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Pourcelot E, El Samra G, Mossuz P, Moulis JM. Molecular Insight into Iron Homeostasis of Acute Myeloid Leukemia Blasts. Int J Mol Sci 2023; 24:14307. [PMID: 37762610 PMCID: PMC10531764 DOI: 10.3390/ijms241814307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Revised: 09/12/2023] [Accepted: 09/15/2023] [Indexed: 09/29/2023] Open
Abstract
Acute myeloid leukemia (AML) remains a disease of gloomy prognosis despite intense efforts to understand its molecular foundations and to find efficient treatments. In search of new characteristic features of AML blasts, we first examined experimental conditions supporting the amplification of hematological CD34+ progenitors ex vivo. Both AML blasts and healthy progenitors heavily depended on iron availability. However, even if known features, such as easier engagement in the cell cycle and amplification factor by healthy progenitors, were observed, multiplying progenitors in a fully defined medium is not readily obtained without modifying their cellular characteristics. As such, we measured selected molecular data including mRNA, proteins, and activities right after isolation. Leukemic blasts showed clear signs of metabolic and signaling shifts as already known, and we provide unprecedented data emphasizing disturbed cellular iron homeostasis in these blasts. The combined quantitative data relative to the latter pathway allowed us to stratify the studied patients in two sets with different iron status. This categorization is likely to impact the efficiency of several therapeutic strategies targeting cellular iron handling that may be applied to eradicate AML blasts.
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Affiliation(s)
- Emmanuel Pourcelot
- Laboratory of Fundamental and Applied Bioenergetics (LBFA), University Grenoble Alpes, INSERM U1055, 38000 Grenoble, France; (E.P.); (G.E.S.)
- Department of Biological Hematology, Institute of Biology and Pathology, Hospital of Grenoble Alpes (CHUGA), CS 20217, 38043 Grenoble, CEDEX a9, France;
| | - Ghina El Samra
- Laboratory of Fundamental and Applied Bioenergetics (LBFA), University Grenoble Alpes, INSERM U1055, 38000 Grenoble, France; (E.P.); (G.E.S.)
| | - Pascal Mossuz
- Department of Biological Hematology, Institute of Biology and Pathology, Hospital of Grenoble Alpes (CHUGA), CS 20217, 38043 Grenoble, CEDEX a9, France;
- Team “Epigenetic and Cellular Signaling”, Institute for Advanced Biosciences, University Grenoble Alpes (UGA), INSERM U1209/CNRS 5309, 38700 Grenoble, France
| | - Jean-Marc Moulis
- Laboratory of Fundamental and Applied Bioenergetics (LBFA), University Grenoble Alpes, INSERM U1055, 38000 Grenoble, France; (E.P.); (G.E.S.)
- University Grenoble Alpes, CEA, IRIG, 38000 Grenoble, France
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2
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Storozynsky QT, Han X, Komant S, Agopsowicz KC, Potts KG, Gamper AM, Godbout R, Evans DH, Hitt MM. Radiation-Induced Cellular Senescence Reduces Susceptibility of Glioblastoma Cells to Oncolytic Vaccinia Virus. Cancers (Basel) 2023; 15:3341. [PMID: 37444452 DOI: 10.3390/cancers15133341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 06/15/2023] [Accepted: 06/16/2023] [Indexed: 07/15/2023] Open
Abstract
Glioblastoma (GBM) is a malignant brain cancer refractory to the current standard of care, prompting an extensive search for novel strategies to improve outcomes. One approach under investigation is oncolytic virus (OV) therapy in combination with radiotherapy. In addition to the direct cytocidal effects of radiotherapy, radiation induces cellular senescence in GBM cells. Senescent cells cease proliferation but remain viable and are implicated in promoting tumor progression. The interaction of viruses with senescent cells is nuanced; some viruses exploit the senescent state to their benefit, while others are hampered, indicating senescence-associated antiviral activity. It is unknown how radiation-induced cellular senescence may impact the oncolytic properties of OVs based on the vaccinia virus (VACV) that are used in combination with radiotherapy. To better understand this, we induced cellular senescence by treating GBM cells with radiation, and then evaluated the growth kinetics, infectivity, and cytotoxicity of an oncolytic VACV, ∆F4LΔJ2R, as well as wild-type VACV in irradiated senescence-enriched and non-irradiated human GBM cell lines. Our results show that both viruses display attenuated oncolytic activities in irradiated senescence-enriched GBM cell populations compared to non-irradiated controls. These findings indicate that radiation-induced cellular senescence is associated with antiviral activity and highlight important considerations for the combination of VACV-based oncolytic therapies with senescence-inducing agents such as radiotherapy.
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Affiliation(s)
- Quinn T Storozynsky
- Department of Oncology, University of Alberta, Edmonton, AB T6G 1Z2, Canada
- Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB T6G 2E1, Canada
- Cancer Research Institute of Northern Alberta (CRINA), University of Alberta, Edmonton, AB T6G 2R3, Canada
| | - Xuefei Han
- Department of Oncology, University of Alberta, Edmonton, AB T6G 1Z2, Canada
| | - Shae Komant
- Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB T6G 2E1, Canada
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB T6G 2R3, Canada
| | - Kate C Agopsowicz
- Department of Oncology, University of Alberta, Edmonton, AB T6G 1Z2, Canada
| | - Kyle G Potts
- Alberta Children's Hospital Research Institute, Faculty of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
- Arnie Charbonneau Cancer Institute, Faculty of Medicine, University of Calgary, Calgary, AB T2N 4Z6, Canada
- Alberta Cellular Therapy and Immune Oncology (ACTION) Initiative, Faculty of Medicine, University of Calgary, Calgary, AB T2N 4Z6, Canada
| | - Armin M Gamper
- Department of Oncology, University of Alberta, Edmonton, AB T6G 1Z2, Canada
- Cross Cancer Institute, Edmonton, AB T6G 1Z2, Canada
| | - Roseline Godbout
- Department of Oncology, University of Alberta, Edmonton, AB T6G 1Z2, Canada
- Cancer Research Institute of Northern Alberta (CRINA), University of Alberta, Edmonton, AB T6G 2R3, Canada
- Cross Cancer Institute, Edmonton, AB T6G 1Z2, Canada
| | - David H Evans
- Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB T6G 2E1, Canada
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB T6G 2R3, Canada
| | - Mary M Hitt
- Department of Oncology, University of Alberta, Edmonton, AB T6G 1Z2, Canada
- Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB T6G 2E1, Canada
- Cancer Research Institute of Northern Alberta (CRINA), University of Alberta, Edmonton, AB T6G 2R3, Canada
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3
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Kitab B, Tsukiyama-Kohara K. Regulatory Role of Ribonucleotide Reductase Subunit M2 in Hepatocyte Growth and Pathogenesis of Hepatitis C Virus. Int J Mol Sci 2023; 24:ijms24032619. [PMID: 36768940 PMCID: PMC9916403 DOI: 10.3390/ijms24032619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/27/2023] [Accepted: 01/27/2023] [Indexed: 01/31/2023] Open
Abstract
Hepatitis C virus (HCV) frequently causes chronic infection in the human liver, which may progress to advanced hepatic fibrosis, cirrhosis, and hepatocellular carcinoma. HCV primarily infects highly differentiated quiescent hepatocytes and can modulate cell cycle-regulatory genes and proliferation pathways, which ultimately contribute to persistent infection and pathogenesis. On the other hand, several studies have shown differential regulation of HCV RNA and viral protein expression levels, depending on the proliferation state of hepatocytes and the phase of the cell cycle. HCV typically requires factors provided by host cells for efficient and persistent viral replication. Previously, we found that HCV infection upregulates the expression of ribonucleotide reductase subunit M2 (RRM2) in quiescent hepatocytes. RRM2 is a rate-limiting protein that catalyzes de novo synthesis of deoxyribonucleotide triphosphates, and its expression is highly regulated during various phases of the cell cycle. RRM2 functions as a pro-viral factor essential for HCV RNA synthesis, but its functional role in HCV-induced liver diseases remains unknown. Here, we present a comprehensive review of the role of the hepatocyte cell cycle, in correlation with RRM2 expression, in the regulation of HCV replication. We also discuss the potential relevance of this protein in the pathogenesis of HCV, particularly in the development of hepatocellular carcinoma.
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Bowen NE, Oo A, Kim B. Mechanistic Interplay between HIV-1 Reverse Transcriptase Enzyme Kinetics and Host SAMHD1 Protein: Viral Myeloid-Cell Tropism and Genomic Mutagenesis. Viruses 2022; 14:v14081622. [PMID: 35893688 PMCID: PMC9331428 DOI: 10.3390/v14081622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 07/21/2022] [Accepted: 07/22/2022] [Indexed: 11/23/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) has been the primary interest among studies on antiviral discovery, viral replication kinetics, drug resistance, and viral evolution. Following infection and entry into target cells, the HIV-1 core disassembles, and the viral RT concomitantly converts the viral RNA into double-stranded proviral DNA, which is integrated into the host genome. The successful completion of the viral life cycle highly depends on the enzymatic DNA polymerase activity of RT. Furthermore, HIV-1 RT has long been known as an error-prone DNA polymerase due to its lack of proofreading exonuclease properties. Indeed, the low fidelity of HIV-1 RT has been considered as one of the key factors in the uniquely high rate of mutagenesis of HIV-1, which leads to efficient viral escape from immune and therapeutic antiviral selective pressures. Interestingly, a series of studies on the replication kinetics of HIV-1 in non-dividing myeloid cells and myeloid specific host restriction factor, SAM domain, and HD domain-containing protein, SAMHD1, suggest that the myeloid cell tropism and high rate of mutagenesis of HIV-1 are mechanistically connected. Here, we review not only HIV-1 RT as a key antiviral target, but also potential evolutionary and mechanistic crosstalk among the unique enzymatic features of HIV-1 RT, the replication kinetics of HIV-1, cell tropism, viral genetic mutation, and host SAMHD1 protein.
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Affiliation(s)
- Nicole E. Bowen
- Department of Pediatrics, School of Medicine, Emory University, Atlanta, GA 30329, USA; (N.E.B.); (A.O.)
| | - Adrian Oo
- Department of Pediatrics, School of Medicine, Emory University, Atlanta, GA 30329, USA; (N.E.B.); (A.O.)
| | - Baek Kim
- Department of Pediatrics, School of Medicine, Emory University, Atlanta, GA 30329, USA; (N.E.B.); (A.O.)
- Center for Drug Discovery, Children’s Healthcare of Atlanta, Atlanta, GA 30329, USA
- Correspondence:
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Bajagai YS, Petranyi F, J Yu S, Lobo E, Batacan R, Kayal A, Horyanto D, Ren X, M Whitton M, Stanley D. Phytogenic supplement containing menthol, carvacrol and carvone ameliorates gut microbiota and production performance of commercial layers. Sci Rep 2022; 12:11033. [PMID: 35773309 PMCID: PMC9246849 DOI: 10.1038/s41598-022-14925-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 06/15/2022] [Indexed: 11/17/2022] Open
Abstract
Consumer push towards open and free-range production systems makes biosecurity on farms challenging, leading to increased disease and animal welfare issues. Phytogenic products are increasingly becoming a viable alternative for the use of antibiotics in livestock production. Here we present a study of the effects of commercial phytogenic supplement containing menthol, carvacrol and carvone on intestinal microbiota of layer hens, microbial functional capacity, and intestinal morphology. A total of 40,000 pullets were randomly assigned to two sides of the experimental shed. Growth performance, mortality, egg production and egg quality parameters were recorded throughout the trial period (18–30 weeks of age). Microbial community was investigated using 16S amplicon sequencing and functional difference using metagenomic sequencing. Phytogen supplemented birds had lower mortality and number of dirty eggs, and their microbial communities showed reduced richness. Although phytogen showed the ability to control the range of poultry pathogens, its action was not restricted to pathogenic taxa, and it involved functional remodelling the intestinal community towards increased cofactor production, heterolactic fermentation and salvage and recycling of metabolites. The phytogen did not alter the antimicrobial resistance profile or the number of antibiotic resistance genes. The study indicates that phytogenic supplementation can mimic the action of antibiotics in altering the gut microbiota and be used as their alternative in industry-scale layer production.
