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At least 19 recordsLinked to original sources

PubMed1979

DNA damage and DNA repair in cultured human cells exposed to chromate.

DNA damage and DNA repair have been observed in cultured human skin fibroblasts exposed to potassium chromate but not to a chromic glycine complex. DNA repair synthesis (unscheduled incorporation of [3H]thymidine (TdR)) was measured in cells during or following exposure to chromate and was significant for chromate concentrations above 10(-6) M. Maximal DNA repair was observed at about 10(-4) M chromate. DNA repair capacity was found to be saturated at this concentration. Chromate was stable for at least 8 h in culture medium and produced approximately a linear increase in repair with duration of exposure. DNA damage as determined by alkaline sucrose gradient sedimentation was detected after treatment for 1.5 h with 5 . 10(-4) M chromate. Exposure to 10(-7) M chromate solution for 7 days inhibited colony formation while acute (1 h) treatment was toxic at 5 . 10(-6) M. The chromic glycine complex was toxic above 10(-3) M for a 1-week exposure but was not observably toxic after a 1-h treatment. These results indicate that chromate and not chromic compounds may be the carcinogenic form for man. The nature of the ultimate carcinogen is discussed. These findings illustrate the utility of the DNA repair technique to study the effects on human cells of inorganic carcinogens and mutagens.

Adult↗

PubMed2021

DNA Damage Responses during the Cell Cycle: Insights from Model Organisms and Beyond.

Genome damage is a threat to all organisms. To respond to such damage, DNA damage responses (DDRs) lead to cell cycle arrest, DNA repair, and cell death. Many DDR components are highly conserved, whereas others have adapted to specific organismal needs. Immense progress in this field has been driven by model genetic organism research. This review has two main purposes. First, we provide a survey of model organism-based efforts to study DDRs. Second, we highlight how model organism study has contributed to understanding how specific DDRs are influenced by cell cycle stage. We also look forward, with a discussion of how future study can be expanded beyond typical model genetic organisms to further illuminate how the genome is protected.

Animals↗

PubMed1977

In vitro packaging of UV radiation-damaged DNA from bacteriophage T7.

When DNA from bacteriophage T7 is irradiated with UV light, the efficiency with which this DNA can be packaged in vitro to form viable phage particles is reduced. A comparison between irradiated DNA packaged in vitro and irradiated intact phage particles shows almost identical survival as a function of UV dose when Escherichia coli wild type or polA or uvrA mutants are used as the host. Although uvrA mutants perform less host cell reactivation, the polA strains are identical with wild type in their ability to support the growth of irradiated T7 phage or irradiated T7 DNA packaged in vitro into complete phage. An examination of in vitro repair performed by extracts of T7-infected E.coli suggests that T7 DNA polymerase may substitute for E. coli DNA polymerase I in the resynthesis step of excision repair. Also tested was the ability of a similar in vitro repair system that used extracts from uninfected cells to restore biological activity of irradiated DNA. When T7 DNA damaged by UV irradiation was treated with an endonuclease from Micrococcus luteus that is specific for pyrimidine dimers and then was incubated with an extract of uninfected E. coli capable of removing pyrimidine dimers and restoring the DNA of its original (whole genome size) molecular weight, this DNA showed a higher packaging efficiency than untreated DNA, thus demonstrating that the in vitro repair system partially restored the biological activity of UV-damaged DNA.

Cell-Free System↗

PubMed2026

Chemogenomic maps reveal a PRDX1-dependent iron-damage axis in the DNA damage response.

The DNA damage response (DDR) is a sophisticated network of cellular pathways whose perturbation leads to genome instability and is a key hallmark of oncogenesis. Here, we present data from 32 genome-scale loss-of-function CRISPR interference chemical-genetic screens with inhibitors targeting core constituents of the DDR machinery (PARP, ATR, ATM, DNAPK and WEE1), as both single agents and in combination with poly(ADP-ribose) polymerase inhibitors. These experiments identify >1,000 genes whose perturbation modifies the DDR and provides a rich resource to the DDR community. In addition, this compendium of functional genomics data reveals key principles governing the DDR and highlights a strong chemical-genetic interaction between loss of activity of the peroxiredoxin PRDX1 and all tested DDR inhibitors through a mechanism involving iron availability mediated by an MRGBP-PAX7-IREB2 axis. Our data position PRDX1 as a key suppressor of DNA damage accumulation and potential druggable target in combination with DDR inhibitors.

