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Ye H, Zhang H, Xiang J, Shen G, Yang F, Wang F, Wang J, Tang Y. Advances and prospects of natural dietary polyphenols as G-quadruplex stabilizers in biomedical applications. Int J Biol Macromol 2024; 254:127825. [PMID: 37926317 DOI: 10.1016/j.ijbiomac.2023.127825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 10/09/2023] [Accepted: 10/16/2023] [Indexed: 11/07/2023]
Abstract
G-quadruplexes (G4s) have arrested continuous interest in cancer research, and targeting G4s with small molecules has become an ideal approach for drug development. Plant-based dietary polyphenols have attracted much attention for their remarkable anti-cancer effects. Studies have suggested that polyphenols exhibit interesting scaffolds to bind G4s, which can effectively downregulate the proto-oncogenes by stabilizing those G4 structures. Therefore, this review not only summarizes studies on natural dietary polyphenols (including analogs) as G4 stabilizers, but also reveals their anti-cancer activities. Furthermore, the structural and antioxidant insights of polyphenols with G4s are discussed, and future development is proposed. These insights may pave the way for the development of the next generation of anti-cancer drugs targeting nucleic acids.
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Affiliation(s)
- Huanfeng Ye
- National Laboratory for Molecular Sciences, Center for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Hong Zhang
- National Laboratory for Molecular Sciences, Center for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, PR China; Beijing National Laboratory for Molecular Sciences (BNLMS), PR China.
| | - Junfeng Xiang
- National Laboratory for Molecular Sciences, Center for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Gang Shen
- National Laboratory for Molecular Sciences, Center for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, PR China; Beijing National Laboratory for Molecular Sciences (BNLMS), PR China
| | - Fengmin Yang
- National Laboratory for Molecular Sciences, Center for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, PR China; Beijing National Laboratory for Molecular Sciences (BNLMS), PR China
| | - Fangfang Wang
- National Laboratory for Molecular Sciences, Center for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China
| | - Jie Wang
- Department of Cardiology, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, PR China.
| | - Yalin Tang
- National Laboratory for Molecular Sciences, Center for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China; Beijing National Laboratory for Molecular Sciences (BNLMS), PR China.
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2
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Romano F, Di Porzio A, Iaccarino N, Riccardi G, Di Lorenzo R, Laneri S, Pagano B, Amato J, Randazzo A. G-quadruplexes in cancer-related gene promoters: from identification to therapeutic targeting. Expert Opin Ther Pat 2023; 33:745-773. [PMID: 37855085 DOI: 10.1080/13543776.2023.2271168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 10/11/2023] [Indexed: 10/20/2023]
Abstract
INTRODUCTION Guanine-rich DNA sequences can fold into four-stranded noncanonical secondary structures called G-quadruplexes (G4s) which are widely distributed in functional regions of the human genome, such as telomeres and gene promoter regions. Compelling evidence suggests their involvement in key genome functions such as gene expression and genome stability. Notably, the abundance of G4-forming sequences near transcription start sites suggests their potential involvement in regulating oncogenes. AREAS COVERED This review provides an overview of current knowledge on G4s in human oncogene promoters. The most representative G4-binding ligands have also been documented. The objective of this work is to present a comprehensive overview of the most promising targets for the development of novel and highly specific anticancer drugs capable of selectively impacting the expression of individual or a limited number of genes. EXPERT OPINION Modulation of G4 formation by specific ligands has been proposed as a powerful new tool to treat cancer through the control of oncogene expression. Actually, most of G4-binding small molecules seem to simultaneously target a range of gene promoter G4s, potentially influencing several critical driver genes in cancer, thus producing significant therapeutic benefits.