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Affiliation(s)
- Yadav S Bajagai
- Institute for Future Farming Systems, Central Queensland University, Rockhampton, QLD, 4702, Australia
| | - Friedrich Petranyi
- Institute for Future Farming Systems, Central Queensland University, Rockhampton, QLD, 4702, Australia
| | - Sung J Yu
- Institute for Future Farming Systems, Central Queensland University, Rockhampton, QLD, 4702, Australia
| | - Edina Lobo
- Institute for Future Farming Systems, Central Queensland University, Rockhampton, QLD, 4702, Australia
| | - Romeo Batacan
- Institute for Future Farming Systems, Central Queensland University, Rockhampton, QLD, 4702, Australia
| | - Advait Kayal
- Institute for Future Farming Systems, Central Queensland University, Rockhampton, QLD, 4702, Australia
| | - Darwin Horyanto
- Institute for Future Farming Systems, Central Queensland University, Rockhampton, QLD, 4702, Australia
| | - Xipeng Ren
- Institute for Future Farming Systems, Central Queensland University, Rockhampton, QLD, 4702, Australia
| | - Maria M Whitton
- Institute for Future Farming Systems, Central Queensland University, Rockhampton, QLD, 4702, Australia
| | - Dragana Stanley
- Institute for Future Farming Systems, Central Queensland University, Rockhampton, QLD, 4702, Australia.
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6
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Causes and consequences of DNA damage-induced autophagy. Matrix Biol 2021; 100-101:39-53. [DOI: 10.1016/j.matbio.2021.02.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 02/12/2021] [Accepted: 02/12/2021] [Indexed: 02/06/2023]
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7
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SAMHD1 Functions and Human Diseases. Viruses 2020; 12:v12040382. [PMID: 32244340 PMCID: PMC7232136 DOI: 10.3390/v12040382] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 03/27/2020] [Accepted: 03/28/2020] [Indexed: 12/12/2022] Open
Abstract
Deoxynucleoside triphosphate (dNTP) molecules are essential for the replication and maintenance of genomic information in both cells and a variety of viral pathogens. While the process of dNTP biosynthesis by cellular enzymes, such as ribonucleotide reductase (RNR) and thymidine kinase (TK), has been extensively investigated, a negative regulatory mechanism of dNTP pools was recently found to involve sterile alpha motif (SAM) domain and histidine-aspartate (HD) domain-containing protein 1, SAMHD1. When active, dNTP triphosphohydrolase activity of SAMHD1 degrades dNTPs into their 2'-deoxynucleoside (dN) and triphosphate subparts, steadily depleting intercellular dNTP pools. The differential expression levels and activation states of SAMHD1 in various cell types contributes to unique dNTP pools that either aid (i.e., dividing T cells) or restrict (i.e., nondividing macrophages) viral replication that consumes cellular dNTPs. Genetic mutations in SAMHD1 induce a rare inflammatory encephalopathy called Aicardi-Goutières syndrome (AGS), which phenotypically resembles viral infection. Recent publications have identified diverse roles for SAMHD1 in double-stranded break repair, genome stability, and the replication stress response through interferon signaling. Finally, a series of SAMHD1 mutations were also reported in various cancer cell types while why SAMHD1 is mutated in these cancer cells remains to investigated. Here, we reviewed a series of studies that have begun illuminating the highly diverse roles of SAMHD1 in virology, immunology, and cancer biology.
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8
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Zhou X, Curbo S, Zhao Q, Krishnan S, Kuiper R, Karlsson A. Severe mtDNA depletion and dependency on catabolic lipid metabolism in DGUOK knockout mice. Hum Mol Genet 2020; 28:2874-2884. [PMID: 31127938 DOI: 10.1093/hmg/ddz103] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 05/06/2019] [Accepted: 05/13/2019] [Indexed: 12/26/2022] Open
Abstract
Deoxyguanosine kinase (DGUOK) provides guanosine and adenosine nucleotides for mitochondrial DNA (mtDNA) replication, and its deficiency in humans leads to hepatocerebral mtDNA depletion syndrome or to isolated hepatic disease. There are poor treatment options for DGUOK deficiency and the aim of this study was to generate a model for further studies of the disease that could reveal novel treatment strategies. We report a Dguok-deficient mouse strain that, similar to humans, is most severely affected in the liver. The Dguok complete knockout mice (Dguok-/-) were born normal, but began to lose weight at week 6. A change of fur color from black to blueish grey started at week 16 and was complete at week 20. The movements and behavior were indistinguishable compared to wild-type (wt) mice. A decrease of mtDNA copy number occurred in multiple tissues, with the liver being the most severely affected. The mtDNA-encoded protein cytochrome c oxidase was much lower in Dguok-/- liver tissue than in the wt, whereas the expression of the nuclear-encoded succinate dehydrogenase complex subunit A was unaffected. Histopathology showed severe alterations and immunohistochemistry showed signs of both oxidative stress and regeneration in Dguok-/- liver. The subcutaneous fat layer was undetectable in Dguok-/-, which, in addition to gene expression analysis, indicated an altered lipid metabolism. We conclude that Dguok has a major role for the synthesis of deoxyribonucleotides for mtDNA replication particularly in the liver, similar to the human disorder. Our data also show a catabolic lipid metabolism in liver tissue of Dguok-/-.
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Affiliation(s)
- Xiaoshan Zhou
- Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, 141 86 Stockholm, Sweden
| | - Sophie Curbo
- Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, 141 86 Stockholm, Sweden
| | - Qian Zhao
- Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, 141 86 Stockholm, Sweden
| | - Shuba Krishnan
- Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, 141 86 Stockholm, Sweden
| | - Raoul Kuiper
- Division of Pathology, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, 141 86 Stockholm, Sweden
| | - Anna Karlsson
- Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institute, Karolinska University Hospital, 141 86 Stockholm, Sweden
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9
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Lan X, Field MS, Stover PJ. Cell cycle regulation of folate-mediated one-carbon metabolism. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2018; 10:e1426. [DOI: 10.1002/wsbm.1426] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 04/26/2018] [Accepted: 04/27/2018] [Indexed: 12/25/2022]
Affiliation(s)
- Xu Lan
- Division of Nutritional Sciences; Cornell University; Ithaca New York
| | - Martha S. Field
- Division of Nutritional Sciences; Cornell University; Ithaca New York
| | - Patrick J. Stover
- Division of Nutritional Sciences; Cornell University; Ithaca New York
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10
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Song Y, Marmion RA, Park JO, Biswas D, Rabinowitz JD, Shvartsman SY. Dynamic Control of dNTP Synthesis in Early Embryos. Dev Cell 2017; 42:301-308.e3. [PMID: 28735680 DOI: 10.1016/j.devcel.2017.06.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 05/13/2017] [Accepted: 06/16/2017] [Indexed: 02/06/2023]
Abstract
Exponential increase of cell numbers in early embryos requires large amounts of DNA precursors (deoxyribonucleoside triphosphates (dNTPs)). Little is understood about how embryos satisfy this demand. We examined dNTP metabolism in the early Drosophila embryo, in which gastrulation is preceded by 13 sequential nuclear cleavages within only 2 hr of fertilization. Surprisingly, despite the breakneck speed at which Drosophila embryos synthesize DNA, maternally deposited dNTPs can generate less than half of the genomes needed to reach gastrulation. The rest of the dNTPs are synthesized "on the go." The rate-limiting enzyme of dNTP synthesis, ribonucleotide reductase, is inhibited by endogenous levels of deoxyATP (dATP) present at fertilization and is activated as dATP is depleted via DNA polymerization. This feedback inhibition renders the concentration of dNTPs at gastrulation robust, with respect to large variations in maternal supplies, and is essential for normal progression of embryogenesis.
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Affiliation(s)
- Yonghyun Song
- The Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Robert A Marmion
- The Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Junyoung O Park
- The Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Debopriyo Biswas
- The Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Joshua D Rabinowitz
- The Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Stanislav Y Shvartsman
- The Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA; Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544, USA.
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11
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The Cell Killing Mechanisms of Hydroxyurea. Genes (Basel) 2016; 7:genes7110099. [PMID: 27869662 PMCID: PMC5126785 DOI: 10.3390/genes7110099] [Citation(s) in RCA: 126] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 11/03/2016] [Accepted: 11/09/2016] [Indexed: 11/23/2022] Open
Abstract
Hydroxyurea is a well-established inhibitor of ribonucleotide reductase that has a long history of scientific interest and clinical use for the treatment of neoplastic and non-neoplastic diseases. It is currently the staple drug for the management of sickle cell anemia and chronic myeloproliferative disorders. Due to its reversible inhibitory effect on DNA replication in various organisms, hydroxyurea is also commonly used in laboratories for cell cycle synchronization or generating replication stress. However, incubation with high concentrations or prolonged treatment with low doses of hydroxyurea can result in cell death and the DNA damage generated at arrested replication forks is generally believed to be the direct cause. Recent studies in multiple model organisms have shown that oxidative stress and several other mechanisms may contribute to the majority of the cytotoxic effect of hydroxyurea. This review aims to summarize the progress in our understanding of the cell-killing mechanisms of hydroxyurea, which may provide new insights towards the improvement of chemotherapies that employ this agent.
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12
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Anacker DC, Aloor HL, Shepard CN, Lenzi GM, Johnson BA, Kim B, Moody CA. HPV31 utilizes the ATR-Chk1 pathway to maintain elevated RRM2 levels and a replication-competent environment in differentiating Keratinocytes. Virology 2016; 499:383-396. [PMID: 27764728 DOI: 10.1016/j.virol.2016.09.028] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 09/26/2016] [Accepted: 09/27/2016] [Indexed: 01/19/2023]
Abstract
Productive replication of human papillomaviruses (HPV) is restricted to the uppermost layers of the differentiating epithelia. How HPV ensures an adequate supply of cellular substrates for viral DNA synthesis in a differentiating environment is unclear. Here, we demonstrate that HPV31 positive cells exhibit increased dNTP pools and levels of RRM2, a component of the ribonucleotide reductase (RNR) complex, which is required for de novo synthesis of dNTPs. RRM2 depletion blocks productive replication, suggesting RRM2 provides dNTPs for viral DNA synthesis in differentiating cells. We demonstrate that HPV31 regulates RRM2 levels through expression of E7 and activation of the ATR-Chk1-E2F1 DNA damage response, which is essential to combat replication stress upon entry into S-phase, as well as for productive replication. Our findings suggest a novel way in which viral DNA synthesis is regulated through activation of ATR and Chk1 and highlight an intriguing new virus/host interaction utilized for viral replication.
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Affiliation(s)
- Daniel C Anacker
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, North Carolina, USA
| | - Heather L Aloor
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, North Carolina, USA
| | - Caitlin N Shepard
- The Center for Drug Discovery, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA
| | - Gina M Lenzi
- The Center for Drug Discovery, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA
| | - Bryan A Johnson
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, North Carolina, USA
| | - Baek Kim
- The Center for Drug Discovery, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA; Children's Healthcare of Atlanta, USA
| | - Cary A Moody
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, North Carolina, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, North Carolina, USA.
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13
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Watson E, Yilmaz LS, Walhout AJM. Understanding Metabolic Regulation at a Systems Level: Metabolite Sensing, Mathematical Predictions, and Model Organisms. Annu Rev Genet 2016; 49:553-75. [PMID: 26631516 DOI: 10.1146/annurev-genet-112414-055257] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Metabolic networks are extensively regulated to facilitate tissue-specific metabolic programs and robustly maintain homeostasis in response to dietary changes. Homeostatic metabolic regulation is achieved through metabolite sensing coupled to feedback regulation of metabolic enzyme activity or expression. With a wealth of transcriptomic, proteomic, and metabolomic data available for different cell types across various conditions, we are challenged with understanding global metabolic network regulation and the resulting metabolic outputs. Stoichiometric metabolic network modeling integrated with "omics" data has addressed this challenge by generating nonintuitive, testable hypotheses about metabolic flux rewiring. Model organism studies have also yielded novel insight into metabolic networks. This review covers three topics: the feedback loops inherent in metabolic regulatory networks, metabolic network modeling, and interspecies studies utilizing Caenorhabditis elegans and various bacterial diets that have revealed novel metabolic paradigms.