Journal Article↗

PubMed1979

The metabolically mediated DNA damage and subsequent DNA repair by 4-chlorobiphenyl in Chinese hamster ovary cells.

The metabolism of [3H]-4-chlorobiphenyl (CB) by Chinese hamster ovary cell cultures resulted in the formation of lipophilic hydroxylated metabolites, trichloroacetic acid soluble conjugates and covalent macromolecular adducts. The major lipophilic metabolite was chromatographically similar to 4'-chloro-4-biphenylol. The intracellular macromolecules were fractionated into protein, RNA and DNA. Although protein was the major target of covalent interaction with [3H]-CB and contributes 85% of the macromolecular binding, the specific binding of [3H]-CB to DNA was 3.5 and 1.4 times higher than that observed for protein and RNA respectively. Incubation of the CHO cells with 10 mM CB, [3H]-thymidine and 10 mM hydroxyurea for 2.5 hr resulted in a 1.6 fold increase in unscheduled DNA synthesis. The data demonstrated that the readily metabolized CB congener not only reacts with mammalian cell macromolecules, including DNA, but the DNA damage can also be demonstrated by its subsequent repair.

Animals↗

PubMed1977

Characterization of human enzymes specific for damaged DNA: resolution of endonuclease for irradiated DNA from an apparent N-glycosidase active on alkylated DNA.

An endonuclease partially purified from human lymphoblasts, and active against ultraviolet-irradiated DNA, was found to act additionally on DNA damaged by either x-radiation or methylmethanesulfonate. To determine if these activities were truly endonucleolytic, the reaction products were analyzed under conditions that prevented conversion of apurinic or apyrimidinic sites to single-strand breaks. With either ultraviolet- or x-irradiated DNA, strand breakage remained maximal, hence confirming the endonucleolytic character of the enzyme. By contrast, with DNA alkylated with methylmethanesulfonate, strand breakage was sharply reduced. Additional experiments indicated that the activity for alkylated DNA induces strand breaks only in concert with a purified endonuclease specific for apurinic sites, suggesting that it is an N-glycosidase that depurinates alkylated bases. This enzyme was separated from the endonuclease specific for irradiated DNA, by chromatography on DNA-agarose.

Cell Line↗

PubMed2026

Berberine shows potential in mitigating PM2.5-induced breast cancer progression by inducing DNA damage and inhibiting error-prone DNA repair pathways.

Breast cancer remains the most common cancer among women, with 2.3 million new cases reported globally in 2022. Alongside established risk factors such as age, family history, genetics, obesity, smoking, and alcohol, exposure to fine particulate matter (PM2.5) has recently emerged as an environmental contributor. This risk is especially concerning for low- and middle-income countries (LMICs), where both PM2.5 exposure and cancer burden are disproportionately high; however, mechanistic studies from these regions remain limited. To address this gap and develop mitigation strategies, we investigated the oncogenic potential of water-soluble PM2.5 collected from ambient air on breast cancer and evaluated the potential role of nutraceuticals in mitigating these effects. PM2.5 exposure increased proliferation, migration, and ROS generation, while promoting the formation of multinucleated giant cells, leading to genomic instability. Berberine, a natural alkaloid, countered these effects by increasing DNA damage and exploiting tumor-specific genomic vulnerabilities through disruption of DNA damage response and repair networks, thereby promoting programmed cell death. Transcriptomic profiling of Delhi PM2.5-treated MCF7 cells revealed a Delhi PM2.5-associated carcinogenic gene signature enriched in MAPK signalling, reactive oxygen species, metabolic, lysosomal, and ribosomal pathways. We also found that several genes, including BIRC5, WSB1, and RCC1, within this PM2.5-induced gene signature were dysregulated in breast cancer patients and were inversely regulated by berberine treatment, suggesting that berberine counteracts the transcriptional effects of PM2.5. Our findings highlight ambient PM2.5 exposure as a driver of breast cancer progression and identify berberine as a promising candidate in mitigating PM2.5 effects; however, thorough preclinical and clinical validations are warranted.

