scholarly journals Conservation in the Iron Responsive Element Family

Genes ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1365
Author(s):  
Karl Volz
Keyword(s):  
Translational Control ◽  
Tertiary Structure ◽  
Stem Loop ◽  
Iron Regulatory Proteins ◽  
Iron Responsive Element ◽  
Responsive Element ◽  
Iron Responsive Elements ◽  
Irp1 And Irp2 ◽  
Family Membership ◽  
Secondary And Tertiary Structure

Iron responsive elements (IREs) are mRNA stem-loop targets for translational control by the two iron regulatory proteins IRP1 and IRP2. They are found in the untranslated regions (UTRs) of genes that code for proteins involved in iron metabolism. There are ten “classic” IRE types that define the conserved secondary and tertiary structure elements necessary for proper IRP binding, and there are 83 published “IRE-like” sequences, most of which depart from the established IRE model. Here are structurally-guided discussions regarding the essential features of an IRE and what is important for IRE family membership.

scholarly journals Hereditary Hyperferritinemia-Cataract Syndrome Caused by a 29-Base Pair Deletion in the Iron Responsive Element of Ferritin L-Subunit Gene

Blood ◽  
1997 ◽  
Vol 90 (5) ◽  
pp. 2084-2088 ◽  
Author(s):  
Domenico Girelli ◽  
Roberto Corrocher ◽  
Luigi Bisceglia ◽  
Oliviero Olivieri ◽  
Leopoldo Zelante ◽  
...  
Keyword(s):  
Base Pair ◽  
Genetic Disorder ◽  
Dna Amplification ◽  
Negative Control ◽  
Stem Loop ◽  
Iron Regulatory Proteins ◽  
Iron Responsive Element ◽  
Ferritin Synthesis ◽  
Base Pair Deletion ◽  
Responsive Element

Abstract Iron availability regulates ferritin synthesis posttranscriptionally by the interaction between iron-regulatory proteins (IRPs) and an iron responsive element (IRE), a stem-loop sequence located on the 5′ untranslated region of ferritin mRNA. IRPs recognize IREs as a sequence/structure motif, blocking ferritin translation. Recently, we and others independently described families with a combination of hyperferritinemia (serum L-ferritin ≥ 1,000 μg/L, without iron overload) and congenital bilateral cataract, transmitted as an autosomal-dominant trait. The molecular basis were two distinct point mutations in the highly conserved CAGUG(X) hexaloop of L-ferritin IRE on chromosome 19. A new three-generation family with a similar phenotype and a unique genotype is here reported. DNA amplification by polymerase chain reaction and sequence analysis showed a 29-base pair deletion in the L-ferritin IRE, involving the whole 5′ sequence essential to the base pairing of the IRE stem. This deletion is predicted to cause the disruption of IRE stem-loop secondary structure and the nearly complete abolition of the negative control of ferritin synthesis by IRE/IRP binding. Hereditary Hyperferritinemia-Cataract Syndrome (HHCS) appears as a new genetic disorder with a unique phenotype associated with at least four different mutations in the L-ferritin IRE. Hematologists should take into account HHCS in the differential diagnosis of unexplained hyperferritinemia.

scholarly journals Relevance of the iron-responsive element (IRE) pseudotriloop structure for IRP1/2 binding and validation of IRE-like structures using the yeast three-hybrid system

2019 ◽  
Author(s):  
Shih-Cheng Chen ◽  
René C.L. Olsthoorn
Keyword(s):  
Mutational Analysis ◽  
Binding Modes ◽  
Rna Structures ◽  
Stem Loop ◽  
Aminolevulinate Synthase ◽  
Iron Responsive Element ◽  
Bona Fide ◽  
Responsive Element ◽  
Iron Responsive Elements ◽  
Post Transcriptional Regulation

