The topology of the kinetoplast DNA network

Chen, Junghuei; Rauch, Carol A.; White, James H.; Englund, Paul T.; Cozzarelli, Nicholas R.

doi:10.1016/0092-8674(95)90451-4

Cited by 169 publications

(209 citation statements)

References 24 publications

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“…The high copy number of this sequence may explain the intensity of the ISH signal without prior amplification (Degrave et al 1998). In addition, topological constraints involved in the physical organization of minicircles within the kinetoplast may inhibit efficient amplification (Chen et al 1995). Our results confirm previous data demonstrating that MCS is consistently found in myocardial tissue from chagasic patients with cardiomyopathy using either fluid phase or in situ PCR followed by hybridization (Lane et al 1997, Olivares-Villagomez et al 1998.…”

supporting

confidence: 81%

Detection of Trypanosoma cruzi DNA within murine cardiac tissue sections by in situ polymerase chain reaction

Lane

Ribeiro‐Rodrigues

Olivares–Villagómez

et al. 2003

Mem. Inst. Oswaldo Cruz

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supporting

confidence: 81%

Detection of Trypanosoma cruzi DNA within murine cardiac tissue sections by in situ polymerase chain reaction

Lane

Ribeiro‐Rodrigues

Olivares–Villagómez

et al. 2003

Mem. Inst. Oswaldo Cruz

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“…In vivo, the kDNA exists as a condensed disk structure 1 m in diameter and Ϸ0.4 m thick. Each minicircle in the kDNA disk is linked to three other minicircles on average and is relaxed, unlike most other circular DNAs in nature, which are negatively supercoiled (5). Electron microscopic observation of sections through the kDNA disk shows fibers aligned parallel to the axis of the disk.…”

mentioning

confidence: 98%

Mitochondrial DNA ligase in Crithidia fasciculata

Sinha

Hines

Downey

2004

Proc. Natl. Acad. Sci. U.S.A.

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Kinetoplast DNA (kDNA), the form of mitochondrial DNA in trypanosomatids, consists of thousands of interlocked circular DNAs organized into a compact disk structure. A type II DNA topoisomerase, a DNA polymerase ␤, and a structure-specific endonuclease have been localized to antipodal sites flanking the kDNA disk along with nascent DNA minicircles. We have cloned a gene (LIG k) encoding a mitochondrial DNA ligase in the trypanosomatid Crithidia fasciculata, and we show that an epitope-tagged form of the ligase colocalizes with the other replication proteins at the antipodal sites and also at the two faces of the kDNA disk. DNA LIG k becomes adenylated in reactions with ATP, and the adenylate moiety is removed by incubation with pyrophosphate or nicked DNA. The ligase interacts physically with the ␤ polymerase and is proposed to be involved in the repair of gaps in the newly synthesized minicircles. In yeast and mammals, a single gene encodes both nuclear and mitochondrial forms of DNA ligase. The LIG K protein sequence has low similarity to mitochondrial DNA ligases in other eukaryotes and is distinct from the C. fasciculata nuclear DNA ligase (LIG I).T he mitochondrial DNA of trypanosomatid protozoa (kinetoplast DNA, or kDNA) consists of two forms of topologically interlocked circular DNAs, minicircles, and maxicircles (for recent reviews of kDNA structure and replication, see refs. 1-3). The kDNA of the trypanosomatid Crithidia fasciculata contains 5,000 minicircles of 2.5 kb each and 20-30 maxicircles of 37 kb each. The maxicircles encode genes for mitochondrial proteins and ribosomal RNAs. Minicircles encode small guide RNAs that serve as templates for RNA editing of maxicircle transcripts (4). In vivo, the kDNA exists as a condensed disk structure 1 m in diameter and Ϸ0.4 m thick. Each minicircle in the kDNA disk is linked to three other minicircles on average and is relaxed, unlike most other circular DNAs in nature, which are negatively supercoiled (5). Electron microscopic observation of sections through the kDNA disk shows fibers aligned parallel to the axis of the disk. This observation together with the thickness of the disk corresponding to approximately one half of the minicircle circumference (6) suggests that individual minicircles may have a topology like that of a rubber band stretched taut from opposite sides of the circle (7). Maxicircles appear to be present throughout the kDNA and exist as a catenated network within the overall network (8). The kDNA isolated from nonreplicating C. fasciculata is a planar elliptical network of interlocked circles with dimensions of Ϸ10 by 15 m.The kDNA disk is always located at the base of the flagellum, with the flagellum perpendicular to the face of the disk. Recent studies (9) have shown that in trypanosomes the kDNA disk is connected physically to the flagellar basal bodies and is segregated by them at cell division. The attachment was found to involve three components that penetrate the inner and outer mitochondrial membranes to link the kDNA physically ...

