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Mustelin T, Ukadike KC. How Retroviruses and Retrotransposons in Our Genome May Contribute to Autoimmunity in Rheumatological Conditions. Front Immunol 2020; 11:593891. [PMID: 33281822 PMCID: PMC7691656 DOI: 10.3389/fimmu.2020.593891] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 10/19/2020] [Indexed: 12/14/2022] Open
Abstract
More than 200 human disorders include various manifestations of autoimmunity. The molecular events that lead to these diseases are still incompletely understood and their causes remain largely unknown. Numerous potential triggers of autoimmunity have been proposed over the years, but very few of them have been conclusively confirmed or firmly refuted. Viruses have topped the lists of suspects for decades, and it seems that many viruses, including those of the Herpesviridae family, indeed can influence disease initiation and/or promote exacerbations by a number of mechanisms that include prolonged anti-viral immunity, immune subverting factors, and mechanisms, and perhaps “molecular mimicry”. However, no specific virus has yet been established as being truly causative. Here, we discuss a different, but perhaps mechanistically related possibility, namely that retrotransposons or retroviruses that infected us in the past and left a lasting copy of themselves in our genome still can provoke an escalating immune response that leads to autoimmune disease. Many of these loci still encode for retroviral proteins that have retained some, or all, of their original functions. Importantly, these endogenous proviruses cannot be eliminated by the immune system the way it can eliminate exogenous viruses. Hence, if not properly controlled, they may drive a frustrated and escalating chronic, or episodic, immune response to the point of a frank autoimmune disorder. Here, we discuss the evidence and the proposed mechanisms, and assess the therapeutic options that emerge from the current understanding of this field.
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Affiliation(s)
- Tomas Mustelin
- Division of Rheumatology, Department of Medicine, University of Washington, Seattle, WA, United States
| | - Kennedy C Ukadike
- Division of Rheumatology, Department of Medicine, University of Washington, Seattle, WA, United States
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Schulman AH. Retrotransposon replication in plants. Curr Opin Virol 2013; 3:604-14. [PMID: 24035277 DOI: 10.1016/j.coviro.2013.08.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Revised: 08/16/2013] [Accepted: 08/19/2013] [Indexed: 12/31/2022]
Abstract
Retrotransposons comprise the bulk of large plant genomes, replicating via an RNA intermediate whereby the original, integrated element remains in place. Of the two main orders, the LTR retrotransposons considerably outnumber the LINEs. LINEs integrate into target sites simultaneously with the RNA transcript being copied into cDNA by target-primed reverse transcription. LTR retrotransposon replication is basically equivalent to the intracellular phase of retroviral life cycles. The envelope gene giving extracellular mobility to retroviruses is in fact widespread in plants and their retrotransposons. Evolutionary analyses of the retrotransposons and retroviruses suggest that both form an ancient monophyletic group. The particular adaptations of LTR retrotransposons to plant life cycles enabling their success remain to be clarified.
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Affiliation(s)
- Alan H Schulman
- Institute of Biotechnology, Viikki Biocenter, University of Helsinki, P.O. Box 65, Helsinki FIN-00014, Finland; Biotechnology and Food Research, MTT Agrifood Research Finland, Jokioinen FIN-31600, Finland.
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Bucher E, Reinders J, Mirouze M. Epigenetic control of transposon transcription and mobility in Arabidopsis. CURRENT OPINION IN PLANT BIOLOGY 2012; 15:503-10. [PMID: 22940592 DOI: 10.1016/j.pbi.2012.08.006] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Accepted: 08/16/2012] [Indexed: 05/23/2023]
Abstract
The mobility of genetic elements called transposable elements (TEs) was discovered half a century ago by Barbara McClintock. Although she had recognized them as chromosomal controlling elements, for much of the consequent time TEs were primarily considered as parasites of the host genome. However the recent explosion of discoveries in the fields of genomics and epigenetics have unambiguously shown the importance of TEs in genome function and evolution. Bursts of endogenous TEs have been reported in plants with epigenetic misregulation, revealing the molecular mechanisms underlying their control. We review here the different steps in TE invasion of the host genome involving epigenetic control and environmental stress responses. As TEs propagate in plant genomes and attract epigenetic marks, their neo-insertions can lead to the formation of new, heritable epigenetic variants (epialleles) of genes in their vicinity and impact on host gene regulatory networks. The epigenetic interplay between TE and genes thus plays a crucial role in the TE-host co-evolution.
