scholarly journals Colon cancer-associated mutator DNA polymerase δ variant causes expansion of dNTP pools increasing its own infidelity

2015 ◽  
Vol 112 (19) ◽  
pp. E2467-E2476 ◽  
Author(s):  
Tony M. Mertz ◽  
Sushma Sharma ◽  
Andrei Chabes ◽  
Polina V. Shcherbakova
Keyword(s):  
Dna Synthesis ◽  
Human Cancer ◽  
Mutagenic Potential ◽  
Mutator Phenotype ◽  
Replication Errors ◽  
Intracellular Dntp ◽  
Mutator Effect ◽  
Dna Replication Errors

Defects in DNA polymerases δ (Polδ) and ε (Polε) cause hereditary colorectal cancer and have been implicated in the etiology of some sporadic colorectal and endometrial tumors. We previously reported that the yeast pol3-R696W allele mimicking a human cancer-associated variant, POLD1-R689W, causes a catastrophic increase in spontaneous mutagenesis. Here, we describe the mechanism of this extraordinary mutator effect. We found that the mutation rate increased synergistically when the R696W mutation was combined with defects in Polδ proofreading or mismatch repair, indicating that pathways correcting DNA replication errors are not compromised in pol3-R696W mutants. DNA synthesis by purified Polδ-R696W was error-prone, but not to the extent that could account for the unprecedented mutator phenotype of pol3-R696W strains. In a search for cellular factors that augment the mutagenic potential of Polδ-R696W, we discovered that pol3-R696W causes S-phase checkpoint-dependent elevation of dNTP pools. Abrogating this elevation by strategic mutations in dNTP metabolism genes eliminated the mutator effect of pol3-R696W, whereas restoration of high intracellular dNTP levels restored the mutator phenotype. Further, the use of dNTP concentrations present in pol3-R696W cells for in vitro DNA synthesis greatly decreased the fidelity of Polδ-R696W and produced a mutation spectrum strikingly similar to the spectrum observed in vivo. The results support a model in which (i) faulty synthesis by Polδ-R696W leads to a checkpoint-dependent increase in dNTP levels and (ii) this increase mediates the hypermutator effect of Polδ-R696W by facilitating the extension of mismatched primer termini it creates and by promoting further errors that continue to fuel the mutagenic pathway.

scholarly journals Functional Analysis of the RdxA and RdxB Nitroreductases of Campylobacter jejuni Reveals that Mutations in rdxA Confer Metronidazole Resistance

2010 ◽  
Vol 192 (7) ◽  
pp. 1890-1901 ◽  
Author(s):  
Deborah A. Ribardo ◽  
Lacey K. Bingham-Ramos ◽  
David R. Hendrixson
Keyword(s):  
Campylobacter Jejuni ◽  
Biochemical Analysis ◽  
Normal Growth ◽  
Deletion Mutations ◽  
Replication Errors ◽  
Metronidazole Resistance ◽  
H Pylori ◽  
Dna Replication Errors

ABSTRACT Campylobacter jejuni is a leading cause of gastroenteritis in humans and a commensal bacterium of the intestinal tracts of many wild and agriculturally significant animals. We identified and characterized a locus, which we annotated as rdxAB, encoding two nitroreductases. RdxA was found to be responsible for sensitivity to metronidazole (Mtz), a common therapeutic agent for another epsilonproteobacterium, Helicobacter pylori. Multiple, independently derived mutations in rdxA but not rdxB resulted in resistance to Mtz (Mtzr), suggesting that, unlike the case in H. pylori, Mtzr might not be a polygenic trait. Similarly, Mtzr C. jejuni was isolated after both in vitro and in vivo growth in the absence of selection that contained frameshift, point, insertion, or deletion mutations within rdxA, possibly revealing genetic variability of this trait in C. jejuni due to spontaneous DNA replication errors occurring during normal growth of the bacterium. Similar to previous findings with H. pylori RdxA, biochemical analysis of C. jejuni RdxA showed strong oxidase activity, with reduction of Mtz occurring only under anaerobic conditions. RdxB showed similar characteristics but at levels lower than those for RdxA. Genetic analysis confirmed that rdxA and rdxB are cotranscribed and induced during in vivo growth in the chick intestinal tract, but an absence of these genes did not strongly impair C. jejuni for commensal colonization. Further studies indicate that rdxA is a convenient locus for complementation of mutants in cis. Our work contributes to the growing knowledge of determinants contributing to susceptibility to Mtz (Mtzs) and supports previous observations of the fundamental differences in the activities of nitroreductases from epsilonproteobacteria.

