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Rappol T, Waldl M, Chugunova A, Hofacker IL, Pauli A, Vilardo E. tRNA expression and modification landscapes, and their dynamics during zebrafish embryo development. Nucleic Acids Res 2024:gkae595. [PMID: 38989621 DOI: 10.1093/nar/gkae595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 06/19/2024] [Accepted: 06/26/2024] [Indexed: 07/12/2024] Open
Abstract
tRNA genes exist in multiple copies in the genome of all organisms across the three domains of life. Besides the sequence differences across tRNA copies, extensive post-transcriptional modification adds a further layer to tRNA diversification. Whilst the crucial role of tRNAs as adapter molecules in protein translation is well established, whether all tRNAs are actually expressed, and whether the differences across isodecoders play any regulatory role is only recently being uncovered. Here we built upon recent developments in the use of NGS-based methods for RNA modification detection and developed tRAM-seq, an experimental protocol and in silico analysis pipeline to investigate tRNA expression and modification. Using tRAM-seq, we analysed the full ensemble of nucleo-cytoplasmic and mitochondrial tRNAs during embryonic development of the model vertebrate zebrafish. We show that the repertoire of tRNAs changes during development, with an apparent major switch in tRNA isodecoder expression and modification profile taking place around the start of gastrulation. Taken together, our findings suggest the existence of a general reprogramming of the expressed tRNA pool, possibly gearing the translational machinery for distinct stages of the delicate and crucial process of embryo development.
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Affiliation(s)
- Tom Rappol
- Center for Anatomy & Cell Biology, Medical University of Vienna, 1090 Vienna, Austria
| | - Maria Waldl
- Center for Anatomy & Cell Biology, Medical University of Vienna, 1090 Vienna, Austria
- Department of Theoretical Chemistry, University of Vienna, 1090 Vienna, Austria
- Vienna Doctoral School in Chemistry (DoSChem), University of Vienna, 1090 Vienna, Austria
- Institute of Computer Science and Interdisciplinary Center for Bioinformatics, Leipzig University, D-04107 Leipzig, Germany
| | - Anastasia Chugunova
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Ivo L Hofacker
- Department of Theoretical Chemistry, University of Vienna, 1090 Vienna, Austria
- Faculty of Computer Science, Research Group Bioinformatics and Computational Biology, University of Vienna, 1090 Vienna, Austria
| | - Andrea Pauli
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Elisa Vilardo
- Center for Anatomy & Cell Biology, Medical University of Vienna, 1090 Vienna, Austria
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2
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Koli S, Shetty S. Ribosomal dormancy at the nexus of ribosome homeostasis and protein synthesis. Bioessays 2024; 46:e2300247. [PMID: 38769702 DOI: 10.1002/bies.202300247] [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: 12/28/2023] [Revised: 02/05/2024] [Accepted: 05/02/2024] [Indexed: 05/22/2024]
Abstract
Dormancy or hibernation is a non-proliferative state of cells with low metabolic activity and gene expression. Dormant cells sequester ribosomes in a translationally inactive state, called dormant/hibernating ribosomes. These dormant ribosomes are important for the preservation of ribosomes and translation shut-off. While recent studies attempted to elucidate their modes of formation, the regulation and roles of the diverse dormant ribosomal populations are still largely understudied. The mechanistic details of the formation of dormant ribosomes in stress and especially their disassembly during recovery remain elusive. In this review, we discuss the roles of dormant ribosomes and their potential regulatory mechanisms. Furthermore, we highlight the paradigms that need to be answered in the field of ribosomal dormancy.
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Affiliation(s)
- Saloni Koli
- Advanced Centre for Treatment Research and Education in Cancer (ACTREC), Tata Memorial Centre, Navi Mumbai, India
| | - Sunil Shetty
- Advanced Centre for Treatment Research and Education in Cancer (ACTREC), Tata Memorial Centre, Navi Mumbai, India
- Homi Bhabha National Institute, Mumbai, India
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3
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Volarić M, Despot-Slade E, Veseljak D, Pavlek M, Vojvoda Zeljko T, Mravinac B, Meštrović N. The Genome Organization of 5S rRNA Genes in the Model Organism Tribolium castaneum and Its Sibling Species Tribolium freemani. Genes (Basel) 2024; 15:776. [PMID: 38927712 PMCID: PMC11202950 DOI: 10.3390/genes15060776] [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: 04/11/2024] [Revised: 06/07/2024] [Accepted: 06/11/2024] [Indexed: 06/28/2024] Open
Abstract
5S ribosomal DNAs (rDNAs) are arranged in tandem and are often under-represented in genome assemblies. In the present study, we performed a global and in-depth analysis of the 5S rDNAs in the model insect Tribolium castaneum and its closely related species Tribolium freemani. To accomplish this goal, we used our recently published genome assemblies based on Nanopore and PacBio long-read sequencing. Although these closely related species share the 5S rRNA gene sequence with high homology, they show a different organization of the 5S rDNA locus. Analysis of 5S rDNA arrays in T. castaneum revealed a typical tandemly repeated organization characterized by repeat units consisting of the 121 bp long 5S rRNA gene and the 71 bp long nontranscribed spacer (NTS). In contrast, T. freemani showed a much more complex organization of 5S rDNA arrays characterized by two patterns. The first is based on the association of 5S rRNA gene with arrays of a satellite DNA, representing the NTS sequence of the 5S rDNA genes in T. freemani. The second, more complex type is characterized by a somewhat less frequent occurrence of the 5S rRNA gene and its association with longer satellite DNA arrays that are regularly interrupted by Jockey-like retrotransposons. This organization, in which the ribosomal gene is associated with two completely different repetitive elements such as satellite DNAs and retrotransposons, suggests that the 5S rRNA gene, regardless of its crucial function in the genome, could be a subject of extremely dynamic genomic rearrangements.
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Affiliation(s)
| | | | | | | | | | | | - Nevenka Meštrović
- Ruđer Bošković Institute, Bijenička Cesta 54, 10000 Zagreb, Croatia; (M.V.); (E.D.-S.); (D.V.); (M.P.); (T.V.Z.); (B.M.)
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Wilson CA, Postlethwait JH. A maternal-to-zygotic-transition gene block on the zebrafish sex chromosome. G3 (BETHESDA, MD.) 2024; 14:jkae050. [PMID: 38466753 PMCID: PMC11075544 DOI: 10.1093/g3journal/jkae050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 02/22/2024] [Accepted: 03/01/2024] [Indexed: 03/13/2024]
Abstract
Wild zebrafish (Danio rerio) have a ZZ/ZW chromosomal sex-determination system with the major sex locus on the right arm of chromosome-4 (Chr4R) near the largest heterochromatic block in the genome, suggesting that Chr4R transcriptomics might differ from the rest of the genome. To test this hypothesis, we conducted an RNA-seq analysis of adult ZW ovaries and ZZ testes in the Nadia strain and identified 4 regions of Chr4 with different gene expression profiles. Unique in the genome, protein-coding genes in a 41.7 Mb section (Region-2) were expressed in testis but silent in ovary. The AB lab strain, which lacks sex chromosomes, verified this result, showing that testis-biased gene expression in Region-2 depends on gonad biology, not on sex-determining mechanism. RNA-seq analyses in female and male brains and livers validated reduced transcripts from Region-2 in somatic cells, but without sex specificity. Region-2 corresponds to the heterochromatic portion of Chr4R and its content of genes and repetitive elements distinguishes it from the rest of the genome. Region-2 lacks protein-coding genes with human orthologs; has zinc finger genes expressed early in zygotic genome activation; has maternal 5S rRNA genes, maternal spliceosome genes, a concentration of tRNA genes, and a distinct set of repetitive elements. The colocalization of (1) genes silenced in ovaries but not in testes that are (2) expressed in embryos briefly at the onset of zygotic genome activation; (3) maternal-specific genes for translation machinery; (4) maternal-specific spliceosome components; and (5) adjacent genes encoding miR-430, which mediates maternal transcript degradation, suggest that this is a maternal-to-zygotic-transition gene regulatory block.
