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Modenini G, Abondio P, Boattini A. The coevolution between APOBEC3 and retrotransposons in primates. Mob DNA 2022; 13:27. [PMID: 36443831 PMCID: PMC9706992 DOI: 10.1186/s13100-022-00283-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 10/31/2022] [Indexed: 12/02/2022] Open
Abstract
Retrotransposons are genetic elements with the ability to replicate in the genome using reverse transcriptase: they have been associated with the development of different biological structures, such as the Central Nervous System (CNS), and their high mutagenic potential has been linked to various diseases, including cancer and neurological disorders. Throughout evolution and over time, Primates and Homo had to cope with infections from viruses and bacteria, and also with endogenous retroelements. Therefore, host genomes have evolved numerous methods to counteract the activity of endogenous and exogenous pathogens, and the APOBEC3 family of mutators is a prime example of a defensive mechanism in this context.In most Primates, there are seven members of the APOBEC3 family of deaminase proteins: among their functions, there is the ability to inhibit the mobilization of retrotransposons and the functionality of viruses. The evolution of the APOBEC3 proteins found in Primates is correlated with the expansion of two major families of retrotransposons, i.e. ERV and LINE-1.In this review, we will discuss how the rapid expansion of the APOBEC3 family is linked to the evolution of retrotransposons, highlighting the strong evolutionary arms race that characterized the history of APOBEC3s and endogenous retroelements in Primates. Moreover, the possible role of this relationship will be assessed in the context of embryonic development and brain-associated diseases.
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Affiliation(s)
- Giorgia Modenini
- grid.6292.f0000 0004 1757 1758Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy
| | - Paolo Abondio
- grid.6292.f0000 0004 1757 1758Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy ,grid.6292.f0000 0004 1757 1758Department of Cultural Heritage, University of Bologna, Ravenna, Italy
| | - Alessio Boattini
- grid.6292.f0000 0004 1757 1758Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy
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2
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On the Base Composition of Transposable Elements. Int J Mol Sci 2022; 23:ijms23094755. [PMID: 35563146 PMCID: PMC9099904 DOI: 10.3390/ijms23094755] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 04/22/2022] [Accepted: 04/23/2022] [Indexed: 01/27/2023] Open
Abstract
Transposable elements exhibit a base composition that is often different from the genomic average and from hosts’ genes. The most common compositional bias is towards Adenosine and Thymine, although this bias is not universal, and elements with drastically different base composition can coexist within the same genome. The AT-richness of transposable elements is apparently maladaptive because it results in poor transcription and sub-optimal translation of proteins encoded by the elements. The cause(s) of this unusual base composition remain unclear and have yet to be investigated. Here, I review what is known about the nucleotide content of transposable elements and how this content can affect the genome of their host as well as their own replication. The compositional bias of transposable elements could result from several non-exclusive processes including horizontal transfer, mutational bias, and selection. It appears that mutation alone cannot explain the high AT-content of transposons and that selection plays a major role in the evolution of the compositional bias. The reason why selection would favor a maladaptive nucleotide content remains however unexplained and is an area of investigation that clearly deserves attention.
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3
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Activation of Endogenous Retrovirus, Brain Infections and Environmental Insults in Neurodegeneration and Alzheimer's Disease. Int J Mol Sci 2021; 22:ijms22147263. [PMID: 34298881 PMCID: PMC8303979 DOI: 10.3390/ijms22147263] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 06/29/2021] [Accepted: 07/03/2021] [Indexed: 12/18/2022] Open
Abstract
Chronic neurodegenerative diseases are complex, and their pathogenesis is uncertain. Alzheimer’s disease (AD) is a neurodegenerative brain alteration that is responsible for most dementia cases in the elderly. AD etiology is still uncertain; however, chronic neuroinflammation is a constant component of brain pathology. Infections have been associated with several neurological diseases and viruses of the Herpes family appear to be a probable cause of AD neurodegenerative alterations. Several different factors may contribute to the AD clinical progression. Exogeneous viruses or other microbes and environmental pollutants may directly induce neurodegeneration by activating brain inflammation. In this paper, we suggest that exogeneous brain insults may also activate retrotransposons and silent human endogenous retroviruses (HERVs). The initial inflammation of small brain areas induced by virus infections or other brain insults may activate HERV dis-regulation that contributes to neurodegenerative mechanisms. Chronic HERV activation in turn may cause progressive neurodegeneration that thereafter merges in cognitive impairment and dementia in genetically susceptible people. Specific treatment for exogenous end endogenous pathogens and decreasing pollutant exposure may show beneficial effect in early intervention protocol to prevent the progression of cognitive deterioration in the elderly.
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4
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Buchumenski I, Holler K, Appelbaum L, Eisenberg E, Junker JP, Levanon EY. Systematic identification of A-to-I RNA editing in zebrafish development and adult organs. Nucleic Acids Res 2021; 49:4325-4337. [PMID: 33872356 PMCID: PMC8096273 DOI: 10.1093/nar/gkab247] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 03/05/2021] [Accepted: 04/15/2021] [Indexed: 11/18/2022] Open
Abstract
A-to-I RNA editing is a common post transcriptional mechanism, mediated by the Adenosine deaminase that acts on RNA (ADAR) enzymes, that increases transcript and protein diversity. The study of RNA editing is limited by the absence of editing maps for most model organisms, hindering the understanding of its impact on various physiological conditions. Here, we mapped the vertebrate developmental landscape of A-to-I RNA editing, and generated the first comprehensive atlas of editing sites in zebrafish. Tens of thousands unique editing events and 149 coding sites were identified with high-accuracy. Some of these edited sites are conserved between zebrafish and humans. Sequence analysis of RNA over seven developmental stages revealed high levels of editing activity in early stages of embryogenesis, when embryos rely on maternal mRNAs and proteins. In contrast to the other organisms studied so far, the highest levels of editing were detected in the zebrafish ovary and testes. This resource can serve as the basis for understanding of the role of editing during zebrafish development and maturity.