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Affiliation(s)
- Emma Watson
- Program in Systems Biology, Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605; , ,
| | - L Safak Yilmaz
- Program in Systems Biology, Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605; , ,
| | - Albertha J M Walhout
- Program in Systems Biology, Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605; , ,
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14
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Jang S, Zhou X, Ahn J. Substrate Specificity of SAMHD1 Triphosphohydrolase Activity Is Controlled by Deoxyribonucleoside Triphosphates and Phosphorylation at Thr592. Biochemistry 2016; 55:5635-5646. [PMID: 27588835 DOI: 10.1021/acs.biochem.6b00627] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The sterile alpha motif (SAM) and histidine-aspartate (HD) domain containing protein 1 (SAMHD1) constitute a triphosphohydrolase that converts deoxyribonucleoside triphosphates (dNTPs) into deoxyribonucleosides and triphosphates. SAMHD1 exists in multiple states. The monomer and apo- or GTP-bound dimer are catalytically inactive. Binding of dNTP at allosteric site 2 (AS2), adjacent to GTP-binding allosteric site 1 (AS1), induces formation of the tetramer, the catalytically active form. We have developed an enzyme kinetic assay, tailored to control specific dNTP binding at each site, allowing us to determine the kinetic binding parameters of individual dNTPs at both the AS2 and catalytic sites for all possible combinations of dNTP binding at both sites. Here, we show that the apparent Km values of dNTPs at AS2 vary in the order of dCTP < dGTP < dATP < dTTP. Interestingly, dCTP binding at AS2 significantly reduces the dCTP hydrolysis rate, which is restored to a rate comparable to that of other dNTPs upon dGTP, dATP, or dTTP binding at AS2. Strikingly, a phosphomimetic mutant, Thr592Asp SAMHD1 as well as phospho-Thr592, show a significantly altered substrate specificity, with the rate of dCTP hydrolysis being selectively reduced regardless of which dNTP binds at AS2. Furthermore, cyclin A2 binding at the C-terminus of SAMHD1 induces the disassembly of the SAMHD1 tetramer, suggesting an additional layer of SAMHD1 activity modulation by cyclin A2/CDK2 kinase. Together, our results reveal multiple allosteric mechanisms for controlling the rate of dNTP destruction by SAMHD1.
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Affiliation(s)
- Sunbok Jang
- Department of Structural Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States
| | - Xiaohong Zhou
- Department of Structural Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States
| | - Jinwoo Ahn
- Department of Structural Biology, University of Pittsburgh School of Medicine , Pittsburgh, Pennsylvania 15260, United States
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Human Cytomegalovirus Can Procure Deoxyribonucleotides for Viral DNA Replication in the Absence of Retinoblastoma Protein Phosphorylation. J Virol 2016; 90:8634-43. [PMID: 27440891 DOI: 10.1128/jvi.00731-16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 07/13/2016] [Indexed: 01/31/2023] Open
Abstract
UNLABELLED Viral DNA replication requires deoxyribonucleotide triphosphates (dNTPs). These molecules, which are found at low levels in noncycling cells, are generated either by salvage pathways or through de novo synthesis. Nucleotide synthesis utilizes the activity of a series of nucleotide-biosynthetic enzymes (NBEs) whose expression is repressed in noncycling cells by complexes between the E2F transcription factors and the retinoblastoma (Rb) tumor suppressor. Rb-E2F complexes are dissociated and NBE expression is activated during cell cycle transit by cyclin-dependent kinase (Cdk)-mediated Rb phosphorylation. The DNA virus human cytomegalovirus (HCMV) encodes a viral Cdk (v-Cdk) (the UL97 protein) that phosphorylates Rb, induces the expression of cellular NBEs, and is required for efficient viral DNA synthesis. A long-held hypothesis proposed that viral proteins with Rb-inactivating activities functionally similar to those of UL97 facilitated viral DNA replication in part by inducing the de novo production of dNTPs. However, we found that dNTPs were limiting even in cells infected with wild-type HCMV in which UL97 is expressed and Rb is phosphorylated. Furthermore, we revealed that both de novo and salvage pathway enzymes contribute to viral DNA replication during HCMV infection and that Rb phosphorylation by cellular Cdks does not correct the viral DNA replication defect observed in cells infected with a UL97-deficient virus. We conclude that HCMV can obtain dNTPs in the absence of Rb phosphorylation and that UL97 can contribute to the efficiency of DNA replication in an Rb phosphorylation-independent manner. IMPORTANCE Transforming viral oncoproteins, such as adenovirus E1A and papillomavirus E7, inactivate Rb. The standard hypothesis for how Rb inactivation facilitates infection with these viruses is that it is through an increase in the enzymes required for DNA synthesis, which include nucleotide-biosynthetic enzymes. However, HCMV UL97, which functionally mimics these viral oncoproteins through phosphorylation of Rb, fails to induce the production of nonlimiting amounts of dNTPs. This finding challenges the paradigm of the role of Rb inactivation during DNA virus infection and uncovers the existence of an alternative mechanism by which UL97 contributes to HCMV DNA synthesis. The ineffectiveness of the UL97 inhibitor maribavir in clinical trials might be better explained with a fuller understanding of the role of UL97 during infection. Furthermore, as the nucleoside analog ganciclovir is the current drug of choice for treating HCMV, knowing the provenance of the dNTPs incorporated into viral DNA may help inform antiviral therapeutic regimens.
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Daly MB, Roth ME, Bonnac L, Maldonado JO, Xie J, Clouser CL, Patterson SE, Kim B, Mansky LM. Dual anti-HIV mechanism of clofarabine. Retrovirology 2016; 13:20. [PMID: 27009333 PMCID: PMC4806454 DOI: 10.1186/s12977-016-0254-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 03/17/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND HIV-1 replication kinetics inherently depends on the availability of cellular dNTPs for viral DNA synthesis. In activated CD4(+) T cells and other rapidly dividing cells, the concentrations of dNTPs are high and HIV-1 reverse transcription occurs in an efficient manner. In contrast, nondividing cells such as macrophages have lower dNTP pools, which restricts efficient reverse transcription. Clofarabine is an FDA approved ribonucleotide reductase inhibitor, which has shown potent antiretroviral activity in transformed cell lines. Here, we explore the potency, toxicity and mechanism of action of clofarabine in the human primary HIV-1 target cells: activated CD4(+) T cells and macrophages. RESULTS Clofarabine is a potent HIV-1 inhibitor in both activated CD4(+) T cells and macrophages. Due to its minimal toxicity in macrophages, clofarabine displays a selectivity index over 300 in this nondividing cell type. The anti-HIV-1 activity of clofarabine correlated with a significant decrease in both cellular dNTP levels and viral DNA synthesis. Additionally, we observed that clofarabine triphosphate was directly incorporated into DNA by HIV-1 reverse transcriptase and blocked processive DNA synthesis, particularly at the low dNTP levels found in macrophages. CONCLUSIONS Taken together, these data provide strong mechanistic evidence that clofarabine is a dual action inhibitor of HIV-1 replication that both limits dNTP substrates for viral DNA synthesis and directly inhibits the DNA polymerase activity of HIV-1 reverse transcriptase.
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Affiliation(s)
- Michele B Daly
- Center for Drug Discovery, Department of Pediatrics, Emory Center for AIDS Research, Emory University, Children's Healthcare of Atlanta, 1760 Haygood Dr., Atlanta, GA, 30322, USA
| | - Megan E Roth
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware St SE, Minneapolis, MN, 55455, USA.,Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, 55455, USA.,Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Laurent Bonnac
- Center for Drug Design, Academic Health Center, University of Minnesota, Minneapolis, MN, 55455, USA
| | - José O Maldonado
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware St SE, Minneapolis, MN, 55455, USA.,Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, 55455, USA.,Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Jiashu Xie
- Center for Drug Design, Academic Health Center, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Christine L Clouser
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware St SE, Minneapolis, MN, 55455, USA
| | - Steven E Patterson
- Center for Drug Design, Academic Health Center, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Baek Kim
- Center for Drug Discovery, Department of Pediatrics, Emory Center for AIDS Research, Emory University, Children's Healthcare of Atlanta, 1760 Haygood Dr., Atlanta, GA, 30322, USA.
| | - Louis M Mansky
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware St SE, Minneapolis, MN, 55455, USA. .,Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, 55455, USA. .,Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN, 55455, USA. .,Center for Drug Design, Academic Health Center, University of Minnesota, Minneapolis, MN, 55455, USA.
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Kirschbaum MH, Frankel P, Synold TW, Xie Z, Yen Y, Popplewell L, Chen R, Aljitawi O, Tuscano JM, Chan KK, Newman EM. A phase I pharmacodynamic study of GTI-2040, an antisense oligonucleotide against ribonuclotide reductase, in acute leukemias: a California Cancer Consortium study. Leuk Lymphoma 2016; 57:2307-14. [PMID: 26895565 DOI: 10.3109/10428194.2016.1146947] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We performed a phase I study of GTI-2040, an antisense oligonucleotide against ribonucleotide reductase mRNA, on a novel dosing schedule of days 1-4 and 15-18 by continuous infusion to examine efficacy and tolerability in patients with leukemia. A dose of 11 mg/kg/d was safely reached. Dose-limiting toxicities (DLTs) at the higher levels included elevated troponin I and liver function enzymes. There were no objective responses to GTI-2040 in this study; 7/24 patients were able to complete the predetermined three infusion cycles. Pharmacokinetic and pharmacodynamic studies were performed, indicating a trend towards increasing intracellular drug levels and decreasing RRM2 gene expression with increasing doses. This dose schedule may be considered if appropriate combinations are identified in preclinical studies.
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Affiliation(s)
| | - Paul Frankel
- a City of Hope Comprehensive Cancer Center , Duarte , CA , USA
| | | | - Zhiliang Xie
- b Ohio State University Comprehensive Cancer Center , Columbus , OH , USA
| | - Yun Yen
- a City of Hope Comprehensive Cancer Center , Duarte , CA , USA
| | | | - Robert Chen
- a City of Hope Comprehensive Cancer Center , Duarte , CA , USA
| | - Omar Aljitawi
- a City of Hope Comprehensive Cancer Center , Duarte , CA , USA
| | - Joseph M Tuscano
- c Davis Comprehensive Cancer Center, University of California , Sacramento , CA , USA
| | - Kenneth K Chan
- b Ohio State University Comprehensive Cancer Center , Columbus , OH , USA
| | - Edward M Newman
- a City of Hope Comprehensive Cancer Center , Duarte , CA , USA
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dNTP pool levels modulate mutator phenotypes of error-prone DNA polymerase ε variants. Proc Natl Acad Sci U S A 2015; 112:E2457-66. [PMID: 25827226 DOI: 10.1073/pnas.1422948112] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mutator phenotypes create genetic diversity that fuels tumor evolution. DNA polymerase (Pol) ε mediates leading strand DNA replication. Proofreading defects in this enzyme drive a number of human malignancies. Here, using budding yeast, we show that mutator variants of Pol ε depend on damage uninducible (Dun)1, an S-phase checkpoint kinase that maintains dNTP levels during a normal cell cycle and up-regulates dNTP synthesis upon checkpoint activation. Deletion of DUN1 (dun1Δ) suppresses the mutator phenotype of pol2-4 (encoding Pol ε proofreading deficiency) and is synthetically lethal with pol2-M644G (encoding altered Pol ε base selectivity). Although pol2-4 cells cycle normally, pol2-M644G cells progress slowly through S-phase. The pol2-M644G cells tolerate deletions of mediator of the replication checkpoint (MRC) 1 (mrc1Δ) and radiation sensitive (Rad) 9 (rad9Δ), which encode mediators of checkpoint responses to replication stress and DNA damage, respectively. The pol2-M644G mutator phenotype is partially suppressed by mrc1Δ but not rad9Δ; neither deletion suppresses the pol2-4 mutator phenotype. Thus, checkpoint activation augments the Dun1 effect on replication fidelity but is not required for it. Deletions of genes encoding key Dun1 targets that negatively regulate dNTP synthesis, suppress the dun1Δ pol2-M644G synthetic lethality and restore the mutator phenotype of pol2-4 in dun1Δ cells. DUN1 pol2-M644G cells have constitutively high dNTP levels, consistent with checkpoint activation. In contrast, pol2-4 and POL2 cells have similar dNTP levels, which decline in the absence of Dun1 and rise in the absence of the negative regulators of dNTP synthesis. Thus, dNTP pool levels correlate with Pol ε mutator severity, suggesting that treatments targeting dNTP pools could modulate mutator phenotypes for therapy.