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Affiliation(s)
- Francesca Romano
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
| | - Anna Di Porzio
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
| | - Nunzia Iaccarino
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
| | | | | | - Sonia Laneri
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
| | - Bruno Pagano
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
| | - Jussara Amato
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
| | - Antonio Randazzo
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
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Li G, Su G, Wang Y, Wang W, Shi J, Li D, Sui G. Integrative genomic analyses of promoter G-quadruplexes reveal their selective constraint and association with gene activation. Commun Biol 2023; 6:625. [PMID: 37301913 PMCID: PMC10257653 DOI: 10.1038/s42003-023-05015-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Accepted: 06/05/2023] [Indexed: 06/12/2023] Open
Abstract
G-quadruplexes (G4s) regulate DNA replication and gene transcription, and are enriched in promoters without fully appreciated functional relevance. Here we show high selection pressure on putative G4 (pG4) forming sequences in promoters through investigating genetic and genomic data. Analyses of 76,156 whole-genome sequences reveal that G-tracts and connecting loops in promoter pG4s display lower or higher allele frequencies, respectively, than pG4-flanking regions, and central guanines (Gs) in G-tracts show higher selection pressure than other Gs. Additionally, pG4-promoters produce over 72.4% of transcripts, and promoter G4-containing genes are expressed at relatively high levels. Most genes repressed by TMPyP4, a G4-ligand, regulate epigenetic processes, and promoter G4s are enriched with gene activation histone marks, chromatin remodeler and transcription factor binding sites. Consistently, cis-expression quantitative trait loci (cis-eQTLs) are enriched in promoter pG4s and their G-tracts. Overall, our study demonstrates selective constraint of promoter G4s and reinforces their stimulative role in gene expression.
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Affiliation(s)
- Guangyue Li
- College of Life Science, Northeast Forestry University, Harbin, 150040, China
| | - Gongbo Su
- College of Life Science, Northeast Forestry University, Harbin, 150040, China
| | - Yunxuan Wang
- Department of Medical Oncology, Harbin Medical University Cancer Hospital, Harbin, 150081, China
| | - Wenmeng Wang
- College of Life Science, Northeast Forestry University, Harbin, 150040, China
| | - Jinming Shi
- College of Life Science, Northeast Forestry University, Harbin, 150040, China
| | - Dangdang Li
- College of Life Science, Northeast Forestry University, Harbin, 150040, China
| | - Guangchao Sui
- College of Life Science, Northeast Forestry University, Harbin, 150040, China.
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4
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Liu M, Yu K, Lian W, Zhou N, Wu C, Bao J. G-Quadruplex Structures as a "Switch" Regulate ATF4 Expression in Ferroptotic HepG2 Cells. ACS Chem Biol 2023; 18:273-284. [PMID: 36722101 DOI: 10.1021/acschembio.2c00615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
G-quadruplex (G4) is a noncanonical structure folded in a widespread manner by guanine-rich tandem repeated sequences. As a key response factor, activating transcription factor 4 (ATF4) has dual functions in managing iron-dependent ferroptosis by regulating amino acid synthesis and antioxidant-related gene expression. In our study, the activity of ATF4 expression was elevated in HepG2 cells induced by erastin. Based on preliminary bioinformatics analyses, the G-tract region, named WT, had high potential to form G4, and it was found that PDS could markedly weaken the increase of ATF4 expression by reducing the sensitivity of HepG2 cells toward erastin. In circular dichroism spectra, WT oligonucleotides showed characteristic molar ellipticity at specific wavelengths of parallel G4 structures, while corresponding single-base mutants possessed a weaker ability to form G4, which were consistent with immunostaining results. In addition, endogenous G4 formed by the WT motif was significantly destroyed in HepG2 cells treated with erastin. After being transfected with WT oligonucleotides, the levels of ATF4 mRNA decreased significantly regardless of being treated with erastin or not. Meanwhile, mutations of G-tracts could advantageously impact the luciferase expression downstream of an ATF4 promoter in reporter assays, manifesting that the decrease of endogenous G4 in the ATF4 promoter was positively associated with the expression enhanced by erastin in HepG2 cells.
