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Montgomery T, Uh K, Lee K. TET enzyme driven epigenetic reprogramming in early embryos and its implication on long-term health. Front Cell Dev Biol 2024; 12:1358649. [PMID: 39149518 PMCID: PMC11324557 DOI: 10.3389/fcell.2024.1358649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Accepted: 07/23/2024] [Indexed: 08/17/2024] Open
Abstract
Mammalian embryo development is initiated by the union of paternal and maternal gametes. Upon fertilization, their epigenome landscape is transformed through a series of finely orchestrated mechanisms that are crucial for survival and successful embryogenesis. Specifically, maternal or oocyte-specific reprogramming factors modulate germ cell specific epigenetic marks into their embryonic states. Rapid and dynamic changes in epigenetic marks such as DNA methylation and histone modifications are observed during early embryo development. These changes govern the structure of embryonic genome prior to zygotic genome activation. Differential changes in epigenetic marks are observed between paternal and maternal genomes because the structure of the parental genomes allows interaction with specific oocyte reprogramming factors. For instance, the paternal genome is targeted by the TET family of enzymes which oxidize the 5-methylcytosine (5mC) epigenetic mark into 5-hydroxymethylcytosine (5hmC) to lower the level of DNA methylation. The maternal genome is mainly protected from TET3-mediated oxidation by the maternal factor, STELLA. The TET3-mediated DNA demethylation occurs at the global level and is clearly observed in many mammalian species. Other epigenetic modulating enzymes, such as DNA methyltransferases, provide fine tuning of the DNA methylation level by initiating de novo methylation. The mechanisms which initiate the epigenetic reprogramming of gametes are critical for proper activation of embryonic genome and subsequent establishment of pluripotency and normal development. Clinical cases or diseases linked to mutations in reprogramming modulators exist, emphasizing the need to understand mechanistic actions of these modulators. In addition, embryos generated via in vitro embryo production system often present epigenetic abnormalities. Understanding mechanistic actions of the epigenetic modulators will potentially improve the well-being of individuals suffering from these epigenetic disorders and correct epigenetic abnormalities in embryos produced in vitro. This review will summarize the current understanding of epigenetic reprogramming by TET enzymes during early embryogenesis and highlight its clinical relevance and potential implication for assisted reproductive technologies.
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Affiliation(s)
- Ty Montgomery
- Division of Animal Sciences, University of Missouri, Columbia, MO, United States
| | - Kyungjun Uh
- Futuristic Animal Resource and Research Center, Korea Research Institute of Bioscience and Biotechnology, Cheongju-si, Republic of Korea
| | - Kiho Lee
- Division of Animal Sciences, University of Missouri, Columbia, MO, United States
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2
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Meng WY, Wang ZX, Zhang Y, Hou Y, Xue JH. Epigenetic marks or not? The discovery of novel DNA modifications in eukaryotes. J Biol Chem 2024; 300:106791. [PMID: 38403247 PMCID: PMC11065753 DOI: 10.1016/j.jbc.2024.106791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2023] [Revised: 01/24/2024] [Accepted: 02/04/2024] [Indexed: 02/27/2024] Open
Abstract
DNA modifications add another layer of complexity to the eukaryotic genome to regulate gene expression, playing critical roles as epigenetic marks. In eukaryotes, the study of DNA epigenetic modifications has been confined to 5mC and its derivatives for decades. However, rapid developing approaches have witnessed the expansion of DNA modification reservoirs during the past several years, including the identification of 6mA, 5gmC, 4mC, and 4acC in diverse organisms. However, whether these DNA modifications function as epigenetic marks requires careful consideration. In this review, we try to present a panorama of all the DNA epigenetic modifications in eukaryotes, emphasizing recent breakthroughs in the identification of novel DNA modifications. The characterization of their roles in transcriptional regulation as potential epigenetic marks is summarized. More importantly, the pathways for generating or eliminating these DNA modifications, as well as the proteins involved are comprehensively dissected. Furthermore, we briefly discuss the potential challenges and perspectives, which should be taken into account while investigating novel DNA modifications.
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Affiliation(s)
- Wei-Ying Meng
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Tongji Hospital affiliated to Tongji University, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Zi-Xin Wang
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Tongji Hospital affiliated to Tongji University, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Yunfang Zhang
- Clinical and Translational Research Center of Shanghai First Maternity and Infant Hospital, Shanghai Key Laboratory of Signaling and Disease Research, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Yujun Hou
- Institute for Regenerative Medicine, Shanghai East Hospital, Shanghai Key Laboratory of Signaling and Disease Research, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China.
| | - Jian-Huang Xue
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Tongji Hospital affiliated to Tongji University, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai, China.
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3
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de Vries I, Ammerlaan D, Heidebrecht T, Celie PH, Geerke DP, Joosten RP, Perrakis A. Distant sequence regions of JBP1 contribute to J-DNA binding. Life Sci Alliance 2023; 6:e202302150. [PMID: 37328191 PMCID: PMC10276184 DOI: 10.26508/lsa.202302150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 06/05/2023] [Accepted: 06/06/2023] [Indexed: 06/18/2023] Open
Abstract
Base-J (β-D-glucopyranosyloxymethyluracil) is a modified DNA nucleotide that replaces 1% of thymine in kinetoplastid flagellates. The biosynthesis and maintenance of base-J depends on the base-J-binding protein 1 (JBP1) that has a thymidine hydroxylase domain and a J-DNA-binding domain (JDBD). How the thymidine hydroxylase domain synergizes with the JDBD to hydroxylate thymine in specific genomic sites, maintaining base-J during semi-conservative DNA replication, remains unclear. Here, we present a crystal structure of the JDBD including a previously disordered DNA-contacting loop and use it as starting point for molecular dynamics simulations and computational docking studies to propose recognition models for JDBD binding to J-DNA. These models guided mutagenesis experiments, providing additional data for docking, which reveals a binding mode for JDBD onto J-DNA. This model, together with the crystallographic structure of the TET2 JBP1-homologue in complex with DNA and the AlphaFold model of full-length JBP1, allowed us to hypothesize that the flexible JBP1 N-terminus contributes to DNA-binding, which we confirmed experimentally. Α high-resolution JBP1:J-DNA complex, which must involve conformational changes, would however need to be determined experimentally to further understand this unique underlying molecular mechanism that ensures replication of epigenetic information.
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Affiliation(s)
- Ida de Vries
- Oncode Institute and Division of Biochemistry, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Danique Ammerlaan
- Oncode Institute and Division of Biochemistry, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Tatjana Heidebrecht
- Oncode Institute and Division of Biochemistry, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Patrick Hn Celie
- Oncode Institute and Division of Biochemistry, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Daan P Geerke
- Department of Chemistry and Pharmaceutical Sciences, Amsterdam Institute of Molecular and Life Sciences (AIMMS) and Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Robbie P Joosten
- Oncode Institute and Division of Biochemistry, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Anastassis Perrakis
- Oncode Institute and Division of Biochemistry, Netherlands Cancer Institute, Amsterdam, The Netherlands
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4
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Zhang X, Zhang Y, Wang C, Wang X. TET (Ten-eleven translocation) family proteins: structure, biological functions and applications. Signal Transduct Target Ther 2023; 8:297. [PMID: 37563110 PMCID: PMC10415333 DOI: 10.1038/s41392-023-01537-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 05/24/2023] [Accepted: 06/05/2023] [Indexed: 08/12/2023] Open
Abstract
Ten-eleven translocation (TET) family proteins (TETs), specifically, TET1, TET2 and TET3, can modify DNA by oxidizing 5-methylcytosine (5mC) iteratively to yield 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxycytosine (5caC), and then two of these intermediates (5fC and 5caC) can be excised and return to unmethylated cytosines by thymine-DNA glycosylase (TDG)-mediated base excision repair. Because DNA methylation and demethylation play an important role in numerous biological processes, including zygote formation, embryogenesis, spatial learning and immune homeostasis, the regulation of TETs functions is complicated, and dysregulation of their functions is implicated in many diseases such as myeloid malignancies. In addition, recent studies have demonstrated that TET2 is able to catalyze the hydroxymethylation of RNA to perform post-transcriptional regulation. Notably, catalytic-independent functions of TETs in certain biological contexts have been identified, further highlighting their multifunctional roles. Interestingly, by reactivating the expression of selected target genes, accumulated evidences support the potential therapeutic use of TETs-based DNA methylation editing tools in disorders associated with epigenetic silencing. In this review, we summarize recent key findings in TETs functions, activity regulators at various levels, technological advances in the detection of 5hmC, the main TETs oxidative product, and TETs emerging applications in epigenetic editing. Furthermore, we discuss existing challenges and future directions in this field.
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Affiliation(s)
- Xinchao Zhang
- Department of Pathology, Ruijin Hospital and College of Basic Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Yue Zhang
- Department of Pathology, Ruijin Hospital and College of Basic Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Chaofu Wang
- Department of Pathology, Ruijin Hospital and College of Basic Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
| | - Xu Wang
- Department of Pathology, Ruijin Hospital and College of Basic Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
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5
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Peng Z, Ma J, Christov CZ, Karabencheva-Christova T, Lehnert N, Li D. Kinetic Studies on the 2-Oxoglutarate/Fe(II)-Dependent Nucleic Acid Modifying Enzymes from the AlkB and TET Families. DNA 2023; 3:65-84. [PMID: 38698914 PMCID: PMC11065319 DOI: 10.3390/dna3020005] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/05/2024]
Abstract
Nucleic acid methylations are important genetic and epigenetic biomarkers. The formation and removal of these markers is related to either methylation or demethylation. In this review, we focus on the demethylation or oxidative modification that is mediated by the 2-oxoglutarate (2-OG)/Fe(II)-dependent AlkB/TET family enzymes. In the catalytic process, most enzymes oxidize 2-OG to succinate, in the meantime oxidizing methyl to hydroxymethyl, leaving formaldehyde and generating demethylated base. The AlkB enzyme from Escherichia coli has nine human homologs (ALKBH1-8 and FTO) and the TET family includes three members, TET1 to 3. Among them, some enzymes have been carefully studied, but for certain enzymes, few studies have been carried out. This review focuses on the kinetic properties of those 2-OG/Fe(II)-dependent enzymes and their alkyl substrates. We also provide some discussions on the future directions of this field.
