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Häußermann L, Singh A, Swart EC. Two paralogous PHD finger proteins participate in natural genome editing in Paramecium tetraurelia. J Cell Sci 2024; 137:jcs261979. [PMID: 39212120 PMCID: PMC11385659 DOI: 10.1242/jcs.261979] [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: 01/24/2024] [Accepted: 06/28/2024] [Indexed: 09/04/2024] Open
Abstract
The unicellular eukaryote Paramecium tetraurelia contains functionally distinct nuclei: germline micronuclei (MICs) and a somatic macronucleus (MAC). During sex, the MIC genome is reorganized into a new MAC genome and the old MAC is lost. Almost 45,000 unique internal eliminated sequences (IESs) distributed throughout the genome require precise excision to guarantee a functional new MAC genome. Here, we characterize a pair of paralogous PHD finger proteins involved in DNA elimination. DevPF1, the early-expressed paralog, is present in only some of the gametic and post-zygotic nuclei during meiosis. Both DevPF1 and DevPF2 localize in the new developing MACs, where IES excision occurs. Upon DevPF2 knockdown (KD), long IESs are preferentially retained and late-expressed small RNAs decrease; no length preference for retained IESs was observed in DevPF1-KD and development-specific small RNAs were abolished. The expression of at least two genes from the new MAC with roles in genome reorganization seems to be influenced by DevPF1- and DevPF2-KD. Thus, both PHD fingers are crucial for new MAC genome development, with distinct functions, potentially via regulation of non-coding and coding transcription in the MICs and new MACs.
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Affiliation(s)
- Lilia Häußermann
- Max Planck Institute for Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany
| | - Aditi Singh
- Max Planck Institute for Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany
| | - Estienne C Swart
- Max Planck Institute for Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany
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2
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Seah BKB, Swart EC. When cleaning facilitates cluttering - genome editing in ciliates. Trends Genet 2023; 39:344-346. [PMID: 36949004 DOI: 10.1016/j.tig.2023.02.016] [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: 07/29/2022] [Revised: 02/27/2023] [Accepted: 02/28/2023] [Indexed: 03/24/2023]
Abstract
Many organisms remove DNA from their genomes during development. This has foremost been characterized as a means of defending genomes against mobile elements. However, genome editing actually hides such elements from purifying selection, with the survivors evolving approximately neutrally, 'cluttering' the germline genome, enabling it to enlarge over time.
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3
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MITE infestation accommodated by genome editing in the germline genome of the ciliate Blepharisma. Proc Natl Acad Sci U S A 2023; 120:e2213985120. [PMID: 36669106 PMCID: PMC9942856 DOI: 10.1073/pnas.2213985120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
During their development following sexual conjugation, ciliates excise numerous internal eliminated sequences (IESs) from a copy of the germline genome to produce the functional somatic genome. Most IESs are thought to have originated from transposons, but the presumed homology is often obscured by sequence decay. To obtain more representative perspectives on the nature of IESs and ciliate genome editing, we assembled 40,000 IESs of Blepharisma stoltei, a species belonging to a lineage (Heterotrichea) that diverged early from those of the intensively studied model ciliate species. About a quarter of IESs were short (<115 bp), largely nonrepetitive, and with a pronounced ~10 bp periodicity in length; the remainder were longer (up to 7 kbp) and nonperiodic and contained abundant interspersed repeats. Contrary to the expectation from current models, the assembled Blepharisma germline genome encodes few transposases. Instead, its most abundant repeat (8,000 copies) is a Miniature Inverted-repeat Transposable Element (MITE), apparently a deletion derivative of a germline-limited Pogo-family transposon. We hypothesize that MITEs are an important source of IESs whose proliferation is eventually self-limiting and that rather than defending the germline genomes against mobile elements, transposase domestication actually facilitates the accumulation of junk DNA.
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4
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Singh A, Maurer‐Alcalá XX, Solberg T, Häußermann L, Gisler S, Ignarski M, Swart EC, Nowacki M. Chromatin remodeling is required for sRNA-guided DNA elimination in Paramecium. EMBO J 2022; 41:e111839. [PMID: 36221862 PMCID: PMC9670198 DOI: 10.15252/embj.2022111839] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 09/14/2022] [Accepted: 09/19/2022] [Indexed: 01/13/2023] Open
Abstract
Small RNAs mediate the silencing of transposable elements and other genomic loci, increasing nucleosome density and preventing undesirable gene expression. The unicellular ciliate Paramecium is a model to study dynamic genome organization in eukaryotic cells, given its unique feature of nuclear dimorphism. Here, the formation of the somatic macronucleus during sexual reproduction requires eliminating thousands of transposon remnants (IESs) and transposable elements scattered throughout the germline micronuclear genome. The elimination process is guided by Piwi-associated small RNAs and leads to precise cleavage at IES boundaries. Here we show that IES recognition and precise excision are facilitated by recruiting ISWI1, a Paramecium homolog of the chromatin remodeler ISWI. ISWI1 knockdown substantially inhibits DNA elimination, quantitatively similar to development-specific sRNA gene knockdowns but with much greater aberrant IES excision at alternative boundaries. We also identify key development-specific sRNA biogenesis and transport proteins, Ptiwi01 and Ptiwi09, as ISWI1 cofactors in our co-immunoprecipitation studies. Nucleosome profiling indicates that increased nucleosome density correlates with the requirement for ISWI1 and other proteins necessary for IES excision. We propose that chromatin remodeling together with small RNAs is essential for efficient and precise DNA elimination in Paramecium.
