Roles for the 8-Oxoguanine DNA Repair System in Protecting Telomeres From Oxidative Stress

Telomeres are protective nucleoprotein structures that cap linear chromosome ends and safeguard genome stability. Progressive telomere shortening at each somatic cell division eventually leads to critically short and dysfunctional telomeres, which can contribute to either cellular senescence and aging, or tumorigenesis. Human reproductive cells, some stem cells, and most cancer cells, express the enzyme telomerase to restore telomeric DNA. Numerous studies have shown that oxidative stress caused by excess reactive oxygen species is associated with accelerated telomere shortening and dysfunction. Telomeric repeat sequences are remarkably susceptible to oxidative damage and are preferred sites for the production of the mutagenic base lesion 8-oxoguanine, which can alter telomere length homeostasis and integrity. Therefore, knowledge of the repair pathways involved in the processing of 8-oxoguanine at telomeres is important for advancing understanding of the pathogenesis of degenerative diseases and cancer associated with telomere instability. The highly conserved guanine oxidation (GO) system involves three specialized enzymes that initiate distinct pathways to specifically mitigate the adverse effects of 8-oxoguanine. Here we introduce the GO system and review the studies focused on investigating how telomeric 8-oxoguanine processing affects telomere integrity and overall genome stability. We also discuss newly developed technologies that target oxidative damage selectively to telomeres to investigate roles for the GO system in telomere stability.

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Folic Acid Decreases Astrocyte Apoptosis by Preventing Oxidative Stress-Induced Telomere Attrition

International Journal of Molecular Sciences ◽

10.3390/ijms21010062 ◽

2019 ◽

Vol 21 (1) ◽

pp. 62 ◽

Cited By ~ 1

Author(s):

Wen Li ◽

Yue Ma ◽

Zhenshu Li ◽

Xin Lv ◽

Xinyan Wang ◽

...

Keyword(s):

Oxidative Stress ◽

Cell Proliferation ◽

Folic Acid ◽

Oxidative Damage ◽

Telomere Length ◽

Primary Cultures ◽

Folic Acid Deficiency ◽

Telomeric Dna ◽

Telomere Attrition ◽

Dna Oxidative Damage

Astrocytes are the most widely distributed cells in the brain, and astrocyte apoptosis may play an important role in the pathogenesis of neurodegenerative diseases. Folate is required for the normal development of the nervous system, but its effect on astrocyte apoptosis is unclear. In this study, we hypothesized that folic acid (the therapeutic form of folate) decreases astrocyte apoptosis by preventing oxidative stress-induced telomere attrition. Primary cultures of astrocytes were incubated for 12 days with various concentrations of folic acid (0–40 μmol/L), then cell proliferation, apoptosis, intracellular folate concentration, intracellular homocysteine (Hcy) concentration, intracellular reactive oxygen species (ROS) levels, telomeric DNA oxidative damage, and telomere length were determined. The results showed that folic acid deficiency decreased intracellular folate, cell proliferation, and telomere length, whereas it increased Hcy concentration, ROS levels, telomeric DNA oxidative damage, and apoptosis. In contrast, folic acid dose-dependently increased intracellular folate, cell proliferation, and telomere length but it decreased Hcy concentration, ROS levels, telomeric DNA oxidative damage, and apoptosis. In conclusion, folic acid inhibited apoptosis in astrocytes. The underlying mechanism for this protective effect may be that folic acid decreased oxidative stress and thereby prevented telomeric DNA oxidative damage and telomere attrition.

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CtIP is essential for telomere replication

Nucleic Acids Research ◽

10.1093/nar/gkz652 ◽

2019 ◽

Vol 47 (17) ◽

pp. 8927-8940 ◽

Cited By ~ 2

Author(s):

Susanna Stroik ◽

Kevin Kurtz ◽

Eric A Hendrickson

Keyword(s):

