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Feng Y, Ma X, Yang Y, Tao S, Ahmed A, Gong Z, Cheng X, Zhang W. The roles of DNA methylation on pH dependent i-motif (iM) formation in rice. Nucleic Acids Res 2024; 52:1243-1257. [PMID: 38180820 PMCID: PMC10853798 DOI: 10.1093/nar/gkad1245] [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: 06/27/2023] [Revised: 12/14/2023] [Accepted: 12/19/2023] [Indexed: 01/07/2024] Open
Abstract
I-motifs (iMs) are four-stranded non-B DNA structures containing C-rich DNA sequences. The formation of iMs is sensitive to pH conditions and DNA methylation, although the extent of which is still unknown in both humans and plants. To investigate this, we here conducted iMab antibody-based immunoprecipitation and sequencing (iM-IP-seq) along with bisulfite sequencing using CK (original genomic DNA without methylation-related treatments) and hypermethylated or demethylated DNA at both pH 5.5 and 7.0 in rice, establishing a link between pH, DNA methylation and iM formation on a genome-wide scale. We found that iMs folded at pH 7.0 displayed higher methylation levels than those formed at pH 5.5. DNA demethylation and hypermethylation differently influenced iM formation at pH 7.0 and 5.5. Importantly, CG hypo-DMRs (differentially methylated regions) and CHH (H = A, C and T) hyper-DMRs alone or coordinated with CG/CHG hyper-DMRs may play determinant roles in the regulation of pH dependent iM formation. Thus, our study shows that the nature of DNA sequences alone or combined with their methylation status plays critical roles in determining pH-dependent formation of iMs. It therefore deepens the understanding of the pH and methylation dependent modulation of iM formation, which has important biological implications and practical applications.
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Affiliation(s)
- Yilong Feng
- State Key Laboratory of Crop Genetics and Germplasm Enhancement and Utilization, CIC-MCP, Nanjing Agricultural University, No.1 Weigang, Nanjing, Jiangsu 210095, China
| | - Xing Ma
- State Key Laboratory of Crop Genetics and Germplasm Enhancement and Utilization, CIC-MCP, Nanjing Agricultural University, No.1 Weigang, Nanjing, Jiangsu 210095, China
| | - Ying Yang
- State Key Laboratory of Crop Genetics and Germplasm Enhancement and Utilization, CIC-MCP, Nanjing Agricultural University, No.1 Weigang, Nanjing, Jiangsu 210095, China
| | - Shentong Tao
- State Key Laboratory of Crop Genetics and Germplasm Enhancement and Utilization, CIC-MCP, Nanjing Agricultural University, No.1 Weigang, Nanjing, Jiangsu 210095, China
| | - Asgar Ahmed
- State Key Laboratory of Crop Genetics and Germplasm Enhancement and Utilization, CIC-MCP, Nanjing Agricultural University, No.1 Weigang, Nanjing, Jiangsu 210095, China
- Bangladesh Wheat and Maize Research Institute (BWMRI), Nashipur, Dinajpur 5200, Bangladesh
| | - Zhiyun Gong
- Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding, Agricultural College of Yangzhou University, Yangzhou 225009, China
| | - Xuejiao Cheng
- State Key Laboratory of Crop Genetics and Germplasm Enhancement and Utilization, CIC-MCP, Nanjing Agricultural University, No.1 Weigang, Nanjing, Jiangsu 210095, China
| | - Wenli Zhang
- State Key Laboratory of Crop Genetics and Germplasm Enhancement and Utilization, CIC-MCP, Nanjing Agricultural University, No.1 Weigang, Nanjing, Jiangsu 210095, China
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2
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Huang R, Feng Y, Gao Z, Ahmed A, Zhang W. The Epigenomic Features and Potential Functions of PEG- and PDS-Favorable DNA G-Quadruplexes in Rice. Int J Mol Sci 2024; 25:634. [PMID: 38203805 PMCID: PMC10779103 DOI: 10.3390/ijms25010634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 12/26/2023] [Accepted: 12/29/2023] [Indexed: 01/12/2024] Open
Abstract
A G-quadruplex (G4) is a typical non-B DNA structure and involved in various DNA-templated events in eukaryotic genomes. PEG and PDS chemicals have been widely applied for promoting the folding of in vivo or in vitro G4s. However, how PEG and PDS preferentially affect a subset of G4 formation genome-wide is still largely unknown. We here conducted a BG4-based IP-seq in vitro under K++PEG or K++PDS conditions in the rice genome. We found that PEG-favored IP-G4s+ have distinct sequence features, distinct genomic distributions and distinct associations with TEGs, non-TEGs and subtypes of TEs compared to PDS-favored ones. Strikingly, PEG-specific IP-G4s+ are associated with euchromatin with less enrichment levels of DNA methylation but with more enriched active histone marks, while PDS-specific IP-G4s+ are associated with heterochromatin with higher enrichment levels of DNA methylation and repressive marks. Moreover, we found that genes with PEG-specific IP-G4s+ are more expressed than those with PDS-specific IP-G4s+, suggesting that PEG/PDS-specific IP-G4s+ alone or coordinating with epigenetic marks are involved in the regulation of the differential expression of related genes, therefore functioning in distinct biological processes. Thus, our study provides new insights into differential impacts of PEG and PDS on G4 formation, thereby advancing our understanding of G4 biology.
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Affiliation(s)
| | | | | | | | - Wenli Zhang
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, CIC-MCP, Nanjing Agricultural University, No.1 Weigang, Nanjing 210095, China; (R.H.); (Y.F.); (Z.G.); (A.A.)
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3
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Nain N, Singh A, Khan S, Kukreti S. G-quadruplex formation at human DAT1 gene promoter: Effect of cytosine methylation. Biochem Biophys Rep 2023; 34:101464. [PMID: 37096205 PMCID: PMC10121379 DOI: 10.1016/j.bbrep.2023.101464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 03/28/2023] [Accepted: 03/31/2023] [Indexed: 04/26/2023] Open
Abstract
The dopamine transporter gene (DAT1), a recognized genetic risk factor for attention deficit hyperactivity disorder (ADHD) is principally responsible for the regulation of dopamine synaptic levels and serves as a key target in many psychostimulants drugs. DAT1 gene methylation has been considered an epigenetic marker in ADHD. The identification of G-rich sequence motifs potential to form G-quadruplexes is correlated with functionally important genomic regions. Herein, biophysical and biochemical techniques are employed to investigate the structural polymorphism along with the effect of cytosine methylation on a 26-nt G-rich sequence present in the promoter region of the DAT1 gene. The gel electrophoresis, circular dichroism spectroscopy, and UV-thermal melting data are well correlated and conclude the formation of a parallel (bimolecular), as well as antiparallel (tetramolecular) G-quadruplex in Na+ solution. Interestingly, the existence of uni-, bi-, tri-, and tetramolecular quadruplex structures in K+ solution exhibited only the parallel type G-quadruplex. The results demonstrate that in presence of either cation (Na+ or K+) the cytosine methylation reserved the structural topologies unaltered. However, methylation lowers the thermal stability of G-quadruplexes and the duplex structures, as well. These findings provide insights to understand the regulatory mechanisms underlying the formation of the G-quadruplex structure induced by DNA methylation.
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Affiliation(s)
- Nishu Nain
- Nucleic Acids Research Lab, Department of Chemistry, University of Delhi, Delhi, 110007, India
| | - Anju Singh
- Nucleic Acids Research Lab, Department of Chemistry, University of Delhi, Delhi, 110007, India
- Department of Chemistry, Ramjas College, University of Delhi, Delhi, 110007, India
| | - Shoaib Khan
- Nucleic Acids Research Lab, Department of Chemistry, University of Delhi, Delhi, 110007, India
| | - Shrikant Kukreti
- Nucleic Acids Research Lab, Department of Chemistry, University of Delhi, Delhi, 110007, India
- Corresponding author.
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Vijay Kumar MJ, Morales R, Tsvetkov AS. G-quadruplexes and associated proteins in aging and Alzheimer's disease. FRONTIERS IN AGING 2023; 4:1164057. [PMID: 37323535 PMCID: PMC10267416 DOI: 10.3389/fragi.2023.1164057] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Accepted: 05/17/2023] [Indexed: 06/17/2023]
Abstract
Aging is a prominent risk factor for many neurodegenerative disorders, such as Alzheimer's disease (AD). Alzheimer's disease is characterized by progressive cognitive decline, memory loss, and neuropsychiatric and behavioral symptoms, accounting for most of the reported dementia cases. This disease is now becoming a major challenge and burden on modern society, especially with the aging population. Over the last few decades, a significant understanding of the pathophysiology of AD has been gained by studying amyloid deposition, hyperphosphorylated tau, synaptic dysfunction, oxidative stress, calcium dysregulation, and neuroinflammation. This review focuses on the role of non-canonical secondary structures of DNA/RNA G-quadruplexes (G4s, G4-DNA, and G4-RNA), G4-binding proteins (G4BPs), and helicases, and their roles in aging and AD. Being critically important for cellular function, G4s are involved in the regulation of DNA and RNA processes, such as replication, transcription, translation, RNA localization, and degradation. Recent studies have also highlighted G4-DNA's roles in inducing DNA double-strand breaks that cause genomic instability and G4-RNA's participation in regulating stress granule formation. This review emphasizes the significance of G4s in aging processes and how their homeostatic imbalance may contribute to the pathophysiology of AD.
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Affiliation(s)
- M. J. Vijay Kumar
- The Department of Neurology, The University of Texas McGovern Medical School at Houston, Houston, TX, United States
| | - Rodrigo Morales
- The Department of Neurology, The University of Texas McGovern Medical School at Houston, Houston, TX, United States
- Centro Integrativo de Biologia y Quimica Aplicada (CIBQA), Universidad Bernardo O’Higgins, Santiago, Chile
| | - Andrey S. Tsvetkov
- The Department of Neurology, The University of Texas McGovern Medical School at Houston, Houston, TX, United States
- The University of Texas Graduate School of Biomedical Sciences, Houston, TX, United States
- UTHealth Consortium on Aging, The University of Texas McGovern Medical School, Houston, TX, United States
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5
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High-throughput techniques enable advances in the roles of DNA and RNA secondary structures in transcriptional and post-transcriptional gene regulation. Genome Biol 2022; 23:159. [PMID: 35851062 PMCID: PMC9290270 DOI: 10.1186/s13059-022-02727-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 07/07/2022] [Indexed: 12/27/2022] Open
Abstract
The most stable structure of DNA is the canonical right-handed double helix termed B DNA. However, certain environments and sequence motifs favor alternative conformations, termed non-canonical secondary structures. The roles of DNA and RNA secondary structures in transcriptional regulation remain incompletely understood. However, advances in high-throughput assays have enabled genome wide characterization of some secondary structures. Here, we describe their regulatory functions in promoters and 3’UTRs, providing insights into key mechanisms through which they regulate gene expression. We discuss their implication in human disease, and how advances in molecular technologies and emerging high-throughput experimental methods could provide additional insights.
