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Replication stalling activates SSB for recruitment of DNA damage tolerance factors. Proc Natl Acad Sci U S A 2022; 119:e2208875119. [PMID: 36191223 PMCID: PMC9565051 DOI: 10.1073/pnas.2208875119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Translesion synthesis (TLS) polymerases bypass DNA lesions that block replicative polymerases, allowing cells to tolerate DNA damage encountered during replication. It is well known that most bacterial TLS polymerases must interact with the sliding-clamp processivity factor to carry out TLS, but recent work in Escherichia coli has revealed that single-stranded DNA-binding protein (SSB) plays a key role in enriching the TLS polymerase Pol IV at stalled replication forks in the presence of DNA damage. It remains unclear how this interaction with SSB enriches Pol IV in a stalling-dependent manner given that SSB is always present at the replication fork. In this study, we use single-molecule imaging in live E. coli cells to investigate this SSB-dependent enrichment of Pol IV. We find that Pol IV is enriched through its interaction with SSB in response to a range of different replication stresses and that changes in SSB dynamics at stalled forks may explain this conditional Pol IV enrichment. Finally, we show that other SSB-interacting proteins are likewise selectively enriched in response to replication perturbations, suggesting that this mechanism is likely a general one for enrichment of repair factors near stalled replication forks.
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Alyahya MY, Khan S, Bhadra S, Samuel RE, Xu YJ. Replication stress induced by the ribonucleotide reductase inhibitor guanazole, triapine and gemcitabine in fission yeast. FEMS Yeast Res 2022; 22:6545798. [PMID: 35262697 PMCID: PMC8951221 DOI: 10.1093/femsyr/foac014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 02/05/2022] [Accepted: 03/07/2022] [Indexed: 11/13/2022] Open
Abstract
Schizosaccharomyces pombe is an established yeast model for studying the cellular mechanisms conserved in humans, such as the DNA replication checkpoint. The replication checkpoint deals with replication stress caused by numerous endogenous and exogenous factors that perturb fork movement. If undealt with, perturbed forks collapse, causing chromosomal DNA damage or cell death. Hydroxyurea (HU) is an inhibitor of ribonucleotide reductase (RNR) commonly used in checkpoint studies. It produces replication stress by depleting dNTPs, which slows the movement of ongoing forks and thus activates the replication checkpoint. However, HU also causes side effects such as oxidative stress, particularly under chronic exposure conditions, which complicates the studies. To find a drug that generates replication stress more specifically, we tested three other RNR inhibitors gemcitabine, guanazole and triapine in S. pombe under various experimental conditions. Our results show that guanazole and triapine can produce replication stress more specifically than HU under chronic, not acute drug treatment conditions. Therefore, using the two drugs in spot assay, the method commonly used for testing drug sensitivity in yeasts, should benefit the checkpoint studies in S. pombe and likely the research in other model systems.
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Affiliation(s)
- Mashael Y Alyahya
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, OH, 45435, USA
| | - Saman Khan
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, OH, 45435, USA
| | - Sankhadip Bhadra
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, OH, 45435, USA
| | - Rittu E Samuel
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, OH, 45435, USA
| | - Yong-Jie Xu
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, OH, 45435, USA
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3
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Geng K, Fu N, Yang X, Xia W. Adjudin delays cellular senescence through Sirt3‑mediated attenuation of ROS production. Int J Mol Med 2018; 42:3522-3529. [DOI: 10.3892/ijmm.2018.3917] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2016] [Accepted: 01/06/2018] [Indexed: 11/06/2022] Open
Affiliation(s)
- Keyi Geng
- State Key Laboratory of Oncogenes and Related Genes, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200030, P.R. China
| | - Ningzhen Fu
- State Key Laboratory of Oncogenes and Related Genes, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200030, P.R. China
| | - Xiao Yang
- State Key Laboratory of Oncogenes and Related Genes, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200030, P.R. China
| | - Weiliang Xia
- State Key Laboratory of Oncogenes and Related Genes, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200030, P.R. China
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4
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Rawson JMO, Roth ME, Xie J, Daly MB, Clouser CL, Landman SR, Reilly CS, Bonnac L, Kim B, Patterson SE, Mansky LM. Synergistic reduction of HIV-1 infectivity by 5-azacytidine and inhibitors of ribonucleotide reductase. Bioorg Med Chem 2016; 24:2410-2422. [PMID: 27117260 DOI: 10.1016/j.bmc.2016.03.052] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Revised: 03/18/2016] [Accepted: 03/27/2016] [Indexed: 11/29/2022]
Abstract
Although many compounds have been approved for the treatment of human immunodeficiency type-1 (HIV-1) infection, additional anti-HIV-1 drugs (particularly those belonging to new drug classes) are still needed due to issues such as long-term drug-associated toxicities, transmission of drug-resistant variants, and development of multi-class resistance. Lethal mutagenesis represents an antiviral strategy that has not yet been clinically translated for HIV-1 and is based on the use of small molecules to induce excessive levels of deleterious mutations within the viral genome. Here, we show that 5-azacytidine (5-aza-C), a ribonucleoside analog that induces the lethal mutagenesis of HIV-1, and multiple inhibitors of the enzyme ribonucleotide reductase (RNR) interact in a synergistic fashion to more effectively reduce the infectivity of HIV-1. In these drug combinations, RNR inhibitors failed to significantly inhibit the conversion of 5-aza-C to 5-aza-2'-deoxycytidine, suggesting that 5-aza-C acts primarily as a deoxyribonucleoside even in the presence of RNR inhibitors. The mechanism of antiviral synergy was further investigated for the combination of 5-aza-C and one specific RNR inhibitor, resveratrol, as this combination improved the selectivity index of 5-aza-C to the greatest extent. Antiviral synergy was found to be primarily due to the reduced accumulation of reverse transcription products rather than the enhancement of viral mutagenesis. To our knowledge, these observations represent the first demonstration of antiretroviral synergy between a ribonucleoside analog and RNR inhibitors, and encourage the development of additional ribonucleoside analogs and RNR inhibitors with improved antiretroviral activity.
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Affiliation(s)
- Jonathan M O Rawson
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Molecular, Cellular, Developmental Biology & Genetics Graduate Program, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, USA
| | - Megan E Roth
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, 515 Delaware Street SE, Minneapolis, MN 55455, USA
| | - Jiashu Xie
- Center for Drug Design, Academic Health Center, University of Minnesota, 516 Delaware Street SE, Minneapolis, MN 55455, USA
| | - Michele B Daly
- Emory Center for AIDS Research, Emory University, 1518 Clifton Road NE, Suite 8050, Atlanta, GA 30322, USA
| | - Christine L Clouser
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, 515 Delaware Street SE, Minneapolis, MN 55455, USA
| | - Sean R Landman
- Department of Computer Science and Engineering, University of Minnesota, 4-192 Keller Hall, 200 Union Street SE, Minneapolis, MN 55455, USA
| | - Cavan S Reilly
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Division of Biostatistics, School of Public Health, University of Minnesota, 420 Delaware Street SE, Minneapolis, MN 55455, USA
| | - Laurent Bonnac
- Center for Drug Design, Academic Health Center, University of Minnesota, 516 Delaware Street SE, Minneapolis, MN 55455, USA
| | - Baek Kim
- Emory Center for AIDS Research, Emory University, 1518 Clifton Road NE, Suite 8050, Atlanta, GA 30322, USA
| | - Steven E Patterson
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Center for Drug Design, Academic Health Center, University of Minnesota, 516 Delaware Street SE, Minneapolis, MN 55455, USA
| | - Louis M Mansky
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Department of Microbiology and Immunology, Medical School, University of Minnesota, 689 23rd Avenue SE, Minneapolis, MN 55455, USA; Molecular, Cellular, Developmental Biology & Genetics Graduate Program, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, USA; Center for Drug Design, Academic Health Center, University of Minnesota, 516 Delaware Street SE, Minneapolis, MN 55455, USA.