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Affiliation(s)
- Aditi Singh
- Institute of Cell BiologyUniversity of BernBernSwitzerland,Graduate School for Cellular and Biomedical SciencesUniversity of BernBernSwitzerland,Max Planck Institute for BiologyTubingenGermany
| | | | - Therese Solberg
- Institute of Cell BiologyUniversity of BernBernSwitzerland,Graduate School for Cellular and Biomedical SciencesUniversity of BernBernSwitzerland
| | | | - Silvan Gisler
- Institute of Cell BiologyUniversity of BernBernSwitzerland
| | | | - Estienne C Swart
- Institute of Cell BiologyUniversity of BernBernSwitzerland,Max Planck Institute for BiologyTubingenGermany
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5
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Bechara ST, Kabbani LES, Maurer-Alcalá XX, Nowacki M. Identification of novel, functional, long noncoding RNAs involved in programmed, large-scale genome rearrangements. RNA (NEW YORK, N.Y.) 2022; 28:1110-1127. [PMID: 35680167 PMCID: PMC9297840 DOI: 10.1261/rna.079134.122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Accepted: 05/26/2022] [Indexed: 06/15/2023]
Abstract
Noncoding RNAs (ncRNAs) make up to ∼98% percent of the transcriptome of a given organism. In recent years, one relatively new class of ncRNAs, long noncoding RNAs (lncRNAs), were shown to be more than mere by-products of gene expression and regulation. The unicellular eukaryote Paramecium tetraurelia is a member of the ciliate phylum, an extremely heterogeneous group of organisms found in most bodies of water across the globe. A hallmark of ciliate genetics is nuclear dimorphism and programmed elimination of transposons and transposon-derived DNA elements, the latter of which is essential for the maintenance of the somatic genome. Paramecium and ciliates in general harbor a plethora of different ncRNA species, some of which drive the process of large-scale genome rearrangements, including DNA elimination, during sexual development. Here, we identify and validate the first known functional lncRNAs in ciliates to date. Using deep-sequencing and subsequent bioinformatic processing and experimental validation, we show that Paramecium expresses at least 15 lncRNAs. These candidates were predicted by a highly conservative pipeline, and informatic analyses hint at differential expression during development. Depletion of two lncRNAs, lnc1 and lnc15, resulted in clear phenotypes, decreased survival, morphological impairment, and a global effect on DNA elimination.
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Affiliation(s)
- Sebastian T Bechara
- Institute of Cell Biology, University of Bern, Bern 3012, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern 3012, Switzerland
| | - Lyna E S Kabbani
- Institute of Cell Biology, University of Bern, Bern 3012, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern 3012, Switzerland
| | - Xyrus X Maurer-Alcalá
- Institute of Cell Biology, University of Bern, Bern 3012, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern 3012, Switzerland
| | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, Bern 3012, Switzerland
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6
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Rzeszutek I, Swart EC, Pabian-Jewuła S, Russo A, Nowacki M. Early developmental, meiosis-specific proteins - Spo11, Msh4-1, and Msh5 - Affect subsequent genome reorganization in Paramecium tetraurelia. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2022; 1869:119239. [PMID: 35181406 DOI: 10.1016/j.bbamcr.2022.119239] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 02/07/2022] [Accepted: 02/10/2022] [Indexed: 06/14/2023]
Abstract
Developmental DNA elimination in Paramecium tetraurelia occurs through a trans-nuclear comparison of the genomes of two distinct types of nuclei: the germline micronucleus (MIC) and the somatic macronucleus (MAC). During sexual reproduction, which starts with meiosis of the germline nuclei, MIC-limited sequences including Internal Eliminated Sequences (IESs) and transposons are eliminated from the developing MAC in a process guided by noncoding RNAs (scnRNAs and iesRNAs). However, our current understanding of this mechanism is still very limited. Therefore, studying both genetic and epigenetic aspects of these processes is a crucial step to understand this phenomenon in more detail. Here, we describe the involvement of homologs of classical meiotic proteins, Spo11, Msh4-1, and Msh5 in this phenomenon. Based on our analyses, we propose that proper functioning of Spo11, Msh4-1, and Msh5 during Paramecium sexual reproduction are necessary for genome reorganization and viable progeny. Also, we show that double-strand breaks (DSBs) in DNA induced during meiosis by Spo11 are crucial for proper IESs excision. In summary, our investigations show that early sexual reproduction processes may significantly influence later somatic genome integrity.
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Affiliation(s)
- Iwona Rzeszutek
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Bern, Freiestrasse 1, 3012 Bern, Switzerland; Institute of Biology and Biotechnology, Department of Biotechnology, University of Rzeszow, Pigonia 1, 35-310 Rzeszow, Poland
| | - Estienne C Swart
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland; Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, 72076 Tuebingen, Germany
| | - Sylwia Pabian-Jewuła
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland; Centre of Postgraduate Medical Education, Department of Clinical Cytology, Marymoncka 99/103, 01-813 Warsaw, Poland
| | - Antonietta Russo
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland; Medical Biochemistry and Molecular Biology Department, UKS, Saarland Medical Center, Kirrberger Str. 100, 66421 Homburg, Germany
| | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland.
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7
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Plattner H. Ciliate Research. From Myth to Trendsetting Science. J Eukaryot Microbiol 2022; 69:e12926. [PMID: 35608570 DOI: 10.1111/jeu.12926] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 05/18/2022] [Accepted: 05/18/2022] [Indexed: 11/28/2022]
Abstract
This special issue of the Journal of Eukaryotic Microbiology (JEM) summarizes achievements obtained by generations of researchers with ciliates in widely different disciplines. In fact, ciliates range among the first cells seen under the microscope centuries ago. Their beauty made them an object of scientia amabilis and their manifold reactions made them attractive for college experiments and finally challenged causal analyses at the cellular level. Some of this work was honored by a Nobel Prize. Some observations yielded a baseline for additional novel discoveries, occasionally facilitated by specific properties of some ciliates. This also offers some advantage in the exploration of closely related parasites (malaria). Articles contributed here by colleagues from all over the world encompass a broad spectrum of ciliate life, from genetics to evolution, from molecular cell biology to ecology, from intercellular signaling to epigenetics etc. This introductory chapter, largely based on my personal perception, aims at integrating work presented in this special issue of JEM into a broader historical context up to current research.
