51
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Fontdevila A. Hybrid Genome Evolution by Transposition: An Update. J Hered 2019; 110:124-136. [PMID: 30107415 DOI: 10.1093/jhered/esy040] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 08/06/2018] [Indexed: 02/02/2023] Open
Abstract
Contrary to the view that hybrids are lineages devoid of evolutionary value, a number of case studies that have been lately reported show how hybrids are at the origin of many species. Some well-documented cases demonstrate that bursts of transposition often follow hybridization, generating new genetic variability. Studies in hybrid transposition strongly suggest that epigenetic changes and divergence in piRNA pathways drive deregulation in TE landscapes. Here, I have focused on mechanisms acting in Drosophila hybrids between two cactophilic species. The results reported here show that while hybrid instability by transposition is a genome-wide event, deregulation by TE overexpression in hybrid ovaries is not a general rule. When piRNA pools of ovaries are studied, results show that TEs with parental differences higher than 2-fold in their piRNA amounts are not more commonly deregulated in hybrids than TEs with similar levels, partially discrediting the generality of the maternal cytotype hypothesis. Some promising results on the piRNA pathway global failure hypothesis, which states that accumulated divergence of piRNA effector proteins is responsible for hybrid TE deregulation, have also been obtained. Altogether, these results suggest that TE deregulation might be driven by several interacting mechanisms. A natural scenario is proposed in which genome instability by transposition leads to hybrid genome reorganization. Small hybrid populations, subjected to natural selection helped by genetic drift, evolve new adaptations adapted to novel environments. The final step is either introgression or even a new hybrid species.
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Affiliation(s)
- Antonio Fontdevila
- Grup de Genòmica, Bioinformàtica i Biologia Evolutiva, Departament de Genètica i Microbiologia, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Bellaterra, Spain
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52
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Czech B, Munafò M, Ciabrelli F, Eastwood EL, Fabry MH, Kneuss E, Hannon GJ. piRNA-Guided Genome Defense: From Biogenesis to Silencing. Annu Rev Genet 2018; 52:131-157. [PMID: 30476449 PMCID: PMC10784713 DOI: 10.1146/annurev-genet-120417-031441] [Citation(s) in RCA: 362] [Impact Index Per Article: 51.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
PIWI-interacting RNAs (piRNAs) and their associated PIWI clade Argonaute proteins constitute the core of the piRNA pathway. In gonadal cells, this conserved pathway is crucial for genome defense, and its main function is to silence transposable elements. This is achieved through posttranscriptional and transcriptional gene silencing. Precursors that give rise to piRNAs require specialized transcription and transport machineries because piRNA biogenesis is a cytoplasmic process. The ping-pong cycle, a posttranscriptional silencing mechanism, combines the cleavage-dependent silencing of transposon RNAs with piRNA production. PIWI proteins also function in the nucleus, where they scan for nascent target transcripts with sequence complementarity, instructing transcriptional silencing and deposition of repressive chromatin marks at transposon loci. Although studies have revealed numerous factors that participate in each branch of the piRNA pathway, the precise molecular roles of these factors often remain unclear. In this review, we summarize our current understanding of the mechanisms involved in piRNA biogenesis and function.
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Affiliation(s)
- Benjamin Czech
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Marzia Munafò
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Filippo Ciabrelli
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Evelyn L Eastwood
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Martin H Fabry
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Emma Kneuss
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Gregory J Hannon
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
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53
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Song MJ, Schaack S. Evolutionary Conflict between Mobile DNA and Host Genomes. Am Nat 2018; 192:263-273. [DOI: 10.1086/698482] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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54
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Genetic Analyses of Elys Mutations in Drosophila Show Maternal-Effect Lethality and Interactions with Nucleoporin Genes. G3-GENES GENOMES GENETICS 2018; 8:2421-2431. [PMID: 29773558 PMCID: PMC6027884 DOI: 10.1534/g3.118.200361] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
ELYS determines the subcellular localizations of Nucleoporins (Nups) during interphase and mitosis. We made loss-of-function mutations of Elys in Drosophila melanogaster and found that ELYS is dispensable for zygotic viability and male fertility but the maternal supply is necessary for embryonic development. Subsequent to fertilization, mitotic progression of the embryos produced by the mutant females is severely disrupted at the first cleavage division, accompanied by irregular behavior of mitotic centrosomes. The Nup160 introgression from D. simulans shows close resemblance to that of the Elys mutations, suggesting a common role for those proteins in the first cleavage division. Our genetic experiments indicated critical interactions between ELYS and three Nup107-160 subcomplex components; hemizygotes of either Nup37, Nup96 or Nup160 were lethal in the genetic background of the Elys mutation. Not only Nup96 and Nup160 but also Nup37 of D. simulans behave as recessive hybrid incompatibility genes with D. melanogaster An evolutionary analysis indicated positive natural selection in the ELYS-like domain of ELYS. Here we propose that genetic incompatibility between Elys and Nups may lead to reproductive isolation between D. melanogaster and D. simulans, although direct evidence is necessary.
