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Ketkar A, Sewilam RS, McCrury MJ, Hall JS, Bell A, Paxton BC, Tripathi S, Gunderson JEC, Eoff RL. Conservation of the insert-2 motif confers Rev1 from different species with an ability to disrupt G-quadruplexes and stimulate translesion DNA synthesis. RSC Chem Biol 2023; 4:466-485. [PMID: 37415867 PMCID: PMC10320842 DOI: 10.1039/d3cb00027c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 05/08/2023] [Indexed: 07/08/2023] Open
Abstract
In some organisms, the replication of G-quadruplex (G4) structures is supported by the Rev1 DNA polymerase. We previously showed that residues in the insert-2 motif of human Rev1 (hRev1) increased the affinity of the enzyme for G4 DNA and mediated suppression of mutagenic replication near G4 motifs. We have now investigated the conservation of G4-selective properties in Rev1 from other species. We compared Rev1 from Danio rerio (zRev1), Saccharomyces cerevisiae (yRev1), and Leishmania donovani (lRev1) with hRev1, including an insert-2 mutant form of hRev1 (E466A/Y470A or EY). We found that zRev1 retained all of the G4-selective prowess of the human enzyme, but there was a marked attenuation of G4 binding affinity for the EY hRev1 mutant and the two Rev1 proteins lacking insert-2 (yRev1 and lRev1). Perhaps most strikingly, we found that insert-2 was important for disruption of the G4 structure and optimal stimulation of processive DNA synthesis across the guanine-rich motif by DNA polymerase kappa (pol κ). Our findings have implications for how Rev1 might contribute to G4 replication in different species spanning the evolutionary tree - signaling the importance of selection for enzymes with robust G4-selective properties in organisms where these non-B DNA structures may fulfill taxa-specific physiological functions.
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Affiliation(s)
- Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences Little Rock AR 72205 USA +1 501 686 8169 +1 501 686 8343
| | - Reham S Sewilam
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences Little Rock AR 72205 USA +1 501 686 8169 +1 501 686 8343
| | - Mason J McCrury
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences Little Rock AR 72205 USA +1 501 686 8169 +1 501 686 8343
| | - Jaycelyn S Hall
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences Little Rock AR 72205 USA +1 501 686 8169 +1 501 686 8343
| | - Ashtyn Bell
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences Little Rock AR 72205 USA +1 501 686 8169 +1 501 686 8343
| | - Bethany C Paxton
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences Little Rock AR 72205 USA +1 501 686 8169 +1 501 686 8343
| | - Shreyam Tripathi
- Arkansas School for Mathematics, Sciences, and the Arts Hot Springs AR 71901 USA
| | | | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences Little Rock AR 72205 USA +1 501 686 8169 +1 501 686 8343
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2
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Urbaniak A, Reed MR, Heflin B, Gaydos J, Piña-Oviedo S, Jędrzejczyk M, Klejborowska G, Stępczyńska N, Chambers TC, Tackett AJ, Rodriguez A, Huczyński A, Eoff RL, MacNicol AM. Anti-glioblastoma activity of monensin and its analogs in an organoid model of cancer. Biomed Pharmacother 2022; 153:113440. [PMID: 36076555 PMCID: PMC9472755 DOI: 10.1016/j.biopha.2022.113440] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/13/2022] [Accepted: 07/15/2022] [Indexed: 11/30/2022] Open
Abstract
Glioblastoma (GBM) remains the most frequently diagnosed primary malignant brain cancer in adults. Despite recent progress in understanding the biology of GBM, the clinical outcome for patients remains poor, with a median survival of approximately one year after diagnosis. One factor contributing to failure in clinical trials is the fact that traditional models used in GBM drug discovery poorly recapitulate patient tumors. Previous studies have shown that monensin (MON) analogs, namely esters and amides on C-26 were potent towards various types of cancer cell lines. In the present study we have investigated the activity of these molecules in GBM organoids, as well as in a host:tumor organoid model. Using a mini-ring cell viability assay we have identified seven analogs (IC50 = 91.5 ± 54.4–291.7 ± 68.8 nM) more potent than parent MON (IC50 = 612.6 ± 184.4 nM). Five of these compounds induced substantial DNA fragmentation in GBM organoids, suggestive of apoptotic cell death. The most active analog, compound 1, significantly reduced GBM cell migration, induced PARP degradation, diminished phosphorylation of STAT3, Akt and GSK3β, increased ɣH2AX signaling and upregulated expression of the autophagy associated marker LC3-II. To investigate the activity of MON and compound 1 in a tumor microenvironment, we developed human cerebral organoids (COs) from human induced pluripotent stem cells (iPSCs). The COs showed features of early developing brain such as multiple neural rosettes with a proliferative zone of neural stem cells (Nestin+), neurons (TUJ1 +), primitive ventricular system (SOX2 +/Ki67 +), intermediate zone (TBR2 +) and cortical plate (MAP2 +). In order to generate host:tumor organoids, we co-cultured RFP-labeled U87MG cells with fully formed COs. Compound 1 and MON reduced U87MG tumor size in the COs after four days of treatment and induced a significant reduction of PARP expression. These findings highlight the therapeutic potential of MON analogs towards GBM and support the application of organoid models in anti-cancer drug discovery.
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Affiliation(s)
- Alicja Urbaniak
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Megan R Reed
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Billie Heflin
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - John Gaydos
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Sergio Piña-Oviedo
- Department of Pathology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Marta Jędrzejczyk
- Department of Medical Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Uniwersytetu Poznańskiego 8, 61-614 Poznań, Poland
| | - Greta Klejborowska
- Department of Medical Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Uniwersytetu Poznańskiego 8, 61-614 Poznań, Poland
| | - Natalia Stępczyńska
- Department of Medical Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Uniwersytetu Poznańskiego 8, 61-614 Poznań, Poland
| | - Timothy C Chambers
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Alan J Tackett
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Analiz Rodriguez
- Department of Neurosurgery, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Adam Huczyński
- Department of Medical Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Uniwersytetu Poznańskiego 8, 61-614 Poznań, Poland
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Angus M MacNicol
- Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
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3
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Urbaniak A, Reed MR, Heflin B, Gaydos J, Piña‐Oviedo S, Jędrzejczyk M, Klejborowska G, Stępczyńska N, Chambers TC, Tackett AJ, Rodriguez A, Huczyński A, Eoff RL, MacNicol AM. Monensin and its analogues show anti‐glioblastoma activity in an organoid model of cancer. FASEB J 2022. [DOI: 10.1096/fasebj.2022.36.s1.r5150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Alicja Urbaniak
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockAR
| | - Megan R. Reed
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockAR
| | - Billie Heflin
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockAR
| | - John Gaydos
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockAR
| | - Sergio Piña‐Oviedo
- Department of PathologyUniversity of Arkansas for Medical SciencesLittle RockAR
| | | | | | | | - Timothy C. Chambers
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockAR
| | - Alan J. Tackett
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockAR
| | - Analiz Rodriguez
- Department of NeurosurgeryUniversity of Arkansas for Medical SciencesLittle RockAR
| | - Adam Huczyński
- Department of Medical ChemistryAdam Mickiewicz UniversityPoznań
| | - Robert L. Eoff
- Department of Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockAR
| | - Angus M. MacNicol
- Department of Neurobiology and Developmental SciencesUniversity of Arkansas for Medical SciencesLittle RockAR
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4
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Christov PP, Richie-Jannetta R, Kingsley PJ, Vemulapalli A, Kim K, Sulikowski GA, Rizzo CJ, Ketkar A, Eoff RL, Rouzer CA, Marnett LJ. Site-Specific Synthesis of Oligonucleotides Containing 6-Oxo-M 1dG, the Genomic Metabolite of M 1dG, and Liquid Chromatography-Tandem Mass Spectrometry Analysis of Its In Vitro Bypass by Human Polymerase ι. Chem Res Toxicol 2021; 34:2567-2578. [PMID: 34860508 PMCID: PMC10518890 DOI: 10.1021/acs.chemrestox.1c00334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The lipid peroxidation product malondialdehyde and the DNA peroxidation product base-propenal react with dG to generate the exocyclic adduct, M1dG. This mutagenic lesion has been found in human genomic and mitochondrial DNA. M1dG in genomic DNA is enzymatically oxidized to 6-oxo-M1dG, a lesion of currently unknown mutagenic potential. Here, we report the synthesis of an oligonucleotide containing 6-oxo-M1dG and the results of extension experiments aimed at determining the effect of the 6-oxo-M1dG lesion on the activity of human polymerase iota (hPol ι). For this purpose, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was developed to obtain reliable quantitative data on the utilization of poorly incorporated nucleotides. Results demonstrate that hPol ι primarily incorporates deoxycytidine triphosphate (dCTP) and thymidine triphosphate (dTTP) across from 6-oxo-M1dG with approximately equal efficiency, whereas deoxyadenosine triphosphate (dATP) and deoxyguanosine triphosphate (dGTP) are poor substrates. Following the incorporation of a single nucleotide opposite the lesion, 6-oxo-M1dG blocks further replication by the enzyme.
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Affiliation(s)
- Plamen P. Christov
- Department of Chemistry, Vanderbilt University; Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Robyn Richie-Jannetta
- A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, and Pharmacology, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Philip J. Kingsley
- A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, and Pharmacology, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Anoop Vemulapalli
- A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, and Pharmacology, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Kwangho Kim
- Department of Chemistry, Vanderbilt University; Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Gary A. Sulikowski
- Department of Chemistry, Vanderbilt University; Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Carmelo J. Rizzo
- Departments of Chemistry and Biochemistry, Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235
| | - Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, United States
| | - Robert L. Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, United States
| | - Carol A. Rouzer
- A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, and Pharmacology, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Lawrence J. Marnett
- Department of Chemistry, Vanderbilt University; Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
- A. B. Hancock, Jr., Memorial Laboratory for Cancer Research, Departments of Biochemistry, and Pharmacology, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
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5
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Reed MR, Lyle AG, De Loose A, Maddukuri L, Learned K, Beale HC, Kephart ET, Cheney A, van den Bout A, Lee MP, Hundley KN, Smith AM, DesRochers TM, Vibat CRT, Gokden M, Salama S, Wardell CP, Eoff RL, Vaske OM, Rodriguez A. A Functional Precision Medicine Pipeline Combines Comparative Transcriptomics and Tumor Organoid Modeling to Identify Bespoke Treatment Strategies for Glioblastoma. Cells 2021; 10:cells10123400. [PMID: 34943910 PMCID: PMC8699481 DOI: 10.3390/cells10123400] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/25/2021] [Accepted: 11/29/2021] [Indexed: 12/15/2022] Open
Abstract
Li Fraumeni syndrome (LFS) is a hereditary cancer predisposition syndrome caused by germline mutations in TP53. TP53 is the most common mutated gene in human cancer, occurring in 30-50% of glioblastomas (GBM). Here, we highlight a precision medicine platform to identify potential targets for a GBM patient with LFS. We used a comparative transcriptomics approach to identify genes that are uniquely overexpressed in the LFS GBM patient relative to a cancer compendium of 12,747 tumor RNA sequencing data sets, including 200 GBMs. STAT1 and STAT2 were identified as being significantly overexpressed in the LFS patient, indicating ruxolitinib, a Janus kinase 1 and 2 inhibitors, as a potential therapy. The LFS patient had the highest level of STAT1 and STAT2 expression in an institutional high-grade glioma cohort of 45 patients, further supporting the cancer compendium results. To empirically validate the comparative transcriptomics pipeline, we used a combination of adherent and organoid cell culture techniques, including ex vivo patient-derived organoids (PDOs) from four patient-derived cell lines, including the LFS patient. STAT1 and STAT2 expression levels in the four patient-derived cells correlated with levels identified in the respective parent tumors. In both adherent and organoid cultures, cells from the LFS patient were among the most sensitive to ruxolitinib compared to patient-derived cells with lower STAT1 and STAT2 expression levels. A spheroid-based drug screening assay (3D-PREDICT) was performed and used to identify further therapeutic targets. Two targeted therapies were selected for the patient of interest and resulted in radiographic disease stability. This manuscript supports the use of comparative transcriptomics to identify personalized therapeutic targets in a functional precision medicine platform for malignant brain tumors.
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Affiliation(s)
- Megan R. Reed
- Department of Biochemistry, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (M.R.R.); (L.M.); (R.L.E.)
- Department of Neurosurgery, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (A.D.L.); (M.P.L.); (K.N.H.)
| | - A. Geoffrey Lyle
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA 95064, USA; (A.G.L.); (H.C.B.); (A.C.); (A.v.d.B.); (S.S.); (O.M.V.)
- UC Santa Cruz Genomics Institute, University of California Santa Cruz, Santa Cruz, CA 95064, USA; (K.L.); (E.T.K.)
| | - Annick De Loose
- Department of Neurosurgery, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (A.D.L.); (M.P.L.); (K.N.H.)
| | - Leena Maddukuri
- Department of Biochemistry, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (M.R.R.); (L.M.); (R.L.E.)
| | - Katrina Learned
- UC Santa Cruz Genomics Institute, University of California Santa Cruz, Santa Cruz, CA 95064, USA; (K.L.); (E.T.K.)
| | - Holly C. Beale
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA 95064, USA; (A.G.L.); (H.C.B.); (A.C.); (A.v.d.B.); (S.S.); (O.M.V.)
