1
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Fan PH, Geng Y, Romo AJ, Zhong A, Zhang J, Yeh YC, Lee YH, Liu HW. Two Radical SAM Enzymes Are Necessary and Sufficient for the In Vitro Production of the Oxetane Nucleoside Antiviral Agent Albucidin. Angew Chem Int Ed Engl 2022; 61:e202210362. [PMID: 36064953 PMCID: PMC9561071 DOI: 10.1002/anie.202210362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Indexed: 11/09/2022]
Abstract
Oxetanocin A and albucidin are two oxetane natural products. While the biosynthesis of oxetanocin A has been described, less is known about albucidin. In this work, the albucidin biosynthetic gene cluster is identified in Streptomyces. Heterologous expression in a nonproducing strain demonstrates that the genes alsA and alsB are necessary and sufficient for albucidin biosynthesis confirming a previous study (Myronovskyi et al. Microorganisms 2020, 8, 237). A two-step construction of albucidin 4'-phosphate from 2'-deoxyadenosine monophosphate (2'-dAMP) is shown to be catalyzed in vitro by the cobalamin dependent radical S-adenosyl-l-methionine (SAM) enzyme AlsB, which catalyzes a ring contraction, and the radical SAM enzyme AlsA, which catalyzes elimination of a one-carbon fragment. Isotope labelling studies show that AlsB catalysis begins with stereospecific H-atom transfer of the C2'-pro-R hydrogen from 2'-dAMP to 5'-deoxyadenosine, and that the eliminated one-carbon fragment originates from C3' of 2'-dAMP.
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Affiliation(s)
- Po-Hsun Fan
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Yujie Geng
- Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, United States
| | - Anthony J. Romo
- Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, United States
| | - Aoshu Zhong
- Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, United States
| | - Jiawei Zhang
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Yu-Cheng Yeh
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Yu-Hsuan Lee
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Hung-wen Liu
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
- Division of Chemical Biology and Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, United States
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2
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Fan PH, Geng Y, Romo AJ, Zhong A, Zhang J, Yeh YC, Lee YH, Liu HW. Two Radical SAM Enzymes Are Necessary and Sufficient for the In Vitro Production of the Oxetane Nucleoside Antiviral Agent Albucidin. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202210362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Po-Hsun Fan
- The University of Texas at Austin Chemistry The University of Texas at Austin 78712-1139 Austin UNITED STATES
| | - Yujie Geng
- The University of Texas at Austin College of Pharmacy College of Pharmacy 78712-1139 Austin UNITED STATES
| | - Anthony J Romo
- The University of Texas at Austin College of Pharmacy College of Pharmacy 78712-1139 Austin UNITED STATES
| | - Aoshu Zhong
- The University of Texas at Austin College of Pharmacy College of Pharmacy 78712-1139 Austin UNITED STATES
| | - Jiawei Zhang
- The University of Texas at Austin Chemistry The University of Texas at Austin 78712-1139 Austin UNITED STATES
| | - Yu-Cheng Yeh
- UT Austin: The University of Texas at Austin Chemistry The University of Texas at Austin 78712-1139 Austin UNITED STATES
| | - Yu-Hsuan Lee
- UT Austin: The University of Texas at Austin Chemistry The University of Texas at Austin 78712-1139 Austin UNITED STATES
| | - Hung-wen Liu
- University of Texas at Austin Phar-Med Chem/3.206 1 University Station A1935PHR 3.206B 78712-0128 Austin UNITED STATES
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3
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Francisco KR, Ballatore C. Thietanes and derivatives thereof in medicinal chemistry. Curr Top Med Chem 2022; 22:1219-1234. [PMID: 35546768 DOI: 10.2174/1568026622666220511154228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 03/04/2022] [Accepted: 03/13/2022] [Indexed: 11/22/2022]
Abstract
Unlike the oxetane ring, which, as evidenced by numerous studies, is known to play an increasingly important role in medicinal chemistry, the thietane ring has thus far received comparatively limited attention. Nonetheless, a growing number of reports now indicate that this 4-membered ring heterocycle may provide opportunities in analog design. In the present review article, we discuss the possible use and utility of the thietane fragment in medicinal chemistry and provide an overview of its properties and recent applications with a focus on isosteric replacements.