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Drews F, Boenigk J, Simon M. Paramecium epigenetics in development and proliferation. J Eukaryot Microbiol 2022; 69:e12914. [PMID: 35363910 DOI: 10.1111/jeu.12914] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The term epigenetics is used for any layer of genetic information aside from the DNA base-sequence information. Mammalian epigenetic research increased our understanding of chromatin dynamics in terms of cytosine methylation and histone modification during differentiation, aging, and disease. Instead, ciliate epigenetics focused more on small RNA-mediated effects. On the one hand, these do concern the transport of RNA from parental to daughter nuclei, representing a regulated transfer of epigenetic information across generations. On the other hand, studies of Paramecium, Tetrahymena, Oxytricha, and Stylonychia revealed an almost unique function of transgenerational RNA. Rather than solely controlling chromatin dynamics, they control sexual progeny's DNA content quantitatively and qualitatively. Thus epigenetics seems to control genetics, at least genetics of the vegetative macronucleus. This combination offers ciliates, in particular, an epigenetically controlled genetic variability. This review summarizes the epigenetic mechanisms that contribute to macronuclear heterogeneity and relates these to nuclear dimorphism. This system's adaptive and evolutionary possibilities raise the critical question of whether such a system is limited to unicellular organisms or binuclear cells. We discuss here the relevance of ciliate genetics and epigenetics to multicellular organisms.
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Affiliation(s)
- Franziska Drews
- Molecular Cell Biology and Microbiology, School of Mathematics and Natural Sciences, University of Wuppertal
| | | | - Martin Simon
- Molecular Cell Biology and Microbiology, School of Mathematics and Natural Sciences, University of Wuppertal
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9
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Zangarelli C, Arnaiz O, Bourge M, Gorrichon K, Jaszczyszyn Y, Mathy N, Escoriza L, Bétermier M, Régnier V. Developmental timing of programmed DNA elimination in Paramecium tetraurelia recapitulates germline transposon evolutionary dynamics. Genome Res 2022; 32:2028-2042. [PMID: 36418061 PMCID: PMC9808624 DOI: 10.1101/gr.277027.122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 11/11/2022] [Indexed: 11/24/2022]
Abstract
With its nuclear dualism, the ciliate Paramecium constitutes a unique model to study how host genomes cope with transposable elements (TEs). P. tetraurelia harbors two germline micronuclei (MICs) and a polyploid somatic macronucleus (MAC) that develops from one MIC at each sexual cycle. Throughout evolution, the MIC genome has been continuously colonized by TEs and related sequences that are removed from the somatic genome during MAC development. Whereas TE elimination is generally imprecise, excision of approximately 45,000 TE-derived internal eliminated sequences (IESs) is precise, allowing for functional gene assembly. Programmed DNA elimination is concomitant with genome amplification. It is guided by noncoding RNAs and repressive chromatin marks. A subset of IESs is excised independently of this epigenetic control, raising the question of how IESs are targeted for elimination. To gain insight into the determinants of IES excision, we established the developmental timing of DNA elimination genome-wide by combining fluorescence-assisted nuclear sorting with high-throughput sequencing. Essentially all IESs are excised within only one endoreplication round (32C to 64C), whereas TEs are eliminated at a later stage. We show that DNA elimination proceeds independently of replication. We defined four IES classes according to excision timing. The earliest excised IESs tend to be independent of epigenetic factors, display strong sequence signals at their ends, and originate from the most ancient integration events. We conclude that old IESs have been optimized during evolution for early and accurate excision by acquiring stronger sequence determinants and escaping epigenetic control.
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Affiliation(s)
- Coralie Zangarelli
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Olivier Arnaiz
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Mickaël Bourge
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Kevin Gorrichon
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Yan Jaszczyszyn
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Nathalie Mathy
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Loïc Escoriza
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Mireille Bétermier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France
| | - Vinciane Régnier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette Cedex, France;,Université Paris Cité, UFR Sciences du Vivant, 75205 Paris Cedex 13, France
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10
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Seah BKB, Swart EC. BleTIES: annotation of natural genome editing in ciliates using long read sequencing. Bioinformatics 2021; 37:3929-3931. [PMID: 34487139 PMCID: PMC11301610 DOI: 10.1093/bioinformatics/btab613] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 08/18/2021] [Indexed: 01/10/2023] Open
Abstract
SUMMARY Ciliates are single-celled eukaryotes that eliminate specific, interspersed DNA sequences (internally eliminated sequences, IESs) from their genomes during development. These are challenging to annotate and assemble because IES-containing sequences are typically much less abundant in the cell than those without, and IES sequences themselves often contain repetitive and low-complexity sequences. Long-read sequencing technologies from Pacific Biosciences and Oxford Nanopore have the potential to reconstruct longer IESs than has been possible with short reads but require a different assembly strategy. Here we present BleTIES, a software toolkit for detecting, assembling, and analyzing IESs using mapped long reads. AVAILABILITY AND IMPLEMENTATION BleTIES is implemented in Python 3. Source code is available at https://github.com/Swart-lab/bleties (MIT license) and also distributed via Bioconda. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Brandon K B Seah
- Max Planck Institute for Developmental Biology, Tübingen 72076, Germany
| | - Estienne C Swart
- Max Planck Institute for Developmental Biology, Tübingen 72076, Germany
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11
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Weiner AKM, Katz LA. Epigenetics as Driver of Adaptation and Diversification in Microbial Eukaryotes. Front Genet 2021; 12:642220. [PMID: 33796133 PMCID: PMC8007921 DOI: 10.3389/fgene.2021.642220] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 02/15/2021] [Indexed: 11/17/2022] Open
Affiliation(s)
- Agnes K M Weiner
- Department of Biological Sciences, Smith College, Northampton, MA, United States
| | - Laura A Katz
- Department of Biological Sciences, Smith College, Northampton, MA, United States.,Program in Organismic and Evolutionary Biology, University of Massachusetts Amherst, Amherst, MA, United States
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12
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Sawka-Gądek N, Potekhin A, Singh DP, Grevtseva I, Arnaiz O, Penel S, Sperling L, Tarcz S, Duret L, Nekrasova I, Meyer E. Evolutionary Plasticity of Mating-Type Determination Mechanisms in Paramecium aurelia Sibling Species. Genome Biol Evol 2021; 13:evaa258. [PMID: 33313646 PMCID: PMC7900874 DOI: 10.1093/gbe/evaa258] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/09/2020] [Indexed: 12/15/2022] Open
Abstract
The Paramecium aurelia complex, a group of morphologically similar but sexually incompatible sibling species, is a unique example of the evolutionary plasticity of mating-type systems. Each species has two mating types, O (Odd) and E (Even). Although O and E types are homologous in all species, three different modes of determination and inheritance have been described: genetic determination by Mendelian alleles, stochastic developmental determination, and maternally inherited developmental determination. Previous work in three species of the latter kind has revealed the key roles of the E-specific transmembrane protein mtA and its highly specific transcription factor mtB: type O clones are produced by maternally inherited genome rearrangements that inactivate either mtA or mtB during development. Here we show, through transcriptome analyses in five additional species representing the three determination systems, that mtA expression specifies type E in all cases. We further show that the Mendelian system depends on functional and nonfunctional mtA alleles, and identify novel developmental rearrangements in mtA and mtB which now explain all cases of maternally inherited mating-type determination. Epistasis between these genes likely evolved from less specific interactions between paralogs in the P. aurelia common ancestor, after a whole-genome duplication, but the mtB gene was subsequently lost in three P. aurelia species which appear to have returned to an ancestral regulation mechanism. These results suggest a model accounting for evolutionary transitions between determination systems, and highlight the diversity of molecular solutions explored among sibling species to maintain an essential mating-type polymorphism in cell populations.
