Ribonuclease J-Mediated mRNA Turnover Modulates Cell Shape, Metabolism and Virulence in Corynebacterium diphtheriae

Controlled RNA degradation is a crucial process in bacterial cell biology for maintaining proper transcriptome homeostasis and adaptation to changing environments. mRNA turnover in many Gram-positive bacteria involves a specialized ribonuclease called RNase J (RnJ). To date, however, nothing is known about this process in the diphtheria-causative pathogen Corynebacterium diphtheriae, nor is known the identity of this ribonuclease in this organism. Here, we report that C. diphtheriae DIP1463 encodes a predicted RnJ homolog, comprised of a conserved N-terminal beta-lactamase domain, followed by beta-CASP and C-terminal domains. A recombinant protein encompassing the beta-lactamase domain alone displays 5 '-exoribonuclease activity, which is abolished by alanine-substitution of the conserved catalytic residues His(186) and His(188). Intriguingly, deletion of DIP1463/rnj in C. diphtheriae reduces bacterial growth and generates cell shape abnormality with markedly augmented cell width. Comparative RNA-seq analysis revealed that RnJ controls a large regulon encoding many factors predicted to be involved in biosynthesis, regulation, transport, and iron acquisition. One upregulated gene in the increment rnj mutant is ftsH, coding for a membrane protease (FtsH) involved in cell division, whose overexpression in the wild-type strain also caused cell-width augmentation. Critically, the increment rnj mutant is severely attenuated in virulence in a Caenorhabditis elegans model of infection, while the FtsH-overexpressing and toxin-less strains exhibit full virulence as the wild-type strain. Evidently, RNase J is a key ribonuclease in C. diphtheriae that post-transcriptionally influences the expression of numerous factors vital to corynebacterial cell physiology and virulence. Our findings have significant implications for basic biological processes and mechanisms of corynebacterial pathogenesis.

Automated summary

Controlled RNA degradation is crucial for proper cell biology in bacteria, and the ribonuclease RNase J plays a key role in this process. By studying Corynebacterium diphtheriae, researchers have identified a homolog of RNase J, DIP1463, which affects the expression of multiple factors involved in bacterial cell physiology and virulence. The deletion of RNase J leads to reduced bacterial growth, abnormal cell shape, and attenuation in virulence, highlighting its importance in pathogenesis.