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6
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Quantitative detection of CpG methylation level on G-quadruplex and i-motif-forming DNA by recombinase polymerase amplification. Anal Bioanal Chem 2022; 414:6223-6231. [PMID: 35788871 DOI: 10.1007/s00216-022-04192-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 06/13/2022] [Accepted: 06/21/2022] [Indexed: 11/01/2022]
Abstract
Detection of CpG methylation levels holds immense potential for application in medical diagnosis of various diseases. In this study, we report the development of a recombinase polymerase amplification (RPA)-based CpG methylation level sensing system on G-quadruplex (G4) and intercalated motif (i-motif)-forming regions, which are stabilized by CpG methylation. This detection system is based on the principle that DNA polymerase is stalled at the methylated G4 and i-motif-forming region, which results in a decrease in the initial elongation efficiency of RPA. This reduction in turn affects the onset of amplification depending on the extent of CpG methylation; therefore, the methylation level is quantified by RPA. We demonstrate that the onset of amplification was delayed by CpG methylation when PCR products containing the vascular endothelial growth factor (VEGF) G4 and i-motif-forming region were used as the template. Furthermore, onset of amplification was delayed with the increase in CpG methylation of the VEGF region on genomic DNA. These results demonstrate that the sensing system is capable of directly detecting the methylation level at a constant temperature (39 °C) within 30 min without performing bisulfite conversion or affinity capture of methylated DNA.
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7
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The Dynamic Regulation of G-Quadruplex DNA Structures by Cytosine Methylation. Int J Mol Sci 2022; 23:ijms23052407. [PMID: 35269551 PMCID: PMC8910436 DOI: 10.3390/ijms23052407] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 02/16/2022] [Accepted: 02/17/2022] [Indexed: 02/01/2023] Open
Abstract
It is well known that certain non B-DNA structures, including G-quadruplexes, are key elements that can regulate gene expression. Here, we explore the theory that DNA modifications, such as methylation of cytosine, could act as a dynamic switch by promoting or alleviating the structural formation of G-quadruplex structures in DNA or RNA. The interaction between epigenetic DNA modifications, G4 formation, and the 3D architecture of the genome is a complex and developing area of research. Although there is growing evidence for such interactions, a great deal still remains to be discovered. In vivo, the potential effect that cytosine methylation may have on the formation of DNA structures has remained largely unresearched, despite this being a potential mechanism through which epigenetic factors could regulate gene activity. Such interactions could represent novel mechanisms for important biological functions, including altering nucleosome positioning or regulation of gene expression. Furthermore, promotion of strand-specific G-quadruplex formation in differentially methylated genes could have a dynamic role in directing X-inactivation or the control of imprinting, and would be a worthwhile focus for future research.
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Lokanga RA, Kumari D, Usdin K. Common Threads: Aphidicolin-Inducible and Folate-Sensitive Fragile Sites in the Human Genome. Front Genet 2021; 12:708860. [PMID: 34567068 PMCID: PMC8456018 DOI: 10.3389/fgene.2021.708860] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 07/28/2021] [Indexed: 11/13/2022] Open
Abstract
The human genome has many chromosomal regions that are fragile, demonstrating chromatin breaks, gaps, or constrictions on exposure to replication stress. Common fragile sites (CFSs) are found widely distributed in the population, with the largest subset of these sites being induced by aphidicolin (APH). Other fragile sites are only found in a subset of the population. One group of these so-called rare fragile sites (RFSs) is induced by folate stress. APH-inducible CFSs are generally located in large transcriptionally active genes that are A + T rich and often enriched for tracts of AT-dinucleotide repeats. In contrast, all the folate-sensitive sites mapped to date consist of transcriptionally silenced CGG microsatellites. Thus, all the folate-sensitive fragile sites may have a very similar molecular basis that differs in key ways from that of the APH CFSs. The folate-sensitive FSs include FRAXA that is associated with Fragile X syndrome (FXS), the most common heritable form of intellectual disability. Both CFSs and RFSs can cause chromosomal abnormalities. Recent work suggests that both APH-inducible fragile sites and FRAXA undergo Mitotic DNA synthesis (MiDAS) when exposed to APH or folate stress, respectively. Interestingly, blocking MiDAS in both cases prevents chromosome fragility but increases the risk of chromosome mis-segregation. MiDAS of both APH-inducible and FRAXA involves conservative DNA replication and POLD3, an accessory subunit of the replicative polymerase Pol δ that is essential for break-induced replication (BIR). Thus, MiDAS is thought to proceed via some form of BIR-like process. This review will discuss the recent work that highlights the similarities and differences between these two groups of fragile sites and the growing evidence for the presence of many more novel fragile sites in the human genome.
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Affiliation(s)
| | - Daman Kumari
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Karen Usdin
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
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9
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Balasubramaniyam T, Oh KI, Jin HS, Ahn HB, Kim BS, Lee JH. Non-Canonical Helical Structure of Nucleic Acids Containing Base-Modified Nucleotides. Int J Mol Sci 2021; 22:9552. [PMID: 34502459 PMCID: PMC8430589 DOI: 10.3390/ijms22179552] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 08/27/2021] [Accepted: 08/29/2021] [Indexed: 12/12/2022] Open
Abstract
Chemically modified nucleobases are thought to be important for therapeutic purposes as well as diagnosing genetic diseases and have been widely involved in research fields such as molecular biology and biochemical studies. Many artificially modified nucleobases, such as methyl, halogen, and aryl modifications of purines at the C8 position and pyrimidines at the C5 position, are widely studied for their biological functions. DNA containing these modified nucleobases can form non-canonical helical structures such as Z-DNA, G-quadruplex, i-motif, and triplex. This review summarizes the synthesis of chemically modified nucleotides: (i) methylation, bromination, and arylation of purine at the C8 position and (ii) methylation, bromination, and arylation of pyrimidine at the C5 position. Additionally, we introduce the non-canonical structures of nucleic acids containing these modifications.
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Affiliation(s)
- Thananjeyan Balasubramaniyam
- Department of Chemistry, Gyeongsang National University, Jinju 52828, Gyeongnam, Korea; (T.B.); (K.-I.O.); (H.-S.J.); (H.-B.A.)
- The Research Institute of Natural Science, Gyeongsang National University, Jinju 52828, Gyeongnam, Korea
| | - Kwnag-Im Oh
- Department of Chemistry, Gyeongsang National University, Jinju 52828, Gyeongnam, Korea; (T.B.); (K.-I.O.); (H.-S.J.); (H.-B.A.)
- The Research Institute of Natural Science, Gyeongsang National University, Jinju 52828, Gyeongnam, Korea
| | - Ho-Seong Jin
- Department of Chemistry, Gyeongsang National University, Jinju 52828, Gyeongnam, Korea; (T.B.); (K.-I.O.); (H.-S.J.); (H.-B.A.)
| | - Hye-Bin Ahn
- Department of Chemistry, Gyeongsang National University, Jinju 52828, Gyeongnam, Korea; (T.B.); (K.-I.O.); (H.-S.J.); (H.-B.A.)
| | - Byeong-Seon Kim
- The Research Institute of Natural Science, Gyeongsang National University, Jinju 52828, Gyeongnam, Korea
- Department of Chemistry Education, Gyeongsang National University, Jinju 52828, Gyeongnam, Korea
| | - Joon-Hwa Lee
- Department of Chemistry, Gyeongsang National University, Jinju 52828, Gyeongnam, Korea; (T.B.); (K.-I.O.); (H.-S.J.); (H.-B.A.)
- The Research Institute of Natural Science, Gyeongsang National University, Jinju 52828, Gyeongnam, Korea
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10
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Mishra S, Kota S, Chaudhary R, Misra HS. Guanine quadruplexes and their roles in molecular processes. Crit Rev Biochem Mol Biol 2021; 56:482-499. [PMID: 34162300 DOI: 10.1080/10409238.2021.1926417] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The role of guanine quadruplexes (G4) in fundamental biological processes like DNA replication, transcription, translation and telomere maintenance is recognized. G4 structure dynamics is regulated by G4 structure binding proteins and is thought to be crucial for the maintenance of genome integrity in both prokaryotic and eukaryotic cells. Growing research over the last decade has expanded the existing knowledge of the functional diversity of G4 (DNA and RNA) structures across the working models. The control of G4 structure dynamics using G4 binding drugs has been suggested as the putative targets in the control of cancer and bacterial pathogenesis. This review has brought forth the collections of recent information that indicate G4 (mostly G4 DNA) roles in microbial pathogenesis, DNA damaging stress response in bacteria and mammalian cells. Studies in mitochondrial gene function regulation by G4s have also been underscored. Finally, the interdependence of G4s and epigenetic modifications and their speculated medical implications through G4 interacting proteins has been discussed.
