1
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Mabin JW, Lewis PW, Brow DA, Dvinge H. Human spliceosomal snRNA sequence variants generate variant spliceosomes. RNA (NEW YORK, N.Y.) 2021; 27:1186-1203. [PMID: 34234030 PMCID: PMC8457000 DOI: 10.1261/rna.078768.121] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Accepted: 06/29/2021] [Indexed: 06/02/2023]
Abstract
Human pre-mRNA splicing is primarily catalyzed by the major spliceosome, comprising five small nuclear ribonucleoprotein complexes, U1, U2, U4, U5, and U6 snRNPs, each of which contains the corresponding U-rich snRNA. These snRNAs are encoded by large gene families exhibiting significant sequence variation, but it remains unknown if most human snRNA genes are untranscribed pseudogenes or produce variant snRNAs with the potential to differentially influence splicing. Since gene duplication and variation are powerful mechanisms of evolutionary adaptation, we sought to address this knowledge gap by systematically profiling human U1, U2, U4, and U5 snRNA variant gene transcripts. We identified 55 transcripts that are detectably expressed in human cells, 38 of which incorporate into snRNPs and spliceosomes in 293T cells. All U1 snRNA variants are more than 1000-fold less abundant in spliceosomes than the canonical U1, whereas at least 1% of spliceosomes contain a variant of U2 or U4. In contrast, eight U5 snRNA sequence variants occupy spliceosomes at levels of 1% to 46%. Furthermore, snRNA variants display distinct expression patterns across five human cell lines and adult and fetal tissues. Different RNA degradation rates contribute to the diverse steady state levels of snRNA variants. Our findings suggest that variant spliceosomes containing noncanonical snRNAs may contribute to different tissue- and cell-type-specific alternative splicing patterns.
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Affiliation(s)
- Justin W Mabin
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA
| | - Peter W Lewis
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA
| | - David A Brow
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA
| | - Heidi Dvinge
- Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA
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2
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Akinyi MV, Frilander MJ. At the Intersection of Major and Minor Spliceosomes: Crosstalk Mechanisms and Their Impact on Gene Expression. Front Genet 2021; 12:700744. [PMID: 34354740 PMCID: PMC8329584 DOI: 10.3389/fgene.2021.700744] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 06/28/2021] [Indexed: 11/17/2022] Open
Abstract
Many eukaryotic species contain two separate molecular machineries for removing non-coding intron sequences from pre-mRNA molecules. The majority of introns (more than 99.5% in humans) are recognized and excised by the major spliceosome, which utilizes relatively poorly conserved sequence elements at the 5′ and 3′ ends of the intron that are used for intron recognition and in subsequent catalysis. In contrast, the minor spliceosome targets a rare group of introns (approximately 0.5% in humans) with highly conserved sequences at the 5′ and 3′ ends of the intron. Minor introns coexist in the same genes with major introns and while the two intron types are spliced by separate spliceosomes, the two splicing machineries can interact with one another to shape mRNA processing events in genes containing minor introns. Here, we review known cooperative and competitive interactions between the two spliceosomes and discuss the mechanistic basis of the spliceosome crosstalk, its regulatory significance, and impact on spliceosome diseases.
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Affiliation(s)
- Maureen V Akinyi
- Institute of Biotechnology/Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Mikko J Frilander
- Institute of Biotechnology/Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
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3
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Martí E, Milani D, Bardella VB, Albuquerque L, Song H, Palacios-Gimenez OM, Cabral-de-Mello DC. Cytogenomic analysis unveils mixed molecular evolution and recurrent chromosomal rearrangements shaping the multigene families on Schistocerca grasshopper genomes. Evolution 2021; 75:2027-2041. [PMID: 34155627 DOI: 10.1111/evo.14287] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 05/11/2021] [Accepted: 05/26/2021] [Indexed: 11/26/2022]
Abstract
Multigene families are essential components of eukaryotic genomes and play key roles either structurally and functionally. Their modes of evolution remain elusive even in the era of genomics, because multiple multigene family sequences coexist in genomes, particularly in large repetitive genomes. Here, we investigate how the multigene families 18S rDNA, U2 snDNA, and H3 histone evolved in 10 species of Schistocerca grasshoppers with very large and repeat-enriched genomes. Using sequenced genomes and fluorescence in situ hybridization mapping, we find substantial differences between species, including the number of chromosomal clusters, changes in sequence abundance and nucleotide composition, pseudogenization, and association with transposable elements (TEs). The intragenomic analysis of Schistocerca gregaria using long-read sequencing and genome assembly unveils conservation for H3 histone and recurrent pseudogenization for 18S rDNA and U2 snDNA, likely promoted by association with TEs and sequence truncation. Remarkably, TEs were frequently associated with truncated copies, were also among the most abundant in the genome, and revealed signatures of recent activity. Our findings suggest a combined effect of concerted and birth-and-death models driving the evolution of multigene families in Schistocerca over the last 8 million years, and the occurrence of intra- and interchromosomal rearrangements shaping their chromosomal distribution. Despite the conserved karyotype in Schistocerca, our analysis highlights the extensive reorganization of repetitive DNAs in Schistocerca, contributing to the advance of comparative genomics for this important grasshopper genus.
