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Yang W, Ji W, Liao B, Li Z, Wang J, Lin H, Wang J, He Q. Genome-wide sequencing identified extrachromosomal circular DNA as a transcription factor-binding motif of the senescence genes that govern replicative senescence in human mesenchymal stem cells. Front Cell Neurosci 2024; 18:1421342. [PMID: 39157757 PMCID: PMC11327076 DOI: 10.3389/fncel.2024.1421342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Accepted: 07/17/2024] [Indexed: 08/20/2024] Open
Abstract
Introduction Mesenchymal stem cells (MSCs) have long been postulated as an important source cell in regenerative medicine. During subculture expansion, mesenchymal stem cell (MSC) senescence diminishes their multi-differentiation capabilities, leading to a loss of therapeutic potential. Up to date, the extrachromosomal circular DNAs (eccDNAs) have been demonstrated to be involved in senescence but the roles of eccDNAs during MSC. Methods Here we explored eccDNA profiles in human bone marrow MSCs (BM-MSCs). EccDNA and mRNA was purified and sequenced, followed by quantification and functional annotation. Moreover, we mapped our datasets with the downloading enhancer and transcription factor-regulated genes to explore the potential role of eccDNAs. Results Sequentially, gene annotation analysis revealed that the majority of eccDNA were mapped in the intron regions with limited BM-MSC enhancer overlaps. We discovered that these eccDNA motifs in senescent BMSCs acted as motifs for binding transcription factors (TFs) of senescence-related genes. Discussion These findings are highly significant for identifying biomarkers of senescence and therapeutic targets in mesenchymal stem cells (MSCs) for future clinical applications. The potential of eccDNA as a stable therapeutic target for senescence-related disorders warrants further investigation, particularly exploring chemically synthesized eccDNAs as transcription factor regulatory elements to reverse cellular senescence.
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Affiliation(s)
- Wei Yang
- School of Food and Drug, Shenzhen Polytechnic University, Shenzhen, China
| | - Wei Ji
- School of Life Science and Technology, Changchun University of Science and Technology, Changchun, China
| | - Boyu Liao
- College of Pharmacy, Shenzhen Technology University, Shenzhen, China
- School of Pharmaceutical Sciences, Health Science Center, Shenzhen University, Shenzhen, China
| | - Zhongbo Li
- School of Food and Drug, Shenzhen Polytechnic University, Shenzhen, China
- School of Life Science and Technology, Changchun University of Science and Technology, Changchun, China
| | - Jian Wang
- School of Food and Drug, Shenzhen Polytechnic University, Shenzhen, China
- School of Life Science and Technology, Changchun University of Science and Technology, Changchun, China
| | - Haishu Lin
- College of Pharmacy, Shenzhen Technology University, Shenzhen, China
- School of Pharmaceutical Sciences, Health Science Center, Shenzhen University, Shenzhen, China
| | - Jingbo Wang
- College of Pharmacy, Shenzhen Technology University, Shenzhen, China
- School of Pharmaceutical Sciences, Health Science Center, Shenzhen University, Shenzhen, China
| | - Qian He
- School of Food and Drug, Shenzhen Polytechnic University, Shenzhen, China
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2
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Wu N, Wei L, Zhu Z, Liu Q, Li K, Mao F, Qiao J, Zhao X. Innovative insights into extrachromosomal circular DNAs in gynecologic tumors and reproduction. Protein Cell 2024; 15:6-20. [PMID: 37233789 PMCID: PMC10762679 DOI: 10.1093/procel/pwad032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 05/03/2023] [Indexed: 05/27/2023] Open
Abstract
Originating but free from chromosomal DNA, extrachromosomal circular DNAs (eccDNAs) are organized in circular form and have long been found in unicellular and multicellular eukaryotes. Their biogenesis and function are poorly understood as they are characterized by sequence homology with linear DNA, for which few detection methods are available. Recent advances in high-throughput sequencing technologies have revealed that eccDNAs play crucial roles in tumor formation, evolution, and drug resistance as well as aging, genomic diversity, and other biological processes, bringing it back to the research hotspot. Several mechanisms of eccDNA formation have been proposed, including the breakage-fusion-bridge (BFB) and translocation-deletion-amplification models. Gynecologic tumors and disorders of embryonic and fetal development are major threats to human reproductive health. The roles of eccDNAs in these pathological processes have been partially elucidated since the first discovery of eccDNA in pig sperm and the double minutes in ovarian cancer ascites. The present review summarized the research history, biogenesis, and currently available detection and analytical methods for eccDNAs and clarified their functions in gynecologic tumors and reproduction. We also proposed the application of eccDNAs as drug targets and liquid biopsy markers for prenatal diagnosis and the early detection, prognosis, and treatment of gynecologic tumors. This review lays theoretical foundations for future investigations into the complex regulatory networks of eccDNAs in vital physiological and pathological processes.
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Affiliation(s)
- Ning Wu
- State Key Laboratory of Female Fertility Promotion, Center for Reproductive Medicine, Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing 100191, China
- National Clinical Research Center for Obstetrics and Gynecology, Peking University Third Hospital, Beijing 100191, China
- Key Laboratory of Assisted Reproduction (Peking University), Ministry of Education, Beijing 100191, China
- Beijing Key Laboratory of Reproductive Endocrinology and Assisted Reproductive Technology, Beijing 100191, China
| | - Ling Wei
- Institute of Medical Innovation and Research, Peking University Third Hospital, Beijing 100191, China
- Cancer Center, Peking University Third Hospital, Beijing 100191, China
| | - Zhipeng Zhu
- Institute of Medical Innovation and Research, Peking University Third Hospital, Beijing 100191, China
- Cancer Center, Peking University Third Hospital, Beijing 100191, China
| | - Qiang Liu
- State Key Laboratory of Female Fertility Promotion, Center for Reproductive Medicine, Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing 100191, China
- National Clinical Research Center for Obstetrics and Gynecology, Peking University Third Hospital, Beijing 100191, China
- Key Laboratory of Assisted Reproduction (Peking University), Ministry of Education, Beijing 100191, China
- Beijing Key Laboratory of Reproductive Endocrinology and Assisted Reproductive Technology, Beijing 100191, China
| | - Kailong Li
- Department of Biochemistry and Biophysics, Beijing Key Laboratory of Protein Posttranslational Modifications and Cell Function, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, China
| | - Fengbiao Mao
- Institute of Medical Innovation and Research, Peking University Third Hospital, Beijing 100191, China
- Cancer Center, Peking University Third Hospital, Beijing 100191, China
| | - Jie Qiao
- State Key Laboratory of Female Fertility Promotion, Center for Reproductive Medicine, Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing 100191, China
- National Clinical Research Center for Obstetrics and Gynecology, Peking University Third Hospital, Beijing 100191, China
- Key Laboratory of Assisted Reproduction (Peking University), Ministry of Education, Beijing 100191, China
- Beijing Key Laboratory of Reproductive Endocrinology and Assisted Reproductive Technology, Beijing 100191, China
- Beijing Advanced Innovation Center for Genomics, Beijing 100191, China
- Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100191, China
| | - Xiaolu Zhao
- State Key Laboratory of Female Fertility Promotion, Center for Reproductive Medicine, Department of Obstetrics and Gynecology, Center for Reproductive Medicine, Peking University Third Hospital, Beijing 100191, China
- National Clinical Research Center for Obstetrics and Gynecology, Peking University Third Hospital, Beijing 100191, China
- Key Laboratory of Assisted Reproduction (Peking University), Ministry of Education, Beijing 100191, China
- Beijing Key Laboratory of Reproductive Endocrinology and Assisted Reproductive Technology, Beijing 100191, China
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3
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Yüksel A, Altungöz O. Gene amplifications and extrachromosomal circular DNAs: function and biogenesis. Mol Biol Rep 2023; 50:7693-7703. [PMID: 37433908 DOI: 10.1007/s11033-023-08649-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 06/28/2023] [Indexed: 07/13/2023]
Abstract
Gene amplification is an increase in the copy number of restricted chromosomal segments that contain gene(s) and frequently results in the over-expression of the corresponding gene(s). Amplification may be found in the form of extrachromosomal circular DNAs (eccDNAs) or as linear repetitive amplicon regions that are integrated into chromosomes, which may form cytogenetically observable homogeneously staining regions or may be scattered throughout the genome. eccDNAs are structurally circular and in terms of their function and content, they can be classified into various subtypes. They play pivotal roles in many physiological and pathological phenomena such as tumor pathogenesis, aging, maintenance of telomere length and ribosomal DNAs (rDNAs), and gain of resistance against chemotherapeutic agents. Amplification of oncogenes is consistently seen in various types of cancers and can be associated with prognostic factors. eccDNAs are known to be originated from chromosomes as a consequence of various cellular events such as repair processes of damaged DNA or DNA replication errors. In this review, we highlighted the role of gene amplification in cancer, the functional aspects of eccDNAs subtypes, the proposed biogenesis mechanisms, and their role in gene or segmental-DNA amplification.
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Affiliation(s)
- Ali Yüksel
- Department of Medical Biology and Genetics, Institute of Health Sciences, Dokuz Eylul University, 35330, Izmir, Turkey.
| | - Oğuz Altungöz
- Department of Medical Biology and Genetics, Institute of Health Sciences, Dokuz Eylul University, 35330, Izmir, Turkey.
- Department of Medical Biology, Dokuz Eylül Medical School, 35330, Izmir, Turkey.
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4
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Chitwood DG, Wang Q, Klaubert SR, Green K, Wu CH, Harcum SW, Saski CA. Microevolutionary dynamics of eccDNA in Chinese hamster ovary cells grown in fed-batch cultures under control and lactate-stressed conditions. Sci Rep 2023; 13:1200. [PMID: 36681715 PMCID: PMC9862248 DOI: 10.1038/s41598-023-27962-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 01/10/2023] [Indexed: 01/22/2023] Open
Abstract
Chinese hamster ovary (CHO) cell lines are widely used to manufacture biopharmaceuticals. However, CHO cells are not an optimal expression host due to the intrinsic plasticity of the CHO genome. Genome plasticity can lead to chromosomal rearrangements, transgene exclusion, and phenotypic drift. A poorly understood genomic element of CHO cell line instability is extrachromosomal circular DNA (eccDNA) in gene expression and regulation. EccDNA can facilitate ultra-high gene expression and are found within many eukaryotes including humans, yeast, and plants. EccDNA confers genetic heterogeneity, providing selective advantages to individual cells in response to dynamic environments. In CHO cell cultures, maintaining genetic homogeneity is critical to ensuring consistent productivity and product quality. Understanding eccDNA structure, function, and microevolutionary dynamics under various culture conditions could reveal potential engineering targets for cell line optimization. In this study, eccDNA sequences were investigated at the beginning and end of two-week fed-batch cultures in an ambr®250 bioreactor under control and lactate-stressed conditions. This work characterized structure and function of eccDNA in a CHO-K1 clone. Gene annotation identified 1551 unique eccDNA genes including cancer driver genes and genes involved in protein production. Furthermore, RNA-seq data is integrated to identify transcriptionally active eccDNA genes.