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Affiliation(s)
- Shruti Mishra
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India.,Life Sciences, Homi Bhabha National Institute (DAE Deemed to be University), Mumbai, India
| | - Swathi Kota
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India.,Life Sciences, Homi Bhabha National Institute (DAE Deemed to be University), Mumbai, India
| | - Reema Chaudhary
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India.,Life Sciences, Homi Bhabha National Institute (DAE Deemed to be University), Mumbai, India
| | - H S Misra
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, India.,Life Sciences, Homi Bhabha National Institute (DAE Deemed to be University), Mumbai, India
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Costa Dos Santos G, Renovato-Martins M, de Brito NM. The remodel of the "central dogma": a metabolomics interaction perspective. Metabolomics 2021; 17:48. [PMID: 33969452 PMCID: PMC8106972 DOI: 10.1007/s11306-021-01800-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 04/30/2021] [Indexed: 12/30/2022]
Abstract
BACKGROUND In 1957, Francis Crick drew a linear diagram on a blackboard. This diagram is often called the "central dogma." Subsequently, the relationships between different steps of the "central dogma" have been shown to be considerably complex, mostly because of the emerging world of small molecules. It is noteworthy that metabolites can be generated from the diet through gut microbiome metabolism, serve as substrates for epigenetic modifications, destabilize DNA quadruplexes, and follow Lamarckian inheritance. Small molecules were once considered the missing link in the "central dogma"; however, recently they have acquired a central role, and their general perception as downstream products has become reductionist. Metabolomics is a large-scale analysis of metabolites, and this emerging field has been shown to be the closest omics associated with the phenotype and concomitantly, the basis for all omics. AIM OF REVIEW Herein, we propose a broad updated perspective for the flux of information diagram centered in metabolomics, including the influence of other factors, such as epigenomics, diet, nutrition, and the gut- microbiome. KEY SCIENTIFIC CONCEPTS OF REVIEW Metabolites are the beginning and the end of the flux of information.
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Affiliation(s)
- Gilson Costa Dos Santos
- Laboratory of NMR Metabolomics, IBRAG, Department of Genetics, State University of Rio de Janeiro, Rio de Janeiro, 20551-030, Brazil.
| | - Mariana Renovato-Martins
- Department of Cellular and Molecular Biology, IB, Federal Fluminense University, Niterói, 24210-200, Brazil
| | - Natália Mesquita de Brito
- Laboratory of Cellular and Molecular Pharmacology, IBRAG, Department of Cell Biology, State University of Rio de Janeiro, Rio de Janeiro, 20551-030, Brazil.
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12
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Laddachote S, Ishii R, Yoshida W. Effects of CpG methylation on the thermal stability of c-kit2, c-kit*, and c-kit1 G-quadruplex structures. BBA ADVANCES 2021; 1:100007. [PMID: 37082005 PMCID: PMC10074881 DOI: 10.1016/j.bbadva.2021.100007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/24/2021] [Accepted: 03/10/2021] [Indexed: 11/25/2022] Open
Abstract
In genomic DNA, G-quadruplex (G4)-forming DNA can form either a duplex or G4 structure, suggesting that understanding the factors regulating G4 formation is important for revealing the cellular functions controlled by G4 formation. Cytosine DNA methylation in the CpG islands is known to play an important role in transcriptional regulation. Additionally, CpG methylation increases the thermal stability of G4 structures such as BCL2 and VEGF G4. In this study, we evaluated the effects of CpG methylation in three G4 structures (c-kit2, c-kit*, and c-kit1) produced by the c-KIT promoter. Each was analyzed using circular dichroism (CD) melting analysis. The results demonstrate that CpG methylation does not alter the thermal stability of c-kit2 G4 structure when formed in the presence of K+; a single-CpG methylation at C1 or C11 decreases the thermal stability of any c-kit2 G4 structure formed in the presence of Na+ and Mg2+ while methylation at C5 increases the thermal stability; CpG methylation does not alter the thermal stability of c-kit1 or c-kit* G4 structures formed in the presence of K+; and the c-kit1 and c-kit* G4-forming oligonucleotides do not form G4 structures in the presence of Na+ and Mg2+. These results provide important clues for understanding the regulatory mechanisms underlying the formation of CpG methylation-induced G4 structures.
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Masai H, Tanaka T. G-quadruplex DNA and RNA: Their roles in regulation of DNA replication and other biological functions. Biochem Biophys Res Commun 2020; 531:25-38. [PMID: 32826060 DOI: 10.1016/j.bbrc.2020.05.132] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 05/15/2020] [Accepted: 05/18/2020] [Indexed: 12/19/2022]
Abstract
G-quadruplex is one of the best-studied non-B type DNA that is now known to be prevalently present in the genomes of almost all the biological species. Recent studies reveal roles of G-quadruplex (G4) structures in various nucleic acids and chromosome transactions. In this short article, we will first describe recent findings on the roles of G4 in regulation of DNA replication. G4 is involved in regulation of spatio-temporal regulation of DNA replication through interaction with a specific binding protein, Rif1. This regulation is at least partially mediated by generation of specific chromatin architecture through Rif1-G4 interactions. We will also describe recent studies showing the potential roles of G4 in initiation of DNA replication. Next, we will present showcases of highly diversified roles of DNA G4 and RNA G4 in regulation of nucleic acid and chromosome functions. Finally, we will discuss how the formation of cellular G4 could be regulated.
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Affiliation(s)
- Hisao Masai
- Department of Basic Medical Sciences, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo, 156-8506, Japan.
| | - Taku Tanaka
- Department of Basic Medical Sciences, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo, 156-8506, Japan
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14
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Abstract
Several decades elapsed between the first descriptions of G-quadruplex nucleic acid structures (G4s) assembled in vitro and the emergence of experimental findings indicating that such structures can form and function in living systems. A large body of evidence now supports roles for G4s in many aspects of nucleic acid biology, spanning processes from transcription and chromatin structure, mRNA processing, protein translation, DNA replication and genome stability, and telomere and mitochondrial function. Nonetheless, it must be acknowledged that some of this evidence is tentative, which is not surprising given the technical challenges associated with demonstrating G4s in biology. Here I provide an overview of evidence for G4 biology, focusing particularly on the many potential pitfalls that can be encountered in its investigation, and briefly discuss some of broader biological processes that may be impacted by G4s including cancer.
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Affiliation(s)
- F. Brad Johnson
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States
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15
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Reina C, Cavalieri V. Epigenetic Modulation of Chromatin States and Gene Expression by G-Quadruplex Structures. Int J Mol Sci 2020; 21:E4172. [PMID: 32545267 PMCID: PMC7312119 DOI: 10.3390/ijms21114172] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/07/2020] [Accepted: 06/10/2020] [Indexed: 02/07/2023] Open
Abstract
G-quadruplexes are four-stranded helical nucleic acid structures formed by guanine-rich sequences. A considerable number of studies have revealed that these noncanonical structural motifs are widespread throughout the genome and transcriptome of numerous organisms, including humans. In particular, G-quadruplexes occupy strategic locations in genomic DNA and both coding and noncoding RNA molecules, being involved in many essential cellular and organismal functions. In this review, we first outline the fundamental structural features of G-quadruplexes and then focus on the concept that these DNA and RNA structures convey a distinctive layer of epigenetic information that is critical for the complex regulation, either positive or negative, of biological activities in different contexts. In this framework, we summarize and discuss the proposed mechanisms underlying the functions of G-quadruplexes and their interacting factors. Furthermore, we give special emphasis to the interplay between G-quadruplex formation/disruption and other epigenetic marks, including biochemical modifications of DNA bases and histones, nucleosome positioning, and three-dimensional organization of chromatin. Finally, epigenetic roles of RNA G-quadruplexes in post-transcriptional regulation of gene expression are also discussed. Undoubtedly, the issues addressed in this review take on particular importance in the field of comparative epigenetics, as well as in translational research.
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Affiliation(s)
- Chiara Reina
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical Specialties (PROMISE), University of Palermo, 90127 Palermo, Italy;
| | - Vincenzo Cavalieri
- Department of Biological, Chemical and Pharmaceutical Sciences and Technologies (STEBICEF), University of Palermo, 90128 Palermo, Italy
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16
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Yuan WF, Wan LY, Peng H, Zhong YM, Cai WL, Zhang YQ, Ai WB, Wu JF. The influencing factors and functions of DNA G-quadruplexes. Cell Biochem Funct 2020; 38:524-532. [PMID: 32056246 PMCID: PMC7383576 DOI: 10.1002/cbf.3505] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 01/10/2020] [Accepted: 01/14/2020] [Indexed: 12/28/2022]
Abstract
G‐quadruplexes form folded structures because of tandem repeats of guanine sequences in DNA or RNA. They adopt a variety of conformations, depending on many factors, including the type of loops and cations, the nucleotide strand number, and the main strand polarity of the G‐quadruplex. Meanwhile, the different conformations of G‐quadruplexes have certain influences on their biological functions, such as the inhibition of transcription, translation, and DNA replication. In addition, G‐quadruplex binding proteins also affect the structure and function of G‐quadruplexes. Some chemically synthesized G‐quadruplex sequences have been shown to have biological activities. For example, bimolecular G‐quadruplexes of AS1411 act as targets of exogenous drugs that inhibit the proliferation of malignant tumours. G‐quadruplexes are also used as vehicles to deliver nanoparticles. Thus, it is important to identify the factors that influence G‐quadruplex structures and maintain the stability of G‐quadruplexes. Herein, we mainly discuss the factors influencing G‐quadruplexes and the synthetic G‐quadruplex, AS1411. Significance of the study This review summarizes the factors that influence G‐quadruplexes and the functions of the synthetic G‐quadruplex, AS1411. It also discusses the use of G‐quadruplexes for drug delivery in tumour therapy.
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Affiliation(s)
- Wen-Fang Yuan
- Medical College, China Three Gorges University, Yichang, China.,Institute of Organ Fibrosis and Targeted Drug Delivery, China Three Gorges University, Yichang, China.,Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, China Three Gorges University, Yichang, China
| | - Lin-Yan Wan
- The People's Hospital, China Three Gorges University, Yichang, China.,Institute of Organ Fibrosis and Targeted Drug Delivery, China Three Gorges University, Yichang, China
| | - Hu Peng
- Medical College, China Three Gorges University, Yichang, China.,Institute of Organ Fibrosis and Targeted Drug Delivery, China Three Gorges University, Yichang, China.,Surgeon, The Yiling Hospital of Yichang, Yichang, China.,Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, China Three Gorges University, Yichang, China
| | - Yuan-Mei Zhong
- Medical College, China Three Gorges University, Yichang, China
| | - Wen-Li Cai
- Medical College, China Three Gorges University, Yichang, China
| | - Yan-Qiong Zhang
- Medical College, China Three Gorges University, Yichang, China.,Institute of Organ Fibrosis and Targeted Drug Delivery, China Three Gorges University, Yichang, China.,Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, China Three Gorges University, Yichang, China
| | - Wen-Bing Ai
- Surgeon, The Yiling Hospital of Yichang, Yichang, China
| | - Jiang-Feng Wu
- Medical College, China Three Gorges University, Yichang, China.,The People's Hospital, China Three Gorges University, Yichang, China.,Institute of Organ Fibrosis and Targeted Drug Delivery, China Three Gorges University, Yichang, China.,Surgeon, The Yiling Hospital of Yichang, Yichang, China.,Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, China Three Gorges University, Yichang, China
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17
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Abstract
Guanine-rich DNA sequences can fold into four-stranded, noncanonical secondary structures called G-quadruplexes (G4s). G4s were initially considered a structural curiosity, but recent evidence suggests their involvement in key genome functions such as transcription, replication, genome stability, and epigenetic regulation, together with numerous connections to cancer biology. Collectively, these advances have stimulated research probing G4 mechanisms and consequent opportunities for therapeutic intervention. Here, we provide a perspective on the structure and function of G4s with an emphasis on key molecules and methodological advances that enable the study of G4 structures in human cells. We also critically examine recent mechanistic insights into G4 biology and protein interaction partners and highlight opportunities for drug discovery.
