126
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Karginov VA, Yohannes A, Robinson TM, Fahmi NE, Alibek K, Hecht SM. β-Cyclodextrin derivatives that inhibit anthrax lethal toxin. Bioorg Med Chem 2006; 14:33-40. [PMID: 16169738 DOI: 10.1016/j.bmc.2005.07.054] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Revised: 07/27/2005] [Accepted: 07/27/2005] [Indexed: 11/16/2022]
Abstract
Recently, we demonstrated that simultaneous blocking of bacterial growth by antibiotics and inhibition of anthrax toxin action with antibodies against protective antigen were beneficial for the treatment of anthrax. The present study examined the hypothesis that blocking the pore formed by protective antigen can inhibit the action of anthrax toxin. The potential inhibitors were chosen by a structure-based design using beta-cyclodextrin as the starting molecule. Several beta-cyclodextrin derivatives were evaluated for their ability to protect RAW 264.7 cells from the action of anthrax lethal toxin. Per-substituted aminoalkyl derivatives displayed inhibitory activity and were protective against anthrax lethal toxin action at low micromolar concentrations. These results provide the basis for a structure-based drug discovery program, with the goal of identifying new drug candidates for anthrax treatment.
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127
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Abstract
[reaction: see text] The synthesis of the naturally occurring kaempferol glycoside SL0101 has been accomplished, as has its biochemical evaluation. SL0101 exhibits selective and potent p90 Rsk inhibitory activity at nanomolar concentrations without inhibiting the function of upstream kinases such as MEK, Raf, or PKC. The synthesis verified the structural assignment of the natural product and has provided access to material sufficient for detailed biological evaluation.
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128
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Lodder M, Wang B, Hecht SM. The N-pentenoyl protecting group for aminoacyl-tRNAs. Methods 2005; 36:245-51. [PMID: 16076450 DOI: 10.1016/j.ymeth.2005.04.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Accepted: 04/28/2005] [Indexed: 11/30/2022] Open
Abstract
The elaboration of misacylated transfer RNAs by T4 RNA ligase-mediated condensation of an aminoacylated pdCpA derivative and a tRNA (transcript) missing the two 3'-terminal nucleotides requires that the aminoacyl moiety of the dinucleotide be stabilized during the ligation reaction. This can be done conveniently by the use of a simple 4-pentenoyl group attached to N(alpha) of the amino acid. The pentenoyl amide can be deblocked readily with aqueous iodine, presumably via an iodolactone intermediate. This protecting group can be used in conjunction with side chain protecting group for amino acids having side chain functionality, thus permitting the elaboration of proteins bearing side chain protecting groups that can be removed in a subsequent step (e.g., caged proteins). In addition, an aminated analogue of the pentenoyl protecting group, the unnatural amino acid allylglycine, can be employed as part of the peptide backbone to afford a protein cleavable by iodine.
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129
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Deng JZ, Starck SR, Li S, Hecht SM. (+)-Myristinins A and D from Knema elegans, which inhibit DNA polymerase beta and cleave DNA. JOURNAL OF NATURAL PRODUCTS 2005; 68:1625-8. [PMID: 16309311 DOI: 10.1021/np058064g] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
A survey of crude plant extracts for DNA polymerase beta inhibitors resulted in the identification of a methyl ethyl ketone extract prepared from Knema elegans that strongly inhibited the enzyme. Subsequent bioassay-guided fractionation of the extract, using an assay to monitor the activity of DNA polymerase beta, led to the isolation of two potent inhibitors, (+)-myristinins A (1) and D (2), which are known flavans having unusual structures. (+)-Myristinins A and D exhibited IC50 values of 12 and 4.3 microM, respectively, as inhibitors of DNA polymerase beta in the presence of bovine serum albumin (BSA), and 2.7 and 1.2 microM in the absence of BSA. As such, they are the most potent DNA polymerase beta inhibitors reported to date. Compounds 1 and 2 potentiated the cytotoxicity of bleomycin toward cultured P388D1 cells, reducing the number of viable cells by at least 30% when employed at 9 microM concentration for 6 h in the presence of an otherwise nontoxic concentration of bleomycin (75 nM). Principles 1 and 2 also induced strong Cu2+-dependent DNA strand scission in a DNA cleavage assay. Accordingly, 1 and 2 exhibit two activities, namely, DNA polymerase beta inhibition and DNA damage.