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5
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Gebre AA, Okada H, Kim C, Kubo K, Ohnuki S, Ohya Y. Profiling of the effects of antifungal agents on yeast cells based on morphometric analysis. FEMS Yeast Res 2015; 15:fov040. [DOI: 10.1093/femsyr/fov040] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/01/2015] [Indexed: 12/14/2022] Open
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6
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Rosen DM, Younkin EM, Miller SD, Casper AM. Fragile site instability in Saccharomyces cerevisiae causes loss of heterozygosity by mitotic crossovers and break-induced replication. PLoS Genet 2013; 9:e1003817. [PMID: 24068975 PMCID: PMC3778018 DOI: 10.1371/journal.pgen.1003817] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 08/06/2013] [Indexed: 11/19/2022] Open
Abstract
Loss of heterozygosity (LOH) at tumor suppressor loci is a major contributor to cancer initiation and progression. Both deletions and mitotic recombination can lead to LOH. Certain chromosomal loci known as common fragile sites are susceptible to DNA lesions under replication stress, and replication stress is prevalent in early stage tumor cells. There is extensive evidence for deletions stimulated by common fragile sites in tumors, but the role of fragile sites in stimulating mitotic recombination that causes LOH is unknown. Here, we have used the yeast model system to study the relationship between fragile site instability and mitotic recombination that results in LOH. A naturally occurring fragile site, FS2, exists on the right arm of yeast chromosome III, and we have analyzed LOH on this chromosome. We report that the frequency of spontaneous mitotic BIR events resulting in LOH on the right arm of yeast chromosome III is higher than expected, and that replication stress by low levels of polymerase alpha increases mitotic recombination 12-fold. Using single-nucleotide polymorphisms between the two chromosome III homologs, we mapped the locations of recombination events and determined that FS2 is a strong hotspot for both mitotic reciprocal crossovers and break-induced replication events under conditions of replication stress.
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Affiliation(s)
- Danielle M. Rosen
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan, United States of America
| | - Ellen M. Younkin
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan, United States of America
| | - Shaylynn D. Miller
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan, United States of America
| | - Anne M. Casper
- Department of Biology, Eastern Michigan University, Ypsilanti, Michigan, United States of America
- * E-mail:
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Rahmati A, Eskandari-Vashareh M, Alizadeh-Kouzehrash M. Synthesis of 3-(benzylideneamino)-2-phenyl-5H-imidazo[1,2-b]pyrazole-7-carbonitriles via a four-component condensation reaction. Tetrahedron 2013. [DOI: 10.1016/j.tet.2013.03.103] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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8
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Ulbricht U, Sommer A, Beckmann G, Lutzenberger M, Seidel H, Kreft B, Toschi L. Isogenic human mammary epithelial cell lines: novel tools for target identification and validation. Breast Cancer Res Treat 2013; 138:437-56. [DOI: 10.1007/s10549-013-2472-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Accepted: 02/28/2013] [Indexed: 10/27/2022]
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9
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Spivak JL, Hasselbalch H. Hydroxycarbamide: a user's guide for chronic myeloproliferative disorders. Expert Rev Anticancer Ther 2011; 11:403-14. [PMID: 21417854 DOI: 10.1586/era.11.10] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hydroxycarbamide is a nonalkylating antiproliferative and antiviral agent that has been used for over 40 years to treat a variety of neoplastic and non-neoplastic conditions. Hydroxycarbamide is readily absorbed and widely distributed throughout the body. It acts primarily to inhibit DNA synthesis, which underpins its use in solid tumors, viral infections and chronic myeloproliferative disorders. Hydroxycarbamide is an effective treatment for preventing transient ischemic attacks associated with thrombocytosis in chronic myeloproliferative disorders because it is a nitric oxide donor. While its mechanism of action and side-effect profile are well defined, its potential for leukemic transformation as a single agent is still a matter of controversy. Based on a search of the Medline database, this article encompasses the pharmacokinetics, pharmacodynamics, clinical use and tolerability of hydroxycarbamide, plus its potential for mutagenicity with special reference to the chronic myeloproliferative disorders. The toxicity profile of hydroxycarbamide is also discussed to enable clinicians to balance potential risks with therapeutic benefits.
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Affiliation(s)
- Jerry L Spivak
- Traylor 924 Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA.
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10
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Cohen D, Adamovich Y, Reuven N, Shaul Y. Hepatitis B virus activates deoxynucleotide synthesis in nondividing hepatocytes by targeting the R2 gene. Hepatology 2010; 51:1538-46. [PMID: 20155784 DOI: 10.1002/hep.23519] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
UNLABELLED Hepatitis B virus (HBV) causes liver diseases from acute hepatitis to cirrhosis and liver cancer. Currently, more than 350 million people are chronic HBV carriers, with devastating prognosis. HBV is a small enveloped noncytopathic virus, containing a circular partially double-stranded DNA genome, and exhibits strong tropism for human liver cells. Infected individuals (acute and chronic) secrete about 10(7) to 10(11) virions per day to the bloodstream, with each infected cell releasing 50-300 viruses per day. HBV infects nondividing hepatocytes and replicates by reverse-transcribing the pregenomic RNA to DNA in the host cells. The level of deoxyribonucleotide triphosphates (dNTPs) in nondividing cells is too low to support viral replication and enable the high yield of secreted virions. Here, we report production of dNTPs by viral-dependent transcription activation of R2, the key component of ribonucleotide reductase (RNR), and show that this process is critical for the HBV life-cycle. This was found in an established HBV-positive cell line and was reproduced by HBV DNA-transduced cells, in both culture and mice. Furthermore, the viral hepatitis B X protein is essential in activating R2 expression by blocking access of Regulatory factor x1, a repressor of the R2 gene. CONCLUSION Our findings demonstrate that the hepatitis B X protein is critical in infecting nonproliferating hepatocytes, which contain a low dNTP level. In addition, we provide molecular evidence for a new mechanism of HBV-host cell interaction where RNR-R2, a critical cell-cycle gene, is selectively activated in nonproliferating cells. This mechanism may set the stage for formulating a new category of anti-HBV drugs.
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Affiliation(s)
- Dorit Cohen
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
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11
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Davies BW, Kohanski MA, Simmons LA, Winkler JA, Collins JJ, Walker GC. Hydroxyurea induces hydroxyl radical-mediated cell death in Escherichia coli. Mol Cell 2010; 36:845-60. [PMID: 20005847 DOI: 10.1016/j.molcel.2009.11.024] [Citation(s) in RCA: 150] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2009] [Revised: 07/13/2009] [Accepted: 08/13/2009] [Indexed: 01/18/2023]
Abstract
Hydroxyurea (HU) specifically inhibits class I ribonucleotide reductase (RNR), depleting dNTP pools and leading to replication fork arrest. Although HU inhibition of RNR is well recognized, the mechanism by which it leads to cell death remains unknown. To investigate the mechanism of HU-induced cell death, we used a systems-level approach to determine the genomic and physiological responses of E. coli to HU treatment. Our results suggest a model by which HU treatment rapidly induces a set of protective responses to manage genomic instability. Continued HU stress activates iron uptake and toxins MazF and RelE, whose activity causes the synthesis of incompletely translated proteins and stimulation of envelope stress responses. These effects alter the properties of one of the cell's terminal cytochrome oxidases, causing an increase in superoxide production. The increased superoxide production, together with the increased iron uptake, fuels the formation of hydroxyl radicals that contribute to HU-induced cell death.
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Affiliation(s)
- Bryan W Davies
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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12
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Ishiki H, do Amaral A. Three-Dimensional Quantitative Structure-Activity Relationship Study of Antitumor 2-Formylpyridine Thiosemicarbazones Derivatives as Inhibitors of Ribonucleotide Reductase. ACTA ACUST UNITED AC 2009. [DOI: 10.1002/qsar.200960057] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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13
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A reduction in ribonucleotide reductase activity slows down the chromosome replication fork but does not change its localization. PLoS One 2009; 4:e7617. [PMID: 19898675 PMCID: PMC2773459 DOI: 10.1371/journal.pone.0007617] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Accepted: 10/04/2009] [Indexed: 11/25/2022] Open
Abstract
Background It has been proposed that the enzymes of nucleotide biosynthesis may be compartmentalized or concentrated in a structure affecting the organization of newly replicated DNA. Here we have investigated the effect of changes in ribonucleotide reductase (RNR) activity on chromosome replication and organization of replication forks in Escherichia coli. Methodology/Principal Findings Reduced concentrations of deoxyribonucleotides (dNTPs) obtained by reducing the activity of wild type RNR by treatment with hydroxyurea or by mutation, resulted in a lengthening of the replication period. The replication fork speed was found to be gradually reduced proportionately to moderate reductions in nucleotide availability. Cells with highly extended C periods showed a “delay” in cell division i.e. had a higher cell mass. Visualization of SeqA structures by immunofluorescence indicated no change in organization of the new DNA upon moderate limitation of RNR activity. Severe nucleotide limitation led to replication fork stalling and reversal. Well defined SeqA structures were not found in situations of extensive replication fork repair. In cells with stalled forks obtained by UV irradiation, considerable DNA compaction was observed, possibly indicating a reorganization of the DNA into a “repair structure” during the initial phase of the SOS response. Conclusion/Significance The results indicate that the replication fork is slowed down in a controlled manner during moderate nucleotide depletion and that a change in the activity of RNR does not lead to a change in the organization of newly replicated DNA. Control of cell division but not control of initiation was affected by the changes in replication elongation.