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Affiliation(s)
- Ilana Buchumenski
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Karoline Holler
- Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Lior Appelbaum
- The Faculty of Life Sciences and the Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Eli Eisenberg
- Raymond and Beverly Sackler School of Physics and Astronomy and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Jan Philipp Junker
- Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Erez Y Levanon
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan 5290002, Israel
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5
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Ferrari R, Grandi N, Tramontano E, Dieci G. Retrotransposons as Drivers of Mammalian Brain Evolution. Life (Basel) 2021; 11:life11050376. [PMID: 33922141 PMCID: PMC8143547 DOI: 10.3390/life11050376] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 04/20/2021] [Accepted: 04/21/2021] [Indexed: 12/11/2022] Open
Abstract
Retrotransposons, a large and diverse class of transposable elements that are still active in humans, represent a remarkable force of genomic innovation underlying mammalian evolution. Among the features distinguishing mammals from all other vertebrates, the presence of a neocortex with a peculiar neuronal organization, composition and connectivity is perhaps the one that, by affecting the cognitive abilities of mammals, contributed mostly to their evolutionary success. Among mammals, hominids and especially humans display an extraordinarily expanded cortical volume, an enrichment of the repertoire of neural cell types and more elaborate patterns of neuronal connectivity. Retrotransposon-derived sequences have recently been implicated in multiple layers of gene regulation in the brain, from transcriptional and post-transcriptional control to both local and large-scale three-dimensional chromatin organization. Accordingly, an increasing variety of neurodevelopmental and neurodegenerative conditions are being recognized to be associated with retrotransposon dysregulation. We review here a large body of recent studies lending support to the idea that retrotransposon-dependent evolutionary novelties were crucial for the emergence of mammalian, primate and human peculiarities of brain morphology and function.
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Affiliation(s)
- Roberto Ferrari
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, 43124 Parma, Italy;
| | - Nicole Grandi
- Laboratory of Molecular Virology, Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria di Monserrato, 09042 Monserrato, Italy; (N.G.); (E.T.)
| | - Enzo Tramontano
- Laboratory of Molecular Virology, Department of Life and Environmental Sciences, University of Cagliari, Cittadella Universitaria di Monserrato, 09042 Monserrato, Italy; (N.G.); (E.T.)
- Istituto di Ricerca Genetica e Biomedica, Consiglio Nazionale delle Ricerche, 09042 Monserrato, Italy
| | - Giorgio Dieci
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, 43124 Parma, Italy;
- Correspondence:
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6
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Gazquez-Gutierrez A, Witteveldt J, R Heras S, Macias S. Sensing of transposable elements by the antiviral innate immune system. RNA (NEW YORK, N.Y.) 2021; 27:rna.078721.121. [PMID: 33888553 PMCID: PMC8208052 DOI: 10.1261/rna.078721.121] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 04/17/2021] [Indexed: 05/15/2023]
Abstract
Around half of the genome in mammals is composed of transposable elements (TEs) such as DNA transposons and retrotransposons. Several mechanisms have evolved to prevent their activity and the detrimental impact of their insertional mutagenesis. Despite these potentially negative effects, TEs are essential drivers of evolution, and in certain settings, beneficial to their hosts. For instance, TEs have rewired the antiviral gene regulatory network and are required for early embryonic development. However, due to structural similarities between TE-derived and viral nucleic acids, cells can misidentify TEs as invading viruses and trigger the major antiviral innate immune pathway, the type I interferon (IFN) response. This review will focus on the different settings in which the role of TE-mediated IFN activation has been documented, including cancer and senescence. Importantly, TEs may also play a causative role in the development of complex autoimmune diseases characterised by constitutive type I IFN activation. All these observations suggest the presence of strong but opposing forces driving the coevolution of TEs and antiviral defence. A better biological understanding of the TE replicative cycle as well as of the antiviral nucleic acid sensing mechanisms will provide insights into how these two biological processes interact and will help to design better strategies to treat human diseases characterised by aberrant TE expression and/or type I IFN activation.
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Affiliation(s)
| | - Jeroen Witteveldt
- University of Edinburgh - Institute of Immunology and Infection Research
| | - Sara R Heras
- GENYO. Centre for Genomics and Oncological Research, Pfizer University of Granada
| | - Sara Macias
- Institute of Immunology and Infection Research
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Granadillo Rodríguez M, Flath B, Chelico L. The interesting relationship between APOBEC3 deoxycytidine deaminases and cancer: a long road ahead. Open Biol 2020; 10:200188. [PMID: 33292100 PMCID: PMC7776566 DOI: 10.1098/rsob.200188] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Accepted: 10/26/2020] [Indexed: 12/24/2022] Open
Abstract
Cancer is considered a group of diseases characterized by uncontrolled growth and spread of abnormal cells and is propelled by somatic mutations. Apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3 (APOBEC3) family of enzymes are endogenous sources of somatic mutations found in multiple human cancers. While these enzymes normally act as an intrinsic immune defence against viruses, they can also catalyse 'off-target' cytidine deamination in genomic single-stranded DNA intermediates. The deamination of cytosine forms uracil, which is promutagenic in DNA. Key factors to trigger the APOBEC 'off-target' activity are overexpression in a non-normal cell type, nuclear localization and replication stress. The resulting uracil-induced mutations contribute to genomic variation, which may result in neutral, beneficial or harmful consequences for the cancer. This review summarizes the functional and biochemical basis of the APOBEC3 enzyme activity and highlights their relationship with the most well-studied cancers in this particular context such as breast, lung, bladder, and human papillomavirus-associated cancers. We focus on APOBEC3A, APOBEC3B and APOBEC3H haplotype I because they are the leading candidates as sources of somatic mutations in these and other cancers. Also, we discuss the prognostic value of the APOBEC3 expression in drug resistance and response to therapies.
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Affiliation(s)
| | | | - Linda Chelico
- Department of Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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Ruggiero RP, Boissinot S. Variation in base composition underlies functional and evolutionary divergence in non-LTR retrotransposons. Mob DNA 2020; 11:14. [PMID: 32280379 PMCID: PMC7140322 DOI: 10.1186/s13100-020-00209-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 03/24/2020] [Indexed: 12/03/2022] Open
Abstract
Background Non-LTR retrotransposons often exhibit base composition that is markedly different from the nucleotide content of their host’s gene. For instance, the mammalian L1 element is AT-rich with a strong A bias on the positive strand, which results in a reduced transcription. It is plausible that the A-richness of mammalian L1 is a self-regulatory mechanism reflecting a trade-off between transposition efficiency and the deleterious effect of L1 on its host. We examined if the A-richness of L1 is a general feature of non-LTR retrotransposons or if different clades of elements have evolved different nucleotide content. We also investigated if elements belonging to the same clade evolved towards different base composition in different genomes or if elements from different clades evolved towards similar base composition in the same genome. Results We found that non-LTR retrotransposons differ in base composition among clades within the same host but also that elements belonging to the same clade differ in base composition among hosts. We showed that nucleotide content remains constant within the same host over extended period of evolutionary time, despite mutational patterns that should drive nucleotide content away from the observed base composition. Conclusions Our results suggest that base composition is evolving under selection and may be reflective of the long-term co-evolution between non-LTR retrotransposons and their host. Finally, the coexistence of elements with drastically different base composition suggests that these elements may be using different strategies to persist and multiply in the genome of their host.