scholarly journals Palm Mutants in DNA Polymerases α and η Alter DNA Replication Fidelity and Translesion Activity

2004 ◽  
Vol 24 (7) ◽  
pp. 2734-2746 ◽  
Author(s):  
Atsuko Niimi ◽  
Siripan Limsirichaikul ◽  
Shonen Yoshida ◽  
Shigenori Iwai ◽  
Chikahide Masutani ◽  
...  
Keyword(s):  
Dna Synthesis ◽  
Dna Polymerase ◽  
Dna Polymerases ◽  
Pyrimidine Dimer ◽  
Replication Fidelity ◽  
Dna Polymerase Α ◽  
Replication Errors ◽  
Translesion Dna

ABSTRACT We isolated active mutants in Saccharomyces cerevisiae DNA polymerase α that were associated with a defect in error discrimination. Among them, L868F DNA polymerase α has a spontaneous error frequency of 3 in 100 nucleotides and 570-fold lower replication fidelity than wild-type (WT) polymerase α. In vivo, mutant DNA polymerases confer a mutator phenotype and are synergistic with msh2 or msh6, suggesting that DNA polymerase α-dependent replication errors are recognized and repaired by mismatch repair. In vitro, L868F DNA polymerase α catalyzes efficient bypass of a cis-syn cyclobutane pyrimidine dimer, extending the 3′ T 26,000-fold more efficiently than the WT. Phe34 is equivalent to residue Leu868 in translesion DNA polymerase η, and the F34L mutant of S. cerevisiae DNA polymerase η has reduced translesion DNA synthesis activity in vitro. These data suggest that high-fidelity DNA synthesis by DNA polymerase α is required for genomic stability in yeast. The data also suggest that the phenylalanine and leucine residues in translesion and replicative DNA polymerases, respectively, might have played a role in the functional evolution of these enzyme classes.

Inhibition of Cellular DNA Synthesis and Lack of Antileukemic Activity by Non-Photoactivated Hematoporphyrin Derivative

1981 ◽  
Vol 67 (3) ◽  
pp. 183-189 ◽  
Author(s):  
Paola Franco ◽  
Susanna Morelli ◽  
Filippo Sarra ◽  
Angelo Nicolin
Keyword(s):  
Dna Synthesis ◽  
Cell Viability ◽  
Thymidine Incorporation ◽  
Human Cancer ◽  
Antileukemic Activity ◽  
Order Of Magnitude ◽  
Cellular Dna ◽  
Dose Dependent

It has been reported that cytocidal activity of light-activated hematoporphyrin (HPD) within the cells might be exploited in the therapy of experimental and human cancer. As part of a project from this laboratory aimed to study some major biologic features of HPD, it was found that [3H]thymidine incorporation in tumor cells was highly inhibited as a consequence of HPD treatment. HPD-mediated inhibition, obtained by a treatment either in vitro or in vivo, was long lasting and independent of light activation. Cellular DNA synthesis was inhibited by non toxic doses of HPD which were not influential either cell viability or cell oncogenicity. In preliminary studies, HPD-treated cells accumulated in the G1 phase of the cell cycle as detected by cytofluorometric analysis. This finding is in keeping with a likely inhibition exerted in late G, or at the beginning of the S phase of cell the cycle and might exclude a direct damage of the DNA synthetic machinery. Definitive loss of cell viability and cellular DNA inhibition was obtained immediately after the exposure of HPD-treated cells to He-Ne laser light. HPD-mediated cell lysis was dose dependent and in the order of magnitude of cytocidal doses in different cell systems. HPD antileukemic activity or HPD interactions with chemotherapeutic drugs was ruled out in L1210 leukemic mice.

scholarly journals A New Smoothened Antagonist Bearing the Purine Scaffold Shows Antitumour Activity In Vitro and In Vivo