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Jones J, Studholme DJ, Knight CG, Preston GM. Integrated bioinformatic and phenotypic analysis of RpoN-dependent traits in the plant growth-promoting bacterium Pseudomonas fluorescens SBW25. Environ Microbiol 2007; 9:3046-64. [DOI: 10.1111/j.1462-2920.2007.01416.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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15
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Stubbe J. Ribonucleotide reductases. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 63:349-419. [PMID: 2407066 DOI: 10.1002/9780470123096.ch6] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- J Stubbe
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139
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Jiang ZG, Lebowitz MS, Ghanbari HA. Neuroprotective activity of 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (PAN-811), a cancer therapeutic agent. CNS DRUG REVIEWS 2006; 12:77-90. [PMID: 16834759 PMCID: PMC6741723 DOI: 10.1111/j.1527-3458.2006.00077.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP) is a highly-hydrophobic small molecule that was originally developed for cancer therapy (Triapine, Vion Pharmaceuticals) due to its ability to inhibit ribonucleotide reductase, a key enzyme required for DNA synthesis. 3-AP has a high affinity for divalent cations, chelating the Fe(2+) at the R2 subunit of the enzyme and inhibiting formation of a tyrosyl radical essential for ribonucleotide reduction. We have demonstrated that 3-AP is also a potent neuroprotectant (as such, it is referred to as "PAN-811"). In vitro it completely blocks ischemic neurotoxicity at a concentration of 0.5 microM (EC(50) approximate, equals 0.35 microM) and hypoxic toxicity at 1.2 microM (EC(50) approximate, equals 0.75 microM). Full protection of primary cortical and striatal neurons can be achieved with 3-AP when it is added to the medium at up to six hours after an ischemic insult. 3-AP also suppresses cell death induced by neurotoxic agents, including staurosporine, veratridine and glutamate, indicating activity against a central target(s) in the neurodegenerative process. 3-AP acts via neutralization of two important intracellular effectors of excitatory neurotoxicity; calcium and free radicals. Its reported ability to elevate anti-apoptotic proteins is likely to be a consequence of the suppression of excessive intracellular free calcium. In a rat model of transient ischemia, a single bolus delivery of 3-AP 1 h after the initiation of ischemic attack reduced infarct volume by 59% when administered i.c.v. (50 mug per rat) and by 35% when administered i.v. (1 mg/kg). In Phase I clinical trials in cancer therapy 3-AP had no cardiovascular, CNS or other major adverse effects. Thus, 3-AP has a high potential for development as a novel, potent neuroprotectant for the treatment of neurodegenerative diseases.
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Affiliation(s)
- Zhi-Gang Jiang
- Neurodegenerative Diseases, Panacea Pharmaceuticals, Inc., Gaithersburg, Maryland 20877, USA.
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Barker CA, Burgan WE, Carter DJ, Cerna D, Gius D, Hollingshead MG, Camphausen K, Tofilon PJ. In vitro and in vivo radiosensitization induced by the ribonucleotide reductase inhibitor Triapine (3-aminopyridine-2-carboxaldehyde-thiosemicarbazone). Clin Cancer Res 2006; 12:2912-8. [PMID: 16675588 DOI: 10.1158/1078-0432.ccr-05-2860] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Because ribonucleotide reductase (RR) plays a role in DNA repair, it may serve as a molecular target for radiosensitization. Unlike previously investigated RR inhibitors, Triapine potently inhibits both RR holoenzymes. Therefore, the effects of Triapine on tumor cell radiosensitivity were investigated. EXPERIMENTAL DESIGN The effects of Triapine on the in vitro radiosensitivity of three human tumor cell lines and one normal cell line were evaluated using a clonogenic assay. Growth delay was used to evaluate the effects of Triapine on in vivo tumor radiosensitivity. The levels of the RR subunits were determined using immunoblot analysis and DNA damage and repair were evaluated using gammaH2AX foci. RESULTS Exposure of the tumor cell lines to Triapine before or immediately after irradiation resulted in an increase in radiosensitivity. In contrast, Triapine enhanced the radiosensitivity of the normal fibroblast cell line only when the exposure was before irradiation. There were no consistent differences between cell lines with respect to the expression of the RR subunits. Whereas Triapine had no effect on radiation-induced gammaH2AX foci at 1 hour, the number of gammaH2AX foci per cell was significantly greater in the Triapine-treated cells at 24 hours after irradiation, suggesting the presence of unrepaired DNA damage. Triapine administration to mice bearing tumor xenografts immediately after irradiation resulted in a greater than additive increase in radiation-induced tumor growth delay. CONCLUSIONS These results indicate that Triapine can enhance tumor cell radiosensitivity in vitro and in vivo and suggest that this effect involves an inhibition of DNA repair.
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Kim HS, Yeo EJ, Park SH, Park JI, Park SC, Shin JY, Kim MJ, Oh SJ, Won MH, Kang TC, Park JB, Kim J, Kim JI, Lee HY, Lee JY. p21WAF/CIP1/SDI1 is upregulated due to increased mRNA stability during hydroxyurea-induced senescence of human fibroblasts. Mech Ageing Dev 2005; 126:1255-61. [PMID: 16111738 DOI: 10.1016/j.mad.2005.07.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/06/2005] [Indexed: 11/17/2022]
Abstract
Hydoxyurea induces senescence-like growth arrest in normal human fibroblasts. p21(WAF/CIP1/SDI1), a cyclin dependent kinase inhibitor, was found to be upregulated during this growth arrest. Levels of p21(WAF/CIP1/SDI1) protein and mRNA were increased nine-fold by hydroxyurea in these cells. In order to determine whether p21(WAF/CIP1/SDI1) mRNA is increased by hydroxyurea at the transcriptional level, human fibroblast cells were transfected with reporter constructs containing a p21(WAF/CIP1/SDI1) promoter fragment and then treated with hydroxyurea. The luciferase activities in the reporter-transfected fibroblast cells were not increased by hydroxyurea, indicating that p21(WAF/CIP1/SDI1) transcription was not elevated by hydroxyurea. The half-life of the p21(WAF/CIP1/SDI1) mRNA was increased by 2.5-fold but that of p21(WAF/CIP1/SDI1) protein was not. Our results suggest that increased mRNA stability is the major mechanism of p21(WAF/CIP1/SDI1) elevation in the hydroxyurea-induced growth arrest of human fibroblasts.
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Affiliation(s)
- Hyun-Seok Kim
- Department of Biochemistry, College of Medicine, Hallym University, 1 Okchon-dong, Chuncheon, Gangwon-do 200-702, South Korea
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Toussaint M, Dionne I, Wellinger RJ. Limited TTP supply affects telomere length regulation in a telomerase-independent fashion. Nucleic Acids Res 2005; 33:704-13. [PMID: 15681620 PMCID: PMC548361 DOI: 10.1093/nar/gki219] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
An adequate supply of nucleotides is essential for DNA replication and DNA repair. Moreover, inhibition of TTP synthesis can cause cell death by a poorly characterized mechanism called thymine-less death. In the yeast Saccharomyces cerevisiae, the genes encoding thymidylate synthetase (CDC21) and thymidylate kinase (CDC8) are both essential for de novo TTP synthesis. The effects of temperature-sensitive mutations in these genes have been characterized and, curiously, the phenotypes displayed by cells harboring them include shortened telomeric repeat tracts. This finding raised the possibility that the enzyme telomerase is very sensitive to TTP-pools. We tested this possibility in vivo by assessing telomerase-dependent extension in situations of lowered TTP supply. The results show that the above-mentioned short telomere phenotype is not a consequence of an inability of telomerase to elongate telomeres when TTP synthesis is impaired. Moreover, this telomere shortening was abolished in cells harboring a mutation in DNA polymerase α. Previously, this same mutation was shown to affect the coordination between conventional replication and telomerase-mediated extension. These results thus re-emphasize the importance of the interplay between conventional replication and telomerase-mediated addition of telomeric repeats in telomere replication.