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Affiliation(s)
- Dylan G Chitwood
- Department of Bioengineering, Clemson University, Clemson, SC, USA
| | - Qinghua Wang
- Center for Bioinformatics and Computational Biology, University of Delaware, Newark, DE, USA
| | - Stephanie R Klaubert
- Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, SC, USA
| | - Kiana Green
- Department of Biological Sciences, University of South Carolina, Columbia, SC, USA
| | - Cathy H Wu
- Center for Bioinformatics and Computational Biology, University of Delaware, Newark, DE, USA
| | - Sarah W Harcum
- Department of Bioengineering, Clemson University, Clemson, SC, USA
- Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, SC, USA
| | - Christopher A Saski
- Department of Plant and Environmental Sciences, Clemson University, Clemson, SC, USA.
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5
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De Carvalho M, Jia GS, Nidamangala Srinivasa A, Billmyre RB, Xu YH, Lange JJ, Sabbarini IM, Du LL, Zanders SE. The wtf meiotic driver gene family has unexpectedly persisted for over 100 million years. eLife 2022; 11:e81149. [PMID: 36227631 PMCID: PMC9562144 DOI: 10.7554/elife.81149] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Accepted: 09/21/2022] [Indexed: 11/21/2022] Open
Abstract
Meiotic drivers are selfish elements that bias their own transmission into more than half of the viable progeny produced by a driver+/driver- heterozygote. Meiotic drivers are thought to exist for relatively short evolutionary timespans because a driver gene or gene family is often found in a single species or in a group of very closely related species. Additionally, drivers are generally considered doomed to extinction when they spread to fixation or when suppressors arise. In this study, we examine the evolutionary history of the wtf meiotic drivers first discovered in the fission yeast Schizosaccharomyces pombe. We identify homologous genes in three other fission yeast species, S. octosporus, S. osmophilus, and S. cryophilus, which are estimated to have diverged over 100 million years ago from the S. pombe lineage. Synteny evidence supports that wtf genes were present in the common ancestor of these four species. Moreover, the ancestral genes were likely drivers as wtf genes in S. octosporus cause meiotic drive. Our findings indicate that meiotic drive systems can be maintained for long evolutionary timespans.
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Affiliation(s)
- Mickaël De Carvalho
- Stowers Institute for Medical ResearchKansas CityUnited States
- Open UniversityMilton KeynesUnited Kingdom
| | - Guo-Song Jia
- PTN Joint Graduate Program, School of Life Sciences, Tsinghua UniversityBeijingChina
- National Institute of Biological Sciences, BeijingBeijingChina
| | - Ananya Nidamangala Srinivasa
- Stowers Institute for Medical ResearchKansas CityUnited States
- Department of Molecular and Integrative Physiology, University of Kansas Medical CenterKansas CityUnited States
| | | | - Yan-Hui Xu
- National Institute of Biological Sciences, BeijingBeijingChina
| | - Jeffrey J Lange
- Stowers Institute for Medical ResearchKansas CityUnited States
| | | | - Li-Lin Du
- National Institute of Biological Sciences, BeijingBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua UniversityBeijingChina
| | - Sarah E Zanders
- Stowers Institute for Medical ResearchKansas CityUnited States
- Department of Molecular and Integrative Physiology, University of Kansas Medical CenterKansas CityUnited States
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6
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Extrachromosomal circular DNA: biogenesis, structure, functions and diseases. Signal Transduct Target Ther 2022; 7:342. [PMID: 36184613 PMCID: PMC9527254 DOI: 10.1038/s41392-022-01176-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 08/14/2022] [Accepted: 09/01/2022] [Indexed: 11/08/2022] Open
Abstract
Extrachromosomal circular DNA (eccDNA), ranging in size from tens to millions of base pairs, is independent of conventional chromosomes. Recently, eccDNAs have been considered an unanticipated major source of somatic rearrangements, contributing to genomic remodeling through chimeric circularization and reintegration of circular DNA into the linear genome. In addition, the origin of eccDNA is considered to be associated with essential chromatin-related events, including the formation of super-enhancers and DNA repair machineries. Moreover, our understanding of the properties and functions of eccDNA has continuously and greatly expanded. Emerging investigations demonstrate that eccDNAs serve as multifunctional molecules in various organisms during diversified biological processes, such as epigenetic remodeling, telomere trimming, and the regulation of canonical signaling pathways. Importantly, its special distribution potentiates eccDNA as a measurable biomarker in many diseases, especially cancers. The loss of eccDNA homeostasis facilitates tumor initiation, malignant progression, and heterogeneous evolution in many cancers. An in-depth understanding of eccDNA provides novel insights for precision cancer treatment. In this review, we summarized the discovery history of eccDNA, discussed the biogenesis, characteristics, and functions of eccDNA. Moreover, we emphasized the role of eccDNA during tumor pathogenesis and malignant evolution. Therapeutically, we summarized potential clinical applications that target aberrant eccDNA in multiple diseases.
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7
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Arrey G, Keating ST, Regenberg B. A unifying model for extrachromosomal circular DNA load in eukaryotic cells. Semin Cell Dev Biol 2022; 128:40-50. [PMID: 35292190 DOI: 10.1016/j.semcdb.2022.03.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 03/03/2022] [Accepted: 03/03/2022] [Indexed: 02/06/2023]
Abstract
Extrachromosomal circular DNA (eccDNA) with exons and whole genes are common features of eukaryotic cells. Work from especially tumours and the yeast Saccharomyces cerevisiae has revealed that eccDNA can provide large selective advantages and disadvantages. Besides the phenotypic effect due to expression of an eccDNA fragment, eccDNA is different from other mutations in that it is released from 1:1 segregation during cell division. This means that eccDNA can quickly change copy number, pickup secondary mutations and reintegrate into a chromosome to establish substantial genetic variation that could not have evolved via canonical mechanisms. We propose a unifying 5-factor model for conceptualizing the eccDNA load of a eukaryotic cell, emphasizing formation, replication, segregation, selection and elimination. We suggest that the magnitude of these sequential events and their interactions determine the copy number of eccDNA in mitotically dividing cells. We believe that our model will provide a coherent framework for eccDNA research, to understand its biology and the factors that can be manipulated to modulate eccDNA load in eukaryotic cells.
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Affiliation(s)
- Gerard Arrey
- Section for Ecology and Evolution, University of Copenhagen, Copenhagen, Denmark
| | - Samuel T Keating
- Section for Ecology and Evolution, University of Copenhagen, Copenhagen, Denmark
| | - Birgitte Regenberg
- Section for Ecology and Evolution, University of Copenhagen, Copenhagen, Denmark.
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8
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Noer JB, Hørsdal OK, Xiang X, Luo Y, Regenberg B. Extrachromosomal circular DNA in cancer: history, current knowledge, and methods. Trends Genet 2022; 38:766-781. [PMID: 35277298 DOI: 10.1016/j.tig.2022.02.007] [Citation(s) in RCA: 47] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 02/10/2022] [Accepted: 02/11/2022] [Indexed: 12/12/2022]
Abstract
Extrachromosomal circular DNA (eccDNA) is a closed-circle, nuclear, nonplasmid DNA molecule found in all tested eukaryotes. eccDNA plays important roles in cancer pathogenesis, evolution of tumor heterogeneity, and therapeutic resistance. It is known under many names, including very large cancer-specific circular extrachromosomal DNA (ecDNA), which carries oncogenes and is often amplified in cancer cells. Our understanding of eccDNA has historically been limited and fragmented. To provide better a context of new and previous research on eccDNA, in this review we give an overview of the various names given to eccDNA at different times. We describe the different mechanisms for formation of eccDNA and the methods used to study eccDNA thus far. Finally, we explore the potential clinical value of eccDNA.
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Affiliation(s)
- Julie B Noer
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Oskar K Hørsdal
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Xi Xiang
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; Lars Bolund Institute of Regenerative Medicine, Qingdao-Europe Advanced Institute for Life Sciences, BGI-Shenzhen, Qingdao, China
| | - Yonglun Luo
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; Lars Bolund Institute of Regenerative Medicine, Qingdao-Europe Advanced Institute for Life Sciences, BGI-Shenzhen, Qingdao, China; Steno Diabetes Center Aarhus, Aarhus University Hospital, Aarhus, Denmark.
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9
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Zuo S, Yi Y, Wang C, Li X, Zhou M, Peng Q, Zhou J, Yang Y, He Q. Extrachromosomal Circular DNA (eccDNA): From Chaos to Function. Front Cell Dev Biol 2022; 9:792555. [PMID: 35083218 PMCID: PMC8785647 DOI: 10.3389/fcell.2021.792555] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Accepted: 12/16/2021] [Indexed: 11/15/2022] Open
Abstract
Extrachromosomal circular DNA (eccDNA) is a type of double-stranded circular DNA that is derived and free from chromosomes. It has a strong heterogeneity in sequence, length, and origin and has been identified in both normal and cancer cells. Although many studies suggested its potential roles in various physiological and pathological procedures including aging, telomere and rDNA maintenance, drug resistance, and tumorigenesis, the functional relevance of eccDNA remains to be elucidated. Recently, due to technological advancements, accumulated evidence highlighted that eccDNA plays an important role in cancers by regulating the expression of oncogenes, chromosome accessibility, genome replication, immune response, and cellular communications. Here, we review the features, biogenesis, physiological functions, potential functions in cancer, and research methods of eccDNAs with a focus on some open problems in the field and provide a perspective on how eccDNAs evolve specific functions out of the chaos in cells.