- UC Santa Cruz Genomics Institute, University of California Santa Cruz, Santa Cruz, CA 95064, USA; (K.L.); (E.T.K.)
| | - Ellen T. Kephart
- UC Santa Cruz Genomics Institute, University of California Santa Cruz, Santa Cruz, CA 95064, USA; (K.L.); (E.T.K.)
| | - Allison Cheney
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA 95064, USA; (A.G.L.); (H.C.B.); (A.C.); (A.v.d.B.); (S.S.); (O.M.V.)
- UC Santa Cruz Genomics Institute, University of California Santa Cruz, Santa Cruz, CA 95064, USA; (K.L.); (E.T.K.)
| | - Anouk van den Bout
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA 95064, USA; (A.G.L.); (H.C.B.); (A.C.); (A.v.d.B.); (S.S.); (O.M.V.)
- UC Santa Cruz Genomics Institute, University of California Santa Cruz, Santa Cruz, CA 95064, USA; (K.L.); (E.T.K.)
| | - Madison P. Lee
- Department of Neurosurgery, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (A.D.L.); (M.P.L.); (K.N.H.)
| | - Kelsey N. Hundley
- Department of Neurosurgery, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (A.D.L.); (M.P.L.); (K.N.H.)
| | - Ashley M. Smith
- KIYATEC Inc., Greenville, SC 29605, USA; (A.M.S.); (T.M.D.); (C.R.T.V.)
| | | | | | - Murat Gokden
- Department of Pathology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA;
| | - Sofie Salama
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA 95064, USA; (A.G.L.); (H.C.B.); (A.C.); (A.v.d.B.); (S.S.); (O.M.V.)
- Howard Hughes Medical Institute, University of California Santa Cruz, Santa Cruz, CA 95064, USA
| | - Christopher P. Wardell
- Department of Biomedical Informatics, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA;
| | - Robert L. Eoff
- Department of Biochemistry, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (M.R.R.); (L.M.); (R.L.E.)
| | - Olena M. Vaske
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA 95064, USA; (A.G.L.); (H.C.B.); (A.C.); (A.v.d.B.); (S.S.); (O.M.V.)
| | - Analiz Rodriguez
- Department of Neurosurgery, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (A.D.L.); (M.P.L.); (K.N.H.)
- Correspondence: ; Tel.: +1-501-686-8078; Fax: +1-501-686-8767
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6
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Darrigues E, Zhao EH, De Loose A, Lee MP, Borrelli MJ, Eoff RL, Galileo DS, Penthala NR, Crooks PA, Rodriguez A. Biobanked Glioblastoma Patient-Derived Organoids as a Precision Medicine Model to Study Inhibition of Invasion. Int J Mol Sci 2021; 22:ijms221910720. [PMID: 34639060 PMCID: PMC8509225 DOI: 10.3390/ijms221910720] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 09/25/2021] [Accepted: 09/26/2021] [Indexed: 12/11/2022] Open
Abstract
Glioblastoma (GBM) is highly resistant to treatment and invasion into the surrounding brain is a cancer hallmark that leads to recurrence despite surgical resection. With the emergence of precision medicine, patient-derived 3D systems are considered potentially robust GBM preclinical models. In this study, we screened a library of 22 anti-invasive compounds (i.e., NF-kB, GSK-3-B, COX-2, and tubulin inhibitors) using glioblastoma U-251 MG cell spheroids. We evaluated toxicity and invasion inhibition using a 3D Matrigel invasion assay. We next selected three compounds that inhibited invasion and screened them in patient-derived glioblastoma organoids (GBOs). We developed a platform using available macros for FIJI/ImageJ to quantify invasion from the outer margin of organoids. Our data demonstrated that a high-throughput invasion screening can be done using both an established cell line and patient-derived 3D model systems. Tubulin inhibitor compounds had the best efficacy with U-251 MG cells, however, in ex vivo patient organoids the results were highly variable. Our results indicate that the efficacy of compounds is highly related to patient intra and inter-tumor heterogeneity. These results indicate that such models can be used to evaluate personal oncology therapeutic strategies.
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Affiliation(s)
- Emilie Darrigues
- Department of Neurosurgery, Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (E.D.); (E.H.Z.); (A.D.L.); (M.P.L.)
| | - Edward H. Zhao
- Department of Neurosurgery, Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (E.D.); (E.H.Z.); (A.D.L.); (M.P.L.)
| | - Annick De Loose
- Department of Neurosurgery, Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (E.D.); (E.H.Z.); (A.D.L.); (M.P.L.)
| | - Madison P. Lee
- Department of Neurosurgery, Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (E.D.); (E.H.Z.); (A.D.L.); (M.P.L.)
| | - Michael J. Borrelli
- Department of Radiology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA;
| | - Robert L. Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA;
| | - Deni S. Galileo
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA;
| | - Narsimha R. Penthala
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (N.R.P.); (P.A.C.)
| | - Peter A. Crooks
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (N.R.P.); (P.A.C.)
| | - Analiz Rodriguez
- Department of Neurosurgery, Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (E.D.); (E.H.Z.); (A.D.L.); (M.P.L.)
- Correspondence:
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7
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Urbaniak A, Reed MR, Fil D, Moorjani A, Heflin S, Antoszczak M, Sulik M, Huczyński A, Kupsik M, Eoff RL, MacNicol MC, Chambers TC, MacNicol AM. Single and double modified salinomycin analogs target stem-like cells in 2D and 3D breast cancer models. Biomed Pharmacother 2021; 141:111815. [PMID: 34130123 PMCID: PMC8429223 DOI: 10.1016/j.biopha.2021.111815] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/25/2021] [Accepted: 06/07/2021] [Indexed: 01/05/2023] Open
Abstract
Breast cancer remains one of the leading cancers among women. Cancer stem cells (CSCs) are tumor-initiating cells which drive progression, metastasis, and reoccurrence of the disease. CSCs are resistant to conventional chemo- and radio-therapies and their ability to survive such treatment enables tumor reestablishment. Metastasis is the main cause of mortality in women with breast cancer, thus advances in treatment will depend on therapeutic strategies targeting CSCs. Salinomycin (SAL) is a naturally occurring polyether ionophore antibiotic known for its anticancer activity towards several types of tumor cells. In the present work, a library of 17 C1-single and C1/C20-double modified SAL analogs was screened to identify compounds with improved activity against breast CSCs. Six single- and two double-modified analogs were more potent (IC50 range of 1.1 ± 0.1-1.4 ± 0.2 µM) toward the breast cancer cell line MDA-MB-231 compared to SAL (IC50 of 4.9 ± 1.6 µM). Double-modified compound 17 was found to be more efficacious than SAL against the majority of cancer cell lines in the NCI-60 Human Tumor Cell Line Panel. Compound 17 was more potent than SAL in inhibiting cell migration and cell renewal properties of MDA-MB-231 cells, as well as inducing selective loss of the CD44+/CD24/low stem-cell-like subpopulation in both monolayer (2D) and organoid (3D) culture. The present findings highlight the therapeutic potential of SAL analogs towards breast CSCs and identify select compounds that merit further study and clinical development.
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Affiliation(s)
- Alicja Urbaniak
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States.
| | - Megan R Reed
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Daniel Fil
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Anika Moorjani
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Sarah Heflin
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Michał Antoszczak
- Department of Medical Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Uniwersytetu Poznańskiego 8, 61-614 Poznań, Poland
| | - Michał Sulik
- Department of Medical Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Uniwersytetu Poznańskiego 8, 61-614 Poznań, Poland
| | - Adam Huczyński
- Department of Medical Chemistry, Faculty of Chemistry, Adam Mickiewicz University, Uniwersytetu Poznańskiego 8, 61-614 Poznań, Poland
| | | | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Melanie C MacNicol
- Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Timothy C Chambers
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Angus M MacNicol
- Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
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8
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Reed MR, Maddukuri L, Ketkar A, Byrum SD, Zafar MK, Bostian ACL, Tackett AJ, Eoff RL. Inhibition of tryptophan 2,3-dioxygenase impairs DNA damage tolerance and repair in glioma cells. NAR Cancer 2021; 3:zcab014. [PMID: 33870196 PMCID: PMC8034706 DOI: 10.1093/narcan/zcab014] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 03/15/2021] [Accepted: 03/23/2021] [Indexed: 01/21/2023] Open
Abstract
Expression of tryptophan 2,3-dioxygenase (TDO) is a determinant of malignancy in gliomas through kynurenine (KYN) signaling. We report that inhibition of TDO activity attenuated recovery from replication stress and increased the genotoxic effects of bis-chloroethylnitrosourea (BCNU). Activation of the Chk1 arm of the replication stress response (RSR) was reduced when TDO activity was blocked prior to BCNU treatment, whereas phosphorylation of serine 33 (pS33) on replication protein A (RPA) was enhanced—indicative of increased fork collapse. Analysis of quantitative proteomic results revealed that TDO inhibition reduced nuclear 53BP1 and sirtuin levels. We confirmed that cells lacking TDO activity exhibited elevated gamma-H2AX signal and defective recruitment of 53BP1 to chromatin following BCNU treatment, which corresponded with delayed repair of DNA breaks. Addition of exogenous KYN increased the rate of break repair. TDO inhibition diminished SIRT7 deacetylase recruitment to chromatin, which increased histone H3K18 acetylation—a key mark involved in preventing 53BP1 recruitment to sites of DNA damage. TDO inhibition also sensitized cells to ionizing radiation (IR)-induced damage, but this effect did not involve altered 53BP1 recruitment. These experiments support a model where TDO-mediated KYN signaling helps fuel a robust response to replication stress and DNA damage.
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Affiliation(s)
- Megan R Reed
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Leena Maddukuri
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Stephanie D Byrum
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Maroof K Zafar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - April C L Bostian
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Alan J Tackett
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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9
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Ketkar A, Smith L, Johnson C, Richey A, Berry M, Hartman JH, Maddukuri L, Reed MR, Gunderson JEC, Leung JWC, Eoff RL. Human Rev1 relies on insert-2 to promote selective binding and accurate replication of stabilized G-quadruplex motifs. Nucleic Acids Res 2021; 49:2065-2084. [PMID: 33555350 PMCID: PMC7913688 DOI: 10.1093/nar/gkab041] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 01/06/2021] [Accepted: 01/15/2021] [Indexed: 12/18/2022] Open
Abstract
We previously reported that human Rev1 (hRev1) bound to a parallel-stranded G-quadruplex (G4) from the c-MYC promoter with high affinity. We have extended those results to include other G4 motifs, finding that hRev1 exhibited stronger affinity for parallel-stranded G4 than either anti-parallel or hybrid folds. Amino acids in the αE helix of insert-2 were identified as being important for G4 binding. Mutating E466 and Y470 to alanine selectively perturbed G4 binding affinity. The E466K mutant restored wild-type G4 binding properties. Using a forward mutagenesis assay, we discovered that loss of hRev1 increased G4 mutation frequency >200-fold compared to the control sequence. Base substitutions and deletions occurred around and within the G4 motif. Pyridostatin (PDS) exacerbated this effect, as the mutation frequency increased >700-fold over control and deletions upstream of the G4 site more than doubled. Mutagenic replication of G4 DNA (±PDS) was partially rescued by wild-type and E466K hRev1. The E466A or Y470A mutants failed to suppress the PDS-induced increase in G4 mutation frequency. These findings have implications for the role of insert-2, a motif conserved in vertebrates but not yeast or plants, in Rev1-mediated suppression of mutagenesis during G4 replication.
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Affiliation(s)
- Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Lane Smith
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Callie Johnson
- Arkansas School for Mathematics, Sciences, and the Arts, Hot Springs, AR 71901, USA
| | - Alyssa Richey
- Arkansas School for Mathematics, Sciences, and the Arts, Hot Springs, AR 71901, USA
| | - Makayla Berry
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Jessica H Hartman
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
| | - Leena Maddukuri
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Megan R Reed
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | | | - Justin W C Leung
- Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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10
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Urbaniak AJ, Reed MR, Antoszczak M, Sulik M, Huczyński A, Eoff RL, MacNicol MC, Chambers TC, MacNicol AM. Abstract PS18-46: Inhibition of breast cancer stem cells in 2- and 3-dimensional culture by novel salinomycin analogs. Cancer Res 2021. [DOI: 10.1158/1538-7445.sabcs20-ps18-46] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Breast cancer remains one of the leading cancers among women and an estimated 90% of breast cancer deaths are due to metastasis. Cancer stem cells (CSCs) are a sub-population of cancer cells which are responsible for its initiation, progression and metastasis. CSCs are resistant to conventional chemo- and radio-therapies and therefore therapeutic strategies targeting CSCs hold great potential for novel advances in cancer treatment. Salinomycin (SAL) is a naturally occurring polyether ionophore antibiotic which was shown to effectively target breast CSCs. A library of 17 novel SAL analogs was synthesized and screened to identify compounds with improved selectivity against breast cancer stem cells. SAL analogs were either single modified esters or amides in the C1 position or double-modified C20-oxo derivatives. Eight single- and two double-modified analogs were more potent (IC50 range of 1.13 ± 0.19 to 3.93 ± 0.39 µM) towards the breast cancer cell line MDA-MB-231 compared to parent SAL (IC50 of 4.90 ± 1.60 µM). These analogs induced DNA fragmentation suggestive of apoptotic cell death. Compounds 2 (butyl ester analog of SAL) and 17 (double-modified C20-oxosalinomycin with benzhydroxamic acid) have been chosen for follow-up screening due to their improved activity and selectivity versus parent SAL. This included clonogenic assays to assess the ability of the compounds to affect cell renewal, and wound healing assays to assess cell migratory properties. In both assays, compound 17 showed superior properties over SAL. Furthermore, analog 17 showed improved targeting of breast CSCs in both cell monolayer and organoid culture as assessed in assays measuring the CD44+/CD24- stem cell sub-population. Analogs and parent compound were further studied examining (ADP-ribose) polymerase (PARP) cleavage and Bcl-2 levels by immunoblotting. All three compounds induced loss of 116 kDa PARP expression within 48h, with the highest effect induced by analog 17. In addition, treatment with compound 17 caused a decrease in Bcl-2 expression as early as 24 h. Select analogs were next screened against the NCI-60 Human Tumor Cell Line Panel. The described above double-modified analog was found to be more potent than SAL towards all 6 breast cancer cell lines in the panel as well as other tumor types. The present findings highlight the therapeutic potential of SAL analogs towards breast stem cells and support further research and clinical development of these compounds.
