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Liu M, Jia L, Guo X, Zhai X, Li H, Liu Y, Han J, Zhang B, Wang X, Li T, Wang Y, Li J, Yu C, Li L. Identification and Characterization of the HERV-K (HML-8) Group of Human Endogenous Retroviruses in the Genome. AIDS Res Hum Retroviruses 2023; 39:176-194. [PMID: 36656667 DOI: 10.1089/aid.2022.0084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Human endogenous retroviruses (HERVs) can be vertically transmitted in a Mendelian fashion, are stably maintained in the human genome, and are estimated to constitute ∼8% of the genome. HERVs affect human physiology and pathology through their provirus-encoded protein or long terminal repeat (LTR) element effect. Characterization of the genomic distribution is an essential step to understanding the relationships between endogenous retrovirus expression and diseases. However, the poor characterization of human MMTV-like (HML)-8 prevents a detailed understanding of the regulation of the expression of this family in humans and its impact on the host genome. In light of this, the definition of an accurate and updated HERV-K HML-8 genomic map is urgently needed. In this study, we report the results of a comprehensive analysis of HERV-K HML-8 sequence presence and distribution within the human genome and hominoids, with a detailed description of the different structural and phylogenetic aspects characterizing the group. A total of 40 proviruses and 5 solo LTR elements for human were characterized, which included a detailed description of provirus structure, integration time, potentially regulated genes, transcription factor-binding sites, and primer-binding site features. Besides, 9 chimpanzee sequences, 8 gorilla sequences, and 10 orangutan sequences belonging to the HML-8 subgroup were identified. The integration time results showed that the HML-8 elements were integrated into the primate lineage around 35 and 42 million years ago (mya), during primates evolutionary speciation. Overall, the results clarified the composition of the HML-8 groups, providing an exhaustive background for subsequent functional studies.
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Affiliation(s)
- Mengying Liu
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
| | - Lei Jia
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
| | - Xing Guo
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China.,Department of Microbiology, School of Basic Medicine, Anhui Medical University, Hefei, China
| | - Xiuli Zhai
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China.,Department of Microbiology, School of Basic Medicine, Anhui Medical University, Hefei, China
| | - Hanping Li
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
| | - Yongjian Liu
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
| | - Jingwan Han
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
| | - Bohan Zhang
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
| | - Xiaolin Wang
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
| | - Tianyi Li
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
| | - Yanglan Wang
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
| | - Jingyun Li
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
| | - Changyuan Yu
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, China
| | - Lin Li
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, China
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2
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Burn A, Roy F, Freeman M, Coffin JM. Widespread expression of the ancient HERV-K (HML-2) provirus group in normal human tissues. PLoS Biol 2022; 20:e3001826. [PMID: 36256614 PMCID: PMC9578601 DOI: 10.1371/journal.pbio.3001826] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 09/13/2022] [Indexed: 11/11/2022] Open
Abstract
Human endogenous retrovirus (HERV) transcripts are known to be highly expressed in cancers, yet their activity in nondiseased tissue is largely unknown. Using the GTEx RNA-seq dataset from normal tissue sampled at autopsy, we characterized individual expression of the recent HERV-K (HML-2) provirus group across 13,000 different samples of 54 different tissues from 948 individuals. HML-2 transcripts could be identified in every tissue sampled and were elevated in the cerebellum, pituitary, testis, and thyroid. A total of 37 different individual proviruses were expressed in 1 or more tissues, representing all 3 LTR5 subgroups. Nine proviruses were identified as having long terminal repeat (LTR)-driven transcription, 7 of which belonged to the most recent LTR5HS subgroup. Proviruses of different subgroups displayed a bias in tissue expression, which may be associated with differences in transcription factor binding sites in their LTRs. Provirus expression was greater in evolutionarily older proviruses with an earliest shared ancestor of gorilla or older. HML-2 expression was significantly affected by biological sex in 1 tissue, while age and timing of death (Hardy score) had little effect. Proviruses containing intact gag, pro, and env open reading frames (ORFs) were expressed in the dataset, with almost every tissue measured potentially expressing at least 1 intact ORF (gag). Human endogenous retrovirus (HERV) transcripts are known to be highly expressed in cancers, but what is their activity in normal tissue? This study uses unique patterns of HERV-K RNA expression in the large GEx dataset from non-diseased tissue sites to provide new insights into both the coevolution of HERV-K with our primate ancestors and their current role in human biology.
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Affiliation(s)
- Aidan Burn
- Program in Genetics, Graduate School of Biomedical Sciences, Tufts University, Boston, Massachusetts, United States of America
| | - Farrah Roy
- Immuneering Corporation, Cambridge, Massachusetts, United States of America
| | - Michael Freeman
- Program in Genetics, Graduate School of Biomedical Sciences, Tufts University, Boston, Massachusetts, United States of America
| | - John M. Coffin
- Program in Genetics, Graduate School of Biomedical Sciences, Tufts University, Boston, Massachusetts, United States of America
- Department of Molecular Biology and Microbiology, Tufts University, Boston, Massachusetts, United States of America
- * E-mail:
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3
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Jia L, Liu M, Yang C, Li H, Liu Y, Han J, Zhai X, Wang X, Li T, Li J, Zhang B, Yu C, Li L. Comprehensive identification and characterization of the HERV-K (HML-9) group in the human genome. Retrovirology 2022; 19:11. [PMID: 35676699 PMCID: PMC9178832 DOI: 10.1186/s12977-022-00596-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 05/09/2022] [Indexed: 12/14/2022] Open
Abstract
Background Human endogenous retroviruses (HERVs) result from ancestral infections caused by exogenous retroviruses that became incorporated into the germline DNA and evolutionarily fixed in the human genome. HERVs can be transmitted vertically in a Mendelian fashion and be stably maintained in the human genome, of which they are estimated to comprise approximately 8%. HERV-K (HML1-10) transcription has been confirmed to be associated with a variety of diseases, such as breast cancer, lung cancer, prostate cancer, melanoma, rheumatoid arthritis, and amyotrophic lateral sclerosis. However, the poor characterization of HML-9 prevents a detailed understanding of the regulation of the expression of this family in humans and its impact on the host genome. In light of this, a precise and updated HERV-K HML-9 genomic map is urgently needed to better evaluate the role of these elements in human health. Results We report a comprehensive analysis of the presence and distribution of HERV-K HML-9 elements within the human genome, with a detailed characterization of the structural and phylogenetic properties of the group. A total of 23 proviruses and 47 solo LTR elements were characterized, with a detailed description of the provirus structure, integration time, potential regulated genes, transcription factor binding sites (TFBS), and primer binding site (PBS) features. The integration time results showed that the HML-9 elements found in the human genome integrated into the primate lineage between 17.5 and 48.5 million years ago (mya). Conclusion The results provide a clear characterization of HML-9 and a comprehensive background for subsequent functional studies. Supplementary Information The online version contains supplementary material available at 10.1186/s12977-022-00596-2.
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Affiliation(s)
- Lei Jia
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, 100071, China
| | - Mengying Liu
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, China
| | - Caiqin Yang
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, 100071, China
| | - Hanping Li
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, 100071, China
| | - Yongjian Liu
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, 100071, China
| | - Jingwan Han
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, 100071, China
| | - Xiuli Zhai
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, 100071, China
| | - Xiaolin Wang
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, 100071, China
| | - Tianyi Li
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, 100071, China
| | - Jingyun Li
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, 100071, China
| | - Bohan Zhang
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China.,State Key Laboratory of Pathogen and Biosecurity, Beijing, 100071, China
| | - Changyuan Yu
- College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, China.
| | - Lin Li
- Department of Virology, Beijing Institute of Microbiology and Epidemiology, Beijing, 100071, China. .,State Key Laboratory of Pathogen and Biosecurity, Beijing, 100071, China.
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4
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Yang C, Guo X, Li J, Han J, Jia L, Wen HL, Sun C, Wang X, Zhang B, Li J, Chi Y, An T, Wang Y, Wang Z, Li H, Li L. Significant Upregulation of HERV-K (HML-2) Transcription Levels in Human Lung Cancer and Cancer Cells. Front Microbiol 2022; 13:850444. [PMID: 35359739 PMCID: PMC8960717 DOI: 10.3389/fmicb.2022.850444] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 02/15/2022] [Indexed: 12/14/2022] Open
Abstract
Lung cancer is the second most common cancer worldwide and the leading cause of cancer death in the world. Therefore, there is an urgent need to develop new and effective biomarkers for diagnosis and treatment. Under this circumstance, human endogenous retroviruses (HERVs) were recently introduced as novel biomarkers for cancer diagnosis. This study focused on the correlation between lung cancer and HERV-K (HML-2) transcription levels. At the cellular level, different types of lung cancer cells and human normal lung epithelial cells were used to analyze the transcription levels of the HERV-K (HML-2) gag, pol, and env genes by RT–qPCR. At the level of lung cancer patients, blood samples with background information from 734 lung cancer patients and 96 healthy persons were collected to analyze the transcription levels of HERV-K (HML-2) gag, pol, and env genes. The results showed that the transcriptional levels of the HERV-K (HML-2) gag, pol, and env genes in lung cancer cells and lung cancer patient blood samples were significantly higher than those in the healthy controls, which was also verified by RNAScope ISH technology. In addition, we also found that there was a correlation between the abnormal transcription levels of HERV-K (HML-2) genes in lung cancer patients and the clinicopathological parameters of lung cancer. We also identified the distribution locations of the gag, pol, and env primer sequences on each chromosome and analyzed the function of these loci. In conclusion, HERV-K (HML-2) genes may be a potential biomarker for the diagnosis of lung cancer.
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Affiliation(s)
- Caiqin Yang
- Department of Virology, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, AMMS, Beijing, China
| | - Xin Guo
- Department of Nutrition and Food Hygiene, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Jianjie Li
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Thoracic Medical Oncology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Jingwan Han
- Department of Virology, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, AMMS, Beijing, China
| | - Lei Jia
- Department of Virology, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, AMMS, Beijing, China
| | - Hong-Ling Wen
- Key Laboratory for the Prevention and Control of Infectious Diseases, Department of Microbiological Laboratory Technology, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Chengxi Sun
- Department of Clinical Laboratory, Cheeloo College of Medicine, Shandong University, Jinan, China
| | - Xiaolin Wang
- Department of Virology, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, AMMS, Beijing, China
| | - Bohan Zhang
- Department of Virology, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, AMMS, Beijing, China
| | - Jingyun Li
- Department of Virology, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, AMMS, Beijing, China
| | - Yujia Chi
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Thoracic Medical Oncology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Tongtong An
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Thoracic Medical Oncology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Yuyan Wang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Thoracic Medical Oncology, Peking University Cancer Hospital & Institute, Beijing, China
| | - Ziping Wang
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Thoracic Medical Oncology, Peking University Cancer Hospital & Institute, Beijing, China
- *Correspondence: Ziping Wang,
| | - Hanping Li
- Department of Virology, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, AMMS, Beijing, China
- Hanping Li,
| | - Lin Li
- Department of Virology, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, AMMS, Beijing, China
- Lin Li,
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5
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Niu Y, Teng X, Zhou H, Shi Y, Li Y, Tang Y, Zhang P, Luo H, Kang Q, Xu T, He S. Characterizing mobile element insertions in 5675 genomes. Nucleic Acids Res 2022; 50:2493-2508. [PMID: 35212372 PMCID: PMC8934628 DOI: 10.1093/nar/gkac128] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 02/07/2022] [Accepted: 02/11/2022] [Indexed: 12/30/2022] Open
Abstract
Mobile element insertions (MEIs) are a major class of structural variants (SVs) and have been linked to many human genetic disorders, including hemophilia, neurofibromatosis, and various cancers. However, human MEI resources from large-scale genome sequencing are still lacking compared to those for SNPs and SVs. Here, we report a comprehensive map of 36 699 non-reference MEIs constructed from 5675 genomes, comprising 2998 Chinese samples (∼26.2×, NyuWa) and 2677 samples from the 1000 Genomes Project (∼7.4×, 1KGP). We discovered that LINE-1 insertions were highly enriched in centromere regions, implying the role of chromosome context in retroelement insertion. After functional annotation, we estimated that MEIs are responsible for about 9.3% of all protein-truncating events per genome. Finally, we built a companion database named HMEID for public use. This resource represents the latest and largest genomewide study on MEIs and will have broad utility for exploration of human MEI findings.
