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Morales ME, Servant G, Ade C, Roy-Enge AM. Altering Genomic Integrity: Heavy Metal Exposure Promotes Transposable Element-Mediated Damage. Biol Trace Elem Res 2015; 166:24-33. [PMID: 25774044 PMCID: PMC4696754 DOI: 10.1007/s12011-015-0298-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 03/03/2015] [Indexed: 12/13/2022]
Abstract
Maintenance of genomic integrity is critical for cellular homeostasis and survival. The active transposable elements (TEs) composed primarily of three mobile element lineages LINE-1, Alu, and SVA comprise approximately 30% of the mass of the human genome. For the past 2 decades, studies have shown that TEs significantly contribute to genetic instability and that TE-caused damages are associated with genetic diseases and cancer. Different environmental exposures, including several heavy metals, influence how TEs interact with its host genome increasing their negative impact. This mini-review provides some basic knowledge on TEs, their contribution to disease, and an overview of the current knowledge on how heavy metals influence TE-mediated damage.
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Affiliation(s)
- Maria E. Morales
- Department of Epidemiology and Tulane Cancer Center, SL-66, Tulane University Health Sciences Center, 1430 Tulane Ave., New Orleans, LA 70112
| | - Geraldine Servant
- Department of Epidemiology and Tulane Cancer Center, SL-66, Tulane University Health Sciences Center, 1430 Tulane Ave., New Orleans, LA 70112
| | - Catherine Ade
- Department of Cellular and Molecular Biology, Tulane University Health Sciences Center, 1430 Tulane Ave., New Orleans, LA 70112
| | - Astrid M. Roy-Enge
- Department of Epidemiology and Tulane Cancer Center, SL-66, Tulane University Health Sciences Center, 1430 Tulane Ave., New Orleans, LA 70112
- Corresponding author: Astrid M. Roy-Engel, Ph.D., Department of Epidemiology, Tulane Cancer Center, SL66, Tulane University Health Sciences Center, 1430 Tulane Ave., New Orleans, LA 70112. , Phone: (504) 988-6316, Fax: (504) 988-5516
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202
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Miousse IR, Chalbot MCG, Lumen A, Ferguson A, Kavouras IG, Koturbash I. Response of transposable elements to environmental stressors. MUTATION RESEARCH. REVIEWS IN MUTATION RESEARCH 2015; 765:19-39. [PMID: 26281766 PMCID: PMC4544780 DOI: 10.1016/j.mrrev.2015.05.003] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 05/27/2015] [Accepted: 05/28/2015] [Indexed: 12/21/2022]
Abstract
Transposable elements (TEs) comprise a group of repetitive sequences that bring positive, negative, as well as neutral effects to the host organism. Earlier considered as "junk DNA," TEs are now well-accepted driving forces of evolution and critical regulators of the expression of genetic information. Their activity is regulated by epigenetic mechanisms, including methylation of DNA and histone modifications. The loss of epigenetic control over TEs, exhibited as loss of DNA methylation and decondensation of the chromatin structure, may result in TEs reactivation, initiation of their insertional mutagenesis (retrotransposition) and has been reported in numerous human diseases, including cancer. Accumulating evidence suggests that these alterations are not the simple consequences of the disease, but often may drive the pathogenesis, as they can be detected early during disease development. Knowledge derived from the in vitro, in vivo, and epidemiological studies, clearly demonstrates that exposure to ubiquitous environmental stressors, many of which are carcinogens or suspected carcinogens, are capable of causing alterations in methylation and expression of TEs and initiate retrotransposition events. Evidence summarized in this review suggests that TEs are the sensitive endpoints for detection of effects caused by such environmental stressors, as ionizing radiation (terrestrial, space, and UV-radiation), air pollution (including particulate matter [PM]-derived and gaseous), persistent organic pollutants, and metals. Furthermore, the significance of these effects is characterized by their early appearance, persistence and presence in both, target organs and peripheral blood. Altogether, these findings suggest that TEs may potentially be introduced into safety and risk assessment and serve as biomarkers of exposure to environmental stressors. Furthermore, TEs also show significant potential to become invaluable surrogate biomarkers in clinic and possible targets for therapeutic modalities for disease treatment and prevention.
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Affiliation(s)
- Isabelle R Miousse
- Department of Environmental and Occupational Health, Fay W. Boozman College of Public Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
| | - Marie-Cecile G Chalbot
- Department of Environmental and Occupational Health, Fay W. Boozman College of Public Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
| | - Annie Lumen
- Division of Biochemical Toxicology, National Center for Toxicological Research, US Food and Drug Administration, Jefferson, AR 72079, USA.
| | - Alesia Ferguson
- Department of Environmental and Occupational Health, Fay W. Boozman College of Public Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
| | - Ilias G Kavouras
- Department of Environmental and Occupational Health, Fay W. Boozman College of Public Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
| | - Igor Koturbash
- Department of Environmental and Occupational Health, Fay W. Boozman College of Public Health, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
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203
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Sciamanna I, Gualtieri A, Piazza PF, Spadafora C. Regulatory roles of LINE-1-encoded reverse transcriptase in cancer onset and progression. Oncotarget 2015; 5:8039-51. [PMID: 25478632 PMCID: PMC4226666 DOI: 10.18632/oncotarget.2504] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
LINE-1 retrotransposons encode the reverse transcriptase (RT) enzyme, required for their own mobility, the expression of which is inhibited in differentiated tissues while being active in tumors. Experimental evidence indicate that the inhibition of LINE-1-derived RT restores differentiation in cancer cells, inhibits tumor progression and yields globally reprogrammed transcription profiles. Newly emerging data suggest that LINE-1-encoded RT modulates the biogenesis of miRNAs, by governing the balance between the production of regulatory double-stranded RNAs and RNA:DNA hybrid molecules, with a direct impact on global gene expression. Abnormally high RT activity unbalances the transcriptome in cancer cells, while RT inhibition restores ‘normal’ miRNA profiles and their regulatory networks. This RT-dependent mechanism can target the myriad of transcripts - both coding and non-coding, sense and antisense - in eukaryotic transcriptomes, with a profound impact on cell fates. LINE-1-encoded RT emerges therefore as a key regulator of a previously unrecognized mechanism in tumorigenesis
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204
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Lin X, Stenvang J, Rasmussen MH, Zhu S, Jensen NF, Tarpgaard LS, Yang G, Belling K, Andersen CL, Li J, Bolund L, Brünner N. The potential role of Alu Y in the development of resistance to SN38 (Irinotecan) or oxaliplatin in colorectal cancer. BMC Genomics 2015; 16:404. [PMID: 25997618 PMCID: PMC4440512 DOI: 10.1186/s12864-015-1552-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2014] [Accepted: 04/17/2015] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Irinotecan (SN38) and oxaliplatin are chemotherapeutic agents used in the treatment of colorectal cancer. However, the frequent development of resistance to these drugs represents a considerable challenge in the clinic. Alus as retrotransposons comprise 11% of the human genome. Genomic toxicity induced by carcinogens or drugs can reactivate Alus by altering DNA methylation. Whether or not reactivation of Alus occurs in SN38 and oxaliplatin resistance remains unknown. RESULTS We applied reduced representation bisulfite sequencing (RRBS) to investigate the DNA methylome in SN38 or oxaliplatin resistant colorectal cancer cell line models. Moreover, we extended the RRBS analysis to tumor tissue from 14 patients with colorectal cancer who either did or did not benefit from capecitabine + oxaliplatin treatment. For the clinical samples, we applied a concept of 'DNA methylation entropy' to estimate the diversity of DNA methylation states of the identified resistance phenotype-associated methylation loci observed in the cell line models. We identified different loci being characteristic for the different resistant cell lines. Interestingly, 53% of the identified loci were Alu sequences- especially the Alu Y subfamily. Furthermore, we identified an enrichment of Alu Y sequences that likely results from increased integration of new copies of Alu Y sequence in the drug-resistant cell lines. In the clinical samples, SOX1 and other SOX gene family members were shown to display variable DNA methylation states in their gene regions. The Alu Y sequences showed remarkable variation in DNA methylation states across the clinical samples. CONCLUSION Our findings imply a crucial role of Alu Y in colorectal cancer drug resistance. Our study underscores the complexity of colorectal cancer aggravated by mobility of Alu elements and stresses the importance of personalized strategies, using a systematic and dynamic view, for effective cancer therapy.
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Affiliation(s)
- Xue Lin
- Department of Biomedicine, University of Aarhus, the Bartholin Building, DK-8000, Aarhus C, Denmark.
| | - Jan Stenvang
- Department of Veterinary Disease Biology, Section of Molecular Disease Biology, Faculty of Health and Medical Sciences, Copenhagen University, Strandboulevarden 49, Copenhagen, Denmark.
| | - Mads Heilskov Rasmussen
- Department of Molecular Medicine, Aarhus University Hospital, Brendstrupgårdsvej 100, DK-8200, Aarhus N, Denmark.
| | - Shida Zhu
- BGI (Beijing Genomics Institute), Shenzhen, 518083, China.
| | - Niels Frank Jensen
- Department of Veterinary Disease Biology, Section of Molecular Disease Biology, Faculty of Health and Medical Sciences, Copenhagen University, Strandboulevarden 49, Copenhagen, Denmark.
| | - Line S Tarpgaard
- Department of Oncology, Odense University Hospital, Sdr. Boulevard 29, DK-5000, Odense C, Denmark.
| | - Guangxia Yang
- BGI (Beijing Genomics Institute), Shenzhen, 518083, China.
| | - Kirstine Belling
- Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, 2800, Lyngby, Denmark.
| | - Claus Lindbjerg Andersen
- Department of Molecular Medicine, Aarhus University Hospital, Brendstrupgårdsvej 100, DK-8200, Aarhus N, Denmark.
| | - Jian Li
- Department of Biomedicine, University of Aarhus, the Bartholin Building, DK-8000, Aarhus C, Denmark.
- BGI (Beijing Genomics Institute), Shenzhen, 518083, China.
- The Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing, 210096, China.
| | - Lars Bolund
- Department of Biomedicine, University of Aarhus, the Bartholin Building, DK-8000, Aarhus C, Denmark.
- BGI (Beijing Genomics Institute), Shenzhen, 518083, China.
| | - Nils Brünner
- Department of Veterinary Disease Biology, Section of Molecular Disease Biology, Faculty of Health and Medical Sciences, Copenhagen University, Strandboulevarden 49, Copenhagen, Denmark.
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205
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Mehta A, Dobersch S, Romero-Olmedo AJ, Barreto G. Epigenetics in lung cancer diagnosis and therapy. Cancer Metastasis Rev 2015; 34:229-41. [DOI: 10.1007/s10555-015-9563-3] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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206
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Lu X, Miousse IR, Pirela SV, Melnyk S, Koturbash I, Demokritou P. Short-term exposure to engineered nanomaterials affects cellular epigenome. Nanotoxicology 2015; 10:140-50. [PMID: 25938281 DOI: 10.3109/17435390.2015.1025115] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Extensive incorporation of engineered nanomaterials (ENMs) into industrial and biomedical applications increases the risks of exposure to these potentially hazardous materials. While the geno- and cytotoxic effects of ENMs have been investigated, the potential of ENMs to target the cellular epigenome remains largely unknown. Our goal was to determine whether industry relevant ENMs can affect the epigenome at low cytotoxic doses. A panel of cells relevant to inhalation exposures such as human and murine macrophages (THP-1 and RAW264.7, respectively) and human small airway epithelial cells (SAEC) were exposed to printer-emitted engineered nanoparticles (PEPs), mild steel welding fumes (MS-WF), copper oxide (CuO) and titanium dioxide nanoparticles. Toxicological effects, including cytotoxicity, oxidative stress and inflammatory responses were assessed, taking into consideration in vitro dosimetry. The effects of ENMs on cellular epigenome were determined by addressing the global and transposable elements (TEs)-associated DNA methylation and expression of DNA methylation machinery and TEs. The percentage of ENMs-induced cytotoxicity for all cell lines was in the range of 0-15%. Oxidative stress was evident in SAEC after exposure to PEPs and in THP-1 when exposed to CuO. In addition, exposure to ENMs resulted in modest alterations in DNA methylation of two most abundant TEs in mammalian genomes, LINE-1 and Alu/SINE, their transcriptional reactivation, and decreased expression of DNA methylation machinery in a cell-, dose- and ENM-dependent manner. These results indicate that exposure to ENMs at environmentally relevant concentrations, aside from the geno- and cytotoxic effects, can also affect the epigenome of target cells.
