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DNA Repair Mar 2015A number of endogenous and exogenous agents, and cellular processes create abasic (AP) sites in DNA. If unrepaired, AP sites cause mutations, strand breaks and cell...
A number of endogenous and exogenous agents, and cellular processes create abasic (AP) sites in DNA. If unrepaired, AP sites cause mutations, strand breaks and cell death. Aldehyde-reactive agent methoxyamine reacts with AP sites and blocks their repair. Another alkoxyamine, ARP, tags AP sites with a biotin and is used to quantify these sites. We have combined both these abilities into one alkoxyamine, AA3, which reacts with AP sites with a better pH profile and reactivity than ARP. Additionally, AA3 contains an alkyne functionality for bioorthogonal click chemistry that can be used to link a wide variety of biochemical tags to AP sites. We used click chemistry to tag AP sites with biotin and a fluorescent molecule without the use of proteins or enzymes. AA3 has a better reactivity profile than ARP and gives much higher product yields at physiological pH than ARP. It is simpler to use than ARP and its use results in lower background and greater sensitivity for AP site detection. We also show that AA3 inhibits the first enzyme in the repair of abasic sites, APE-1, to about the same extent as methoxyamine. Furthermore, AA3 enhances the ability of an alkylating agent, methylmethane sulfonate, to kill human cells and is more effective in such combination chemotherapy than methoxyamine.
Topics: Alkynes; Biotin; Cell Death; DNA; DNA Damage; DNA Mutational Analysis; DNA Repair; DNA-(Apurinic or Apyrimidinic Site) Lyase; HeLa Cells; Humans; Hydroxylamines; Methyl Methanesulfonate; Sensitivity and Specificity
PubMed: 25616257
DOI: 10.1016/j.dnarep.2014.12.006 -
International Journal of Molecular... Jan 2019Chemotherapeutic dosing, is largely based on the tolerance levels of toxicity today. Molecular imaging strategies can be leveraged to quantify DNA cytotoxicity and...
Chemotherapeutic dosing, is largely based on the tolerance levels of toxicity today. Molecular imaging strategies can be leveraged to quantify DNA cytotoxicity and thereby serve as a theranostic tool to improve the efficacy of treatments. Methoxyamine-modified cyanine-7 (Cy7MX) is a molecular probe which binds to apurinic/apyrimidinic (AP)-sites, inhibiting DNA-repair mechanisms implicated by cytotoxic chemotherapies. Herein, we loaded (Cy7MX) onto polyethylene glycol-coated gold nanoparticles (AuNP) to selectively and stably deliver the molecular probe intravenously to tumors. We optimized the properties of Cy7MX-loaded AuNPs using optical spectroscopy and tested the delivery mechanism and binding affinity using the DLD1 colon cancer cell line in vitro. A 10:1 ratio of Cy7MX-AuNPs demonstrated a strong AP site-specific binding and the cumulative release profile demonstrated 97% release within 12 min from a polar to a nonpolar environment. We further demonstrated targeted delivery using imaging and biodistribution studies in vivo in an xenografted mouse model. This work lays a foundation for the development of real-time molecular imaging techniques that are poised to yield quantitative measures of the efficacy and temporal profile of cytotoxic chemotherapies.
Topics: Cell Line, Tumor; DNA Damage; DNA Repair; Gold; Humans; Metal Nanoparticles; Molecular Structure; Theranostic Nanomedicine
PubMed: 30678294
DOI: 10.3390/ijms20030471 -
Molecular Cancer Therapeutics Oct 2013Uracil misincorporation into DNA is a consequence of pemetrexed inhibition of thymidylate synthase. The base excision repair (BER) enzyme uracil-DNA glycosylase (UNG) is...