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Wilson CA, Postlethwait JH. A maternal-to-zygotic-transition gene block on the zebrafish sex chromosome. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.06.570431. [PMID: 38106184 PMCID: PMC10723407 DOI: 10.1101/2023.12.06.570431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Wild zebrafish (Danio rerio) have a ZZ/ZW chromosomal sex determination system with the major sex locus on the right arm of chromosome-4 (Chr4R) near the largest heterochromatic block in the genome, suggesting the hypothesis that the Chr4R transcriptome might be different from the rest of the genome. We conducted an RNA-seq analysis of adult ZW ovaries and ZZ testes and identified four regions of Chr4 with different gene expression profiles. Unique in the genome, protein-coding genes in a 41.7 Mb section (Region-2) were expressed in testis but silent in ovary. The AB lab strain, which lacks sex chromosomes, verified this result, showing that testis-biased gene expression in Region-2 depends on gonad biology, not on sex-determining mechanism. RNA-seq analyses in female and male brain and liver validated few transcripts from Region-2 in somatic cells, but without sex-specificity. Region-2 corresponds to the heterochromatic portion of Chr4R and its content of genes and repetitive elements distinguishes it from the rest of the genome. In Region-2, protein-coding genes lack human orthologs; it has zinc finger genes expressed early in zygotic genome activation; it has maternal 5S rRNA genes, maternal spliceosome genes, a concentration of tRNA genes, and an distinct set of repetitive elements. The colocalization of 1) genes silenced in ovaries but not in testes that are 2) expressed in embryos briefly at the onset of zygotic genome activation; 3) maternal-specific genes for translation machinery; 4) maternal-specific spliceosome components; and 4) adjacent genes encoding miR-430, which mediates maternal transcript degradation, suggest that this is a Maternal-to-Zygotic-Transition Gene Regulatory Block.
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Dyomin A, Galkina S, Ilina A, Gaginskaya E. Single Copies of the 5S rRNA Inserted into 45S rDNA Intergenic Spacers in the Genomes of Nototheniidae (Perciformes, Actinopterygii). Int J Mol Sci 2023; 24:ijms24087376. [PMID: 37108537 PMCID: PMC10138776 DOI: 10.3390/ijms24087376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 04/13/2023] [Accepted: 04/14/2023] [Indexed: 04/29/2023] Open
Abstract
In the vast majority of Animalia genomes, the 5S rRNA gene repeats are located on chromosomes outside of the 45S rDNA arrays of the nucleolar organiser (NOR). We analysed the genomic databases available and found that a 5S rDNA sequence is inserted into the intergenic spacer (IGS) between the 45S rDNA repeats in ten species of the family Nototheniidae (Perciformes, Actinopterigii). We call this sequence the NOR-5S rRNA gene. Along with Testudines and Crocodilia, this is the second case of a close association between four rRNA genes within one repetitive unit in deuterostomes. In both cases, NOR-5S is oriented opposite the 45S rDNA. None of the three nucleotide substitutions compared to the canonical 5S rRNA gene influenced the 5S rRNA secondary structure. In transcriptomes of the Patagonian toothfish, we only found NOR-5S rRNA reads in ovaries and early embryos, but not in testis or somatic tissues of adults. Thus, we consider the NOR-5S gene to be a maternal-type 5S rRNA template. The colocalization of the 5S and 45S ribosomal genes appears to be essential for the equimolar production of all four rRNAs in the species that show rDNA amplification during oogenesis. Most likely, the integration of 5S and NOR rRNA genes occurred prior to Nototheniidae lineage diversification.
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Affiliation(s)
- Alexander Dyomin
- Biological Faculty, St. Petersburg State University, Universitetskaya Emb. 7/9, St. Petersburg 199034, Russia
| | - Svetlana Galkina
- Biological Faculty, St. Petersburg State University, Universitetskaya Emb. 7/9, St. Petersburg 199034, Russia
| | - Arina Ilina
- Biological Faculty, St. Petersburg State University, Universitetskaya Emb. 7/9, St. Petersburg 199034, Russia
| | - Elena Gaginskaya
- Biological Faculty, St. Petersburg State University, Universitetskaya Emb. 7/9, St. Petersburg 199034, Russia
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Watt KE, Macintosh J, Bernard G, Trainor PA. RNA Polymerases I and III in development and disease. Semin Cell Dev Biol 2023; 136:49-63. [PMID: 35422389 PMCID: PMC9550887 DOI: 10.1016/j.semcdb.2022.03.027] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 03/18/2022] [Accepted: 03/21/2022] [Indexed: 12/18/2022]
Abstract
Ribosomes are macromolecular machines that are globally required for the translation of all proteins in all cells. Ribosome biogenesis, which is essential for cell growth, proliferation and survival, commences with transcription of a variety of RNAs by RNA Polymerases I and III. RNA Polymerase I (Pol I) transcribes ribosomal RNA (rRNA), while RNA Polymerase III (Pol III) transcribes 5S ribosomal RNA and transfer RNAs (tRNA) in addition to a wide variety of small non-coding RNAs. Interestingly, despite their global importance, disruptions in Pol I and Pol III function result in tissue-specific developmental disorders, with craniofacial anomalies and leukodystrophy/neurodegenerative disease being among the most prevalent. Furthermore, pathogenic variants in genes encoding subunits shared between Pol I and Pol III give rise to distinct syndromes depending on whether Pol I or Pol III function is disrupted. In this review, we discuss the global roles of Pol I and III transcription, the consequences of disruptions in Pol I and III transcription, disorders arising from pathogenic variants in Pol I and Pol III subunits, and mechanisms underpinning their tissue-specific phenotypes.
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Affiliation(s)
- Kristin En Watt
- Stowers Institute for Medical Research, Kansas City, MO, USA
| | - Julia Macintosh
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada; Child Health and Human Development Program, Research Institute of the McGill University Health Center, Montreal, QC, Canada
| | - Geneviève Bernard
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada; Child Health and Human Development Program, Research Institute of the McGill University Health Center, Montreal, QC, Canada; Departments of Pediatrics and Human Genetics, McGill University, Montreal, QC, Canada; Department of Specialized Medicine, Division of Medical Genetics, McGill University Health Center, Montreal, QC, Canada.
| | - Paul A Trainor
- Stowers Institute for Medical Research, Kansas City, MO, USA; Department of Anatomy & Cell Biology, University of Kansas Medical Center, Kansas City, KS, USA.
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Leesch F, Lorenzo-Orts L, Pribitzer C, Grishkovskaya I, Roehsner J, Chugunova A, Matzinger M, Roitinger E, Belačić K, Kandolf S, Lin TY, Mechtler K, Meinhart A, Haselbach D, Pauli A. A molecular network of conserved factors keeps ribosomes dormant in the egg. Nature 2023; 613:712-720. [PMID: 36653451 PMCID: PMC7614339 DOI: 10.1038/s41586-022-05623-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Accepted: 12/02/2022] [Indexed: 01/20/2023]
Abstract
Ribosomes are produced in large quantities during oogenesis and are stored in the egg. However, the egg and early embryo are translationally repressed1-4. Here, using mass spectrometry and cryo-electron microscopy analyses of ribosomes isolated from zebrafish (Danio rerio) and Xenopus laevis eggs and embryos, we provide molecular evidence that ribosomes transition from a dormant state to an active state during the first hours of embryogenesis. Dormant ribosomes are associated with four conserved factors that form two modules, consisting of Habp4-eEF2 and death associated protein 1b (Dap1b) or Dap in complex with eIF5a. Both modules occupy functionally important sites and act together to stabilize ribosomes and repress translation. Dap1b (also known as Dapl1 in mammals) is a newly discovered translational inhibitor that stably inserts into the polypeptide exit tunnel. Addition of recombinant zebrafish Dap1b protein is sufficient to block translation and reconstitute the dormant egg ribosome state in a mammalian translation extract in vitro. Thus, a developmentally programmed, conserved ribosome state has a key role in ribosome storage and translational repression in the egg.
