G-Quadruplex DNA Suppresses Transcriptional Pause Release During DNA Replication
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus Homo sapiens
PROVIDER: GSE287896 | GEO | 2025/01/29
REPOSITORIES: GEO
Similar Datasets
Project description:Human DNA topoisomerase 1 (Top1) is a crucial enzyme responsible for alleviating torsional stress on DNA during transcription and replication, thereby maintaining genome stability. Previous researches had found that non-working Top1 interacted extensively with chromosomal DNA in human cells. However, the reason for its retention on chromosomal DNA remained unclear. In this study, we discovered a close association between Top1 and chromosomal DNA, specifically linked to the presence of G-quadruplex (G4) structures. G4 structures, formed during transcription, trap Top1 and hinder its ability to relax neighboring DNAs. Disruption of the Top1-G4 interaction using G4 ligand relieved the inhibitory effect of G4 on Top1 activity, resulting in a further reduction of R-loop levels in cells. Additionally, the activation of Top1 through the use of a G4 ligand enhanced the toxicity of Top1 inhibitors towards cancer cells. Our study uncovers a negative regulation mechanism of human Top1 and highlights a novel pathway for activating Top1.
2024-01-01 | GSE239692 | GEO
Project description:Human DNA topoisomerase 1 (Top1) is a crucial enzyme responsible for alleviating torsional stress on DNA during transcription and replication, thereby maintaining genome stability. Previous researches had found that non-working Top1 interacted extensively with chromosomal DNA in human cells. However, the reason for its retention on chromosomal DNA remained unclear. In this study, we discovered a close association between Top1 and chromosomal DNA, specifically linked to the presence of G-quadruplex (G4) structures. G4 structures, formed during transcription, trap Top1 and hinder its ability to relax neighboring DNAs. Disruption of the Top1-G4 interaction using G4 ligand relieved the inhibitory effect of G4 on Top1 activity, resulting in a further reduction of R-loop levels in cells. Additionally, the activation of Top1 through the use of a G4 ligand enhanced the toxicity of Top1 inhibitors towards cancer cells. Our study uncovers a negative regulation mechanism of human Top1 and highlights a novel pathway for activating Top1.
2024-01-01 | GSE239690 | GEO
Project description:DNA sequences of high guanine (G) content have the potential to fold into G quadruplex (G4) structures. DNA G4 is known to play important roles in various cellular processes including DNA replication, transcriptional regulation, and maintenance of genomic integrity. A more complete understanding about the biological functions of G4 DNA requires the investigation about how these structures are recognized by cellular proteins. Here, we conducted exhaustive quantitative proteomic experiments to profile the interaction proteomes of three well-defined G4 structures derived from the human telomere and the promoters of cMYC and cKIT genes. Our results led to the identification of a number of candidate G4-interacting proteins; some were previously reported, e.g., FUS, TOP1, and PARP1, and many others were discovered here for the first time. These included three proteins that can bind to all three DNA G4 structures and many proteins that can bind specifically to selected DNA G4 structure(s). We also validated that GRSF1 can bind directly and selectively toward G4 DNA structure derived from the cMYC promoter. Taken together, we uncovered a number of cellular proteins that exhibit general and selective recognitions of G4 folding patterns, which underscore the complexity of G4 DNA in biology and the importance in understanding fully the G4-interaction proteome.
2021-09-29 | PXD026794 | Pride
Project description:G-quadruplex (or G4) structures are non-canonical DNA structures that form in guanine-rich sequences and threaten genome stability when not properly resolved. G4 unwinding occurs during S phase via an unknown mechanism. Using Xenopus egg extracts, we define a three-step G4 unwinding mechanism that acts during DNA replication. First, the replicative helicase (CMG) stalls at a leading strand G4 structure. Second, the DHX36 helicase mediates the bypass of the CMG past the intact G4 structure, which allows approach of the leading strand to the G4. Third, G4 structure unwinding by the FANCJ helicase enables the DNA polymerase to synthesize past the G4 motif. A G4 on the lagging strand template does not stall CMG, but still requires active DNA replication for unwinding. DHX36 and FANCJ have partially redundant roles, conferring robustness to this pathway. Our data reveal a novel genome maintenance pathway that promotes faithful G4 replication thereby avoiding genome instability.
2022-02-17 | PXD027623 | Pride
Project description:In the presence of monovalent alkali metal ions, G-rich DNA sequences containing four runs of contiguous guanines can fold into G-quadruplex (G4) structures. Recent studies showed that these structures are located in critical regions of the human genome and assume important functions in many essential DNA metabolic processes, including replication, transcription and repair. However, not all potential G4-forming sequences are actually folded into G4 structures in cells, where G4 structures are known to be dynamic and modulated by G4-binding proteins as well as helicases. It remains unclear whether there are other factors influencing the formation and stability of G4 structures in cells. Herein, we showed that DNA G4s can undergo phase separation in vitro. In addition, immunofluorescence microscopy and ChIP-Seq experiments with the use of BG4, a G4 structure-specific antibody, revealed that disruption of phase separation in cells could result in global destabilization of G4 structures. Together, our work revealed phase separation as a new determinant in regulating the formation and stability of G4 structures in human cells.
