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Quantitative visualization of DNA G-quadruplex structures in human cells.

ABSTRACT: Four-stranded G-quadruplex nucleic acid structures are of great interest as their high thermodynamic stability under near-physiological conditions suggests that they could form in cells. Here we report the generation and application of an engineered, structure-specific antibody employed to quantitatively visualize DNA G-quadruplex structures in human cells. We show explicitly that G-quadruplex formation in DNA is modulated during cell-cycle progression and that endogenous G-quadruplex DNA structures can be stabilized by a small-molecule ligand. Together these findings provide substantive evidence for the formation of G-quadruplex structures in the genome of mammalian cells and corroborate the application of stabilizing ligands in a cellular context to target G-quadruplexes and intervene with their function.

SUBMITTER: Biffi G

PROVIDER: S-EPMC3622242 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature

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Quantitative visualization of DNA G-quadruplex structures in human cells.

Biffi Giulia G Tannahill David D McCafferty John J Balasubramanian Shankar S

Nature chemistry 20130120 3

Four-stranded G-quadruplex nucleic acid structures are of great interest as their high thermodynamic stability under near-physiological conditions suggests that they could form in cells. Here we report the generation and application of an engineered, structure-specific antibody employed to quantitatively visualize DNA G-quadruplex structures in human cells. We show explicitly that G-quadruplex formation in DNA is modulated during cell-cycle progression and that endogenous G-quadruplex DNA struct ...[more]

PMID: 23422559

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Project description:DNA secondary structures are important for fundamental genome functions such as transcription and replication1. The G-quadruplex (G4) structural motif has been linked to gene regulation2,3 and genome instability4,5 and may be important to cancer development and other diseases6-8. Recently, ~700,000 discrete G4s have been observed in naked human single-stranded genomic DNA using G4-seq, a high-throughput sequencing technique that detects structural features in vitro.9 It is of vital importance to investigate G4 structures within an endogenous chromatin context, which until now remained elusive10,11. Herein, we address this via the development of G4 ChIP-seq, an antibody-based G4 chromatin immunoprecipitation and high-throughput sequencing approach. We identified ~10,000 endogenous G4 structures and show that G4s are predominantly seen in regulatory, nucleosome-depleted, chromatin regions. G4s were enriched in the promoters and 5âUTR regions of highly transcribed genes, particularly in genes related to cancer and in somatic copy number amplifications, such as MYC. Reorganization of the chromatin landscape using a histone deacetylase inhibitor, resulted in de novo G4 formation in new and more prominent regulatory, nucleosome-depleted regions associated with increased transcriptional output. Our findings suggest a striking relationship between promoter nucleosome-depleted regions, G4 formation and elevated transcriptional activity. Comparison between normal human epidermal keratinocytes and their immortalized counterparts revealed a ï¾7-fold greater G4 abundance in immortalized cells, of which 80 % were found in regulatory, nucleosome-depleted regions common to both cell types. Consequently, cells exhibiting more G4s displayed significantly increased transcriptional output and were more sensitive to growth inhibition by a small molecule G4 ligand. Overall, our results provide new mechanistic insights into where and when DNA adopts G4 structure in vivo. Our findings show for the first time that regulatory, nucleosome-depleted chromatin and transcriptional states predominantly shape the endogenous G4 DNA landscape. Two cell lines, treated with entinostat or untreated, analyzed to detect gene expression differences, presence of G-Qudruplexes and chromatin state. Each combination of conditions replicated in duplicates or triplicates.

Dataset Information

Quantitative visualization of DNA G-quadruplex structures in human cells.

Publications

Quantitative visualization of DNA G-quadruplex structures in human cells.

Similar Datasets

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