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Affiliation(s)
- Emiliano Martí
- Departamento de Biologia Geral e Aplicada, UNESP - Univ Estadual Paulista, Instituto de Biociências/IB, Rio Claro, 13506-900, Brazil
| | - Diogo Milani
- Departamento de Biologia Geral e Aplicada, UNESP - Univ Estadual Paulista, Instituto de Biociências/IB, Rio Claro, 13506-900, Brazil
| | - Vanessa B Bardella
- Departamento de Biologia Geral e Aplicada, UNESP - Univ Estadual Paulista, Instituto de Biociências/IB, Rio Claro, 13506-900, Brazil
| | - Lucas Albuquerque
- Departamento de Biologia Geral e Aplicada, UNESP - Univ Estadual Paulista, Instituto de Biociências/IB, Rio Claro, 13506-900, Brazil
| | - Hojun Song
- Department of Entomology, Texas A&M University, College Station, Texas, 77843
| | - Octavio M Palacios-Gimenez
- Department of Organismal Biology - Systematic Biology, Evolutionary Biology Centre, Uppsala University, Uppsala, SE-75236, Sweden.,Population Ecology Group, Institute of Ecology and Evolution, Friedrich Schiller University Jena, Jena, DE-07743, Germany
| | - Diogo C Cabral-de-Mello
- Departamento de Biologia Geral e Aplicada, UNESP - Univ Estadual Paulista, Instituto de Biociências/IB, Rio Claro, 13506-900, Brazil
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4
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Provazníková I, Hejníčková M, Visser S, Dalíková M, Carabajal Paladino LZ, Zrzavá M, Voleníková A, Marec F, Nguyen P. Large-scale comparative analysis of cytogenetic markers across Lepidoptera. Sci Rep 2021; 11:12214. [PMID: 34108567 PMCID: PMC8190105 DOI: 10.1038/s41598-021-91665-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 05/24/2021] [Indexed: 11/25/2022] Open
Abstract
Fluorescence in situ hybridization (FISH) allows identification of particular chromosomes and their rearrangements. Using FISH with signal enhancement via antibody amplification and enzymatically catalysed reporter deposition, we evaluated applicability of universal cytogenetic markers, namely 18S and 5S rDNA genes, U1 and U2 snRNA genes, and histone H3 genes, in the study of the karyotype evolution in moths and butterflies. Major rDNA underwent rather erratic evolution, which does not always reflect chromosomal changes. In contrast, the hybridization pattern of histone H3 genes was well conserved, reflecting the stable organisation of lepidopteran genomes. Unlike 5S rDNA and U1 and U2 snRNA genes which we failed to detect, except for 5S rDNA in a few representatives of early diverging lepidopteran lineages. To explain the negative FISH results, we used quantitative PCR and Southern hybridization to estimate the copy number and organization of the studied genes in selected species. The results suggested that their detection was hampered by long spacers between the genes and/or their scattered distribution. Our results question homology of 5S rDNA and U1 and U2 snRNA loci in comparative studies. We recommend the use of histone H3 in studies of karyotype evolution.
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Affiliation(s)
- Irena Provazníková
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
- Institute of Entomology, Biology Centre CAS, České Budějovice, Czech Republic
- European Molecular Biology Laboratory, Heidelberg, Germany
| | - Martina Hejníčková
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
- Institute of Entomology, Biology Centre CAS, České Budějovice, Czech Republic
| | - Sander Visser
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
- Institute of Entomology, Biology Centre CAS, České Budějovice, Czech Republic
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands
| | - Martina Dalíková
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
- Institute of Entomology, Biology Centre CAS, České Budějovice, Czech Republic
| | | | - Magda Zrzavá
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
- Institute of Entomology, Biology Centre CAS, České Budějovice, Czech Republic
| | - Anna Voleníková
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
- Institute of Entomology, Biology Centre CAS, České Budějovice, Czech Republic
| | - František Marec
- Institute of Entomology, Biology Centre CAS, České Budějovice, Czech Republic
| | - Petr Nguyen
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic.
- Institute of Entomology, Biology Centre CAS, České Budějovice, Czech Republic.
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5
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Huang M, Dong J, Guo H, Wang D. Effects of Dinotefuran on Brain miRNA Expression Profiles in Young Adult Honey Bees (Hymenopptera: Apidae). JOURNAL OF INSECT SCIENCE (ONLINE) 2021; 21:3. [PMID: 33400795 PMCID: PMC7785045 DOI: 10.1093/jisesa/ieaa131] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Indexed: 05/05/2023]
Abstract
Honey bees are important pollinators of wild plants and crops. MicroRNAs (miRNAs) are endogenous regulators of gene expression. In this study, we initially determined that the lethal concentration 50 (LC50) of dinotefuran was 0.773 mg/l. Then, the expression profiles and differentially expressed miRNAs (DE miRNAs) in honey bee brains after 1, 5, and 10 d of treatment with the lethal concentration 10 (LC10) of dinotefuran were explored via deep small-RNA sequencing and bioinformatics. In total, 2, 23, and 27 DE miRNAs were identified after persistent exposure to the LC10 of dinotefuran for 1, 5, and 10 d, respectively. Some abundant miRNAs, such as ame-miR-375-3p, ame-miR-281-5p, ame-miR-3786-3p, ame-miR-10-5p, and ame-miR-6037-3p, were extremely significantly differentially expressed. Enrichment analysis suggested that the candidate target genes of the DE miRNAs are involved in the regulation of biological processes, cellular processes, and behaviors. These results expand our understanding of the regulatory roles of miRNAs in honey bee Apis mellifera (Hymenopptera: Apidae) responses to neonicotinoid insecticides and facilitate further studies on the functions of miRNAs in honey bees.