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“…No alterations to replication rate were seen when wild type PCF cells were grown in the presence of tetracycline. 2 The role of TbDLP in the maintenance of the normal morphology of the T. brucei mitochondrion was assessed following RNAi by live cell fluorescence imaging using MitoTracker Green FM. Wild type PCF trypanosomes have a single mitochondrion that runs the length of the cell (Fig.…”

Section: Dynamin-like Protein Regulates Mitochondrial Divisionmentioning

confidence: 99%

“…Given their extreme evolutionary distance, estimated at a divergence time of ϳ3 billion years from the crown eukaryotes, it is not unexpected that these organisms display many unusual biological features. One example is a unique configuration of the mitochondrial genome, the kinetoplast DNA, which is composed of several thousand DNA circles catenated into a single network (2). This network is condensed into a disk-shaped structure in the matrix of the single mitochondrion of the cell and is structurally linked to the flagellar basal bodies through a transmembrane complex (3,4).…”

mentioning

confidence: 99%

The Single Dynamin-like Protein of Trypanosoma brucei Regulates Mitochondrial Division and Is Not Required for Endocytosis

Morgan

Goulding

Field

2004

Journal of Biological Chemistry

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Members of the evolutionarily conserved dynamin-related GTPase family mediate numerous cellular membrane remodeling events. Dynamin family functions include the scission of clathrin-coated pits from the plasma membrane, mitochondrial fission, and chloroplast division. Here we report that the divergent eukaryote Trypanosoma brucei possesses a single dynamin family gene, which we have designated TbDLP. Furthermore, a single dynamin family gene is also found in the Leishmania major and Trypanosoma vivax genomes, indicating that this is a conserved feature among the kinetoplastida. TbDLP is most homologous to the DMN/DRP family of dynamin-like proteins. Indirect immunofluorescence microscopy reveals that TbDLP is distributed in punctate structures within the cell that partially co-localize with the mitochondrion when labeled with MitoTracker. To define TbDLP function, we have used RNA interference to silence the TbDLP gene. Reduction of TbDLP protein levels causes a profound alteration in mitochondrial morphology without affecting the structure of other membrane-bound compartments, including the endocytic and exocytic apparatus. The mitochondrial profiles present in wild type trypanosomes fuse and collapse in the mutant cells, and by electron microscopy the mitochondria are found to contain an accumulation of constriction sites. These findings demonstrate TbDLP functions in division of the mitochondrial membrane. Most significantly, as TbDLP is the sole member of the dynamin family in this organism, scission of clathrin-coated pits involved in protein trafficking through the highly active endocytic system in trypanosomes must function in the absence of dynamin. The evolutionary implications of these findings are discussed.

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The topology of the kinetoplast DNA network

Cited by 169 publications

References 24 publications

Detection of Trypanosoma cruzi DNA within murine cardiac tissue sections by in situ polymerase chain reaction

Detection of Trypanosoma cruzi DNA within murine cardiac tissue sections by in situ polymerase chain reaction

Mitochondrial DNA ligase in Crithidia fasciculata

The Single Dynamin-like Protein of Trypanosoma brucei Regulates Mitochondrial Division and Is Not Required for Endocytosis

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