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Affiliation(s)
- Zhiyuan Peng
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
| | - Jian Ma
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
| | - Christo Z. Christov
- Department of Chemistry, Michigan Technological University, Houghton, MI 49931, USA
| | | | - Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, MI 48109, USA
| | - Deyu Li
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
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Del Moral-Morales A, Salgado-Albarrán M, Sánchez-Pérez Y, Wenke NK, Baumbach J, Soto-Reyes E. CTCF and Its Multi-Partner Network for Chromatin Regulation. Cells 2023; 12:1357. [PMID: 37408191 DOI: 10.3390/cells12101357] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/05/2023] [Accepted: 05/09/2023] [Indexed: 07/07/2023] Open
Abstract
Architectural proteins are essential epigenetic regulators that play a critical role in organizing chromatin and controlling gene expression. CTCF (CCCTC-binding factor) is a key architectural protein responsible for maintaining the intricate 3D structure of chromatin. Because of its multivalent properties and plasticity to bind various sequences, CTCF is similar to a Swiss knife for genome organization. Despite the importance of this protein, its mechanisms of action are not fully elucidated. It has been hypothesized that its versatility is achieved through interaction with multiple partners, forming a complex network that regulates chromatin folding within the nucleus. In this review, we delve into CTCF's interactions with other molecules involved in epigenetic processes, particularly histone and DNA demethylases, as well as several long non-coding RNAs (lncRNAs) that are able to recruit CTCF. Our review highlights the importance of CTCF partners to shed light on chromatin regulation and pave the way for future exploration of the mechanisms that enable the finely-tuned role of CTCF as a master regulator of chromatin.
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Affiliation(s)
- Aylin Del Moral-Morales
- Departamento de Ciencias Naturales, Universidad Autónoma Metropolitana-Cuajimalpa (UAM-C), Mexico City 05348, Mexico
- Institute for Computational Systems Biology, University of Hamburg, D-22607 Hamburg, Germany
| | - Marisol Salgado-Albarrán
- Departamento de Ciencias Naturales, Universidad Autónoma Metropolitana-Cuajimalpa (UAM-C), Mexico City 05348, Mexico
- Institute for Computational Systems Biology, University of Hamburg, D-22607 Hamburg, Germany
| | - Yesennia Sánchez-Pérez
- Subdirección de Investigación, Instituto Nacional de Cancerología, Mexico City 14080, Mexico
| | - Nina Kerstin Wenke
- Institute for Computational Systems Biology, University of Hamburg, D-22607 Hamburg, Germany
| | - Jan Baumbach
- Institute for Computational Systems Biology, University of Hamburg, D-22607 Hamburg, Germany
- Computational BioMedicine Lab., University of Southern Denmark, DK-5230 Odense, Denmark
| | - Ernesto Soto-Reyes
- Departamento de Ciencias Naturales, Universidad Autónoma Metropolitana-Cuajimalpa (UAM-C), Mexico City 05348, Mexico
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7
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Behind Base J: The Roles of JBP1 and JBP2 on Trypanosomatids. Pathogens 2023; 12:pathogens12030467. [PMID: 36986389 PMCID: PMC10057400 DOI: 10.3390/pathogens12030467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 03/08/2023] [Accepted: 03/08/2023] [Indexed: 03/18/2023] Open
Abstract
β-D-glucopyranosyloxymethiluracil (Base J) is a modified thymidine base found in kinetoplastids and some related organisms. Interestingly, Base J distribution into the genome can vary depending on the organism and its life stage. Base J is reported to be found mostly at telomeric repeats, on inactive variant surface glycoproteins (VSG’s) expression sites (e.g., T. brucei), in RNA polymerase II termination sites and sub-telomeric regions (e.g., Leishmania). This hypermodified nucleotide is synthesized in two steps with the participation of two distinct thymidine hydroxylases, J-binding protein 1 and 2 (JBP1 and JBP2, respectively) and a β-glucosyl transferase. A third J-binding protein, named JBP3, was recently identified as part of a multimeric complex. Although its structural similarities with JBP1, it seems not to be involved in J biosynthesis but to play roles in gene expression regulation in trypanosomatids. Over the years, with the characterization of JBP1 and JBP2 mutant lines, Base J functions have been targeted and shone a light on that matter, showing genus-specific features. This review aims to explore Base J’s reported participation as a regulator of RNA polymerase II transcription termination and to summarize the functional and structural characteristics and similarities of the remarkable JBP proteins in pathogenic trypanosomatids.
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Epigenetic Modification of Cytosines in Hematopoietic Differentiation and Malignant Transformation. Int J Mol Sci 2023; 24:ijms24021727. [PMID: 36675240 PMCID: PMC9863985 DOI: 10.3390/ijms24021727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Revised: 01/13/2023] [Accepted: 01/13/2023] [Indexed: 01/18/2023] Open
Abstract
The mammalian DNA methylation landscape is established and maintained by the combined activities of the two key epigenetic modifiers, DNA methyltransferases (DNMT) and Ten-eleven-translocation (TET) enzymes. Once DNMTs produce 5-methylcytosine (5mC), TET proteins fine-tune the DNA methylation status by consecutively oxidizing 5mC to 5-hydroxymethylcytosine (5hmC) and further oxidized derivatives. The 5mC and oxidized methylcytosines are essential for the maintenance of cellular identity and function during differentiation. Cytosine modifications with DNMT and TET enzymes exert pleiotropic effects on various aspects of hematopoiesis, including self-renewal of hematopoietic stem/progenitor cells (HSPCs), lineage determination, differentiation, and function. Under pathological conditions, these enzymes are frequently dysregulated, leading to loss of function. In particular, the loss of DNMT3A and TET2 function is conspicuous in diverse hematological disorders, including myeloid and lymphoid malignancies, and causally related to clonal hematopoiesis and malignant transformation. Here, we update recent advances in understanding how the maintenance of DNA methylation homeostasis by DNMT and TET proteins influences normal hematopoiesis and malignant transformation, highlighting the potential impact of DNMT3A and TET2 dysregulation on clonal dominance and evolution of pre-leukemic stem cells to full-blown malignancies. Clarification of the normal and pathological functions of DNA-modifying epigenetic regulators will be crucial to future innovations in epigenetic therapies for treating hematological disorders.
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Structure and Function of TET Enzymes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1389:239-267. [DOI: 10.1007/978-3-031-11454-0_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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10
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Role of chromatin modulation in the establishment of protozoan parasite infection for developing targeted chemotherapeutics. THE NUCLEUS 2021. [DOI: 10.1007/s13237-021-00356-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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11
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Reversal of nucleobase methylation by dioxygenases. Nat Chem Biol 2020; 16:1160-1169. [DOI: 10.1038/s41589-020-00675-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Accepted: 09/11/2020] [Indexed: 12/12/2022]
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Kieft R, Zhang Y, Marand AP, Moran JD, Bridger R, Wells L, Schmitz RJ, Sabatini R. Identification of a novel base J binding protein complex involved in RNA polymerase II transcription termination in trypanosomes. PLoS Genet 2020; 16:e1008390. [PMID: 32084124 PMCID: PMC7055916 DOI: 10.1371/journal.pgen.1008390] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 03/04/2020] [Accepted: 01/08/2020] [Indexed: 11/18/2022] Open
Abstract
Base J, β-D-glucosyl-hydroxymethyluracil, is a modification of thymine DNA base involved in RNA Polymerase (Pol) II transcription termination in kinetoplastid protozoa. Little is understood regarding how specific thymine residues are targeted for J-modification or the mechanism of J regulated transcription termination. To identify proteins involved in J-synthesis, we expressed a tagged version of the J-glucosyltransferase (JGT) in Leishmania tarentolae, and identified four co-purified proteins by mass spectrometry: protein phosphatase (PP1), a homolog of Wdr82, a potential PP1 regulatory protein (PNUTS) and a protein containing a J-DNA binding domain (named JBP3). Gel shift studies indicate JBP3 is a J-DNA binding protein. Reciprocal tagging, co-IP and sucrose gradient analyses indicate PP1, JGT, JBP3, Wdr82 and PNUTS form a multimeric complex in kinetoplastids, similar to the mammalian PTW/PP1 complex involved in transcription termination via PP1 mediated dephosphorylation of Pol II. Using RNAi and analysis of Pol II termination by RNA-seq and RT-PCR, we demonstrate that ablation of PNUTS, JBP3 and Wdr82 lead to defects in Pol II termination at the 3'-end of polycistronic gene arrays in Trypanosoma brucei. Mutants also contain increased antisense RNA levels upstream of transcription start sites, suggesting an additional role of the complex in regulating termination of bi-directional transcription. In addition, PNUTS loss causes derepression of silent Variant Surface Glycoprotein genes involved in host immune evasion. Our results suggest a novel mechanistic link between base J and Pol II polycistronic transcription termination in kinetoplastids.