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Affiliation(s)
- Jochen Spiegel
- Cancer Research UK, Cambridge Institute, Li Ka Shing Centre, Cambridge CB2 0RE, UK
| | - Santosh Adhikari
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK
| | - Shankar Balasubramanian
- Cancer Research UK, Cambridge Institute, Li Ka Shing Centre, Cambridge CB2 0RE, UK
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK
- School of Clinical Medicine, University of Cambridge, Cambridge CB2 0SP, UK
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18
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Islam I, Baba Y, Witarto AB, Yoshida W. G-quadruplex–forming GGA repeat region functions as a negative regulator of the Ccnb1ip1 enhancer. Biosci Biotechnol Biochem 2019; 83:1697-1702. [DOI: 10.1080/09168451.2019.1611412] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
ABSTRACT
An enhancer located upstream of the transcriptional start site of Ccnb1ip1 containing two GGA-rich regions and a 14-GGA repeat (GGA)14 region has been previously identified. Three copies of four GGA repeats in the c-myb promoter that form a tetrad:heptad:heptad:tetrad (T:H:H:T) dimerized G-quadruplex (G4) structure reportedly functions as both a transcriptional repressor and activator. Here, the secondary structures of the two GGA-rich and (GGA)14 regions were analyzed using circular dichroism spectral analysis, which indicated that the two GGA-rich DNAs formed parallel-type G4 structures, whereas (GGA)14 DNA formed the T:H:H:T dimerized G4 structure. Reporter assays demonstrated that individual regions did not show enhancer activity; however, the deletion of the (GGA)14 region resulted in 1.5-fold higher enhancer activity than that of the whole enhancer. These results indicate that the (GGA)14 region that forms the T:H:H:T dimerized G4 structure functions as a negative regulator of the Ccnb1ip1 enhancer.
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Affiliation(s)
- Izzul Islam
- Graduate School of Bionics, Tokyo University of Technology, Hachioji, Japan
- Department of Biotechnology, Sumbawa University of Technology, Sumbawa Besar, Indonesia
| | - Yuji Baba
- Graduate School of Bionics, Tokyo University of Technology, Hachioji, Japan
| | - Arief Budi Witarto
- Department of Biotechnology, Sumbawa University of Technology, Sumbawa Besar, Indonesia
| | - Wataru Yoshida
- Graduate School of Bionics, Tokyo University of Technology, Hachioji, Japan
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19
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Naphthalene Diimides as Multimodal G-Quadruplex-Selective Ligands. Molecules 2019; 24:molecules24030426. [PMID: 30682828 PMCID: PMC6384834 DOI: 10.3390/molecules24030426] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 01/11/2019] [Accepted: 01/22/2019] [Indexed: 02/03/2023] Open
Abstract
G-quadruplexes are four-stranded nucleic acids structures that can form in guanine-rich sequences. Following the observation that G-quadruplexes are particularly abundant in genomic regions related to cancer, such as telomeres and oncogenes promoters, several G-quadruplex-binding molecules have been developed for therapeutic purposes. Among them, naphthalene diimide derivatives have reported versatility, consistent selectivity and high affinity toward the G-quadruplex structures. In this review, we present the chemical features, synthesis and peculiar optoelectronic properties (absorption, emission, redox) that make naphtalene diimides so versatile for biomedical applications. We present the latest developments on naphthalene diimides as G-quadruplex ligands, focusing on their ability to bind G-quadruplexes at telomeres and oncogene promoters with consequent anticancer activity. Their different binding modes (reversible versus irreversible/covalent) towards G-quadruplexes and their additional use as antimicrobial agents are also presented and discussed.
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20
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Non-duplex G-Quadruplex Structures Emerge as Mediators of Epigenetic Modifications. Trends Genet 2018; 35:129-144. [PMID: 30527765 DOI: 10.1016/j.tig.2018.11.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 10/10/2018] [Accepted: 11/02/2018] [Indexed: 12/16/2022]
Abstract
The role of non-duplex DNA, the guanine-quadruplex structure in particular, is becoming widely appreciated. Increasing evidence in the last decade implicates quadruplexes in important processes such as transcription and replication. Interestingly, more recent work suggests roles for quadruplexes, in association with quadruplex-interacting proteins, in epigenetics through both DNA and histone modifications. Here, we review the effect of the quadruplex structure on post-replication epigenetic memory and quadruplex-induced promoter DNA/histone modifications. Furthermore, we highlight the epigenetic state of the telomerase promoter where quadruplexes could play a key regulatory role. Finally, we discuss the possibility that DNA structures such as quadruplexes, within a largely duplex DNA background, could act as molecular anchors for locally induced epigenetic modifications.
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21
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Stabilization of G-quadruplex structure on vascular endothelial growth factor gene promoter depends on CpG methylation site and cation type. Biochim Biophys Acta Gen Subj 2018; 1862:1933-1937. [DOI: 10.1016/j.bbagen.2018.06.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 06/01/2018] [Accepted: 06/18/2018] [Indexed: 11/19/2022]
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22
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Morgan RK, Molnar MM, Batra H, Summerford B, Wadkins RM, Brooks TA. Effects of 5-Hydroxymethylcytosine Epigenetic Modification on the Stability and Molecular Recognition of VEGF i-Motif and G-Quadruplex Structures. J Nucleic Acids 2018; 2018:9281286. [PMID: 29862069 PMCID: PMC5976936 DOI: 10.1155/2018/9281286] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 03/31/2018] [Accepted: 04/03/2018] [Indexed: 12/14/2022] Open
Abstract
Promoters often contain asymmetric G- and C-rich strands, in which the cytosines are prone to epigenetic modification via methylation (5-mC) and 5-hydroxymethylation (5-hmC). These sequences can also form four-stranded G-quadruplex (G4) or i-motif (iM) secondary structures. Although the requisite sequences for epigenetic modulation and iM/G4 formation are similar and can overlap, they are unlikely to coexist. Despite 5-hmC being an oxidization product of 5-mC, the two modified bases cluster at distinct loci. This study focuses on the intersection of G4/iM formation and 5-hmC modification using the vascular endothelial growth factor (VEGF) gene promoter's CpG sites and examines whether incorporation of 5-hmC into iM/G4 structures had any physicochemical effect on formation, stability, or recognition by nucleolin or the cationic porphyrin, TMPyP4. No marked changes were found in the formation or stability of iM and G4 structures; however, changes in recognition by nucleolin or TMPyP4 occurred with 5-hmC modification wherein protein and compound binding to 5-hmC modified G4s was notably reduced. G4/iM structures in the VEGF promoter are promising therapeutic targets for antiangiogenic therapy, and this work contributes to a comprehensive understanding of their governing principles related to potential transcriptional control and targeting.
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Affiliation(s)
- Rhianna K. Morgan
- School of Pharmacy, Department of BioMolecular Sciences, Division of Pharmacology, University of Mississippi, University, MS 38677, USA
| | - Michael M. Molnar
- Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA
| | - Harshul Batra
- School of Pharmacy, Department of BioMolecular Sciences, Division of Pharmacology, University of Mississippi, University, MS 38677, USA
| | - Bethany Summerford
- Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA
| | - Randy M. Wadkins
- Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA
| | - Tracy A. Brooks
- School of Pharmacy, Department of BioMolecular Sciences, Division of Pharmacology, University of Mississippi, University, MS 38677, USA
- School of Pharmacy and Pharmaceutical Sciences, Department of Pharmaceutical Sciences, Binghamton University, Binghamton, NY 13902, USA
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23
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Tsukakoshi K, Saito S, Yoshida W, Goto S, Ikebukuro K. CpG Methylation Changes G-Quadruplex Structures Derived from Gene Promoters and Interaction with VEGF and SP1. Molecules 2018; 23:molecules23040944. [PMID: 29670067 PMCID: PMC6017926 DOI: 10.3390/molecules23040944] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Revised: 04/13/2018] [Accepted: 04/15/2018] [Indexed: 12/14/2022] Open
Abstract
G-quadruplex (G4) is a DNA/RNA conformation that consists of two or more G-tetrads resulting from four-guanine bases connected by Hoogsteen-type hydrogen bonds, which is often found in the telomeres of chromatin, as well as in the promoter regions of genes. The function of G4 in the genomic DNA is being elucidated and some G4-protein interactions have been reported; these are believed to play a role in vital cellular functions. In this study, we focused on CpG methylation, a well-known epigenetic modification of the genomic DNA, especially found in the promoter regions. Although many G4-forming sequences within the genomic DNA harbor CpG sites, the relationship between CpG methylation and the binding properties of associated proteins remains unclear. We demonstrated that the binding ability of vascular endothelial growth factor (VEGF) G4 DNA to VEGF165 protein was significantly decreased by CpG methylation. We identified the binding activity of G4 DNA oligonucleotides derived from gene promoter regions to SP1, a transcription factor that interacts with a G4-forming DNA and is also altered by CpG methylation. The effect of methylation on binding affinity was accompanied by changes in G4 structure and/or topology. Therefore, this study suggested that CpG methylation might be involved in protein binding to G4-forming DNA segments for purposes of transcriptional regulation.