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Affiliation(s)
- Karol R Francisco
- Department of Chemistry & Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA
| | - Carlo Ballatore
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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4
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Zhi N, Zhu H, Qiao J, Dong M. Recent progress in radical SAM enzymes: New reactions and mechanisms. CHINESE SCIENCE BULLETIN-CHINESE 2021. [DOI: 10.1360/tb-2021-1067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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5
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Sun SQ, Chen SL. An Unprecedented Ring-Contraction Mechanism in Cobalamin-Dependent Radical S-Adenosylmethionine Enzymes. J Phys Chem Lett 2020; 11:6812-6818. [PMID: 32787210 DOI: 10.1021/acs.jpclett.0c01725] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A unique member of the family of cobalamin (Cbl)-dependent radical S-adenosylmethionine (SAM) enzymes, OxsB, catalyzes the ring constriction of deoxyadenosine triphosphate (dATP) to the base oxetane aldehyde phosphate, a crucial precursor for oxetanocin A (OXT-A), which is an antitumor, antiviral, and antibacterial compound. This enzyme reveals a new catalytic function for this big family that is different from the common methylation. On the basis of density functional theory calculations, a mechanism has been proposed to mainly include that the generation of 5'-deoxyadenosine radical, a hydrogen transfer forming 2'-dATP radical, and a Cbl-catalyzed ring contraction of the deoxyribose in 2'-dATP radical. The ring contraction is a concerted rearrangement step accompanied by an electron transfer from the deoxyribose hydroxyl oxygen to CoIII without any ring-opening intermediate. CoIICbl has been ruled out as an active state. Other mechanistic characteristics are also revealed. This unprecedented non-methylation mechanism provides a new catalytic repertoire for the family of radical SAM enzymes, representing a new class of ring-contraction enzymes.
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Affiliation(s)
- Shuo-Qi Sun
- Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
| | - Shi-Lu Chen
- Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China
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6
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Xu S, Kennedy MA. Structural dynamics of pentapeptide repeat proteins. Proteins 2020; 88:1493-1512. [PMID: 32548861 DOI: 10.1002/prot.25969] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 03/19/2020] [Accepted: 06/06/2020] [Indexed: 12/14/2022]
Abstract
Pentapeptide repeat proteins (PRPs) represent a large superfamily with more than 38 000 sequences in nearly 3500 species, the majority belonging to cyanobacteria but represented among all branches of life. PRPs contain at least eight consecutive pentapeptide repeats with the consensus (A/C/S/V/T/L/I)(D/N/S/K/E/I/R)(L/F)(S/T/R/E/Q/K/V/D)(G/D/E/N/R/Q/K). PRPs fold into right-handed quadrilateral β helices, also known as repeat-five-residue (Rfr)-folds, with four consecutive pentapeptide repeats comprising a single coil, the ~90° change in polypeptide direction in square-shaped coils achieved by type I, II and IV β turns, and hydrogen bonds between coils establishing β ladders on each Rfr-fold face. PRPs are broadly categorized into group 1 and 2 involved in antibiotic resistance and group 3 currently having unknown functions. Motivated by their intriguing structures, we are investigating PRP biophysical characteristics, including Rfr-fold thermal stability, β turn and β ladder hydrogen bond amide exchange rates and backbone dynamics. Here, we present analysis of 20 ns molecular dynamics (MD) simulations and all atom normal mode analysis (aaNMA) calculations for four group 1 and group 2 and four group 3 PRPs whose structures have been determined by X-ray crystallography. The MD cross-correlation matrices and aaNMA indicated strong correlated motion between adjacent coils and weak coupled motion between coils separated by one or more intervening coils. Slow anticorrelated motions were detected between adjacent coils in aaNMA modes that we hypothesize are requisite to access exchange-competent states necessary to permit solvent exchange of amide hydrogens involved in β-ladder and β-turns hydrogen bonds, which can have lifetimes on the order of months.
