Direct evidence for a G-quadruplex in a promoter region and its targeting with a small molecule to repress c-
            <i>MYC</i>
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Siddiqui‐Jain, Adam; Grand, Cory L.; Bearss, David J.; Hurley, Laurence H.

doi:10.1073/pnas.182256799

Cited by 2,063 publications

(2,324 citation statements)

References 47 publications

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“…12 The same approach may also apply to the c-kit oncogene. Because the G-quadruplex structure formed by c-kit87up is quite unique, it appears to be a specific target for drug design.…”

Section: Discussionmentioning

confidence: 99%

“…13 G-quadruplexes, which may have transient stability by themselves when embedded within the double-stranded DNA of a eukaryotic gene, may be stabilized further by a small-molecule ligand such as the porphyrin molecule TMPyP4. 12 The topology and structure of the c-myc DNA quadruplexes containing four 14 and five 15 G-tracts have been determined by nuclear magnetic resonance (NMR) spectroscopy, together with that of a TMPyP4 complex for the five-guanine-tract quadruplex. 15 The latter are parallel-stranded quadruplexes, with several strand-reversal loops and base-pair platforms.…”

Section: Introductionmentioning

confidence: 99%

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Structure of an Unprecedented G-Quadruplex Scaffold in the Human c-kit Promoter

et al. 2007

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The c-kit oncogene is an important target in the treatment of gastrointestinal tumors. A potential approach to inhibition of the expression of this gene involves selective stabilization of Gquadruplex structures that may be induced to form in the c-kit promoter region. Here we report on the structure of an unprecedented intramolecular G-quadruplex formed by a G-rich sequence in the c-kit promoter in K + solution. The structure represents a new folding topology with several unique features. Most strikingly, an isolated guanine is involved in G-tetrad core formation, despite the presence of four three-guanine tracts. There are four loops: two single-residue double-chainreversal loops, a two-residue loop, and a five-residue stem-loop, which contain base-pairing alignments. This unique structural scaffold provides a highly specific platform for the future design of ligands specifically targeted to the promoter DNA of c-kit.

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“…12 The same approach may also apply to the c-kit oncogene. Because the G-quadruplex structure formed by c-kit87up is quite unique, it appears to be a specific target for drug design.…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structure of an Unprecedented G-Quadruplex Scaffold in the Human c-kit Promoter

et al. 2007

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“…75 Since MYC is an oncogene with a G-quadruplex structure in the promoter region, 34,76 it was important to determine whether GTC365 effects the repression of hTERT promoter activity directly by binding to the hTERT promoter G-quadruplex or by indirectly modulating MYC transcription through the MYC promoter G-quadruplex. To distinguish between these possibilities, two constructs were prepared, the first being the pGL3-WT plasmid encoding luciferase as a reporter gene and contains the 360 base-pair hTERT promoter region including the upstream E-box (CACGTG) and the core region, and the second (pGL3-E-box mutant) being the same plasmid but with a E-box mutation (TTTGTG.…”

Section: Gtc365 Work Directly Through the Htert Promoter To Lower Htmentioning

confidence: 99%

A Pharmacological Chaperone Molecule Induces Cancer Cell Death by Restoring Tertiary DNA Structures in Mutant hTERT Promoters

et al. 2016

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Activation of human telomerase reverse transcriptase (hTERT) is necessary for limitless replication in tumorigenesis. Whereas hTERT is transcriptionally silenced in normal cells, most tumor cells reactivate hTERT expression by alleviating transcriptional repression through diverse genetic and epigenetic mechanisms. Transcription-activating hTERT promoter mutations have been found to occur at high frequencies in multiple cancer types. These mutations have been shown to form new transcription factor binding sites that drive hTERT expression, but this model cannot fully account for differences in wildtype (WT) and mutant promoter activation and has not yet enabled a selective therapeutic strategy. Here we demonstrate a novel mechanism by which promoter mutations activate hTERT transcription, which also sheds light on a unique therapeutic opportunity. Promoter mutations occur in a core promoter region that forms tertiary structures consisting of a pair of G-quadruplexes involved in transcriptional silencing.We show that promoter mutations exert a detrimental effect on the folding of one of these Gquadruplexes, resulting in a nonfunctional silencer element that alleviates transcriptional repression. We have also identified a small drug-like pharmacological chaperone (pharmacoperone) molecule, GTC365, that acts at an early step in the G-quadruplex folding pathway to redirect mutant promoter G-quadruplex misfolding, partially reinstate the correct folding pathway, and reduce hTERT activity through transcriptional repression. This transcription-mediated repression effects cancer cell death through multiple routes including both induction of apoptosis through inhibition of hTERT's role in regulating apoptosis-related proteins and inducing senescence by decreasing telomerase activity and telomere length.We demonstrate the selective therapeutic potential of this strategy in melanoma cells that overexpress hTERT.3