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Affiliation(s)
- Xiaoyan Lu
- a Center for Nanotechnology and Nanotoxicology , Department of Environmental Health , Harvard School of Public Health , Boston , MA , USA
| | - Isabelle R Miousse
- b Department of Environmental and Occupational Health , College of Public Health, University of Arkansas for Medical Sciences , Little Rock , AR , USA , and
| | - Sandra V Pirela
- a Center for Nanotechnology and Nanotoxicology , Department of Environmental Health , Harvard School of Public Health , Boston , MA , USA
| | - Stepan Melnyk
- c Department of Pediatrics , University of Arkansas for Medical Sciences , Little Rock , AR , USA
| | - Igor Koturbash
- b Department of Environmental and Occupational Health , College of Public Health, University of Arkansas for Medical Sciences , Little Rock , AR , USA , and
| | - Philip Demokritou
- a Center for Nanotechnology and Nanotoxicology , Department of Environmental Health , Harvard School of Public Health , Boston , MA , USA
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207
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Macfarlane CM, Badge RM. Genome-wide amplification of proviral sequences reveals new polymorphic HERV-K(HML-2) proviruses in humans and chimpanzees that are absent from genome assemblies. Retrovirology 2015; 12:35. [PMID: 25927962 PMCID: PMC4422153 DOI: 10.1186/s12977-015-0162-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 03/30/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND To date, the human population census of proviruses of the Betaretrovirus-like human endogenous retroviral (HERV-K) (HML-2) family has been compiled from a limited number of complete genomes, making it certain that rare polymorphic loci are under-represented and are yet to be described. RESULTS Here we describe a suppression PCR-based method called genome-wide amplification of proviral sequences (GAPS) that selectively amplifies DNA fragments containing the termini of HERV-K(HML-2) proviral sequences and their flanking genomic sequences. We analysed the HERV-K(HML-2) proviral content of 101 unrelated humans, 4 common chimpanzees and three centre d'etude du polymorphisme humain (CEPH) pedigrees (44 individuals). The technique isolated HERV-K(HML-2) proviruses that had integrated in the genomes of the great apes throughout their divergence and included evolutionarily young elements still unfixed for presence/absence. CONCLUSIONS By examining the HERV-K(HML-2) proviral content of 145 humans we detected a new insertionally polymorphic Type I HERV-K(HML-2) provirus. We also observed provirus versus solo long terminal repeat (LTR) polymorphism within humans at a previously unreported, but ancient, locus. Finally, we report two novel chimpanzee specific proviruses, one of which is dimorphic for a provirus versus solo LTR. Thus GAPS enables the isolation of uncharacterised HERV-K(HML-2) proviral sequences and provides a direct means to assess inter-individual genetic variation associated with HERV-K(HML-2) proviruses.
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Affiliation(s)
- Catriona M Macfarlane
- Department of Genetics, University of Leicester, University Road, Leicester, LE1 7RH, UK.
| | - Richard M Badge
- Department of Genetics, University of Leicester, University Road, Leicester, LE1 7RH, UK.
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208
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Silencing of LINE-1 retrotransposons contributes to variation in small noncoding RNA expression in human cancer cells. Oncotarget 2015; 5:4103-17. [PMID: 24980824 PMCID: PMC4147309 DOI: 10.18632/oncotarget.1822] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Noncoding RNAs are key players in the maintenance of genomic integrity, particularly in silencing the expression of repetitive elements, some of which are retrotransposable and capable of causing genomic instability. Recent computational studies suggest an association between L1 expression and the generation of small RNAs. However, whether L1 expression has a role in the activation of small RNA expression has yet to be determined experimentally.; Here we report a global analysis of small RNAs in deep sequencing from L1-active and L1-silenced breast cancer cells. We found that cells in which L1 expression was silenced exhibited greatly increased expression of a number of miRNAs and in particular, members of the let-7 family. In addition, we found differential expression of a few piRNAs that might potentially regulate gene expression. We also report the identification of several repeat RNAs against LTRs, LINEs and SINE elements. Although most of the repeat RNAs mapped to L1 elements, in general we found no significant differences in the expression levels of repeat RNAs in the presence or absence of L1 expression except for a few RNAs targeting subclasses of L1 elements. These differentially expressed small RNAs may function in human genome defence responses.
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209
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piRNA involvement in genome stability and human cancer. J Hematol Oncol 2015; 8:38. [PMID: 25895683 PMCID: PMC4412036 DOI: 10.1186/s13045-015-0133-5] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 03/31/2015] [Indexed: 12/16/2022] Open
Abstract
PIWI-interacting RNAs (piRNAs) are a large family of small, single-stranded, non-coding RNAs present throughout the animal kingdom. They form complexes with several members of the PIWI clade of Argonaute proteins and carry out regulatory functions. Their best established biological role is the inhibition of transposon mobilization, which they enforce both at the transcriptional level, through regulation of heterochromatin formation, and by promoting transcript degradation. In this capacity, piRNAs and PIWI proteins are at the heart of the germline cells’ efforts to preserve genome integrity. Additional regulatory roles of piRNAs and PIWI proteins in gene expression are becoming increasingly apparent. PIWI proteins and piRNAs are often detected in human cancers deriving from germline cells as well as somatic tissues. Their detection in cancer correlates with poorer clinical outcomes, suggesting that they play a functional role in the biology of cancer. Nonetheless, the currently available information, while highly suggestive, is still not sufficient to entirely discriminate between a ‘passenger’ role for the ectopic expression of piRNAs and PIWI proteins in cancer from a ‘driver’ role in the pathogenesis of these diseases. In this article, we review some of the key available evidence for the role of piRNAs and PIWI in human cancer and discuss ways in which our understanding of their functions may be improved.
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210
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Abstract
Although members of the L1 (LINE-1) clade of non-LTR retrotransposons can be deleterious, the L1 clade has remained active in most mammals for ∼100 million years and generated almost 40% of the human genome. The details of L1-host interaction are largely unknown, however. Here we report that L1 activity requires phosphorylation of the protein encoded by the L1 ORF1 (ORF1p). Critical phospho-acceptor residues (two serines and two threonines) reside in four conserved proline-directed protein kinase (PDPK) target sites. The PDPK family includes mitogen-activated protein kinases and cyclin-dependent kinases. Mutation of any PDPK phospho-acceptor inhibits L1 retrotransposition. The phosphomimetic aspartic acid can restore activity at the two serine sites, but not at either threonine site, where it is strongly inhibitory. ORF1p also contains conserved PDPK docking sites, which promote specific interaction of PDPKs with their targets. As expected, mutations in these sites also inhibit L1 activity. PDPK mutations in ORF1p that inactivate L1 have no significant effect on the ability of ORF1p to anneal RNA in vitro, an important biochemical property of the protein. We show that phosphorylated PDPK sites in ORF1p are required for an interaction with the peptidyl prolyl isomerase 1 (Pin1), a critical component of PDPK-mediated regulation. Pin1 acts via isomerization of proline side chains at phosphorylated PDPK motifs, thereby affecting substrate conformation and activity. Our demonstration that L1 activity is dependent on and integrated with cellular phosphorylation regulatory cascades significantly increases our understanding of interactions between L1 and its host.
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211
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Streva VA, Jordan VE, Linker S, Hedges DJ, Batzer MA, Deininger PL. Sequencing, identification and mapping of primed L1 elements (SIMPLE) reveals significant variation in full length L1 elements between individuals. BMC Genomics 2015; 16:220. [PMID: 25887476 PMCID: PMC4381410 DOI: 10.1186/s12864-015-1374-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 02/20/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND There are over a half a million copies of L1 retroelements in the human genome which are responsible for as much as 0.5% of new human genetic diseases. Most new L1 inserts arise from young source elements that are polymorphic in the human genome. Highly active polymorphic "hot" L1 source elements have been shown to be capable of extremely high levels of mobilization and result in numerous instances of disease. Additionally, hot polymorphic L1s have been described to be highly active within numerous cancer genomes. These hot L1s result in mutagenesis by insertion of new L1 copies elsewhere in the genome, but also have been shown to generate additional full length L1 insertions which are also hot and able to further retrotranspose. Through this mechanism, hot L1s may amplify within a tumor and result in a continued cycle of mutagenesis. RESULTS AND CONCLUSIONS We have developed a method to detect full-length, polymorphic L1 elements using a targeted next generation sequencing approach, Sequencing Identification and Mapping of Primed L1 Elements (SIMPLE). SIMPLE has 94% sensitivity and detects nearly all full-length L1 elements in a genome. SIMPLE will allow researchers to identify hot mutagenic full-length L1s as potential drivers of genome instability. Using SIMPLE we find that the typical individual has approximately 100 non-reference, polymorphic L1 elements in their genome. These elements are at relatively low population frequencies relative to previously identified polymorphic L1 elements and demonstrate the tremendous diversity in potentially active L1 elements in the human population.
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Affiliation(s)
- Vincent A Streva
- Tulane Cancer Center and Department of Epidemiology, Tulane University, New Orleans, LA, USA. .,Present Address: Division of Infectious Diseases, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA.
| | - Vallmer E Jordan
- Department of Biology, Louisiana State University, Baton Rouge, LA, USA.
| | - Sara Linker
- Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL, USA.
| | - Dale J Hedges
- Department of Internal Medicine, The Ohio State University, Columbus, OH, USA.
| | - Mark A Batzer
- Department of Biology, Louisiana State University, Baton Rouge, LA, USA.
| | - Prescott L Deininger
- Tulane Cancer Center and Department of Epidemiology, Tulane University, New Orleans, LA, USA.
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212
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Doucet AJ, Droc G, Siol O, Audoux J, Gilbert N. U6 snRNA Pseudogenes: Markers of Retrotransposition Dynamics in Mammals. Mol Biol Evol 2015; 32:1815-32. [PMID: 25761766 PMCID: PMC4476161 DOI: 10.1093/molbev/msv062] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Transposable elements comprise more than 45% of the human genome and long interspersed nuclear element 1 (LINE-1 or L1) is the only autonomous mobile element remaining active. Since its identification, it has been proposed that L1 contributes to the mobilization and amplification of other cellular RNAs and more recently, experimental demonstrations of this function has been described for many transcripts such as Alu, a nonautonomous mobile element, cellular mRNAs, or small noncoding RNAs. Detailed examination of the mobilization of various cellular RNAs revealed distinct pathways by which they could be recruited during retrotransposition; template choice or template switching. Here, by analyzing genomic structures and retrotransposition signatures associated with small nuclear RNA (snRNA) sequences, we identified distinct recruiting steps during the L1 retrotransposition cycle for the formation of snRNA-processed pseudogenes. Interestingly, some of the identified recruiting steps take place in the nucleus. Moreover, after comparison to other vertebrate genomes, we established that snRNA amplification by template switching is common to many LINE families from several LINE clades. Finally, we suggest that U6 snRNA copies can serve as markers of L1 retrotransposition dynamics in mammalian genomes.