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Nguyen LA, Domaoal RA, Kennedy EM, Kim DH, Schinazi RF, Kim B. Pre-steady state kinetic analysis of HIV-1 reverse transcriptase for non-canonical ribonucleoside triphosphate incorporation and DNA synthesis from ribonucleoside-containing DNA template. Antiviral Res 2015; 115:75-82. [PMID: 25557601 PMCID: PMC4323949 DOI: 10.1016/j.antiviral.2014.12.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Revised: 12/15/2014] [Accepted: 12/22/2014] [Indexed: 12/12/2022]
Abstract
Non-dividing macrophages maintain extremely low cellular deoxyribonucleotide triphosphate (dNTP) levels, but high ribonucleotide triphosphate (rNTP) concentrations. The disparate nucleotide pools kinetically forces Human Immunodeficiency Virus 1 (HIV-1) reverse transcriptase (RT) to incorporate non-canonical rNTPs during reverse transcription. HIV-1 RT pauses near ribonucleoside monophosphates (rNMPs) embedded in the template DNA, which has previously been shown to enhance mismatch extension. Here, pre-steady state kinetic analysis shows rNTP binding affinity (Kd) of HIV-1 RT for non-canonical rNTPs was 1.4- to 43-fold lower, and the rNTP rate of incorporation (kpol) was 15- to 1551-fold slower than for dNTPs. This suggests that RT is more selective for incorporation of dNTPs rather than rNTPs. HIV-1 RT selectivity for dNTP versus rNTP is the lowest for ATP, implying that HIV-1 RT preferentially incorporates ATP when dATP concentration is limited. We observed that incorporation of a dNTP occurring one nucleotide before an embedded rNMP in the template had a 29-fold greater Kd and a 20-fold slower kpol as compared to the same template containing dNMP. This reduced the overall dNTP incorporation efficiency of HIV-1 RT by 581-fold. Finally, the RT mutant Y115F displayed lower discrimination against rNTPs due to its increase in binding affinity for non-canonical rNTPs. Overall, these kinetic results demonstrate that HIV-1 RT utilizes both substrate binding and a conformational change during: (1) enzymatic discrimination of non-canonical rNTPs from dNTPs and (2) during dNTP primer extension with DNA templates containing embedded rNMP.
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Affiliation(s)
- Laura A Nguyen
- Department of Pathology, University of Rochester Medical Center, Rochester, NY, USA
| | - Robert A Domaoal
- Center for Drug Discovery, Emory Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA
| | - Edward M Kennedy
- Department of Pathology, University of Rochester Medical Center, Rochester, NY, USA
| | - Dong-Hyun Kim
- College of Pharmacy, Kyung-Hee University, Seoul, South Korea
| | - Raymond F Schinazi
- Center for Drug Discovery, Emory Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA; Veterans Affairs Medical Center, Decatur, GA, USA
| | - Baek Kim
- Center for Drug Discovery, Emory Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA.
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20
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Zhang C. Essential functions of iron-requiring proteins in DNA replication, repair and cell cycle control. Protein Cell 2014; 5:750-60. [PMID: 25000876 PMCID: PMC4180463 DOI: 10.1007/s13238-014-0083-7] [Citation(s) in RCA: 179] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 05/04/2014] [Indexed: 02/06/2023] Open
Abstract
Eukaryotic cells contain numerous iron-requiring proteins such as iron-sulfur (Fe-S) cluster proteins, hemoproteins and ribonucleotide reductases (RNRs). These proteins utilize iron as a cofactor and perform key roles in DNA replication, DNA repair, metabolic catalysis, iron regulation and cell cycle progression. Disruption of iron homeostasis always impairs the functions of these iron-requiring proteins and is genetically associated with diseases characterized by DNA repair defects in mammals. Organisms have evolved multi-layered mechanisms to regulate iron balance to ensure genome stability and cell development. This review briefly provides current perspectives on iron homeostasis in yeast and mammals, and mainly summarizes the most recent understandings on iron-requiring protein functions involved in DNA stability maintenance and cell cycle control.
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Affiliation(s)
- Caiguo Zhang
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO, 80045, USA,
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21
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ZHANG C, LIU G, HUANG M. Ribonucleotide reductase metallocofactor: assembly, maintenance and inhibition. FRONTIERS IN BIOLOGY 2014; 9:104-113. [PMID: 24899886 PMCID: PMC4041730 DOI: 10.1007/s11515-014-1302-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Ribonucleotide reductase (RNR) supplies cellular deoxyribonucleotide triphosphates (dNTP) pools by converting ribonucleotides to the corresponding deoxy forms using radical-based chemistry. Eukaryotic RNR comprises α and β subunits: α contains the catalytic and allosteric sites; β houses a diferric-tyrosyl radical cofactor (FeIII2-Y•) that is required to initiates nucleotide reduction in α. Cells have evolved multi-layered mechanisms to regulate RNR level and activity in order to maintain the adequate sizes and ratios of their dNTP pools to ensure high-fidelity DNA replication and repair. The central role of RNR in nucleotide metabolism also makes it a proven target of chemotherapeutics. In this review, we discuss recent progress in understanding the function and regulation of eukaryotic RNRs, with a focus on studies revealing the cellular machineries involved in RNR metallocofactor biosynthesis and its implication in RNR-targeting therapeutics.
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Affiliation(s)
- Caiguo ZHANG
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Guoqi LIU
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Mingxia HUANG
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80045, USA
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Shao J, Liu X, Zhu L, Yen Y. Targeting ribonucleotide reductase for cancer therapy. Expert Opin Ther Targets 2013; 17:1423-37. [PMID: 24083455 DOI: 10.1517/14728222.2013.840293] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
INTRODUCTION Ribonucleotide reductase (RR) is a unique enzyme, because it is responsible for reducing ribonucleotides to their corresponding deoxyribonucleotides, which are the building blocks required for DNA replication and repair. Dysregulated RR activity is associated with genomic instability, malignant transformation and cancer development. The use of RR inhibitors, either as a single agent or combined with other therapies, has proven to be a promising approach for treating solid tumors and hematological malignancies. AREAS COVERED This review covers recent publications in the area of RR, which include: i) the structure, function and regulation of RR; ii) the roles of RR in cancer development; iii) the classification, mechanisms and clinical application of RR inhibitors for cancer therapy and iv) strategies for developing novel RR inhibitors in the future. EXPERT OPINION Exploring the possible nonenzymatic roles of RR subunit proteins in carcinogenesis may lead to new rationales for developing novel anticancer drugs. Updated information about the structure and holoenzyme models of RR will help in identifying potential sites in the protein that could be targets for novel RR inhibitors. Determining RR activity and subunit levels in clinical samples will provide a rational platform for developing personalized cancer therapies that use RR inhibitors.
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Affiliation(s)
- Jimin Shao
- Zhejiang University, School of Medicine, Department of Pathology and Pathophysiology , Hangzhou 310058 , China
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23
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p21-mediated RNR2 repression restricts HIV-1 replication in macrophages by inhibiting dNTP biosynthesis pathway. Proc Natl Acad Sci U S A 2013; 110:E3997-4006. [PMID: 24082141 DOI: 10.1073/pnas.1306719110] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Macrophages are a major target cell for HIV-1, and their infection contributes to HIV pathogenesis. We have previously shown that the cyclin-dependent kinase inhibitor p21 inhibits the replication of HIV-1 and other primate lentiviruses in human monocyte-derived macrophages by impairing reverse transcription of the viral genome. In the attempt to understand the p21-mediated restriction mechanisms, we found that p21 impairs HIV-1 and simian immunodeficiency virus (SIV)mac reverse transcription in macrophages by reducing the intracellular deoxyribonucleotide (dNTP) pool to levels below those required for viral cDNA synthesis by a SAM domain and HD domain-containing protein 1 (SAMHD1)-independent pathway. We found that p21 blocks dNTP biosynthesis by down-regulating the expression of the RNR2 subunit of ribonucleotide reductase, an enzyme essential for the reduction of ribonucleotides to dNTP. p21 inhibits RNR2 transcription by repressing E2F1 transcription factor, its transcriptional activator. Our findings unravel a cellular pathway that restricts HIV-1 and other primate lentiviruses by affecting dNTP synthesis, thereby pointing to new potential cellular targets for anti-HIV therapeutic strategies.
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Sandoval MR, Balakrishnan K, Luthra R, Keating M, Gandhi V. DNA repair initiation induces expression of ribonucleotide reductase in human chronic lymphocytic leukemia cells. Leuk Lymphoma 2013; 55:876-83. [PMID: 23772636 DOI: 10.3109/10428194.2013.813497] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mammalian ribonucleotide reductase (RR) is a heterodimer enzyme responsible for maintaining levels of deoxynucleotides needed for DNA replication. The M2 subunit of RR is known to increase in tandem with progression of cells into S phase, whereas the M1 subunit is expressed at steady-state. Since the expression level of the M2 subunit increases because the cells need deoxyribonucleoside triphosphates (dNTPs) for replication, it is logical to hypothesize that the same increase will be seen during DNA repair. To test this, we used chronic lymphocytic leukemia (CLL) cells, which are replicationally quiescent and have low endogenous levels of RR and dNTPs. Cyclophosphamide was selected as the DNA damaging agent because of its clinical use in the treatment of CLL. DNA repair, measured by [(3)H]thymidine incorporation after 4 h treatment with 4-hydroperoxycyclophosphamide, increased in a dose-dependent manner at 3, 10 and 50 μM. The induction of DNA repair concomitantly increased the mRNA and protein levels of M2 subunit (median 1.6-fold; range 0.9-5.3). Maximum induction occurred at 10 μM after 4 h and correlated with [(3)H]thymidine incorporation (p = 0.02). In contrast, no change was observed in mRNA or protein levels of M1 subunit. We conclude that RR is regulated not only during replication but also during DNA repair, and in both cases M2 subunit expression is increased.
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Luo LF, Hou CC, Yang WX. Nuclear factors: roles related to mitochondrial deafness. Gene 2013; 520:79-89. [PMID: 23510774 DOI: 10.1016/j.gene.2013.03.041] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Accepted: 03/08/2013] [Indexed: 12/16/2022]
Abstract
Hearing loss (HL) is a common disorder with mitochondrial dysfunction as one of the major causes leading to deafness. Mitochondrial dysfunction may be caused by either mutations in nuclear genes leading to defective nuclear-encoded proteins or mutations in mitochondrial genes leading to defective mitochondrial-encoded products. The specific nuclear genes involved in HL can be classified into two categories depending on whether mitochondrial gene mutations co-exist (modifier genes) or not (deafness-causing genes). TFB1M, MTO1, GTPBP3, and TRMU are modifier genes. A mutation in any of these modifier genes may lead to a deafness phenotype when accompanied by the mitochondrial gene mutation. OPA1, TIMM8A, SMAC/DIABLO, MPV17, PDSS1, BCS1L, SUCLA2, C10ORF2, COX10, PLOG1and RRM2B are deafness-causing genes. A mutation in any of these deafness-causing genes will directly induce variable phenotypic HL.