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55
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Yu B, Lin YA, Parhad SS, Jin Z, Ma J, Theurkauf WE, Zhang ZZ, Huang Y. Structural insights into Rhino-Deadlock complex for germline piRNA cluster specification. EMBO Rep 2018; 19:embr.201745418. [PMID: 29858487 DOI: 10.15252/embr.201745418] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 04/28/2018] [Accepted: 05/14/2018] [Indexed: 11/09/2022] Open
Abstract
PIWI-interacting RNAs (piRNAs) silence transposons in germ cells to maintain genome stability and animal fertility. Rhino, a rapidly evolving heterochromatin protein 1 (HP1) family protein, binds Deadlock in a species-specific manner and so defines the piRNA-producing loci in the Drosophila genome. Here, we determine the crystal structures of Rhino-Deadlock complex in Drosophila melanogaster and simulans In both species, one Rhino binds the N-terminal helix-hairpin-helix motif of one Deadlock protein through a novel interface formed by the beta-sheet in the Rhino chromoshadow domain. Disrupting the interface leads to infertility and transposon hyperactivation in flies. Our structural and functional experiments indicate that electrostatic repulsion at the interaction interface causes cross-species incompatibility between the sibling species. By determining the molecular architecture of this piRNA-producing machinery, we discover a novel HP1-partner interacting mode that is crucial to piRNA biogenesis and transposon silencing. We thus explain the cross-species incompatibility of two sibling species at the molecular level.
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Affiliation(s)
- Bowen Yu
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Science Research Center, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Yu An Lin
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, USA
| | - Swapnil S Parhad
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Zhaohui Jin
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Science Research Center, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Jinbiao Ma
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for Genetics and Development, Department of Biochemistry, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai, China
| | - William E Theurkauf
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Zz Zhao Zhang
- Department of Embryology, Carnegie Institution for Science, Baltimore, MD, USA
| | - Ying Huang
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Science Research Center, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
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56
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Teo RYW, Anand A, Sridhar V, Okamura K, Kai T. Heterochromatin protein 1a functions for piRNA biogenesis predominantly from pericentric and telomeric regions in Drosophila. Nat Commun 2018; 9:1735. [PMID: 29728561 PMCID: PMC5935673 DOI: 10.1038/s41467-018-03908-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 03/22/2018] [Indexed: 02/06/2023] Open
Abstract
In metazoan germline, Piwi-interacting RNAs (piRNAs) provide defence against transposons. Piwi-piRNA complex mediates transcriptional silencing of transposons in nucleus. Heterochromatin protein 1a (HP1a) has been proposed to function downstream of Piwi-piRNA complex in Drosophila. Here we show that HP1a germline knockdown (HP1a-GLKD) leads to a reduction in the total and Piwi-bound piRNAs mapping to clusters and transposons insertions, predominantly in the regions close to telomeres and centromeres, resulting in derepression of a limited number of transposons from these regions. In addition, HP1a-GLKD increases the splicing of transcripts arising from clusters in above regions, suggesting HP1a also functions upstream to piRNA processing. Evolutionarily old transposons enriched in the pericentric regions exhibit significant loss in piRNAs targeting these transposons upon HP1a-GLKD. Our study suggests that HP1a functions to repress transposons in a chromosomal compartmentalised manner.