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Affiliation(s)
- Minjie Huang
- Institute of Animal Husbandry and Veterinary Science, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Jie Dong
- Institute of Animal Husbandry and Veterinary Science, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Haikun Guo
- Institute of Quality and Standard for Agro-Products, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Deqian Wang
- Institute of Animal Husbandry and Veterinary Science, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
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6
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Anderson MAE, Purcell J, Verkuijl SAN, Norman VC, Leftwich PT, Harvey-Samuel T, Alphey LS. Expanding the CRISPR Toolbox in Culicine Mosquitoes: In Vitro Validation of Pol III Promoters. ACS Synth Biol 2020; 9:678-681. [PMID: 32129976 PMCID: PMC7093051 DOI: 10.1021/acssynbio.9b00436] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
CRISPR-Cas9-based "gene drive" technologies have been proposed as a novel and effective means of controlling human diseases vectored by mosquitoes. However, more complex designs than those demonstrated to date-and an expanded molecular toolbox with which to build them-will be required to overcome the issues of resistance formation/evolution and drive spatial/temporal limitation. Foreseeing this need, we assessed the sgRNA transcriptional activities of 33 phylogenetically diverse insect Polymerase III promoters using three disease-relevant Culicine mosquito cell lines (Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus). We show that U6 promoters work across species with a range of transcriptional activity levels and find 7SK promoters to be especially promising because of their broad phylogenetic activity. We further show that U6 promoters can be substantially truncated without affecting transcriptional levels. These results will be of great utility to researchers involved in developing the next generation of gene drives.
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Affiliation(s)
| | - Jessica Purcell
- Arthropod Genetics, The Pirbright Institute, Ash Road, Pirbright GU24 0NF, U.K
| | - Sebald A. N. Verkuijl
- Arthropod Genetics, The Pirbright Institute, Ash Road, Pirbright GU24 0NF, U.K
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, U.K
| | - Victoria C. Norman
- Arthropod Genetics, The Pirbright Institute, Ash Road, Pirbright GU24 0NF, U.K
| | - Philip T. Leftwich
- Arthropod Genetics, The Pirbright Institute, Ash Road, Pirbright GU24 0NF, U.K
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, Norfolk NR4 7TJ, U.K
| | - Tim Harvey-Samuel
- Arthropod Genetics, The Pirbright Institute, Ash Road, Pirbright GU24 0NF, U.K
| | - Luke S. Alphey
- Arthropod Genetics, The Pirbright Institute, Ash Road, Pirbright GU24 0NF, U.K
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7
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Baumgartner M, Drake K, Kanadia RN. An Integrated Model of Minor Intron Emergence and Conservation. Front Genet 2019; 10:1113. [PMID: 31798628 PMCID: PMC6865273 DOI: 10.3389/fgene.2019.01113] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Accepted: 10/16/2019] [Indexed: 12/12/2022] Open
Abstract
Minor introns constitute <0.5% of the introns in the human genome and have remained an enigma since their discovery. These introns are removed by a distinct splicing complex, the minor spliceosome. Both are ancient, tracing back to the last eukaryotic common ancestor (LECA), which is reflected by minor intron enrichment in specific gene families, such as the mitogen activated-protein kinase kinases, voltage-gated sodium and calcium ion channels, and E2F transcription factors. Most minor introns occur as single introns in genes with predominantly major introns. Due to this organization, minor intron-containing gene (MIG) expression requires the coordinated action of two spliceosomes, which increases the probability of missplicing. Thus, one would expect loss of minor introns via purifying selection. This has resulted in complete minor intron loss in at least nine eukaryotic lineages. However, minor introns are highly conserved in land plants and metazoans, where their importance is underscored by embryonic lethality when the minor spliceosome is inactivated. Conditional inactivation of the minor spliceosome has shown that rapidly dividing progenitor cells are highly sensitive to minor spliceosome loss. Indeed, we found that MIGs were significantly enriched in a screen for genes essential for survival in 341 cycling cell lines. Here, we propose that minor introns inserted randomly into genes in LECA or earlier and were subsequently conserved in genes crucial for cycling cell survival. We hypothesize that the essentiality of MIGs allowed minor introns to endure through the unicellularity of early eukaryotic evolution. Moreover, we identified 59 MIGs that emerged after LECA, and that many of these are essential for cycling cell survival, reinforcing our essentiality model for MIG conservation. This suggests that minor intron emergence is dynamic across eukaryotic evolution, and that minor introns should not be viewed as molecular fossils. We also posit that minor intron splicing was co-opted in multicellular evolution as a regulatory switch for en masse control of MIG expression and the biological processes they regulate. Specifically, this mode of regulation could control cell proliferation and thus body size, an idea supported by domestication syndrome, wherein MIGs are enriched in common candidate animal domestication genes.
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Affiliation(s)
- Marybeth Baumgartner
- Department of Physiology and Neurobiology, University of Connecticut, Mansfield, CT, United States.,Institute of Brain and Cognitive Sciences, University of Connecticut, Mansfield, CT, United States
| | - Kyle Drake
- Department of Physiology and Neurobiology, University of Connecticut, Mansfield, CT, United States
| | - Rahul N Kanadia
- Department of Physiology and Neurobiology, University of Connecticut, Mansfield, CT, United States.,Institute of Systems Genomics, University of Connecticut, Mansfield, CT, United States
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8
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Liu M, Huang J, Zhang G, Liu X, An J. Analysis of miRNAs in the Heads of Different Castes of the Bumblebee Bombus lantschouensis (Hymenoptera: Apidae). INSECTS 2019; 10:E349. [PMID: 31623265 PMCID: PMC6835379 DOI: 10.3390/insects10100349] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 10/11/2019] [Accepted: 10/14/2019] [Indexed: 12/13/2022]
Abstract
Bumblebees are important insect pollinators for many wildflowers and crops. MicroRNAs (miRNAs) are endogenous non-coding small RNAs that regulate different biological functions in insects. In this study, the miRNAs in the heads of the three castes of the bumblebee Bombus lantschouensis were identified and characterized by small RNA deep sequencing. The significant differences in the expression of miRNAs and their target genes were analyzed. The results showed that the length of the small RNA reads from males, queens, and workers was distributed between 18 and 30 nt, with a peak at 22 nt. A total of 364 known and 89 novel miRNAs were identified from the heads of the three castes. The eight miRNAs with the highest expressed levels in males, queens, and workers were identical, although the order of these miRNAs based on expression differed. The male vs. queen, male vs. worker, and worker vs. queen comparisons identified nine, fourteen, and four miRNAs with significant differences in expression, respectively. The different castes were clustered based on the differentially expressed miRNAs (DE miRNAs), and the expression levels of the DE miRNAs obtained by RT-qPCR were consistent with the read counts obtained through Solexa sequencing. The putative target genes of these DE miRNAs were enriched in 29 Gene Ontology (GO) terms, and catalytic activity was the most enriched GO term, as demonstrated by its association with 2837 target genes in the male vs. queen comparison, 3535 target genes in the male vs. worker comparison, and 2185 target genes in the worker vs. queen comparison. This study highlights the characteristics of the miRNAs in the three B. lantschouensis castes and will aid further studies on the functions of miRNAs in bumblebees.