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Affiliation(s)
- Friederike Leesch
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Laura Lorenzo-Orts
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria.
| | - Carina Pribitzer
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
| | - Irina Grishkovskaya
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
| | - Josef Roehsner
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Anastasia Chugunova
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
| | - Manuel Matzinger
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
| | - Elisabeth Roitinger
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
| | - Katarina Belačić
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Susanne Kandolf
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
| | - Tzi-Yang Lin
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Karl Mechtler
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
| | - Anton Meinhart
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria
| | - David Haselbach
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria.
| | - Andrea Pauli
- Research Institute of Molecular Pathology (IMP), Vienna BioCenter (VBC), Vienna, Austria.
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Mlinarec J, Boštjančić LL, Malenica N, Jurković A, Boland T, Yakovlev SS, Besendorfer V. Structure and Methylation of 35S rDNA in Allopolyploids Anemone multifida (2 n = 4 x = 32, BBDD) and Anemone baldensis (2 n = 6 x = 48, AABBDD) and Their Parental Species Show Evidence of Nucleolar Dominance. FRONTIERS IN PLANT SCIENCE 2022; 13:908218. [PMID: 35874014 PMCID: PMC9296772 DOI: 10.3389/fpls.2022.908218] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 06/07/2022] [Indexed: 05/26/2023]
Abstract
Transcriptional silencing of 35S rDNA loci inherited from one parental species is occurring relatively frequently in allopolyploids. However, molecular mechanisms by which it is selected for transcriptional silencing remain unclear. We applied NGS, silver staining and bisulfite sequencing to study the structure, expression and methylation landscape of 35S rDNA in two allopolyploids of common origin, allotetraploid Anemone multifida (2n = 4x = 32, genome composition BBDD) and allohexaploid A. baldensis (2n = 6x = 48, AABBDD), and their genome donors, A. sylvestris (2n = 16, AA), A. cylindrica (2n = 16, BB) and A. parviflora (2n = 16, DD). The size of the recovered 35S rDNA units varied from 10,489 bp in A. cylindrica to 12,084 bp in A. sylvestris. Anemone showed an organization typical of most ribosomal 35S rDNA composed of NTS, ETS, rRNA genes, TTS and TIS with structural features of plant IGS sequences and all functional elements needed for rRNA gene activity. The NTS was more variable than the ETS and consisted of SRs which are highly variable among Anemone. Five to six CpG-rich islands were found within the ETS. CpG island located adjacent to the transcription initiation site (TIS) was highly variable regarding the sequence size and methylation level and exhibited in most of the species lower levels of methylation than CpG islands located adjacent to the 18S rRNA gene. Our results uncover hypomethylation of A. sylvestris- and A. parviflora-derived 35S rDNA units in allopolyploids A. multifida and A. baldensis. Hypomethylation of A. parviflora-derived 35S rDNA was more prominent in A. baldensis than in A. multifida. We showed that A. baldensis underwent coupled A. sylvestris-derived 35S rDNA array expansion and A. parviflora-derived 35S rDNA copy number decrease that was accompanied by lower methylation level of A. sylvestris-derived 35S rDNA units in comparison to A. parviflora-derived 35S rDNA units. These observations suggest that in A. baldensis nucleolar dominance is directed toward A. sylvestris-derived chromosomes. This work broadens our current knowledge of the 35S rDNA organization in Anemone and provides evidence of the progenitor-specific 35S rDNA methylation in nucleolar dominance.
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Affiliation(s)
| | - Ljudevit Luka Boštjančić
- LOEWE Centre for Translational Biodiversity Genomics (LOEWE-TBG), Senckenberg Biodiversity and Climate Research Centre, Senckenberg Gesellschaft für Naturforschung, Frankfurt, Germany
- Department of Computer Science, ICube, UMR 7357, CNRS, Centre de Recherche en Biomédecine de Strasbourg, University of Strasbourg, Strasbourg, France
| | - Nenad Malenica
- Division of Molecular Biology, Department of Biology, University of Zagreb, Horvatovac, Croatia
| | - Adela Jurković
- Division of Molecular Biology, Department of Biology, University of Zagreb, Horvatovac, Croatia
| | - Todd Boland
- Memorial University of Newfoundland’s Botanical Gardens, St. John’s, NL, Canada
| | - Sonja Siljak Yakovlev
- CNRS, AgroParisTech, Ecologie Systématique Evolution, Université Paris-Saclay, Orsay, France
| | - Višnja Besendorfer
- Division of Molecular Biology, Department of Biology, University of Zagreb, Horvatovac, Croatia
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Davidian AG, Dyomin AG, Galkina SA, Makarova NE, Dmitriev SE, Gaginskaya ER. 45S rDNA Repeats of Turtles and Crocodiles Harbor a Functional 5S rRNA Gene Specifically Expressed in Oocytes. Mol Biol Evol 2021; 39:6432055. [PMID: 34905062 PMCID: PMC8789306 DOI: 10.1093/molbev/msab324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In most eukaryotic genomes, tandemly repeated copies of 5S rRNA genes are clustered outside the nucleolus organizer region (NOR), which normally encodes three other major rRNAs: 18S, 5.8S, and 28S. Our analysis of turtle rDNA sequences has revealed a 5S rDNA insertion into the NOR intergenic spacer in antisense orientation. The insertion (hereafter called NOR-5S rRNA gene) has a length of 119 bp and coexists with the canonical 5S rDNA clusters outside the NOR. Despite the ∼20% nucleotide difference between the two 5S gene sequences, their internal control regions for RNA polymerase III are similar. Using the turtle Trachemys scripta as a model species, we showed the NOR-5S rDNA specific expression in oocytes. This expression is concurrent with the NOR rDNA amplification during oocyte growth. We show that in vitellogenic oocytes, the NOR-5S rRNA prevails over the canonical 5S rRNA in the ribosomes, suggesting a role of modified ribosomes in oocyte-specific translation. The orders Testudines and Crocodilia seem to be the only taxa of vertebrates with such a peculiar rDNA organization. We speculate that the amplification of the 5S rRNA genes as a part of the NOR DNA during oogenesis provides a dosage balance between transcription of all the four ribosomal RNAs while producing a maternal pool of extra ribosomes. We further hypothesize that the NOR-5S rDNA insertion appeared in the Archelosauria clade during the Permian period and was lost later in the ancestors of Aves.
