G-quadruplex structures moulds the DNA methylome
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE107690 | GEO | 2018/07/16
REPOSITORIES: GEO
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Project description:G-quadruplex (G4) sites in the human genome frequently colocalize with CCCTC-binding factor (CTCF)-bound sites within topologically associating domains (TADs) or at TAD boundaries. We investigated three mechanisms by which G4s may contribute to CTCF recruitment. One involved direct interactions between CTCF and G4s that persisted in the G0/G1 phase of the cell cycle. Synthetic G4s from CpG islands (CGIs) formed complexes with CTCF in vitro, and CTCF occupancy at the respective sites in the genome was modulated by a G4-stabilizing ligand. Another possible mechanism was through G4 interference with DNA methyltransferase activity in CGIs. Bioinformatics analysis confirmed that G4s underlie the association between CTCF and CGIs, but did not support a critical role for methylation in CTCF recruitment to G4-harboring CGIs. The third mechanism was through attracting additional protein factors. We found that G4s are recognized by the nucleosome density modulating high-mobility group (HMG) proteins and the cohesin-interacting protein additional sex combs-like 1. The affinity for these proteins is the basis for indirect G4 contributions to CTCF positioning and TAD demarcation.
2021-04-23 | GSE173074 | GEO
Project description:G-quadruplex structures (G4s) have been identified in genomes of multiple organisms and proven to play important epigenetic regulatory roles in various cellular functions. However, the G4 formation mechanism remains largely unknown. Here, we found a negative correlation between DNA 5mC methylation and G4 abundance. The abundance of genomic G4s significantly increased when the whole-genome methylation level was reduced in DNMT1-knockout cells. This increase was then suppressed by DNMT1 over-expression. And more G4s were detected in the hypomethylated cancer cell line HepG2 and rectal cancer tissues. Besides, 5mC modification significantly inhibited G4 formation of the potential G-quadruplex sequences (PQSs). The transcription of genes with 5mC modification sites in their promoter PQSs was affected after treatment with G4 stabilizer pyridostatin or methylation inhibitor 5-aza-dC. The global reduction of genomic methylation elevates gene transcription levels through increased G4s. Taken together, DNA 5mC methylation prevents PQSs from folding into G4s in genomes.
2022-12-20 | GSE221435 | GEO
Project description:G-quadruplex structures (G4s) have been identified in genomes of multiple organisms and proven to play important epigenetic regulatory roles in various cellular functions. However, the G4 formation mechanism remains largely unknown. Here, we found a negative correlation between DNA 5mC methylation and G4 abundance. The abundance of genomic G4s significantly increased when the whole-genome methylation level was reduced in DNMT1-knockout cells. This increase was then suppressed by DNMT1 over-expression. And more G4s were detected in the hypomethylated cancer cell line HepG2 and rectal cancer tissues. Besides, 5mC modification significantly inhibited G4 formation of the potential G-quadruplex sequences (PQSs). The transcription of genes with 5mC modification sites in their promoter PQSs was affected after treatment with G4 stabilizer pyridostatin or methylation inhibitor 5-aza-dC. The global reduction of genomic methylation elevates gene transcription levels through increased G4s. Taken together, DNA 5mC methylation prevents PQSs from folding into G4s in genomes.
2022-12-20 | GSE221436 | GEO
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.
2016-08-05 | E-GEOD-76688 | biostudies-arrayexpress
Project description:DNA G-quadruplex (G4) is a non-canonical four-stranded nucleic acid structure functioning in various biological processes in mammals. G4 ChIP-seq assay, In this study, we developed a robust BG4-DNA ChIP-seq for global identification of DNA G4 in rice..We found that G4s harbored some functional motifs for binding of certain trans-factors, were co-localized with R-loops and DHSs in the rice genome. Importantly, G4s exhibited differential effects on DNA methylation between TE and non-TE genes in rice. Especially, G4 intensity-dependent enrichment occurred between DNA 5mC and 6mA.These DNA-related features suggest potential regulatory roles of G4 in rice. Thus, our study will pave the way for prompting intensive characterization towards identifying novel functions of G4 in plants, especially for agronomic important crops.
2021-07-01 | GSE132775 | GEO
Project description:DNA (cytosine-5) methyltransferase 1 (DNMT1) is essential for mammalian development and maintenance of DNA methylation following DNA replication in cells. The DNA methylation process generates S-adenosyl-L-homocysteine, a strong inhibitor of DNMT1. Here we report that S-adenosylhomocysteine hydrolase (SAHH/AHCY), the only mammalian enzyme capable of hydrolyzing S-adenosyl-L-homocysteine binds to DNMT1 during DNA replication. SAHH activates DNMT1 in vitro and its overexpression in mammalian cells leads to hypermethylation of the genome, whereas its inhibition by adenosine periodate resulted in hypomethylation of the genome. Hypermethylation was consistent in both gene bodies and repetitive DNA elements leading to both down- and up-regulation of genes. Similarly, hypomethylation led to both up- and down-regulation of genes suggesting methylated regions influence gene expression either positively or negatively. Cells overexpressing SAHH specifically up-regulated metabolic pathway genes and down-regulated PPAR and MAPK signaling pathways genes. Therefore, we suggest that alteration of SAHH level in the cell leads to aberrant DNA methylation, altered metabolite levels and gene expression.