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Affiliation(s)
- Meijuan Liu
- Key Laboratory for Insect-Pollinator Biology of the Ministry of Agriculture and Rural Affairs, Institute of Apicultural Research, Chinese Academy of Agricultural Sciences, Beijing 100093, China.
| | - Jiaxing Huang
- Key Laboratory for Insect-Pollinator Biology of the Ministry of Agriculture and Rural Affairs, Institute of Apicultural Research, Chinese Academy of Agricultural Sciences, Beijing 100093, China.
| | - Guangshuo Zhang
- Key Laboratory for Insect-Pollinator Biology of the Ministry of Agriculture and Rural Affairs, Institute of Apicultural Research, Chinese Academy of Agricultural Sciences, Beijing 100093, China.
| | - Xiaofeng Liu
- School of Life Science, Peking University, Beijing 100871, China.
| | - Jiandong An
- School of Life Science, Peking University, Beijing 100871, China.
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9
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Lopez-Ezquerra A, Harrison MC, Bornberg-Bauer E. Comparative analysis of lincRNA in insect species. BMC Evol Biol 2017; 17:155. [PMID: 28673235 PMCID: PMC5494802 DOI: 10.1186/s12862-017-0985-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 06/02/2017] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND The ever increasing availability of genomes makes it possible to investigate and compare not only the genomic complements of genes and proteins, but also of RNAs. One class of RNAs, the long noncoding RNAs (lncRNAs) and, in particular, their subclass of long intergenic noncoding RNAs (lincRNAs) have recently gained much attention because of their roles in regulation of important biological processes such as immune response or cell differentiation and as possible evolutionary precursors for protein coding genes. lincRNAs seem to be poorly conserved at the sequence level but at least some lincRNAs have conserved structural elements and syntenic genomic positions. Previous studies showed that transposable elements are a main contribution to the evolution of lincRNAs in mammals. In contrast, plant lincRNA emergence and evolution has been linked with local duplication events. However, little is known about their evolutionary dynamics in general and in insect genomes in particular. RESULTS Here we compared lincRNAs between seven insect genomes and investigated possible evolutionary changes and functional roles. We find very low sequence conservation between different species and that similarities within a species are mostly due to their association with transposable elements (TE) and simple repeats. Furthermore, we find that TEs are less frequent in lincRNA exons than in their introns, indicating that TEs may have been removed by selection. When we analysed the predicted thermodynamic stabilities of lincRNAs we found that they are more stable than their randomized controls which might indicate some selection pressure to maintain certain structural elements. We list several of the most stable lincRNAs which could serve as prime candidates for future functional studies. We also discuss the possibility of de novo protein coding genes emerging from lincRNAs. This is because lincRNAs with high GC content and potentially with longer open reading frames (ORF) are candidate loci where de novo gene emergence might occur. CONCLUSION The processes responsible for the emergence and diversification of lincRNAs in insects remain unclear. Both duplication and transposable elements may be important for the creation of new lincRNAs in insects.
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Affiliation(s)
- Alberto Lopez-Ezquerra
- Institute of Evolution and Biodiversity, University of Münster, Hüfferstrasse,1, Münster, Münster, Germany
| | - Mark C Harrison
- Institute of Evolution and Biodiversity, University of Münster, Hüfferstrasse,1, Münster, Münster, Germany
| | - Erich Bornberg-Bauer
- Institute of Evolution and Biodiversity, University of Münster, Hüfferstrasse,1, Münster, Münster, Germany.
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10
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Abstract
Introns inserted within introns are commonly referred to as twintrons, however the original definition for twintron implied that splicing of the external member of the twintron could only proceed upon splicing of the internal member. This review examines the various types of twintron-like arrangements that have been reported and assigns them to either nested or twintron categories that are subdivided further into subtypes based on differences of their mode of splicing. Twintron-like arrangements evolved independently by fortuitous events among different types of introns but once formed they offer opportunities for the evolution of new regulatory strategies and/or novel genetic elements.
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Affiliation(s)
- Mohamed Hafez
- a Department of Biochemistry ; Faculty of Medicine; University of Montreal ; Montréal , QC Canada.,b Department of Botany and Microbiology ; Faculty of Science; Suez University ; Suez , Egypt
| | - Georg Hausner
- c Department of Microbiology ; University of Manitoba ; Winnipeg , MB Canada
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11
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Nyberg KG, Machado CA. Comparative Expression Dynamics of Intergenic Long Noncoding RNAs in the Genus Drosophila. Genome Biol Evol 2016; 8:1839-58. [PMID: 27189981 PMCID: PMC4943187 DOI: 10.1093/gbe/evw116] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Thousands of long noncoding RNAs (lncRNAs) have been annotated in eukaryotic genomes, but comparative transcriptomic approaches are necessary to understand their biological impact and evolution. To facilitate such comparative studies in Drosophila, we identified and characterized lncRNAs in a second Drosophilid—the evolutionary model Drosophila pseudoobscura. Using RNA-Seq and computational filtering of protein-coding potential, we identified 1,589 intergenic lncRNA loci in D. pseudoobscura. We surveyed multiple sex-specific developmental stages and found, like in Drosophila melanogaster, increasingly prolific lncRNA expression through male development and an overrepresentation of lncRNAs in the testes. Other trends seen in D. melanogaster, like reduced pupal expression, were not observed. Nonrandom distributions of female-biased and non-testis-specific male-biased lncRNAs between the X chromosome and autosomes are consistent with selection-based models of gene trafficking to optimize genomic location of sex-biased genes. The numerous testis-specific lncRNAs, however, are randomly distributed between the X and autosomes, and we cannot reject the hypothesis that many of these are likely to be spurious transcripts. Finally, using annotated lncRNAs in both species, we identified 134 putative lncRNA homologs between D. pseudoobscura and D. melanogaster and find that many have conserved developmental expression dynamics, making them ideal candidates for future functional analyses.