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“…Such structures are implicated in several physiologically important regulatory processes, with special emphasis on carcinogenesis [4][5][6][7][8][9][10][11][12]. Most of the structural studies on these elements have been performed by NMR spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Diffusion-ordered nuclear magnetic resonance spectroscopy for analysis of DNA secondary structural elements

Ambrus¹,

Yang²

2007

Analytical Biochemistry

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Structure determination of secondary DNA structural elements, such as G-quadruplexes, gains an increasing importance as fundamental physiological roles are being associated with the formation of such structures in vivo. A truncated native DNA sequence generally requires further optimization to obtain a candidate with desired NMR properties for structural analysis in solution. The optimum sequence is expected to form one dominant, stable molecular entity in solution with well-resolved NMR peaks. However, DNA sequences are prone to form structures composed of one, two, three or four strands depending on sequence and solution conditions. The thorough characterization of the molecularity (stoichiometry and molecular weight) and appropriate solution conditions for sequences with different modifications traditionally applies analytical techniques that generally do not represent the solution conditions for NMR structure determination. Here we present the application of diffusion ordered NMR spectroscopy as a useful analytical tool for the optimization and analysis of DNA secondary structural elements, specifically, the DNA G-quadruplex structures, including those formed in the human telomeric sequence and in the promoter regions of bcl-2 and c-myc genes. KeywordsDNA; NMR; DOSY; quadruplex; bcl-2; human telomere; c-myc Structural analysis of unusual DNA motifs with particular emphasis on G-quadruplexes and imotifs has a central role in the identification and characterization of molecular targets related to these structures [1][2][3][4][5][6][7]. Such structures are implicated in several physiologically important regulatory processes, with special emphasis on carcinogenesis [4][5][6][7][8][9][10][11][12]. Most of the structural studies on these elements have been performed by NMR spectroscopy. In most cases the related nucleotide sequence bearing the actual physiological function in vivo needs to be truncated/ elongated and/or mutated in order to obtain a successful candidate for NMR structure determination [3][4][5][6][7]13]. This NMR candidate should be a well-defined molecular entity in physiologically relevant solution conditions (ionic strength, pH, temperature) representing the same conformation as the original sequence. Appropriate modification of the sequence by mutation/truncation/elongation will force the molecule to form a single stable structure without altering crucial connectivities (conformation) of the structure.* To whom correspondence should be addressed at the Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, 1703 E. Mabel St., P.O. Box 210207, room 101/406, Tucson, Arizona 85721, USA; Tel: +1 520 626 6749/626 5969, Fax: +1 520 626 2466, E-mail: ambrus@pharmacy.arizona.edu, yangd@pharmacy.arizona.edu.Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of ...

show abstract

Direct evidence for a G-quadruplex in a promoter region and its targeting with a small molecule to repress c- MYC transcription

Cited by 2,063 publications

References 47 publications

Structure of an Unprecedented G-Quadruplex Scaffold in the Human c-kit Promoter

Structure of an Unprecedented G-Quadruplex Scaffold in the Human c-kit Promoter

A Pharmacological Chaperone Molecule Induces Cancer Cell Death by Restoring Tertiary DNA Structures in Mutant hTERT Promoters

Diffusion-ordered nuclear magnetic resonance spectroscopy for analysis of DNA secondary structural elements

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