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Affiliation(s)
- Etienne Bucher
- Botanical Institute, University of Basel, Hebelstrasse 1, 4056 Basel, Switzerland.
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Tramontano A, Donath A, Bernhart SH, Reiche K, Böhmdorfer G, Stadler PF, Bachmair A. Deletion analysis of the 3' long terminal repeat sequence of plant retrotransposon Tto1 identifies 125 base pairs redundancy as sufficient for first strand transfer. Virology 2011; 412:75-82. [PMID: 21262516 PMCID: PMC3061985 DOI: 10.1016/j.virol.2010.12.059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 10/29/2010] [Accepted: 12/31/2010] [Indexed: 11/30/2022]
Abstract
Retroviruses and many retrotransposons are flanked by sequence repeats called long terminal repeats (LTRs). These sequences contain a promoter region, which is active in the 5′ LTR, and transcription termination signals, which are active in the LTR copy present at the 3′ end. A section in the middle of the LTR, called Redundancy region, occurs at both ends of the mRNA. Here we show that in the copia type retrotransposon Tto1, the promoter and terminator functions of the LTR can be supplied by heterologous sequences, thereby converting the LTR into a significantly shorter sub-terminal repeat. An engineered Tto1 element with 125 instead of the usual 574 base pairs repeated in the 5′ and 3′ region can still promote strand transfer during cDNA synthesis, defining a minimal Redundancy region for this element. Based on this finding, we propose a model for first strand transfer of Tto1.
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Affiliation(s)
- Andrea Tramontano
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna, Austria
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, D-50829 Cologne, Germany
| | - Alexander Donath
- Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center of Bioinformatics, University of Leipzig, Härtelstrasse 16–18, D-04107 Leipzig, Germany
| | - Stephan H. Bernhart
- Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center of Bioinformatics, University of Leipzig, Härtelstrasse 16–18, D-04107 Leipzig, Germany
- Institute for Theoretical Chemistry, University of Vienna, Währingerstraße 17, A-1090 Vienna, Austria
| | - Kristin Reiche
- RNomics Group, Fraunhofer Institute for Cell Therapy and Immunology IZI, Perlickstr. 1, D-04103 Leipzig, Germany
| | - Gudrun Böhmdorfer
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna, Austria
| | - Peter F. Stadler
- Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center of Bioinformatics, University of Leipzig, Härtelstrasse 16–18, D-04107 Leipzig, Germany
- Institute for Theoretical Chemistry, University of Vienna, Währingerstraße 17, A-1090 Vienna, Austria
- RNomics Group, Fraunhofer Institute for Cell Therapy and Immunology IZI, Perlickstr. 1, D-04103 Leipzig, Germany
- Max Planck Institute for Mathematics in the Sciences, Inselstrasse 22, D-04103 Leipzig, Germany
- Santa Fe Institute, 1399 Hyde Park Rd., Santa Fe, NM 87501, USA
| | - Andreas Bachmair
- Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna, Austria
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, D-50829 Cologne, Germany
- Corresponding author. Department of Biochemistry and Cell Biology, Max F. Perutz Laboratories, University of Vienna, Dr. Bohr-Gasse 9, A-1030 Vienna, Austria.
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Böhmdorfer G, Tramontano A, Luxa K, Bachmair A. A synthetic biology approach allows inducible retrotransposition in whole plants. SYSTEMS AND SYNTHETIC BIOLOGY 2010; 4:133-8. [PMID: 20805932 PMCID: PMC2923297 DOI: 10.1007/s11693-010-9053-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 02/20/2010] [Accepted: 02/22/2010] [Indexed: 11/30/2022]
Abstract
Retrotransposons are mobile genetic elements that transpose by reverse transcription of element RNA, followed by insertion of the cDNA into new positions of the host genome. Although they are major constituents of eukaryotic genomes, many facets of their biology remain to be understood. Transposition is generally rare, suggesting that it is subject to tight regulation. However, only the first regulatory step (transcriptional induction) is currently amenable to investigation in higher eukaryotes. To investigate the complete life cycle of a long terminal repeat (LTR) retrotransposon in plants, we established a synthetic biology program on tobacco retrotransposon Tto1, and achieved transposition in whole plants triggered by an inducible promoter. The engineered element, iTto (inducible Tto1), is a novel tool for analysis of retrotransposition in plants. In addition, it allows to explore the potential of an inducible retrotransposon for insertional mutagenesis.
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