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IscR of Rhodobacter sphaeroides functions as repressor of genes for iron-sulphur metabolism and represents a new type of iron-sulphur binding protein

ABSTRACT: Iron-sulphur (Fe-S) clusters are ensembles of iron and sulphide centres. They are found in all life forms and are important components of many enzymes involved in diverse cellular processes, including respiration, DNA synthesis or gene regulation. However, the increase in oxygen after the emergence of oxygenic photosynthesis created a threat to FeM-bM-^@M-^SS proteins and, consequently, to the organisms relying on them. Therefore, bacteria have evolved mechanisms to maintain a precise intracellular iron concentration. A major role of IscR in R. sphaeroides iron dependent regulation was suggested in a bioinformatic study , which predicted a binding site in the upstream regions of several iron uptake genes. Most known IscR proteins have Fe-S clusters featuring (Cys)3(His)1 ligation. However, IscR proteins from Rhodobacteraceae harbour only one Cys residue and it was considered unlikely that they can ligate an Fe-S cluster. In this study, the role of R. sphaeroides IscR as transcriptional regulator and sensor of the Fe-S cluster status of the cell was analysed. The results provide evidence that R. sphaeroides IscR functions as transcriptional repressor of genes involved in iron metabolism by binding to the predicted DNA binding motif. Furthermore, IscR possesses a unique Fe-S cluster ligation scheme with only a single cysteine involved. RNA samples collected from a control strain (wild type 2.4.1) and of the iscR deletion strain (2.4.1M-bM-^HM-^FiscR) were analyzed by two-color microarrays

ORGANISM(S): Rhodobacter sphaeroides 2.4.1

SUBMITTER: Gabriele Klug

PROVIDER: E-GEOD-65537 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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IscR of Rhodobacter sphaeroides functions as repressor of genes for iron-sulphur metabolism and represents a new type of iron-sulphur binding protein

Project description:Iron-sulphur (Fe-S) clusters are ensembles of iron and sulphide centres. They are found in all life forms and are important components of many enzymes involved in diverse cellular processes, including respiration, DNA synthesis or gene regulation. However, the increase in oxygen after the emergence of oxygenic photosynthesis created a threat to Fe–S proteins and, consequently, to the organisms relying on them. Therefore, bacteria have evolved mechanisms to maintain a precise intracellular iron concentration. A major role of IscR in R. sphaeroides iron dependent regulation was suggested in a bioinformatic study , which predicted a binding site in the upstream regions of several iron uptake genes. Most known IscR proteins have Fe-S clusters featuring (Cys)3(His)1 ligation. However, IscR proteins from Rhodobacteraceae harbour only one Cys residue and it was considered unlikely that they can ligate an Fe-S cluster. In this study, the role of R. sphaeroides IscR as transcriptional regulator and sensor of the Fe-S cluster status of the cell was analysed. The results provide evidence that R. sphaeroides IscR functions as transcriptional repressor of genes involved in iron metabolism by binding to the predicted DNA binding motif. Furthermore, IscR possesses a unique Fe-S cluster ligation scheme with only a single cysteine involved.

2015-02-03 | GSE65537 | GEO

E. coli monothiol glutaredoxin GrxD replenishes Fe-S clusters to the essential ErpA A-type carrier under low iron stress  

Project description:Iron-sulfur (Fe-S) clusters are required for essential biological pathways, including respiration and isoprenoid biosynthesis. Complex Fe-S cluster biogenesis systems have evolved to maintain an adequate supply of this critical protein cofactor. In Escherichia coli, two Fe-S biosynthetic systems, the “housekeeping” Isc and “stress responsive” Suf pathways, interface with a network of cluster trafficking proteins, such as ErpA, IscA, SufA, and NfuA. GrxD, a Fe-S cluster-binding monothiol glutaredoxin, also participates in Fe-S protein biogenesis in both prokaryotes and eukaryotes. Previous studies in E. coli showed that the ∆grxD mutation causes sensitivity to iron depletion, spotlighting a critical role for GrxD under conditions that disrupt Fe-S homeostasis. Here, we utilized a global chemoproteomic mass spectrometry (MS) approach to analyse the contribution of GrxD to the Fe-S proteome. Our results demonstrate that 1) GrxD is required for biogenesis of a specific subset of Fe-S proteins under iron-depleted conditions, 2) GrxD is required for cluster delivery to ErpA under iron limitation, 3) GrxD is functionally distinct from other Fe-S trafficking proteins and, 4) GrxD Fe-S cluster binding is responsive to iron limitation. All these results lead to the proposal that GrxD is required to maintain Fe-S cluster delivery to the essential trafficking protein ErpA during iron limitation conditions.