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Affiliation(s)
- Shanru Zuo
- Department of Pharmacy, The Third Xiangya Hospital, Central South University, Changsha, China.,The Key Laboratory of Model Animals and Stem Cell Biology in Hunan Province, School of Medicine, Hunan Normal University, Changsha, China
| | - Yihu Yi
- Department of Orthopaedics, Wuhan Union Hospital, Wuhan, China
| | - Chen Wang
- Department of Obstetrics and Gynecology, The Third Xiangya Hospital of Central South University, Changsha, China
| | - Xueguang Li
- The Key Laboratory of Model Animals and Stem Cell Biology in Hunan Province, School of Medicine, Hunan Normal University, Changsha, China
| | - Mingqing Zhou
- Zhongshan Hospital Affiliated to Sun Yat-Sen University, Zhongshan People's Hospital, Zhongshan, China
| | - Qiyao Peng
- Institute of Chinese Medicine, Hunan Academy of Traditional Chinese Medicine and Innovation Centre for Science and Technology, Hunan University of Chinese Medicine, Changsa, China.,Chongqing Key Laboratory for Pharmaceutical Metabolism Research, College of Pharmacy, College of Traditional Chinese Medicine, Chongqing Medical University, Chongqing, China
| | - Junhua Zhou
- The Key Laboratory of Model Animals and Stem Cell Biology in Hunan Province, School of Medicine, Hunan Normal University, Changsha, China
| | - Yide Yang
- The Key Laboratory of Model Animals and Stem Cell Biology in Hunan Province, School of Medicine, Hunan Normal University, Changsha, China
| | - Quanyuan He
- The Key Laboratory of Model Animals and Stem Cell Biology in Hunan Province, School of Medicine, Hunan Normal University, Changsha, China
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10
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Zhang P, Peng H, Llauro C, Bucher E, Mirouze M. ecc_finder: A Robust and Accurate Tool for Detecting Extrachromosomal Circular DNA From Sequencing Data. FRONTIERS IN PLANT SCIENCE 2021; 12:743742. [PMID: 34925397 PMCID: PMC8672306 DOI: 10.3389/fpls.2021.743742] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 10/25/2021] [Indexed: 06/06/2023]
Abstract
Extrachromosomal circular DNA (eccDNA) has been observed in different species for decades, and more and more evidence shows that this specific type of DNA molecules may play an important role in rapid adaptation. Therefore, characterizing the full landscape of eccDNA has become critical, and there are several protocols for enriching eccDNAs and performing short-read or long-read sequencing. However, there is currently no available bioinformatic tool to identify eccDNAs from Nanopore reads. More importantly, the current tools based on Illumina short reads lack an efficient standardized pipeline notably to identify eccDNA originating from repeated loci and cannot be applied to very large genomes. Here, we introduce a comprehensive tool to solve both of these two issues. Applying ecc_finder to eccDNA-seq data (either mobilome-seq, Circle-Seq and CIDER-seq) from Arabidopsis, human, and wheat (with genome sizes ranging from 120Mb to 17 Gb), we document the improvement of computational time, sensitivity, and accuracy and demonstrate ecc_finder wide applicability and functionality.
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Affiliation(s)
- Panpan Zhang
- Institut de Recherche pour le Développement (IRD), Montpellier, France
- Laboratory of Plant Genome and Development, University of Perpignan, Perpignan, France
| | - Haoran Peng
- Crop Genome Dynamics Group, Agroscope Changins, Nyon, Switzerland
- Department of Botany and Plant Biology, Section of Biology, Faculty of Science, University of Geneva, Geneva, Switzerland
| | - Christel Llauro
- Laboratory of Plant Genome and Development, University of Perpignan, Perpignan, France
- Laboratory of Plant Genome and Development, Centre National de la Recherche Scientifique (CNRS), Perpignan, France
| | - Etienne Bucher
- Crop Genome Dynamics Group, Agroscope Changins, Nyon, Switzerland
| | - Marie Mirouze
- Institut de Recherche pour le Développement (IRD), Montpellier, France
- Laboratory of Plant Genome and Development, University of Perpignan, Perpignan, France
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11
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Quantitative assessment reveals the dominance of duplicated sequences in germline-derived extrachromosomal circular DNA. Proc Natl Acad Sci U S A 2021; 118:2102842118. [PMID: 34789574 PMCID: PMC8617514 DOI: 10.1073/pnas.2102842118] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/04/2021] [Indexed: 01/08/2023] Open
Abstract
Extrachromosomal circular DNA (eccDNA) plays a role in human diseases such as cancer, but little is known about the impact of eccDNA in healthy human biology. Since eccDNA is a tiny fraction of nuclear DNA, artificial amplification has been employed to increase eccDNA amounts, resulting in the loss of native compositions. We developed an approach to enrich eccDNA populations at the native state (naïve small circular DNA, nscDNA) and investigated their origins in the human genome. We found that, in human sperm, the vast majority of nscDNA came from high-copy genomic regions, including the most variable regions between individuals. Because eccDNA can be incorporated back into chromosomes, eccDNA may promote human genetic variation. Extrachromosomal circular DNA (eccDNA) originates from linear chromosomal DNA in various human tissues under physiological and disease conditions. The genomic origins of eccDNA have largely been investigated using in vitro–amplified DNA. However, in vitro amplification obscures quantitative information by skewing the total population stoichiometry. In addition, the analyses have focused on eccDNA stemming from single-copy genomic regions, leaving eccDNA from multicopy regions unexamined. To address these issues, we isolated eccDNA without in vitro amplification (naïve small circular DNA, nscDNA) and assessed the populations quantitatively by integrated genomic, molecular, and cytogenetic approaches. nscDNA of up to tens of kilobases were successfully enriched by our approach and were predominantly derived from multicopy genomic regions including segmental duplications (SDs). SDs, which account for 5% of the human genome and are hotspots for copy number variations, were significantly overrepresented in sperm nscDNA, with three times more sequencing reads derived from SDs than from the entire single-copy regions. SDs were also overrepresented in mouse sperm nscDNA, which we estimated to comprise 0.2% of nuclear DNA. Considering that eccDNA can be integrated into chromosomes, germline-derived nscDNA may be a mediator of genome diversity.
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12
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Feliciello I, Pezer Ž, Kordiš D, Bruvo Mađarić B, Ugarković Đ. Evolutionary History of Alpha Satellite DNA Repeats Dispersed within Human Genome Euchromatin. Genome Biol Evol 2021; 12:2125-2138. [PMID: 33078196 PMCID: PMC7719264 DOI: 10.1093/gbe/evaa224] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/14/2020] [Indexed: 01/03/2023] Open
Abstract
Major human alpha satellite DNA repeats are preferentially assembled within (peri)centromeric regions but are also dispersed within euchromatin in the form of clustered or short single repeat arrays. To study the evolutionary history of single euchromatic human alpha satellite repeats (ARs), we analyzed their orthologous loci across the primate genomes. The continuous insertion of euchromatic ARs throughout the evolutionary history of primates starting with the ancestors of Simiformes (45-60 Ma) and continuing up to the ancestors of Homo is revealed. Once inserted, the euchromatic ARs were stably transmitted to the descendant species, some exhibiting copy number variation, whereas their sequence divergence followed the species phylogeny. Many euchromatic ARs have sequence characteristics of (peri)centromeric alpha repeats suggesting heterochromatin as a source of dispersed euchromatic ARs. The majority of euchromatic ARs are inserted in the vicinity of other repetitive elements such as L1, Alu, and ERV or are embedded within them. Irrespective of the insertion context, each AR insertion seems to be unique and once inserted, ARs do not seem to be subsequently spread to new genomic locations. In spite of association with (retro)transposable elements, there is no indication that such elements play a role in ARs proliferation. The presence of short duplications at most of ARs insertion sites suggests site-directed recombination between homologous motifs in ARs and in the target genomic sequence, probably mediated by extrachromosomal circular DNA, as a mechanism of spreading within euchromatin.
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Affiliation(s)
- Isidoro Feliciello
- Department of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia.,Dipartimento di Medicina Clinica e Chirurgia, Universita' degli Studi di Napoli Federico II, Italy
| | - Željka Pezer
- Department of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
| | - Dušan Kordiš
- Department of Molecular and Biomedical Sciences, Jožef Stefan Institute, Ljubljana, Slovenia
| | | | - Đurđica Ugarković
- Department of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
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13
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Wang T, Zhang H, Zhou Y, Shi J. Extrachromosomal circular DNA: a new potential role in cancer progression. J Transl Med 2021; 19:257. [PMID: 34112178 PMCID: PMC8194206 DOI: 10.1186/s12967-021-02927-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 06/04/2021] [Indexed: 12/15/2022] Open
Abstract
Extrachromosomal circular DNA (eccDNA) is considered a circular DNA molecule that exists widely in nature and is independent of conventional chromosomes. eccDNA can be divided into small polydispersed circular DNA (spcDNA), telomeric circles (t-circles), microDNA, and extrachromosomal DNA (ecDNA) according to its size and sequence. Multiple studies have shown that eccDNA is the product of genomic instability, has rich and important biological functions, and is involved in the occurrence of many diseases, including cancer. In this review, we focus on the discovery history, formation process, characteristics, and physiological functions of eccDNAs; the potential functions of various eccDNAs in human cancer; and the research methods employed to study eccDNA.
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Affiliation(s)
- Tianyi Wang
- Nantong Key Laboratory of Translational Medicine in Cardiothoracic Diseases, and Research Institution of Translational Medicine in Cardiothoracic Diseases, Affiliated Hospital of Nantong University, No. 20, Xisi Road, Nantong, 226001, Jiangsu, China.,Department of Thoracic Surgery, Affiliated Hospital of Nantong University, No. 20, Xisi Road, Nantong, 226001, Jiangsu, China
| | - Haijian Zhang
- Research Center of Clinical Medicine, Affiliated Hospital of Nantong University, No. 20, Xisi Road, Nantong, 226001, Jiangsu, China
| | - Youlang Zhou
- Research Center of Clinical Medicine, Affiliated Hospital of Nantong University, No. 20, Xisi Road, Nantong, 226001, Jiangsu, China
| | - Jiahai Shi
- Nantong Key Laboratory of Translational Medicine in Cardiothoracic Diseases, and Research Institution of Translational Medicine in Cardiothoracic Diseases, Affiliated Hospital of Nantong University, No. 20, Xisi Road, Nantong, 226001, Jiangsu, China. .,Department of Thoracic Surgery, Affiliated Hospital of Nantong University, No. 20, Xisi Road, Nantong, 226001, Jiangsu, China.
