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Gao Y, Solberg T, Wang R, Yu Y, Al-Rasheid KAS, Gao F. Application of RNA interference and protein localization to investigate housekeeping and developmentally regulated genes in the emerging model protozoan Paramecium caudatum. Commun Biol 2024; 7:204. [PMID: 38374195 PMCID: PMC10876655 DOI: 10.1038/s42003-024-05906-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 02/09/2024] [Indexed: 02/21/2024] Open
Abstract
Unicellular eukaryotes represent tremendous evolutionary diversity. However, the molecular mechanisms underlying this diversity remain largely unexplored, partly due to a limitation of genetic tools to only a few model species. Paramecium caudatum is a well-known unicellular eukaryote with an unexpectedly large germline genome, of which only two percent is retained in the somatic genome following sexual processes, revealing extensive DNA elimination. However, further progress in understanding the molecular mechanisms governing this process is hampered by a lack of suitable genetic tools. Here, we report the successful application of gene knockdown and protein localization methods to interrogate the function of both housekeeping and developmentally regulated genes in P. caudatum. Using these methods, we achieved the expected phenotypes upon RNAi by feeding, and determined the localization of these proteins by microinjection of fusion constructs containing fluorescent protein or antibody tags. Lastly, we used these methods to reveal that P. caudatum PiggyMac, a domesticated piggyBac transposase, is essential for sexual development, and is likely to be an active transposase directly involved in DNA cleavage. The application of these methods lays the groundwork for future studies of gene function in P. caudatum and can be used to answer important biological questions in the future.
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Affiliation(s)
- Yunyi Gao
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education), and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China
| | - Therese Solberg
- Department of Molecular Biology, Keio University School of Medicine, Tokyo, 160-8582, Japan
- Human Biology Microbiome Quantum Research Center (WPI-Bio2Q), Keio University, Tokyo, 108-8345, Japan
| | - Rui Wang
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education), and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China
| | - Yueer Yu
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education), and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China
| | - Khaled A S Al-Rasheid
- Zoology Department, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia
| | - Feng Gao
- Key Laboratory of Evolution & Marine Biodiversity (Ministry of Education), and Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao, 266003, China.
- Laoshan Laboratory, Qingdao, 266237, China.
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2
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Constitutive Heterochromatin in Eukaryotic Genomes: A Mine of Transposable Elements. Cells 2022; 11:cells11050761. [PMID: 35269383 PMCID: PMC8909793 DOI: 10.3390/cells11050761] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/10/2022] [Accepted: 02/18/2022] [Indexed: 12/22/2022] Open
Abstract
Transposable elements (TEs) are abundant components of constitutive heterochromatin of the most diverse evolutionarily distant organisms. TEs enrichment in constitutive heterochromatin was originally described in the model organism Drosophila melanogaster, but it is now considered as a general feature of this peculiar portion of the genomes. The phenomenon of TE enrichment in constitutive heterochromatin has been proposed to be the consequence of a progressive accumulation of transposable elements caused by both reduced recombination and lack of functional genes in constitutive heterochromatin. However, this view does not take into account classical genetics studies and most recent evidence derived by genomic analyses of heterochromatin in Drosophila and other species. In particular, the lack of functional genes does not seem to be any more a general feature of heterochromatin. Sequencing and annotation of Drosophila melanogaster constitutive heterochromatin have shown that this peculiar genomic compartment contains hundreds of transcriptionally active genes, generally larger in size than that of euchromatic ones. Together, these genes occupy a significant fraction of the genomic territory of heterochromatin. Moreover, transposable elements have been suggested to drive the formation of heterochromatin by recruiting HP1 and repressive chromatin marks. In addition, there are several pieces of evidence that transposable elements accumulation in the heterochromatin might be important for centromere and telomere structure. Thus, there may be more complexity to the relationship between transposable elements and constitutive heterochromatin, in that different forces could drive the dynamic of this phenomenon. Among those forces, preferential transposition may be an important factor. In this article, we present an overview of experimental findings showing cases of transposon enrichment into the heterochromatin and their positive evolutionary interactions with an impact to host genomes.