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Affiliation(s)
- Robert P Ruggiero
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi, United Arab Emirates PO 129188
| | - Stéphane Boissinot
- New York University Abu Dhabi, Saadiyat Island, Abu Dhabi, United Arab Emirates PO 129188
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9
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Abstract
Endogenous retroviruses (ERVs) consist of interspersed genomic elements derived from retroviral infections that invaded our ancestral germ lines. Notably, ERVs compose 8 to 10% of the human and mouse genomes. Until recently, ERVs were considered unimportant, so-called “junk” DNA. However, this naïve characterization has changed dramatically as distinct ERV-related functions are revealed in heath and disease. In this study, we demonstrate that chronic ERV activation is associated with cognitive impairment, measured with hippocampus-related tasks, in a mouse model. We confirm these findings in an independent mouse model of acute retroviral activation and show that cognitive deficits are mitigated in the absence of the retroviral RNA sensor protein MAVS. Our results point to an underappreciated therapeutic modality for impaired cognition. Retrotransposons compose a staggering 40% of the mammalian genome. Among them, endogenous retroviruses (ERV) represent sequences that closely resemble the proviruses created from exogenous retroviral infection. ERVs make up 8 to 10% of human and mouse genomes and range from evolutionarily ancient sequences to recent acquisitions. Studies in Drosophila have provided a causal link between genomic retroviral elements and cognitive decline; however, in mammals, the role of ERVs in learning and memory remains unclear. Here we studied 2 independent murine models for ERV activation: muMT strain (lacking B cells and antibody production) and intracerebroventricular injection of streptozotocin (ICVI-STZ). We conducted behavioral assessments (contextual fear memory and spatial learning), as well as gene and protein analysis (RNA sequencing, PCR, immunohistochemistry, and western blot assays). Mice lacking mitochondrial antiviral-signaling protein (MAVS) and mice lacking stimulator of IFN genes protein (STING), 2 downstream sensors of ERV activation, provided confirmation of ERV impact. We found that muMT mice and ICVI-STZ mice induced hippocampal ERV activation, as shown by increased gene and protein expression of the Gag sequence of the transposable element intracisternal A-particle. ERV activation was accompanied by significant hippocampus-related memory impairment in both models. Notably, the deficiency of the MAVS pathway was protective against ICVI-STZ–induced cognitive pathology. Overall, our results demonstrate that ERV activation is associated with cognitive impairment in mice. Moreover, they provide a molecular target for strategies aimed at attenuating retroviral element sensing, via MAVS, to treat dementia and neuropsychiatric disorders.
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10
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Bitar M, Barry G. Multiple Innovations in Genetic and Epigenetic Mechanisms Cooperate to Underpin Human Brain Evolution. Mol Biol Evol 2019; 35:263-268. [PMID: 29177456 DOI: 10.1093/molbev/msx303] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Our knowledge of how the human brain differs from those of other species in terms of evolutionary adaptations and functionality is limited. Comparative genomics reveal valuable insight, especially the expansion of human-specific noncoding regulatory and repeat-containing regions. Recent studies add to our knowledge of evolving brain function by investigating cellular mechanisms such as protein emergence, extensive sequence editing, retrotransposon activity, dynamic epigenetic modifications, and multiple noncoding RNA functions. These findings present an opportunity to combine newly discovered genetic and epigenetic mechanisms with more established concepts into a more comprehensive picture to better understand the uniquely evolved human brain.
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Affiliation(s)
- Mainá Bitar
- QIMR Berghofer Medical Research Institute, Herston, QLD, Australia
| | - Guy Barry
- QIMR Berghofer Medical Research Institute, Herston, QLD, Australia
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11
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Ricci M, Peona V, Guichard E, Taccioli C, Boattini A. Transposable Elements Activity is Positively Related to Rate of Speciation in Mammals. J Mol Evol 2018; 86:303-310. [PMID: 29855654 PMCID: PMC6028844 DOI: 10.1007/s00239-018-9847-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Accepted: 05/24/2018] [Indexed: 02/05/2023]
Abstract
Transposable elements (TEs) play an essential role in shaping eukaryotic genomes and generating variability. Speciation and TE activity bursts could be strongly related in mammals, in which simple gradualistic models of differentiation do not account for the currently observed species variability. In order to test this hypothesis, we designed two parameters: the Density of insertion (DI) and the Relative rate of speciation (RRS). DI is the ratio between the number of TE insertions in a genome and its size, whereas the RRS is a conditional parameter designed to identify potential speciation bursts. Thus, by analyzing TE insertions in mammals, we defined the genomes as “hot” (high DI) and “cold” (low DI). Then, comparing TE activity among 29 taxonomical families of the whole Mammalia class, 16 intra-order pairs of mammalian species, and four superorders of Eutheria, we showed that taxa with high rates of speciation are associated with “hot” genomes, whereas taxa with low ones are associated with “cold” genomes. These results suggest a remarkable correlation between TE activity and speciation, also being consistent with patterns describing variable rates of differentiation and accounting for the different time frames of the speciation bursts.
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Affiliation(s)
- Marco Ricci
- Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
| | - Valentina Peona
- Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy
- Department of Ecology and Genetics, University of Uppsala, Uppsala, Sweden
| | - Etienne Guichard
- Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy.
| | - Cristian Taccioli
- Department of Animal Medicine, Health and Production, University of Padova, Padova, Italy
| | - Alessio Boattini
- Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy
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12
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Shevchenko G, Morris KV. All I's on the RADAR: role of ADAR in gene regulation. FEBS Lett 2018; 592:2860-2873. [PMID: 29770436 DOI: 10.1002/1873-3468.13093] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 04/26/2018] [Accepted: 05/05/2018] [Indexed: 12/12/2022]
Abstract
Adenosine to inosine (A-to-I) editing is the most abundant form of RNA modification in mammalian cells, which is catalyzed by adenosine deaminase acting on the double-stranded RNA (ADAR) protein family. A-to-I editing is currently known to be involved in the regulation of the immune system, RNA splicing, protein recoding, microRNA biogenesis, and formation of heterochromatin. Editing occurs within regions of double-stranded RNA, particularly within inverted Alu repeats, and is associated with many diseases including cancer, neurological disorders, and metabolic syndromes. However, the significance of RNA editing in a large portion of the transcriptome remains unknown. Here, we review the current knowledge about the prevalence and function of A-to-I editing by the ADAR protein family, focusing on its role in the regulation of gene expression. Furthermore, RNA editing-independent regulation of cellular processes by ADAR and the putative role(s) of this process in gene regulation will be discussed.
