In vivo inhibition of trypanosome mitochondrial topoisomerase II: effects on kinetoplast DNA maxicircles.

Kinetoplast DNA, the mitochondrial DNA of trypanosomes, is a topologically complex structure composed of interlocked minicircles and maxicircles. We previously reported that etoposide, a potent inhibitor of topoisomerase II, promotes the cleavage of about 20% of network minicircle DNA (T. A. Shapiro, V. A. Klein, and P. T. Englund, J. Biol. Chem. 264:4173-4178, 1989). We now find that virtually all maxicircles are released from kinetoplast DNA networks after trypanosomes are treated with etoposide. As expected for a topoisomerase II cleavage product, the linearized maxicircles have protein bound to both 5' ends. After etoposide treatment, the residual minicircle catenanes have a sedimentation coefficient which is only 70% that of controls, and by electron microscopy the networks are less compact. Double-size networks, the characteristic dumbbell-shape forms that normally arise in the final stages of network replication, are replaced by aberrant unit-size forms.

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Mitochondrial topoisomerase II activity is essential for kinetoplast DNA minicircle segregation

Molecular and Cellular Biology ◽

10.1128/mcb.14.6.3660-3667.1994 ◽

1994 ◽

Vol 14 (6) ◽

pp. 3660-3667

Author(s):

T A Shapiro

Keyword(s):

Replication Fork ◽

Topoisomerase Ii ◽

Potent Inhibitor ◽

Late Replication ◽

Kinetoplast Dna ◽

Two Dimensional Gel Electrophoresis ◽

Trypanosoma Equiperdum ◽

Replication Intermediates ◽

Novel Structures

Etoposide, a nonintercalating antitumor drug, is a potent inhibitor of topoisomerase II activity. When Trypanosoma equiperdum is treated with etoposide, cleavable complexes are stabilized between topoisomerase II and kinetoplast DNA minicircles, a component of trypanosome mitochondrial DNA (T. A. Shapiro, V. A. Klein, and P. T. Englund, J. Biol. Chem. 264:4173-4178, 1989). Etoposide also promotes the time-dependent accumulation of small minicircle catenanes. These catenanes are radiolabeled in vivo with [3H]thymidine. Dimers are most abundant, but novel structures containing up to five noncovalently closed minicircles are detectable. Analysis by two-dimensional gel electrophoresis and electron microscopy indicates that dimers joined by up to six interlocks are late replication intermediates that accumulate when topoisomerase II activity is blocked. The requirement for topoisomerase II is particularly interesting because minicircles do not share the features postulated to make this enzyme essential in other systems: for minicircles, the replication fork is unidirectional, access to the DNA is not blocked by nucleosomes, and daughter circles are extensively nicked and (or) gapped.

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Mitochondrial topoisomerase II activity is essential for kinetoplast DNA minicircle segregation.

Molecular and Cellular Biology ◽

10.1128/mcb.14.6.3660 ◽

1994 ◽

Vol 14 (6) ◽

pp. 3660-3667 ◽

Cited By ~ 15

Author(s):

T A Shapiro

Keyword(s):

Replication Fork ◽

Topoisomerase Ii ◽

Potent Inhibitor ◽

Late Replication ◽

Kinetoplast Dna ◽

Two Dimensional Gel Electrophoresis ◽

Trypanosoma Equiperdum ◽

Replication Intermediates ◽

Novel Structures

Etoposide, a nonintercalating antitumor drug, is a potent inhibitor of topoisomerase II activity. When Trypanosoma equiperdum is treated with etoposide, cleavable complexes are stabilized between topoisomerase II and kinetoplast DNA minicircles, a component of trypanosome mitochondrial DNA (T. A. Shapiro, V. A. Klein, and P. T. Englund, J. Biol. Chem. 264:4173-4178, 1989). Etoposide also promotes the time-dependent accumulation of small minicircle catenanes. These catenanes are radiolabeled in vivo with [3H]thymidine. Dimers are most abundant, but novel structures containing up to five noncovalently closed minicircles are detectable. Analysis by two-dimensional gel electrophoresis and electron microscopy indicates that dimers joined by up to six interlocks are late replication intermediates that accumulate when topoisomerase II activity is blocked. The requirement for topoisomerase II is particularly interesting because minicircles do not share the features postulated to make this enzyme essential in other systems: for minicircles, the replication fork is unidirectional, access to the DNA is not blocked by nucleosomes, and daughter circles are extensively nicked and (or) gapped.