AbstractIron-responsive-elements (IREs) are ~35-nucleotide (nt) stem-loop RNA structures located in 5′ or 3′ untranslated regions (UTRs) of mRNAs, and mediate post-transcriptional regulation by their association with IRE-binding proteins (IRPs). IREs are characterized by their apical 6-nt loop motif 5′-CAGWGH-3′ (W = A or U and H= A, C or U), the so-called pseudotriloop, of which the loop nts C1 and G5 are paired, and the none-paired C between the two stem regions. In this study, the yeast three-hybrid (Y3H) system was used to investigate the relevance of the pseudotriloop structure of ferritin light chain (FTL) for the IRE-IRP interaction and the binding affinities between variant IRE(-like) structures and the two IRP isoforms, IRP1 and 2. Mutational analysis of FTL IRE showed that deletion of the bulged-out U6 of the pseudotriloop does not significantly affect its binding to either IRP1 or 2, but substitution with C enhances binding of both IRPs. In addition, IRP1 was found more sensitive toward changes in the pseudotriloop-stabilizing C1-G5 base pair than IRP2, while mutation of the conserved G3 was lowering the binding of both IRPs. In comparison to FTL IRE other variant IREs, IRE of 5′-aminolevulinate synthase 2 (ALAS2), SLC40A1 (also known as Ferroportin-1), and endothelial PAS domain protein 1 (EPAS1) mRNA showed slightly higher, similar, and slightly weaker affinity for IRPs, respectively, while SLC11A2 IRE exhibited very weak binding to IRP1 and medium binding to IRP2, indicating the different binding modes of IRP1 and 2. Notably, α-Synuclein IRE showed no detectable binding to either IRP1 or 2. Our results indicate that Y3H represents a bona fide system to characterize binding between IRPs and various IRE-like structures.

Regulation of interaction of the iron-responsive element binding protein with iron-responsive RNA elements

1989 ◽  
Vol 9 (11) ◽  
pp. 5055-5061
Author(s):  
D J Haile ◽  
M W Hentze ◽  
T A Rouault ◽  
J B Harford ◽  
R D Klausner
Keyword(s):  
Binding Protein ◽  
Reduced Form ◽  
Scatchard Analysis ◽  
Stem Loop ◽  
Lower Affinity ◽  
Translational Repressor ◽  
High Affinity ◽  
Iron Responsive Element ◽  
Responsive Element

The 5' untranslated region of the ferritin heavy-chain mRNA contains a stem-loop structure called an iron-responsive element (IRE), that is solely responsible for the iron-mediated control of ferritin translation. A 90-kilodalton protein, called the IRE binding protein (IRE-BP), binds to the IRE and acts as a translational repressor. IREs also explain the iron-dependent control of the degradation of the mRNA encoding the transferrin receptor. Scatchard analysis reveals that the IRE-BP exists in two states, each of which is able to specifically interact with the IRE. The higher-affinity state has a Kd of 10 to 30 pM, and the lower affinity state has a Kd of 2 to 5 nM. The reversible oxidation or reduction of a sulfhydryl is critical to this switching, and the reduced form is of the higher affinity while the oxidized form is of lower affinity. The in vivo rate of ferritin synthesis is correlated with the abundance of the high-affinity form of the IRE-BP. In lysates of cells treated with iron chelators, which decrease ferritin biosynthesis, a four- to fivefold increase in the binding activity is seen and this increase is entirely caused by an increase in high-affinity binding sites. In desferrioxamine-treated cells, the high-affinity form makes up about 50% of the total IRE-BP, whereas in hemin-treated cells, the high-affinity form makes up less than 1%. The total amount of IRE-BP in the cytosol of cells is the same regardless of the prior iron treatment of the cell. Furthermore, a mutated IRE is not able to interact with the IRE-BP in a high-affinity form but only at a single lower affinity Kd of 0.7 nM. Its interaction with the IRE-BP is insensitive to the sulfhydryl status of the protein.