2023-07-05 | GSE225772 | GEO
Project description:Topoisomerase I (Top1) is a key enzyme acting at the interface between DNA replication, transcription and mRNA maturation. Here, we show that Top1 suppresses genomic instability in mammalian cells by preventing conflicts between transcription and DNA replication. Using DNA combing and ChIP-on-chip, we found that Top1-deficient cells accumulate stalled replication forks and chromosome breaks in S phase and that breaks occur preferentially at gene-rich regions of the genome. Strikingly, these phenotypes were suppressed by preventing the formation of RNA-DNA hybrids (R-loops) during transcription. Moreover, these defects could be mimicked by depletion of the splicing factor ASF/SF2, which interacts functionally with Top1. Taken together, these data indicate that Top1 prevents replication fork collapse by suppressing the formation of R-loops in an ASF/SF2-dependent manner. We propose that interference between replication and transcription represents a major source of spontaneous replication stress, which could drive genomic instability during early stages of tumorigenesis. Bed files contain the gamma-H2AX enrichment sites described in the paper
2009-08-08 | GSE17552 | GEO
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:Background G-quadruplexes (G4s) are stable non-canonical DNA secondary structures consisting of stacked arrays of four guanines, each held together by Hoogsteen hydrogen bonds. Sequences with the ability to form these structures in vitro, G4 motifs, are found throughout bacterial and eukaryotic genomes. The budding yeast Pif1 DNA helicase, as well as several bacterial Pif1 family helicases, unwind G4 structures robustly in vitro and suppress G4-induced DNA damage in S. cerevisiae in vivo. Results We determined the genomic distribution and evolutionary conservation of G4 motifs in four fission yeast species and investigated the relationship between G4 motifs and Pfh1, the sole S. pombe Pif1 family helicase. Using chromatin immunoprecipitation combined with deep sequencing, we found that many G4 motifs in the S. pombe genome were associated with Pfh1. Cells depleted of Pfh1 had increased fork pausing and DNA damage near G4 motifs, as indicated by high DNA polymerase occupancy and phosphorylated histone H2A, respectively. In general, G4 motifs were underrepresented in genes. However, Pfh1-associated G4 motifs were located on the transcribed strand of highly transcribed genes significantly more often than expected, suggesting that Pfh1 has a function in replication or transcription at these sites. Conclusions In the absence of functional Pfh1, unresolved G4 structures cause fork pausing and DNA damage of the sort associated with human tumors.
2014-12-03 | GSE59178 | GEO
Project description:Eukaryotic topoisomerase 1 (TOP1) regulates DNA topology to ensure efficient DNA replication and transcription. TOP1 is also a major driver of endogenous genome instability, particularly when its catalytic intermediate - a covalent TOP1-DNA adduct known as a TOP1 cleavage complex (TOP1cc) - is stabilised. TOP1ccs are highly cytotoxic and a failure to resolve them underlies the pathology of neurological disorders but is also exploited in cancer therapy where TOP1ccs are the target of widely used frontline anti-cancer drugs. A critical enzyme for TOP1cc resolution is the tyrosyl-DNA phosphodiesterase, TDP1, which hydrolyses the bond that links a tyrosine in the active site of TOP1 to a 3’ phosphate group on a single-stranded (ss)DNA break. However, TDP1 can only process small peptide fragments from ssDNA ends, raising the question of how the ~90 kDa TOP1 protein is processed upstream of TDP1. We find that TEX264 fulfils this role by forming a complex with the p97 ATPase and the SPRTN metalloprotease. We show that TEX264 recognises both unmodified and SUMO1-modifed TOP1 and initiates TOP1cc repair by recruiting p97 and SPRTN. TEX264 localises to the nuclear periphery, associates with DNA replication forks, and counteracts TOP1ccs during DNA replication. Altogether, our study elucidates the existence of a specialised repair complex required for upstream proteolysis of TOP1ccs and their subsequent resolution.
2020-03-13 | PXD017239 | Pride
Project description:DNA structure can regulate genome function. Four-stranded DNA G-quadruplex (G4) structures have been implicated in transcriptional regulation; however, previous studies have not directly addressed the role of an individual G4 within its endogenous cellular context. Using CRISPR to genetically abrogate endogenous G4 structure folding, we directly interrogate the G4 found within the upstream regulatory region of the critical human MYC oncogene. G4 loss leads to suppression of MYC transcription from the P1 promoter that is mediated by the deposition of a de novo nucleosome alongside alterations in RNA polymerase recruitment. We also show that replacement of the endogenous MYC G4 with a different G4 structure from the KRAS oncogene restores G4 folding and MYC transcription. Moreover, we demonstrate that the MYC G4 structure itself, rather than its sequence, recruits transcription factors and histone modifiers. Overall, our work establishes that G4 structures are important features of transcriptional regulation that coordinate recruitment of key chromatin proteins and the transcriptional machinery through interactions with DNA secondary structure, rather than primary sequence.
2024-02-06 | GSE223370 | GEO