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Sanghavi HM, Majumdar S. Oligomerization of THAP9 Transposase via Amino-Terminal Domains. Biochemistry 2021; 60:1822-1835. [PMID: 34033475 DOI: 10.1021/acs.biochem.1c00010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Active DNA transposases like the Drosophila P element transposase (DmTNP) undergo oligomerization as a prerequisite for transposition. Human THAP9 (hTHAP9) is a catalytically active but functionally uncharacterized homologue of DmTNP. Here we report (using co-immunoprecipitation, pull down, colocalization, and proximity ligation assays) that both full length and truncated hTHAP9 (corresponding to amino-terminal DNA binding and predicted coiled coil domains) undergo homo-oligomerization, predominantly in the nuclei of HEK293T cells. Interestingly, the oligomerization is shown to be partially mediated by DNA. However, mutating the leucines (either individually or together) or deleting the predicted coiled coil region did not significantly affect oligomerization. Thus, we highlight the importance of DNA and the amino-terminal regions of hTHAP9 for their ability to form higher-order oligomeric states. We also report that Hcf-1, THAP1, THAP10, and THAP11 are possible protein interaction partners of hTHAP9. Elucidating the functional relevance of the different putative oligomeric state(s) of hTHAP9 would help answer questions about its interaction partners as well as its unknown physiological roles.
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Affiliation(s)
- Hiral M Sanghavi
- Discipline of Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat 382355, India
| | - Sharmistha Majumdar
- Discipline of Biological Engineering, Indian Institute of Technology Gandhinagar, Gandhinagar, Gujarat 382355, India
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4
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Guérineau M, Bessa L, Moriau S, Lescop E, Bontems F, Mathy N, Guittet E, Bischerour J, Bétermier M, Morellet N. The unusual structure of the PiggyMac cysteine-rich domain reveals zinc finger diversity in PiggyBac-related transposases. Mob DNA 2021; 12:12. [PMID: 33926516 PMCID: PMC8086355 DOI: 10.1186/s13100-021-00240-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 03/09/2021] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Transposons are mobile genetic elements that colonize genomes and drive their plasticity in all organisms. DNA transposon-encoded transposases bind to the ends of their cognate transposons and catalyze their movement. In some cases, exaptation of transposon genes has allowed novel cellular functions to emerge. The PiggyMac (Pgm) endonuclease of the ciliate Paramecium tetraurelia is a domesticated transposase from the PiggyBac family. It carries a core catalytic domain typical of PiggyBac-related transposases and a short cysteine-rich domain (CRD), flanked by N- and C-terminal extensions. During sexual processes Pgm catalyzes programmed genome rearrangements (PGR) that eliminate ~ 30% of germline DNA from the somatic genome at each generation. How Pgm recognizes its DNA cleavage sites in chromatin is unclear and the structure-function relationships of its different domains have remained elusive. RESULTS We provide insight into Pgm structure by determining the fold adopted by its CRD, an essential domain required for PGR. Using Nuclear Magnetic Resonance, we show that the Pgm CRD binds two Zn2+ ions and forms an unusual binuclear cross-brace zinc finger, with a circularly permutated treble-clef fold flanked by two flexible arms. The Pgm CRD structure clearly differs from that of several other PiggyBac-related transposases, among which is the well-studied PB transposase from Trichoplusia ni. Instead, the arrangement of cysteines and histidines in the primary sequence of the Pgm CRD resembles that of active transposases from piggyBac-like elements found in other species and of human PiggyBac-derived domesticated transposases. We show that, unlike the PB CRD, the Pgm CRD does not bind DNA. Instead, it interacts weakly with the N-terminus of histone H3, whatever its lysine methylation state. CONCLUSIONS The present study points to the structural diversity of the CRD among transposases from the PiggyBac family and their domesticated derivatives, and highlights the diverse interactions this domain may establish with chromatin, from sequence-specific DNA binding to contacts with histone tails. Our data suggest that the Pgm CRD fold, whose unusual arrangement of cysteines and histidines is found in all PiggyBac-related domesticated transposases from Paramecium and Tetrahymena, was already present in the ancestral active transposase that gave rise to ciliate domesticated proteins.
