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

It has been shown recently that apoptotic degradation of genomic DNA in mammalian cells starts by excision of large DNA fragments ranging in size from 50 kilobases to more than 300 kilobases. Although it was suggested that the above fragments could represent chromosomal DNA loops, the supposition was not supported by direct experimental evidence. In present work, we have studied the specificity of nucleolar and euchromatic gene long-range fragmentation in mouse and human cells triggered to undergo apoptosis either by tumor necrosis factor or by serum deprivation. Separation of the excised large DNA fragments by pulsed field gel electrophoresis followed by Southern analysis has demonstrated that in all cases studied the above fragmentation proceeds in a specific way. Furthermore, the patterns of DNA long-range fragmentation in the cells undergoing apoptosis were indistinguishable from the patterns of DNA cleavage into chromosomal loops by the high salt-insoluble topoisomerase II of the nuclear matrix. These results suggest the conclusion that apoptotic degradation of chromosomal DNA starts by excision of DNA loops and their oligomers.
J Biol Chem 1995 Sep 01
PMID:Large-scale fragmentation of mammalian DNA in the course of apoptosis proceeds via excision of chromosomal DNA loops and their oligomers. 765 90

In prokaryotic type II topoisomerases (DNA gyrases), mutations that result in resistance to quinolones frequently occur at Ser83 or Ser84 of the gyrA subunit. Mutations to Trp, Ala, and Leu have been identified, all of which confer high levels of quinolone resistance. Extensive segments of DNA gyrase are homologous to eukaryotic topoisomerase II, and Ser741 of yeast TOP2 is homologous to Ser83 of prokaryotic DNA gyrA. Introduction of the Ser741-->Trp mutation into yeast TOP2 confers resistance to 6,8-difluoro-7-(4'-hydroxyphenyl)-1-cyclopropyl- 4-quinolone-3-carboxylic acid (CP-115,953), a fluoroquinolone with substantial activity against eukaryotic topoisomerase II, whereas changing Ser741 to either Leu or Ala does not change sensitivity to quinolones. Interestingly, Ser741-->Trp in the yeast TOP2 also confers hypersensitivity to etoposide. Sensitivity to intercalating anti-topoisomerase II agents such as amsacrine is not changed by any of the three mutations. The topoisomerase II protein carrying the Ser741-->Trp mutation was overexpressed and purified. The purified mutant enzyme had enhanced levels of etoposide stabilized covalent complex as compared with the wild type enzyme and reduced cleavage with CP-115,953. Unlike the wild type enzyme, etoposide-stabilized cleavage is not readily reversible by heat. We suggest that Ser741 is near a binding site for both quinolones and etoposide and that the Ser741-->Trp mutation leads to a more stable ternary complex between etoposide, DNA, and the mutant enzyme.
J Biol Chem 1995 Sep 01
PMID:A mutation in yeast TOP2 homologous to a quinolone-resistant mutation in bacteria. Mutation of the amino acid homologous to Ser83 of Escherichia coli gyrA alters sensitivity to eukaryotic topoisomerase inhibitors. 765 8

We describe the occurrence of a variant Ph chromosome (v-Ph) in a therapy-related acute leukemia (s-AL), developed after 8-year treatment for a NHL with alkylating agents, anthracyclines and topoisomerase II inhibitors. The v-Ph originated from a complex t(2;9;22) translocation, expressed a p190bcr-abl fusion protein, and was associated to other specific changes, such as dup(3) (q21q26) and -7. The s-AL, apparently not preceded by a dysplastic phase, presented with signs of trilineage dysplasia with 10% micromegakaryocytes; it was classified as M5 according to FAB. The complex genetic changes observed in the present case may reflect distinct leukemogenic effects by different chemotherapeutic agents.
Leukemia 1995 Sep
PMID:Acute leukemia presenting a variant Ph chromosome with p190 expression, dup 3q and -7, developed after malignant lymphoma treated with alkylating agents and topoisomerase II inhibitors. 765 16