Funding: The present study was funded by grants (to AM and TCC) from the Arkansas Breast Cancer Research Program. Testing was performed by the Developmental Therapeutics Program, Division of Cancer Treatment and Diagnosis, National Cancer Institute, http://dtp.cancer.gov.
Citation Format: Alicja Joanna Urbaniak, Megan R. Reed, Michał Antoszczak, Michał Sulik, Adam Huczyński, Robert L. Eoff, Melanie C. MacNicol, Timothy C. Chambers, Angus M. MacNicol. Inhibition of breast cancer stem cells in 2- and 3-dimensional culture by novel salinomycin analogs [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS18-46.
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Affiliation(s)
| | - Megan R. Reed
- 1University of Arkansas for Medical Sciences, Little Rock, AR
| | | | | | | | - Robert L. Eoff
- 1University of Arkansas for Medical Sciences, Little Rock, AR
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11
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Gujarathi S, Zafar MK, Liu X, Eoff RL, Zheng G. A Facile Semisynthesis and Evaluation of Garcinoic Acid and Its Analogs for the Inhibition of Human DNA Polymerase β. Molecules 2020; 25:E5847. [PMID: 33322249 PMCID: PMC7763917 DOI: 10.3390/molecules25245847] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 12/09/2020] [Indexed: 11/17/2022] Open
Abstract
Garcinoic acid has been identified as an inhibitor of DNA polymerase β (pol β). However, no structure-activity relationship (SAR) studies of garcinoic acid as a pol β inhibitor have been conducted, in part due to the lack of an efficient synthetic method for this natural product and its analogs. We developed an efficient semi-synthetic method for garcinoic acid and its analogs by starting from natural product δ-tocotrienol. Our preliminary SAR studies provided a valuable insight into future discovery of garcinoic acid-based pol β inhibitors.
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Affiliation(s)
- Satheesh Gujarathi
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (S.G.); (X.L.)
| | - Maroof Khan Zafar
- Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (M.K.Z.); (R.L.E.)
| | - Xingui Liu
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (S.G.); (X.L.)
| | - Robert L. Eoff
- Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (M.K.Z.); (R.L.E.)
| | - Guangrong Zheng
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA; (S.G.); (X.L.)
- Department of Medicinal Chemistry, College of Pharmacy, University of Florida, Gainesville, FL 32610, USA
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12
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Urbaniak A, Reed MR, Antoszczak M, Sulik M, Huczyñski A, Eoff RL, MacNicol MC, MacNicol AM, Chambers TC. Novel Salinomycin Analogs Show Improved Selectivity Towards Breast Cancer Stem Cells. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.06110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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13
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West KL, Kelliher JL, Xu Z, An L, Reed MR, Eoff RL, Wang J, Huen MSY, Leung JWC. LC8/DYNLL1 is a 53BP1 effector and regulates checkpoint activation. Nucleic Acids Res 2020; 47:6236-6249. [PMID: 30982887 DOI: 10.1093/nar/gkz263] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2018] [Revised: 03/15/2019] [Accepted: 04/01/2019] [Indexed: 01/05/2023] Open
Abstract
The tumor suppressor protein 53BP1 plays key roles in response to DNA double-strand breaks (DSBs) by serving as a master scaffold at the damaged chromatin. Current evidence indicates that 53BP1 assembles a cohort of DNA damage response (DDR) factors to distinctly execute its repertoire of DSB responses, including checkpoint activation and non-homologous end joining (NHEJ) repair. Here, we have uncovered LC8 (a.k.a. DYNLL1) as an important 53BP1 effector. We found that LC8 accumulates at laser-induced DNA damage tracks in a 53BP1-dependent manner and requires the canonical H2AX-MDC1-RNF8-RNF168 signal transduction cascade. Accordingly, genetic inactivation of LC8 or its interaction with 53BP1 resulted in checkpoint defects. Importantly, loss of LC8 alleviated the hypersensitivity of BRCA1-depleted cells to ionizing radiation and PARP inhibition, highlighting the 53BP1-LC8 module in counteracting BRCA1-dependent functions in the DDR. Together, these data establish LC8 as an important mediator of a subset of 53BP1-dependent DSB responses.
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Affiliation(s)
- Kirk L West
- Department of Radiation Oncology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Jessica L Kelliher
- Department of Radiation Oncology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Zhanzhan Xu
- Department of Radiation Medicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Liwei An
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Megan R Reed
- Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Jiadong Wang
- Department of Radiation Medicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Michael S Y Huen
- School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China
| | - Justin W C Leung
- Department of Radiation Oncology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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14
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Madadi NR, Penthala NR, Ketkar A, Eoff RL, Trujullo-Alonso V, Guzman ML, Crooks PA. Synthesis and Evaluation of 2-Naphthaleno trans-Stilbenes and Cyanostilbenes as Anticancer Agents. Anticancer Agents Med Chem 2019; 18:556-564. [PMID: 28403783 DOI: 10.2174/1871521409666170412115703] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 03/01/2017] [Accepted: 04/04/2017] [Indexed: 01/08/2023]
Abstract
BACKGROUND Naphthalene is a good structural replacement for the isovanillin moiety (i.e. the 3- hydroxy-4-methoxyphenyl unit) in the combretastatin A-4 molecule, a natural product structurally related to resveratrol, which consistently led to the generation of highly cytotoxic naphthalene analogues when combined with a 3,4,5-trimethoxyphenyl or related aromatic system. Also, the naphthalene ring system is present in many current drug molecules that are utilized for anti-tumor, anti-arrhythmia and antioxidant therapy. OBJECTIVE In our continuing quest to improve the potencies of naturally occurring anti-cancer molecules through chemical modification, we have now synthesized a small library of 2-naphthaleno trans- stilbenes and cyanostilbenes that are structurally related to both resveratrol and DMU-212, and have evaluated these novel analogs against a panel of 54 human tumor cell lines. METHOD A series of 2-naphthaleno-containing trans-stilbenes 3a-3h (Scheme 1) were synthesized by Wittig reaction of a variety of aromatic substituted benzyl-triphenylphosphonium bromide reactants with 2- naphthaldehyde using n-BuLi as a base in THF. A second series of 2-naphthaleno trans-cyanostilbenes analogs 5a-5h was synthesized by reaction of 2-naphthaldehyde (2; 1 mmol) with an appropriately substituted 2- phenylacrylonitrile 4a-4h; 1 mmol) in 5% sodium methoxide/methanol. The reaction mixture was stirred at room temperature for 2-3 hours and the reaction allowed to go to completion (TLC monitoring), during which time the desired product precipitated out of the solution as a solid. The resulting precipitate was filtered off, washed with water and dried to yield the desired compound in yields ranging from 70-95% (Scheme 2). RESULTS The percentage growth inhibition of 54 human cancer cell lines in a primary NCI screen after exposure to compounds 3a, 3d, 5b and 5c was carried out. The results showed that only compounds 5b and 5c met the criteria for subsequent testing to determine growth inhibition values (GI50) in dose-response studies. At 10-5 M concentration, compounds 5b and 5c exhibited cytotoxic activity against leukemia cell lines HL-60(TB) and SR, lung cancer cell line NCI-H522, colon cancer cell lines COLO 205 and HCT-116, CNS-cancer cell line SF-539, melanoma cell line MDA-MB-435, and breast cancer cell line BT-549. The naphthalene trans-stilbene analogue 3a, exhibited significant growth inhibition against only one cell line, melanoma cell line MDA-MB-435 (96 % growth inhibition). Compound 3d was inactive in the 10-5 M single dose screen. CONCLUSION We have synthesized a small set of novel 2-naphthaleno stilbenes and cyanostilbenes and evaluated several of these compounds for their anticancer properties against a panel of 54 human tumor cell lines. The most active analogs, 5b and 5c, showed significantly improved growth inhibition against the human cancer cells in the NCI panel when compared to DMU-212. Of these compounds, analog 5c was found to be the most potent anticancer agent and exhibited significant growth inhibitory effects against COLO 205, CNS SF 539 and melanoma SK-MEL 5 and MDA-MB-435 cell lines with GI50 values ≤ 25 nM. Analog 5b also exhibited GI50 values in the range 25-41 nM against CNS SF 295 and melanoma MDA-MB-435 and UACC-62 cell lines. Compounds 5b and 5c were also cytotoxic towards the MV4-11 leukemia cell line with LD50 value of 450 nM and 200 nM, respectively, and demonstrated >50% inhibition of tubulin polymerization at concentrations below their LD50 values in these cells. In silico docking studies suggest that compounds 5b and 5c bind favorably at the colchicine- binding pocket of the tubulin dimer, indicating that both 5b and 5c may inhibit tubulin polymerization through a mechanism similar to that exhibited by colchicine. Derivative 5c demonstrated more favorable binding based on the docking score and buried surface area, as compared to compound 5b, in agreement with the higher observed potency of 5c against a broader range of tumor cell lines. Based on these results, analog 5c is considered to be a lead compound for further optimization as a clinical candidate for treating a variety of cancers.
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Affiliation(s)
- Nikhil R Madadi
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Narsimha R Penthala
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
| | - Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, United States
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, United States
| | | | - Monica L Guzman
- Weill Cornell Medical College, New York, NY 10021, United States
| | - Peter A Crooks
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, United States
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15
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Ketkar A, Maddukuri L, Penthala NR, Reed MR, Zafar MK, Crooks PA, Eoff RL. Inhibition of Human DNA Polymerases Eta and Kappa by Indole-Derived Molecules Occurs through Distinct Mechanisms. ACS Chem Biol 2019; 14:1337-1351. [PMID: 31082191 DOI: 10.1021/acschembio.9b00304] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Overexpression of human DNA polymerase kappa (hpol κ) in glioblastoma is associated with shorter survival time and resistance to the alkylating agent temozolomide (TMZ), making it an attractive target for the development of small-molecule inhibitors. We previously reported on the development and characterization of indole barbituric acid-derived (IBA) inhibitors of translesion DNA synthesis polymerases (TLS pols). We have now identified a potent and selective inhibitor of hpol κ based on the indole-aminoguanidine (IAG) chemical scaffold. The most promising IAG analogue, IAG-10, exhibited greater inhibitory action against hpol κ than any other human Y-family member, as well as pols from the A-, B-, and X-families. Inhibition of hpol κ by IAG analogues appears to proceed through a mechanism that is distinct from inhibition of hpol η based on changes in DNA binding affinity and nucleotide insertion kinetics. By way of comparison, both IAG and IBA analogues inhibited binary complex formation by hpol κ and ternary complex formation by hpol η. Decreasing the concentration of enzyme and DNA in the reaction mixture lowered the IC50 value of IAG-10 to submicromolar values, consistent with inhibition of binary complex formation for hpol κ. Chemical footprinting experiments revealed that IAG-10 binds to a cleft between the finger, little finger, and N-clasp domains on hpol κ and that this likely disrupts the interaction between the N-clasp and the TLS pol core. In cell culture, IAG-10 potentiated the antiproliferative activity and DNA damaging effects of TMZ in hpol κ-proficient cells but not in hpol κ-deficient cells, indicative of a target-dependent effect. Mutagenic replication across alkylation damage increased in hpol κ-proficient cells treated with IAG-10, while no change in mutation frequency was observed for hpol κ-deficient cells. In summary, we developed a potent and selective small-molecule inhibitor of hpol κ that takes advantage of structural features unique to this TLS enzyme to potentiate TMZ, a standard-of-care drug used in the treatment of malignant brain tumors. Furthermore, the IAG scaffold represents a new chemical space for the exploration of TLS pol inhibitors, which could prove useful as a strategy for improving patient response to genotoxic drugs.