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Affiliation(s)
- Asya G Davidian
- Biological Faculty, Saint Petersburg State University, Saint Petersburg, Russia
| | - Alexander G Dyomin
- Laboratory of Cell Technologies, Saratov State Medical University, Saratov, Russia
| | - Svetlana A Galkina
- Biological Faculty, Saint Petersburg State University, Saint Petersburg, Russia
| | - Nadezhda E Makarova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Sergey E Dmitriev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Elena R Gaginskaya
- Biological Faculty, Saint Petersburg State University, Saint Petersburg, Russia
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11
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Mercer M, Jang S, Ni C, Buszczak M. The Dynamic Regulation of mRNA Translation and Ribosome Biogenesis During Germ Cell Development and Reproductive Aging. Front Cell Dev Biol 2021; 9:710186. [PMID: 34805139 PMCID: PMC8595405 DOI: 10.3389/fcell.2021.710186] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 10/07/2021] [Indexed: 01/21/2023] Open
Abstract
The regulation of mRNA translation, both globally and at the level of individual transcripts, plays a central role in the development and function of germ cells across species. Genetic studies using flies, worms, zebrafish and mice have highlighted the importance of specific RNA binding proteins in driving various aspects of germ cell formation and function. Many of these mRNA binding proteins, including Pumilio, Nanos, Vasa and Dazl have been conserved through evolution, specifically mark germ cells, and carry out similar functions across species. These proteins typically influence mRNA translation by binding to specific elements within the 3′ untranslated region (UTR) of target messages. Emerging evidence indicates that the global regulation of mRNA translation also plays an important role in germ cell development. For example, ribosome biogenesis is often regulated in a stage specific manner during gametogenesis. Moreover, oocytes need to produce and store a sufficient number of ribosomes to support the development of the early embryo until the initiation of zygotic transcription. Accumulating evidence indicates that disruption of mRNA translation regulatory mechanisms likely contributes to infertility and reproductive aging in humans. These findings highlight the importance of gaining further insights into the mechanisms that control mRNA translation within germ cells. Future work in this area will likely have important impacts beyond germ cell biology.
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Affiliation(s)
- Marianne Mercer
- Department of Molecular Biology, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Seoyeon Jang
- Department of Molecular Biology, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Chunyang Ni
- Department of Molecular Biology, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Michael Buszczak
- Department of Molecular Biology, The University of Texas Southwestern Medical Center, Dallas, TX, United States
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12
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Regulatory roles of nucleolus organizer region-derived long non-coding RNAs. Mamm Genome 2021; 33:402-411. [PMID: 34436664 DOI: 10.1007/s00335-021-09906-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 08/20/2021] [Indexed: 12/13/2022]
Abstract
The nucleolus is the largest sub-nuclear domain, serving primarily as the place for ribosome biogenesis. A delicately regulated function of the nucleolus is vital to the cell not only for maintaining proper protein synthesis but is also tightly associated with responses to different types of cellular stresses. Recently, several long non-coding RNAs (lncRNAs) were found to be part of the regulatory network that modulate nucleolar functions. Several of these lncRNAs are encoded in the ribosomal DNA (rDNA) repeats or are transcribed from the genomic regions that are located near the nucleolus organizer regions (NORs). In this review, we first discuss the current understanding of the sequence of the NORs and variations between different NORs. We then focus on the NOR-derived lncRNAs in mammalian cells and their functions in rRNA transcription and the organization of nucleolar structure under different cellular conditions. The identification of these lncRNAs reveals great potential of the NORs in harboring novel genes involved in the regulation of nucleolar functions.
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13
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Jaafar M, Paraqindes H, Gabut M, Diaz JJ, Marcel V, Durand S. 2'O-Ribose Methylation of Ribosomal RNAs: Natural Diversity in Living Organisms, Biological Processes, and Diseases. Cells 2021; 10:1948. [PMID: 34440717 PMCID: PMC8393311 DOI: 10.3390/cells10081948] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 07/28/2021] [Accepted: 07/29/2021] [Indexed: 01/21/2023] Open
Abstract
Recent findings suggest that ribosomes, the translational machineries, can display a distinct composition depending on physio-pathological contexts. Thanks to outstanding technological breakthroughs, many studies have reported that variations of rRNA modifications, and more particularly the most abundant rRNA chemical modification, the rRNA 2'O-ribose methylation (2'Ome), intrinsically occur in many organisms. In the last 5 years, accumulating reports have illustrated that rRNA 2'Ome varies in human cell lines but also in living organisms (yeast, plant, zebrafish, mouse, human) during development and diseases. These rRNA 2'Ome variations occur either within a single cell line, organ, or patient's sample (i.e., intra-variability) or between at least two biological conditions (i.e., inter-variability). Thus, the ribosomes can tolerate the absence of 2'Ome at some specific positions. These observations question whether variations in rRNA 2'Ome could provide ribosomes with particular translational regulatory activities and functional specializations. Here, we compile recent studies supporting the heterogeneity of ribosome composition at rRNA 2'Ome level and provide an overview of the natural diversity in rRNA 2'Ome that has been reported up to now throughout the kingdom of life. Moreover, we discuss the little evidence that suggests that variations of rRNA 2'Ome can effectively impact the ribosome activity and contribute to the etiology of some human diseases.
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Affiliation(s)
| | | | | | | | - Virginie Marcel
- Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon, Université Claude Bernard Lyon 1, Centre Léon Bérard, CEDEX 08, F-69373 Lyon, France; (M.J.); (H.P.); (M.G.); (J.-J.D.)
| | - Sébastien Durand
- Inserm U1052, CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon, Université de Lyon, Université Claude Bernard Lyon 1, Centre Léon Bérard, CEDEX 08, F-69373 Lyon, France; (M.J.); (H.P.); (M.G.); (J.-J.D.)
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14
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Norris K, Hopes T, Aspden JL. Ribosome heterogeneity and specialization in development. WILEY INTERDISCIPLINARY REVIEWS. RNA 2021; 12:e1644. [PMID: 33565275 PMCID: PMC8647923 DOI: 10.1002/wrna.1644] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 01/08/2021] [Accepted: 01/11/2021] [Indexed: 12/13/2022]
Abstract
Regulation of protein synthesis is a vital step in controlling gene expression, especially during development. Over the last 10 years, it has become clear that rather than being homogeneous machines responsible for mRNA translation, ribosomes are highly heterogeneous and can play an active part in translational regulation. These "specialized ribosomes" comprise of specific protein and/or rRNA components, which are required for the translation of particular mRNAs. However, while there is extensive evidence for ribosome heterogeneity, support for specialized functions is limited. Recent work in a variety of developmental model organisms has shed some light on the biological relevance of ribosome heterogeneity. Tissue-specific expression of ribosomal components along with phenotypic analysis of ribosomal gene mutations indicate that ribosome heterogeneity and potentially specialization are common in key development processes like embryogenesis, spermatogenesis, oogenesis, body patterning, and neurogenesis. Several examples of ribosome specialization have now been proposed but strong links between ribosome heterogeneity, translation of specific mRNAs by defined mechanisms, and role of these translation events remain elusive. Furthermore, several studies have indicated that heterogeneous ribosome populations are a product of tissue-specific expression rather than specialized function and that ribosomal protein phenotypes are the result of extra-ribosomal function or overall reduced ribosome levels. Many important questions still need to be addressed in order to determine the functional importance of ribosome heterogeneity to development and disease, which is likely to vary across systems. It will be essential to dissect these issues to fully understand diseases caused by disruptions to ribosomal composition, such as ribosomopathies. This article is categorized under: Translation > Translation Regulation Translation > Ribosome Structure/Function RNA in Disease and Development > RNA in Development.