We report a case of therapy-related acute myeloid leukemia (t-AML), M4 FAB subtype, with t(10;11)(p14;q21) chromosome abnormality developed in a patient treated for acute promyelocytic leukemia (APL) after 4 years of continuous complete remission (CCR). Two distinct forms of t-AML have been described: the classical type and the second type. Our case has many characteristics in common with the second type of t-AML such as: exposure to topoisomerase II active agents (idarubicin (IDA), mitoxantrone (MITOX), etoposide (VP16)), M4 FAB subtype, a latency period of 39 months and absence of a preleukemic phase. However, it differs in the chromosome 11 breakpoint (band q21 instead of q23) and absence of ALL-1 (Hrx, MLL, Htrx) gene involvement. This can represent the second observation of t-AML occurring after treatment for APL.
Leukemia 1995 Sep
PMID:Therapy-related acute myelomonocytic leukemia following successful treatment for acute promyelocytic leukemia. 765 28

Several clinically relevant anticancer drugs induce genomic mutations and cell death by increasing topoisomerase II-mediated DNA breakage. To determine whether endogenous DNA damage also affects this cleavage event, the effects of abasic sites (the most commonly formed spontaneous DNA lesion) on topoisomerase II activity were investigated. The presence of 3 abasic sites/plasmid stimulated enzyme-mediated DNA breakage > 6-fold, primarily by enhancing the forward rate of cleavage. This corresponds to a potency that is > 2000-fold higher than that of the anticancer drug, etoposide. These findings suggest that abasic sites represent endogenous topoisomerase II poisons and imply that anticancer drugs mimic the cleavage-enhancing actions of naturally occurring DNA lesions.
J Biol Chem 1995 Sep 15
PMID:Abasic sites stimulate double-stranded DNA cleavage mediated by topoisomerase II. DNA lesions as endogenous topoisomerase II poisons. 766 52

A mitochondrial type I-like, ATP-independent, DNA topoisomerase, isolated from highly purified yeast mitochondria, is genetically related to nuclear topoisomerase I. We found that the mitochondrial topoisomerase activity cannot be detected in yeast mitochondrial extracts prepared from strains in which the topoisomerase I gene (TOP1) is disrupted. Thus, the topoisomerase activity associated with mitochondria is dependent upon the expression of the nuclear topoisomerase I gene.
Biochem Biophys Res Commun 1995 Sep 14
PMID:On the relationship of the ATP-independent, mitochondrial associated DNA topoisomerase of Saccharomyces cerevisiae to the nuclear topoisomerase I. 767 87

Vaccinia DNA topoisomerase specifically binds and forms a covalent adduct at DNA sites containing a conserved sequence element 5'(C/T)CCTT decreases in the scissile strand. The molecular interactions that contribute to recognition of the CCCTT motif in a synthetic DNA substrate have been examined using modification interference, modification protection, and analog substitution techniques. We report that topoisomerase makes contact with guanine nucleotide bases of the pentamer motif complementary strand (3'GGGAA) within the major groove of the DNA helix and that alteration of the binding surface by chemical modification is deleterious to the interaction. Additional contacts are made with guanine residues located outside the pentamer element. The enzyme is unable to form a covalent adduct with synthetic RNA substrates. Analysis of the cleavage of DNA duplexes containing 2'OMe sugars suggests that the inability of the vaccinia topoisomerase to cleave either an RNA duplex or an RNA:DNA hybrid can be accounted for by the interfering effects of a 2' sugar substituent at two or more sites within the pentamer. Interaction with the sugar at the +2T nucleotide appears to be the most critical, as judged by the effects of single sugar substitutions.
J Biol Chem 1993 Sep 05
PMID:Site-specific interaction of vaccinia virus topoisomerase I with base and sugar moieties in duplex DNA. 768 62

