scholarly journals HERC2 promotes BLM and WRN to suppress G-quadruplex DNA

2018 ◽  
Author(s):  
Wenwen Wu ◽  
Nana Rokutanda ◽  
Jun Takeuchi ◽  
Yongqiang Lai ◽  
Reo Maruyama ◽  
...  
Keyword(s):  
Essential Role ◽  
Protein A ◽  
Genomic Stability ◽  
S Phase ◽  
Dna Helicases ◽  
Quadruplex Dna ◽  
G4 Dna ◽  
G Quadruplex ◽  
Ubiquitin Binding

SUMMARYBLM and WRN are RecQ DNA helicases essential for genomic stability. Here we demonstrate that HERC2, a HECT E3 ligase, is critical for their functions to suppress G-quadruplex (G4) DNA. HERC2 interacts with BLM, WRN, and replication protein A (RPA) complexes during S-phase of the cell cycle. Depletion of HERC2 dissociates RPA from BLM and WRN complexes and significantly increases G4 formation. Triple depletion revealed that HERC2 has an epistatic relationship with BLM and WRN in their G4- suppressing function.In vitro, HERC2 releases RPA onto single-stranded DNA (ssDNA), rather than anchoring onto RPA-coated ssDNA. CRISPR/Cas9-mediated deletion of the catalytic ubiquitin-binding site of HERC2 causes RPA accumulation in the helicase complexes and increases G4, indicating an essential role for E3 activity in G4 suppression. Both HERC2 depletion and E3 inactivation sensitize cells to the G4-interacting compounds, telomestatin and pyridostatin. Overall, HERC2 is a master regulator of G4 suppression and affects the sensitivity of cells to G4 stabilizers.

scholarly journals FANCJ Helicase Defective in Fanconia Anemia and Breast Cancer Unwinds G-Quadruplex DNA To Defend Genomic Stability

2008 ◽  
Vol 28 (12) ◽  
pp. 4116-4128 ◽  
Author(s):  
Yuliang Wu ◽  
Kazuo Shin-ya ◽  
Robert M. Brosh
Keyword(s):  
Breast Cancer ◽  
Sequence Similarity ◽  
Protein A ◽  
Genomic Stability ◽  
Dependent Manner ◽  
Quadruplex Dna ◽  
Bone Marrow Disease ◽  
G4 Dna ◽  
G Quadruplex ◽  
Interfering Rna

ABSTRACT FANCJ mutations are associated with breast cancer and genetically linked to the bone marrow disease Fanconi anemia (FA). The genomic instability of FA-J mutant cells suggests that FANCJ helicase functions in the replicational stress response. A putative helicase with sequence similarity to FANCJ in Caenorhabditis elegans (DOG-1) and mouse (RTEL) is required for poly(G) tract maintenance, suggesting its involvement in the resolution of alternate DNA structures that impede replication. Under physiological conditions, guanine-rich sequences spontaneously assemble into four-stranded structures (G quadruplexes [G4]) that influence genomic stability. FANCJ unwound G4 DNA substrates in an ATPase-dependent manner. FANCJ G4 unwinding is specific since another superfamily 2 helicase, RECQ1, failed to unwind all G4 substrates tested under conditions in which the helicase unwound duplex DNA. Replication protein A stimulated FANCJ G4 unwinding, whereas the mismatch repair complex MSH2/MSH6 inhibited this activity. FANCJ-depleted cells treated with the G4-interactive compound telomestatin displayed impaired proliferation and elevated levels of apoptosis and DNA damage compared to small interfering RNA control cells, suggesting that G4 DNA is a physiological substrate of FANCJ. Although the FA pathway has been classically described in terms of interstrand cross-link (ICL) repair, the cellular defects associated with FANCJ mutation extend beyond the reduced ability to repair ICLs and involve other types of DNA structural roadblocks to replication.

scholarly journals G-quadruplex DNA drives genomic instability and represents a targetable molecular abnormality in ATRX-deficient malignant glioma

2018 ◽  
Author(s):  
Yuxiang Wang ◽  
Jie Yang ◽  
Wei Wu ◽  
Rachna Shah ◽  
Carla Danussi ◽  
...  
Keyword(s):  
Dna Damage ◽  
Malignant Glioma ◽  
Model Systems ◽  
Copy Number Alterations ◽  
Molecular Alteration ◽  
Quadruplex Dna ◽  
G4 Dna ◽  
G Quadruplex

AbstractMutational inactivation of ATRX (α-thalassemia mental retardation X-linked) represents a defining molecular alteration in large subsets of malignant glioma. Yet the pathogenic consequences of ATRX deficiency remain unclear, as do tractable mechanisms for its therapeutic targeting. Here we report that ATRX loss in isogenic glioma model systems induces replication stress and DNA damage by way of G-quadruplex (G4) DNA secondary structure. Moreover, these effects are associated with the acquisition of disease-relevant copy number alterations over time. We then demonstrate, both in vitro and in vivo, that ATRX deficiency selectively enhances DNA damage and cell death following chemical G4 stabilization. Finally, we show that G4 stabilization synergizes with other DNA-damaging therapies, including ionizing radiation, in the ATRX-deficient context. Our findings reveal novel pathogenic mechanisms driven by ATRX deficiency in glioma, while also pointing to tangible strategies for drug development.

