Small molecule inhibitor of OGG1 blocks oxidative DNA damage repair at telomeres and potentiates methotrexate anticancer effects

Abstract Background: The most common oxidative DNA lesion is 8-oxoguanine (8-oxoG) which is mainly recognized and excised by the glycosylase OGG1, initiating the Base Excision Repair (BER) pathway. Telomeres are particularly sensitive to oxidative stress which disrupts telomere homeostasis triggering genome instability. Methods: We used U2OS OGG1-GFP osteosarcoma cell line to study the role of OGG1 at the telomeres in response to oxidative stress. Next, we investigated the effects of inactivating pharmacologically the BER during oxidative stress (OS) conditions by using a specific small molecule inhibitor of OGG1 (TH5487) in different human cell lines. Results: We have found that during OS, TH5487 effectively blocks BER initiation at telomeres causing accumulation of oxidized bases at this region, correlating with other phenotypes such as telomere losses, micronuclei formation and mild proliferation defects. Besides, the antimetabolite Methotrexate synergizes with TH5487 through induction of intracellular ROS formation, which potentiates TH5487 mediated telomere and genome instability in different cell lines. Conclusions: Our findings demonstrate that OGG1 is required to protect telomeres from OS and present OGG1 inhibitors as a tool to induce oxidative DNA damage at telomeres, with the potential for developing new combination therapies for cancer treatment.

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Small molecule inhibitor of OGG1 blocks oxidative DNA damage repair at telomeres and potentiates Methotrexate anticancer effects

10.21203/rs.3.rs-57290/v1 ◽

2020 ◽

Author(s):

Juan Miguel Baquero ◽

Carlos Benítez-Buelga ◽

Varshni Rajagopal ◽

Zhao Zhenjun ◽

Raúl Torres-Ruiz ◽

...

Keyword(s):

Oxidative Stress ◽

Dna Damage ◽

Cell Lines ◽

Small Molecule ◽

Oxidative Dna Damage ◽

Genome Instability ◽

Excision Repair ◽

Small Molecule Inhibitor ◽

Osteosarcoma Cell ◽

Molecule Inhibitor

Abstract Background: The most common oxidative DNA lesion is 8-oxoguanine (8-oxoG) which is mainly recognized and excised by the glycosylase OGG1, initiating the Base Excision Repair (BER) pathway. Telomeres are particularly sensitive to oxidative stress which disrupts telomere homeostasis triggering genome instability. Methods: We used U2OS OGG1-GFP osteosarcoma cell line to study the role of OGG1 at the telomeres in response to oxidative stress. Next, we investigated the effects of inactivating pharmacologically the BER during oxidative stress (OS) conditions by using a specific small molecule inhibitor of OGG1 (TH5487) in different human cell lines. Results: We have found that during OS, TH5487 effectively blocks BER initiation at telomeres causing accumulation of oxidized bases at this region, correlating with other phenotypes such as telomere losses, micronuclei formation and mild proliferation defects. Besides, the antimetabolite Methotrexate synergizes with TH5487 through induction of intracellular ROS formation, which potentiates TH5487 mediated telomere and genome instability in different cell lines. Conclusions: Our findings demonstrate that OGG1 is required to protect telomeres from OS and present OGG1 inhibitors as a tool to induce oxidative DNA damage at telomeres, with the potential for developing new combination therapies for cancer treatment.

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Oxygen-Dependent Accumulation of Purine DNA Lesions in Cockayne Syndrome Cells

Cells ◽

10.3390/cells9071671 ◽

2020 ◽

Vol 9 (7) ◽

pp. 1671 ◽

Cited By ~ 1

Author(s):

Marios G. Krokidis ◽

Mariarosaria D’Errico ◽

Barbara Pascucci ◽

Eleonora Parlanti ◽

Annalisa Masi ◽

...

Keyword(s):

Dna Damage ◽

Oxidative Dna Damage ◽

Excision Repair ◽

Enzymatic Digestion ◽

Cockayne Syndrome ◽

Dna Lesions ◽

Premature Aging ◽

Neurological Features ◽

Oxygen Tensions ◽

Base Excision

Cockayne Syndrome (CS) is an autosomal recessive neurodegenerative premature aging disorder associated with defects in nucleotide excision repair (NER). Cells from CS patients, with mutations in CSA or CSB genes, present elevated levels of reactive oxygen species (ROS) and are defective in the repair of a variety of oxidatively generated DNA lesions. In this study, six purine lesions were ascertained in wild type (wt) CSA, defective CSA, wtCSB and defective CSB-transformed fibroblasts under different oxygen tensions (hyperoxic 21%, physioxic 5% and hypoxic 1%). In particular, the four 5′,8-cyclopurine (cPu) and the two 8-oxo-purine (8-oxo-Pu) lesions were accurately quantified by LC-MS/MS analysis using isotopomeric internal standards after an enzymatic digestion procedure. cPu levels were found comparable to 8-oxo-Pu in all cases (3–6 lesions/106 nucleotides), slightly increasing on going from hyperoxia to physioxia to hypoxia. Moreover, higher levels of four cPu were observed under hypoxia in both CSA and CSB-defective cells as compared to normal counterparts, along with a significant enhancement of 8-oxo-Pu. These findings revealed that exposure to different oxygen tensions induced oxidative DNA damage in CS cells, repairable by NER or base excision repair (BER) pathways. In NER-defective CS patients, these results support the hypothesis that the clinical neurological features might be connected to the accumulation of cPu. Moreover, the elimination of dysfunctional mitochondria in CS cells is associated with a reduction in the oxidative DNA damage.

