Kinetoplast DNA of Bodo caudatus: a noncatenated structure

1986 ◽  
Vol 6 (12) ◽  
pp. 4372-4378
Author(s):  
S L Hajduk ◽  
A M Siqueira ◽  
K Vickerman
Keyword(s):  
Complex Network ◽  
Network Structure ◽  
Minor Component ◽  
Kinetoplast Dna ◽  
Dna Molecules ◽  
Free Living ◽  
Circular Dna ◽  
Large Size ◽  
Cellular Dna ◽  
A Minor

The kinetoplast DNA (kDNA) of trypanosomes and other parasitic members of the order Kinetoplastida is organized as a complex network containing thousands of catenated circular DNA molecules. We found that the kDNA of a free-living kinetoplastida, Bodo caudatus, exists as a noncatenated structure. The kDNA of B. caudatus represents about 40% of the total cellular DNA, and the major components of this DNA are large circles of 10 and 12 kilobases (kb). Our results indicate that these circles are analogous to trypanosome kDNA minicircles despite their large size and noncatenated form. The kDNA of B. caudatus also contains a minor component of 19 kb which is transcribed. The 19-kb molecules are probably analogous to the maxicircles of trypanosomes. The properties of the B. caudatus kDNA suggest that the catenated network structure of trypanosome kDNA is not required for maxicircle segregation during kinetoplast division or for the expression of the maxicircle genome.

scholarly journals Kinetoplast DNA of Bodo caudatus: a noncatenated structure.

1986 ◽  
Vol 6 (12) ◽  
pp. 4372-4378 ◽  
Author(s):  
S L Hajduk ◽  
A M Siqueira ◽  
K Vickerman
Keyword(s):  
Complex Network ◽  
Network Structure ◽  
Minor Component ◽  
Kinetoplast Dna ◽  
Dna Molecules ◽  
Free Living ◽  
Circular Dna ◽  
Large Size ◽  
Cellular Dna ◽  
A Minor

The kinetoplast DNA (kDNA) of trypanosomes and other parasitic members of the order Kinetoplastida is organized as a complex network containing thousands of catenated circular DNA molecules. We found that the kDNA of a free-living kinetoplastida, Bodo caudatus, exists as a noncatenated structure. The kDNA of B. caudatus represents about 40% of the total cellular DNA, and the major components of this DNA are large circles of 10 and 12 kilobases (kb). Our results indicate that these circles are analogous to trypanosome kDNA minicircles despite their large size and noncatenated form. The kDNA of B. caudatus also contains a minor component of 19 kb which is transcribed. The 19-kb molecules are probably analogous to the maxicircles of trypanosomes. The properties of the B. caudatus kDNA suggest that the catenated network structure of trypanosome kDNA is not required for maxicircle segregation during kinetoplast division or for the expression of the maxicircle genome.

Adsorption evaluation of large-size HDEHP/SiO2-P adsorbent investigated by micro-PIXE analysis

2021 ◽  
pp. 1950017
Author(s):  
Y. Miyazaki ◽  
I. Goto ◽  
S. Watanabe ◽  
Y. Sano ◽  
H. Kofuji ◽  
...  
Keyword(s):  
Current Issue ◽  
Packed Column ◽  
Minor Component ◽  
Lanthanide Ions ◽  
Adsorption Experiment ◽  
Pixe Analysis ◽  
Vibration Cutting ◽  
Large Size ◽  
A Minor ◽  
Polymerization Method

The Zr and Mo removal from HLLW is the current issue for repeated usage of the CMPO/SiO2-P-packed column. The adsorbability of the 2-mm-sized HDEHP/SiO2-P adsorbent, which was prepared by fabricating a SiO2 particle from the vibration cutting method and adapting a new polymerization method, was evaluated by the batch-wise adsorption experiment. In spite of the impregnation ratio of the HDEHP extractant, the extraction of Zr and Mo ions from the simulated HLLW was achieved but lanthanide ions e.g., Nd and Gd were also extracted as a minor component. Such unusual adsorption behavior of lanthanide ions could be only provided by accurate, sensitive and reliable micro-PIXE analysis.

A calculus for rational tangles: applications to DNA recombination

1990 ◽  
Vol 108 (3) ◽  
pp. 489-515 ◽  
Author(s):  
C. Ernst ◽  
D. W. Sumners
Keyword(s):  
Dna Recombination ◽  
Enzyme Reaction ◽  
Enzyme Mechanism ◽  
Dna Molecules ◽  
Reaction Products ◽  
Circular Dna ◽  
Enzyme Action ◽  
Rational Tangles ◽  
Cellular Dna

There exist naturally occurring enzymes (topoisomerases and recombinases), which, in order to mediate the vital life processes of replication, transcription, and recombination, manipulate cellular DNA in topologically interesting and non-trivial ways [24, 30]. These enzyme actions include promoting the coiling up (supercoiling) of DNA molecules, passing one strand of DNA through another via a transient enzyme-bridged break in one of the strands (a move performed by topoisomerase), and breaking a pair of strands and recombining them to different ends (a move performed by recombinase). An interesting development for topology has been the emergence of a new experimental protocol, the topological approach to enzymology [30], which directly exploits knot theory in an effort to understand enzyme action. In this protocol, one reacts artificial circular DNA substrate with purified enzyme in vitro (in the laboratory); the enzyme acts on the circular DNA, causing changes in both the euclidean geometry (supercoiling) of the molecules and in the topology (knotting and linking) of the molecules. These enzyme-caused changes are experimental observables, using gel electrophoresis to fractionate the reaction products, and rec A enhanced electron microscopy [15] to visualize directly and to determine unambiguously the DNA knots and links which result as products of an enzyme reaction. This experimental technique calls for the building of knot-theoretic models for enzyme action, in which one wishes mathematically to extract information about enzyme mechanism from the observed changes in the DNA molecules.

scholarly journals The configuration of DNA replication sites within the Trypanosoma brucei kinetoplast.

