The oxidative stress response, in particular thekatYgene, is temperature-regulated inYersinia pseudotuberculosis

Abstract

AbstractPathogenic bacteria, such asYersinia pseudotuberculosisencounter reactive oxygen species (ROS) as one of the first lines of defense in the mammalian host. In return, the bacteria react by mounting an oxidative stress response. Previous global RNA structure probing studies provided evidence for temperature-modulated RNA structures in the 5’-untranslated region (5’-UTR) of various oxidative stress response transcripts, suggesting that opening of these RNA thermometer (RNAT) structures at host-body temperature relieves translational repression. Here, we systematically analyzed the transcriptional and translational regulation of ROS defense genes by RNA-sequencing, qRT-PCR, translational reporter gene fusions, enzymatic RNA structure probing and toeprinting assays. Transcription of four ROS defense genes was upregulated at 37°C. ThetrxAgene is transcribed into two mRNA isoforms, of which the short one contains a functional RNAT. Biochemical assays validated temperature-responsive RNAT-like structures in the 5’-UTRs ofsodB,sodCandkatA. However, they barely conferred translational repression inY. pseudotuberculosisat 25°C suggesting partially open structures available to the ribosome in the living cell. Upstream ofkatYwe uncovered a novel, highly efficient RNAT that was primarily responsible for massive induction of KatY at 37°C. By phenotypic characterization of catalase mutants and through fluorometric real-time measurements of the redox-sensitive roGFP2-Orp1 reporter in these strains, we revealed KatA as the primary H2O2scavenger. Consistent with temperature regulation ofkatY, we observed an improved protection ofY. pseudotuberculosisat 37°C. Our findings suggest a multilayered regulation of the oxidative stress response inYersiniaand an important role of RNAT-controlledkatYexpression at host body temperature.Author summaryThe external conditions dramatically change when a bacterial pathogen enters a mammalian host. Sensing the new situation and rapidly responding to it is of critical importance for pathogens, likeYersinia pseudotuberculosis, since they often circulate between their environmental reservoirs and a warm-blooded host. Many virulence-related genes encode a temperature-sensitive mRNA element, a so-called RNA thermometer (RNAT), in the 5’-end of their transcript. Melting of this structure at 37°C allows ribosome binding and translation initiation. The host immune system typically fights microbial pathogens by the production of reactive oxygen species (ROS). Here, we find that several ROS defense genes inYersiniaare upregulated at host body temperature to counteract the ROS attack. In particular, the massive RNAT-mediated upregulation of the catalase KatY confers protection against H2O2at 37°C. Our study reveals a close regulatory link between temperature sensing and the oxidative stress response in a notorious food borne pathogen.