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Affiliation(s)
- Galina Shevchenko
- Hematological Malignancy and Stem Cell Transplantation Institute, Center for Gene Therapy, City of Hope-Beckman Research Institute, Duarte, CA, USA
| | - Kevin V Morris
- Hematological Malignancy and Stem Cell Transplantation Institute, Center for Gene Therapy, City of Hope-Beckman Research Institute, Duarte, CA, USA
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13
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Feng Y, Goubran MH, Follack TB, Chelico L. Deamination-independent restriction of LINE-1 retrotransposition by APOBEC3H. Sci Rep 2017; 7:10881. [PMID: 28883657 PMCID: PMC5589869 DOI: 10.1038/s41598-017-11344-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 08/18/2017] [Indexed: 12/16/2022] Open
Abstract
The APOBEC3 family of cytosine deaminase enzymes are able to restrict replication of retroelements, such as LINE-1. However, each of the seven APOBEC3 enzymes have been reported to act differentially to prevent LINE-1 retrotransposition and the mechanisms of APOBEC3-mediated LINE-1 inhibition has not been well understood. The prevailing view for many years was that APOBEC3-mediated LINE-1 inhibition was deamination-independent and relied on APOBEC3s blocking the LINE-1 reverse transcriptase DNA polymerization or transport of the LINE-1 RNA into the nucleus. However, recently it was shown that APOBEC3A can deaminate cytosine, to form uracil, on transiently exposed single-stranded LINE-1 cDNA and this leads to LINE-1 cDNA degradation. In this study, we confirmed that APOBEC3A is a potent deamination-dependent inhibitor of LINE-1 retrotransposition, but show that in contrast, A3H haplotype II and haplotype V restrict LINE-1 activity using a deamination-independent mechanism. Our study supports the model that different APOBEC3 proteins have evolved to inhibit LINE-1 retrotransposition through distinct mechanisms.
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Affiliation(s)
- Yuqing Feng
- Department of Microbiology & Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E5, Canada
| | - Mariam H Goubran
- Department of Microbiology & Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E5, Canada
| | - Tyson B Follack
- Department of Microbiology & Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E5, Canada
| | - Linda Chelico
- Department of Microbiology & Immunology, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E5, Canada.
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Abstract
Autoimmune diseases are classified into about 80 different types based on their specificity related to system, organ and/or tissue. About 5% of the western population is affected by this anomaly, but its worldwide incidence is unknown. Autoimmune diseases are heterogeneous in nature and clinical manifestations range from benign disorders to life-threatening conditions. Autoimmunity strikes at any stage of life, but age and/or gender also play role in onset of some of these anomalies. The autoimmune pathogenesis is initiated by the origination of autoantigens, which leads to the development of autoantibodies followed by auto-immunogenicity and the ultimate onset of autoimmunity. There is a lack of suitable therapies to treat autoimmune diseases, because mechanisms involved in the onset of these anomalies were poorly understood. Present therapies are limited to symptomatic treatment and come with severe side effects. Here, I described the molecular mechanisms and cellular events involved in the initiation of autoimmunity and proposed better strategies to modulate such molecular and cellular anomalies, which will help in preventing and/or controlling autoimmune pathogenesis and ultimately aid in enhancing the quality of life.
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Affiliation(s)
- Dama Laxminarayana
- Editor in Chief, Clinical Medicine Insights: Pathology; Sathya Krishna Genomics LLC, Winston-Salem, NC, USA
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15
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Chen J, MacCarthy T. The preferred nucleotide contexts of the AID/APOBEC cytidine deaminases have differential effects when mutating retrotransposon and virus sequences compared to host genes. PLoS Comput Biol 2017; 13:e1005471. [PMID: 28362825 PMCID: PMC5391955 DOI: 10.1371/journal.pcbi.1005471] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 04/14/2017] [Accepted: 03/21/2017] [Indexed: 12/22/2022] Open
Abstract
The AID / APOBEC genes are a family of cytidine deaminases that have evolved in vertebrates, and particularly mammals, to mutate RNA and DNA at distinct preferred nucleotide contexts (or “hotspots”) on foreign genomes such as viruses and retrotransposons. These enzymes play a pivotal role in intrinsic immunity defense mechanisms, often deleteriously mutating invading retroviruses or retrotransposons and, in the case of AID, changing antibody sequences to drive affinity maturation. We investigate the strength of various hotspots on their known biological targets by evaluating the potential impact of mutations on the DNA coding sequences of these targets, and compare these results to hypothetical hotspots that did not evolve. We find that the existing AID / APOBEC hotspots have a large impact on retrotransposons and non-mammalian viruses while having a much smaller effect on vital mammalian genes, suggesting co-evolution with AID / APOBECs may have had an impact on the genomes of the viruses we analyzed. We determine that GC content appears to be a significant, but not sole, factor in resistance to deaminase activity. We discuss possible mechanisms AID and APOBEC viral targets have adopted to escape the impacts of deamination activity, including changing the GC content of the genome. The APOBEC family of cytidine deaminases are important enzymes in most vertebrates. The ancestral member of this gene family is activation induced deaminase (AID), which mutates the Immunoglobulin loci in B Cells during antibody affinity maturation in jawed vertebrates. The APOBEC family has expanded particularly in the mammals and in primates, where they have evolved roles in restriction of viruses and retrotransposons. Biochemical studies have established that AID preferentially targets “hotspots” such as AGC and avoids “coldspots” such as CCC. Other APOBECs have evolved distinct hotspots. For example, APOBEC3G, which targets retroviruses including HIV, has evolved to target the motif CCC as a hotspot, but it is unclear why. Here we ask why the AID/APOBEC cytidine deaminases evolved their particular mutational hotspots. Our results show that a wide range of unrelated genes including mammalian LINE1 ORFs and non- mammalian (ancestral-like) viruses are highly susceptible to mutations in APOBEC hotspots and less susceptible to the hypothetical non-APOBEC hotspots. On the other hand, mammalian viruses tend to exhibit low susceptibility to the same APOBEC hotspots, suggesting these viruses have co-evolved to minimize potential damaging mutations, and that the native GC content plays a large role in this behavior.
