Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Molluscum contagiosum virus (MCV), the only member of the Molluscipoxvirus genus, causes benign papules in healthy people but disfiguring lesions in immunocompromised patients. The sequence of MCV has been completed, revealing that MCV encodes a probable type I topoisomerase enzyme. All poxviruses sequenced to date also encode type I topoisomerases, and in the case of vaccinia virus the topoisomerase has been shown to be essential for replication. Thus, inhibitors of the MCV topoisomerase might be useful as antiviral agents. We have cloned the gene for MCV topoisomerase, overexpressed and purified the protein, and begun to characterize its activities in vitro. Like other eukaryotic type I topoisomerases, MCV topoisomerase can relax both positive and negative supercoils. An analysis of the cleavage of plasmid and oligonucleotide substrates indicates that cleavage by MCV topoisomerase is favored just 3' of the sequence 5' (T/C)CCTT 3', resulting in formation of a covalent bond to the 3' T residue, as with other poxvirus topoisomerases. We identified solution conditions favorable for activity and measured the rate of formation and decay of the covalent intermediate. MCV topoisomerase is sensitive to inhibition by coumermycin A1 (50% inhibitory concentration, 32 microM) but insensitive to five other previously reported topoisomerase inhibitors. This work provides the point of departure for studies of the mechanism of function of MCV topoisomerase and the development of medically useful inhibitors.
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PMID:Molluscum contagiosum virus topoisomerase: purification, activities, and response to inhibitors. 952 70

Eukaryotic type 1B topoisomerases act by forming covalent enzyme-DNA intermediates that transiently nick DNA and thereby release DNA supercoils. Here we present a study of the topoisomerase encoded by the pathogenic poxvirus molluscum contagiosum. Our studies of DNA sites favored for catalysis reveal a larger recognition site than the 5'-(T/C)CCTT-3' sequence previously identified for poxvirus topoisomerases. Separate assays of initial DNA binding and covalent complex formation revealed that different DNA sequences were important for each reaction step. The location of the protein-DNA contacts was mapped by analyzing mutant sites and inosine-substituted DNAs. Some of the bases flanking the 5'-(T/C)CCTT-3' sequence were selectively important for covalent complex formation but not initial DNA binding. Interactions important for catalysis were probed with 5'-bridging phosphorothiolates at the site of strand cleavage, which permitted covalent complex formation but prevented subsequent religation. Kinetic studies revealed that the flanking sequences that promoted recovery of covalent complexes increased initial cleavage instead of inhibiting resealing of the nicked intermediate. These data 1) indicate that previously unidentified DNA contacts can accelerate a step between initial binding and covalent complex formation and 2) help specify models for conformational changes promoting catalysis.
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PMID:DNA contacts stimulate catalysis by a poxvirus topoisomerase. 1009 87

At present no antiviral agents are available for treatment of infection by the pathogenic poxvirus molluscum contagiosum virus (MCV). Here we report the identification and characterization of an inhibitor active against the virus-encoded type-1 topoisomerase, an enzyme likely to be required for MCV replication. We screened a library of marine extracts and natural products from microorganisms using MCV topoisomerase assays in vitro. The cyclic depsipeptide sansalvamide A was found to inhibit topoisomerase-catalyzed DNA relaxation. Sansalvamide A was inactive against two other DNA-modifying enzymes tested as a counterscreen. Assays of discrete steps in the topoisomerase reaction cycle revealed that sansalvamide A inhibited DNA binding and thereby covalent complex formation, but not resealing of a DNA nick in a preformed covalent complex. Sansalvamide A also inhibits DNA binding by the isolated catalytic domain, thereby specifying the part of the protein sensitive to sansalvamide A. These data specify the mechanism by which sansalvamide A inhibits MCV topoisomerase. Cyclic depsipeptides related to sansalvamide A represent a potentially promising chemical family for development of anti-MCV agents.
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PMID:Mechanism of inhibition of a poxvirus topoisomerase by the marine natural product sansalvamide A. 1034 47