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130
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Abstract
[reaction: see text] A concise stereoselective total synthesis of a naturally occurring polymerase beta inhibitor, delta-trans-tocotrienoloic acid (2), is described. The key step in the synthesis is an acid-catalyzed cyclodehydration reaction. Additionally, this report corrects a previously reported structural assignment, defines the absolute stereochemistry of 2, and defines key structural requirements for polymerase beta inhibition.
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131
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Nakanishi I, Nishizawa C, Ohkubo K, Takeshita K, Suzuki KT, Ozawa T, Hecht SM, Tanno M, Sueyoshi S, Miyata N, Okuda H, Fukuzumi S, Ikota N, Fukuhara K. Hydroxyl radical generation via photoreduction of a simple pyridine N-oxide by an NADH analogue. Org Biomol Chem 2005; 3:3263-5. [PMID: 16132086 DOI: 10.1039/b509447j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photoreduction of pyridine N-oxide, which has a key structure of antitumor agents for hypoxic solid tumors, by 1-benzyl-1,4-dihydronicotinamide in deaerated aprotic media resulted in generation of hydroxyl radical, leading to the oxidation of salicylic acid to 2,3- and 2,5-dihydroxybenzoic acids, and catechol.
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132
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Pham VC, Ma J, Thomas SJ, Xu Z, Hecht SM. Alkaloids from Alangium javanicum and Alangium grisolleoides that mediate Cu2+-dependent DNA strand scission. JOURNAL OF NATURAL PRODUCTS 2005; 68:1147-52. [PMID: 16124751 DOI: 10.1021/np058013j] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Crude CH2Cl2-MeOH extracts prepared from Alangium javanicum and A. grisolleoides were found to induce DNA strand breakage in the presence of Cu2+ and were subjected to bioassay-guided fractionation to permit identification of the active principle(s). Javaniside (1), a novel alkaloid possessing an unusual monoterpenoid oxindole skeleton, was identified as an active principle contributing to the DNA cleavage activity observed for the crude extract of A. javanicum. Alangiside (2), a tetrahydroisoquinoline monoterpene glucoside widely distributed in the genus Alangium, was also isolated from A. grisolleoides as a new type of Cu2+-dependent DNA cleavage agent. The relative configuration of the asymmetric centers in javaniside was established by analysis of 1H-1H coupling constants and NOESY correlations. Semisynthesis of javaniside from secologanin (3) established the absolute stereochemistry of javaniside.
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133
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Hecht SM. Camptothecin: Roles of the D and E Rings in Binding to the Topoisomerase I-DNA Covalent Binary Complex. ACTA ACUST UNITED AC 2005; 5:353-62. [PMID: 16101487 DOI: 10.2174/1568011054222373] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The alkaloid camptothecin is the prototypical DNA topoisomerase I poison. This core structure has formed the basis for two marketed antitumor agents and numerous clinical candidates, and has been the focus of many synthetic and medicinal chemistry studies. Recent reports have furthered our understanding of the roles played by the D and E rings of camptothecin in stabilization of the enzyme-DNA-camptothecin ternary complex. Important parameters for further study and optimization include the facility of E-ring lactone hydrolysis and the prospects for replacing the E ring with more stable structures, the role of the 14-CH group in binary complex binding, and the effect of ternary complex dynamics on the expression of cytotoxicity by the camptothecins.