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Affiliation(s)
- Kevin G Nyberg
- Department of Biology, University of Maryland, College Park
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12
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Abstract
Pre-mRNA splicing is a critical step in eukaryotic gene expression that contributes to proteomic, cellular, and developmental complexity. Small nuclear (sn)RNAs are core spliceosomal components; however, the extent to which differential expression of snRNA isoforms regulates splicing is completely unknown. This is partly due to difficulties in the accurate analysis of the spatial and temporal expression patterns of snRNAs. Here, we use high-throughput RNA-sequencing (RNA-seq) data to profile expression of four major snRNAs throughout Drosophila development. This analysis shows that individual isoforms of each snRNA have distinct expression patterns in the embryo, larva, and pharate adult stages. Expression of these isoforms is more heterogeneous during embryogenesis; as development progresses, a single isoform from each snRNA subtype gradually dominates expression. Despite the lack of stable snRNA orthologous groups during evolution, this developmental switching of snRNA isoforms also occurs in distantly related vertebrate species, such as Xenopus, mouse, and human. Our results indicate that expression of snRNA isoforms is regulated and lays the foundation for functional studies of individual snRNA isoforms.
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13
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Kang YS, Kurano M, Stumph WE. The Myb domain of the largest subunit of SNAPc adopts different architectural configurations on U1 and U6 snRNA gene promoter sequences. Nucleic Acids Res 2014; 42:12440-54. [PMID: 25324315 PMCID: PMC4227766 DOI: 10.1093/nar/gku905] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The small nuclear RNA (snRNA) activating protein complex (SNAPc) is essential for transcription of genes that encode the snRNAs. Drosophila melanogaster SNAPc (DmSNAPc) consists of three subunits (DmSNAP190, DmSNAP50 and DmSNAP43) that form a stable complex that recognizes an snRNA gene promoter element called the PSEA. Although all three subunits are required for sequence-specific DNA binding activity, only DmSNAP190 possesses a canonical DNA binding domain consisting of 4.5 tandem Myb repeats homologous to the Myb repeats in the DNA binding domain of the Myb oncoprotein. In this study, we use site-specific protein–DNA photo-cross-linking technology followed by site-specific protein cleavage to map domains of DmSNAP190 that interact with specific phosphate positions in the U6 PSEA. The results indicate that at least two DmSNAP190 Myb repeats contact the DNA in a significantly different manner when DmSNAPc binds to a U6 PSEA versus a U1 PSEA, even though the two PSEA sequences differ at only 5 of 21 nucleotide positions. The results are consistent with a model in which the specific DNA sequences of the U1 and U6 PSEAs differentially alter the conformation of DmSNAPc, leading to the subsequent recruitment of different RNA polymerases to the U1 and U6 gene promoters.
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Affiliation(s)
- Yoon Soon Kang
- Department of Chemistry and Biochemistry, Molecular Biology Institute, San Diego State University, San Diego, CA 92182-1030, USA
| | - Michelle Kurano
- Department of Biology, Molecular Biology Institute, San Diego State University, San Diego, CA 92182-1030, USA
| | - William E Stumph
- Department of Chemistry and Biochemistry, Molecular Biology Institute, San Diego State University, San Diego, CA 92182-1030, USA
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14
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U1 snDNA clusters in grasshoppers: chromosomal dynamics and genomic organization. Heredity (Edinb) 2014; 114:207-19. [PMID: 25248465 DOI: 10.1038/hdy.2014.87] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 08/14/2014] [Accepted: 08/18/2014] [Indexed: 11/08/2022] Open
Abstract
The spliceosome, constituted by a protein set associated with small nuclear RNA (snRNA), is responsible for mRNA maturation through intron removal. Among snRNA genes, U1 is generally a conserved repetitive sequence. To unveil the chromosomal/genomic dynamics of this multigene family in grasshoppers, we mapped U1 genes by fluorescence in situ hybridization in 70 species belonging to the families Proscopiidae, Pyrgomorphidae, Ommexechidae, Romaleidae and Acrididae. Evident clusters were observed in all species, indicating that, at least, some U1 repeats are tandemly arrayed. High conservation was observed in the first four families, with most species carrying a single U1 cluster, frequently located in the third or fourth longest autosome. By contrast, extensive variation was observed among Acrididae, from a single chromosome pair carrying U1 to all chromosome pairs carrying it, with occasional occurrence of two or more clusters in the same chromosome. DNA sequence analysis in Eyprepocnemis plorans (species carrying U1 clusters on seven different chromosome pairs) and Locusta migratoria (carrying U1 in a single chromosome pair) supported the coexistence of functional and pseudogenic lineages. One of these pseudogenic lineages was truncated in the same nucleotide position in both species, suggesting that it was present in a common ancestor to both species. At least in E. plorans, this U1 snDNA pseudogenic lineage was associated with 5S rDNA and short interspersed elements (SINE)-like mobile elements. Given that we conclude in grasshoppers that the U1 snDNA had evolved under the birth-and-death model and that its intragenomic spread might be related with mobile elements.