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14
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Qiu GH, Zheng X, Fu M, Huang C, Yang X. The decreased exclusion of nuclear eccDNA: From molecular and subcellular levels to human aging and age-related diseases. Ageing Res Rev 2021; 67:101306. [PMID: 33610814 DOI: 10.1016/j.arr.2021.101306] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 02/15/2021] [Accepted: 02/16/2021] [Indexed: 12/11/2022]
Abstract
Extrachromosomal circular DNA (eccDNA) accumulates within the nucleus of eukaryotic cells during physiological aging and in age-related diseases (ARDs) and the accumulation could be caused by the declined exclusion of nuclear eccDNA in these states. This review focuses on the formation of eccDNA and the roles of some main factors, such as nuclear pore complexes (NPCs), nucleoplasmic reticulum (NR), and nuclear actin, in eccDNA exclusion. eccDNAs are mostly formed from non-coding DNA during DNA damage repair. They move to NPCs along nuclear actin and are excluded out of the nucleus through functional NPCs in young and healthy cells. However, it has been demonstrated that defective NPCs, abnormal NPC components and nuclear actin rods are increased in aged cells, various cancers and certain other ARDs such as cardiovascular diseases, premature aging, neurodegenerative diseases and myopathies. Therefore, mainly resulting from the increase of dysfunctional NPCs, the exclusion of nuclear eccDNAs may be reduced and eccDNAs thus accumulate within the nucleus in aging and the aforementioned ARDs. In addition, the protective function of non-coding DNA in tumorigenesis is further discussed.
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Affiliation(s)
- Guo-Hua Qiu
- Fujian Provincial Key Laboratory for the Prevention and Control of Animal Infectious Diseases and Biotechnology, Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province Universities, College of Life Sciences, Longyan University, Longyan 364012, People's Republic of China.
| | - Xintian Zheng
- Fujian Provincial Key Laboratory for the Prevention and Control of Animal Infectious Diseases and Biotechnology, Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province Universities, College of Life Sciences, Longyan University, Longyan 364012, People's Republic of China
| | - Mingjun Fu
- Fujian Provincial Key Laboratory for the Prevention and Control of Animal Infectious Diseases and Biotechnology, Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province Universities, College of Life Sciences, Longyan University, Longyan 364012, People's Republic of China
| | - Cuiqin Huang
- Fujian Provincial Key Laboratory for the Prevention and Control of Animal Infectious Diseases and Biotechnology, Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province Universities, College of Life Sciences, Longyan University, Longyan 364012, People's Republic of China
| | - Xiaoyan Yang
- Fujian Provincial Key Laboratory for the Prevention and Control of Animal Infectious Diseases and Biotechnology, Key Laboratory of Preventive Veterinary Medicine and Biotechnology, Fujian Province Universities, College of Life Sciences, Longyan University, Longyan 364012, People's Republic of China
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15
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Wang Y, Huang R, Zheng G, Shen J. Small ring has big potential: insights into extrachromosomal DNA in cancer. Cancer Cell Int 2021; 21:236. [PMID: 33902601 PMCID: PMC8077740 DOI: 10.1186/s12935-021-01936-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Accepted: 04/13/2021] [Indexed: 12/23/2022] Open
Abstract
Recent technical advances have led to the discovery of novel functions of extrachromosomal DNA (ecDNA) in multiple cancer types. Studies have revealed that cancer-associated ecDNA shows a unique circular shape and contains oncogenes that are more frequently amplified than that in linear chromatin DNA. Importantly, the ecDNA-mediated amplification of oncogenes was frequently found in most cancers but rare in normal tissues. Multiple reports have shown that ecDNA has a profound impact on oncogene activation, genomic instability, drug sensitivity, tumor heterogeneity and tumor immunology, therefore may offer the potential for cancer diagnosis and therapeutics. Nevertheless, the underlying mechanisms and future applications of ecDNA remain to be determined. In this review, we summarize the basic concepts, biological functions and molecular mechanisms of ecDNA. We also provide novel insights into the fundamental role of ecDNA in cancer.
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Affiliation(s)
- Yihao Wang
- Department of Ophthalmology, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, 200025, China
- Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, 200025, China
| | - Rui Huang
- Department of Ophthalmology, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, 200025, China
- Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, 200025, China
| | - Guopei Zheng
- Department of Ophthalmology, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, 200025, China
- Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, 200025, China
| | - Jianfeng Shen
- Department of Ophthalmology, Ninth People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, 200025, China.
- Shanghai Key Laboratory of Orbital Diseases and Ocular Oncology, Shanghai, 200025, China.
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16
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Shiras A, Mondal A. Extrachromosomal DNA: Redefining the pathogenesis of glioblastoma. Biochim Biophys Acta Rev Cancer 2021; 1876:188551. [PMID: 33892052 DOI: 10.1016/j.bbcan.2021.188551] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 03/30/2021] [Accepted: 04/16/2021] [Indexed: 12/19/2022]
Abstract
Glioblastoma is an incurable most prevalent primary malignant brain tumor in adults. Surgery followed by radiotherapy with concomitant chemotherapy is the standard of care in patients with glioblastoma. Although, prognosis remains poor with a median survival in the range of 12-15 months. Over the decades of research has identified the gene mutation, angiogenesis, cell signaling for the development novel therapeutics. However, recent understanding on extrachromosomal DNA (ecDNA) put extra-layer of complexity in glioblastoma pathogenesis. These ecDNAs are present in significantly higher copy number in the nucleus of the cancer cells and contains several oncogenes which are instrumental for intra-tumoral genetic heterogeneity, accelerated tumor evolution and therapy resistance. In this review, we will discuss the current understanding on biogenesis, disease progression and potential therapeutic implications of ecDNAs in glioblastoma.
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Affiliation(s)
- Anjali Shiras
- Lab-03, Old Building, National Centre for Cell Science, Pune, India
| | - Abir Mondal
- Department of Life Sciences, Shiv Nadar University, India.
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17
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Wang M, Chen X, Yu F, Ding H, Zhang Y, Wang K. Extrachromosomal Circular DNAs: Origin, formation and emerging function in Cancer. Int J Biol Sci 2021; 17:1010-1025. [PMID: 33867825 PMCID: PMC8040306 DOI: 10.7150/ijbs.54614] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Accepted: 02/05/2021] [Indexed: 02/06/2023] Open
Abstract
The majority of cellular DNAs in eukaryotes are organized into linear chromosomes. In addition to chromosome DNAs, genes also reside on extrachromosomal elements. The extrachromosomal DNAs are commonly found to be circular, and they are referred to as extrachromosomal circular DNAs (eccDNAs). Recent technological advances have enriched our knowledge of eccDNA biology. There is currently increasing concern about the connection between eccDNA and cancer. Gene amplification on eccDNAs is prevalent in cancer. Moreover, eccDNAs commonly harbor oncogenes or drug resistance genes, hence providing a growth or survival advantage to cancer cells. eccDNAs play an important role in tumor heterogeneity and evolution, facilitating tumor adaptation to challenging circumstances. In addition, eccDNAs have recently been identified as cell-free DNAs in circulating system. The altered level of eccDNAs is observed in cancer patients relative to healthy controls. Particularly, eccDNAs are associated with cancer progression and poor outcomes. Thus, eccDNAs could be useful as novel biomarkers for the diagnosis and prognosis of cancer. In this review, we summarize current knowledge regarding the formation, characteristics and biological importance of eccDNAs, with a focus on the molecular mechanisms associated with their roles in cancer progression. We also discuss their potential applications in the detection and treatment of cancer. A better understanding of the functional role of eccDNAs in cancer would facilitate the comprehensive analysis of molecular mechanisms involved in cancer pathogenesis.
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Affiliation(s)
- Man Wang
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao 266021, China
| | - Xinzhe Chen
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao 266021, China
| | - Fei Yu
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao 266021, China
| | - Han Ding
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao 266021, China
| | - Yuan Zhang
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao 266021, China
| | - Kun Wang
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao 266021, China
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18
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Liang X, Chen H, Li L, An R, Komiyama M. Ring-Structured DNA and RNA as Key Players In Vivoand In Vitro. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20200235] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Xingguo Liang
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
- Laboratory for Marine Drugs and Bioproducts of Qingdao National Laboratory for Marine Science and Technology, Qingdao 266235, P. R. China
| | - Hui Chen
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
| | - Lin Li
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
| | - Ran An
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
| | - Makoto Komiyama
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, P. R. China
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19
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Lauria Sneideman MP, Meller VH. Drosophila Satellite Repeats at the Intersection of Chromatin, Gene Regulation and Evolution. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2021; 60:1-26. [PMID: 34386870 DOI: 10.1007/978-3-030-74889-0_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Satellite repeats make up a large fraction of the genomes of many higher eukaryotes. Until recently these sequences were viewed as molecular parasites with few functions. Drosophila melanogaster and related species have a wealth of diverse satellite repeats. Comparative studies of Drosophilids have been instrumental in understanding how these rapidly evolving sequences change and move. Remarkably, satellite repeats have been found to modulate gene expression and mediate genetic conflicts between chromosomes and between closely related fly species. This suggests that satellites play a key role in speciation. We have taken advantage of the depth of research on satellite repeats in flies to review the known functions of these sequences and consider their central role in evolution and gene expression.
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Affiliation(s)
| | - Victoria H Meller
- Department of Biological Sciences, Wayne State University, Detroit, MI, USA.
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20
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Feliciello I, Pezer Ž, Sermek A, Bruvo Mađarić B, Ljubić S, Ugarković Đ. Satellite DNA-Mediated Gene Expression Regulation: Physiological and Evolutionary Implication. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2021; 60:145-167. [PMID: 34386875 DOI: 10.1007/978-3-030-74889-0_6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Satellite DNAs are tandemly repeated sequences organized in large clusters within (peri)centromeric and/or subtelomeric heterochromatin. However, in many species, satellite DNAs are not restricted to heterochromatin but are also dispersed as short arrays within euchromatin. Such genomic organization together with transcriptional activity seems to be a prerequisite for the gene-modulatory effect of satellite DNAs which was first demonstrated in the beetle Tribolium castaneum upon heat stress. Namely, enrichment of a silent histone mark at euchromatic repeats of a major beetle satellite DNA results in epigenetic silencing of neighboring genes. In addition, human satellite III transcripts induced by heat shock contribute to genome-wide gene silencing, providing protection against stress-induced cell death. Gene silencing mediated by satellite RNA was also shown to be fundamental for the early embryonic development of the mosquito Aedes aegypti. Apart from a physiological role during embryogenesis and heat stress response, activation of satellite DNAs in terms of transcription and proliferation can have an evolutionary impact. Spreading of satellite repeats throughout euchromatin promotes the variation of epigenetic landscapes and gene expression diversity, contributing to the evolution of gene regulatory networks and to genome adaptation in fluctuating environmental conditions.
