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MS2-affinity purification coupled with RNA sequencing (MAPS) reveals S. aureus IsrR sRNA targetome

ABSTRACT: Bacterial regulatory RNAs (sRNAs) are commonly short non-coding RNAs that function as pleiotropic regulators by post-transcriptionally impacting mRNA stability and/or translation. They play significant roles in bacterial physiology and are typically expressed in response to specific environmental stimuli such as nutrient limitation. The bacterial pathogen Staphylococcus aureus faces decreased access to essential metal ions, including iron, in the mammalian host in a process called nutritional immunity. In response to host-mediated iron limitation, S. aureus expresses the sRNA IsrR, which coordinates an iron-sparing response by downregulating the expression of mRNAs coding for iron-requiring proteins. Herein, we utilized MS2-Affinity Purification coupled with RNA Sequencing (MAPS) to reveal the in vivo IsrR interaction network. Analysis of co-purified RNAs revealed previously unpredicted putative IsrR targets coding for proteins associated with iron-requiring processes. We validated that IsrR directly interacts with eight of these targets in vitro. We demonstrate physiological roles for IsrR in mediating heme biosynthesis, aerobic respiration, and the metabolism of oxygen radicals. These activities are critical for pathogenesis, and this study establishes how S. aureus leverages these processes to adapt to iron scarcity, which is commonly encountered in the mammalian host.

ORGANISM(S): Staphylococcus aureus

PROVIDER: GSE296222 | GEO | 2025/10/02

REPOSITORIES: GEO

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Project description:The Gram-positive pathogenic bacterium Staphylococcus aureus permanently colonizes the nasal mucosa in about 30% of the healthy population. However, as an opportunistic pathogen, S. aureus can also cause a variety of diseases, the treatment of which is becoming increasingly difficult due to antibiotic resistance. Adaptation to changing environmental conditions during colonization and infection of the host requires precise regulation of the expression of genes for virulence factors and metabolic functions. The host conditions essentially include low iron availability, with the majority of iron in the human organism being present intracellularly in the form of haemoglobin. Therefore, S. aureus has various adaptive mechanisms, in particular iron uptake systems, which are regulated by the global iron uptake regulator Fur (ferric-uptake regulator). Iron deficiency conditions lead to the derepression of Fur-dependent genes. In many bacteria, these genes also include regulatory RNAs (small regulatory RNAs, sRNAs), which mediate an iron-sparing response by inhibiting the synthesis of non-essential iron-containing proteins. A Fur-dependent sRNA (S596) was identified in a transcriptome analysis of S. aureus. In a study by Coronel-Tellez et al. (2022) it was shown that S596/IsrR (“iron sparing response regulator”) is necessary for the virulence of S. aureus. In the presented secretome analysis, the S. aureus HG001 wild type (WT) was compared with an isogenic isrR mutant (ΔisrR) under iron-limiting conditions and a constitutively isrR-expressing strain (HG001 pJLisrR) with an empty vector control (HG001 pJLctrl) under iron-rich conditions as well as corresponding sae mutant (Δsae) strains. Culture supernatants were collected in the exponential and stationary growth phases and extracellular proteins were subsequently analyzed by mass spectrometry. Statistical data analysis was performed to identify proteins with significantly altered amounts between the respective strains. We demonstrate that IsrR positively influences the protein levels of numerous virulence factors which in particular belong to the Sae regulon.

Project description:Iron is an essential cofactor in many metabolic reactions. Mechanisms controlling iron homeostasis need to respond to changes in extracellular conditions, but must also keep the concentration of intracellular iron under strict control, as free ferrous iron (Fe2+) can lead to the generation of reactive oxygen species. Due to its role as redox carrier in photosynthesis, the iron quota in cyanobacteria is about 10 times higher than in model enterobacteria, but the molecular details how such high quota is tightly regulated have remained obscure. Here, we measured time-resolved gene expression changes after iron depletion in the cyanobacterium Synechocystis sp. PCC 6803 using a comprehensive microarray platform monitoring both protein-coding and non-coding transcripts. In total, 644 protein-coding genes were differentially expressed during the first 72h. Many of these proteins are associated with iron transport, photosynthesis or ATP synthesis. Comparing our data with three previous studies, we identified a core set of 28 genes involved in the iron stress response. Among them were genes encoding proteins important for assimilation of inorganic carbon, suggesting a previously unknown link between the carbon and iron regulatory networks. Nine of the 28 genes are of unknown function and constitute key targets for detailed functional analysis. Applying identical statistical and clustering criteria as for the protein-coding fraction, we also identified 10 small RNAs, 62 anti-sense RNAs, four 5M-bM-^@M-^YUTRs and 7 intergenic elements as likely to be involved in the iron regulatory network. Hence, our genome-wide profiling results indicate an unprecedented complexity in the iron-related regulatory network of cyanobacteria. We monitored iron limitation stress induced gene expression changes in the cyanobacterial model organism Synechocystis sp. PCC 6803. We included a control sample without iron-stress (0h) and 5 samples from timepoints after stress induction (3h, 12h, 24h, 48h, 72h). Each timepoint was sampled from two independent biological replicates.

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MS2-affinity purification coupled with RNA sequencing (MAPS) reveals S. aureus IsrR sRNA targetome

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