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Affiliation(s)
- Kaori Tsukakoshi
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
| | - Shiori Saito
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
| | - Wataru Yoshida
- School of Bioscience and Biotechnology, Tokyo University of Technology, 1404-1 Katakuramachi, Hachioji, Tokyo 192-0982, Japan.
| | - Shinichi Goto
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
| | - Kazunori Ikebukuro
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
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24
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Carr CE, Ganugula R, Shikiya R, Soto AM, Marky LA. Effect of dC → d(m 5C) substitutions on the folding of intramolecular triplexes with mixed TAT and C +GC base triplets. Biochimie 2018; 146:156-165. [PMID: 29277568 PMCID: PMC5811340 DOI: 10.1016/j.biochi.2017.12.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 12/19/2017] [Indexed: 12/31/2022]
Abstract
Oligonucleotide-directed triple helix formation has been recognized as a potential tool for targeting genes with high specificity. Cystosine methylation in the 5' position is both ubiquitous and a stable regulatory modification, which could potentially stabilize triple helix formation. In this work, we have used a combination of calorimetric and spectroscopic techniques to study the intramolecular unfolding of four triplexes and two duplexes. We used the following triplex control sequence, named Control Tri, d(AGAGAC5TCTCTC5TCTCT), where C5 are loops of five cytosines. From this sequence, we studied three other sequences with dC → d(m5C) substitutions on the Hoogsteen strand (2MeH), Crick strand (2MeC) and both strands (4MeHC). Calorimetric studies determined that methylation does increase the thermal and enthalpic stability, leading to an overall favorable free energy, and that this increased stability is cumulative, i.e. methylation on both the Hoogsteen and Crick strands yields the largest favorable free energy. The differential uptake of protons, counterions and water was determined. It was found that methylation increases cytosine protonation by shifting the apparent pKa value to a higher pH; this increase in proton uptake coincides with a release of counterions during folding of the triplex, likely due to repulsion from the increased positive charge from the protonated cytosines. The immobilization of water was not affected for triplexes with methylated cytosines on their Hoogsteen or Crick strands, but was seen for the triplex where both strands are methylated. This may be due to the alignment in the major groove of the methyl groups on the cytosines with the methyl groups on the thymines which causes an increase in structural water along the spine of the triplex.
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Affiliation(s)
- Carolyn E Carr
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, 68198-6025, USA
| | - Rajkumar Ganugula
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, 68198-6025, USA
| | - Ronald Shikiya
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, 68198-6025, USA
| | - Ana Maria Soto
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, 68198-6025, USA
| | - Luis A Marky
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, 68198-6025, USA.
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25
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Li PT, Wang ZF, Chu IT, Kuan YM, Li MH, Huang MC, Chiang PC, Chang TC, Chen CT. Expression of the human telomerase reverse transcriptase gene is modulated by quadruplex formation in its first exon due to DNA methylation. J Biol Chem 2017; 292:20859-20870. [PMID: 29084850 DOI: 10.1074/jbc.m117.808022] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 09/23/2017] [Indexed: 11/06/2022] Open
Abstract
DNA secondary structures and methylation are two well-known mechanisms that regulate gene expression. The catalytic subunit of telomerase, human telomerase reverse transcriptase (hTERT), is overexpressed in ∼90% of human cancers to maintain telomere length for cell immortalization. Binding of CCCTC-binding factor (CTCF) to the first exon of the hTERT gene can down-regulate its expression. However, DNA methylation in the first exon can prevent CTCF binding in most cancers, but the molecular mechanism is unknown. The NMR analysis showed that a stretch of guanine-rich sequence in the first exon of hTERT and located within the CTCF-binding region can form two secondary structures, a hairpin and a quadruplex. A key finding was that the methylation of cytosine at the specific CpG dinucleotides will participate in quartet formation, causing the shift of the equilibrium from the hairpin structure to the quadruplex structure. Of further importance was the finding that the quadruplex formation disrupts CTCF protein binding, which results in an increase in hTERT gene expression. Our results not only identify quadruplex formation in the first exon promoted by CpG dinucleotide methylation as a regulator of hTERT expression but also provide a possible mechanistic insight into the regulation of gene expression via secondary DNA structures.
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Affiliation(s)
- Pei-Tzu Li
- From the Departments of Biochemical Science and Technology and
| | - Zi-Fu Wang
- the Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - I-Te Chu
- the Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan.,Chemistry, National Taiwan University and
| | - Yen-Min Kuan
- From the Departments of Biochemical Science and Technology and
| | - Ming-Hao Li
- the Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
| | - Mu-Ching Huang
- From the Departments of Biochemical Science and Technology and
| | - Pei-Chi Chiang
- From the Departments of Biochemical Science and Technology and
| | - Ta-Chau Chang
- the Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan .,Chemistry, National Taiwan University and
| | - Chin-Tin Chen
- From the Departments of Biochemical Science and Technology and
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26
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Stevens AJ, Kennedy MA. Methylated Cytosine Maintains G-Quadruplex Structures during Polymerase Chain Reaction and Contributes to Allelic Dropout. Biochemistry 2017; 56:3691-3698. [DOI: 10.1021/acs.biochem.7b00480] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Aaron J. Stevens
- Department of Pathology, University of Otago, Christchurch, New Zealand
| | - Martin A. Kennedy
- Department of Pathology, University of Otago, Christchurch, New Zealand
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27
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Stevens AJ, Kennedy MA. Structural Analysis of G-Quadruplex Formation at the Human MEST Promoter. PLoS One 2017; 12:e0169433. [PMID: 28052120 PMCID: PMC5214457 DOI: 10.1371/journal.pone.0169433] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 12/01/2016] [Indexed: 11/22/2022] Open
Abstract
The promoter region of the imprinted gene MEST contains several motifs capable of forming G-quadruplex (G4) structures, which appear to contribute to consistent allelic dropout during polymerase chain reaction (PCR) analysis of this region. Here, we extend our previous analysis of MEST G4 structures by applying fluorescent footprinting techniques to assess non B-DNA structure and topology in dsDNA from the full MEST promoter region, under conditions that mimic PCR. We demonstrate that the buffer used for PCR provides an extremely favourable milieu for G4 formation, and that cytosine methylation helps maintain G4 structures during PCR. Additionally, we demonstrate G4 formation at motifs not previously identified through bioinformatic analysis of the MEST promoter, and provide nucleotide level resolution for topological reconstruction of these structures. These observations increase our understanding of the mechanisms through which methylation and G4 contribute towards allelic drop-out during PCR.
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Affiliation(s)
- Aaron J. Stevens
- Department of Pathology, School of Medicine, University of Otago, Christchurch, New Zealand
- * E-mail:
| | - Martin A. Kennedy
- Department of Pathology, School of Medicine, University of Otago, Christchurch, New Zealand
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28
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Cao Y, Gao S, Yan Y, Bruist MF, Wang B, Guo X. Assembly of supramolecular DNA complexes containing both G-quadruplexes and i-motifs by enhancing the G-repeat-bearing capacity of i-motifs. Nucleic Acids Res 2016; 45:26-38. [PMID: 27899568 PMCID: PMC5224476 DOI: 10.1093/nar/gkw1049] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 10/17/2016] [Accepted: 10/20/2016] [Indexed: 12/13/2022] Open
Abstract
The single-step assembly of supramolecular complexes containing both i-motifs and G-quadruplexes (G4s) is demonstrated. This can be achieved because the formation of four-stranded i-motifs appears to be little affected by certain terminal residues: a five-cytosine tetrameric i-motif can bear ten-base flanking residues. However, things become complex when different lengths of guanine-repeats are added at the 3′ or 5′ ends of the cytosine-repeats. Here, a series of oligomers d(XGiXC5X) and d(XC5XGiX) (X = A, T or none; i < 5) are designed to study the impact of G-repeats on the formation of tetrameric i-motifs. Our data demonstrate that tetramolecular i-motif structure can tolerate specific flanking G-repeats. Assemblies of these oligonucleotides are polymorphic, but may be controlled by solution pH and counter ion species. Importantly, we find that the sequences d(TGiAC5) can form the tetrameric i-motif in large quantities. This leads to the design of two oligonucleotides d(TG4AC7) and d(TGBrGGBrGAC7) that self-assemble to form quadruplex supramolecules under certain conditions. d(TG4AC7) forms supramolecules under acidic conditions in the presence of K+ that are mainly V-shaped or ring-like containing parallel G4s and antiparallel i-motifs. d(TGBrGGBrGAC7) forms long linear quadruplex wires under acidic conditions in the presence of Na+ that consist of both antiparallel G4s and i-motifs.
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Affiliation(s)
- Yanwei Cao
- College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China
| | - Shang Gao
- College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China
| | - Yuting Yan
- College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China
| | - Michael F Bruist
- Department of Chemistry & Biochemistry, University of the Sciences, 600 South 43rd Street, Philadelphia, PA 19104, USA
| | - Bing Wang
- College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China
| | - Xinhua Guo
- College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P. R. China
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29
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McKim M, Buxton A, Johnson C, Metz A, Sheardy RD. Loop Sequence Context Influences the Formation and Stability of the i-Motif for DNA Oligomers of Sequence (CCCXXX)4, where X = A and/or T, under Slightly Acidic Conditions. J Phys Chem B 2016; 120:7652-61. [DOI: 10.1021/acs.jpcb.6b04561] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Mikeal McKim
- Department of Chemistry and
Biochemistry, Texas Woman’s University, P.O. Box 425859, Denton, Texas 76204, United States
| | - Alexander Buxton
- Department of Chemistry and
Biochemistry, Texas Woman’s University, P.O. Box 425859, Denton, Texas 76204, United States
| | - Courtney Johnson
- Department of Chemistry and
Biochemistry, Texas Woman’s University, P.O. Box 425859, Denton, Texas 76204, United States
| | - Amanda Metz
- Department of Chemistry and
Biochemistry, Texas Woman’s University, P.O. Box 425859, Denton, Texas 76204, United States
| | - Richard D. Sheardy
- Department of Chemistry and
Biochemistry, Texas Woman’s University, P.O. Box 425859, Denton, Texas 76204, United States
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30
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Wu RR, Yang B, Frieler CE, Berden G, Oomens J, Rodgers MT. Diverse mixtures of 2,4-dihydroxy tautomers and O4 protonated conformers of uridine and 2'-deoxyuridine coexist in the gas phase. Phys Chem Chem Phys 2016. [PMID: 26225730 DOI: 10.1039/c5cp02227d] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The gas-phase conformations of protonated uridine, [Urd+H](+), and its modified form, protonated 2'-deoxyuridine, [dUrd+H](+), generated by electrospray ionization are investigated using infrared multiple photon dissociation (IRMPD) action spectroscopy techniques. IRMPD action spectra of [Urd+H](+) and [dUrd+H](+) are measured over the IR fingerprint and hydrogen-stretching regions. [Urd+H](+) and [dUrd+H](+) exhibit very similar IRMPD spectral profiles. However, the IRMPD yields of [Urd+H](+) exceed those of [dUrd+H](+) in both the IR fingerprint and hydrogen-stretching regions. The measured spectra are compared to the linear IR spectra predicted for the stable low-energy structures of these species computed at the B3LYP/6-311+G(d,p) level of theory to determine the tautomeric conformations populated by electrospray ionization. Both B3LYP and MP2 methods find O4 and O2 protonated canonical as well as 2,4-dihydroxy tautomers among the stable low-energy structures of [Urd+H](+) and [dUrd+H](+). Comparison between the measured IRMPD and calculated linear IR spectra suggests that these species exist in their ring-closed forms and that both 2,4-dihydroxy tautomers as well as O4 protonated canonical conformers coexist in the population generated by electrospray ionization for both [Urd+H](+) and [dUrd+H](+). The 2'-deoxy modification of [dUrd+H](+) reduces the variety of 2,4-dihydroxy tautomers populated in the experiments vs. those of [Urd+H](+).