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Affiliation(s)
- Isidoro Feliciello
- Department of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia.,Dipartimento di Medicina Clinica e Chirurgia, Universita' degli Studi di Napoli Federico II, Naples, Italy
| | - Željka Pezer
- Department of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
| | - Antonio Sermek
- Department of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
| | | | - Sven Ljubić
- Department of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
| | - Đurđica Ugarković
- Department of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia.
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21
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Xing J, Ning Q, Tang D, Mo Z, Lei X, Tang S. Progress on the role of extrachromosomal DNA in tumor pathogenesis and evolution. Clin Genet 2020; 99:503-512. [PMID: 33314031 DOI: 10.1111/cge.13896] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 12/03/2020] [Accepted: 12/09/2020] [Indexed: 12/23/2022]
Abstract
The amplification of oncogenes on extrachromosomal DNA (ecDNA) provides a new mechanism for cancer cells to adapt to the changes in the tumor microenvironment and accelerate tumor evolution. These extrachromosomal elements contain oncogenes, and their chromatin structures are more open than linear chromosomes and therefore have stronger oncogene transcriptional activity. ecDNA always contains enhancer elements, and genes on ecDNA can be reintegrated into the linear genome to regulate the selective expression of genes. ecDNA lacks centromeres, and the inheritance from the parent cell to the daughter cell is uneven. This non-Mendelian genetic mechanism results in the increase of tumor heterogeneity with daughter cells that can gain a competitive advantage through a large number of copies of oncogenes. ecDNA promotes tumor invasiveness and provides a mechanism for drug resistance associated with poorer survival outcomes. Recent studies have demonstrated that the overall proportion of ecDNA in tumors is approximately 40%. In this review, we summarize the current knowledge of ecDNA in the field of tumorigenesis and development.
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Affiliation(s)
- Jichen Xing
- Hunan Provincial Key Laboratory of Tumor Microenvironment Responsive Drug Research, and Institute of Pharmacy & Pharmacology, University of South China, Hengyang, China.,Hunan Province Key Laboratory for Antibody-Based Drug and Intelligent Delivery System, Hunan University of Medicine, Huaihua, China
| | - Qian Ning
- Hunan Province Key Laboratory for Antibody-Based Drug and Intelligent Delivery System, Hunan University of Medicine, Huaihua, China
| | - Diya Tang
- Department of Medical Oncology, Xiangya Hospital Central South University, Changsha, China
| | - Zhongcheng Mo
- Institute of Basic Medical Sciences, College of Basic Medicine, Guilin Medical University, Guilin, Guangxi, China
| | - Xiaoyong Lei
- Hunan Provincial Key Laboratory of Tumor Microenvironment Responsive Drug Research, and Institute of Pharmacy & Pharmacology, University of South China, Hengyang, China
| | - Shengsong Tang
- Hunan Provincial Key Laboratory of Tumor Microenvironment Responsive Drug Research, and Institute of Pharmacy & Pharmacology, University of South China, Hengyang, China.,Hunan Province Key Laboratory for Antibody-Based Drug and Intelligent Delivery System, Hunan University of Medicine, Huaihua, China
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22
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Yan Y, Guo G, Huang J, Gao M, Zhu Q, Zeng S, Gong Z, Xu Z. Current understanding of extrachromosomal circular DNA in cancer pathogenesis and therapeutic resistance. J Hematol Oncol 2020; 13:124. [PMID: 32928268 PMCID: PMC7491193 DOI: 10.1186/s13045-020-00960-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 09/03/2020] [Indexed: 02/08/2023] Open
Abstract
Extrachromosomal circular DNA was recently found to be particularly abundant in multiple human cancer cells, although its frequency varies among different tumor types. Elevated levels of extrachromosomal circular DNA have been considered an effective biomarker of cancer pathogenesis. Multiple reports have demonstrated that the amplification of oncogenes and therapeutic resistance genes located on extrachromosomal DNA is a frequent event that drives intratumoral genetic heterogeneity and provides a potential evolutionary advantage. This review highlights the current understanding of the extrachromosomal circular DNA present in the tissues and circulation of patients with advanced cancers and provides a detailed discussion of their substantial roles in tumor regulation. Confirming the presence of cancer-related extrachromosomal circular DNA would provide a putative testing strategy for the precision diagnosis and treatment of human malignancies in clinical practice.
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Affiliation(s)
- Yuanliang Yan
- Department of Pharmacy, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China.,Department of Oncology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Guijie Guo
- Department of Oncology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Jinzhou Huang
- Department of Oncology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Ming Gao
- Department of Oncology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Qian Zhu
- Department of Oncology, Mayo Clinic, Rochester, MN, 55905, USA
| | - Shuangshuang Zeng
- Department of Pharmacy, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
| | - Zhicheng Gong
- Department of Pharmacy, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
| | - Zhijie Xu
- Department of Pathology, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China. .,National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China.
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23
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Sproul JS, Khost DE, Eickbush DG, Negm S, Wei X, Wong I, Larracuente AM. Dynamic Evolution of Euchromatic Satellites on the X Chromosome in Drosophila melanogaster and the simulans Clade. Mol Biol Evol 2020; 37:2241-2256. [PMID: 32191304 PMCID: PMC7403614 DOI: 10.1093/molbev/msaa078] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Satellite DNAs (satDNAs) are among the most dynamically evolving components of eukaryotic genomes and play important roles in genome regulation, genome evolution, and speciation. Despite their abundance and functional impact, we know little about the evolutionary dynamics and molecular mechanisms that shape satDNA distributions in genomes. Here, we use high-quality genome assemblies to study the evolutionary dynamics of two complex satDNAs, Rsp-like and 1.688 g/cm3, in Drosophila melanogaster and its three nearest relatives in the simulans clade. We show that large blocks of these repeats are highly dynamic in the heterochromatin, where their genomic location varies across species. We discovered that small blocks of satDNA that are abundant in X chromosome euchromatin are similarly dynamic, with repeats changing in abundance, location, and composition among species. We detail the proliferation of a rare satellite (Rsp-like) across the X chromosome in D. simulans and D. mauritiana. Rsp-like spread by inserting into existing clusters of the older, more abundant 1.688 satellite, in events likely facilitated by microhomology-mediated repair pathways. We show that Rsp-like is abundant on extrachromosomal circular DNA in D. simulans, which may have contributed to its dynamic evolution. Intralocus satDNA expansions via unequal exchange and the movement of higher order repeats also contribute to the fluidity of the repeat landscape. We find evidence that euchromatic satDNA repeats experience cycles of proliferation and diversification somewhat analogous to bursts of transposable element proliferation. Our study lays a foundation for mechanistic studies of satDNA proliferation and the functional and evolutionary consequences of satDNA movement.
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Affiliation(s)
- John S Sproul
- Department of Biology, University of Rochester, Rochester, NY
| | | | | | - Sherif Negm
- Department of Biology, University of Rochester, Rochester, NY
| | - Xiaolu Wei
- Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, NY
| | - Isaac Wong
- Department of Biology, University of Rochester, Rochester, NY
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24
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Liao Z, Jiang W, Ye L, Li T, Yu X, Liu L. Classification of extrachromosomal circular DNA with a focus on the role of extrachromosomal DNA (ecDNA) in tumor heterogeneity and progression. Biochim Biophys Acta Rev Cancer 2020; 1874:188392. [PMID: 32735964 DOI: 10.1016/j.bbcan.2020.188392] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 06/26/2020] [Accepted: 07/10/2020] [Indexed: 02/08/2023]
Abstract
Although the eukaryotic genome is mainly comprised of linear chromosomal DNA, genes can also be found outside of chromosomes. The unconventional presence of extrachromosomal genes is usually found to be circular, and these structures are named extrachromosomal circular DNA (eccDNA), which are often observed in cancer cells. Various types of eccDNA including small polydispersed DNA (spcDNA), telomeric cirlces, microDNA, etc. have been discovered. Among these eccDNA, extrachromosomal DNA (ecDNA), which encompasses the full spectrum of large, gene-containing extrachromosomal particles, has regained great research interest due to recent technological advances such as next-generation sequencing and super-resolution microscopy. In this review, we summarize the different types of eccDNA and discuss the role of eccDNA, especially ecDNA in tumor heterogeneity and progression. Additionally, we discuss some possible future investigative directions related to ecDNA biogenesis and its clinical application.
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Affiliation(s)
- Zhenyu Liao
- Department of Pancreatic Surgery, Shanghai Cancer Centre, Fudan University, Shanghai, China; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Pancreatic Cancer Institute, Shanghai, China; Pancreatic Cancer Institute, Fudan University, Shanghai, China
| | - Wang Jiang
- Department of Pancreatic Surgery, Shanghai Cancer Centre, Fudan University, Shanghai, China; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Pancreatic Cancer Institute, Shanghai, China; Pancreatic Cancer Institute, Fudan University, Shanghai, China
| | - Longyun Ye
- Department of Pancreatic Surgery, Shanghai Cancer Centre, Fudan University, Shanghai, China; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Pancreatic Cancer Institute, Shanghai, China; Pancreatic Cancer Institute, Fudan University, Shanghai, China
| | - Tianjiao Li
- Department of Pancreatic Surgery, Shanghai Cancer Centre, Fudan University, Shanghai, China; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Pancreatic Cancer Institute, Shanghai, China; Pancreatic Cancer Institute, Fudan University, Shanghai, China
| | - Xianjun Yu
- Department of Pancreatic Surgery, Shanghai Cancer Centre, Fudan University, Shanghai, China; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Pancreatic Cancer Institute, Shanghai, China; Pancreatic Cancer Institute, Fudan University, Shanghai, China.
| | - Liang Liu
- Department of Pancreatic Surgery, Shanghai Cancer Centre, Fudan University, Shanghai, China; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, China; Shanghai Pancreatic Cancer Institute, Shanghai, China; Pancreatic Cancer Institute, Fudan University, Shanghai, China.