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Affiliation(s)
- Shenyuan Xu
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA
| | - Michael A Kennedy
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio, USA
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7
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Lopez SS, Jaworski AA, Scheidt KA. NHC-Catalyzed Formal [2+2] Annulations of Allenoates for the Synthesis of Substituted Oxetanes. J Org Chem 2018; 83:14637-14645. [DOI: 10.1021/acs.joc.8b02464] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Susana S. Lopez
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, Northwestern University, Silverman Hall, Evanston, Illinois 60208, United States
| | - Ashley A. Jaworski
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, Northwestern University, Silverman Hall, Evanston, Illinois 60208, United States
| | - Karl A. Scheidt
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, Northwestern University, Silverman Hall, Evanston, Illinois 60208, United States
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8
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Yokoyama K, Lilla EA. C-C bond forming radical SAM enzymes involved in the construction of carbon skeletons of cofactors and natural products. Nat Prod Rep 2018; 35:660-694. [PMID: 29633774 PMCID: PMC6051890 DOI: 10.1039/c8np00006a] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Covering: up to the end of 2017 C-C bond formations are frequently the key steps in cofactor and natural product biosynthesis. Historically, C-C bond formations were thought to proceed by two electron mechanisms, represented by Claisen condensation in fatty acids and polyketide biosynthesis. These types of mechanisms require activated substrates to create a nucleophile and an electrophile. More recently, increasing number of C-C bond formations catalyzed by radical SAM enzymes are being identified. These free radical mediated reactions can proceed between almost any sp3 and sp2 carbon centers, allowing introduction of C-C bonds at unconventional positions in metabolites. Therefore, free radical mediated C-C bond formations are frequently found in the construction of structurally unique and complex metabolites. This review discusses our current understanding of the functions and mechanisms of C-C bond forming radical SAM enzymes and highlights their important roles in the biosynthesis of structurally complex, naturally occurring organic molecules. Mechanistic consideration of C-C bond formation by radical SAM enzymes identifies the significance of three key mechanistic factors: radical initiation, acceptor substrate activation and radical quenching. Understanding the functions and mechanisms of these characteristic enzymes will be important not only in promoting our understanding of radical SAM enzymes, but also for understanding natural product and cofactor biosynthesis.
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Affiliation(s)
- Kenichi Yokoyama
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
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9
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A B 12-dependent radical SAM enzyme involved in oxetanocin A biosynthesis. Nature 2017; 544:322-326. [PMID: 28346939 PMCID: PMC5398914 DOI: 10.1038/nature21689] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 02/03/2017] [Indexed: 11/22/2022]
Abstract
Oxetanocin-A (OXT-A, 1) is a potent antitumor, antiviral, and
antibacterial compound. Biosynthesis of OXT-A has been linked to a
plasmid-borne, Bacillus megaterium gene cluster that contains
four genes, oxsA, oxsB, oxrA,
and oxrB. Here, we show that the oxsA and
oxsB genes are both required for the production of OXT-A.
Biochemical analysis of the encoded proteins, a cobalamin (Cbl)-dependent
S-adenosylmethionine (AdoMet) radical enzyme, OxsB, and an
HD-domain phosphohydrolase, OxsA, revealed that OXT-A is derived from
2′-deoxyadenosine phosphate in an OxsB-catalyzed ring contraction
reaction initiated by H-atom abstraction from C2′. Hence, OxsB
represents the first biochemically characterized non-methylating Cbl-dependent
AdoMet radical enzyme. X-ray analysis of OxsB reveals the fold of a
Cbl-dependent AdoMet radical enzyme for which there are an estimated 7000
members. Overall, this work provides a framework for understanding the interplay
of AdoMet and Cbl cofactors and expands the catalytic repertoire of
Cbl-dependent AdoMet radical enzymes.
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10
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An HD domain phosphohydrolase active site tailored for oxetanocin-A biosynthesis. Proc Natl Acad Sci U S A 2016; 113:13750-13755. [PMID: 27849620 DOI: 10.1073/pnas.1613610113] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
HD domain phosphohydrolase enzymes are characterized by a conserved set of histidine and aspartate residues that coordinate an active site metallocenter. Despite the important roles these enzymes play in nucleotide metabolism and signal transduction, few have been both biochemically and structurally characterized. Here, we present X-ray crystal structures and biochemical characterization of the Bacillus megaterium HD domain phosphohydrolase OxsA, involved in the biosynthesis of the antitumor, antiviral, and antibacterial compound oxetanocin-A. These studies reveal a previously uncharacterized reaction for this family; OxsA catalyzes the conversion of a triphosphorylated compound into a nucleoside, releasing one molecule of inorganic phosphate at a time. Remarkably, this functionality is a result of the OxsA active site, which based on structural and kinetic analyses has been tailored to bind the small, four-membered ring of oxetanocin-A over larger substrates. Furthermore, our OxsA structures show an active site that switches from a dinuclear to a mononuclear metal center as phosphates are eliminated from substrate.