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Affiliation(s)
- Rudo Kieft
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Yang Zhang
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Alexandre P. Marand
- Department of Genetics, University of Georgia, Athens, Georgia, United States of America
| | - Jose Dagoberto Moran
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Robert Bridger
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Lance Wells
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Robert J. Schmitz
- Department of Genetics, University of Georgia, Athens, Georgia, United States of America
| | - Robert Sabatini
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
- * E-mail:
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14
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LIO CHANWANGJ, YUE XIAOJING, LÓPEZ-MOYADO ISAACF, TAHILIANI MAMTA, ARAVIND L, RAO ANJANA. TET methylcytosine oxidases: new insights from a decade of research. J Biosci 2020; 45:21. [PMID: 31965999 PMCID: PMC7216820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In mammals, DNA methyltransferases transfer a methyl group from S-adenosylmethionine to the 5 position of cytosine in DNA. The product of this reaction, 5-methylcytosine (5mC), has many roles, particularly in suppressing transposable and repeat elements in DNA. Moreover, in many cellular systems, cell lineage specification is accompanied by DNA demethylation at the promoters of genes expressed at high levels in the differentiated cells. However, since direct cleavage of the C-C bond connecting the methyl group to the 5 position of cytosine is thermodynamically disfavoured, the question of whether DNA methylation was reversible remained unclear for many decades. This puzzle was solved by our discovery of the TET (Ten- Eleven Translocation) family of 5-methylcytosine oxidases, which use reduced iron, molecular oxygen and the tricarboxylic acid cycle metabolite 2-oxoglutarate (also known as a-ketoglutarate) to oxidise the methyl group of 5mC to 5-hydroxymethylcytosine (5hmC) and beyond. TET-generated oxidised methylcytosines are intermediates in at least two pathways of DNA demethylation, which differ in their dependence on DNA replication. In the decade since their discovery, TET enzymes have been shown to have important roles in embryonic development, cell lineage specification, neuronal function and cancer. We review these findings and discuss their implications here.
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Affiliation(s)
- CHAN-WANG J. LIO
- Division of Signaling and Gene Expression, La Jolla Institute for Immunology, La Jolla, CA 92037, USA
| | - XIAOJING YUE
- Division of Signaling and Gene Expression, La Jolla Institute for Immunology, La Jolla, CA 92037, USA
| | - ISAAC F. LÓPEZ-MOYADO
- Division of Signaling and Gene Expression, La Jolla Institute for Immunology, La Jolla, CA 92037, USA
- Bioinformatics and Systems Biology Graduate Program, University of California San Diego, La Jolla, CA 92093, USA
- Sanford Consortium for Regenerative Medicine, La Jolla, CA 92093, USA
| | - MAMTA TAHILIANI
- Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10012, USA
- Department of Biology, New York University, New York, NY 10003, USA
| | - L. ARAVIND
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20892, USA
| | - ANJANA RAO
- Division of Signaling and Gene Expression, La Jolla Institute for Immunology, La Jolla, CA 92037, USA
- Bioinformatics and Systems Biology Graduate Program, University of California San Diego, La Jolla, CA 92093, USA
- Sanford Consortium for Regenerative Medicine, La Jolla, CA 92093, USA
- Department of Pharmacology, University of California San Diego, La Jolla, CA 92093, USA
- Moores Cancer Center, University of California San Diego, La Jolla, CA 92093, USA
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15
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Adamopoulos A, Heidebrecht T, Roosendaal J, Touw WG, Phan IQ, Beijnen J, Perrakis A. The domain architecture of the protozoan protein J-DNA-binding protein 1 suggests synergy between base J DNA binding and thymidine hydroxylase activity. J Biol Chem 2019; 294:12815-12825. [PMID: 31292194 DOI: 10.1074/jbc.ra119.007393] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Revised: 07/04/2019] [Indexed: 11/06/2022] Open
Abstract
J-DNA-binding protein 1 (JBP1) contributes to the biosynthesis and maintenance of base J (β-d-glucosyl-hydroxymethyluracil), an epigenetic modification of thymidine (T) confined to pathogenic protozoa such as Trypanosoma and Leishmania JBP1 has two known functional domains: an N-terminal T hydroxylase (TH) homologous to the 5-methylcytosine hydroxylase domain in TET proteins and a J-DNA-binding domain (JDBD) that resides in the middle of JBP1. Here, we show that removing JDBD from JBP1 results in a soluble protein (Δ-JDBD) with the N- and C-terminal regions tightly associated together in a well-ordered structure. We found that this Δ-JDBD domain retains TH activity in vitro but displays a 15-fold lower apparent rate of hydroxylation compared with JBP1. Small-angle X-ray scattering (SAXS) experiments on JBP1 and JDBD in the presence or absence of J-DNA and on Δ-JDBD enabled us to generate low-resolution three-dimensional models. We conclude that Δ-JDBD, and not the N-terminal region of JBP1 alone, is a distinct folding unit. Our SAXS-based model supports the notion that binding of JDBD specifically to J-DNA can facilitate T hydroxylation 12-14 bp downstream on the complementary strand of the J-recognition site. We postulate that insertion of the JDBD module into the Δ-JDBD scaffold during evolution provided a mechanism that synergized J recognition and T hydroxylation, ensuring inheritance of base J in specific sequence patterns following DNA replication in kinetoplastid parasites.
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Affiliation(s)
- Athanassios Adamopoulos
- Department of Biochemistry, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Tatjana Heidebrecht
- Department of Biochemistry, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Jeroen Roosendaal
- Department of Clinical Pharmacology, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Wouter G Touw
- Department of Biochemistry, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Isabelle Q Phan
- Seattle Structural Genomics Center for Infectious Disease, Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, Washington 98109
| | - Jos Beijnen
- Department of Clinical Pharmacology, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Anastassis Perrakis
- Department of Biochemistry, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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16
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Flodman K, Tsai R, Xu MY, Corrêa IR, Copelas A, Lee YJ, Xu MQ, Weigele P, Xu SY. Type II Restriction of Bacteriophage DNA With 5hmdU-Derived Base Modifications. Front Microbiol 2019; 10:584. [PMID: 30984133 PMCID: PMC6449724 DOI: 10.3389/fmicb.2019.00584] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2019] [Accepted: 03/07/2019] [Indexed: 11/13/2022] Open
Abstract
To counteract bacterial defense systems, bacteriophages (phages) make extensive base modifications (substitutions) to block endonuclease restriction. Here we evaluated Type II restriction of three thymidine (T or 5-methyldeoxyuridine, 5mdU) modified phage genomes: Pseudomonas phage M6 with 5-(2-aminoethyl)deoxyuridine (5-NedU), Salmonella phage ViI (Vi1) with 5-(2-aminoethoxy)methyldeoxyuridine (5-NeOmdU) and Delftia phage phi W-14 (a.k.a. ΦW-14) with α-putrescinylthymidine (putT). Among >200 commercially available restriction endonucleases (REases) tested, phage M6, ViI, and phi W-14 genomic DNAs (gDNA) show resistance against 48.4, 71.0, and 68.8% of Type II restrictions, respectively. Inspection of the resistant sites indicates the presence of conserved dinucleotide TG or TC (TS, S=C, or G), implicating the specificity of TS sequence as the target that is converted to modified base in the genomes. We also tested a number of DNA methyltransferases (MTases) on these phage DNAs and found some MTases can fully or partially modify the DNA to confer more resistance to cleavage by REases. Phage M6 restriction fragments can be efficiently ligated by T4 DNA ligase. Phi W-14 restriction fragments show apparent reduced rate in E. coli exonuclease III degradation. This work extends previous studies that hypermodified T derived from 5hmdU provides additional resistance to host-encoded restrictions, in parallel to modified cytosines, guanine, and adenine in phage genomes. The results reported here provide a general guidance to use REases to map and clone phage DNA with hypermodified thymidine.
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Affiliation(s)
| | - Rebecca Tsai
- New England Biolabs, Inc., Ipswich, MA, United States
| | - Michael Y Xu
- New England Biolabs, Inc., Ipswich, MA, United States
| | - Ivan R Corrêa
- New England Biolabs, Inc., Ipswich, MA, United States
| | | | - Yan-Jiun Lee
- New England Biolabs, Inc., Ipswich, MA, United States
| | - Ming-Qun Xu
- New England Biolabs, Inc., Ipswich, MA, United States
| | - Peter Weigele
- New England Biolabs, Inc., Ipswich, MA, United States
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17
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Park SH, Suh SW, Song HK. A cytosine modification mechanism revealed by the structure of a ternary complex of deoxycytidylate hydroxymethylase from bacteriophage T4 with its cofactor and substrate. IUCRJ 2019; 6:206-217. [PMID: 30867918 PMCID: PMC6400193 DOI: 10.1107/s2052252518018274] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 12/24/2018] [Indexed: 06/09/2023]
Abstract
To protect viral DNA against the host bacterial restriction system, bacterio-phages utilize a special modification system - hydroxymethylation - in which dCMP hydroxymethylase (dCH) converts dCMP to 5-hydroxymethyl-dCMP (5hm-dCMP) using N5,N10-methylenetetrahydrofolate as a cofactor. Despite shared similarity with thymidylate synthase (TS), dCH catalyzes hydroxylation through an exocyclic methylene intermediate during the last step, which is different from the hydride transfer that occurs with TS. In contrast to the extensively studied TS, the hydroxymethylation mechanism of a cytosine base is not well understood due to the lack of a ternary complex structure of dCH in the presence of both its substrate and cofactor. This paper reports the crystal structure of the ternary complex of dCH from bacteriophage T4 (T4dCH) with dCMP and tetrahydrofolate at 1.9 Å resolution. The authors found key residues of T4dCH for accommodating the cofactor without a C-terminal tail, an optimized network of ordered water molecules and a hydrophobic gating mechanism for cofactor regulation. In combination with biochemical data on structure-based mutants, key residues within T4dCH and a substrate water molecule for hydroxymethylation were identified. Based on these results, a complete enzyme mechanism of dCH and signature residues that can identify dCH enzymes within the TS family have been proposed. These findings provide a fundamental basis for understanding the pyrimidine modification system.