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134
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Gao R, Zhang Y, Choudhury AK, Dedkova LM, Hecht SM. Analogues of vaccinia virus DNA topoisomerase I modified at the active site tyrosine. J Am Chem Soc 2005; 127:3321-31. [PMID: 15755148 DOI: 10.1021/ja044182z] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanism of type IB topoisomerase-mediated DNA relaxation was studied by modification of vaccinia topoisomerase I at the active site tyrosine (position 274) with several tyrosine analogues. These analogues had varied steric, electronic, and stereochemical features to permit assessment of those structural elements required to support topoisomerase function. Eleven tyrosine analogues were successfully incorporated into the active site of vaccinia topoisomerase I. It was found that only tyrosine analogues having the phenolic -OH group in the normal position relative to the protein backbone were active. Modifications that replaced the nucleophilic tyrosine OH (pKa approximately 10.0) group with NH2 (pKa 4.6), SH (pKa approximately 7.0), or I groups or that changed the orientation of the nucleophilic OH group essentially eliminated topoisomerase I function. For the active analogues, the electronic effects and H-bonding characteristics of substituents in the meta-position of the aromatic ring may be important in modulating topoisomerase I function. The pH profile for the functional analogues revealed a small shift toward lower pH when compared with wild-type topoisomerase I.
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MESH Headings
- Amino Acid Sequence
- Binding Sites
- DNA Topoisomerases, Type I/chemistry
- DNA Topoisomerases, Type I/genetics
- DNA Topoisomerases, Type I/metabolism
- Hydrogen-Ion Concentration
- Kinetics
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Plasmids/genetics
- RNA, Transfer, Amino Acyl/chemistry
- RNA, Transfer, Amino Acyl/genetics
- RNA, Transfer, Phe/chemistry
- RNA, Transfer, Phe/genetics
- Structure-Activity Relationship
- Tyrosine/chemistry
- Tyrosine/genetics
- Tyrosine/metabolism
- Vaccinia virus/enzymology
- Vaccinia virus/genetics
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135
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Arimondo PB, Laco GS, Thomas CJ, Halby L, Pez D, Schmitt P, Boutorine A, Garestier T, Pommier Y, Hecht SM, Sun JS, Bailly C. Activation of camptothecin derivatives by conjugation to triple helix-forming oligonucleotides. Biochemistry 2005; 44:4171-80. [PMID: 15766244 DOI: 10.1021/bi048031k] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Topoisomerase I (topo I) is a ubiquitous DNA-cleaving enzyme and an important therapeutic target in cancer chemotherapy. Camptothecins (CPTs) reversibly trap topo I in covalent complex with DNA but exhibit limited sequence preference. The utilization of conjugates such as triplex-forming oligonucleotides (TFOs) to target a medicinal agent (like CPT) to a specific genetic sequence and orientation within the DNA has been accomplished successfully. In this study, different attachment points of the TFO to CPT (including positions 7, 9, 10, and 12) were investigated and our findings confirmed and extended previous conclusions. Interestingly, the conjugates induced specific DNA cleavage by topo I at the triplex site even when poorly active or inactive CPT derivatives were used. This suggests that the positioning of the drug in the cleavage complex by the sequence-specific DNA ligand is able to stabilize the ternary complex, even when important interactions between topo I and CPT are disrupted. Finally, certain TFO-CPT conjugates were able to induce sequence-specific DNA cleavage with the topo I mutants R364H and N722S that are resistant to camptothecin. The TFO-CPT conjugates are thus valuable tools to study the interactions involved in the formation of the ternary complex and also to enlarge the family of compounds that poison topo I. The fact that an inactive CPT analogue can act as a topo I poison when appropriately coupled to a TFO provides a new perspective at the level of drug design.
