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R2 and Non-Site-Specific R2-Like Retrotransposons of the German Cockroach, Blattella germanica. Genes (Basel) 2020; 11:genes11101202. [PMID: 33076367 PMCID: PMC7650587 DOI: 10.3390/genes11101202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 10/10/2020] [Accepted: 10/12/2020] [Indexed: 11/17/2022] Open
Abstract
The structural and functional organization of the ribosomal RNA gene cluster and the full-length R2 non-LTR retrotransposon (integrated into a specific site of 28S ribosomal RNA genes) of the German cockroach, Blattella germanica, is described. A partial sequence of the R2 retrotransposon of the cockroach Rhyparobia maderae is also analyzed. The analysis of previously published next-generation sequencing data from the B. germanica genome reveals a new type of retrotransposon closely related to R2 retrotransposons but with a random distribution in the genome. Phylogenetic analysis reveals that these newly described retrotransposons form a separate clade. It is shown that proteins corresponding to the open reading frames of newly described retrotransposons exhibit unequal structural domains. Within these retrotransposons, a recombination event is described. New mechanism of transposition activity is discussed. The essential structural features of R2 retrotransposons are conserved in cockroaches and are typical of previously described R2 retrotransposons. However, the investigation of the number and frequency of 5′-truncated R2 retrotransposon insertion variants in eight B. germanica populations suggests recent mobile element activity. It is shown that the pattern of 5′-truncated R2 retrotransposon copies can be an informative molecular genetic marker for revealing genetic distances between insect populations.
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Khadgi BB, Govindaraju A, Christensen SM. Completion of LINE integration involves an open '4-way' branched DNA intermediate. Nucleic Acids Res 2019; 47:8708-8719. [PMID: 31392993 PMCID: PMC6895275 DOI: 10.1093/nar/gkz673] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 06/26/2019] [Accepted: 07/29/2019] [Indexed: 12/20/2022] Open
Abstract
Long Interspersed Elements (LINEs), also known as non-LTR retrotransposons, encode a multifunctional protein that reverse transcribes its mRNA into DNA at the site of insertion by target primed reverse transcription. The second half of the integration reaction remains very poorly understood. Second-strand DNA cleavage and second-strand DNA synthesis were investigated in vitro using purified components from a site-specific restriction-like endonuclease (RLE) bearing LINE. DNA structure was shown to be a critical component of second-strand DNA cleavage. A hitherto unknown and unexplored integration intermediate, an open ‘4-way’ DNA junction, was recognized by the element protein and cleaved in a Holliday junction resolvase-like reaction. Cleavage of the 4-way junction resulted in a natural primer-template pairing used for second-strand DNA synthesis. A new model for RLE LINE integration is presented.
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Affiliation(s)
- Brijesh B Khadgi
- Department of Biology, University of Texas at Arlington, Arlington, TX 76019, USA
| | - Aruna Govindaraju
- Department of Biology, University of Texas at Arlington, Arlington, TX 76019, USA
| | - Shawn M Christensen
- Department of Biology, University of Texas at Arlington, Arlington, TX 76019, USA
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Oyun NY, Zagoskina AS, Mukha DV. Inheritance of 5'-Truncated Copies of R2 Retrotransposon in a Series of Generations of German Cockroach, Blattella germanica. RUSS J GENET+ 2018. [DOI: 10.1134/s1022795418120116] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Bonandin L, Scavariello C, Mingazzini V, Luchetti A, Mantovani B. Obligatory parthenogenesis and TE load: Bacillus stick insects and the R2 non-LTR retrotransposon. INSECT SCIENCE 2017; 24:409-417. [PMID: 26813995 DOI: 10.1111/1744-7917.12322] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Revised: 12/17/2015] [Accepted: 01/03/2016] [Indexed: 06/05/2023]
Abstract
Transposable elements (TEs) are selfish genetic elements whose self-replication is contrasted by the host genome. In this context, host reproductive strategies are predicted to impact on both TEs load and activity. The presence and insertion distribution of the non-LTR retrotransposon R2 was here studied in populations of the strictly bisexual Bacillus grandii maretimi and of the obligatory parthenogenetic Bacillus atticus atticus. Furthermore, data were also obtained from the offspring of selected B. a. atticus females. At the population level, the gonochoric B. g. maretimi showed a significantly higher R2 load than the obligatory parthenogenetic B. a. atticus. The comparison with bisexual and unisexual Bacillus rossius populations showed that their values were higher than those recorded for B. a. atticus and similar, or even higher, than those of B. g. maretimi. Consistently, an R2 load reduction is scored in B. a. atticus offspring even if with a great variance. On the whole, data here produced indicate that in the obligatory unisexual B. a. atticus R2 is active and that mechanisms of molecular turnover are effective. Furthermore, progeny analyses show that, at variance of the facultative parthenogenetic B. rossius, the R2 activity is held at a lower rate. Modeling parental-offspring inheritance, suggests that in B. a. atticus recombination plays a major role in eliminating insertions rather than selection, as previously suggested for unisexual B. rossius progeny, even if in both cases a high variance is observed. In addition to this, mechanisms of R2 silencing or chances of clonal selection cannot be ruled out.