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Affiliation(s)
- Yiwei Niu
- Key Laboratory of RNA Biology, Center for Big Data Research in Health, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xueyi Teng
- Key Laboratory of RNA Biology, Center for Big Data Research in Health, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Honghong Zhou
- Key Laboratory of RNA Biology, Center for Big Data Research in Health, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Yirong Shi
- Key Laboratory of RNA Biology, Center for Big Data Research in Health, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yanyan Li
- Key Laboratory of RNA Biology, Center for Big Data Research in Health, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yiheng Tang
- Key Laboratory of RNA Biology, Center for Big Data Research in Health, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Peng Zhang
- Key Laboratory of RNA Biology, Center for Big Data Research in Health, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Huaxia Luo
- Key Laboratory of RNA Biology, Center for Big Data Research in Health, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Quan Kang
- Key Laboratory of RNA Biology, Center for Big Data Research in Health, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Tao Xu
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.,National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Shunmin He
- Key Laboratory of RNA Biology, Center for Big Data Research in Health, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
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6
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Ben Amara W, Quesneville H, Khemakhem MM. A Genomic Survey of Mayetiola destructor Mobilome Provides New Insights into the Evolutionary History of Transposable Elements in the Cecidomyiid Midges. PLoS One 2021; 16:e0257996. [PMID: 34634072 PMCID: PMC8504770 DOI: 10.1371/journal.pone.0257996] [Citation(s) in RCA: 3] [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: 10/29/2020] [Accepted: 09/16/2021] [Indexed: 11/19/2022] Open
Abstract
The availability of the Whole-Genome Sequence of the wheat pest Mayetiola destructor offers the opportunity to investigate the Transposable Elements (TEs) content and their relationship with the genes involved in the insect virulence. In this study, de novo annotation carried out using REPET pipeline showed that TEs occupy approximately 16% of the genome and are represented by 1038 lineages. Class II elements were the most frequent and most TEs were inactive due to the deletions they have accumulated. The analyses of TEs ages revealed a first burst at 20% of divergence from present that mobilized many TE families including mostly Tc1/mariner and Gypsy superfamilies and a second burst at 2% of divergence, which involved mainly the class II elements suggesting new TEs invasions. Additionally, 86 TEs insertions involving recently transposed elements were identified. Among them, several MITEs and Gypsy retrotransposons were inserted in the vicinity of SSGP and chemosensory genes. The findings represent a valuable resource for more in-depth investigation of the TE impact onto M. destructor genome and their possible influence on the expression of the virulence and chemosensory genes and consequently the behavior of this pest towards its host plants.
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Affiliation(s)
- Wiem Ben Amara
- Laboratory of Biochemistry and Biotechnology (LR01ES05), Faculty of Sciences of Tunis, University of Tunis El Manar, Tunis, Tunisia
| | - Hadi Quesneville
- INRAE, URGI, Université Paris-Saclay, Versailles, France
- INRAE, BioinfOmics, Plant Bioinformatics Facility, Université Paris-Saclay, Versailles, France
| | - Maha Mezghani Khemakhem
- Laboratory of Biochemistry and Biotechnology (LR01ES05), Faculty of Sciences of Tunis, University of Tunis El Manar, Tunis, Tunisia
- * E-mail:
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7
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Almojil D, Bourgeois Y, Falis M, Hariyani I, Wilcox J, Boissinot S. The Structural, Functional and Evolutionary Impact of Transposable Elements in Eukaryotes. Genes (Basel) 2021; 12:genes12060918. [PMID: 34203645 PMCID: PMC8232201 DOI: 10.3390/genes12060918] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Revised: 06/04/2021] [Accepted: 06/07/2021] [Indexed: 12/22/2022] Open
Abstract
Transposable elements (TEs) are nearly ubiquitous in eukaryotes. The increase in genomic data, as well as progress in genome annotation and molecular biology techniques, have revealed the vast number of ways mobile elements have impacted the evolution of eukaryotes. In addition to being the main cause of difference in haploid genome size, TEs have affected the overall organization of genomes by accumulating preferentially in some genomic regions, by causing structural rearrangements or by modifying the recombination rate. Although the vast majority of insertions is neutral or deleterious, TEs have been an important source of evolutionary novelties and have played a determinant role in the evolution of fundamental biological processes. TEs have been recruited in the regulation of host genes and are implicated in the evolution of regulatory networks. They have also served as a source of protein-coding sequences or even entire genes. The impact of TEs on eukaryotic evolution is only now being fully appreciated and the role they may play in a number of biological processes, such as speciation and adaptation, remains to be deciphered.
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Affiliation(s)
- Dareen Almojil
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates; (D.A.); (M.F.); (I.H.); (J.W.)
| | - Yann Bourgeois
- School of Biological Sciences, University of Portsmouth, Portsmouth, UK;
| | - Marcin Falis
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates; (D.A.); (M.F.); (I.H.); (J.W.)
| | - Imtiyaz Hariyani
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates; (D.A.); (M.F.); (I.H.); (J.W.)
| | - Justin Wilcox
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates; (D.A.); (M.F.); (I.H.); (J.W.)
- Center for Genomics and Systems Biology, New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates
| | - Stéphane Boissinot
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates; (D.A.); (M.F.); (I.H.); (J.W.)
- Center for Genomics and Systems Biology, New York University Abu Dhabi, Saadiyat Island, Abu Dhabi P.O. Box 129188, United Arab Emirates
- Correspondence:
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8
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Gao Y, Yu XF, Chen T. Human endogenous retroviruses in cancer: Expression, regulation and function. Oncol Lett 2020; 21:121. [PMID: 33552242 PMCID: PMC7798031 DOI: 10.3892/ol.2020.12382] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 11/27/2020] [Indexed: 12/16/2022] Open
Abstract
Human endogenous retroviruses (HERVs) are the remnants of ancient retroviruses that infected human germline cells and became integrated into the human genome millions of years ago. Although most of these sequences are incomplete and silent, several potential pathological roles of HERVs have been observed in numerous diseases, such as multiple sclerosis and rheumatoid arthritis, and especially cancer, including breast cancer and pancreatic carcinoma. The present review investigates the expression signatures and complex regulatory mechanisms of HERVs in cancer. The long terminal repeats-driven transcriptional initiation of HERVs are regulated by transcription factors (such as Sp3) and epigenetic modifications (such as DNA methylation), and are influenced by environmental factors (such as ultraviolet radiation). In addition, this review focuses on the dual opposing effects of HERVs in cancer. HERVs can suppress cancer via immune activation; however, they can also promote cancer. HERV env gene serves a prime role in promoting carcinogenesis in certain malignant tumors, including breast cancer, pancreatic cancer, germ cell tumors, leukemia and Kaposi's sarcoma. Also, HERV ENV proteins can promote cancer via immune suppression. Targeting ENV proteins is a potential future antitumor treatment modality.
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Affiliation(s)
- Yuan Gao
- Cancer Institute, Key Laboratory of Cancer Prevention and Intervention, Ministry of Education, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zheijang 310009, P.R. China
| | - Xiao-Fang Yu
- Cancer Institute, Key Laboratory of Cancer Prevention and Intervention, Ministry of Education, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zheijang 310009, P.R. China
| | - Ting Chen
- Cancer Institute, Key Laboratory of Cancer Prevention and Intervention, Ministry of Education, Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zheijang 310009, P.R. China
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9
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RNA-Seq Transcriptome Analysis Reveals Long Terminal Repeat Retrotransposon Modulation in Human Peripheral Blood Mononuclear Cells after In Vivo Lipopolysaccharide Injection. J Virol 2020; 94:JVI.00587-20. [PMID: 32669333 DOI: 10.1128/jvi.00587-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 07/07/2020] [Indexed: 12/30/2022] Open
Abstract
Human endogenous retroviruses (HERVs) and mammalian apparent long terminal repeat (LTR) retrotransposons (MaLRs) are retroviral sequences that integrated into germ line cells millions of years ago. Transcripts of these LTR retrotransposons are present in several tissues, and their expression is modulated in pathological conditions, although their function remains often far from being understood. Here, we focused on the HERV/MaLR expression and modulation in a scenario of immune system activation. We used a public data set of human peripheral blood mononuclear cells (PBMCs) RNA-Seq from 15 healthy participants to a clinical trial before and after exposure to lipopolysaccharide (LPS), for which we established an RNA-Seq workflow for the identification of expressed and modulated cellular genes and LTR retrotransposon elements.IMPORTANCE We described the HERV and MaLR transcriptome in PBMCs, finding that about 8.4% of the LTR retrotransposon loci were expressed and identifying the betaretrovirus-like HERVs as those with the highest percentage of expressed loci. We found 4,607 HERV and MaLR loci that were modulated as a result of in vivo stimulation with LPS. The HERV-H group showed the highest number of differentially expressed most intact proviruses. We characterized the HERV and MaLR loci as differentially expressed, checking their genomic context of insertion and observing a general colocalization with genes that are involved and modulated in the immune response, as a consequence of LPS stimulation. The analyses of HERV and MaLR expression and modulation show that these LTR retrotransposons are expressed in PBMCs and regulated in inflammatory settings. The similar regulation of HERVs/MaLRs and genes after LPS stimulation suggests possible interactions of LTR retrotransposons and the immune host response.
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10
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Abstract
Multicellular eukaryotic genomes show enormous differences in size. A substantial part of this variation is due to the presence of transposable elements (TEs). They contribute significantly to a cell's mass of DNA and have the potential to become involved in host gene control. We argue that the suppression of their activities by methylation of the C-phosphate-G (CpG) dinucleotide in DNA is essential for their long-term accommodation in the host genome and, therefore, to its expansion. An inevitable consequence of cytosine methylation is an increase in C-to-T transition mutations via deamination, which causes CpG loss. Cytosine deamination is often needed for TEs to take on regulatory functions in the host genome. Our study of the whole-genome sequences of 53 organisms showed a positive correlation between the size of a genome and the percentage of TEs it contains, as well as a negative correlation between size and the CpG observed/expected (O/E) ratio in both TEs and the host DNA. TEs are seldom found at promoters and transcription start sites, but they are found more at enhancers, particularly after they have accumulated C-to-T and other mutations. Therefore, the methylation of TE DNA allows for genome expansion and also leads to new opportunities for gene control by TE-based regulatory sites.
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11
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Lanciano S, Cristofari G. Measuring and interpreting transposable element expression. Nat Rev Genet 2020; 21:721-736. [PMID: 32576954 DOI: 10.1038/s41576-020-0251-y] [Citation(s) in RCA: 164] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/19/2020] [Indexed: 12/21/2022]
Abstract
Transposable elements (TEs) are insertional mutagens that contribute greatly to the plasticity of eukaryotic genomes, influencing the evolution and adaptation of species as well as physiology or disease in individuals. Measuring TE expression helps to understand not only when and where TE mobilization can occur but also how this process alters gene expression, chromatin accessibility or cellular signalling pathways. Although genome-wide gene expression assays such as RNA sequencing include transposon-derived transcripts, most computational analytical tools discard or misinterpret TE-derived reads. Emerging approaches are improving the identification of expressed TE loci and helping to discriminate TE transcripts that permit TE mobilization from chimeric gene-TE transcripts or pervasive transcription. Here we review the main challenges associated with the detection of TE expression, including mappability, insertional and internal sequence polymorphisms, and the diversity of the TE transcriptional landscape, as well as the different experimental and computational strategies to solve them.
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12
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Pisano MP, Grandi N, Tramontano E. High-Throughput Sequencing is a Crucial Tool to Investigate the Contribution of Human Endogenous Retroviruses (HERVs) to Human Biology and Development. Viruses 2020; 12:E633. [PMID: 32545287 PMCID: PMC7354619 DOI: 10.3390/v12060633] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 06/07/2020] [Accepted: 06/10/2020] [Indexed: 01/19/2023] Open
Abstract
Human Endogenous retroviruses (HERVs) are remnants of ancient retroviral infections that represent a large fraction of our genome. Their transcriptional activity is finely regulated in early developmental stages and their expression is modulated in different cell types and tissues. Such activity has an impact on human physiology and pathology that is only partially understood up to date. Novel high-throughput sequencing tools have recently allowed for a great advancement in elucidating the various HERV expression patterns in different tissues as well as the mechanisms controlling their transcription, and overall, have helped in gaining better insights in an all-inclusive understanding of the impact of HERVs in biology of the host.
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Affiliation(s)
- Maria Paola Pisano
- Laboratory of Molecular Virology, Department of Life and Environmental Sciences, University of Cagliari, 09042 Cagliari, Italy; (M.P.P.); (N.G.)
| | - Nicole Grandi
- Laboratory of Molecular Virology, Department of Life and Environmental Sciences, University of Cagliari, 09042 Cagliari, Italy; (M.P.P.); (N.G.)
| | - Enzo Tramontano
- Laboratory of Molecular Virology, Department of Life and Environmental Sciences, University of Cagliari, 09042 Cagliari, Italy; (M.P.P.); (N.G.)