Uracil misincorporation into DNA is a consequence of pemetrexed inhibition of thymidylate synthase. The base excision repair (BER) enzyme uracil-DNA glycosylase (UNG) is the major glycosylase responsible for removal of misincorporated uracil. We previously illustrated hypersensitivity to pemetrexed in UNG(-/-) human colon cancer cells. Here, we examined the relationship between UNG expression and pemetrexed sensitivity in human lung cancer. We observed a spectrum of UNG expression in human lung cancer cells. Higher levels of UNG are associated with pemetrexed resistance and are present in cell lines derived from pemetrexed-resistant histologic subtypes (small cell and squamous cell carcinoma). Acute pemetrexed exposure induces UNG protein and mRNA, consistent with upregulation of uracil-DNA repair machinery. Chronic exposure of H1299 adenocarcinoma cells to increasing pemetrexed concentrations established drug-resistant sublines. Significant induction of UNG protein confirmed upregulation of BER as a feature of acquired pemetrexed resistance. Cotreatment with the BER inhibitor methoxyamine overrides pemetrexed resistance in chronically exposed cells, underscoring the use of BER-directed therapeutics to offset acquired drug resistance. Expression of UNG-directed siRNA and shRNA enhanced sensitivity in A549 and H1975 cells, and in drug-resistant sublines, confirming that UNG upregulation is protective. In human lung cancer, UNG deficiency is associated with pemetrexed-induced retention of uracil in DNA that destabilizes DNA replication forks resulting in DNA double-strand breaks and cell death. Thus, in experimental models, UNG is a critical mediator of pemetrexed sensitivity that warrants evaluation to determine clinical value.
Topics: Cell Line, Tumor; DNA Breaks, Double-Stranded; DNA Damage; DNA Replication; Drug Resistance, Neoplasm; Gene Expression Regulation, Neoplastic; Glutamates; Guanine; Humans; Lung Neoplasms; Pemetrexed; RNA, Small Interfering; Uracil-DNA Glycosidase
PubMed: 23873851
DOI: 10.1158/1535-7163.MCT-13-0172 -
Langmuir : the ACS Journal of Surfaces... Feb 2011Patterning proteins on the nanoscale is important for applications in biology and medicine. As feature sizes are reduced, it is critical that immobilization strategies...
Patterning proteins on the nanoscale is important for applications in biology and medicine. As feature sizes are reduced, it is critical that immobilization strategies provide site-specific attachment of the biomolecules. In this study, oxime chemistry was exploited to conjugate proteins onto nanometer-sized features. Poly(Boc-aminooxy tetra(ethylene glycol) methacrylate) was synthesized by free radical polymerization. The polymer was patterned onto silicon wafers using an electron beam writer. Trifluoroacetic acid removal of the Boc groups provided the desired aminooxy functionality. In this manner, patterns of concentric squares and contiguous bowtie shapes were fabricated with 150-170-nm wide features. Ubiquitin modified at the N-terminus with an α-ketoamide group and N(ε)-levulinyl lysine-modified bovine serum albumin were subsequently conjugated to the polymer nanopatterns. Protein immobilization was confirmed by fluorescence microscopy. Control studies on protected surfaces and using proteins presaturated with O-methoxyamine indicated that attachment occurred via oxime bond formation.
Topics: Magnetic Resonance Spectroscopy; Microscopy, Atomic Force; Microscopy, Fluorescence; Molecular Structure; Nanostructures; Oximes; Polymers; Proteins
PubMed: 21192671
DOI: 10.1021/la103978x -
Neuro-oncology May 2011Temozolomide (TMZ) is the preferred chemotherapeutic agent in the treatment of glioma following surgical resection and/or radiation. Resistance to TMZ is attributed to...
Temozolomide (TMZ) is the preferred chemotherapeutic agent in the treatment of glioma following surgical resection and/or radiation. Resistance to TMZ is attributed to efficient repair and/or tolerance of TMZ-induced DNA lesions. The majority of the TMZ-induced DNA base adducts are repaired by the base excision repair (BER) pathway and therefore modulation of this pathway can enhance drug sensitivity. N-methylpurine DNA glycosylase (MPG) initiates BER by removing TMZ-induced N3-methyladenine and N7-methylguanine base lesions, leaving abasic sites (AP sites) in DNA for further processing by BER. Using the human glioma cell lines LN428 and T98G, we report here that potentiation of TMZ via BER inhibition [methoxyamine (MX), the PARP inhibitors PJ34 and ABT-888 or depletion (knockdown) of PARG] is greatly enhanced by over-expression of the BER initiating enzyme MPG. We also show that methoxyamine-induced potentiation of TMZ in MPG expressing glioma cells is abrogated by elevated-expression of the rate-limiting BER enzyme DNA polymerase β (Polβ), suggesting that cells proficient for BER readily repair AP sites in the presence of MX. Further, depletion of Polβ increases PARP inhibitor-induced potentiation in the MPG over-expressing glioma cells, suggesting that expression of Polβ modulates the cytotoxic effect of combining increased repair initiation and BER inhibition. This study demonstrates that MPG overexpression, together with inhibition of BER, sensitizes glioma cells to the alkylating agent TMZ in a Polβ-dependent manner, suggesting that the expression level of both MPG and Polβ might be used to predict the effectiveness of MX and PARP-mediated potentiation of TMZ in cancer treatment.