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Affiliation(s)
- Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
| | - Leena Maddukuri
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
| | - Narsimha R. Penthala
- Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
| | - Megan R. Reed
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
| | - Maroof K. Zafar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
| | - Peter A. Crooks
- Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
| | - Robert L. Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
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16
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Zafar MK, Maddukuri L, Ketkar A, Penthala NR, Reed MR, Eddy S, Crooks PA, Eoff RL. A Small-Molecule Inhibitor of Human DNA Polymerase η Potentiates the Effects of Cisplatin in Tumor Cells. Biochemistry 2018; 57:1262-1273. [PMID: 29345908 DOI: 10.1021/acs.biochem.7b01176] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Translesion DNA synthesis (TLS) performed by human DNA polymerase eta (hpol η) allows tolerance of damage from cis-diamminedichloroplatinum(II) (CDDP or cisplatin). We have developed hpol η inhibitors derived from N-aryl-substituted indole barbituric acid (IBA), indole thiobarbituric acid (ITBA), and indole quinuclidine scaffolds and identified 5-((5-chloro-1-(naphthalen-2-ylmethyl)-1H-indol-3-yl)methylene)-2-thioxodihydropyrimidine-4,6(1H,5H)-dione (PNR-7-02), an ITBA derivative that inhibited hpol η activity with an IC50 value of 8 μM and exhibited 5-10-fold specificity for hpol η over replicative pols. We conclude from kinetic analyses, chemical footprinting assays, and molecular docking that PNR-7-02 binds to a site on the little finger domain and interferes with the proper orientation of template DNA to inhibit hpol η. A synergistic increase in CDDP toxicity was observed in hpol η-proficient cells co-treated with PNR-7-02 (combination index values = 0.4-0.6). Increased γH2AX formation accompanied treatment of hpol η-proficient cells with CDDP and PNR-7-02. Importantly, PNR-7-02 did not impact the effect of CDDP on cell viability or γH2AX in hpol η-deficient cells. In summary, we observed hpol η-dependent effects on DNA damage/replication stress and sensitivity to CDDP in cells treated with PNR-7-02. The ability to employ a small-molecule inhibitor of hpol η to improve the cytotoxic effect of CDDP may aid in the development of more effective chemotherapeutic strategies.
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Affiliation(s)
- Maroof K Zafar
- Department of Biochemistry and Molecular Biology, ‡Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Leena Maddukuri
- Department of Biochemistry and Molecular Biology, ‡Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Amit Ketkar
- Department of Biochemistry and Molecular Biology, ‡Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Narsimha R Penthala
- Department of Biochemistry and Molecular Biology, ‡Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Megan R Reed
- Department of Biochemistry and Molecular Biology, ‡Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Sarah Eddy
- Department of Biochemistry and Molecular Biology, ‡Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Peter A Crooks
- Department of Biochemistry and Molecular Biology, ‡Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, ‡Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
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17
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Abstract
The genomic landscape of cancer is one marred by instability, but the mechanisms that underlie these alterations are multifaceted and remain a topic of intense research. Cellular responses to DNA damage and/or replication stress can affect genome stability in tumors and influence the response of patients to therapy. In addition to direct repair, DNA damage tolerance (DDT) is an element of genomic maintenance programs that contributes to the etiology of several types of cancer. DDT mechanisms primarily act to resolve replication stress, and this can influence the effectiveness of genotoxic drugs. Translesion DNA synthesis (TLS) is an important component of DDT that facilitates direct bypass of DNA adducts and other barriers to replication. The central role of TLS in the bypass of drug-induced DNA lesions, the promotion of tumor heterogeneity, and the involvement of these enzymes in the maintenance of the cancer stem cell niche presents an opportunity to leverage inhibition of TLS as a way of improving existing therapies. In the review that follows, we summarize mechanisms of DDT, misregulation of TLS in cancer, and discuss the potential for targeting these pathways as a means of improving cancer therapies.
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Affiliation(s)
- Maroof K Zafar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
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18
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Abstract
Uncovering the mechanisms by which single-stranded binding proteins both protect and expose single-stranded DNA has important implications for our understanding of DNA replication and repair. A new study serves up a master class in developing a full kinetic model for one such protein, mtSSB, showing how DNA can be reeled in and set free to control accessibility.
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Affiliation(s)
- Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205.
| | - Kevin D Raney
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205.
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19
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Ketkar A, Voehler M, Mukiza T, Eoff RL. Residues in the RecQ C-terminal Domain of the Human Werner Syndrome Helicase Are Involved in Unwinding G-quadruplex DNA. J Biol Chem 2017; 292:3154-3163. [PMID: 28069813 DOI: 10.1074/jbc.m116.767699] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 01/04/2017] [Indexed: 12/11/2022] Open
Abstract
The structural and biophysical properties typically associated with G-quadruplex (G4) structures render them a significant block for DNA replication, which must be overcome for cell division to occur. The Werner syndrome protein (WRN) is a RecQ family helicase that has been implicated in the efficient processing of G4 DNA structures. The aim of this study was to identify the residues of WRN involved in the binding and ATPase-driven unwinding of G4 DNA. Using a c-Myc G4 DNA model sequence and recombinant WRN, we have determined that the RecQ-C-terminal (RQC) domain of WRN imparts a 2-fold preference for binding to G4 DNA relative to non-G4 DNA substrates. NMR studies identified residues involved specifically in interactions with G4 DNA. Three of the amino acids in the WRN RQC domain that exhibited the largest G4-specific changes in NMR signal were then mutated alone or in combination. Mutating individual residues implicated in G4 binding had a modest effect on WRN binding to DNA, decreasing the preference for G4 substrates by ∼25%. Mutating two G4-interacting residues (T1024G and T1086G) abrogated preferential binding of WRN to G4 DNA. Very modest decreases in G4 DNA-stimulated ATPase activity were observed for the mutant enzymes. Most strikingly, G4 unwinding by WRN was inhibited ∼50% for all three point mutants and >90% for the WRN double mutant (T1024G/T1086G) relative to normal B-form dsDNA substrates. Our work has helped to identify residues in the WRN RQC domain that are involved specifically in the interaction with G4 DNA.
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Affiliation(s)
- Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199
| | - Markus Voehler
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235
| | - Tresor Mukiza
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199.
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20
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Yadlapalli JSK, Ford BM, Ketkar A, Wan A, Penthala NR, Eoff RL, Prather PL, Dobretsov M, Crooks PA. Antinociceptive effects of the 6-O-sulfate ester of morphine in normal and diabetic rats: Comparative role of mu- and delta-opioid receptors. Pharmacol Res 2016; 113:335-347. [PMID: 27637375 DOI: 10.1016/j.phrs.2016.09.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 08/30/2016] [Accepted: 09/12/2016] [Indexed: 12/20/2022]
Abstract
This study determined the antinociceptive effects of morphine and morphine-6-O-sulfate (M6S) in both normal and diabetic rats, and evaluated the comparative role of mu-opioid receptors (mu-ORs) and delta-opioid receptors (delta-ORs) in the antinociceptive action of these opioids. In vitro characterization of mu-OR and delta-OR-mediated signaling by M6S and morphine in stably transfected Chinese hamster ovary (CHO-K1) cells showed that M6S exhibited a 6-fold higher affinity for delta-ORs and modulated G-protein and adenylyl cyclase activity via delta-ORs more potently than morphine. Interestingly, while morphine acted as a full agonist at delta-ORs in both functional assays examined, M6S exhibited either partial or full agonist activity for modulation of G-protein or adenylyl cyclase activity, respectively. Molecular docking studies indicated that M6S but not morphine binds equally well at the ligand binding site of both mu- and delta-ORs. In vivo analgesic effects of M6S and morphine in both normal and streptozotocin-induced diabetic Sprague-Dawley rats utilizing the hot water tail flick latency test showed that M6S produced more potent antinociception than morphine in both normal rats and diabetic rats. This difference in potency was abrogated following antagonism of delta- but not mu- or kappa (kappa-ORs) opioid receptors. During 9days of chronic treatment, tolerance developed to morphine-treated but not to M6S-treated rats. Rats that developed tolerance to morphine still remained responsive to M6S. Collectively, this study demonstrates that M6S is a potent and efficacious mu/delta opioid analgesic with a delayed tolerance profile when compared to morphine in both normal and diabetic rats. PERSPECTIVE This study demonstrates that M6S acts at both mu- and delta-ORs, and adds to the growing evidence that the use of mixed mu/delta opioid agonists in pain treatment may have clinical benefit.
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Affiliation(s)
- Jai Shankar K Yadlapalli
- Departments of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Benjamin M Ford
- Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Amit Ketkar
- Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Anqi Wan
- Departments of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Narasimha R Penthala
- Departments of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Robert L Eoff
- Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Paul L Prather
- Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Maxim Dobretsov
- Anesthesiology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Peter A Crooks
- Departments of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA.
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21
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Eddy S, Tillman M, Maddukuri L, Ketkar A, Zafar MK, Eoff RL. Human Translesion Polymerase κ Exhibits Enhanced Activity and Reduced Fidelity Two Nucleotides from G-Quadruplex DNA. Biochemistry 2016; 55:5218-29. [PMID: 27525498 DOI: 10.1021/acs.biochem.6b00374] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have investigated the in vitro properties of human Y-family polymerase κ (hpol κ) on G-quadruplex DNA (G4 DNA). Similar to hpol η, another Y-family member implicated in replication of G4 motifs, hpol κ bound G4 DNA with a 5.7-fold preference over control, non-G4 DNA. Results from pol extension assays are consistent with the notion that G-quadruplexes present a stronger barrier to DNA synthesis by hpol κ than they do to that by hpol η. However, kinetic analysis revealed that hpol κ activity increases considerably when the enzyme is 2-3 nucleotides from the G4 motif, a trend that was reported previously for hpol η, though the increase was less pronounced. The increase in hpol κ activity on G4 DNA was readily observed in the presence of either potassium or sodium but much less so when lithium was used in the buffer. The increased activity 2-3 nucleotides from the G4 motif was accompanied by a decrease in the fidelity of hpol κ when the counterion was either potassium or sodium but not in the presence of lithium. The activity of hpol κ decreased progressively as the primer was moved closer than 2 nucleotides from the G4 motif when either potassium or sodium was used to stabilize the G-quadruplex. Interestingly, the decrease in catalytic activity at the site of the quadruplex observed in potassium-containing buffer was accompanied by an increase in fidelity on G4 substrates versus control non-G4 substrates. This trend of increased fidelity in copying a tetrad-associated guanine was observed previously for hpol η, but not for the B-family member hpol ε, which exhibited a large decrease in both efficiency and fidelity in the attempt to copy the first guanine in the G4 motif. In summary, hpol κ activity was enhanced relative to those of other Y-family members when the enzyme is 2-3 nucleotides from the G4 motif, but hpol κ appears to be less competent than hpol η at copying tetrad-associated guanines.
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Affiliation(s)
- Sarah Eddy
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Magdalena Tillman
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Leena Maddukuri
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Maroof K Zafar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
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22
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Penthala NR, Ketkar A, Sekhar KR, Freeman ML, Eoff RL, Balusu R, Crooks PA. 1-Benzyl-2-methyl-3-indolylmethylene barbituric acid derivatives: Anti-cancer agents that target nucleophosmin 1 (NPM1). Bioorg Med Chem 2016; 23:7226-33. [PMID: 26602084 DOI: 10.1016/j.bmc.2015.10.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 10/06/2015] [Accepted: 10/13/2015] [Indexed: 10/22/2022]
Abstract
In the present study, we have designed and synthesized a series of 1-benzyl-2-methyl-3-indolylmethylene barbituric acid analogs (7a-7h) and 1-benzyl-2-methyl-3-indolylmethylene thiobarbituric acid analogs (7 i-7 l) as nucleophosmin 1 (NPM1) inhibitors and have evaluated them for their anti-cancer activity against a panel of 60 different human cancer cell lines. Among these analogs 7 i, 7 j, and 7 k demonstrated potent growth inhibitory effects in various cancer cell types with GI50 values <2 μM. Compound 7 k exhibited growth inhibitory effects on a sub-panel of six leukemia cell lines with GI50 values in the range 0.22-0.35 μM. Analog 7 i also exhibited GI50 values <0.35 μM against three of the leukemia cell lines in the sub-panel. Analogs 7 i, 7 j, 7 k and 7 l were also evaluated against the mutant NPM1 expressing OCI-AML3 cell line and compounds 7 k and 7 l were found to cause dose-dependent apoptosis (AP50 = 1.75 μM and 3.3 μM, respectively). Compound 7k also exhibited potent growth inhibition against a wide variety of solid tumor cell lines: that is, A498 renal cancer (GI50 = 0.19 μM), HOP-92 and NCI-H522 lung cancer (GI50 = 0.25 μM), COLO 205 and HCT-116 colon cancer (GI50 = 0.20 and 0.26 μM, respectively), CNS cancer SF-539 (GI50 = 0.22 μM), melanoma MDA-MB-435 (GI50 = 0.22 μM), and breast cancer HS 578T (GI50 = 0.22 μM) cell lines. Molecular docking studies suggest that compounds 7 k and 7 l exert their anti-leukemic activity by binding to a pocket in the central channel of the NPM1 pentameric structure. These results indicate that the small molecule inhibitors 7 i, 7 j, 7 k, and 7 l could be potentially developed into anti-NPM1 drugs for the treatment of a variety of hematologic malignancies and solid tumors.
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23
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Abstract
Metabolism of the essential amino acid L-tryptophan (TRP) is implicated in a number of neurological conditions including depression, neurodegenerative diseases, and cancer. The TRP catabolite kynurenine (KYN) has recently emerged as an important neuroactive factor in brain tumor pathogenesis, with additional studies implicating KYN in other types of cancer. Often highlighted as a modulator of the immune response and a contributor to immune escape for malignant tumors, it is well-known that KYN has effects on the production of the coenzyme nicotinamide adenine dinucleotide (NAD(+)), which can have a direct impact on DNA repair, replication, cell division, redox signaling, and mitochondrial function. Additional effects of KYN signaling are imparted through its role as an endogenous agonist for the aryl hydrocarbon receptor (AhR), and it is largely through activation of the AhR that KYN appears to mediate malignant progression in gliomas. We have recently reported on the ability of KYN signaling to modulate expression of human DNA polymerase kappa (hpol κ), a translesion enzyme involved in bypass of bulky DNA lesions and activation of the replication stress response. Given the impact of KYN on NAD(+) production, AhR signaling, and translesion DNA synthesis, it follows that dysregulation of KYN signaling in cancer may promote malignancy through alterations in the level of endogenous DNA damage and replication stress. In this perspective, we discuss the connections between KYN signaling, DNA damage tolerance, and genomic instability, as they relate to cancer.
