Directed evolution reveals the mechanism of HitRS signaling transduction in Bacillus anthracis

Pi, Huifeng; Chu, Michelle; Ivan, Samuel J.; Latario, Casey J.; Toth, A.; Carlin, Sophia M.; Hillebrand, Gideon H; Lin, Hannah K.; Reppart, J.; Stauff, Devin L.; Skaar, Eric P.

doi:10.1371/journal.ppat.1009148

Cited by 7 publications

(2 citation statements)

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“…1). The relE gene encodes an mRNA endoribonuclease that, upon activation of HssRS by '882 or heme, cleaves mRNA resulting in cell death (38). Colonies obtained from this selection represent strains with mutations impairing their ability to activate HssRS-dependent signal sensing and gene activation (Fig.…”

Section: Identification Of Regulatory Factors Involved In Hssrs Signa...mentioning

confidence: 99%

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FapR regulates HssRS-mediated heme homeostasis inBacillus anthracis

Pi,

Carlin,

Beavers

et al. 2024

Preprint

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Bacillus anthracis, a Gram-positive facultative anaerobe and the causative agent of anthrax, multiplies to extraordinarily high numbers in vertebrate blood, resulting in considerable heme exposure. Heme is an essential nutrient and the preferred iron source for bacteria during vertebrate colonization, but its high redox potential makes it toxic in excess. To regulate heme homeostasis, many Gram-positive bacteria, includingB. anthracis, rely on the two-component signaling system HssRS. HssRS comprises the heme sensing histidine kinase HssS, which modulates the activity of the HssR transcription factor to enable bacteria to circumvent heme toxicity. However, the regulation of the HssRS system remains unclear. Here we identify FapR, the transcriptional regulator of fatty acid biosynthesis, as a key factor in HssRS function. FapR plays an important role in maintaining membrane integrity and the localization of the histidine kinase HssS. Specifically, disruption offapRleads to increased membrane rigidity, which hinders the penetration of HssRS inducers, resulting in the inactivation of HssRS. Furthermore, deletion offapRaffects the loading of HssS onto the cell membrane, compromising its heme sensing function and subsequently reducing endogenous heme biosynthesis. These findings shed light on the molecular mechanisms governing bacterial adaptation to heme stress and provide potential targets for antimicrobial intervention strategies.IMPORTANCEUnderstanding the mechanisms by whichB. anthracisregulates heme homeostasis is crucial for developing new strategies to combat anthrax, a serious disease affecting both humans and animals. This study uncovers the role of the transcriptional regulator FapR in maintaining membrane integrity and facilitating the proper function of the HssRS two-component signaling system, which is essential for managing heme toxicity inB. anthracis, as well as other Gram-positive pathogens. By elucidating the connection between FapR and HssRS, our findings provide new insights into the molecular adaptation of bacteria to heme stress and expand our knowledge of bacterial physiology and pathogenicity. More importantly, targeting the regulatory pathways involved in heme sensing and homeostasis presents a promising approach for developing novel therapeutics against anthrax and potentially other bacterial infections that rely on similar mechanisms.

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Section: Identification Of Regulatory Factors Involved In Hssrs Signa...mentioning

confidence: 99%

“…To isolate spontaneous suppressor mutants that inactivate HitRS signaling, we utilized a 2xRelE strain (bas3009::Phrt-relE bas4599::Phrt-relE) (38). The 2xRelE strain was streaked onto an LB agar plate and single colonies were grown in 5 ml LB amended with 50 µM '882 for 18 hours at 37°C with vigorous shaking.…”

Section: Genetic Selectionmentioning

confidence: 99%

FapR regulates HssRS-mediated heme homeostasis inBacillus anthracis

Pi,

Carlin,

Beavers

et al. 2024

Preprint

Self Cite

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Structural and biophysical characterization of the cytoplasmic domains of HprS kinase and its interactions with the cognate regulator HprR

Koczurowska,

Carrillo,

Alai

et al. 2025

Archives of Biochemistry and Biophysics

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An RNA-binding protein acts as a major post-transcriptional modulator in Bacillus anthracis

Weiss

Laut

et al. 2022

Nat Commun

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HitRS is a two-component system that responds to cell envelope damage in the human pathogen Bacillus anthracis. Here we identify an RNA-binding protein, KrrA, that regulates HitRS function by modulating the stability of the hitRS mRNA. In addition to hitRS, KrrA binds to over 70 RNAs and, directly or indirectly, affects the expression of over 150 genes involved in multiple processes, including genetic competence, sporulation, RNA turnover, DNA repair, transport, and cellular metabolism. KrrA does not exhibit detectable nuclease activity in vitro, and thus the mechanism by which it modulates mRNA stability remains unclear.

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Directed evolution reveals the mechanism of HitRS signaling transduction in Bacillus anthracis

Cited by 7 publications

References 60 publications

FapR regulates HssRS-mediated heme homeostasis inBacillus anthracis

FapR regulates HssRS-mediated heme homeostasis inBacillus anthracis

Structural and biophysical characterization of the cytoplasmic domains of HprS kinase and its interactions with the cognate regulator HprR

An RNA-binding protein acts as a major post-transcriptional modulator in Bacillus anthracis

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