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Kinetoplast maxicircle DNA replication in Crithidia fasciculata and Trypanosoma brucei.

Molecular and Cellular Biology ◽

10.1128/mcb.15.12.6794 ◽

1995 ◽

Vol 15 (12) ◽

pp. 6794-6803 ◽

Cited By ~ 31

Author(s):

L R Carpenter ◽

P T Englund

Keyword(s):

Electron Microscopy ◽

Trypanosoma Brucei ◽

Topoisomerase Ii ◽

Repetitive Sequences ◽

Variable Region ◽

Kinetoplast Dna ◽

Crithidia Fasciculata ◽

Interstrand Cross Links ◽

Replication Intermediates

Kinetoplast DNA, the mitochondrial DNA of trypanosomatids, is composed of several thousand minicircles and a few dozen maxicircles, all of which are topologically interlocked in a giant network. We have studied the replication of maxicircle DNA, using electron microscopy to analyze replication intermediates from both Crithidia fasciculata and Trypanosoma brucei. Replication intermediates were stabilized against branch migration by introducing DNA interstrand cross-links in vivo with 4,5',8-trimethylpsoralen and UV radiation. Electron microscopy of individual maxicircles resulting from a topoisomerase II decatenation of kinetoplast DNA networks revealed intact maxicircle theta structures. Analysis of maxicircle DNA linearized by restriction enzyme cleavage revealed branched replication intermediates derived from theta structures. Measurements of the linearized branched molecules in both parasites indicate that replication initiates in the variable region (a noncoding segment characterized by repetitive sequences) and proceeds unidirectionally, clockwise on the standard map.

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Maleimide Is a Potent Inhibitor of Topoisomerase II in Vitro and in Vivo: A New Mode of Catalytic Inhibition

Molecular Pharmacology ◽

10.1124/mol.61.5.1235 ◽

2002 ◽

Vol 61 (5) ◽

pp. 1235-1243 ◽

Cited By ~ 34

Author(s):

Lars H. Jensen ◽

Axelle Renodon-Corniere ◽

Irene Wessel ◽

Seppo W. Langer ◽

Birgitte Søkilde ◽

...

Keyword(s):

Topoisomerase Ii ◽

Potent Inhibitor

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ICRF-187 rescue in etoposide treatment in vivo. A model targeting high-dose topoisomerase II poisons to CNS tumors

Cancer Chemotherapy and Pharmacology ◽

10.1007/s002800050472 ◽

1996 ◽

Vol 38 (3) ◽

pp. 203-209 ◽

Cited By ~ 20

Author(s):

B. Holm ◽

Peter Buhl Jensen ◽

Maxwell Sehested

Keyword(s):

Topoisomerase Ii ◽

Cns Tumors ◽

High Dose ◽

Topoisomerase Ii Poisons ◽

Etoposide Treatment

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Melatonin Loading Chitosan-Tripolyphosphate Nanoparticles: Application in Attenuating Etoposide-Induced Genotoxicity in HepG2 Cells

Pharmacology ◽

10.1159/000489667 ◽

2018 ◽

Vol 102 (1-2) ◽

pp. 74-80 ◽

Cited By ~ 11

Author(s):

Mohammad Shokrzadeh ◽

Nasrin Ghassemi-Barghi

Keyword(s):

Hepg2 Cells ◽

Topoisomerase Ii ◽

Reactive Oxygen Species Generation ◽

Chemotherapeutic Agents ◽

Free Radical Scavenger ◽

Control Group ◽

Radical Scavenger ◽

Etoposide Treatment

Etoposide is one of the most effective chemotherapeutic agents used in the treatment of various types of cancers. However, as a Topoisomerase II inhibitor, during clinical use, several side effects may occur. In addition, in several in vivo and in vitro studies, etoposide has been shown to have a range of genotoxic effects including single and double strand breaks. Melatonin is an anti-aging and antioxidant hormone synthesized from the pineal gland. The genoprotective, antioxidant, and free radical scavenger properties of melatonin have been well explained in various studies. The aim of this study was to explore whether melatonin nanoparticles protects against etoposide-induced genotoxicity in the HepG2 cell line. HepG2 cells (25 × 104 cells/well) were cultured in 24-well plates: a control group and 3 melatonin and its nanoparticles + etoposide groups (pre- and cotreatment conditions). Our results show that etoposide induced a noticeable genotoxic effect in HepG2 cells. Melatonin reduced the effects of etoposide significantly in both types of experiment conditions, through the reduction of the level of DNA damage measured via comet assay. Furthermore, melatonin decreased the intracellular reactive oxygen species generation. It also increased the intracellular glutathione levels in HepG2 cells. Nano melatonin is more effective than regular melatonin. The most protective effect was observed with melatonin when it was administrated 24 h before etoposide treatment.