A number of DNA minor groove-binding ligands (MGBLs) are known to exhibit antitumor and antimicrobial activities. We show that DNA topoisomerase (Topo) I may be a pharmacological target of MGBLs. In the presence of calf thymus Topo I, MGBLs induced limited but highly specific single-strand DNA breaks. The 3' ends of the broken DNA strands are covalently linked to Topo I polypeptides. Protein-linked DNA breaks are readily reversed by a brief heating to 65 degrees C or the addition of 0.5 M NaCl. These results suggest that MGBLs, like camptothecin, abort Topo I reactions by trapping reversible cleavable complexes. The sites of cleavage induced by MGBLs are distinctly different from those induced by camptothecin. Two of the major cleavage sites have been sequenced and shown to be highly A + T-rich, suggesting the possible involvement of a Topo I-drug-DNA ternary complex at the sites of cleavage. Different MGBLs also exhibit varying efficiency in inducing Topo I-cleavable complexes, and the order of efficiency is as follows: Hoechst 33342 and 33258 >> distamycin A > berenil > netropsin. The lack of correlation between DNA binding and cleavage efficiency suggest that, in addition to binding to the minor grooves of DNA, MGBLs must also interact with Topo I in trapping Topo I-cleavable complexes.
Proc Natl Acad Sci U S A 1993 Sep 01
PMID:DNA minor groove-binding ligands: a different class of mammalian DNA topoisomerase I inhibitors. 769 Jan 43

We have determined that the major mitotic phosphoprotein in chromosomes recognized by the antiphosphoprotein antibody MPM-2 is the 170-kDa isoform of topoisomerase II (topo II), the isoform predominant in proliferating cells. As a prerequisite to making this discovery, it was necessary to develop protocols to protect chromosomal proteins from dephosphorylation during cell extraction and chromosome isolation procedures. Immunofluorescence analysis of the large chromosomes prepared from Indian Muntjac cells revealed colocalization of MPM-2 and anti-topo II antibodies to the chromosomal centromeres and to the axial regions of the chromosomal arms. For biochemical fractionation studies, large quantities of chromosomes from the P388D1 mouse lymphocyte cell line were isolated and treated to remove DNA and histone proteins. Immunoblot and immunoprecipitation experiments with this chromosome scaffold fraction identified the major MPM-2-reactive phosphoprotein to be DNA topo II. Using a panel of anti-peptide antibodies specific to the isoforms of topo II, we determined that the major phosphoprotein recognized by MPM-2 is the 170-kDa isoform of topo II, topo II alpha. The 180-kDa isoform, topo II beta, present in the isolated chromosomes in much smaller quantities, is also recognized by MPM-2. The mitotic phosphorylation of the topo II proteins may be critical for proper chromosome condensation and segregation.
Proc Natl Acad Sci U S A 1993 Sep 15
PMID:DNA topoisomerase II alpha is the major chromosome protein recognized by the mitotic phosphoprotein antibody MPM-2. 769 Sep 61

The human melanoma cell line FEM-X was selected in multiple steps with VP-16 (etoposide) and an inhibitor of P-glycoprotein (Campain et al., 1993). The resulting clones, FVP1b and FVP3, are highly resistant to the nonintercalative epipodophyllotoxins and exhibit moderate levels of resistance to doxorubicin. The topoisomerase II activity present in crude nuclear extracts from mutant and wild-type cells is similar in amount and equally sensitive to VP-16. However, in live cells, the topoisomerase II from FVP1b and FVP3 is much less susceptible to drug-induced cleavable complex formation than is that from FEM-X. Using reverse transcription followed by the polymerase chain reaction (RT-PCR), we have cloned and sequenced the entire cDNA for topoisomerase II alpha from FEM-X and FVP3. The only sequence change unique to the cDNA from drug-resistant cells is a 3 bp deletion of nucleotide 1320-1322, resulting in a deletion of Ala429. Three FEM-X sublines of increasing resistance were tested, and the prevalence of the mutant RNA over wild-type increases in these cells in parallel with their resistance to VP-16. In FVP3, the most highly resistant line, expression of the wild-type allele is barely detectable. Analysis of genomic DNA shows that FEM-X is homozygous for the wild-type topoisomerase II alpha sequence and that each of the drug-resistant clones possesses both wild-type and mutant alleles. Although not definitive, these genetic results suggest that the deletion of Ala429 from topoisomerase II alpha makes the enzyme less susceptible to drug-induced cleavable complex formation and confers a growth advantage upon cells in the presence of VP-16.(ABSTRACT TRUNCATED AT 250 WORDS)
Biochemistry 1994 Sep 20
PMID:A novel mutant topoisomerase II alpha present in VP-16-resistant human melanoma cell lines has a deletion of alanine 429. 772 83


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