Cyclophosphamide induces a significant increase in iron content in the liver and spleen of mice

2020 ◽  
Vol 39 (7) ◽  
pp. 973-983
Author(s):  
Y Sheng ◽  
Y-J Chen ◽  
Z-M Qian ◽  
J Zheng ◽  
Y Liu
Keyword(s):  
Oxidative Stress ◽  
Iron Content ◽  
Related Factor ◽  
Iron Regulatory Proteins ◽  
Iron Responsive Element ◽  
Ferroportin 1 ◽  
Tissue Iron ◽  
Transferrin Receptor 1 ◽  
Responsive Element ◽  
Available Information

Objective: Oxidative stress is one of the major mechanisms of cyclophosphamide (CPX)-induced toxicities. However, it is unknown how CPX induces oxidative stress. Based on the available information, we speculated that CPX could increase iron content in the tissues and then induce oxidative stress. Method: We tested this hypothesis by investigating the effects of CPX on iron and ferritin contents, expression of transferrin receptor 1 (TfR1), ferroportin 1 (Fpn1), iron regulatory proteins (IRPs), hepcidin, and nuclear factor erythroid 2-related factor-2 (Nrf2) in the liver and spleen, and also on reticulocyte count, immature reticulocyte fraction, and hemoglobin (Hb) in the blood in c57/B6 mouse. Results: We demonstrated that CPX could induce a significant increase in iron contents and ferritin expression in the liver and spleen, notably inhibit erythropoiesis and Hb synthesis and lead to a reduction in iron usage. The reduced expression in TfR1 and Fpn1 is a secondary effect of CPX-induced iron accumulation in the liver and spleen and also partly associated with the suppressed IRP/iron-responsive element system, upregulation of hepcidin, and downregulation of Nrf2. Conclusions: The reduced iron usage is one of the causes for iron overload in the liver and spleen and the increased tissue iron might be one of the mechanisms for CPX to induce oxidative stress and toxicities.

Modulation of IRP Binding Activity by Oxygen in Primary Erythroid Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2662-2662
Author(s):  
Matthias Schranzhofer ◽  
Manfred Schifrer ◽  
Prem Ponka ◽  
Ernst W. Muellner
Keyword(s):  
Rna Binding ◽  
Rna Binding Proteins ◽  
Binding Activity ◽  
Ammonium Citrate ◽  
Ferric Ammonium Citrate ◽  
Erythroid Cells ◽  
Stem Loop ◽  
Iron Regulatory Proteins ◽  
Protein Levels ◽  
Irp1 And Irp2

Abstract Iron regulatory proteins 1 and 2 (IRP1 and IRP2) are cytoplasmic RNA-binding proteins that target specific stem-loop RNA structures known as iron responsive elements (IRE). Binding of IRPs to IREs inhibits translation of ferritin mRNA and stabilizes transferrin receptor (TfR) mRNA. Various factors have been reported to regulate binding activity of IRPs, such as iron, phosphorylation, nitric oxide and hypoxia. While there is a consistent agreement on the negative effect of iron on the interaction between IRPs and IREs, reports regarding the influence of hypoxia on the IRE-binding activity of IRPs vary in a species and cell specific manner. It was the aim of this work to study the effect of hypoxic (3% oxygen) and normoxic (20% oxygen) conditions on IRP binding activity in primary erythroid cells. The cells were induced for differentiation and incubated under physiological, low (Desferrioxamine) and high (ferric ammonium citrate) iron conditions. Binding activity of IRPs and protein levels of ferritin and TfR as well as cell proliferation and differentiation parameters were determined to analyze the regulation of iron metabolism during terminal differentiation. The data show, that in developing red blood cells binding activities of IRP1 and IRP2 are reduced at 3% oxygen. This reduction correlates with increased ferritin protein levels and decreased TfR protein levels. Moreover, incubation under hypoxia strongly decreased cell expansion and reduces hemoglobinization. These results suggest that terminal erythroid differentiation in the bone marrow might occur under normoxic rather than hypoxic conditions.

scholarly journals Novel Translational Control through an Iron-Responsive Element by Interaction of Multifunctional Protein YB-1 and IRP2

2002 ◽  
Vol 22 (18) ◽  
pp. 6375-6383 ◽  
Author(s):  
Megumi Ashizuka ◽  
Takao Fukuda ◽  
Takanori Nakamura ◽  
Kanemitsu Shirasuna ◽  
Kazuhiro Iwai ◽  
...  
Keyword(s):  
Translational Control ◽  
Ribosomal Proteins ◽  
Translational Regulation ◽  
Regulatory Protein ◽  
Direct Interaction ◽  
In Vitro Translation ◽  
High Concentration ◽  
Iron Responsive Element ◽  
Responsive Element