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136
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Tian L, Claeboe CD, Hecht SM, Shuman S. Mechanistic Plasticity of DNA Topoisomerase IB: Phosphate Electrostatics Dictate the Need for a Catalytic Arginine. Structure 2005; 13:513-20. [PMID: 15837190 DOI: 10.1016/j.str.2005.02.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2004] [Revised: 12/16/2004] [Accepted: 12/17/2004] [Indexed: 11/24/2022]
Abstract
Four conserved amino acids of type IB topoisomerases (Arg130, Lys167, Arg223, and His265 in vaccinia topoisomerase) catalyze the attack by tyrosine on the scissile phosphodiester to form a DNA-(3'-phosphotyrosyl)-enzyme intermediate. The mechanism entails general acid catalysis (by Lys167 and Arg130) and transition-state stabilization (via contact of His265 with the pro-Sp oxygen). Here we query the function of Arg223, which accelerates transesterification by a factor of 10(5). The requirement for Arg223 is alleviated by a neutral Sp methylphosphonate (MeP) linkage at the cleavage site. Arg223 is not required for the 30,000-fold activation of the latent endonuclease activity of topoisomerase by the Sp MeP. The rate of autohydrolysis by the DNA-(3'-MeP)-topoisomerase intermediate approaches 10% of the rate of religation to a 5'-OH DNA strand. These findings underscore the importance of transition-state electrostatics in determining the composition of the active site and dictating the balance between strand transferase and hydrolase functions.
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137
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Deng JZ, Newman DJ, Hecht SM. Umbelactonyl cinnamate derivatives from Crypteronia paniculata that mediate DNA strand scission. JOURNAL OF NATURAL PRODUCTS 2005; 68:465-467. [PMID: 15787463 DOI: 10.1021/np0401112] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
As part of an initiative to discover functional natural product analogues of bleomycin guided by the use of the COMPARE algorithm, a CH(2)Cl(2)-MeOH extract prepared from Crypteronia paniculata was found to exhibit relaxation of supercoiled pSP64 DNA in the presence of Cu(2+). Bioassay-guided fractionation employing a DNA strand scission assay resulted in the isolation of three novel DNA cleavage agents. Their structures were elucidated as umbelactonyl cinnamate derivatives 1-3 through their NMR and MS spectral data analyses. This is the first example of the isolation and structural characterization of naturally occurring umbelactonyl cinnamate derivatives. Compound 1 exhibited strong Cu(2+)-dependent relaxation of supercoiled pSP64 DNA, while compounds 2 and 3 had only weak DNA cleavage activity.
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138
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Maloney DJ, Deng JZ, Starck SR, Gao Z, Hecht SM. (+)-Myristinin A, a Naturally Occurring DNA Polymerase β Inhibitor and Potent DNA-Damaging Agent. J Am Chem Soc 2005; 127:4140-1. [PMID: 15783174 DOI: 10.1021/ja042727j] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The first stereoselective total synthesis of the naturally occurring flavan myristinin A has been accomplished, as well as its biochemical evaluation. This synthesis verified the structural assignment and allowed for the determination of the absolute stereochemistry. Myristinin A exhibits biochemical activity both as a potent DNA-damaging agent and DNA polymerase beta inhibitor. Relaxation of supercoiled plasmid DNA was observed at picomolar concentrations, in addition to inhibition of polymerase beta at low micromolar concentrations.
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139
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Rahier NJ, Cheng K, Gao R, Eisenhauer BM, Hecht SM. Synthesis of 14-Azacamptothecin, a Water-Soluble Topoisomerase I Poison. Org Lett 2005; 7:835-7. [PMID: 15727453 DOI: 10.1021/ol0400701] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
14-Azacamptothecin, a potent, water-soluble analogue of the antitumor agent camptothecin, has been prepared by a convergent synthesis. The key condensation of the AB and DE rings with concomitant formation of ring C of 14-aza CPT was carried out in two stages, the latter of which involved a radical cyclization strategy. [structure: see text]
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140
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Rahier NJ, Eisenhauer BM, Gao R, Thomas SJ, Hecht SM. On the role of E-ring oxygen atoms in the binding of camptothecin to the topoisomerase I–DNA covalent binary complex. Bioorg Med Chem 2005; 13:1381-6. [PMID: 15670945 DOI: 10.1016/j.bmc.2004.11.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2004] [Accepted: 11/04/2004] [Indexed: 12/20/2022]
Abstract
A recent X-ray crystallographic analysis of the binding of a water soluble camptothecin analogue to the human topoisomerase I-DNA covalent binary complex has suggested the existence of some novel features in the way that camptothecin is bound to the binary complex. Four additional models based on chemical and biochemical data have also been proposed. Presently we describe S-containing analogues of camptothecin prepared on the basis of these models, and report their ability to form stable ternary complexes with human topoisomerase I, and to mediate cytotoxicity at the locus of topoisomerase I. The results indicate that replacement of the 20-OH group of CPT with a SH functionality results in diminution of the potency of CPT as a topoisomerase I poison, while replacement of the O atoms at positions 20 and 21 with S atoms results in essentially complete loss of topoisomerase I inhibitory activity.