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Ain Q, Schmeer C, Wengerodt D, Witte OW, Kretz A. Extrachromosomal Circular DNA: Current Knowledge and Implications for CNS Aging and Neurodegeneration. Int J Mol Sci 2020; 21:E2477. [PMID: 32252492 PMCID: PMC7177960 DOI: 10.3390/ijms21072477] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 03/26/2020] [Accepted: 03/30/2020] [Indexed: 12/13/2022] Open
Abstract
Still unresolved is the question of how a lifetime accumulation of somatic gene copy number alterations impact organ functionality and aging and age-related pathologies. Such an issue appears particularly relevant in the broadly post-mitotic central nervous system (CNS), where non-replicative neurons are restricted in DNA-repair choices and are prone to accumulate DNA damage, as they remain unreplaced over a lifetime. Both DNA injuries and consecutive DNA-repair strategies are processes that can evoke extrachromosomal circular DNA species, apparently from either part of the genome. Due to their capacity to amplify gene copies and related transcripts, the individual cellular load of extrachromosomal circular DNAs will contribute to a dynamic pool of additional coding and regulatory chromatin elements. Analogous to tumor tissues, where the mosaicism of circular DNAs plays a well-characterized role in oncogene plasticity and drug resistance, we suggest involvement of the "circulome" also in the CNS. Accordingly, we summarize current knowledge on the molecular biogenesis, homeostasis and gene regulatory impacts of circular extrachromosomal DNA and propose, in light of recent discoveries, a critical role in CNS aging and neurodegeneration. Future studies will elucidate the influence of individual extrachromosomal DNA species according to their sequence complexity and regional distribution or cell-type-specific abundance.
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Affiliation(s)
- Quratul Ain
- Hans-Berger Department of Neurology, Jena University Hospital, 07747 Jena, Thuringia, Germany; (Q.A.); (C.S.); (D.W.); (O.W.W.)
| | - Christian Schmeer
- Hans-Berger Department of Neurology, Jena University Hospital, 07747 Jena, Thuringia, Germany; (Q.A.); (C.S.); (D.W.); (O.W.W.)
- Jena Center for Healthy Ageing, Jena University Hospital, 07747 Jena, Thuringia, Germany
| | - Diane Wengerodt
- Hans-Berger Department of Neurology, Jena University Hospital, 07747 Jena, Thuringia, Germany; (Q.A.); (C.S.); (D.W.); (O.W.W.)
| | - Otto W. Witte
- Hans-Berger Department of Neurology, Jena University Hospital, 07747 Jena, Thuringia, Germany; (Q.A.); (C.S.); (D.W.); (O.W.W.)
- Jena Center for Healthy Ageing, Jena University Hospital, 07747 Jena, Thuringia, Germany
| | - Alexandra Kretz
- Hans-Berger Department of Neurology, Jena University Hospital, 07747 Jena, Thuringia, Germany; (Q.A.); (C.S.); (D.W.); (O.W.W.)
- Jena Center for Healthy Ageing, Jena University Hospital, 07747 Jena, Thuringia, Germany
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Yerlici VT, Lu MW, Hoge CR, Miller RV, Neme R, Khurana JS, Bracht JR, Landweber LF. Programmed genome rearrangements in Oxytricha produce transcriptionally active extrachromosomal circular DNA. Nucleic Acids Res 2019; 47:9741-9760. [PMID: 31504770 PMCID: PMC6765146 DOI: 10.1093/nar/gkz725] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 08/02/2019] [Accepted: 08/20/2019] [Indexed: 11/13/2022] Open
Abstract
Extrachromosomal circular DNA (eccDNA) is both a driver of eukaryotic genome instability and a product of programmed genome rearrangements, but its extent had not been surveyed in Oxytricha, a ciliate with elaborate DNA elimination and translocation during development. Here, we captured rearrangement-specific circular DNA molecules across the genome to gain insight into its processes of programmed genome rearrangement. We recovered thousands of circularly excised Tc1/mariner-type transposable elements and high confidence non-repetitive germline-limited loci. We verified their bona fide circular topology using circular DNA deep-sequencing, 2D gel electrophoresis and inverse polymerase chain reaction. In contrast to the precise circular excision of transposable elements, we report widespread heterogeneity in the circular excision of non-repetitive germline-limited loci. We also demonstrate that circular DNAs are transcribed in Oxytricha, producing rearrangement-specific long non-coding RNAs. The programmed formation of thousands of eccDNA molecules makes Oxytricha a model system for studying nucleic acid topology. It also suggests involvement of eccDNA in programmed genome rearrangement.
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Affiliation(s)
- V Talya Yerlici
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.,Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Michael W Lu
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.,Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Carla R Hoge
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Richard V Miller
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.,Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Rafik Neme
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Jaspreet S Khurana
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - John R Bracht
- Department of Biology, American University, Washington, DC 20016, USA
| | - Laura F Landweber
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.,Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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Tandon I, Pal R, Pal JK, Sharma NK. Extrachromosomal circular DNAs: an extra piece of evidence to depict tumor heterogeneity. Future Sci OA 2019; 5:FSO390. [PMID: 31285839 PMCID: PMC6609892 DOI: 10.2144/fsoa-2019-0024] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The tumor microenvironment (TME) comprises a heterogeneous number and type of cellular and noncellular components that vary in the context of molecular, genomic and epigenomic levels. The genotypic diversity and plasticity within cancer cells are known to be affected by genomic instability and genome alterations. Besides genomic instability within the chromosomal linear DNA, an extra factor appears in the form of extrachromosomal circular DNAs (eccDNAs; 2-20 kbp) and microDNAs (200-400 bp). This extra heterogeneity within cancer cells in the form of an abundance of eccDNAs adds another dimension to the expression of procancer players, such as oncoproteins, acting as a driver for cancer cell survival and proliferation. This article reviews research into eccDNAs centering around cancer plasticity and hallmarks, and discusses these facts in light of therapeutics and biomarker development.
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Affiliation(s)
- Ishita Tandon
- Cancer & Translational Research Lab, Dr DY Patil Biotechnology & Bioinformatics Institute, Dr DY Patil Vidyapeeth, Pune, Maharashtra 411033, India
| | - Roshni Pal
- Cancer & Translational Research Lab, Dr DY Patil Biotechnology & Bioinformatics Institute, Dr DY Patil Vidyapeeth, Pune, Maharashtra 411033, India
| | - Jayanta K Pal
- Cancer & Translational Research Lab, Dr DY Patil Biotechnology & Bioinformatics Institute, Dr DY Patil Vidyapeeth, Pune, Maharashtra 411033, India
| | - Nilesh K Sharma
- Cancer & Translational Research Lab, Dr DY Patil Biotechnology & Bioinformatics Institute, Dr DY Patil Vidyapeeth, Pune, Maharashtra 411033, India
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Zhu J, Zhang F, Du M, Zhang P, Fu S, Wang L. Molecular characterization of cell-free eccDNAs in human plasma. Sci Rep 2017; 7:10968. [PMID: 28887493 PMCID: PMC5591271 DOI: 10.1038/s41598-017-11368-w] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 08/23/2017] [Indexed: 12/18/2022] Open
Abstract
Extrachromosomal circular DNAs (eccDNAs) have been reported in most eukaryotes. However, little is known about the cell-free eccDNA profiles in circulating system such as blood. To characterize plasma cell-free eccDNAs, we performed sequencing analysis in 26 libraries from three blood donors and negative controls. We identified thousands of unique plasma eccDNAs in the three subjects. We observed proportional eccDNA increase with initial DNA input. The detected eccDNAs were also associated with circular DNA enrichment efficiency. Increasing the sequencing depth in an additional sample identified many more eccDNAs with highly heterogenous molecular structure. Size distribution of eccDNAs varied significantly from 31 bp to 19,989 bp. We found significantly higher GC content in smaller eccDNAs (<500 bp) than the larger ones (>500 bp) (p < 0.01). We also found an enrichment of eccDNAs at exons and 3′UTR (enrichment folds from 1.36 to 3.1) as well as the DNase hypersensitive sites (1.58–2.42 fold), H3K4Me1 (1.23–1.42 fold) and H3K27Ac (1.33–1.62 fold) marks. Junction sequence analysis suggested fundamental role of nonhomologous end joining mechanism during eccDNA formation. Further characterization of the extracellular eccDNAs in peripheral blood will facilitate understanding of their molecular mechanisms and potential clinical utilities.
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Affiliation(s)
- Jing Zhu
- Laboratory of Medical Genetics, Harbin Medical University, Harbin, Heilongjiang, 150081, China.,Department of Pathology and MCW Cancer Center, Medical College of Wisconsin, Milwaukee, WI, 53226, USA
| | - Fan Zhang
- School of Computer Science and Technology, Harbin Institute of Technology, Harbin, Heilongjiang, 150001, China
| | - Meijun Du
- Department of Pathology and MCW Cancer Center, Medical College of Wisconsin, Milwaukee, WI, 53226, USA
| | - Peng Zhang
- Department of Pathology and MCW Cancer Center, Medical College of Wisconsin, Milwaukee, WI, 53226, USA
| | - Songbin Fu
- Laboratory of Medical Genetics, Harbin Medical University, Harbin, Heilongjiang, 150081, China
| | - Liang Wang
- Department of Pathology and MCW Cancer Center, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.
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Lithium promotes DNA stability and survival of ischemic retinal neurocytes by upregulating DNA ligase IV. Cell Death Dis 2016; 7:e2473. [PMID: 27853172 PMCID: PMC5260892 DOI: 10.1038/cddis.2016.341] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 09/08/2016] [Accepted: 09/13/2016] [Indexed: 02/01/2023]
Abstract
Neurons display genomic fragility and show fragmented DNA in pathological degeneration. A failure to repair DNA breaks may result in cell death or apoptosis. Lithium protects retinal neurocytes following nutrient deprivation or partial nerve crush, but the underlying mechanisms are not well defined. Here we demonstrate that pretreatment with lithium protects retinal neurocytes from ischemia-induced damage and enhances light response in rat retina following ischemia–reperfusion injury. Moreover, we found that DNA nonhomologous end-joining (NHEJ) repair is implicated in this process because in ischemic retinal neurocytes, lithium significantly reduces the number of γ-H2AX foci (well-characterized markers of DNA double-strand breaks in situ) and increases the DNA ligase IV expression level. Furthermore, we also demonstrate that nuclear respiratory factor 1 (Nrf-1) and phosphorylated cyclic AMP-response element binding protein-1 (P-CREB1) bind to ligase IV promoter to cause upregulation of ligase IV in neurocytes. The ischemic upregulation of Nrf-1 and lithium-induced increase of P-CREB1 cooperate to promote transcription of ligase IV. Short hairpin RNAs against Nrf-1 and CREB1 could significantly inhibit the increase in promoter activity and expression of ligase IV observed in the control oligos following lithium treatment in retinal neurocytes. More importantly, ischemic stimulation triggers the expression of ligase IV. Taken together, our results thus reveal a novel mechanism that lithium offers neuroprotection from ischemia-induced damage by enhancing DNA NHEJ repair.
