Identification of a novel large extrachromosomal DNA (LED) in the Trypanosomatidae

Wagner, Wilma; So, Magdalene

doi:10.1111/j.1365-2958.1992.tb01405.x

Cited by 9 publications

(8 citation statements)

References 45 publications

(43 reference statements)

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“…The linear plasmids range in size from 50 to 150 kbp, sizes that are too long to be separated by conventional gels. Although large circular plasmids can be visualized on conventional gels, such as the 75 kbp rDNA plasmid from Trypanosoma cruzi (Wagner and So, 1992), the size of our plasmid, reported here, was estimated to be much larger, 1.2 Mbp (see below).…”

Section: Resultsmentioning

confidence: 69%

“…These plasmids can be found in both pathogens and non‐pathogenic organisms, making their role in pathogenesis dubious. For example, the presence of a large rDNA containing circle in distant protozoa of the family Trypanosomatidae prompted the authors to speculate on its important role in the biology of these parasites (Wagner and So, 1992). Another prominent example is the pathogen Plasmodium falciparum , which has two coexisting rDNA plasmids, linear and circular (Feagin et al ., 1992).…”

Section: Discussionmentioning

confidence: 99%

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Large circular and linear rDNA plasmids inCandida albicans

Huber

Rustchenko

2001

Yeast

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Although plasmids containing rRNA genes (rDNA) are commonly found in fungi, they have not been reported in Candida. We discovered that the yeast opportunistic pathogen Candida albicans contains two types of rDNA plasmids which differ in their structure and number of rDNA repeats. A large circular plasmid of unknown size consists of multiple rDNA repeats, each of which includes an associated autonomously replicating sequence (ARS). In contrast, a linear plasmid, which is represented by a series of molecules with a spread of sizes ranging from 50–150 kbp, carries a limited number of rDNA units and associated ARSs, as well as telomeres. The number of linear plasmids per cell is growth cycle‐dependent, accumulating in abundance in actively growing cells. We suggest that the total copy number of rDNA is better controlled when a portion of copies are on a linear extrachromosomal plasmid, thus allowing a rapid shift in the number of corresponding genes and, as a result, better adaptation to the environment. This is the first report of a linear rDNA plasmid in yeast, as well as of the coexistence of circular and linear plasmids. In addition, this is a first report of naturally occurring plasmids in C. albicans. Copyright © 2000 John Wiley & Sons, Ltd.

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Section: Resultsmentioning

confidence: 69%

Section: Discussionmentioning

confidence: 99%

Large circular and linear rDNA plasmids inCandida albicans

Huber

Rustchenko

2001

Yeast

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“…Several laboratories including ours have previously obtained elements that can exist extrachromosomally in other members of the family Kinetoplastidiae (Bellofatto et al, 1990;Kapler et al, 1990;Kelly et al, 1992;Wagner and So, 1992). In each case these elements exist at a moderate to high copy number and usually as a multimer.…”

Section: Discussionmentioning

confidence: 99%

Autonomously replicating single-copy episomes in Trypanosoma brucei show unusual stability.

1993

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We have obtained several autonomously replicating plasmids in procyclic Trypanosoma brucei. Two of these have been analyzed in detail. Both exist as monomeric single‐copy episomes, which nevertheless demonstrate significant stability. These episomes transform procyclics at frequencies that are at least 60‐fold higher than those achieved earlier with non‐replicating molecules. A modified version of one of these episomes is able to replicate autonomously in bloodstream form T. brucei but it is unstable in this developmental stage of the organism. These episomes will prove useful as shuttle vectors, in functional complementation studies, in the construction of promoter‐traps for the isolation of transcriptional promoters in T. brucei, and importantly, as models for the analysis of DNA replication in this ancient eukaryotic lineage.

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“…One of the best characterized examples is the generation of extrachromosomal DNA after exposure of Leishmania cells to methotrexate during the development drug resistance (Beverley et al ., 1984; Grondin et al ., 1998). Extrachromosomal DNA can also arise independent of drug selection, such as the circular 75 kbp LED in Trypanosoma cruzi that contains multiple copies of the 18S ribosomal RNA gene, spliced leader sequences and copies of a 196 bp repeat (Wagner and So, 1992).…”

Section: Introductionmentioning

confidence: 99%

The identification of circular extrachromosomal DNA in the nuclear genome ofTrypanosoma brucei

Alsford

Navarro

Jamnadass

et al. 2003

Molecular Microbiology

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SummaryNuclear extrachromosomal DNA elements have been identified in several kinetoplastids such as Leishmania and Trypanosoma cruzi , but never in Trypanosoma brucei . They can occur naturally or arise spontaneously as the result of sublethal drug exposure of parasites. In most cases, they are represented as circular elements and are mitotically unstable. In this study we describe the presence of circular DNA in the nucleus of Trypanosoma brucei . This novel type of DNA was termed NR-element ( N laIII r epeat element). In contrast to drug-induced episomes in other kinetoplastids, the T. brucei extrachromosomal NRelement is not generated by drug selection. Furthermore, the element is stable during mitosis over many generations. Restriction analysis of tagged NRelement DNA, unusual migration patterns during pulsed field gel electrophoresis (PFGE) and CsCl/ ethidium bromide equilibrium centrifugation demonstrates that the NR-element represents circular DNA. Whereas it has been found in all field isolates of the parasites we analysed, it is not detectable in some laboratory strains notably the genome reference strain 927. The DNA sequence of this element is related to a 29 bp repeat present in the subtelomeric region of VSG-bearing chromosomes of T. brucei . It has been suggested that this subtelomeric region is part of a transition zone on chromosomes separating the relatively stable telomeric repeats from the recombinationaly active region downstream of VSG genes. Therefore, we discuss a functional connection between the occurrence of this circular DNA and subtelomeric recombination events in T. brucei .

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Identification of a novel large extrachromosomal DNA (LED) in the Trypanosomatidae

Cited by 9 publications

References 45 publications

Large circular and linear rDNA plasmids inCandida albicans

Large circular and linear rDNA plasmids inCandida albicans

Autonomously replicating single-copy episomes in Trypanosoma brucei show unusual stability.

The identification of circular extrachromosomal DNA in the nuclear genome ofTrypanosoma brucei

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