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141
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Smith JA, Poteet-Smith CE, Xu Y, Errington TM, Hecht SM, Lannigan DA. Identification of the first specific inhibitor of p90 ribosomal S6 kinase (RSK) reveals an unexpected role for RSK in cancer cell proliferation. Cancer Res 2005; 65:1027-34. [PMID: 15705904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Abstract
p90 ribosomal S6 kinase (RSK) is an important downstream effector of mitogen-activated protein kinase, but its biological functions are not well understood. We have now identified the first small-molecule, RSK-specific inhibitor, which we isolated from the tropical plant Forsteronia refracta. We have named this novel inhibitor SL0101. SL0101 shows remarkable specificity for RSK. The major determinant of SL0101-binding specificity is the unique ATP-interacting sequence in the amino-terminal kinase domain of RSK. SL0101 inhibits proliferation of the human breast cancer cell line MCF-7, producing a cell cycle block in G(1) phase with an efficacy paralleling its ability to inhibit RSK in intact cells. RNA interference of RSK expression confirmed that RSK regulates MCF-7 proliferation. Interestingly, SL0101 does not alter proliferation of a normal human breast cell line MCF-10A, although SL0101 inhibits RSK in these cells. We show that RSK is overexpressed in approximately 50% of human breast cancer tissue samples, suggesting that regulation of RSK has been compromised. Thus, we show that RSK has an unexpected role in proliferation of transformed cells and may be a useful new target for chemotherapeutic agents. SL0101 will provide a powerful new tool to dissect the molecular functions of RSK in cancer cells.
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142
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Xu YM, Johnson RK, Hecht SM. Polybrominated diphenyl ethers from a sponge of the Dysidea genus that inhibit Tie2 kinase. Bioorg Med Chem 2005; 13:657-9. [PMID: 15653332 DOI: 10.1016/j.bmc.2004.10.061] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2004] [Accepted: 10/27/2004] [Indexed: 10/26/2022]
Abstract
Tie2 kinase, an enzyme that supports angiogenesis essential for tumor growth and survival, was selected as a target in a search for naturally occurring inhibitors of potential utility for antitumor therapy. Two polybrominated diphenyl ethers, 3,5-dibromo-2-(2',4'-dibromophenoxy)phenol (1) and 4,6-dibromo-2-(2',4'-dibromophenoxy)phenol (2) were isolated from an extract prepared from Dysidea sp. after bioassay-guided fractionation.
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143
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Ma J, Jones SH, Marshall R, Wu X, Hecht SM. DNA topoisomerase I inhibitors from Rinorea anguifera. Bioorg Med Chem Lett 2005; 15:813-6. [PMID: 15664863 DOI: 10.1016/j.bmcl.2004.10.095] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2004] [Accepted: 10/29/2004] [Indexed: 10/26/2022]
Abstract
An organic extract prepared from Rinorea anguifera was investigated in order to identify the natural principle(s) responsible for stabilization of a topoisomerase I-DNA covalent binary complex. Bioassay-guided fractionation resulted in the isolation of mauritianin and (+)-syringaresinol as new topoisomerase I inhibitors, and also of the known inhibitor camptothecin.