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Affiliation(s)
- Livia Bonandin
- Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, Bologna, Italy
| | - Claudia Scavariello
- Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, Bologna, Italy
| | - Valentina Mingazzini
- Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, Bologna, Italy
| | - Andrea Luchetti
- Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, Bologna, Italy
| | - Barbara Mantovani
- Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, Bologna, Italy
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McCullers TJ, Steiniger M. Transposable elements in Drosophila. Mob Genet Elements 2017; 7:1-18. [PMID: 28580197 PMCID: PMC5443660 DOI: 10.1080/2159256x.2017.1318201] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 04/07/2017] [Accepted: 04/07/2017] [Indexed: 11/09/2022] Open
Abstract
Transposable elements (TEs) are mobile genetic elements that can mobilize within host genomes. As TEs comprise more than 40% of the human genome and are linked to numerous diseases, understanding their mechanisms of mobilization and regulation is important. Drosophila melanogaster is an ideal model organism for the study of eukaryotic TEs as its genome contains a diverse array of active TEs. TEs universally impact host genome size via transposition and deletion events, but may also adopt unique functional roles in host organisms. There are 2 main classes of TEs: DNA transposons and retrotransposons. These classes are further divided into subgroups of TEs with unique structural and functional characteristics, demonstrating the significant variability among these elements. Despite this variability, D. melanogaster and other eukaryotic organisms utilize conserved mechanisms to regulate TEs. This review focuses on the transposition mechanisms and regulatory pathways of TEs, and their functional roles in D. melanogaster.
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Affiliation(s)
| | - Mindy Steiniger
- Department of Biology, University of Missouri, St. Louis, MO, USA
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Govindaraju A, Cortez JD, Reveal B, Christensen SM. Endonuclease domain of non-LTR retrotransposons: loss-of-function mutants and modeling of the R2Bm endonuclease. Nucleic Acids Res 2016; 44:3276-87. [PMID: 26961309 PMCID: PMC4838377 DOI: 10.1093/nar/gkw134] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 02/22/2016] [Accepted: 02/23/2016] [Indexed: 01/07/2023] Open
Abstract
Non-LTR retrotransposons are an important class of mobile elements that insert into host DNA by target-primed reverse transcription (TPRT). Non-LTR retrotransposons must bind to their mRNA, recognize and cleave their target DNA, and perform TPRT at the site of DNA cleavage. As DNA binding and cleavage are such central parts of the integration reaction, a better understanding of the endonuclease encoded by non-LTR retrotransposons is needed. This paper explores the R2 endonuclease domain from Bombyx mori using in vitro studies and in silico modeling. Mutations in conserved sequences located across the putative PD-(D/E)XK endonuclease domain reduced DNA cleavage, DNA binding and TPRT. A mutation at the beginning of the first α-helix of the modeled endonuclease obliterated DNA cleavage and greatly reduced DNA binding. It also reduced TPRT when tested on pre-cleaved DNA substrates. The catalytic K was located to a non-canonical position within the second α-helix. A mutation located after the fourth β-strand reduced DNA binding and cleavage. The motifs that showed impaired activity form an extensive basic region. The R2 biochemical and structural data are compared and contrasted with that of two other well characterized PD-(D/E)XK endonucleases, restriction endonucleases and archaeal Holliday junction resolvases.