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 Stiff-Stilbene Ligands Target G-Quadruplex DNA and Exhibit Selective Anticancer and Antiparasitic Activity

2019 ◽  
Author(s):  
Michael O'Hagan ◽  
pablo Peñalver ◽  
Rosina S. L. Gibson ◽  
Juan Carlos Morales ◽  
M. Carmen Galan
Keyword(s):  
Molecular Geometry ◽  
Substitution Pattern ◽  
Biophysical Characterization ◽  
Antiparasitic Activity ◽  
Quadruplex Dna ◽  
G4 Dna ◽  
G Quadruplex ◽  
Exciting Potential ◽  
Nucleic Acid Structures

<p>G-quadruplex nucleic acid structures have long been studied as potential anticancer targets while their potential in antiparasitic therapy has only recently been recognized but barely explored. Herein we report the synthesis, biophysical characterization and <i>in vitro </i>screening of a series of stiff-stilbene G4 binding ligands featuring differing electronics, side-chain chemistries and molecular geometries. The ligands display selectivity for G4 DNA over duplex DNA and exhibit nanomolar toxicity against <i>Trypasanoma brucei </i>and HeLa cancer cells whist remaining up to two orders of magnitude less toxic to non-tumoral mammalian cell line MRC5. Our study demonstrates that stiff-stilbenes show exciting potential as the basis of selective anticancer and antiparasitic therapies. In order to achieve the most efficient G4 recognition the scaffold must possess the optimal electronics and substitution pattern and correct molecular geometry. <br></p>

scholarly journals Stiff-Stilbene Ligands Target G-Quadruplex DNA and Exhibit Selective Anticancer and Antiparasitic Activity

2019 ◽  
Author(s):  
Michael O'Hagan ◽  
pablo Peñalver ◽  
Rosina S. L. Gibson ◽  
Juan Carlos Morales ◽  
M. Carmen Galan
Keyword(s):  
Molecular Geometry ◽  
Substitution Pattern ◽  
Biophysical Characterization ◽  
Antiparasitic Activity ◽  
Quadruplex Dna ◽  
G4 Dna ◽  
G Quadruplex ◽  
Exciting Potential ◽  
Nucleic Acid Structures

<p>G-quadruplex nucleic acid structures have long been studied as potential anticancer targets while their potential in antiparasitic therapy has only recently been recognized but barely explored. Herein we report the synthesis, biophysical characterization and <i>in vitro </i>screening of a series of stiff-stilbene G4 binding ligands featuring differing electronics, side-chain chemistries and molecular geometries. The ligands display selectivity for G4 DNA over duplex DNA and exhibit nanomolar toxicity against <i>Trypasanoma brucei </i>and HeLa cancer cells whist remaining up to two orders of magnitude less toxic to non-tumoral mammalian cell line MRC5. Our study demonstrates that stiff-stilbenes show exciting potential as the basis of selective anticancer and antiparasitic therapies. In order to achieve the most efficient G4 recognition the scaffold must possess the optimal electronics and substitution pattern and correct molecular geometry. <br></p>

scholarly journals Role of the p68 Subunit of Human DNA Polymerase α-Primase in Simian Virus 40 DNA Replication

2002 ◽  
Vol 22 (16) ◽  
pp. 5669-5678 ◽  
Author(s):  
Robert D. Ott ◽  
Christoph Rehfuess ◽  
Vladimir N. Podust ◽  
Jill E. Clark ◽  
Ellen Fanning
Keyword(s):  
Dna Replication ◽  
Dna Polymerase ◽  
Essential Role ◽  
Protein A ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
S Phase ◽  
Dna Polymerase Α