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144
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Ma J, Jones SH, Hecht SM. A dihydroflavonol glucoside from Commiphora africana that mediates DNA strand scission. JOURNAL OF NATURAL PRODUCTS 2005; 68:115-117. [PMID: 15679332 DOI: 10.1021/np0400510] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A crude CH(2)Cl(2)-MeOH extract prepared from Commiphora africana was found to mediate Cu(2+)-dependent relaxation of supercoiled plasmid DNA. Bioassay-guided fractionation of this extract was carried out and was monitored by the use of an in vitro DNA strand scission assay. The dihydroflavonol glucoside phellamurin (1) was identified as the active principle responsible for the DNA cleavage activity of the crude extract.
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145
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Cheng K, Rahier NJ, Eisenhauer BM, Gao R, Thomas SJ, Hecht SM. 14-Azacamptothecin: A Potent Water-Soluble Topoisomerase I Poison. J Am Chem Soc 2004; 127:838-9. [PMID: 15656613 DOI: 10.1021/ja0442769] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
On the basis of an analysis of luotonin A and its D-ring deaza analogue as topoisomerase I poisons and topoisomerase I-dependent cytotoxic agents, a novel analogue of the structurally related antitumor antibiotic camptothecin (CPT) was prepared. 14-Azacamptothecin was found to have much greater aqueous solubility than CPT, to inhibit topoisomerase I-mediated DNA relaxation more efficiently than CPT, and to stabilize the covalent binary complex to almost the same extent. 14-Aza CPT was found to be slightly less active than CPT in mediating cytotoxicity toward yeast expressing human topoisomerase I, possibly as a consequence of its greater off-rate from the CPT-topoisomerase I-DNA ternary complex.
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146
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Chaturvedula VSP, Zhou BN, Gao Z, Thomas SJ, Hecht SM, Kingston DGI. New lupane triterpenoids from Solidago canadensis that inhibit the lyase activity of DNA polymerase β. Bioorg Med Chem 2004; 12:6271-5. [PMID: 15519169 DOI: 10.1016/j.bmc.2004.08.048] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2004] [Revised: 08/27/2004] [Accepted: 08/27/2004] [Indexed: 10/26/2022]
Abstract
Bioassay-directed fractionation of a methyl ethyl ketone extract of Solidago canadensis L. (Asteraceae), using an assay to detect the lyase activity of DNA polymerase beta, resulted in the isolation of the four new lupane triterpenoids 1-4 and the seven known compounds lupeol, lupeyl acetate, ursolic acid, cycloartenol, cycloartenyl palmitate, alpha-amyrin acetate, and stigmasterol. The structures of the new compounds were established as 3beta-(3R-acetoxyhexadecanoyloxy)-lup-20(29)-ene (1), 3beta-(3-ketohexadecanoyloxy)-lup-20(29)-ene (2), 3beta-(3R-acetoxyhexadecanoyloxy)-29-nor-lupan-20-one (3), and 3beta-(3-hetohexadecanoyloxy)-29-nor-lupan-20-one (4), respectively, on the basis of extensive 1D and 2D NMR spectroscopic interpretation and chemical modification studies. All 11 compounds were inhibitory to the lyase activity of DNA polymerase beta.
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147
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Cagir A, Eisenhauer BM, Gao R, Thomas SJ, Hecht SM. Synthesis and topoisomerase I inhibitory properties of luotonin A analogues. Bioorg Med Chem 2004; 12:6287-99. [PMID: 15519171 DOI: 10.1016/j.bmc.2004.08.052] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2004] [Accepted: 08/18/2004] [Indexed: 10/26/2022]
Abstract
Luotonin A, a naturally occurring pyrroloquinazolinoquinoline alkaloid, has been previously demonstrated to be a topoisomerase I poison. A number of luotonin A derivatives have now been prepared through the condensation of anthranilic acid derivatives and 1,2-dihydropyrrolo[3,4-b]quinoline-3-one in the presence of phosphorus oxychloride. When dichloromethane was used as solvent the reaction proceeded to a single product. In contrast when the reaction was carried out in tetrahydrofuran or in phosphorus oxychloride, an additional isomeric product was obtained. The luotonin A analogues were evaluated for their ability to effect stabilization of the covalent binary complex formed between human topoisomerase I and DNA, and for cytotoxicity toward a yeast strain expressing the human topoisomerase I.