Berberine↗

PubMed2024

Angiopoietin-like protein 8 directs DNA damage responses towards apoptosis by stabilizing PARP1-DNA condensates.

Upon genotoxic stresses, cells employ various DNA damage responses (DDRs), including DNA damage repair or apoptosis, to safeguard genome integrity. However, the determinants among different DDRs choices are largely unknown. Here, we report angiopoietin-like protein 8 (ANGPTL8), a secreted regulator of lipid metabolism, localizes to the nucleus and acts as a dynamic switch that directs DDRs towards apoptosis rather than DNA repair after genotoxin exposure. ANGPTL8 deficiency alleviates DNA damage and apoptosis in cells exposed to genotoxins, as well as in the liver or kidney of mice injured by hepatic ischemia/reperfusion or cisplatin treatment. Mechanistically, ANGPTL8 physically interacts with Poly (ADP-ribose) polymerase 1 (PARP1), in a PARylation-independent manner, and reduces the fluidity of PARP1-DNA condensates, thereby enhancing the pro-apoptotic accumulation of PARP1 and PAR chains on DNA lesions. However, the transcription of ANGPTL8 is gradually decreased following genotoxin treatment, partly due to downregulation of CCAAT enhancer binding protein alpha (CEBPA), presumably to avoid further cytotoxicity. Together, we provide new insights by which genotoxic stress induced DDRs are channeled to suicidal apoptosis to safeguard genome integrity.

Animals↗

PubMed2026

Linker Histone H1 Phosphorylation Promotes DNA Damage Repair during Replication Stress.

DNA replication fidelity depends on the integrity of the replication fork to prevent DNA damage and preserve genome stability. Disruptions to this process can trigger replication stress, leading to the accumulation of single-strand DNA (ssDNA) and double-strand breaks (DSBs), which drive mutagenesis and ultimately contribute to disease. While the roles of core histones and their post-translational modifications in this context have been more well-studied, far less is known about how linker histones regulate the replication stress response. Here, we demonstrate that the S-phase-phosphorylated form of the linker histone H1 (pH1) plays a key role in DNA damage repair at collapsed replication forks, both in vitro and in cells. Using phosphomimic and phosphonull H1 mutants, we show that phosphorylation enhances H1 assembly with ssDNA. Utilizing intein chemistry for the site-specific incorporation of a photocrosslinker to the C-terminus of H1, we map the direct interactors of H1. We identify phosphorylated H1 at replication forks, where it engages replication machinery and DNA damage response factors, including Histone PARylation Factor 1 (HPF1). We further demonstrate that ssDNA induces pH1-HPF1 interactions that promote liquid-like assemblies, correlating with reduced DNA damage and histone PARylation. Consistent with this role, reduction of total H1 increases cellular sensitivity to DNA damage, a phenotype that is partially rescued by reintroduction of H1.4. Together, these findings establish pH1 as a new regulator of DNA damage repair at collapsed replication forks through the controlled sequestration of repair factors.

Journal Article↗

PubMedDate not supplied

DNA damage and repair in vivo.

DNA damage has been implicated in carcinogenesis, mutagenesis, and aging. DNA excision repair has been implicated as an ameliorating factor for such damage. It has been proposed that there is an error-prone post-replication repair system which is both mutagenic and carcinogenic. Assay of DNA damage and repair may thus illuminate the mechanism of carcinogenesis and serve as an indicator of the carcinogenic potential of environmental agents. DNA damage induction and repair can differ in vitro and in vivo. In order to rationally evaluate environmental health effects, it is therefore important to examine DNA damage induction and repair in vivo. An in vivo method is defined here as one in which the DNA is damaged and repaired in cells in situ in the organism. In vivo methods for studying DNA adducts and excision repair, strand-breaks and strand-break repair, post-replication repair, and photoreactivation repair, and the current state of knowledge of DNA damage induction and repair in vivo, are reviewed and evaluated.