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11
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Buchko GW, Ni S, Robinson H, Welsh EA, Pakrasi HB, Kennedy MA. Characterization of two potentially universal turn motifs that shape the repeated five-residues fold--crystal structure of a lumenal pentapeptide repeat protein from Cyanothece 51142. Protein Sci 2006; 15:2579-95. [PMID: 17075135 PMCID: PMC2242410 DOI: 10.1110/ps.062407506] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2006] [Revised: 08/21/2006] [Accepted: 08/22/2006] [Indexed: 10/24/2022]
Abstract
The genome of the diurnal cyanobacterium Cyanothece sp. PCC 51142 has recently been sequenced and observed to contain 35 pentapeptide repeat proteins (PRPs). These proteins, while present throughout the prokaryotic and eukaryotic kingdoms, are most abundant in cyanobacteria. The sheer number of PRPs in cyanobacteria coupled with their predicted location in every cellular compartment argues for important, yet unknown, physiological and biochemical functions. To gain biochemical insights, the crystal structure for Rfr32, a 167-residue PRP with an N-terminal 29-residue signal peptide, was determined at 2.1 A resolution. The structure is dominated by 21 tandem pentapeptide repeats that fold into a right-handed quadrilateral beta-helix, or Rfr-fold, as observed for the tandem pentapeptide repeats in the only other PRP structure, the mycobacterial fluoroquinoline resistance protein MfpA from Mycobacterium tuberculosis. Sitting on top of the Rfr-fold are two short, antiparallel alpha-helices, bridged with a disulfide bond, that perhaps prevent edge-to-edge aggregation at the C terminus. Analysis of the main-chain (Phi,Psi) dihedral orientations for the pentapeptide repeats in Rfr32 and MfpA makes it possible to recognize the structural details for the two distinct types of four-residue turns adopted by the pentapeptide repeats in the Rfr-fold. These turns, labeled type II and type IV beta-turns, may be universal motifs that shape the Rfr-fold in all PRPs.
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Affiliation(s)
- Garry W Buchko
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
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12
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Izuta S, Yoshida S. Chain Termination With Sugar- Modified Nucleotide Analogs in the DNA Synthesis by DNA Polymerase γ. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/07328319608002415] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Shunji Izuta
- a Laboratory of Cancer Cell Biology, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine , Showa-ku, Nagoya , 466 , Japan
| | - Shonen Yoshida
- a Laboratory of Cancer Cell Biology, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine , Showa-ku, Nagoya , 466 , Japan
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13
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Vetting MW, Hegde SS, Fajardo JE, Fiser A, Roderick SL, Takiff HE, Blanchard JS. Pentapeptide repeat proteins. Biochemistry 2006; 45:1-10. [PMID: 16388575 PMCID: PMC2566302 DOI: 10.1021/bi052130w] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The pentapeptide repeat protein (PRP) family has more than 500 members in the prokaryotic and eukaryotic kingdoms. These proteins are composed of, or contain domains composed of, tandemly repeated amino acid sequences with a consensus sequence of [S,T,A,V][D,N][L,F][S,T,R][G]. The biochemical function of the vast majority of PRP family members is unknown. The three-dimensional structure of the first member of the PRP family was determined for the fluoroquinolone resistance protein (MfpA) from Mycobacterium tuberculosis. The structure revealed that the pentapeptide repeats encode the folding of a novel right-handed quadrilateral beta-helix. MfpA binds to DNA gyrase and inhibits its activity. The rod-shaped, dimeric protein exhibits remarkable similarity in size, shape, and electrostatics to DNA.