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Affiliation(s)
| | | | - Raymund J. Wellinger
- To whom correspondence should be addressed. Tel: +819 564 5214; Fax: +819 564 5392;
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Subramanian B, Nakeff A, Media J, Wentland M, Valeriote F. Cellular drug action profile paradigm applied to XK469. JOURNAL OF EXPERIMENTAL THERAPEUTICS AND ONCOLOGY 2002; 2:253-63. [PMID: 12416029 DOI: 10.1046/j.1359-4117.2002.01040.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cellular paradigm presented here defines the cellular action profile of new anticancer agents that complements our discovery and development paradigm. The main elements of this profile include a concentration clonogenicity response relationship on proliferating and plateau phase cells, flow cytometry studies assessing progression delay and apoptosis, macromolecular synthesis inhibition, and DNA damage assessment by the comet assay; other specific assessments then derive from these findings such as topoisomerase assays. XK469 is a new anticancer agent derived from the herbicide Assure that is the inactive parent compound of a family of quinoxaline analogs found to have anticancer activity in vivo. We have applied the described cellular action profile paradigm to XK469 to define a novel action at the cellular level. XK469 is a G2M phase-specific, antiproliferative agent whose activity is related to the 7-position of the chlorine ion in the benzene ring and expressed through a unique cellular action profile resulting in the irreversible increase in cyclin B1 (possibly by specific inhibition of its ubiquitination) and leading, in the absence of apoptosis, to the final mitotic arrest of HCT-116 cells in prophase with subsequent loss of clonogenicity.
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Affiliation(s)
- Balanehru Subramanian
- Drug Discovery and Development Program, Josephine Ford Cancer Center, Henry Ford Health System, Detroit, MI, USA.
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Gazitt Y, Reddy SV, Alcantara O, Yang J, Boldt DH. A new molecular role for iron in regulation of cell cycling and differentiation of HL-60 human leukemia cells: iron is required for transcription of p21(WAF1/CIP1) in cells induced by phorbol myristate acetate. J Cell Physiol 2001; 187:124-35. [PMID: 11241357 DOI: 10.1002/1097-4652(2001)9999:9999<::aid-jcp1061>3.0.co;2-e] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
To investigate the role of iron in hematopoiesis, we studied effects of iron deprivation on PMA-induced monocyte/macrophage differentiation in HL-60 cells. Iron deprivation induced by desferrioxamine (DF) blocked PMA-induced differentiation and induced S-phase arrest and apoptosis in up to 60% of cells. Apoptosis was not related to a decrease of bcl-2 or to c-myc overexpression. In the presence of DF, PMA-induced upregulation of the cyclin dependent kinase inhibitor (CDKI), p21(WAF1/CIP1), was blocked and its expression could be restored in the presence of DF by supplementation with ferric citrate. Furthermore, ferrioxamine (iron saturated DF) did not block induction of p21(WAF1/CIP1) indicating that the changes were not due to a nonspecific toxic effect of DF. Similarly, hydroxyurea, an inhibitor of ribonucleotide reductase, did not block p21 expression. p21(WAF1/CIP1) antisense oligonucleotides caused cell cycle alterations similar to DF and p21 overexpression overcame effects of iron deprivation on both cell cycling and differentiation. Therefore, p21 is a key target for the effects of iron deprivation on HL-60 cell cycling and differentiation. Nuclear run-on transcription assays and p21 mRNA half-life studies indicated that iron was required to support transcriptional activation of p21(WAF1/CIP1) after a PMA stimulus. By contrast, iron deprivation did not inhibit expression of a second CDKI, p27(KIP1). These data demonstrate a new role for iron during monocyte/macrophage differentiation. A key role of iron is to allow induction of p21(WAF1/CIP1) in response to a differentiation stimulus subsequently blocking cells at the G(1)/S cell cycle interface and preventing premature apoptosis. This effect of iron is independent of its requirement in supporting the activity of the enzyme, ribonucleotide reductase. Because of the central role of p21(WAF1/CIP1) as regulator of the G(1)/S cell cycle checkpoint this requirement for iron to support p21 expression represents an important mechanism by which iron may modulate hematopoietic cell growth and differentiation. Published 2001 Wiley-Liss, Inc.
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Affiliation(s)
- Y Gazitt
- Division of Hematology, Department of Medicine, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX78229-3900, USA.
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Abstract
Abstract
Hydroxyurea (HU) is an effective therapeutic agent for patients with myeloproliferative disorders (MPDs) or sickle cell disease (SCD). Short-term HU toxicities primarily include transient myelosuppression, but long-term HU risks have not been defined. The mutagenic and carcinogenic potential of HU is not established, although HU has been associated with an increased risk of leukemia in some patients with MPD. In this study, 2 assays were used to quantitate acquired somatic DNA mutations in peripheral blood mononuclear cells (PBMCs) after in vivo HU exposure. The HPRT assay measures hypoxanthine phosphoribosyl transferase (hprt) mutations, while the VDJ assay identifies “illegitimate” T-cell receptor Vγ-Jβ interlocus recombination events. PBMCs were analyzed from patients with MPD, adults and children with SCD, and normal controls. MPD patients with prolonged HU exposure had numbers of DNA mutations equivalent to patients with low HU exposure or controls. Similarly, adults with SCD had equivalent numbers of DNA mutations regardless of HU exposure. Children with SCD and 30-month HU exposure had equivalenthprt− mutations but significantly more VDJ mutations (1.82 ± 1.20 events per μg DNA) than children with 7-month HU exposure (1.58 ± 0.87 events) or no HU exposure (1.06 ± 0.45 events), P = .04 by analysis of variance. Taken together, these data suggest that the mutagenic and carcinogenic potential of in vivo HU therapy is low. Although increased numbers of illegitimate VDJ recombination events do not directly portend leukemia, young patients with SCD and HU exposure should be monitored serially for increases in DNA mutations.
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Abstract
Hydroxyurea (HU) is an effective therapeutic agent for patients with myeloproliferative disorders (MPDs) or sickle cell disease (SCD). Short-term HU toxicities primarily include transient myelosuppression, but long-term HU risks have not been defined. The mutagenic and carcinogenic potential of HU is not established, although HU has been associated with an increased risk of leukemia in some patients with MPD. In this study, 2 assays were used to quantitate acquired somatic DNA mutations in peripheral blood mononuclear cells (PBMCs) after in vivo HU exposure. The HPRT assay measures hypoxanthine phosphoribosyl transferase (hprt) mutations, while the VDJ assay identifies “illegitimate” T-cell receptor Vγ-Jβ interlocus recombination events. PBMCs were analyzed from patients with MPD, adults and children with SCD, and normal controls. MPD patients with prolonged HU exposure had numbers of DNA mutations equivalent to patients with low HU exposure or controls. Similarly, adults with SCD had equivalent numbers of DNA mutations regardless of HU exposure. Children with SCD and 30-month HU exposure had equivalenthprt− mutations but significantly more VDJ mutations (1.82 ± 1.20 events per μg DNA) than children with 7-month HU exposure (1.58 ± 0.87 events) or no HU exposure (1.06 ± 0.45 events), P = .04 by analysis of variance. Taken together, these data suggest that the mutagenic and carcinogenic potential of in vivo HU therapy is low. Although increased numbers of illegitimate VDJ recombination events do not directly portend leukemia, young patients with SCD and HU exposure should be monitored serially for increases in DNA mutations.
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Mayhew CN, Phillips JD, Greenberg RN, Birch NJ, Elford HL, Gallicchio VS. In vivo and in vitro comparison of the short-term hematopoietic toxicity between hydroxyurea and trimidox or didox, novel ribonucleotide reductase inhibitors with potential anti-HIV-1 activity. Stem Cells 1999; 17:345-56. [PMID: 10606163 DOI: 10.1002/stem.170345] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Inhibitors of the cellular enzyme ribonucleotide reductase (hydroxyurea, [HU]) have been proposed as a new therapeutic strategy for the treatment of HIV type-1 (HIV-1) infection. However, HU use may be limited by the frequent development of hematopoietic toxicity. We report here short-term hematopoietic toxicity in mice receiving HU when compared to either of two more potent enzyme inhibitors, didox (DX) and trimidox (TX). High dose HU, DX, and TX monotherapy (500, 460, and 220 mg/kg/day respectively) was administered by daily i.p. injection (Monday-Friday) to C57BL/6 mice for 10 weeks. Effects on hematopoiesis were established by quantitating peripheral blood indices (hematocrit, hemoglobin, mean corpuscular volume, mean cell hemoglobin, mean corpuscular hemoglobin concentration, RBC, and WBC) and numbers of colony-forming units-granulocyte-macrophage (CFU-GM) and BFU-E from bone marrow and spleen. HU produced rapid induction of a macrocytic hypochromic anemia and altered white blood cell kinetics associated with myelosuppression defined as reduced marrow organ cellularity and induction of splenic extramedullary hematopoiesis. Compared to HU, TX and DX induced fewer changes in peripheral blood indices and CFU-GM and BFU-E per hematopoietic organ. In vitro human and murine marrow CFU-GM and BFU-E colony formations were assayed in the presence of dose escalation HU, DX, or TX (0, 1, 10, 50, 100, and 200 microM). HU inhibited colony formation more than either DX or TX. These in vivo and in vitro studies suggest that novel ribonucleotide reductase inhibitors TX and DX may provide an effective alternative to HU in HIV-1 therapy because they demonstrate reduced hematopoietic toxicity.