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Affiliation(s)
- Ling-Feng Luo
- Institute of Cell and Developmental Biology, Zhejiang University, Hangzhou 310058, China
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Nishigaki M, Kawada Y, Misaki T, Murata K, Goshima T, Hirokawa T, Yamada C, Shimada M, Nakanishi M. Mitotic phosphorylation of MPP8 by cyclin-dependent kinases regulates chromatin dissociation. Biochem Biophys Res Commun 2013; 432:654-9. [DOI: 10.1016/j.bbrc.2013.02.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 02/04/2013] [Indexed: 11/26/2022]
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Frangini M, Franzolin E, Chemello F, Laveder P, Romualdi C, Bianchi V, Rampazzo C. Synthesis of mitochondrial DNA precursors during myogenesis, an analysis in purified C2C12 myotubes. J Biol Chem 2013; 288:5624-35. [PMID: 23297407 PMCID: PMC3581417 DOI: 10.1074/jbc.m112.441147] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
During myogenesis, myoblasts fuse into multinucleated myotubes that acquire the contractile fibrils and accessory structures typical of striated skeletal muscle fibers. To support the high energy requirements of muscle contraction, myogenesis entails an increase in mitochondrial (mt) mass with stimulation of mtDNA synthesis and consumption of DNA precursors (dNTPs). Myotubes are quiescent cells and as such down-regulate dNTP production despite a high demand for dNTPs. Although myogenesis has been studied extensively, changes in dNTP metabolism have not been examined specifically. In differentiating cultures of C2C12 myoblasts and purified myotubes, we analyzed expression and activities of enzymes of dNTP biosynthesis, dNTP pools, and the expansion of mtDNA. Myotubes exibited pronounced post-mitotic modifications of dNTP synthesis with a particularly marked down-regulation of de novo thymidylate synthesis. Expression profiling revealed the same pattern of enzyme down-regulation in adult murine muscles. The mtDNA increased steadily after myoblast fusion, turning over rapidly, as revealed after treatment with ethidium bromide. We individually down-regulated p53R2 ribonucleotide reductase, thymidine kinase 2, and deoxyguanosine kinase by siRNA transfection to examine how a further reduction of these synthetic enzymes impacted myotube development. Silencing of p53R2 had little effect, but silencing of either mt kinase caused 50% mtDNA depletion and an unexpected decrease of all four dNTP pools independently of the kinase specificity. We suggest that during development of myotubes the shortage of even a single dNTP may affect all four pools through dysregulation of ribonucleotide reduction and/or dissipation of the non-limiting dNTPs during unproductive elongation of new DNA chains.
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Affiliation(s)
- Miriam Frangini
- Department of Biology, University of Padova, 35131 Padova, Italy
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Amie SM, Noble E, Kim B. Intracellular nucleotide levels and the control of retroviral infections. Virology 2012; 436:247-54. [PMID: 23260109 DOI: 10.1016/j.virol.2012.11.010] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Revised: 09/24/2012] [Accepted: 11/17/2012] [Indexed: 11/30/2022]
Abstract
Retroviruses consume cellular deoxynucleoside triphosphates (dNTPs) to convert their RNA genomes into proviral DNA through reverse transcription. While all retroviruses replicate in dividing cells, lentiviruses uniquely replicate in nondividing cells such as macrophages. Importantly, dNTP levels in nondividing cells are extremely low, compared to dividing cells. Indeed, a recently discovered anti-HIV/SIV restriction factor, SAMHD1, which is a dNTP triphosphohydrolase, is responsible for the limited dNTP pool of nondividing cells. Lentiviral reverse transcriptases (RT) uniquely stay functional even at the low dNTP concentrations in nondividing cells. Interestingly, Vpx of HIV-2/SIVsm proteosomally degrades SAMHD1, which elevates cellular dNTP pools and accelerates lentiviral replication in nondividing cells. These Vpx-encoding lentiviruses rapidly replicate in nondividing cells by encoding both highly functional RTs and Vpx. Here, we discuss a series of mechanistic and virological studies that have contributed to conceptually linking cellular dNTP levels and the adaptation of lentiviral replication in nondividing cells.
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Affiliation(s)
- Sarah M Amie
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY, USA
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Mannava S, Moparthy KC, Wheeler LJ, Natarajan V, Zucker SN, Fink EE, Im M, Flanagan S, Burhans WC, Zeitouni NC, Shewach DS, Mathews CK, Nikiforov MA. Depletion of deoxyribonucleotide pools is an endogenous source of DNA damage in cells undergoing oncogene-induced senescence. THE AMERICAN JOURNAL OF PATHOLOGY 2012; 182:142-51. [PMID: 23245831 DOI: 10.1016/j.ajpath.2012.09.011] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 08/10/2012] [Accepted: 09/18/2012] [Indexed: 12/26/2022]
Abstract
In normal human cells, oncogene-induced senescence (OIS) depends on induction of DNA damage response. Oxidative stress and hyperreplication of genomic DNA have been proposed as major causes of DNA damage in OIS cells. Here, we report that down-regulation of deoxyribonucleoside pools is another endogenous source of DNA damage in normal human fibroblasts (NHFs) undergoing HRAS(G12V)-induced senescence. NHF-HRAS(G12V) cells underexpressed thymidylate synthase (TS) and ribonucleotide reductase (RR), two enzymes required for the entire de novo deoxyribonucleotide biosynthesis, and possessed low dNTP levels. Chromatin at the promoters of the genes encoding TS and RR was enriched with retinoblastoma tumor suppressor protein and histone H3 tri-methylated at lysine 9. Importantly, ectopic coexpression of TS and RR or addition of deoxyribonucleosides substantially suppressed DNA damage, senescence-associated phenotypes, and proliferation arrest in two types of NHF-expressing HRAS(G12V). Reciprocally, short hairpin RNA-mediated suppression of TS and RR caused DNA damage and senescence in NHFs, although less efficiently than HRAS(G12V). However, overexpression of TS and RR in quiescent NHFs did not overcome proliferation arrest, suggesting that unlike quiescence, OIS requires depletion of dNTP pools and activated DNA replication. Our data identify a previously unknown role of deoxyribonucleotides in regulation of OIS.
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Affiliation(s)
- Sudha Mannava
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA
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Lu AG, Feng H, Wang PXZ, Han DP, Chen XH, Zheng MH. Emerging roles of the ribonucleotide reductase M2 in colorectal cancer and ultraviolet-induced DNA damage repair. World J Gastroenterol 2012; 18:4704-13. [PMID: 23002339 PMCID: PMC3442208 DOI: 10.3748/wjg.v18.i34.4704] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2012] [Revised: 06/11/2012] [Accepted: 06/28/2012] [Indexed: 02/06/2023] Open
Abstract
AIM To investigate the roles of the ribonucleotide reductase M2 (RRM2) subunit in colorectal cancer (CRC) and ultraviolet (UV)-induced DNA damage repair. METHODS Immunohistochemical staining of tissue microarray was performed to detect the expression of RRM2. Seven CRC cell lines were cultured and three human colon cancer cell lines, i.e., HCT116, SW480 and SW620, were used. Reverse transcription polymerase chain reaction and Western blotting were performed to determine the mRNA and protein expression levels of RRM2, respectively. Cell proliferation assay, cell cycle analysis were performed. Cell apoptosis was evaluated by double staining with fluorescein isothiocyanate-conjugated Annexin V and propidium iodide (PI) using Annexin V/PI apoptosis kit. The motility and invasion of CRC cells were assessed by the Transwell chamber assay. Cells were irradiated with a 254 nm UV-C lamp to detect the UV sensitivity after RRM2 depletion. RESULTS Immunohistochemical staining revealed elevated RRM2 levels in CRC tissues. RRM2 overexpression was positively correlated with invasion depth (P < 0.05), poorly differentiated type (P = 0.0051), and tumor node metastasis stage (P = 0.0015). The expression of RRM2 in HCT116 cells was downregulated after transfection, and HCT116 cell proliferation was obviously suppressed compared to control groups (P < 0.05). In the invasion test, the number of cells that passed through the chambers in the RRM2-siRNA group was 81 ± 3, which was lower than that in the negative control (289 ± 7) and blank control groups (301 ± 7.2). These differences were statistically significant (P < 0.01). Our data suggest that RRM2 overexpression may be associated with CRC progression. RRM2 silencing by siRNA may inhibit the hyperplasia and invasiveness of CRC cells, suggesting that RRM2 may play an important role in the infiltration and metastasis of CRC, which is a potential therapeutic strategy in CRC. In addition, RRM2 depletion increased UV sensitivity. CONCLUSION These findings suggest that RRM2 may be a facilitating factor in colorectal tumorigenesis and UV-induced DNA damage repair.
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Sandvik GK, Tomter AB, Bergan J, Zoppellaro G, Barra AL, Røhr AK, Kolberg M, Ellefsen S, Andersson KK, Nilsson GE. Studies of ribonucleotide reductase in crucian carp-an oxygen dependent enzyme in an anoxia tolerant vertebrate. PLoS One 2012; 7:e42784. [PMID: 22916159 PMCID: PMC3419237 DOI: 10.1371/journal.pone.0042784] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 07/11/2012] [Indexed: 11/19/2022] Open
Abstract
The enzyme ribonucleotide reductase (RNR) catalyzes the conversion of ribonucleotides to deoxyribonucleotides, the precursors for DNA. RNR requires a thiyl radical to activate the substrate. In RNR of eukaryotes (class Ia RNR), this radical originates from a tyrosyl radical formed in reaction with oxygen (O(2)) and a ferrous di-iron center in RNR. The crucian carp (Carassius carassius) is one of very few vertebrates that can tolerate several months completely without oxygen (anoxia), a trait that enables this fish to survive under the ice in small ponds that become anoxic during the winter. Previous studies have found indications of cell division in this fish after 7 days of anoxia. This appears nearly impossible, as DNA synthesis requires the production of new deoxyribonucleotides and therefore active RNR. We have here characterized RNR in crucian carp, to search for adaptations to anoxia. We report the full-length sequences of two paralogs of each of the RNR subunits (R1i, R1ii, R2i, R2ii, p53R2i and p53R2ii), obtained by cloning and sequencing. The mRNA levels of these subunits were measured with quantitative PCR and were generally well maintained in hypoxia and anoxia in heart and brain. We also report maintained or increased mRNA levels of the cell division markers proliferating cell nuclear antigen (PCNA), brain derived neurotrophic factor (BDNF) and Ki67 in anoxic hearts and brains. Electron paramagnetic resonance (EPR) measurements on in vitro expressed crucian carp R2 and p53R2 proteins gave spectra similar to mammalian RNRs, including previously unpublished human and mouse p53R2 EPR spectra. However, the radicals in crucian carp RNR small subunits, especially in the p53R2ii subunit, were very stable at 0°C. A long half-life of the tyrosyl radical during wintertime anoxia could allow for continued cell division in crucian carp.
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Affiliation(s)
- Guro K Sandvik
- Department of Molecular Biosciences, University of Oslo, Oslo, Norway.
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A phase I study of prolonged infusion of triapine in combination with fixed dose rate gemcitabine in patients with advanced solid tumors. Invest New Drugs 2012; 31:685-95. [PMID: 22847785 DOI: 10.1007/s10637-012-9863-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 07/18/2012] [Indexed: 12/21/2022]
Abstract
PURPOSE Prolonged exposure of cancer cells to triapine, an inhibitor of ribonucleotide reductase, followed by gemcitabine enhances gemcitabine activity in vitro. Fixed-dose-rate gemcitabine (FDR-G) has improved efficacy compared to standard-dose. We conducted a phase I trial to determine the maximum tolerated dose (MTD), safety, pharmacokinetics (PK), pharmacodynamics (PD), and preliminary efficacy of prolonged triapine infusion followed by FDR-G. EXPERIMENTAL DESIGN Triapine was given as a 24-hour infusion, immediately followed by FDR-G (1000 mg/m(2) over 100-minute). Initially, this combination was administered days 1 and 8 of a 21-day cycle (Arm A, triapine starting dose 120 mg); but because of myelosuppression, it was changed to days 1 and 15 of a 28-day cycle (Arm B, starting dose of triapine 75 mg). Triapine steady-state concentrations (Css) and circulating ribonucleotide reductase M2-subunit (RRM2) were measured. RESULTS Thirty-six patients were enrolled. The MTD was determined to be triapine 90 mg (24-hour infusion) immediately followed by gemcitabine 1000 mg/m(2) (100-minute infusion), every 2 weeks of a 4-week cycle. DLTs included grade 4 thrombocytopenia, leukopenia and neutropenia. The treatment was well tolerated with fatigue, nausea/vomiting, fever, transaminitis, and cytopenias being the most common toxicities. Among 30 evaluable patients, 1 had a partial response and 15 had stable disease. Triapine PK was similar, although more variable, compared to previous studies using doses normalized to body-surface-area. Steady decline in circulating levels of RRM2 may correlate with outcome. CONCLUSIONS This combination was well tolerated and showed evidence of preliminary activity in this heavily pretreated patient population, including prior gemcitabine failure.