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Affiliation(s)
- Ryan Yee Wei Teo
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, 117604, Singapore, Singapore
- Department of Biological Sciences, National University of Singapore, 117543, Singapore, Singapore
- Department of Pathology, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore, 308433, Singapore
| | - Amit Anand
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, 117604, Singapore, Singapore.
| | - Vishweshwaren Sridhar
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, 117604, Singapore, Singapore
| | - Katsutomo Okamura
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, 117604, Singapore, Singapore
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore, Singapore
| | - Toshie Kai
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, 565-0871, Japan.
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57
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Horizontal acquisition of transposable elements and viral sequences: patterns and consequences. Curr Opin Genet Dev 2018; 49:15-24. [PMID: 29505963 DOI: 10.1016/j.gde.2018.02.007] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Revised: 02/13/2018] [Accepted: 02/14/2018] [Indexed: 12/30/2022]
Abstract
It is becoming clear that most eukaryotic transposable elements (TEs) owe their evolutionary success in part to horizontal transfer events, which enable them to invade new species. Recent large-scale studies are beginning to unravel the mechanisms and ecological factors underlying this mode of transmission. Viruses are increasingly recognized as vectors in the process but also as a direct source of genetic material horizontally acquired by eukaryotic organisms. Because TEs and endogenous viruses are major catalysts of variation and innovation in genomes, we argue that horizontal inheritance has had a more profound impact in eukaryotic evolution than is commonly appreciated. To support this proposal, we compile a list of examples, including some previously unrecognized, whereby new host functions and phenotypes can be directly attributed to horizontally acquired TE or viral sequences. We predict that the number of examples will rapidly grow in the future as the prevalence of horizontal transfer in the life cycle of TEs becomes even more apparent, firmly establishing this form of non-Mendelian inheritance as a consequential facet of eukaryotic evolution.
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Yamashiro H, Siomi MC. PIWI-Interacting RNA in Drosophila: Biogenesis, Transposon Regulation, and Beyond. Chem Rev 2017; 118:4404-4421. [PMID: 29281264 DOI: 10.1021/acs.chemrev.7b00393] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
PIWI-interacting RNAs (piRNAs) are germline-enriched small RNAs that control transposons to maintain genome integrity. To achieve this, upon being processed from piRNA precursors, most of which are transcripts of intergenic piRNA clusters, piRNAs bind PIWI proteins, germline-specific Argonaute proteins, to form effector complexes. The mechanism of this piRNA-mediated transposon silencing pathway is fundamentally similar to that of siRNA/miRNA-dependent gene silencing in that a small RNA guides its partner Argonaute protein to target gene transcripts for repression via RNA-RNA base pairing. However, the uniqueness of this piRNA pathway has emerged through intensive genetic, biochemical, bioinformatic, and structural investigations. Here, we review the studies that elucidated the piRNA pathway, mainly in Drosophila, by describing both historical and recent progress. Studies in other species that have made important contributions to the field are also described.
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Affiliation(s)
- Haruna Yamashiro
- Department of Biological Sciences, Graduate School of Science , The University of Tokyo , Tokyo 113-0032 , Japan
| | - Mikiko C Siomi
- Department of Biological Sciences, Graduate School of Science , The University of Tokyo , Tokyo 113-0032 , Japan
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59
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Lee YCG, Levine MT. Germline Genome Protection on an Evolutionary Treadmill. Dev Cell 2017; 43:1-3. [PMID: 29017026 DOI: 10.1016/j.devcel.2017.09.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Preservation of genome integrity is a conserved, essential function, yet genome defense machinery evolves rapidly. In this issue of Developmental Cell, Parhad et al. (2017) harness an evolution-guided approach to define the genetic determinants of genome defense and to reveal the molecular and cellular mechanisms shaped by adaptive evolution.
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Affiliation(s)
- Yuh Chwen G Lee
- Division of Biological Systems and Engineering, Lawrence Berkeley National Lab, One Cyclotron Road, Berkeley, CA 94720, USA
| | - Mia T Levine
- Department of Biology and Epigenetics Institute, University of Pennsylvania, Philadelphia, PA 19109, USA.
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