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Affiliation(s)
- Marc Guérineau
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
| | - Luiza Bessa
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
- Present addresses: Université Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), 71 Avenue des Martyrs, 38000, Grenoble, France
| | - Séverine Moriau
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
| | - Ewen Lescop
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
| | - François Bontems
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
| | - Nathalie Mathy
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
- Reproduction et Développement des Plantes UMR 5667, Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, 69364, Lyon Cedex 07, France
| | - Eric Guittet
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
| | - Julien Bischerour
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France
| | - Mireille Bétermier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France.
| | - Nelly Morellet
- Université Paris-Saclay, CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198, Gif sur Yvette Cedex, France.
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The Paramecium histone chaperone Spt16-1 is required for Pgm endonuclease function in programmed genome rearrangements. PLoS Genet 2020; 16:e1008949. [PMID: 32702045 PMCID: PMC7402521 DOI: 10.1371/journal.pgen.1008949] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 08/04/2020] [Accepted: 06/24/2020] [Indexed: 12/31/2022] Open
Abstract
In Paramecium tetraurelia, a large proportion of the germline genome is reproducibly removed from the somatic genome after sexual events via a process involving small (s)RNA-directed heterochromatin formation and DNA excision and repair. How germline limited DNA sequences are specifically recognized in the context of chromatin remains elusive. Here, we use a reverse genetics approach to identify factors involved in programmed genome rearrangements. We have identified a P. tetraurelia homolog of the highly conserved histone chaperone Spt16 subunit of the FACT complex, Spt16-1, and show its expression is developmentally regulated. A functional GFP-Spt16-1 fusion protein localized exclusively in the nuclei where genome rearrangements take place. Gene silencing of Spt16-1 showed it is required for the elimination of all germline-limited sequences, for the survival of sexual progeny, and for the accumulation of internal eliminated sequence (ies)RNAs, an sRNA population produced when elimination occurs. Normal accumulation of 25 nt scanRNAs and deposition of silent histone marks H3K9me3 and H3K27me3 indicated that Spt16-1 does not regulate the scanRNA-directed heterochromatin pathway involved in the early steps of DNA elimination. We further show that Spt16-1 is required for the correct nuclear localization of the PiggyMac (Pgm) endonuclease, which generates the DNA double-strand breaks required for DNA elimination. Thus, Spt16-1 is essential for Pgm function during programmed genome rearrangements. We propose a model in which Spt16-1 mediates interactions between the excision machinery and chromatin, facilitating endonuclease access to DNA cleavage sites during genome rearrangements. The genome is generally similar in all the cells of an organism. However, in the ciliate Paramecium tetraurelia, massive and reproducible programmed DNA elimination leads to a highly streamlined somatic genome. In eukaryotes, DNA is packaged into nucleosomes, which ensure genome integrity but act as a barrier to enzymes acting on DNA. How the endonuclease PiggyMac gains access to the genome to initiate DNA elimination remains elusive. Here, we identified four P. tetraurelia genes encoding homologs of the conserved histone chaperone Spt16, which can modulate access to DNA by promoting nucleosome assembly and disassembly. We demonstrated that the most divergent gene, SPT16-1, has a highly specialized expression pattern, similar to that of PiggyMac, and a specific role in programmed DNA elimination. We show that the Spt16-1 protein, like PiggyMac, is exclusively localized in the differentiating somatic nucleus, and is also required for the dramatic elimination of germline-limited sequences. We further show that Spt16-1 directs the correct nuclear localization of the PiggyMac endonuclease. Thus, Spt16-1 is essential for PiggyMac function during programmed DNA elimination. We propose that Spt16-1 mediates the interaction between PiggyMac and chromatin or DNA, facilitating endonuclease access to DNA cleavage sites.
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6
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Allen SE, Nowacki M. Roles of Noncoding RNAs in Ciliate Genome Architecture. J Mol Biol 2020; 432:4186-4198. [PMID: 31926952 PMCID: PMC7374600 DOI: 10.1016/j.jmb.2019.12.042] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 12/19/2019] [Accepted: 12/20/2019] [Indexed: 11/29/2022]
Abstract
Ciliates are an interesting model system for investigating diverse functions of noncoding RNAs, especially in genome defence pathways. During sexual development, the ciliate somatic genome undergoes massive rearrangement and reduction through removal of transposable elements and other repetitive DNA. This is guided by a multitude of noncoding RNAs of different sizes and functions, the extent of which is only recently becoming clear. The genome rearrangement pathways evolved as a defence against parasitic DNA, but interestingly also use the transposable elements and transposases to execute their own removal. Thus, ciliates are also a good model for the coevolution of host and transposable element, and the mutual dependence between the two. In this review, we summarise the genome rearrangement pathways in three diverse species of ciliate, with focus on recent discoveries and the roles of noncoding RNAs. Ciliate genomes undergo massive rearrangement and reduction during development. Transposon elimination is guided by small RNAs and carried out by transposases. New pathways for noncoding RNA production have recently been discovered in ciliates. Diverse ciliate species have different mechanisms for RNA-guided genome remodeling.