2018-06-06 | PXD006476 | Pride
Project description:G-quadruplexes (G4s) are noncanonical DNA secondary structures formed through the self-association of guanines, and they are distributed widely across the genome. G4 participates in multiple biological processes including gene transcription, and G4-targeted ligands serve as potential therapeutic agents for DNA-targeted therapies. However, genome-wide studies of the exact roles of G4s in transcriptional regulation are still lacking. We found that drug-induced promoter-proximal RNA polymerase II pausing promotes nearby G4 formation, and oppositely, G4 stabilization by G4-targeted ligands globally reduces RNA polymerase II occupancy at gene promoters as well as nascent RNA synthesis. To study the underlying mechanisms by which native G4 affects transcriptional regulation, we annealed the biotin-labeled core promoter DNA to form G4s and performed pull-down assays with nuclear extraction proteins in the presence or absence of TMPyP4. Mass spectrometry analysis was performed to identify the interacting proteins with G4-forming core promoter DNA.
2021-07-19 | PXD026830 | Pride
Project description:DNA methylation is a heritable chromatin modification essential to mammalian development that functions with histone post-translational modifications to regulate chromatin structure and gene expression programs. The epigenetic inheritance of DNA methylation requires the combined actions of DNMT1 and UHRF1, a histone- and DNA-binding RING E3 ubiquitin ligase that facilitates DNMT1 recruitment to sites of newly replicated DNA through the ubiquitylation of histone H3. UHRF1 binds DNA with modest selectivity towards hemi-methylated CpG dinucleotides (HeDNA); however, the contribution of HeDNA sensing to UHRF1 function remains elusive. Here, we reveal that the interaction of UHRF1 with HeDNA is required for DNA methylation inheritance but is dispensable for chromatin interaction, which is governed by reciprocal positive cooperativity between the UHRF1 histone- and DNA-binding domains. We further show that HeDNA functions as an allosteric regulator of UHRF1 ubiquitin ligase activity, directing ubiquitylation towards multiple lysines on the H3 tail adjacent to the UHRF1 histone-binding site. Collectively, our studies define a highly orchestrated epigenetic control mechanism involving modifications both to histones and DNA that facilitate UHRF1 chromatin targeting, H3 ubiquitylation, and DNA methylation inheritance.
2016-08-25 | PXD003983 | Pride
Project description:The E3 ligase UHRF1 is an essential epigenetic cofactor for DNMT1 dependent maintenance DNA methylation, which provides a binding platform for DNMT1 by both cooperative binding of histones and hemi-methylated DNA as well as by ubiquitinating histone H3. Here, we conduct a comprehensive screen to identify novel ubiquitination targets of UHRF1 and its paralogue UHRF2 by comparing the ubiquitome of wildtype (wt), UHRF1- and UHRF2-deficient mouse embryonic stem cells. With an antibody-dependent enrichment of ubiquitin remnant motif-containing peptides followed by isobaric-labeling based quantitative mass spectrometry, we find both known and novel E3 ligase substrates of UHRF1 involved in a variety of biological processes such as RNA processing, DNA methylation and DNA damage repair.
2017-10-24 | PXD006593 | Pride
Project description:Single-stranded genomic DNA can fold into G-quadruplex (G4) structures or form DNA:RNA hybrids (R loops). Recent evidence suggests that such non-canonical DNA structures affect gene expression, DNA methylation, replication fork progression and genome stability. When and how G4 structures form and are resolved remains unclear. Here we report the use of Cleavage Under Targets and Tagmentation (CUT&Tag) for mapping native G4 in mammalian cell lines at high resolution and low background. Mild native conditions used for the procedure retain more G4 structures and provide a higher signal-to-noise ratio than ChIP-based methods. We determine the G4 landscape of mouse embryonic stem cells (mESC), discovering G4 formation at active and poised promoters and enhancers. We discover that the presence of G4 motifs and G4 structures distinguishes active and primed enhancers in mESCs. Further performing R-loop CUT&Tag, we demonstrate the widespread co-occurence of single-stranded DNA, G4s and R loops, suggesting an intricate interrelation of non-canonical DNA structures, transcription and the formation and turnover of G4s.
2021-04-27 | GSE173103 | GEO