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Affiliation(s)
- R R Wu
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
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31
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González C, Salces-Ortiz J, Calvo JH, Serrano MM. In silico analysis of regulatory and structural motifs of the ovine HSP90AA1 gene. Cell Stress Chaperones 2016; 21:415-27. [PMID: 26810179 PMCID: PMC4837184 DOI: 10.1007/s12192-016-0668-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 01/02/2016] [Accepted: 01/06/2016] [Indexed: 01/21/2023] Open
Abstract
Gene promoters are essential regions of DNA where the transcriptional molecular machinery to produce RNA molecules is recruited. In this process, DNA epigenetic modifications can acquire a fundamental role in the regulation of gene expression. Recently, in a previous work of our group, functional features and DNA methylation involved in the ovine HSP90AA1 gene expression regulation have been observed. In this work, we report a combination of methylation analysis by bisulfite sequencing in several tissues and at different developmental stages together with in silico bioinformatic analysis of putative regulating factors in order to identify regulative mechanisms both at the promoter and gene body. Our results show a "hybrid structure" (TATA box + CpG island) of the ovine HSP90AA1 gene promoter both in somatic and non-differentiated germ tissues, revealing the ability of the HSP90AA1 gene to be regulated both in an inducible and constitutive fashion. In addition, in silico analysis showed that several putative alternative spliced regulatory motifs, exonic splicing enhancers (ESEs), and G-quadruplex secondary structures were somehow related to the DNA methylation pattern found. The results obtained here could help explain the differences in cell-type transcripts, tissue expression rate, and transcription silencing mechanisms found in this gene.
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Affiliation(s)
| | | | - Jorge H Calvo
- Unidad de Tecnología en Producción Animal, CITA, 59059, Zaragoza, Spain
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32
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François M, Leifert WR, Tellam R, Fenech MF. Folate deficiency and DNA-methyltransferase inhibition modulate G-quadruplex frequency. Mutagenesis 2016; 31:409-16. [DOI: 10.1093/mutage/gev088] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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33
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Zamiri B, Mirceta M, Bomsztyk K, Macgregor RB, Pearson CE. Quadruplex formation by both G-rich and C-rich DNA strands of the C9orf72 (GGGGCC)8•(GGCCCC)8 repeat: effect of CpG methylation. Nucleic Acids Res 2015; 43:10055-64. [PMID: 26432832 PMCID: PMC4787773 DOI: 10.1093/nar/gkv1008] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 09/22/2015] [Indexed: 12/13/2022] Open
Abstract
Unusual DNA/RNA structures of the C9orf72 repeat may participate in repeat expansions or pathogenesis of amyotrophic lateral sclerosis and frontotemporal dementia. Expanded repeats are CpG methylated with unknown consequences. Typically, quadruplex structures form by G-rich but not complementary C-rich strands. Using CD, UV and electrophoresis, we characterized the structures formed by (GGGGCC)8 and (GGCCCC)8 strands with and without 5-methylcytosine (5mCpG) or 5-hydroxymethylcytosine (5hmCpG) methylation. All strands formed heterogenous mixtures of structures, with features of quadruplexes (at pH 7.5, in K(+), Na(+) or Li(+)), but no feature typical of i-motifs. C-rich strands formed quadruplexes, likely stabilized by G•C•G•C-tetrads and C•C•C•C-tetrads. Unlike G•G•G•G-tetrads, some G•C•G•C-tetrad conformations do not require the N7-Guanine position, hence C9orf72 quadruplexes still formed when N7-deazaGuanine replace all Guanines. 5mCpG and 5hmCpG increased and decreased the thermal stability of these structures. hnRNPK, through band-shift analysis, bound C-rich but not G-rich strands, with a binding preference of unmethylated > 5hmCpG > 5mCpG, where methylated DNA-protein complexes were retained in the wells, distinct from unmethylated complexes. Our findings suggest that for C-rich sequences interspersed with G-residues, one must consider quadruplex formation and that methylation of quadruplexes may affect epigenetic processes.
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Affiliation(s)
- Bita Zamiri
- Graduate Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
| | - Mila Mirceta
- Program of Genetics & Genome Biology, The Hospital for Sick Children, Toronto, Ontario M5G 1L7, Canada Program of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A1, Canada
| | - Karol Bomsztyk
- UW Medicine South Lake Union, University of Washington, Seattle WA 98109, USA
| | - Robert B Macgregor
- Graduate Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
| | - Christopher E Pearson
- Program of Genetics & Genome Biology, The Hospital for Sick Children, Toronto, Ontario M5G 1L7, Canada Program of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A1, Canada
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34
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Brčić J, Plavec J. Solution structure of a DNA quadruplex containing ALS and FTD related GGGGCC repeat stabilized by 8-bromodeoxyguanosine substitution. Nucleic Acids Res 2015; 43:8590-600. [PMID: 26253741 PMCID: PMC4787828 DOI: 10.1093/nar/gkv815] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 07/30/2015] [Indexed: 12/13/2022] Open
Abstract
A prolonged expansion of GGGGCC repeat within non-coding region of C9orf72 gene has been identified as the most common cause of familial amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), which are devastating neurodegenerative disorders. Formation of unusual secondary structures within expanded GGGGCC repeat, including DNA and RNA G-quadruplexes and R-loops was proposed to drive ALS and FTD pathogenesis. Initial NMR investigation on DNA oligonucleotides with four repeat units as the shortest model with the ability to form an unimolecular G-quadruplex indicated their folding into multiple G-quadruplex structures in the presence of K+ ions. Single dG to 8Br-dG substitution at position 21 in oligonucleotide d[(G4C2)3G4] and careful optimization of folding conditions enabled formation of mostly a single G-quadruplex species, which enabled determination of a high-resolution structure with NMR. G-quadruplex structure adopted by d[(G4C2)3GGBrGG] is composed of four G-quartets, which are connected by three edgewise C-C loops. All four strands adopt antiparallel orientation to one another and have alternating syn-anti progression of glycosidic conformation of guanine residues. One of the cytosines in every loop is stacked upon the G-quartet contributing to a very compact and stable structure.
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Affiliation(s)
- Jasna Brčić
- Slovenian NMR Center, National Institute of Chemistry, Hajdrihova 19, SI-1000, Ljubljana, Slovenia
| | - Janez Plavec
- Slovenian NMR Center, National Institute of Chemistry, Hajdrihova 19, SI-1000, Ljubljana, Slovenia Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia EN-FIST Center of Excellence, Ljubljana, Slovenia
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35
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Nesterova IV, Elsiddieg SO, Nesterov EE. A dual input DNA-based molecular switch. MOLECULAR BIOSYSTEMS 2015; 10:2810-4. [PMID: 25099914 DOI: 10.1039/c4mb00363b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We have designed and characterized a DNA-based molecular switch which processes two physiologically relevant inputs: pH (i.e. alkalinisation) and enzymatic activity, and generates a chemical output (in situ synthesized oligonucleotide). The design, based on allosteric interactions between i-motif and hairpin stem within the DNA molecule, addresses such critical physiological system parameters as molecular simplicity, tunability, orthogonality of the two input sensing domains, and compatibility with intracellular operation/delivery.
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Affiliation(s)
- Irina V Nesterova
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA.
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36
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François M, Leifert W, Tellam R, Fenech M. G-quadruplexes: A possible epigenetic target for nutrition. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2015; 764:101-7. [PMID: 26041269 DOI: 10.1016/j.mrrev.2015.03.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 03/30/2015] [Accepted: 03/31/2015] [Indexed: 12/29/2022]
Abstract
G-quadruplexes (G4) are highly stable tetra-stranded secondary DNA structures known to mediate gene regulation. These structures are resolved by DNA helicases and are believed to be a causal factor in the phenotype of premature ageing disorders following mutations in DNA helicase genes. The relevance of G4 structures in ageing may be further implicated by their dynamic relationship with DNA modification mechanisms. When DNA methylation and oxidation occur at the vicinity of G4 elements, they can affect the stability of G4 structures which may in turn mediate gene expression resulting in deleterious effects on genome integrity. Therefore, the influence of nutritional deficiencies or excess on oxidation and methylation mechanisms may be contributing factors affecting the stability of G4 structures and their balance in the human genome. We propose that dietary nutrients such as folate and antioxidants may play a beneficial role in reducing G4-induced DNA damage through changes in G4 structure stability. The current knowledge advocates the importance of resolving G4 structures by DNA helicases for sustained genome integrity, and the existence of stability changes in G4 structures when associated with DNA methylation and oxidation modifications.