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Affiliation(s)
- Karl Norris
- Faculty of Biological Sciences, School of Molecular and Cellular BiologyUniversity of LeedsLeedsUK
- Leeds OmicsUniversity of LeedsLeedsUK
| | - Tayah Hopes
- Faculty of Biological Sciences, School of Molecular and Cellular BiologyUniversity of LeedsLeedsUK
- Leeds OmicsUniversity of LeedsLeedsUK
| | - Julie Louise Aspden
- Faculty of Biological Sciences, School of Molecular and Cellular BiologyUniversity of LeedsLeedsUK
- Leeds OmicsUniversity of LeedsLeedsUK
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15
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Phelps WA, Carlson AE, Lee MT. Optimized design of antisense oligomers for targeted rRNA depletion. Nucleic Acids Res 2021; 49:e5. [PMID: 33221877 PMCID: PMC7797071 DOI: 10.1093/nar/gkaa1072] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Revised: 10/01/2020] [Accepted: 10/21/2020] [Indexed: 11/14/2022] Open
Abstract
RNA sequencing (RNA-seq) is extensively used to quantify gene expression transcriptome-wide. Although often paired with polyadenylate (poly(A)) selection to enrich for messenger RNA (mRNA), many applications require alternate approaches to counteract the high proportion of ribosomal RNA (rRNA) in total RNA. Recently, digestion using RNaseH and antisense DNA oligomers tiling target rRNAs has emerged as an alternative to commercial rRNA depletion kits. Here, we present a streamlined, more economical RNaseH-mediated rRNA depletion with substantially lower up-front costs, using shorter antisense oligos only sparsely tiled along the target RNA in a 5-min digestion reaction. We introduce a novel Web tool, Oligo-ASST, that simplifies oligo design to target regions with optimal thermodynamic properties, and additionally can generate compact, common oligo pools that simultaneously target divergent RNAs, e.g. across different species. We demonstrate the efficacy of these strategies by generating rRNA-depletion oligos for Xenopus laevis and for zebrafish, which expresses two distinct versions of rRNAs during embryogenesis. The resulting RNA-seq libraries reduce rRNA to <5% of aligned reads, on par with poly(A) selection, and also reveal expression of many non-adenylated RNA species. Oligo-ASST is freely available at https://mtleelab.pitt.edu/oligo to design antisense oligos for any taxon or to target any abundant RNA for depletion.
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Affiliation(s)
- Wesley A Phelps
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Anne E Carlson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Miler T Lee
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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16
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Tao B, Lo LJ, Peng J, He J. rDNA subtypes and their transcriptional expression in zebrafish at different developmental stages. Biochem Biophys Res Commun 2020; 529:819-825. [PMID: 32571523 DOI: 10.1016/j.bbrc.2020.05.196] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 05/26/2020] [Indexed: 01/21/2023]
Abstract
Eukaryotic 18S, 5.8S and 28S rRNAs are processed from a single transcript transcribed from the 45S rDNA gene, which is normally tandemly arrayed over hundred copies in a genome. Recently, a maternal (M) subtype and a somatic (S) subtype of rDNA were identified in zebrafish, with M-subtype on chromosome 4 and S-subtype on chromosome 5. It appears that the M-subtype is only expressed in eggs whilst the expression of the S-subtype is coupled with the initiation of zygotic gene expression. In this report, we identified three novel but transcriptionally inactive 18S variants in zebrafish genome with chromosome location different from the M- and S-subtype, suggesting translocation of 18S rDNA fragment during zebrafish evolution. Furthermore, we confirmed that the unfertilized eggs only have the M-subtype transcripts while brain, heart and liver have only the S-subtype transcripts. Both the M- and S-subtype transcripts were detected in female gonad. Our results support that the expression of different subtypes of rDNA is differentially regulated to meet the requirement for 'specialized ribosomes' during different developmental stages.
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Affiliation(s)
- Boxiang Tao
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Li Jan Lo
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Jinrong Peng
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China.
| | - Jin He
- MOE Key Laboratory for Molecular Animal Nutrition, College of Animal Sciences, Zhejiang University, Hangzhou, 310058, China.
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17
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Li D, Wang J. Ribosome heterogeneity in stem cells and development. J Cell Biol 2020; 219:e202001108. [PMID: 32330234 PMCID: PMC7265316 DOI: 10.1083/jcb.202001108] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 04/03/2020] [Accepted: 04/06/2020] [Indexed: 02/08/2023] Open
Abstract
Translation control is critical to regulate protein expression. By directly adjusting protein levels, cells can quickly respond to dynamic transitions during stem cell differentiation and embryonic development. Ribosomes are multisubunit cellular assemblies that mediate translation. Previously seen as invariant machines with the same composition of components in all conditions, recent studies indicate that ribosomes are heterogeneous and that different ribosome types can preferentially translate specific subsets of mRNAs. Such heterogeneity and specialized translation functions are very important in stem cells and development, as they allow cells to quickly respond to stimuli through direct changes of protein abundance. In this review, we discuss ribosome heterogeneity that arises from multiple features of rRNAs, including rRNA variants and rRNA modifications, and ribosomal proteins, including their stoichiometry, compositions, paralogues, and posttranslational modifications. We also discuss alterations of ribosome-associated proteins (RAPs), with a particular focus on their consequent specialized translational control in stem cells and development.
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Affiliation(s)
- Dan Li
- Department of Cell, Developmental and Regenerative Biology, The Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY
- The Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Jianlong Wang
- Department of Cell, Developmental and Regenerative Biology, The Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY
- The Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine, Columbia Center for Human Development, Columbia University Irving Medical Center, New York, NY
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18
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Ford D. Ribosomal heterogeneity - A new inroad for pharmacological innovation. Biochem Pharmacol 2020; 175:113874. [PMID: 32105657 DOI: 10.1016/j.bcp.2020.113874] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Accepted: 02/20/2020] [Indexed: 12/13/2022]
Abstract
The paradigm of ribosome usage in protein translation has shifted from a stance proposed as scientists began to unpick the genetic code that each mRNA was partnered by its own, unique ribosome to a rapid reversal of this view that ribosomes are completely interchangeable and simply recruited to mRNAs from a completely homogenous cellular pool. Evidence that the ribosomal proteome, ribosomal gene transcriptome and ribosome protein and RNA modifications differ between cells and tissues points to the fact that ribosomes are heterogeneous in their composition and have a degree of specialisation in their function. It has also been posited that the tissue-specificity of ribosome diseases provides an indication of functional ribosome heterogeneity, but there are substantial caveats to this interpretation. Only now have proteomic technologies developed to a level enabling accurate stoichiometric comparison of the abundance of specific ribosomal proteins in actively translating ribosomes and to measure protein in non-denatured ribosomes. This poises the field for the provocation that ribosome heterogeneity offers a novel and powerful inroad for the pharmacological targeting of disease. Such ribosome-targeted treatments may extend beyond specific ribosomopathies through strategies such as targeting features of ribosomes that are unique to diseased cells, particularly cancer cells, or to activated immune cells, as well as augmenting the action of other drugs through weakening the production of new proteins in target tissues. We may also be able to harness the potential power in ribosome diversity and specialism to better tune synthetic biology for the production of pharmaceutical proteins.
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Affiliation(s)
- Dianne Ford
- Northumbria University, Northumberland Building, Northumberland Road, Newcastle upon Tyne, NE1 8ST, United Kingdom.
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19
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Dual-initiation promoters with intertwined canonical and TCT/TOP transcription start sites diversify transcript processing. Nat Commun 2020; 11:168. [PMID: 31924754 PMCID: PMC6954239 DOI: 10.1038/s41467-019-13687-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 11/19/2019] [Indexed: 12/26/2022] Open
Abstract
Variations in transcription start site (TSS) selection reflect diversity of preinitiation complexes and can impact on post-transcriptional RNA fates. Most metazoan polymerase II-transcribed genes carry canonical initiation with pyrimidine/purine (YR) dinucleotide, while translation machinery-associated genes carry polypyrimidine initiator (5’-TOP or TCT). By addressing the developmental regulation of TSS selection in zebrafish we uncovered a class of dual-initiation promoters in thousands of genes, including snoRNA host genes. 5’-TOP/TCT initiation is intertwined with canonical initiation and used divergently in hundreds of dual-initiation promoters during maternal to zygotic transition. Dual-initiation in snoRNA host genes selectively generates host and snoRNA with often different spatio-temporal expression. Dual-initiation promoters are pervasive in human and fruit fly, reflecting evolutionary conservation. We propose that dual-initiation on shared promoters represents a composite promoter architecture, which can function both coordinately and divergently to diversify RNAs. The functional significance of start site choice in promoter architectures is little understood. Here the authors identify in zebrafish development and mammalian cells a class of dual-initiation promoters, in which non-canonical YC dinucleotides reflecting 5’-TOP/TCT initiation are intertwined with canonical YR-initiation.