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Affiliation(s)
- Aurélien J Doucet
- Institut de Génétique Humaine, CNRS, UPR 1142, Montpellier, France Institute for Research on Cancer and Aging, Nice (IRCAN), INSERM, U1081, CNRS UMR 7284, Nice, France
| | - Gaëtan Droc
- Institut de Génétique Humaine, CNRS, UPR 1142, Montpellier, France Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), UMR AGAP, Montpellier, France
| | - Oliver Siol
- Institut de Génétique Humaine, CNRS, UPR 1142, Montpellier, France Institut de Génétique Humaine, CNRS, UPR 1142, Montpellier, France
| | - Jérôme Audoux
- Institute for Regenerative Medicine and Biotherapy, INSERM, U1183, Montpellier, France
| | - Nicolas Gilbert
- Institut de Génétique Humaine, CNRS, UPR 1142, Montpellier, France Institute for Regenerative Medicine and Biotherapy, INSERM, U1183, Montpellier, France
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213
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Abstract
Nucleotide substitutions, small (<50 bp) insertions or deletions (indels), and large (>50 bp) deletions are well-known causes of genetic variation within the human genome. We recently reported a previously unrecognized form of polymorphic insertions, termed templated sequence insertion polymorphism (TSIP), in which the inserted sequence was templated from a distant genomic region, and was inserted in the genome through reverse transcription of an RNA intermediate. TSIPs can be grouped into two classes based on nucleotide sequence features at the insertion junctions; class 1 TSIPs show target site duplication, polyadenylation, and preference for insertion at a 5′-TTTT/A-3′ sequence, suggesting a LINE-1 based insertion mechanism, whereas class 2 TSIPs show features consistent with repair of a DNA double strand break by nonhomologous end joining. To gain a more complete picture of TSIPs throughout the human population, we evaluated whole-genome sequence from 52 individuals, and identified 171 TSIPs. Most individuals had 25–30 TSIPs, and common (present in >20% of individuals) TSIPs were found in individuals throughout the world, whereas rare TSIPs tended to cluster in specific geographic regions. The number of rare TSIPs was greater than the number of common TSIPs, suggesting that TSIP generation is an ongoing process. Intriguingly, mitochondrial sequences were a frequent template for class 2 insertions, used more commonly than any nuclear chromosome. Similar to single nucleotide polymorphisms and indels, we suspect that these TSIPs may be important for the generation of human diversity and genetic diseases, and can be useful in tracking historical migration of populations.
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Affiliation(s)
- Masahiro Onozawa
- Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Liat Goldberg
- Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Peter D Aplan
- Genetics Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
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214
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Brečević L, Rinčić M, Krsnik Ž, Sedmak G, Hamid AB, Kosyakova N, Galić I, Liehr T, Borovečki F. Association of new deletion/duplication region at chromosome 1p21 with intellectual disability, severe speech deficit and autism spectrum disorder-like behavior: an all-in approach to solving the DPYD enigma. Transl Neurosci 2015; 6:59-86. [PMID: 28123791 PMCID: PMC4936614 DOI: 10.1515/tnsci-2015-0007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 12/29/2014] [Indexed: 12/14/2022] Open
Abstract
We describe an as yet unreported neocentric small supernumerary marker chromosome (sSMC) derived from chromosome 1p21.3p21.2. It was present in 80% of the lymphocytes in a male patient with intellectual disability, severe speech deficit, mild dysmorphic features, and hyperactivity with elements of autism spectrum disorder (ASD). Several important neurodevelopmental genes are affected by the 3.56 Mb copy number gain of 1p21.3p21.2, which may be considered reciprocal in gene content to the recently recognized 1p21.3 microdeletion syndrome. Both 1p21.3 deletions and the presented duplication display overlapping symptoms, fitting the same disorder category. Contribution of coding and non-coding genes to the phenotype is discussed in the light of cellular and intercellular homeostasis disequilibrium. In line with this the presented 1p21.3p21.2 copy number gain correlated to 1p21.3 microdeletion syndrome verifies the hypothesis of a cumulative effect of the number of deregulated genes - homeostasis disequilibrium leading to overlapping phenotypes between microdeletion and microduplication syndromes. Although miR-137 appears to be the major player in the 1p21.3p21.2 region, deregulation of the DPYD (dihydropyrimidine dehydrogenase) gene may potentially affect neighboring genes underlying the overlapping symptoms present in both the copy number loss and copy number gain of 1p21. Namely, the all-in approach revealed that DPYD is a complex gene whose expression is epigenetically regulated by long non-coding RNAs (lncRNAs) within the locus. Furthermore, the long interspersed nuclear element-1 (LINE-1) L1MC1 transposon inserted in DPYD intronic transcript 1 (DPYD-IT1) lncRNA with its parasites, TcMAR-Tigger5b and pair of Alu repeats appears to be the “weakest link” within the DPYD gene liable to break. Identification of the precise mechanism through which DPYD is epigenetically regulated, and underlying reasons why exactly the break (FRA1E) happens, will consequently pave the way toward preventing severe toxicity to the antineoplastic drug 5-fluorouracil (5-FU) and development of the causative therapy for the dihydropyrimidine dehydrogenase deficiency.
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Affiliation(s)
- Lukrecija Brečević
- Croatian Institute for Brain Research, University of Zagreb Medical School, Šalata 12, 10000 Zagreb, Croatia
- Department for Functional Genomics, Center for Translational and Clinical Research, University of Zagreb Medical School, University Hospital Center Zagreb, Šalata 2, 10000 Zagreb, Croatia
- E-mail: ;
| | - Martina Rinčić
- Croatian Institute for Brain Research, University of Zagreb Medical School, Šalata 12, 10000 Zagreb, Croatia
- Department for Functional Genomics, Center for Translational and Clinical Research, University of Zagreb Medical School, University Hospital Center Zagreb, Šalata 2, 10000 Zagreb, Croatia
- Jena University Hospital, Friedrich Schiller University, Institute of Human Genetics, Kollegiengasse 10, 07743 Jena, Germany
| | - Željka Krsnik
- Croatian Institute for Brain Research, University of Zagreb Medical School, Šalata 12, 10000 Zagreb, Croatia
| | - Goran Sedmak
- Croatian Institute for Brain Research, University of Zagreb Medical School, Šalata 12, 10000 Zagreb, Croatia
| | - Ahmed B. Hamid
- Jena University Hospital, Friedrich Schiller University, Institute of Human Genetics, Kollegiengasse 10, 07743 Jena, Germany
| | - Nadezda Kosyakova
- Jena University Hospital, Friedrich Schiller University, Institute of Human Genetics, Kollegiengasse 10, 07743 Jena, Germany
| | - Ivan Galić
- Center for Rehabilitation Stančić, Stančić bb, 10370 Stančić, Croatia
| | - Thomas Liehr
- Jena University Hospital, Friedrich Schiller University, Institute of Human Genetics, Kollegiengasse 10, 07743 Jena, Germany
| | - Fran Borovečki
- Department for Functional Genomics, Center for Translational and Clinical Research, University of Zagreb Medical School, University Hospital Center Zagreb, Šalata 2, 10000 Zagreb, Croatia
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215
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Otsubo T, Okamura T, Hagiwara T, Ishizaka Y, Dohi T, Kawamura YI. Retrotransposition of long interspersed nucleotide element-1 is associated with colitis but not tumors in a murine colitic cancer model. PLoS One 2015; 10:e0116072. [PMID: 25710700 PMCID: PMC4339839 DOI: 10.1371/journal.pone.0116072] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 12/05/2014] [Indexed: 12/22/2022] Open
Abstract
Long interspersed element-1 (L1) is a transposable element that can move within the genome, potentially leading to genome diversity and modified gene function. Although L1 activity in somatic cells is normally suppressed through DNA methylation, some L1s are activated in tumors including colorectal carcinoma. However, how L1-retrotransposition (L1-RTP) is involved in gastrointestinal disorders remains to be elucidated. We hypothesized that L1-RTP in somatic cells might contribute to colitis-associated cancer (CAC). To address this, we employed an experimental model of CAC using transgenic L1-reporter mice carrying a human L1-EGFP reporter gene. Mice were subjected to repeated cycles of colitis induced by administration of dextran sodium sulfate (DSS) in drinking water with injection of carcinogen azoxymethane (AOM). L1-RTP levels were measured by a quantitative polymerase chain reaction targeting the newly inserted reporter EGFP in various tissues and cell types, including samples obtained by laser microdissection and cell sorting with flow cytometry. DNA methylation levels of the human L1 promoter were analyzed by bisulfite pyrosequencing. AOM+DSS-treated mice exhibited significantly higher levels of L1-RTP in whole colon tissue during the acute phase of colitis when compared with control naïve mice. L1-RTP levels in whole colon tissue were positively correlated with the histological severity of colitis and degree of neutrophil infiltration into the lamina propria (LP), but not with tumor development in the colon. L1-RTP was enriched in LP mesenchymal cells rather than epithelial cells (ECs), myeloid, or lymphoid cells. DNA methylation levels of the human L1 promoter region showed a negative correlation with L1-RTP levels. L1-RTP was absent from most tumors found in 22-week-old mice. In conclusion, we demonstrated that L1-RTP was induced in the mouse CAC mucosa in accordance with the acute inflammatory response; however, retrotransposition appears not to have direct relevance to colitis-induced cancer initiation.
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Affiliation(s)
- Takeshi Otsubo
- Department of Gastroenterology, Research Center for Hepatitis and Immunology, Research Institute, National Center for Global Health and Medicine, Ichikawa 272-8516, Japan
| | - Tadashi Okamura
- Section of Animal Models, Department of Infectious Diseases, Research Institute, National Center for Global Health and Medicine, 1-21-1, Toyama, Shinjuku-ku, 162-8655, Tokyo, Japan
| | - Teruki Hagiwara
- Department of Gastroenterology, Research Center for Hepatitis and Immunology, Research Institute, National Center for Global Health and Medicine, Ichikawa 272-8516, Japan
| | - Yukihito Ishizaka
- Department of Intractable Diseases, Research Institute, National Center for Global Health and Medicine, 1-21-1, Toyama, Shinjuku-ku, 162-8655, Tokyo, Japan
| | - Taeko Dohi
- Department of Gastroenterology, Research Center for Hepatitis and Immunology, Research Institute, National Center for Global Health and Medicine, Ichikawa 272-8516, Japan
- * E-mail: (TD); (YIK)
| | - Yuki I. Kawamura
- Department of Gastroenterology, Research Center for Hepatitis and Immunology, Research Institute, National Center for Global Health and Medicine, Ichikawa 272-8516, Japan
- * E-mail: (TD); (YIK)
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216
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The evidence for increased L1 activity in the site of human adult brain neurogenesis. PLoS One 2015; 10:e0117854. [PMID: 25689626 PMCID: PMC4331437 DOI: 10.1371/journal.pone.0117854] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 01/04/2015] [Indexed: 01/19/2023] Open
Abstract
Retroelement activity is a common source of polymorphisms in human genome. The mechanism whereby retroelements contribute to the intraindividual genetic heterogeneity by inserting into the DNA of somatic cells is gaining increasing attention. Brain tissues are suspected to accumulate genetic heterogeneity as a result of the retroelements somatic activity. This study aims to expand our understanding of the role retroelements play in generating somatic mosaicism of neural tissues. Whole-genome Alu and L1 profiling of genomic DNA extracted from the cerebellum, frontal cortex, subventricular zone, dentate gyrus, and the myocardium revealed hundreds of somatic insertions in each of the analyzed tissues. Interestingly, the highest concentration of such insertions was detected in the dentate gyrus—the hotspot of adult neurogenesis. Insertions of retroelements and their activity could produce genetically diverse neuronal subsets, which can be involved in hippocampal-dependent learning and memory.