- Istituto di Ricerca Genetica e Biomedica, Consiglio Nazionale delle Ricerche, 09042 Cagliari, Italy
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13
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Pisano MP, Grandi N, Cadeddu M, Blomberg J, Tramontano E. Comprehensive Characterization of the Human Endogenous Retrovirus HERV-K(HML-6) Group: Overview of Structure, Phylogeny, and Contribution to the Human Genome. J Virol 2019; 93:e00110-19. [PMID: 31167914 PMCID: PMC6675890 DOI: 10.1128/jvi.00110-19] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 05/27/2019] [Indexed: 11/20/2022] Open
Abstract
Eight percent of the human genome is composed of human endogenous retroviruses (HERVs), remnants of ancestral germ line infections by exogenous retroviruses, which have been vertically transmitted as Mendelian characters. The HML-6 group, a member of the class II betaretrovirus-like viruses, includes several proviral loci with an increased transcriptional activity in cancer and at least two elements that are known for retaining an intact open reading frame and for encoding small proteins such as ERVK3-1, which is expressed in various healthy tissues, and HERV-K-MEL, a small Env peptide expressed in samples of cutaneous and ocular melanoma but not in normal tissues.IMPORTANCE We reported the distribution and genetic composition of 66 HML-6 elements. We analyzed the phylogeny of the HML-6 sequences and identified two main clusters. We provided the first description of a Rec domain within the env sequence of 23 HML-6 elements. A Rec domain was also predicted within the ERVK3-1 transcript sequence, revealing its expression in various healthy tissues. Evidence about the context of insertion and colocalization of 19 HML-6 elements with functional human genes are also reported, including the sequence 16p11.2, whose 5' long terminal repeat overlapped the exon of one transcript variant of a cellular zinc finger upregulated and involved in hepatocellular carcinoma. The present work provides the first complete overview of the HML-6 elements in GRCh37(hg19), describing the structure, phylogeny, and genomic context of insertion of each locus. This information allows a better understanding of the genetics of one of the most expressed HERV groups in the human genome.
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Affiliation(s)
- Maria Paola Pisano
- Laboratory of Molecular Virology, Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Nicole Grandi
- Laboratory of Molecular Virology, Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Marta Cadeddu
- Laboratory of Molecular Virology, Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Jonas Blomberg
- Section of Virology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Enzo Tramontano
- Laboratory of Molecular Virology, Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
- Istituto di Ricerca Genetica e Biomedica, Consiglio Nazionale delle Ricerche, Cagliari, Italy
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14
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Gagnier L, Belancio VP, Mager DL. Mouse germ line mutations due to retrotransposon insertions. Mob DNA 2019; 10:15. [PMID: 31011371 PMCID: PMC6466679 DOI: 10.1186/s13100-019-0157-4] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 04/01/2019] [Indexed: 12/24/2022] Open
Abstract
Transposable element (TE) insertions are responsible for a significant fraction of spontaneous germ line mutations reported in inbred mouse strains. This major contribution of TEs to the mutational landscape in mouse contrasts with the situation in human, where their relative contribution as germ line insertional mutagens is much lower. In this focussed review, we provide comprehensive lists of TE-induced mouse mutations, discuss the different TE types involved in these insertional mutations and elaborate on particularly interesting cases. We also discuss differences and similarities between the mutational role of TEs in mice and humans.
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Affiliation(s)
- Liane Gagnier
- Terry Fox Laboratory, BC Cancer and Department of Medical Genetics, University of British Columbia, V5Z1L3, Vancouver, BC Canada
| | - Victoria P. Belancio
- Department of Structural and Cellular Biology, Tulane University School of Medicine, Tulane Cancer Center, Tulane Center for Aging, New Orleans, LA 70112 USA
| | - Dixie L. Mager
- Terry Fox Laboratory, BC Cancer and Department of Medical Genetics, University of British Columbia, V5Z1L3, Vancouver, BC Canada
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15
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Whole-Genome Analysis of Domestic Chicken Selection Lines Suggests Segregating Variation in ERV Makeups. Genes (Basel) 2019; 10:genes10020162. [PMID: 30791656 PMCID: PMC6410134 DOI: 10.3390/genes10020162] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/13/2019] [Accepted: 02/15/2019] [Indexed: 01/04/2023] Open
Abstract
Retroviruses have invaded vertebrate hosts for millions of years and left an extensive endogenous retrovirus (ERV) record in the host genomes, which provides a remarkable source for an evolutionary perspective on retrovirus-host associations. Here we identified ERV variation across whole-genomes from two chicken lines, derived from a common founder population subjected to 50 years of bi-directional selection on body weight, and a distantly related domestic chicken line as a comparison outgroup. Candidate ERV loci, where at least one of the chicken lines indicated distinct differences, were analyzed for adjacent host genomic landscapes, selective sweeps, and compared by sequence associations to reference assembly ERVs in phylogenetic analyses. Current data does not support selection acting on specific ERV loci in the domestic chicken lines, as determined by presence inside selective sweeps or composition of adjacent host genes. The varying ERV records among the domestic chicken lines associated broadly across the assembly ERV phylogeny, indicating that the observed insertion differences result from pre-existing and segregating ERV loci in the host populations. Thus, data suggest that the observed differences between the host lineages are best explained by substantial standing ERV variation within host populations, and indicates that even truncated, presumably old, ERVs have not yet become fixed in the host population.
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16
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Matteucci C, Balestrieri E, Argaw-Denboba A, Sinibaldi-Vallebona P. Human endogenous retroviruses role in cancer cell stemness. Semin Cancer Biol 2018; 53:17-30. [PMID: 30317035 DOI: 10.1016/j.semcancer.2018.10.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 09/30/2018] [Accepted: 10/05/2018] [Indexed: 12/18/2022]
Abstract
Cancer incidence and mortality, metastasis, drug resistance and recurrence are still the critical issues of oncological diseases. In this scenario, increasing scientific evidences demonstrate that the activation of human endogenous retroviruses (HERVs) is involved in the aggressiveness of tumors such as melanoma, breast, germ cell, renal, ovarian, liver and haematological cancers. In their dynamic regulation, HERVs have also proved to be important determinants of pluripotency in human embryonic stem cells (ESC) and of the reprogramming process of induced pluripotent stem cells (iPSCs). In many types of tumors, essential characteristics of aggressiveness have been associated with the achievement of stemness features, often accompanied with the identification of defined subpopulations, termed cancer stem cells (CSCs), which possess stem cell-like properties and sustain tumorigenesis. Indeed, CSCs show high self-renewal capacity with a peculiar potential in tumor initiation, progression, metastasis, heterogeneity, recurrence, radiotherapy and drug resistance. However, HERVs role in CSCs biology is still not fully elucidated. In this regard, CD133 is a widely recognized marker of CSCs, and our group demonstrated, for the first time, the requirement of HERV-K activation to expand and maintain a CD133+ melanoma cell subpopulation with stemness features in response to microenvironmental modifications. The review will discuss HERVs expression as cancer hallmark, with particular focus on their role in the regulation of cancer stemness features and the potential involvement as targets for therapy.
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Affiliation(s)
- Claudia Matteucci
- Department of Experimental Medicine and Surgery, University of Rome "Tor Vergata", Via Montpellier, 1, 00133, Rome, Italy.
| | - Emanuela Balestrieri
- Department of Experimental Medicine and Surgery, University of Rome "Tor Vergata", Via Montpellier, 1, 00133, Rome, Italy
| | - Ayele Argaw-Denboba
- Department of Experimental Medicine and Surgery, University of Rome "Tor Vergata", Via Montpellier, 1, 00133, Rome, Italy; European Molecular Biology Laboratory (EMBL), Adriano Buzzati-Traverso Campus, Monterotondo, Rome, Italy
| | - Paola Sinibaldi-Vallebona
- Department of Experimental Medicine and Surgery, University of Rome "Tor Vergata", Via Montpellier, 1, 00133, Rome, Italy; Institute of Translational Pharmacology, National Research Council, Via Fosso del Cavaliere, 100, 00133, Rome, Italy
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Human Endogenous Retrovirus-K HML-2 integration within RASGRF2 is associated with intravenous drug abuse and modulates transcription in a cell-line model. Proc Natl Acad Sci U S A 2018; 115:10434-10439. [PMID: 30249655 DOI: 10.1073/pnas.1811940115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
HERV-K HML-2 (HK2) has been proliferating in the germ line of humans at least as recently as 250,000 years ago, with some integrations that remain polymorphic in the modern human population. One of the solitary HK2 LTR polymorphic integrations lies between exons 17 and 18 of RASGRF2, a gene that affects dopaminergic activity and is thus related to addiction. Here we show that this antisense HK2 integration (namely RASGRF2-int) is found more frequently in persons who inject drugs compared with the general population. In a Greek HIV-1-positive population (n = 202), we found RASGRF2-int 2.5 times (14 versus 6%) more frequently in patients infected through i.v. drug use compared with other transmission route controls (P = 0.03). Independently, in a United Kingdom-based hepatitis C virus-positive population (n = 184), we found RASGRF2-int 3.6 times (34 versus 9.5%) more frequently in patients infected during chronic drug abuse compared with controls (P < 0.001). We then tested whether RASGRF2-int could be mechanistically responsible for this association by modulating transcription of RASGRF2 We show that the CRISPR/Cas9-mediated insertion of HK2 in HEK293 cells in the exact RASGRF2 intronic position found in the population resulted in significant transcriptional and phenotypic changes. We also explored mechanistic features of other intronic HK2 integrations and show that HK2 LTRs can be responsible for generation of cis-natural antisense transcripts, which could interfere with the transcription of nearby genes. Our findings suggest that RASGRF2-int is a strong candidate for dopaminergic manipulation, and emphasize the importance of accurate mapping of neglected HERV polymorphisms in human genomic studies.
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18
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Berrens RV, Andrews S, Spensberger D, Santos F, Dean W, Gould P, Sharif J, Olova N, Chandra T, Koseki H, von Meyenn F, Reik W. An endosiRNA-Based Repression Mechanism Counteracts Transposon Activation during Global DNA Demethylation in Embryonic Stem Cells. Cell Stem Cell 2018; 21:694-703.e7. [PMID: 29100015 PMCID: PMC5678422 DOI: 10.1016/j.stem.2017.10.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 08/14/2017] [Accepted: 10/12/2017] [Indexed: 12/28/2022]
Abstract
Erasure of DNA methylation and repressive chromatin marks in the mammalian germline leads to risk of transcriptional activation of transposable elements (TEs). Here, we used mouse embryonic stem cells (ESCs) to identify an endosiRNA-based mechanism involved in suppression of TE transcription. In ESCs with DNA demethylation induced by acute deletion of Dnmt1, we saw an increase in sense transcription at TEs, resulting in an abundance of sense/antisense transcripts leading to high levels of ARGONAUTE2 (AGO2)-bound small RNAs. Inhibition of Dicer or Ago2 expression revealed that small RNAs are involved in an immediate response to demethylation-induced transposon activation, while the deposition of repressive histone marks follows as a chronic response. In vivo, we also found TE-specific endosiRNAs present during primordial germ cell development. Our results suggest that antisense TE transcription is a “trap” that elicits an endosiRNA response to restrain acute transposon activity during epigenetic reprogramming in the mammalian germline. Global DNA demethylation in embryonic stem cells leads to transposon activation Transposon activation increases the abundance of sense/antisense transcripts ARGONAUTE2-bound endosiRNAs accumulate at high levels for acute repression Longer-term transposon repression depends on repressive histone marks
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Affiliation(s)
- Rebecca V Berrens
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK; University of Cambridge, The Old Schools, Trinity Lane, Cambridge CB2 1TN, UK.
| | - Simon Andrews
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | | | - Fátima Santos
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK; University of Cambridge, The Old Schools, Trinity Lane, Cambridge CB2 1TN, UK
| | - Wendy Dean
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | - Poppy Gould
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | - Jafar Sharif
- RIKEN Research Center for Allergy and Immunology, 1-7-22 Suehiro-cho, Tsurumi, Yokohama, 230-0045 Kanagawa, Japan
| | - Nelly Olova
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | - Tamir Chandra
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK
| | - Haruhiko Koseki
- RIKEN Research Center for Allergy and Immunology, 1-7-22 Suehiro-cho, Tsurumi, Yokohama, 230-0045 Kanagawa, Japan
| | | | - Wolf Reik
- Epigenetics Programme, Babraham Institute, Cambridge CB22 3AT, UK; University of Cambridge, The Old Schools, Trinity Lane, Cambridge CB2 1TN, UK; Wellcome Trust Sanger Institute, Hinxton CB10 1SA, UK.
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19
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Küry P, Nath A, Créange A, Dolei A, Marche P, Gold J, Giovannoni G, Hartung HP, Perron H. Human Endogenous Retroviruses in Neurological Diseases. Trends Mol Med 2018; 24:379-394. [PMID: 29551251 PMCID: PMC7185488 DOI: 10.1016/j.molmed.2018.02.007] [Citation(s) in RCA: 175] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Revised: 02/12/2018] [Accepted: 02/15/2018] [Indexed: 12/12/2022]
Abstract
The causes of multiple sclerosis and amyotrophic lateral sclerosis have long remained elusive. A new category of pathogenic components, normally dormant within human genomes, has been identified: human endogenous retroviruses (HERVs). These represent ∼8% of the human genome, and environmental factors have reproducibly been shown to trigger their expression. The resulting production of envelope (Env) proteins from HERV-W and HERV-K appears to engage pathophysiological pathways leading to the pathognomonic features of MS and ALS, respectively. Pathogenic HERV elements may thus provide a missing link in understanding these complex diseases. Moreover, their neutralization may represent a promising strategy to establish novel and more powerful therapeutic approaches.
