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Seetharaman A, Galagali H, Linarte E, Liu MHX, Cohen JD, Chetal K, Sadreyev R, Tate AJ, Montgomery TA, Ruvkun G. Caenorhabditis elegans SynMuv B gene activity is down-regulated during a viral infection to enhance RNA interference. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.12.603258. [PMID: 39071373 PMCID: PMC11275910 DOI: 10.1101/2024.07.12.603258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
Small RNA pathways regulate eukaryotic antiviral defense. Many of the Caenorhabditis elegans mutations that were identified based on their enhanced RNAi, the synMuv B genes, also emerged from unrelated genetic screens for increased growth factor signaling. The dozen synMuv B genes encode homologues of the mammalian dREAM complex found in nearly all animals and plants, which includes the lin-35 /retinoblastoma oncogene. We show that a set of highly induced mRNAs in synMuv B mutants is congruent with mRNAs induced by Orsay RNA virus infection of C. elegans . In wild type animals, a combination of a synMuv A mutation and a synMuv B mutation are required for the Muv phenotype of increased growth factor signaling. But we show that Orsay virus infection of a single synMuv A mutant can induce a Muv phenotype, unlike the uninfected single synMuv A mutant. This suggests that decreased synMuv B activity, which activates the antiviral RNAi pathway, is a defense response to viral infection. Small RNA deep sequencing analysis of various dREAM complex mutants uncovers distinct siRNA profiles indicative of such an siRNA response. We conclude that the synMuv B mutants maintain an antiviral readiness state even in the absence of actual infection. The enhanced RNAi and conservation of the dREAM complex mutants suggests new therapeutic avenues to boost antiviral defenses.
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2
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Schiksnis EC, Nicastro IA, Pasquinelli AE. Full-length direct RNA sequencing reveals extensive remodeling of RNA expression, processing and modification in aging Caenorhabditis elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.18.599640. [PMID: 38948813 PMCID: PMC11213008 DOI: 10.1101/2024.06.18.599640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Organismal aging is marked by decline in cellular function and anatomy, ultimately resulting in death. To inform our understanding of the mechanisms underlying this degeneration, we performed standard RNA sequencing and Nanopore direct RNA sequencing over an adult time course in Caenorhabditis elegans. Long reads allowed for identification of hundreds of novel isoforms and age-associated differential isoform accumulation, resulting from alternative splicing and terminal exon choice. Genome-wide analysis reveals a decline in RNA processing fidelity and a rise in inosine and pseudouridine editing events in transcripts from older animals. In this first map of pseudouridine modifications for C. elegans, we find that they largely reside in coding sequences and that the number of genes with this modification increases with age. Collectively, this analysis discovers transcriptomic signatures associated with age and is a valuable resource to understand the many processes that dictate altered gene expression patterns and post-transcriptional regulation in aging.
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Affiliation(s)
- Erin C Schiksnis
- Molecular Biology Department, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0349, USA
| | - Ian A Nicastro
- Molecular Biology Department, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0349, USA
| | - Amy E Pasquinelli
- Molecular Biology Department, School of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0349, USA
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3
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Tushir S, Jhanwar P, Benda M, Horáčková V, Doležal P, Tatu U. In vivo Validation of Hsp90 Trans-splicing in Giardia lamblia: Highlighting the Role of Cis-elements. J Mol Biol 2024; 436:168440. [PMID: 38218367 DOI: 10.1016/j.jmb.2024.168440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 12/24/2023] [Accepted: 01/04/2024] [Indexed: 01/15/2024]
Abstract
Giardia lambliacauses giardiasis, one of the most common human infectious diseases globally. Previous studies from our lab have shown that hsp90 gene ofGiardia is split into two halves, namely hspN and hspC. The independent pre-mRNAs of these split genes join by trans-splicing, producing a full-length Hsp90 (FlHsp90) mRNA. Genetic manipulation of the participating genes is necessary to understand the mechanism and significance of such trans-splicing based expression of Hsp90. In this study, we have performed transfection based exogenous expression of hspN and/or hspC in G. lamblia. We electroporated a plasmid containing the Avi-tagged hspN component of Hsp90 and examined its fate in G. lamblia. We show that the exogenously expressed hspN RNA gets trans-spliced to endogenously expressed hspC RNA, giving rise to a hybrid-FlHsp90. We highlight the importance of cis-elements in this trans-splicing reaction through mutational analysis. The episomal plasmid carrying deletions in the intronic region of hspN, showed inhibition of the trans-splicing reaction.Additionally, exogenous hspC RNA also followed the same fate as of exogenous hspN, while upon co-transfection with episomal hspN, they underwent trans-splicing with each other. Using eGFP as a test protein, we have shown that intronic sequences of hsp90 gene can guide trans-splicing mediated repair of any associated exonic sequences. Our study provides in vivo validation of Hsp90 trans-splicing, showing crucial role of cis-elements and importantly highlights the potential of hsp90 intronic sequences to function as a minimal splicing tool.
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Affiliation(s)
- Sheetal Tushir
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - Pratima Jhanwar
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - Martin Benda
- Dept. of Parasitology, Faculty of Science, BIOCEV, Charles University, Czech Republic
| | - Vendula Horáčková
- Dept. of Parasitology, Faculty of Science, BIOCEV, Charles University, Czech Republic
| | - Pavel Doležal
- Dept. of Parasitology, Faculty of Science, BIOCEV, Charles University, Czech Republic
| | - Utpal Tatu
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India.
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Evolutionary honing in and mutational replacement: how long-term directed mutational responses to specific environmental pressures are possible. Theory Biosci 2023; 142:87-105. [PMID: 36899155 DOI: 10.1007/s12064-023-00387-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 01/13/2023] [Indexed: 03/12/2023]
Abstract
Recent results have shown that the human malaria-resistant hemoglobin S mutation originates de novo more frequently in the gene and in the population where it is of adaptive significance, namely, in the hemoglobin subunit beta gene compared to the nonresistant but otherwise identical 20A[Formula: see text]T mutation in the hemoglobin subunit delta gene, and in sub-Saharan Africans, who have been subject to intense malarial pressure for many generations, compared to northern Europeans, who have not. This finding raises a fundamental challenge to the traditional notion of accidental mutation. Here, we address this finding with the replacement hypothesis, according to which preexisting genetic interactions can lead directly and mechanistically to mutations that simplify and replace them. Thus, an evolutionary process under selection can gradually hone in on interactions of importance for the currently evolving adaptations, from which large-effect mutations follow that are relevant to these adaptations. We exemplify this hypothesis using multiple types of mutation, including gene fusion mutations, gene duplication mutations, A[Formula: see text]G mutations in RNA-edited sites and transcription-associated mutations, and place it in the broader context of a system-level view of mutation origination called interaction-based evolution. Potential consequences include that similarity of mutation pressures may contribute to parallel evolution in genetically related species, that the evolution of genome organization may be driven by mutational mechanisms, that transposable element movements may also be explained by replacement, and that long-term directed mutational responses to specific environmental pressures are possible. Such mutational phenomena need to be further tested by future studies in natural and artificial settings.
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5
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Genes that are Used Together are More Likely to be Fused Together in Evolution by Mutational Mechanisms: A Bioinformatic Test of the Used-Fused Hypothesis. Evol Biol 2023; 50:30-55. [PMID: 36816837 PMCID: PMC9925542 DOI: 10.1007/s11692-022-09579-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Accepted: 09/11/2022] [Indexed: 12/05/2022]
Abstract
Cases of parallel or recurrent gene fusions in evolution as well as in genetic disease and cancer are difficult to explain, because unlike point mutations, they can require the repetition of a similar configuration of multiple breakpoints rather than the repetition of a single point mutation. The used-together-fused-together hypothesis holds that genes that are used together repeatedly and persistently in a specific context are more likely to undergo fusion mutation in the course of evolution for mechanistic reasons. This hypothesis offers to explain gene fusion in both evolution and disease under one umbrella. Using bioinformatic data, we tested this hypothesis against alternatives, including that all gene pairs can fuse by random mutation, but among pairs thus fused, those that had interacted previously are more likely to be favored by selection. Results show that across multiple measures of gene interaction, human genes whose orthologs are fused in one or more species are more likely to interact with each other than random pairs of genes of the same genomic distance between pair members; that an overlap exists between genes that fused in the course of evolution in non-human species and genes that undergo fusion in human cancers; and that across six primate species studied, fusions predominate over fissions and exhibit substantial evolutionary parallelism. Together, these results support the used-together-fused-together hypothesis over its alternatives. Multiple implications are discussed, including the relevance of mutational mechanisms to the evolution of genome organization, to the distribution of fitness effects of mutation, to evolutionary parallelism and more. Supplementary Information The online version contains supplementary material available at 10.1007/s11692-022-09579-9.
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6
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Hou S, Li G, Xu B, Dong H, Zhang S, Fu Y, Shi J, Li L, Fu J, Shi F, Meng Y, Jin Y. Trans-splicing facilitated by RNA pairing greatly expands sDscam isoform diversity but not homophilic binding specificity. SCIENCE ADVANCES 2022; 8:eabn9458. [PMID: 35857463 PMCID: PMC9258826 DOI: 10.1126/sciadv.abn9458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 05/21/2022] [Indexed: 06/15/2023]
Abstract
The Down syndrome cell adhesion molecule 1 (Dscam1) gene can generate tens of thousands of isoforms via alternative splicing, which is essential for nervous and immune functions. Chelicerates generate approximately 50 to 100 shortened Dscam (sDscam) isoforms by alternative promoters, similar to mammalian protocadherins. Here, we reveal that trans-splicing markedly increases the repository of sDscamβ isoforms in Tetranychus urticae. Unexpectedly, every variable exon cassette engages in trans-splicing with constant exons from another cluster. Moreover, we provide evidence that competing RNA pairing not only governs alternative cis-splicing but also facilitates trans-splicing. Trans-spliced sDscam isoforms mediate cell adhesion ability but exhibit the same homophilic binding specificity as their cis-spliced counterparts. Thus, we reveal a single sDscam locus that generates diverse adhesion molecules through cis- and trans-splicing coupled with alternative promoters. These findings expand understanding of the mechanism underlying molecular diversity and have implications for the molecular control of neuronal and/or immune specificity.