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Franzolin E, Miazzi C, Frangini M, Palumbo E, Rampazzo C, Bianchi V. The pyrimidine nucleotide carrier PNC1 and mitochondrial trafficking of thymidine phosphates in cultured human cells. Exp Cell Res 2012; 318:2226-36. [PMID: 22677043 DOI: 10.1016/j.yexcr.2012.05.028] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Revised: 05/26/2012] [Accepted: 05/28/2012] [Indexed: 10/28/2022]
Abstract
In cycling cells cytosolic de novo synthesis of deoxynucleotides is the main source of precursors for mitochondrial (mt) DNA synthesis. The transfer of deoxynucleotides across the inner mt membrane requires protein carriers. PNC1, a SLC25 family member, exchanges pyrimidine nucleoside triphosphates in liposomes and its downregulation decreases mtUTP concentration in cultured cells. By an isotope-flow protocol we confirmed transport of uridine nucleotides by PNC1 in intact cultured cells and investigated PNC1 involvement in the mt trafficking of thymidine phosphates. Key features of our approach were the manipulation of PNC1 expression by RNA interference or inducible overexpression, the employment of cells proficient or deficient for cytosolic thymidine kinase (TK1) to distinguish the direction of flow of thymidine nucleotides across the mt membrane during short pulses with [(3)H]-thymidine, the determination of mtdTTP specific radioactivity to quantitate the rate of mtdTTP export to the cytoplasm. Downregulation of PNC1 in TK1(-) cells increased labeled dTTP in mitochondria due to a reduced rate of export. Overexpression of PNC1 in TK1(+) cells increased mtdTTP pool size and radioactivity, suggesting an involvement in the import of thymidine phosphates. Thus PNC1 is a component of the network regulating the mtdTTP pool in human cells.
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Affiliation(s)
- Elisa Franzolin
- Department of Biology, University of Padova, Via Ugo Bassi 58B, I-35131 Padova, Italy
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Mock DJ, Hollenbaugh JA, Daddacha W, Overstreet MG, Lazarski CA, Fowell DJ, Kim B. Leishmania induces survival, proliferation and elevated cellular dNTP levels in human monocytes promoting acceleration of HIV co-infection. PLoS Pathog 2012; 8:e1002635. [PMID: 22496656 PMCID: PMC3320607 DOI: 10.1371/journal.ppat.1002635] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 02/24/2012] [Indexed: 12/18/2022] Open
Abstract
Leishmaniasis is a parasitic disease that is widely prevalent in many tropical and sub-tropical regions of the world. Infection with Leishmania has been recognized to induce a striking acceleration of Human Immunodeficiency Virus Type 1 (HIV-1) infection in coinfected individuals through as yet incompletely understood mechanisms. Cells of the monocyte/macrophage lineage are the predominant cell types coinfected by both pathogens. Monocytes and macrophages contain extremely low levels of deoxynucleoside triphosphates (dNTPs) due to their lack of cell cycling and S phase, where dNTP biosynthesis is specifically activated. Lentiviruses, such as HIV-1, are unique among retroviruses in their ability to replicate in these non-dividing cells due, at least in part, to their highly efficient reverse transcriptase (RT). Nonetheless, viral replication progresses more efficiently in the setting of higher intracellular dNTP concentrations related to enhanced enzyme kinetics of the viral RT. In the present study, in vitro infection of CD14+ peripheral blood-derived human monocytes with Leishmania major was found to induce differentiation, marked elevation of cellular p53R2 ribonucleotide reductase subunit and R2 subunit expression. The R2 subunit is restricted to the S phase of the cell cycle. Our dNTP assay demonstrated significant elevation of intracellular monocyte-derived macrophages (MDMs) dNTP concentrations in Leishmania-infected cell populations as compared to control cells. Infection of Leishmania-maturated MDMs with a pseudotyped GFP expressing HIV-1 resulted in increased numbers of GFP+ cells in the Leishmania-maturated MDMs as compared to control cells. Interestingly, a sub-population of Leishmania-maturated MDMs was found to have re-entered the cell cycle, as demonstrated by BrdU labeling. In conclusion, Leishmania infection of primary human monocytes promotes the induction of an S phase environment and elevated dNTP levels with notable elevation of HIV-1 expression in the setting of coinfection. Leishmaniasis is a parasitic disease that infects several human host immune cells, including neutrophils, monocytes, and macrophages. Moreover, while HIV-1 infects monocytes and macrophages, only the infected macrophages productively release viral progenies. Importantly, patients coinfected with both pathogens progress more rapidly to AIDS. In this study, we examine how Leishmania major changes the cellular environment of monocytes in vitro. We found that Leishmania-infected monocytes actively mature into macrophages in the absence of GM-CSF, and that these cells up-regulate the expression of ribonucleotide reductase, an enzyme that catalyzes the formation of deoxynucleoside triphosphates (dNTPs). We confirmed the elevation of dNTP concentrations using a very sensitive dNTP assay for monocytes and monocyte-maturated macrophages. Collectively, these data support a model in which infection of monocytes with Leishmania elevates the intracellular dNTP pools, which is one of the natural anti-viral blocks to HIV-1 infection in monocytes and macrophages in patients.
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Affiliation(s)
- David J. Mock
- Department of Biomolecular Genetics, University of Rochester Medical Center, Rochester, New York, United States of America
- * E-mail: (DJM); (BK)
| | - Joseph A. Hollenbaugh
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Waaqo Daddacha
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Michael G. Overstreet
- Center of Vaccine Biology and Immunology, University of Rochester Medical Center, Rochester, New York, United States of America
| | | | - Deborah J. Fowell
- Center of Vaccine Biology and Immunology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Baek Kim
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York, United States of America
- * E-mail: (DJM); (BK)
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Lei W, Feng XH, Deng WB, Ni H, Zhang ZR, Jia B, Yang XL, Wang TS, Liu JL, Su RW, Liang XH, Qi QR, Yang ZM. Progesterone and DNA damage encourage uterine cell proliferation and decidualization through up-regulating ribonucleotide reductase 2 expression during early pregnancy in mice. J Biol Chem 2012; 287:15174-92. [PMID: 22403396 DOI: 10.1074/jbc.m111.308023] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Embryo implantation into the maternal uterus is a crucial step for the successful establishment of mammalian pregnancy. Following the attachment of embryo to the uterine luminal epithelium, uterine stromal cells undergo steroid hormone-dependent decidualization, which is characterized by stromal cell proliferation and differentiation. The mechanisms underlying steroid hormone-induced stromal cell proliferation and differentiation during decidualization are still poorly understood. Ribonucleotide reductase, consisting of two subunits (RRM1 and RRM2), is a rate-limiting enzyme in deoxynucleotide production for DNA synthesis and plays an important role in cell proliferation and tumorgenicity. Based on our microarray analysis, Rrm2 expression was significantly higher at implantation sites compared with interimplantation sites in mouse uterus. However, the expression, regulation, and function of RRM2 in mouse uterus during embryo implantation and decidualization are still unknown. Here we show that although both RRM1 and RRM2 expression are markedly induced in mouse uterine stromal cells undergoing decidualization, only RRM2 is regulated by progesterone, a key regulator of decidualization. Further studies showed that the induction of progesterone on RRM2 expression in stromal cells is mediated by the AKT/c-MYC pathway. RRM2 can also be induced by replication stress and DNA damage during decidualization through the ATR/ATM-CHK1-E2F1 pathway. The weight of implantation sites and deciduoma was effectively reduced by specific inhibitors for RRM2. The expression of decidual/trophoblast prolactin-related protein (Dtprp), a reliable marker for decidualization in mice, was significantly reduced in deciduoma and steroid-induced decidual cells after HU treatment. Therefore, RRM2 may be an important effector of progesterone signaling to induce cell proliferation and decidualization in mouse uterus.
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Affiliation(s)
- Wei Lei
- Department of Biology, Shantou University, Shantou 515063, China
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Kennedy EM, Amie SM, Bambara RA, Kim B. Frequent incorporation of ribonucleotides during HIV-1 reverse transcription and their attenuated repair in macrophages. J Biol Chem 2012; 287:14280-8. [PMID: 22383524 DOI: 10.1074/jbc.m112.348482] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Macrophages are well known long-lived reservoirs of HIV-1. Unlike activated CD4(+) T cells, this nondividing HIV-1 target cell type contains a very low level of the deoxynucleoside triphosphates (dNTPs) required for proviral DNA synthesis whereas the ribonucleoside triphosphate (rNTP) levels remain in the millimolar range, resulting in an extremely low dNTP/rNTP ratio. Biochemical simulations demonstrate that HIV-1 reverse transcriptase (RT) efficiently incorporates ribonucleoside monophosphates (rNMPs) during DNA synthesis at this ratio, predicting frequent rNMP incorporation by the virus specifically in macrophages. Indeed, HIV-1 RT incorporates rNMPs at a remarkable rate of 1/146 nucleotides during macrophage infection. This greatly exceeds known rates for cellular replicative polymerases. In contrast, little or no rNMP incorporation is detected in CD4(+) T cells. Repair of these rNMP lesions is also substantially delayed in macrophages compared with CD4(+) T cells. Single rNMPs embedded in a DNA template are known to induce cellular DNA polymerase pausing, which mechanistically contributes to mutation synthesis. Indeed, we also observed that embedded rNMPs in a dsDNA template also induce HIV-1 RT DNA synthesis pausing. Moreover, unrepaired rNMPs incorporated into the provirus during HIV-1 reverse transcription would be generally mutagenic as was shown in Saccharomyces cerevisiae. Most importantly, the frequent incorporation of rNMPs makes them an ideal candidate for development of a new class of HIV RT inhibitors.
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Affiliation(s)
- Edward M Kennedy
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, USA
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HDM-2 inhibition suppresses expression of ribonucleotide reductase subunit M2, and synergistically enhances gemcitabine-induced cytotoxicity in mantle cell lymphoma. Blood 2011; 118:4140-9. [PMID: 21844567 DOI: 10.1182/blood-2011-03-340323] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Mantle cell lymphoma (MCL) usually responds well to initial therapy but is prone to relapses with chemoresistant disease, indicating the need for novel therapeutic approaches. Inhibition of the p53 E3 ligase human homolog of the murine double minute protein-2 (HDM-2) with MI-63 has been validated as one such strategy in wild-type (wt) p53 models, and our genomic and proteomic analyses demonstrated that MI-63 suppressed the expression of the ribonucleotide reductase (RNR) subunit M2 (RRM2). This effect occurred in association with induction of p21 and cell-cycle arrest at G(1)/S and prompted us to examine combinations with the RNR inhibitor 2',2'-difluoro-2'-deoxycytidine (gemcitabine). The regimen of MI-63-gemcitabine induced enhanced, synergistic antiproliferative, and proapoptotic effects in wtp53 MCL cell lines. Addition of exogenous dNTPs reversed this effect, whereas shRNA-mediated inhibition of RRM2 was sufficient to induce synergy with gemcitabine. Combination therapy of MCL murine xenografts with gemcitabine and MI-219, the in vivo analog of MI-63, resulted in enhanced antitumor activity. Finally, synergy was seen with MI-63-gemcitabine in primary patient samples that were found to express high levels of RRM2 compared with MCL cell lines. These findings provide a framework for translation of the rational combination of an HDM-2 and RNR inhibitor to the clinic for patients with relapsed wtp53 MCL.
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Kennedy EM, Daddacha W, Slater R, Gavegnano C, Fromentin E, Schinazi RF, Kim B. Abundant non-canonical dUTP found in primary human macrophages drives its frequent incorporation by HIV-1 reverse transcriptase. J Biol Chem 2011; 286:25047-55. [PMID: 21454906 PMCID: PMC3137078 DOI: 10.1074/jbc.m111.234047] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 03/29/2011] [Indexed: 01/21/2023] Open
Abstract
Terminally differentiated/non-dividing macrophages contain extremely low cellular dNTP concentrations (20-40 nm), compared with activated CD4(+) T cells (2-5 μm). However, our LC-MS/MS study revealed that the non-canonical dUTP concentration (2.9 μm) is ∼60 times higher than TTP in macrophages, whereas the concentrations of dUTP and TTP in dividing human primary lymphocytes are very similar. Specifically, we evaluated the contribution of HIV-1 reverse transcriptase to proviral DNA uracilation under the physiological conditions found in HIV-1 target cells. Indeed, biochemical simulation of HIV-1 reverse transcription demonstrates that HIV-1 RT efficiently incorporates dUTP in the macrophage nucleotide pools but not in the T cell nucleotide pools. Measurement of both pre-steady state and steady state kinetic parameters of dUTP incorporation reveals minimal selectivity of HIV-1 RT for TTP over dUTP, implying that the cellular dUTP/TTP ratio determines the frequency of HIV-1 RT-mediated dUTP incorporation. The RT of another lentivirus, simian immunodeficiency virus, also displays efficient dUTP incorporation in the dNTP/dUTP pools found in macrophages but not in T cells. Finally, 2',3'-dideoxyuridine was inhibitory to HIV-1 proviral DNA synthesis in macrophages but not in T cells. The data presented demonstrates that the non-canonical dUTP was abundant relative to TTP, and efficiently incorporated during HIV-1 reverse transcription, particularly in non-dividing macrophages.