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Affiliation(s)
- Jeffrey Chen
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Book, New York, United States of America
| | - Thomas MacCarthy
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Book, New York, United States of America
- * E-mail:
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16
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Abstract
It has been long understood that mutation distribution is not completely random across genomic space and in time. Indeed, recent surprising discoveries identified multiple simultaneous mutations occurring in tiny regions within chromosomes while the rest of the genome remains relatively mutation-free. Mechanistic elucidation of these phenomena, called mutation showers, mutation clusters, or kataegis, in parallel with findings of abundant clustered mutagenesis in cancer genomes, is ongoing. So far, the combination of factors most important for clustered mutagenesis is the induction of DNA lesions within unusually long and persistent single-strand DNA intermediates. In addition to being a fascinating phenomenon, clustered mutagenesis also became an indispensable tool for identifying a previously unrecognized major source of mutation in cancer, APOBEC cytidine deaminases. Future research on clustered mutagenesis may shed light onto important mechanistic details of genome maintenance, with potentially profound implications for human health.
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Affiliation(s)
- Kin Chan
- Mechanisms of Genome Dynamics Group, National Institute of Environmental Health Sciences, Department of Health and Human Services, National Institutes of Health, Durham, North Carolina 27709; ,
| | - Dmitry A Gordenin
- Mechanisms of Genome Dynamics Group, National Institute of Environmental Health Sciences, Department of Health and Human Services, National Institutes of Health, Durham, North Carolina 27709; ,
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17
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Abstract
Retrotransposons have generated about 40 % of the human genome. This review examines the strategies the cell has evolved to coexist with these genomic "parasites", focussing on the non-long terminal repeat retrotransposons of humans and mice. Some of the restriction factors for retrotransposition, including the APOBECs, MOV10, RNASEL, SAMHD1, TREX1, and ZAP, also limit replication of retroviruses, including HIV, and are part of the intrinsic immune system of the cell. Many of these proteins act in the cytoplasm to degrade retroelement RNA or inhibit its translation. Some factors act in the nucleus and involve DNA repair enzymes or epigenetic processes of DNA methylation and histone modification. RISC and piRNA pathway proteins protect the germline. Retrotransposon control is relaxed in some cell types, such as neurons in the brain, stem cells, and in certain types of disease and cancer, with implications for human health and disease. This review also considers potential pitfalls in interpreting retrotransposon-related data, as well as issues to consider for future research.
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Affiliation(s)
- John L. Goodier
- McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD USA 212051
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18
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Transcriptome, genetic editing, and microRNA divergence substantiate sympatric speciation of blind mole rat, Spalax. Proc Natl Acad Sci U S A 2016; 113:7584-9. [PMID: 27339131 DOI: 10.1073/pnas.1607497113] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Incipient sympatric speciation in blind mole rat, Spalax galili, in Israel, caused by sharp ecological divergence of abutting chalk-basalt ecologies, has been proposed previously based on mitochondrial and whole-genome nuclear DNA. Here, we present new evidence, including transcriptome, DNA editing, microRNA, and codon usage, substantiating earlier evidence for adaptive divergence in the abutting chalk and basalt populations. Genetic divergence, based on the previous and new evidence, is ongoing despite restricted gene flow between the two populations. The principal component analysis, neighbor-joining tree, and genetic structure analysis of the transcriptome clearly show the clustered divergent two mole rat populations. Gene-expression level analysis indicates that the population transcriptome divergence is displayed not only by soil divergence but also by sex. Gene ontology enrichment of the differentially expressed genes from the two abutting soil populations highlights reproductive isolation. Alternative splicing variation of the two abutting soil populations displays two distinct splicing patterns. L-shaped FST distribution indicates that the two populations have undergone divergence with gene flow. Transcriptome divergent genes highlight neurogenetics and nutrition characterizing the chalk population, and energetics, metabolism, musculature, and sensory perception characterizing the abutting basalt population. Remarkably, microRNAs also display divergence between the two populations. The GC content is significantly higher in chalk than in basalt, and stress-response genes mostly prefer nonoptimal codons. The multiple lines of evidence of ecological-genomic and genetic divergence highlight that natural selection overrules the gene flow between the two abutting populations, substantiating the sharp ecological chalk-basalt divergence driving sympatric speciation.
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Abstract
All true metazoans modify their RNAs by converting specific adenosine residues to inosine. Because inosine binds to cytosine, it is a biological mimic for guanosine. This subtle change, termed RNA editing, can have diverse effects on various RNA-mediated cellular pathways, including RNA interference, innate immunity, retrotransposon defense and messenger RNA recoding. Because RNA editing can be regulated, it is an ideal tool for increasing genetic diversity, adaptation and environmental acclimation. This review will cover the following themes related to RNA editing: (1) how it is used to modify different cellular RNAs, (2) how frequently it is used by different organisms to recode mRNA, (3) how specific recoding events regulate protein function, (4) how it is used in adaptation and (5) emerging evidence that it can be used for acclimation. Organismal biologists with an interest in adaptation and acclimation, but with little knowledge of RNA editing, are the intended audience.
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Affiliation(s)
- Joshua J C Rosenthal
- Universidad de Puerto Rico, Recinto de Ciencias Medicas, Instituto de Neurobiologia, 201 Blvd. del Valle, San Juan, PR 00901, USA
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20
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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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21
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Pinto Y, Gabay O, Arbiza L, Sams AJ, Keinan A, Levanon EY. Clustered mutations in hominid genome evolution are consistent with APOBEC3G enzymatic activity. Genome Res 2016; 26:579-87. [PMID: 27056836 PMCID: PMC4864454 DOI: 10.1101/gr.199240.115] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 03/16/2016] [Indexed: 11/29/2022]
Abstract
The gradual accumulation of mutations by any of a number of mutational processes is a major driving force of divergence and evolution. Here, we investigate a potentially novel mutational process that is based on the activity of members of the AID/APOBEC family of deaminases. This gene family has been recently shown to introduce—in multiple types of cancer—enzyme-induced clusters of co-occurring somatic mutations caused by cytosine deamination. Going beyond somatic mutations, we hypothesized that APOBEC3—following its rapid expansion in primates—can introduce unique germline mutation clusters that can play a role in primate evolution. In this study, we tested this hypothesis by performing a comprehensive comparative genomic screen for APOBEC3-induced mutagenesis patterns across different hominids. We detected thousands of mutation clusters introduced along primate evolution which exhibit features that strongly fit the known patterns of APOBEC3G mutagenesis. These results suggest that APOBEC3G-induced mutations have contributed to the evolution of all genomes we studied. This is the first indication of site-directed, enzyme-induced genome evolution, which played a role in the evolution of both modern and archaic humans. This novel mutational mechanism exhibits several unique features, such as its higher tendency to mutate transcribed regions and regulatory elements and its ability to generate clusters of concurrent point mutations that all occur in a single generation. Our discovery demonstrates the exaptation of an anti-viral mechanism as a new source of genomic variation in hominids with a strong potential for functional consequences.