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20
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Genuth NR, Barna M. Heterogeneity and specialized functions of translation machinery: from genes to organisms. Nat Rev Genet 2019; 19:431-452. [PMID: 29725087 DOI: 10.1038/s41576-018-0008-z] [Citation(s) in RCA: 141] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Regulation of mRNA translation offers the opportunity to diversify the expression and abundance of proteins made from individual gene products in cells, tissues and organisms. Emerging evidence has highlighted variation in the composition and activity of several large, highly conserved translation complexes as a means to differentially control gene expression. Heterogeneity and specialized functions of individual components of the ribosome and of the translation initiation factor complexes eIF3 and eIF4F, which are required for recruitment of the ribosome to the mRNA 5' untranslated region, have been identified. In this Review, we summarize the evidence for selective mRNA translation by components of these macromolecular complexes as a means to dynamically control the translation of the proteome in time and space. We further discuss the implications of this form of gene expression regulation for a growing number of human genetic disorders associated with mutations in the translation machinery.
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Affiliation(s)
- Naomi R Genuth
- Departments of Genetics and Developmental Biology, Stanford University, Stanford, CA, USA.,Department of Biology, Stanford University, Stanford, CA, USA
| | - Maria Barna
- Departments of Genetics and Developmental Biology, Stanford University, Stanford, CA, USA.
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21
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Prakash V, Carson BB, Feenstra JM, Dass RA, Sekyrova P, Hoshino A, Petersen J, Guo Y, Parks MM, Kurylo CM, Batchelder JE, Haller K, Hashimoto A, Rundqivst H, Condeelis JS, Allis CD, Drygin D, Nieto MA, Andäng M, Percipalle P, Bergh J, Adameyko I, Farrants AKÖ, Hartman J, Lyden D, Pietras K, Blanchard SC, Vincent CT. Ribosome biogenesis during cell cycle arrest fuels EMT in development and disease. Nat Commun 2019; 10:2110. [PMID: 31068593 PMCID: PMC6506521 DOI: 10.1038/s41467-019-10100-8] [Citation(s) in RCA: 129] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 04/16/2019] [Indexed: 12/15/2022] Open
Abstract
Ribosome biogenesis is a canonical hallmark of cell growth and proliferation. Here we show that execution of Epithelial-to-Mesenchymal Transition (EMT), a migratory cellular program associated with development and tumor metastasis, is fueled by upregulation of ribosome biogenesis during G1/S arrest. This unexpected EMT feature is independent of species and initiating signal, and is accompanied by release of the repressive nucleolar chromatin remodeling complex (NoRC) from rDNA, together with recruitment of the EMT-driving transcription factor Snai1 (Snail1), RNA Polymerase I (Pol I) and the Upstream Binding Factor (UBF). EMT-associated ribosome biogenesis is also coincident with increased nucleolar recruitment of Rictor, an essential component of the EMT-promoting mammalian target of rapamycin complex 2 (mTORC2). Inhibition of rRNA synthesis in vivo differentiates primary tumors to a benign, Estrogen Receptor-alpha (ERα) positive, Rictor-negative phenotype and reduces metastasis. These findings implicate the EMT-associated ribosome biogenesis program with cellular plasticity, de-differentiation, cancer progression and metastatic disease.
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Affiliation(s)
- Varsha Prakash
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77, Stockholm, Sweden
- Department of Immunology, Genetics and Pathology, Uppsala University, 751 85, Uppsala, Sweden
| | - Brittany B Carson
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77, Stockholm, Sweden
| | - Jennifer M Feenstra
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77, Stockholm, Sweden
- Department of Immunology, Genetics and Pathology, Uppsala University, 751 85, Uppsala, Sweden
| | - Randall A Dass
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Petra Sekyrova
- Department of Immunology, Genetics and Pathology, Uppsala University, 751 85, Uppsala, Sweden
| | - Ayuko Hoshino
- Meyer Cancer Center, Weill Cornell Medicine, New York, NY, 10065, USA
- Department of Pediatrics and Cell and Developmental Biology, Weill Cornell Medicine College, New York, NY, 10065, USA
| | - Julian Petersen
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77, Stockholm, Sweden
- Department for Brain Research, Medical University of Vienna, 1090, Vienna, Austria
| | - Yuan Guo
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, S-10691, Stockholm, Sweden
| | - Matthew M Parks
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
- Meyer Cancer Center, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Chad M Kurylo
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
- Meyer Cancer Center, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Jake E Batchelder
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA
- Meyer Cancer Center, Weill Cornell Medicine, New York, NY, 10065, USA
| | - Kristian Haller
- Department of Laboratory Medicine, Center for Molecular Pathology, Lund University, Lund, SE-223 81, Sweden
| | - Ayako Hashimoto
- Meyer Cancer Center, Weill Cornell Medicine, New York, NY, 10065, USA
- Department of Pediatrics and Cell and Developmental Biology, Weill Cornell Medicine College, New York, NY, 10065, USA
| | - Helene Rundqivst
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, SE-171 77, Sweden
| | - John S Condeelis
- Gruss Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, 10461, NY, USA
- Department of Pathology, Montefiore Medical Center, Bronx, 10461, NY, USA
| | - C David Allis
- Laboratory of Chromatin Biology and Epigenetics, The Rockefeller University, New York, NY, 10065, USA
| | - Denis Drygin
- Pimera, Inc, 3210 Merryfield Row, San Diego, CA, 92121, USA
| | - M Angela Nieto
- Instituto de Neurociencias, CSIC-UMH, Alicante, 03550, Spain
| | - Michael Andäng
- Department of Immunology, Genetics and Pathology, Uppsala University, 751 85, Uppsala, Sweden
| | - Piergiorgio Percipalle
- Science Division, Biology Program, New York University Abu Dhabi, Abu Dhabi, 129188, UAE
| | - Jonas Bergh
- Department of Oncology and Pathology, Karolinska Institutet and University Hospital, S-171 76, Solna, Sweden
| | - Igor Adameyko
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77, Stockholm, Sweden
- Department for Brain Research, Medical University of Vienna, 1090, Vienna, Austria
| | - Ann-Kristin Östlund Farrants
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, S-10691, Stockholm, Sweden
| | - Johan Hartman
- Department of Oncology and Pathology, Karolinska Institutet and University Hospital, S-171 76, Solna, Sweden
| | - David Lyden
- Meyer Cancer Center, Weill Cornell Medicine, New York, NY, 10065, USA
- Department of Pediatrics and Cell and Developmental Biology, Weill Cornell Medicine College, New York, NY, 10065, USA
| | - Kristian Pietras
- Department of Laboratory Medicine, Center for Molecular Pathology, Lund University, Lund, SE-223 81, Sweden
| | - Scott C Blanchard
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA.
- Meyer Cancer Center, Weill Cornell Medicine, New York, NY, 10065, USA.
- Tri-Institutional Training Program in Chemical Biology, Weill Cornell Medicine, New York, NY, 10065, USA.
| | - C Theresa Vincent
- Department of Physiology and Pharmacology, Karolinska Institutet, 171 77, Stockholm, Sweden.
- Department of Immunology, Genetics and Pathology, Uppsala University, 751 85, Uppsala, Sweden.
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, 10065, USA.