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Affiliation(s)
- Si Hoon Park
- Department of Life Sciences, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - Se Won Suh
- Departments of Chemistry, Seoul National University, Kwanak-ro 1, Kwanak-gu, Seoul 08826, Republic of Korea
| | - Hyun Kyu Song
- Department of Life Sciences, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
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18
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Parker MJ, Weigele PR, Saleh L. Insights into the Biochemistry, Evolution, and Biotechnological Applications of the Ten-Eleven Translocation (TET) Enzymes. Biochemistry 2019; 58:450-467. [PMID: 30571101 DOI: 10.1021/acs.biochem.8b01185] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
A tight link exists between patterns of DNA methylation at carbon 5 of cytosine and differential gene expression in mammalian tissues. Indeed, aberrant DNA methylation results in various human diseases, including neurologic and immune disorders, and contributes to the initiation and progression of various cancers. Proper DNA methylation depends on the fidelity and control of the underlying mechanisms that write, maintain, and erase these epigenetic marks. In this Perspective, we address one of the key players in active demethylation: the ten-eleven translocation enzymes or TETs. These enzymes belong to the Fe2+/α-ketoglutarate-dependent dioxygenase superfamily and iteratively oxidize 5-methylcytosine (5mC) in DNA to produce 5-hydroxymethylcytosine, 5-formylcytosine, and 5-carboxycytosine. The latter three bases may convey additional layers of epigenetic information in addition to being intermediates in active demethylation. Despite the intense interest in understanding the physiological roles TETs play in active demethylation and cell regulation, less has been done, in comparison, to illuminate details of the chemistry and factors involved in regulating the three-step oxidation mechanism. Herein, we focus on what is known about the biochemical features of TETs and explore questions whose answers will lead to a more detailed understanding of the in vivo modus operandi of these enzymes. We also summarize the membership and evolutionary history of the TET/JBP family and highlight the prokaryotic homologues as a reservoir of potentially diverse functionalities awaiting discovery. Finally, we spotlight sequencing methods that utilize TETs for mapping 5mC and its oxidation products in genomic DNA and comment on possible improvements in these approaches.
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Affiliation(s)
- Mackenzie J Parker
- Research Department , New England Biolabs, Inc. , 240 County Road , Ipswich , Massachusetts 01938 , United States
| | - Peter R Weigele
- Research Department , New England Biolabs, Inc. , 240 County Road , Ipswich , Massachusetts 01938 , United States
| | - Lana Saleh
- Research Department , New England Biolabs, Inc. , 240 County Road , Ipswich , Massachusetts 01938 , United States
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19
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Ahmadian S, Eslami G, Fatahi A, Hosseini SS, Vakili M, Ajamein Fahadan V, Elloumi M. J- binding protein 1 and J- binding protein 2 expression in clinical Leishmania major no response-antimonial isolates. J Parasit Dis 2018; 43:39-45. [PMID: 30956444 DOI: 10.1007/s12639-018-1052-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Accepted: 11/07/2018] [Indexed: 12/12/2022] Open
Abstract
Cutaneous leishmaniasis (CL) is a major disease in many parts of the world. Since no vaccine has been developed, treatment is the best way to control it. In most areas, antimonial resistance whose mechanisms have not been completely understood has been reported. The main aim of this study is gene expression assessing of J-binging protein 1 and J-binding protein 2 in clinical Leishmania major isolates. The patients with CL from central and north Iran were considered for this study. The samples were transferred in RNAlater solution and stored in - 20 °C. RNA extraction and cDNA synthesis were performed. The gene expression analysis was done with SYBR Green real-time PCR using ∆∆CT. Written informed consent forms were filled out by patients, and then, information forms were filled out based on the Helsinki Declaration. Statistical analysis was done with SPSS (16.0; SPSS Inc, Chicago) using independent t test, Shapiro-Wilk, and Pearson's and Spearman's rank correlation coefficients. P ≤ 0.05 was considered significant. The gene expression of JBP1 and JBP2 had no relation with sex and age. The JBP1 gene expression was high in sensitive isolates obtained from north of the country. The JBP2 gene expression was significant in sensitive and no response-antimonial isolates from the north, but no significant differences were detected in sensitive and resistant isolates from central Iran. Differential gene expression of JBP1 and JBP2 in various clinical resistances isolates in different geographical areas shows multifactorial ways of developing resistance in different isolates.
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Affiliation(s)
- Salman Ahmadian
- 1Research Center for Food Hygiene and Safety, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
- 2Department of Parasitology and Mycology, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Gilda Eslami
- 1Research Center for Food Hygiene and Safety, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
- 2Department of Parasitology and Mycology, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Ali Fatahi
- 2Department of Parasitology and Mycology, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Saeede Sadat Hosseini
- 1Research Center for Food Hygiene and Safety, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Mahmoud Vakili
- 3Department of Community and Preventive Medicine, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Vahid Ajamein Fahadan
- 1Research Center for Food Hygiene and Safety, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
- 2Department of Parasitology and Mycology, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Mourad Elloumi
- 4Laboratory of Technologies of Information and Communication and Electrical Engineering (LaTICE), University of Tunis, Tunis, Tunisia
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20
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Thomson JP, Meehan RR. Affinity-Based Enrichment Techniques for the Genome-Wide Analysis of 5-Hydroxymethylcytosine. Methods Mol Biol 2018; 1708:679-696. [PMID: 29224170 DOI: 10.1007/978-1-4939-7481-8_35] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Since its initial characterization in 2009 there has been a great degree of interest in comparative profiling of 5-hydroxymethylcytosine (5hmC) nucleotides in vertebrate DNA. Through a host of genome-wide studies the distribution of 5hmC has been mapped in a range of cell lines, tissue types and organisms; the majority of which have been generated through affinity-based methods for 5hmC enrichment. Although recent advances in the field have resulted in the ability to investigate the levels of both methylated and hydroxymethylated cytosines at single base resolution, such studies are still relatively cost-prohibitive as well as technically challenging. As such affinity-based methods for the enrichment of 5hmC-modified DNA fragments represent a cost-effective and highly informative method for profiling 5hmC residency in genomic DNA. Here we will outline protocols for two independent affinity based methods to generate 5hmC enriched fractions for subsequent locus specific and genome-wide analysis; immunoprecipitation using highly specific 5hmC antibodies as well as a chemical capture based method.
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Affiliation(s)
- John P Thomson
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Road, Edinburgh, EH4 2XU, UK
| | - Richard R Meehan
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Road, Edinburgh, EH4 2XU, UK.
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21
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Shi DQ, Ali I, Tang J, Yang WC. New Insights into 5hmC DNA Modification: Generation, Distribution and Function. Front Genet 2017; 8:100. [PMID: 28769976 PMCID: PMC5515870 DOI: 10.3389/fgene.2017.00100] [Citation(s) in RCA: 131] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2017] [Accepted: 07/05/2017] [Indexed: 01/10/2023] Open
Abstract
Dynamic DNA modifications, such as methylation/demethylation on cytosine, are major epigenetic mechanisms to modulate gene expression in both eukaryotes and prokaryotes. In addition to the common methylation on the 5th position of the pyrimidine ring of cytosine (5mC), other types of modifications at the same position, such as 5-hydroxymethyl (5hmC), 5-formyl (5fC), and 5-carboxyl (5caC), are also important. Recently, 5hmC, a product of 5mC demethylation by the Ten-Eleven Translocation family proteins, was shown to regulate many cellular and developmental processes, including the pluripotency of embryonic stem cells, neuron development, and tumorigenesis in mammals. Here, we review recent advances on the generation, distribution, and function of 5hmC modification in mammals and discuss its potential roles in plants.
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Affiliation(s)
- Dong-Qiao Shi
- State Key Laboratory of Molecular Developmental Biology, National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, University of Chinese Academy of SciencesBeijing, China
| | - Iftikhar Ali
- State Key Laboratory of Molecular Developmental Biology, National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, University of Chinese Academy of SciencesBeijing, China
| | - Jun Tang
- State Key Laboratory of Molecular Developmental Biology, National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, University of Chinese Academy of SciencesBeijing, China
| | - Wei-Cai Yang
- State Key Laboratory of Molecular Developmental Biology, National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, University of Chinese Academy of SciencesBeijing, China
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22
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Yin X, Xu Y. Structure and Function of TET Enzymes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 945:275-302. [PMID: 27826843 DOI: 10.1007/978-3-319-43624-1_12] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Mammalian DNA methylation mainly occurs at the carbon-C5 position of cytosine (5mC). TET enzymes were discovered to successively oxidize 5mC to 5-hydromethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC). TET enzymes and oxidized 5mC derivatives play important roles in various biological and pathological processes, including regulation of DNA demethylation, gene transcription, embryonic development, and oncogenesis. In this chapter, we will discuss the discovery of TET-mediated 5mC oxidation and the structure, function, and regulation of TET enzymes.
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Affiliation(s)
- Xiaotong Yin
- Fudan University Shanghai Cancer Center, Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China
| | - Yanhui Xu
- Fudan University Shanghai Cancer Center, Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.
- Key Laboratory of Molecular Medicine, Ministry of Education, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai, 200032, China.
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai, 200433, China.
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23
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Abstract
In mammals, DNA methylation in the form of 5-methylcytosine (5mC) can be actively reversed to unmodified cytosine (C) through TET dioxygenase-mediated oxidation of 5mC to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC), followed by replication-dependent dilution or thymine DNA glycosylase (TDG)-dependent base excision repair. In the past few years, biochemical and structural studies have revealed mechanistic insights into how TET and TDG mediate active DNA demethylation. Additionally, many regulatory mechanisms of this process have been identified. Technological advances in mapping and tracing the oxidized forms of 5mC allow further dissection of their functions. Furthermore, the biological functions of active DNA demethylation in various biological contexts have also been revealed. In this Review, we summarize the recent advances and highlight key unanswered questions.
