Effects of nucleases on cell-free extrachromosomal circular DNA
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ABSTRACT:
PROVIDER: EGAS00001005873 | EGA |
REPOSITORIES: EGA
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Project description:Extrachromosomal circular DNA (eccDNA) is double-stranded circular DNA that is derived from but independent of chromosomal DNA. Owing to its nonchromosomal inheritance, eccDNA facilitates the amplification of oncogenes and expedites the process of genome evolution in tumor. However, the role of eccDNA in RB remains enigmatic. We combined Circle-Seq and RNA-Seq to identified crucial extrachromosomal circular oncogene amplicons. Herein, we revealed that extrachromosomal circular SUZ12 amplicon regulates H3K27me3 modification during the oncogenic progression of retinoblastoma. Conclusively, our study initially delineated an integrated picture of the eccDNA landscape in retinoblastoma and unveiled a novel SUZ12-containing eccDNA/H3K27me3 oncogenic mechanism where eccDNA dictates retinoblastoma progression through regulating transcription levels of linear DNA.
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Project description:Circular RNAs (CircRNAs) are stable RNAs present in cell-free RNA, comprising cellular debris and pathogen genomes. As a prerequisite for the development of efficient circRNA-based therapies, we investigated the phenomenon and mechanism of cellular uptake and intracellular fate of circRNAs. Human myeloid cells and B cells selectively internalize extracellular circRNAs. Macrophage uptake of circRNA is rapid, energy-dependent, and saturable. CircRNA uptake can lead to translation of encoded sequences and antigen presentation. The route of internalization influences immune activation after circRNA uptake, with distinct gene expression programs depending on the mechanism involved. Genome-scale CRISPR screens and chemical inhibitor studies nominate macrophage scavenger receptor MSR1, toll-like receptors, and mTOR signaling as key regulators of receptor-mediated phagocytosis of circRNAs, a dominant pathway to internalize circRNAs in parallel to macropinocytosis. These results suggest that cell-free circRNA serves as an "eat me" signal and a danger-associated molecular pattern, indicating orderly pathways of recognition and disposal.
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Project description:ATAC-seq identifies thousands of extrachromosomal circular DNA in cancers and cell lines
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Project description:Oncogenes are commonly amplified on extrachromosomal DNA particles (ecDNA) in cancer, but our understanding of the structure of ecDNA and its impact on gene regulation is limited. We integrated ultrastructural imaging, long range-optical mapping, and computational analysis of whole genome sequencing to demonstrate unequivocally that ecDNA is circular. Pan-cancer analyses reveal that the oncogenes encoded on ecDNA are among the most highly expressed genes in the transcriptome of tumours, linking elevated copy with very high levels of transcription. Quantitative assessment of the chromatin state, including ATAC-seq to map the accessible genome and ATAC-see to examine spatial distribution of open chromatin, reveal that while ecDNA is chromatinized, it lacks higher order compaction typical of chromosomes. In fact, ecDNA contains the most accessible DNA in the tumour genome. Using chromosome conformation capture technologies and CRISPR interference, we reveal the differential organization of active chromatin in cancer that is dictated by the circular shape of ecDNA. Lastly, we develop comprehensive maps that provide new insight into how circular ecDNA structure determines oncogene function, bridging ecDNA biology with modern cancer genomics and epigenetics.
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Project description:In eukaryotic cells, most introns are degraded soon after splicing in the nucleus but some persist either due to lack of splicing (detained/retained introns) or because they contain important functional elements, for example, sno/scaRNAs. Few introns are detectable outside the nucleus. To hunt for interesting new phenomena in cytoplasmic introns and splicing, we conducted a multimodal study of total RNA within projections (axons, dendrites, glial projections) of rat hippocampal neurons and discovered a class of free circular introns enriched in distal projections.
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Project description:Extrachromosomal circular DNAs (eccDNAs) are usually somatically mosaic and a source of intercellular heterogeneity in normal and tumor cells. Because short eccDNAs are poorly chromatinized, we hypothesized that they are sequenced by tagmentation in ATAC-seq experiments, without any enrichment of circular DNA, and thus identified thousands of eccDNAs. The eccDNAs identified in cell lines were validated by inverse PCR on DNA that survives exonuclease digestion of linear DNA, and by metaphase FISH. ATAC-seq in Gliomas and Glioblastomas identify hundreds of eccDNAs, including one containing the well-known EGFR gene amplicon from chr7. Over 18,000 eccDNAs, many carrying known cancer driver genes, are identified in a pan-cancer analysis of 360 ATAC-seq libraries from 23 tumor types. Because of somatic mosaicism, eccDNAs are identified by ATAC-seq even before amplification of the locus is recognized by genome-wide copy number variation measurements. Thus, standard ATAC-seq is a sensitive method to detect eccDNA present in a subset of tumor cells, ready to be amplified under appropriate selection, as during therapy.
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