scholarly journals Stabilization of G-quadruplex DNA structures in Schizosaccharomyces pombe causes single-strand DNA lesions and impedes DNA replication

2020 ◽  
Vol 48 (19) ◽  
pp. 10998-11015 ◽  
Author(s):  
Ikenna Obi ◽  
Matilda Rentoft ◽  
Vandana Singh ◽  
Jan Jamroskovic ◽  
Karam Chand ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Dna Replication ◽  
Schizosaccharomyces Pombe ◽  
Dna Lesions ◽  
Single Strand ◽  
Quadruplex Dna ◽  
Dna Structures ◽  
Replication Fork Progression ◽  
G Quadruplex

Abstract G-quadruplex (G4) structures are stable non-canonical DNA structures that are implicated in the regulation of many cellular pathways. We show here that the G4-stabilizing compound PhenDC3 causes growth defects in Schizosaccharomyces pombe cells, especially during S-phase in synchronized cultures. By visualizing individual DNA molecules, we observed shorter DNA fragments of newly replicated DNA in the PhenDC3-treated cells, suggesting that PhenDC3 impedes replication fork progression. Furthermore, a novel single DNA molecule damage assay revealed increased single-strand DNA lesions in the PhenDC3-treated cells. Moreover, chromatin immunoprecipitation showed enrichment of the leading-strand DNA polymerase at sites of predicted G4 structures, suggesting that these structures impede DNA replication. We tested a subset of these sites and showed that they form G4 structures, that they stall DNA synthesis in vitro and that they can be resolved by the breast cancer-associated Pif1 family helicases. Our results thus suggest that G4 structures occur in S. pombe and that stabilized/unresolved G4 structures are obstacles for the replication machinery. The increased levels of DNA damage might further highlight the association of the human Pif1 helicase with familial breast cancer and the onset of other human diseases connected to unresolved G4 structures.

scholarly journals Human Rev1 polymerase disrupts G-quadruplex DNA

2013 ◽  
Vol 42 (5) ◽  
pp. 3272-3285 ◽  
Author(s):  
Sarah Eddy ◽  
Amit Ketkar ◽  
Maroof K. Zafar ◽  
Leena Maddukuri ◽  
Jeong-Yun Choi ◽  
...  
Keyword(s):  
Genome Maintenance ◽  
Quadruplex Dna ◽  
Dna Structures ◽  
G4 Dna ◽  
G Quadruplex ◽  
Steady State Rate ◽  
Dna Substrates ◽  
Successful Replication ◽  
Y Family

Abstract The Y-family DNA polymerase Rev1 is required for successful replication of G-quadruplex DNA (G4 DNA) in higher eukaryotes. Here we show that human Rev1 (hRev1) disrupts G4 DNA structures and prevents refolding in vitro. Nucleotidyl transfer by hRev1 is not necessary for mechanical unfolding to occur. hRev1 binds G4 DNA substrates with Kd,DNA values that are 4–15-fold lower than those of non-G4 DNA substrates. The pre-steady-state rate constant of deoxycytidine monophosphate (dCMP) insertion opposite the first tetrad-guanine by hRev1 is ∼56% as fast as that observed for non-G4 DNA substrates. Thus, hRev1 can promote fork progression by either dislodging tetrad guanines to unfold the G4 DNA, which could assist in extension by other DNA polymerases, or hRev1 can prevent refolding of G4 DNA structures. The hRev1 mechanism of action against G-quadruplexes helps explain why replication progress is impeded at G4 DNA sites in Rev1-deficient cells and illustrates another unique feature of this enzyme with important implications for genome maintenance.

scholarly journals Sites of instability in the human TCF3 (E2A) gene adopt G-quadruplex DNA structures in vitro

2015 ◽  
Vol 6 ◽  
Author(s):  
Jonathan D. Williams ◽  
Sara Fleetwood ◽  
Alexandra Berroyer ◽  
Nayun Kim ◽  
Erik D. Larson
Keyword(s):  
Quadruplex Dna ◽  
Dna Structures ◽  
G Quadruplex

scholarly journals Mitochondrial genetic variation is enriched in G-quadruplex regions that stall DNA synthesis in vitro

2020 ◽  
Vol 29 (8) ◽  
pp. 1292-1309 ◽  
Author(s):  
Thomas J Butler ◽  
Katrina N Estep ◽  
Joshua A Sommers ◽  
Robert W Maul ◽  
Ann Zenobia Moore ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Genetic Variation ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Dna Sequences ◽  
Computational Analysis ◽  
Italian Population ◽  
Dna Structures ◽  
G Quadruplex

Abstract As the powerhouses of the eukaryotic cell, mitochondria must maintain their genomes which encode proteins essential for energy production. Mitochondria are characterized by guanine-rich DNA sequences that spontaneously form unusual three-dimensional structures known as G-quadruplexes (G4). G4 structures can be problematic for the essential processes of DNA replication and transcription because they deter normal progression of the enzymatic-driven processes. In this study, we addressed the hypothesis that mitochondrial G4 is a source of mutagenesis leading to base-pair substitutions. Our computational analysis of 2757 individual genomes from two Italian population cohorts (SardiNIA and InCHIANTI) revealed a statistically significant enrichment of mitochondrial mutations within sequences corresponding to stable G4 DNA structures. Guided by the computational analysis results, we designed biochemical reconstitution experiments and demonstrated that DNA synthesis by two known mitochondrial DNA polymerases (Pol γ, PrimPol) in vitro was strongly blocked by representative stable G4 mitochondrial DNA structures, which could be overcome in a specific manner by the ATP-dependent G4-resolving helicase Pif1. However, error-prone DNA synthesis by PrimPol using the G4 template sequence persisted even in the presence of Pif1. Altogether, our results suggest that genetic variation is enriched in G-quadruplex regions that impede mitochondrial DNA replication.