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Affiliation(s)
- Natalia Sawka-Gądek
- Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Kraków, Poland
| | - Alexey Potekhin
- Department of Microbiology, Faculty of Biology, Saint Petersburg State University, Saint Petersburg, Russia
| | - Deepankar Pratap Singh
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Université PSL, Paris, France
| | - Inessa Grevtseva
- Department of Microbiology, Faculty of Biology, Saint Petersburg State University, Saint Petersburg, Russia
| | - Olivier Arnaiz
- CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, Gif-sur-Yvette, France
| | - Simon Penel
- CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Université de Lyon, Villeurbanne, France
| | - Linda Sperling
- CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, Gif-sur-Yvette, France
| | - Sebastian Tarcz
- Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Kraków, Poland
| | - Laurent Duret
- CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, Université de Lyon, Villeurbanne, France
| | - Irina Nekrasova
- Department of Microbiology, Faculty of Biology, Saint Petersburg State University, Saint Petersburg, Russia
| | - Eric Meyer
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Université PSL, Paris, France
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13
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Rzeszutek I, Maurer-Alcalá XX, Nowacki M. Programmed genome rearrangements in ciliates. Cell Mol Life Sci 2020; 77:4615-4629. [PMID: 32462406 PMCID: PMC7599177 DOI: 10.1007/s00018-020-03555-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 05/11/2020] [Accepted: 05/15/2020] [Indexed: 12/14/2022]
Abstract
Ciliates are a highly divergent group of unicellular eukaryotes with separate somatic and germline genomes found in distinct dimorphic nuclei. This characteristic feature is tightly linked to extremely laborious developmentally regulated genome rearrangements in the development of a new somatic genome/nuclei following sex. The transformation from germline to soma genome involves massive DNA elimination mediated by non-coding RNAs, chromosome fragmentation, as well as DNA amplification. In this review, we discuss the similarities and differences in the genome reorganization processes of the model ciliates Paramecium and Tetrahymena (class Oligohymenophorea), and the distantly related Euplotes, Stylonychia, and Oxytricha (class Spirotrichea).
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Affiliation(s)
- Iwona Rzeszutek
- Institute of Biology and Biotechnology, Department of Biotechnology, University of Rzeszow, Pigonia 1, 35-310, Rzeszow, Poland.
| | - Xyrus X Maurer-Alcalá
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012, Bern, Switzerland
| | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012, Bern, Switzerland.
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14
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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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15
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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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16
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Maurer-Alcalá XX, Nowacki M. Evolutionary origins and impacts of genome architecture in ciliates. Ann N Y Acad Sci 2019; 1447:110-118. [PMID: 31074010 PMCID: PMC6767857 DOI: 10.1111/nyas.14108] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 03/18/2019] [Accepted: 04/03/2019] [Indexed: 01/24/2023]
Abstract
Genome architecture is well diversified among eukaryotes in terms of size and content, with many being radically shaped by ancient and ongoing genome conflicts with transposable elements (e.g., the large transposon‐rich genomes common among plants). In ciliates, a group of microbial eukaryotes with distinct somatic and germ‐line genomes present in a single cell, the consequences of these genome conflicts are most apparent in their developmentally programmed genome rearrangements. This complicated developmental phenomenon has largely overshadowed and outpaced our understanding of how germ‐line and somatic genome architectures have influenced the evolutionary dynamism and potential in these taxa. In our review, we highlight three central concepts: how the evolution of atypical ciliate germ‐line genome architectures is linked to ancient genome conflicts; how the complex, epigenetically guided transformation of germline to soma during development can generate widespread genetic variation; and how these features, coupled with their unusual life cycle, have increased the rate of molecular evolution linked to genome architecture in these taxa.
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Affiliation(s)
| | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, Bern, Switzerland
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17
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Hoehener C, Hug I, Nowacki M. Dicer-like Enzymes with Sequence Cleavage Preferences. Cell 2019; 173:234-247.e7. [PMID: 29551264 PMCID: PMC5871716 DOI: 10.1016/j.cell.2018.02.029] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 12/08/2017] [Accepted: 02/09/2018] [Indexed: 01/18/2023]
Abstract
Dicer proteins are known to produce small RNAs (sRNAs) from long double-stranded RNA (dsRNA) templates. These sRNAs are bound by Argonaute proteins, which select the guide strand, often with a 5' end sequence bias. However, Dicer proteins have never been shown to have sequence cleavage preferences. In Paramecium development, two classes of sRNAs that are required for DNA elimination are produced by three Dicer-like enzymes: Dcl2, Dcl3, and Dcl5. Through in vitro cleavage assays, we demonstrate that Dcl2 has a strict size preference for 25 nt and a sequence preference for 5' U and 5' AGA, while Dcl3 has a sequence preference for 5' UNG. Dcl5, however, has cleavage preferences for 5' UAG and 3' CUAC/UN, which leads to the production of RNAs precisely matching short excised DNA elements with corresponding end base preferences. Thus, we characterize three Dicer-like enzymes that are involved in Paramecium development and propose a biological role for their sequence-biased cleavage products.