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24
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Bullard W, Kieft R, Sabatini R. A method for the efficient and selective identification of 5-hydroxymethyluracil in genomic DNA. Biol Methods Protoc 2017; 2. [PMID: 29276783 PMCID: PMC5741180 DOI: 10.1093/biomethods/bpw006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Recently, 5-hydroxymethyluracil (5hmU) was identified in mammalian genomic DNA as an oxidative product of thymine by the ten-eleven translocation (TET) proteins. While the biological role of this modification remains unclear, identifying its genomic location will assist in elucidating function. Here we present a rapid and robust method to selectively tag and enrich genomic regions containing 5hmU. This method involves the selective glucosylation of 5hmU residues by the base J glucosyltransferase from trypanosomes creating glucosylhydroxymethyluracil (base J). The base J can then be efficiently and selectively pulled down by antibodies against base J or by J-binding protein 1. DNA that is enriched is suitable for analysis by quantitative PCR or sequencing. We utilized this tagging reaction to provide proof of concept for the enrichment of 5hmU containing DNA from a pool that contains modified and unmodified DNA. Furthermore, we demonstrate that the base J pull-down assay identifies 5hmU at specific regions of the trypanosome genome involved in transcriptional repression. The method described here will allow for a greater understanding of the functional role and dynamics of 5hmU in biology.
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Affiliation(s)
- Whitney Bullard
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Rudo Kieft
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Robert Sabatini
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
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25
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Bullard W, Cliffe L, Wang P, Wang Y, Sabatini R. Base J glucosyltransferase does not regulate the sequence specificity of J synthesis in trypanosomatid telomeric DNA. Mol Biochem Parasitol 2016; 204:77-80. [PMID: 26815240 DOI: 10.1016/j.molbiopara.2016.01.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 01/08/2016] [Accepted: 01/11/2016] [Indexed: 12/24/2022]
Abstract
Telomeric DNA of trypanosomatids possesses a modified thymine base, called base J, that is synthesized in a two-step process; the base is hydroxylated by a thymidine hydroxylase forming hydroxymethyluracil (hmU) and a glucose moiety is then attached by the J-associated glucosyltransferase (JGT). To examine the importance of JGT in modifiying specific thymine in DNA, we used a Leishmania episome system to demonstrate that the telomeric repeat (GGGTTA) stimulates J synthesis in vivo while mutant telomeric sequences (GGGTTT, GGGATT, and GGGAAA) do not. Utilizing an in vitro GT assay we find that JGT can glycosylate hmU within any sequence with no significant change in Km or kcat, even mutant telomeric sequences that are unable to be J-modified in vivo. The data suggests that JGT possesses no DNA sequence specificity in vitro, lending support to the hypothesis that the specificity of base J synthesis is not at the level of the JGT reaction.
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Affiliation(s)
- Whitney Bullard
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Laura Cliffe
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Pengcheng Wang
- Environmental Toxicology Graduate Program, United States
| | - Yinsheng Wang
- Environmental Toxicology Graduate Program, United States; Department of Chemistry, University of California, Riverside, CA, United States
| | - Robert Sabatini
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States.
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26
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Borst P. Maxi-circles, glycosomes, gene transposition, expression sites, transsplicing, transferrin receptors and base J. Mol Biochem Parasitol 2016; 205:39-52. [DOI: 10.1016/j.molbiopara.2016.03.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 03/22/2016] [Accepted: 03/22/2016] [Indexed: 01/05/2023]
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27
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TET proteins in cancer: Current 'state of the art'. Crit Rev Oncol Hematol 2015; 96:425-36. [PMID: 26276226 DOI: 10.1016/j.critrevonc.2015.07.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2014] [Revised: 05/26/2015] [Accepted: 07/16/2015] [Indexed: 12/31/2022] Open
Abstract
Aberrations in DNA methylation patterns are observed from the early stages of carcinogenesis. However, the mechanisms that drive these changes remain elusive. The recent characterization of ten-eleven translocation (TET) enzymes as a source of newly modified cytosines (5-hydroxymethylcytosine, 5-formylcytosine and 5-carboxylcytosine) has shed new light on the DNA demethylation process. These cytosines are intermediates of an active DNA demethylation process and are epigenetic markers per se. In this review, we discuss the mechanism and function of TET proteins in biological processes as well as current knowledge regarding their expression and regulation in cancer.
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28
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Kundu S. Co-operative intermolecular kinetics of 2-oxoglutarate dependent dioxygenases may be essential for system-level regulation of plant cell physiology. FRONTIERS IN PLANT SCIENCE 2015; 6:489. [PMID: 26236316 PMCID: PMC4502536 DOI: 10.3389/fpls.2015.00489] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 06/19/2015] [Indexed: 05/24/2023]
Abstract
Can the stimulus-driven synergistic association of 2-oxoglutarate dependent dioxygenases be influenced by the kinetic parameters of binding and catalysis?In this manuscript, I posit that these indices are necessary and specific for a particular stimulus, and are key determinants of a dynamic clustering that may function to mitigate the effects of this trigger. The protein(s)/sequence(s) that comprise this group are representative of all major kingdoms of life, and catalyze a generic hydroxylation, which is, in most cases accompanied by a specialized conversion of the substrate molecule. Iron is an essential co-factor for this transformation and the response to waning levels is systemic, and mandates the simultaneous participation of molecular sensors, transporters, and signal transducers. Here, I present a proof-of-concept model, that an evolving molecular network of 2OG-dependent enzymes can maintain iron homeostasis in the cytosol of root hair cells of members of the family Gramineae by actuating a non-reductive compensatory chelation by the phytosiderophores. Regression models of empirically available kinetic data (iron and alpha-ketoglutarate) were formulated, analyzed, and compared. The results, when viewed in context of the superfamily responding as a unit, suggest that members can indeed, work together to accomplish system-level function. This is achieved by the establishment of transient metabolic conduits, wherein the flux is dictated by kinetic compatibility of the participating enzymes. The approach adopted, i.e., predictive mathematical modeling, is integral to the hypothesis-driven acquisition of experimental data points and, in association with suitable visualization aids may be utilized for exploring complex plant biochemical systems.
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Affiliation(s)
- Siddhartha Kundu
- *Correspondence: Siddhartha Kundu, School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Mehrauli Road, New Delhi 110067, India ;
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29
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Efimova OA, Pendina AA, Tikhonov AV, Kuznetzova TV, Baranov VS. Oxidized form of 5-methylcytosine—5-hydroxymethylcytosine: a new insight into the biological significance in the mammalian genome. ACTA ACUST UNITED AC 2015. [DOI: 10.1134/s2079059715020033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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30
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Hong K, Kim YJ, Choi Y. Function of TET proteins in germ cell reprogramming. Genes Genomics 2015. [DOI: 10.1007/s13258-014-0254-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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31
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Lu X, Zhao BS, He C. TET family proteins: oxidation activity, interacting molecules, and functions in diseases. Chem Rev 2015; 115:2225-39. [PMID: 25675246 DOI: 10.1021/cr500470n] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Xingyu Lu
- †Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States.,‡Howard Hughes Medical Institute, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States
| | - Boxuan Simen Zhao
- †Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States.,‡Howard Hughes Medical Institute, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States
| | - Chuan He
- †Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States.,‡Howard Hughes Medical Institute, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States
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32
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Genest PA, Baugh L, Taipale A, Zhao W, Jan S, van Luenen HGAM, Korlach J, Clark T, Luong K, Boitano M, Turner S, Myler PJ, Borst P. Defining the sequence requirements for the positioning of base J in DNA using SMRT sequencing. Nucleic Acids Res 2015; 43:2102-15. [PMID: 25662217 PMCID: PMC4344527 DOI: 10.1093/nar/gkv095] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Base J (β-D-glucosyl-hydroxymethyluracil) replaces 1% of T in the Leishmania genome and is only found in telomeric repeats (99%) and in regions where transcription starts and stops. This highly restricted distribution must be co-determined by the thymidine hydroxylases (JBP1 and JBP2) that catalyze the initial step in J synthesis. To determine the DNA sequences recognized by JBP1/2, we used SMRT sequencing of DNA segments inserted into plasmids grown in Leishmania tarentolae. We show that SMRT sequencing recognizes base J in DNA. Leishmania DNA segments that normally contain J also picked up J when present in the plasmid, whereas control sequences did not. Even a segment of only 10 telomeric (GGGTTA) repeats was modified in the plasmid. We show that J modification usually occurs at pairs of Ts on opposite DNA strands, separated by 12 nucleotides. Modifications occur near G-rich sequences capable of forming G-quadruplexes and JBP2 is needed, as it does not occur in JBP2-null cells. We propose a model whereby de novo J insertion is mediated by JBP2. JBP1 then binds to J and hydroxylates another T 13 bp downstream (but not upstream) on the complementary strand, allowing JBP1 to maintain existing J following DNA replication.