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Bersani F, Lee E, Kharchenko PV, Xu AW, Liu M, Xega K, MacKenzie OC, Brannigan BW, Wittner BS, Jung H, Ramaswamy S, Park PJ, Maheswaran S, Ting DT, Haber DA. Pericentromeric satellite repeat expansions through RNA-derived DNA intermediates in cancer. Proc Natl Acad Sci U S A 2015; 112:15148-53. [PMID: 26575630 PMCID: PMC4679016 DOI: 10.1073/pnas.1518008112] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Aberrant transcription of the pericentromeric human satellite II (HSATII) repeat is present in a wide variety of epithelial cancers. In deriving experimental systems to study its deregulation, we observed that HSATII expression is induced in colon cancer cells cultured as xenografts or under nonadherent conditions in vitro, but it is rapidly lost in standard 2D cultures. Unexpectedly, physiological induction of endogenous HSATII RNA, as well as introduction of synthetic HSATII transcripts, generated cDNA intermediates in the form of DNA/RNA hybrids. Single molecule sequencing of tumor xenografts showed that HSATII RNA-derived DNA (rdDNA) molecules are stably incorporated within pericentromeric loci. Suppression of RT activity using small molecule inhibitors reduced HSATII copy gain. Analysis of whole-genome sequencing data revealed that HSATII copy number gain is a common feature in primary human colon tumors and is associated with a lower overall survival. Together, our observations suggest that cancer-associated derepression of specific repetitive sequences can promote their RNA-driven genomic expansion, with potential implications on pericentromeric architecture.
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Affiliation(s)
- Francesca Bersani
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129
| | - Eunjung Lee
- Center for Biomedical Informatics, Harvard Medical School, Boston, MA 02115; Division of Genetics, Brigham and Women's Hospital, Boston, MA 02115
| | - Peter V Kharchenko
- Center for Biomedical Informatics, Harvard Medical School, Boston, MA 02115; Hematology/Oncology Program, Children's Hospital, Boston, MA 02115
| | - Andrew W Xu
- Center for Biomedical Informatics, Harvard Medical School, Boston, MA 02115
| | - Mingzhu Liu
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129; Howard Hughes Medical Institute, Chevy Chase, MD 20815
| | - Kristina Xega
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129
| | - Olivia C MacKenzie
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129
| | - Brian W Brannigan
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129
| | - Ben S Wittner
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129
| | | | - Sridhar Ramaswamy
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129; Department of Medicine, Massachusetts General Hospital, Boston, MA 02114
| | - Peter J Park
- Center for Biomedical Informatics, Harvard Medical School, Boston, MA 02115; Division of Genetics, Brigham and Women's Hospital, Boston, MA 02115; Informatics Program, Children's Hospital, Boston, MA 02115
| | - Shyamala Maheswaran
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129; Department of Surgery, Massachusetts General Hospital, Boston, MA 02114
| | - David T Ting
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129; Department of Medicine, Massachusetts General Hospital, Boston, MA 02114;
| | - Daniel A Haber
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129; Howard Hughes Medical Institute, Chevy Chase, MD 20815; Department of Medicine, Massachusetts General Hospital, Boston, MA 02114;
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31
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Schneider JS, Cheng X, Zhao Q, Underbayev C, Gonzalez JP, Raveche ES, Fraidenraich D, Ivessa AS. Reversible mitochondrial DNA accumulation in nuclei of pluripotent stem cells. Stem Cells Dev 2014; 23:2712-9. [PMID: 24964274 DOI: 10.1089/scd.2013.0630] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
According to the endosymbiotic hypothesis, the precursor of mitochondria invaded the precursor of eukaryotic cells, a process that began roughly 2 billion years ago. Since then, the majority of the genetic material translocated from the mitochondria to the nucleus, where now almost all mitochondrial proteins are expressed. Only a tiny amount of DNA remained in the mitochondria, known as mitochondrial DNA (mtDNA). In this study, we report that the transfer of mtDNA fragments to the nucleus of pluripotent stem cells is still ongoing. We show by in situ hybridization and agarose DNA two-dimensional gel technique that induced pluripotent stem (iPS) cells contain high levels of mtDNA in the nucleus. We found that a large proportion of the accumulated mtDNA sequences appear to be extrachromosomal. Accumulation of mtDNA in the nucleus is present not only in the iPS cells, but also in embryonic stem (ES) cells. However upon differentiation, the level of mtDNA in the nuclei of iPS and ES cells is substantially reduced. This reversible accumulation of mtDNA in the nucleus supports the notion that the nuclear copy number of mtDNA sequences may provide a novel mechanism by which chromosomal DNA is dynamically regulated in pluripotent stem cells.
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Affiliation(s)
- Joel S Schneider
- 1 Department of Cell Biology and Molecular Medicine, Rutgers Biomedical and Health Sciences , Newark, New Jersey
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32
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Interstitial telomeric repeats are enriched in the centromeres of chromosomes in Solanum species. Chromosome Res 2012; 21:5-13. [PMID: 23250588 DOI: 10.1007/s10577-012-9332-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2012] [Revised: 11/27/2012] [Accepted: 12/06/2012] [Indexed: 01/05/2023]
Abstract
Interstitial telomeric repeats (ITRs) were reported in a number of animal and plant species. Most ITRs are organized as short tandem arrays and are likely evolutionary relics derived from chromosomal rearrangements and DNA repairs. However, megabase-sized ITR arrays were reported in Solanum species. Here, we report a fluorescence in situ hybridization (FISH) survey of ITRs in all representative diploid Solanum species, including potato, tomato, and eggplant. FISH revealed massive amplification of ITRs in the centromeric regions of chromosomes from the Solanum species containing the B and P genomes. A significant proportion of the ITR FISH signals was mapped within the primary constrictions of the pachytene chromosomes of Solanum pinnatisectum (B genome). In addition, some ITR sites overlapped with St49, a satellite repeat enriched in centromeric DNA sequences associated with CENH3 nucleosomes, in both A and B genome Solanum species. These results show that some ITR subfamilies have been amplified and invaded in the functional centromeres of chromosomes in Solanum species.
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Gong Z, Wu Y, Koblížková A, Torres GA, Wang K, Iovene M, Neumann P, Zhang W, Novák P, Buell CR, Macas J, Jiang J. Repeatless and repeat-based centromeres in potato: implications for centromere evolution. THE PLANT CELL 2012; 24:3559-74. [PMID: 22968715 PMCID: PMC3480287 DOI: 10.1105/tpc.112.100511] [Citation(s) in RCA: 173] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Revised: 08/18/2012] [Accepted: 08/30/2012] [Indexed: 05/18/2023]
Abstract
Centromeres in most higher eukaryotes are composed of long arrays of satellite repeats. By contrast, most newly formed centromeres (neocentromeres) do not contain satellite repeats and instead include DNA sequences representative of the genome. An unknown question in centromere evolution is how satellite repeat-based centromeres evolve from neocentromeres. We conducted a genome-wide characterization of sequences associated with CENH3 nucleosomes in potato (Solanum tuberosum). Five potato centromeres (Cen4, Cen6, Cen10, Cen11, and Cen12) consisted primarily of single- or low-copy DNA sequences. No satellite repeats were identified in these five centromeres. At least one transcribed gene was associated with CENH3 nucleosomes. Thus, these five centromeres structurally resemble neocentromeres. By contrast, six potato centromeres (Cen1, Cen2, Cen3, Cen5, Cen7, and Cen8) contained megabase-sized satellite repeat arrays that are unique to individual centromeres. The satellite repeat arrays likely span the entire functional cores of these six centromeres. At least four of the centromeric repeats were amplified from retrotransposon-related sequences and were not detected in Solanum species closely related to potato. The presence of two distinct types of centromeres, coupled with the boom-and-bust cycles of centromeric satellite repeats in Solanum species, suggests that repeat-based centromeres can rapidly evolve from neocentromeres by de novo amplification and insertion of satellite repeats in the CENH3 domains.
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Affiliation(s)
- Zhiyun Gong
- Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706
- Key Laboratory of Crop Genetics and Physiology of Jiangsu Province/Key Laboratory of Plant Functional Genomics of Ministry of Education, Yangzhou University, Yangzhou 225009, China
| | - Yufeng Wu
- Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706
| | - Andrea Koblížková
- Institute of Plant Molecular Biology, Biology Centre, Academy of Sciences of the Czech Republic, CZ-37005 Ceske Budejovice, Czech Republic
| | - Giovana A. Torres
- Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706
- Departmento de Biologia, Universidade Federal de Lavras, Lavras, Minas Gerais 37200, Brazil
| | - Kai Wang
- Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706
| | - Marina Iovene
- Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706
| | - Pavel Neumann
- Institute of Plant Molecular Biology, Biology Centre, Academy of Sciences of the Czech Republic, CZ-37005 Ceske Budejovice, Czech Republic
| | - Wenli Zhang
- Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706
| | - Petr Novák
- Institute of Plant Molecular Biology, Biology Centre, Academy of Sciences of the Czech Republic, CZ-37005 Ceske Budejovice, Czech Republic
| | - C. Robin Buell
- Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824
| | - Jiří Macas
- Institute of Plant Molecular Biology, Biology Centre, Academy of Sciences of the Czech Republic, CZ-37005 Ceske Budejovice, Czech Republic
| | - Jiming Jiang
- Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706
- Address correspondence to
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Cohen S, Agmon N, Sobol O, Segal D. Extrachromosomal circles of satellite repeats and 5S ribosomal DNA in human cells. Mob DNA 2010; 1:11. [PMID: 20226008 PMCID: PMC3225859 DOI: 10.1186/1759-8753-1-11] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Accepted: 03/08/2010] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Extrachomosomal circular DNA (eccDNA) is ubiquitous in eukaryotic organisms and was detected in every organism tested, including in humans. A two-dimensional gel electrophoresis facilitates the detection of eccDNA in preparations of genomic DNA. Using this technique we have previously demonstrated that most of eccDNA consists of exact multiples of chromosomal tandemly repeated DNA, including both coding genes and satellite DNA. RESULTS Here we report the occurrence of eccDNA in every tested human cell line. It has heterogeneous mass ranging from less than 2 kb to over 20 kb. We describe eccDNA homologous to human alpha satellite and the SstI mega satellite. Moreover, we show, for the first time, circular multimers of the human 5S ribosomal DNA (rDNA), similar to previous findings in Drosophila and plants. We further demonstrate structures that correspond to intermediates of rolling circle replication, which emerge from the circular multimers of 5S rDNA and SstI satellite. CONCLUSIONS These findings, and previous reports, support the general notion that every chromosomal tandem repeat is prone to generate eccDNA in eukryoric organisms including humans. They suggest the possible involvement of eccDNA in the length variability observed in arrays of tandem repeats. The implications of eccDNA on genome biology may include mechanisms of centromere evolution, concerted evolution and homogenization of tandem repeats and genomic plasticity.