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Affiliation(s)
- Miaomiao Liu
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610065, China
| | - Kangkang Yu
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610065, China
| | - Weishao Lian
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610065, China
| | - Nan Zhou
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610065, China
| | - Chuanfang Wu
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610065, China
| | - Jinku Bao
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan 610065, China
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Deng Z, Zhang Y, Gao C, Shen W, Wang S, Ni X, Liu S, Li X. A transposon-introduced G-quadruplex motif is selectively retained and constrained to downregulate CYP321A1. INSECT SCIENCE 2022; 29:1629-1642. [PMID: 35226400 DOI: 10.1111/1744-7917.13021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Revised: 01/18/2022] [Accepted: 01/28/2022] [Indexed: 06/14/2023]
Abstract
Insects utilize xenobiotic compounds to up- and downregulate cytochrome P450 monooxygenases (P450s) involved in detoxification of toxic xenobiotics including phytochemicals and pesticides. G-quadruplexes (G4)-forming DNA motifs are enriched in the promoter regions of transcription factors and function as cis-acting elements to regulate these genes. Whether and how P450s gain and keep G4 DNA motifs to regulate their expression still remain unexplored. Here, we show that CYP321A1, a xenobiotic-metabolizing P450 from Helicoverpa zea, a polyphagous insect of economic importance, has acquired and preserved a G4 DNA motif by selectively retaining a transposon known as HzIS1-3 that carries this G4 DNA motif in its promoter region. The HzIS1-3 G4 DNA motif acts as a silencer to suppress the constitutive and induced expression of CYP321A1 by plant allelochemicals flavone and xanthotoxin through folding into an intramolecular parallel or hybrid-1 conformation in the absence or presence of K+ . The G4 ligand N-methylmesoporphyrin IX (NMM) strengthens the silencing effect of HzIS1-3 G4 DNA motif by switching its structure from hybrid-1 to hybrid-2. The enrichment of transposons in P450s and other environment-adaptation genes implies that selective retention of G4 DNA motif-carrying transposons may be the main evolutionary route for these genes to obtain G4 DNA motifs.
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Affiliation(s)
- Zhongyuan Deng
- School of Agricultural Sciences, Zhengzhou University, Zhengzhou, China
- Department of Entomology and BIO5 Institute, University of Arizona, Tucson, AZ, USA
| | - Yuting Zhang
- School of Agricultural Sciences, Zhengzhou University, Zhengzhou, China
| | - Chao Gao
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China
| | - Wei Shen
- College of Science, Huazhong Agricultural University, Wuhan, China
| | - Shan Wang
- School of Agricultural Sciences, Zhengzhou University, Zhengzhou, China
| | - Xinzhi Ni
- USDA-ARS, Crop Genetics and Breeding Research Unit, University of Georgia, Tifton Campus, Tifton, GA, USA
| | - Sisi Liu
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China
- College of Science, Huazhong Agricultural University, Wuhan, China
| | - Xianchun Li
- Department of Entomology and BIO5 Institute, University of Arizona, Tucson, AZ, USA
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Zhang L, Yan T, Wang W, Wu Q, Li G, Li D, Stovall DB, Wang Y, Li Y, Sui G. AKT1 is positively regulated by G-quadruplexes in its promoter and 3'-UTR. Biochem Biophys Res Commun 2021; 561:93-100. [PMID: 34020144 DOI: 10.1016/j.bbrc.2021.05.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Accepted: 05/08/2021] [Indexed: 10/21/2022]
Abstract
AKT1 plays a key role in cell growth and survival, and its activation in cancers is mediated by different mechanisms. In this study, we investigated the potential of G-quadruplex (G4) formation by multiple consecutive G-tracts in the AKT1 promoter and its 3'-UTR. In circular dichroism analyses, synthetic oligonucleotides based on these G-tract regions showed molar ellipticity peaks at specific wavelengths of G4 structures. We verified G4 forming potential of these oligonucleotides using dimethyl sulfate footprinting, gel-shift and immunostaining assays. In reporter assays, mutations of the G-tracts in either the promoter or the 3'-UTR of AKT1 reduced expression mediated by these G-rich regions, suggesting positive regulation of AKT1 gene expression by these G4 structures. Furthermore, SP1 bound to its consensus sites regardless of the presence of G4 motifs in the AKT1 promoter, and both the G4 motifs and SP1 binding sites were needed to reach the strongest promoter strength.
