Dna Topoisomerases
Mostrando 13-24 de 192 artigos, teses e dissertações.
-
13. DNA topoisomerase inhibitors: biflavonoids from Ouratea species
Topoisomerase inhibitors are agents with anticancer activity. 7"-O-Methyl-agathisflavone (I) and amentoflavone (II) are biflavonoids and were isolated from the Brazilian plants Ouratea hexasperma and O. semiserrata, respectively. These biflavonoids and the acetyl derivative of II (IIa) are inhibitors of human DNA topoisomerases I at 200 µM, as demonstrated
Brazilian Journal of Medical and Biological Research. Publicado em: 2002-07
-
14. Anti-topoisomerase drugs as potent inducers of chromosomal aberrations
As topoisomerases de DNA catalisam alterações topológicas no DNA que são essenciais para a progressão do ciclo celular normal e, portanto, são um alvo preferencial para o desenvolvimento de drogas anticâncer. Drogas anti-topoisomerases podem ser divididas em duas classes principais: drogas anti-"complexos cliváveis" e inibidores catalíticos. As drog
Genetics and Molecular Biology. Publicado em: 2000-12
-
15. Thirteen-exon-motif signature for vertebrate nuclear and mitochondrial type IB topoisomerases
DNA topoisomerases contribute to various cellular activities that involve DNA. We previously identified a human nuclear gene that encodes a mitochondrial DNA topoisomerase. Here we show that genes for mitochondrial DNA topoisomerases (type IB) exist only in vertebrates. A 13-exon topoisomerase motif was identified as a characteristic of genes for both nuclea
Oxford University Press.
-
16. Catenation and knotting of duplex DNA by type 1 topoisomerases: a mechanistic parallel with type 2 topoisomerases.
Escherichia coli omega protein, a type 1 topoisomerase, can catenate and knot duplex DNA circles. Previously, these activities were thought to be limited to type 2 topoisomerases. Catenation by omega requires a nick in one of the participating molecules, but it is not necessary that both be nicked. Catenation does not depend on sequence homology and is great
-
17. Archaebacterial reverse gyrase cleavage-site specificity is similar to that of eubacterial DNA topoisomerases I.
ATP-dependent type I topoisomerases from extremely thermophilic archaebacteria--reverse gyrases--drive positive supercoiling of DNA. We showed that reverse gyrase from Desulfurococcus amylolyticus breaks the DNA at specific sites and covalently binds to the 5' end. In 30 out of 31 sites located in pBR322 DNA fragments, cleavage occurs at the sequence 5'---CN
-
18. Eukaryotic topoisomerases recognize nucleic acid topology by preferentially interacting with DNA crossovers.
Eukaryotic topoisomerases recognize DNA topology and preferentially react with positively or negatively supercoiled molecules over relaxed substrates. To elucidate the mechanism of this recognition, we examined the interaction of topoisomerases with DNA by electron microscopy. Under all conditions employed, approximately 90% of the bound type I or II enzyme
-
19. Novel topologically knotted DNA from bacteriophage P4 capsids: studies with DNA topoisomerases.
DNA molecules isolated from bacteriophage P4 are mostly linear with cohesive ends capable of forming circular and concatemeric structures. In contrast, almost all DNA molecules isolated form P4 tailless capsids (heads) are monomeric DNA circles with their cohesive ends hydrogen-bonded. Different form simple DNA circles, such P4 head DNA circles contain topol
-
20. Helicase-appended Topoisomerases: New Insight into the Mechanism of Directional Strand Transfer*
DNA strand passage through an enzyme-mediated gate is a key step in the catalytic cycle of topoisomerases to produce topological transformations in DNA. In most of the reactions catalyzed by topoisomerases, strand passage is not directional; thus, the enzyme simply provides a transient DNA gate through which DNA transport is allowed and thereby resolves the
American Society for Biochemistry and Molecular Biology.
-
21. Roles of DNA topoisomerases in simian virus 40 DNA replication in vitro.
We examined the roles of DNA topoisomerases in the replication of simian virus 40 (SV40) DNA in a cell-free system composed of an extract from HeLa cells supplemented with purified SV40 tumor antigen. When the activities of both topoisomerase I (EC 5.99.1.2) and topoisomerase II (EC 5.99.1.3) in the extract were blocked with specific inhibitors or antibodies
-
22. Mechanism of topology simplification by type II DNA topoisomerases
Type II DNA topoisomerases actively reduce the fractions of knotted and catenated circular DNA below thermodynamic equilibrium values. To explain this surprising finding, we designed a model in which topoisomerases introduce a sharp bend in DNA. Because the enzymes have a specific orientation relative to the bend, they act like Maxwell's demon, providin
The National Academy of Sciences.
-
23. Eukaryotic DNA topoisomerases: two forms of type I DNA topoisomerases from HeLa cell nuclei.
Two type I DNA topoisomerases have been purified to homogeneity from the nuclei of HeLa cells. One topoisomerase has a peptide molecular weight of 100,000 and the other, a molecular weight of 67,000. Several lines of evidence indicate that these two topoisomerases are closely related, (a) Both exhibit similar enzymatic activities on DNA. (b) The chromatograp
-
24. Sensitivity of human type II topoisomerases to DNA damage: stimulation of enzyme-mediated DNA cleavage by abasic, oxidized and alkylated lesions
Type II topoisomerases are essential enzymes that are also the primary cellular targets for a number of important anticancer drugs. These drugs act by increasing levels of topoisomerase II-mediated DNA cleavage. Recent studies indicate that endogenous forms of DNA damage, such as abasic sites and base mismatches, also stimulate the DNA scission activity of t
Oxford University Press.