G4 quadruplex landscape and its regulation revealed by a new antibody capture method
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE202456 | GEO | 2024/03/20
REPOSITORIES: GEO
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Project description:G-quadruplexes (G4) are non-canonical nucleic acid structures that can form at certain DNA or RNA guanine-rich sequences. G4 motifs are dispersed throughout the genome and considerably enriched at promoters, where they flank the transcription start site (TSS) and cluster at the 5’ end of the first intron, which suggests potential regulatory roles of quadruplexes in transcription. To improve our understanding of these roles, we have associated gene expression with the frequency of canonical G4 motifs near gene promoters and characterized perturbations caused by treatment with three G-quadruplex ligands, Pyridostatin and the two bisquinolinium compounds PhenDC3 and PhenDC6. We show that enrichment of G4 motifs characterizes the most actively transcribed genes, challenging the notion that quadruplexes chiefly exert negative regulation by blocking progress of RNA polymerase. G4 ligand-treatment altered splicing of transcripts at genes enriched for G4 motifs at the 5’-end of intron 1, suggesting that G-quadruplexes in the pre-mRNA can regulate splicing. Furthermore, our analysis also revealed some of the effects of G4 ligand treatment that likely reflect quadruplex-dependent replication stress leading to the induction of transcriptional signatures compatible with impaired cell cycle progression. Collectively, our results support the view that G-quadruplexes typically function as positive regulators of transcription, suggesting that quadruplexes may stabilize promoter architecture to enable efficient transcription. This analysis provides strong support for function of quadruplexes near the promoter as regulators of transcription and splicing.
2020-11-02 | GSE133419 | GEO
Project description:The identification of DNA G-quadruplexes (G4s) in the genome is important to study different biological processes in which these structures play a role, such as genome rearrangement, transcriptional regulation and DNA replication. G4-seq allowed the high-throughput experimental mapping of G-quadruplexes in the human genome. We developed here an improved version of this method, named G4-seq2, which we applied to generate G-quadruplexes genomic maps for 12 species, selected as important models organism to study development or as pathogens of clinical relevance. Those multi-species maps, publicly available for the community, will allow to further understand the design principle of G-quadruplex formation in genomic context, to study G-quadruplex biology in those model organisms, to predict ligand targeting for therapeutic usage and to design G-quadruplex computational predictors based on genome-wide experimental measurements.
2018-08-01 | GSE110582 | GEO
Project description:G-quadruplexes (G4s) are noncanonical DNA secondary structures formed through the self-association of guanines. They are distributed genome-widely and participate in multiple biological processes including gene transcription, and quadruplex-targeted ligands serve as potential therapeutic agents for DNA-targeted therapies. However, the roles of G-quadruplexes in transcriptional regulation remains elusive. Here, we establish a sensitive G4-CUT&Tag method for genome-wide profiling of native G-quadruplexes with high resolution and specificity. We find that native G-quadruplex signals are cell-type specific and are associated with transcriptional regulatory elements with active epigenetic modifications. Promoter-proximal RNA polymerase II pausing promotes native G-quadruplex formation, oppositely, G-quadruplex stabilization by quadruplex-targeted ligands globally reduces RNA polymerase II occupancy at gene promoters as well as nascent RNA synthesis. Moreover, G-quadruplex stabilization modulates chromatin states and impedes transcription initiation via inhibiting the loading of general transcription factors to promoters.Together, these studies reveal a reciprocal regulation between native G-quadruplex dynamics and gene transcription in the genome, which will deepen our knowledge of G-quadruplex biology towards considering therapeutically targeting G-quadruplexes in human diseases.
2021-07-19 | GSE178668 | GEO
Project description:The G-quadruplex is an alternative DNA structural motif that is considered to be functionally important in the mammalian genome. Herein, we address the hypothesis that G-quadruplex structures can exist within double-stranded genomic DNA using a G-quadruplex-specific probe. An engineered antibody is employed to enrich for DNA containing G-quadruplex structures, followed by deep sequencing to detect and map G-quadruplexes at high resolution in genomic DNA from human breast adenocarcinoma cells. Our high sensitivity structure-based pull-down strategy enables the isolation of genomic DNA fragments bearing a single as well as multiple G-quadruplex structures. Stable G-quadruplex structures are found in sub-telomeres, gene bodies and gene regulatory regions. For a sample of identified target genes, we show that G-quadruplex stabilizing ligands can modulate transcription. These results confirm the existence of G-quadruplex structures and their persistence in human genomic DNA. Four independent libraries have been enriched in DNA G-quadruplex structures using a G-quadruplex-specific probe. One genomic input library was sequenced as control. Deep-sequencing of these libraries allowed the mapping of G-quadruplexes on the genome.
2013-05-08 | E-GEOD-45241 | biostudies-arrayexpress
Project description:G-quadruplex motifs are frequently located near TSS and in the first introns of transcribed genes. We investigated the role that G4 structures play in transcription by stabilizing G4 DNA with the selective G4 ligand PhenDC3 in the HT-1080 human fibrosarcoma cell line. After treatment of triplicate samples with PhenDC3 or a negative control (DMSO carrier only), we performed RNA-Seq after poly-dT selection to assess changes in gene expression. Heme is an essential cofactor for many enzymes, but free heme is toxic and its levels are tightly regulated. G-quadruplexes bind heme avidly in vitro, raising the possibility that they may sequester heme in vivo. If so, then treatment that displaces heme from quadruplexes is predicted to induce expression of genes involved in iron and heme homeostasis. Here we show that PhenDC3, a G-quadruplex ligand structurally unrelated to heme, displaces quadruplex-bound heme in vitro and alters transcription in cultured human cells, up-regulating genes that support heme degradation and iron homeostasis, and most strikingly causing a 30-fold induction of heme oxidase 1, the key enzyme in heme degradation. We propose that G-quadruplexes sequester heme to protect cells from the pathophysiological consequences of free heme. This identifies a new function for G-quadruplexes and a new mechanism for protection of cells from heme.