Topics: Antineoplastic Agents, Alkylating; Apoptosis; Blotting, Western; Brain; Brain Neoplasms; Cell Line, Tumor; Cell Proliferation; DNA Glycosylases; DNA Modification Methylases; DNA Polymerase beta; DNA Repair; DNA Repair Enzymes; Dacarbazine; Drug Synergism; Glioma; Guanine; Humans; Hydroxylamines; Promoter Regions, Genetic; RNA, Messenger; Reverse Transcriptase Polymerase Chain Reaction; Temozolomide; Tumor Suppressor Proteins
PubMed: 21377995
DOI: 10.1093/neuonc/nor011 -
Biochimica Et Biophysica Acta Oct 2008The effects of oxidatively modified phospholipids on the association with model biomembranes of four antimicrobial peptides (AMPs), temporin B and L, indolicidin, and...
The effects of oxidatively modified phospholipids on the association with model biomembranes of four antimicrobial peptides (AMPs), temporin B and L, indolicidin, and LL-37(F27W) were studied by Langmuir balance and fluorescence spectroscopy. In keeping with previous reports the negatively charged phospholipid phosphatidylglycerol (PG) enhanced the intercalation of all four peptides into lipid monolayers and liposomal bilayers under low ionic strength conditions. Interestingly, similar effect was observed for 1-palmitoyl-2-(9'-oxo-nonanoyl)-sn-glycero-3-phosphocholine (PoxnoPC), a zwitterionic oxidized phospholipid bearing an aldehyde function at the end of its truncated sn-2 acyl chain. Instead, the structurally similar 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC) containing a carboxylic moiety was less efficient in promoting the membrane association of these peptides. Physiological saline reduced the binding of the above peptides to membranes containing PG, whereas interactions with PoxnoPC were found to be insensitive to ionic strength. Notably, membrane intercalation of temporin L, the most surface active of the above peptides could be into PoxnoPC containing monolayers was strongly attenuated by methoxyamine, suggesting the importance of Schiff base formation between peptide amino groups and the lipid aldehyde function. PoxnoPC and similar aldehyde bearing oxidatively modified phospholipids could represent novel molecular targets for AMPs.
Topics: Animals; Anti-Infective Agents; Antimicrobial Cationic Peptides; Buffers; Humans; Liposomes; Oxidation-Reduction; Peptides; Phospholipids; Proteins; Cathelicidins
PubMed: 18440299
DOI: 10.1016/j.bbamem.2008.03.020 -
Cell Death & Disease Jan 2012Uracil DNA glycosylase (UDG) specifically removes uracil bases from DNA, and its repair activity determines the sensitivity of the cell to anticancer agents that are...
Uracil DNA glycosylase (UDG) specifically removes uracil bases from DNA, and its repair activity determines the sensitivity of the cell to anticancer agents that are capable of introducing uracil into DNA. In the present study, the participation of UDG in the response to pemetrexed-induced incorporation of uracil into DNA was studied using isogenic human tumor cell lines with or without UDG (UDG(+/+)/UDG(-/-)). UDG(-/-) cells were very sensitive to pemetrexed. Cell killing by pemetrexed was associated with genomic uracil accumulation, stalled DNA replication, and catastrophic DNA strand breaks. By contrast, UDG(+/+) cells were >10 times more resistant to pemetrexed due to the rapid removal of uracil from DNA by UDG and subsequent repair of the resultant AP sites (abasic sites) via the base excision repair (BER). The resistance to pemetrexed in UDG(+/+) cells could be reversed by the addition of methoxyamine (MX), which binds to AP sites and interrupts BER pathway. Furthermore, MX-bound AP sites induced cell death was related to their cytotoxic effect of dual inactivation of UDG and topoisomerase IIα, two genes that are highly expressed in lung cancer cells in comparison with normal cells. Thus, targeting BER-based therapy exhibits more selective cytotoxicity on cancer cells through a synthetic lethal mechanism.