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Affiliation(s)
- Patrick Küry
- Department of Neurology, Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany
| | - Avindra Nath
- Section of infections of the Nervous System, National Institute of Neurological Diseases and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Alain Créange
- Service de Neurologie, Groupe Hospitalier Henri Mondor, Assistance Publique Hopitaux de Paris (APHP), Université Paris Est, Créteil, France
| | - Antonina Dolei
- Department of Virology, University of Sassari, Sassari, Italy
| | - Patrice Marche
- Institute for Advanced Biosciences (IAB), University of Grenoble-Alpes, La Tronche, France; Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 1209, La Tronche, France
| | - Julian Gold
- Centre for Neuroscience and Trauma, Blizard Institute, Queen Mary University, London, UK; The Albion Centre, Prince of Wales Hospital, Sydney, Australia
| | - Gavin Giovannoni
- Centre for Neuroscience and Trauma, Blizard Institute, Queen Mary University, London, UK
| | - Hans-Peter Hartung
- Department of Neurology, Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany.
| | - Hervé Perron
- Geneuro, Plan les Ouates, Geneva, Switzerland; University of Lyon, Lyon, France
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20
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Mechanisms of HERV-K (HML-2) Transcription during Human Mammary Epithelial Cell Transformation. J Virol 2017; 92:JVI.01258-17. [PMID: 29046454 DOI: 10.1128/jvi.01258-17] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 10/12/2017] [Indexed: 01/10/2023] Open
Abstract
Increasing evidence suggests that repetitive elements may play a role in host gene regulation, particularly through the donation of alternative promoters, enhancers, splice sites, and termination signals. Elevated transcript expression of the endogenous retrovirus group HERV-K (HML-2) is seen in many human cancers, although the identities of the individual proviral loci contributing to this expression as well as their mechanisms of activation have been unclear. Using high-throughput next-generation sequencing techniques optimized for the capture of HML-2 expression, we characterized the HML-2 transcriptome and means of activation in an in vitro model of human mammary epithelial cell transformation. Our analysis showed significant expression originating from 15 HML-2 full-length proviruses, through four modes of transcription. The majority of expression was in the antisense orientation and from proviruses integrated within introns. We found two instances of long terminal repeat (LTR)-driven provirus transcription but no evidence to suggest that these active 5' LTRs were influencing nearby host gene expression. Importantly, LTR-driven transcription was restricted to tumorigenic cells, suggesting that LTR promoter activity is dependent upon the transcriptional environment of a malignant cell.IMPORTANCE Here, we use an in vitro model of human mammary epithelial cell transformation to assess how malignancy-associated shifts in the transcriptional milieu of a cell may impact HML-2 activity. We found 15 proviruses to be significantly expressed through four different mechanisms, with the majority of transcripts being antisense copies of proviruses located within introns. We saw active 5' LTR use in tumorigenic cells only, suggesting that the cellular environment of a cancer cell is a critical component for induction of LTR promoter activity. These findings have implications for future studies investigating HML-2 as a target for immunotherapy or as a biomarker for disease.
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21
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A protein complex regulates RNA processing of intronic heterochromatin-containing genes in Arabidopsis. Proc Natl Acad Sci U S A 2017; 114:E7377-E7384. [PMID: 28808009 DOI: 10.1073/pnas.1710683114] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In several eukaryotic organisms, heterochromatin (HC) in the introns of genes can regulate RNA processing, including polyadenylation, but the mechanism underlying this regulation is poorly understood. By promoting distal polyadenylation, the bromo-adjacent homology (BAH) domain-containing and RNA recognition motif-containing protein ASI1 and the H3K9me2-binding protein EDM2 are required for the expression of functional full-length transcripts of intronic HC-containing genes in Arabidopsis Here we report that ASI1 and EDM2 form a protein complex in vivo via a bridge protein, ASI1-Immunoprecipitated Protein 1 (AIPP1), which is another RNA recognition motif-containing protein. The complex also may contain the Pol II CTD phosphatase CPL2, the plant homeodomain-containing protein AIPP2, and another BAH domain protein, AIPP3. As is the case with dysfunction of ASI1 and EDM2, dysfunction of AIPP1 impedes the use of distal polyadenylation sites at tested intronic HC-containing genes, such as the histone demethylase gene IBM1, resulting in a lack of functional full-length transcripts. A mutation in AIPP1 causes silencing of the 35S-SUC2 transgene and genome-wide CHG hypermethylation at gene body regions, consistent with the lack of full-length functional IBM1 transcripts in the mutant. Interestingly, compared with asi1, edm2, and aipp1 mutations, mutations in CPL2, AIPP2, and AIPP3 cause the opposite effects on the expression of intronic HC-containing genes and other genes, suggesting that CPL2, AIPP2, and AIPP3 may form a distinct subcomplex. These results advance our understanding of the interplay between heterochromatic epigenetic modifications and RNA processing in higher eukaryotes.
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22
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Franke V, Ganesh S, Karlic R, Malik R, Pasulka J, Horvat F, Kuzman M, Fulka H, Cernohorska M, Urbanova J, Svobodova E, Ma J, Suzuki Y, Aoki F, Schultz RM, Vlahovicek K, Svoboda P. Long terminal repeats power evolution of genes and gene expression programs in mammalian oocytes and zygotes. Genome Res 2017; 27:1384-1394. [PMID: 28522611 PMCID: PMC5538554 DOI: 10.1101/gr.216150.116] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 05/15/2017] [Indexed: 12/11/2022]
Abstract
Retrotransposons are "copy-and-paste" insertional mutagens that substantially contribute to mammalian genome content. Retrotransposons often carry long terminal repeats (LTRs) for retrovirus-like reverse transcription and integration into the genome. We report an extraordinary impact of a group of LTRs from the mammalian endogenous retrovirus-related ERVL retrotransposon class on gene expression in the germline and beyond. In mouse, we identified more than 800 LTRs from ORR1, MT, MT2, and MLT families, which resemble mobile gene-remodeling platforms that supply promoters and first exons. The LTR-mediated gene remodeling also extends to hamster, human, and bovine oocytes. The LTRs function in a stage-specific manner during the oocyte-to-embryo transition by activating transcription, altering protein-coding sequences, producing noncoding RNAs, and even supporting evolution of new protein-coding genes. These functions result, for example, in recycling processed pseudogenes into mRNAs or lncRNAs with regulatory roles. The functional potential of the studied LTRs is even higher, because we show that dormant LTR promoter activity can rescue loss of an essential upstream promoter. We also report a novel protein-coding gene evolution-D6Ertd527e-in which an MT LTR provided a promoter and the 5' exon with a functional start codon while the bulk of the protein-coding sequence evolved through a CAG repeat expansion. Altogether, ERVL LTRs provide molecular mechanisms for stochastically scanning, rewiring, and recycling genetic information on an extraordinary scale. ERVL LTRs thus offer means for a comprehensive survey of the genome's expression potential, tightly intertwining with gene expression and evolution in the germline.
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Affiliation(s)
- Vedran Franke
- Bioinformatics Group, Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, 10000, Zagreb, Croatia
| | - Sravya Ganesh
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Rosa Karlic
- Bioinformatics Group, Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, 10000, Zagreb, Croatia
| | - Radek Malik
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Josef Pasulka
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Filip Horvat
- Bioinformatics Group, Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, 10000, Zagreb, Croatia
| | - Maja Kuzman
- Bioinformatics Group, Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, 10000, Zagreb, Croatia
| | - Helena Fulka
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Marketa Cernohorska
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Jana Urbanova
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Eliska Svobodova
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Jun Ma
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Yutaka Suzuki
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8562, Japan
| | - Fugaku Aoki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, 277-8562, Japan
| | - Richard M Schultz
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Kristian Vlahovicek
- Bioinformatics Group, Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, 10000, Zagreb, Croatia
| | - Petr Svoboda
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
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Pasini EM, Böhme U, Rutledge GG, Voorberg-Van der Wel A, Sanders M, Berriman M, Kocken CH, Otto TD. An improved Plasmodium cynomolgi genome assembly reveals an unexpected methyltransferase gene expansion. Wellcome Open Res 2017; 2:42. [PMID: 28748222 PMCID: PMC5500898 DOI: 10.12688/wellcomeopenres.11864.1] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/15/2017] [Indexed: 11/20/2022] Open
Abstract
Background:
Plasmodium cynomolgi, a non-human primate malaria parasite species, has been an important model parasite since its discovery in 1907. Similarities in the biology of
P. cynomolgi to the closely related, but less tractable, human malaria parasite
P. vivax make it the model parasite of choice for liver biology and vaccine studies pertinent to
P. vivax malaria. Molecular and genome-scale studies of
P. cynomolgi have relied on the current reference genome sequence, which remains highly fragmented with 1,649 unassigned scaffolds and little representation of the subtelomeres. Methods: Using long-read sequence data (Pacific Biosciences SMRT technology), we assembled and annotated a new reference genome sequence, PcyM, sourced from an Indian rhesus monkey. We compare the newly assembled genome sequence with those of several other
Plasmodium species, including a re-annotated
P. coatneyi assembly. Results: The new PcyM genome assembly is of significantly higher quality than the existing reference, comprising only 56 pieces, no gaps and an improved average gene length. Detailed manual curation has ensured a comprehensive annotation of the genome with 6,632 genes, nearly 1,000 more than previously attributed to
P. cynomolgi. The new assembly also has an improved representation of the subtelomeric regions, which account for nearly 40% of the sequence. Within the subtelomeres, we identified more than 1300
Plasmodium interspersed repeat (
pir) genes, as well as a striking expansion of 36 methyltransferase pseudogenes that originated from a single copy on chromosome 9. Conclusions: The manually curated PcyM reference genome sequence is an important new resource for the malaria research community. The high quality and contiguity of the data have enabled the discovery of a novel expansion of methyltransferase in the subtelomeres, and illustrates the new comparative genomics capabilities that are being unlocked by complete reference genomes.
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Affiliation(s)
- Erica M Pasini
- Biomedical Primate Research Centre, Rijswijk, Lange Kleiweg 161, 2288GJ Rijswijk, Netherlands
| | - Ulrike Böhme
- The Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK
| | - Gavin G Rutledge
- The Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK
| | | | - Mandy Sanders
- The Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK
| | - Matt Berriman
- The Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK
| | - Clemens Hm Kocken
- Biomedical Primate Research Centre, Rijswijk, Lange Kleiweg 161, 2288GJ Rijswijk, Netherlands
| | - Thomas Dan Otto
- The Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK
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Grandi N, Cadeddu M, Blomberg J, Tramontano E. Contribution of type W human endogenous retroviruses to the human genome: characterization of HERV-W proviral insertions and processed pseudogenes. Retrovirology 2016; 13:67. [PMID: 27613107 PMCID: PMC5016936 DOI: 10.1186/s12977-016-0301-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 08/23/2016] [Indexed: 12/21/2022] Open
Abstract
Background Human endogenous retroviruses (HERVs) are ancient sequences integrated in the germ line cells and vertically transmitted through the offspring constituting about 8 % of our genome. In time, HERVs accumulated mutations that compromised their coding capacity. A prominent exception is HERV-W locus 7q21.2, producing a functional Env protein (Syncytin-1) coopted for placental syncytiotrophoblast formation. While expression of HERV-W sequences has been investigated for their correlation to disease, an exhaustive description of the group composition and characteristics is still not available and current HERV-W group information derive from studies published a few years ago that, of course, used the rough assemblies of the human genome available at that time. This hampers the comparison and correlation with current human genome assemblies. Results In the present work we identified and described in detail the distribution and genetic composition of 213 HERV-W elements. The bioinformatics analysis led to the characterization of several previously unreported features and provided a phylogenetic classification of two main subgroups with different age and structural characteristics. New facts on HERV-W genomic context of insertion and co-localization with sequences putatively involved in disease development are also reported. Conclusions The present work is a detailed overview of the HERV-W contribution to the human genome and provides a robust genetic background useful to clarify HERV-W role in pathologies with poorly understood etiology, representing, to our knowledge, the most complete and exhaustive HERV-W dataset up to date. Electronic supplementary material The online version of this article (doi:10.1186/s12977-016-0301-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Nicole Grandi
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria di Monserrato SS554, 09042, Monserrato, Cagliari, Italy
| | - Marta Cadeddu
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria di Monserrato SS554, 09042, Monserrato, Cagliari, Italy
| | - Jonas Blomberg
- Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Enzo Tramontano
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria di Monserrato SS554, 09042, Monserrato, Cagliari, Italy. .,Istituto di Ricerca Genetica e Biomedica, Consiglio Nazionale delle Ricerche (CNR), Monserrato, Cagliari, Italy.
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25
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Li F, Karlsson H. Expression and regulation of human endogenous retrovirus W elements. APMIS 2016; 124:52-66. [PMID: 26818262 DOI: 10.1111/apm.12478] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 10/12/2015] [Indexed: 01/06/2023]
Abstract
Human endogenous retroviruses (HERV) comprise 8% of the human genome and can be classified into at least 31 families. A typical HERV provirus consists of internal gag, pol and env genes, flanked by two long terminal repeats (LTRs). No single provirus is capable of engendering infectious particles. HERV are by nature repetitive and have with few notable exceptions lost their protein-coding capacity. Therefore, HERV have consistently been excluded from array-based expression studies and hence little is known of their expression, regulation, and potential functional significance. An increasing number of studies have, however, observed expression of the W family of HERV in various human tissues and cells, predominantly in placenta. HERV-W LTRs act as promoters in directing transcription of HERV-W members, contribute to their tissue-specific and highly diversified expression pattern. Furthermore, leaky transcription originating from adjacent genes plays a role in the transcription initiation of HERV-W psudoelements. It has been reported that HERV-W elements, including ERVWE1 (the so far only known HERV-W locus harboring a gene (env) functionally adopted by the human host to critically participate in placenta biogenesis), can become transactivated in a range of human non-placental cell-lines during exogenous virus infections. Aberrant expression of HERV-W has been associated with human diseases, such as cancer, multiple sclerosis, and schizophrenia. Based on published reports, transcriptional activities of HERV-W appear to be influenced by several mechanisms; binding of transcription factors to LTR promoters and enhancers outside of LTRs, genetic variation and alteration in DNA methylation and histone modification. Emerging mechanistic studies support the notion that HERV-W represents a potential marker or mediator of environmental exposures (e.g., virus infection) in the development of chronic complex diseases.