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15
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Flipphi M, Fekete E, Ag N, Scazzocchio C, Karaffa L. Spliceosome twin introns in fungal nuclear transcripts. Fungal Genet Biol 2013; 57:48-57. [PMID: 23792080 DOI: 10.1016/j.fgb.2013.06.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Revised: 06/07/2013] [Accepted: 06/09/2013] [Indexed: 10/26/2022]
Abstract
The spliceosome is an RNA/protein complex, responsible for intron excision from eukaryotic nuclear transcripts. In bacteria, mitochondria and plastids, intron excision does not involve the spliceosome, but occurs through mechanisms dependent on intron RNA secondary and tertiary structure. For group II/III chloroplast introns, "twintrons" (introns within introns) have been described. The excision of the external intron, and thus proper RNA maturation, necessitates prior removal of the internal intron, which interrupts crucial sequences of the former. We have here predicted analogous instances of spliceosomal twintrons ("stwintrons") in filamentous fungi. In two specific cases, where the internal intron interrupts the donor of the external intron after the first or after the second nucleotide, respectively, we show that intermediates with the sequence predicted by the "stwintron" hypothesis, are produced in the splicing process. This implies that two successive rounds of RNA scanning by the spliceosome are necessary to produce the mature mRNA. The phylogenetic distributions of the stwintrons we have identified suggest that they derive from "late" events, subsequent to the appearance of the host intron. They may well not be limited to fungal nuclear transcripts, and their generation and eventual disappearance in the evolutionary process are relevant to hypotheses of intron origin and alternative splicing.
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Affiliation(s)
- Michel Flipphi
- Department of Biochemical Engineering, Faculty of Science and Technology, University of Debrecen, 4010 Debrecen, Hungary.
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16
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Li L, Liu F, Li W, Li Z, Pan J, Yan L, Zhang S, Huang ZY, Su S. Differences in microRNAs and their expressions between foraging and dancing honey bees, Apis mellifera L. JOURNAL OF INSECT PHYSIOLOGY 2012; 58:1438-1443. [PMID: 23000740 DOI: 10.1016/j.jinsphys.2012.08.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Revised: 08/15/2012] [Accepted: 08/16/2012] [Indexed: 06/01/2023]
Abstract
Many studies have established that microRNAs (miRNAs) regulate gene expression in various biological processes in mammals and insects including honey bees. Dancing behavior is a form of communication unique to honey bees. However, it remains unclear which miRNAs regulate the dancing behavior in honey bees, and how. In the present study, total small RNAs (sRNAs) in Apis mellifera foragers and dancers were extracted and analyzed by a Solexa Sequencer to determine differentially expressed miRNAs. A small percentage (12.62%) of the unique sRNAs (the number of sequence types) were shared between foragers and dancers, but their expression accounted for 92.92% of the total sRNAs (the number of all sequence reads), and the length of them centered around 22nt. Out of 58 previously identified miRNAs, 54 were present in both foragers and dancers and most of them were down-regulated in dancers. The fold-changes of ame-miR-34, ame-miR-210, ame-miR-278 and ame-miR-282 were higher than 2. 86 and 104 novel miRNAs were detected in foragers and dancers, respectively. Furthermore, two known miRNAs (ame-miR-278 and ame-miR-282) were confirmed, by qPCR, to have lower expressions in dancers. The target genes of ame-miR-278 and ame-miR-282 were associated with kinase, neural function, synaptotagmin and energy. These results indicate that miRNAs are substantially different between the foraging and dancing stages, and suggest that miRNAs might play important roles in regulating dancing behaviors in honey bees.
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Affiliation(s)
- Li Li
- College of Animal Sciences, Zhejiang University, Hangzhou, China
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17
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Janice J, Pande A, Weiner J, Lin CF, Makałowski W. U12-type spliceosomal introns of Insecta. Int J Biol Sci 2012; 8:344-52. [PMID: 22393306 PMCID: PMC3291851 DOI: 10.7150/ijbs.3933] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 01/25/2012] [Indexed: 11/05/2022] Open
Abstract
Most of eukaryotic genes are interrupted by introns that need to be removed from pre-mRNAs before they can perform their function. This is done by complex machinery called spliceosome. Many eukaryotes possess two separate spliceosomal systems that process separate sets of introns. The major (U2) spliceosome removes majority of introns, while minute fraction of intron repertoire is processed by the minor (U12) spliceosome. These two populations of introns are called U2-type and U12-type, respectively. The latter fall into two subtypes based on the terminal dinucleotides. The minor spliceosomal system has been lost independently in some lineages, while in some others few U12-type introns persist. We investigated twenty insect genomes in order to better understand the evolutionary dynamics of U12-type introns. Our work confirms dramatic drop of U12-type introns in Diptera, leaving these genomes just with a handful cases. This is mostly the result of intron deletion, but in a number of dipteral cases, minor type introns were switched to a major type, as well. Insect genes that harbor U12-type introns belong to several functional categories among which proteins binding ions and nucleic acids are enriched and these few categories are also overrepresented among these genes that preserved minor type introns in Diptera.