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Affiliation(s)
- Cristina Hoehener
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
| | - Iris Hug
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
| | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland.
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18
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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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19
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Gruchota J, Denby Wilkes C, Arnaiz O, Sperling L, Nowak JK. A meiosis-specific Spt5 homolog involved in non-coding transcription. Nucleic Acids Res 2017; 45:4722-4732. [PMID: 28053118 PMCID: PMC5416832 DOI: 10.1093/nar/gkw1318] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 12/20/2016] [Indexed: 12/18/2022] Open
Abstract
Spt5 is a conserved and essential transcriptional regulator that binds directly to RNA polymerase and is involved in transcription elongation, polymerase pausing and various co-transcriptional processes. To investigate the role of Spt5 in non-coding transcription, we used the unicellular model Paramecium tetraurelia. In this ciliate, development is controlled by epigenetic mechanisms that use different classes of non-coding RNAs to target DNA elimination. We identified two SPT5 genes. One (STP5v) is involved in vegetative growth, while the other (SPT5m) is essential for sexual reproduction. We focused our study on SPT5m, expressed at meiosis and associated with germline nuclei during sexual processes. Upon Spt5m depletion, we observed absence of scnRNAs, piRNA-like 25 nt small RNAs produced at meiosis. The scnRNAs are a temporal copy of the germline genome and play a key role in programming DNA elimination. Moreover, Spt5m depletion abolishes elimination of all germline-limited sequences, including sequences whose excision was previously shown to be scnRNA-independent. This suggests that in addition to scnRNA production, Spt5 is involved in setting some as yet uncharacterized epigenetic information at meiosis. Our study establishes that Spt5m is crucial for developmental genome rearrangements and necessary for scnRNA production.
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Affiliation(s)
- Julita Gruchota
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Cyril Denby Wilkes
- Institute for Integrative Biology of the Cell (I2BC), CNRS, CEA, University of Paris Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France
| | - Olivier Arnaiz
- Institute for Integrative Biology of the Cell (I2BC), CNRS, CEA, University of Paris Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France
| | - Linda Sperling
- Institute for Integrative Biology of the Cell (I2BC), CNRS, CEA, University of Paris Sud, Université Paris-Saclay, 91198, Gif-sur-Yvette cedex, France
| | - Jacek K Nowak
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
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20
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Allen SE, Hug I, Pabian S, Rzeszutek I, Hoehener C, Nowacki M. Circular Concatemers of Ultra-Short DNA Segments Produce Regulatory RNAs. Cell 2017; 168:990-999.e7. [PMID: 28283070 PMCID: PMC5346157 DOI: 10.1016/j.cell.2017.02.020] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 01/10/2017] [Accepted: 02/09/2017] [Indexed: 12/13/2022]
Abstract
In the ciliated protozoan Paramecium tetraurelia, Piwi-associated small RNAs are generated upon the elimination of tens of thousands of short transposon-derived DNA segments as part of development. These RNAs then target complementary DNA for elimination in a positive feedback process, contributing to germline defense and genome stability. In this work, we investigate the formation of these RNAs, which we show to be transcribed directly from the short (length mode 27 bp) excised DNA segments. Our data support a mechanism whereby the concatenation and circularization of excised DNA segments provides a template for RNA production. This process allows the generation of a double-stranded RNA for Dicer-like protein cleavage to give rise to a population of small regulatory RNAs that precisely match the excised DNA sequences. Video Abstract
In Paramecium, pieces of deleted DNA are transcribed to form regulatory RNAs Ultra-short DNA segments are concatenated and circularized, allowing transcription This concatenation is carried out by Ligase IV, which also repairs DNA ends Concatenation is random, which leads to diversity in the resulting sRNA population
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Affiliation(s)
- Sarah E Allen
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
| | - Iris Hug
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
| | - Sylwia Pabian
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
| | - Iwona Rzeszutek
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
| | - Cristina Hoehener
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
| | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland.
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21
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Pilling OA, Rogers AJ, Gulla-Devaney B, Katz LA. Insights into transgenerational epigenetics from studies of ciliates. Eur J Protistol 2017; 61:366-375. [PMID: 28689743 DOI: 10.1016/j.ejop.2017.05.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 05/06/2017] [Accepted: 05/09/2017] [Indexed: 12/23/2022]
Abstract
Epigenetics, a term with many meanings, can be broadly defined as the study of dynamic states of the genome. Ciliates, a clade of unicellular eukaryotes, can teach us about the intersection of epigenetics and evolution due to the advantages of working with cultivable ciliate lineages, plus their tendency to express extreme phenotypes such as heritable doublet morphology. Moreover, ciliates provide a powerful model for studying epigenetics given the presence of dimorphic nuclei - a somatic macronucleus and germline micronucleus - within each cell. Here, we exemplify the power of studying ciliates to learn about epigenetic phenomena. We highlight "classical" examples from morphology and physiology including cortical inheritance, mating type determination, and serotype expression. In addition, we detail molecular studies of epigenetic phenomena, including: DNA elimination; alternative processing and unscrambling; and copy number determination. Based on the implications of these studies, we discuss epigenetics as a possible functional mechanism for rapid speciation in ciliates.
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Affiliation(s)
- Olivia A Pilling
- Department of Biological Sciences, Smith College, Northampton, MA 01063, USA
| | - Anna J Rogers
- Department of Biological Sciences, Smith College, Northampton, MA 01063, USA
| | | | - Laura A Katz
- Department of Biological Sciences, Smith College, Northampton, MA 01063, USA; Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, MA 01003, USA.