- Meyer Cancer Center, Weill Cornell Medicine, New York, NY, 10065, USA.
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22
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Symonová R. Integrative rDNAomics-Importance of the Oldest Repetitive Fraction of the Eukaryote Genome. Genes (Basel) 2019; 10:genes10050345. [PMID: 31067804 PMCID: PMC6562748 DOI: 10.3390/genes10050345] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Revised: 04/17/2019] [Accepted: 04/25/2019] [Indexed: 02/06/2023] Open
Abstract
Nuclear ribosomal RNA (rRNA) genes represent the oldest repetitive fraction universal to all eukaryotic genomes. Their deeply anchored universality and omnipresence during eukaryotic evolution reflects in multiple roles and functions reaching far beyond ribosomal synthesis. Merely the copy number of non-transcribed rRNA genes is involved in mechanisms governing e.g., maintenance of genome integrity and control of cellular aging. Their copy number can vary in response to environmental cues, in cellular stress sensing, in development of cancer and other diseases. While reaching hundreds of copies in humans, there are records of up to 20,000 copies in fish and frogs and even 400,000 copies in ciliates forming thus a literal subgenome or an rDNAome within the genome. From the compositional and evolutionary dynamics viewpoint, the precursor 45S rDNA represents universally GC-enriched, highly recombining and homogenized regions. Hence, it is not accidental that both rDNA sequence and the corresponding rRNA secondary structure belong to established phylogenetic markers broadly used to infer phylogeny on multiple taxonomical levels including species delimitation. However, these multiple roles of rDNAs have been treated and discussed as being separate and independent from each other. Here, I aim to address nuclear rDNAs in an integrative approach to better assess the complexity of rDNA importance in the evolutionary context.
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Affiliation(s)
- Radka Symonová
- Faculty of Science, Department of Biology, University of Hradec Králové, 500 03 Hradec Králové, Czech Republic.
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23
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Genuth NR, Barna M. The Discovery of Ribosome Heterogeneity and Its Implications for Gene Regulation and Organismal Life. Mol Cell 2018; 71:364-374. [PMID: 30075139 DOI: 10.1016/j.molcel.2018.07.018get] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 07/08/2018] [Accepted: 07/16/2018] [Indexed: 05/27/2023]
Abstract
The ribosome has recently transitioned from being viewed as a passive, indiscriminate machine to a more dynamic macromolecular complex with specialized roles in the cell. Here, we discuss the historical milestones from the discovery of the ribosome itself to how this ancient machinery has gained newfound appreciation as a more regulatory participant in the central dogma of gene expression. The first emerging examples of direct changes in ribosome composition at the RNA and protein level, coupled with an increased awareness of the role individual ribosomal components play in the translation of specific mRNAs, is opening a new field of study centered on ribosome-mediated control of gene regulation. In this Perspective, we discuss our current understanding of the known functions for ribosome heterogeneity, including specialized translation of individual transcripts, and its implications for the regulation and expression of key gene regulatory networks. In addition, we suggest what the crucial next steps are to ascertain the extent of ribosome heterogeneity and specialization and its importance for regulation of the proteome within subcellular space, across different cell types, and during multi-cellular organismal development.
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Affiliation(s)
- Naomi R Genuth
- Department of Developmental Biology, Stanford University, Stanford, CA, 94305, USA; Department of Genetics, Stanford University, Stanford, CA, 94305, USA; Department of Biology, Stanford University, Stanford, CA, 94305, USA
| | - Maria Barna
- Department of Developmental Biology, Stanford University, Stanford, CA, 94305, USA; Department of Genetics, Stanford University, Stanford, CA, 94305, USA.
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24
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Genuth NR, Barna M. The Discovery of Ribosome Heterogeneity and Its Implications for Gene Regulation and Organismal Life. Mol Cell 2018; 71:364-374. [PMID: 30075139 PMCID: PMC6092941 DOI: 10.1016/j.molcel.2018.07.018] [Citation(s) in RCA: 260] [Impact Index Per Article: 43.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 07/08/2018] [Accepted: 07/16/2018] [Indexed: 12/24/2022]
Abstract
The ribosome has recently transitioned from being viewed as a passive, indiscriminate machine to a more dynamic macromolecular complex with specialized roles in the cell. Here, we discuss the historical milestones from the discovery of the ribosome itself to how this ancient machinery has gained newfound appreciation as a more regulatory participant in the central dogma of gene expression. The first emerging examples of direct changes in ribosome composition at the RNA and protein level, coupled with an increased awareness of the role individual ribosomal components play in the translation of specific mRNAs, is opening a new field of study centered on ribosome-mediated control of gene regulation. In this Perspective, we discuss our current understanding of the known functions for ribosome heterogeneity, including specialized translation of individual transcripts, and its implications for the regulation and expression of key gene regulatory networks. In addition, we suggest what the crucial next steps are to ascertain the extent of ribosome heterogeneity and specialization and its importance for regulation of the proteome within subcellular space, across different cell types, and during multi-cellular organismal development.
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Affiliation(s)
- Naomi R Genuth
- Department of Developmental Biology, Stanford University, Stanford, CA, 94305, USA; Department of Genetics, Stanford University, Stanford, CA, 94305, USA; Department of Biology, Stanford University, Stanford, CA, 94305, USA
| | - Maria Barna
- Department of Developmental Biology, Stanford University, Stanford, CA, 94305, USA; Department of Genetics, Stanford University, Stanford, CA, 94305, USA.
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25
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Walker-Kopp N, Jackobel AJ, Pannafino GN, Morocho PA, Xu X, Knutson BA. Treacher Collins syndrome mutations in Saccharomyces cerevisiae destabilize RNA polymerase I and III complex integrity. Hum Mol Genet 2018; 26:4290-4300. [PMID: 28973381 DOI: 10.1093/hmg/ddx317] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 08/08/2017] [Indexed: 01/16/2023] Open
Abstract
Treacher Collins syndrome (TCS) is a craniofacial disorder that is characterized by the malformation of the facial bones. Mutations in three genes (TCOF1, POLR1C and POLR1D) involved in RNA polymerase I (Pol I) transcription account for more than 90% of disease cases. Two of these TCS-associated genes, POLR1C and POLR1D, encode for essential Pol I/III subunits that form a heterodimer necessary for Pol I/III assembly, and many TCS mutations lie along their evolutionarily conserved dimerization interface. Here we elucidate the molecular basis of TCS mutations in Saccharomyces cerevisiae, and present a new model for how TCS mutations may disrupt Pol I and III complex integrity.
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Affiliation(s)
- Nancy Walker-Kopp
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Ashleigh J Jackobel
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Gianno N Pannafino
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Paola A Morocho
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA.,Department of Clinical Laboratory Science, Medical Scholars Master in Medical Technology Program, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Xia Xu
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Bruce A Knutson
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
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Locati MD, Pagano JFB, Abdullah F, Ensink WA, van Olst M, van Leeuwen S, Nehrdich U, Spaink HP, Rauwerda H, Jonker MJ, Dekker RJ, Breit TM. Identifying small RNAs derived from maternal- and somatic-type rRNAs in zebrafish development. Genome 2018; 61:371-378. [PMID: 29425468 DOI: 10.1139/gen-2017-0202] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
rRNAs are non-coding RNAs present in all prokaryotes and eukaryotes. In eukaryotes there are four rRNAs: 18S, 5.8S, 28S, originating from a common precursor (45S), and 5S. We have recently discovered the existence of two distinct developmental types of rRNA: a maternal-type, present in eggs and a somatic-type, expressed in adult tissues. Lately, next-generation sequencing has allowed the discovery of new small-RNAs deriving from longer non-coding RNAs, including small-RNAs from rRNAs (srRNAs). Here, we systemically investigated srRNAs of maternal- or somatic-type 18S, 5.8S, 28S, with small-RNAseq from many zebrafish developmental stages. We identified new srRNAs for each rRNA. For 5.8S, we found srRNA consisting of the 5' or 3' halves, with only the latter having different sequence for the maternal- and somatic-types. For 18S, we discovered 21 nt srRNA from the 5' end of the 18S rRNA with a striking resemblance to microRNAs; as it is likely processed from a stem-loop precursor and present in human and mouse Argonaute-complexed small-RNA. For 28S, an abundant 80 nt srRNA from the 3' end of the 28S rRNA was found. The expression levels during embryogenesis of these srRNA indicate they are not generated from rRNA degradation and might have a role in the zebrafish development.