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Affiliation(s)
- Jessin Janice
- Institute of Bioinformatics, University of Muenster, Muenster, Germany
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18
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Vierna J, Jensen KT, Martínez-Lage A, González-Tizón AM. The linked units of 5S rDNA and U1 snDNA of razor shells (Mollusca: Bivalvia: Pharidae). Heredity (Edinb) 2011; 107:127-42. [PMID: 21364693 DOI: 10.1038/hdy.2010.174] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The linkage between 5S ribosomal DNA and other multigene families has been detected in many eukaryote lineages, but whether it provides any selective advantage remains unclear. In this work, we report the occurrence of linked units of 5S ribosomal DNA (5S rDNA) and U1 small nuclear DNA (U1 snDNA) in 10 razor shell species (Mollusca: Bivalvia: Pharidae) from four different genera. We obtained several clones containing partial or complete repeats of both multigene families in which both types of genes displayed the same orientation. We provide a comprehensive collection of razor shell 5S rDNA clones, both with linked and nonlinked organisation, and the first bivalve U1 snDNA sequences. We predicted the secondary structures and characterised the upstream and downstream conserved elements, including a region at -25 nucleotides from both 5S rDNA and U1 snDNA transcription start sites. The analysis of 5S rDNA showed that some nontranscribed spacers (NTSs) are more closely related to NTSs from other species (and genera) than to NTSs from the species they were retrieved from, suggesting birth-and-death evolution and ancestral polymorphism. Nucleotide conservation within the functional regions suggests the involvement of purifying selection, unequal crossing-overs and gene conversions. Taking into account this and other studies, we discuss the possible mechanisms by which both multigene families could have become linked in the Pharidae lineage. The reason why 5S rDNA is often found linked to other multigene families seems to be the result of stochastic processes within genomes in which its high copy number is determinant.
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Affiliation(s)
- J Vierna
- Department of Molecular and Cell Biology, Evolutionary Biology Group (GIBE), Universidade da Coruña, La Coruña, Spain.
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19
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Jung CH, Hansen MA, Makunin IV, Korbie DJ, Mattick JS. Identification of novel non-coding RNAs using profiles of short sequence reads from next generation sequencing data. BMC Genomics 2010; 11:77. [PMID: 20113528 PMCID: PMC2825236 DOI: 10.1186/1471-2164-11-77] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Accepted: 02/01/2010] [Indexed: 11/30/2022] Open
Abstract
Background The increasing interest in small non-coding RNAs (ncRNAs) such as microRNAs (miRNAs), small interfering RNAs (siRNAs) and Piwi-interacting RNAs (piRNAs) and recent advances in sequencing technology have yielded large numbers of short (18-32 nt) RNA sequences from different organisms, some of which are derived from small nucleolar RNAs (snoRNAs) and transfer RNAs (tRNAs). We observed that these short ncRNAs frequently cover the entire length of annotated snoRNAs or tRNAs, which suggests that other loci specifying similar ncRNAs can be identified by clusters of short RNA sequences. Results We combined publicly available datasets of tens of millions of short RNA sequence tags from Drosophila melanogaster, and mapped them to the Drosophila genome. Approximately 6 million perfectly mapping sequence tags were then assembled into 521,302 tag-contigs (TCs) based on tag overlap. Most transposon-derived sequences, exons and annotated miRNAs, tRNAs and snoRNAs are detected by TCs, which show distinct patterns of length and tag-depth for different categories. The typical length and tag-depth of snoRNA-derived TCs was used to predict 7 previously unrecognized box H/ACA and 26 box C/D snoRNA candidates. We also identified one snRNA candidate and 86 loci with a high number of tags that are yet to be annotated, 7 of which have a particular 18mer motif and are located in introns of genes involved in development. A subset of new snoRNA candidates and putative ncRNA candidates was verified by Northern blot. Conclusions In this study, we have introduced a new approach to identify new members of known classes of ncRNAs based on the features of TCs corresponding to known ncRNAs. A large number of the identified TCs are yet to be examined experimentally suggesting that many more novel ncRNAs remain to be discovered.
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Affiliation(s)
- Chol-Hee Jung
- Institute for Molecular Bioscience, University of Queensland, St. Lucia QLD 4072, Australia
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20
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Mosig A, Zhu L, Stadler PF. Customized strategies for discovering distant ncRNA homologs. BRIEFINGS IN FUNCTIONAL GENOMICS AND PROTEOMICS 2009; 8:451-60. [PMID: 19779009 DOI: 10.1093/bfgp/elp035] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A large fraction of non-coding RNAs is short and/or poorly conserved in sequence. Most of the longer examples, furthermore, consist of a collection of conserved structural motifs rather than a coherent globally conserved secondary structure. As a consequence, the conceptually simple problem of homology search becomes a complex and technically demanding task. Despite the best efforts of databases such as Rfam, the situation is complicated further by the sparsity of information in many--in particular prokaryotic--RNA families. In this contribution, we review recent efforts to customize sequence-based search tools for ncRNA applications. In particular, semi-global alignments and the development of methods for fragmented pattern search have brought significant practical advances. Current developments in this area focus on the integration of fragmented sequence pattern search with search algorithms for secondary structure patterns. We focus here, in particular, on strategies that can be successful in the 'twilight zone' where generic approaches from blast to infernal to start to fail.
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Affiliation(s)
- Axel Mosig
- Chair of Bioinformatics, Department of Computer Science, University of Leipzig, Härtelstrasse 16-18, D-04107 Leipzig, Germany
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21
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Marz M, Kirsten T, Stadler PF. Evolution of spliceosomal snRNA genes in metazoan animals. J Mol Evol 2009; 67:594-607. [PMID: 19030770 DOI: 10.1007/s00239-008-9149-6] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2008] [Accepted: 07/14/2008] [Indexed: 11/28/2022]
Abstract
While studies of the evolutionary histories of protein families are commonplace, little is known on noncoding RNAs beyond microRNAs and some snoRNAs. Here we investigate in detail the evolutionary history of the nine spliceosomal snRNA families (U1, U2, U4, U5, U6, U11, U12, U4atac, and U6atac) across the completely or partially sequenced genomes of metazoan animals. Representatives of the five major spliceosomal snRNAs were found in all genomes. None of the minor splicesomal snRNAs were detected in nematodes or in the shotgun traces of Oikopleura dioica, while in all other animal genomes at most one of them is missing. Although snRNAs are present in multiple copies in most genomes, distinguishable paralogue groups are not stable over long evolutionary times, although they appear independently in several clades. In general, animal snRNA secondary structures are highly conserved, albeit, in particular, U11 and U12 in insects exhibit dramatic variations. An analysis of genomic context of snRNAs reveals that they behave like mobile elements, exhibiting very little syntenic conservation.