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Affiliation(s)
- Shouqing Hou
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Guo Li
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Bingbing Xu
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Haiyang Dong
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Shixin Zhang
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Ying Fu
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Jilong Shi
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Lei Li
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Jiayan Fu
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Feng Shi
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
| | - Yijun Meng
- College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, Zhejiang ZJ310018, P. R. China
| | - Yongfeng Jin
- MOE Laboratory of Biosystems Homeostasis and Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang ZJ310058, P. R. China
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7
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Braun M, Shoshani S, Teixeira J, Mellul Shtern A, Miller M, Granot Z, Fischer SE, Garcia SMA, Tabach Y. Asymmetric inheritance of RNA toxicity in C. elegans expressing CTG repeats. iScience 2022; 25:104246. [PMID: 35494247 PMCID: PMC9051633 DOI: 10.1016/j.isci.2022.104246] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 03/01/2022] [Accepted: 04/07/2022] [Indexed: 11/18/2022] Open
Abstract
Nucleotide repeat expansions are a hallmark of over 40 neurodegenerative diseases and cause RNA toxicity and multisystemic symptoms that worsen with age. Through an unclear mechanism, RNA toxicity can trigger severe disease manifestation in infants if the repeats are inherited from their mother. Here we use Caenorhabditis elegans bearing expanded CUG repeats to show that this asymmetric intergenerational inheritance of toxicity contributes to disease pathogenesis. In addition, we show that this mechanism is dependent on small RNA pathways with maternal repeat-derived small RNAs causing transcriptomic changes in the offspring, reduced motility, and shortened lifespan. We rescued the toxicity phenotypes in the offspring by perturbing the RNAi machinery in the affected hermaphrodites. This points to a novel mechanism linking maternal bias and the RNAi machinery and suggests that toxic RNA is transmitted to offspring, causing disease phenotypes through intergenerational epigenetic inheritance. Maternal origin of expanded CUG repeats induces RNA toxicity in Caenorhabditis elegans offspring Offspring of affected hermaphrodites show molecular and phenotypic disease phenotypes The RNAi machinery is directly related to the maternal inheritance of RNA toxicity Altering the RNAi machinery in affected hermaphrodites rescues toxicity in offspring
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Affiliation(s)
- Maya Braun
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hebrew University of Jerusalem, Jerusalem 9112102, Israel
| | - Shachar Shoshani
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hebrew University of Jerusalem, Jerusalem 9112102, Israel
| | - Joana Teixeira
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki 00790 Finland
| | - Anna Mellul Shtern
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hebrew University of Jerusalem, Jerusalem 9112102, Israel
| | - Maya Miller
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hebrew University of Jerusalem, Jerusalem 9112102, Israel
| | - Zvi Granot
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hebrew University of Jerusalem, Jerusalem 9112102, Israel
| | - Sylvia E.J. Fischer
- Division of Infectious Diseases, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Susana M.D. A. Garcia
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki 00790 Finland
- Corresponding author
| | - Yuval Tabach
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, Hebrew University of Jerusalem, Jerusalem 9112102, Israel
- Corresponding author
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8
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Rzepnikowska W, Kochański A. Models for IGHMBP2-associated diseases: an overview and a roadmap for the future. Neuromuscul Disord 2021; 31:1266-1278. [PMID: 34785121 DOI: 10.1016/j.nmd.2021.08.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 07/16/2021] [Accepted: 08/06/2021] [Indexed: 12/13/2022]
Abstract
Models are practical tools with which to establish the basic aspects of a diseases. They allow systematic research into the significance of mutations, of cellular and molecular pathomechanisms, of therapeutic options and of functions of diseases associated proteins. Thus, disease models are an integral part of the study of enigmatic proteins such as immunoglobulin mu-binding protein 2 (IGHMBP2). IGHMBP2 has been well defined as a helicase, however there is little known about its role in cellular processes. Notably, it is unclear why changes in such an abundant protein lead to specific neuronal disorders including spinal muscular atrophy with respiratory distress type 1 (SMARD1) and Charcot-Marie-Tooth type 2S (CMT2S). SMARD1 is caused by a loss of motor neurons in the spinal cord that results in muscle atrophy and is accompanied by rapid respiratory failure. In contrast, CMT2S manifests as a severe neuropathy, but typically without critical breathing problems. Here, we present the clinical manifestation of IGHMBP2 mutations, function of protein and models that may be used for the study of IGHMBP2-associated disorders. We highlight the strengths and weaknesses of specific models and discuss the orthologs of IGHMBP2 that are found in different systems with regard to their similarity to human IGHMBP2.
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Affiliation(s)
- Weronika Rzepnikowska
- Neuromuscular Unit, Mossakowski Medical Research Institute Polish Academy of Sciences, Warsaw 02-106, Poland.
| | - Andrzej Kochański
- Neuromuscular Unit, Mossakowski Medical Research Institute Polish Academy of Sciences, Warsaw 02-106, Poland
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9
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Lidak T, Baloghova N, Korinek V, Sedlacek R, Balounova J, Kasparek P, Cermak L. CRL4-DCAF12 Ubiquitin Ligase Controls MOV10 RNA Helicase during Spermatogenesis and T Cell Activation. Int J Mol Sci 2021; 22:5394. [PMID: 34065512 PMCID: PMC8161014 DOI: 10.3390/ijms22105394] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Revised: 05/12/2021] [Accepted: 05/16/2021] [Indexed: 12/27/2022] Open
Abstract
Multisubunit cullin-RING ubiquitin ligase 4 (CRL4)-DCAF12 recognizes the C-terminal degron containing acidic amino acid residues. However, its physiological roles and substrates are largely unknown. Purification of CRL4-DCAF12 complexes revealed a wide range of potential substrates, including MOV10, an "ancient" RNA-induced silencing complex (RISC) complex RNA helicase. We show that DCAF12 controls the MOV10 protein level via its C-terminal motif in a proteasome- and CRL-dependent manner. Next, we generated Dcaf12 knockout mice and demonstrated that the DCAF12-mediated degradation of MOV10 is conserved in mice and humans. Detailed analysis of Dcaf12-deficient mice revealed that their testes produce fewer mature sperms, phenotype accompanied by elevated MOV10 and imbalance in meiotic markers SCP3 and γ-H2AX. Additionally, the percentages of splenic CD4+ T and natural killer T (NKT) cell populations were significantly altered. In vitro, activated Dcaf12-deficient T cells displayed inappropriately stabilized MOV10 and increased levels of activated caspases. In summary, we identified MOV10 as a novel substrate of CRL4-DCAF12 and demonstrated the biological relevance of the DCAF12-MOV10 pathway in spermatogenesis and T cell activation.
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Affiliation(s)
- Tomas Lidak
- Laboratory of Cancer Biology, Institute of Molecular Genetics of the Czech Academy of Sciences, 252 42 Vestec, Czech Republic; (T.L.); (N.B.); (V.K.)
- Faculty of Science, Charles University, 128 00 Prague, Czech Republic
| | - Nikol Baloghova
- Laboratory of Cancer Biology, Institute of Molecular Genetics of the Czech Academy of Sciences, 252 42 Vestec, Czech Republic; (T.L.); (N.B.); (V.K.)
| | - Vladimir Korinek
- Laboratory of Cancer Biology, Institute of Molecular Genetics of the Czech Academy of Sciences, 252 42 Vestec, Czech Republic; (T.L.); (N.B.); (V.K.)
- Laboratory of Cell and Developmental Biology, Institute of Molecular Genetics of the Czech Academy of Sciences, 252 42 Vestec, Czech Republic
| | - Radislav Sedlacek
- Czech Centre for Phenogenomics, Institute of Molecular Genetics of the Czech Academy of Sciences, 252 50 Vestec, Czech Republic; (R.S.); (J.B.); (P.K.)
| | - Jana Balounova
- Czech Centre for Phenogenomics, Institute of Molecular Genetics of the Czech Academy of Sciences, 252 50 Vestec, Czech Republic; (R.S.); (J.B.); (P.K.)
| | - Petr Kasparek
- Czech Centre for Phenogenomics, Institute of Molecular Genetics of the Czech Academy of Sciences, 252 50 Vestec, Czech Republic; (R.S.); (J.B.); (P.K.)
| | - Lukas Cermak
- Laboratory of Cancer Biology, Institute of Molecular Genetics of the Czech Academy of Sciences, 252 42 Vestec, Czech Republic; (T.L.); (N.B.); (V.K.)
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10
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Mao K, Breen P, Ruvkun G. Mitochondrial dysfunction induces RNA interference in C. elegans through a pathway homologous to the mammalian RIG-I antiviral response. PLoS Biol 2020; 18:e3000996. [PMID: 33264285 PMCID: PMC7735679 DOI: 10.1371/journal.pbio.3000996] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 12/14/2020] [Accepted: 11/09/2020] [Indexed: 12/27/2022] Open
Abstract
RNA interference (RNAi) is an antiviral pathway common to many eukaryotes that detects and cleaves foreign nucleic acids. In mammals, mitochondrially localized proteins such as mitochondrial antiviral signaling (MAVS), retinoic acid-inducible gene I (RIG-I), and melanoma differentiation-associated protein 5 (MDA5) mediate antiviral responses. Here, we report that mitochondrial dysfunction in Caenorhabditis elegans activates RNAi-directed silencing via induction of a pathway homologous to the mammalian RIG-I helicase viral response pathway. The induction of RNAi also requires the conserved RNA decapping enzyme EOL-1/DXO. The transcriptional induction of eol-1 requires DRH-1 as well as the mitochondrial unfolded protein response (UPRmt). Upon mitochondrial dysfunction, EOL-1 is concentrated into foci that depend on the transcription of mitochondrial RNAs that may form double-stranded RNA (dsRNA), as has been observed in mammalian antiviral responses. Enhanced RNAi triggered by mitochondrial dysfunction is necessary for the increase in longevity that is induced by mitochondrial dysfunction. Surveillance of mitochondrial dysfunction in the nematode Caenorhabditis elegans triggers the activation of an RNA interference pathway to mediate antiviral defense, in a manner homologous to the mammalian RIG-I helicase viral response pathway.
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Affiliation(s)
- Kai Mao
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Peter Breen
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Gary Ruvkun
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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11
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Rogers AK, Phillips CM. A Small-RNA-Mediated Feedback Loop Maintains Proper Levels of 22G-RNAs in C. elegans. Cell Rep 2020; 33:108279. [PMID: 33086057 PMCID: PMC7603289 DOI: 10.1016/j.celrep.2020.108279] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 08/27/2020] [Accepted: 09/24/2020] [Indexed: 02/06/2023] Open
Abstract
RNA interference (RNAi) is an essential regulatory mechanism in all animals. In Caenorhabditis elegans, several classes of small RNAs act to silence or license expression of mRNA targets. ERI-6/7 is required for the production of some endogenous small interfering RNAs (siRNAs) and acts as a negative regulator of the exogenous RNAi pathway. We find that the genomic locus encoding eri-6/7 contains two distinct regions that are targeted by endogenous siRNAs. Loss of these siRNAs disrupts eri-6/7 mRNA expression, resulting in increased production of siRNAs from other small RNA pathways because these pathways compete with eri-6/7-dependent transcripts for access to the downstream siRNA amplification machinery. Thus, the pathway acts like a small-RNA-mediated feedback loop to ensure homeostasis of gene expression by small RNA pathways. Similar feedback loops that maintain chromatin homeostasis have been identified in yeast and Drosophila melanogaster, suggesting an evolutionary conservation of feedback mechanisms in gene regulatory pathways.
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Affiliation(s)
- Alicia K Rogers
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Carolyn M Phillips
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA.
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12
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Xu B, Meng Y, Jin Y. RNA structures in alternative splicing and back-splicing. WILEY INTERDISCIPLINARY REVIEWS-RNA 2020; 12:e1626. [PMID: 32929887 DOI: 10.1002/wrna.1626] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 08/14/2020] [Accepted: 08/22/2020] [Indexed: 12/12/2022]
Abstract
Alternative splicing greatly expands the transcriptomic and proteomic diversities related to physiological and developmental processes in higher eukaryotes. Splicing of long noncoding RNAs, and back- and trans- splicing further expanded the regulatory repertoire of alternative splicing. RNA structures were shown to play an important role in regulating alternative splicing and back-splicing. Application of novel sequencing technologies made it possible to identify genome-wide RNA structures and interaction networks, which might provide new insights into RNA splicing regulation in vitro to in vivo. The emerging transcription-folding-splicing paradigm is changing our understanding of RNA alternative splicing regulation. Here, we review the insights into the roles and mechanisms of RNA structures in alternative splicing and back-splicing, as well as how disruption of these structures affects alternative splicing and then leads to human diseases. This article is categorized under: RNA Processing > Splicing Regulation/Alternative Splicing RNA Structure and Dynamics > Influence of RNA Structure in Biological Systems.