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Affiliation(s)
- Sarah E Allen
- Institute of Cell Biology, University of Bern, Switzerland
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7
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Arnaiz O, Meyer E, Sperling L. ParameciumDB 2019: integrating genomic data across the genus for functional and evolutionary biology. Nucleic Acids Res 2020; 48:D599-D605. [PMID: 31733062 PMCID: PMC7145670 DOI: 10.1093/nar/gkz948] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 10/03/2019] [Accepted: 10/09/2019] [Indexed: 01/28/2023] Open
Abstract
ParameciumDB (https://paramecium.i2bc.paris-saclay.fr) is a community model organism database for the genome and genetics of the ciliate Paramecium. ParameciumDB development relies on the GMOD (www.gmod.org) toolkit. The ParameciumDB web site has been publicly available since 2006 when the P. tetraurelia somatic genome sequence was released, revealing that a series of whole genome duplications punctuated the evolutionary history of the species. The genome is linked to available genetic data and stocks. ParameciumDB has undergone major changes in its content and website since the last update published in 2011. Genomes from multiple Paramecium species, especially from the P. aurelia complex, are now included in ParameciumDB. A new modern web interface accompanies this transition to a database for the whole Paramecium genus. Gene pages have been enriched with orthology relationships, among the Paramecium species and with a panel of model organisms across the eukaryotic tree. This update also presents expert curation of Paramecium mitochondrial genomes.
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Affiliation(s)
- Olivier Arnaiz
- I2BC, Institute of Integrative Biology of the Cell, UMR9198, CNRS, CEA, Univ Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
- Correspondence may also be addressed to Olivier Arnaiz.
| | - Eric Meyer
- IBENS, Département de Biologie, Ecole Normale Supérieure, CNRS, Inserm, PSL Research University, F-75005 Paris, France
| | - Linda Sperling
- I2BC, Institute of Integrative Biology of the Cell, UMR9198, CNRS, CEA, Univ Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
- To whom correspondence should be addressed.
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Functional diversification of Paramecium Ku80 paralogs safeguards genome integrity during precise programmed DNA elimination. PLoS Genet 2020; 16:e1008723. [PMID: 32298257 PMCID: PMC7161955 DOI: 10.1371/journal.pgen.1008723] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 03/18/2020] [Indexed: 11/19/2022] Open
Abstract
Gene duplication and diversification drive the emergence of novel functions during evolution. Because of whole genome duplications, ciliates from the Paramecium aurelia group constitute a remarkable system to study the evolutionary fate of duplicated genes. Paramecium species harbor two types of nuclei: a germline micronucleus (MIC) and a somatic macronucleus (MAC) that forms from the MIC at each sexual cycle. During MAC development, ~45,000 germline Internal Eliminated Sequences (IES) are excised precisely from the genome through a 'cut-and-close' mechanism. Here, we have studied the P. tetraurelia paralogs of KU80, which encode a key DNA double-strand break repair factor involved in non-homologous end joining. The three KU80 genes have different transcription patterns, KU80a and KU80b being constitutively expressed, while KU80c is specifically induced during MAC development. Immunofluorescence microscopy and high-throughput DNA sequencing revealed that Ku80c stably anchors the PiggyMac (Pgm) endonuclease in the developing MAC and is essential for IES excision genome-wide, providing a molecular explanation for the previously reported Ku-dependent licensing of DNA cleavage at IES ends. Expressing Ku80a under KU80c transcription signals failed to complement a depletion of endogenous Ku80c, indicating that the two paralogous proteins have distinct properties. Domain-swap experiments identified the α/β domain of Ku80c as the major determinant for its specialized function, while its C-terminal part is required for excision of only a small subset of IESs located in IES-dense regions. We conclude that Ku80c has acquired the ability to license Pgm-dependent DNA cleavage, securing precise DNA elimination during programmed rearrangements. The present study thus provides novel evidence for functional diversification of genes issued from a whole-genome duplication.