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Affiliation(s)
- Edward M. Kennedy
- From the Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642 and
| | - Waaqo Daddacha
- From the Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642 and
| | - Rebecca Slater
- From the Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642 and
| | - Christina Gavegnano
- the Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine and Veterans Affairs Medical Center, Decatur, Georgia 30033
| | - Emilie Fromentin
- the Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine and Veterans Affairs Medical Center, Decatur, Georgia 30033
| | - Raymond F. Schinazi
- the Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine and Veterans Affairs Medical Center, Decatur, Georgia 30033
| | - Baek Kim
- From the Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642 and
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Pontarin G, Ferraro P, Rampazzo C, Kollberg G, Holme E, Reichard P, Bianchi V. Deoxyribonucleotide metabolism in cycling and resting human fibroblasts with a missense mutation in p53R2, a subunit of ribonucleotide reductase. J Biol Chem 2011; 286:11132-40. [PMID: 21297166 PMCID: PMC3064167 DOI: 10.1074/jbc.m110.202283] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Ribonucleotide reduction provides deoxynucleotides for nuclear and mitochondrial (mt) DNA replication and DNA repair. In cycling mammalian cells the reaction is catalyzed by two proteins, R1 and R2. A third protein, p53R2, with the same function as R2, occurs in minute amounts. In quiescent cells, p53R2 replaces the absent R2. In humans, genetic inactivation of p53R2 causes early death with mtDNA depletion, especially in muscle. We found that cycling fibroblasts from a patient with a lethal mutation in p53R2 contained a normal amount of mtDNA and showed normal growth, ribonucleotide reduction, and deoxynucleoside triphosphate (dNTP) pools. However, when made quiescent by prolonged serum starvation the mutant cells strongly down-regulated ribonucleotide reduction, decreased their dCTP and dGTP pools, and virtually abolished the catabolism of dCTP in substrate cycles. mtDNA was not affected. Also, nuclear DNA synthesis and the cell cycle-regulated enzymes R2 and thymidine kinase 1 decreased strongly, but the mutant cell populations retained unexpectedly larger amounts of the two enzymes than the controls. This difference was probably due to their slightly larger fraction of S phase cells and therefore not induced by the absence of p53R2 activity. We conclude that loss of p53R2 affects ribonucleotide reduction only in resting cells and leads to a decrease of dNTP catabolism by substrate cycles that counterweigh the loss of anabolic activity. We speculate that this compensatory mechanism suffices to maintain mtDNA in fibroblasts but not in muscle cells with a larger content of mtDNA necessary for their high energy requirements.
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Kennedy EM, Gavegnano C, Nguyen L, Slater R, Lucas A, Fromentin E, Schinazi RF, Kim B. Ribonucleoside triphosphates as substrate of human immunodeficiency virus type 1 reverse transcriptase in human macrophages. J Biol Chem 2010; 285:39380-91. [PMID: 20924117 PMCID: PMC2998149 DOI: 10.1074/jbc.m110.178582] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 10/04/2010] [Indexed: 01/04/2023] Open
Abstract
We biochemically simulated HIV-1 DNA polymerization in physiological nucleotide pools found in two HIV-1 target cell types: terminally differentiated/non-dividing macrophages and activated/dividing CD4(+) T cells. Quantitative tandem mass spectrometry shows that macrophages harbor 22-320-fold lower dNTP concentrations and a greater disparity between ribonucleoside triphosphate (rNTP) and dNTP concentrations than dividing target cells. A biochemical simulation of HIV-1 reverse transcription revealed that rNTPs are efficiently incorporated into DNA in the macrophage but not in the T cell environment. This implies that HIV-1 incorporates rNTPs during viral replication in macrophages and also predicts that rNTP chain terminators lacking a 3'-OH should inhibit HIV-1 reverse transcription in macrophages. Indeed, 3'-deoxyadenosine inhibits HIV-1 proviral DNA synthesis in human macrophages more efficiently than in CD4(+) T cells. This study reveals that the biochemical landscape of HIV-1 replication in macrophages is unique and that ribonucleoside chain terminators may be a new class of anti-HIV-1 agents specifically targeting viral macrophage infection.
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Affiliation(s)
- Edward M. Kennedy
- From the Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, and
| | - Christina Gavegnano
- the Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine and Veterans Affairs Medical Center, Decatur, Georgia 30033
| | - Laura Nguyen
- From the Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, and
| | - Rebecca Slater
- From the Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, and
| | - Amanda Lucas
- From the Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, and
| | - Emilie Fromentin
- the Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine and Veterans Affairs Medical Center, Decatur, Georgia 30033
| | - Raymond F. Schinazi
- the Center for AIDS Research, Laboratory of Biochemical Pharmacology, Department of Pediatrics, Emory University School of Medicine and Veterans Affairs Medical Center, Decatur, Georgia 30033
| | - Baek Kim
- From the Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, and
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41
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Niida H, Shimada M, Murakami H, Nakanishi M. Mechanisms of dNTP supply that play an essential role in maintaining genome integrity in eukaryotic cells. Cancer Sci 2010; 101:2505-9. [PMID: 20874841 PMCID: PMC11158391 DOI: 10.1111/j.1349-7006.2010.01719.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Optimization of intracellular concentrations of dNTPs is critical for the fidelity of DNA synthesis during DNA replication and repair because levels that are too high or too low can easily lead to increased rates of mutagenesis. Recent advances in the analysis of intracellular concentrations of dNTPs have suggested that eukaryotes use diverse mechanisms in supplying dNTPs for DNA synthesis during DNA replication and repair. The enzyme ribonucleotide reductase (RNR) is a key enzyme involved in the synthesis of dNTPs. We found that Tip60-dependent recruitment of RNR at sites of DNA damage is essential for supplying a sufficient amount of dNTPs for mammalian DNA repair. In this review, we focus on recent findings related to RNR regulation in eukaryotes of the dNTPs supplied for DNA synthesis. We also discuss the effect of this regulation on mutagenesis and tumorigenesis.
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Affiliation(s)
- Hiroyuki Niida
- Department of Cell Biology, Graduate School of Medical Sciences, Nagoya City University, Mizuho-ku, Nagoya, Japan
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42
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Abstract
Proteins with oxidizable thiols are essential to many functions of cell nuclei, including transcription, chromatin stability, nuclear protein import and export, and DNA replication and repair. Control of the nuclear thiol-disulfide redox states involves both the elimination of oxidants to prevent oxidation and the reduction of oxidized thiols to restore function. These processes depend on the common thiol reductants, glutathione (GSH) and thioredoxin-1 (Trx1). Recent evidence shows that these systems are controlled independent of the cytoplasmic counterparts. In addition, the GSH and Trx1 couples are not in redox equilibrium, indicating that these reductants have nonredundant functions in their support of proteins involved in transcriptional regulation, nuclear protein trafficking, and DNA repair. Specific isoforms of glutathione peroxidases, glutathione S-transferases, and peroxiredoxins are enriched in nuclei, further supporting the interpretation that functions of the thiol-dependent systems in nuclei are at least quantitatively distinct, and probably also qualitatively distinct, from similar processes in the cytoplasm. Elucidation of the distinct nuclear functions and regulation of the thiol redox pathways in nuclei can be expected to improve understanding of nuclear processes and also to provide the basis for novel approaches to treat aging and disease processes associated with oxidative stress in the nuclei.
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Affiliation(s)
- Young-Mi Go
- Department of Medicine, Emory University, Atlanta, GA, USA
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43
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Saletta F, Suryo Rahmanto Y, Richardson DR. The translational regulator eIF3a: the tricky eIF3 subunit! Biochim Biophys Acta Rev Cancer 2010; 1806:275-86. [PMID: 20647036 DOI: 10.1016/j.bbcan.2010.07.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Revised: 07/07/2010] [Accepted: 07/11/2010] [Indexed: 01/10/2023]
Abstract
Regulation of gene expression is a fundamental step in cellular physiology as abnormalities in this process may lead to de-regulated growth and cancer. Translation of mRNA is mainly regulated at the rate-limiting initiation step, where many eukaryotic initiation factors (eIFs) are involved. The largest and most complex initiation factor is eIF3 which plays a role in translational regulation, cell growth and cancer. The largest subunit of eIF3 is eIF3a, although it is not required for the general function of eIF3 in translation initiation. However, eIF3a may play a role as a regulator of a subset of mRNAs and has been demonstrated to regulate the expression of p27(kip1), tyrosinated α-tubulin and ribonucleotide reductase M2 subunit. These molecules have a pivotal role in the regulation of the cell cycle. Moreover, the eIF3a mRNA is ubiquitously expressed in all tissues at different levels and is found elevated in a number of cancer types. eIF3a can modulate the cell cycle and may be a translational regulator for proteins important for entrance into S phase. The expression of eIF3a is decreased in differentiated cells in culture and the suppression of eIF3a expression can reverse the malignant phenotype and change the sensitivity of cells to cell cycle modulators. However, the role of eIF3a in cancer is still unclear. In fact, some studies have identified eIF3a to be involved in cancer development, while other results indicate that it could provide protection against evolution into higher malignancy. Together, these findings highlight the "tricky" and interesting nature of eIF3a.
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Affiliation(s)
- Federica Saletta
- Iron Metabolism and Chelation Program, Department of Pathology and Bosch Institute, Blackburn Building (D06), University of Sydney, Sydney, New South Wales, 2006 Australia
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44
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Gammon DB, Gowrishankar B, Duraffour S, Andrei G, Upton C, Evans DH. Vaccinia virus-encoded ribonucleotide reductase subunits are differentially required for replication and pathogenesis. PLoS Pathog 2010; 6:e1000984. [PMID: 20628573 PMCID: PMC2900304 DOI: 10.1371/journal.ppat.1000984] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 06/03/2010] [Indexed: 11/19/2022] Open
Abstract
Ribonucleotide reductases (RRs) are evolutionarily-conserved enzymes that catalyze the rate-limiting step during dNTP synthesis in mammals. RR consists of both large (R1) and small (R2) subunits, which are both required for catalysis by the R12R22 heterotetrameric complex. Poxviruses also encode RR proteins, but while the Orthopoxviruses infecting humans [e.g. vaccinia (VACV), variola, cowpox, and monkeypox viruses] encode both R1 and R2 subunits, the vast majority of Chordopoxviruses encode only R2 subunits. Using plaque morphology, growth curve, and mouse model studies, we investigated the requirement of VACV R1 (I4) and R2 (F4) subunits for replication and pathogenesis using a panel of mutant viruses in which one or more viral RR genes had been inactivated. Surprisingly, VACV F4, but not I4, was required for efficient replication in culture and virulence in mice. The growth defects of VACV strains lacking F4 could be complemented by genes encoding other Chordopoxvirus R2 subunits, suggesting conservation of function between poxvirus R2 proteins. Expression of F4 proteins encoding a point mutation predicted to inactivate RR activity but still allow for interaction with R1 subunits, caused a dominant negative phenotype in growth experiments in the presence or absence of I4. Co-immunoprecipitation studies showed that F4 (as well as other Chordopoxvirus R2 subunits) form hybrid complexes with cellular R1 subunits. Mutant F4 proteins that are unable to interact with host R1 subunits failed to rescue the replication defect of strains lacking F4, suggesting that F4-host R1 complex formation is critical for VACV replication. Our results suggest that poxvirus R2 subunits form functional complexes with host R1 subunits to provide sufficient dNTPs for viral replication. Our results also suggest that R2-deficient poxviruses may be selective oncolytic agents and our bioinformatic analyses provide insights into how poxvirus nucleotide metabolism proteins may have influenced the base composition of these pathogens. Efficient genome replication is central to the virulence of all DNA viruses, including poxviruses. To ensure replication efficiency, many of the more virulent poxviruses encode their own nucleotide metabolism machinery, including ribonucleotide reductase (RR) enzymes, which act to provide ample DNA precursors for replication. RR enzymes require both large (R1) and small (R2) subunit proteins for activity. Curiously, some poxviruses only encode R2 subunits. Other poxviruses, such as the smallpox vaccine strain, vaccinia virus (VACV), encode both R1 and R2 subunits. We report here that the R2, but not the R1, subunit of VACV RR is required for efficient replication and virulence. We also provide evidence that several poxvirus R2 proteins form novel complexes with host R1 subunits and this interaction is required for efficient VACV replication in primate cells. Our study explains why some poxviruses only encode R2 subunits and identifies a role for these proteins in poxvirus pathogenesis. Furthermore, we provide evidence that mutant poxviruses unable to generate R2 proteins may become entirely dependent upon host RR activity. This may restrict their replication to cells that over-express RR proteins such as cancer cells, making them potential therapeutics for human malignancies.