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Affiliation(s)
- April C L Bostian
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , 4301 W. Markham Street, Little Rock, Arkansas 72205-7199, United States
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , 4301 W. Markham Street, Little Rock, Arkansas 72205-7199, United States
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24
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Byrd AK, Zybailov BL, Maddukuri L, Gao J, Marecki JC, Jaiswal M, Bell MR, Griffin WC, Reed MR, Chib S, Mackintosh SG, MacNicol AM, Baldini G, Eoff RL, Raney KD. Evidence That G-quadruplex DNA Accumulates in the Cytoplasm and Participates in Stress Granule Assembly in Response to Oxidative Stress. J Biol Chem 2016; 291:18041-57. [PMID: 27369081 DOI: 10.1074/jbc.m116.718478] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Indexed: 12/13/2022] Open
Abstract
Cells engage numerous signaling pathways in response to oxidative stress that together repair macromolecular damage or direct the cell toward apoptosis. As a result of DNA damage, mitochondrial DNA or nuclear DNA has been shown to enter the cytoplasm where it binds to "DNA sensors," which in turn initiate signaling cascades. Here we report data that support a novel signaling pathway in response to oxidative stress mediated by specific guanine-rich sequences that can fold into G-quadruplex DNA (G4DNA). In response to oxidative stress, we demonstrate that sequences capable of forming G4DNA appear at increasing levels in the cytoplasm and participate in assembly of stress granules. Identified proteins that bind to endogenous G4DNA in the cytoplasm are known to modulate mRNA translation and participate in stress granule formation. Consistent with these findings, stress granule formation is known to regulate mRNA translation during oxidative stress. We propose a signaling pathway whereby cells can rapidly respond to DNA damage caused by oxidative stress. Guanine-rich sequences that are excised from damaged genomic DNA are proposed to enter the cytoplasm where they can regulate translation through stress granule formation. This newly proposed role for G4DNA provides an additional molecular explanation for why such sequences are prevalent in the human genome.
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Affiliation(s)
- Alicia K Byrd
- From the Departments of Biochemistry and Molecular Biology and
| | - Boris L Zybailov
- From the Departments of Biochemistry and Molecular Biology and the University of Arkansas at Little Rock/University of Arkansas for Medical Sciences (UALR/UAMS) Joint Graduate Program in Bioinformatics, University of Arkansas at Little Rock, Little Rock, Arkansas 72204
| | - Leena Maddukuri
- From the Departments of Biochemistry and Molecular Biology and
| | - Jun Gao
- From the Departments of Biochemistry and Molecular Biology and
| | - John C Marecki
- From the Departments of Biochemistry and Molecular Biology and
| | - Mihir Jaiswal
- the University of Arkansas at Little Rock/University of Arkansas for Medical Sciences (UALR/UAMS) Joint Graduate Program in Bioinformatics, University of Arkansas at Little Rock, Little Rock, Arkansas 72204
| | - Matthew R Bell
- From the Departments of Biochemistry and Molecular Biology and
| | | | - Megan R Reed
- From the Departments of Biochemistry and Molecular Biology and
| | - Shubeena Chib
- From the Departments of Biochemistry and Molecular Biology and
| | - Samuel G Mackintosh
- From the Departments of Biochemistry and Molecular Biology and the Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205 and
| | - Angus M MacNicol
- the Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205 and Neurobiology and Developmental Sciences and
| | - Giulia Baldini
- From the Departments of Biochemistry and Molecular Biology and
| | - Robert L Eoff
- From the Departments of Biochemistry and Molecular Biology and the Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205 and
| | - Kevin D Raney
- From the Departments of Biochemistry and Molecular Biology and the Winthrop P. Rockefeller Cancer Institute, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205 and
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25
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Madadi NR, Ketkar A, Penthala NR, Bostian ACL, Eoff RL, Crooks PA. Dioxol and dihydrodioxin analogs of 2- and 3-phenylacetonitriles as potent anti-cancer agents with nanomolar activity against a variety of human cancer cells. Bioorg Med Chem Lett 2016; 26:2164-9. [PMID: 27017113 PMCID: PMC5930014 DOI: 10.1016/j.bmcl.2016.03.068] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 03/15/2016] [Accepted: 03/16/2016] [Indexed: 10/22/2022]
Abstract
A small library of (Z)-2-(benzo[d][1,3]dioxol-5-yl) and (Z)-2,3-dihydrobenzo[b][1,4]dioxin-6-yl analogs of 2- and 3-phenylacetonitriles has been synthesized and evaluated for their anti-cancer activities against a panel of 60 human cancer cell lines. The dihydrodioxin analog 3j and dioxol analogs 5e and 7e exhibited the most potent anti-cancer activity of all the analogs synthesized in this study, with GI50 values of <100 nM against almost all of the cell lines in the human cancer cell panel. Of these three, only compound 3j inhibited tubulin polymerization to any degree in vitro. The binding modes of 3j and the structurally related tubulin-inhibitor DMU-212 were determined by virtual docking studies with tubulin dimer. Compound 3j docked at the colchicine-binding site at the dimer interface of tubulin. The Full-Fitness (FF) score of 3j was observed to be substantially higher than DMU-212, which agrees well with the observed anti-cancer potency (GI50 values). The mechanism by which dioxol analogs 5e and 7e exert their cytotoxic effects remains unknown at this stage, but it is unlikely that they affect tubulin dynamics. Nevertheless, these findings suggest that both dioxol and dihydrodioxin analogs of phenylacrylonitrile may have potential for development as clinical candidates to treat a variety of human cancers.
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Affiliation(s)
- Nikhil R Madadi
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Amit Ketkar
- Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Narsimha R Penthala
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - April C L Bostian
- Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Peter A Crooks
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
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26
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Yeom M, Kim IH, Kim JK, Kang K, Eoff RL, Guengerich FP, Choi JY. Effects of Twelve Germline Missense Variations on DNA Lesion and G-Quadruplex Bypass Activities of Human DNA Polymerase REV1. Chem Res Toxicol 2016; 29:367-79. [PMID: 26914252 DOI: 10.1021/acs.chemrestox.5b00513] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The Y-family DNA polymerase REV1 is involved in replicative bypass of damaged DNA and G-quadruplex (G4) DNA. In addition to a scaffolding role in the replicative bypass, REV1 acts in a catalytic role as a deoxycytidyl transferase opposite some replication stall sites, e.g., apurinic/apyrimidinic (AP) sites, N(2)-guanyl lesions, and G4 sites. We characterized the biochemical properties of 12 reported germline missense variants of human REV1, including the N373S variant associated with high risk of cervical cancer, using the recombinant REV1 (residues 330-833) proteins and DNA templates containing a G, AP site, N(2)-CH2(2-naphthyl)G (N(2)-NaphG), or G4. In steady-state kinetic analyses, the F427L, R434Q, M656V, D700N, R704Q, and P831L variants displayed 2- to 8-fold decreases in kcat/Km for dCTP insertion opposite all four templates, compared to that of wild-type, while the N373S, M407L, and N497S showed 2- to 3-fold increases with all four and the former three or two templates, respectively. The F427L, R434Q, M656V, and R704Q variants also had 2- to 3-fold lower binding affinities to DNA substrates containing G, an AP site, and/or N(2)-NaphG than wild-type. Distinctively, the N373S variant had a 3-fold higher binding affinity to G4 DNA than the wild-type, as well as a 2-fold higher catalytic activity opposite the first tetrad G, suggesting a facilitating effect of this variation on replication of G4 DNA sequences in certain human papillomavirus genomes. Our results suggest that the catalytic function of REV1 is moderately or slightly altered by at least nine genetic variations, and the G4 DNA processing function of REV1 is slightly enhanced by the N373S variation, which might provide the possibility that certain germline missense REV1 variations affect the individual susceptibility to carcinogenesis by modifying the capability of REV1 for replicative bypass past DNA lesions and G4 motifs derived from chemical and viral carcinogens.
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Affiliation(s)
| | | | | | | | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - F Peter Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
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27
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Bostian ACL, Maddukuri L, Reed MR, Savenka T, Hartman JH, Davis L, Pouncey DL, Miller GP, Eoff RL. Kynurenine Signaling Increases DNA Polymerase Kappa Expression and Promotes Genomic Instability in Glioblastoma Cells. Chem Res Toxicol 2015; 29:101-8. [PMID: 26651356 DOI: 10.1021/acs.chemrestox.5b00452] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Overexpression of the translesion synthesis polymerase hpol κ in glioblastomas has been linked to poor patient prognosis; however, the mechanism promoting higher expression in these tumors remains unknown. We determined that activation of the aryl hydrocarbon receptor (AhR) pathway in glioblastoma cells leads to increased hpol κ mRNA and protein levels. We blocked nuclear translocation and DNA binding by AhR in glioblastoma cells using a small-molecule and observed decreased hpol κ expression. Pharmacological inhibition of tryptophan-2,3-dioxygenase (TDO), the enzyme largely responsible for activating AhR in glioblastoma, led to a decrease in the endogenous AhR agonist kynurenine and a corresponding decrease in hpol κ protein levels. Importantly, we discovered that inhibiting TDO activity, AhR signaling, or suppressing hpol κ expression with RNA interference led to decreased chromosomal damage in glioblastoma cells. Epistasis assays further supported the idea that TDO activity, activation of AhR signaling, and the resulting overexpression of hpol κ function primarily in the same pathway to increase endogenous DNA damage. These findings indicate that upregulation of hpol κ through glioblastoma-specific TDO activity and activation of AhR signaling likely contributes to the high levels of replication stress and genomic instability observed in these tumors.
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Affiliation(s)
- April C L Bostian
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Leena Maddukuri
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Megan R Reed
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Tatsiana Savenka
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Jessica H Hartman
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Lauren Davis
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Dakota L Pouncey
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Grover P Miller
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
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28
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Penthala NR, Madhukuri L, Thakkar S, Madadi NR, Lamture G, Eoff RL, Crooks PA. Synthesis and anti-cancer screening of novel heterocyclic-(2 H)-1,2,3-triazoles as potential anti-cancer agents. Medchemcomm 2015; 6:1535-1543. [PMID: 27066215 DOI: 10.1039/c5md00219b] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
trans-Cyanocombretastatin A-4 (trans-CA-4) analogues have been structurally modified to afford their more stable CA-4-(2H)-1,2,3-triazole analogues. Fifteen novel, stable 4-heteroaryl-5-aryl-(2H)-1,2,3-triazole CA-4 analogues (8a-i, 9 and 11a-e) were evaluated for anti-cancer activity against a panel of 60 human cancer cell lines. These analogues displayed potent cytotoxic activity against both hematological and solid tumor cell lines with GI50 values in the low nanomolar range. The most potent compound, 8a, was a benzothiophen-2-yl analogue that incorporated a 3,4,5-trimethoxyphenyl moiety connected to the (2H)-1,2,3-triazole ring system. Compound 8a exhibited GI50 values of <10 nM against 80% of the cancer cell lines in the panel. Three triazole analogues, 8a, 8b and 8g, showed particularly potent growth inhibition against the triple negative Hs578T breast cancer cell line with GI50 values of 10.3 nM, 66.5 nM and 20.3 nM, respectively. Molecular docking studies suggest that these compounds bind to the same hydrophobic pocket at the interface of α- and β-tubulin that is occupied by colchicine and cis-CA-4, and are stabilized by Van der Waals' interactions with surrounding amino acid residues. Compound 8a was found to inhibit tubulin polymerization in vitro with an IC50 value of 1.7 µM. The potent cytotoxicity of these novel compounds and their inhibition of tubulin dynamics make these triazole analogues promising candidates for development as anti-cancer drugs.
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Affiliation(s)
- Narsimha Reddy Penthala
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Leena Madhukuri
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, U.S.A
| | - Shraddha Thakkar
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Nikhil Reddy Madadi
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Gauri Lamture
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, U.S.A
| | - Peter A Crooks
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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29
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Eddy S, Maddukuri L, Ketkar A, Zafar MK, Henninger EE, Pursell ZF, Eoff RL. Evidence for the kinetic partitioning of polymerase activity on G-quadruplex DNA. Biochemistry 2015; 54:3218-30. [PMID: 25903680 DOI: 10.1021/acs.biochem.5b00060] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We have investigated the action of the human DNA polymerase ε (hpol ε) and η (hpol η) catalytic cores on G-quadruplex (G4) DNA substrates derived from the promoter of the c-MYC proto-oncogene. The translesion enzyme hpol η exhibits a 6.2-fold preference for binding to G4 DNA over non-G4 DNA, while hpol ε binds both G4 and non-G4 substrates with nearly equal affinity. Kinetic analysis of single-nucleotide insertion by hpol η reveals that it is able to maintain >25% activity on G4 substrates compared to non-G4 DNA substrates, even when the primer template junction is positioned directly adjacent to G22 (the first tetrad-associated guanine in the c-MYC G4 motif). Surprisingly, hpol η fidelity increases ~15-fold when copying G22. By way of comparison, hpol ε retains ~4% activity and has a 33-fold decrease in fidelity when copying G22. The fidelity of hpol η is ~100-fold greater than that of hpol ε when comparing the misinsertion frequencies of the two enzymes opposite a tetrad-associated guanine. The kinetic differences observed for the B- and Y-family pols on G4 DNA support a model in which a simple kinetic switch between replicative and TLS pols could help govern fork progress during G4 DNA replication.