2024-07-13 | PXD053317 | Pride

Iron-Regulated Assembly of the Cytosolic Iron-Sulfur Cluster Biogenesis Machinery

Project description:The cytosolic iron-sulfur (Fe-S) cluster assembly (CIA) pathway delivers Fe-S clusters to nuclear and cytosolic Fe-S proteins involved in essential cellular functions. Although the delivery process is regulated by the availability of iron and oxygen, it remains unclear how CIA components orchestrate the cluster transfer under varying cellular environments. Here, we utilized a targeted proteomics assay for monitoring CIA factors and substrates to characterize the CIA machinery. We find that NUBP1 (NBP35), CIAO3 (NARFL) and CIA substrates associate with NUBP2 (CFD1), a component of the CIA scaffold complex. We also show that NUBP2 weakly associates with the CIA targeting complex (MMS19, CIAO1, CIAO2B) indicating the possible existence of a higher order complex. Interactions between CIAO3 and the CIA scaffold complex are strengthened upon iron supplementation or low oxygen tension, while iron chelation and reactive oxygen species weaken CIAO3 interactions with CIA components. We further demonstrate that CIAO3 mutants defective in Fe-S cluster binding fail to integrate into the higher order complexes. However, these mutants exhibit stronger associations with CIA substrates under conditions in which the association with the CIA targeting complex is reduced suggesting that CIAO3 and CIA substrates may associate in complexes independently of the CIA targeting complex. Together, our data suggest that CIA components potentially form a metabolon whose assembly is regulated by environmental cues and requires Fe-S cluster incorporation in CIAO3. These findings provide additional evidence that the CIA pathway adapts to changes in cellular environment through complex reorganization.

2022-06-06 | PXD033557 | panorama

Effect of small RNA RyhB on global iron use in Escherichia coli

Project description:RyhB is a non-coding RNA regulated by the Fur repressor. It has previously been shown to cause the rapid degradation of a number of mRNAs that encode proteins that utilize iron. Here we examine the effect of ectopic RyhB production on global gene expression by microarray analysis. Many of the previously identified targets were found, as well as other mRNAs encoding iron-binding proteins, bringing the total number of regulated operons to at least 18, encoding 56 genes. The two major operons involved in Fe-S cluster assembly showed different behavior; the isc operon appears to be a direct target of RyhB action, while the suf operon does not. This is consistent with previous findings suggesting that the suf genes but not the isc genes are important for Fe-S cluster synthesis under iron-limiting conditions, presumably for essential iron-binding proteins. In addition, we observed repression of Fur-regulated genes upon RyhB expression, interpreted as due to intracellular iron-sparing resulting from reduced synthesis of iron-binding proteins. Our results demonstrate the broad effects of a single non-coding RNA on iron homeostasis. Keywords: RNA degradation, iron stavation, RyhB small RNA, iron-using proteins

2005-08-31 | GSE3105 | GEO

Dynamic Assembly of the Cytosolic Iron-Sulfur Cluster Biogenesis Machinery Requires Iron-Sulfur Cluster Incorporation of CIAO3

Project description:Cytosolic iron-sulfur (Fe-S) cluster assembly (CIA) pathway delivers Fe-S clusters to nuclear and cytosolic Fe-S proteins involved in essential cellular functions. This delivery process is regulated by availability of iron and oxygen, but it remains unclear how CIA components orchestrate the cluster transfer under varying cellular environments. Here, we investigated the organization of CIA machinery under various conditions. We developed a targeted proteomics assay monitoring known CIA factors. Using this assay, we were able to detect NUBP1, CIAO3 and CIA substrates in immunoprecipitates of NUBP2, a component of the CIA scaffold complex. We also revealed that NUBP2 transiently associates with the CIA targeting complex (MMS19, CIAO1, CIAO2B), indicating the possible existence of CIA metabolons. We observed stronger interactions between CIAO3 and the CIA scaffold complex upon iron supplementation or low oxygen tension, while iron chelation and reactive oxygen species weaken CIAO3 interactions with CIA components. We further demonstrated that CIAO3 mutant with defective Fe-S cluster binding failed to integrate into the metabolons. However, these mutants unexpectedly exhibit stronger association with CIA substrates regardless of their reduced association with the CIA targeting complex, implicating that CIAO3 and CIA substrates may present in complexes independent of the CIA targeting complex. Together, our data suggested that CIA components potentially form metabolons whose assembly are regulated by environmental cues and require Fe-S cluster incorporation in CIAO3. These findings provided additional evidence that the CIA pathway adapts to changes in cellular environment through complex reorganization.

2021-11-16 | MSV000088394 | MassIVE

A pathogenic role for histone H3 copper reductase activity in a yeast model of Friedreich’s Ataxia

Project description:Disruptions to iron-sulfur (Fe-S) clusters, essential cofactors for a broad range of proteins, cause widespread cellular defects resulting in human disease. An underappreciated source of damage to Fe-S clusters are cuprous (Cu1+) ions. Since histone H3 enzymatically produces Cu1+ to support copper-dependent functions, we asked whether this activity could become detrimental to Fe-S clusters. Here, we report that histone H3-mediated Cu1+ toxicity is a major determinant of cellular functional pool of Fe-S clusters. Inadequate Fe-S cluster supply, either due to diminished assembly as occurs in Friedreich’s Ataxia or defective distribution, causes severe metabolic and growth defects in S. cerevisiae. Decreasing Cu1+ abundance, through attenuation of histone cupric reductase activity or depletion of total cellular copper, restored Fe-S cluster-dependent metabolism and growth. Our findings reveal a novel interplay between chromatin and mitochondria in Fe-S cluster homeostasis, and a potential pathogenic role for histone enzyme activity and Cu1+ in diseases with Fe-S cluster dysfunction.