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Affiliation(s)
- Fang Li
- Department of Basic Medical Science, Changsha Medical University, Changsha, China.,Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Håkan Karlsson
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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26
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Hanke K, Hohn O, Bannert N. HERV-K(HML-2), a seemingly silent subtenant - but still waters run deep. APMIS 2016; 124:67-87. [PMID: 26818263 DOI: 10.1111/apm.12475] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 10/12/2015] [Indexed: 01/26/2023]
Abstract
A large proportion of the human genome consists of endogenous retroviruses, some of which are well preserved, showing transcriptional activity, and expressing retroviral proteins. The HERV-K(HML-2) family represents the most intact members of these elements, with some having open and intact reading frames for viral proteins and the ability to form virus-like particles. Although generally suppressed in most healthy tissues by a variety of epigenetic processes and antiviral mechanisms, there is evidence that some members of this family are (at least partly) still active - particularly in certain stem cells and various tumors. This raises the possibility of their involvement in tumor induction or in developmental processes. In recent years, many new insights into this fascinating field have been attained, and this review focuses on new discoveries about coevolutionary events and intracellular defense mechanisms against HERV-K(HML-2) activity. We also describe what might occur when these mechanisms fail or become modulated by viral proteins or other viruses and discuss the new vistas opened up by the reconstitution of ancestral viral proteins and even complete HML-2 viruses.
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Affiliation(s)
- Kirsten Hanke
- Department HIV and Other Retroviruses, Robert Koch Institute, Berlin, Germany
| | - Oliver Hohn
- Department HIV and Other Retroviruses, Robert Koch Institute, Berlin, Germany
| | - Norbert Bannert
- Department HIV and Other Retroviruses, Robert Koch Institute, Berlin, Germany
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27
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Garcia-Etxebarria K, Jugo BM. Genome-wide reexamination of endogenous retroviruses in Rattus norvegicus. Virology 2016; 494:119-28. [PMID: 27107945 DOI: 10.1016/j.virol.2016.04.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 04/02/2016] [Accepted: 04/04/2016] [Indexed: 01/18/2023]
Abstract
Endogenous retroviruses (ERVs) are remnants of retroviral infections that are present in a large number of vertebrate genomes. Based on the proposal that the rat could act as a reservoir of retroviruses, rat ERVs were analysed in silico using a whole-genome approach. To enrich the detected ERV groups, we applied an upgraded approach based on the hidden Markov model. We found 2637 elements that were classified into the following groups: 9 groups of Class I; 15 of Class II, 7 of them previously described; 1 of Class III; and 3 groups whose classification was unclear but were distantly related to Class I. Sixteen ERV groups seemed to be specific to rat. The high number of rat-specific groups might be related to the contact of rats with retroviruses and their role as a reservoir. In addition, the env gene of the more extended groups seemed to be undetectable.
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Affiliation(s)
- Koldo Garcia-Etxebarria
- Genetika, Antropologia Fisikoa eta Animalien Fisiologia Saila, Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea (UPV/EHU), 644 Postakutxa, E-48080 Bilbao, Spain
| | - Begoña M Jugo
- Genetika, Antropologia Fisikoa eta Animalien Fisiologia Saila, Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea (UPV/EHU), 644 Postakutxa, E-48080 Bilbao, Spain.
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28
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Suntsova M, Garazha A, Ivanova A, Kaminsky D, Zhavoronkov A, Buzdin A. Molecular functions of human endogenous retroviruses in health and disease. Cell Mol Life Sci 2015; 72:3653-75. [PMID: 26082181 PMCID: PMC11113533 DOI: 10.1007/s00018-015-1947-6] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2015] [Revised: 05/29/2015] [Accepted: 06/03/2015] [Indexed: 12/13/2022]
Abstract
Human endogenous retroviruses (HERVs) and related genetic elements form 504 distinct families and occupy ~8% of human genome. Recent success of high-throughput experimental technologies facilitated understanding functional impact of HERVs for molecular machinery of human cells. HERVs encode active retroviral proteins, which may exert important physiological functions in the body, but also may be involved in the progression of cancer and numerous human autoimmune, neurological and infectious diseases. The spectrum of related malignancies includes, but not limits to, multiple sclerosis, psoriasis, lupus, schizophrenia, multiple cancer types and HIV. In addition, HERVs regulate expression of the neighboring host genes and modify genomic regulatory landscape, e.g., by providing regulatory modules like transcription factor binding sites (TFBS). Indeed, recent bioinformatic profiling identified ~110,000 regulatory active HERV elements, which formed at least ~320,000 human TFBS. These and other peculiarities of HERVs might have played an important role in human evolution and speciation. In this paper, we focus on the current progress in understanding of normal and pathological molecular niches of HERVs, on their implications in human evolution, normal physiology and disease. We also review the available databases dealing with various aspects of HERV genetics.
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Affiliation(s)
- Maria Suntsova
- Group for Genomic Regulation of Cell Signaling Systems, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, 117997, Russia.
- Laboratory of Bioinformatics, D. Rogachyov Federal Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, 117198, Russia.
| | - Andrew Garazha
- Group for Genomic Regulation of Cell Signaling Systems, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, 117997, Russia.
- Laboratory of Bioinformatics, D. Rogachyov Federal Research Center of Pediatric Hematology, Oncology and Immunology, Moscow, 117198, Russia.
| | - Alena Ivanova
- Group for Genomic Regulation of Cell Signaling Systems, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, 117997, Russia.
- Pathway Pharmaceuticals, Wan Chai, Hong Kong, Hong Kong SAR.
| | - Dmitry Kaminsky
- Pathway Pharmaceuticals, Wan Chai, Hong Kong, Hong Kong SAR.
| | - Alex Zhavoronkov
- Pathway Pharmaceuticals, Wan Chai, Hong Kong, Hong Kong SAR.
- Department of Translational and Regenerative Medicine, Moscow Institute of Physics and Technology, 9 Institutskiy per., Dolgoprudny, Moscow, 141700, Russia.
| | - Anton Buzdin
- Group for Genomic Regulation of Cell Signaling Systems, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, 117997, Russia.
- Pathway Pharmaceuticals, Wan Chai, Hong Kong, Hong Kong SAR.
- National Research Centre "Kurchatov Institute", Centre for Convergence of Nano-, Bio-, Information and Cognitive Sciences and Technologies, 1, Akademika Kurchatova sq., Moscow, 123182, Russia.
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To TK, Saze H, Kakutani T. DNA Methylation within Transcribed Regions. PLANT PHYSIOLOGY 2015; 168:1219-25. [PMID: 26143255 PMCID: PMC4528756 DOI: 10.1104/pp.15.00543] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Accepted: 07/02/2015] [Indexed: 05/10/2023]
Abstract
DNA methylation within transcribed genes is commonly found in diverse animals and plants. Here, we provide an overview of recent advances and the remaining mystery regarding intragenic DNA methylation.
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Affiliation(s)
- Taiko K To
- Department of Integrated Genetics, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan (T.K.T., T.K.); andOkinawa Institute of Science and Technology, Onna-son, Okinawa 904-0412, Japan (H.S.)
| | - Hidetoshi Saze
- Department of Integrated Genetics, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan (T.K.T., T.K.); andOkinawa Institute of Science and Technology, Onna-son, Okinawa 904-0412, Japan (H.S.)
| | - Tetsuji Kakutani
- Department of Integrated Genetics, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan (T.K.T., T.K.); andOkinawa Institute of Science and Technology, Onna-son, Okinawa 904-0412, Japan (H.S.)
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30
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Sokol M, Jessen KM, Pedersen FS. Human endogenous retroviruses sustain complex and cooperative regulation of gene-containing loci and unannotated megabase-sized regions. Retrovirology 2015; 12:32. [PMID: 25927889 PMCID: PMC4422309 DOI: 10.1186/s12977-015-0161-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 03/30/2015] [Indexed: 12/19/2022] Open
Abstract
Background Evidence suggests that some human endogenous retroviruses and endogenous retrovirus-like repeats (here collectively ERVs) regulate the expression of neighboring genes in normal and disease states; e.g. the human globin locus is regulated by an ERV9 that coordinates long-range gene switching during hematopoiesis and activates also intergenic transcripts. While complex transcription regulation is associated with integration of certain exogenous retroviruses, comparable regulation sustained by ERVs is less understood. Findings We analyzed ERV transcription using ERV9 consensus sequences and publically available RNA-sequencing, chromatin immunoprecipitation with sequencing (ChIP-seq) and cap analysis gene expression (CAGE) data from ENCODE. We discovered previously undescribed and advanced transcription regulation mechanisms in several human reference cell lines. We show that regulation by ERVs involves long-ranging activations including complex RNA splicing patterns, and transcription of large unannotated regions ranging in size from several hundred kb to around 1 Mb. Moreover, regulation was found to be cooperatively sustained in some loci by multiple ERVs and also non-LTR repeats. Conclusion Our analyses show that endogenous retroviruses sustain advanced transcription regulation in human cell lines, which shows similarities to complex insertional mutagenesis effects exerted by exogenous retroviruses. By exposing previously undescribed regulation effects, this study should prove useful for understanding fundamental transcription mechanisms resulting from evolutionary acquisition of retroviral sequence in the human genome. Electronic supplementary material The online version of this article (doi:10.1186/s12977-015-0161-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Martin Sokol
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, DK-8000, Denmark.
| | - Karen Margrethe Jessen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, DK-8000, Denmark.
| | - Finn Skou Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, DK-8000, Denmark.
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31
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Le TN, Miyazaki Y, Takuno S, Saze H. Epigenetic regulation of intragenic transposable elements impacts gene transcription in Arabidopsis thaliana. Nucleic Acids Res 2015; 43:3911-21. [PMID: 25813042 PMCID: PMC4417168 DOI: 10.1093/nar/gkv258] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Accepted: 03/17/2015] [Indexed: 11/30/2022] Open
Abstract
Genomes of higher eukaryotes, including plants, contain numerous transposable elements (TEs), that are often silenced by epigenetic mechanisms, such as histone modifications and DNA methylation. Although TE silencing adversely affects expression of nearby genes, recent studies reveal the presence of intragenic TEs marked by repressive heterochromatic epigenetic marks within transcribed genes. However, even for the well-studied plant model Arabidopsis thaliana, the abundance of intragenic TEs, how they are epigenetically regulated, and their potential impacts on host gene expression, remain unexplored. In this study, we comprehensively analyzed genome-wide distribution and epigenetic regulation of intragenic TEs in A. thaliana. Our analysis revealed that about 3% of TEs are located within gene bodies, dominantly at intronic regions. Most of them are shorter and less methylated than intergenic TEs, but they are still targeted by RNA-directed DNA methylation-dependent and independent pathways. Surprisingly, the heterochromatic epigenetic marks at TEs are maintained within actively transcribed genes. Moreover, the heterochromatic state of intronic TEs is critical for proper transcription of associated genes. Our study provides the first insight into how intragenic TEs affect the transcriptional landscape of the A. thaliana genome, and suggests the importance of epigenetic mechanisms for regulation of TEs within transcriptional gene units.
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Affiliation(s)
- Tu N Le
- Plant Epigenetics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japan
| | - Yuji Miyazaki
- Plant Epigenetics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japan
| | - Shohei Takuno
- Department of Evolutionary Studies of Biosystems, School of Advanced Sciences, SOKENDAI (Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan
| | - Hidetoshi Saze
- Plant Epigenetics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japan
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32
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Human endogenous retrovirus group E and its involvement in diseases. Viruses 2015; 7:1238-57. [PMID: 25785516 PMCID: PMC4379568 DOI: 10.3390/v7031238] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 02/12/2015] [Accepted: 02/23/2015] [Indexed: 02/07/2023] Open
Abstract
Human endogenous retrovirus group E (HERV-E) elements are stably integrated into the human genome, transmitted vertically in a Mendelian manner, and are endowed with transcriptional activity as alternative promoters or enhancers. Such effects are under the control of the proviral long terminal repeats (LTR) that are organized into three HERV-E phylogenetic subgroups, namely LTR2, LTR2B, and LTR2C. Moreover, HERV-E expression is tissue-specific, and silenced by epigenetic constraints that may be disrupted in cancer, autoimmunity, and human placentation. Interest in HERV-E with regard to these conditions has been stimulated further by concerns regarding the capacity of HERV-E elements to modify the expression of neighboring genes and/or to produce retroviral proteins, including immunosuppressive env peptides, which in turn may induce (auto)-antibody (Ab) production. Finally, better understanding of HERV-E elements may have clinical applications for prevention, diagnosis, prognosis, and therapy.