2021 ◽  
Vol 22 (16) ◽  
pp. 8372
Author(s):  
Ana María Zárate ◽  
Christian Espinosa-Bustos ◽  
Simón Guerrero ◽  
Angélica Fierro ◽  
Felipe Oyarzún-Ampuero ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Human Cancer ◽  
Antitumour Activity ◽  
Anticancer Compounds ◽  
Human Cancer Cells ◽  
Cycle Arrest ◽  
Apoptosis Inducer ◽  
Purine Ring

The Smoothened (SMO) receptor is the most druggable target in the Hedgehog (HH) pathway for anticancer compounds. However, SMO antagonists such as vismodegib rapidly develop drug resistance. In this study, new SMO antagonists having the versatile purine ring as a scaffold were designed, synthesised, and biologically tested to provide an insight to their mechanism of action. Compound 4s was the most active and the best inhibitor of cell growth and selectively cytotoxic to cancer cells. 4s induced cell cycle arrest, apoptosis, a reduction in colony formation and downregulation of PTCH and GLI1 expression. BODIPY-cyclopamine displacement assays confirmed 4s is a SMO antagonist. In vivo, 4s strongly inhibited tumour relapse and metastasis of melanoma cells in mice. In vitro, 4s was more efficient than vismodegib to induce apoptosis in human cancer cells and that might be attributed to its dual ability to function as a SMO antagonist and apoptosis inducer.

Thrombopoietin-Induced Stimulation of Megakaryocyte- Enriched Bone Marrow Cultures

1979 ◽  
Author(s):  
K. L. Kellar ◽  
B. L. Evatt ◽  
C. R. McGrath ◽  
R. B. Ramsey
Keyword(s):  
Bone Marrow ◽  
Dna Synthesis ◽  
Bone Marrow Cells ◽  
Rabbit Plasma ◽  
Bone Marrow Cultures ◽  
Plasma Fractions ◽  
Marrow Cultures ◽  
Stimulation Of

Liquid cultures of bone marrow cells enriched for megakaryocytes were assayed for incorporation of 3H-thymidine (3H-TdR) into acid-precipitable cell digests to determine the effect of thrombopoietin on DNA synthesis. As previously described, thrombopoietin was prepared by ammonium sulfate fractionation of pooled plasma obtained from thrombocytopenic rabbits. A control fraction was prepared from normal rabbit plasma. The thrombopoietic activity of these fractions was determined in vivo with normal rabbits as assay animals and the rate of incorporation of 75Se-selenomethionine into newly formed platelets as an index of thrombopoietic activity of the infused material. Guinea pig megakaryocytes were purified using bovine serum albumin gradients. Bone marrow cultures containing 1.5-3.0x104 cells and 31%-71% megakaryocytes were incubated 18 h in modified Dulbecco’s MEM containing 10% of the concentrated plasma fractions from either thrombocytopenic or normal rabbits. In other control cultures, 0.9% NaCl was substituted for the plasma fractions. 3H-TdR incorporation was measured after cells were incubated for 3 h with 1 μCi/ml. The protein fraction containing thrombopoietin-stimulating activity caused a 25%-31% increase in 3H-TdR incorporation over that in cultures which were incubated with the similar fraction from normal plasma and a 29% increase over the activity in control cultures to which 0.9% NaCl had been added. These data suggest that thrombopoietin stimulates DNA synthesis in megakaryocytes and that this tecnique may be useful in assaying thrombopoietin in vitro.

scholarly journals New insights on CRISPR/Cas9-based therapy for breast Cancer

2021 ◽  
Vol 43 (1) ◽  
Author(s):  
Hussein Sabit ◽  
Shaimaa Abdel-Ghany ◽  
Huseyin Tombuloglu ◽  
Emre Cevik ◽  
Amany Alqosaibi ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Research ◽  
Animal Models ◽  
Human Cancer ◽  
Step Process ◽  
Cancer Initiation ◽  
Malignant State ◽  
Treat Breast Cancer