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Affiliation(s)
- Bingbing Xu
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Zhejiang, Hangzhou, China
| | - Yijun Meng
- College of Life and Environmental Sciences, Hangzhou Normal University, Zhejiang, Hangzhou, China
| | - Yongfeng Jin
- MOE Laboratory of Biosystems Homeostasis & Protection and Innovation Center for Cell Signaling Network, College of Life Sciences, Zhejiang University, Zhejiang, Hangzhou, China
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13
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Ye C, Jiang S, Gong M, Min Q, Fan M, Gao J, Meng Y. Expressional Localization and Functionally Identifying an RNA Editing Enzyme BmADARa of the Silkworm Bombyx mori. INSECTS 2020; 11:insects11080523. [PMID: 32806497 PMCID: PMC7469206 DOI: 10.3390/insects11080523] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Revised: 08/04/2020] [Accepted: 08/07/2020] [Indexed: 11/16/2022]
Abstract
The most common type of RNA editing in metazoans is the deamination of adenosine into inosine (A-to-I) catalyzed by the adenosine deaminase acting on the RNA (ADAR) family of proteins. The deletion or dysfunction of ADAR enzymes in higher eukaryotes can affect the efficiency of substrate editing and cause neurological disorders. However, the information concerning A-to-I RNA editing and ADAR members in the silkworm, Bombyx mori (BmADAR), is limited. In this study, a first molecular comprehensive cloning and sequence analysis of BmADAR transcripts was presented. A complete open reading frame (ORF) (BmADARa) was obtained using RT-PCR and RACE and its expression pattern, subcellular localization and A-to-I RNA-editing function on the silkworm synaptotagmin I (BmSyt I) were investigated. Subcellular localization analysis observed that BmADARa was mainly localized in the nucleus. To further study the A-to-I RNA-editing function of BmADARa, BmSyt I-pIZ-EGFP was constructed and co-transfected with BmADARa-pIZ-EGFP into BmN cells. The result demonstrates that BmADARa can functionally edit the specific site of BmSyt I. Taken together, this study not only provides insight into the function of the first ADAR enzyme in B. mori, but also lays foundations for further exploration of the functional domain of BmADARa and its editing substrates and target sites.
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Affiliation(s)
- Chongjun Ye
- School of Life Sciences, Anhui Agricultural University, 130 West Changjiang Road, Hefei 230036, China; (C.Y.); (S.J.); (Q.M.); (M.F.)
- Institute of Sericulture, Anhui Academy of Agricultural Sciences, 15 Huoshan Road, Hefei 230061, China
| | - Song Jiang
- School of Life Sciences, Anhui Agricultural University, 130 West Changjiang Road, Hefei 230036, China; (C.Y.); (S.J.); (Q.M.); (M.F.)
- Anhui International Joint Research and Development Center of Sericulture Resources Utilization, Hefei 230036, China
| | - Meixia Gong
- Guangxi Zhuang Autonomous Region Research Academy of Sericultural Science, 10 Xiajun Road, Nanning 530007, China;
| | - Qin Min
- School of Life Sciences, Anhui Agricultural University, 130 West Changjiang Road, Hefei 230036, China; (C.Y.); (S.J.); (Q.M.); (M.F.)
| | - Manli Fan
- School of Life Sciences, Anhui Agricultural University, 130 West Changjiang Road, Hefei 230036, China; (C.Y.); (S.J.); (Q.M.); (M.F.)
| | - Junshan Gao
- School of Life Sciences, Anhui Agricultural University, 130 West Changjiang Road, Hefei 230036, China; (C.Y.); (S.J.); (Q.M.); (M.F.)
- Anhui International Joint Research and Development Center of Sericulture Resources Utilization, Hefei 230036, China
- Correspondence: (J.G.); (Y.M.); Tel.: +86-551-65786967 (Y.M.)
| | - Yan Meng
- School of Life Sciences, Anhui Agricultural University, 130 West Changjiang Road, Hefei 230036, China; (C.Y.); (S.J.); (Q.M.); (M.F.)
- Anhui International Joint Research and Development Center of Sericulture Resources Utilization, Hefei 230036, China
- Correspondence: (J.G.); (Y.M.); Tel.: +86-551-65786967 (Y.M.)
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14
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Manage KI, Rogers AK, Wallis DC, Uebel CJ, Anderson DC, Nguyen DAH, Arca K, Brown KC, Cordeiro Rodrigues RJ, de Albuquerque BF, Ketting RF, Montgomery TA, Phillips CM. A tudor domain protein, SIMR-1, promotes siRNA production at piRNA-targeted mRNAs in C. elegans. eLife 2020; 9:56731. [PMID: 32338603 PMCID: PMC7255803 DOI: 10.7554/elife.56731] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Accepted: 04/24/2020] [Indexed: 02/06/2023] Open
Abstract
piRNAs play a critical role in the regulation of transposons and other germline genes. In Caenorhabditis elegans, regulation of piRNA target genes is mediated by the mutator complex, which synthesizes high levels of siRNAs through the activity of an RNA-dependent RNA polymerase. However, the steps between mRNA recognition by the piRNA pathway and siRNA amplification by the mutator complex are unknown. Here, we identify the Tudor domain protein, SIMR-1, as acting downstream of piRNA production and upstream of mutator complex-dependent siRNA biogenesis. Interestingly, SIMR-1 also localizes to distinct subcellular foci adjacent to P granules and Mutator foci, two phase-separated condensates that are the sites of piRNA-dependent mRNA recognition and mutator complex-dependent siRNA amplification, respectively. Thus, our data suggests a role for multiple perinuclear condensates in organizing the piRNA pathway and promoting mRNA regulation by the mutator complex. In the biological world, a process known as RNA interference helps cells to switch genes on and off and to defend themselves against harmful genetic material. This mechanism works by deactivating RNA sequences, the molecular templates cells can use to create proteins. Overall, RNA interference relies on the cell creating small RNA molecules that can target and inhibit the harmful RNA sequences that need to be silenced. More precisely, in round worms such as Caenorhabditis elegans, RNA interference happens in two steps. First, primary small RNAs identify the target sequences, which are then combatted by newly synthetised, secondary small RNAs. A number of proteins are also involved in both steps of the process. RNA interference is particularly important to preserve fertility, guarding sex cells against ‘rogue’ segments of genetic information that could be passed on to the next generation. In future sex cells, the proteins involved in RNA interference cluster together, forming a structure called a germ granule. Yet, little is known about the roles and identity of these proteins. To fill this knowledge gap, Manage et al. focused on the second stage of the RNA interference pathway in the germ granules of C. elegans, examining the molecules that physically interact with a key protein. This work revealed a new protein called SIMR-1. Looking into the role of SIMR-1 showed that the protein is required to amplify secondary small RNAs, but not to identify target sequences. However, it only promotes the creation of secondary small RNAs if a specific subtype of primary small RNAs have recognized the target RNAs for silencing. Further experiments also showed that within the germ granule, SIMR-1 is present in a separate substructure different from any compartment previously identified. This suggests that each substep of the RNA interference process takes place at a different location in the granule. In both C. elegans and humans, disruptions in the RNA interference pathway can lead to conditions such as cancer or infertility. Dissecting the roles of the proteins involved in this process in roundworms may help to better grasp how this process unfolds in mammals, and how it could be corrected in the case of disease.
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Affiliation(s)
- Kevin I Manage
- Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Alicia K Rogers
- Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Dylan C Wallis
- Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Celja J Uebel
- Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Dorian C Anderson
- Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Dieu An H Nguyen
- Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Katerina Arca
- Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Kristen C Brown
- Department of Biology, Colorado State University, Fort Collins, United States.,Cell and Molecular Biology Program, Colorado State University, Fort Collins, United States
| | - Ricardo J Cordeiro Rodrigues
- Biology of Non-coding RNA Group, Institute of Molecular Biology, Mainz, Germany.,International PhD Programme on Gene Regulation, Epigenetics, and Genome Stability, Mainz, Germany
| | | | - René F Ketting
- Biology of Non-coding RNA Group, Institute of Molecular Biology, Mainz, Germany
| | - Taiowa A Montgomery
- Department of Biology, Colorado State University, Fort Collins, United States
| | - Carolyn Marie Phillips
- Department of Biological Sciences, University of Southern California, Los Angeles, United States
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15
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Xiao Y, Kang B, Li M, Xiao L, Xiao H, Shen H, Yang W. Transcription of lncRNA ACoS-AS1 is essential to trans-splicing between SlPsy1 and ACoS-AS1 that causes yellow fruit in tomato. RNA Biol 2020; 17:596-607. [PMID: 31983318 PMCID: PMC7237131 DOI: 10.1080/15476286.2020.1721095] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 11/28/2019] [Accepted: 12/23/2019] [Indexed: 10/25/2022] Open
Abstract
Phytoene synthase (PSY) has been considered as an important regulatory enzyme in carotenoids biosynthesis pathway. Previous study finds that the yellow fruit in Solanum lycopersicum var. cerasiforme accession PI 114490 is caused by loss-of-function of SlPSY1 due to trans-splicing between SlPsy1 and an unknown gene transcribed from neighbour opposite strand DNA of SlPsy1. The genomic DNA sequences of SlPsy1 between red and yellow-fruited tomato lines have one single-nucleotide polymorphism (SNP) in the fourth intron and one SSR in the intergenic region. In the current study, the cause of trans-splicing event was further investigated. The data showed that the previously defined unknown gene was a putative long non-coding RNA ACoS-AS1 with three variants in many yellow-fruited tomato lines. The intronic SNP and intergenic SSR were tightly associated with trans-splicing event SlPsy1-ACoS-AS1. However, transgenic tomato lines carrying the genomic DNA of SlPsy1 from PI 114490 did not generate transcripts of ACoS-AS1and SlPsy1-ACoS-AS1 suggesting that only the intronic SNP could not cause the trans-splicing event. Over-expression of SlPsy1-ACoS-AS1 in red-fruited tomato line M82 did not have any phenotype change while over-expression of wild type SlPsy1 resulted in altered leaf colour. Sub-cellular localization analysis showed that SlPSY1-ACoS-AS1 could not enter plastids where SlPSY1 has its enzyme activity. Mutation of ACoS-AS1 in PI 114490 generated by CRISPR/Cas9 techniques resulted in red fruits implying that ACoS-AS1 was essential to trans-splicing event SlPsy1-ACoS-AS1. The results obtained here will extend knowledge to understand the mechanism of trans-splicing event SlPsy1-ACoS-AS1 and provide additional information for the regulation of carotenoids biosynthesis.