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Affiliation(s)
- Lanlan Zhang
- Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Science, Northeast Forestry University, Harbin, 150040, China
| | - Ting Yan
- Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Science, Northeast Forestry University, Harbin, 150040, China
| | - Wenmeng Wang
- Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Science, Northeast Forestry University, Harbin, 150040, China
| | - Qiong Wu
- Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Science, Northeast Forestry University, Harbin, 150040, China
| | - Guangyue Li
- Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Science, Northeast Forestry University, Harbin, 150040, China
| | - Dangdang Li
- Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Science, Northeast Forestry University, Harbin, 150040, China
| | - Daniel B Stovall
- College of Arts and Sciences, Winthrop University, Rock Hill, SC, 29733, United States
| | - Yunxuan Wang
- Department of Medical Oncology, Harbin Medical University Cancer Hospital, Harbin, 150081, China
| | - Yuhua Li
- Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Science, Northeast Forestry University, Harbin, 150040, China.
| | - Guangchao Sui
- Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, College of Life Science, Northeast Forestry University, Harbin, 150040, China.
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7
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Odnokoz O, Wavelet-Vermuse C, Hophan SL, Bulun S, Wan Y. ARID1 proteins: from transcriptional and post-translational regulation to carcinogenesis and potential therapeutics. Epigenomics 2021; 13:809-823. [PMID: 33890484 PMCID: PMC8738980 DOI: 10.2217/epi-2020-0414] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The ARID1 proteins are mutually exclusive subunits of the BRG1/BRM-associated factor (BAF) complexes that play an important role in chromatin remodeling and regulate many fundamental cell functions. The role of ARID1s is well defined as a tumor-suppressive. The cancer cells evolve different mechanisms to downregulate ARID1s and inactivate their functions. ARID1s are frequently mutated in human cancer. The recent findings of ARID1A/B downregulation at transcriptional and translational levels along with their low levels in human cancers indicate the significance of regulatory mechanisms of ARID1s in cancers. In this review, we present the current knowledge on the regulation and alterations of ARID1 protein expression in human cancers and indicate the importance of regulators of ARID1s as a prognostic marker and in potential therapeutic strategies.
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Affiliation(s)
- Olena Odnokoz
- Department of Obstetrics & Gynecology & Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA,Department of Pharmacology & Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Cindy Wavelet-Vermuse
- Department of Obstetrics & Gynecology & Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA,Department of Pharmacology & Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Shelby L Hophan
- Department of Obstetrics & Gynecology & Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA,Department of Pharmacology & Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Serdar Bulun
- Department of Obstetrics & Gynecology & Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
| | - Yong Wan
- Department of Obstetrics & Gynecology & Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA,Department of Pharmacology & Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA,Author for correspondence: Tel.: +1 312 503 2769;
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Xiang X, Bao Y, Sun L, Zhang Y, Guo X. A stable uncompleted tetramolecular G-quadruplex formed by d(AG nA) under acidic condition. Int J Biol Macromol 2021; 176:66-71. [PMID: 33577823 DOI: 10.1016/j.ijbiomac.2021.02.059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 02/06/2021] [Accepted: 02/07/2021] [Indexed: 01/12/2023]
Abstract
In this work, the effects of terminal adenines on the formation and stability of tetramolecular G-quadruplexes (G4s) have been studied by electrospray ionization mass spectrometry (ESI-MS), UV, CD and NMR spectroscopy. Several evidences suggested that the sequences d(AGnA) (n = 4 or 5) form stable uncompleted tetramolecular G4 at acidic condition which is different from the canonical one in the neutral condition. In addition, hydrolysis of guanine has also been observed in acidic condition that may occur for unpaired strands rather than in complete G4. Thus, a new G4 topology containing incomplete G-quartet is proposed that is very stable and particularly presents in acidic ammonium ions solution. The information presented in this study provides the new insight on the polymorphism of G4s in acidic environment, which may help understand of the special role of adenines on the formation of G4s.