1994 ◽  
Vol 126 (3) ◽  
pp. 641-648 ◽  
Author(s):  
D R Robinson ◽  
K Gull
Keyword(s):  
Cell Cycle ◽  
Trypanosoma Brucei ◽  
S Phase ◽  
Immunogold Labeling ◽  
Kinetoplast Dna ◽  
Dna Molecules ◽  
Circular Dna ◽  
Replication Sites ◽  
Or Organization

The kinetoplast is a concatenated network of circular DNA molecules found in the mitochondrion of many trypanosomes. This mass of DNA is replicated in a discrete "S" phase in the cell cycle. We have tracked the incorporation of the thymidine analogue 5-bromodeoxyuridine into newly replicated DNA by immunofluorescence and novel immunogold labeling procedures. This has allowed the detection of particular sites of replicated DNA in the replicating and segregating kinetoplast. These studies provide a new method for observing kinetoplast DNA (kDNA) replication patterns at high resolution. The techniques reveal that initially the pattern of replicated DNA is antipodal and can be detected both on isolated complexes and in replicating kDNA in vivo. In Trypanosoma brucei the opposing edges of replicating kDNA never extend around the complete circumference of the network, as seen in other kinetoplastids. Furthermore, crescent-shaped labeling patterns are formed which give way to labeling of most of the replicating kDNA except the characteristic midzone. The configuration of these sites of replicated DNA molecules is different to previous studies on organisms such as Crithidia fasciculata, suggesting differences in the timing of replication of mini and maxicircles and/or organization of the replicative apparatus in the kinetoplast of the African trypanosome.

Characterization of circular DNA molecules from cotton plants with leaf curl disease

2018 ◽  
Vol 51 (1) ◽  
Author(s):  
Sohail Akhtar ◽  
Muhammad Nouman Tahir ◽  
Imran Amin ◽  
Rana Binyamin ◽  
Shahid Mansoor
Keyword(s):  
Dna Molecules ◽  
Circular Dna ◽  
Cotton Plants ◽  
Leaf Curl Disease ◽  
Leaf Curl

Protonation effects on dynamic flux properties of aqueous metal complexes

2009 ◽  
Vol 74 (10) ◽  
pp. 1543-1557 ◽  
Author(s):  
Herman P. Van Leeuwen ◽  
Raewyn M. Town
Keyword(s):  
Complex Formation ◽  
Metal Ion ◽  
Good Description ◽  
Minor Component ◽  
Outer Sphere ◽  
Metal Species ◽  
Central Metal ◽  
Inner Sphere ◽  
A Minor ◽  
Protonated Ligand

The degree of (de)protonation of aqueous metal species has significant consequences for the kinetics of complex formation/dissociation. All protonated forms of both the ligand and the hydrated central metal ion contribute to the rate of complex formation to an extent weighted by the pertaining outer-sphere stabilities. Likewise, the lifetime of the uncomplexed metal is determined by all the various protonated ligand species. Therefore, the interfacial reaction layer thickness, μ, and the ensuing kinetic flux, Jkin, are more involved than in the conventional case. All inner-sphere complexes contribute to the overall rate of dissociation, as weighted by their respective rate constants for dissociation, kd. The presence of inner-sphere deprotonated H2O, or of outer-sphere protonated ligand, generally has a great impact on kd of the inner-sphere complex. Consequently, the overall flux can be dominated by a species that is a minor component of the bulk speciation. The concepts are shown to provide a good description of experimental stripping chronopotentiometric data for several protonated metal–ligand systems.

scholarly journals Excision of Oxidatively Generated Guanine Lesions by Competitive DNA Repair Pathways

2021 ◽  
Vol 22 (5) ◽  
pp. 2698
Author(s):  
Vladimir Shafirovich ◽  
Nicholas E. Geacintov
Keyword(s):  
Excision Repair ◽  
Dna Lesions ◽  
Dna Templates ◽  
Circular Dna ◽  
Damage Sensing ◽  
Cell Extracts ◽  
Dna Base ◽  
Nucleotide Excision ◽  
Repair Pathways ◽  
Cellular Dna

The base and nucleotide excision repair pathways (BER and NER, respectively) are two major mechanisms that remove DNA lesions formed by the reactions of genotoxic intermediates with cellular DNA. It is generally believed that small non-bulky oxidatively generated DNA base modifications are removed by BER pathways, whereas DNA helix-distorting bulky lesions derived from the attack of chemical carcinogens or UV irradiation are repaired by the NER machinery. However, existing and growing experimental evidence indicates that oxidatively generated DNA lesions can be repaired by competitive BER and NER pathways in human cell extracts and intact human cells. Here, we focus on the interplay and competition of BER and NER pathways in excising oxidatively generated guanine lesions site-specifically positioned in plasmid DNA templates constructed by a gapped-vector technology. These experiments demonstrate a significant enhancement of the NER yields in covalently closed circular DNA plasmids (relative to the same, but linearized form of the same plasmid) harboring certain oxidatively generated guanine lesions. The interplay between the BER and NER pathways that remove oxidatively generated guanine lesions are reviewed and discussed in terms of competitive binding of the BER proteins and the DNA damage-sensing NER factor XPC-RAD23B to these lesions.

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