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Dynamic Compartmentalization of Base Excision Repair Proteins in Response to Nuclear and Mitochondrial Oxidative Stress

Molecular and Cellular Biology ◽

10.1128/mcb.01357-08 ◽

2008 ◽

Vol 29 (3) ◽

pp. 794-807 ◽

Cited By ~ 31

Author(s):

Lyra M. Griffiths ◽

Dan Swartzlander ◽

Kellen L. Meadows ◽

Keith D. Wilkinson ◽

Anita H. Corbett ◽

...

Keyword(s):

Oxidative Stress ◽

Dna Damage ◽

Dna Repair ◽

Base Excision Repair ◽

Oxidative Dna Damage ◽

Excision Repair ◽

Intracellular Localization ◽

Genotoxic Stress ◽

Mitochondrial Oxidative Stress ◽

Base Excision

ABSTRACT DNAs harbored in both nuclei and mitochondria of eukaryotic cells are subject to continuous oxidative damage resulting from normal metabolic activities or environmental insults. Oxidative DNA damage is primarily reversed by the base excision repair (BER) pathway, initiated by N-glycosylase apurinic/apyrimidinic (AP) lyase proteins. To execute an appropriate repair response, BER components must be distributed to accommodate levels of genotoxic stress that may vary considerably between nuclei and mitochondria, depending on the growth state and stress environment of the cell. Numerous examples exist where cells respond to signals, resulting in relocalization of proteins involved in key biological transactions. To address whether such dynamic localization contributes to efficient organelle-specific DNA repair, we determined the intracellular localization of the Saccharomyces cerevisiae N-glycosylase/AP lyases, Ntg1 and Ntg2, in response to nuclear and mitochondrial oxidative stress. Fluorescence microscopy revealed that Ntg1 is differentially localized to nuclei and mitochondria, likely in response to the oxidative DNA damage status of the organelle. Sumoylation is associated with targeting of Ntg1 to nuclei containing oxidative DNA damage. These studies demonstrate that trafficking of DNA repair proteins to organelles containing high levels of oxidative DNA damage may be a central point for regulating BER in response to oxidative stress.

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Base excision repair of oxidative DNA damage and association with cancer and aging

Carcinogenesis ◽

10.1093/carcin/bgn250 ◽

2008 ◽

Vol 30 (1) ◽

pp. 2-10 ◽

Cited By ~ 344

Author(s):

S. Maynard ◽

S. H. Schurman ◽

C. Harboe ◽

N. C. de Souza-Pinto ◽

V. A. Bohr

Keyword(s):

Dna Damage ◽

Base Excision Repair ◽

Oxidative Dna Damage ◽

Excision Repair ◽

Base Excision

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The Effect ofMsh2Knockdown on Toxicity Induced bytert-Butyl-hydroperoxide, Potassium Bromate, and Hydrogen Peroxide in Base Excision Repair Proficient and Deficient Cells

BioMed Research International ◽

10.1155/2013/152909 ◽

2013 ◽

Vol 2013 ◽

pp. 1-9 ◽

Cited By ~ 3

Author(s):

N. Cooley ◽

R. H. Elder ◽

A. C. Povey

Keyword(s):

Dna Damage ◽

Base Excision Repair ◽

Oxidative Dna Damage ◽

Excision Repair ◽

Shrna Expression ◽

Cellular Toxicity ◽

Dna Mismatch ◽

Shrna Expression Vector ◽

Repair Systems ◽

Base Excision

The DNA mismatch repair (MMR) and base excision repair (BER) systems are important determinants of cellular toxicity following exposure to agents that cause oxidative DNA damage. To examine the interactions between these different repair systems, we examined whether toxicity, induced byt-BOOH and KBrO3, differs in BER proficient (Mpg+/+,Nth1+/+) and deficient (Mpg−/−,Nth1−/−) mouse embryonic fibroblasts (MEFs) followingMsh2knockdown of between 79 and 88% using an shRNA expression vector.Msh2knockdown inNth1+/+cells had no effect ont-BOOH and KBrO3induced toxicity as assessed by an MTT assay; knockdown inNth1−/−cells resulted in increased resistance tot-BOOH and KBrO3, a result consistent with Nth1 removing oxidised pyrimidines.Msh2knockdown inMpg+/+cells had no effect ont-BOOH toxicity but increased resistance to KBrO3; inMpg−/−cells,Msh2knockdown increased cellular sensitivity to KBrO3but increased resistance to t-BOOH, suggesting a role forMpgin removing DNA damage induced by these agents. MSH2 dependent and independent pathways then determine cellular toxicity induced by oxidising agents. A complex interaction between MMR and BER repair systems, that is, exposure dependent, also exists to determine cellular toxicity.

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