Dna Repair ◽

Genome Stability ◽

Telomere Dysfunction ◽

Replication Forks ◽

Telomeric Dna ◽

Telomere Shortening ◽

Repair Protein ◽

Dna Repair Protein ◽

Telomere Replication ◽

Human Telomere

Abstract The maintenance of telomere length is critical to longevity and survival. Specifically, the failure to properly replicate, resect, and/or form appropriate telomeric structures drives telomere shortening and, in turn, genomic instability. The endonuclease CtIP is a DNA repair protein that is well-known to promote genome stability through the resection of endogenous DNA double-stranded breaks. Here, we describe a novel role for CtIP. We show that in the absence of CtIP, human telomeres shorten rapidly to non-viable lengths. This telomere dysfunction results in an accumulation of fusions, breaks, and frank telomere loss. Additionally, CtIP suppresses the generation of circular, extrachromosomal telomeric DNA. These latter structures appear to arise from arrested DNA replication forks that accumulate in the absence of CtIP. Hence, CtIP is required for faithful replication through telomeres via its roles at stalled replication tracts. Our findings demonstrate a new role for CtIP as a protector of human telomere integrity.

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A multilayered repair system protects the mycobacterial chromosome from endogenous and antibiotic-induced oxidative damage

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2006792117 ◽

2020 ◽

Vol 117 (32) ◽

pp. 19517-19527

Author(s):

Pierre Dupuy ◽

Mir Howlader ◽

Michael S. Glickman

Keyword(s):

Oxidative Stress ◽

Oxidative Damage ◽

Dna Polymerases ◽

Repair System ◽

Genomic Integrity ◽

Chromosomal Dna ◽

Living Organisms ◽

Oxidative Damage To Dna

Oxidative damage to DNA is a threat to the genomic integrity and coding accuracy of the chromosomes of all living organisms. Guanine is particularly susceptible to oxidation, and 8-oxo-dG (OG), when produced in situ or incorporated by DNA polymerases, is highly mutagenic due to mispairing with adenine. In many bacteria, defense against OG depends on MutT enzymes, which sanitize OG in the nucleotide pool, and the MutM/Y system, which counteracts OG in chromosomal DNA. InEscherichia coli, antibiotic lethality has been linked to oxidative stress and the downstream consequences of OG processing. However, in mycobacteria, the role of these systems in genomic integrity and antibiotic lethality is not understood, in part because mycobacteria encode four MutT enzymes and two MutMs, suggesting substantial redundancy. Here, we definitively probe the role of OG handling systems in mycobacteria. We find that, although MutT4 is the only MutT enzyme required for resistance to oxidative stress, this effect is not due to OG processing. We find that the dominant system that defends against OG-mediated mutagenesis is MutY/MutM1, and this system is dedicated to in situ chromosomal oxidation rather than correcting OG incorporated by accessory polymerases (DinB1/DinB2/DinB3/DnaE2). In addition, we uncover that mycobacteria resist antibiotic lethality through nucleotide sanitization by MutTs, and in the absence of this system, accessory DNA polymerases and MutY/M contribute to antibiotic-induced lethality. These results reveal a complex, multitiered system of OG handling in mycobacteria with roles in oxidative stress resistance, mutagenesis, and antibiotic lethality.

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670 Oxidative stress originating in the mitochondria damages telomeres sufficient to drive certain features of T cell dysfunction

Journal for ImmunoTherapy of Cancer ◽

10.1136/jitc-2021-sitc2021.670 ◽

2021 ◽

Vol 9 (Suppl 3) ◽

pp. A698-A698

Author(s):

Dayana Rivadeneira ◽

Jess Yana ◽

Sanjana Thosar ◽

Marcel Bruchez ◽

Patricia Lynn ◽

...

Keyword(s):