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Affiliation(s)
- Yishay Pinto
- Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Orshay Gabay
- Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - Leonardo Arbiza
- Department of Biological Statistics and Computational Biology, Cornell University, Ithaca, New York 14853, USA
| | - Aaron J Sams
- Department of Biological Statistics and Computational Biology, Cornell University, Ithaca, New York 14853, USA
| | - Alon Keinan
- Department of Biological Statistics and Computational Biology, Cornell University, Ithaca, New York 14853, USA
| | - Erez Y Levanon
- Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan 5290002, Israel
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22
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Knisbacher BA, Gerber D, Levanon EY. DNA Editing by APOBECs: A Genomic Preserver and Transformer. Trends Genet 2016; 32:16-28. [PMID: 26608778 DOI: 10.1016/j.tig.2015.10.005] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Revised: 10/18/2015] [Accepted: 10/22/2015] [Indexed: 10/22/2022]
Abstract
Information warfare is not limited to the cyber world because it is waged within our cells as well. The unique AID (activation-induced cytidine deaminase)/APOBEC (apolipoprotein B mRNA editing enzyme, catalytic polypeptide) family comprises proteins that alter DNA sequences by converting deoxycytidines to deoxyuridines through deamination. This C-to-U DNA editing enables them to inhibit parasitic viruses and retrotransposons by disrupting their genomic content. In addition to attacking genomic invaders, APOBECs can target their host genome, which can be beneficial by initiating processes that create antibody diversity needed for the immune system or by accelerating the rate of evolution. AID can also alter gene regulation by removing epigenetic modifications from genomic DNA. However, when uncontrolled, these powerful agents of change can threaten genome stability and eventually lead to cancer.
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Affiliation(s)
- Binyamin A Knisbacher
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 52900 Israel
| | - Doron Gerber
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 52900 Israel
| | - Erez Y Levanon
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 52900 Israel.
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23
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Knisbacher BA, Levanon EY. DNA Editing of LTR Retrotransposons Reveals the Impact of APOBECs on Vertebrate Genomes. Mol Biol Evol 2015; 33:554-67. [PMID: 26541172 PMCID: PMC4866542 DOI: 10.1093/molbev/msv239] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Long terminal repeat retrotransposons (LTR) are widespread in vertebrates and their dynamism facilitates genome evolution. However, these endogenous retroviruses (ERVs) must be restricted to maintain genomic stability. The APOBECs, a protein family that can edit C-to-U in DNA, do so by interfering with reverse transcription and hypermutating retrotransposon DNA. In some cases, a retrotransposon may integrate into the genome despite being hypermutated. Such an event introduces a unique sequence into the genome, increasing retrotransposon diversity and the probability of developing new function at the locus of insertion. The prevalence of this phenomenon and its effects on vertebrate genomes are still unclear. In this study, we screened ERV sequences in the genomes of 123 diverse species and identified hundreds of thousands of edited sites in multiple vertebrate lineages, including placental mammals, marsupials, and birds. Numerous edited ERVs carry high mutation loads, some with greater than 350 edited sites, profoundly damaging their open-reading frames. For many of the species studied, this is the first evidence that APOBECs are active players in their innate immune system. Unexpectedly, some birds and especially zebra finch and medium ground-finch (one of Darwin’s finches) are exceptionally enriched in DNA editing. We demonstrate that edited retrotransposons may be preferentially retained in active genomic regions, as reflected from their enrichment in genes, exons, promoters, and transcription start sites, thereby raising the probability of their exaptation for novel function. In conclusion, DNA editing of retrotransposons by APOBECs has a substantial role in vertebrate innate immunity and may boost genome evolution.
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Affiliation(s)
- Binyamin A Knisbacher
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 52900, Israel
| | - Erez Y Levanon
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat Gan, 52900, Israel
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24
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Knisbacher BA, Levanon EY. DNA and RNA editing of retrotransposons accelerate mammalian genome evolution. Ann N Y Acad Sci 2015; 1341:115-25. [PMID: 25722083 DOI: 10.1111/nyas.12713] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Genome evolution is commonly viewed as a gradual process that is driven by random mutations that accumulate over time. However, DNA- and RNA-editing enzymes have been identified that can accelerate evolution by actively modifying the genomically encoded information. The apolipoprotein B mRNA editing enzymes, catalytic polypeptide-like (APOBECs) are potent restriction factors that can inhibit retroelements by cytosine-to-uridine editing of retroelement DNA after reverse transcription. In some cases, a retroelement may successfully integrate into the genome despite being hypermutated. Such events introduce unique sequences into the genome and are thus a source of genomic innovation. adenosine deaminases that act on RNA (ADARs) catalyze adenosine-to-inosine editing in double-stranded RNA, commonly formed by oppositely oriented retroelements. The RNA editing confers plasticity to the transcriptome by generating many transcript variants from a single genomic locus. If the editing produces a beneficial variant, the genome may maintain the locus that produces the RNA-edited transcript for its novel function. Here, we discuss how these two powerful editing mechanisms, which both target inserted retroelements, facilitate expedited genome evolution.
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Affiliation(s)
- Binyamin A Knisbacher
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
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25
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Retroviral transcriptional regulation and embryonic stem cells: war and peace. Mol Cell Biol 2014; 35:770-7. [PMID: 25547290 DOI: 10.1128/mcb.01293-14] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Retroviruses have evolved complex transcriptional enhancers and promoters that allow their replication in a wide range of tissue and cell types. Embryonic stem (ES) cells, however, characteristically suppress transcription of proviruses formed after infection by exogenous retroviruses and also of most members of the vast array of endogenous retroviruses in the genome. These cells have unusual profiles of transcribed genes and are poised to make rapid changes in those profiles upon induction of differentiation. Many of the transcription factors in ES cells control both host and retroviral genes coordinately, such that retroviral expression patterns can serve as markers of ES cell pluripotency. This overlap is not coincidental; retrovirus-derived regulatory sequences are often used to control cellular genes important for pluripotency. These sequences specify the temporal control and perhaps "noisy" control of cellular genes that direct proper cell gene expression in primitive cells and their differentiating progeny. The evidence suggests that the viral elements have been domesticated for host needs, reflecting the wide-ranging exploitation of any and all available DNA sequences in assembling regulatory networks.