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Affiliation(s)
- Maxime François
- CSIRO Food and Nutrition Flagship, Nutrigenomics and DNA Damage, Adelaide, South Australia 5000, Australia.
| | - Wayne Leifert
- CSIRO Food and Nutrition Flagship, Nutrigenomics and DNA Damage, Adelaide, South Australia 5000, Australia
| | - Ross Tellam
- CSIRO Agriculture Flagship, St Lucia, Brisbane, Queensland 4067, Australia
| | - Michael Fenech
- CSIRO Food and Nutrition Flagship, Nutrigenomics and DNA Damage, Adelaide, South Australia 5000, Australia
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37
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Stevens AJ, Stuffrein-Roberts S, Cree SL, Gibb A, Miller AL, Doudney K, Aitchison A, Eccles MR, Joyce PR, Filichev VV, Kennedy MA. G-quadruplex structures and CpG methylation cause drop-out of the maternal allele in polymerase chain reaction amplification of the imprinted MEST gene promoter. PLoS One 2014; 9:e113955. [PMID: 25437198 PMCID: PMC4249981 DOI: 10.1371/journal.pone.0113955] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 10/31/2014] [Indexed: 12/03/2022] Open
Abstract
We observed apparent non-Mendelian behaviour of alleles when genotyping a region in a CpG island at the 5′ end of the maternally imprinted human MEST isoform. This region contains three single nucleotide polymorphisms (SNPs) in total linkage disequilibrium, such that only two haplotypes occur in the human population. Only one haplotype was detectable in each subject, never both, despite the use of multiple primers and several genotyping methods. We observed that this region contains motifs capable of forming several G-quadruplex structures. Circular dichroism spectroscopy and native polyacrylamide gel electrophoresis confirmed that at least three G-quadruplexes form in vitro in the presence of potassium ions, and one of these structures has a Tm of greater than 99°C in polymerase chain reaction (PCR) buffer. We demonstrate that it is the methylated maternal allele that is always lost during PCR amplification, and that formation of G-quadruplexes and presence of methylated cytosines both contributed to this phenomenon. This observed parent-of-origin specific allelic drop-out has important implications for analysis of imprinted genes in research and diagnostic settings.
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Affiliation(s)
- Aaron J. Stevens
- Department of Pathology, University of Otago, Christchurch 8140, New Zealand
| | | | - Simone L. Cree
- Department of Pathology, University of Otago, Christchurch 8140, New Zealand
| | - Andrew Gibb
- Department of Pathology, University of Otago, Christchurch 8140, New Zealand
| | - Allison L. Miller
- Department of Pathology, University of Otago, Christchurch 8140, New Zealand
| | - Kit Doudney
- Department of Pathology, University of Otago, Christchurch 8140, New Zealand
| | - Alan Aitchison
- Department of Pathology, University of Otago, Christchurch 8140, New Zealand
| | - Michael R. Eccles
- Department of Pathology, University of Otago, Dunedin School of Medicine, Dunedin, New Zealand
| | - Peter R. Joyce
- Department of Psychological Medicine, University of Otago, Christchurch 8140, New Zealand
| | | | - Martin A. Kennedy
- Department of Pathology, University of Otago, Christchurch 8140, New Zealand
- * E-mail:
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38
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Stabilization of G-quadruplex DNA by C-5-methyl-cytosine in bcl-2 promoter: implications for epigenetic regulation. Biochem Biophys Res Commun 2012; 433:368-73. [PMID: 23261425 DOI: 10.1016/j.bbrc.2012.12.040] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 12/08/2012] [Indexed: 11/20/2022]
Abstract
The C-5-methylation of cytosine in the CpG islands is an important pattern for epigenetic modification of gene, which plays a key role in regulating gene transcription. G-quadruplex is an unusual DNA secondary structure formed in G-rich regions and is identified as a transcription repressor in some oncogenes, such as c-myc and bcl-2. In the present study, the results from CD spectrum and FRET assay showed that the methylation of cytosine in the CpG islands could induce a conformational change of the G-quadruplex in the P1 promoter of bcl-2, and greatly increase the thermal-stability of this DNA oligomer. Moreover, the methylation of cytosine in the G-quadruplex could protect the structure from the disruption by the complementary strand, showing with the increasing ability to arrest the polymerase in PCR stop assay. This data indicated that the stabilization of the G-quadruplex structure in the CpG islands might be involved in the epigenetical transcriptional regulation for specific genes through the C-5-methylation modification pattern.
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39
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Affiliation(s)
- Ofer I. Wilner
- Institute of Chemistry, Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Itamar Willner
- Institute of Chemistry, Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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40
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Abstract
Using spectroscopic techniques, we demonstrate the effect of LNA (locked nucleic acid) nucleotides in modulating the formation and stability of the i-motif structure formed by the c-MYC sequence.
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Affiliation(s)
- Niti Kumar
- Structural Biology Unit, Institute of Genomics and Integrative Biology, CSIR, Mall Road, New Delhi 110 007, India
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41
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Lindroth AM, Park YJ, McLean CM, Dokshin GA, Persson JM, Herman H, Pasini D, Miró X, Donohoe ME, Lee JT, Helin K, Soloway PD. Antagonism between DNA and H3K27 methylation at the imprinted Rasgrf1 locus. PLoS Genet 2008; 4:e1000145. [PMID: 18670629 PMCID: PMC2475503 DOI: 10.1371/journal.pgen.1000145] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2008] [Accepted: 06/30/2008] [Indexed: 12/18/2022] Open
Abstract
At the imprinted Rasgrf1 locus in mouse, a cis-acting sequence controls DNA methylation at a differentially methylated domain (DMD). While characterizing epigenetic marks over the DMD, we observed that DNA and H3K27 trimethylation are mutually exclusive, with DNA and H3K27 methylation limited to the paternal and maternal sequences, respectively. The mutual exclusion arises because one mark prevents placement of the other. We demonstrated this in five ways: using 5-azacytidine treatments and mutations at the endogenous locus that disrupt DNA methylation; using a transgenic model in which the maternal DMD inappropriately acquired DNA methylation; and by analyzing materials from cells and embryos lacking SUZ12 and YY1. SUZ12 is part of the PRC2 complex, which is needed for placing H3K27me3, and YY1 recruits PRC2 to sites of action. Results from each experimental system consistently demonstrated antagonism between H3K27me3 and DNA methylation. When DNA methylation was lost, H3K27me3 encroached into sites where it had not been before; inappropriate acquisition of DNA methylation excluded normal placement of H3K27me3, and loss of factors needed for H3K27 methylation enabled DNA methylation to appear where it had been excluded. These data reveal the previously unknown antagonism between H3K27 and DNA methylation and identify a means by which epigenetic states may change during disease and development. Methylation of DNA and histones exert profound and inherited effects on gene expression. These occur without changes to the underlying DNA sequence and are considered epigenetic effects. Disrupting epigenetic states can cause developmental abnormalities and cancer. Very little is known about how locations in the mammalian genome are chosen to receive these chemical modifications, or how their placement is regulated. We have identified a DNA sequence that acts as a methylation programmer at the Rasgrf1 locus in mice. It is required for methylation of nearby DNA sequences and can also influence the levels of local histone methylation. The methylation programmer has different effects on paternally and maternally derived chromosomes, directing DNA methylation on the paternal allele and histone H3 lysine 27 trimethylation on the maternal allele. These two methylation marks are not only mutually exclusive; they are also mutually antagonizing, whereby one blocks the placement of the other. Manipulations that cause aberrant changes in the levels of one of these marks had the opposite effect on the other mark. These observations identify novel mechanisms that specify epigenetic states in vivo and provide a framework for understanding how pathological epigenetic changes can arise, including those emerging at tumor suppressors during carcinogenesis.
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Affiliation(s)
- Anders M. Lindroth
- Division of Nutritional Sciences, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York, United States of America
| | - Yoon Jung Park
- Division of Nutritional Sciences, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York, United States of America
| | - Chelsea M. McLean
- Division of Nutritional Sciences, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York, United States of America
| | - Gregoriy A. Dokshin
- Division of Nutritional Sciences, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York, United States of America
| | - Jenna M. Persson
- Division of Nutritional Sciences, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York, United States of America
| | - Herry Herman
- Division of Nutritional Sciences, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York, United States of America
- Department of Orthopaedic Surgery, School of Medicine, Padjadjaran State University–Hasan Sadikin General Hospital, Bandung, West Java, Indonesia
| | - Diego Pasini
- Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
- Centre for Epigenetics, University of Copenhagen, Copenhagen, Denmark
| | - Xavier Miró
- Department of Molecular Cell Biology, Max-Planck-Institute of Biophysical Chemistry, Göttingen, Germany
| | - Mary E. Donohoe
- Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Jeannie T. Lee
- Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Kristian Helin
- Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen, Denmark
- Centre for Epigenetics, University of Copenhagen, Copenhagen, Denmark
| | - Paul D. Soloway
- Division of Nutritional Sciences, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York, United States of America
- * E-mail:
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42
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Mergny JL, De Cian A, Ghelab A, Saccà B, Lacroix L. Kinetics of tetramolecular quadruplexes. Nucleic Acids Res 2005; 33:81-94. [PMID: 15642696 PMCID: PMC546136 DOI: 10.1093/nar/gki148] [Citation(s) in RCA: 243] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2004] [Revised: 12/07/2004] [Accepted: 12/07/2004] [Indexed: 11/12/2022] Open
Abstract
The melting of tetramolecular DNA or RNA quadruplexes is kinetically irreversible. However, rather than being a hindrance, this kinetic inertia allows us to study association and dissociation processes independently. From a kinetic point of view, the association reaction is fourth order in monomer and the dissociation first order in quadruplex. The association rate constant k (on), expressed in M(-3) x s(-1) decreases with increasing temperature, reflecting a negative activation energy (E (on)) for the sequences presented here. Association is favored by an increase in monocation concentration. The first-order dissociation process is temperature dependent, with a very positive activation energy E (off), but nearly ionic strength independent. General rules may be drawn up for various DNA and RNA sequence motifs, involving 3-6 consecutive guanines and 0-5 protruding bases. RNA quadruplexes are more stable than their DNA counterparts as a result of both faster association and slower dissociation. In most cases, no dissociation is found for G-tracts of 5 guanines or more in sodium, 4 guanines or more in potassium. The data collected here allow us to predict the amount of time required for 50% (or 90%) quadruplex formation as a function of strand sequence and concentration, temperature and ionic strength.
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Affiliation(s)
- Jean-Louis Mergny
- Laboratoire de Biophysique, Muséum National d'Histoire Naturelle USM503 INSERM U565, CNRS UMR 5153, 43 rue Cuvier, 75231 Paris Cedex 05, France.