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217
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Library Construction for High-Throughput Mobile Element Identification and Genotyping. Methods Mol Biol 2015; 1589:1-15. [PMID: 26025622 DOI: 10.1007/7651_2015_265] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Mobile genetic elements are discrete DNA elements that can move around and copy themselves in a genome. As a ubiquitous component of the genome, mobile elements contribute to both genetic and epigenetic variation. Therefore, it is important to determine the genome-wide distribution of mobile elements. Here we present a targeted high-throughput sequencing protocol called Mobile Element Scanning (ME-Scan) for genome-wide mobile element detection. We will describe oligonucleotides design, sequencing library construction, and computational analysis for the ME-Scan protocol.
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218
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Grandér D, Johnsson P. Pseudogene-Expressed RNAs: Emerging Roles in Gene Regulation and Disease. Curr Top Microbiol Immunol 2015; 394:111-26. [DOI: 10.1007/82_2015_442] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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219
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White TB, McCoy AM, Streva VA, Fenrich J, Deininger PL. A droplet digital PCR detection method for rare L1 insertions in tumors. Mob DNA 2014; 5:30. [PMID: 25598847 PMCID: PMC4297411 DOI: 10.1186/s13100-014-0030-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 11/19/2014] [Indexed: 01/17/2023] Open
Abstract
Background The active human mobile element, long interspersed element 1 (L1) currently populates human genomes in excess of 500,000 copies per haploid genome. Through its mobility via a process called target primed reverse transcription (TPRT), L1 mobilization has resulted in over 100 de novo cases of human disease and has recently been associated with various cancer types. Large advances in high-throughput sequencing (HTS) technology have allowed for an increased understanding of the role of L1 in human cancer; however, researchers are still limited by the ability to validate potentially rare L1 insertion events detected by HTS that may occur in only a small fraction of tumor cells. Additionally, HTS detection of rare events varies greatly as a function of read depth, and new tools for de novo element discovery are needed to fill in gaps created by HTS. Results We have employed droplet digital PCR (ddPCR) to detect rare L1 loci in mosaic human genomes. Our assay allows for the detection of L1 insertions as rare as one cell in every 10,000. Conclusions ddPCR represents a robust method to be used alongside HTS techniques for detecting, validating and quantitating rare L1 insertion events in tumors and other tissues. Electronic supplementary material The online version of this article (doi:10.1186/s13100-014-0030-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Travis B White
- Tulane Cancer Center, 1430 Tulane Avenue, New Orleans, LA 70112 USA
| | - Adam M McCoy
- Bio-Rad Laboratories, 750 Alfred Nobel Drive, Hercules, CA 94547 USA.,Present Address: Eureka Genomics, 2000 Alfred Nobel Drive, Hercules, CA 94547 USA
| | - Vincent A Streva
- Tulane Cancer Center, 1430 Tulane Avenue, New Orleans, LA 70112 USA.,Present Address: Division of Infectious Diseases, Boston Children's Hospital and Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115 USA
| | - Joshua Fenrich
- Bio-Rad Laboratories, 750 Alfred Nobel Drive, Hercules, CA 94547 USA
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220
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Fiston-Lavier AS, Barrón MG, Petrov DA, González J. T-lex2: genotyping, frequency estimation and re-annotation of transposable elements using single or pooled next-generation sequencing data. Nucleic Acids Res 2014; 43:e22. [PMID: 25510498 PMCID: PMC4344482 DOI: 10.1093/nar/gku1250] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Transposable elements (TEs) constitute the most active, diverse and ancient component in a broad range of genomes. Complete understanding of genome function and evolution cannot be achieved without a thorough understanding of TE impact and biology. However, in-depth analysis of TEs still represents a challenge due to the repetitive nature of these genomic entities. In this work, we present a broadly applicable and flexible tool: T-lex2. T-lex2 is the only available software that allows routine, automatic and accurate genotyping of individual TE insertions and estimation of their population frequencies both using individual strain and pooled next-generation sequencing data. Furthermore, T-lex2 also assesses the quality of the calls allowing the identification of miss-annotated TEs and providing the necessary information to re-annotate them. The flexible and customizable design of T-lex2 allows running it in any genome and for any type of TE insertion. Here, we tested the fidelity of T-lex2 using the fly and human genomes. Overall, T-lex2 represents a significant improvement in our ability to analyze the contribution of TEs to genome function and evolution as well as learning about the biology of TEs. T-lex2 is freely available online at http://sourceforge.net/projects/tlex.
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Affiliation(s)
- Anna-Sophie Fiston-Lavier
- Department of Biology, Stanford University, Stanford, CA 94305-5020, USA Institut des Sciences de l'Evolution de Montpellier (ISEM), UMR5554 CNRS-Université Montpellier 2, France
| | - Maite G Barrón
- Genomics, Bioinformatics and Evolution Group, Institut de Biotecnologia i de Biomedicina - IBB/Department of Genetics and Microbiology, Campus Universitat Autònoma de Barcelona, Bellaterra 08193, Spain Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra), Barcelona 08003, Spain
| | - Dmitri A Petrov
- Department of Biology, Stanford University, Stanford, CA 94305-5020, USA
| | - Josefa González
- Institute of Evolutionary Biology (CSIC-Universitat Pompeu Fabra), Barcelona 08003, Spain
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221
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Bae JH, Eo J, Kim TO, Yi JM. Biological changes of transposable elements by radiation: recent progress. Genes Genomics 2014. [DOI: 10.1007/s13258-014-0256-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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222
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Computational and Statistical Analyses of Insertional Polymorphic Endogenous Retroviruses in a Non-Model Organism. COMPUTATION 2014. [DOI: 10.3390/computation2040221] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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223
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Affiliation(s)
- Sandra R. Richardson
- Mater Research Institute, The University of Queensland, Translational Research Institute, Woolloongabba QLD 4102, Australia;
| | - Santiago Morell
- Mater Research Institute, The University of Queensland, Translational Research Institute, Woolloongabba QLD 4102, Australia;
| | - Geoffrey J. Faulkner
- Mater Research Institute, The University of Queensland, Translational Research Institute, Woolloongabba QLD 4102, Australia;
- School of Biomedical Sciences, The University of Queensland, Brisbane QLD 4072, Australia
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224
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Xu H, Yan Y, Deb S, Rangasamy D, Germann M, Malaterre J, Eder NC, Ward RL, Hawkins NJ, Tothill RW, Chen L, Mortensen NJ, Fox SB, McKay MJ, Ramsay RG. Cohesin Rad21 mediates loss of heterozygosity and is upregulated via Wnt promoting transcriptional dysregulation in gastrointestinal tumors. Cell Rep 2014; 9:1781-1797. [PMID: 25464844 DOI: 10.1016/j.celrep.2014.10.059] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 08/29/2014] [Accepted: 10/27/2014] [Indexed: 01/22/2023] Open
Abstract
Loss of heterozygosity (LOH) of the adenomatous polyposis coli (APC) gene triggers a series of molecular events leading to intestinal adenomagenesis. Haploinsufficiency of the cohesin Rad21 influences multiple initiating events in colorectal cancer (CRC). We identify Rad21 as a gatekeeper of LOH and a β-catenin target gene and provide evidence that Wnt pathway activation drives RAD21 expression in human CRC. Genome-wide analyses identified Rad21 as a key transcriptional regulator of critical CRC genes and long interspersed element (LINE-1 or L1) retrotransposons. Elevated RAD21 expression tracks with reactivation of L1 expression in human sporadic CRC, implicating cohesin-mediated L1 expression in global genomic instability and gene dysregulation in cancer.
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Affiliation(s)
- Huiling Xu
- Differentiation and Transcription Laboratory, Peter MacCallum Cancer Centre (PMCC), East Melbourne, VIC 3002, Australia; Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, VIC 3000, Australia; Department of Pathology, The University of Melbourne, Parkville, VIC 3000, Australia
| | - Yuqian Yan
- Differentiation and Transcription Laboratory, Peter MacCallum Cancer Centre (PMCC), East Melbourne, VIC 3002, Australia
| | - Siddhartha Deb
- Pathology Department, PMCC, East Melbourne, VIC 3002, Australia; Victorian Cancer Biobank, Carlton, VIC 3053, Australia
| | - Danny Rangasamy
- John Curtin School of Medical Research, The Australian National University, Acton, ACT 2601, Australia
| | - Markus Germann
- Differentiation and Transcription Laboratory, Peter MacCallum Cancer Centre (PMCC), East Melbourne, VIC 3002, Australia; Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, VIC 3000, Australia
| | - Jordane Malaterre
- Differentiation and Transcription Laboratory, Peter MacCallum Cancer Centre (PMCC), East Melbourne, VIC 3002, Australia; Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, VIC 3000, Australia
| | - Noreen C Eder
- Differentiation and Transcription Laboratory, Peter MacCallum Cancer Centre (PMCC), East Melbourne, VIC 3002, Australia
| | - Robyn L Ward
- Prince of Wales Clinical School, University of New South Wales (UNSW), Sydney, NSW 2052, Australia
| | | | - Richard W Tothill
- Cancer Therapeutics Program, Cancer Research Division, PMCC, East Melbourne, VIC 3002, Australia
| | - Long Chen
- John Curtin School of Medical Research, The Australian National University, Acton, ACT 2601, Australia
| | - Neil J Mortensen
- Department of Colorectal Surgery, Oxford University Hospitals, Oxford Cancer Centre, Churchill Hospital, Oxford OX3 7LJ, UK
| | - Stephen B Fox
- Department of Pathology, The University of Melbourne, Parkville, VIC 3000, Australia; Pathology Department, PMCC, East Melbourne, VIC 3002, Australia
| | - Michael J McKay
- University of Sydney and North Coast Cancer Institute, Lismore, NSW 2480, Australia
| | - Robert G Ramsay
- Differentiation and Transcription Laboratory, Peter MacCallum Cancer Centre (PMCC), East Melbourne, VIC 3002, Australia; Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, VIC 3000, Australia.
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225
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Mir AA, Philippe C, Cristofari G. euL1db: the European database of L1HS retrotransposon insertions in humans. Nucleic Acids Res 2014; 43:D43-7. [PMID: 25352549 PMCID: PMC4383891 DOI: 10.1093/nar/gku1043] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Retrotransposons account for almost half of our genome. They are mobile genetics elements—also known as jumping genes—but only the L1HS subfamily of Long Interspersed Nuclear Elements (LINEs) has retained the ability to jump autonomously in modern humans. Their mobilization in germline—but also some somatic tissues—contributes to human genetic diversity and to diseases, such as cancer. Here, we present euL1db, the European database of L1HS retrotransposon insertions in humans (available at http://euL1db.unice.fr). euL1db provides a curated and comprehensive summary of L1HS insertion polymorphisms identified in healthy or pathological human samples and published in peer-reviewed journals. A key feature of euL1db is its sample-wise organization. Hence L1HS insertion polymorphisms are connected to samples, individuals, families and clinical conditions. The current version of euL1db centralizes results obtained in 32 studies. It contains >900 samples, >140 000 sample-wise insertions and almost 9000 distinct merged insertions. euL1db will help understanding the link between L1 retrotransposon insertion polymorphisms and phenotype or disease.
