Abstract
Bacteria utilize endoribonuclease-mediated RNA processing and decay to rapidly adapt to environmental changes. Here, we report that the modulation of hns mRNA stability by the endoribonuclease RNase G plays a key role in Salmonella Typhimurium pathogenicity. We found that RNase G determines the half-life of hns mRNA by cleaving its 5′ untranslated region and that altering its cleavage sites by genome editing stabilizes hns mRNA, thus decreasing S. Typhimurium virulence in mice. Under anaerobic conditions, the FNR-mediated transcriptional repression of rnc encoding RNase III, which degrades rng mRNA, and simultaneous induction of rng transcription resulted in rapid hns mRNA degradation, leading to the derepression of genes involved in the Salmonella pathogenicity island 1 (SPI-1) type III secretion system (T3SS). Together, our findings show that RNase III and RNase G levels-mediated control of hns mRNA abundance acts as a regulatory pathway upstream of a complex feed-forward loop for SPI-1 expression.
Highlights
Bacterial ribonucleases regulate gene expression via RNA processing and decay
E. coli lacking rne can be made viable by overexpressing RNase G; rngcomplementation affects the abundance of a small portion of mRNAs in rne-deficient cells [9], indicating that RNase G and E play distinct physiological roles
Typhimurium strains following the infection of human intestinal epithelial cells (HCT116; Fig 1A)
Summary
Bacterial ribonucleases regulate gene expression via RNA processing and decay. They are essential for processing RNA precursors into mature, functional RNAs, and initiate the reactions that cleave and differentially regulate certain polycistronic mRNAs [1,2,3,4,5]. In Escherichia coli, mRNA decay is heavily dependent on endoribonuclease E (RNase E) [8,9,10], whose paralog endoribonuclease G (RNase G; encoded by rng) has a 36% amino acid sequence identity with the RNase E N-terminal catalytic domain [11,12]. Both enzymes are single-stranded RNA-specific endoribonucleases with a preference for cleaving AU-rich sequences [11,13,14]. E. coli lacking rne can be made viable by overexpressing RNase G; rngcomplementation affects the abundance of a small portion of mRNAs in rne-deficient cells [9], indicating that RNase G and E play distinct physiological roles
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