Oxidative Stress ◽

T Cells ◽

T Cell ◽

Oxidative Damage ◽

Telomeric Dna ◽

Cell Dysfunction ◽

Ros Accumulation ◽

T Cell Dysfunction ◽

Infiltrating Lymphocytes

BackgroundThe functional state of infiltrating lymphocytes is a critical determinant of antitumor immunity and immunotherapy response. Key factors responsible for driving T cell dysfunction are metabolic barriers such as nutrient competition, low oxygen tension and damaging byproducts, like reactive oxygen species (ROS). ROS are critical contributors to T cell dysfunction observed during aging as well as in the tumor microenvironment. While we have shown ROS accumulation drives T cell exhaustion in part by altering signaling, ROS can affect other cellular functions further contributing to T cell dysfunction. One of the main downstream consequences observed with ROS accumulation is DNA damage, in particular telomeric DNA. However, little is known on whether telomeric shortening vs damage and the associated response affects T cell fate and function.MethodsWe performed telomeric analyses of endogenous tumor-infiltrating T cells. In vitro, direct induction of oxidative stress in mitochondria or telomeres was performed using a photosensitizer approach employing fluorogen-activating peptide (FAP)1 targeted to the mitochondria (COXVIII-FAP) or to the telomeric shelterin protein TRF1, which produces singlet oxygen and 8-oxoguanine specifically in the mitochondria or at the telomeres.2 Our lab generated mouse models to express this telomeric-FAP (Rosa26-LSL-TRF1-FAP) or mitochondrial-FAP (Rosa26-LSL-COXVIII-FAP) specifically in T cells (Cd4Cre).ResultsTelomere analysis of tumor-infiltrating exhausted (PD1hiTim3+) vs non-exhausted (PD1int) cells revealed exhausted T cells do not have shorter telomeres (like senescent T cells), but rather damaged telomeres. Using a photosensitizer strategy to specifically induce oxidative damage to the mitochondria, we recapitulated our previous work in vitro, resulting in ROS cascades, severe T cell dysfunction, and damage to telomeres. We next directly assessed the role of telomere oxidative damage using a telomeric-targeted photosensitizer, showing oxidative damage to telomeres promotes a persistent T cell dysfunction, resulting in sustained Tim3 and PD1 expression and severely decreased functions. However, oxidative damage to telomeric DNA alone does not induce all of the features of T cell exhaustion, suggesting that telomere damage is a crucial piece, but not fully sufficient to drive T cell dysfunction.ConclusionsOur data support a model where oxidative stress originating in the mitochondria alters cellular biology in part by damaging telomeric DNA. While this activity does not shorten telomeres, it induces stress responses sufficient to deviate differentiation into a dysfunctional phenotype. While telomeric damage alone does not fully recapitulate exhaustion, it nevertheless remains a crucial part of the dysfunctional phenotype in tumor infiltrating lymphocytes.ReferencesHe J, Wang Y, Missinato MA, Onuoha E, Perkins LA, Watkins SC, St Croix CM, Tsang M, Bruchez MP. A genetically targetable near-infrared photosensitizer Nat Methods 2016;13:263–268.Fouquerel E, Barnes RP, Uttam S, Watkins SC, Bruchez MP, Opresko PL. Targeted and persistent 8-Oxoguanine base damage at telomeres promotes telomere loss and crisis. Mol Cell 2019;75(1):117–130.e6.

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Oxidative injury associated with stenting of asymptomatic carotid artery stenosis

VASA ◽

10.1024/0301-1526/a000621 ◽

2017 ◽

Vol 46 (4) ◽

pp. 268-274

Author(s):

Erhan Saraçoğlu ◽

Ertan Vuruşkan ◽

Yusuf Çekici ◽

Salih Kiliç ◽

Halil Ay ◽

...

Keyword(s):

Oxidative Stress ◽

Carotid Artery ◽

Oxidative Damage ◽

Carotid Artery Stenosis ◽

Artery Stenosis ◽

Oxidative Stress Marker ◽

Asymptomatic Carotid ◽

Imaging Methods ◽

Neurological Findings ◽

Asymptomatic Carotid Artery Stenosis

Abstract. Background: After carotid artery stenting (CAS), neurological complications that cannot be explained with imaging methods may develop. In our study we aimed to show, using oxidative stress markers, isolated oxidative damage and resulting neurological findings following CAS in patients with asymptomatic carotid artery stenosis. Patients and methods: We included 131 neurologically asymptomatic patients requiring CAS. The neurological findings were evaluated using the modified Rankin Scale (mRS) prior to the procedure, one hour post-procedure, and two days after. Patients with elevated mRS scores but with or without typical hyperintense lesions observed on an MRI and with changes of oxidative stress marker levels at the time (Δtotal-thiol, Δtotal antioxidative status [TAS], and Δtotal oxidant status [TOS]) were evaluated. Results: In the neurological examination carried out one hour prior to the procedure, there were 92 patients with mRS = 0, 20 with mRS = 1, and 12 with mRS = 2. When Δtotal-thiol, ΔTAS, and ΔTOS values and the mRS were compared, it was observed that as the difference in oxidative parameters increased, clinical deterioration also increased proportionally (p = 0.001). Conclusions: We demonstrate a possible correlation between oxidative damage and neurological findings after CAS which could not be explained by routine imaging methods.

