Iron deprivation decreases ribonucleotide reductase activity and DNA synthesis

doi:10.1016/0024-3205(92)90572-7

Life Sciences

Volume 50, Issue 26, 1992, Pages 2059-2065

https://doi.org/10.1016/0024-3205(92)90572-7 Get rights and content

Abstract

The effects of the iron-chelator, desferrioxamine, and monoclonal antibodies against transferrin receptors of DNA synthesis and ribonucleotide reductase activity were examined in human leukemia K562 cells. Treatment of the cells with desferrioxamine resulted in decreases of ribonucleotide reductase activity, DNA synthesis, and cell growth. Exposure of the cells to anti-transferrin receptor antibody, $426$ , which blocks iron supplement into cells caused decreases of ribonucleotide reductase activity and DNA synthesis, in a parallel fashion. Decreases of ribonucleotide reductase activity and DNA synthesis by $426$ were restored by the addition of ferric nitriloacetate. These results indicate that ribonucleotide reductase activity is dependent on the iron-supply and also regulates cell proliferation.

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Iron is essential for deoxyribonucleotides production and for enzymes containing an Fe-S cluster involved in DNA replication and repair. How iron bioavailability and DNA metabolism are coordinated remains poorly understood. NCOA4 protein mediates autophagic degradation of ferritin to maintain iron homeostasis and inhibits DNA replication origin activation via hindrance of the MCM2-7 DNA helicase. Here, we show that iron deficiency inhibits DNA replication, parallel to nuclear NCOA4 stabilization. In iron-depleted cells, NCOA4 knockdown leads to unscheduled DNA synthesis, with replication stress, genome instability, and cell death. In mice, NCOA4 genetic inactivation causes defective intestinal regeneration upon dextran sulfate sodium-mediated injury, with DNA damage, defective cell proliferation, and cell death; in intestinal organoids, this is fostered by iron depletion. In summary, we describe a NCOA4-dependent mechanism that coordinates iron bioavailability and DNA replication. This function prevents replication stress, maintains genome integrity, and sustains high rates of cell proliferation during tissue regeneration.
Toxicity of the iron siderophore mycobactin J in mouse macrophages: Evidence for a hypoxia response
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Further searching reveals that 25 of the 38 genes have been linked to hypoxia (Table 2). This hypoxia-like response is a known effect of iron chelation, due to removal of catalytic iron from prolyl-4-hydroxylases (P4ha1, P4ha2, Egln1 and Egln3 in Fig. 3 and Table 2) [40a,41]. Under normal conditions, prolyl-hydroxylases utilize their catalytic iron centers to hydroxylate HIF-1α, which leads to HIF-1α degradation.
Mycobacterium tuberculosis, the causative agent of tuberculosis, is an obligate intracellular pathogen that lives within the phagosome of macrophages. Here we demonstrate that the siderophore mycobactin J, produced by the closely related intracellular pathogen Mycobacterium paratuberculosis, is toxic to murine macrophage cells. Its median lethal dose, 10 μM, is lower than that of the iron chelators desferrioxamine B and TrenCAM, an enterobactin analog. To determine the source of this toxicity, we conducted microarray, ELISA, and metabolite profiling experiments. The primary response is hypoxia-like, which implies iron starvation as the underlying cause of the toxicity. This observation is consistent with our recent finding that mycobactin J is a stronger iron chelator than had been inferred from previous studies. Mycobactin J is known to partition into cell membranes and hydrophobic organelles indicating that enhanced membrane penetration is also a likely factor. Thus, mycobactin J is shown to be toxic, eliciting a hypoxia-like response under physiological conditions.
Aneuploidy assessed by DNA index influences the effect of iron status on plasma and/or supernatant cytokine levels and progression of cells through the cell cycle in a mouse model
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Aneuploidy, a condition associated with altered chromosome number, hence DNA index, is frequently seen in many diseases including cancers and affects immunity. Iron, an essential nutrient for humans, modulates the immune function and the proliferation of normal and cancer cells. To determine whether impaired immunity seen in iron-deficient subjects may be related to aneuploidy, we measured spleen cell DNA index, percent of cells in different phases of the cell cycle, plasma and/or supernatant IL-2, IL-10, IL-12, and interferon-gamma in control, pair-fed, iron-deficient, and iron-replete mice (N = 20–22/group). The test and control diets differed only in iron content (0.09 mmol/kg versus 0.9 mmol/kg) and were fed for 68 days. Mean levels of hemoglobin and liver iron stores of iron-deficient and iron-replete mice were 40–60% lower than those of control and pair-fed mice (P < 0.05). Mean plasma levels of IL-10, interferon-gamma and percent of cells in S + G2/M phases were lower in mice with than in those without aneuploidy (P < 0.05). Lowest plasma IL-12 and interferon-gamma concentrations were observed in iron-deficient mice with aneuploidy. Mean percents of cultures with aneuploidy and DNA indexes were higher in iron-deficient and iron-replete than in control and pair-fed mice likely due to delayed cell division (P < 0.05). Aneuploidy decreased the concentration of IL-2 and interferon-gamma in baseline cultures while it increased that of interferon-gamma in anti-CD3 treated cultures. Aneuploidic indexes negatively correlated with cytokine levels, percents of cells in S + G2/M phases and indicators of iron status (P < 0.05). Although chromosome cytogenetics was not performed, for the first time, we report that increased aneuploidy rate may modulate the immune function during iron-deficiency.
When less is more: Novel mechanisms of iron conservation
2013, Trends in Endocrinology and Metabolism
Citation Excerpt :