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9
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Bhullar S, Denby Wilkes C, Arnaiz O, Nowacki M, Sperling L, Meyer E. A mating-type mutagenesis screen identifies a zinc-finger protein required for specific DNA excision events in Paramecium. Nucleic Acids Res 2019; 46:9550-9562. [PMID: 30165457 PMCID: PMC6182129 DOI: 10.1093/nar/gky772] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 08/24/2018] [Indexed: 12/16/2022] Open
Abstract
In the ciliate Paramecium tetraurelia, functional genes are reconstituted during development of the somatic macronucleus through the precise excision of ∼45 000 single-copy Internal Eliminated Sequences (IESs), thought to be the degenerate remnants of ancient transposon insertions. Like introns, IESs are marked only by a weak consensus at their ends. How such a diverse set of sequences is faithfully recognized and precisely excised remains unclear: specialized small RNAs have been implicated, but in their absence up to ∼60% of IESs are still correctly excised. To get further insight, we designed a mutagenesis screen based on the hypersensitivity of a specific excision event in the mtA gene, which determines mating types. Unlike most IES-containing genes, the active form of mtA is the unexcised one, allowing the recovery of hypomorphic alleles of essential IES recognition/excision factors. Such is the case of one mutation recovered in the Piwi gene PTIWI09, a key player in small RNA-mediated IES recognition. Another mutation identified a novel protein with a C2H2 zinc finger, mtGa, which is required for excision of a small subset of IESs characterized by enrichment in a 5-bp motif. The unexpected implication of a sequence-specific factor establishes a new paradigm for IES recognition and/or excision.
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Affiliation(s)
- Simran Bhullar
- IBENS, Ecole Normale Supérieure, CNRS, Inserm, PSL University, F-75005 Paris, France.,Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland
| | - Cyril Denby Wilkes
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Olivier Arnaiz
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland
| | - Linda Sperling
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Eric Meyer
- IBENS, Ecole Normale Supérieure, CNRS, Inserm, PSL University, F-75005 Paris, France
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10
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Bischerour J, Bhullar S, Denby Wilkes C, Régnier V, Mathy N, Dubois E, Singh A, Swart E, Arnaiz O, Sperling L, Nowacki M, Bétermier M. Six domesticated PiggyBac transposases together carry out programmed DNA elimination in Paramecium. eLife 2018; 7:37927. [PMID: 30223944 PMCID: PMC6143343 DOI: 10.7554/elife.37927] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 08/29/2018] [Indexed: 02/06/2023] Open
Abstract
The domestication of transposable elements has repeatedly occurred during evolution and domesticated transposases have often been implicated in programmed genome rearrangements, as remarkably illustrated in ciliates. In Paramecium, PiggyMac (Pgm), a domesticated PiggyBac transposase, carries out developmentally programmed DNA elimination, including the precise excision of tens of thousands of gene-interrupting germline Internal Eliminated Sequences (IESs). Here, we report the discovery of five groups of distant Pgm-like proteins (PgmLs), all able to interact with Pgm and essential for its nuclear localization and IES excision genome-wide. Unlike Pgm, PgmLs lack a conserved catalytic site, suggesting that they rather have an architectural function within a multi-component excision complex embedding Pgm. PgmL depletion can increase erroneous targeting of residual Pgm-mediated DNA cleavage, indicating that PgmLs contribute to accurately position the complex on IES ends. DNA rearrangements in Paramecium constitute a rare example of a biological process jointly managed by six distinct domesticated transposases.