Animals↗

PubMed2025

Enzymatic and Structural Roles of Candida albicans Rev1 in DNA Damage Response and Disseminated Candidiasis.

Translesion DNA synthesis (TLS) is a fundamental biological process that enables DNA replication through various lesions to ensure genome stability and to prevent cell death due to replication fork collapse. Rev1, a member of Y-family DNA polymerase (Pol), functions in concert with a B-family enzyme Polζ in promoting TLS through various lesions. Interestingly, for such a function, the catalytic activity of Rev1 seems to be dispensable in Saccharomyces cerevisiae. Unlike Polζ, which possesses robust DNA polymerase activity, biochemical assays suggest that Rev1 predominantly incorporates a "C" opposite any templating residues, but the biological relevance of this activity of Rev1 remains elusive. Here we characterized Rev1 from Candida albicans, an opportunistic fungal pathogen responsible for maximum casualties due to systemic candidiasis in immunosuppressed individuals. Concerted genetic analyses of several Rev1 mutants in various DNA-damaging conditions suggested that in most lesion bypasses except 4-NQO-induced DNA lesions, the catalytic role of Rev1 is not important. However, simultaneous interactions of BRCT and the C-terminal domain of Rev1 with PCNA and Polζ, respectively, enable Rev1 to be essential during TLS. DNA damage recovery and mutagenesis assays further confirmed the lesion-specific roles of various domains of Rev1. Contrary to ex vivo data, animal studies suggested that CaRev1 is dispensable for systemic candidiasis development. We discuss the possible involvement of other TLS DNA polymerases in DNA damage response while C. albicans replicates and establishes itself in the host.

Candida albicans↗

PubMed2026

Overlapping RAD18- and DNA-binding interfaces in DNA polymerase η contribute to UV-induced DNA damage tolerance.

DNA polymerase η (Polη) bypasses UV-induced pyrimidine dimers and thereby confers tolerance to UV irradiation. Although the C-terminus of Polη has been reported to interact with ubiquitinated PCNA and RAD18, how Polη engages RAD18 is not fully understood. Here, we show that Polη and RAD18 interact through two distinct modes in human cells: a ubiquitinated-PCNA-dependent mode that requires the Polη C-terminus, and an unexpected PCNA-independent mode mediated by its N-terminal region. We focused our subsequent analyses on this newly identified PCNA-independent mode. Using purified recombinant proteins, we demonstrate direct binding of the N-terminal region of human Polη (PolηΔC) to RAD18 in vitro. Although PolηΔC and RAD18 each bound primer-template DNA, we were unable to detect a ternary PolηΔC-RAD18-DNA complex, and DNA competitively inhibited RAD18 binding to both PolηΔC and full-length Polη. Mutational analyses revealed that the DNA-binding and RAD18-binding domains within Polη overlap. A separation-of-function mutant, PolηΔC(K317A), which retains near-normal DNA-binding and polymerase activities but exhibits reduced RAD18 binding in vitro, displayed a diminished ability to rescue the UV sensitivity of Polη-deficient cells. Notably, the detrimental impact of the K317A persisted in a PCNA-binding-defective background but was attenuated in RAD18-knockout cells. These findings demonstrate that RAD18 binding to the N-terminal domain of Polη contributes to efficient bypass of pyrimidine dimers independently of the Polη-PCNA interaction and provide mechanistic insights into how Polη-RAD18 complexes assemble and dissociate during translesion DNA synthesis.

Journal Article↗

PubMed2024

Loss of Gst1 enhances resistance to MMS by reprogramming the transcription of DNA damage response genes in a Rad53-dependent manner in Candida albicans.

