Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:5.99.1.2 (topoisomerase)
9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously shown that cells mutant for TOP3, a gene encoding a prokaryotic-like type I topoisomerase in Saccharomyces cerevisiae, display a pleiotropic phenotype including slow growth and genome instability. We identified a mutation, sgs1 (slow growth suppressor), that suppresses both the growth defect and the increased genomic instability of top3 mutants. Here we report the independent isolation of the SGS1 gene in a screen for proteins that interact with Top3. DNA sequence analysis reveals that the putative Sgs1 protein is highly homologous to the helicase encoded by the Escherichia coli recQ gene. These results imply that Sgs1 creates a deleterious topological substrate that Top3 preferentially resolves. The interaction of the Sgs1 helicase homolog and the Top3 topoisomerase is reminiscent of the recently described structure of reverse gyrase from Sulfolobus acidocaldarius, in which a type I DNA topoisomerase and a helicase-like domain are fused in a single polypeptide.
...
PMID:The yeast type I topoisomerase Top3 interacts with Sgs1, a DNA helicase homolog: a potential eukaryotic reverse gyrase. 796 74

A two-step lysine-modification procedure has been devised to chemically footprint protein surfaces involved in macromolecular interactions. A protein tagged at one particular end, in the free state or in a complex, is first treated lightly with a reversible lysine-modifying reagent. The protein is then unfolded and treated extensively with an irreversible lysine reagent to block those lysines that did not react previously; next, the first lysine modification is reversed, and a lysine-specific endoproteinase is used to cleave the tagged polypeptide at the deblocked lysines. Separation of the proteolytic products by size and identification of the tagged fragments map the positions of these lysines. In this procedure, the reversible lysine reagent serves as the chemical footprinting agent, as cleavage of the polypeptide ensues only at the sites of reaction with this reagent. Lysines involved in macromolecular contacts are identified from differences in proteolytic patterns of the tagged protein when the first lysine modification is done with the protein in the free form and in a complex. Application of the method to vaccinia virus topoisomerase identifies a number of lysines that are involved in its binding to DNA.
...
PMID:Protein footprinting by the combined use of reversible and irreversible lysine modifications. 799 55

By using both conventional and confocal laser scanning microscopy with three monoclonal antibodies recognizing nuclear matrix proteins we have investigated by means of indirect fluorescence whether an incubation of isolated nuclei at the physiological temperature of 37 degrees C induces a redistribution of nuclear components in human K562 erythroleukemia cells. Upon incubation of isolated nuclei for 45 min at 37 degrees C, we have found that two of the antibodies, directed against proteins of the inner matrix network (M(r) 125 and 160 kDa), gave a fluorescent pattern different from that observed in permeabilized cells. By contrast, the fluorescent pattern did not change if nuclei were kept at 0 degrees C. The difference was more marked in case of the 160-kDa polypeptide. The fluorescent pattern detected by the third antibody, which recognizes the 180-kDa nucleolar isoform of DNA topoisomerase II, was unaffected by heat exposure of isolated nuclei. When isolated nuclear matrices prepared from heat-stabilized nuclei were stained by means of the same three antibodies, it was possible to see that the distribution of the 160-kDa matrix protein no longer corresponded to that observable in permeabilized cells, whereas the fluorescent pattern given by the antibody to the 125-kDa polypeptide resembled that detectable in permeabilized cells. The 180-kDa isoform of topoisomerase II was still present in the matrix nucleolar remnants. We conclude that a 37 degrees C incubation of isolated nuclei induces a redistribution of some nuclear matrix antigens and cannot prevent the rearrangement in the spatial organization of one of these antigens that takes place during matrix isolation in human erythroleukemia cells. The practical relevance of these findings is discussed.
...
PMID:In vitro heat exposure induces a redistribution of nuclear matrix proteins in human K562 erythroleukemia cells. 802 May 99