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Changes in lipid peroxidation during pregnancy and after delivery in rats: effect of pinealectomy

Reproduction ◽

10.1530/reprod/119.1.143 ◽

2000 ◽

pp. 143-149 ◽

Cited By ~ 9

Author(s):

RM Sainz ◽

RJ Reiter ◽

JC Mayo ◽

J Cabrera ◽

DX Tan ◽

...

Keyword(s):

Oxidative Stress ◽

Lipid Peroxidation ◽

Oxidative Damage ◽

Energy Demand ◽

Physiological State ◽

High Energy ◽

Free Radical Scavengers ◽

Radical Scavengers ◽

Oxygen Requirement ◽

Pregnant Rats

Pregnancy is a physiological state accompanied by a high energy demand of many bodily functions and an increased oxygen requirement. Because of the increased intake and utilization of oxygen, increased levels of oxidative stress would be expected. In the present study, the degree of lipid peroxidation was examined in different tissues from non-pregnant and pregnant rats after the delivery of their young. Melatonin and other indole metabolites are known to be direct free radical scavengers and indirect antioxidants. Thus the effect of pinealectomy at 1 month before pregnancy on the accumulation of lipid damage was investigated in non-pregnant and pregnant rats after the delivery of their young. Malonaldehyde and 4-hydroxyalkenal concentrations were measured in the lung, uterus, liver, brain, kidney, thymus and spleen from intact and pinealectomized pregnant rats soon after birth of their young and at 14 and 21 days after delivery. The same parameters were also evaluated in intact and pinealectomized non-pregnant rats. Shortly after delivery, lipid oxidative damage was increased in lung, uterus, brain, kidney and thymus of the mothers. No differences were detected in liver and spleen. Pinealectomy enhanced this effect in the uterus and lung. It is concluded that during pregnancy high levels of oxidative stress induce an increase in oxidative damage to lipids, which in some cases is inhibited by the antioxidative actions of pineal indoles.

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Glial cytotoxicity of low doses of cadmium as a model of heavy metal pollution influence on vertebrates

Ecology and Noospherology ◽

10.15421/032001 ◽

2020 ◽

Vol 31 (1) ◽

pp. 3-10

Author(s):

V. S. Nedzvetsky ◽

V. Ya. Gasso ◽

A. M. Hahut ◽

I. A. Hasso

Keyword(s):