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Affiliation(s)
- C N Mayhew
- School of Health Sciences, University of Wolverhampton, United Kingdom
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Robins MJ. Mechanism-based inhibition of ribonucleotide reductases: new mechanistic considerations and promising biological applications. NUCLEOSIDES & NUCLEOTIDES 1999; 18:779-93. [PMID: 10432680 DOI: 10.1080/15257779908041565] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Ribonucleotide reductases (RNRs) perform the de novo biosynthesis of 2'-deoxynucleoside 5'-(di or tri)phosphates. Inhibition of RNRs removes a crucial source of genetic components and enhances the probability of salvage incorporation of analogues into DNA. Several laboratories have clarified aspects of the reaction cascades initiated by generation of substrate nucleotide C3' free radicals by RNRs. New considerations for radical-mediated mechanism-based inhibition and biological applications are discussed.
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Affiliation(s)
- M J Robins
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602-5700, USA
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27
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Sciorati C, Nisticò G, Meldolesi J, Clementi E. Nitric oxide effects on cell growth: GMP-dependent stimulation of the AP-1 transcription complex and cyclic GMP-independent slowing of cell cycling. Br J Pharmacol 1997; 122:687-97. [PMID: 9375965 PMCID: PMC1564973 DOI: 10.1038/sj.bjp.0701413] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
1. The role of nitric oxide (NO) in the control of cell growth is controversial since both stimulation and (more often) inhibition have been demonstrated in various cell types. In order to reinvestigate the problem and identify the sites of NO action, we have employed murine NIH-3T3 fibroblasts overexpressing epidermal growth factor (EGF) receptors. 2. The effects of four structurally-unrelated NO donors: S-nitroso-N-acetyl penicillamine, S-nitroso-L-glutathione, 3-morpholinosydnonimine and isosorbide dinitrate (0.01-3 mM) on EGF (10 nM)-stimulated cell growth were estimated by both thymidine incorporation and the colorimetric MTT assay, while those of a messenger generated in response to NO, cyclic GMP, were revealed by the use of 8-Br cyclic GMP (0.01-3 mM) as well as of blockers of guanylyl cyclase and cyclic GMP-dependent kinase I. 3. Studies were focused on: (i) multiple signalling events, including receptor-induced tyrosine phosphorylations, phosphorylation of mitogen-activated protein kinase, activation of the AP-1 transcription complex and deoxyribonucleotide synthesis; (ii) the progression through the cell cycle, dissected out by the use of staurosporine (1 nM), lovastatin (10 microM), mimosine (200 microM), hydroxyurea (1 mM) and nocodazole (1.5 microM). 4. NO was found to have no effects on the phosphorylation events of the growth factor cascade. In contrast, later processes were modified by the messenger but with opposite effects. 5. A cyclic GMP-dependent stimulation of growth was shown to be sustained in part by the activation of the AP-1 transcription complex, while a predominant, cyclic GMP-independent inhibition was found to be mediated by both the negative regulation of ribonucleotide reductase and the marked slowing down of the cell cycle occurring at early and late G1 and during the S phase. 6. Although multiple and apparently conflicting, the effects of NO here described could work coordinately in a general programme of cell growth regulation. In particular, the cyclic GMP-dependent actions might function as rapid modulatory events, while the effects on cell cycle might operate collectively as a multi-switch process whenever growth inhibition is required.
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Affiliation(s)
- C Sciorati
- Consiglio Nazionale delle Ricerche Cellular and Molecular Pharmacology Center, DIBIT-H San Raffaele Scientific Institute, University of Milano, Italy
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Kang SH, Sinhababu AK, Cory JG, Mitchell BS, Thakker DR, Cho MJ. Cellular delivery of nucleoside diphosphates: a prodrug approach. Pharm Res 1997; 14:706-12. [PMID: 9210185 DOI: 10.1023/a:1012133902314] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
PURPOSE This study is concerned with cellular delivery/generation of 2'-azido-2'-deoxyuridine and -deoxycytidine diphosphate (N3UDP or N3CDP), potent inhibitors of ribonucleotide reductase. It characterizes the phosphorylation steps involved in the conversion of 2'-azido-2'-deoxyuridine (N3Urd) and 2'-azido-2'-deoxycytidine (N3Cyd) to the corresponding diphosphates and explores a prodrug approach in cellular delivery of the inhibitor which circumvents the requirement of deoxynucleoside kinases. METHODS Cell growth of CHO and 3T6 cells of known deoxycytidine kinase level was determined in the presence of N3Urd and N3Cyd. Activity of ribonucleotide reductase was determined in the presence of the azidonucleosides as well as their mono- or di-phosphates in a Tween 80-containing permeabilizing buffer. A prodrug of 5'-monophosphate of N3Urd was prepared and its biological activity was evaluated with CHO cells as well as with cells transfected with deoxycytidine kinase. RESULTS N3Urd failed to inhibit the growth of both cell lines, while N3Cyd was active against 3T6 cells and moderately active against CHO cells. These results correlate with the deoxycytidine kinase levels found in the cells. Importance of the kinase was further established with the finding that the nucleoside analogs were inactive as reductase inhibitors in a permeabilized cell assay system while their mono- and di-phosphates were equally active. The prodrug was active in cell growth inhibition regardless of the deoxycytidine kinase level. CONCLUSIONS The azidonucleosides become potent inhibitors of the reductase by two sequential phosphorylation steps. The present study indicates that the first step to monophosphate is rate-limiting, justifying a prodrug approach with the monophosphate.
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Affiliation(s)
- S H Kang
- Division of Pharmaceutics, University of North Carolina School of Pharmacy, Chapel Hill 27599-7360, USA
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Currid P, Wightman RH. Synthesis of Some Hydroxamic Acids Related to Uridine: Potential Inhibitors of Ribonucleoside Diphosphate Reductase. ACTA ACUST UNITED AC 1997. [DOI: 10.1080/07328319708002527] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Galli A, Schiestl RH. Hydroxyurea induces recombination in dividing but not in G1 or G2 cell cycle arrested yeast cells. Mutat Res 1996; 354:69-75. [PMID: 8692208 DOI: 10.1016/0027-5107(96)00037-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Hydroxyurea, a chemotherapeutic and radiosensitizing agent, inhibits ribonucleotide reductase, arrests cells in the S-phase and is mutagenic and recombinagenic. In this paper we investigated whether the recombinagenic activity of hydroxyurea is due to the same activity that leads to arrest in the S-phase or to a more direct action on DNA. The effect of hydroxyurea on intrachromosomal and interchromosomal recombination was investigated in dividing and in G1 or G2 cell cycle-arrested cells of the yeast Saccharomyces cerevisiae. Treatment of dividing cells with hydroxyurea resulted in a large increase in recombination frequencies, even at low non-toxic doses. In contrast, in cells arrested in the G1 or G2 phase, hydroxyurea failed to induce recombination, even at 60-fold higher toxic doses. The presence of metabolic activation (S9 mix) did not change the effects of hydroxyurea on recombination. The data suggest that the recombinagenic activity of hydroxyurea may not be due to any direct effect of hydroxyurea on DNA, but may be linked to the inhibition of ribonucleotide reductase causing inhibition of DNA synthesis leading to S-phase arrest and possibly causing recombinagenic lesions.