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Affiliation(s)
- Julien Bischerour
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Simran Bhullar
- Institute of Cell Biology, University of Bern, Bern, Switzerland.,Institut de Biologie de l'Ecole Normale Supérieure, Paris, France
| | - Cyril Denby Wilkes
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Vinciane Régnier
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France.,Univ Paris Diderot, Paris, France
| | - Nathalie Mathy
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Emeline Dubois
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Aditi Singh
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | - Estienne Swart
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | - Olivier Arnaiz
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Linda Sperling
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | - Mireille Bétermier
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
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11
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Saudemont B, Popa A, Parmley JL, Rocher V, Blugeon C, Necsulea A, Meyer E, Duret L. The fitness cost of mis-splicing is the main determinant of alternative splicing patterns. Genome Biol 2017; 18:208. [PMID: 29084568 PMCID: PMC5663052 DOI: 10.1186/s13059-017-1344-6] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 10/09/2017] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Most eukaryotic genes are subject to alternative splicing (AS), which may contribute to the production of protein variants or to the regulation of gene expression via nonsense-mediated messenger RNA (mRNA) decay (NMD). However, a fraction of splice variants might correspond to spurious transcripts and the question of the relative proportion of splicing errors to functional splice variants remains highly debated. RESULTS We propose a test to quantify the fraction of AS events corresponding to errors. This test is based on the fact that the fitness cost of splicing errors increases with the number of introns in a gene and with expression level. We analyzed the transcriptome of the intron-rich eukaryote Paramecium tetraurelia. We show that in both normal and in NMD-deficient cells, AS rates strongly decrease with increasing expression level and with increasing number of introns. This relationship is observed for AS events that are detectable by NMD as well as for those that are not, which invalidates the hypothesis of a link with the regulation of gene expression. Our results show that in genes with a median expression level, 92-98% of observed splice variants correspond to errors. We observed the same patterns in human transcriptomes and we further show that AS rates correlate with the fitness cost of splicing errors. CONCLUSIONS These observations indicate that genes under weaker selective pressure accumulate more maladaptive substitutions and are more prone to splicing errors. Thus, to a large extent, patterns of gene expression variants simply reflect the balance between selection, mutation, and drift.
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Affiliation(s)
- Baptiste Saudemont
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, Inserm, Ecole Normale Supérieure, PSL Research University, F-75005 Paris, France
- (Epi)genomics of Animal Development Unit, Department of Developmental and Stem Cell Biology, Institut Pasteur, 75015 Paris, France
| | - Alexandra Popa
- Université de Lyon, Université Claude Bernard, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, F-69100 Villeurbanne, France
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14 AKH BT25.3, 1090 Vienna, Austria
| | - Joanna L. Parmley
- Université de Lyon, Université Claude Bernard, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, F-69100 Villeurbanne, France
- General Bioinformatics, Reading Enterprise Centre, The University of Reading, Whiteknights Road, Reading, RG6 6BU UK
| | - Vincent Rocher
- Université de Lyon, Université Claude Bernard, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, F-69100 Villeurbanne, France
| | - Corinne Blugeon
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, Inserm, Ecole Normale Supérieure, PSL Research University, F-75005 Paris, France
| | - Anamaria Necsulea
- Université de Lyon, Université Claude Bernard, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, F-69100 Villeurbanne, France
| | - Eric Meyer
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), CNRS, Inserm, Ecole Normale Supérieure, PSL Research University, F-75005 Paris, France
| | - Laurent Duret
- Université de Lyon, Université Claude Bernard, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, F-69100 Villeurbanne, France
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Jangam D, Feschotte C, Betrán E. Transposable Element Domestication As an Adaptation to Evolutionary Conflicts. Trends Genet 2017; 33:817-831. [PMID: 28844698 DOI: 10.1016/j.tig.2017.07.011] [Citation(s) in RCA: 142] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/21/2017] [Accepted: 07/25/2017] [Indexed: 12/26/2022]
Abstract
Transposable elements (TEs) are selfish genetic units that typically encode proteins that enable their proliferation in the genome and spread across individual hosts. Here we review a growing number of studies that suggest that TE proteins have often been co-opted or 'domesticated' by their host as adaptations to a variety of evolutionary conflicts. In particular, TE-derived proteins have been recurrently repurposed as part of defense systems that protect prokaryotes and eukaryotes against the proliferation of infectious or invasive agents, including viruses and TEs themselves. We argue that the domestication of TE proteins may often be the only evolutionary path toward the mitigation of the cost incurred by their own selfish activities.
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Affiliation(s)
- Diwash Jangam
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA
| | - Cédric Feschotte
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT, USA; Present address: Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA.
| | - Esther Betrán
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA.
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