ABSTRACT DNA polymerase α-primase (pol-prim) is a heterotetramer with DNA polymerase and primase activities. The polymerase (p180) and primase (p48 and p58) subunits synthesize primers and extend them, but the function of the remaining subunit (p68) is poorly understood. Genetic studies in yeast suggested an essential role for the p68 ortholog in early S phase prior to the hydroxyurea-sensitive step, possibly a regulatory role in initiation of DNA replication, but found no evidence for an essential function of p68 later in S phase. To investigate whether the human p68 subunit has an essential role in DNA replication, we examined the ability of a purified trimeric human pol-prim lacking p68 to initiate simian virus 40 DNA replication in vitro and to synthesize and elongate primers on single-stranded DNA in the presence of T antigen and replication protein A (RPA). Both activities of trimeric pol-prim were defective, but activity was recovered upon addition of separately purified p68. Phosphorylation of p68 by cyclin A-dependent protein kinase also inhibited both activities of pol-prim. The data strongly suggest that the p68 subunit is required for priming activity of pol-prim in the presence of RPA and T antigen, both during initiation at the origin and during lagging strand replication.

scholarly journals Disclosing the actual efficiency of G-quadruplex-DNA–disrupting small molecules

2020 ◽  
Author(s):  
Jérémie Mitteaux ◽  
Pauline Lejault ◽  
Marc Pirrotta ◽  
Filip Wojciechowski ◽  
Alexandra Joubert ◽  
...  
Keyword(s):  
Small Molecules ◽  
Chemical Biology ◽  
Research Field ◽  
Molecular Tools ◽  
Quadruplex Dna ◽  
G4 Dna ◽  
Age Related ◽  
G Quadruplex ◽  
Unique Chemical

AbstractThe quest for small molecules that avidly bind to G-quadruplex-DNA (G4-DNA, or G4), so called G4-ligands, has invigorated the G4 research field from its very inception. Massive efforts have been invested to i- screen or design G4-ligands, ii- evaluate their G4-interacting properties in vitro through a series of now widely accepted and routinely implemented assays, and iii- use them as unique chemical biology tools to interrogate cellular networks that might involve G4s. In sharp contrast, only uncoordinated efforts at developing small molecules aimed at destabilizing G4s have been invested to date, even though it is now recognized that such molecular tools would have tremendous application to neurobiology as many genetic and age-related diseases are caused by an over-representation of G4s, itself caused by a deficiency of G4-resolving enzymes, the G4-helicases. Herein, we report on our double effort to i- develop a reliable in vitro assay to identify molecules able to destabilize G4s, the G4-unfold assay, and ii- fully characterize the first prototype of G4-disrupting small molecule, a phenylpyrrolcytosine (PhpC)-based G-clamp analog.

scholarly journals G-quadruplex DNA inhibits unwinding activity but promotes liquid–liquid phase separation by the DEAD-box helicase Ded1p

2021 ◽  
Author(s):  
Jun Gao ◽  
Zhaofeng Gao ◽  
Andrea A. Putnam ◽  
Alicia K. Byrd ◽  
Sarah L. Venus ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Liquid Phase Separation ◽  
Intrinsically Disordered ◽  
Dead Box ◽  
G4 Dna ◽  
G Quadruplex ◽  
The Dead ◽  
Liquid Liquid Phase Separation

G-quadruplex (G4) DNA inhibits RNA unwinding activity but promotes liquid–liquid phase separation of the DEAD-box helicase Ded1p in vitro and in cells. This highlights multifaceted effects of G4DNA on an enzyme with intrinsically disordered domains.

scholarly journals ATRX promotes heterochromatin formation to protect cells from G-quadruplex DNA-mediated stress

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yu-Ching Teng ◽  
Aishwarya Sundaresan ◽  
Ryan O’Hara ◽  
Vincent U. Gant ◽  
Minhua Li ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Genome Stability ◽  
Helicase Domain ◽  
Quadruplex Dna ◽  
Heterochromatin Formation ◽  
Replicative Stress ◽  
G4 Dna ◽  
Mutation Burden ◽  
G Quadruplex ◽  
Dna Replication Stress

AbstractATRX is a tumor suppressor that has been associated with protection from DNA replication stress, purportedly through resolution of difficult-to-replicate G-quadruplex (G4) DNA structures. While several studies demonstrate that loss of ATRX sensitizes cells to chemical stabilizers of G4 structures, the molecular function of ATRX at G4 regions during replication remains unknown. Here, we demonstrate that ATRX associates with a number of the MCM replication complex subunits and that loss of ATRX leads to G4 structure accumulation at newly synthesized DNA. We show that both the helicase domain of ATRX and its H3.3 chaperone function are required to protect cells from G4-induced replicative stress. Furthermore, these activities are upstream of heterochromatin formation mediated by the histone methyltransferase, ESET, which is the critical molecular event that protects cells from G4-mediated stress. In support, tumors carrying mutations in either ATRX or ESET show increased mutation burden at G4-enriched DNA sequences. Overall, our study provides new insights into mechanisms by which ATRX promotes genome stability with important implications for understanding impacts of its loss on human disease.

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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