A number of studies in humans and animals have revealed a link between reduced systemic iron and a vast array of gross physiologic abnormalities, including delayed development, reduced physical endurance and mental cognition, immune dysfunction, and impaired thermoregulation [5–7]. In addition to its well-recognized role in oxygen and carbon dioxide transport as a part of the hemoglobin molecule, iron serves as an essential cofactor for a number of critical enzymes that regulate virtually all aspects of cellular and whole-body physiology, including mitochondrial respiration and energy production [8], DNA replication and repair [9,10], protein and lipid biosynthesis [11,12], antioxidation and detoxification of foreign compounds [13,14], and more. Insufficient iron stores can potentially disrupt these processes, particularly in iron-rich tissues such as the brain, heart, and hematopoietic system.
Disorders of iron homeostasis are very common, yet the molecular mechanisms of iron regulation remain understudied. Over 20 years have passed since the first characterization of iron-regulatory proteins (IRP) as mediators of cellular iron-deficiency response in mammals through iron acquisition. However, little is known about other mechanisms necessary for adaptation to low-iron states. In this review, we present recent evidence that establishes the existence of a new iron-regulatory pathway aimed at iron conservation and optimization of iron use through suppression of nonessential iron-consuming processes. Moreover, we discuss the possible links between iron homeostasis and energy metabolism uncovered by studies of iron-deficiency response.
Iron and genome stability: An update
2012, Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis
Citation Excerpt :
Regarding nucleic acid metabolism, iron is a co-factor of ribonucleotide reductase [31], a DNA primase [32], a DNA glycosylase [26], a DNA endonuclease, an alkyltransferase [21] and DNA helicases [25]. Iron deprivation was shown to reduce ribonucleotide reductase activity, DNA synthesis and cell proliferation [31]. In certain DNA repair enzymes (XPD, FANCJ, MUTYH, NTHL1) Fe–S cluster seems to be involved in the recognition of DNA damage or in another functions [25].
Iron is an essential micronutrient which is required in a relatively narrow range for maintaining metabolic homeostasis and genome stability. Iron participates in oxygen transport and mitochondrial respiration as well as in antioxidant and nucleic acid metabolism. Iron deficiency impairs these biological pathways, leading to oxidative stress and possibly carcinogenesis. Iron overload has been linked to genome instability as well as to cancer risk increase, as seen in hereditary hemochromatosis. Iron is an extremely reactive transition metal that can interact with hydrogen peroxide to generate hydroxyl radicals that form the 8-hydroxy-guanine adduct, cause point mutations as well as DNA single and double strand breaks. Iron overload also induces DNA hypermethylation and can reduce telomere length. The current Recommended Dietary Allowances (RDA) for iron, according with Institute of Medicine Dietary Reference Intake (DRI), is based in the concept of preventing anemia, and ranges from 7 mg/day to 18 mg/day depending on life stage and gender. Pregnant women need 27 mg/day. The maximum safety level for iron intake, the Upper Level (UL), is 40–45 mg/day, based on the prevention of gastrointestinal distress associated to high iron intakes. Preliminary evidence indicates that 20 mg/day iron, an intake slightly higher than the RDA, may reduce the risk of gastrointestinal cancer in the elderly as well as increasing genome stability in lymphocytes of children and adolescents. Current dietary recommendations do not consider the concept of genome stability which is of concern because damage to the genome has been linked to the origin and progression of many diseases and is the most fundamental pathology. Given the importance of iron for homeostasis and its potential influence over genome stability and cancer it is recommended to conduct further studies that conclusively define these relationships.
Regulation of ribonucleotide reductase in response to iron deficiency
2011, Molecular Cell
Citation Excerpt :
Such a substitution is not possible in eukaryotes because the only RNR enzyme available fully depends on Fe as a cofactor. In mammals, a severe reduction in Fe bioavailability leads to significant decreases in RNR activity, dNTP pools, DNA synthesis, and consequently cell proliferation (Cavanaugh et al., 1985; Furukawa et al., 1992). Interestingly, in some cases RNR activity seems to be maintained or increased during the early stages of Fe deficiency (Furukawa et al., 1992), suggesting that cells may possess strategies to optimize the essential function of RNR over other less important Fe-using pathways when Fe becomes limiting.
Ribonucleotide reductase (RNR) is an essential enzyme required for DNA synthesis and repair. Although iron is necessary for class Ia RNR activity, little is known about the mechanisms that control RNR in response to iron deficiency. In this work, we demonstrate that yeast cells control RNR function during iron deficiency by redistributing the Rnr2-Rnr4 small subunit from the nucleus to the cytoplasm. Our data support a Mec1/Rad53-independent mechanism in which the iron-regulated Cth1/Cth2 mRNA-binding proteins specifically interact with the WTM1 mRNA in response to iron scarcity and promote its degradation. The resulting decrease in the nuclear-anchoring Wtm1 protein levels leads to the redistribution of the Rnr2-Rnr4 heterodimer to the cytoplasm, where it assembles as an active RNR complex and increases deoxyribonucleoside triphosphate levels. When iron is scarce, yeast selectively optimizes RNR function at the expense of other non-essential iron-dependent processes that are repressed, to allow DNA synthesis and repair.

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Iron deprivation decreases ribonucleotide reductase activity and DNA synthesis

Abstract

J. Biol. Chem.

Blood

Anal. Biochem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

Biochem. Biophys. Res. Commun.

Biochem. Pharmacol.

J. Biochem. (Tokyo)