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Affiliation(s)
- Yao Xiao
- Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetable Science, China Agricultural University, Beijing, China
- Joint Laboratory for International Cooperation in Crop Molecular Breeding, Ministry of Education of the People’s Republic of China, Beijing, China
| | - Baoshan Kang
- Zhengzhou Fruit Research Institute, Chinese Academy of Agricultural Sciences, Zhengzhou, China
| | - Meng Li
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Liangjun Xiao
- Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetable Science, China Agricultural University, Beijing, China
| | - Han Xiao
- National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, China
| | - Huolin Shen
- Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetable Science, China Agricultural University, Beijing, China
| | - Wencai Yang
- Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetable Science, China Agricultural University, Beijing, China
- Joint Laboratory for International Cooperation in Crop Molecular Breeding, Ministry of Education of the People’s Republic of China, Beijing, China
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16
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Caenorhabditis elegans ADAR editing and the ERI-6/7/MOV10 RNAi pathway silence endogenous viral elements and LTR retrotransposons. Proc Natl Acad Sci U S A 2020; 117:5987-5996. [PMID: 32123111 PMCID: PMC7084138 DOI: 10.1073/pnas.1919028117] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Silencing of transposable elements and viruses is critical for the maintenance of genome integrity, cellular homeostasis, and organismal health. Here we describe multiple factors that control different types of transposable elements, providing insight into how they are regulated. We also identify stress response pathways that are triggered upon misregulation of these transposable elements. The conservation of these factors and pathways in human suggests that our studies in Caenorhabditis elegans can provide general insight into the regulation of and response to transposable elements and viruses. Endogenous retroviruses and long terminal repeat (LTR) retrotransposons are mobile genetic elements that are closely related to retroviruses. Desilenced endogenous retroviruses are associated with human autoimmune disorders and neurodegenerative diseases. Caenorhabditis elegans and related Caenorhabditis spp. contain LTR retrotransposons and, as described here, numerous integrated viral genes including viral envelope genes that are part of LTR retrotransposons. We found that both LTR retrotransposons and endogenous viral elements are silenced by ADARs [adenosine deaminases acting on double-stranded RNA (dsRNA)] together with the endogenous RNA interference (RNAi) factor ERI-6/7, a homolog of MOV10 helicase, a retrotransposon and retrovirus restriction factor in human. siRNAs corresponding to integrated viral genes and LTR retrotransposons, but not to DNA transposons, are dependent on the ADARs and ERI-6/7. siRNAs corresponding to palindromic repeats are independent of the ADARs and ERI-6/7, and are in fact increased in adar- and eri-6/7–defective mutants because of an antiviral RNAi response to dsRNA. Silencing of LTR retrotransposons is dependent on downstream RNAi factors and P granule components but is independent of the viral sensor DRH-1/RIG-I and the nuclear Argonaute NRDE-3. The activation of retrotransposons in the ADAR- and ERI-6/7/MOV10–defective mutant is associated with the induction of the unfolded protein response (UPR), a common response to viral infection. The overlap between genes induced upon viral infection and infection with intracellular pathogens and genes coexpressed with retrotransposons suggests that there is a common response to different types of foreign elements that includes a response to proteotoxicity presumably caused by the burden of replicating pathogens and expressed retrotransposons.
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17
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Tian L, Zeng Y, Xie W, Wu Q, Wang S, Zhou X, Zhang Y. Genome-wide identification and analysis of genes associated with RNA interference in Bemisia tabaci. PEST MANAGEMENT SCIENCE 2019; 75:3005-3014. [PMID: 30891929 DOI: 10.1002/ps.5415] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 03/10/2019] [Accepted: 03/16/2019] [Indexed: 05/14/2023]
Abstract
BACKGROUND As a method of RNA-mediated gene silencing, RNA interference (RNAi) is a useful reverse genetic tool with which to study gene function, and holds great promise for pest management. Bemisia tabaci is a cosmopolitan pest that causes extensive damage to crops. The mechanism underlying RNAi efficiency in B. tabaci is not well known. We identified and analyzed candidate genes in the RNAi pathway to understand the RNAi mechanism and provide a basis for the application of RNAi in pest management. RESULTS We identified 33 genes putatively involved in the RNAi pathway from the B. tabaci Q genome. Phylogenetic and structural analyses confirmed the characteristics of these genes. Furthermore, quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) and transcriptomic analysis profiled gene expression patterns during different developmental stages. Gene expression levels estimated by qRT-PCR and RNA-seq analyses were significantly correlated. Moreover, gene functions were verified by RNAi. When accompanied by knockdown of AGO2, Dicer2 and Sid1, the efficiency of CYP6DB3 RNAi decreased correspondingly. CONCLUSION In this study, we annotated and validated genes involved in B. tabaci RNAi. A better understanding of the building blocks of the RNAi process in B. tabaci facilitates integration of this novel biotechnology into the management of this emerging pest, either directly or indirectly. © 2019 Society of Chemical Industry.
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Affiliation(s)
- Lixia Tian
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Yang Zeng
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Wen Xie
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Qingjun Wu
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Shaoli Wang
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Xuguo Zhou
- Department of Entomology, University of Kentucky, Lexington, KY, USA
| | - Youjun Zhang
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, China
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18
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Roy SW, Bowser BA. Molecular Evolution: RNA Splicing Machinery Moonlights in Junk Removal. Curr Biol 2019; 29:R920-R922. [PMID: 31593665 DOI: 10.1016/j.cub.2019.08.046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A close relative of vertebrates solves the problem of gene-disrupting transposable element insertions by splicing them out at the RNA level. Why is such an elegant solution so rare across eukaryotes?
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Affiliation(s)
- Scott W Roy
- Department of Biology, San Francisco State University, San Francisco, CA 94132, USA; Molecular Cell Biology, University of California-Merced, Merced, CA 95343, USA.
| | - Bradley A Bowser
- Molecular Cell Biology, University of California-Merced, Merced, CA 95343, USA
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19
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Chuang TJ, Chen YJ, Chen CY, Mai TL, Wang YD, Yeh CS, Yang MY, Hsiao YT, Chang TH, Kuo TC, Cho HH, Shen CN, Kuo HC, Lu MY, Chen YH, Hsieh SC, Chiang TW. Integrative transcriptome sequencing reveals extensive alternative trans-splicing and cis-backsplicing in human cells. Nucleic Acids Res 2019; 46:3671-3691. [PMID: 29385530 PMCID: PMC6283421 DOI: 10.1093/nar/gky032] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 01/13/2018] [Indexed: 01/16/2023] Open
Abstract
Transcriptionally non-co-linear (NCL) transcripts can originate from trans-splicing (trans-spliced RNA; 'tsRNA') or cis-backsplicing (circular RNA; 'circRNA'). While numerous circRNAs have been detected in various species, tsRNAs remain largely uninvestigated. Here, we utilize integrative transcriptome sequencing of poly(A)- and non-poly(A)-selected RNA-seq data from diverse human cell lines to distinguish between tsRNAs and circRNAs. We identified 24,498 NCL events and found that a considerable proportion (20-35%) of them arise from both tsRNAs and circRNAs, representing extensive alternative trans-splicing and cis-backsplicing in human cells. We show that sequence generalities of exon circularization are also observed in tsRNAs. Recapitulation of NCL RNAs further shows that inverted Alu repeats can simultaneously promote the formation of tsRNAs and circRNAs. However, tsRNAs and circRNAs exhibit quite different, or even opposite, expression patterns, in terms of correlation with the expression of their co-linear counterparts, expression breadth/abundance, transcript stability, and subcellular localization preference. These results indicate that tsRNAs and circRNAs may play different regulatory roles and analysis of NCL events should take the joint effects of different NCL-splicing types and joint effects of multiple NCL events into consideration. This study describes the first transcriptome-wide analysis of trans-splicing and cis-backsplicing, expanding our understanding of the complexity of the human transcriptome.
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Affiliation(s)
- Trees-Juen Chuang
- Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan.,Genome and Systems Biology Degree Program, National Taiwan University, Taipei 10617 & Academia Sinica, Taipei 11529, Taiwan
| | - Yen-Ju Chen
- Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan.,Genome and Systems Biology Degree Program, National Taiwan University, Taipei 10617 & Academia Sinica, Taipei 11529, Taiwan
| | - Chia-Ying Chen
- Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Te-Lun Mai
- Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Yi-Da Wang
- Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Chung-Shu Yeh
- Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan.,Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 11221, Taiwan
| | - Min-Yu Yang
- Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Yu-Ting Hsiao
- Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan
| | | | - Tzu-Chien Kuo
- Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Hsin-Hua Cho
- Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Chia-Ning Shen
- Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Hung-Chih Kuo
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Mei-Yeh Lu
- High Throughput Genomics Core, Biodiversity Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Yi-Hua Chen
- High Throughput Genomics Core, Biodiversity Research Center, Academia Sinica, Taipei 11529, Taiwan
| | - Shan-Chi Hsieh
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Tai-Wei Chiang
- Genomics Research Center, Academia Sinica, Taipei 11529, Taiwan
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20
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Iyer V, Chettiar ST, Grover M, Rajyaguru P, Nageshan RK, Tatu U. Giardia lamblia
Hsp90 pre‐
mRNA
s undergo self‐splicing to generate mature
RNA
in an
in vitro
trans‐splicing reaction. FEBS Lett 2019; 593:433-442. [DOI: 10.1002/1873-3468.13324] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 12/26/2018] [Indexed: 11/06/2022]
Affiliation(s)
- Vinithra Iyer
- Department of Biochemistry Indian Institute of Science Bangalore India
| | | | - Manish Grover
- Department of Biochemistry Indian Institute of Science Bangalore India
| | | | | | - Utpal Tatu
- Department of Biochemistry Indian Institute of Science Bangalore India
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21
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Almeida MV, Andrade-Navarro MA, Ketting RF. Function and Evolution of Nematode RNAi Pathways. Noncoding RNA 2019; 5:E8. [PMID: 30650636 PMCID: PMC6468775 DOI: 10.3390/ncrna5010008] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 01/07/2019] [Accepted: 01/08/2019] [Indexed: 12/11/2022] Open
Abstract
Selfish genetic elements, like transposable elements or viruses, are a threat to genomic stability. A variety of processes, including small RNA-based RNA interference (RNAi)-like pathways, has evolved to counteract these elements. Amongst these, endogenous small interfering RNA and Piwi-interacting RNA (piRNA) pathways were implicated in silencing selfish genetic elements in a variety of organisms. Nematodes have several incredibly specialized, rapidly evolving endogenous RNAi-like pathways serving such purposes. Here, we review recent research regarding the RNAi-like pathways of Caenorhabditis elegans as well as those of other nematodes, to provide an evolutionary perspective. We argue that multiple nematode RNAi-like pathways share piRNA-like properties and together form a broad nematode toolkit that allows for silencing of foreign genetic elements.
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Affiliation(s)
| | - Miguel A Andrade-Navarro
- Institute of Molecular Biology, Ackermannweg 4, 55128 Mainz, Germany.
- Faculty of Biology, Johannes Gutenberg Universität, 55122 Mainz, Germany.
| | - René F Ketting
- Institute of Molecular Biology, Ackermannweg 4, 55128 Mainz, Germany.
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22
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Newman MA, Ji F, Fischer SEJ, Anselmo A, Sadreyev RI, Ruvkun G. The surveillance of pre-mRNA splicing is an early step in C. elegans RNAi of endogenous genes. Genes Dev 2018; 32:670-681. [PMID: 29739806 PMCID: PMC6004069 DOI: 10.1101/gad.311514.118] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 04/03/2018] [Indexed: 01/03/2023]
Abstract
Here, Newman et al. provide insight into the role of mRNA splicing in C. elegans RNAi and show that viable null mutations in U1 and U2 snRNP-specific splicing factor genes cause defects in RNAi. They also demonstrate that RNAi targeted transcripts are tightly bound to spliceosomes, which suggests multiple layers of regulation by the spliceosome at early steps of small RNA-mediated gene silencing. RNAi pathways detect and silence foreign nucleic acids such as viruses as well as endogenous genes in many species. The phylogenetic profile across eukaryotes of proteins that mediate key steps in RNAi is correlated with the profiles of multiple mRNA splicing proteins and with intron number, suggesting that RNAi may surveil mRNA splicing to detect the divergent or absent introns of viruses. Here we examine the role of mRNA splicing in Caenorhabditis elegans RNAi. We found that viable null mutations in U1 and U2 small nuclear ribonucleic protein (snRNP)-specific splicing factor genes cause defects in RNAi. The U1A ortholog rnp-2 is required for normal ERGO-1 Argonaute class 26G siRNA biogenesis, trans-splicing of the eri-6/7 transcript, and targeting of poorly conserved gene transcripts by WAGO Argonaute class 22G siRNAs. We found that gene transcripts engaged by the siRNA-generating machinery are poorly conserved, possess few introns, and often have introns that are divergent from introns with strong consensus splicing sites found in highly conserved genes. We present biochemical evidence that RNAi targeted transcripts are tightly bound to spliceosomes. These findings suggest multiple layers of regulation by the spliceosome at early steps of small RNA-mediated gene silencing.