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22
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Allen SE, Nowacki M. Necessity Is the Mother of Invention: Ciliates, Transposons, and Transgenerational Inheritance. Trends Genet 2017; 33:197-207. [PMID: 28174020 DOI: 10.1016/j.tig.2017.01.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 01/09/2017] [Accepted: 01/11/2017] [Indexed: 01/01/2023]
Abstract
Ciliates are a fascinating model system for the study of the interaction between eukaryotic germlines and somatic lines, especially with regard to the invasion and defence against transposable elements. They separate their germline and somatic line into two nuclei within the same cell, and they silence transposons and repetitive elements by way of deleting them from their somatic genome. This large-scale deletion event uses a series of intricate sequence targeting pathways involving small RNAs and transposases, part of which consists of a transnuclear comparison between maternal soma and daughter germline. We present recent progress in this dynamic field, and argue that these DNA targeting pathways provide an optimal system for the transgenerational inheritance of acquired traits. Ciliates thus also demonstrate the evolutionary value of transposable elements, both as sources of sequence diversity and also as drivers of adaptive evolution by necessitating defensive systems.
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Affiliation(s)
- Sarah E Allen
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland
| | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, 3012 Bern, Switzerland.
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23
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Epigenetic events in male common urogenital organs cancer. JOURNAL OF CANCER RESEARCH AND PRACTICE 2016. [DOI: 10.1016/j.jcrpr.2016.06.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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24
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Plattner H. Signalling in ciliates: long- and short-range signals and molecular determinants for cellular dynamics. Biol Rev Camb Philos Soc 2015; 92:60-107. [PMID: 26487631 DOI: 10.1111/brv.12218] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 07/28/2015] [Accepted: 08/21/2015] [Indexed: 12/30/2022]
Abstract
In ciliates, unicellular representatives of the bikont branch of evolution, inter- and intracellular signalling pathways have been analysed mainly in Paramecium tetraurelia, Paramecium multimicronucleatum and Tetrahymena thermophila and in part also in Euplotes raikovi. Electrophysiology of ciliary activity in Paramecium spp. is a most successful example. Established signalling mechanisms include plasmalemmal ion channels, recently established intracellular Ca2+ -release channels, as well as signalling by cyclic nucleotides and Ca2+ . Ca2+ -binding proteins (calmodulin, centrin) and Ca2+ -activated enzymes (kinases, phosphatases) are involved. Many organelles are endowed with specific molecules cooperating in signalling for intracellular transport and targeted delivery. Among them are recently specified soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), monomeric GTPases, H+ -ATPase/pump, actin, etc. Little specification is available for some key signal transducers including mechanosensitive Ca2+ -channels, exocyst complexes and Ca2+ -sensor proteins for vesicle-vesicle/membrane interactions. The existence of heterotrimeric G-proteins and of G-protein-coupled receptors is still under considerable debate. Serine/threonine kinases dominate by far over tyrosine kinases (some predicted by phosphoproteomic analyses). Besides short-range signalling, long-range signalling also exists, e.g. as firmly installed microtubular transport rails within epigenetically determined patterns, thus facilitating targeted vesicle delivery. By envisaging widely different phenomena of signalling and subcellular dynamics, it will be shown (i) that important pathways of signalling and cellular dynamics are established already in ciliates, (ii) that some mechanisms diverge from higher eukaryotes and (iii) that considerable uncertainties still exist about some essential aspects of signalling.
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Affiliation(s)
- Helmut Plattner
- Department of Biology, University of Konstanz, PO Box M625, 78457, Konstanz, Germany
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25
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Ferro D, Lepennetier G, Catania F. Cis-acting signals modulate the efficiency of programmed DNA elimination in Paramecium tetraurelia. Nucleic Acids Res 2015; 43:8157-68. [PMID: 26304543 PMCID: PMC4787833 DOI: 10.1093/nar/gkv843] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 08/01/2015] [Indexed: 12/12/2022] Open
Abstract
In Paramecium, the regeneration of a functional somatic genome at each sexual event relies on the elimination of thousands of germline DNA sequences, known as Internal Eliminated Sequences (IESs), from the zygotic nuclear DNA. Here, we provide evidence that IESs’ length and sub-terminal bases jointly modulate IES excision by affecting DNA conformation in P. tetraurelia. Our study reveals an excess of complementary base pairing between IESs’ sub-terminal and contiguous sites, suggesting that IESs may form DNA loops prior to cleavage. The degree of complementary base pairing between IESs’ sub-terminal sites (termed Cin-score) is positively associated with IES length and is shaped by natural selection. Moreover, it escalates abruptly when IES length exceeds 45 nucleotides (nt), indicating that only sufficiently large IESs may form loops. Finally, we find that IESs smaller than 46 nt are favored targets of the cellular surveillance systems, presumably because of their relatively inefficient excision. Our findings extend the repertoire of cis-acting determinants for IES recognition/excision and provide unprecedented insights into the distinct selective pressures that operate on IESs and somatic DNA regions. This information potentially moves current models of IES evolution and of mechanisms of IES recognition/excision forward.
