Document Detail

Extrachromosomal circular DNA in eukaryotes: possible involvement in the plasticity of tandem repeats.
MedLine Citation:
PMID:  19556784     Owner:  NLM     Status:  MEDLINE    
Extrachromosomal circular DNA (eccDNA) is ubiquitous in eukaryotic organisms, and has been noted for more than 3 decades. eccDNA occurs in normal tissues and in cultured cells, is heterogeneous in size, consists of chromosomal sequences and reflects plasticity of the genome. Two-dimensional (2D) gel electrophoresis has been adapted for the detection and characterization of eccDNA. It shows that most eccDNA consists of chromosomal tandem repeats, both coding genes and satellite DNA and is organized as circular multimers of the repeating sequence. 2D gels were unable to detect dispersed repeats within the population of eccDNA. eccDNA, organized as circular multimers, can be formed de novo in Xenopus egg extracts, in the absence of DNA replication. These findings support a mechanism for the formation of eccDNA that involves intra-chromosomal homologous recombination between tandem repeats and looping-out. Furthermore, eccDNA appears to undergo extrachromosomal replication via a rolling circle mechanism. Hence, the formation of eccDNA from arrays of tandem repeats may cause deletions, and the possible re-integration of rolling-circle replication products could expand these arrays. This review summarizes recent experimental data which characterizes eccDNA in several organisms using 2D gel electrophoresis, and discusses its possible implications on the dynamics of chromosomal tandem repeats.
S Cohen; D Segal
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Review     Date:  2009-06-25
Journal Detail:
Title:  Cytogenetic and genome research     Volume:  124     ISSN:  1424-859X     ISO Abbreviation:  Cytogenet. Genome Res.     Publication Date:  2009  
Date Detail:
Created Date:  2009-06-26     Completed Date:  2009-07-30     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101142708     Medline TA:  Cytogenet Genome Res     Country:  Switzerland    
Other Details:
Languages:  eng     Pagination:  327-38     Citation Subset:  IM    
Copyright Information:
(c) 2009 S. Karger AG, Basel.
Department of Molecular Microbiology and Biotechnology, Tel-Aviv University, Tel-Aviv, Israel.
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MeSH Terms
Chromosomes / physiology*
DNA Replication / physiology*
DNA, Circular / chemistry,  physiology*
DNA, Satellite / physiology*
Tandem Repeat Sequences / physiology*
Reg. No./Substance:
0/DNA, Circular; 0/DNA, Satellite

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