A DNA polymerase alpha-associated multienzyme complex isolated from mouse LP1-1 cells transfected with the thymidine kinase gene of herpes simplex virus type I (1) showed activities of DNA polymerase alpha, topoisomerase II, and thymidine kinase (TK) in the complex. TK antiserum recognized a 43 kDa polypeptide only in the fraction of the multienzyme complex prepared from the LP1-1 cells but not that from L-M(TK-) cells. In permeabilized cells, hydroxyurea did not show any inhibitory effect on either DNA polymerase or TK, whereas aphidicolin, novobiocin, and TK antiserum inhibited both enzymes. These results provide evidence for the functional association and an allosteric interaction between the viral TK and host DNA polymerase alpha.
...
PMID:Allosteric interaction of a herpes simplex viral thymidine kinase with host DNA polymerase alpha in mouse LP1-1 cells. 803 16

The gene for topoisomerase II has been isolated from genomic libraries of strain K1 of the human malarial parasite, Plasmodium falciparum. The sequence reveals an open reading frame of 4194 nucleotides which predicts a polypeptide of 1398 amino acids. There are apparently no introns. The sequence is present as a single copy which has an identity of 47.4% and a similarity of 65.4% with its human homologue. Sequences conserved in topoisomerase II from other species are present in Pftopoisomerase II but in addition it has two adjacent asparagine-rich insertions which are unique to it. We have also detected asparagine-rich regions in the gene for PfDNA polymerase alpha. The gene for Pftopoisomerase II has been localised to chromosome 14 and northern analysis reveals a transcript of 5.8 kb. Two independent antisera raised in mice against glutathione-S-transferase fusion proteins containing the amino terminal portion of the malarial protein detect a weak band on western blots at about 160kDa, the expected size of the protein. Use of the same antisera for immunofluorescence analysis suggests that the protein is present at all stages of intraerythrocytic growth of the parasite.
...
PMID:The gene encoding topoisomerase II from Plasmodium falciparum. 804 16

DNA topoisomerase V is a novel prokaryotic enzyme related to eukaryotic topoisomerase I. The enzyme is a type I DNA topoisomerase and is recognized by polyclonal antibody against human topoisomerase I. We describe its purification from the hyperthermophilic methanogen Methanopyrus kandleri. The enzyme has high activity in crude extracts and is present in at least 1,500 copies/cell. Topoisomerase V migrates as a 110-kDa polypeptide in SDS-polyacrylamide gel electrophoresis and as a 142-kDa globular protein in gel filtration. It is active up to at least 100 degrees C on both positively and negatively supercoiled DNA and is not inhibited by single-stranded DNA. The enzyme works from 1 to 650 mM NaCl and up to 3.1 M potassium glutamate. It acts processively at low ionic strength and distributively at high NaCl or KCl concentration. Magnesium is not required and does not stimulate the enzymatic activity. Under DNA denaturing conditions, topoisomerase V catalyzes an unlinking reaction which results in substantial reduction in the linking number of closed circular DNA. The driving force for this process is DNA melting. Camptothecin is not nearly as good an inhibitor for topoisomerase V as it is for eukaryotic topoisomerase I. The unique occurrence of two major type I topoisomerases (reverse gyrase and topoisomerase V) in M. kandleri may shed new light on the evolution of this family of enzymes and supports the concept of a distant but significant relationship between some hyperthermophilic organisms and eukaryotes.
...
PMID:Purification and characterization of DNA topoisomerase V. An enzyme from the hyperthermophilic prokaryote Methanopyrus kandleri that resembles eukaryotic topoisomerase I. 810 68

The three-dimensional structure of the 67K amino-terminal fragment of Escherichia coli DNA topoisomerase I has been determined to 2.2 A resolution. The polypeptide folds in an unusual way to give four distinct domains enclosing a hole large enough to accommodate a double-stranded DNA. The active-site tyrosyl residue, which is involved in the transient breakage of a DNA strand and the formation of a covalent enzyme-DNA intermediate, is present at the interface of two domains. The structure suggests a plausible mechanism by which E. coli DNA topoisomerase I and other members of the same DNA topoisomerase subfamily could catalyse the passage of one DNA strand through a transient break in another strand.
...
PMID:Three-dimensional structure of the 67K N-terminal fragment of E. coli DNA topoisomerase I. 811 10