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26
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A genome-wide map of hyper-edited RNA reveals numerous new sites. Nat Commun 2014; 5:4726. [PMID: 25158696 PMCID: PMC4365171 DOI: 10.1038/ncomms5726] [Citation(s) in RCA: 165] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 07/16/2014] [Indexed: 01/14/2023] Open
Abstract
Adenosine-to-inosine editing is one of the most frequent post-transcriptional modifications, manifested as A-to-G mismatches when comparing RNA sequences with their source DNA. Recently, a number of RNA-seq data sets have been screened for the presence of A-to-G editing, and hundreds of thousands of editing sites identified. Here we show that existing screens missed the majority of sites by ignoring reads with excessive (‘hyper’) editing that do not easily align to the genome. We show that careful alignment and examination of the unmapped reads in RNA-seq studies reveal numerous new sites, usually many more than originally discovered, and in precisely those regions that are most heavily edited. Specifically, we discover 327,096 new editing sites in the heavily studied Illumina Human BodyMap data and more than double the number of detected sites in several published screens. We also identify thousands of new sites in mouse, rat, opossum and fly. Our results establish that hyper-editing events account for the majority of editing sites. Common methods to detect adenosine-to-inosine RNA editing sites rely on mapping short RNA reads to the genome while allowing only a limited number of mismatches. Here, Porath et al. present a novel RNA-seq based approach to identify hyper-edited reads that significantly expands the RNA editome.
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27
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Antiretroviral restriction factors in mice. Virus Res 2014; 193:130-4. [PMID: 25018022 DOI: 10.1016/j.virusres.2014.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 06/30/2014] [Accepted: 07/01/2014] [Indexed: 12/31/2022]
Abstract
One of the most exciting areas in contemporary retrovirus research is the discovery of "restriction factors". These are cellular proteins that act after virus entry to inhibit infection by or replication of retroviruses (and other viruses and intracellular pathogens). We briefly discuss here three antiretroviral restriction factors in mice: Fv1, APOBEC3, and tetherin, touching on both biological and molecular aspects of these restriction systems.
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28
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Genome-wide adaptive complexes to underground stresses in blind mole rats Spalax. Nat Commun 2014; 5:3966. [DOI: 10.1038/ncomms4966] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 04/28/2014] [Indexed: 12/20/2022] Open
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Laxminarayana D. Molecular insights into systemic lupus erythematosus pathogenesis. Clin Med Insights Pathol 2014; 7:7-9. [PMID: 24678246 PMCID: PMC3964202 DOI: 10.4137/cpath.s14814] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Affiliation(s)
- Dama Laxminarayana
- Editor in Chief, Clinical Medicine Insights: Pathology, Formerly with Section on Rheumatology and Immunology, Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, USA
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30
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Lindič N, Budič M, Petan T, Knisbacher BA, Levanon EY, Lovšin N. Differential inhibition of LINE1 and LINE2 retrotransposition by vertebrate AID/APOBEC proteins. Retrovirology 2013; 10:156. [PMID: 24344916 PMCID: PMC3880073 DOI: 10.1186/1742-4690-10-156] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2013] [Accepted: 12/02/2013] [Indexed: 01/06/2023] Open
Abstract
Background The role of AID/APOBEC proteins in the mammalian immune response against retroviruses and retrotransposons is well established. G to A hypermutations, the hallmark of their cytidine deaminase activity, are present in several mammalian retrotransposons. However, the role of AID/APOBEC proteins in non-mammalian retroelement restriction is not completely understood. Results Here we provide the first evidence of anti-retroelement activity of a reptilian APOBEC protein. The green anole lizard A1 protein displayed potent DNA mutator activity and inhibited ex vivo retrotransposition of LINE1 and LINE2 ORF1 protein encoding elements, displaying a mechanism of action similar to that of the human A1 protein. In contrast, the human A3 proteins did not require ORF1 protein to inhibit LINE retrotransposition, suggesting a differential mechanism of anti-LINE action of A1 proteins, which emerged in amniotes, and A3 proteins, exclusive to placental mammals. In accordance, genomic analyses demonstrate differential G to A DNA editing of LINE retrotransposons in the lizard genome, which is also the first evidence for G to A DNA editing in non-mammalian genomes. Conclusion Our data suggest that vertebrate APOBEC proteins differentially inhibit the retrotransposition of LINE elements and that the anti-retroelement activity of APOBEC proteins predates mammals.
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Affiliation(s)
| | | | | | | | | | - Nika Lovšin
- Department of Chemistry and Biochemistry, Chair of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000, Ljubljana, Slovenia.
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31
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Dewannieux M, Heidmann T. Endogenous retroviruses: acquisition, amplification and taming of genome invaders. Curr Opin Virol 2013; 3:646-56. [DOI: 10.1016/j.coviro.2013.08.005] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 08/13/2013] [Accepted: 08/14/2013] [Indexed: 12/12/2022]
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32
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Horn AV, Klawitter S, Held U, Berger A, Vasudevan AAJ, Bock A, Hofmann H, Hanschmann KMO, Trösemeier JH, Flory E, Jabulowsky RA, Han JS, Löwer J, Löwer R, Münk C, Schumann GG. Human LINE-1 restriction by APOBEC3C is deaminase independent and mediated by an ORF1p interaction that affects LINE reverse transcriptase activity. Nucleic Acids Res 2013; 42:396-416. [PMID: 24101588 PMCID: PMC3874205 DOI: 10.1093/nar/gkt898] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
LINE-1 (L1) retrotransposons are mobile genetic elements whose extensive proliferation resulted in the generation of ≈ 34% of the human genome. They have been shown to be a cause of single-gene diseases. Moreover, L1-encoded endonuclease can elicit double-strand breaks that may lead to genomic instability. Mammalian cells adopted strategies restricting mobility and deleterious consequences of uncontrolled retrotransposition. The human APOBEC3 protein family of polynucleotide cytidine deaminases contributes to intracellular defense against retroelements. APOBEC3 members inhibit L1 retrotransposition by 35-99%. However, genomic L1 retrotransposition events that occurred in the presence of L1-restricting APOBEC3 proteins are devoid of detectable G-to-A hypermutations, suggesting one or multiple deaminase-independent L1 restricting mechanisms. We set out to uncover the mechanism of APOBEC3C (A3C)-mediated L1 inhibition and found that it is deaminase independent, requires an intact dimerization site and the RNA-binding pocket mutation R122A abolishes L1 restriction by A3C. Density gradient centrifugation of L1 ribonucleoprotein particles, subcellular co-localization of L1-ORF1p and A3C and co-immunoprecipitation experiments indicate that an RNA-dependent physical interaction between L1 ORF1p and A3C dimers is essential for L1 restriction. Furthermore, we demonstrate that the amount of L1 complementary DNA synthesized by L1 reverse transcriptase is reduced by ≈ 50% if overexpressed A3C is present.
