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The UzcRS two-component system integrates regulatory input from a diverse set of auxiliary regulators

ABSTRACT: The UzcRS two-component system in Caulobacter crescentus functions as a global activator of an extracytoplasmic stress response pathway and is induced by the metals U, Zn and Cu. Unexpectedly, a screen for mutations that affected the activity of the UzcR-regulated urcA promoter (PurcA) revealed four previously uncharacterized proteins whose inactivation led to metal-independent induction of PurcA. Using molecular genetics and functional genomics, we found that these auxiliary regulators regulate PurcA expression by modulating the activity of UzcRS through distinct mechanisms. The membrane protein UzcX, whose expression is positively regulated by UzcR, forms a regulatory complex with UzcS, providing a mechanism of feedback inhibition within the UzcRS circuit. UrtAP, an ABC transporter with a periplasmic metallo-aminopeptidase domain, negatively regulates UzcRS activity and antagonizes metal dependent stimulation by virtue of its enzymatic activity. Lastly, two MarR family transcription factors, MarR1 and MarR2, synergistically regulate UzcRS activity by repressing the expression of the membrane proteins UzcY and UzcZ, respectively, which function as UzcRS activators. In addition to modulating basal UzcRS activity, UzcY and UzcZ enhance the U/Zn/Cu sensitivity of UzcRS, shifting its responsiveness to more environmentally-relevant metal concentrations. Collectively, these data suggest that UzcRS functions as the core-signaling unit within a multicomponent signal transduction pathway that includes an unusually diverse set of auxiliary regulators.

ORGANISM(S): Caulobacter vibrioides

PROVIDER: GSE108075 | GEO | 2018/02/20

REPOSITORIES: GEO

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Project description:Thermococcus gammatolerans, the most radioresistant archaeon known to date, is an anaerobic and hyperthermophilic sulfur-reducing organism living in deep-sea hydrothermal vents. Knowledge of mechanisms underlying archaeal metal tolerance in such metal-rich ecosystem is still poorly documented. We showed that T. gammatolerans exhibits high resistance to cadmium (Cd), cobalt (Co) and zinc (Zn), a weaker tolerance to nickel (Ni), copper (Cu) and arsenate (AsO4) and that cells exposed to 1mM Cd exhibit a cellular Cd concentration of 67µM. A time-dependent transcriptomic analysis using microarrays was performed at a non-toxic (100μM) and a toxic (1mM) Cd dose. The reliability of microarray data was strengthened by real time RT-PCR validations. Altogether, 114 Cd responsive genes were revealed and a substantial subset of genes is related to metal homeostasis, drug detoxification, re-oxidization of cofactors and ATP production. This first genome-wide expression profiling study of archaeal cells challenged with Cd showed that T. gammatolerans withstands induced stress through pathways observed in both prokaryotes and eukaryotes but also through new and original strategies. T. gammatolerans cells challenged with 1mM Cd basically promote: 1) the induction of several transporter/permease encoding genes, probably to detoxify the cell; 2) the upregulation of Fe transporters encoding genes to likely compensate Cd damages in iron-containing proteins; 3) the induction of membrane-bound hydrogenase (Mbh) and membrane-bound hydrogenlyase (Mhy2) subunits encoding genes involved in recycling reduced cofactors and/or in proton translocation for energy production. By contrast to other organisms, redox homeostasis genes appear constitutively expressed and only a few genes encoding DNA repair proteins are regulated. We compared the expression of 27 Cd responsive genes in other stress conditions (Zn, Ni, heat shock, γ-rays), and showed that the Cd transcriptional pattern is comparable to other metal stress transcriptional responses (Cd, Zn, Ni) but not to a general stress response.

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The UzcRS two-component system integrates regulatory input from a diverse set of auxiliary regulators

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