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Affiliation(s)
- Diana Ferro
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstrasse 1, 48149 Münster, Germany
| | - Gildas Lepennetier
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstrasse 1, 48149 Münster, Germany
| | - Francesco Catania
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstrasse 1, 48149 Münster, Germany
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26
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Maliszewska-Olejniczak K, Gruchota J, Gromadka R, Denby Wilkes C, Arnaiz O, Mathy N, Duharcourt S, Bétermier M, Nowak JK. TFIIS-Dependent Non-coding Transcription Regulates Developmental Genome Rearrangements. PLoS Genet 2015; 11:e1005383. [PMID: 26177014 PMCID: PMC4503560 DOI: 10.1371/journal.pgen.1005383] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 06/22/2015] [Indexed: 02/07/2023] Open
Abstract
Because of their nuclear dimorphism, ciliates provide a unique opportunity to study the role of non-coding RNAs (ncRNAs) in the communication between germline and somatic lineages. In these unicellular eukaryotes, a new somatic nucleus develops at each sexual cycle from a copy of the zygotic (germline) nucleus, while the old somatic nucleus degenerates. In the ciliate Paramecium tetraurelia, the genome is massively rearranged during this process through the reproducible elimination of repeated sequences and the precise excision of over 45,000 short, single-copy Internal Eliminated Sequences (IESs). Different types of ncRNAs resulting from genome-wide transcription were shown to be involved in the epigenetic regulation of genome rearrangements. To understand how ncRNAs are produced from the entire genome, we have focused on a homolog of the TFIIS elongation factor, which regulates RNA polymerase II transcriptional pausing. Six TFIIS-paralogs, representing four distinct families, can be found in P. tetraurelia genome. Using RNA interference, we showed that TFIIS4, which encodes a development-specific TFIIS protein, is essential for the formation of a functional somatic genome. Molecular analyses and high-throughput DNA sequencing upon TFIIS4 RNAi demonstrated that TFIIS4 is involved in all kinds of genome rearrangements, including excision of ~48% of IESs. Localization of a GFP-TFIIS4 fusion revealed that TFIIS4 appears specifically in the new somatic nucleus at an early developmental stage, before IES excision. RT-PCR experiments showed that TFIIS4 is necessary for the synthesis of IES-containing non-coding transcripts. We propose that these IES+ transcripts originate from the developing somatic nucleus and serve as pairing substrates for germline-specific short RNAs that target elimination of their homologous sequences. Our study, therefore, connects the onset of zygotic non coding transcription to the control of genome plasticity in Paramecium, and establishes for the first time a specific role of TFIIS in non-coding transcription in eukaryotes. Paramecium tetraurelia provides an excellent model for studying the mechanisms involved in the production of non-coding transcripts and their mode of action. Different types of non-coding RNAs (ncRNAs) were shown to be implicated in the programmed DNA elimination process that occurs in this organism. At each sexual cycle, during development of the somatic nucleus from the germline nucleus, the genome is massively rearranged through the reproducible elimination of germline-specific sequences including thousands of short, single copy, non-coding Internal Eliminated Sequences (IES). Here, we demonstrate, using RNA interference, that the TFIIS4 gene encoding a development-specific homolog of RNA polymerase II elongation factor TFIIS, is indispensable for ncRNA synthesis in the new somatic nucleus. TFIIS4 depletion impairs the assembly of a functional somatic genome and affects excision of a large fraction of IESs, which leads to strong lethality in the sexual progeny. We propose that TFIIS4-dependent ncRNAs provide an important component of the molecular machinery that is responsible for developmental genome remodeling in Paramecium.
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Affiliation(s)
| | - Julita Gruchota
- Institute of Biochemistry and Biophysics, PAS, Warsaw, Poland
| | - Robert Gromadka
- Institute of Biochemistry and Biophysics, PAS, Warsaw, Poland
| | - Cyril Denby Wilkes
- Institute for Integrative Biology of the Cell (I2BC), CNRS, CEA, Université Paris Sud, Gif-sur-Yvette, France
| | - Olivier Arnaiz
- Institute for Integrative Biology of the Cell (I2BC), CNRS, CEA, Université Paris Sud, Gif-sur-Yvette, France
| | - Nathalie Mathy
- Institute for Integrative Biology of the Cell (I2BC), CNRS, CEA, Université Paris Sud, Gif-sur-Yvette, France
| | - Sandra Duharcourt
- Institut Jacques Monod, CNRS, UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Mireille Bétermier
- Institute for Integrative Biology of the Cell (I2BC), CNRS, CEA, Université Paris Sud, Gif-sur-Yvette, France
| | - Jacek K. Nowak
- Institute of Biochemistry and Biophysics, PAS, Warsaw, Poland
- * E-mail:
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27
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Catania F, Schmitz J. On the path to genetic novelties: insights from programmed DNA elimination and RNA splicing. WILEY INTERDISCIPLINARY REVIEWS-RNA 2015; 6:547-61. [PMID: 26140477 DOI: 10.1002/wrna.1293] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 04/29/2015] [Accepted: 06/06/2015] [Indexed: 12/17/2022]
Abstract
Understanding how genetic novelties arise is a central goal of evolutionary biology. To this end, programmed DNA elimination and RNA splicing deserve special consideration. While programmed DNA elimination reshapes genomes by eliminating chromatin during organismal development, RNA splicing rearranges genetic messages by removing intronic regions during transcription. Small RNAs help to mediate this class of sequence reorganization, which is not error-free. It is this imperfection that makes programmed DNA elimination and RNA splicing excellent candidates for generating evolutionary novelties. Leveraging a number of these two processes' mechanistic and evolutionary properties, which have been uncovered over the past years, we present recently proposed models and empirical evidence for how splicing can shape the structure of protein-coding genes in eukaryotes. We also chronicle a number of intriguing similarities between the processes of programmed DNA elimination and RNA splicing, and highlight the role that the variation in the population-genetic environment may play in shaping their target sequences.
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Affiliation(s)
- Francesco Catania
- Institute for Evolution and Biodiversity, University of Münster, Münster, Germany
| | - Jürgen Schmitz
- Institute of Experimental Pathology (ZMBE), University of Münster, Münster, Germany
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Swart EC, Nowacki M. The eukaryotic way to defend and edit genomes by sRNA-targeted DNA deletion. Ann N Y Acad Sci 2015; 1341:106-14. [PMID: 25581723 DOI: 10.1111/nyas.12636] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
While there is currently burgeoning interest in the application of the CRISPR/Cas (clustered regularly interspaced short palindromic repeats/CRISPR-associated genes) to genome editing, it is perhaps not widely appreciated that this is the second discovery of a small RNA (sRNA)-targeted DNA-deletion system. The first sRNA-targeted DNA-deletion system to be discovered, which we call IES/Ias (internal eliminated sequence/IES-associated genes) to contrast with CRISPR/Cas, is found in ciliates, and, like CRISPR/Cas, is thought to serve as a form of immune defense against invasive DNAs. The manner in which the ciliate IES/Ias system functions is distinct from that of the CRISPR/Cas system in archaea and bacteria, and arose independently through a synthesis of RNA interference-derived and DNA-specific molecular components. Despite the major differences between CRISPR/Cas and IES/Ias, both systems face similar conceptual challenges in targeting invasive DNAs. In this review, we focus on the discovery, effects, function, and evolutionary consequences of the IES/Ias system.