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Affiliation(s)
- Ashfaq A Mir
- INSERM, U1081, Institute for Research on Cancer and Aging of Nice (IRCAN), F-06100 Nice, France CNRS, UMR 7284, Institute for Research on Cancer and Aging of Nice (IRCAN), F-06100 Nice, France Faculty of Medicine, Institute for Research on Cancer and Aging of Nice (IRCAN), University of Nice-Sophia-Antipolis, F-06100 Nice, France
| | - Claude Philippe
- INSERM, U1081, Institute for Research on Cancer and Aging of Nice (IRCAN), F-06100 Nice, France CNRS, UMR 7284, Institute for Research on Cancer and Aging of Nice (IRCAN), F-06100 Nice, France Faculty of Medicine, Institute for Research on Cancer and Aging of Nice (IRCAN), University of Nice-Sophia-Antipolis, F-06100 Nice, France
| | - Gaël Cristofari
- INSERM, U1081, Institute for Research on Cancer and Aging of Nice (IRCAN), F-06100 Nice, France CNRS, UMR 7284, Institute for Research on Cancer and Aging of Nice (IRCAN), F-06100 Nice, France Faculty of Medicine, Institute for Research on Cancer and Aging of Nice (IRCAN), University of Nice-Sophia-Antipolis, F-06100 Nice, France
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226
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Bergman CM. A proposal for the reference-based annotation of de novo transposable element insertions. Mob Genet Elements 2014; 2:51-54. [PMID: 22754753 PMCID: PMC3383450 DOI: 10.4161/mge.19479] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Understanding the causes and consequences of transposable element (TE) activity in the genomic era requires sophisticated bioinformatics approaches to accurately identify individual insertion sites. Next-generation sequencing technology now makes it possible to rapidly identify new TE insertions using resequencing data, opening up new possibilities to study the nature of TE-induced mutation and the target site preferences of different TE families. While the identification of new TE insertion sites is seemingly a simple task, the mechanisms of transposition present unique challenges for the annotation of de novo transposable element insertions mapped to a reference genome. Here I discuss these challenges and propose a framework for the annotation of de novo TE insertions that accommodates known mechanisms of TE insertion and established coordinate systems for genome annotation.
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Affiliation(s)
- Casey M Bergman
- Faculty of Life Sciences; University of Manchester; Manchester, UK
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227
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228
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Chen L, Dahlstrom JE, Lee SH, Rangasamy D. Naturally occurring endo-siRNA silences LINE-1 retrotransposons in human cells through DNA methylation. Epigenetics 2014; 7:758-71. [DOI: 10.4161/epi.20706] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
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229
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Ohms S, Lee SH, Rangasamy D. LINE-1 retrotransposons and let-7 miRNA: partners in the pathogenesis of cancer? Front Genet 2014; 5:338. [PMID: 25339972 PMCID: PMC4188135 DOI: 10.3389/fgene.2014.00338] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2014] [Accepted: 09/09/2014] [Indexed: 11/13/2022] Open
Abstract
Long interspersed nuclear element-1 (LINE-1 or L1) retrotransposons are insertional mutagens capable of altering the genomic landscape in many ways. Activation of the normally silent LINE-1 retrotransposon is associated with a high level of cancer-associated DNA damage and genomic instability. Studies of LINE-1 have so far focused mainly on changes in gene expression, and our knowledge of its impact on functional non-coding RNAs is in its infancy. However, current evidence suggests that a significant number of human miRNAs originate from retrotransposon sequences. Furthermore, LINE-1 is generally not expressed in normal tissues while its expression is widespread in epithelial cancers. Based on our recent studies, we demonstrate a functional link between aberrant LINE-1 expression and deregulation of let-7 miRNA expression. Since the expression of let-7 is modulated by LINE-1 activity, we discuss possible mechanisms for this effect and how the silencing of LINE-1 activation could provide new therapeutic options for cancer treatment. Based on the deep sequencing of small RNAs in parallel with gene expression profiling in breast cancer cells, we have identified potential pathways linking L1 activity to let-7 processing and maturation and ultimately to the control of stemness in human cancer cells.
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Affiliation(s)
- Stephen Ohms
- Department of Molecular Bioscience, John Curtin School of Medical Research, The Australian National University Canberra, ACT, Australia
| | - Sung-Hun Lee
- Department of Molecular Bioscience, John Curtin School of Medical Research, The Australian National University Canberra, ACT, Australia ; Molecular and Cellular Oncology, University of Texas MD Anderson Cancer Center Houston, TX, USA
| | - Danny Rangasamy
- Department of Molecular Bioscience, John Curtin School of Medical Research, The Australian National University Canberra, ACT, Australia
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230
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Arokium H, Kamata M, Kim S, Kim N, Liang M, Presson AP, Chen IS. Deep sequencing reveals low incidence of endogenous LINE-1 retrotransposition in human induced pluripotent stem cells. PLoS One 2014; 9:e108682. [PMID: 25289675 PMCID: PMC4188539 DOI: 10.1371/journal.pone.0108682] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 09/03/2014] [Indexed: 01/27/2023] Open
Abstract
Long interspersed element-1 (LINE-1 or L1) retrotransposition induces insertional mutations that can result in diseases. It was recently shown that the copy number of L1 and other retroelements is stable in induced pluripotent stem cells (iPSCs). However, by using an engineered reporter construct over-expressing L1, another study suggests that reprogramming activates L1 mobility in iPSCs. Given the potential of human iPSCs in therapeutic applications, it is important to clarify whether these cells harbor somatic insertions resulting from endogenous L1 retrotransposition. Here, we verified L1 expression during and after reprogramming as well as potential somatic insertions driven by the most active human endogenous L1 subfamily (L1Hs). Our results indicate that L1 over-expression is initiated during the reprogramming process and is subsequently sustained in isolated clones. To detect potential somatic insertions in iPSCs caused by L1Hs retotransposition, we used a novel sequencing strategy. As opposed to conventional sequencing direction, we sequenced from the 3′ end of L1Hs to the genomic DNA, thus enabling the direct detection of the polyA tail signature of retrotransposition for verification of true insertions. Deep coverage sequencing thus allowed us to detect seven potential somatic insertions with low read counts from two iPSC clones. Negative PCR amplification in parental cells, presence of a polyA tail and absence from seven L1 germline insertion databases highly suggested true somatic insertions in iPSCs. Furthermore, these insertions could not be detected in iPSCs by PCR, likely due to low abundance. We conclude that L1Hs retrotransposes at low levels in iPSCs and therefore warrants careful analyses for genotoxic effects.
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Affiliation(s)
- Hubert Arokium
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Masakazu Kamata
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Sanggu Kim
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Namshin Kim
- Korean Bioinformation Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea
| | - Min Liang
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Angela P. Presson
- Department of Biostatistics, University of California Los Angeles School of Public Health, University of California Los Angeles, Los Angeles, California, United States of America
| | - Irvin S. Chen
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, David Geffen School of Medicine, Los Angeles, California, United States of America
- * E-mail:
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231
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SIRT6 represses LINE1 retrotransposons by ribosylating KAP1 but this repression fails with stress and age. Nat Commun 2014; 5:5011. [PMID: 25247314 PMCID: PMC4185372 DOI: 10.1038/ncomms6011] [Citation(s) in RCA: 254] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 08/18/2014] [Indexed: 02/08/2023] Open
Abstract
L1 retrotransposons are an abundant class of transposable elements which pose a threat to genome stability and may play a role in age-related pathologies such as cancer. Recent evidence indicates that L1s become more active in somatic tissues during the course of aging; the mechanisms underlying this phenomenon remain unknown, however. Here we report that the longevity regulating protein, SIRT6, is a powerful repressor of L1 activity. Specifically, SIRT6 binds to the 5′UTR of L1 loci, where it mono-ADP ribosylates the nuclear corepressor protein, KAP1, and facilitates KAP1 interaction with the heterochromatin factor, HP1α, thereby contributing to the packaging of L1 elements into transcriptionally repressive heterochromatin. During the course of aging, and also in response to DNA damage, however, we find that SIRT6 is depleted from L1 loci, allowing for the activation of these previously silenced retroelements.
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232
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Repetitive elements dynamics in cell identity programming, maintenance and disease. Curr Opin Cell Biol 2014; 31:67-73. [PMID: 25240822 DOI: 10.1016/j.ceb.2014.09.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 09/02/2014] [Accepted: 09/03/2014] [Indexed: 01/08/2023]
Abstract
The days of 'junk DNA' seem to be over. The rapid progress of genomics technologies has been unveiling unexpected mechanisms by which repetitive DNA and in particular transposable elements (TEs) have evolved, becoming key issues in understanding genome structure and function. Indeed, rather than 'parasites', recent findings strongly suggest that TEs may have a positive function by contributing to tissue specific transcriptional programs, in particular as enhancer-like elements and/or modules for regulation of higher order chromatin structure. Further, it appears that during development and aging genomes experience several waves of TEs activation, and this contributes to individual genome shaping during lifetime. Interestingly, TEs activity is major target of epigenomic regulation. These findings are shedding new light on the genome-phenotype relationship and set the premises to help to explain complex disease manifestation, as consequence of TEs activity deregulation.
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233
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Shaknovich R, De S, Michor F. Epigenetic diversity in hematopoietic neoplasms. Biochim Biophys Acta Rev Cancer 2014; 1846:477-84. [PMID: 25240947 DOI: 10.1016/j.bbcan.2014.09.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 09/09/2014] [Accepted: 09/11/2014] [Indexed: 12/31/2022]
Abstract
Tumor cell populations display a remarkable extent of variability in non-genetic characteristics such as DNA methylation, histone modification patterns, and differentiation levels of individual cells. It remains to be elucidated whether non-genetic heterogeneity is simply a byproduct of tumor evolution or instead a manifestation of a higher-order tissue organization that is maintained within the neoplasm to establish a differentiation hierarchy, a favorable microenvironment, or a buffer against changing selection pressures during tumorigenesis. Here, we review recent findings on epigenetic diversity, particularly heterogeneity in DNA methylation patterns in hematologic malignancies. We also address the implications of epigenetic heterogeneity for the clonal evolution of tumors and discuss its effects on gene expression and other genome functions in cancer.
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Affiliation(s)
- Rita Shaknovich
- Division of Hematology/Oncology, Department of Medicine, Weill Cornell Medical College, New York, NY 10021, USA; Division of Immunopathology, Department of Pathology, Weill Cornell Medical College, New York, NY 10021, USA
| | - Subhajyoti De
- Department of Medicine, University of Colorado School of Medicine, Aurora, CO 80045, USA; University of Colorado Cancer Center, Aurora, CO 80045, USA
| | - Franziska Michor
- Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute, Harvard School of Public Health, Boston, MA 02215, USA; Department of Biostatistics, Harvard School of Public Health, Boston, MA 02215, USA.