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Affiliation(s)
- Paul-Andre Genest
- Division of Molecular Oncology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Loren Baugh
- Seattle Biomedical Research Institute, 307 Westlake Avenue, Seattle, WA 98109-5219, USA
| | - Alex Taipale
- Seattle Biomedical Research Institute, 307 Westlake Avenue, Seattle, WA 98109-5219, USA
| | - Wanqi Zhao
- Division of Molecular Oncology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Sabrina Jan
- Division of Molecular Oncology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Henri G A M van Luenen
- Division of Molecular Oncology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Jonas Korlach
- Pacific Biosciences, 1380 Willow Road, Menlo Park, CA 94025, USA
| | - Tyson Clark
- Pacific Biosciences, 1380 Willow Road, Menlo Park, CA 94025, USA
| | - Khai Luong
- Pacific Biosciences, 1380 Willow Road, Menlo Park, CA 94025, USA
| | - Matthew Boitano
- Pacific Biosciences, 1380 Willow Road, Menlo Park, CA 94025, USA
| | - Steve Turner
- Pacific Biosciences, 1380 Willow Road, Menlo Park, CA 94025, USA
| | - Peter J Myler
- Seattle Biomedical Research Institute, 307 Westlake Avenue, Seattle, WA 98109-5219, USA Department of Biomedical Informatics and Medical Education, University of Washington, Seattle, WA 98195, USA Department of Global Health, University of Washington, Seattle, WA 98195, USA
| | - Piet Borst
- Division of Molecular Oncology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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Liu S, Ji D, Cliffe L, Bullard W, Sabatini R, Wang Y. Quantitative mass spectrometry-based analysis of β-D-glucosyl-5-hydroxymethyluracil in genomic DNA of Trypanosoma brucei. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:1763-1770. [PMID: 25078157 PMCID: PMC4163122 DOI: 10.1007/s13361-014-0960-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 07/01/2014] [Accepted: 07/02/2014] [Indexed: 06/03/2023]
Abstract
β-D-glucosyl-5-hydroxymethyluracil (base J) is a hyper-modified nucleobase found in the nuclear DNA of kinetoplastid parasites. With replacement of a fraction of thymine in DNA, J is localized primarily in telomeric regions of all organisms carrying this modified base. The biosynthesis of J occurs in two putative steps: first, a specific thymine in DNA is recognized and converted into 5-hydroxymethyluracil (5-HmU) by J-binding proteins (JBP1 and JBP2); a glucosyl transferase (GT) subsequently glucosylates the 5-HmU to yield J. Although several recent studies revealed the roles of internal J in regulating transcription in kinetoplastids, functions of telomeric J and proteins involved in J synthesis remain elusive. Assessing the functions of base J and understanding fully its biosynthesis necessitate the measurement of its level in cells and organisms. In this study, we reported a reversed-phase HPLC coupled with tandem mass spectrometry (LC-MS/MS) method, together with the use of a surrogate internal standard (β-D-glucosyl-5-hydroxymethyl-2'-deoxycytidine, 5-gHmdC), for the accurate detection of β-D-glucosyl-5-hydroxymethyl-2'-deoxyuridine (dJ) in Trypanosoma brucei DNA. For comparison, we also measured the level of the precursor for dJ synthesis [i.e. 5-hydroxymethyl-2'-deoxyuridine (5-HmdU)]. We found that base J was not detectable in the JBP-null cells whereas it replaced approximately 0.5% thymine in wild-type cells, which was accompanied with a markedly decreased level of 5-HmdU in JBP1/JBP2-null strain relative to the wild-type strain. These results provided direct evidence supporting that JBP proteins play an important role in oxidizing thymidine to form 5-HmdU, which facilitated the generation of dJ. This is the first report about the application of LC-MS/MS for the quantification of base J. The analytical method built a solid foundation for dissecting the molecular mechanisms of J biosynthesis and assessing the biological functions of base J in the future.ᅟ
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Affiliation(s)
- Shuo Liu
- Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521, USA
| | - Debin Ji
- Department of Chemistry, University of California, Riverside, CA 92521, USA
| | - Laura Cliffe
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, USA
| | - Whitney Bullard
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, USA
| | - Robert Sabatini
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, USA
| | - Yinsheng Wang
- Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521, USA
- Department of Chemistry, University of California, Riverside, CA 92521, USA
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Facile enzymatic synthesis of base J-containing oligodeoxyribonucleotides and an analysis of the impact of base J on DNA replication in cells. PLoS One 2014; 9:e103335. [PMID: 25061973 PMCID: PMC4111573 DOI: 10.1371/journal.pone.0103335] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 06/26/2014] [Indexed: 12/17/2022] Open
Abstract
We reported here the use of T4 bacteriophage β-glucosyltransferase (T4 β-GT) for the facile synthesis of base J-containing oligodeoxyribonucleotides (ODNs). We found that the enzyme could catalyze the glucosylation of 5-hydroxymethyl-2-deoxyuridine (5hmU) in both single- and double-stranded ODNs, though the latter reaction occurred only when 5hmU was mispaired with a guanine. In addition, base J blocked moderately DNA replication, but it did not induce mutations during replication in human cells.
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Lu L, Zhu C, Xia B, Yi C. Oxidative Demethylation of DNA and RNA Mediated by Non-Heme Iron-Dependent Dioxygenases. Chem Asian J 2014; 9:2018-29. [DOI: 10.1002/asia.201402148] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Indexed: 11/10/2022]
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Bullard W, Lopes da Rosa-Spiegler J, Liu S, Wang Y, Sabatini R. Identification of the glucosyltransferase that converts hydroxymethyluracil to base J in the trypanosomatid genome. J Biol Chem 2014; 289:20273-82. [PMID: 24891501 DOI: 10.1074/jbc.m114.579821] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
O-linked glucosylation of thymine in DNA (base J) is an important regulatory epigenetic mark in trypanosomatids. β-d-glucopyranosyloxymethyluracil (base J) synthesis is initiated by the JBP1/2 enzymes that hydroxylate thymine, forming 5-hydroxymethyluracil (hmU). hmU is then glucosylated by a previously unknown glucosyltransferase. A recent computational screen identified a possible candidate for the base J-associated glucosyltransferase (JGT) in trypanosomatid genomes. We demonstrate that recombinant JGT utilizes uridine diphosphoglucose to transfer glucose to hmU in the context of dsDNA. Mutation of conserved residues typically involved in glucosyltransferase catalysis impairs DNA glucosylation in vitro. The deletion of both alleles of JGT from the genome of Trypanosoma brucei generates a cell line that completely lacks base J. Reintroduction of JGT in the JGT KO restores J synthesis. Ablation of JGT mRNA levels by RNAi leads to the sequential reduction in base J and increased levels of hmU that dissipate rapidly. The analysis of JGT function confirms the two-step J synthesis model and demonstrates that JGT is the only glucosyltransferase enzyme required for the second step of the pathway. Similar to the activity of the related Ten-Eleven Translocation (TET) family of dioxygenases on 5mC, our studies also suggest the ability of the base J-binding protein enzymes to catalyze iterative oxidation of thymine in trypanosome DNA. Here we discuss the regulation of hmU and base J formation in the trypanosome genome by JGT and base J-binding protein.
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Affiliation(s)
- Whitney Bullard
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602 and
| | | | - Shuo Liu
- the Environmental Toxicology Graduate Program and
| | - Yinsheng Wang
- the Environmental Toxicology Graduate Program and Department of Chemistry, University of California, Riverside, California 92521
| | - Robert Sabatini
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602 and
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Pfeifer GP, Xiong W, Hahn MA, Jin SG. The role of 5-hydroxymethylcytosine in human cancer. Cell Tissue Res 2014; 356:631-41. [PMID: 24816989 DOI: 10.1007/s00441-014-1896-7] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 04/10/2014] [Indexed: 12/22/2022]
Abstract
The patterns of DNA methylation in human cancer cells are highly abnormal and often involve the acquisition of DNA hypermethylation at hundreds or thousands of CpG islands that are usually unmethylated in normal tissues. The recent discovery of 5-hydroxymethylcytosine (5hmC) as an enzymatic oxidation product of 5-methylcytosine (5mC) has led to models and experimental data in which the hypermethylation and 5mC oxidation pathways seem to be connected. Key discoveries in this setting include the findings that several genes coding for proteins involved in the 5mC oxidation reaction are mutated in human tumors, and that a broad loss of 5hmC occurs across many types of cancer. In this review, we will summarize current knowledge and discuss models of the potential roles of 5hmC in human cancer biology.
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Affiliation(s)
- Gerd P Pfeifer
- Beckman Research Institute, City of Hope Medical Center, 1500 East Duarte Road, Duarte, CA 91010, USA,
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Wyatt MD. Advances in understanding the coupling of DNA base modifying enzymes to processes involving base excision repair. Adv Cancer Res 2014; 119:63-106. [PMID: 23870509 DOI: 10.1016/b978-0-12-407190-2.00002-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This chapter describes some of the recent, exciting developments that have characterized and connected processes that modify DNA bases with DNA repair pathways. It begins with AID/APOBEC or TET family members that covalently modify bases within DNA. The modified bases, such as uracil or 5-formylcytosine, are then excised by DNA glycosylases including UNG or TDG to initiate base excision repair (BER). BER is known to preserve genome integrity by removing damaged bases. The newer studies underscore the necessity of BER following enzymes that deliberately damage DNA. This includes the role of BER in antibody diversification and more recently, its requirement for demethylation of 5-methylcytosine in mammalian cells. The recent advances have shed light on mechanisms of DNA demethylation, and have raised many more questions. The potential hazards of these processes have also been revealed. Dysregulation of the activity of base modifying enzymes, and resolution by unfaithful or corrupt means can be a driver of genome instability and tumorigenesis. The understanding of both DNA and histone methylation and demethylation is now revealing the true extent to which epigenetics influence normal development and cancer, an abnormal development.
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Affiliation(s)
- Michael D Wyatt
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina, USA.
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Hu L, Li Z, Cheng J, Rao Q, Gong W, Liu M, Shi YG, Zhu J, Wang P, Xu Y. Crystal structure of TET2-DNA complex: insight into TET-mediated 5mC oxidation. Cell 2013; 155:1545-55. [PMID: 24315485 DOI: 10.1016/j.cell.2013.11.020] [Citation(s) in RCA: 297] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2013] [Revised: 11/14/2013] [Accepted: 11/15/2013] [Indexed: 12/27/2022]
Abstract
TET proteins oxidize 5-methylcytosine (5mC) on DNA and play important roles in various biological processes. Mutations of TET2 are frequently observed in myeloid malignance. Here, we present the crystal structure of human TET2 bound to methylated DNA at 2.02 Å resolution. The structure shows that two zinc fingers bring the Cys-rich and DSBH domains together to form a compact catalytic domain. The Cys-rich domain stabilizes the DNA above the DSBH core. TET2 specifically recognizes CpG dinucleotide and shows substrate preference for 5mC in a CpG context. 5mC is inserted into the catalytic cavity with the methyl group orientated to catalytic Fe(II) for reaction. The methyl group is not involved in TET2-DNA contacts so that the catalytic cavity allows TET2 to accommodate 5mC derivatives for further oxidation. Mutations of Fe(II)/NOG-chelating, DNA-interacting, and zinc-chelating residues are frequently observed in human cancers. Our studies provide a structural basis for understanding the mechanisms of TET-mediated 5mC oxidation.