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Affiliation(s)
- Don B. Gammon
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
| | - Branawan Gowrishankar
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
| | - Sophie Duraffour
- Laboratory of Virology and Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Graciela Andrei
- Laboratory of Virology and Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Chris Upton
- Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - David H. Evans
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
- * E-mail:
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45
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Sridhar SS, Canil CM, Chi KN, Hotte SJ, Ernst S, Wang L, Chen EX, Juhasz A, Yen Y, Murray P, Zwiebel JA, Moore MJ. A phase II study of the antisense oligonucleotide GTI-2040 plus docetaxel and prednisone as first-line treatment in castration-resistant prostate cancer. Cancer Chemother Pharmacol 2010; 67:927-33. [PMID: 20602233 DOI: 10.1007/s00280-010-1389-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Accepted: 06/20/2010] [Indexed: 10/19/2022]
Abstract
PURPOSE GTI-2040 is a novel antisense oligonucleotide to the R2 subunit of ribonucleotide reductase. This phase II trial was conducted to determine the efficacy and tolerability of GTI-2040 when combined with docetaxel and prednisone for the treatment of patients with castration-resistant prostate cancer (CRPC). METHODS Chemo-naïve CRPC patients with adequate performance status and organ function were treated with docetaxel 75 mg/m(2) IV on day 1 plus GTI-2040 5 mg/kg/day by continuous intravenous infusion day 1-14 on a 21 day cycle, with prednisone 5 mg orally twice daily. The primary endpoint was PSA response rate. Pharmacokinetic studies of GTI-2040 and pharmacodynamic studies on peripheral blood mononuclear cells (PBMC) were also performed. RESULTS Twenty-two patients in total (19 from this study and 3 from a prior phase I/II study at this institution) were treated at the recommended phase II dose. A confirmed PSA response was seen in 9/22 patients (41%). Of 16 patients with measurable disease, there was 1 partial response (PR) and 12 stable disease (SD) lasting 3.6 months (median), as best response. The most common toxicities were anemia, fatigue, lymphopenia, leucopenia and neutropenia. Grade 3+ toxicities included neutropenia, lymphopenia, leucopenia, fatigue, febrile neutropenia and hypophosphatemia. CONCLUSIONS The PSA response rate of GTI-2040 in combination with docetaxel and prednisone just met the minimum phase II criteria for further enrollment. However, after evaluation of all the clinical data, further study of this dose and schedule of GTI-2040 in CRPC was not recommended.
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Affiliation(s)
- Srikala S Sridhar
- Princess Margaret Hospital, Phase II Consortium, University of Toronto, 610 University Avenue, Suite 5-222, Toronto, ON M5G 2M9, USA.
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46
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Wenemoser D, Reddien PW. Planarian regeneration involves distinct stem cell responses to wounds and tissue absence. Dev Biol 2010; 344:979-91. [PMID: 20599901 DOI: 10.1016/j.ydbio.2010.06.017] [Citation(s) in RCA: 225] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Accepted: 06/11/2010] [Indexed: 10/19/2022]
Abstract
Regeneration requires signaling from a wound site for detection of the wound and a mechanism that determines the nature of the injury to specify the appropriate regenerative response. Wound signals and tissue responses to wounds that elicit regeneration remain poorly understood. Planarians are able to regenerate from essentially any type of injury and present a novel system for the study of wound responses in regeneration initiation. Newly developed molecular and cellular tools now enable study of regeneration initiation using the planarian Schmidtea mediterranea. Planarian regeneration requires adult stem cells called neoblasts and amputation triggers two peaks in neoblast mitoses early in regeneration. We demonstrate that the first mitotic peak is a body-wide response to any injury and that a second, local, neoblast response is induced only when injury results in missing tissue. This second response was characterized by recruitment of neoblasts to wounds, even in areas that lack neoblasts in the intact animal. Subsequently, these neoblasts were induced to divide and differentiate near the wound, leading to formation of new tissue. We conclude that there exist two functionally distinct signaling phases of the stem cell wound response that distinguish between simple injury and situations that require the regeneration of missing tissue.
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Affiliation(s)
- Danielle Wenemoser
- Howard Hughes Medical Institute, Whitehead Institute, Cambridge, MA, USA
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47
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Chen YL, Eriksson S, Chang ZF. Regulation and functional contribution of thymidine kinase 1 in repair of DNA damage. J Biol Chem 2010; 285:27327-27335. [PMID: 20554529 DOI: 10.1074/jbc.m110.137042] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellular supply of dNTPs is essential in the DNA replication and repair processes. Here we investigated the regulation of thymidine kinase 1 (TK1) in response to DNA damage and found that genotoxic insults in tumor cells cause up-regulation and nuclear localization of TK1. During recovery from DNA damage, TK1 accumulates in p53-null cells due to a lack of mitotic proteolysis as these cells are arrested in the G(2) phase by checkpoint activation. We show that in p53-proficient cells, p21 expression in response to DNA damage prohibits G(1)/S progression, resulting in a smaller G(2) fraction and less TK1 accumulation. Thus, the p53 status of tumor cells affects the level of TK1 after DNA damage through differential cell cycle control. Furthermore, it was shown that in HCT-116 p53(-/-) cells, TK1 is dispensable for cell proliferation but crucial for dTTP supply during recovery from DNA damage, leading to better survival. Depletion of TK1 decreases the efficiency of DNA repair during recovery from DNA damage and generates more cell death. Altogether, our data suggest that more dTTP synthesis via TK1 take place after genotoxic insults in tumor cells, improving DNA repair during G(2) arrest.
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Affiliation(s)
- Yen-Ling Chen
- Graduate Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1, Section 1, Jen-Ai Road, Taipei 100, Taiwan
| | - Staffan Eriksson
- Department of Anatomy, Physiology and Biochemistry, The Swedish University of Agricultural Sciences, Biomedical Center, S-751 23 Uppsala, Sweden
| | - Zee-Fen Chang
- Graduate Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1, Section 1, Jen-Ai Road, Taipei 100, Taiwan; Institute of Biochemistry and Molecular Biology, National Yang-Ming University, No. 155, Section 2, Linong Street, Taipei 112, Taiwan.
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48
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Kunos CA, Chiu SM, Pink J, Kinsella TJ. Modulating radiation resistance by inhibiting ribonucleotide reductase in cancers with virally or mutationally silenced p53 protein. Radiat Res 2009; 172:666-76. [PMID: 19929413 DOI: 10.1667/rr1858.1] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Therapeutic ionizing radiation damages DNA, increasing p53-regulated ribonucleotide reductase (RNR) activity required for de novo synthesis of the deoxyribonucleotide triphosphates used during DNA repair. This study investigated the pharmacological inhibition of RNR in cells of virally or mutationally silenced p53 cancer cell lines using 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (3-AP, Triapine(R), NSC #663249), a chemotherapeutic radiosensitizer that equally inhibits RNR M2 and p53R2 small subunits. The effects of 3-AP on RNR inhibition and resulting radiosensitization were evaluated in cervical (CaSki, HeLa and C33-a) and colon (RKO, RKO-E6) cancer cells. 3-AP treatment significantly enhanced radiation-related cytotoxicity in cervical and colon cancer cells. 3-AP treatment significantly decreased RNR activity, caused prolonged radiation-induced DNA damage, and resulted in an extended G(1)/S-phase cell cycle arrest in all cell lines. Similar effects were observed in both RKO and RKO-E6 cells, suggesting a p53-independent mechanism of radiosensitization. We conclude that inhibition of ribonucleotide reductase by 3-AP enhances radiation-mediated cytotoxicity independent of p53 regulation by impairing repair processes that rely on deoxyribonucleotide production, thereby substantially increasing the radiation sensitivity of human cancers.
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Affiliation(s)
- Charles A Kunos
- Departments of Radiation Oncology, Case Comprehensive Cancer Center, University Hospitals Case Medical Center and Case Western Reserve School of Medicine, 11100 Euclid Avenue, Cleveland, Ohio 44106, USA.
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Chimploy K, Díaz GD, Li Q, Carter O, Dashwood WM, Mathews CK, Williams DE, Bailey GS, Dashwood RH. E2F4 and ribonucleotide reductase mediate S-phase arrest in colon cancer cells treated with chlorophyllin. Int J Cancer 2009; 125:2086-94. [PMID: 19585502 DOI: 10.1002/ijc.24559] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Chlorophyllin (CHL) is a water-soluble derivative of chlorophyll that exhibits cancer chemopreventive properties, but which also has been studied for its possible cancer therapeutic effects. We report here that human colon cancer cells treated with CHL accumulate in S-phase of the cell cycle, and this is associated with reduced expression levels of p53, p21, and other G(1)/S checkpoint controls. At the same time, E2F1 and E2F4 transcription factors become elevated and exhibit increased DNA binding activity. In CHL-treated colon cancer cells, bromodeoxyuridine pulse-chase experiments provided evidence for the inhibition of DNA synthesis. Ribonucleotide reductase (RR), a pivotal enzyme for DNA synthesis and repair, was reduced at the mRNA and protein level after CHL treatment, and the enzymatic activity was inhibited in a concentration-dependent manner both in vitro and in vivo. Immunoblotting revealed that expression levels of RR subunits R1, R2, and p53R2 were reduced by CHL treatment in HCT116 (p53(+/+)) and HCT116 (p53(-/-)) cells, supporting a p53-independent mechanism. Prior studies have shown that reduced levels of RR small subunits can increase the sensitivity of colon cancer cells to clinically used DNA-damaging agents and RR inhibitors. We conclude that by inhibiting R1, R2, and p53R2, CHL has the potential to be effective in the clinical setting, when used alone or in combination with currently available cancer therapeutic agents.
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Affiliation(s)
- Korakod Chimploy
- Linus Pauling Institute, Oregon State University, Corvallis, OR 97331-6512, USA
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50
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Rueda C, Fernández MA, Peddada SD. Estimation of Parameters Subject to Order Restrictions on a Circle With Application to Estimation of Phase Angles of Cell Cycle Genes. J Am Stat Assoc 2009; 104:338-347. [PMID: 19750145 DOI: 10.1198/jasa.2009.0120] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Motivated by a problem encountered in the analysis of cell cycle gene expression data, this article deals with the estimation of parameters subject to order restrictions on a unit circle. A normal eukaryotic cell cycle has four major phases during cell division, and a cell cycle gene has its peak expression (phase angle) during the phase that may correspond to its biological function. Because the phases are ordered along a circle, the phase angles of cell cycle genes are ordered unknown parameters on a unit circle. The problem of interest is to estimate the phase angles using the information regarding the order among them. We address this problem by developing a circular version of the well-known isotonic regression for Euclidean data. Because of the underlying geometry, the standard pool adjacent violator algorithm (PAVA) cannot be used for deriving the circular isotonic regression estimator (CIRE). However, PAVA can be modified to obtain a computationally efficient algorithm for deriving the CIRE. We illustrate the CIRE by estimating the phase angles of some of well-known cell cycle genes using the unrestricted estimators obtained in the literature.
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Affiliation(s)
- Cristina Rueda
- Department of Statistics and Operations Research, University of Valladolid, Valladolid, Spain
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