoribonucleolytic decay. In this study, we analyzed the importance of the Rhodobacter sphaeroides PNPase regarding the physiology and sRNA homeostasis. Moreover, we developed a pipeline to globally identify differential RNA 3’-ends in RNA NGS sequencing data obtained from PNPase, RNase E and RNase III mutants. The Rhodobacter sphaeroides PNPase mutant exhibits several phenotypical characteristics, including diminished adaption to low temperature, reduced resistance to organic peroxide induced stress and altered growth behavior. Furthermore, the transcriptome composition differs in the pnp mutant strain, resulting in a decreased abundance of most tRNAs and rRNAs. In addition, the PNPase has a major influence on the half-lives of several regulatory sRNAs and can have both a stabilizing or a destabilizing effect. The RNA 3’-end analysis reveals that 82% of all differential 3’-ends are enriched in the pnp mutant and are mostly located in coding sequences or untranslated regions (UTR). A fair percentage of these ends was also identified as differential RNA 3’-end in RNase E and RNase III mutant strains. The PNPase has a major influence in RNA processing and maturation and thus modulates the transcriptome. This includes regulatory sRNAs, stressing the role of PNPase in cellular homeostasis and its importance in regulatory networks. The 3’-end analysis indicates a sequential processing of UTR- and non-UTR derived sRNAs by several ribonucleases. Moreover, we provide a modular pipeline which greatly facilitates the identification of RNA 5’/3’-ends. It is publicly available on GitHub and is distributed under ICS licence.

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Pivotal Roles for Ribonucleases in Streptococcus pneumoniae Pathogenesis

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