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Affiliation(s)
- Lulu Hu
- Fudan University Shanghai Cancer Center, Department of Oncology and Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China; State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai 200433, China
| | - Ze Li
- Fudan University Shanghai Cancer Center, Department of Oncology and Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Jingdong Cheng
- Fudan University Shanghai Cancer Center, Department of Oncology and Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Qinhui Rao
- Fudan University Shanghai Cancer Center, Department of Oncology and Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Wei Gong
- Fudan University Shanghai Cancer Center, Department of Oncology and Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Mengjie Liu
- Fudan University Shanghai Cancer Center, Department of Oncology and Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Yujiang Geno Shi
- Fudan University Shanghai Cancer Center, Department of Oncology and Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China; Division of Endocrinology, Diabetes and Hypertension, Department of Medicine and Department of Biological Chemistry & Molecular Pharmacology, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Jiayu Zhu
- Fudan University Shanghai Cancer Center, Department of Oncology and Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Ping Wang
- Fudan University Shanghai Cancer Center, Department of Oncology and Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China
| | - Yanhui Xu
- Fudan University Shanghai Cancer Center, Department of Oncology and Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China; State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai 200433, China.
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Cadet J, Wagner JR. TET enzymatic oxidation of 5-methylcytosine, 5-hydroxymethylcytosine and 5-formylcytosine. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2013; 764-765:18-35. [PMID: 24045206 DOI: 10.1016/j.mrgentox.2013.09.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Accepted: 09/04/2013] [Indexed: 12/14/2022]
Abstract
5-Methylcytosine and methylated histones have been considered for a long time as stable epigenetic marks of chromatin involved in gene regulation. This concept has been recently revisited with the detection of large amounts of 5-hydroxymethylcytosine, now considered as the sixth DNA base, in mouse embryonic stem cells, Purkinje neurons and brain tissues. The dioxygenases that belong to the ten eleven translocation (TET) oxygenase family have been shown to initiate the formation of this methyl oxidation product of 5-methylcytosine that is also generated although far less efficiently by radical reactions involving hydroxyl radical and one-electron oxidants. It was found as additional striking data that iterative TET-mediated oxidation of 5-hydroxymethylcytosine gives rise to 5-formylcytosine and 5-carboxylcytosine. This survey focuses on chemical and biochemical aspects of the enzymatic oxidation reactions of 5-methylcytosine that are likely to be involved in active demethylation pathways through the implication of enzymatic deamination of 5-methylcytosine oxidation products and/or several base excision repair enzymes. The high biological relevance of the latter modified bases explains why major efforts have been devoted to the design of a broad range of assays aimed at measuring globally or at the single base resolution, 5-hydroxymethylcytosine and the two other oxidation products in the DNA of cells and tissues. Another critical issue that is addressed in this review article deals with the assessment of the possible role of 5-methylcytosine oxidation products, when present in elevated amounts in cellular DNA, in terms of mutagenesis and interference with key cellular enzymes including DNA and RNA polymerases.
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Affiliation(s)
- Jean Cadet
- Direction des Sciences de la Matière, Institut Nanosciences et Cryogénie, CEA/Grenoble, 38054 Grenoble, France; Département de médecine nucléaire et radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Québec JIH 5N4, Canada.
| | - J Richard Wagner
- Département de médecine nucléaire et radiobiologie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Québec JIH 5N4, Canada.
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Gómez MA, Navas A, Márquez R, Rojas LJ, Vargas DA, Blanco VM, Koren R, Zilberstein D, Saravia NG. Leishmania panamensis infection and antimonial drugs modulate expression of macrophage drug transporters and metabolizing enzymes: impact on intracellular parasite survival. J Antimicrob Chemother 2013; 69:139-49. [PMID: 23975742 DOI: 10.1093/jac/dkt334] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
OBJECTIVES Treatment failure is multifactorial. Despite the importance of host cell drug transporters and metabolizing enzymes in the accumulation, distribution and metabolism of drugs targeting intracellular pathogens, their impact on the efficacy of antileishmanials is unknown. We examined the contribution of pharmacologically relevant determinants in human macrophages in the antimony-mediated killing of intracellular Leishmania panamensis and its relationship with the outcome of treatment with meglumine antimoniate. METHODS Patients with cutaneous leishmaniasis who failed (n = 8) or responded (n =8) to treatment were recruited. Gene expression profiling of pharmacological determinants in primary macrophages was evaluated by quantitative RT-PCR and correlated to the drug-mediated intracellular parasite killing. Functional validation was conducted through short hairpin RNA gene knockdown. RESULTS Survival of L. panamensis after exposure to antimonials was significantly higher in macrophages from patients who failed treatment. Sixteen macrophage drug-response genes were modulated by infection and exposure to meglumine antimoniate. Correlation analyses of gene expression and intracellular parasite survival revealed the involvement of host cell metallothionein-2A and ABCB6 in the survival of Leishmania during exposure to antimonials. ABCB6 was functionally validated as a transporter of antimonial compounds localized in both the cell and phagolysosomal membranes of macrophages, revealing a novel mechanism of host cell-mediated regulation of intracellular drug exposure and parasite survival within phagocytes. CONCLUSIONS These results provide insight into host cell mechanisms regulating the intracellular exposure of Leishmania to antimonials and variations among individuals that impact parasite survival. Understanding of host cell determinants of intracellular pharmacokinetics/pharmacodynamics opens new avenues to improved drug efficacy for intracellular pathogens.
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Affiliation(s)
- Maria Adelaida Gómez
- Centro Internacional de Entrenamiento e Investigaciones Médicas (CIDEIM), Carrera 125 No. 19-225 Cali, Colombia
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TETonic shift: biological roles of TET proteins in DNA demethylation and transcription. Nat Rev Mol Cell Biol 2013; 14:341-56. [PMID: 23698584 DOI: 10.1038/nrm3589] [Citation(s) in RCA: 654] [Impact Index Per Article: 59.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In many organisms, the methylation of cytosine in DNA has a key role in silencing 'parasitic' DNA elements, regulating transcription and establishing cellular identity. The recent discovery that ten-eleven translocation (TET) proteins are 5-methylcytosine oxidases has provided several chemically plausible pathways for the reversal of DNA methylation, thus triggering a paradigm shift in our understanding of how changes in DNA methylation are coupled to cell differentiation, embryonic development and cancer.
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Ten eleven translocation enzymes and 5-hydroxymethylation in mammalian development and cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 754:57-79. [PMID: 22956496 DOI: 10.1007/978-1-4419-9967-2_3] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
5-Hydroxymethylcytosine (5hmC) is an oxidative product of 5-methylcytosine (5mC), catalyzed by the ten eleven translocation (TET) family of enzymes. Although 5hmC was discovered several decades ago, it was only after its recent identification in murine brain and stem cell DNA that it has become a major focus of epigenomic research. Part of the reason for this delay is due to the difficulty in detecting both global and locus-specific 5hmC levels. Several studies have addressed this issue with the development of novel techniques to locate and measure 5hmC, which led to multiple reports detailing 5hmC patterns in stem cells and global 5hmC levels during embryogenesis. Based on these studies of 5hmC levels and reports of tissue-specific TET expression, these enzymes are thought to play a role in mammalian development and differentiation. In addition, the TET enzymes are mutated in several types of cancer, affecting their activity and likely altering genomic 5hmC and 5mC patterns. Furthermore, oxidation of 5mC appears to be a step in several active DNA demethylation pathways, which may be important for normal processes, as well as global hypomethylation during cancer development and progression. Much has been revealed about this interesting DNA modification in recent years, but more research is needed for understanding the role of TET proteins and 5hmC in gene regulation and disease.
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van Luenen HGAM, Farris C, Jan S, Genest PA, Tripathi P, Velds A, Kerkhoven RM, Nieuwland M, Haydock A, Ramasamy G, Vainio S, Heidebrecht T, Perrakis A, Pagie L, van Steensel B, Myler PJ, Borst P. Glucosylated hydroxymethyluracil, DNA base J, prevents transcriptional readthrough in Leishmania. Cell 2012; 150:909-21. [PMID: 22939620 DOI: 10.1016/j.cell.2012.07.030] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 05/16/2012] [Accepted: 07/25/2012] [Indexed: 12/25/2022]
Abstract
Some Ts in nuclear DNA of trypanosomes and Leishmania are hydroxylated and glucosylated to yield base J (β-D-glucosyl-hydroxymethyluracil). In Leishmania, about 99% of J is located in telomeric repeats. We show here that most of the remaining J is located at chromosome-internal RNA polymerase II termination sites. This internal J and telomeric J can be reduced by a knockout of J-binding protein 2 (JBP2), an enzyme involved in the first step of J biosynthesis. J levels are further reduced by growing Leishmania JBP2 knockout cells in BrdU-containing medium, resulting in cell death. The loss of internal J in JBP2 knockout cells is accompanied by massive readthrough at RNA polymerase II termination sites. The readthrough varies between transcription units but may extend over 100 kb. We conclude that J is required for proper transcription termination and infer that the absence of internal J kills Leishmania by massive readthrough of transcriptional stops.