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43
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Pudi R, Srinivasan P, Das S. La protein binding at the GCAC site near the initiator AUG facilitates the ribosomal assembly on the hepatitis C virus RNA to influence internal ribosome entry site-mediated translation. J Biol Chem 2004; 279:29879-88. [PMID: 15138264 DOI: 10.1074/jbc.m403417200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Human La autoantigen has been shown to influence internal initiation of translation of hepatitis C virus (HCV) RNA. Previously, we have demonstrated that, among the three RRMs of La protein, the RRM2 interacts with HCV internal ribosome entry site (IRES) around the GCAC motif near the initiator AUG present in the stem region of stem-loop IV (SL IV) (Pudi, R., Abhiman, S., Srinivasan, N., and Das S. (2003) J. Biol. Chem. 278, 12231-12240). Here, we have demonstrated that the mutations in the GCAC motif, which altered the binding to RRM2, had drastic effect on HCV IRES-mediated translation, both in vitro and in vivo. The results indicated that the primary sequence of the stem region of SL IV plays an important role in mediating internal initiation. Furthermore, we have shown that the mutations also altered the ability to bind to ribosomal protein S5 (p25), through which 40 S ribosomal subunit is known to contact the HCV IRES RNA. Interestingly, binding of La protein to SL IV region induced significant changes in the circular dichroism spectra of the HCV RNA indicating conformational alterations that might assist correct positioning of the initiation complex. Finally, the ribosome assembly analysis using sucrose gradient centrifugation implied that the mutations within SL IV of HCV IRES impair the formation of functional ribosomal complexes. These observations strongly support the hypothesis that La protein binding near the initiator AUG facilitates the interactions with ribosomal protein S5 and 48 S ribosomal assembly and influences the formation of functional initiation complex on the HCV IRES RNA to mediate efficient internal initiation of translation.
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Affiliation(s)
- Renuka Pudi
- Department of Microbiology and Cell Biology, Indian Institute of Science, Sir C.V. Raman Avenue, Bangalore 560012, India
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44
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Green JJ, Ying L, Klenerman D, Balasubramanian S. Kinetics of unfolding the human telomeric DNA quadruplex using a PNA trap. J Am Chem Soc 2003; 125:3763-7. [PMID: 12656607 DOI: 10.1021/ja029149w] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The kinetics of opening of the DNA quadruplex formed by the human telomeric repeat have been investigated using real-time fluorescence resonance energy transfer (FRET) measurements with a peptide nucleic acid (PNA) trap. It has been found that this opening is zero-order with respect to PNA, indicating that the initial step is a rate-limiting internal rearrangement of the quadruplex. A study of the temperature dependence of the rate of quadruplex opening was performed and the activation energy of the process estimated to be 98 +/- 8 kJ mol(-1).
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Affiliation(s)
- Jeremy J Green
- Department of Chemistry, University of Cambridge, Lensfield Road, UK
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45
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Vargason JM, Ho PS. The effect of cytosine methylation on the structure and geometry of the Holliday junction: the structure of d(CCGGTACm5CGG) at 1.5 A resolution. J Biol Chem 2002; 277:21041-9. [PMID: 11919197 DOI: 10.1074/jbc.m201357200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The single crystal structure of the methylated sequence d(CCGGTACm(5)CGG) has been solved as an antiparallel stacked X Holliday junction to 1.5 A resolution. When compared with the parent nonmethylated d(CCGGTACCGG) structure, the duplexes are translated by 3.4 A along the helix axis and rotated by 10.8 degrees relative to each other, rendering the major grooves more accessible overall. A Ca(2+) complex is seen in the minor groove opposite the junction but is related to the B conformation of the stacked arms. At the junction itself, the hydrogen bond from the N4 nitrogen of cytosine C8 to the C7 phosphate at the crossover in the parent structure has been replaced by a water bridge. Thus, this direct interaction is not absolutely required to stabilize the junction at the previously defined ACC trinucleotide core. The more compact methylated junction forces the Na(+) of the protected central cavity of the nonmethylated junction into a solvent cluster that spans the space between the junction crossover and the stacked arms. A series of void volumes within the methylated and the nonmethylated structures suggests that small monovalent cations can fill and vacate this central cavity without the need to unfold the four-stranded Holliday junction completely.
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Affiliation(s)
- Jeffrey M Vargason
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon 97331, USA
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Abstract
The dissociation and assembly of quadruplex DNA structures (and a few quadruplex RNAs) have been characterized at several levels of rigor, ranging from gross descriptions of factors that govern each process, to semiquantitative comparisons of the relative abilities of these factors to induce stabilization or destabilization, to quantitative studies of binding energies (thermodynamics), transformational rates (kinetics), and analysis of their transition-state energies and mechanisms. This survey classifies these factors, describes the trends and focuses on their interdependencies. Quadruplex assembly is induced most efficiently by added K(+) and elevating the strand concentration; however, Na(+), NH(4)(+), Sr(2+), and Pb(2+) are also very effective stabilizers. Quadruplex dissociation is typically accomplished by thermal denaturation, "melting"; however, when the quadruplex and monovalent cation concentrations are low enough, or the temperature is sufficiently high, several divalent cations, e.g., Ca(2+), Co(2+), Mn(2+), Zn(2+), Ni(2+) and Mg(2+) can induce dissociation. Stabilization also depends on the type of structure adopted by the strand (or strands) in question. Variants include intramolecular, two- and four-stranded quadruplexes. Other important variables include strand sequence, the size of intervening loops and pH, especially when cytosines are present, base methylation, and the replacement of backbone phosphates with phosphorothioates. Competitive equilibria can also modulate the formation of quadruplex DNAs. For example, reactions leading to Watson-Crick (WC) duplex and hairpin DNAs, triplex DNAs, and even other types of quadruplexes can compete with quadruplex association reactions for strands. Others include nonprotein catalysts, small molecules such as aromatic dyes, metalloporphyrins, and carbohydrates (osmolytes). Other nucleic acid strands have been found to drive quadruplex formation. To help reinforce the implications of each piece of information, each functional conclusion drawn from each cited piece of thermodynamic or kinetic data has been summarized briefly in a standardized table entry.
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Affiliation(s)
- C C Hardin
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695-7622, USA.
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47
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Abstract
DNA oligonucleotides that have repetitive tracts of guanine bases can form G-quadruplex structures that display an amazing polymorphism. Structures of several new G-quadruplexes have been solved recently that greatly expand the known structural motifs observed in nucleic acid quadruplexes. Base triads, base hexads, and quartets that contain cytosine have recently been identified stacked over the familiar G-quartets. The current status of the diverse array of structural features in quadruplexes is described and used to provide insight into the polymorphism and folding pathways. This review also summarizes recent progress in the techniques used to probe the structures of G-quadruplexes and discusses the role of ion binding in quadruplex formation. Several of the quadruplex structures featured in this review can be accessed in the online version of this review as CHIME representations.
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Affiliation(s)
- M A Keniry
- Research School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia.
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48
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Metzler DE, Metzler CM, Sauke DJ. The Nucleic Acids. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50008-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Hardin CC, Sneeden JL, Lemon SM, Brown BA, Guenther RH, Sierzputowska-Gracz H. Folding of pyrimidine-enriched RNA fragments from the vicinity of the internal ribosomal entry site of hepatitis A virus. Nucleic Acids Res 1999; 27:665-73. [PMID: 9862995 PMCID: PMC148230 DOI: 10.1093/nar/27.2.665] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Two RNA fragments from the region just upstream of the internal ribosome entry site of Hepatitis A virus (HAV) were studied, a 35mer (HAV-35), 5'U4C3U3C3U4C3U3C2UAU2C3U33(4), and a 23mer (HAV-23), 5(4)U4C3U3C3U4C3U33(4). Secondary structural predictions and nuclease digestion patterns obtained with genomic RNAs suggested that they link two stable Watson-Crick (WC) hairpins in the genomic RNA and do not form conventional WC secondary structure, but do fold to form a condensed, stacked 'domain'. To obtain more information, folding of HAV-23 and -35 RNA fragments was characterized using 1H nuclear magnetic resonance, in H2O as a function of pH and temperature, circular dichroism as a function of NaCl concentration, pH and temperature, and square-wave voltammetry as a function of pH. The results indicate that these oligo-nucleotides form intramolecular structures that contain transient U*U base pairs at pH 7 and moderate ionic strength (100 mM NaCl). This folded structure becomes destabilized and loses the U*U base pairs above and below neutral pH, especially at ionic strengths above 0.1. All of the cytidine protons exchange relatively rapidly with solvent protons (exchange lifetimes shorter than 1 ms), so the structure contains few if any C*CH+base pairs at neutral pH, but can apparently form them at pH values below 6. We present a series of possible models in which chain folding draws the strand termini closer together, possibly serving to pull the attached WC hairpin domains together and providing a functional advantage by nucleating reversible formation of a more viable RNA substrate.
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Affiliation(s)
- C C Hardin
- Department of Biochemistry and Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA.
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50
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Abstract
Several studies have been made to elucidate the nature of secondary structures in the single strands of d(CGG).d(CCG) repeat tracts but with conflicting conclusions. Here, we review this work and attempt to come towards consensus. Some investigators find that the G-rich strand forms hairpins. Of these, some conclude that pairing is in the alignment d(GGC).d(GGC) with two Watson-Crick bonds and one G.G bond per duplex repeat, others conclude that the alignment is d(GCG).d(GCG) with two G.G bonds and one C.C bond per duplex repeat. Others find quadruplex formation and conclude that this is in the latter alignment with two G4-quartets per quadruplex repeat and C.C bonds. We investigate why these different results were obtained and conclude that quadruplexes are likely to form under physiological conditions. We argue that they are probably bonded in the alignment d(GGC).d(GGC) with one G4-quartet and two C.G.C.G. quartets per quadruplex repeat. The C-rich strand does not appear to form quadruplexes under physiological conditions but forms hairpins. Apparently, short hairpins adopt the alignment d(CCG).d(CCG) with mismatched cytosine residues stacked into the helix but with 15 or more repeat units, the dominant form is a distorted hairpin aligned as d(GCC).d(GCC) with unpaired cytosine residues possibly turned outwards and stacked in the minor groove.
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Affiliation(s)
- J M Darlow
- Institute of Cell and Molecular Biology, University of Edinburgh, UK
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