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234
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Wu J, Lee WP, Ward A, Walker JA, Konkel MK, Batzer MA, Marth GT. Tangram: a comprehensive toolbox for mobile element insertion detection. BMC Genomics 2014; 15:795. [PMID: 25228379 PMCID: PMC4180832 DOI: 10.1186/1471-2164-15-795] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 09/03/2014] [Indexed: 11/10/2022] Open
Abstract
Background Mobile elements (MEs) constitute greater than 50% of the human genome as a result of repeated insertion events during human genome evolution. Although most of these elements are now fixed in the population, some MEs, including ALU, L1, SVA and HERV-K elements, are still actively duplicating. Mobile element insertions (MEIs) have been associated with human genetic disorders, including Crohn’s disease, hemophilia, and various types of cancer, motivating the need for accurate MEI detection methods. To comprehensively identify and accurately characterize these variants in whole genome next-generation sequencing (NGS) data, a computationally efficient detection and genotyping method is required. Current computational tools are unable to call MEI polymorphisms with sufficiently high sensitivity and specificity, or call individual genotypes with sufficiently high accuracy. Results Here we report Tangram, a computationally efficient MEI detection program that integrates read-pair (RP) and split-read (SR) mapping signals to detect MEI events. By utilizing SR mapping in its primary detection module, a feature unique to this software, Tangram is able to pinpoint MEI breakpoints with single-nucleotide precision. To understand the role of MEI events in disease, it is essential to produce accurate individual genotypes in clinical samples. Tangram is able to determine sample genotypes with very high accuracy. Using simulations and experimental datasets, we demonstrate that Tangram has superior sensitivity, specificity, breakpoint resolution and genotyping accuracy, when compared to other, recently developed MEI detection methods. Conclusions Tangram serves as the primary MEI detection tool in the 1000 Genomes Project, and is implemented as a highly portable, memory-efficient, easy-to-use C++ computer program, built under an open-source development model.
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Affiliation(s)
| | | | | | | | | | | | - Gabor T Marth
- Department of Human Genetics and USTAR Center for Genetic Discovery, University of Utah, Salt Lake City, Utah, USA.
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235
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Increased expression and copy number amplification of LINE-1 and SINE B1 retrotransposable elements in murine mammary carcinoma progression. Oncotarget 2014; 4:1882-93. [PMID: 24231191 PMCID: PMC3875756 DOI: 10.18632/oncotarget.1188] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
In higher eukaryotic genomes, Long Interspersed Nuclear Element 1 (LINE-1) retrotransposons and endogenous retroviruses represent large families of repeated elements encoding reverse transcriptase (RT) proteins. Short Interspersed Nuclear Element B1 (SINE B1) retrotrasposons do not encode RT, but use LINE-1-derived RT for their retrotransposition. We previously showed that many cancer types have an abundant endogenous RT activity. Inhibition of that activity, by either RNA interference-dependent silencing of active LINE-1 elements or by RT inhibitory drugs, reduced proliferation and promoted differentiation in cancer cells, indicating that LINE-1-encoded RT is required for tumor progression. Using MMTV-PyVT transgenic mice as a well-defined model of breast cancer progression, we now report that both LINE-1 and SINE B1 retrotransposons are up-regulated at a very early stage of tumorigenesis; LINE-1-encoded RT product and enzymatic activity were detected in tumor tissues as early as stage 1, preceding the widespread appearance of histological alterations and specific cancer markers, and further increased in later progression stages, while neither was present in non-pathological breast tissues. Importantly, both LINE-1 and SINE B1 retrotransposon families undergo copy number amplification during tumor progression. These findings therefore indicate that RT activity is distinctive of breast cancer cells and that, furthermore, LINE-1 and SINE B1 undergo copy number amplification during cancer progression.
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236
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Dynamic Alu methylation during normal development, aging, and tumorigenesis. BIOMED RESEARCH INTERNATIONAL 2014; 2014:784706. [PMID: 25243180 PMCID: PMC4163490 DOI: 10.1155/2014/784706] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 08/16/2014] [Indexed: 12/15/2022]
Abstract
DNA methylation primarily occurs on CpG dinucleotides and plays an important role in transcriptional regulations during tissue development and cell differentiation. Over 25% of CpG dinucleotides in the human genome reside within Alu elements, the most abundant human repeats. The methylation of Alu elements is an important mechanism to suppress Alu transcription and subsequent retrotransposition. Decades of studies revealed that Alu methylation is highly dynamic during early development and aging. Recently, many environmental factors were shown to have a great impact on Alu methylation. In addition, aberrant Alu methylation has been documented to be an early event in many tumors and Alu methylation levels have been associated with tumor aggressiveness. The assessment of the Alu methylation has become an important approach for early diagnosis and/or prognosis of cancer. This review focuses on the dynamic Alu methylation during development, aging, and tumor genesis. The cause and consequence of Alu methylation changes will be discussed.
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237
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Kines KJ, Sokolowski M, deHaro DL, Christian CM, Belancio VP. Potential for genomic instability associated with retrotranspositionally-incompetent L1 loci. Nucleic Acids Res 2014; 42:10488-502. [PMID: 25143528 PMCID: PMC4176336 DOI: 10.1093/nar/gku687] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Expression of the L1 retrotransposon can damage the genome through insertional mutagenesis and the generation of DNA double-strand breaks (DSBs). The majority of L1 loci in the human genome are 5'-truncated and therefore incapable of retrotransposition. While thousands of full-length L1 loci remain, most are retrotranspositionally-incompetent due to inactivating mutations. However, mutations leading to premature stop codons within the L1 ORF2 sequence may yield truncated proteins that retain a functional endonuclease domain. We demonstrate that some truncated ORF2 proteins cause varying levels of toxicity and DNA damage when chronically overexpressed in mammalian cells. Furthermore, transfection of some ORF2 constructs containing premature stop codons supported low levels of Alu retrotransposition, demonstrating the potential for select retrotranspositionally-incompetent L1 loci to generate genomic instability. This result suggests yet another plausible explanation for the relative success of Alu elements in populating the human genome. Our data suggest that a subset of retrotranspositionally-incompetent L1s, previously considered to be harmless to genomic integrity, may have the potential to cause chronic DNA damage by introducing DSBs and mobilizing Alu. These results imply that the number of known L1 loci in the human genome that potentially threaten its stability may not be limited to the retrotranspositionally active loci.
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Affiliation(s)
- Kristine J Kines
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, and Tulane Center for Aging, New Orleans, LA 70112, USA
| | - Mark Sokolowski
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, and Tulane Center for Aging, New Orleans, LA 70112, USA
| | - Dawn L deHaro
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, and Tulane Center for Aging, New Orleans, LA 70112, USA
| | - Claiborne M Christian
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, and Tulane Center for Aging, New Orleans, LA 70112, USA
| | - Victoria P Belancio
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, and Tulane Center for Aging, New Orleans, LA 70112, USA
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238
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Distinct isoform of FABP7 revealed by screening for retroelement-activated genes in diffuse large B-cell lymphoma. Proc Natl Acad Sci U S A 2014; 111:E3534-43. [PMID: 25114248 DOI: 10.1073/pnas.1405507111] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Remnants of ancient transposable elements (TEs) are abundant in mammalian genomes. These sequences harbor multiple regulatory motifs and hence are capable of influencing expression of host genes. In response to environmental changes, TEs are known to be released from epigenetic repression and to become transcriptionally active. Such activation could also lead to lineage-inappropriate activation of oncogenes, as one study described in Hodgkin lymphoma. However, little further evidence for this mechanism in other cancers has been reported. Here, we reanalyzed whole transcriptome data from a large cohort of patients with diffuse large B-cell lymphoma (DLBCL) compared with normal B-cell centroblasts to detect genes ectopically expressed through activation of TE promoters. We have identified 98 such TE-gene chimeric transcripts that were exclusively expressed in primary DLBCL cases and confirmed several in DLBCL-derived cell lines. We further characterized a TE-gene chimeric transcript involving a fatty acid-binding protein gene (LTR2-FABP7), normally expressed in brain, that was ectopically expressed in a subset of DLBCL patients through the use of an endogenous retroviral LTR promoter of the LTR2 family. The LTR2-FABP7 chimeric transcript encodes a novel chimeric isoform of the protein with characteristics distinct from native FABP7. In vitro studies reveal a dependency for DLBCL cell line proliferation and growth on LTR2-FABP7 chimeric protein expression. Taken together, these data demonstrate the significance of TEs as regulators of aberrant gene expression in cancer and suggest that LTR2-FABP7 may contribute to the pathogenesis of DLBCL in a subgroup of patients.
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239
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Tubio JMC, Li Y, Ju YS, Martincorena I, Cooke SL, Tojo M, Gundem G, Pipinikas CP, Zamora J, Raine K, Menzies A, Roman-Garcia P, Fullam A, Gerstung M, Shlien A, Tarpey PS, Papaemmanuil E, Knappskog S, Van Loo P, Ramakrishna M, Davies HR, Marshall J, Wedge DC, Teague JW, Butler AP, Nik-Zainal S, Alexandrov L, Behjati S, Yates LR, Bolli N, Mudie L, Hardy C, Martin S, McLaren S, O'Meara S, Anderson E, Maddison M, Gamble S, Foster C, Warren AY, Whitaker H, Brewer D, Eeles R, Cooper C, Neal D, Lynch AG, Visakorpi T, Isaacs WB, Veer LV, Caldas C, Desmedt C, Sotiriou C, Aparicio S, Foekens JA, Eyfjörd JE, Lakhani SR, Thomas G, Myklebost O, Span PN, Børresen-Dale AL, Richardson AL, Van de Vijver M, Vincent-Salomon A, Van den Eynden GG, Flanagan AM, Futreal PA, Janes SM, Bova GS, Stratton MR, McDermott U, Campbell PJ. Mobile DNA in cancer. Extensive transduction of nonrepetitive DNA mediated by L1 retrotransposition in cancer genomes. Science 2014; 345:1251343. [PMID: 25082706 PMCID: PMC4380235 DOI: 10.1126/science.1251343] [Citation(s) in RCA: 285] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Long interspersed nuclear element-1 (L1) retrotransposons are mobile repetitive elements that are abundant in the human genome. L1 elements propagate through RNA intermediates. In the germ line, neighboring, nonrepetitive sequences are occasionally mobilized by the L1 machinery, a process called 3' transduction. Because 3' transductions are potentially mutagenic, we explored the extent to which they occur somatically during tumorigenesis. Studying cancer genomes from 244 patients, we found that tumors from 53% of the patients had somatic retrotranspositions, of which 24% were 3' transductions. Fingerprinting of donor L1s revealed that a handful of source L1 elements in a tumor can spawn from tens to hundreds of 3' transductions, which can themselves seed further retrotranspositions. The activity of individual L1 elements fluctuated during tumor evolution and correlated with L1 promoter hypomethylation. The 3' transductions disseminated genes, exons, and regulatory elements to new locations, most often to heterochromatic regions of the genome.