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Affiliation(s)
- Martin A Newman
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Fei Ji
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Sylvia E J Fischer
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Anthony Anselmo
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Ruslan I Sadreyev
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Gary Ruvkun
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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23
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Davidsson M, Díaz-Fernández P, Torroba M, Schwich OD, Aldrin-Kirk P, Quintino L, Heuer A, Wang G, Lundberg C, Björklund T. Molecular barcoding of viral vectors enables mapping and optimization of mRNA trans-splicing. RNA (NEW YORK, N.Y.) 2018; 24:673-687. [PMID: 29386333 PMCID: PMC5900565 DOI: 10.1261/rna.063925.117] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 01/25/2018] [Indexed: 05/04/2023]
Abstract
Genome editing has proven to be highly potent in the generation of functional gene knockouts in dividing cells. In the CNS however, efficient technologies to repair sequences are yet to materialize. Reprogramming on the mRNA level is an attractive alternative as it provides means to perform in situ editing of coding sequences without nuclease dependency. Furthermore, de novo sequences can be inserted without the requirement of homologous recombination. Such reprogramming would enable efficient editing in quiescent cells (e.g., neurons) with an attractive safety profile for translational therapies. In this study, we applied a novel molecular-barcoded screening assay to investigate RNA trans-splicing in mammalian neurons. Through three alternative screening systems in cell culture and in vivo, we demonstrate that factors determining trans-splicing are reproducible regardless of the screening system. With this screening, we have located the most permissive trans-splicing sequences targeting an intron in the Synapsin I gene. Using viral vectors, we were able to splice full-length fluorophores into the mRNA while retaining very low off-target expression. Furthermore, this approach also showed evidence of functionality in the mouse striatum. However, in its current form, the trans-splicing events are stochastic and the overall activity lower than would be required for therapies targeting loss-of-function mutations. Nevertheless, the herein described barcode-based screening assay provides a unique possibility to screen and map large libraries in single animals or cell assays with very high precision.
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Affiliation(s)
- Marcus Davidsson
- Molecular Neuromodulation, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden
| | - Paula Díaz-Fernández
- Molecular Neuromodulation, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden
| | - Marcos Torroba
- Molecular Neuromodulation, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden
| | - Oliver D Schwich
- Molecular Neuromodulation, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden
| | - Patrick Aldrin-Kirk
- Molecular Neuromodulation, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden
| | - Luis Quintino
- CNS Gene Therapy, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden
| | - Andreas Heuer
- Molecular Neuromodulation, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden
| | - Gang Wang
- Molecular Neuromodulation, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden
| | - Cecilia Lundberg
- CNS Gene Therapy, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden
| | - Tomas Björklund
- Molecular Neuromodulation, Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden
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Fontenla S, Rinaldi G, Smircich P, Tort JF. Conservation and diversification of small RNA pathways within flatworms. BMC Evol Biol 2017; 17:215. [PMID: 28893179 PMCID: PMC5594548 DOI: 10.1186/s12862-017-1061-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 09/05/2017] [Indexed: 02/04/2023] Open
Abstract
Background Small non-coding RNAs, including miRNAs, and gene silencing mediated by RNA interference have been described in free-living and parasitic lineages of flatworms, but only few key factors of the small RNA pathways have been exhaustively investigated in a limited number of species. The availability of flatworm draft genomes and predicted proteomes allowed us to perform an extended survey of the genes involved in small non-coding RNA pathways in this phylum. Results Overall, findings show that the small non-coding RNA pathways are conserved in all the analyzed flatworm linages; however notable peculiarities were identified. While Piwi genes are amplified in free-living worms they are completely absent in all parasitic species. Remarkably all flatworms share a specific Argonaute family (FL-Ago) that has been independently amplified in different lineages. Other key factors such as Dicer are also duplicated, with Dicer-2 showing structural differences between trematodes, cestodes and free-living flatworms. Similarly, a very divergent GW182 Argonaute interacting protein was identified in all flatworm linages. Contrasting to this, genes involved in the amplification of the RNAi interfering signal were detected only in the ancestral free living species Macrostomum lignano. We here described all the putative small RNA pathways present in both free living and parasitic flatworm lineages. Conclusion These findings highlight innovations specifically evolved in platyhelminths presumably associated with novel mechanisms of gene expression regulation mediated by small RNA pathways that differ to what has been classically described in model organisms. Understanding these phylum-specific innovations and the differences between free living and parasitic species might provide clues to adaptations to parasitism, and would be relevant for gene-silencing technology development for parasitic flatworms that infect hundreds of million people worldwide. Electronic supplementary material The online version of this article (10.1186/s12862-017-1061-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Santiago Fontenla
- Departamento de Genética, Facultad de Medicina, Universidad de la República (UDELAR), Gral. Flores 2125, CP11800, Montevideo, MVD, Uruguay
| | - Gabriel Rinaldi
- Parasite Genomics, Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - Pablo Smircich
- Departamento de Genética, Facultad de Medicina, Universidad de la República (UDELAR), Gral. Flores 2125, CP11800, Montevideo, MVD, Uruguay.,Laboratorio de Interacciones Moleculares, Facultad de Ciencias, Universidad de la República (UdelaR), Montevideo, Uruguay
| | - Jose F Tort
- Departamento de Genética, Facultad de Medicina, Universidad de la República (UDELAR), Gral. Flores 2125, CP11800, Montevideo, MVD, Uruguay.
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Silencing of Repetitive DNA Is Controlled by a Member of an Unusual Caenorhabditis elegans Gene Family. Genetics 2017; 207:529-545. [PMID: 28801529 DOI: 10.1534/genetics.117.300134] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 08/10/2017] [Indexed: 01/08/2023] Open
Abstract
Repetitive DNA sequences are subject to gene silencing in various animal species. Under specific circumstances repetitive DNA sequences can escape such silencing. For example, exogenously added, extrachromosomal DNA sequences that are stably inherited in multicopy repetitive arrays in the nematode Caenorhabditis elegans are frequently silenced in the germline, whereas such silencing often does not occur in the soma. This indicates that somatic cells might utilize factors that prevent repetitive DNA silencing. Indeed, such "antisilencing" factors have been revealed through genetic screens that identified mutant loci in which repetitive transgenic arrays are aberrantly silenced in the soma. We describe here a novel locus, pals-22 (for protein containing ALS2CR12 signature), required to prevent silencing of repetitive transgenes in neurons and other somatic tissue types. pals-22 deficiency also severely impacts animal vigor and confers phenotypes reminiscent of accelerated aging. We find that pals-22 is a member of a large family of divergent genes (39 members), defined by homology to the ALS2CR12 protein family. While gene family members are highly divergent, they show striking patterns of chromosomal clustering. The family expansion appears C. elegans-specific and has not occurred to the same extent in other nematode species for which genome sequences are available. The transgene-silencing phenotype observed upon loss of PALS-22 protein depends on the biogenesis of small RNAs. We speculate that the pals gene family may be part of a species-specific cellular defense mechanism.
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Simplification, Innateness, and the Absorption of Meaning from Context: How Novelty Arises from Gradual Network Evolution. Evol Biol 2017; 44:145-189. [PMID: 28572690 PMCID: PMC5429377 DOI: 10.1007/s11692-017-9407-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 01/06/2017] [Indexed: 02/07/2023]
Abstract
How does new genetic information arise? Traditional thinking holds that mutation happens by accident and then spreads in the population by either natural selection or random genetic drift. There have been at least two fundamental conceptual problems with imagining an alternative. First, it seemed that the only alternative is a mutation that responds "smartly" to the immediate environment; but in complex multicellulars, it is hard to imagine how this could be implemented. Second, if there were mechanisms of mutation that "knew" what genetic changes would be favored in a given environment, this would have only begged the question of how they acquired that particular knowledge to begin with. This paper offers an alternative that avoids these problems. It holds that mutational mechanisms act on information that is in the genome, based on considerations of simplicity, parsimony, elegance, etc. (which are different than fitness considerations). This simplification process, under the performance pressure exerted by selection, not only leads to the improvement of adaptations but also creates elements that have the capacity to serve in new contexts they were not originally selected for. Novelty, then, arises at the system level from emergent interactions between such elements. Thus, mechanistically driven mutation neither requires Lamarckian transmission nor closes the door on novelty, because the changes it implements interact with one another globally in surprising and beneficial ways. Finally, I argue, for example, that genes used together are fused together; that simplification leads to complexity; and that evolution and learning are conceptually linked.
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Zhao Y, Holmgren BT, Hinas A. The conserved SNARE SEC-22 localizes to late endosomes and negatively regulates RNA interference in Caenorhabditis elegans. RNA (NEW YORK, N.Y.) 2017; 23:297-307. [PMID: 27974622 PMCID: PMC5311485 DOI: 10.1261/rna.058438.116] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 12/09/2016] [Indexed: 06/06/2023]
Abstract
Small RNA pathways, including RNA interference (RNAi), play crucial roles in regulation of gene expression. Initially considered to be cytoplasmic, these processes have later been demonstrated to associate with membranes. For example, maturation of late endosomes/multivesicular bodies (MVBs) is required for efficient RNAi, whereas fusion of MVBs to lysosomes appears to reduce silencing efficiency. SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) mediate membrane fusion and are thus at the core of membrane trafficking. In spite of this, no SNARE has previously been reported to affect RNAi. Here, we demonstrate that in Caenorhabditis elegans, loss of the conserved SNARE SEC-22 results in enhanced RNAi upon ingestion of double-stranded RNA. Furthermore, SEC-22 overexpression inhibits RNAi in wild-type animals. We find that overexpression of SEC-22 in the target tissue (body wall muscle) strongly suppresses the sec-22(-) enhanced RNAi phenotype, supporting a primary role for SEC-22 in import of RNAi silencing signals or cell autonomous RNAi. A functional mCherry::SEC-22 protein localizes primarily to late endosomes/MVBs and these compartments are enlarged in animals lacking sec-22 SEC-22 interacts with late endosome-associated RNA transport protein SID-5 in a yeast two-hybrid assay and functions in a sid-5-dependent manner. Taken together, our data indicate that SEC-22 reduces RNAi efficiency by affecting late endosome/MVB function, for example, by promoting fusion between late endosomes/MVBs and lysosomes. To our knowledge, this is the first report of a SNARE with a function in small RNA-mediated gene silencing.
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Affiliation(s)
- Yani Zhao
- Department of Cell and Molecular Biology, Uppsala University, 751 24 Uppsala, Sweden
| | - Benjamin T Holmgren
- Department of Cell and Molecular Biology, Uppsala University, 751 24 Uppsala, Sweden
| | - Andrea Hinas
- Department of Cell and Molecular Biology, Uppsala University, 751 24 Uppsala, Sweden
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Iqbal S, Fosu-Nyarko J, Jones MGK. Genomes of parasitic nematodes (Meloidogyne hapla, Meloidogyne incognita, Ascaris suum and Brugia malayi) have a reduced complement of small RNA interference pathway genes: knockdown can reduce host infectivity of M. incognita. Funct Integr Genomics 2016; 16:441-57. [PMID: 27126863 DOI: 10.1007/s10142-016-0495-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 04/08/2016] [Accepted: 04/18/2016] [Indexed: 12/15/2022]
Abstract
The discovery of RNA interference (RNAi) as an endogenous mechanism of gene regulation in a range of eukaryotes has resulted in its extensive use as a tool for functional genomic studies. It is important to study the mechanisms which underlie this phenomenon in different organisms, and in particular to understand details of the effectors that modulate its effectiveness. The aim of this study was to identify and compare genomic sequences encoding genes involved in the RNAi pathway of four parasitic nematodes: the plant parasites Meloidogyne hapla and Meloidogyne incognita and the animal parasites Ascaris suum and Brugia malayi because full genomic sequences were available-in relation to those of the model nematode Caenorhabditis elegans. The data generated was then used to identify some potential targets for control of the root knot nematode, M. incognita. Of the 84 RNAi pathway genes of C. elegans used as model in this study, there was a 42-53 % reduction in the number of effectors in the parasitic nematodes indicating substantial differences in the pathway between species. A gene each from six functional groups of the RNAi pathway of M. incognita was downregulated using in vitro RNAi, and depending on the gene (drh-3, tsn-1, rrf-1, xrn-2, mut-2 and alg-1), subsequent plant infection was reduced by up to 44 % and knockdown of some genes (i.e. drh-3, mut-2) also resulted in abnormal nematode development. The information generated here will contribute to defining targets for more robust nematode control using the RNAi technology.