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Affiliation(s)
- Sarah Eddy
- †Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
| | - Leena Maddukuri
- †Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
| | - Amit Ketkar
- †Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
| | - Maroof K Zafar
- †Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
| | - Erin E Henninger
- ‡Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, Louisiana 70112, United States
| | - Zachary F Pursell
- ‡Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, Louisiana 70112, United States
| | - Robert L Eoff
- †Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
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30
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Madadi NR, Zong H, Ketkar A, Zheng C, Penthala NR, Janganati V, Bommagani S, Eoff RL, Guzman ML, Crooks PA. Synthesis and evaluation of a series of resveratrol analogues as potent anti-cancer agents that target tubulin. Medchemcomm 2015; 6:788-794. [PMID: 26257861 PMCID: PMC4527554 DOI: 10.1039/c4md00478g] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A series of novel diarylacrylonitrile and trans-stilbene analogues of resveratrol has been synthesized and evaluated for their anticancer activities against a panel of 60 human cancer cell lines. The diarylacrylonitrile analogues 3b and 4a exhibited the most potent anticancer activity of all the analogues synthesized in this study, with GI50 values of < 10 nM against almost all the cell lines in the human cancer cell panel. Compounds 3b and 4a were also screened against the acute myeloid leukemia (AML) cell line, MV4-11, and were found to have potent cytotoxic properties that are likely mediated through inhibition of tubulin polymerization. Results from molecular docking studies indicate a common binding site for 4a and 3b on the 3,3-tubulin heterodimer, with a slightly more favorable binding for 3b compared to 4a; this is consistent with the results from the microtubule assays, which demonstrate that 4a is more potent than 3b in inhibiting tubulin polymerization in MV4-11 cells. Taken together, these data suggest that diarylacrylonitriles 3b and 4a may have potential as antitubulin therapeutics for treatment of both solid and hematological tumors.
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Affiliation(s)
- Nikhil R. Madadi
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Hongliang Zong
- Division of Hematology and Medical Oncology, Department of Medicine, Weill Medical College of Cornell University, New York, NY
| | - Amit Ketkar
- Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Chen Zheng
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Narsimha R. Penthala
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Venumadhav Janganati
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Shobanbabu Bommagani
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Robert L. Eoff
- Department of Biochemistry and Molecular Biology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Monica L. Guzman
- Division of Hematology and Medical Oncology, Department of Medicine, Weill Medical College of Cornell University, New York, NY
| | - Peter A. Crooks
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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31
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Penthala NR, Zong H, Ketkar A, Madadi NR, Janganati V, Eoff RL, Guzman ML, Crooks PA. Synthesis, anticancer activity and molecular docking studies on a series of heterocyclic trans-cyanocombretastatin analogues as antitubulin agents. Eur J Med Chem 2014; 92:212-20. [PMID: 25557492 DOI: 10.1016/j.ejmech.2014.12.050] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2014] [Revised: 11/21/2014] [Accepted: 12/28/2014] [Indexed: 10/24/2022]
Abstract
A series of heterocyclic combretastatin analogues have been synthesized and evaluated for their anticancer activity against a panel of 60 human cancer cell lines. The most potent compounds were two 3,4,5-trimethoxy phenyl analogues containing either an (Z)-indol-2-yl (8) or (Z)-benzo[b]furan-2-yl (12) moiety; these compounds exhibited GI50 values of <10 nM against 74% and 70%, respectively, of the human cancer cell lines in the 60-cell panel. Compounds 8, and 12 and two previously reported compounds in the same structural class, i.e. 29 and 31, also showed potent anti-leukemic activity against leukemia MV4-11 cell lines with LD50 values = 44 nM, 47 nM, 18 nM, and 180 nM, respectively. From the NCI anti-cancer screening results and the data from the in vitro toxicity screening on cultured AML cells, seven compounds: 8, 12, 21, 23, 25, 29 and 31 were screened for their in vitro inhibitory activity on tubulin polymerization in MV4-11 AML cells; at 50 nM, 8 and 29 inhibited polymerization of tubulin by >50%. The binding modes of the three most active compounds (8, 12 and 29) to tubulin were also investigated utilizing molecular docking studies. All three molecules were observed to bind in the same hydrophobic pocket at the interface of α- and β-tubulin that is occupied by colchicine, and were stabilized by van der Waals' interactions with surrounding tubulin residues. The results from the tubulin polymerization and molecular docking studies indicate that compounds 8 and 29 are the most potent anti-leukemic compounds in this structural class, and are considered lead compounds for further development as anti-leukemic drugs.
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Affiliation(s)
- Narsimha Reddy Penthala
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA
| | - Hongliang Zong
- Division of Hematology/Oncology, Department of Medicine, Weill Cornell Medical College, New York, NY 10021, USA
| | - Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA
| | - Nikhil Reddy Madadi
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA
| | - Venumadav Janganati
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA
| | - Monica L Guzman
- Division of Hematology/Oncology, Department of Medicine, Weill Cornell Medical College, New York, NY 10021, USA
| | - Peter A Crooks
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA.
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Zafar MK, Ketkar A, Lodeiro MF, Cameron CE, Eoff RL. Kinetic analysis of human PrimPol DNA polymerase activity reveals a generally error-prone enzyme capable of accurately bypassing 7,8-dihydro-8-oxo-2'-deoxyguanosine. Biochemistry 2014; 53:6584-94. [PMID: 25255211 PMCID: PMC4204878 DOI: 10.1021/bi501024u] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
![]()
Recent studies have identified human
PrimPol as a new RNA/DNA primase
and translesion DNA synthesis polymerase (TLS pol) that contributes
to nuclear and mitochondrial DNA replication. We investigated the
mechanism of PrimPol polymerase activity on both undamaged and damaged
DNA substrates. With Mg2+ as a cofactor, PrimPol binds
primer-template DNA with low affinity Kd,DNA values (∼200–1200 nM). DNA binding is enhanced 34-fold
by Mn2+ (Kd,DNA = 27 nM). The
pol activity of PrimPol is increased 400–1000-fold by Mn2+ compared to Mg2+ based on steady-state kinetic
parameters. PrimPol makes a mistake copying undamaged DNA once every
∼100–2500 insertions events, which is comparable to
other TLS pols, and the fidelity of PrimPol is ∼1.7-fold more
accurate when Mg2+ is the cofactor compared to Mn2+. PrimPol inserts dCMP opposite 8-oxo-dG with 2- (Mn2+) to 6-fold (Mg2+) greater efficiency than dAMP misinsertion.
PrimPol-catalyzed dCMP insertion opposite 8-oxo-dG proceeds at ∼25%
efficiency relative to unmodified template dG, and PrimPol readily
extends from dC:8-oxo-dG base pairs (bps) with ∼2-fold greater
efficiency than dA:8-oxo-dG bps. A tetrahydrofuran (THF) abasic-site
mimic decreases PrimPol activity to ∼0.04%. In summary, PrimPol
exhibits the fidelity typical of other TLS pols, is rather unusual
in the degree of activation afforded by Mn2+, and accurately
bypasses 8-oxo-dG, a DNA lesion of special relevance to mitochondrial
DNA replication and transcription.
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Affiliation(s)
- Maroof K Zafar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences , Little Rock, Arkansas 72205-7199, United States
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Maddukuri L, Ketkar A, Eddy S, Zafar MK, Eoff RL. The Werner syndrome protein limits the error-prone 8-oxo-dG lesion bypass activity of human DNA polymerase kappa. Nucleic Acids Res 2014; 42:12027-40. [PMID: 25294835 PMCID: PMC4231769 DOI: 10.1093/nar/gku913] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Human DNA polymerase kappa (hpol κ) is the only Y-family member to preferentially insert dAMP opposite 7,8-dihydro-8-oxo-2′-deoxyguanosine (8-oxo-dG) during translesion DNA synthesis. We have studied the mechanism of action by which hpol κ activity is modulated by the Werner syndrome protein (WRN), a RecQ helicase known to influence repair of 8-oxo-dG. Here we show that WRN stimulates the 8-oxo-dG bypass activity of hpol κ in vitro by enhancing the correct base insertion opposite the lesion, as well as extension from dC:8-oxo-dG base pairs. Steady-state kinetic analysis reveals that WRN improves hpol κ-catalyzed dCMP insertion opposite 8-oxo-dG ∼10-fold and extension from dC:8-oxo-dG by 2.4-fold. Stimulation is primarily due to an increase in the rate constant for polymerization (kpol), as assessed by pre-steady-state kinetics, and it requires the RecQ C-terminal (RQC) domain. In support of the functional data, recombinant WRN and hpol κ were found to physically interact through the exo and RQC domains of WRN, and co-localization of WRN and hpol κ was observed in human cells treated with hydrogen peroxide. Thus, WRN limits the error-prone bypass of 8-oxo-dG by hpol κ, which could influence the sensitivity to oxidative damage that has previously been observed for Werner's syndrome cells.
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Affiliation(s)
- Leena Maddukuri
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA
| | - Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA
| | - Sarah Eddy
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA
| | - Maroof K Zafar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA
| | - Robert L Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA
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Kim J, Song I, Jo A, Shin JH, Cho H, Eoff RL, Guengerich FP, Choi JY. Biochemical analysis of six genetic variants of error-prone human DNA polymerase ι involved in translesion DNA synthesis. Chem Res Toxicol 2014; 27:1837-52. [PMID: 25162224 PMCID: PMC4203391 DOI: 10.1021/tx5002755] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
![]()
DNA
polymerase (pol) ι is the most error-prone among the
Y-family polymerases that participate in translesion synthesis (TLS).
Pol ι can bypass various DNA lesions, e.g., N2-ethyl(Et)G, O6-methyl(Me)G,
8-oxo-7,8-dihydroguanine (8-oxoG), and an abasic site, though frequently
with low fidelity. We assessed the biochemical effects of six reported
genetic variations of human pol ι on its TLS properties, using
the recombinant pol ι (residues 1–445) proteins and DNA
templates containing a G, N2-EtG, O6-MeG, 8-oxoG, or abasic site. The Δ1–25
variant, which is the N-terminal truncation of 25
residues resulting from an initiation codon variant (c.3G > A)
and
also is the formerly misassigned wild-type, exhibited considerably
higher polymerase activity than wild-type with Mg2+ (but
not with Mn2+), coinciding with its steady-state kinetic
data showing a ∼10-fold increase in kcat/Km for nucleotide incorporation
opposite templates (only with Mg2+). The R96G variant,
which lacks a R96 residue known to interact with the incoming nucleotide,
lost much of its polymerase activity, consistent with the kinetic
data displaying 5- to 72-fold decreases in kcat/Km for nucleotide incorporation
opposite templates either with Mg2+ or Mn2+,
except for that opposite N2-EtG with Mn2+ (showing a 9-fold increase for dCTP incorporation). The
Δ1–25 variant bound DNA 20- to 29-fold more tightly than
wild-type (with Mg2+), but the R96G variant bound DNA 2-fold
less tightly than wild-type. The DNA-binding affinity of wild-type,
but not of the Δ1–25 variant, was ∼7-fold stronger
with 0.15 mM Mn2+ than with Mg2+. The results
indicate that the R96G variation severely impairs most of the Mg2+- and Mn2+-dependent TLS abilities of pol ι,
whereas the Δ1–25 variation selectively and substantially
enhances the Mg2+-dependent TLS capability of pol ι,
emphasizing the potential translational importance of these pol ι
genetic variations, e.g., individual differences in TLS, mutation,
and cancer susceptibility to genotoxic carcinogens.
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Affiliation(s)
- Jinsook Kim
- Division of Pharmacology, Department of Molecular Cell Biology, and ‡Department of Physiology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine , Suwon, Gyeonggi-do 440-746, Republic of Korea
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35
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Zhao L, Pence MG, Eoff RL, Yuan S, Fercu CA, Guengerich FP. Elucidation of kinetic mechanisms of human translesion DNA polymerase κ using tryptophan mutants. FEBS J 2014; 281:4394-410. [PMID: 25065501 DOI: 10.1111/febs.12947] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 07/18/2014] [Accepted: 07/23/2014] [Indexed: 02/05/2023]
Abstract
To investigate the conformational dynamics of human DNA polymerase κ (hpol κ), we generated two mutants, Y50W (N-clasp region) and Y408W (linker between the thumb and little finger domains), using a Trp-null mutant (W214Y/W392H) of the hpol κ catalytic core enzyme. These mutants retained catalytic activity and similar patterns of selectivity for bypassing the DNA adduct 7,8-dihydro-8-oxo-2'-deoxyguanosine, as indicated by the results of steady-state and pre-steady-state kinetic experiments. Stopped-flow kinetic assays with hpol κ Y50W and T408W revealed a decrease in Trp fluorescence with the template G:dCTP pair but not for any mispairs. This decrease in fluorescence was not rate-limiting and is considered to be related to a conformational change necessary for correct nucleotidyl transfer. When a free 3'-hydroxyl was present on the primer, the Trp fluorescence returned to the baseline level at a rate similar to the observed kcat , suggesting that this change occurs during or after nucleotidyl transfer. However, polymerization rates (kpol ) of extended-product formation were fast, indicating that the slow fluorescence step follows phosphodiester bond formation and is rate-limiting. Pyrophosphate formation and release were fast and are likely to precede the slower relaxation step. The available kinetic data were used to fit a simplified minimal model. The extracted rate constants confirmed that the conformational change after phosphodiester bond formation was rate-limiting for hpol κ catalysis with the template G:dCTP pair.