The DNA damage response is a highly conserved protective mechanism that enables cells to cope with various lesions in the genome. Extensive studies across different eukaryotic cells have identified the crucial roles played by components required for response to DNA damage. When compared to the essential signal transducers and repair factors in the DNA damage response circuitry, the negative regulators and underlying mechanisms of this circuitry have been relatively under-examined. In this study, we investigated Gst1, a putative glutathione transferase in the fungal pathogen Candida albicans. We found that under stress caused by the DNA damage agent MMS, GST1 expression was significantly upregulated, and this upregulation was further enhanced by the loss of the checkpoint kinases and DNA repair factors. Somewhat counterintuitively, deletion of GST1 conferred increased resistance to MMS, potentially via enhancing the phosphorylation of Rad53. Furthermore, overexpression of RAD53 or deletion of GST1 resulted in upregulated transcription of DNA damage repair genes, including CAS1, RAD7, and RAD30, while repression of RAD7 transcription in the GST1 deletion reversed the strain's heightened resistance to MMS. Finally, Gst1 physically interacted with Rad53, and their interaction weakened in response to MMS-induced stress. Overall, our findings suggest a negative regulatory role for GST1 in DNA damage response in C. albicans, and position Gst1 within the Rad53-mediated signaling pathway. These findings hold significant implications for understanding the mechanisms underlying the DNA damage response in this fungal pathogen and supply new potential targets for therapeutic intervention.

Candida albicans↗

PubMed1978

Nitrofurazone-induced DNA damage to tissues of mice.

Cytotoxicity and DNA damage by nitrofurans has previously been correlated with metabolic reduction of these drugs in vitro. In the present study, nitrofurazone increased the rate of disappearance of stable [3H]thymidine labelled DNA from tissues of mice fed 0.1% nitrofurazone in the diet. Significant loss of labelled DNA occurred within 25 days after the start of the diet in all tissue observed, and loss was in relation to the rate of metabolic reduction of nitrofurazone. A similar correlation was found when another endpoint for DNA damage was used; nitrofurazone reduced by mouse tissue slices caused DNA single-strand breaks in cultured mouse L cells incubated in vitro with the tissues. Again, the ability of each tissue to produce toxic nitrofurazone metabolites determined the amount of DNA damage to the L cells.

Animals↗

PubMed1977

Normal endonuclease activities for damaged DNA during hepatocarcinogenesis.

Two endonuclease activities in rat liver for damaged DNA were assayed. Double-stranded, covalently closed DNA from phage PM2 was damaged by either ultraviolet irradiation or by heating at acid pH, and used as substrate for endonucleases specific for ultraviolet DNA damage and for DNA apurinic sites, respectively. The levels of both enzyme activities in livers of normal rats were compared to levels in livers of rats fed N-2-acetylaminofluorene. At critical stages of the carcinogenic regimen levels of both endonuclease activities were normal. This, together with other data, suggests that depression of excision-repair of DNA damage does not take place during experimental carcinogenesis.

2-Acetylaminofluorene↗

PubMed2026

Protein persulfidation emerges as a conserved component of the redox response to DNA damage.