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Affiliation(s)
- Estienne C Swart
- Institute of Cell Biology, University of Bern, Bern, Switzerland
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Altermatt F, Fronhofer EA, Garnier A, Giometto A, Hammes F, Klecka J, Legrand D, Mächler E, Massie TM, Pennekamp F, Plebani M, Pontarp M, Schtickzelle N, Thuillier V, Petchey OL. Big answers from small worlds: a user's guide for protist microcosms as a model system in ecology and evolution. Methods Ecol Evol 2014. [DOI: 10.1111/2041-210x.12312] [Citation(s) in RCA: 135] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Florian Altermatt
- Department of Aquatic Ecology Eawag: Swiss Federal Institute of Aquatic Science and Technology Überlandstrasse 133 CH‐8600 Dübendorf Switzerland
- Institute of Evolutionary Biology and Environmental Studies University of Zurich Winterthurerstr. 190 CH‐8057 Zürich Switzerland
| | - Emanuel A. Fronhofer
- Department of Aquatic Ecology Eawag: Swiss Federal Institute of Aquatic Science and Technology Überlandstrasse 133 CH‐8600 Dübendorf Switzerland
| | - Aurélie Garnier
- Institute of Evolutionary Biology and Environmental Studies University of Zurich Winterthurerstr. 190 CH‐8057 Zürich Switzerland
| | - Andrea Giometto
- Department of Aquatic Ecology Eawag: Swiss Federal Institute of Aquatic Science and Technology Überlandstrasse 133 CH‐8600 Dübendorf Switzerland
- Laboratory of Ecohydrology School of Architecture Civil and Environmental Engineering École Polytechnique Fédérale de Lausanne CH‐1015 Lausanne Switzerland
| | - Frederik Hammes
- Department of Environmental Microbiology Eawag: Swiss Federal Institute of Aquatic Science and Technology Überlandstrasse 133 CH‐8600 Dübendorf Switzerland
| | - Jan Klecka
- Laboratory of Theoretical Ecology Institute of Entomology Biology Centre ASCR Branišovská 31 České Budějovice 37005 Czech Republic
- Department of Fish Ecology and Evolution Eawag: Swiss Federal Institute of Aquatic Science and Technology Seestrasse 79 CH‐6047 Kastanienbaum Switzerland
| | - Delphine Legrand
- Earth and Life Institute Biodiversity Research Centre Université catholique de Louvain Croix du Sud 4 L7.07.04 B‐1348 Louvain‐la‐Neuve Belgium
| | - Elvira Mächler
- Department of Aquatic Ecology Eawag: Swiss Federal Institute of Aquatic Science and Technology Überlandstrasse 133 CH‐8600 Dübendorf Switzerland
| | - Thomas M. Massie
- Institute of Evolutionary Biology and Environmental Studies University of Zurich Winterthurerstr. 190 CH‐8057 Zürich Switzerland
| | - Frank Pennekamp
- Institute of Evolutionary Biology and Environmental Studies University of Zurich Winterthurerstr. 190 CH‐8057 Zürich Switzerland
| | - Marco Plebani
- Institute of Evolutionary Biology and Environmental Studies University of Zurich Winterthurerstr. 190 CH‐8057 Zürich Switzerland
| | - Mikael Pontarp
- Institute of Evolutionary Biology and Environmental Studies University of Zurich Winterthurerstr. 190 CH‐8057 Zürich Switzerland
| | - Nicolas Schtickzelle
- Earth and Life Institute Biodiversity Research Centre Université catholique de Louvain Croix du Sud 4 L7.07.04 B‐1348 Louvain‐la‐Neuve Belgium
| | - Virginie Thuillier
- Earth and Life Institute Biodiversity Research Centre Université catholique de Louvain Croix du Sud 4 L7.07.04 B‐1348 Louvain‐la‐Neuve Belgium
| | - Owen L. Petchey
- Department of Aquatic Ecology Eawag: Swiss Federal Institute of Aquatic Science and Technology Überlandstrasse 133 CH‐8600 Dübendorf Switzerland
- Institute of Evolutionary Biology and Environmental Studies University of Zurich Winterthurerstr. 190 CH‐8057 Zürich Switzerland
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Arambasic M, Sandoval PY, Hoehener C, Singh A, Swart EC, Nowacki M. Pdsg1 and Pdsg2, novel proteins involved in developmental genome remodelling in Paramecium. PLoS One 2014; 9:e112899. [PMID: 25397898 PMCID: PMC4232520 DOI: 10.1371/journal.pone.0112899] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 10/16/2014] [Indexed: 01/25/2023] Open
Abstract
The epigenetic influence of maternal cells on the development of their progeny has long been studied in various eukaryotes. Multicellular organisms usually provide their zygotes not only with nutrients but also with functional elements required for proper development, such as coding and non-coding RNAs. These maternally deposited RNAs exhibit a variety of functions, from regulating gene expression to assuring genome integrity. In ciliates, such as Paramecium these RNAs participate in the programming of large-scale genome reorganization during development, distinguishing germline-limited DNA, which is excised, from somatic-destined DNA. Only a handful of proteins playing roles in this process have been identified so far, including typical RNAi-derived factors such as Dicer-like and Piwi proteins. Here we report and characterize two novel proteins, Pdsg1 and Pdsg2 (Paramecium protein involved in Development of the Somatic Genome 1 and 2), involved in Paramecium genome reorganization. We show that these proteins are necessary for the excision of germline-limited DNA during development and the survival of sexual progeny. Knockdown of PDSG1 and PDSG2 genes affects the populations of small RNAs known to be involved in the programming of DNA elimination (scanRNAs and iesRNAs) and chromatin modification patterns during development. Our results suggest an association between RNA-mediated trans-generational epigenetic signal and chromatin modifications in the process of Paramecium genome reorganization.
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Affiliation(s)
| | | | | | - Aditi Singh
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | | | - Mariusz Nowacki
- Institute of Cell Biology, University of Bern, Bern, Switzerland
- * E-mail:
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