Topics: Animals; Antigens, Neoplasm; Antineoplastic Agents; Cell Line, Tumor; DNA; DNA Damage; DNA Repair; DNA Topoisomerases, Type II; DNA-Binding Proteins; Female; Gene Expression; Gene Knockout Techniques; Glutamates; Guanine; Humans; Hydroxylamines; Mice; Mice, Nude; Pemetrexed; Signal Transduction; Uracil; Uracil-DNA Glycosidase; Xenograft Model Antitumor Assays
PubMed: 22237209
DOI: 10.1038/cddis.2011.135 -
Journal of Fungi (Basel, Switzerland) Feb 2021Pathogenic microbes are exposed to a number of potential DNA-damaging stimuli during interaction with the host immune system. Microbial survival in this situation...
Pathogenic microbes are exposed to a number of potential DNA-damaging stimuli during interaction with the host immune system. Microbial survival in this situation depends on a fine balance between the maintenance of DNA integrity and the adaptability provided by mutations. In this study, we investigated the association of the DNA repair response with the virulence of , a basidiomycete that causes life-threatening meningoencephalitis in immunocompromised individuals. We focused on the characterization of and putative genes, aiming to evaluate a possible role of the predicted Apurinic/apyrimidinic (AP) endonucleases 1 and 2 of the base excision repair (BER) pathway on response to stress conditions and virulence. Our results demonstrated the involvement of the putative AP-endonucleases Apn1 and Apn2 in the cellular response to DNA damage induced by alkylation and by UV radiation, in melanin production, in tolerance to drugs and in virulence of in vivo. We also pointed out the potential use of DNA repair inhibitor methoxy-amine in combination with conventional antifungal drugs, for the development of new therapeutic approaches against this human fungal pathogen. This work provides new information about the DNA damage response of the highly important pathogenic fungus .
PubMed: 33673204
DOI: 10.3390/jof7020133 -
Genes & Genetic Systems Apr 2019Apurinic/apyrimidinic (AP) sites are the most common form of cytotoxic DNA damage. Since AP sites inhibit DNA replication and transcription, repairing them is critical...
Apurinic/apyrimidinic (AP) sites are the most common form of cytotoxic DNA damage. Since AP sites inhibit DNA replication and transcription, repairing them is critical for cell growth. However, the significance of repairing AP sites during early embryonic development has not yet been clearly determined. Here, we focused on APEX1 from the ascidian Ciona intestinalis (CiApex1), a homolog of human AP endonuclease 1 (APEX1), and examined its role in early embryonic development. Recombinant CiApex1 protein complemented the drug sensitivities of an AP endonuclease-deficient Escherichia coli mutant, and exhibited Mg-dependent AP endonuclease activity, like human APEX1, in vitro. Next, the effects of abnormal AP site repair on embryonic development were investigated. Treatment with methyl methanesulfonate, which alkylates DNA bases and generates AP sites, induced abnormal embryonic development. This abnormal phenotype was also caused by treatment with methoxyamine, which inhibits AP endonuclease activity. Furthermore, we constructed dominant-negative CiApex1, which inhibits CiApex1 action, and found that its expression impaired embryonic growth. These results suggested that AP site repair is essential for embryonic development and CiApex1 plays an important role in AP site repair during early embryonic development in C. intestinalis.
Topics: Animals; Ciona intestinalis; DNA Repair; DNA-(Apurinic or Apyrimidinic Site) Lyase; Embryonic Development; Mutation
PubMed: 30930342
DOI: 10.1266/ggs.18-00043 -
Acta Pharmaceutica (Zagreb, Croatia) Jun 2023Methoxamine (Mox) is a well-known α1-adrenoceptor agonist, clinically used as a longer-acting analogue of epinephrine. 1,2-Mox (NRL001) has been also undergoing...
Methoxamine (Mox) is a well-known α1-adrenoceptor agonist, clinically used as a longer-acting analogue of epinephrine. 1,2-Mox (NRL001) has been also undergoing clinical testing to increase the canal resting pressure in patients with bowel incontinence. Here we show, that Mox hydrochloride acts as an inhibitor of base excision repair (BER). The effect is mediated by the inhibition of apurinic/apyrimidinic endonuclease APE1. We link this observation to our previous report showing the biologically relevant effect of Mox on BER - prevention of converting oxidative DNA base damage to double-stranded breaks. We demonstrate that its effect is weaker, but still significant when compared to a known BER inhibitor methoxyamine (MX). We further determined Mox's relative at 19 mmol L, demonstrating a significant effect of Mox on APE1 activity in clinically relevant concentrations.
Topics: Humans; Methoxamine; DNA Repair; Epinephrine; Receptors, Adrenergic; Endonucleases
PubMed: 37307375
DOI: 10.2478/acph-2023-0012