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Affiliation(s)
- Linlin Zhao
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Chemistry and Biochemistry, Central Michigan University, Mount Pleasant, MI, USA
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36
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Abstract
The Y-family DNA polymerase Rev1 is required for successful replication of G-quadruplex DNA (G4 DNA) in higher eukaryotes. Here we show that human Rev1 (hRev1) disrupts G4 DNA structures and prevents refolding in vitro. Nucleotidyl transfer by hRev1 is not necessary for mechanical unfolding to occur. hRev1 binds G4 DNA substrates with Kd,DNA values that are 4–15-fold lower than those of non-G4 DNA substrates. The pre-steady-state rate constant of deoxycytidine monophosphate (dCMP) insertion opposite the first tetrad-guanine by hRev1 is ∼56% as fast as that observed for non-G4 DNA substrates. Thus, hRev1 can promote fork progression by either dislodging tetrad guanines to unfold the G4 DNA, which could assist in extension by other DNA polymerases, or hRev1 can prevent refolding of G4 DNA structures. The hRev1 mechanism of action against G-quadruplexes helps explain why replication progress is impeded at G4 DNA sites in Rev1-deficient cells and illustrates another unique feature of this enzyme with important implications for genome maintenance.
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Affiliation(s)
- Sarah Eddy
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA and Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Gyeonggi-do 440-746, Republic of Korea
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37
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Maddukuri L, Shuck SC, Eoff RL, Zhao L, Rizzo CJ, Guengerich FP, Marnett LJ. Replication, repair, and translesion polymerase bypass of N⁶-oxopropenyl-2'-deoxyadenosine. Biochemistry 2013; 52:8766-76. [PMID: 24171480 DOI: 10.1021/bi401103k] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The oxidative stress products malondialdehyde and base propenal react with DNA bases forming the adduction products 3-(2'-deoxy-β-D-erythro-pentofuranosyl)pyrimido[1,2-a]purin-10(3H)-one (M1dG) and N(6)-(oxypropenyl)-2'-deoxyadenosine (OPdA). M1dG is mutagenic in vivo and miscodes in vitro, but little work has been done on OPdA. To improve our understanding of the effect of OPdA on polymerase activity and mutagenicity, we evaluated the ability of the translesion DNA polymerases hPols η, κ, and ι to bypass OPdA in vitro. hPols η and κ inserted dNTPs opposite the lesion and extended the OPdA-modified primer to the terminus. hPol ι inserted dNTPs opposite OPdA but failed to fully extend the primer. Steady-state kinetic analysis indicated that these polymerases preferentially insert dTTP opposite OPdA, although less efficiently than opposite dA. Minimal incorrect base insertion was observed for all polymerases, and dCTP was the primary mis-insertion event. Examining replicative and repair polymerases revealed little effect of OPdA on the Sulfolobus solfataricus polymerase Dpo1 or the Klenow fragment of Escherichia coli DNA polymerase I. Bacteriophage T7 DNA polymerase displayed a reduced level of OPdA bypass compared to unmodified DNA, and OPdA nearly completely blocked the activity of base excision repair polymerase hPol β. This work demonstrates that bypass of OPdA is generally error-free, modestly decreases the catalytic activity of most polymerases, and blocks hPol β polymerase activity. Although mis-insertion opposite OPdA is relatively weak, the efficiency of bypass may introduce A → G transitions observed in vivo.
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Affiliation(s)
- Leena Maddukuri
- A. B. Hancock Jr. Memorial Laboratory for Cancer Research, †Department of Biochemistry, ‡Department of Chemistry, and §Department of Pharmacology, Center in Molecular Toxicology, Vanderbilt Institute of Chemical Biology, and Vanderbilt-Ingram Cancer Center, Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
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38
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Coggins GE, Maddukuri L, Penthala NR, Hartman JH, Eddy S, Ketkar A, Crooks PA, Eoff RL. N-Aroyl indole thiobarbituric acids as inhibitors of DNA repair and replication stress response polymerases. ACS Chem Biol 2013; 8:1722-9. [PMID: 23679919 DOI: 10.1021/cb400305r] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Using a robust and quantitative assay, we have identified a novel class of DNA polymerase inhibitors that exhibits some specificity against an enzyme involved in resistance to anti-cancer drugs, namely, human DNA polymerase eta (hpol η). In our initial screen, we identified the indole thiobarbituric acid (ITBA) derivative 5-((1-(2-bromobenzoyl)-5-chloro-1H-indol-3-yl)methylene)-2-thioxodihydropyrimidine-4,6(1H,5H)-dione (ITBA-12) as an inhibitor of the Y-family DNA member hpol η, an enzyme that has been associated with increased resistance to cisplatin and doxorubicin treatments. An additional seven DNA polymerases from different subfamilies were tested for inhibition by ITBA-12. Hpol η was the most potently inhibited enzyme (30 ± 3 μM), with hpol β, hpol γ, and hpol κ exhibiting comparable but higher IC50 values of 41 ± 24, 49 ± 6, and 59 ± 11 μM, respectively. The other polymerases tested had IC50 values closer to 80 μM. Steady-state kinetic analysis was used to investigate the mechanism of polymerase inhibition by ITBA-12. Based on changes in the Michaelis constant, it was determined that ITBA-12 acts as an allosteric (or partial) competitive inhibitor of dNTP binding. The parent ITBA scaffold was modified to produce 20 derivatives and establish structure-activity relationships by testing for inhibition of hpol η. Two compounds with N-naphthoyl Ar-substituents, ITBA-16 and ITBA-19, were both found to have improved potency against hpol η with IC50 values of 16 ± 3 μM and 17 ± 3 μM, respectively. Moreover, the specificity of ITBA-16 was improved relative to that of ITBA-12. The presence of a chloro substituent at position 5 on the indole ring appears to be crucial for effective inhibition of hpol η, with the indole N-1-naphthoyl and N-2-naphthoyl analogues being the most potent inhibitors of hpol η. These results provide a framework from which second-generation ITBA derivatives may be developed against specialized polymerases that are involved in mechanisms of radio- and chemo-resistance.
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Affiliation(s)
- Grace E. Coggins
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37232-0146,
United States
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39
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Ketkar A, Zafar MK, Maddukuri L, Penthala NR, Crooks P, Coggins GE, Lloyd RS, Eoff RL. Identification and characterization of novel small molecule inhibitors of the human Y‐family DNA polymerases. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.543.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Amit Ketkar
- Biochemistry & Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockAR
| | - Maroof K Zafar
- Biochemistry & Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockAR
| | - Leena Maddukuri
- Biochemistry & Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockAR
| | - Narsimha R Penthala
- Pharmaceutical SciencesUniversity of Arkansas for Medical SciencesLittle RockAR
| | - Peter Crooks
- Pharmaceutical SciencesUniversity of Arkansas for Medical SciencesLittle RockAR
| | - Grace E Coggins
- Dept. of Biological SciencesVanderbilt UniversityNashvilleTN
| | | | - Robert L Eoff
- Biochemistry & Molecular BiologyUniversity of Arkansas for Medical SciencesLittle RockAR
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40
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Maddukuri L, Eddy SD, Eoff RL. Werner's syndrome protein limits the error‐prone 8‐oxo‐G lesion bypass activity of human DNA polymerase kappa by promoting the error‐free bypass. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.976.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Leena Maddukuri
- Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SchoolLittle RockAR
| | - Sarah D Eddy
- Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SchoolLittle RockAR
| | - Robert L Eoff
- Biochemistry and Molecular BiologyUniversity of Arkansas for Medical SchoolLittle RockAR
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41
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Ketkar A, Zafar MK, Maddukuri L, Yamanaka K, Banerjee S, Egli M, Choi JY, Lloyd RS, Eoff RL. Leukotriene biosynthesis inhibitor MK886 impedes DNA polymerase activity. Chem Res Toxicol 2013; 26:221-32. [PMID: 23305233 DOI: 10.1021/tx300392m] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Specialized DNA polymerases participate in replication stress responses and in DNA repair pathways that function as barriers against cellular senescence and genomic instability. These events can be co-opted by tumor cells as a mechanism to survive chemotherapeutic and ionizing radiation treatments and as such, represent potential targets for adjuvant therapies. Previously, a high-throughput screen of ∼16,000 compounds identified several first generation proof-of-principle inhibitors of human DNA polymerase kappa (hpol κ). The indole-derived inhibitor of 5-lipoxygenase activating protein (FLAP), MK886, was one of the most potent inhibitors of hpol κ discovered in that screen. However, the specificity and mechanism of inhibition remained largely undefined. In the current study, the specificity of MK886 against human Y-family DNA polymerases and a model B-family DNA polymerase was investigated. MK886 was found to inhibit the activity of all DNA polymerases tested with similar IC(50) values, the exception being a 6- to 8-fold increase in the potency of inhibition against human DNA polymerase iota (hpol ι), a highly error-prone enzyme that uses Hoogsteen base-pairing modes during catalysis. The specificity against hpol ι was partially abrogated by inclusion of the recently annotated 25 a.a. N-terminal extension. On the basis of Michaelis-Menten kinetic analyses and DNA binding assays, the mechanism of inhibition by MK886 appears to be mixed. In silico docking studies were used to produce a series of models for MK886 binding to Y-family members. The docking results indicate that two binding pockets are conserved between Y-family polymerases, while a third pocket near the thumb domain appears to be unique to hpol ι. Overall, these results provide insight into the general mechanism of DNA polymerase inhibition by MK886.
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Affiliation(s)
- Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199, USA
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Ketkar A, Zafar MK, Banerjee S, Marquez VE, Egli M, Eoff RL. Differential furanose selection in the active sites of archaeal DNA polymerases probed by fixed-conformation nucleotide analogues. Biochemistry 2012; 51:9234-44. [PMID: 23050956 DOI: 10.1021/bi301043k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
DNA polymerases select for the incorporation of deoxyribonucleotide triphosphates (dNTPs) using amino acid side-chains that act as a "steric-gate" to bar improper incorporation of rNTPs. An additional factor in the selection of nucleotide substrates resides in the preferred geometry for the furanose moiety of the incoming nucleotide triphosphate. We have probed the role of sugar geometry during nucleotide selection by model DNA polymerases from Sulfolobus solfataricus using fixed conformation nucleotide analogues. North-methanocarba-dATP (N-MC-dATP) locks the central ring into a RNA-type (C2'-exo, North) conformation near a C3'-endo pucker, and South-methanocarba-dATP (S-MC-dATP) locks the central ring system into a (C3'-exo, South) conformation near a C2'-endo pucker. Dpo4 preferentially inserts N-MC-dATP and in the crystal structure of Dpo4 in complex with N-MC-dAMP, the nucleotide analogue superimposes almost perfectly with Dpo4 bound to unmodified dATP. Biochemical assays indicate that the S. solfataricus B-family DNA polymerase Dpo1 can insert and extend from both N-MC-dATP and S-MC-dATP. In this respect, Dpo1 is unexpectedly more tolerant of substrate conformation than Dpo4. The crystal structure of Dpo4 bound to S-MC-dADP shows that poor incorporation of the Southern pucker by the Y-family polymerase results from a hydrogen bond between the 3'-OH group of the nucleotide analogue and the OH group of the steric gate residue, Tyr12, shifting the S-MC-dADP molecule away from the dNTP binding pocket and distorting the base pair at the primer-template junction. These results provide insights into substrate specificity of DNA polymerases, as well as molecular mechanisms that act as a barrier against insertion of rNTPs.
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Affiliation(s)
- Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, United States
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Maddukuri L, Ketkar A, Eddy S, Zafar MK, Griffin WC, Eoff RL. Enhancement of human DNA polymerase η activity and fidelity is dependent upon a bipartite interaction with the Werner syndrome protein. J Biol Chem 2012; 287:42312-23. [PMID: 23045531 DOI: 10.1074/jbc.m112.410332] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
We have investigated the interaction between human DNA polymerase η (hpol η) and the Werner syndrome protein (WRN). Functional assays revealed that the WRN exonuclease and RecQ C-terminal (RQC) domains are necessary for full stimulation of hpol η-catalyzed formation of correct base pairs. We find that WRN does not stimulate hpol η-catalyzed formation of mispairs. Moreover, the exonuclease activity of WRN prevents stable mispair formation by hpol η. These results are consistent with a proofreading activity for WRN during single-nucleotide additions. ATP hydrolysis by WRN appears to attenuate stimulation of hpol η. Pre-steady-state kinetic results show that k(pol) is increased 4-fold by WRN. Finally, pulldown assays reveal a bipartite physical interaction between hpol η and WRN that is mediated by the exonuclease and RQC domains. Taken together, these results are consistent with alteration of the rate-limiting step in polymerase catalysis by direct protein-protein interactions between WRN and hpol η. In summary, WRN improves the efficiency and fidelity of hpol η to promote more effective replication of DNA.