All poxviruses studied encode a type 1B topoisomerase that introduces transient nicks into DNA and thereby relaxes DNA supercoils. Here we present a study of the protein domains of the topoisomerase of the poxvirus molluscum contagiosum (MCV), which allows us to specify DNA contacts made by different domains. Partial proteolysis of the enzyme revealed two stable domains separated by a protease-sensitive linker. A fragment encoding the linker and carboxyl-terminal domain (residues 82-323) was overexpressed in Escherichia coli and purified. MCV topoisomerase (MCV-TOP)(82-323) could relax supercoiled plasmids in vitro, albeit with a slower rate than the wild-type enzyme. MCV-TOP(82-323) was sensitive to sequences in the favored 5'-(T/C)CCTT-3' recognition site and also flanking DNA, indicating that some of the sequence-specific contacts are made by residues 82-323. Assays of initial binding and covalent catalysis by MCV-TOP(82-323) identified the contacts flanking the 5'-CCCTT-3' sequence at +10, +9, -2, and -3 to be important. Tests with substrates containing a 5-bridging phosphorothiolate that trap the cleaved complex revealed that correct contacts to the flanking sequences were important in the initial cleavage step. MCV-TOP(82-323) differed from the full-length protein in showing reduced sensitivity to mutations at a position within the 5'-(T/C)CCTT-3' recognition site, consistent with a model in which the amino-terminal domain contacts this region. These findings provide insight into the division of labor within the MCV-TOP enzyme.
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PMID:DNA contacts by protein domains of the molluscum contagiosum virus type-1B topoisomerase. 1050 26

The lamellarins form a group of more than 30 polyaromatic pyrrole alkaloids, isolated from diverse marine organisms, mainly but not exclusively ascidians and sponges. These molecules fall in three structural groups, with the central pyrrole ring fused or unfused (lamellarins O-R) to adjacent aromatic rings and with the quinoline moiety containing a 5, 6-single--as in lamellarins I-L--or a double bond, as it is the case for lamellarins D and M which are both potent cytotoxic agents. The family also includes sulphated members, such as the integrase inhibitor lamellarin alpha 20-sulfate. This review presents the origin and structure of the lamellarins and summarizes the various chemical pathways which have been proposed to synthesize all lamellarins and different structurally related marine pyrrole alkaloids, including ningalins, storniamides and lukianols. The mechanisms of actions of these marine products are also discussed. Inhibition of HIV-1 integrase by lamellarin alpha 20-sulfate and human topoisomerase I by lamellarin D and Molluscum contagiosum virus topoisomerase by lamellarin H, along with other effects on nuclear proteins, provide an experimental basis indicating that DNA manipulating enzymes are important targets for the lamellarins. Some of these marine compounds exhibit cytotoxic activities against tumor cells in vitro and are insensitive to Pgp-mediated drug efflux. The structure-activity relationships are discussed. Other compounds in the series, without being strongly cytotoxic, can reverse the multidrug resistance phenotype and thus may be useful to promote the therapeutic activity of conventional cytotoxic drugs toward chemoresistant tumors. A complete description of the chemistry and pharmacological profiles of the lamellarins is presented here to shed light on this undervalued family of marine alkaloids.
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PMID:Lamellarins, from A to Z: a family of anticancer marine pyrrole alkaloids. 1528 8

Lamellarin H has been shown to be active against the topoisomerase of the Molluscum contagiosum virus (MCV) and to have anti-HIV properties. 1-(3,4-dimethoxy-phenyl)-8,9-dimethoxy-2-(2,4,5-trimethoxy-phenyl)-pyrrolo[2,1-alpha] isoquinoline (intermediate 2) is the skeleton for the synthesis of lamellarin H and its derivatives. The synthesis of intermediate 2 is reported here in detail. The intermediate formed is identified by means of IR spectrum, UV spectrum, MS, (1)H NMR, (13)C NMR and melting point measurements.
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PMID:Pyrrolo[2,1-alpha]isoquinoline as a skeleton for the synthesis of bioactive lamellarin H. 1845 86