Oxidative Stress ◽

Cell Death ◽

Programmed Cell Death ◽

Oxidative Damage ◽

Cadmium Chloride ◽

Glioma Cells ◽

Low Doses ◽

Genotoxic Effects ◽

Cadmium Ions

Cadmium is a common transition metal that entails an extremely wide range of toxic effects in humans and animals. The cytotoxicity of cadmium ions and its compounds is due to various genotoxic effects, including both DNA damage and chromosomal aberrations. Some bone diseases, kidney and digestive system diseases are determined as pathologies that are closely associated with cadmium intoxication. In addition, cadmium is included in the list of carcinogens because of its ability to initiate the development of tumors of several forms of cancer under conditions of chronic or acute intoxication. Despite many studies of the effects of cadmium in animal models and cohorts of patients, in which cadmium effects has occurred, its molecular mechanisms of action are not fully understood. The genotoxic effects of cadmium and the induction of programmed cell death have attracted the attention of researchers in the last decade. In recent years, the results obtained for in vivo and in vitro experimental models have shown extremely high cytotoxicity of sublethal concentrations of cadmium and its compounds in various tissues. One of the most studied causes of cadmium cytotoxicity is the development of oxidative stress and associated oxidative damage to macromolecules of lipids, proteins and nucleic acids. Brain cells are most sensitive to oxidative damage and can be a critical target of cadmium cytotoxicity. Thus, oxidative damage caused by cadmium can initiate genotoxicity, programmed cell death and inhibit their viability in the human and animal brains. To test our hypothesis, cadmium cytotoxicity was assessed in vivo in U251 glioma cells through viability determinants and markers of oxidative stress and apoptosis. The result of the cell viability analysis showed the dose-dependent action of cadmium chloride in glioma cells, as well as the generation of oxidative stress (p <0.05). Calculated for 48 hours of exposure, the LD50 was 3.1 μg×ml-1. The rates of apoptotic death of glioma cells also progressively increased depending on the dose of cadmium ions. A high correlation between cadmium concentration and apoptotic response (p <0.01) was found for cells exposed to 3–4 μg×ml-1 cadmium chloride. Moreover, a significant correlation was found between oxidative stress (lipid peroxidation) and induction of apoptosis. The results indicate a strong relationship between the generation of oxidative damage by macromolecules and the initiation of programmed cell death in glial cells under conditions of low doses of cadmium chloride. The presented results show that cadmium ions can induce oxidative damage in brain cells and inhibit their viability through the induction of programmed death. Such effects of cadmium intoxication can be considered as a model of the impact of heavy metal pollution on vertebrates.

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Chemoprotective Effects of Propolis on Aflatoxin B1-Induced Hepatotoxicity in Rats: Oxidative Damage and Hepatotoxicity by Modulating TP53, Oxidative Stress

Current Proteomics ◽

10.2174/1570164617666190925121720 ◽

2020 ◽

Vol 17 (3) ◽

pp. 191-199

Author(s):

Seval Yilmaz ◽

Fatih Mehmet Kandemir ◽

Emre Kaya ◽

Mustafa Ozkaraca

Keyword(s):

Oxidative Stress ◽

Gene Expression ◽

Oxidative Damage ◽

Aflatoxin B1 ◽

Tp53 Gene ◽

Control Group ◽

Glutathione S Transferase ◽

Gene Expressions ◽

Cat Gene ◽

Gst Activity

Objective: This study aimed to detect hepatic oxidative damage caused by aflatoxin B1 (AFB1), as well as to examine how propolis protects against hepatotoxic effects of AFB1. Method: Rats were split into four groups as control group, AFB1 group, propolis group, AFB1+ propolis group. Results: There was significant increase in malondialdehyde (MDA) level and tumor suppressor protein (TP53) gene expression, Glutathione (GSH) level, Catalase (CAT) activity, CAT gene expression decreased in AFB1 group in blood. MDA level and Glutathione-S-Transferase (GST) activity, GST and TP53 gene expressions increased in AFB1 group, whereas GSH level and CAT activity alongside CAT gene expression decreased in liver. AFB1+propolis group showed significant decrease in MDA level, GST activity, TP53 and GST gene expressions, GSH level and CAT activity and CAT gene expression increased in liver compared to AFB1 group. Conclusion: These results suggest that propolis may potentially be natural agent that prevents AFB1- induced oxidative stress and hepatotoxicity.

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Effect of Shuangdan Mingmu capsule, a Chinese herbal formula, on oxidative stress-induced apoptosis of pericytes through PARP/GAPDH pathway

BMC Complementary Medicine and Therapies ◽

10.1186/s12906-021-03238-w ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Fujiao Nie ◽

Jiazhao Yan ◽

Yanjun Ling ◽

Zhengrong Liu ◽

Chaojun Fu ◽

...

Keyword(s):