scholarly journals Mgs1 function at G-quadruplex structures during DNA replication

2020 ◽  
Author(s):  
Katrin Paeschke ◽  
Peter Burkovics
Keyword(s):  
Dna Replication ◽  
Genome Stability ◽  
Mechanistic Model ◽  
Regulation Of Gene Expression ◽  
Telomere Maintenance ◽  
Dna Structures ◽  
Genomic Deletions ◽  
G Quadruplex

AbstractThe coordinated action of DNA polymerases and DNA helicases is essential at genomic sites that are hard to replicate. Among these are sites that harbour G-quadruplex DNA structures (G4). G4s are stable alternative DNA structures, which have been implicated to be involved in important cellular processes like the regulation of gene expression or telomere maintenance. G4 structures were shown to hinder replication fork progression and cause genomic deletions, mutations and recombination events. Many helicases unwind G4 structures and preserve genome stability, but a detailed understanding of G4 replication and the re-start of stalled replication forks around formed G4 structures is not clear, yet. In our recent study, we identified that Mgs1 preferentially binds to G4 DNA structures in vitro and is associated with putative G4-forming chromosomal regions in vivo. Mgs1 binding to G4 motifs in vivo is partially dependent on the helicase Pif1. Pif1 is the major G4-unwinding helicase in S. cerevisiae. In the absence of Mgs1, we determined elevated gross chromosomal rearrangement (GCR) rates in yeast, similar to Pif1 deletion. Here, we highlight the recent findings and set these into context with a new mechanistic model. We propose that Mgs1's functions support DNA replication at G4-forming regions.

scholarly journals DNA G-quadruplexes for native mass spectrometry in potassium: a database of validated structures in electrospray-compatible conditions

2021 ◽  
Author(s):  
Anirban Ghosh ◽  
Eric Largy ◽  
Valérie Gabelica
Keyword(s):  
Mass Spectrometry ◽  
Drug Targets ◽  
Native Mass Spectrometry ◽  
Drug Binding ◽  
Quadruplex Dna ◽  
Dna Structures ◽  
Nmr Structures ◽  
G Quadruplex ◽  
Screening Assays

Abstract G-quadruplex DNA structures have become attractive drug targets, and native mass spectrometry can provide detailed characterization of drug binding stoichiometry and affinity, potentially at high throughput. However, the G-quadruplex DNA polymorphism poses problems for interpreting ligand screening assays. In order to establish standardized MS-based screening assays, we studied 28 sequences with documented NMR structures in (usually ∼100 mM) potassium, and report here their circular dichroism (CD), melting temperature (Tm), NMR spectra and electrospray mass spectra in 1 mM KCl/100 mM trimethylammonium acetate. Based on these results, we make a short-list of sequences that adopt the same structure in the MS assay as reported by NMR, and provide recommendations on using them for MS-based assays. We also built an R-based open-source application to build and consult a database, wherein further sequences can be incorporated in the future. The application handles automatically most of the data processing, and allows generating custom figures and reports. The database is included in the g4dbr package (https://github.com/EricLarG4/g4dbr) and can be explored online (https://ericlarg4.github.io/G4_database.html).

scholarly journals Subtle structural alterations in G-quadruplex DNA regulate site specificity of fluorescence light-up probes

2020 ◽  
Vol 48 (3) ◽  
pp. 1108-1119 ◽  
Author(s):  
Rajendra Kumar ◽  
Karam Chand ◽  
Sudipta Bhowmik ◽  
Rabindra Nath Das ◽  
Snehasish Bhattacharjee ◽  
...  
Keyword(s):  
Rational Design ◽  
Dna Structure ◽  
Biological Processes ◽  
Chemical Research ◽  
Quadruplex Dna ◽  
Dna Structures ◽  
Future Studies ◽  
G4 Dna ◽  
G Quadruplex ◽  
Fluorescence Light

Abstract G-quadruplex (G4) DNA structures are linked to key biological processes and human diseases. Small molecules that target specific G4 DNA structures and signal their presence would therefore be of great value as chemical research tools with potential to further advance towards diagnostic and therapeutic developments. However, the development of these types of specific compounds remain as a great challenge. In here, we have developed a compound with ability to specifically signal a certain c-MYC G4 DNA structure through a fluorescence light-up mechanism. Despite the compound's two binding sites on the G4 DNA structure, only one of them result in the fluorescence light-up effect. This G-tetrad selectivity proved to originate from a difference in flexibility that affected the binding affinity and tilt the compound out of the planar conformation required for the fluorescence light-up mechanism. The intertwined relation between the presented factors is likely the reason for the lack of examples using rational design to develop compounds with turn-on emission that specifically target certain G4 DNA structures. However, this study shows that it is indeed possible to develop such compounds and present insights into the molecular details of specific G4 DNA recognition and signaling to advance future studies of G4 biology.

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