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Affiliation(s)
- Matthew W Vetting
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA
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14
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Wang P, Abe K, Ojima T, Ohyashiki JH, Satoh H, Maruyama T, Nagata H, Tanaka H, Yamamoto K. (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assays showed a lack of toxicity of ganciclovir (GCV), C.OXTs, and their derivatives, to TaY(OK) cells at 1 microM. Therefore we compared the antiviral potencies of these drugs at 1 microM by monitoring the viral loads produced during a 1-day period during the course of the drug treatment. Among the drugs tested, 3'-fluorocarbocyclic oxetanocin A (3'F-C.OXT-A) was the most effective for inhibiting the virus production, and at concentrations ranging from 0.5 microM to 10 microM, the inhibition of the viral production was dose-dependent. A comparison of the chemical structures of the derivatives with that of C.OXT-A, which is the parental molecule, suggested that the 3'-fluorine-modification might account for the higher anti-HHV-6 activity and lower cytotoxicity. Microbiol Immunol 2002; 45:457-66. [PMID: 11497221 DOI: 10.1111/j.1348-0421.2001.tb02645.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
An infection of TaY cells, which originated from an adult T-cell leukemia, with an HHV-6B OK isolate resulted in a chronically infected culture, termed TaY(OK). Cell cloning analysis revealed that the TaY(OK) culture consisted of a mixture of cells permissive and refractory to the infection, and that the permissive cells were continuously produced from the refractory cell population. Since the chronically infected culture has been maintained for over 2 years without the addition of uninfected TaY cells, we used it for an evaluation of the antiviral potency of nucleoside analogs, especially carbocyclic oxetanocins (C.OXTs).
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Affiliation(s)
- P Wang
- Department of Virology, Medical Research Institute, Tokyo Medical and Dental University, Japan
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15
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Abstract
The incidence of genital herpes continues to increase in epidemic-like fashion. Aciclovir (acyclovir) has been the original gold standard of therapy. The recent addition of famciclovir and valaciclovir as antiherpes drugs has improved convenience as well as the efficacy of treatment. Although aciclovir remains a widely prescribed and reliable drug, its administration schedule falls short of the ease of usage that the newer nucleoside analogues offer, for both episodic and suppressive therapy. Suppression of symptomatic disease and asymptomatic shedding from the genitalia have both become popular approaches, if not the primary targets of antiviral therapy. Knowing that asymptomatic disease leads to most cases of transmission strongly suggests that suppression with antiviral agents could reduce transmission risk in discordant couples. Unfortunately, the role for antivirals in reducing transmission remains to be proven in clinical trials. Neonatal herpes is now successfully treated using aciclovir. Current randomised clinical trials are examining aciclovir and valaciclovir administration, as well as safety and efficacy for post-acute suppressive therapy. Prevention of recurrences in pregnancy is also a topic under investigation, with a view to reducing the medical need for Cesarean section, or alternatively (and far less likely to be accomplished) to protect the neonate. Although resistance is largely limited to the immunocompromised and a change in resistance patterns is not expected, several drugs are available for the treatment of aciclovir-resistant strains of herpes simplex. Foscarnet is the main alternative with proven efficacy in this setting. Unfortunately, administration of foscarnet requires intravenous therapy, although a single anecdote of topical foscarnet efficacy in this setting has been published. Alternatives include cidofovir gel, which is not commercially available but can be formulated locally from the intravenous preparation. Less effective alternatives include trifluridine and interferon. Future possibilities for treatment of genital herpes include a microparticle-based controlled-release formulation of aciclovir and resiquimod (VML-600; R-848). The search for an effective therapeutic vaccine for genital herpes has not been successful to date, although a live virus glycoprotein H-deficient (DISC) vaccine is currently in clinical trials. Recent data suggest that seronegative women are protected (albeit, not fully) by a glycoprotein D recombinant vaccine with adjuvant. Despite the established safety and convenience of current treatment options, better suppressive options and topical treatment options are much needed. Studies using existing agents as potential tools to avoid Cesarean section, or transmission to neonate or partner are ongoing. Both vaccines and antivirals may eventually play a role in prevention of infection.
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Affiliation(s)
- D T Leung
- Wake Forest University School of Medicine, Winston Salem, North Carolina, USA.