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Affiliation(s)
- Mauro D Locati
- a RNA Biology & Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Johanna F B Pagano
- a RNA Biology & Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Farah Abdullah
- a RNA Biology & Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Wim A Ensink
- a RNA Biology & Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Marina van Olst
- a RNA Biology & Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Selina van Leeuwen
- a RNA Biology & Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Ulrike Nehrdich
- b Department of Molecular Cell Biology, Institute of Biology, Leiden University, Gorlaeus Laboratories - Cell Observatorium, Leiden 2333 CE, the Netherlands
| | - Herman P Spaink
- b Department of Molecular Cell Biology, Institute of Biology, Leiden University, Gorlaeus Laboratories - Cell Observatorium, Leiden 2333 CE, the Netherlands
| | - Han Rauwerda
- a RNA Biology & Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Martijs J Jonker
- a RNA Biology & Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Rob J Dekker
- a RNA Biology & Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Timo M Breit
- a RNA Biology & Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
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27
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Locati MD, Pagano JFB, Girard G, Ensink WA, van Olst M, van Leeuwen S, Nehrdich U, Spaink HP, Rauwerda H, Jonker MJ, Dekker RJ, Breit TM. Expression of distinct maternal and somatic 5.8S, 18S, and 28S rRNA types during zebrafish development. RNA (NEW YORK, N.Y.) 2017; 23:1188-1199. [PMID: 28500251 PMCID: PMC5513064 DOI: 10.1261/rna.061515.117] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 05/09/2017] [Indexed: 05/27/2023]
Abstract
There is mounting evidence that the ribosome is not a static translation machinery, but a cell-specific, adaptive system. Ribosomal variations have mostly been studied at the protein level, even though the essential transcriptional functions are primarily performed by rRNAs. At the RNA level, oocyte-specific 5S rRNAs are long known for Xenopus. Recently, we described for zebrafish a similar system in which the sole maternal-type 5S rRNA present in eggs is replaced completely during embryonic development by a somatic-type. Here, we report the discovery of an analogous system for the 45S rDNA elements: 5.8S, 18S, and 28S. The maternal-type 5.8S, 18S, and 28S rRNA sequences differ substantially from those of the somatic-type, plus the maternal-type rRNAs are also replaced by the somatic-type rRNAs during embryogenesis. We discuss the structural and functional implications of the observed sequence differences with respect to the translational functions of the 5.8S, 18S, and 28S rRNA elements. Finally, in silico evidence suggests that expansion segments (ES) in 18S rRNA, previously implicated in ribosome-mRNA interaction, may have a preference for interacting with specific mRNA genes. Taken together, our findings indicate that two distinct types of ribosomes exist in zebrafish during development, each likely conducting the translation machinery in a unique way.
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MESH Headings
- Animals
- Base Pairing
- Base Sequence
- DNA, Ribosomal/genetics
- Embryo, Nonmammalian/cytology
- Embryo, Nonmammalian/metabolism
- Nucleic Acid Conformation
- RNA Processing, Post-Transcriptional
- RNA, Ribosomal, 18S/genetics
- RNA, Ribosomal, 18S/metabolism
- RNA, Ribosomal, 28S/genetics
- RNA, Ribosomal, 28S/metabolism
- RNA, Ribosomal, 5.8S/genetics
- RNA, Ribosomal, 5.8S/metabolism
- Ribosomes/metabolism
- Sequence Alignment
- Zebrafish/genetics
- Zebrafish/growth & development
- Zebrafish/metabolism
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Affiliation(s)
- Mauro D Locati
- RNA Biology and Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Johanna F B Pagano
- RNA Biology and Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Geneviève Girard
- RNA Biology and Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Wim A Ensink
- RNA Biology and Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Marina van Olst
- RNA Biology and Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Selina van Leeuwen
- RNA Biology and Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Ulrike Nehrdich
- Department of Molecular Cell Biology, Institute of Biology, Leiden University, Gorlaeus Laboratories-Cell Observatorium, Leiden 2333 CE, the Netherlands
| | - Herman P Spaink
- Department of Molecular Cell Biology, Institute of Biology, Leiden University, Gorlaeus Laboratories-Cell Observatorium, Leiden 2333 CE, the Netherlands
| | - Han Rauwerda
- RNA Biology and Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Martijs J Jonker
- RNA Biology and Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Rob J Dekker
- RNA Biology and Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
| | - Timo M Breit
- RNA Biology and Applied Bioinformatics Research Group, Swammerdam Institute for Life Sciences, Faculty of Science, University of Amsterdam, Amsterdam 1090 GE, the Netherlands
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Higher-order organisation of extremely amplified, potentially functional and massively methylated 5S rDNA in European pikes (Esox sp.). BMC Genomics 2017; 18:391. [PMID: 28521734 PMCID: PMC5437419 DOI: 10.1186/s12864-017-3774-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 05/09/2017] [Indexed: 12/16/2022] Open
Abstract
Background Pikes represent an important genus (Esox) harbouring a pre-duplication karyotype (2n = 2x = 50) of economically important salmonid pseudopolyploids. Here, we have characterized the 5S ribosomal RNA genes (rDNA) in Esox lucius and its closely related E. cisalpinus using cytogenetic, molecular and genomic approaches. Intragenomic homogeneity and copy number estimation was carried out using Illumina reads. The higher-order structure of rDNA arrays was investigated by the analysis of long PacBio reads. Position of loci on chromosomes was determined by FISH. DNA methylation was analysed by methylation-sensitive restriction enzymes. Results The 5S rDNA loci occupy exclusively (peri)centromeric regions on 30–38 acrocentric chromosomes in both E. lucius and E. cisalpinus. The large number of loci is accompanied by extreme amplification of genes (>20,000 copies), which is to the best of our knowledge one of the highest copy number of rRNA genes in animals ever reported. Conserved secondary structures of predicted 5S rRNAs indicate that most of the amplified genes are potentially functional. Only few SNPs were found in genic regions indicating their high homogeneity while intergenic spacers were more heterogeneous and several families were identified. Analysis of 10–30 kb-long molecules sequenced by the PacBio technology (containing about 40% of total 5S rDNA) revealed that the vast majority (96%) of genes are organised in large several kilobase-long blocks. Dispersed genes or short tandems were less common (4%). The adjacent 5S blocks were directly linked, separated by intervening DNA and even inverted. The 5S units differing in the intergenic spacers formed both homogeneous and heterogeneous (mixed) blocks indicating variable degree of homogenisation between the loci. Both E. lucius and E. cisalpinus 5S rDNA was heavily methylated at CG dinucleotides. Conclusions Extreme amplification of 5S rRNA genes in the Esox genome occurred in the absence of significant pseudogenisation suggesting its recent origin and/or intensive homogenisation processes. The dense methylation of units indicates that powerful epigenetic mechanisms have evolved in this group of fish to silence amplified genes. We discuss how the higher-order repeat structures impact on homogenisation of 5S rDNA in the genome. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3774-7) contains supplementary material, which is available to authorized users.
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