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33
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Garcia-Etxebarria K, Jugo BM. Genomic environment and digital expression of bovine endogenous retroviruses. Gene 2014; 548:14-21. [DOI: 10.1016/j.gene.2014.06.048] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 02/08/2014] [Accepted: 06/23/2014] [Indexed: 10/25/2022]
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Keane TM, Wong K, Adams DJ, Flint J, Reymond A, Yalcin B. Identification of structural variation in mouse genomes. Front Genet 2014; 5:192. [PMID: 25071822 PMCID: PMC4079067 DOI: 10.3389/fgene.2014.00192] [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: 03/14/2014] [Accepted: 06/12/2014] [Indexed: 01/25/2023] Open
Abstract
Structural variation is variation in structure of DNA regions affecting DNA sequence length and/or orientation. It generally includes deletions, insertions, copy-number gains, inversions, and transposable elements. Traditionally, the identification of structural variation in genomes has been challenging. However, with the recent advances in high-throughput DNA sequencing and paired-end mapping (PEM) methods, the ability to identify structural variation and their respective association to human diseases has improved considerably. In this review, we describe our current knowledge of structural variation in the mouse, one of the prime model systems for studying human diseases and mammalian biology. We further present the evolutionary implications of structural variation on transposable elements. We conclude with future directions on the study of structural variation in mouse genomes that will increase our understanding of molecular architecture and functional consequences of structural variation.
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Affiliation(s)
| | - Kim Wong
- Wellcome Trust Sanger Institute Hinxton, Cambridge, UK
| | - David J Adams
- Wellcome Trust Sanger Institute Hinxton, Cambridge, UK
| | | | - Alexandre Reymond
- Center for Integrative Genomics, University of Lausanne Lausanne, Switzerland
| | - Binnaz Yalcin
- Center for Integrative Genomics, University of Lausanne Lausanne, Switzerland ; Institute of Genetics and Molecular and Cellular Biology Illkirch, France
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35
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Lee YCG, Chang HH. The evolution and functional significance of nested gene structures in Drosophila melanogaster. Genome Biol Evol 2014; 5:1978-85. [PMID: 24084778 PMCID: PMC3814207 DOI: 10.1093/gbe/evt149] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Nearly 10% of the genes in the genome of Drosophila melanogaster are in nested structures, in which one gene is completely nested within the intron of another gene (nested and including gene, respectively). Even though the coding sequences and untranslated regions of these nested/including gene pairs do not overlap, their intimate structures and the possibility of shared regulatory sequences raise questions about the evolutionary forces governing the origination and subsequent functional and evolutionary impacts of these structures. In this study, we show that nested genes experience weaker evolutionary constraint, have faster rates of protein evolution, and are expressed in fewer tissues than other genes, while including genes show the opposite patterns. Surprisingly, despite completely overlapping with each other, nested and including genes are less likely to display correlated gene expression and biological function than the nearby yet nonoverlapping genes. Interestingly, significantly fewer nested genes are transcribed from the same strand as the including gene. We found that same-strand nested genes are more likely to be single-exon genes. In addition, same-strand including genes are less likely to have known lethal or sterile phenotypes than opposite-strand including genes only when the corresponding nested genes have introns. These results support our hypothesis that selection against potential erroneous mRNA splicing when nested and including genes are on the same strand plays an important role in the evolution of nested gene structures.
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Affiliation(s)
- Yuh Chwen G Lee
- Center for Population Biology and Department of Evolution and Ecology, University of California
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36
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Xue B, He L. An expanding universe of the non-coding genome in cancer biology. Carcinogenesis 2014; 35:1209-16. [PMID: 24747961 DOI: 10.1093/carcin/bgu099] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Neoplastic transformation is caused by accumulation of genetic and epigenetic alterations that ultimately convert normal cells into tumor cells with uncontrolled proliferation and survival, unlimited replicative potential and invasive growth [Hanahan,D. et al. (2011) Hallmarks of cancer: the next generation. Cell, 144, 646-674]. Although the majority of the cancer studies have focused on the functions of protein-coding genes, emerging evidence has started to reveal the importance of the vast non-coding genome, which constitutes more than 98% of the human genome. A number of non-coding RNAs (ncRNAs) derived from the 'dark matter' of the human genome exhibit cancer-specific differential expression and/or genomic alterations, and it is increasingly clear that ncRNAs, including small ncRNAs and long ncRNAs (lncRNAs), play an important role in cancer development by regulating protein-coding gene expression through diverse mechanisms. In addition to ncRNAs, nearly half of the mammalian genomes consist of transposable elements, particularly retrotransposons. Once depicted as selfish genomic parasites that propagate at the expense of host fitness, retrotransposon elements could also confer regulatory complexity to the host genomes during development and disease. Reactivation of retrotransposons in cancer, while capable of causing insertional mutagenesis and genome rearrangements to promote oncogenesis, could also alter host gene expression networks to favor tumor development. Taken together, the functional significance of non-coding genome in tumorigenesis has been previously underestimated, and diverse transcripts derived from the non-coding genome could act as integral functional components of the oncogene and tumor suppressor network.
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Affiliation(s)
- Bin Xue
- Department of Molecular and Cell Biology, Division of Cellular and Developmental Biology, University of California at Berkeley, Berkeley, CA 94720, USA
| | - Lin He
- Department of Molecular and Cell Biology, Division of Cellular and Developmental Biology, University of California at Berkeley, Berkeley, CA 94720, USA
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Lehoczky JA, Thomas PE, Patrie KM, Owens KM, Villarreal LM, Galbraith K, Washburn J, Johnson CN, Gavino B, Borowsky AD, Millen KJ, Wakenight P, Law W, Van Keuren ML, Gavrilina G, Hughes ED, Saunders TL, Brihn L, Nadeau JH, Innis JW. A novel intergenic ETnII-β insertion mutation causes multiple malformations in polypodia mice. PLoS Genet 2013; 9:e1003967. [PMID: 24339789 PMCID: PMC3854779 DOI: 10.1371/journal.pgen.1003967] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Accepted: 10/04/2013] [Indexed: 11/28/2022] Open
Abstract
Mouse early transposon insertions are responsible for ∼10% of spontaneous mutant phenotypes. We previously reported the phenotypes and genetic mapping of Polypodia, (Ppd), a spontaneous, X-linked dominant mutation with profound effects on body plan morphogenesis. Our new data shows that mutant mice are not born in expected Mendelian ratios secondary to loss after E9.5. In addition, we refined the Ppd genetic interval and discovered a novel ETnII-β early transposon insertion between the genes for Dusp9 and Pnck. The ETn inserted 1.6 kb downstream and antisense to Dusp9 and does not disrupt polyadenylation or splicing of either gene. Knock-in mice engineered to carry the ETn display Ppd characteristic ectopic caudal limb phenotypes, showing that the ETn insertion is the Ppd molecular lesion. Early transposons are actively expressed in the early blastocyst. To explore the consequences of the ETn on the genomic landscape at an early stage of development, we compared interval gene expression between wild-type and mutant ES cells. Mutant ES cell expression analysis revealed marked upregulation of Dusp9 mRNA and protein expression. Evaluation of the 5′ LTR CpG methylation state in adult mice revealed no correlation with the occurrence or severity of Ppd phenotypes at birth. Thus, the broad range of phenotypes observed in this mutant is secondary to a novel intergenic ETn insertion whose effects include dysregulation of nearby interval gene expression at early stages of development. Mobile genetic elements, particularly early transposons (ETn), cause malformations by inserting within genes leading to disruption of exons, splicing or polyadenylation. Few mutagenic early transposon insertions have been found outside genes and the effects of such insertions on surrounding gene regulation is poorly understood. We discovered a novel intergenic ETnII-β insertion in the mouse mutant Polypodia (Ppd). We reproduced the mutant phenotype after engineering the mutation in wild-type cells with homologous recombination, proving that this early transposon insertion is Ppd. Mutant mice are not born in expected Mendelian ratios secondary to loss after E9.5. Embryonic stem cells from mutant mice show upregulated transcription of an adjacent gene, Dusp9. Thus, at an early and critical stage of development, dysregulated gene transcription is one consequence of the insertion mutation. DNA methylation of the ETn 5′ LTR is not correlated with phenotypic outcome in mutant mice. Polypodia is an example of an intergenic mobile element insertion in mice causing dramatic morphogenetic defects and fetal death.
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Affiliation(s)
- Jessica A. Lehoczky
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Peedikayil E. Thomas
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, United States of America
- Pediatrics, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Kevin M. Patrie
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Kailey M. Owens
- Pediatrics, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Lisa M. Villarreal
- Pediatrics, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Kenneth Galbraith
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Joe Washburn
- Biomedical Research Core Facilities, DNA Sequencing Core Lab, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Craig N. Johnson
- Biomedical Research Core Facilities, DNA Sequencing Core Lab, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Bryant Gavino
- Murine Molecular Constructs Laboratory-MMCL Mouse Biology Program, University of California, Davis, California, United States of America
| | - Alexander D. Borowsky
- University of California, Davis, Center for Comparative Medicine and Comprehensive Cancer Center, Department of Pathology and Laboratory Medicine, Davis, California, United States of America
| | - Kathleen J. Millen
- Division of Genetic Medicine, Department of Pediatrics, Seattle Children's Hospital, Seattle, Washington, United States of America
| | - Paul Wakenight
- Division of Genetic Medicine, Department of Pediatrics, Seattle Children's Hospital, Seattle, Washington, United States of America
| | - William Law
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Margaret L. Van Keuren
- Transgenic Animal Model Core Lab, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Galina Gavrilina
- Transgenic Animal Model Core Lab, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Elizabeth D. Hughes
- Transgenic Animal Model Core Lab, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Thomas L. Saunders
- Transgenic Animal Model Core Lab, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Lesil Brihn
- Department of Genetics, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Joseph H. Nadeau
- Pacific Northwest Research Institute, Seattle, Washington, United States of America
| | - Jeffrey W. Innis
- Department of Human Genetics, University of Michigan, Ann Arbor, Michigan, United States of America
- Pediatrics, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail:
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Linker S, Hedges D. Linear decay of retrotransposon antisense bias across genes is contingent upon tissue specificity. PLoS One 2013; 8:e79402. [PMID: 24244495 PMCID: PMC3828378 DOI: 10.1371/journal.pone.0079402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 09/28/2013] [Indexed: 12/23/2022] Open
Abstract
Retrotransposons comprise approximately half of the human genome and contribute to chromatin structure, regulatory motifs, and protein-coding sequences. Since retrotransposon insertions can disrupt functional genetic elements as well as introduce new sequence motifs to a region, they have the potential to affect the function of genes that harbour insertions as well as those nearby. Partly as a result of these effects, the distribution of retrotransposons across the genome is non-uniform and there are observed imbalances in the orientation of insertions with respect to the transcriptional direction of the containing gene. Although some of the factors underlying the observed distributions are understood, much of the variability remains unexplained. Detailed characterization of retrotransposon density in genes could help inform predictions of the functional consequence of de novo as well as polymorphic insertions. In order to characterize the relationship between genes and inserted elements, we have examined the distribution of retrotransposons and their internal motifs within tissue-specific and housekeeping genes. We have identified that the previously established retrotransposon antisense bias decays at a linear rate across genes, resulting in an equal density of sense and antisense retrotransposons near the 3'-UTR. In addition, the decay of antisense bias across genes is less pronounced among tissue-specific genes. Our results provide support for the scenario in which this linear decay in antisense bias is established by natural selection shortly after retrotransposon integration, and that total antisense bias observed is above and beyond any bias introduced by the integration process itself. Finally, we provide an example of a retrotransposon acting as an eQTL on a coincident gene, highlighting one of several possible avenues through which insertions may modulate gene function.
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Affiliation(s)
- Sara Linker
- Hussman Institute for Human Genomics, Dr John T. Macdonald Foundation Department of Human Genetics, Miller School of Medicine, University of Miami, Miami, Florida, United States of America
| | - Dale Hedges
- Division of Human Genetics, Department of Internal Medicine, The Ohio State University, Columbus, Ohio, United States of America
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Visualized computational predictions of transcriptional effects by intronic endogenous retroviruses. PLoS One 2013; 8:e71971. [PMID: 23936536 PMCID: PMC3735543 DOI: 10.1371/journal.pone.0071971] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Accepted: 07/05/2013] [Indexed: 11/19/2022] Open
Abstract
When endogenous retroviruses (ERVs) or other transposable elements (TEs) insert into an intron, the consequence on gene transcription can range from negligible to a complete ablation of normal transcripts. With the advance of sequencing technology, more and more insertionally polymorphic or private TE insertions are being identified in humans and mice, of which some could have a significant impact on host gene expression. Nevertheless, an efficient and low cost approach to prioritize their potential effect on gene transcription has been lacking. By building a computational model based on artificial neural networks (ANN), we demonstrate the feasibility of using machine-learning approaches to predict the likelihood that intronic ERV insertions will have major effects on gene transcription, focusing on the two ERV families, namely Intracisternal A-type Particle (IAP) and Early Transposon (ETn)/MusD elements, which are responsible for the majority of ERV-induced mutations in mice. We trained the ANN model using properties associated with these ERVs known to cause germ-line mutations (positive cases) and properties associated with likely neutral ERVs of the same families (negative cases), and derived a set of prediction plots that can visualize the likelihood of affecting gene transcription by ERV insertions. Our results show a highly reliable prediction power of our model, and offer a potential approach to computationally screen for other types of TE insertions that may affect gene transcription or even cause disease.