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16
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Hayakawa N, Nozawa K, Ogawa A, Kato N, Yoshida K, Akamatsu KI, Tsuchiya M, Nagasaka A, Yoshida S. Isothiazolone derivatives selectively inhibit telomerase from human and rat cancer cells in vitro. Biochemistry 1999; 38:11501-7. [PMID: 10471302 DOI: 10.1021/bi982829k] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The telomere hypothesis postulates stabilization of telomere length and telomerase activation as key events in cellular immortalization and carcinogeneses. Accordingly, telomerase has been suggested as a novel and highly selective target for design of antitumor drugs. Screening of a chemical library including 16 000 synthetic compounds yielded six that strongly inhibited telomerase activity in extracts of cultured human cells, including four isothiazolone derivatives and two unrelated compounds. The most potent inhibitor was 2-[3-(trifluoromethyl)phenyl]isothiazolin-3-one (TMPI), a concentration of 1.0 microM inhibited telomerase activity by 50% according to a telomere repeat amplification protocol (TRAP) assay. Analysis using partially purified telomerase from AH7974 rat hepatoma cells demonstrated noncompetitive inhibition with the telomere-repeat primer and mixed inhibition with the dNTPs; the inhibition constant was 2.5 microM. TMPI did not inhibit eukaryotic DNA polymerase alpha, beta, or human immunodeficiency virus reverse transcriptase (HIV RT). Thus, inhibition by TMPI was highly selective for telomerase. Inhibition by TMPI was quenched by 1 mM of dithiothreitol or glutathione, suggesting that TMPI inhibits telomerase by acting at a cysteine residue. TMPI inhibition of this enzyme may find application as an antineoplastic agent.
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Affiliation(s)
- N Hayakawa
- Department of Internal Medicine, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
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17
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Neyts J, De Clercq E. The immunosuppressive agent mycophenolate mofetil markedly potentiates the activity of lobucavir [1R(1alpha,2beta,3alpha)]-9-[2,3-bis(hydroxymethyl)cyclobutyl]guanine against different herpes viruses. Transplantation 1999; 67:760-4. [PMID: 10096537 DOI: 10.1097/00007890-199903150-00022] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Mycophenolate mofetil (MMF) has been approved as an immunosuppressive agent in kidney transplant recipients and may thus be used concomitantly with antiherpetic agents, the latter for the treatment of intercurrent herpesvirus infections. The parent compound of MMF, mycophenolic acid (MPA), is a potent inhibitor of inosine monophosphate dehydrogenase and causes depletion of the intracellular (deoxy)guanosine triphosphate [(d)GTP] pools. Lobucavir [1R(1alpha,2beta,3alpha)]-9-[2,3-bis(hydroxymethyl)cyc lobutyl]guanine (LBV) is a novel antiviral agent with activity against ganciclovir-resistant cytomegalovirus (CMV) strains, that is in phase II clinical trials for the treatment of CMV infections. LBV triphosphate inhibits the viral DNA polymerase competitively with dGTP. We present the results of our studies on the antiviral effects of the combinations LBV + MMF and LBV + MPA. METHODS The antiviral effects of LBV either alone or in combination with MMF or MPA on the replication of CMV, herpes simplex virus type- (HSV) 1 (HSV-1), HSV-2, and thymidine kinase-deficient HSV-1 were studied by means of plaque or CPE reduction assays. RESULTS When combined with LBV, MPA (at concentrations ranging from 0.25 to 10 microg/ml, which are readily attainable in human plasma) markedly potentiated the antiviral efficacy of LBV against HSV-1 and HSV-2, that is a 10- to 100-fold decrease in EC50. Moreover, the EC50 of LBV against TK- HSV-1 decreased up to 1400-fold upon combination with MPA. MPA by itself had little or no effect on the replication of these viruses. Moreover, MPA and MMF resulted in a marked increase in the anti-CMV activity of LBV minimal FIC (FICmin: 0.24 and 0.26, respectively). Exogenously added guanosine reversed the potentiating effect of MPA on the antiviral activity of LBV, which indicates that this potentiating effect results from a depletion of the endogenous dGTP pools, thus favoring the inhibitory action of the LBV-triphosphate on the viral DNA polymerase. Ribavirin, another inhibitor of inosine monophosphate-dehydrogenase, also caused a marked enhancement of the antiviral activity of LBV against HSV-1 (12-fold), HSV-2 (20-fold), and TK- HSV-1 (25-fold). CONCLUSION MMF markedly potentiates the activity of LBV against HSV-1, HSV-2, TK- HSV-1, and CMV. This drug interaction may have important implications when using LBV in the treatment of intercurrent herpesvirus infections in transplant recipients under MMF therapy.