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Affiliation(s)
- Sadia Iqbal
- Plant Biotechnology Research Group, WA State Agricultural Biotechnology Centre, School of Veterinary and Life Sciences, Murdoch University, Perth, WA, 6150, Australia.
| | - John Fosu-Nyarko
- Plant Biotechnology Research Group, WA State Agricultural Biotechnology Centre, School of Veterinary and Life Sciences, Murdoch University, Perth, WA, 6150, Australia
| | - Michael G K Jones
- Plant Biotechnology Research Group, WA State Agricultural Biotechnology Centre, School of Veterinary and Life Sciences, Murdoch University, Perth, WA, 6150, Australia
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Lei Q, Li C, Zuo Z, Huang C, Cheng H, Zhou R. Evolutionary Insights into RNA trans-Splicing in Vertebrates. Genome Biol Evol 2016; 8:562-77. [PMID: 26966239 PMCID: PMC4824033 DOI: 10.1093/gbe/evw025] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Pre-RNA splicing is an essential step in generating mature mRNA. RNA trans-splicing combines two separate pre-mRNA molecules to form a chimeric non-co-linear RNA, which may exert a function distinct from its original molecules. Trans-spliced RNAs may encode novel proteins or serve as noncoding or regulatory RNAs. These novel RNAs not only increase the complexity of the proteome but also provide new regulatory mechanisms for gene expression. An increasing amount of evidence indicates that trans-splicing occurs frequently in both physiological and pathological processes. In addition, mRNA reprogramming based on trans-splicing has been successfully applied in RNA-based therapies for human genetic diseases. Nevertheless, clarifying the extent and evolution of trans-splicing in vertebrates and developing detection methods for trans-splicing remain challenging. In this review, we summarize previous research, highlight recent advances in trans-splicing, and discuss possible splicing mechanisms and functions from an evolutionary viewpoint.
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Affiliation(s)
- Quan Lei
- Department of Genetics, College of Life Sciences, Wuhan University, P.R. China
| | - Cong Li
- Department of Genetics, College of Life Sciences, Wuhan University, P.R. China
| | - Zhixiang Zuo
- Department of Genetics, College of Life Sciences, Wuhan University, P.R. China
| | - Chunhua Huang
- Department of Cell Biology, College of Life Sciences, Wuhan University, P.R. China
| | - Hanhua Cheng
- Department of Cell Biology, College of Life Sciences, Wuhan University, P.R. China
| | - Rongjia Zhou
- Department of Genetics, College of Life Sciences, Wuhan University, P.R. China
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30
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Kamikawa R, Shiratori T, Ishida KI, Miyashita H, Roger AJ. Group II Intron-Mediated Trans-Splicing in the Gene-Rich Mitochondrial Genome of an Enigmatic Eukaryote, Diphylleia rotans. Genome Biol Evol 2016; 8:458-66. [PMID: 26833505 PMCID: PMC4779616 DOI: 10.1093/gbe/evw011] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Although mitochondria have evolved from a single endosymbiotic event, present day mitochondria of diverse eukaryotes display a great range of genome structures, content and features. Group I and group II introns are two features that are distributed broadly but patchily in mitochondrial genomes across branches of the tree of eukaryotes. While group I intron-mediated trans-splicing has been reported from some lineages distantly related to each other, findings of group II intron-mediated trans-splicing has been restricted to members of the Chloroplastida. In this study, we found the mitochondrial genome of the unicellular eukaryote Diphylleia rotans possesses currently the second largest gene repertoire. On the basis of a probable phylogenetic position of Diphylleia, which is located within Amorphea, current mosaic gene distribution in Amorphea must invoke parallel gene losses from mitochondrial genomes during evolution. Most notably, although the cytochrome c oxidase subunit (cox) 1 gene was split into four pieces which located at a distance to each other, we confirmed that a single mature mRNA that covered the entire coding region could be generated by group II intron-mediated trans-splicing. This is the first example of group II intron-mediated trans-splicing outside Chloroplastida. Similar trans-splicing mechanisms likely work for bipartitely split cox2 and nad3 genes to generate single mature mRNAs. We finally discuss origin and evolution of this type of trans-splicing in D. rotans as well as in eukaryotes.
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Affiliation(s)
- Ryoma Kamikawa
- Graduate School of Human and Environmental Studies, Kyoto University, Japan Graduate School of Global Environmental Studies, Kyoto University, Japan
| | - Takashi Shiratori
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
| | - Ken-Ichiro Ishida
- Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan
| | - Hideaki Miyashita
- Graduate School of Human and Environmental Studies, Kyoto University, Japan Graduate School of Global Environmental Studies, Kyoto University, Japan
| | - Andrew J Roger
- Centre for Comparative Genomics and Evolutionary Bioinformatics, Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada Program in Integrated Microbial Biodiversity, Canadian Institute for Advanced Research, Halifax, Nova Scotia, Canada
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The evolutionary landscape of intergenic trans-splicing events in insects. Nat Commun 2015; 6:8734. [PMID: 26521696 PMCID: PMC4667647 DOI: 10.1038/ncomms9734] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 09/24/2015] [Indexed: 01/29/2023] Open
Abstract
To explore the landscape of intergenic trans-splicing events and characterize their functions and evolutionary dynamics, we conduct a mega-data study of a phylogeny containing eight species across five orders of class Insecta, a model system spanning 400 million years of evolution. A total of 1,627 trans-splicing events involving 2,199 genes are identified, accounting for 1.58% of the total genes. Homology analysis reveals that mod(mdg4)-like trans-splicing is the only conserved event that is consistently observed in multiple species across two orders, which represents a unique case of functional diversification involving trans-splicing. Thus, evolutionarily its potential for generating proteins with novel function is not broadly utilized by insects. Furthermore, 146 non-mod trans-spliced transcripts are found to resemble canonical genes from different species. Trans-splicing preserving the function of 'breakup' genes may serve as a general mechanism for relaxing the constraints on gene structure, with profound implications for the evolution of genes and genomes.
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Gao JL, Fan YJ, Wang XY, Zhang Y, Pu J, Li L, Shao W, Zhan S, Hao J, Xu YZ. A conserved intronic U1 snRNP-binding sequence promotes trans-splicing in Drosophila. Genes Dev 2015; 29:760-71. [PMID: 25838544 PMCID: PMC4387717 DOI: 10.1101/gad.258863.115] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Gao et al. investigate mod(mdg4), a classic trans-spliced gene in Drosophila, and report that two critical RNA sequences in the middle of the last 5′ intron, TSA and TSB, promote trans-splicing of mod(mdg4). In TSA, a 13-nt core motif is conserved across Drosophila species and is essential and sufficient for trans-splicing, which binds U1 snRNP through strong base-pairing with U1 snRNA. In TSB, a conserved secondary structure acts as an enhancer. Deletions of TSA and TSB result in developmental defects in flies. Unlike typical cis-splicing, trans-splicing joins exons from two separate transcripts to produce chimeric mRNA and has been detected in most eukaryotes. Trans-splicing in trypanosomes and nematodes has been characterized as a spliced leader RNA-facilitated reaction; in contrast, its mechanism in higher eukaryotes remains unclear. Here we investigate mod(mdg4), a classic trans-spliced gene in Drosophila, and report that two critical RNA sequences in the middle of the last 5′ intron, TSA and TSB, promote trans-splicing of mod(mdg4). In TSA, a 13-nucleotide (nt) core motif is conserved across Drosophila species and is essential and sufficient for trans-splicing, which binds U1 small nuclear RNP (snRNP) through strong base-pairing with U1 snRNA. In TSB, a conserved secondary structure acts as an enhancer. Deletions of TSA and TSB using the CRISPR/Cas9 system result in developmental defects in flies. Although it is not clear how the 5′ intron finds the 3′ introns, compensatory changes in U1 snRNA rescue trans-splicing of TSA mutants, demonstrating that U1 recruitment is critical to promote trans-splicing in vivo. Furthermore, TSA core-like motifs are found in many other trans-spliced Drosophila genes, including lola. These findings represent a novel mechanism of trans-splicing, in which RNA motifs in the 5′ intron are sufficient to bring separate transcripts into close proximity to promote trans-splicing.
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Affiliation(s)
- Jun-Li Gao
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Yu-Jie Fan
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Xiu-Ye Wang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Yu Zhang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Jia Pu
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Liang Li
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Wei Shao
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Shuai Zhan
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | | | - Yong-Zhen Xu
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China;
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Ni JZ, Chen E, Gu SG. Complex coding of endogenous siRNA, transcriptional silencing and H3K9 methylation on native targets of germline nuclear RNAi in C. elegans. BMC Genomics 2014; 15:1157. [PMID: 25534009 PMCID: PMC4367959 DOI: 10.1186/1471-2164-15-1157] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 12/10/2014] [Indexed: 11/14/2022] Open
Abstract
Background Small RNA-guided transcriptional silencing (nuclear RNAi) is fundamental to genome integrity and epigenetic inheritance. Despite recent progress in identifying the capability and genetic requirements for nuclear RNAi in Caenorhabditis elegans, the natural targets and cellular functions of nuclear RNAi remain elusive. Methods To resolve this gap, we coordinately examined the genome-wide profiles of transcription, histone H3 lysine 9 methylation (H3K9me) and endogenous siRNAs of a germline nuclear Argonaute (hrde-1/wago-9) mutant and identified regions on which transcription activity is markedly increased and/or H3K9me level is markedly decreased relative to wild type animals. Results Our data revealed a distinct set of native targets of germline nuclear RNAi, with the H3K9me response exhibiting both overlapping and non-overlapping distribution with the transcriptional silencing response. Interestingly LTR retrotransposons, but not DNA transposons, are highly enriched in the targets of germline nuclear RNAi. The genomic distribution of the native targets is highly constrained, with >99% of the identified targets present in five autosomes but not in the sex chromosome. By contrast, HRDE-1-associated small RNAs correspond to all chromosomes. In addition, we found that the piRNA pathway is not required for germline nuclear RNAi activity on native targets. Conclusion Germline nuclear RNAi in C. elegans is required to silence retrotransposons but not DNA transposon. Transcriptional silencing and H3K9me can occur independently of each other on the native targets of nuclear RNAi in C. elegans. Our results rule out a simple model in which nuclear Argonaute protein-associated-small RNAs are sufficient to trigger germline nuclear RNAi responses. In addition, the piRNA pathway and germline nuclear RNAi are specialized to target different types of foreign genetic elements for genome surveillance in C. elegans. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-1157) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | - Sam Guoping Gu
- Department of Molecular Biology and Biochemistry, Rutgers the State University of New Jersey, Nelson Labs A125, 604 Allison Road, Piscataway, NJ 08854, USA.