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Affiliation(s)
- A Galli
- Department of Molecular and Cellular Toxicology, Harvard School of Public Health, Boston, MA 02115, USA
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31
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Kunz BA, Kohalmi SE, Kunkel TA, Mathews CK, McIntosh EM, Reidy JA. International Commission for Protection Against Environmental Mutagens and Carcinogens. Deoxyribonucleoside triphosphate levels: a critical factor in the maintenance of genetic stability. Mutat Res 1994; 318:1-64. [PMID: 7519315 DOI: 10.1016/0165-1110(94)90006-x] [Citation(s) in RCA: 185] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
DNA precursor pool imbalances can elicit a variety of genetic effects and modulate the genotoxicity of certain DNA-damaging agents. These and other observations indicate that the control of DNA precursor concentrations is essential for the maintenance of genetic stability, and suggest that factors which offset this control may contribute to environmental mutagenesis and carcinogenesis. In this article, we review the biochemical and genetic mechanisms responsible for regulating the production and relative amounts of intracellular DNA precursors, describe the many outcomes of perturbations in DNA precursor levels, and discuss implications of such imbalances for sensitivity to DNA-damaging agents, population monitoring, and human diseases.
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Affiliation(s)
- B A Kunz
- Microbiology Department, University of Manitoba, Winnipeg, Canada
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Harder J. Ribonucleotide reductases and their occurrence in microorganisms: a link to the RNA/DNA transition. FEMS Microbiol Rev 1993; 12:273-92. [PMID: 8268003 DOI: 10.1111/j.1574-6976.1993.tb00023.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The evolution of a deoxyribonucleotide synthesizing ribonucleotide reductase might have initiated the transition from the ancient RNA world into the prevailing DNA world. At least five classes of ribonucleotide reductases have evolved. The ancient enzyme has not been identified. A reconstruction of the first ribonucleotide reductase requires knowledge of contemporary enzymes and of microbial evolution. Experimental work on the former focuses on few organisms, whereas the latter is now well understood on the basis of ribosomal RNA sequences. Deoxyribonucleotide formation has not been investigated in many evolutionary important microorganisms. This review covers our knowledge on deoxyribonucleotide synthesis in microorganisms and the distribution of ribonucleotide reductases in nature. Ecological constraints on enzyme evolution and knowledge deficiencies emerge from complete coverage of the phylogenetic groups.
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Affiliation(s)
- J Harder
- Max-Planck-Institut for Marine Microbiology, Bremen, FRG
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Covès J, Nivière V, Eschenbrenner M, Fontecave M. NADPH-sulfite reductase from Escherichia coli. A flavin reductase participating in the generation of the free radical of ribonucleotide reductase. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(17)46671-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Foresti M, Gaudio L, Paoletti I, Geraci G. Inhibition of erythroid differentiation in MEL cells by UV irradiation. Cell cycle and DNA repair activity. Mutat Res 1993; 294:69-75. [PMID: 7683760 DOI: 10.1016/0921-8777(93)90059-p] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Irradiation with a 3-s pulse of 254 nm UV light has been used to study sensitivity to mutagenic agents of mouse erythroleukemia (MEL) cell cultures in correlation with the cell cycle. A dose of UV irradiation was chosen that had no consequences for cell viability and growth. For this reason phenotypic effects were monitored on the progeny of all cells of the irradiated cultures by scoring those unable to undergo erythroid differentiation upon induction with dimethyl sulfoxide. The very short period of irradiation made it possible to show that MEL cells, synchronized by two sequential blocks of deoxythymidine and one of hydroxyurea (HU), are sensitive to UV irradiation only in a very short period of time at about 60 min after release from HU block. Determinations of deoxythymidine incorporation into DNA show that this time period corresponds only marginally to the initial part of the S phase during which irradiation has no consequences for cell properties. Cells are not sensitive to UV irradiation in G1 and in G2/M unless, immediately after irradiation and for the following 2 h, cultures are treated with 1 mM HU to interfere with DNA repair. Alkaline sucrose gradient analyses show at all tested times that irradiation leads to fragmentation of cell DNA. The data suggest that an immediate increase of deoxythymidine incorporation into DNA following irradiation is not necessary for the efficient repair of damaged DNA. In fact, the percent of cells expressing the erythroid phenotype is normal in the progeny of cells irradiated in G2/M, when TdR incorporation is at a minimum. Repair activities appear then to be mechanistically divided into two phases, (1) recognition labeling of the altered sites and (2) reconstitution of the DNA sequences. The first activity appears to be operative at all phases of the cycle, the second activity is little or not operative in G2/M, possibly delayed to the following G1 period.
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Affiliation(s)
- M Foresti
- Dipartimento di Genetica, Biologia Generale e Molecolare, Universitá Federico II, Naples, Italy
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Colly LP, Richel DJ, Arentsen-Honders MW, Kester MG, ter Riet PM, Willemze R. Increase in Ara-C sensitivity in Ara-C sensitive and -resistant leukemia by stimulation of the salvage and inhibition of the de novo pathway. Ann Hematol 1992; 65:26-32. [PMID: 1643157 DOI: 10.1007/bf01715122] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In this study the hypothesis that inhibition of the de novo pathway results in stimulation of salvage pathway activity was tested. The key enzyme in the balance between these two pathways is ribonucleotide reductase (RR), which can be inhibited by hydroxyurea (HU). The metabolism of 1-beta-D-arabinofuranosylcytosine and 5-Aza-2 deoxycytidine (Aza-dC), which are activated via the salvage pathway, was evaluated in cells from Ara-C-sensitive and -resistant myelocytic leukemia cell line (BNML-Cl/0 and BNML-Cl/Ara-C). The combination of HU and Ara-C caused as much as a threefold increase of Ara-CTP; it significantly increased the incorporation of Ara-C into DNA and induced synergistic cytotoxicity, as evaluated in a colony assay. Even in the deoxycytidine (CdR) kinase-deficient Ara-C-resistant cell line, HU was partially able to restore sensitivity to Ara-C and Aza-dC. dCTP levels are reduced during the first 10 h after incubation with HU, but this effect vanishes at the time when phosphorylation is maximal. Increased CdR kinase activity in cell-free extracts could explain the enhanced synthetic salvage pathway activity, which is likely due to the fact that more enzyme is present (Vmax has increased by Km unchanged). RR inhibition combined with Ara-C might provide a means of eliminating leukemic cells with suboptimal anabolic salvage pathway activity, which otherwise survive Ara-C chemotherapy.
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Affiliation(s)
- L P Colly
- Department of Hematology, University Medical Center Leiden, The Netherlands
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Kormanec J, Farkasovský M, Potúcková L, Godár S. A gene (hur) from Streptomyces aureofaciens, conferring resistance to hydroxyurea, is related to genes encoding streptomycin phosphotransferase. Gene 1992; 114:133-7. [PMID: 1316866 DOI: 10.1016/0378-1119(92)90719-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
A novel gene (hur) conferring resistance to hydroxyurea (HU) in Escherichia coli has been identified in a Streptomyces aureofaciens genomic library. The expression of hur in E. coli was under the control of the external plasmid tet promoter. Sequence analysis of a minimal fragment revealed an open reading frame (ORF) encoding a protein of 340 amino acids with an M(r) of 36,049 and an average hydropathy index of 1.13. The predicted protein product was similar to streptomycin phosphotransferases from Streptomyces glaucescens and Streptomyces griseus (52.4% and 50.8% identity, respectively), but it did not confer resistance to streptomycin or to any of the other aminoglycoside antibiotics tested. It is inferred that hur encodes a phosphotransferase that inactivates HU by phosphorylation of the hydroxy group in the hydroxylamine moiety.
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Affiliation(s)
- J Kormanec
- Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, Czechoslovakia
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Bey-Liing M, Powis G. Inhibition of cellular thioredoxin reductase by diaziquone and doxorubicin. Biochem Pharmacol 1992. [DOI: 10.1016/0006-2952(92)90221-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Martins-Green M, Tilley C, Schwarz R, Hatier C, Bissell MJ. Wound-factor-induced and cell cycle phase-dependent expression of 9E3/CEF4, the avian gro gene. CELL REGULATION 1991; 2:739-52. [PMID: 1742344 PMCID: PMC361868 DOI: 10.1091/mbc.2.9.739] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The gro genes encode for secreted proteins with sequence homologies to inflammatory mediators. Little is known about the function of these proteins or their regulation. The chicken gro (9E3/CEF4) is expressed abundantly in the cells of proliferating cultures but at very low levels in confluent cultures. In vivo, this gene is expressed in connective tissue and overexpressed at sites of injury, especially in areas of neovascularization. Here we provide a bridge between these observations by examining in culture the effect on 9E3 expression and DNA synthesis induced by cell damage and by addition of factors known to be released on wounding. We mimicked wounding by scraping swaths across confluent cultures of embryonic fibroblasts and determined the time dependence of expression of 9E3 mRNA and incorporation of 3H-thymidine. We find that 9E3 is (1) transiently expressed after "wounding" or serum-stimulation; (2) expressed in a cell cycle phase-dependent manner; it is triggered during the G0-G1 transition or early in G1 and subsides during S-phase; and (3) stimulated to high levels by a-fibroblast growth factor (aFGF), bFGF, transforming growth factor alpha (TGF alpha), and TGF beta, to intermediate levels by platelet-derived growth factor and not stimulated by epidermal growth factor. We also find that cells that are constantly cycling do not express 9E3, indicating that they skip either the portion of the cell cycle where 9E3 is induced or that they constitutively express a repressor of transcription or an RNA-degrading enzyme. Taken together, these observations suggest that the product of this gene could play more than one role in vivo. For example, in normal tissues the 9E3 protein could be involved in the exit of cells from the resting stage, whereas during wound healing the secreted protein or its cleavage products also could play a role in angiogenesis.