2021-10-21 | ST001954 | MetabolomicsWorkbench

Expression of a dominant‐negative AtNEET‐H89C protein disrupts iron–sulfur metabolism and iron homeostasis in Arabidopsis

Project description:Iron–sulfur (Fe–S) clusters play an essential role in plants as protein cofactors mediating diverse electron transfer reactions. Because they can react with oxygen to form reactive oxygen species (ROS) and inflict cellular damage, the biogenesis of Fe–S clusters is highly regulated. A recently discovered group of 2Fe–2S proteins, termed NEET proteins, was proposed to coordinate Fe–S, Fe and ROS homeostasis in mammalian cells. Here we report that disrupting the function of AtNEET, the sole member of the NEET protein family in Arabidopsis thaliana, triggers leaf‐associated Fe–S‐ and Fe‐deficiency responses, elevated Fe content in chloroplasts (1.2–1.5‐fold), chlorosis, structural damage to chloroplasts and a high seedling mortality rate. Our findings suggest that disrupting AtNEET function disrupts the transfer of 2Fe–2S clusters from the chloroplastic 2Fe–2S biogenesis pathway to different cytosolic and chloroplastic Fe–S proteins, as well as to the cytosolic Fe–S biogenesis system, and that uncoupling this process triggers leaf‐associated Fe–S‐ and Fe‐deficiency responses that result in Fe over‐accumulation in chloroplasts and enhanced ROS accumulation. We further show that AtNEET transfers its 2Fe–2S clusters to DRE2, a key protein of the cytosolic Fe–S biogenesis system, and propose that the availability of 2Fe–2S clusters in the chloroplast and cytosol is linked to Fe homeostasis in plants.

2019-12-22 | GSE127300 | GEO

R. sphaeroides Δirr -Fe vs. R. sphaeroides Δirr +Fe under microaerobic conditions

Project description:Transcriptional profiling of R. sphaeroides Δirr under iron limitation (-Fe) compared to control R. sphaeroides Δirr under normal growth conditions (+Fe).

2011-11-09 | GSE33533 | GEO

Acclimation of oxygenic photosynthesis to iron starvation is controlled by the sRNA IsaR1 in cyanobacteria

Project description:Oxygenic photosynthesis contains multiple proteins that possess Fe2+ or Fe/S complexes as co-factors or prosthetic groups. Accordingly, its composition is heavily re-organized when iron becomes limiting as a nutrient factor, a situation that is frequently encountered in nature. However, the molecular mechanisms controlling the reorganization of the photosynthetic system upon iron deprivation have remained enigmatic. Here we show that the small regulatory RNA IsaR1 (Iron-stress activated RNA 1) plays a pivotal role in acclimation to low iron conditions. The transcription factor Fur cannot facilitate iron starvation dependent repression of it’s targets because it requires iron for DNA binding. We show that the Fur repressed sRNA IsaR1 fulfills this repressor function in iron homeostasis. The IsaR1 regulon consists of at least 15 direct targets, including Fe2+-containing proteins involved in photosynthetic electron transfer, the detoxification of anion radicals, citrate cycle, and in tetrapyrrole biogenesis. We demonstrate that IsaR1 is absolutely necessary to maintain physiological levels of Fe/S cluster biogenesis proteins during iron deprivation. Consequently, IsaR1 affects the acclimation of the photosynthetic apparatus to iron starvation at three levels: (i) directly, via posttranscriptional repression of gene expression and indirectly, (ii) via the suppression of Fe/S cluster co-factor and (iii) pigment biosynthesis. Homologs of IsaR1 are widely conserved throughout the cyanobacterial phylum. We conclude that IsaR1 is a riboregulator of central importance. These findings provide a new perspective for studies of the regulation of iron homeostasis in photosynthetic organisms.

2016-10-01 | GSE87496 | GEO

R. sphaeroides Δirr -Fe vs. R. sphaeroides Δirr +Fe under microaerobic conditions

Project description:Transcriptional profiling of R. sphaeroides Δirr under iron limitation (-Fe) compared to control R. sphaeroides Δirr under normal growth conditions (+Fe). Two strain experiment under normal iron (+Fe) and iron limitation (-Fe) conditions. 6 Biological replicates, independently grown and harvested at OD660=0,4; 1-3 pooled in replicate 1, 4-6 pooled in replicate 2

2011-11-09 | E-GEOD-33533 | biostudies-arrayexpress

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