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Affiliation(s)
- Manuela Marz
- Bioinformatics Group, Department of Computer Science, University of Leipzig, Härtelstrasse 16-18, 04107 Leipzig, Germany.
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22
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Gruber AR, Kilgus C, Mosig A, Hofacker IL, Hennig W, Stadler PF. Arthropod 7SK RNA. Mol Biol Evol 2008; 25:1923-30. [PMID: 18566019 DOI: 10.1093/molbev/msn140] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The 7SK small nuclear RNA (snRNA) is a key player in the regulation of polymerase (pol) II transcription. The 7SK RNA was long believed to be specific to vertebrates where it is highly conserved. Homologs in basal deuterostomes and a few lophotrochozoan species were only recently reported. On longer timescales, 7SK evolves rapidly with only few conserved sequence and structure motifs. Previous attempts to identify the Drosophila homolog thus have remained unsuccessful despite considerable efforts. Here we report on the discovery of arthropod 7SK RNAs using a novel search strategy based on pol III promoters, as well as the subsequent verification of its expression. Our results demonstrate that a 7SK snRNA featuring 2 highly structured conserved domains was present already in the bilaterian ancestor.
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Affiliation(s)
- Andreas R Gruber
- Institute for Theoretical Chemistry, University of Vienna, Vienna, Austria.
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23
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Evolution of genes and genomes on the Drosophila phylogeny. Nature 2008; 450:203-18. [PMID: 17994087 DOI: 10.1038/nature06341] [Citation(s) in RCA: 1509] [Impact Index Per Article: 94.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Accepted: 10/05/2007] [Indexed: 12/11/2022]
Abstract
Comparative analysis of multiple genomes in a phylogenetic framework dramatically improves the precision and sensitivity of evolutionary inference, producing more robust results than single-genome analyses can provide. The genomes of 12 Drosophila species, ten of which are presented here for the first time (sechellia, simulans, yakuba, erecta, ananassae, persimilis, willistoni, mojavensis, virilis and grimshawi), illustrate how rates and patterns of sequence divergence across taxa can illuminate evolutionary processes on a genomic scale. These genome sequences augment the formidable genetic tools that have made Drosophila melanogaster a pre-eminent model for animal genetics, and will further catalyse fundamental research on mechanisms of development, cell biology, genetics, disease, neurobiology, behaviour, physiology and evolution. Despite remarkable similarities among these Drosophila species, we identified many putatively non-neutral changes in protein-coding genes, non-coding RNA genes, and cis-regulatory regions. These may prove to underlie differences in the ecology and behaviour of these diverse species.
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Wyder S, Kriventseva EV, Schröder R, Kadowaki T, Zdobnov EM. Quantification of ortholog losses in insects and vertebrates. Genome Biol 2007; 8:R242. [PMID: 18021399 PMCID: PMC2258195 DOI: 10.1186/gb-2007-8-11-r242] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2007] [Revised: 10/04/2007] [Accepted: 11/16/2007] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND The increasing number of sequenced insect and vertebrate genomes of variable divergence enables refined comparative analyses to quantify the major modes of animal genome evolution and allows tracing of gene genealogy (orthology) and pinpointing of gene extinctions (losses), which can reveal lineage-specific traits. RESULTS To consistently quantify losses of orthologous groups of genes, we compared the gene repertoires of five vertebrates and five insects, including honeybee and Tribolium beetle, that represent insect orders outside the previously sequenced Diptera. We found hundreds of lost Urbilateria genes in each of the lineages and assessed their phylogenetic origin. The rate of losses correlates well with the species' rates of molecular evolution and radiation times, without distinction between insects and vertebrates, indicating their stochastic nature. Remarkably, this extends to the universal single-copy orthologs, losses of dozens of which have been tolerated in each species. Nevertheless, the propensity for loss differs substantially among genes, where roughly 20% of the orthologs have an 8-fold higher chance of becoming extinct. Extrapolation of our data also suggests that the Urbilateria genome contained more than 7,000 genes. CONCLUSION Our results indicate that the seemingly higher number of observed gene losses in insects can be explained by their two- to three-fold higher evolutionary rate. Despite the profound effect of many losses on cellular machinery, overall, they seem to be guided by neutral evolution.
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Affiliation(s)
- Stefan Wyder
- Department of Genetic Medicine and Development, University of Geneva Medical School, 1211 Geneva, Switzerland
- Swiss Institute of Bioinformatics, rue Michel-Servet, 1211 Geneva, Switzerland
| | - Evgenia V Kriventseva
- Swiss Institute of Bioinformatics, rue Michel-Servet, 1211 Geneva, Switzerland
- Department of Structural Biology and Bioinformatics, University of Geneva Medical School, rue Michel-Servet, 1211 Geneva, Switzerland
| | - Reinhard Schröder
- Interf. Institut für Zellbiologie, Abt. Genetik der Tiere, Universität Tübingen, 72076 Tübingen, Germany
| | - Tatsuhiko Kadowaki
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan
| | - Evgeny M Zdobnov
- Department of Genetic Medicine and Development, University of Geneva Medical School, 1211 Geneva, Switzerland
- Swiss Institute of Bioinformatics, rue Michel-Servet, 1211 Geneva, Switzerland
- Imperial College London, South Kensington Campus, London SW7 2AZ, UK
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