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148
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Thomas CJ, Rahier NJ, Hecht SM. Camptothecin: current perspectives. Bioorg Med Chem 2004; 12:1585-604. [PMID: 15028252 DOI: 10.1016/j.bmc.2003.11.036] [Citation(s) in RCA: 305] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2003] [Accepted: 11/28/2003] [Indexed: 01/20/2023]
Abstract
This review provides a detailed discussion of recent advances in the medicinal chemistry of camptothecin, a potent antitumor antibiotic. Two camptothecin analogues are presently approved for use in the clinic as antitumor agents and several others are in clinical trials. Camptothecin possesses a novel mechanism of action involving the inhibition of DNA relaxation by DNA topoisomerase I, and more specifically the stabilization of a covalent binary complex formed between topoisomerase I and DNA. This review summarizes the current status of studies of the mechanism of action of camptothecin, including topoisomerase I inhibition and additional cellular responses. Modern synthetic approaches to camptothecin and several of the semi-synthetic methods are also discussed. Finally, a systematic evaluation of novel and important analogues of camptothecin and their contribution to the current structure-activity profile are considered.
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149
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Klarmann GJ, Eisenhauer BM, Zhang Y, Sitaraman K, Chatterjee DK, Hecht SM, Le Grice SFJ. Site- and subunit-specific incorporation of unnatural amino acids into HIV-1 reverse transcriptase. Protein Expr Purif 2004; 38:37-44. [PMID: 15477080 DOI: 10.1016/j.pep.2004.07.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Revised: 07/14/2004] [Indexed: 11/24/2022]
Abstract
A highly efficient cell-free translation system has been combined with suppressor tRNA technology to substitute nor-Tyr and 3-fluoro-Tyr in place of Tyr183 at the DNA polymerase active site of p66 of human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT). Supplementing the wild-type HIV-1 p51 RT subunit into this translation system permitted reconstitution of the biologically relevant p66/p51 heterodimer harboring Tyr analogs exclusively on the catalytically competent p66 subunit. Addition of an affinity tag at the p66 C-terminus allowed rapid, one-step purification of reconstituted and selectively mutated heterodimer HIV-1 RT via strep-Tactin-agarose affinity chromatography. The purified enzyme was demonstrated to be free of contaminating nucleases, allowing characterization of the DNA polymerase and ribonuclease H activities associated with HIV-1 RT. Preliminary characterization of HIV-1 RT(nor-Tyr) and HIV-1 RT(m-fluoro-Tyr) is presented. The success of this strategy will facilitate detailed molecular analysis of structurally and catalytically critical amino acids via their replacement with closely related, unnatural analogs.
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Cao S, Gao Z, Thomas SJ, Hecht SM, Lazo JS, Kingston DGI. Marine sesquiterpenoids that inhibit the lyase activity of DNA polymerase beta. JOURNAL OF NATURAL PRODUCTS 2004; 67:1716-1718. [PMID: 15497946 DOI: 10.1021/np049849+] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Bioassay-directed fractionation of an extract of the marine species Spongia sp. led to the discovery of the new sesquiterpenoid derivative 17-O-isoprenyldictyoceratin-C (1), the known sesquiterpenoid derivative dictyoceratin-C (2), and the sesquiterpenoid quinone ilimaquinone (3), in addition to the nucleoside 2'-deoxyuridine. The structure of the new compound 1 was determined on the basis of spectroscopic methods and by conversion of dictyoceratin-C (2) to 1.
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