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Affiliation(s)
| | - Yilong Li
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Young Seok Ju
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | | | | | - Marta Tojo
- Department of Physiology, School of Medicine–Center for Resesarch in Molecular Medicine and Chronic Diseases, Instituto de Investigaciones Sanitarias, University of Santiago de Compostela, Spain
| | - Gunes Gundem
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | | | - Jorge Zamora
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Keiran Raine
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Andrew Menzies
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | | | - Anthony Fullam
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Moritz Gerstung
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Adam Shlien
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | | | | | - Stian Knappskog
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
- Department of Clinical Science, University of Bergen, Bergen, Norway
- Department of Oncology, Haukeland University Hospital, Bergen, Norway
| | - Peter Van Loo
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
- Human Genome Laboratory, Department of Human Genetics, VIB and KU Leuven, Leuven, Belgium
| | | | - Helen R. Davies
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - John Marshall
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - David C. Wedge
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Jon W. Teague
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Adam P. Butler
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Serena Nik-Zainal
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
- Cambridge University Hospitals National Health Service (NHS) Foundation Trust, Cambridge, UK
| | | | - Sam Behjati
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Lucy R. Yates
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Niccolo Bolli
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
- Department of Haematology, University of Cambridge, Cambridge, UK
| | - Laura Mudie
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Claire Hardy
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Sancha Martin
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Stuart McLaren
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Sarah O'Meara
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | | | - Mark Maddison
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Stephen Gamble
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | | | - Anne Y. Warren
- Cambridge University Hospitals National Health Service (NHS) Foundation Trust, Cambridge, UK
| | - Hayley Whitaker
- Cancer Research UK (CRUK) Cambridge Institute, University of Cambridge, Cambridge, UK
| | - Daniel Brewer
- Institute of Cancer Research, Sutton, London, UK
- University of East Anglia, Norwich, UK
| | | | - Colin Cooper
- Institute of Cancer Research, Sutton, London, UK
- University of East Anglia, Norwich, UK
| | - David Neal
- Cancer Research UK (CRUK) Cambridge Institute, University of Cambridge, Cambridge, UK
| | - Andy G. Lynch
- Cancer Research UK (CRUK) Cambridge Institute, University of Cambridge, Cambridge, UK
| | - Tapio Visakorpi
- Institute of Biosciences and Medical Technology–BioMediTech, University of Tampere and Tampere University Hospital, Tampere, Finland
| | | | | | - Carlos Caldas
- Cancer Research UK (CRUK) Cambridge Institute, University of Cambridge, Cambridge, UK
| | - Christine Desmedt
- Breast Cancer Translational Research Laboratory, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium
| | - Christos Sotiriou
- Breast Cancer Translational Research Laboratory, Institut Jules Bordet, Université Libre de Bruxelles, Brussels, Belgium
| | - Sam Aparicio
- British Columbia Cancer Agency, Vancouver, Canada
| | - John A. Foekens
- Department of Medical Oncology, Erasmus Medical Center Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands
| | | | - Sunil R. Lakhani
- School of Medicine, University of Queensland, Brisbane, Australia
- Pathology Queensland, Royal Brisbane and Women’s Hospital, Brisbane, Australia
- UQ Centre for Clinical Research, University of Queensland, Brisbane, Australia
| | - Gilles Thomas
- Université Lyon 1, Institut National du Cancer (INCa)–Synergie, Lyon, France
| | - Ola Myklebost
- Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Paul N. Span
- Department of Radiation Oncology and Department of Laboratory Medicine, Radboud University Medical Center, Nijmegen, Netherlands
| | | | | | - Marc Van de Vijver
- Department of Pathology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, Netherlands
| | - Anne Vincent-Salomon
- Institut Bergonié, 229 cours de l’Argone, 33076 Bordeaux, France
- Institut Curie, Department of Tumor Biology, 26 rue d’Ulm, 75248 Paris cédex 05, France
| | - Gert G. Van den Eynden
- Translational Cancer Research Unit and Department of Pathology, GZA Hospitals, Antwerp, Belgium
| | - Adrienne M. Flanagan
- Royal National Orthopaedic Hospital, Middlesex, UK
- UCL Cancer Institute, University College London, London, UK
| | - P. Andrew Futreal
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
- MD Anderson Cancer Center, Houston, TX, USA
| | - Sam M. Janes
- Lungs for Living Research Centre, Rayne Institute, University College London (UCL), London, UK
| | - G. Steven Bova
- Institute of Biosciences and Medical Technology–BioMediTech, University of Tampere and Tampere University Hospital, Tampere, Finland
| | | | - Ultan McDermott
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
| | - Peter J. Campbell
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
- Cambridge University Hospitals National Health Service (NHS) Foundation Trust, Cambridge, UK
- Department of Haematology, University of Cambridge, Cambridge, UK
| | | | | | - ICGC Prostate Cancer Group
- Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, UK
- Institute of Cancer Research, Sutton, London, UK
- Cancer Research UK (CRUK) Cambridge Institute, University of Cambridge, Cambridge, UK
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240
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Okudaira N, Ishizaka Y, Nishio H. Retrotransposition of long interspersed element 1 induced by methamphetamine or cocaine. J Biol Chem 2014; 289:25476-85. [PMID: 25053411 PMCID: PMC4162154 DOI: 10.1074/jbc.m114.559419] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Long interspersed element 1 (L1) is a retroelement constituting ∼17% of the human genome. A single human cell has 80–100 copies of L1 capable of retrotransposition (L1-RTP), ∼10% of which are “hot L1” copies, meaning they are primed for “jumping” within the genome. Recent studies demonstrated induction of L1 activity by drugs of abuse or low molecular weight compounds, but little is known about the underlying mechanism. The aim of this study was to identify the mechanism and effects of methamphetamine (METH) and cocaine on L1-RTP. Our results revealed that METH and cocaine induced L1-RTP in neuronal cell lines. This effect was found to be reverse transcriptase-dependent. However, METH and cocaine did not induce double-strand breaks. RNA interference experiments combined with add-back of siRNA-resistant cDNAs revealed that the induction of L1-RTP by METH or cocaine depends on the activation of cAMP response element-binding protein (CREB). METH or cocaine recruited the L1-encoded open reading frame 1 (ORF1) to chromatin in a CREB-dependent manner. These data suggest that the cellular cascades underlying METH- and cocaine-induced L1-RTP are different from those behind L1-RTP triggered by DNA damage; CREB is involved in drug-induced L1-RTP. L1-RTP caused by drugs of abuse is a novel type of genomic instability, and analysis of this phenomenon might be a novel approach to studying substance-use disorders.
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Affiliation(s)
- Noriyuki Okudaira
- From the Department of Legal Medicine, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan and
| | - Yukihito Ishizaka
- Department of Intractable Diseases, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku-ku, Tokyo 162-8655, Japan
| | - Hajime Nishio
- From the Department of Legal Medicine, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan and
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241
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Retrotransposons in pluripotent cells: Impact and new roles in cellular plasticity. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1849:417-26. [PMID: 25042909 DOI: 10.1016/j.bbagrm.2014.07.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 07/08/2014] [Accepted: 07/10/2014] [Indexed: 12/27/2022]
Abstract
Transposable Elements are pieces of DNA able to mobilize from one location to another within genomes. Although they constitute more than 50% of the human genome, they have been classified as selfish DNA, with the only mission to spread within genomes and generate more copies of themselves that will ensure their presence over generations. Despite their remarkable prevalence, only a minor group of transposable elements remain active in the human genome and can sporadically be associated with the generation of a genetic disorder due to their ongoing mobility. Most of the transposable elements identified in the human genome corresponded to fixed insertions that no longer move in genomes. As selfish DNA, transposable element insertions accumulate in cell types where genetic information can be passed to the next generation. Indeed, work from different laboratories has demonstrated that the main heritable load of TE accumulation in humans occurs during early embryogenesis. Thus, active transposable elements have a clear impact on our pluripotent genome. However, recent findings suggest that the main proportion of fixed non-mobile transposable elements might also have emerging roles in cellular plasticity. In this concise review, we provide an overview of the impact of currently active transposable elements in our pluripotent genome and further discuss new roles of transposable elements (active or not) in regulating pluripotency. This article is part of a Special Issue entitled: Stress as a fundamental theme in cell plasticity.
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242
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Guidez F. [Retrotransposons: selfish DNA or active epigenetic players in somatic cells?]. Med Sci (Paris) 2014; 30:659-64. [PMID: 25014457 DOI: 10.1051/medsci/20143006016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Transposable elements (TE) represent around 40% of the human genome. They are endogenous mobile DNA sequences able to jump and duplicate in the host genome. TE have long been considered as "junk" DNA but are now believed to be important regulators of gene expression by participating to the establishment of the DNA methylation profile. Recent advances in genome sequencing reveals a higher transposition frequency and TE driven gene expression in somatic cells than previously thought. As TE propagation is deleterious and may be involved in oncogenic mechanisms, host cells have developed silencing mechanisms mainly described in germinal and embryonic cells. However, somatic cells are also proned to TE transposition and use specific mechanisms involving tumor suppressor proteins including p53, Rb and PLZF. These transcription factors specifically target genomic retrotransposon sequences, histone deacetylase and DNA methylase activities, inducing epigenetic modifications related to gene silencing. Thus, these transcription factors negatively regulate TE expression by the formation of DNA methylation profil in somatic cells possibly associated with oncogenic mechanisms.
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Affiliation(s)
- Fabien Guidez
- Inserm UMRS 1131, université Paris Diderot, institut universitaire d'hématologie (IUH), hôpital Saint-Louis, 1, avenue Claude Vellefaux, 75010 Paris, France
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243
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Mobile DNA elements in the generation of diversity and complexity in the brain. Nat Rev Neurosci 2014; 15:497-506. [PMID: 25005482 DOI: 10.1038/nrn3730] [Citation(s) in RCA: 180] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Mobile elements are DNA sequences that can change their position (retrotranspose) within the genome. Although its biological function is largely unappreciated, DNA derived from mobile elements comprises nearly half of the human genome. It has long been thought that neuronal genomes are invariable; however, recent studies have demonstrated that mobile elements actively retrotranspose during neurogenesis, thereby creating genomic diversity between neurons. In addition, mounting data demonstrate that mobile elements are misregulated in certain neurological disorders, including Rett syndrome and schizophrenia.
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244
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Volkman HE, Stetson DB. The enemy within: endogenous retroelements and autoimmune disease. Nat Immunol 2014; 15:415-22. [PMID: 24747712 DOI: 10.1038/ni.2872] [Citation(s) in RCA: 194] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 03/21/2014] [Indexed: 02/07/2023]
Abstract
Inappropriate or chronic detection of self nucleic acids by the innate immune system underlies many human autoimmune diseases. We discuss here an unexpected source of endogenous immunostimulatory nucleic acids: the reverse-transcribed cDNA of endogenous retroelements. The interplay between innate immune sensing and clearance of retroelement cDNA has important implications for the understanding of immune responses to infectious retroviruses such as human immunodeficiency virus (HIV). Furthermore, the detection of cDNA by the innate immune system reveals an evolutionary tradeoff: selection for a vigorous, sensitive response to infectious retroviruses may predispose the inappropriate detection of endogenous retroelements. We propose that this tradeoff has placed unique constraints on the sensitivity of the DNA-activated antiviral response, with implications for the interactions of DNA viruses and retroviruses with their hosts. Finally, we discuss how better understanding of the intersection of retroelement biology and innate immunity can guide the way to novel therapies for specific autoimmune diseases.
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Affiliation(s)
- Hannah E Volkman
- Department of Immunology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Daniel B Stetson
- Department of Immunology, University of Washington School of Medicine, Seattle, Washington, USA
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245
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deHaro D, Kines KJ, Sokolowski M, Dauchy RT, Streva VA, Hill SM, Hanifin JP, Brainard GC, Blask DE, Belancio VP. Regulation of L1 expression and retrotransposition by melatonin and its receptor: implications for cancer risk associated with light exposure at night. Nucleic Acids Res 2014; 42:7694-707. [PMID: 24914052 PMCID: PMC4081101 DOI: 10.1093/nar/gku503] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 04/30/2014] [Accepted: 05/19/2014] [Indexed: 12/17/2022] Open
Abstract
Expression of long interspersed element-1 (L1) is upregulated in many human malignancies. L1 can introduce genomic instability via insertional mutagenesis and DNA double-strand breaks, both of which may promote cancer. Light exposure at night, a recently recognized carcinogen, is associated with an increased risk of cancer in shift workers. We report that melatonin receptor 1 inhibits mobilization of L1 in cultured cells through downregulation of L1 mRNA and ORF1 protein. The addition of melatonin receptor antagonists abolishes the MT1 effect on retrotransposition in a dose-dependent manner. Furthermore, melatonin-rich, but not melatonin-poor, human blood collected at different times during the circadian cycle suppresses endogenous L1 mRNA during in situ perfusion of tissue-isolated xenografts of human cancer. Supplementation of human blood with exogenous melatonin or melatonin receptor antagonist during the in situ perfusion establishes a receptor-mediated action of melatonin on L1 expression. Combined tissue culture and in vivo data support that environmental light exposure of the host regulates expression of L1 elements in tumors. Our data imply that light-induced suppression of melatonin production in shift workers may increase L1-induced genomic instability in their genomes and suggest a possible connection between L1 activity and increased incidence of cancer associated with circadian disruption.
