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Extrachromosomal circular DNA is common in yeast.

ABSTRACT: Examples of extrachromosomal circular DNAs (eccDNAs) are found in many organisms, but their impact on genetic variation at the genome scale has not been investigated. We mapped 1,756 eccDNAs in the Saccharomyces cerevisiae genome using Circle-Seq, a highly sensitive eccDNA purification method. Yeast eccDNAs ranged from an arbitrary lower limit of 1 kb up to 38 kb and covered 23% of the genome, representing thousands of genes. EccDNA arose both from genomic regions with repetitive sequences ? 15 bases long and from regions with short or no repetitive sequences. Some eccDNAs were identified in several yeast populations. These eccDNAs contained ribosomal genes, transposon remnants, and tandemly repeated genes (HXT6/7, ENA1/2/5, and CUP1-1/-2) that were generally enriched on eccDNAs. EccDNAs seemed to be replicated and 80% contained consensus sequences for autonomous replication origins that could explain their maintenance. Our data suggest that eccDNAs are common in S. cerevisiae, where they might contribute substantially to genetic variation and evolution.

SUBMITTER: Moller HD

PROVIDER: S-EPMC4475933 | biostudies-literature | 2015 Jun

REPOSITORIES: biostudies-literature

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Extrachromosomal circular DNA is common in yeast.

Møller Henrik D HD Parsons Lance L Jørgensen Tue S TS Botstein David D Regenberg Birgitte B

Proceedings of the National Academy of Sciences of the United States of America 20150602 24

Examples of extrachromosomal circular DNAs (eccDNAs) are found in many organisms, but their impact on genetic variation at the genome scale has not been investigated. We mapped 1,756 eccDNAs in the Saccharomyces cerevisiae genome using Circle-Seq, a highly sensitive eccDNA purification method. Yeast eccDNAs ranged from an arbitrary lower limit of 1 kb up to 38 kb and covered 23% of the genome, representing thousands of genes. EccDNA arose both from genomic regions with repetitive sequences ≥ 15 ...[more]

PMID: 26038577

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Project description:BackgroundEsophageal squamous cell carcinoma (ESCC) is the leading cause of cancer-related mortality. While recent studies have documented the presence of extrachromosomal circular DNAs (eccDNAs) in various tumors, to date, there have been no studies examining the distribution and function of eccDNAs in ESCC.MethodsThe eccDNAs from three surgically matched ESCC tissue samples were extracted and amplified by rolling circle amplification after removal of linear DNA and mitochondrial circular DNA. High-throughput eccDNA sequencing and bioinformatics analysis was performed to study the distribution pattern and the level of eccDNA expression. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed on the genes associated with the differentially expressed eccDNAs. Five up-regulated and five down-regulated candidate eccDNAs were validated by routine polymerase chain reaction (PCR), TOPO-TA cloning and Sanger sequencing. The nucleotides flanking the eccDNA junctions were analyzed to explore the mechanisms of eccDNA formation.ResultsA total of 184,557 eccDNAs was identified. The overall length distribution ranged from 33 to 968,842 base pairs (bp), with the peak at approximately 360 bp. These eccDNAs mainly originated from 5'- and 3'-untranslated regions (UTRs), and rarely from exons, introns, LINE, or Alu repeat regions. The chromosome distribution, length distribution, and genomic annotation of the eccDNAs were comparable between ESCC samples and matched normal epithelium. Nevertheless, 16,031 eccDNAs were found to be differentially expressed between ESCC and matched normal epithelium, including 10,126 up-regulated eccDNAs and 5,905 down-regulated eccDNAs. GO analysis and KEGG pathway analysis showed enriched in cancer pathways, mitogen-activated protein kinase (MAPK) pathway, GTPase-related activity, and cytoskeleton function. PCR, TOPO-TA cloning, and Sanger sequencing validated the junctional sites of five up-regulated candidate eccDNAs and four other unexpected eccDNAs. A repeat nucleotide pattern between the position flanking the start site and that flanking the end site was detected.ConclusionsThis study demonstrated the genome-wide presence of eccDNAs, explored the differential expression of eccDNAs, and revealed the potential mechanisms of eccDNAs in ESCC. This work provides further insights into our understanding of genome plasticity, the role of eccDNAs in ESCC, and may contribute to the development of potential clinical therapies.

Dataset Information

Extrachromosomal circular DNA is common in yeast.

Publications

Extrachromosomal circular DNA is common in yeast.

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