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Affiliation(s)
- Sarit Cohen
- Department of Molecular Microbiology & Biotechnology Tel-Aviv University, Tel-Aviv 69978, Israel.
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35
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Cohen Z, Lavi S. Replication independent formation of extrachromosomal circular DNA in mammalian cell-free system. PLoS One 2009; 4:e6126. [PMID: 19568438 PMCID: PMC2699479 DOI: 10.1371/journal.pone.0006126] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2009] [Accepted: 05/29/2009] [Indexed: 02/06/2023] Open
Abstract
Extrachromosomal circular DNA (eccDNA) is a pool of circular double stranded DNA molecules found in all eukaryotic cells and composed of repeated chromosomal sequences. It was proposed to be involved in genomic instability, aging and alternative telomere lengthening. Our study presents novel mammalian cell-free system for eccDNA generation. Using purified protein extract we show that eccDNA formation does not involve de-novo DNA synthesis suggesting that eccDNA is generated through excision of chromosomal sequences. This process is carried out by sequence- independent enzymes as human protein extract can produce mouse- specific eccDNA from high molecular weight mouse DNA, and vice versa. EccDNA production does not depend on ATP, requires residual amounts of Mg2+ and is enhanced by double strand DNA breaks.
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Affiliation(s)
- Zoya Cohen
- Department of Cell Research and Immunology, Tel Aviv University, Tel Aviv, Israel
| | - Sara Lavi
- Department of Cell Research and Immunology, Tel Aviv University, Tel Aviv, Israel
- * E-mail:
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36
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Navrátilová A, Koblížková A, Macas J. Survey of extrachromosomal circular DNA derived from plant satellite repeats. BMC PLANT BIOLOGY 2008; 8:90. [PMID: 18721471 PMCID: PMC2543021 DOI: 10.1186/1471-2229-8-90] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 08/22/2008] [Indexed: 05/19/2023]
Abstract
BACKGROUND Satellite repeats represent one of the most dynamic components of higher plant genomes, undergoing rapid evolutionary changes of their nucleotide sequences and abundance in a genome. However, the exact molecular mechanisms driving these changes and their eventual regulation are mostly unknown. It has been proposed that amplification and homogenization of satellite DNA could be facilitated by extrachromosomal circular DNA (eccDNA) molecules originated by recombination-based excision from satellite repeat arrays. While the models including eccDNA are attractive for their potential to explain rapid turnover of satellite DNA, the existence of satellite repeat-derived eccDNA has not yet been systematically studied in a wider range of plant genomes. RESULTS We performed a survey of eccDNA corresponding to nine different families and three subfamilies of satellite repeats in ten species from various genera of higher plants (Arabidopsis, Oryza, Pisum, Secale, Triticum and Vicia). The repeats selected for this study differed in their monomer length, abundance, and chromosomal localization in individual species. Using two-dimensional agarose gel electrophoresis followed by Southern blotting, eccDNA molecules corresponding to all examined satellites were detected. EccDNA occurred in the form of nicked circles ranging from hundreds to over eight thousand nucleotides in size. Within this range the circular molecules occurred preferentially in discrete size intervals corresponding to multiples of monomer or higher-order repeat lengths. CONCLUSION This work demonstrated that satellite repeat-derived eccDNA is common in plant genomes and thus it can be seriously considered as a potential intermediate in processes driving satellite repeat evolution. The observed size distribution of circular molecules suggests that they are most likely generated by molecular mechanisms based on homologous recombination requiring long stretches of sequence similarity.
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Affiliation(s)
- Alice Navrátilová
- Biology Centre ASCR, Institute of Plant Molecular Biology, Branišovská 31, České Budějovice, CZ-37005, Czech Republic
| | - Andrea Koblížková
- Biology Centre ASCR, Institute of Plant Molecular Biology, Branišovská 31, České Budějovice, CZ-37005, Czech Republic
| | - Jiří Macas
- Biology Centre ASCR, Institute of Plant Molecular Biology, Branišovská 31, České Budějovice, CZ-37005, Czech Republic
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37
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Gómez M, Antequera F. Overreplication of short DNA regions during S phase in human cells. Genes Dev 2008; 22:375-85. [PMID: 18245449 DOI: 10.1101/gad.445608] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
DNA replication origins (ORI) are regulatory regions from which the genome is replicated once every cell cycle. A widely used method for their identification in mammalian chromosomes relies on quantitative PCR of DNA nascent strands across candidate regions. We developed a new high-resolution PCR strategy to localize ORIs directly on total unfractionated human DNA. The increase in sensitivity provided by this approach has revealed that a short region of approximately 200-base-pair overlapping well-characterized replication origins undergoes several rounds of replication, coinciding with their specific time of activation during S phase. This process generates a population of discrete dsDNA fragments detectable as free molecules in preparations of total DNA in normally proliferating cells. Overreplicated regions have precise boundaries at the edge of the nucleosome-free gap that encompasses the transcription initiation sites of CpG island promoters. By itself, active transcription does not induce overreplication but does stimulate it at ORIs associated with promoters. The coincidence in time and space between the overproduction of short DNA fragments and ORI activity predicts the precise localization of thousands of ORIs in the human genome and uncovers a previously unnoticed step in the initiation of DNA replication.
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Affiliation(s)
- María Gómez
- Instituto de Microbiología Bioquímica, Consejo Superior de Investigaciones Científicas (CSIC)/Universidad de Salamanca, Edificio Departamental, Campus Miguel de Unamuno, 37007-Salamanca, Spain.
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38
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Cohen S, Houben A, Segal D. Extrachromosomal circular DNA derived from tandemly repeated genomic sequences in plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 53:1027-1034. [PMID: 18088310 DOI: 10.1111/j.1365-313x.2007.03394.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Extrachromosomal circular DNA (eccDNA) is one characteristic of the plasticity of the eukaryotic genome. It was found in various non-plant organisms from yeast to humans. EccDNA is heterogeneous in size and contains sequences derived primarily from repetitive chromosomal DNA. Here, we report the occurrence of eccDNA in small and large genome plant species, as identified using two-dimensional gel electrophoresis. We show that eccDNA is readily detected in both Arabidopsis thaliana and Brachycome dichromosomatica, reflecting a normal phenomenon that occurs in wild-type plants. The size of plant eccDNA ranges from > 2 kb to < 20 kb, which is similar to the sizes found in other organisms. These DNA molecules correspond to 5S ribosomal DNA (rDNA), non-coding chromosomal high-copy tandem repeats and telomeric DNA of both species. Circular multimers of the repeating unit of 5S rDNA were identified in both species. In addition, similar multimers were also demonstrated with the B. dichromosomatica repetitive element Bdm29. Such circular multimers of tandem repeats were found in animal models, suggesting a common mechanism for eccDNA formation among eukaryotes. This mechanism may involve looping-out via intrachromosomal homologous recombination. The implications of these results on genome plasticity and evolutionary processes are discussed.
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Affiliation(s)
- Sarit Cohen
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv, Israel.
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Peng JC, Karpen GH. H3K9 methylation and RNA interference regulate nucleolar organization and repeated DNA stability. Nat Cell Biol 2007; 9:25-35. [PMID: 17159999 PMCID: PMC2819265 DOI: 10.1038/ncb1514] [Citation(s) in RCA: 301] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Accepted: 10/17/2006] [Indexed: 12/20/2022]
Abstract
Investigations aimed at identifying regulators of nuclear architecture in Drosophila demonstrated that cells lacking H3K9 methylation and RNA interference (RNAi) pathway components displayed disorganized nucleoli, ribosomal DNA (rDNA) and satellite DNAs. The levels of H3K9 dimethylation (H3K9me2) in chromatin associated with repeated DNAs decreased dramatically in Su(var)3-9 and dcr-2 (dicer-2) mutant tissues compared with wild type. We also observed a substantial increase in extrachromosomal circular (ecc) repeated DNAs in mutant tissues. The disorganized nucleolus phenotype depends on the presence of Ligase 4 and ecc DNA formation is not induced by removal of cohesin. We conclude that the structural integrity and organization of repeated DNAs and nucleoli are regulated by the H3K9 methylation and RNAi pathways, and other regulators of heterochromatin-mediated silencing. In addition, repeated DNA stability involves suppression of non-homologous end joining (NHEJ) or other recombination pathways. These results suggest a mechanism for how local chromatin structure can regulate genome stability, and the organization of chromosomal elements and nuclear organelles.
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Affiliation(s)
- Jamy C. Peng
- Department of Genomics and Bioinformatics, Lawrence Berkeley National Lab, One Cyclotron Road, Berkeley, CA 94720, USA
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720, USA
| | - Gary H. Karpen
- Department of Genomics and Bioinformatics, Lawrence Berkeley National Lab, One Cyclotron Road, Berkeley, CA 94720, USA
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720, USA
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Kuttler F, Mai S. Formation of non-random extrachromosomal elements during development, differentiation and oncogenesis. Semin Cancer Biol 2006; 17:56-64. [PMID: 17116402 DOI: 10.1016/j.semcancer.2006.10.007] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2006] [Accepted: 10/17/2006] [Indexed: 11/25/2022]
Abstract
Extrachromosomal elements (EEs) were first discovered as minute chromatin bodies [Cox et al. Minute chromatin bodies in malignant tumors of childhood. Lancet 1965;62:55-8], and subsequently characterized as small circular DNA molecules physically separated from chromosomes. They include episomes, minichromosomes, small polydispersed DNAs or double minutes. This review focuses on eukaryotic EEs generated by genome rearrangements under physiological or pathological conditions. Some of those rearrangements occur randomly, but others are strictly non-random, highly regulated, and involve specific chromosomal locations (V(D)J-recombination, telomere maintenance mechanisms, c-myc deregulation). The multiple mechanisms of EEs formation are strongly interconnected and frequently linked to gene amplification. Identification of genes located on EEs will undoubtedly allow a better understanding of genome dynamics and oncogenic pathways.
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Affiliation(s)
- Fabien Kuttler
- Manitoba Institute of Cell Biology, CancerCare Manitoba, University of Manitoba, 675 McDermot Avenue, Winnipeg, Man. R3E 0V9, Canada.
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