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DNA Demethylation in the Processes of Repair and Epigenetic Regulation Performed by 2-Ketoglutarate-Dependent DNA Dioxygenases.

ABSTRACT: Site-specific DNA methylation plays an important role in epigenetic regulation of gene expression. Chemical methylation of DNA, including the formation of various methylated nitrogenous bases, leads to the formation of genotoxic modifications that impair DNA functions. Despite the fact that different pathways give rise to methyl groups in DNA, the main pathway for their removal is oxidative demethylation, which is catalyzed by nonheme Fe(II)/α-ketoglutarate-dependent DNA dioxygenases. DNA dioxygenases share a common catalytic mechanism of the oxidation of the alkyl groups on nitrogenous bases in nucleic acids. This review presents generalized data on the catalytic mechanism of action of DNA dioxygenases and on the participation of typical representatives of this superfamily, such as prokaryotic enzyme AlkB and eukaryotic enzymes ALKBH1-8 and TET1-3, in both processes of direct repair of alkylated DNA adducts and in the removal of an epigenetic mark (5-methylcytosine).

SUBMITTER: Kuznetsov NA

PROVIDER: S-EPMC8508711 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Butyrate Inhibits Indices of Colorectal Carcinogenesis via Enhancing α-Ketoglutarate-Dependent DNA Demethylation of Mismatch Repair Genes.

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Project description:The Reproducibility Project: Cancer Biology seeks to address growing concerns about reproducibility in scientific research by conducting replications of selected experiments from a number of high-profile papers in the field of cancer biology. The papers, which were published between 2010 and 2012, were selected on the basis of citations and Altmetric scores (Errington et al., 2014). This Registered report describes the proposed replication plan of key experiments from 'Oncometabolite 2-hydroxyglutarate is a competitive inhibitor of ?-ketoglutarate-dependent dioxygenases' by Xu and colleagues, published in Cancer Cell in 2011 (Xu et al., 2011). The key experiments being replicated include Supplemental Figure 3I, which demonstrates that transfection with mutant forms of IDH1 increases levels of 2-hydroxyglutarate (2-HG), Figures 3A and 8A, which demonstrate changes in histone methylation after treatment with 2-HG, and Figures 3D and 7B, which show that mutant IDH1 can effect the same changes as treatment with excess 2-HG. The Reproducibility Project: Cancer Biology is a collaboration between the Center for Open Science and Science Exchange, and the results of the replications will be published by eLife.

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Project description:The methylation of cytosine and subsequent oxidation constitutes a fundamental epigenetic modification in mammalian genomes, and its abnormalities are intimately coupled to various pathogenic processes including cancer development. Enzymes of the Ten-eleven translocation (TET) family catalyze the stepwise oxidation of 5-methylcytosine in DNA to 5-hydroxymethylcytosine and further oxidation products. These oxidized 5-methylcytosine derivatives represent intermediates in the reversal of cytosine methylation, and also serve as stable epigenetic modifications that exert distinctive regulatory roles. It is becoming increasingly obvious that TET proteins and their catalytic products are key regulators of embryonic development, stem cell functions and lineage specification. Over the past several years, the function of TET proteins as a barrier between normal and malignant states has been extensively investigated. Dysregulation of TET protein expression or function is commonly observed in a wide range of cancers. Notably, TET loss-of-function is causally related to the onset and progression of hematologic malignancy in vivo. In this review, we focus on recent advances in the mechanistic understanding of DNA methylation-demethylation dynamics, and their potential regulatory functions in cellular differentiation and oncogenic transformation.

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Project description:Several nucleoside antibiotics from various actinomycetes contain a high-carbon sugar nucleoside that is putatively derived via C-5'-modification of the canonical nucleoside. Two prominent examples are the 5'-C-carbamoyluridine- and 5'-C-glycyluridine-containing nucleosides, both families of which were discovered using screens aimed at finding inhibitors of bacterial translocase I involved in the assembly of the bacterial peptidoglycan cell wall. A shared open reading frame was identified whose gene product is similar to enzymes of the nonheme, Fe(II)-, and ?-ketoglutarate-dependent dioxygenases. The enzyme LipL from the biosynthetic pathway for A-90289, a 5'-C-glycyluridine-containing nucleoside, was functionally characterized as an UMP:?-ketoglutarate dioxygenase, providing the enzymatic imperative for the generation of a nucleoside-5'-aldehdye that serves as a downstream substrate for an aldol or aldol-type reaction leading to the high-carbon sugar scaffold. The functional assignment of LipL and the homologous enzymes-including bioinformatic analysis, iron detection and quantification, and assay development for biochemical characterization-is presented herein.

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Electronic structure analysis of the oxygen-activation mechanism by Fe(II)- and ?-ketoglutarate (?KG)-dependent dioxygenases.

Project description:?-Ketoglutarate (?KG)-dependent nonheme iron enzymes utilize a high-spin (HS) ferrous center to couple the activation of oxygen to the decarboxylation of the cosubstrate ?KG to yield succinate and CO(2), and to generate a high-valent ferryl species that then acts as an oxidant to functionalize the target C-H bond. Herein a detailed analysis of the electronic-structure changes that occur in the oxygen activation by this enzyme was performed. The rate-limiting step, which is identical on the septet and quintet surfaces, is the nucleophilic attack of the distal O atom of the O(2) adduct on the carbonyl group in ?KG through a bicyclic transition state ((5, 7) TS1). Due to the different electronic structures in (5, 7) TS1, the decay of (7)TS1 leads to a ferric oxyl species, which undergoes a rapid intersystem crossing to form the ferryl intermediate. By contrast, a HS ferrous center ligated by a peroxosuccinate is obtained on the quintet surface following (5)TS1. Thus, additional two single-electron transfer steps are required to afford the same Fe(IV)-oxo species. However, the triplet reaction channel is catalytically irrelevant. The biological role of ?KG played in the oxygen-activation reaction is dual. The ?KG LUMO (C=O ?*) serves as an electron acceptor for the nucleophilic attack of the superoxide monoanion. On the other hand, the ?KG HOMO (C1-C2 ?) provides the second and third electrons for the further reduction of the superoxide. In addition to density functional theory, high-level ab initio calculations have been used to calculate the accurate energies of the critical points on the alternative potential-energy surfaces. Overall, the results delivered by the ab initio calculations are largely parallel to those obtained with the B3LYP density functional, thus lending credence to our conclusions.

| S-EPMC3955955 | biostudies-literature

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