AbstractCRISPR/Cas9 has revolutionized genome-editing techniques in various biological fields including human cancer research. Cancer is a multi-step process that encompasses the accumulation of mutations that result in the hallmark of the malignant state. The goal of cancer research is to identify these mutations and correlate them with the underlying tumorigenic process. Using CRISPR/Cas9 tool, specific mutations responsible for cancer initiation and/or progression could be corrected at least in animal models as a first step towards translational applications. In the present article, we review various novel strategies that employed CRISPR/Cas9 to treat breast cancer in both in vitro and in vivo systems.

scholarly journals RuvAB and RecG Are Not Essential for the Recovery of DNA Synthesis Following UV-Induced DNA Damage in Escherichia coli

Genetics ◽  
2004 ◽  
Vol 166 (4) ◽  
pp. 1631-1640 ◽  
Author(s):  
Janet R Donaldson ◽  
Charmain T Courcelle ◽  
Justin Courcelle
Keyword(s):  
Dna Damage ◽  
Dna Synthesis ◽  
Dna Lesions ◽  
Replication Forks ◽  
Wild Type ◽  
Replication Machinery ◽  
Dna Junctions ◽  
Fork Regression

Abstract Ultraviolet light induces DNA lesions that block the progression of the replication machinery. Several models speculate that the resumption of replication following disruption by UV-induced DNA damage requires regression of the nascent DNA or migration of the replication machinery away from the blocking lesion to allow repair or bypass of the lesion to occur. Both RuvAB and RecG catalyze branch migration of three- and four-stranded DNA junctions in vitro and are proposed to catalyze fork regression in vivo. To examine this possibility, we characterized the recovery of DNA synthesis in ruvAB and recG mutants. We found that in the absence of either RecG or RuvAB, arrested replication forks are maintained and DNA synthesis is resumed with kinetics that are similar to those in wild-type cells. The data presented here indicate that RecG- or RuvAB-catalyzed fork regression is not essential for DNA synthesis to resume following arrest by UV-induced DNA damage in vivo.

scholarly journals Mutagenicity evaluation of Anastatica hierochuntica L. aqueous extract in vitro and in vivo

2017 ◽  
Vol 243 (4) ◽  
pp. 375-385 ◽  
Author(s):  
Siti Rosmani Md Zin ◽  
Zahurin Mohamed ◽  
Mohammed A Alshawsh ◽  
Won F Wong ◽  
Normadiah M Kassim
Keyword(s):  
Aqueous Extract ◽  
Positive Control ◽  
In Vitro Assay ◽  
In Vivo Study ◽  
Sufficient Evidence ◽  
Aqueous Extracts ◽  
Mutagenic Potential ◽  
Vitro Assay

Anastatica hierochuntica L. ( A. hierochuntica), a folk medicinal plant, was evaluated for mutagenic potential via in vitro and in vivo assays. The in vitro assay was conducted according to modified Ames test, while the in vivo study was performed according to Organisation for Economic Co-operation and Development guideline for mammalian erythrocyte micronucleus assay. Four groups ( n= 5 males and 5 females per group) Sprague Dawley rats were randomly chosen as the negative control, positive control (received a single intramuscular injection of cyclophosphamide 50 mg/kg), 1000 and, 2000 mg/kg A. hierochuntica aqueous extracts. All groups except the positive control were treated orally for three days. Findings of the in vitro assay showed mutagenic potential of AHAE at 0.04 and 0.2 mg/ml. However, no mutagenic effect was demonstrated in the in vivo study up to 2000 mg/kg. No significant reduction in the polychromatic and normochromatic erythrocytes ratio was noted in any of the groups. Meanwhile, high micronucleated polychromatic erythrocytes frequency was seen in cyclophosphamide-treated group only. These findings could perhaps be due to insufficient dosage of A. hierochuntica aqueous extracts to cause genetic damage on the bone marrow target cells. Further acute and chronic in vivo toxicity studies may be required to draw pertinent conclusion on the safety aspect of A. hierochuntica aqueous extracts consumption. Impact statement In this paper, we report on the mutagenicity evaluation of Anastatica hierochuntica aqueous extract. This is a significant research in view of the popularity of this herb consumption by the people across the globe despite of limited scientific evidence on its toxicity potential. This study is intended to encourage more extensive related research in order to provide sufficient evidence and guidance for determining its safe dosage.