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Byun HM, Motta V, Panni T, Bertazzi PA, Apostoli P, Hou L, Baccarelli AA. Evolutionary age of repetitive element subfamilies and sensitivity of DNA methylation to airborne pollutants. Part Fibre Toxicol 2013; 10:28. [PMID: 23855992 PMCID: PMC3717285 DOI: 10.1186/1743-8977-10-28] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Accepted: 07/05/2013] [Indexed: 02/07/2023] Open
Abstract
Background Repetitive elements take up >40% of the human genome and can change distribution through transposition, thus generating subfamilies. Repetitive element DNA methylation has associated with several diseases and environmental exposures, including exposure to airborne pollutants. No systematic analysis has yet been conducted to examine the effects of exposures across different repetitive element subfamilies. The purpose of the study is to evaluate sensitivity of DNA methylation in differentially‒evolved LINE, Alu, and HERV subfamilies to different types of airborne pollutants. Methods We sampled a total of 120 male participants from three studies (20 high-, 20 low-exposure in each study) of steel workers exposed to metal-rich particulate matter (measured as PM10) (Study 1); gas-station attendants exposed to air benzene (Study 2); and truck drivers exposed to traffic-derived elemental carbon (Study 3). We measured methylation by bisulfite-PCR-pyrosequencing in 10 differentially‒evolved repetitive element subfamilies. Results High-exposure groups exhibited subfamily-specific methylation differences compared to low-exposure groups: L1PA2 showed lower DNA methylation in steel workers (P=0.04) and gas station attendants (P=0.03); L1Ta showed lower DNA methylation in steel workers (P=0.02); AluYb8 showed higher DNA methylation in truck drivers (P=0.05). Within each study, dose–response analyses showed subfamily-specific correlations of methylation with exposure levels. Interaction models showed that the effects of the exposures on DNA methylation were dependent on the subfamily evolutionary age, with stronger effects on older LINEs from PM10 (p‒interaction=0.003) and benzene (p‒interaction=0.04), and on younger Alus from PM10 (p-interaction=0.02). Conclusions The evolutionary age of repetitive element subfamilies determines differential susceptibility of DNA methylation to airborne pollutants.
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Affiliation(s)
- Hyang-Min Byun
- Laboratory of Environmental Epigenetics, Exposure Epidemiology and Risk Program, Harvard School of Public Health, Boston, MA, USA.
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HERV-E-mediated modulation of PLA2G4A transcription in urothelial carcinoma. PLoS One 2012; 7:e49341. [PMID: 23145155 PMCID: PMC3492278 DOI: 10.1371/journal.pone.0049341] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 10/09/2012] [Indexed: 12/30/2022] Open
Abstract
Human endogenous retroviruses (HERV) and related elements account for more than 8% of the human genome and significantly contribute to the human transcriptome by long terminal repeat (LTR) promoter activity. In this context, HERVs are thought to intervene in the expression of adjacent genes by providing regulatory sequences (cis-effect) or via noncoding RNA including natural antisense transcripts. To address the potential impact of HERV activity in urothelial carcinoma, we comparatively analyzed the HERV transcription profiles in paired samples of non-malignant urothelium and urothelial carcinoma derived from 13 patients with bladder cancer by means of a retrovirus-specific microarray (RetroArray). We established a characteristic HERV signature consisting of six ubiquitously active HERV subgroups (E4-1, HERV-Rb, ERV9, HERV-K-T47D, NMWV3, HERV-KC4). The transcription pattern is largely identical in human urothelial carcinoma, non-malignant urothelial tissue, four tumor-derived cell lines and in a non-malignant urothelial cell line (UROtsa). Quantitative reverse transcriptase PCR (qRT-PCR) of HERV-E4-1, HERV-K(HML-6) and HERV-T(S71-TK1) revealed a bias to lower HERV activity in carcinoma samples compared to non-malignant tissue. Determination of active HERV-E4-1 loci by cloning and sequencing revealed six HERV-E4-1 proviral loci that are differentially regulated in urothelial carcinoma cells and normal tissue. Two full-length HERV-E4-1 proviruses, HERV-Ec1 and HERV-Ec6, are located in antisense orientation in introns of the genes PLA2G4A and RNGTT, respectively. PLA2G4A encodes a cytosolic phospholipase A2 (cPLA2) that is dysregulated in many human tumors. PLA2G4A and HERV-Ec1 displayed reciprocal transcript levels in 7 of 11 urothelial carcinoma patients. Moreover, reciprocal shifts were observed after treatment of UROtsa cells with HERV-Ec1 and PLA2G4A-directed siRNAs or 5-aza-2′-deoxycytidine (aza-dC) pointing to an antagonistic regulation of PLA2G4A and HERV-Ec1 transcription in human urothelial cells. We suggest that transcription of HERV-Ec1 contributes to fine tuning of cPLA2 expression, thereby facilitating tumorigenesis.
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Pérot P, Mugnier N, Montgiraud C, Gimenez J, Jaillard M, Bonnaud B, Mallet F. Microarray-based sketches of the HERV transcriptome landscape. PLoS One 2012; 7:e40194. [PMID: 22761958 PMCID: PMC3386233 DOI: 10.1371/journal.pone.0040194] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 06/02/2012] [Indexed: 12/15/2022] Open
Abstract
Human endogenous retroviruses (HERVs) are spread throughout the genome and their long terminal repeats (LTRs) constitute a wide collection of putative regulatory sequences. Phylogenetic similarities and the profusion of integration sites, two inherent characteristics of transposable elements, make it difficult to study individual locus expression in a large-scale approach, and historically apart from some placental and testis-regulated elements, it was generally accepted that HERVs are silent due to epigenetic control. Herein, we have introduced a generic method aiming to optimally characterize individual loci associated with 25-mer probes by minimizing cross-hybridization risks. We therefore set up a microarray dedicated to a collection of 5,573 HERVs that can reasonably be assigned to a unique genomic position. We obtained a first view of the HERV transcriptome by using a composite panel of 40 normal and 39 tumor samples. The experiment showed that almost one third of the HERV repertoire is indeed transcribed. The HERV transcriptome follows tropism rules, is sensitive to the state of differentiation and, unexpectedly, seems not to correlate with the age of the HERV families. The probeset definition within the U3 and U5 regions was used to assign a function to some LTRs (i.e. promoter or polyA) and revealed that (i) autonomous active LTRs are broadly subjected to operational determinism (ii) the cellular gene density is substantially higher in the surrounding environment of active LTRs compared to silent LTRs and (iii) the configuration of neighboring cellular genes differs between active and silent LTRs, showing an approximately 8 kb zone upstream of promoter LTRs characterized by a drastic reduction in sense cellular genes. These gathered observations are discussed in terms of virus/host adaptive strategies, and together with the methods and tools developed for this purpose, this work paves the way for further HERV transcriptome projects.
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Affiliation(s)
- Philippe Pérot
- Joint Unit Hospices Civils de Lyon, bioMérieux, Cancer Biomarkers Research Group, Centre Hospitalier Lyon Sud, Lyon, France
| | - Nathalie Mugnier
- BioMérieux, Data and Knowledge Laboratory, Marcy l’Etoile, France
| | - Cécile Montgiraud
- Joint Unit Hospices Civils de Lyon, bioMérieux, Cancer Biomarkers Research Group, Centre Hospitalier Lyon Sud, Lyon, France
| | - Juliette Gimenez
- Joint Unit Hospices Civils de Lyon, bioMérieux, Cancer Biomarkers Research Group, Centre Hospitalier Lyon Sud, Lyon, France
| | - Magali Jaillard
- BioMérieux, Data and Knowledge Laboratory, Marcy l’Etoile, France
| | - Bertrand Bonnaud
- BioMérieux, Data and Knowledge Laboratory, Marcy l’Etoile, France
| | - François Mallet
- Joint Unit Hospices Civils de Lyon, bioMérieux, Cancer Biomarkers Research Group, Centre Hospitalier Lyon Sud, Lyon, France
- * E-mail:
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Nellåker C, Keane TM, Yalcin B, Wong K, Agam A, Belgard TG, Flint J, Adams DJ, Frankel WN, Ponting CP. The genomic landscape shaped by selection on transposable elements across 18 mouse strains. Genome Biol 2012; 13:R45. [PMID: 22703977 PMCID: PMC3446317 DOI: 10.1186/gb-2012-13-6-r45] [Citation(s) in RCA: 127] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 05/25/2012] [Accepted: 06/15/2012] [Indexed: 12/20/2022] Open
Abstract
Background Transposable element (TE)-derived sequence dominates the landscape of mammalian genomes and can modulate gene function by dysregulating transcription and translation. Our current knowledge of TEs in laboratory mouse strains is limited primarily to those present in the C57BL/6J reference genome, with most mouse TEs being drawn from three distinct classes, namely short interspersed nuclear elements (SINEs), long interspersed nuclear elements (LINEs) and the endogenous retrovirus (ERV) superfamily. Despite their high prevalence, the different genomic and gene properties controlling whether TEs are preferentially purged from, or are retained by, genetic drift or positive selection in mammalian genomes remain poorly defined. Results Using whole genome sequencing data from 13 classical laboratory and 4 wild-derived mouse inbred strains, we developed a comprehensive catalogue of 103,798 polymorphic TE variants. We employ this extensive data set to characterize TE variants across the Mus lineage, and to infer neutral and selective processes that have acted over 2 million years. Our results indicate that the majority of TE variants are introduced though the male germline and that only a minority of TE variants exert detectable changes in gene expression. However, among genes with differential expression across the strains there are twice as many TE variants identified as being putative causal variants as expected. Conclusions Most TE variants that cause gene expression changes appear to be purged rapidly by purifying selection. Our findings demonstrate that past TE insertions have often been highly deleterious, and help to prioritize TE variants according to their likely contribution to gene expression or phenotype variation.
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Affiliation(s)
- Christoffer Nellåker
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
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Li J, Akagi K, Hu Y, Trivett AL, Hlynialuk CJ, Swing DA, Volfovsky N, Morgan TC, Golubeva Y, Stephens RM, Smith DE, Symer DE. Mouse endogenous retroviruses can trigger premature transcriptional termination at a distance. Genome Res 2012; 22:870-84. [PMID: 22367191 PMCID: PMC3337433 DOI: 10.1101/gr.130740.111] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 02/09/2012] [Indexed: 01/15/2023]
Abstract
Endogenous retrotransposons have caused extensive genomic variation within mammalian species, but the functional implications of such mobilization are mostly unknown. We mapped thousands of endogenous retrovirus (ERV) germline integrants in highly divergent, previously unsequenced mouse lineages, facilitating a comparison of gene expression in the presence or absence of local insertions. Polymorphic ERVs occur relatively infrequently in gene introns and are particularly depleted from genes involved in embryogenesis or that are highly expressed in embryonic stem cells. Their genomic distribution implies ongoing negative selection due to deleterious effects on gene expression and function. A polymorphic, intronic ERV at Slc15a2 triggers up to 49-fold increases in premature transcriptional termination and up to 39-fold reductions in full-length transcripts in adult mouse tissues, thereby disrupting protein expression and functional activity. Prematurely truncated transcripts also occur at Polr1a, Spon1, and up to ∼5% of other genes when intronic ERV polymorphisms are present. Analysis of expression quantitative trait loci (eQTLs) in recombinant BxD mouse strains demonstrated very strong genetic associations between the polymorphic ERV in cis and disrupted transcript levels. Premature polyadenylation is triggered at genomic distances up to >12.5 kb upstream of the ERV, both in cis and between alleles. The parent of origin of the ERV is associated with variable expression of nonterminated transcripts and differential DNA methylation at its 5'-long terminal repeat. This study defines an unexpectedly strong functional impact of ERVs in disrupting gene transcription at a distance and demonstrates that ongoing retrotransposition can contribute significantly to natural phenotypic diversity.