Oxidative Stress ◽

Nitric Oxide ◽

Oxidative Damage ◽

Damage Model ◽

B Cell Lymphoma ◽

Cell Counting ◽

Network Pharmacology ◽

Diabetic Patients ◽

Induced Apoptosis

Abstract Background Diabetic retinopathy (DR) has become a worldwide concern because of the rising prevalence rate of diabetes mellitus (DM). Despite much energy has been committed to DR research, it remains a difficulty for diabetic patients all over the world. Since apoptosis of retinal microvascular pericytes (RMPs) is the early characteristic of DR, this study aimed to reveal the mechanism of Shuangdan Mingmu (SDMM) capsule, a Chinese patent medicine, on oxidative stress-induced apoptosis of pericytes implicated with poly (ADP-ribose) polymerase (PARP) / glyceraldehyde 3-phosphate dehydrogenase (GAPDH) pathway. Methods Network pharmacology approach was performed to predict biofunction of components of SDMM capsule dissolved in plasma on DR. Both PARP1 and GAPDH were found involved in the hub network of protein-protein interaction (PPI) of potential targets and were found to take part in many bioprocesses, including responding to the regulation of reactive oxygen species (ROS) metabolic process, apoptotic signaling pathway, and response to oxygen levels through enrichment analysis. Therefore, in vitro research was carried out to validate the prediction. Human RMPs cultured with media containing 0.5 mM hydrogen oxide (H2O2) for 4 h was performed as an oxidative-damage model. Different concentrations of SDMM capsule, PARP1 inhibitor, PARP1 activation, and GAPDH inhibitor were used to intervene the oxidative-damage model with N-Acetyl-L-cysteine (NAC) as a contrast. Flow cytometry was performed to determine the apoptosis rate of cells and the expression of ROS. Cell counting kit 8 (CCK8) was used to determine the activity of pericytes. Moreover, nitric oxide (NO) concentration of cells supernatant and expression of endothelial nitric oxide synthase (eNOS), superoxide dismutase (SOD), B cell lymphoma 2 (BCL2), vascular endothelial growth factor (VEGF), endothelin 1 (ET1), PARP1, and GAPDH were tested through RT-qPCR, western blot (WB), or immunocytochemistry (ICC). Results Overproduction of ROS, high apoptotic rate, and attenuated activity of pericytes were observed after cells were incubated with media containing 0.5 mM H2O2. Moreover, downregulation of SOD, NO, BCL2, and GAPDH, and upregulation of VEGFA, ET1, and PARP1 were discovered after cells were exposed to 0.5 mM H2O2 in this study, which could be improved by PARP1 inhibitor and SDMM capsule in a dose-dependent way, whereas worsened by PARP1 activation and GAPDH inhibitor. Conclusions SDMM capsule may attenuate oxidative stress-induced apoptosis of pericytes through downregulating PARP expression and upregulating GAPDH expression.

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Distinct Responses of Arabidopsis Telomeres and Transposable Elements to Zebularine Exposure

International Journal of Molecular Sciences ◽

10.3390/ijms22010468 ◽

2021 ◽

Vol 22 (1) ◽

pp. 468

Author(s):

Klára Konečná ◽

Pavla Polanská Sováková ◽

Karin Anteková ◽

Jiří Fajkus ◽

Miloslava Fojtová

Keyword(s):

Transposable Elements ◽

Transcriptional Activation ◽

Genome Stability ◽

Cytosine Methylation ◽

Individual Variability ◽

Correlated Response ◽

Telomere Shortening ◽

Treatment Changes ◽

Telomere Homeostasis ◽

Genomic Regions

Involvement of epigenetic mechanisms in the regulation of telomeres and transposable elements (TEs), genomic regions with the protective and potentially detrimental function, respectively, has been frequently studied. Here, we analyzed telomere lengths in Arabidopsis thaliana plants of Columbia, Landsberg erecta and Wassilevskija ecotypes exposed repeatedly to the hypomethylation drug zebularine during germination. Shorter telomeres were detected in plants growing from seedlings germinated in the presence of zebularine with a progression in telomeric phenotype across generations, relatively high inter-individual variability, and diverse responses among ecotypes. Interestingly, the extent of telomere shortening in zebularine Columbia and Wassilevskija plants corresponded to the transcriptional activation of TEs, suggesting a correlated response of these genomic elements to the zebularine treatment. Changes in lengths of telomeres and levels of TE transcripts in leaves were not always correlated with a hypomethylation of cytosines located in these regions, indicating a cytosine methylation-independent level of their regulation. These observations, including differences among ecotypes together with distinct dynamics of the reversal of the disruption of telomere homeostasis and TEs transcriptional activation, reflect a complex involvement of epigenetic processes in the regulation of crucial genomic regions. Our results further demonstrate the ability of plant cells to cope with these changes without a critical loss of the genome stability.

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