Genotoxic stress is frequently accompanied by alterations in cellular redox homeostasis; however, the mechanisms linking redox regulation to the DNA damage response (DDR) remain incompletely understood. Here, we investigated the early redox response to DNA damage induced by methyl methanesulfonate (MMS) in Saccharomyces cerevisiae, focusing on cysteine oxidative post-translational modifications (PTM). We show that activation of the DNA damage response is accompanied by rapid redox changes that occur in the absence of a generalized oxidative stress response. MMS exposure promotes selective remodeling of cysteine oxidative modifications, characterized by decreased free thiols, robust induction of protein persulfidation, and comparatively modest changes in sulfenylation. These alterations are accompanied by increased intracellular hydrogen sulfide levels, supporting the involvement of reactive sulfur species in the cellular response to DNA damage. Proteome-wide analyses revealed that cysteine oxidative modifications preferentially target proteins involved in central metabolism, nucleotide biosynthesis, and genome maintenance. Consistent with these observations, MMS-induced genotoxic stress promotes metabolic adaptation characterized by increased mitochondrial respiration, elevated ATP production, and mitochondrial morphological remodeling, linking bioenergetic adaptation to redox regulation. Importantly, perturbation of intracellular redox balance using N-acetylcysteine compromises survival under DNA-damaging conditions, supporting a functional role for redox signaling during the DDR. Finally, MMS treatment also induces protein persulfidation in mammalian cells. Moreover, exposure to etoposide, a mechanistically distinct genotoxic agent that induces DNA double-strand breaks through topoisomerase II inhibition, showed a similar trend, suggesting that protein persulfidation may not be restricted to alkylation-induced DNA damage. Together our findings identify protein persulfidation as a prominent component of the redox response to DNA damage and provide new insight into the functional interplay between mitochondrial metabolism, cysteine-based redox regulation, and genome maintenance.

Oxidation-Reduction↗

PubMed1977

Specific action of T4 endonuclease V on damaged DNA in xeroderma pigmentosum cells in vivo.

The specific action of T4 endonuclease V on damaged DNA in xeroderma pigmentosum cells was examined using an in vivo assay system with hemagglutinating virus of Japan (Sendai virus) inactivated by UV light. A clear dose response was observed between the level of UV-induce unscheduled DNA synthesis of xeroderma pigmentosum cells and the amount of T4 endonuclease V activity added. The T4 enzyme was unstable in human cells, and its half-life was 3 hr. Fractions derived from an extract of Escherichia coli infected with T4V1, a mutant defective in the endonuclease V gene, showed no ability to restore the UV-induced unscheduled DNA synthesis of xeroderma pigmentosum cells. However, fractions derived from an extract of T4D-infected E. coli with endonuclease V activity were effective. The T4 enzyme was effective in xeroderma pigmentosum cells on DNA damaged by UV light but not in cells damaged by 4-nitroquinoline 1-oxide. The results of these experiments show that the T4 enzyme has a specific action on human cell DNA in vivo. Treatment with the T4 enzyme increased the survival of group A xeroderma pigmentosum cells after UV irradiation.

4-Nitroquinoline-1-oxide↗

PubMed2026

The role of CHAMP1 in chromatin-mediated DNA damage repair.

Defects in the replication stress response are major drivers of cancer development and present key targetable vulnerabilities that can be exploited for anti-cancer therapy. Recent studies have identified CHAMP1 as a novel DNA damage repair factor with roles in double-strand break repair and the replication stress response. Mutations in CHAMP1 are associated with the neurodevelopmental disorder CHAMP1 Syndrome. More recently, children with CHAMP1 Syndrome have developed leukemia, suggesting that CHAMP1 mutations are a potential cancer risk factor. CHAMP1 is part of two DNA damage repair complexes: CHAMP1-POGZ-REV7 (Complex I) and CHAMP1-POGZ-HP1α (Complex II). Complex I promotes homologous recombination by removing the Shieldin complex from the ends of double strand breaks and allowing DSB end resection to occur. Complex II enriches heterochromatin content through the recruitment of the methyltransferase SETDB1 to DNA damage sites. Increased heterochromatin at stalled forks is associated with proper fork stability and restart, demonstrating the importance of CHAMP1 in maintaining genomic integrity. Loss of CHAMP1 leads to increased sensitivity to DNA damaging agents and increased dependence on other DNA damage repair pathways, such as the DNA damage checkpoint and the Fanconi Anemia pathway. CHAMP1 is overexpressed in breast and ovarian cancer cells with high levels of replication stress, providing a molecular mechanism for the tolerance of replication stress. These new findings on the relationship of CHAMP1 with well-established DNA damage repair pathways, suggest that targeting CHAMP1 could present a new synthetic lethality opportunity for cancer cells with high levels of replication stress.

CHAMP1↗