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Affiliation(s)
- J Neyts
- Rega Institute for Medical Research, Katholieke Universiteit Leuven, Belgium
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Ogawa A, Murate T, Izuta S, Takemura M, Furuta K, Kobayashi J, Kamikawa T, Nimura Y, Yoshida S. Sulfated glycoglycerolipid from archaebacterium inhibits eukaryotic DNA polymerase alpha, beta and retroviral reverse transcriptase and affects methyl methanesulfonate cytotoxicity. Int J Cancer 1998; 76:512-8. [PMID: 9590127 DOI: 10.1002/(sici)1097-0215(19980518)76:4<512::aid-ijc12>3.0.co;2-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A sulfated glycoglycerolipid, 1-O-(6'-sulfo-alpha-D-glucopyranosyl)-2,3-di-O-phytanyl- sn-glycerol (KN-208), a derivative of the polar lipid isolated from an archaebacterium, strongly inhibited DNA polymerase (pol) alpha and pol beta in vitro among 5 eukaryotic DNA polymerases (alpha, beta, gamma, delta, and epsilon). It also inhibited Escherichia coli DNA polymerase I Klenow fragment (E. coli pol I) and human immunodeficiency virus reverse transcriptase (HIV RT). The mode of inhibition of these polymerases was competitive with the DNA template primer and was non-competitive with the substrate dTTP. KN-208 inhibited pol beta most strongly, with a Ki value of 0.05 microM, 10-fold lower than that for pol alpha (0.5 microM) and 60- or 140-fold lower than that for HIV RT (3 microM) or for E. coli pol I (7 microM), respectively. The loss of sulfate on the 6'-position of glucopyranoside of this compound completely abrogated inhibition. However, the hydrophilic part of KN-208, glucose 6-sulfate alone, showed no inhibition. Other sulfated compounds containing different hydrophobic structures, such as dodecyl sulfate and cholesterol sulfate, exhibited a much weaker inhibition. Our results suggest that the whole molecular structure of KN-208 is required for inhibition. KN-208 was shown to be modestly cytotoxic for the human leukemic cell line K562. Interestingly, a subcytotoxic dose of KN-208 increased the sensitivity of the human leukemic cells to an alkylating agent, methyl methanesulfonate, while it did not potentiate the effects of ultraviolet light or of cisplatin.
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Affiliation(s)
- A Ogawa
- First Department of Surgery, Nagoya University School of Medicine, Japan
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Tenney DJ, Yamanaka G, Voss SM, Cianci CW, Tuomari AV, Sheaffer AK, Alam M, Colonno RJ. Lobucavir is phosphorylated in human cytomegalovirus-infected and -uninfected cells and inhibits the viral DNA polymerase. Antimicrob Agents Chemother 1997; 41:2680-5. [PMID: 9420038 PMCID: PMC164188 DOI: 10.1128/aac.41.12.2680] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Lobucavir (LBV) is a deoxyguanine nucleoside analog with broad-spectrum antiviral activity. LBV was previously shown to inhibit herpes simplex virus (HSV) DNA polymerase after phosphorylation by the HSV thymidine kinase. Here we determined the mechanism of action of LBV against human cytomegalovirus (HCMV). LBV inhibited HCMV DNA synthesis to a degree comparable to that of ganciclovir (GCV), a drug known to target the viral DNA polymerase. The expression of late proteins and RNA, dependent on viral DNA synthesis, was also inhibited by LBV. Immediate-early and early HCMV gene expression was unaffected, suggesting that LBV acts temporally coincident with HCMV DNA synthesis and not through cytotoxicity. In vitro, the triphosphate of LBV was a potent inhibitor of HCMV DNA polymerase with a Ki of 5 nM. LBV was phosphorylated to its triphosphate form intracellularly in both infected and uninfected cells, with phosphorylated metabolite levels two- to threefold higher in infected cells. GCV-resistant HCMV isolates, with deficient GCV phosphorylation due to mutations in the UL97 protein kinase, remained sensitive to LBV. Overall, these results suggest that LBV-triphosphate halts HCMV DNA replication by inhibiting the viral DNA polymerase and that LBV phosphorylation can occur in the absence of viral factors including the UL97 protein kinase. Furthermore, LBV may be effective in the treatment of GCV-resistant HCMV.
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Affiliation(s)
- D J Tenney
- Department of Virology, Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, Connecticut 06492, USA.
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Nishizono N, Koike N, Yamagata Y, Fujii S, Matsuda A. Nucleosides and nucleotides. 159. Synthesis of thietane nucleosides via the Pummerer reaction as a key step. Tetrahedron Lett 1996. [DOI: 10.1016/0040-4039(96)01719-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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