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Affiliation(s)
- Jingfeng Li
- Human Cancer Genetics Program and Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University Comprehensive Cancer Center, Columbus, Ohio 43210, USA
| | - Keiko Akagi
- Human Cancer Genetics Program and Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University Comprehensive Cancer Center, Columbus, Ohio 43210, USA
| | - Yongjun Hu
- Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA
| | | | - Christopher J.W. Hlynialuk
- Human Cancer Genetics Program and Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University Comprehensive Cancer Center, Columbus, Ohio 43210, USA
| | - Deborah A. Swing
- Mouse Cancer Genetics Program, National Cancer Institute, Frederick, Maryland 21702, USA
| | - Natalia Volfovsky
- Advanced Biomedical Computing Center, Information Systems Program and
| | - Tamara C. Morgan
- Histotechnology Laboratory, SAIC-Frederick, Inc., National Cancer Institute, Frederick, Maryland 21702, USA
| | - Yelena Golubeva
- Histotechnology Laboratory, SAIC-Frederick, Inc., National Cancer Institute, Frederick, Maryland 21702, USA
| | | | - David E. Smith
- Department of Pharmaceutical Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA
| | - David E. Symer
- Human Cancer Genetics Program and Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University Comprehensive Cancer Center, Columbus, Ohio 43210, USA
- Department of Internal Medicine and Department of Biomedical Informatics, The Ohio State University Comprehensive Cancer Center, Columbus, Ohio 43210, USA
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Zhang Y, Mager DL. Gene properties and chromatin state influence the accumulation of transposable elements in genes. PLoS One 2012; 7:e30158. [PMID: 22272293 PMCID: PMC3260225 DOI: 10.1371/journal.pone.0030158] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Accepted: 12/14/2011] [Indexed: 12/03/2022] Open
Abstract
Transposable elements (TEs) are mobile DNA sequences found in the genomes of almost all species. By measuring the normalized coverage of TE sequences within genes, we identified sets of genes with conserved extremes of high/low TE density in the genomes of human, mouse and cow and denoted them as ‘shared upper/lower outliers (SUOs/SLOs)’. By comparing these outlier genes to the genomic background, we show that a large proportion of SUOs are involved in metabolic pathways and tend to be mammal-specific, whereas many SLOs are related to developmental processes and have more ancient origins. Furthermore, the proportions of different types of TEs within human and mouse orthologous SUOs showed high similarity, even though most detectable TEs in these two genomes inserted after their divergence. Interestingly, our computational analysis of polymerase-II (Pol-II) occupancy at gene promoters in different mouse tissues showed that 60% of tissue-specific SUOs show strong Pol-II binding only in embryonic stem cells (ESCs), a proportion significantly higher than the genomic background (37%). In addition, our analysis of histone marks such as H3K4me3 and H3K27me3 in mouse ESCs also suggest a strong association between TE-rich genes and open-chromatin at promoters. Finally, two independent whole-transcriptome datasets show a positive association between TE density and gene expression level in ESCs. While this study focuses on genes with extreme TE densities, the above results clearly show that the probability of TE accumulation/fixation in mammalian genes is not random and is likely associated with different factors/gene properties and, most importantly, an association between the TE insertion/fixation rate and gene activity status in ES cells.
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Affiliation(s)
- Ying Zhang
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Dixie L. Mager
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
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Subramanian RP, Wildschutte JH, Russo C, Coffin JM. Identification, characterization, and comparative genomic distribution of the HERV-K (HML-2) group of human endogenous retroviruses. Retrovirology 2011; 8:90. [PMID: 22067224 PMCID: PMC3228705 DOI: 10.1186/1742-4690-8-90] [Citation(s) in RCA: 292] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Accepted: 11/08/2011] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Integration of retroviral DNA into a germ cell may lead to a provirus that is transmitted vertically to that host's offspring as an endogenous retrovirus (ERV). In humans, ERVs (HERVs) comprise about 8% of the genome, the vast majority of which are truncated and/or highly mutated and no longer encode functional genes. The most recently active retroviruses that integrated into the human germ line are members of the Betaretrovirus-like HERV-K (HML-2) group, many of which contain intact open reading frames (ORFs) in some or all genes, sometimes encoding functional proteins that are expressed in various tissues. Interestingly, this expression is upregulated in many tumors ranging from breast and ovarian tissues to lymphomas and melanomas, as well as schizophrenia, rheumatoid arthritis, and other disorders. RESULTS No study to date has characterized all HML-2 elements in the genome, an essential step towards determining a possible functional role of HML-2 expression in disease. We present here the most comprehensive and accurate catalog of all full-length and partial HML-2 proviruses, as well as solo LTR elements, within the published human genome to date. Furthermore, we provide evidence for preferential maintenance of proviruses and solo LTR elements on gene-rich chromosomes of the human genome and in proximity to gene regions. CONCLUSIONS Our analysis has found and corrected several errors in the annotation of HML-2 elements in the human genome, including mislabeling of a newly identified group called HML-11. HML-elements have been implicated in a wide array of diseases, and characterization of these elements will play a fundamental role to understand the relationship between endogenous retrovirus expression and disease.
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Affiliation(s)
- Ravi P Subramanian
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111, USA
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Martínez Barrio Á, Ekerljung M, Jern P, Benachenhou F, Sperber GO, Bongcam-Rudloff E, Blomberg J, Andersson G. The first sequenced carnivore genome shows complex host-endogenous retrovirus relationships. PLoS One 2011; 6:e19832. [PMID: 21589882 PMCID: PMC3093408 DOI: 10.1371/journal.pone.0019832] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Accepted: 04/18/2011] [Indexed: 11/25/2022] Open
Abstract
Host-retrovirus interactions influence the genomic landscape and have contributed substantially to mammalian genome evolution. To gain further insights, we analyzed a female boxer (Canis familiaris) genome for complexity and integration pattern of canine endogenous retroviruses (CfERV). Intriguingly, the first such in-depth analysis of a carnivore species identified 407 CfERV proviruses that represent only 0.15% of the dog genome. In comparison, the same detection criteria identified about six times more HERV proviruses in the human genome that has been estimated to contain a total of 8% retroviral DNA including solitary LTRs. These observed differences in man and dog are likely due to different mechanisms to purge, restrict and protect their genomes against retroviruses. A novel group of gammaretrovirus-like CfERV with high similarity to HERV-Fc1 was found to have potential for active retrotransposition and possibly lateral transmissions between dog and human as a result of close interactions during at least 10.000 years. The CfERV integration landscape showed a non-uniform intra- and inter-chromosomal distribution. Like in other species, different densities of ERVs were observed. Some chromosomal regions were essentially devoid of CfERVs whereas other regions had large numbers of integrations in agreement with distinct selective pressures at different loci. Most CfERVs were integrated in antisense orientation within 100 kb from annotated protein-coding genes. This integration pattern provides evidence for selection against CfERVs in sense orientation relative to chromosomal genes. In conclusion, this ERV analysis of the first carnivorous species supports the notion that different mammals interact distinctively with endogenous retroviruses and suggests that retroviral lateral transmissions between dog and human may have occurred.
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Affiliation(s)
- Álvaro Martínez Barrio
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Marie Ekerljung
- Department of Animal Breeding and Genetics, Biomedical Centre, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Patric Jern
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Farid Benachenhou
- Department of Animal Breeding and Genetics, Biomedical Centre, Swedish University of Agricultural Sciences, Uppsala, Sweden
- Section of Virology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Göran O. Sperber
- Department of Neuroscience, Physiology, Uppsala University, Uppsala, Sweden
| | - Erik Bongcam-Rudloff
- Department of Animal Breeding and Genetics, Biomedical Centre, Swedish University of Agricultural Sciences, Uppsala, Sweden
- Department of Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Jonas Blomberg
- Section of Virology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Göran Andersson
- Department of Animal Breeding and Genetics, Biomedical Centre, Swedish University of Agricultural Sciences, Uppsala, Sweden
- * E-mail:
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Zhang Y, Romanish MT, Mager DL. Distributions of transposable elements reveal hazardous zones in mammalian introns. PLoS Comput Biol 2011; 7:e1002046. [PMID: 21573203 PMCID: PMC3088655 DOI: 10.1371/journal.pcbi.1002046] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Accepted: 03/25/2011] [Indexed: 11/20/2022] Open
Abstract
Comprising nearly half of the human and mouse genomes, transposable elements (TEs) are found within most genes. Although the vast majority of TEs in introns are fixed in the species and presumably exert no significant effects on the enclosing gene, some markedly perturb transcription and result in disease or a mutated phenotype. Factors determining the likelihood that an intronic TE will affect transcription are not clear. In this study, we examined intronic TE distributions in both human and mouse and found several factors that likely contribute to whether a particular TE can influence gene transcription. Specifically, we observed that TEs near exons are greatly underrepresented compared to random distributions, but the size of these “underrepresentation zones” differs between TE classes. Compared to elsewhere in introns, TEs within these zones are shorter on average and show stronger orientation biases. Moreover, TEs in extremely close proximity (<20 bp) to exons show a strong bias to be near splice-donor sites. Interestingly, disease-causing intronic TE insertions show the opposite distributional trends, and by examining expressed sequence tag (EST) databases, we found that the proportion of TEs contributing to chimeric TE-gene transcripts is significantly higher within their underrepresentation zones. In addition, an analysis of predicted splice sites within human long terminal repeat (LTR) elements showed a significantly lower total number and weaker strength for intronic LTRs near exons. Based on these factors, we selectively examined a list of polymorphic mouse LTR elements in introns and showed clear evidence of transcriptional disruption by LTR element insertions in the Trpc6 and Kcnh6 genes. Taken together, these studies lend insight into the potential selective forces that have shaped intronic TE distributions and enable identification of TEs most likely to exert transcriptional effects on genes. Sequences derived from transposable elements (TEs) are major constituents of mammalian genomes and are found within introns of most genes. While nearly all TEs within introns appear harmless, some de novo intronic TE insertions do disrupt gene transcription and splicing and cause disease. It is unclear why some intronic TEs perturb gene transcription whereas most do not. Here, we examined intronic TE distributions in both human and mouse genes to gain insight into which TEs may be more likely to affect transcription. We found evidence that TEs near exons are likely subject to strong negative selection but the size of the region under selection or “underrepresentation zone” differs for different TE classes. Strikingly, all reported human disease-causing intronic TE insertions fall within these underrepresentation zones, and the proportion of TEs contributing to chimeric TE-gene transcripts is significantly higher when TEs are located in these zones. We also examined insertionally polymorphic mouse TEs located within underrepresentation zones and found evidence of transcriptional disruption in two genes. Given the growing appreciation for ongoing activity of TEs in human, our results should be of value in prioritizing insertionally polymorphic TEs for study of their potential contributions to gene expression differences and phenotypic variability.
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Affiliation(s)
- Ying Zhang
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Mark T. Romanish
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - Dixie L. Mager
- Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
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49
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Li F, Nellåker C, Yolken RH, Karlsson H. A systematic evaluation of expression of HERV-W elements; influence of genomic context, viral structure and orientation. BMC Genomics 2011; 12:22. [PMID: 21226900 PMCID: PMC3031232 DOI: 10.1186/1471-2164-12-22] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Accepted: 01/12/2011] [Indexed: 12/19/2022] Open
Abstract
Background One member of the W family of human endogenous retroviruses (HERV) appears to have been functionally adopted by the human host. Nevertheless, a highly diversified and regulated transcription from a range of HERV-W elements has been observed in human tissues and cells. Aberrant expression of members of this family has also been associated with human disease such as multiple sclerosis (MS) and schizophrenia. It is not known whether this broad expression of HERV-W elements represents transcriptional leakage or specific transcription initiated from the retroviral promoter in the long terminal repeat (LTR) region. Therefore, potential influences of genomic context, structure and orientation on the expression levels of individual HERV-W elements in normal human tissues were systematically investigated. Results Whereas intronic HERV-W elements with a pseudogene structure exhibited a strong anti-sense orientation bias, intronic elements with a proviral structure and solo LTRs did not. Although a highly variable expression across tissues and elements was observed, systematic effects of context, structure and orientation were also observed. Elements located in intronic regions appeared to be expressed at higher levels than elements located in intergenic regions. Intronic elements with proviral structures were expressed at higher levels than those elements bearing hallmarks of processed pseudogenes or solo LTRs. Relative to their corresponding genes, intronic elements integrated on the sense strand appeared to be transcribed at higher levels than those integrated on the anti-sense strand. Moreover, the expression of proviral elements appeared to be independent from that of their corresponding genes. Conclusions Intronic HERV-W provirus integrations on the sense strand appear to have elicited a weaker negative selection than pseudogene integrations of transcripts from such elements. Our current findings suggest that the previously observed diversified and tissue-specific expression of elements in the HERV-W family is the result of both directed transcription (involving both the LTR and internal sequence) and leaky transcription of HERV-W elements in normal human tissues.
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Affiliation(s)
- Fang Li
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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50
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Hancks DC, Kazazian H. SVA retrotransposons: Evolution and genetic instability. Semin Cancer Biol 2010; 20:234-45. [PMID: 20416380 PMCID: PMC2945828 DOI: 10.1016/j.semcancer.2010.04.001] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 04/01/2010] [Accepted: 04/14/2010] [Indexed: 01/21/2023]
Abstract
SINE-VNTR-Alus (SVA) are non-autonomous hominid specific retrotransposons that are associated with disease in humans. SVAs are evolutionarily young and presumably mobilized by the LINE-1 reverse transcriptase in trans. SVAs are currently active and may impact the host through a variety of mechanisms including insertional mutagenesis, exon shuffling, alternative splicing, and the generation of differentially methylated regions (DMR). Here we review SVA biology, including SVA insertions associated with known diseases. Further, we discuss a model describing the initial formation of SVA and the mechanisms by which SVA may impact the host.
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Affiliation(s)
- Dustin C. Hancks
- Department of Genetics, The University of Pennsylvania School of Medicine
| | - Haig Kazazian
- Department of Genetics, The University of Pennsylvania School of Medicine
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