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Kamikawa R, Inagaki Y, Roger AJ, Hashimoto T. Splintrons inGiardia intestinalis. Commun Integr Biol 2014. [DOI: 10.4161/cib.15466] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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35
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Kang B, Gu Q, Tian P, Xiao L, Cao H, Yang W. A chimeric transcript containing Psy1 and a potential mRNA is associated with yellow flesh color in tomato accession PI 114490. PLANTA 2014; 240:1011-21. [PMID: 24663441 DOI: 10.1007/s00425-014-2052-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2013] [Accepted: 03/04/2014] [Indexed: 05/19/2023]
Abstract
Carotenoid content is the primary determinant of fruit color that affects nutritional value and appearance in tomato. Phytoene synthase (PSY) is the key regulatory enzyme in the carotenoid biosynthesis pathway. Absent function of PSY1 in tomato fruit results in yellow flesh phenotype. We, here, report that two different transcripts, a wild-type (Psy1) and a chimeric mRNA (Psy1/Unknown), exist in a yellow-fruited tomato accession PI 114490. Psy1/Unknown is generated by joining exons from two different genes, Psy1 and an unknown gene, transcribed using both complementary DNA strands. The Psy1 shows low expression in the fruit of PI 114490, while the expression of Psy1/Unknown in the fruit of PI 114490 shows the same pattern as Psy1 in red fruit. The PSY1/Unknown has a lower function than PSY1 in a bacterial expression system. Coincidence of one single-nucleotide polymorphism (SNP) in the fourth intron and one simple sequence repeat (SSR) with 19 AT repeats in the downstream sequence of Psy1 gene with Psy1/Unknown in a set of yellow-fruited tomato lines indicates that Psy1/Unknown might be caused by the SNP and/or SSR. One possible explanation of these observations is trans-splicing. Severely reduced Psy1 transcript caused by Psy1/Unknown results in low accumulation of carotenoid and yellow flesh in PI 114490.
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Affiliation(s)
- Baoshan Kang
- Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetable Science, China Agricultural University, No. 2 Yuanmingyuan Xilu, Beijing, 100193, China
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Jividen K, Li H. Chimeric RNAs generated by intergenic splicing in normal and cancer cells. Genes Chromosomes Cancer 2014; 53:963-71. [PMID: 25131334 DOI: 10.1002/gcc.22207] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 07/16/2014] [Indexed: 12/30/2022] Open
Abstract
A hallmark of many neoplasias is chromosomal rearrangement, an event that commonly results in the fusion of two separate genes. The RNA and protein resulting from these gene fusions often play critical roles in cancer development, maintenance, and progression. Traditionally, these fusion products are thought to be produced solely due to DNA level changes and are therefore considered unique to cancer. Recent advances in microarray and deep-sequencing have revealed many more fusion transcripts. Surprisingly, some are without detectable rearrangement at the DNA level. Reports have demonstrated that at least some of these chimeric RNAs are generated via intergenic splicing. In this review, we highlight three examples of these noncanonical chimeric transcripts that are formed by trans-splicing or cis-splicing of adjacent genes and summarize the knowledge we have regarding these noncanonical fusions. We discuss the implications of the chimeric RNAs in both cancer and normal physiology, as some of these fusion transcripts are found in normal, noncancerous cells with sequences identical to those generated by canonical chromosomal translocation found in cancer cells. Finally, we present methods that are currently being used to discover additional chimeric RNAs.
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Affiliation(s)
- Kasey Jividen
- Department of Pathology, University of Virginia, Charlottesville, VA
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Fischer SEJ, Pan Q, Breen PC, Qi Y, Shi Z, Zhang C, Ruvkun G. Multiple small RNA pathways regulate the silencing of repeated and foreign genes in C. elegans. Genes Dev 2014; 27:2678-95. [PMID: 24352423 PMCID: PMC3877757 DOI: 10.1101/gad.233254.113] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Gene segments from other organisms, such as viruses, are detected as foreign and targeted for silencing by RNAi pathways. A deep-sequencing map of the small RNA response to repeated transgenes introduced to Caenorhabditis elegans revealed that specific segments are targeted by siRNAs. Silencing of the foreign gene segments depends on an antiviral response that involves changes in active and silent chromatin modifications and altered levels of antisense siRNAs. Distinct Argonaute proteins target foreign genes for silencing or protection against silencing. We used a repeated transgene in a genome-wide screen to identify gene disruptions that enhance silencing of foreign genetic elements and identified 69 genes. These genes cluster in four groups based on overlapping sets of coexpressed genes, including a group of germline-expressed genes that are likely coregulated by the E2F transcription factor. Many of the gene inactivations enhance exogenous RNAi. About half of the 69 genes have roles in endogenous RNAi pathways that regulate diverse processes, including silencing of duplicated genes and transposons and chromosome segregation. Of these newly identified genes, several are required for siRNA biogenesis or stability in the oocyte-specific ERGO-1 pathway, including eri-12, encoding an interactor of the RNAi-defective protein RDE-10, and ntl-9/CNOT9, one of several CCR4/NOT complex genes that we identified. The conserved ARF-like small GTPase ARL-8 is required specifically for primary siRNA biogenesis or stability in the sperm-specific ALG-3/4 endogenous RNAi pathway.
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Affiliation(s)
- Sylvia E J Fischer
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
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Xu HJ, Chen T, Ma XF, Xue J, Pan PL, Zhang XC, Cheng JA, Zhang CX. Genome-wide screening for components of small interfering RNA (siRNA) and micro-RNA (miRNA) pathways in the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae). INSECT MOLECULAR BIOLOGY 2013; 22:635-47. [PMID: 23937246 DOI: 10.1111/imb.12051] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The brown planthopper (BPH), Nilaparvata lugens, is a major rice pest in Asia, and accumulated evidence indicates that this species is susceptible to RNA interference (RNAi); however, the mechanism underlying RNAi and parental RNAi has not yet been determined. We comprehensively investigated the repertoire of core genes involved in small interfering RNA (siRNA) and micro-RNA (miRNA) pathways in the BPH by comparing its newly assembled transcriptome and genome with those of Drosophila melanogaster, Tribolium castaneum and Caenorhabditis elegans. Our analysis showed that the BPH possesses one drosha and two Dicer (dcr) genes, three dsRNA-binding motif protein genes, two Argonaute (ago) genes, two Eri-1-like genes (eri-1), and a Sid-1-like gene (sid-1). Additionally, we report for first time that parental RNAi might occur in this species, and siRNA pathway and Sid-1 were required for high efficiency of systemic RNAi triggered by exogenous dsRNA. Furthermore, our results also demonstrated that the miRNA pathway was involved in BPH metamorphosis as depletion of the ago1 or dcr1 gene severely impaired ecdysis. The BPH might be a good model system to study the molecular mechanism of systemic RNAi in hemimetabolous insects, and RNAi has potential to be developed to control this pest in agricultural settings.
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Affiliation(s)
- H-J Xu
- State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Science, Zhejiang University, Hangzhou, China
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Massirer KB, Pasquinelli AE. MicroRNAs that interfere with RNAi. WORM 2013; 2:e21835. [PMID: 24058860 PMCID: PMC3670461 DOI: 10.4161/worm.21835] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Accepted: 08/14/2012] [Indexed: 11/28/2022]
Abstract
A recent study by Massirer et al. in the nematode C. elegans has shown that a family of microRNAs (miRNAs), miR-35-41, regulates the efficiency of RNA interference (RNAi), revealing a new connection between these small RNA pathways. In this commentary, we discuss the potential mechanisms for cross regulation in the miRNA and RNAi pathways and the implications for gene expression. While miRNAs are genetically encoded, the small interfering RNAs (siRNAs) that function in RNAi can originate from processing of exogenous dsRNA (exo-RNAi) or from the production of siRNAs from endogenous transcripts (endo-RNAi). These small RNA pathways involve Dicer and Argonaute proteins and typically use antisense base pairing to target mRNAs for downregulated expression. The discovery that loss of miR-35–41 results in enhanced exo-RNAi sensitivity and reduced endo-RNAi effectiveness suggests that these miRNAs normally help balance the RNAi pathways. The effect of mir-35–41 on RNAi is largely through lin-35, the C. elegans homolog of the tumor suppressor Retinoblastoma (Rb) gene. lin-35/Rb previously has been shown to regulate RNAi sensitivity through unclear mechanisms and the new finding that accumulation of LIN-35/Rb protein is dependent on miR-35–41 adds another layer of complexity to this process. The utilization of miRNAs to control the responsiveness of RNAi exemplifies the cross-regulation embedded in small RNA-directed pathways.
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Affiliation(s)
- Katlin B Massirer
- Division of Biology; University of California San Diego; La Jolla, CA USA
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ADAR-mediated RNA editing in non-coding RNA sequences. SCIENCE CHINA-LIFE SCIENCES 2013; 56:944-52. [DOI: 10.1007/s11427-013-4546-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2013] [Accepted: 08/20/2013] [Indexed: 12/22/2022]
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Abstract
The Caenorhabditis elegans nuclear RNA interference defective (Nrde) mutants were identified by their inability to silence polycistronic transcripts in enhanced RNAi (Eri) mutant backgrounds. Here, we report additional nrde-3-dependent RNAi phenomena that extend the mechanisms, roles, and functions of nuclear RNAi. We show that nrde-3 mutants are broadly RNAi deficient and that overexpressing NRDE-3 enhances RNAi. Consistent with NRDE-3 being a dose-dependent limiting resource for effective RNAi, we find that NRDE-3 is required for eri-dependent enhanced RNAi phenotypes, although only for a subset of target genes. We then identify pgl-1 as an additional limiting RNAi resource important for eri-dependent silencing of a nonoverlapping subset of target genes, so that an nrde-3; pgl-1; eri-1 triple mutant fails to show enhanced RNAi for any tested gene. These results suggest that nrde-3 and pgl-1 define separate and independent limiting RNAi resource pathways. Limiting RNAi resources are proposed to primarily act via endogenous RNA silencing pathways. Consistent with this, we find that nrde-3 mutants misexpress genes regulated by endogenous siRNAs and incompletely silence repetitive transgene arrays. Finally, we find that nrde-3 contributes to transitive RNAi, whereby amplified silencing triggers act in trans to silence sequence-similar genes. Because nrde-dependent silencing is thought to act in cis to limit the production of primary transcripts, this result reveals an unexpected role for nuclear processes in RNAi silencing.
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Translocation of sickle cell erythrocyte microRNAs into Plasmodium falciparum inhibits parasite translation and contributes to malaria resistance. Cell Host Microbe 2013; 12:187-99. [PMID: 22901539 DOI: 10.1016/j.chom.2012.06.007] [Citation(s) in RCA: 207] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Revised: 04/09/2012] [Accepted: 06/11/2012] [Indexed: 01/22/2023]
Abstract
Erythrocytes carrying a variant hemoglobin allele (HbS), which causes sickle cell disease and resists infection by the malaria parasite Plasmodium falciparum. The molecular basis of this resistance, which has long been recognized as multifactorial, remains incompletely understood. Here we show that the dysregulated microRNA (miRNA) composition, of either heterozygous HbAS or homozygous HbSS erythrocytes, contributes to resistance against P. falciparum. During the intraerythrocytic life cycle of P. falciparum, a subset of erythrocyte miRNAs translocate into the parasite. Two miRNAs, miR-451 and let-7i, were highly enriched in HbAS and HbSS erythrocytes, and these miRNAs, along with miR-223, negatively regulated parasite growth. Surprisingly, we found that miR-451 and let-7i integrated into essential parasite messenger RNAs and, via impaired ribosomal loading, resulted in translational inhibition. Hence, sickle cell erythrocytes exhibit cell-intrinsic resistance to malaria in part through an atypical miRNA activity, which may represent a unique host defense strategy against complex eukaryotic pathogens.