A type 1 DNA topoisomerase has been purified from the nuclei of the kinetoplast hemoflagellate Leishmania donovani using polyethylene glycol fractionation and chromatography on hydroxylapatite, phosphocellulose and phenylsepharose column. The relaxation activity is ATP independent. Mg2+ is an essential cofactor for the reaction with an optimum at 10 mM. Mg2+ can be substituted by Mn2+ at 5 mM concentration. The relaxation reaction exhibits a salt optimum at 100 mM KCl. The enzyme can not remove supercoils from positive superhelical DNAs nor can induce supercoiling of relaxed DNAs. The topoisomerase activity is associated with a polypeptide of molecular weight about 67 kDa as shown by sephacryl-S200 gel filtration and by electrophoresis on sodium dodecyl sulphate-polyacrylamide gels.
...
PMID:A type 1 DNA topoisomerase from the kinetoplast hemoflagellate Leishmania donovani. 814 68

We have produced two murine monoclonal antibodies (SWT3D1 and SWR1C2) to a recombinant polypeptide corresponding to the carboxyl-terminal one-third (amino acid 854-amino acid 1447) of human topoisomerase II alpha. Each antibody is able to recognize intact human topoisomerase II using immunoblotting and enzyme-linked immunosorbent assay (ELISA) techniques. Data is presented demonstrating that the antibodies bind specifically to topoisomerase II alpha but do not interact with topoisomerase II beta. The monoclonal antibodies do not recognize murine or calf thymus topoisomerase II indicating that each may bind exclusively to the human enzyme. The topoisomerase II binding sites for each monoclonal antibody have been compared in a competition ELISA. The SWT3D1 antibody had no significant effect on the binding efficiency of biotinylated SWR1C2 antibody. Although SWR1C2 was capable of inhibiting the binding of biotinylated SWT3D1, this only occurred at concentrations approximately 1000-fold higher than those required of SWT3D1 to block binding of itself. These results suggest that SWT3D1 and SWR1C2 do not recognize identical epitopes on topoisomerase II.
...
PMID:Isolation and characterization of monoclonal antibodies to a recombinant human topoisomerase II polypeptide. 824 17

Apoptosis is a morphologically and biochemically distinct form of cell death that occurs under a variety of physiological and pathological conditions. In the present study, the proteolytic cleavage of poly(ADP-ribose) polymerase (pADPRp) during the course of chemotherapy-induced apoptosis was examined. Treatment of HL-60 human leukemia cells with the topoisomerase II-directed anticancer agent etoposide resulted in morphological changes characteristic of apoptosis. Endonucleolytic degradation of DNA to generate nucleosomal fragments occurred simultaneously. Western blotting with epitope-specific monoclonal and polyclonal antibodies revealed that these characteristic apoptotic changes were accompanied by early, quantitative cleavage of the M(r) 116,000 pADPRp polypeptide to an M(r) approximately 25,000 fragment containing the amino-terminal DNA-binding domain of pADPRp and an M(r) approximately 85,000 fragment containing the automodification and catalytic domains. Activity blotting revealed that the M(r) approximately 85,000 fragment retained basal pADPRp activity but was not activated by exogenous nicked DNA. Similar cleavage of pADPRp was observed after exposure of HL-60 cells to a variety of chemotherapeutic agents including cis-diaminedichloroplatinum(II), colcemid, 1-beta-D-arabinofuranosylcytosine, and methotrexate; to gamma-irradiation; or to the protein synthesis inhibitors puromycin or cycloheximide. Similar changes were observed in MDA-MB-468 human breast cancer cells treated with trifluorothymidine or 5-fluoro-2'-deoxyuridine and in gamma-irradiated or glucocorticoid-treated rat thymocytes undergoing apoptosis. Treatment with several compounds (tosyl-L-lysine chloromethyl ketone, tosyl-L-phenylalanine chloromethyl ketone, N-ethylmaleimide, iodoacetamide) prevented both the proteolytic cleavage of pADPRp and the internucleosomal fragmentation of DNA. The results suggest that proteolytic cleavage of pADPRp, in addition to being an early marker of chemotherapy-induced apoptosis, might reflect more widespread proteolysis that is a critical biochemical event early during the process of physiological cell death.
...
PMID:Specific proteolytic cleavage of poly(ADP-ribose) polymerase: an early marker of chemotherapy-induced apoptosis. 835 26


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---