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Affiliation(s)
- Axel V Horn
- Section PR2/Retroelements, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, 63225 Langen, Germany, Department of Embryology, Carnegie Institution of Washington, 3520 San Martin Drive, Baltimore, MD 21218, USA, Division of Medical Biotechnology, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, 63225 Langen, Germany, Clinic for Gastroenterology, Hepatology and Infectiology, Medical Faculty, Heinrich-Heine-University, 40225 Düsseldorf, Germany and Biostatistics Section, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, 63225 Langen, Germany
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Arkhipova IR, Rodriguez F. Genetic and epigenetic changes involving (retro)transposons in animal hybrids and polyploids. Cytogenet Genome Res 2013; 140:295-311. [PMID: 23899811 DOI: 10.1159/000352069] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Transposable elements (TEs) are discrete genetic units that have the ability to change their location within chromosomal DNA, and constitute a major and rapidly evolving component of eukaryotic genomes. They can be subdivided into 2 distinct types: retrotransposons, which use an RNA intermediate for transposition, and DNA transposons, which move only as DNA. Rapid advances in genome sequencing significantly improved our understanding of TE roles in genome shaping and restructuring, and studies of transcriptomes and epigenomes shed light on the previously unknown molecular mechanisms underlying genetic and epigenetic TE controls. Knowledge of these control systems may be important for better understanding of reticulate evolution and speciation in the context of bringing different genomes together by hybridization and perturbing the established regulatory balance by ploidy changes. See also sister article focusing on plants by Bento et al. in this themed issue.
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Affiliation(s)
- I R Arkhipova
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA 02543, USA. iarkhipova @ mbl.edu
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34
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Anwar F, Davenport MP, Ebrahimi D. Footprint of APOBEC3 on the genome of human retroelements. J Virol 2013; 87:8195-204. [PMID: 23698293 PMCID: PMC3700199 DOI: 10.1128/jvi.00298-13] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 05/10/2013] [Indexed: 01/01/2023] Open
Abstract
Almost half of the human genome is composed of transposable elements. The genomic structures and life cycles of some of these elements suggest they are a result of waves of retroviral infection and transposition over millions of years. The reduction of retrotransposition activity in primates compared to that in nonprimates, such as mice, has been attributed to the positive selection of several antiretroviral factors, such as apolipoprotein B mRNA editing enzymes. Among these, APOBEC3G is known to mutate G to A within the context of GG in the genome of endogenous as well as several exogenous retroelements (the underlining marks the G that is mutated). On the other hand, APOBEC3F and to a lesser extent other APOBEC3 members induce G-to-A changes within the nucleotide GA. It is known that these enzymes can induce deleterious mutations in the genome of retroviral sequences, but the evolution and/or inactivation of retroelements as a result of mutation by these proteins is not clear. Here, we analyze the mutation signatures of these proteins on large populations of long interspersed nuclear element (LINE), short interspersed nuclear element (SINE), and endogenous retrovirus (ERV) families in the human genome to infer possible evolutionary pressure and/or hypermutation events. Sequence context dependency of mutation by APOBEC3 allows investigation of the changes in the genome of retroelements by inspecting the depletion of G and enrichment of A within the APOBEC3 target and product motifs, respectively. Analysis of approximately 22,000 LINE-1 (L1), 24,000 SINE Alu, and 3,000 ERV sequences showed a footprint of GG→AG mutation by APOBEC3G and GA→AA mutation by other members of the APOBEC3 family (e.g., APOBEC3F) on the genome of ERV-K and ERV-1 elements but not on those of ERV-L, LINE, or SINE.
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Affiliation(s)
- Firoz Anwar
- Centre for Vascular Research, The University of New South Wales, Kensington, NSW, Australia
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Refsland EW, Harris RS. The APOBEC3 family of retroelement restriction factors. Curr Top Microbiol Immunol 2013; 371:1-27. [PMID: 23686230 DOI: 10.1007/978-3-642-37765-5_1] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The ability to regulate and even target mutagenesis is an extremely valuable cellular asset. Enzyme-catalyzed DNA cytosine deamination is a molecular strategy employed by vertebrates to promote antibody diversity and defend against foreign nucleic acids. Ten years ago, a family of cellular enzymes was first described with several proving capable of deaminating DNA and inhibiting HIV-1 replication. Ensuing studies on the apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3 (APOBEC3) restriction factors have uncovered a broad-spectrum innate defense network that suppresses the replication of numerous endogenous and exogenous DNA-based parasites. Although many viruses possess equally elaborate counter-defense mechanisms, the APOBEC3 enzymes offer a tantalizing possibility of leveraging innate immunity to fend off viral infection. Here, we focus on mechanisms of retroelement restriction by the APOBEC3 family of restriction enzymes, and we consider the therapeutic benefits, as well as the possible pathological consequences, of arming cells with active DNA deaminases.
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Affiliation(s)
- Eric W Refsland
- Department of Biochemistry, University of Minnesota, Minneapolis, MN 55455, USA
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Barry G, Mattick JS. The role of regulatory RNA in cognitive evolution. Trends Cogn Sci 2012; 16:497-503. [PMID: 22940578 DOI: 10.1016/j.tics.2012.08.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 08/12/2012] [Accepted: 08/13/2012] [Indexed: 12/18/2022]
Abstract
The evolution of the human brain has resulted in the emergence of higher-order cognitive abilities, such as reasoning, planning and social awareness. Although there has been a concomitant increase in brain size and complexity, and component diversification, we argue that RNA regulation of epigenetic processes, RNA editing, and the controlled mobilization of transposable elements have provided the major substrates for cognitive advance. We also suggest that these expanded capacities and flexibilities have led to the collateral emergence of psychiatric fragilities and conditions.
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Affiliation(s)
- Guy Barry
- Institute for Molecular Bioscience, The University of Queensland, Brisbane Queensland, 4072, Australia.
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