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Affiliation(s)
- Aruna Govindaraju
- Department of Biology, University of Texas at Arlington, Arlington, TX 76019-0498, USA
| | - Jeremy D. Cortez
- Department of Biology, University of Texas at Arlington, Arlington, TX 76019-0498, USA
| | - Brad Reveal
- Department of Biology, University of Texas at Arlington, Arlington, TX 76019-0498, USA
| | - Shawn M. Christensen
- Department of Biology, University of Texas at Arlington, Arlington, TX 76019-0498, USA
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Arkhipova IR, Rice PA. Mobile genetic elements: in silico, in vitro, in vivo. Mol Ecol 2016; 25:1027-31. [PMID: 26822117 DOI: 10.1111/mec.13543] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 01/15/2016] [Indexed: 11/27/2022]
Abstract
Mobile genetic elements (MGEs), also called transposable elements (TEs), represent universal components of most genomes and are intimately involved in nearly all aspects of genome organization, function and evolution. However, there is currently a gap between the fast pace of TE discovery in silico, driven by the exponential growth of comparative genomic studies, and a limited number of experimental models amenable to more traditional in vitro and in vivo studies of structural, mechanistic and regulatory properties of diverse MGEs. Experimental and computational scientists came together to bridge this gap at a recent conference, 'Mobile Genetic Elements: in silico, in vitro, in vivo', held at the Marine Biological Laboratory (MBL) in Woods Hole, MA, USA.
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Affiliation(s)
- Irina R Arkhipova
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA, 02543, USA
| | - Phoebe A Rice
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 E. 57th Street, Chicago, IL, 60637, USA
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Piégu B, Bire S, Arensburger P, Bigot Y. A survey of transposable element classification systems--a call for a fundamental update to meet the challenge of their diversity and complexity. Mol Phylogenet Evol 2015; 86:90-109. [PMID: 25797922 DOI: 10.1016/j.ympev.2015.03.009] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 03/11/2015] [Accepted: 03/12/2015] [Indexed: 10/25/2022]
Abstract
The increase of publicly available sequencing data has allowed for rapid progress in our understanding of genome composition. As new information becomes available we should constantly be updating and reanalyzing existing and newly acquired data. In this report we focus on transposable elements (TEs) which make up a significant portion of nearly all sequenced genomes. Our ability to accurately identify and classify these sequences is critical to understanding their impact on host genomes. At the same time, as we demonstrate in this report, problems with existing classification schemes have led to significant misunderstandings of the evolution of both TE sequences and their host genomes. In a pioneering publication Finnegan (1989) proposed classifying all TE sequences into two classes based on transposition mechanisms and structural features: the retrotransposons (class I) and the DNA transposons (class II). We have retraced how ideas regarding TE classification and annotation in both prokaryotic and eukaryotic scientific communities have changed over time. This has led us to observe that: (1) a number of TEs have convergent structural features and/or transposition mechanisms that have led to misleading conclusions regarding their classification, (2) the evolution of TEs is similar to that of viruses by having several unrelated origins, (3) there might be at least 8 classes and 12 orders of TEs including 10 novel orders. In an effort to address these classification issues we propose: (1) the outline of a universal TE classification, (2) a set of methods and classification rules that could be used by all scientific communities involved in the study of TEs, and (3) a 5-year schedule for the establishment of an International Committee for Taxonomy of Transposable Elements (ICTTE).
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Affiliation(s)
- Benoît Piégu
- UMR INRA-CNRS 7247, PRC, Centre INRA de Nouzilly, 37380 Nouzilly, France
| | - Solenne Bire
- UMR INRA-CNRS 7247, PRC, Centre INRA de Nouzilly, 37380 Nouzilly, France; Institute of Biotechnology, University of Lausanne, Center for Biotechnology UNIL-EPFL, 1015 Lausanne, Switzerland
| | - Peter Arensburger
- UMR INRA-CNRS 7247, PRC, Centre INRA de Nouzilly, 37380 Nouzilly, France; Biological Sciences Department, California State Polytechnic University, Pomona, CA 91768, United States.
| | - Yves Bigot
- UMR INRA-CNRS 7247, PRC, Centre INRA de Nouzilly, 37380 Nouzilly, France.
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