scholarly journals Safety Evaluation of Multiple Strains ofLactobacillus plantarumandPediococcus pentosaceusin Wistar Rats Based on the Ames Test and a 28-Day Feeding Study

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Cheng-Chih Tsai ◽  
Sew-Fen Leu ◽  
Quan-Rong Huang ◽  
Lan-Chun Chou ◽  
Chun-Chih Huang
Keyword(s):  
Wistar Rats ◽  
Clinical Chemistry ◽  
Toxicity Study ◽  
Bacterial Strains ◽  
Oral Toxicity ◽  
Short Term ◽  
Mutagenic Potential ◽  
Multiple Strains

Three lactic acid bacterial strains,Lactobacillus plantarum, HK006, and HK109, andPediococcus pentosaceusPP31 exhibit probiotic potential as antiallergy agents, both in vitro and in vivo. However, the safety of these new strains requires evaluation when isolated from infant faeces or pickled cabbage. Multiple strains (HK006, HK109, and PP31) were subject to a bacterial reverse mutation assay and a short-term oral toxicity study. The powder product exhibited mutagenic potential inSalmonellaTyphimurium strains TA98 and TA1535 (with or without metabolic activation). In the short-term oral toxicity study, rats received a normal dosage of 390 mg/kg/d (approximately9×109 CFU/kg/d) or a high dosage of 1950 mg/kg/d (approximately4.5×1010 CFU/kg/d) for 28 d. No adverse effects were observed regarding the general condition, behaviour, growth, feed and water consumption, haematology, clinical chemistry indices, organ weights, or histopathologic analysis of the rats. These studies have demonstrated that the consumption of multiple bacterial strains is not associated with any signs of mutagenicity ofS.Typhimurium or toxicity in Wistar rats, even after consuming large quantities of bacteria.

scholarly journals Overexpressed Pituitary Tumor-Transforming Gene Causes Aneuploidy in Live Human Cells

Endocrinology ◽  
2003 ◽  
Vol 144 (11) ◽  
pp. 4991-4998 ◽  
Author(s):  
Run Yu ◽  
Wenge Lu ◽  
Jiandong Chen ◽  
Chris J. McCabe ◽  
Shlomo Melmed
Keyword(s):  
Cancer Cells ◽  
Chromosome Segregation ◽  
Pituitary Tumor ◽  
Fluorescent Protein ◽  
Human Cancer ◽  
Live Cells ◽  
Pituitary Tumor Transforming Gene ◽  
Transforming Gene

Abstract The mammalian securin, pituitary tumor-transforming gene (PTTG), is overexpressed in several tumors and transforms cells in vitro and in vivo. To test the hypothesis that PTTG overexpression causes aneuploidy, enhanced green fluorescent protein (EGFP)-tagged PTTG (PTTG-EGFP) was expressed in human H1299 cancer cells (with undetectable endogenous PTTG expression) and mitosis of individual live cells observed. Untransfected cells and cells expressing EGFP alone exhibited appropriate mitosis. PTTG-EGFP markedly prolonged prophase and metaphase, indicating that PTTG blocks progression of mitosis to anaphase. In cells that underwent apparently normal mitosis (35 of 65 cells), PTTG-EGFP was degraded about 1 min before anaphase onset. Cells that failed to degrade PTTG-EGFP exhibited asymmetrical cytokinesis without chromosome segregation (18 of 65 cells) or chromosome decondensation without cytokinesis (9 of 65 cells), resulting in appearance of a macronucleus. Fifty-one of 55 cells expressing a nondegradable mutant PTTG exhibited asymmetrical cytokinesis without chromosome segregation, and some (4 of 55) decondensed chromosomes, both resulting in macronuclear formation. During this abnormal cytokinesis, all chromosomes and spindles and both centrosomes moved to one daughter cell, suggesting potential chaos in the subsequent mitosis. In conclusion, failure of PTTG degradation or enhanced PTTG accumulation, as a consequence of overexpression, inhibits mitosis progression and chromosome segregation but does not directly affect cytokinesis, resulting in aneuploidy. These results demonstrate that PTTG induces aneuploidy in single, live, human cancer cells.

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