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Affiliation(s)
- Henri G A M van Luenen
- Division of Molecular Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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Mello LV, Rigden DJ. A new family of bacterial DNA repair proteins annotated by the integration of non-homology, distant homology and structural bioinformatic methods. FEBS Lett 2012; 586:3908-13. [DOI: 10.1016/j.febslet.2012.09.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 09/13/2012] [Accepted: 09/14/2012] [Indexed: 10/27/2022]
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Kundu S. Distribution and prediction of catalytic domains in 2-oxoglutarate dependent dioxygenases. BMC Res Notes 2012; 5:410. [PMID: 22862831 PMCID: PMC3475032 DOI: 10.1186/1756-0500-5-410] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 06/29/2012] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND The 2-oxoglutarate dependent superfamily is a diverse group of non-haem dioxygenases, and is present in prokaryotes, eukaryotes, and archaea. The enzymes differ in substrate preference and reaction chemistry, a factor that precludes their classification by homology studies and electronic annotation schemes alone. In this work, I propose and explore the rationale of using substrates to classify structurally similar alpha-ketoglutarate dependent enzymes. FINDINGS Differential catalysis in phylogenetic clades of 2-OG dependent enzymes, is determined by the interactions of a subset of active-site amino acids. Identifying these with existing computational methods is challenging and not feasible for all proteins. A clustering protocol based on validated mechanisms of catalysis of known molecules, in tandem with group specific hidden markov model profiles is able to differentiate and sequester these enzymes. Access to this repository is by a web server that compares user defined unknown sequences to these pre-defined profiles and outputs a list of predicted catalytic domains. The server is free and is accessible at the following URL (http://comp-biol.theacms.in/H2OGpred.html). CONCLUSIONS The proposed stratification is a novel attempt at classifying and predicting 2-oxoglutarate dependent function. In addition, the server will provide researchers with a tool to compare their data to a comprehensive list of HMM profiles of catalytic domains. This work, will aid efforts by investigators to screen and characterize putative 2-OG dependent sequences. The profile database will be updated at regular intervals.
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Affiliation(s)
- Siddhartha Kundu
- Department of Biochemistry, Army College of Medical Sciences, Delhi Cantt., New Delhi 110010, India.
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Heidebrecht T, Fish A, von Castelmur E, Johnson KA, Zaccai G, Borst P, Perrakis A. Binding of the J-binding protein to DNA containing glucosylated hmU (base J) or 5-hmC: evidence for a rapid conformational change upon DNA binding. J Am Chem Soc 2012; 134:13357-65. [PMID: 22775585 DOI: 10.1021/ja303423t] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Base J (β-D-glucosyl-hydroxymethyluracil) was discovered in the nuclear DNA of some pathogenic protozoa, such as trypanosomes and Leishmania, where it replaces a fraction of base T. We have found a J-Binding Protein 1 (JBP1) in these organisms, which contains a unique J-DNA binding domain (DB-JBP1) and a thymidine hydroxylase domain involved in the first step of J biosynthesis. This hydroxylase is related to the mammalian TET enzymes that hydroxylate 5-methylcytosine in DNA. We have now studied the binding of JBP1 and DB-JBP1 to oligonucleotides containing J or glucosylated 5-hydroxymethylcytosine (glu-5-hmC) using an equilibrium fluorescence polarization assay. We find that JBP1 binds glu-5-hmC-DNA with an affinity about 40-fold lower than J-DNA (~400 nM), which is still 200 times higher than the JBP1 affinity for T-DNA. The discrimination between glu-5-hmC-DNA and T-DNA by DB-JBP1 is about 2-fold less, but enough for DB-JBP1 to be useful as a tool to isolate 5-hmC-DNA. Pre-steady state kinetic data obtained in a stopped-flow device show that the initial binding of JBP1 to glucosylated DNA is very fast with a second order rate constant of 70 μM(-1) s(-1) and that JBP1 binds to J-DNA or glu-5-hmC-DNA in a two-step reaction, in contrast to DB-JBP1, which binds in a one-step reaction. As the second (slower) step in binding is concentration independent, we infer that JBP1 undergoes a conformational change upon binding to DNA. Global analysis of pre-steady state and equilibrium binding data supports such a two-step mechanism and allowed us to determine the kinetic parameters that describe it. This notion of a conformational change is supported by small-angle neutron scattering experiments, which show that the shape of JBP1 is more elongated in complex with DNA. The conformational change upon DNA binding may allow the hydroxylase domain of JBP1 to make contact with the DNA and hydroxylate T's in spatial proximity, resulting in regional introduction of base J into the DNA.
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Affiliation(s)
- Tatjana Heidebrecht
- Division of Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands
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Cliffe LJ, Hirsch G, Wang J, Ekanayake D, Bullard W, Hu M, Wang Y, Sabatini R. JBP1 and JBP2 proteins are Fe2+/2-oxoglutarate-dependent dioxygenases regulating hydroxylation of thymidine residues in trypanosome DNA. J Biol Chem 2012; 287:19886-95. [PMID: 22514282 DOI: 10.1074/jbc.m112.341974] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
We have recently demonstrated that O-linked glucosylation of thymine in trypanosome DNA (base J) regulates polymerase II transcription initiation. In vivo analysis has indicated that base J synthesis is initiated by the hydroxylation of thymidine by proteins (JBP1 and JBP2) homologous to the Fe(2+)/2-oxoglutarate (2-OG)-dependent dioxygenase superfamily where hydroxylation is driven by the oxidative decarboxylation of 2-OG, forming succinate and CO(2). However, no direct evidence for hydroxylase activity has been reported for the JBP proteins. We now demonstrate recombinant JBP1 hydroxylates thymine specifically in the context of dsDNA in a Fe(2+)-, 2-OG-, and O(2)-dependent manner. Under anaerobic conditions, the addition of Fe(2+) to JBP1/2-OG results in the formation of a broad absorption spectrum centered at 530 nm attributed to metal chelation of 2-OG bound to JBP, a spectroscopic signature of Fe(2+)/2-OG-dependent dioxygenases. The N-terminal thymidine hydroxylase domain of JBP1 is sufficient for full activity and mutation of residues involved in coordinating Fe(2+) inhibit iron binding and thymidine hydroxylation. Hydroxylation in vitro and J synthesis in vivo is inhibited by known inhibitors of Fe(2+)/2-OG-dependent dioxygenases. The data clearly demonstrate the JBP enzymes are dioxygenases acting directly on dsDNA, confirming the two-step J synthesis model. Growth of trypanosomes in hypoxic conditions decreases JBP1 and -2 activity, resulting in reduced levels of J and changes in parasite virulence previously characterized in the JBP KO. The influence of environment upon J biosynthesis via oxygen-sensitive regulation of JBP1/2 has exciting implications for the regulation of gene expression and parasite adaptation to different host niches.
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Affiliation(s)
- Laura J Cliffe
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-7229, USA
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Matarese F, Carrillo-de Santa Pau E, Stunnenberg HG. 5-Hydroxymethylcytosine: a new kid on the epigenetic block? Mol Syst Biol 2011; 7:562. [PMID: 22186736 PMCID: PMC3737735 DOI: 10.1038/msb.2011.95] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 11/18/2011] [Indexed: 12/21/2022] Open
Abstract
The discovery of the Ten-Eleven-Translocation (TET) oxygenases that catalyze the hydroxylation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) has triggered an avalanche of studies aiming to resolve the role of 5hmC in gene regulation if any. Hitherto, TET1 is reported to bind to CpG-island (CGI) and bivalent promoters in mouse embryonic stem cells, whereas binding at DNAseI hypersensitive sites (HS) had escaped previous analysis. Significant enrichment/accumulation of 5hmC but not 5mC can indeed be detected at bivalent promoters and at DNaseI-HS. Surprisingly, however, 5hmC is not detected or present at very low levels at CGI promoters notwithstanding the presence of TET1. Our meta-analysis of DNA methylation profiling points to potential issues with regard to the various methodologies that are part of the toolbox used to detect 5mC and 5hmC. Discrepancies between published studies and technical limitations prevent an unambiguous assignment of 5hmC as a ‘true' epigenetic mark, that is, read and interpreted by other factors and/or as a transiently accumulating intermediary product of the conversion of 5mC to unmodified cytosines.
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Affiliation(s)
- Filomena Matarese
- Department of Molecular Biology, Faculties of Science and Medicine, Radboud University, Nijmegen Center for Molecular Life Sciences, Nijmegen, The Netherlands
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Epigenetic regulation of polymerase II transcription initiation in Trypanosoma cruzi: modulation of nucleosome abundance, histone modification, and polymerase occupancy by O-linked thymine DNA glucosylation. EUKARYOTIC CELL 2011; 10:1465-72. [PMID: 21926332 DOI: 10.1128/ec.05185-11] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Very little is understood regarding how transcription is initiated/regulated in the early-diverging eukaryote Trypanosoma cruzi. Unusually for a eukaryote, genes transcribed by RNA polymerase (Pol) II in T. cruzi are arranged in polycistronic transcription units (PTUs). On the basis of this gene organization, it was previously thought that trypanosomes rely solely on posttranscriptional processes to regulate gene expression. We recently localized a novel glucosylated thymine DNA base, called base J, to potential promoter regions of PTUs throughout the trypanosome genome. Loss of base J, following the deletion of JBP1, a thymidine hydroxylase involved with synthesis, led to a global increase in the Pol II transcription rate and gene expression. In order to determine the mechanism by which base J regulates transcription, we have characterized changes in chromatin structure and Pol II recruitment to promoter regions following the loss of base J. The loss of base J coincides with a decrease in nucleosome abundance, increased histone H3/H4 acetylation, and increased Pol II occupancy at promoter regions, including the well-characterized spliced leader RNA gene promoter. These studies present the first direct evidence for epigenetic regulation of Pol II transcription initiation via DNA modification and chromatin structure in kinetoplastids as well as provide a mechanism for regulation of trypanosome gene expression via the novel hypermodified base J.
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