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Affiliation(s)
- Leena Maddukuri
- Department of Biochemistry and Molecular Biology, The University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, USA
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Yamanaka K, Dorjsuren D, Eoff RL, Egli M, Maloney DJ, Jadhav A, Simeonov A, Lloyd RS. A comprehensive strategy to discover inhibitors of the translesion synthesis DNA polymerase κ. PLoS One 2012; 7:e45032. [PMID: 23056190 PMCID: PMC3466269 DOI: 10.1371/journal.pone.0045032] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 08/11/2012] [Indexed: 11/19/2022] Open
Abstract
Human DNA polymerase kappa (pol κ) is a translesion synthesis (TLS) polymerase that catalyzes TLS past various minor groove lesions including N(2)-dG linked acrolein- and polycyclic aromatic hydrocarbon-derived adducts, as well as N(2)-dG DNA-DNA interstrand cross-links introduced by the chemotherapeutic agent mitomycin C. It also processes ultraviolet light-induced DNA lesions. Since pol κ TLS activity can reduce the cellular toxicity of chemotherapeutic agents and since gliomas overexpress pol κ, small molecule library screens targeting pol κ were conducted to initiate the first step in the development of new adjunct cancer therapeutics. A high-throughput, fluorescence-based DNA strand displacement assay was utilized to screen ∼16,000 bioactive compounds, and the 60 top hits were validated by primer extension assays using non-damaged DNAs. Candesartan cilexetil, manoalide, and MK-886 were selected as proof-of-principle compounds and further characterized for their specificity toward pol κ by primer extension assays using DNAs containing a site-specific acrolein-derived, ring-opened reduced form of γ-HOPdG. Furthermore, candesartan cilexetil could enhance ultraviolet light-induced cytotoxicity in xeroderma pigmentosum variant cells, suggesting its inhibitory effect against intracellular pol κ. In summary, this investigation represents the first high-throughput screening designed to identify inhibitors of pol κ, with the characterization of biochemical and biologically relevant endpoints as a consequence of pol κ inhibition. These approaches lay the foundation for the future discovery of compounds that can be applied to combination chemotherapy.
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Affiliation(s)
- Kinrin Yamanaka
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, Oregon, United States of America
- Center for Research on Occupational and Environmental Toxicology, Oregon Health & Science University, Portland, Oregon, United States of America
| | - Dorjbal Dorjsuren
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Robert L. Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Martin Egli
- Department of Biochemistry, Center in Molecular Toxicology and Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - David J. Maloney
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Ajit Jadhav
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Anton Simeonov
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland, United States of America
| | - R. Stephen Lloyd
- Center for Research on Occupational and Environmental Toxicology, Oregon Health & Science University, Portland, Oregon, United States of America
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, Oregon, United States of America
- * E-mail:
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Ketkar A, Zafar MK, Banerjee S, Marquez VE, Egli M, Eoff RL. A nucleotide-analogue-induced gain of function corrects the error-prone nature of human DNA polymerase iota. J Am Chem Soc 2012; 134:10698-705. [PMID: 22632140 DOI: 10.1021/ja304176q] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Y-family DNA polymerases participate in replication stress and DNA damage tolerance mechanisms. The properties that allow these enzymes to copy past bulky adducts or distorted template DNA can result in a greater propensity for them to make mistakes. Of the four human Y-family members, human DNA polymerase iota (hpol ι) is the most error-prone. In the current study, we elucidate the molecular basis for improving the fidelity of hpol ι through use of the fixed-conformation nucleotide North-methanocarba-2'-deoxyadenosine triphosphate (N-MC-dATP). Three crystal structures were solved of hpol ι in complex with DNA containing a template 2'-deoxythymidine (dT) paired with an incoming dNTP or modified nucleotide triphosphate. The ternary complex of hpol ι inserting N-MC-dATP opposite dT reveals that the adenine ring is stabilized in the anti orientation about the pseudo-glycosyl torsion angle, which mimics precisely the mutagenic arrangement of dGTP:dT normally preferred by hpol ι. The stabilized anti conformation occurs without notable contacts from the protein but likely results from constraints imposed by the bicyclo[3.1.0]hexane scaffold of the modified nucleotide. Unmodified dATP and South-MC-dATP each adopt syn glycosyl orientations to form Hoogsteen base pairs with dT. The Hoogsteen orientation exhibits weaker base-stacking interactions and is less catalytically favorable than anti N-MC-dATP. Thus, N-MC-dATP corrects the error-prone nature of hpol ι by preventing the Hoogsteen base-pairing mode normally observed for hpol ι-catalyzed insertion of dATP opposite dT. These results provide a previously unrecognized means of altering the efficiency and the fidelity of a human translesion DNA polymerase.
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Affiliation(s)
- Amit Ketkar
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205-7199, USA
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Adedeji AO, Marchand B, te Velthuis AJW, Snijder EJ, Weiss S, Eoff RL, Singh K, Sarafianos SG. Mechanism of nucleic acid unwinding by SARS-CoV helicase. PLoS One 2012; 7:e36521. [PMID: 22615777 PMCID: PMC3352918 DOI: 10.1371/journal.pone.0036521] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 04/03/2012] [Indexed: 02/04/2023] Open
Abstract
The non-structural protein 13 (nsp13) of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) is a helicase that separates double-stranded RNA (dsRNA) or DNA (dsDNA) with a 5′→3′ polarity, using the energy of nucleotide hydrolysis. We determined the minimal mechanism of helicase function by nsp13. We showed a clear unwinding lag with increasing length of the double-stranded region of the nucleic acid, suggesting the presence of intermediates in the unwinding process. To elucidate the nature of the intermediates we carried out transient kinetic analysis of the nsp13 helicase activity. We demonstrated that the enzyme unwinds nucleic acid in discrete steps of 9.3 base-pairs (bp) each, with a catalytic rate of 30 steps per second. Therefore the net unwinding rate is ∼280 base-pairs per second. We also showed that nsp12, the SARS-CoV RNA-dependent RNA polymerase (RdRp), enhances (2-fold) the catalytic efficiency of nsp13 by increasing the step size of nucleic acid (RNA/RNA or DNA/DNA) unwinding. This effect is specific for SARS-CoV nsp12, as no change in nsp13 activity was observed when foot-and-mouth-disease virus RdRp was used in place of nsp12. Our data provide experimental evidence that nsp13 and nsp12 can function in a concerted manner to improve the efficiency of viral replication and enhance our understanding of nsp13 function during SARS-CoV RNA synthesis.
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Affiliation(s)
- Adeyemi O. Adedeji
- Christopher Bond Life Sciences Center, Department of Molecular Microbiology and Immunology, University of Missouri, School of Medicine, Columbia, Missouri, United States of America
| | - Bruno Marchand
- Christopher Bond Life Sciences Center, Department of Molecular Microbiology and Immunology, University of Missouri, School of Medicine, Columbia, Missouri, United States of America
| | - Aartjan J. W. te Velthuis
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Eric J. Snijder
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Susan Weiss
- Department of Microbiology, University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Robert L. Eoff
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Kamalendra Singh
- Christopher Bond Life Sciences Center, Department of Molecular Microbiology and Immunology, University of Missouri, School of Medicine, Columbia, Missouri, United States of America
| | - Stefan G. Sarafianos
- Christopher Bond Life Sciences Center, Department of Molecular Microbiology and Immunology, University of Missouri, School of Medicine, Columbia, Missouri, United States of America
- * E-mail:
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Choi JY, Eoff RL, Pence MG, Wang J, Martin MV, Kim EJ, Folkmann LM, Guengerich FP. Roles of the four DNA polymerases of the crenarchaeon Sulfolobus solfataricus and accessory proteins in DNA replication. J Biol Chem 2011. [DOI: 10.1074/jbc.a111.258038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Choi JY, Eoff RL, Pence MG, Wang J, Martin MV, Kim EJ, Folkmann LM, Guengerich FP. Roles of the four DNA polymerases of the crenarchaeon Sulfolobus solfataricus and accessory proteins in DNA replication. J Biol Chem 2011; 286:31180-93. [PMID: 21784862 DOI: 10.1074/jbc.m111.258038] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The hyperthermophilic crenarchaeon Sulfolobus solfataricus P2 encodes three B-family DNA polymerase genes, B1 (Dpo1), B2 (Dpo2), and B3 (Dpo3), and one Y-family DNA polymerase gene, Dpo4, which are related to eukaryotic counterparts. Both mRNAs and proteins of all four DNA polymerases were constitutively expressed in all growth phases. Dpo2 and Dpo3 possessed very low DNA polymerase and 3' to 5' exonuclease activities in vitro. Steady-state kinetic efficiencies (k(cat)/K(m)) for correct nucleotide insertion by Dpo2 and Dpo3 were several orders of magnitude less than Dpo1 and Dpo4. Both the accessory proteins proliferating cell nuclear antigen and the clamp loader replication factor C facilitated DNA synthesis with Dpo3, as with Dpo1 and Dpo4, but very weakly with Dpo2. DNA synthesis by Dpo2 and Dpo3 was remarkably decreased by single-stranded binding protein, in contrast to Dpo1 and Dpo4. DNA synthesis in the presence of proliferating cell nuclear antigen, replication factor C, and single-stranded binding protein was most processive with Dpo1, whereas DNA lesion bypass was most effective with Dpo4. Both Dpo2 and Dpo3, but not Dpo1, bypassed hypoxanthine and 8-oxoguanine. Dpo2 and Dpo3 bypassed uracil and cis-syn cyclobutane thymine dimer, respectively. High concentrations of Dpo2 or Dpo3 did not attenuate DNA synthesis by Dpo1 or Dpo4. We conclude that Dpo2 and Dpo3 are much less functional and more thermolabile than Dpo1 and Dpo4 in vitro but have bypass activities across hypoxanthine, 8-oxoguanine, and either uracil or cis-syn cyclobutane thymine dimer, suggesting their catalytically limited roles in translesion DNA synthesis past deaminated, oxidized base lesions and/or UV-induced damage.
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Affiliation(s)
- Jeong-Yun Choi
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
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Maddukuri L, Eoff RL, Choi JY, Rizzo CJ, Guengerich FP, Marnett LJ. In vitro bypass of the major malondialdehyde- and base propenal-derived DNA adduct by human Y-family DNA polymerases κ, ι, and Rev1. Biochemistry 2010; 49:8415-24. [PMID: 20726503 PMCID: PMC2943251 DOI: 10.1021/bi1009024] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
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3-(2′-Deoxy-β-d-erythro-pentofuranosyl)pyrimido-[1,2-a]purin-10(3H)-one (M1dG) is the major adduct derived from the reaction of DNA with the lipid peroxidation product malondialdehyde and the DNA peroxidation product base propenal. M1dG is mutagenic in Escherichia coli and mammalian cells, inducing base-pair substitutions (M1dG → A and M1dG → T) and frameshift mutations. Y-family polymerases may contribute to the mutations induced by M1dG in vivo. Previous reports described the bypass of M1dG by DNA polymerases η and Dpo4. The present experiments were conducted to evaluate bypass of M1dG by the human Y-family DNA polymerases κ, ι, and Rev1. M1dG was incorporated into template-primers containing either dC or dT residues 5′ to the adduct, and the template-primers were subjected to in vitro replication by the individual DNA polymerases. Steady-state kinetic analysis of single nucleotide incorporation indicates that dCMP is most frequently inserted by hPol κ opposite the adduct in both sequence contexts, followed by dTMP and dGMP. dCMP and dTMP were most frequently inserted by hPol ι, and only dCMP was inserted by Rev1. hPol κ extended template-primers in the order M1dG:dC > M1dG:dG > M1dG:dT ∼ M1dG:dA, but neither hPol ι nor Rev1 extended M1dG-containing template-primers. Liquid chromatography−mass spectrometry analysis of the products of hPol κ-catalyzed extension verified this preference in the 3′-GXC-5′ template sequence but revealed the generation of a series of complex products in which dAMP is incorporated opposite M1dG in the 3′-GXT-5′ template sequence. The results indicate that DNA hPol κ or the combined action of hPol ι or Rev1 and hPol κ bypass M1dG residues in DNA and generate products that are consistent with some of the mutations induced by M1dG in mammalian cells.
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Affiliation(s)
- Leena Maddukuri
- A. B. Hancock Jr. Memorial Laboratory for Cancer Research, Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
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Eoff RL, McGrath CE, Maddukuri L, Salamanca-Pinzón SG, Marquez VE, Marnett LJ, Guengerich FP, Egli M. Selective modulation of DNA polymerase activity by fixed-conformation nucleoside analogues. Angew Chem Int Ed Engl 2010; 49:7481-5. [PMID: 20814997 PMCID: PMC3011974 DOI: 10.1002/anie.201003168] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Robert L. Eoff
- Department of Biochemistry, Center in Molecular Toxicology, & Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA
| | - Colleen E. McGrath
- Department of Biochemistry, Center in Molecular Toxicology, & Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA
| | - Leena Maddukuri
- Department of Biochemistry, Center in Molecular Toxicology, & Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA
| | - S. Giovanna Salamanca-Pinzón
- Department of Biochemistry, Center in Molecular Toxicology, & Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA
| | - Victor E. Marquez
- Chemical Biology Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - Lawrence J. Marnett
- Department of Biochemistry, Center in Molecular Toxicology, & Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA
| | - F. Peter Guengerich
- Department of Biochemistry, Center in Molecular Toxicology, & Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA
| | - Martin Egli
- Department of Biochemistry, Center in Molecular Toxicology, & Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA
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