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Affiliation(s)
- M Martins-Green
- Division of Cell and Molecular Biology, Lawrence Berkeley Laboratory, Berkeley, California 94720
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39
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Slabaugh MB, Howell ML, Wang Y, Mathews CK. Deoxyadenosine reverses hydroxyurea inhibition of vaccinia virus growth. J Virol 1991; 65:2290-8. [PMID: 2016760 PMCID: PMC240578 DOI: 10.1128/jvi.65.5.2290-2298.1991] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Hydroxyurea, an inhibitor of ribonucleotide reductase, blocks replication of vaccinia virus. However, when medium containing hydroxyurea and dialyzed serum was supplemented with deoxyadenosine, the block to viral reproduction was circumvented, provided that an inhibitor of adenosine deaminase was also present. Deoxyguanosine, deoxycytidine, and deoxythymidine were ineffective alone and did not augment the deoxyadenosine effect. In fact, increasing concentrations of deoxyguanosine and deoxythymidine, but not deoxycytidine, eliminated the deoxyadenosine rescue, an effect that was reversed by the addition of low concentrations of deoxycytidine. These results suggested that the inhibition of viral replication by hydroxyurea was primarily due to a deficiency of dATP. Deoxyribonucleoside triphosphate pools in vaccinia virus-infected cells were measured at the height of viral DNA synthesis after a synchronous infection. With 0.5 mM hydroxyurea, the dATP pool was greater than 90% depleted, the dCTP and dGTP pools were 40 to 50% reduced, and the dTTP pool was increased. Assay of ribonucleotide reductase activity in intact virus-infected cells suggested that hydroxyurea may differentially affect reduction of the various substrates of the enzyme.
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Affiliation(s)
- M B Slabaugh
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis 97331-6503
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Cai J, Speed RR, Winkler HH. Reduction of ribonucleotides by the obligate intracytoplasmic bacterium Rickettsia prowazekii. J Bacteriol 1991; 173:1471-7. [PMID: 1899861 PMCID: PMC207284 DOI: 10.1128/jb.173.4.1471-1477.1991] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Rickettsia prowazekii, an obligate intracellular parasitic bacterium, was shown to have a ribonucleotide reductase that would allow the rickettsiae to obtain the deoxyribonucleotides needed for DNA synthesis from rickettsial ribonucleotides rather than from transport. In the presence of hydroxyurea, R. prowazekii failed to grow in mouse L929 cells or SC2 cells (a hydroxyurea-resistant cell line), which suggested that R. prowazekii contains a functional ribonucleotide reductase. This enzymatic activity was demonstrated by the conversion of ADP to dADP and CDP to dCDP, using (i) a crude extract of Renografin-purified R. prowazekii that had been harvested from infected yolk sacs and (ii) high-performance liquid chromatographic analysis. The rickettsial ribonucleotide reductase utilized ribonucleoside diphosphates as substrates, required magnesium and a reducing agent, and was inhibited by hydroxyurea. ADP reduction was stimulated by dGTP and inhibited by dATP. CDP reduction was stimulated by ATP and adenylylimido-diphosphate and inhibited by dATP and dGTP. These characteristics provided strong evidence that the rickettsial enzyme is a nonheme iron-containing enzyme similar to those found in mammalian cells and aerobic Escherichia coli.
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Affiliation(s)
- J Cai
- Department of Microbiology and Immunology, University of South Alabama College of Medicine, Mobile 36688
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41
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Suter W, Romagna F. DNA repair induced by various mutagens in rat hepatocyte primary cultures measured in the presence of hydroxyurea, guanazole or aphidicolin. Mutat Res 1990; 231:251-64. [PMID: 2117252 DOI: 10.1016/0027-5107(90)90031-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Guanazole and aphidicolin were chosen as candidates in the search for a selective, non-genotoxic inhibitor of DNA replication which could be used instead of hydroxyurea to measure DNA repair synthesis in rat hepatocyte primary cultures by liquid scintillation counting. The genotoxicity of these 3 chemicals was studied using the Salmonella/liver homogenate assay and the autoradiographic UDS test in hepatocytes. Hydroxyurea was positive in both of these assays. Guanazole and aphidicolin did not induce DNA repair in hepatocytes. Aphidicolin was not mutagenic for Salmonella typhimurium, whereas guanazole increased the revertant numbers of strain TA102 slightly. The incorporation of [3H]thymidine was measured by liquid scintillation to determine DNA repair induced by 2-acetylaminofluorene (2-AAF), aflatoxin B1, benzo[a]pyrene, cyclophosphamide, H2O2, 6-hydroxydopamine, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), methylnitrosourea (MNU), 4-nitroquinoline-N-oxide and UV irradiation in the presence of either 10 mM hydroxyurea, 15 mM guanazole or 0.015 mM aphidicolin. Aphidicolin had an inhibitory effect on DNA repair. Except for the 3 chemicals mentioned below, the sensitivity of the DNA repair measurement was the same, no matter whether hydroxyurea or guanazole was used to inhibit replicative DNA synthesis. In the presence of hydroxyurea, DNA repair synthesis was found at lower concentrations in the case of aflatoxin B1, due to differences in the solvent control values, and in the case of H2O2, possibly due to a synergistic effect between hydroxyurea and H2O2. Guanazole allowed the detection of DNA repair induced by MNNG at lower concentrations, probably because of an antagonistic effect between hydroxyurea and MNNG. Based on these results, it was concluded that guanazole, but not aphidicolin, could be used instead of hydroxyurea to measure DNA repair synthesis by liquid scintillation in rat hepatocyte primary cultures. Although guanazole does not completely fulfill the criteria for an ideal DNA replication inhibitor, it has the advantage of being less genotoxic than hydroxyurea, and also appears to have a smaller potential to falsify the results by interacting with the test compounds.
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Affiliation(s)
- W Suter
- Toxicology Department, Sandoz Pharma Ltd., Basle, Switzerland
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Liermann B, Lassmann G, Langen P. Quenching of tyrosine radicals of M2 subunit from ribonucleotide reductase in tumor cells by different antitumor agents: an EPR study. Free Radic Biol Med 1990; 9:1-4. [PMID: 2170241 DOI: 10.1016/0891-5849(90)90042-h] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The inhibition of ribonucleotide reductase (RR) of intact Ehrlich ascites tumor cells by different antitumor agents was compared using EPR spectroscopy. The inactivation of M2 subunit was measured via quenching of the functionally essential tyrosine radical. Inhibitors of different classes, for example, hydroxyurea, pyrogallol, and thiosemicarbazones, differ in their efficiency by three orders of magnitude. Most effective inhibition was found for isoquinoline-1-aldehyde-thiosemicarbazone (IQ-1) with an IC50 value of 0.18 microM. Inhibition of RR inside tumor cells is comparable with that reported for isolated enzymes.
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Affiliation(s)
- B Liermann
- Central Institute of Molecular Biology, Academy of Sciences of GDR, Berlin-Buch
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Abstract
Methotrexate-resistant R500 cells slowly lose amplified dihydrofolate reductase (dhrf) genes with biphasic kinetics when grown in the absence of methotrexate. Both phases of gene loss were markedly accelerated by subcytotoxic drug treatments. R500 cells were passed in low concentrations of cytotoxic drugs (inhibitors of ribonucleotide reductase, type I and type II topoisomerases, and polyamine synthesis). At each passage, relative dhfr gene copy number was determined by slot blot analysis. All of these drugs were able to induce rapid loss of dhfr gene dosage in the R500 cell population. The ability of these treatments to cause the rapid emergence of a cell population with substantially reduced dhfr gene dosage indicates that either the amplified genes or those cells with the highest levels of gene amplification are selectively targeted by low-level cytotoxic stress. The complex kinetics of amplified gene loss are suggestive of differential targeting of resistant cell subpopulations.