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Affiliation(s)
- Dawn deHaro
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, New Orleans, LA 70115, USA Tulane Center for Aging, New Orleans, LA 70112, USA
| | - Kristine J Kines
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, New Orleans, LA 70115, USA Tulane Center for Aging, New Orleans, LA 70112, USA
| | - Mark Sokolowski
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, New Orleans, LA 70115, USA Tulane Center for Aging, New Orleans, LA 70112, USA
| | - Robert T Dauchy
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, New Orleans, LA 70115, USA
| | - Vincent A Streva
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, New Orleans, LA 70115, USA
| | - Steven M Hill
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, New Orleans, LA 70115, USA
| | - John P Hanifin
- Department of Neurology, Thomas Jefferson University, Jefferson Medical College, Philadelphia, PA 19107, USA
| | - George C Brainard
- Department of Neurology, Thomas Jefferson University, Jefferson Medical College, Philadelphia, PA 19107, USA
| | - David E Blask
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, New Orleans, LA 70115, USA
| | - Victoria P Belancio
- Department of Structural and Cellular Biology, Tulane School of Medicine, Tulane Cancer Center, New Orleans, LA 70115, USA Tulane Center for Aging, New Orleans, LA 70112, USA
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246
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Helman E, Lawrence MS, Stewart C, Sougnez C, Getz G, Meyerson M. Somatic retrotransposition in human cancer revealed by whole-genome and exome sequencing. Genome Res 2014; 24:1053-63. [PMID: 24823667 PMCID: PMC4079962 DOI: 10.1101/gr.163659.113] [Citation(s) in RCA: 161] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 04/03/2014] [Indexed: 01/27/2023]
Abstract
Retrotransposons constitute a major source of genetic variation, and somatic retrotransposon insertions have been reported in cancer. Here, we applied TranspoSeq, a computational framework that identifies retrotransposon insertions from sequencing data, to whole genomes from 200 tumor/normal pairs across 11 tumor types as part of The Cancer Genome Atlas (TCGA) Pan-Cancer Project. In addition to novel germline polymorphisms, we find 810 somatic retrotransposon insertions primarily in lung squamous, head and neck, colorectal, and endometrial carcinomas. Many somatic retrotransposon insertions occur in known cancer genes. We find that high somatic retrotransposition rates in tumors are associated with high rates of genomic rearrangement and somatic mutation. Finally, we developed TranspoSeq-Exome to interrogate an additional 767 tumor samples with hybrid-capture exome data and discovered 35 novel somatic retrotransposon insertions into exonic regions, including an insertion into an exon of the PTEN tumor suppressor gene. The results of this large-scale, comprehensive analysis of retrotransposon movement across tumor types suggest that somatic retrotransposon insertions may represent an important class of structural variation in cancer.
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Affiliation(s)
- Elena Helman
- Harvard-MIT Division of Health Sciences & Technology, Cambridge, Massachusetts 02139, USA
- Broad Institute of MIT and Harvard, Cambridge, Masachusetts 02142, USA
| | | | - Chip Stewart
- Broad Institute of MIT and Harvard, Cambridge, Masachusetts 02142, USA
| | - Carrie Sougnez
- Broad Institute of MIT and Harvard, Cambridge, Masachusetts 02142, USA
| | - Gad Getz
- Broad Institute of MIT and Harvard, Cambridge, Masachusetts 02142, USA
- Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Matthew Meyerson
- Harvard-MIT Division of Health Sciences & Technology, Cambridge, Massachusetts 02139, USA
- Broad Institute of MIT and Harvard, Cambridge, Masachusetts 02142, USA
- Center for Cancer Genome Discovery and Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA
- Department of Pathology, Brigham & Women’s Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
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247
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Monden Y, Fujii N, Yamaguchi K, Ikeo K, Nakazawa Y, Waki T, Hirashima K, Uchimura Y, Tahara M. Efficient screening of long terminal repeat retrotransposons that show high insertion polymorphism via high-throughput sequencing of the primer binding site. Genome 2014; 57:245-52. [PMID: 25072847 DOI: 10.1139/gen-2014-0031] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Retrotransposons have been used frequently for the development of molecular markers by using their insertion polymorphisms among cultivars, because multiple copies of these elements are dispersed throughout the genome and inserted copies are inherited genetically. Although a large number of long terminal repeat (LTR) retrotransposon families exist in the higher eukaryotic genomes, the identification of families that show high insertion polymorphism has been challenging. Here, we performed an efficient screening of these retrotransposon families using an Illumina HiSeq2000 sequencing platform with comprehensive LTR library construction based on the primer binding site (PBS), which is located adjacent to the 5' LTR and has a motif that is universal and conserved among LTR retrotransposon families. The paired-end sequencing library of the fragments containing a large number of LTR sequences and their insertion sites was sequenced for seven strawberry (Fragaria × ananassa Duchesne) cultivars and one diploid wild species (Fragaria vesca L.). Among them, we screened 24 families with a "unique" insertion site that appeared only in one cultivar and not in any others, assuming that this type of insertion should have occurred quite recently. Finally, we confirmed experimentally the selected LTR families showed high insertion polymorphisms among closely related cultivars.
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Affiliation(s)
- Yuki Monden
- a Graduate School of Environmental and Life Science, Okayama University, 1-1-1 Tsushimanaka Kitaku, Okayama, Okayama 700-8530, Japan
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248
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Karimi A, Madjd Z, Habibi L, Akrami SM. Exposure of hepatocellular carcinoma cells to low-level As₂O₃ causes an extra toxicity pathway via L1 retrotransposition induction. Toxicol Lett 2014; 229:111-7. [PMID: 24960058 DOI: 10.1016/j.toxlet.2014.05.025] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 05/29/2014] [Accepted: 05/30/2014] [Indexed: 11/17/2022]
Abstract
Various mechanisms have been proposed for toxicity and carcinogenesis pattern of arsenic, a naturally occurring metalloid. The extent to which the long interspersed element-1 (LINE-1) retrotransposon, an ubiquitous retroelement with autonomous mobility, can be influenced upon exposure to low-level arsenic remains to be elucidated. The aim of this study was to evaluate the possible effect of low-level As2O3 on L1 retrotransposition alteration in human hepatocellular carcinoma cells (HepG2). L1 retrotransposition in HepG2 cells was performed by the in vitro retrotransposition assay using an EGFP-tagged L1RP. Following determination of non-cytotoxic concentrations of arsenic by a MTT assay, the cells were transfected with pL1RP-EGFP and then exposed to 0.25, 0.50 and 0.75 μM of As2O3. The amount of EGFP and its copy number in retrotransposed cells were evaluated by FACS and qPCR analysis in treated vs. control cells, respectively. Significant increase in retrotransposition frequency was found after 12 days exposure to 0.50 and 0.75 μM of As2O3 by FACS analysis (P<0.05). Obtained results were further confirmed by real time PCR, which showed significant induction of retrotransposition in all mentioned concentrations. Our findings indicate that low-level long-term As2O3 exposure may pave activation of L1 retrotransposon.
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Affiliation(s)
- Abbas Karimi
- Department of Molecular Medicine, Faculty of Advanced Technologies in Medicine (FATiM), Iran University of Medical Sciences, Tehran, Iran; Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Zahra Madjd
- Department of Molecular Medicine, Faculty of Advanced Technologies in Medicine (FATiM), Iran University of Medical Sciences, Tehran, Iran; Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran; Oncopathology Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Laleh Habibi
- Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Seyed Mohammad Akrami
- Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
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249
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Robinson KM, Dunning Hotopp JC. Mobile elements and viral integrations prompt considerations for bacterial DNA integration as a novel carcinogen. Cancer Lett 2014; 352:137-44. [PMID: 24956175 DOI: 10.1016/j.canlet.2014.05.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 04/30/2014] [Accepted: 05/01/2014] [Indexed: 12/11/2022]
Abstract
Insertional mutagenesis has been repeatedly demonstrated in cancer genomes and has a role in oncogenesis. Mobile genetic elements can induce cancer development by random insertion into cancer related genes or by inducing translocations. L1s are typically implicated in cancers of an epithelial cell origin, while Alu elements have been implicated in leukemia as well as epithelial cell cancers. Likewise, viral infections have a significant role in cancer development predominantly through integration into the human genome and mutating or deregulating cancer related genes. Human papilloma virus is the best-known example of viral integrations contributing to carcinogenesis. However, hepatitis B virus, Epstein-Barr virus, and Merkel cell polyomavirus also integrate into the human genome and disrupt cancer related genes. Thus far, the role of microbes in cancer has primarily been attributed to mutations induced through chronic inflammation or toxins, as is the case with Helicobacter pylori and enterotoxigenic Bacteroides fragilis. We hypothesize that like mobile elements and viral DNA, bacterial and parasitic DNA may also integrate into the human somatic genome and be oncogenic. Until recently it was believed that bacterial DNA could not integrate into the human genome, but new evidence demonstrates that bacterial insertional mutagenesis may occur in cancer cells. Although this work does not show causation between bacterial insertions and cancer, it prompts more research in this area. Promising new sequencing technologies may reduce the risk of artifactual chimeric sequences, thus diminishing some of the challenges of identifying novel insertions in the somatic human genome.
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Affiliation(s)
- Kelly M Robinson
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Julie C Dunning Hotopp
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA; Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD, USA; Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD, USA.
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250
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Abstract
One lineage of human endogenous retroviruses (HERVs), HERV-K(HML2), is upregulated in many cancers, some autoimmune/inflammatory diseases, and HIV-infected cells. Despite 3 decades of research, it is not known if these viruses play a causal role in disease, and there has been recent interest in whether they can be used as immunotherapy targets. Resolution of both these questions will be helped by an ability to distinguish between the effects of different integrated copies of the virus (loci). Research so far has concentrated on the 20 or so recently integrated loci that, with one exception, are in the human reference genome sequence. However, this viral lineage has been copying in the human population within the last million years, so some loci will inevitably be present in the human population but absent from the reference sequence. We therefore performed the first detailed search for such loci by mining whole-genome sequences generated by next-generation sequencing. We found a total of 17 loci, and the frequency of their presence ranged from only 2 of the 358 individuals examined to over 95% of them. On average, each individual had six loci that are not in the human reference genome sequence. Comparing the number of loci that we found to an expectation derived from a neutral population genetic model suggests that the lineage was copying until at least ∼250,000 years ago. IMPORTANCE About 5% of the human genome sequence is composed of the remains of retroviruses that over millions of years have integrated into the chromosomes of egg and/or sperm precursor cells. There are indications that protein expression of these viruses is higher in some diseases, and we need to know (i) whether these viruses have a role in causing disease and (ii) whether they can be used as immunotherapy targets in some of them. Answering both questions requires a better understanding of how individuals differ in the viruses that they carry. We carried out the first careful search for new viruses in some of the many human genome sequences that are now available thanks to advances in sequencing technology. We also compared the number that we found to a theoretical expectation to see if it is likely that these viruses are still replicating in the human population today.
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