2016-01-31 | GSE60630 | GEO
Project description:The genome consists of non-B-DNA structures such as G-quadruplexes (G4) that are involved in the regulation of genome stability and transcription. Telomeric-repeat containing RNA (TERRA) is capable of folding into G-quadruplex and interacting with chromatin remodeler ATRX. Here we show that TERRA modulates ATRX occupancy on repetitive sequences and over genes, and maintains DNA G-quadruplex structures at TERRA target and non-target sites in mouse embryonic stem cells. TERRA prevents ATRX from binding to subtelomeric regions and represses H3K9me3 formation. G4 ChIP-seq reveals that G4 abundance decreases at accessible chromatin regions, particularly at transcription start sites (TSS) after TERRA depletion; such G4 reduction at TSS is associated with elevated ATRX occupancy and differentially expressed genes. Loss of ATRX alleviates the effect of gene repression caused by TERRA depletion. Immunostaining analyses demonstrate that knockdown of TERRA diminishes DNA G4 signals, whereas silencing ATRX elevates G4 formation. Our results uncover an epigenetic regulation by TERRA that sequesters ATRX and preserves DNA G4 structures.
2022-11-09 | GSE194038 | GEO
Project description:G4 are noncanonical secondary structures consist in stacked tetrads of Hoogsteen hydrogen-bonded guanines bases. An essential feature of G-quadruplexes is their intrinsic polymorphic nature. Indeed, depending on the length and the composition of the sequence, as well as the environmental conditions (including the nature and concentration of metal cations, and local molecular crowding), a G-quadruplex-forming sequence can adopt different topologies in which the strands are in parallel or antiparallel conformations, with the co-existence of different types of loops (lateral, diagonal or propeller) with variable lengths. The impact of G4 on cellular metabolism is associated with protein or enzymatic factors that promote, inhibits or resolve these structures. Thus, the major impact of G4 on the human cell metabolism is associated with genetic defects affecting proteins that counteract their formation. Although a large number of proteins able to bind and/or "to resolve" G-quadruplex structures have been identified in vitro, less is known about their mode of interaction with G-quadruplex, their specificity versus the topology and finally their specificity for G4 structures relatively to G-rich single-stranded sequences. In this study we aimed to identify and characterize human proteins interacting with locked G4 structures.
2021-07-16 | PXD021003 | Pride
Project description:G-rich DNA sequences can form four-stranded G-quadruplex (G4) secondary structures and are linked to fundamental biological processes such as transcription, replication and telomere maintenance. G4s are also implicated in promoting genome instability, cancer and other diseases. Here, we describe a detailed G4 ChIP-seq method that robustly enables the determination of G4 structure formation genome-wide in chromatin. This protocol adapts traditional ChIP-seq for the detection of DNA secondary structures through the use of a G4-structure-specific phage display antibody with refinements in chromatin immunoprecipitation followed by high-throughput sequencing. Beginning with chromatin isolation and antibody preparation the entire protocol can be completed in less than 1 week including computational analysis.
2017-11-15 | GSE99205 | GEO
Project description:G-quadruplex (G4) structures formed by guanine-rich nucleic acids are implicated in essential physiological and pathological processes and serve as important drug targets. The genome-wide detection of G4s in living cells is important for exploring the functional role of G4s but has not yet been achieved due to the lack of a suitable G4 probe. Here we report an artificial 6.7 kDa G4 probe (G4P) protein that binds G4s with high affinity and specificity. We used it to capture G4s in living human, mouse, and chicken cells with the ChIP-Seq technique, yielding genome-wide landscape as well as details on the positions, frequencies, and sequence identities of G4 formation in these cells. Our results indicate that transcription is accompanied by a robust formation of G4s in genes. In human cells, we detected up to >123,000 G4P peaks, of which >1/3 had a fold increase of ≥5 and were present in >60% promoters and ~70% genes. Being much smaller than a scFv antibody (27 kDa) or even a nanobody (12-15 kDa), we expect that the G4P may find diverse applications in biology, medicine, and molecular devices as a G4 affinity agent.
2020-10-13 | GSE133379 | GEO
Project description:G-quadruplex (G4) structures exist in single-stranded DNA of chromatins and regulate genome function. However, the native chromatin G4 landscape in living cells has yet to be fully characterized. Herein, we fused BG4 antibody and GFP-tag to construct a live-cell G4 identifier (LiveG4ID). We first displayed its function as a high-specificity chromatin G4 probe in living cells by Dox-induced expression LiveG4ID in HEK293T cells and detecting its cellular localization, biocompatibility and G4-binding specificity. By coupling LiveG4ID with CUT&Tag technology, we established LiveG4ID-seq, a method for mapping native chromatin G4 landscape in living cells. LiveG4ID-seq can identify more chromatin G4 motifs than traditional CUT&Tag and ChIP-seq methods. Using LiveG4ID-seq, we profiled the dynamic landscape of chromatin G4 structures during the cell cycle. These data demonstrate the capacity of LiveG4ID-seq to profile a more accurate G4 landscape in living cells and promote future study on chromatin G4 structures.
2022-01-15 | GSE193496 | GEO