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Affiliation(s)
- M A Wani
- Department of Radiology, Ohio State University 43210
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44
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Karlsson A, Reichard P, Eckstein F. Hydroxyurea increases the phosphorylation of 3'-fluorothymidine and 3'-azidothymidine in CEM cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 1989; 186:689-94. [PMID: 2606113 DOI: 10.1111/j.1432-1033.1989.tb15261.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The triphosphates of the nucleoside analogues 3'-azidothymidine and 3'-fluorothymidine inhibit reverse transcriptase and are of therapeutic interest for the treatment of retrovirus infections. At equimolar concentrations 3'-fluorothymidine was more effectively transformed to the triphosphate by human CEM cells than azidothymidine which mainly accumulates as the monophosphate. Hydroxyurea, a drug that inhibits de novo synthesis of deoxyribonucleotides, considerably increased the ability of cells to phosphorylate both analogues. Addition of as little as 50 microM hydroxyurea decreased the amount of dideoxynucleoside required to attain a given intracellular concentration of its triphosphate by an order of magnitude. Hydroxyurea is known to shift the balance of substrate cycles between natural deoxynucleosides and their 5'-phosphates in the direction of synthesis and thereby to increase the import and intracellular phosphorylation of the nucleoside. The present results demonstrate a similar effect for the two analogues and raise the possibility of using this effect in therapy.
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Affiliation(s)
- A Karlsson
- Department of Biochemistry 1, Medical Nobel Institute, Karolinska Institute, Stockholm, Sweden
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Baum KF, Berens RL, Marr JJ, Harrington JA, Spector T. Purine deoxynucleoside salvage in Giardia lamblia. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)30049-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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46
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Weckbecker G, Lien EJ, Cory JG. Properties of N-hydroxy-N'-aminoguanidine derivatives as inhibitors of mammalian ribonucleotide reductase. Biochem Pharmacol 1988; 37:529-34. [PMID: 3276327 DOI: 10.1016/0006-2952(88)90224-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
In previous studies, N-hydroxy-N'-aminoguanidine (HAG) derivatives were demonstrated to suppress growth and clonogenicity of tumor cells which correlated with the inhibition of ribonucleotide reductase and DNA synthesis. The present work has focused on the properties of five HAG derivatives as inhibitors of the ribonucleotide reductase from Ehrlich ascites tumor cells. HAG derivatives acted as non-competitive inhibitors of ribonucleotide reductase with respect to the substrates CDP and ADP. The apparent Ki values for the various HAG derivatives as inhibitors of CDP reductase ranged from 3.4 to 543 microM. However, the apparent Ki values for these inhibitors with respect to ADP reductase were 2- to 10-fold lower than the respective values for CDP reductase. After a preincubation of HAG derivatives and ribonucleotide reductase in the absence of substrates, an increased inhibition was observed. The activity of the inhibited enzyme could be restored by passage over a Sephadex G-25 column and subsequent incubation with dithioerythritol. The addition of either the non-heme iron subunit or the effector-binding subunit to the intact enzyme in the assay mixture resulted in a diminished inhibition of ADP reduction. Inhibition by HAG derivatives of ribonucleotide reductase activity in the test tube was not enhanced by iron chelators. However, a combination of HAG compounds and iron chelators synergistically inhibited the growth of L1210 cells.
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Affiliation(s)
- G Weckbecker
- Department of Internal Medicine, College of Medicine, H. Lee Moffitt Cancer Center and Research Institute, University of South Florida, Tampa 33612
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47
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Abstract
Ribonucleotide reductase, because of the critical role that it plays in DNA replication and the specific properties of the protein subunits, provides a unique metabolic target for chemotherapeutic approaches to cancer treatment. Combinations of ribonucleotide reductase inhibitors resulted in synergistic inhibition of cell growth with concurrent cytotoxicity. The drugs in this combination were targeted at the individual subunits (non-heme iron and effector-binding) of ribonucleotide reductase and at the differential sensitivities of the substrate reductions to these agents. The reduction of the intracellular pools of all four dNTPs through the direct inhibition of ribonucleotide reductase has the effect of reducing DNA polymerase activity in a sigmoidal manner rather than in a hyperbolic fashion due to the requirement of DNA polymerase for all four substrates. As a result relatively small decreases in the intracellular concentrations of the dNTPs cause remarkably large decreases in DNA synthesis and hence cell replication. It appears that there may be a relationship between the capability of the cell to synthesize DNA at a minimal absolute rate and cell viability. That is, if DNA synthesis is decreased to or below a specific level, then the processes leading to cell death takes precedence over the tendency of the cell to complete DNA replication leading to cell division.
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Affiliation(s)
- J G Cory
- Department of Internal Medicine, University of South Florida College of Medicine, H. Lee Moffitt Cancer Center, Tampa 33612
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48
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Szczepańska I, Kopeć-Szlezak J, Malec J. Inhibition of leucocyte migration by cancer chemotherapeutic agents and its prevention by free radical scavengers and thiols. Eur J Haematol 1988; 40:69-74. [PMID: 3125061 DOI: 10.1111/j.1600-0609.1988.tb00799.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The exposure of human blood in vitro to a range of concentrations of adriblastine, hydroxyurea, methotrexate, 5-fluorouracil, 6-mercaptopurine, cytosine arabinoside and nitrogen mustard induced reduction in leucocyte migration rate in all drug dilutions under study. The reduction was dose-dependent. This effect was used to examine the protection of alfa tocopherol, acetylosalicylic acid and thiourea against drug-induced cytotoxicity. It has been found that at the suitable concentration of the protecting agent, a preventive effect of tocopherol against toxicity of all drugs, except nitrogen mustard, can be achieved. Acetylosalicylic acid protected the cells against adriblastine, cytosine arabinoside, hydroxyurea and methotrexate toxicity. Thiourea prevented the toxic effect of adriblastine, fluorouracil, hydroxyurea, methotrexate and nitrogen mustard.
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Affiliation(s)
- I Szczepańska
- Department of Physiopathology, Institute of Haematology, Warsaw, Poland
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49
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Spector T, Stonehuerner JG, Biron KK, Averett DR. Ribonucleotide reductase induced by varicella zoster virus. Characterization, and potentiation of acyclovir by its inhibition. Biochem Pharmacol 1987; 36:4341-6. [PMID: 2825724 DOI: 10.1016/0006-2952(87)90682-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
An enzyme that catalyzes the conversion of CDP to 2'-dCDP in the presence of dithiothreitol (DTT) was detected in ammonium sulfate fractionated-extracts of varicella zoster virus (VZV)-infected cells. This ribonucleotide reductase was antigenically distinguishable from the isofunctional eucaryotic enzyme as well as the ribonucleotide reductases induced by herpes simplex virus types 1 and 2 (HSV-1 and HSV-2). The VZV-induced enzyme was purified to the extent that most of the contaminating enzymes, which would significantly deplete the substrate, were removed. The VZV-induced ribonucleotide reductase exhibited maximum activity in the absence of ATP and/or magnesium and was only weakly inhibited by 2'-deoxynucleoside triphosphates. Furthermore, ADP, UDP and GDP competitively inhibited CDP reduction with Ki (Km) values of 15, 20, 1.8 and 0.88 microM, respectively. These kinetic properties were very similar to those of the correspondingly purified ribonucleotide reductases induced by HSV-1 [Averett et al., J. biol. Chem. 258, 9831 (1983)] and HSV-2 [Averett et al., J. Virol. 52, 981 (1984)] and were dissimilar to the allosterically regulated mammalian enzyme. A723U, an inactivator of HSV-1 ribonucleotide reductase that potentiates the anti-HSV-1 activity of acyclovir [Spector et al., Proc. natn. Acad. Sci. U.S.A. 82, 4254 (1985)], also appeared to inactivate this VZV-induced ribonucleotide reductase and to potentiate the anti-VZV activity of acyclovir.
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Affiliation(s)
- T Spector
- Wellcome Research Laboratories, Research Triangle Park, NC 27709
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50
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Przybyszewski WM, Malec J. Hydroxyurea, methotrexate and adriblastine can mediate non-enzymatic reduction of nitroblue tetrazolium with NADH which is inhibited by superoxide dismutase. Biochem Pharmacol 1987; 36:3312-4. [PMID: 2822050 DOI: 10.1016/0006-2952(87)90652-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- W M Przybyszewski
- Department of Biochemistry, Institute of Haematology, Warsaw, Poland
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