Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.5.1.2 (DNA ligase)
 2,749 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Saintopin is an antitumor antibiotic recently discovered in mechanistically oriented screening using purified calf thymus DNA topoisomerases. Saintopin induced topoisomerase I mediated DNA cleavage comparable to that of camptothecin, and topoisomerase II mediated DNA cleavage equipotent to those of 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) or 4'-demethylepipodophyllotoxin 9-(4,6-O-ethylidene-beta-D-glucopyranoside) (VP-16). Treatment of a reaction mixture containing saintopin and topoisomerase I or II with either elevated temperature (65 degrees C) or higher salt concentration (0.5 M NaCl) resulted in a substantial reduction in DNA cleavage, suggesting that the topoisomerase I and II mediated DNA cleavage induced by saintopin is through the mechanism of stabilizing the reversible enzyme-DNA "cleavable complex". Consistent with the cleavable complex formation with both topoisomerases, saintopin inhibited catalytic activities of both topoisomerase I and topoisomerase II. The DNA cleavage intensity pattern induced by saintopin with topoisomerase I was different from that by camptothecin. A difference in cleavage pattern was also detected between saintopin and m-AMSA or VP-16 in topoisomerase II mediated DNA cleavage. DNA unwinding assay using T4 DNA ligase showed that saintopin is a weak DNA intercalator like m-AMSA. Thus, saintopin represents a new class of antitumor agent that can induce both mammalian DNA topoisomerase I and mammalian DNA topisomerase II mediated DNA cleavage.
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PMID:Induction of mammalian DNA topoisomerase I and II mediated DNA cleavage by saintopin, a new antitumor agent from fungus. 164 1

Human DNA ligase was purified from different kinds of immunocompetent cells: thymocytes, normal and stimulated lymphocytes, blasts from ALL (Burkitt and non-T, non-B) and ANLL (M1, M2, and M5). Based upon the protocol for the treatment of these leukemias, the purified enzymes were assayed in the presence of routinely used combinations of antileukemic drugs. At the range of concentration tested (between 0.1 and 5 microM) some drugs taken separately were totally inactive on the enzyme from the different sources. For those being inhibitory, when used in combination their effect was always different from what was observed when the compound was tested alone. Some combinations were more effective in inhibiting the enzyme from leukemic than from normal cells (vincristine + cyclophosphamide + prednisone in ALL and rubidazone + Ara-C, Ara-C + m-AMSA, in ANLL). However, some combinations of drugs are without effect on ligase from leukemic cells at this dose range (vincristine + rubidazone + Ara-C + prednisone and adriamycin + asparaginase + Ara-C in ALL or etoposide + Ara-C, adriamycin + cyclophosphamide in ANLL). This is the first direct observation of the effect of cytostatic drugs on DNA ligase, a key enzyme of the DNA replication and repair process. The clinical consequences of these observations are discussed in an attempt to selectively inhibit replication, thereby division, of cancer cells.
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PMID:Effects of clinical combinations of antileukemic drugs on DNA ligase from human thymocytes and normal, stimulated, or leukemic lymphocytes. 325 60

Etoposide, an inhibitor of the breakage-reunion reaction associated with cellular type II DNA topoisomerases, was shown to inhibit plaque formation of vaccinia virus. This drug had a major effect on the segregation of newly replicated DNA concatemers. Gene expression and the initiation and elongation phases of viral DNA replication were essentially unaffected. Pulsed-field gel electrophoresis of viral DNA replicated in the presence of etoposide revealed two major classes of DNA: the mature monomeric linear genome and DNA that failed to enter the gel (the relative proportions depending on the concentrations of drug). Restriction enzyme analysis showed a severe defect in telomere resolution. In addition, slowly migrating restriction fragments were suggestive of a general recombination defect. We have isolated several etoposide-resistant mutants and used marker rescue and DNA sequencing to localize the resistance-causing mutation to the amino terminus of the viral DNA ligase gene. Inactivation of the DNA ligase also resulted in an etoposide-resistant phenotype, but to a lesser extent. The telomere resolution and segregation defects were corrected both in the drug-resistant mutants and in the DNA ligase knockout mutants. Reinsertion of wild-type or mutant DNA ligase in the viral thymidine kinase locus confirmed the role of the viral DNA ligase in conferring sensitivity not only to etoposide but also to another topoisomerase II inhibitor, 4'-(9-acridinylamino) methanesulphon-m-anisidide (mAMSA). The data suggest that the nonessential DNA ligase is involved in telomere resolution, possibly as part of a general recombinase.
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PMID:An etoposide-induced block in vaccinia virus telomere resolution is dependent on the virus-encoded DNA ligase. 788 54