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The in vivo distribution and dynamics of DNA topoisomerase II in Drosophila embryonic nuclei and chromosomes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100146217 ◽

1993 ◽

Vol 51 ◽

pp. 74-75

Author(s):

Jason R. Swedlow ◽

Neil Osheroff ◽

Tim Karr ◽

John W. Sedat ◽

David A. Agard

Keyword(s):

Topoisomerase Ii ◽

Biochemical Characterization ◽

Developmental Cycle ◽

Dna Topoisomerase Ii ◽

Chromosomal Distribution ◽

Dna Topoisomerase ◽

Ideal System ◽

Dnase Treatment

DNA topoisomerase II is an ATP-dependent double-stranded DNA strand-passing enzyme that is necessary for full condensation of chromosomes and for complete segregation of sister chromatids at mitosis in vivo and in vitro. Biochemical characterization of chromosomes or nuclei after extraction with high-salt or detergents and DNAse treatment showed that topoisomerase II was a major component of this remnant, termed the chromosome scaffold. The scaffold has been hypothesized to be the structural backbone of the chromosome, so the localization of topoisomerase II to die scaffold suggested that the enzyme might play a structural role in the chromosome. However, topoisomerase II has not been studied in nuclei or chromosomes in vivo. We have monitored the chromosomal distribution of topoisomerase II in vivo during mitosis in the Drosophila embryo. This embryo forms a multi-nucleated syncytial blastoderm early in its developmental cycle. During this time, the embryonic nuclei synchronously progress through 13 mitotic cycles, so this is an ideal system to follow nuclear and chromosomal dynamics.

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SAC3B is a target of CML19, the centrin 2 of Arabidopsis thaliana

Biochemical Journal ◽

10.1042/bcj20190674 ◽

2020 ◽

Vol 477 (1) ◽

pp. 173-189 ◽

Cited By ~ 1

Author(s):

Marco Pedretti ◽

Carolina Conter ◽

Paola Dominici ◽

Alessandra Astegno

Keyword(s):

Excision Repair ◽

Complex Structure ◽

Binding Motif ◽

C Terminus ◽

Repair Protein ◽

Nucleotide Excision ◽

Ef Hand ◽

Molecular Determinants ◽

Structure In Solution

Arabidopsis centrin 2, also known as calmodulin-like protein 19 (CML19), is a member of the EF-hand superfamily of calcium (Ca2+)-binding proteins. In addition to the notion that CML19 interacts with the nucleotide excision repair protein RAD4, CML19 was suggested to be a component of the transcription export complex 2 (TREX-2) by interacting with SAC3B. However, the molecular determinants of this interaction have remained largely unknown. Herein, we identified a CML19-binding site within the C-terminus of SAC3B and characterized the binding properties of the corresponding 26-residue peptide (SAC3Bp), which exhibits the hydrophobic triad centrin-binding motif in a reversed orientation (I8W4W1). Using a combination of spectroscopic and calorimetric experiments, we shed light on the SAC3Bp–CML19 complex structure in solution. We demonstrated that the peptide interacts not only with Ca2+-saturated CML19, but also with apo-CML19 to form a protein–peptide complex with a 1 : 1 stoichiometry. Both interactions involve hydrophobic and electrostatic contributions and include the burial of Trp residues of SAC3Bp. However, the peptide likely assumes different conformations upon binding to apo-CML19 or Ca2+-CML19. Importantly, the peptide dramatically increases the affinity for Ca2+ of CML19, especially of the C-lobe, suggesting that in vivo the protein would be Ca2+-saturated and bound to SAC3B even at resting Ca2+-levels. Our results, providing direct evidence that Arabidopsis SAC3B is a CML19 target and proposing that CML19 can bind to SAC3B through its C-lobe independent of a Ca2+ stimulus, support a functional role for these proteins in TREX-2 complex and mRNA export.

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