ABSTRACT The eukaryotic Y-box-binding protein YB-1 functions in various biological processes, including DNA repair, cell proliferation, and transcriptional and translational controls. To gain further insight into how human YB-1 plays its role in pleiotropic functions, we here used two-hybrid screenings to identify partners of this protein; the results showed that YB-1 itself, iron-regulatory protein 2 (IRP2), and five ribosomal proteins each served as partners to YB-1. We then examined the biological effect of the interaction of YB-1 and IRP2 on translational regulation. Both in vitro binding and coimmunoprecipitation assays showed the direct interaction of YB-1 and IRP2 in the presence of a high concentration of iron. RNA gel shift assays showed that YB-1 reduced the formation of the IRP2-mRNA complex when the iron-responsive element of the ferritin mRNA 5′ untranslated region (UTR) was used as a probe. By using an in vitro translation assay using luciferase mRNA ligated to the ferritin mRNA 5′UTR as a reporter construct, we showed that both YB-1 and IRP2 inhibited the translation of the mRNA. However, coadministration of YB-1 and IRP2 proteins abrogated the inhibition of protein synthesis by each protein. An In vivo coimmunoprecipitation assay showed that IRP2 bound to YB-1 in the presence of iron and a proteasome inhibitor. The direct interaction of YB-1 and IRP2 provides the first evidence of the involvement of YB-1 in the translational regulation of an iron-related protein.

scholarly journals Double-Gradient Denaturing Gradient Gel Electrophoresis Assay for Identification of L-Ferritin Iron-responsive Element Mutations Responsible for Hereditary Hyperferritinemia-Cataract Syndrome: Identification of the New Mutation C14G

2001 ◽  
Vol 47 (3) ◽  
pp. 491-497 ◽  
Author(s):  
Laura Cremonesi ◽  
Antonella Fumagalli ◽  
Nadia Soriani ◽  
Maurizio Ferrari ◽  
Sonia Levi ◽  
...  
Keyword(s):  
Serum Ferritin ◽  
Gel Electrophoresis ◽  
Denaturing Gradient Gel Electrophoresis ◽  
Direct Sequencing ◽  
Large Population ◽  
New Mutation ◽  
Stem Loop ◽  
Iron Responsive Element ◽  
Gradient Gel Electrophoresis ◽  
Responsive Element

Abstract Background: Hereditary hyperferritinemia-cataract syndrome is an autosomic dominant disorder caused by heterogeneous mutations on the iron-responsive element (IRE) of ferritin L-chain mRNA. The mutations described to date were identified by direct sequencing of DNA from probands with hyperferritinemia often associated to bilateral cataracts. A direct genetic approach on a large population is useful to recognize polymorphisms in the DNA region and the prevalence of mutations associated with minor increases in serum ferritin and subclinical cataracts. We developed a rapid DNA scanning technique to detect mutations in a single electrophoretic analysis. Methods: The double-gradient denaturing gradient gel electrophoresis (DG-DGGE) method consisted of PCR amplification of the target genomic DNA with GC-clamped oligonucleotides. The sequence encoded the 5′ untranslated flanking region of ferritin L-chain mRNA, which includes an IRE stem-loop structure. The product was subjected to DG-DGGE (8.5–15% polyacrylamide and 50–95% denaturant) to separate the homo- and heteroduplexes. Results: The method clearly identified all eight accessible mutations, including C-G transversions, which are the most difficult to detect. The method was applied to scan DNA samples from 50 healthy subjects and from 230 subjects with serum ferritin >400 μg/L. The new mutation G14C was identified. Conclusions: The DG-DGGE method detects all the mutations in the L-ferritin IRE sequence, is rapid and economical, and can be applied to scan large populations. The first population study indicated that the mutations are rare and may involve regions of the IRE structure not yet characterized.

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