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Affiliation(s)
- Xiaoxuan Xiang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China
| | - Ying Bao
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China
| | - Likang Sun
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China
| | - Yujing Zhang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China
| | - Xinhua Guo
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China; Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, College of Life Science, Jilin University, Changchun 130012, China.
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Human MYC G-quadruplex: From discovery to a cancer therapeutic target. Biochim Biophys Acta Rev Cancer 2020; 1874:188410. [PMID: 32827579 DOI: 10.1016/j.bbcan.2020.188410] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 07/21/2020] [Accepted: 07/21/2020] [Indexed: 02/06/2023]
Abstract
Overexpression of the MYC oncogene is a molecular hallmark of both cancer initiation and progression. Targeting MYC is a logical and effective cancer therapeutic strategy. A special DNA secondary structure, the G-quadruplex (G4), is formed within the nuclease hypersensitivity element III1 (NHE III1) region, located upstream of the MYC gene's P1 promoter that drives the majority of its transcription. Targeting such G4 structures has been a focus of anticancer therapies in recent decades. Thus, a comprehensive review of the MYC G4 structure and its role as a potential therapeutic target is timely. In this review, we first outline the discovery of the MYC G4 structure and evidence of its formation in vitro and in cells. Then, we describe the functional role of G4 in regulating MYC gene expression. We also summarize three types of MYC G4-interacting proteins that can promote, stabilize and unwind G4 structures. Finally, we discuss G4-binding molecules and the anticancer activities of G4-stabilizing ligands, including small molecular compounds and peptides, and assess their potential as novel anticancer therapeutics.
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The SNAIL1 promoter contains G-quadruplex structures regulating its gene expression and DNA replication. Exp Cell Res 2020; 394:112158. [PMID: 32610184 DOI: 10.1016/j.yexcr.2020.112158] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 06/23/2020] [Accepted: 06/24/2020] [Indexed: 01/17/2023]
Abstract
SNAIL1 is a key regulator of epithelial-mesenchymal transition (EMT) and its expression is associated with tumor progression and poor clinical prognosis of cancer patients. Compared to the studies of SNAIL1 stability and its transcriptional regulation, very limited knowledge is available regarding effective approaches to directly target SNAIL1. In this study, we revealed the potential regulation of SNAIL1 gene expression by G-quadruplex structures in its promoter. We first revealed that the negative strand of the SNAIL1 promoter contained a multi-G-tract region with high potential of forming G-quadruplex structures. In circular dichroism studies, the oligonucleotide based on this region showed characteristic molar ellipticity at specific wavelengths of G-quadruplex structures. We also utilized native polyacrylamide gel electrophoresis, gel-shift assays, immunofluorescent staining, dimethyl sulfate footprinting and chromatin immunoprecipitation studies to verify the G-quadruplex structures formed by the oligonucleotide. In reporter assays, disruption of G-quadruplex potential increased SNAIL1 promoter-mediated transcription, suggesting that G-quadruplexes played a negative role in SNAIL1 expression. In a DNA synthesis study, we detected G-quadruplex-mediated retardation in the SNAIL1 promoter replication. Consistently, we discovered that the G-quadruplex region of the SNAIL1 promoter is highly enriched for mutations, implicating the clinical relevance of G-quadruplexes to the altered SNAIL1 expression in cancer cells.
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