Effect of CPT on the DNA cleavage/religation reaction mediated by calf thymus Topoisomerase I: evidence of an inhibition of DNA religation. Inhibition of Topoisomerase I-mediated DNA religation by CPT. 1994

M C Carboni, and S Coderoni
Department of Molecular, Cellular and Animal Biology, University of Camerino, Italy.

The uncoupling of the calf thymus Topoisomerase I-mediated forward DNA cleavage reaction from the religation event by a rapid shift of cleavage temperature either from 37 degrees C to 0 degrees C or from 37 degrees C to 56 degrees C has been studied and utilized to elucidate the molecular mechanism by which camptothecin, a clinically relevant antineoplastic agent, influences the half reactions of the enzyme. Results of heating and cooling religation-inducing treatments have been compared: both temperature extremes reduce the amount of protein-linked DNA breaks to background levels, thereby affecting cleavage reversal. Camptothecin is found to stabilize the enzyme-DNA intermediate, by inhibition of the Topoisomerase I-mediated rejoining of cleaved DNA, even when the drug is added after formation of the complex. We conclude that: 1. Heating and cooling treatments show a pronounced effect on the DNA cleavage-religation equilibrium. The efficacy of cold is more pronounced than that of heat. 2. Reversal of the enzyme-DNA intermediate favors the DNA resealing versus the closed relaxed form. 3. Camptothecin affects the heat or cold induced religation: in fact in both cases the drug delays the religation step.

UI MeSH Term Description Entries
D011485 Protein Binding The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments. Plasma Protein Binding Capacity,Binding, Protein
D002166 Camptothecin An alkaloid isolated from the stem wood of the Chinese tree, Camptotheca acuminata. This compound selectively inhibits the nuclear enzyme DNA TOPOISOMERASES, TYPE I. Several semisynthetic analogs of camptothecin have demonstrated antitumor activity. Camptothecine
D002417 Cattle Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor. Beef Cow,Bos grunniens,Bos indicus,Bos indicus Cattle,Bos taurus,Cow,Cow, Domestic,Dairy Cow,Holstein Cow,Indicine Cattle,Taurine Cattle,Taurus Cattle,Yak,Zebu,Beef Cows,Bos indicus Cattles,Cattle, Bos indicus,Cattle, Indicine,Cattle, Taurine,Cattle, Taurus,Cattles, Bos indicus,Cattles, Indicine,Cattles, Taurine,Cattles, Taurus,Cow, Beef,Cow, Dairy,Cow, Holstein,Cows,Dairy Cows,Domestic Cow,Domestic Cows,Indicine Cattles,Taurine Cattles,Taurus Cattles,Yaks,Zebus
D003080 Cold Temperature An absence of warmth or heat or a temperature notably below an accustomed norm. Cold,Cold Temperatures,Temperature, Cold,Temperatures, Cold
D004247 DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA, Double-Stranded,Deoxyribonucleic Acid,ds-DNA,DNA, Double Stranded,Double-Stranded DNA,ds DNA
D004264 DNA Topoisomerases, Type I DNA TOPOISOMERASES that catalyze ATP-independent breakage of one of the two strands of DNA, passage of the unbroken strand through the break, and rejoining of the broken strand. DNA Topoisomerases, Type I enzymes reduce the topological stress in the DNA structure by relaxing the superhelical turns and knotted rings in the DNA helix. DNA Nicking-Closing Protein,DNA Relaxing Enzyme,DNA Relaxing Protein,DNA Topoisomerase,DNA Topoisomerase I,DNA Topoisomerase III,DNA Topoisomerase III alpha,DNA Topoisomerase III beta,DNA Untwisting Enzyme,DNA Untwisting Protein,TOP3 Topoisomerase,TOP3alpha,TOPO IIIalpha,Topo III,Topoisomerase III,Topoisomerase III beta,Topoisomerase IIIalpha,Topoisomerase IIIbeta,DNA Nicking-Closing Proteins,DNA Relaxing Enzymes,DNA Type 1 Topoisomerase,DNA Untwisting Enzymes,DNA Untwisting Proteins,Topoisomerase I,Type I DNA Topoisomerase,III beta, Topoisomerase,III, DNA Topoisomerase,III, Topo,III, Topoisomerase,IIIalpha, TOPO,IIIalpha, Topoisomerase,IIIbeta, Topoisomerase,Topoisomerase III, DNA,Topoisomerase, TOP3,beta, Topoisomerase III
D006358 Hot Temperature Presence of warmth or heat or a temperature notably higher than an accustomed norm. Heat,Hot Temperatures,Temperature, Hot,Temperatures, Hot
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D013950 Thymus Gland A single, unpaired primary lymphoid organ situated in the MEDIASTINUM, extending superiorly into the neck to the lower edge of the THYROID GLAND and inferiorly to the fourth costal cartilage. It is necessary for normal development of immunologic function early in life. By puberty, it begins to involute and much of the tissue is replaced by fat. Thymus,Gland, Thymus,Glands, Thymus,Thymus Glands
D059004 Topoisomerase I Inhibitors Compounds that inhibit the activity of DNA TOPOISOMERASE I. DNA Topoisomerase I Inhibitor,DNA Topoisomerase III Inhibitor,DNA Topoisomerase III Inhibitors,DNA Type 1 Topoisomerase Inhibitor,DNA Type III Topoisomerase Inhibitor,DNA Type III Topoisomerase Inhibitors,Topoisomerase 1 Inhibitor,Topoisomerase 1 Inhibitors,Topoisomerase 3 Inhibitor,Topoisomerase 3 Inhibitors,Topoisomerase I Inhibitor,Topoisomerase III Inhibitor,Topoisomerase III Inhibitors,DNA Topoisomerase I Inhibitors,DNA Type 1 Topoisomerase Inhibitors,1 Inhibitor, Topoisomerase,3 Inhibitor, Topoisomerase,3 Inhibitors, Topoisomerase,I Inhibitor, Topoisomerase,III Inhibitor, Topoisomerase,III Inhibitors, Topoisomerase,Inhibitor, Topoisomerase 1,Inhibitor, Topoisomerase 3,Inhibitor, Topoisomerase I,Inhibitor, Topoisomerase III,Inhibitors, Topoisomerase 1,Inhibitors, Topoisomerase 3,Inhibitors, Topoisomerase I,Inhibitors, Topoisomerase III

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