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Abstract
The significance of noncoding RNAs in animal biology is being increasingly recognized. The nematode Caenorhabditis elegans has an extensive system of short RNAs that includes microRNAs, piRNAs, and endogenous siRNAs, which regulate development, control life span, provide resistance to viruses and transposons, and monitor gene duplications. Progress in our understanding of short RNAs was stimulated by the discovery of RNA interference, a phenomenon of sequence-specific gene silencing induced by exogenous double-stranded RNA, at the turn of the twenty-first century. This chapter provides a broad overview of the exogenous and endogenous RNAi processes in C. elegans and describes recent advances in genetic, genomic, and molecular analyses of nematode's short RNAs and proteins involved in the RNAi-related pathways.
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Affiliation(s)
- Alla Grishok
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York, USA.
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Abstract
Adenosine to inosine (A-to-I) RNA editing is a post-transcriptional process by which adenosines are selectively converted to inosines in double-stranded RNA (dsRNA) substrates. A highly conserved group of enzymes, the adenosine deaminase acting on RNA (ADAR) family, mediates this reaction. All ADARs share a common domain architecture consisting of a variable number of amino-terminal dsRNA binding domains (dsRBDs) and a carboxy-terminal catalytic deaminase domain. ADAR family members are highly expressed in the metazoan nervous system, where these enzymes predominantly localize to the neuronal nucleus. Once in the nucleus, ADARs participate in the modification of specific adenosines in pre-mRNAs of proteins involved in electrical and chemical neurotransmission, including pre-synaptic release machineries, and voltage- and ligand-gated ion channels. Most RNA editing sites in these nervous system targets result in non-synonymous codon changes in functionally important, usually conserved, residues and RNA editing deficiencies in various model organisms bear out a crucial role for ADARs in nervous system function. Mutation or deletion of ADAR genes results in striking phenotypes, including seizure episodes, extreme uncoordination, and neurodegeneration. Not only does the process of RNA editing alter important nervous system peptides, but ADARs also regulate gene expression through modification of dsRNA substrates that enter the RNA interference (RNAi) pathway and may then act at the chromatin level. Here, we present a review on the current knowledge regarding the ADAR protein family, including evolutionary history, key structural features, localization, function and mechanism.
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Rosains J, Mango SE. Genetic characterization of smg-8 mutants reveals no role in C. elegans nonsense mediated decay. PLoS One 2012; 7:e49490. [PMID: 23166684 PMCID: PMC3500306 DOI: 10.1371/journal.pone.0049490] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Accepted: 10/12/2012] [Indexed: 12/02/2022] Open
Abstract
The nonsense mediated decay (NMD) pathway degrades mRNAs bearing premature translation termination codons. In mammals, SMG-8 has been implicated in the NMD pathway, in part by its association with SMG-1 kinase. Here we use four independent assays to show that C. elegans smg-8 is not required to degrade nonsense-containing mRNAs. We examine the genetic requirement for smg-8 to destabilize the endogenous, natural NMD targets produced by alternative splicing of rpl-7a and rpl-12. We test smg-8 for degradation of the endogenous, NMD target generated by unc-54(r293), which lacks a normal polyadenylation site. We probe the effect of smg-8 on the exogenous NMD target produced by myo-3::GFP, which carries a long 3′ untranslated region that destabilizes mRNAs. None of these known NMD targets is influenced by smg-8 mutations. In addition, smg-8 animals lack classical Smg mutant phenotypes such as a reduced brood size or abnormal vulva. We conclude that smg-8 is unlikely to encode a component critical for NMD.
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Affiliation(s)
- Jacqueline Rosains
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachussetts, United States of America
| | - Susan E. Mango
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachussetts, United States of America
- * E-mail:
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Abstract
Small RNAs play a variety of regulatory roles, including highly conserved developmental functions. Caenorhabditis elegans not only possesses most known small RNA pathways, it is also an easy system to study their roles and interactions during development. It has been proposed that in C. elegans, some small RNA pathways compete for access to common limiting resources. The strongest evidence supporting this model is that disrupting the production or stability of endogenous short interfering RNAs (endo-siRNAs) enhances sensitivity to experimentally induced exogenous RNA interference (exo-RNAi). Here, we examine the relationship between the endo-siRNA and microRNA (miRNA) pathways, and find that, consistent with competition among these endogenous small RNA pathways, endo-siRNA pathway mutants may enhance miRNA efficacy. Furthermore, we show that exo-RNAi may also compete with both endo-siRNAs and miRNAs. Our data thus provide support that all known Dicer-dependent small RNA pathways may compete for limiting common resources. Finally, we observed that both endo-siRNA mutants and animals experiencing exo-RNAi have increased expression of miRNA-regulated stage-specific developmental genes. These observations suggest that perturbing the small RNA flux and/or the induction of exo-RNAi, even in wild-type animals, may impact development via effects on the endo-RNAi and microRNA pathways.
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Affiliation(s)
| | - Craig P. Hunter
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-617-495-8309; Fax: +1-617-496-0132
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Mishra M, Lee S, Lin MK, Yamashita T, Heese K. Characterizing the neurite outgrowth inhibitory effect of Mani. FEBS Lett 2012; 586:3018-23. [DOI: 10.1016/j.febslet.2012.06.043] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 06/14/2012] [Accepted: 06/18/2012] [Indexed: 12/01/2022]
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Shao W, Zhao QY, Wang XY, Xu XY, Tang Q, Li M, Li X, Xu YZ. Alternative splicing and trans-splicing events revealed by analysis of the Bombyx mori transcriptome. RNA (NEW YORK, N.Y.) 2012; 18:1395-1407. [PMID: 22627775 PMCID: PMC3383970 DOI: 10.1261/rna.029751.111] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 05/02/2012] [Indexed: 06/01/2023]
Abstract
Alternative splicing and trans-splicing events have not been systematically studied in the silkworm Bombyx mori. Here, the silkworm transcriptome was analyzed by RNA-seq. We identified 320 novel genes, modified 1140 gene models, and found thousands of alternative splicing and 58 trans-splicing events. Studies of three SR proteins show that both their alternative splicing patterns and mRNA products are conserved from insect to human, and one isoform of Srsf6 with a retained intron is expressed sex-specifically in silkworm gonads. Trans-splicing of mod(mdg4) in silkworm was experimentally confirmed. We identified integrations from a common 5'-gene with 46 newly identified alternative 3'-exons that are located on both DNA strands over a 500-kb region. Other trans-splicing events in B. mori were predicted by bioinformatic analysis, in which 12 events were confirmed by RT-PCR, six events were further validated by chimeric SNPs, and two events were confirmed by allele-specific RT-PCR in F(1) hybrids from distinct silkworm lines of JS and L10, indicating that trans-splicing is more widespread in insects than previously thought. Analysis of the B. mori transcriptome by RNA-seq provides valuable information of regulatory alternative splicing events. The conservation of splicing events across species and newly identified trans-splicing events suggest that B. mori is a good model for future studies.
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Affiliation(s)
- Wei Shao
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Qiong-Yi Zhao
- Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Xiu-Ye Wang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Xin-Yan Xu
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Qing Tang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Muwang Li
- Sericultural Research Institute, Chinese Academy of Agricultural Sciences, Zhenjiang, Jiangsu 212018, China
| | - Xuan Li
- Key Laboratory of Synthetic Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Yong-Zhen Xu
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
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Kumsta C, Hansen M. C. elegans rrf-1 mutations maintain RNAi efficiency in the soma in addition to the germline. PLoS One 2012; 7:e35428. [PMID: 22574120 PMCID: PMC3344830 DOI: 10.1371/journal.pone.0035428] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 03/16/2012] [Indexed: 12/01/2022] Open
Abstract
Gene inactivation through RNA interference (RNAi) has proven to be a valuable tool for studying gene function in C. elegans. When combined with tissue-specific gene inactivation methods, RNAi has the potential to shed light on the function of a gene in distinct tissues. In this study we characterized C. elegans rrf-1 mutants to determine their ability to process RNAi in various tissues. These mutants have been widely used in RNAi studies to assess the function of genes specifically in the C. elegans germline. Upon closer analysis, we found that two rrf-1 mutants carrying different loss-of-function alleles were capable of processing RNAi targeting several somatically expressed genes. Specifically, we observed that the intestine was able to process RNAi triggers efficiently, whereas cells in the hypodermis showed partial susceptibility to RNAi in rrf-1 mutants. Other somatic tissues in rrf-1 mutants, such as the muscles and the somatic gonad, appeared resistant to RNAi. In addition to these observations, we found that the rrf-1(pk1417) mutation induced the expression of several transgenic arrays, including the FOXO transcription factor DAF-16. Unexpectedly, rrf-1(pk1417) mutants showed increased endogenous expression of the DAF-16 target gene sod-3; however, the lifespan and thermo-tolerance of rrf-1(pk1417) mutants were similar to those of wild-type animals. In sum, these data show that rrf-1 mutants display several phenotypes not previously appreciated, including broader tissue-specific RNAi-processing capabilities, and our results underscore the need for careful characterization of tissue-specific RNAi tools.
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Affiliation(s)
- Caroline Kumsta
- Program of Development and Aging, Sanford-Burnham Medical Research Institute, Del E. Webb Neuroscience, Aging and Stem Cell Research Center, La Jolla, California, United States of America
| | - Malene Hansen
- Program of Development and Aging, Sanford-Burnham Medical Research Institute, Del E. Webb Neuroscience, Aging and Stem Cell Research Center, La Jolla, California, United States of America
- * E-mail:
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50
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Montgomery TA, Rim YS, Zhang C, Dowen RH, Phillips CM, Fischer SEJ, Ruvkun G. PIWI associated siRNAs and piRNAs specifically require the Caenorhabditis elegans HEN1 ortholog henn-1. PLoS Genet 2012; 8:e1002616. [PMID: 22536158 PMCID: PMC3334881 DOI: 10.1371/journal.pgen.1002616] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Accepted: 02/03/2012] [Indexed: 12/29/2022] Open
Abstract
Small RNAs--including piRNAs, miRNAs, and endogenous siRNAs--bind Argonaute proteins to form RNA silencing complexes that target coding genes, transposons, and aberrant RNAs. To assess the requirements for endogenous siRNA formation and activity in Caenorhabditis elegans, we developed a GFP-based sensor for the endogenous siRNA 22G siR-1, one of a set of abundant siRNAs processed from a precursor RNA mapping to the X chromosome, the X-cluster. Silencing of the sensor is also dependent on the partially complementary, unlinked 26G siR-O7 siRNA. We show that 26G siR-O7 acts in trans to initiate 22G siRNA formation from the X-cluster. The presence of several mispairs between 26G siR-O7 and the X-cluster mRNA, as well as mutagenesis of the siRNA sensor, indicates that siRNA target recognition is permissive to a degree of mispairing. From a candidate reverse genetic screen, we identified several factors required for 22G siR-1 activity, including the chromatin factors mes-4 and gfl-1, the Argonaute ergo-1, and the 3' methyltransferase henn-1. Quantitative RT-PCR of small RNAs in a henn-1 mutant and deep sequencing of methylated small RNAs indicate that siRNAs and piRNAs that associate with PIWI clade Argonautes are methylated by HENN-1, while siRNAs and miRNAs that associate with non-PIWI clade Argonautes are not. Thus, PIWI-class Argonaute proteins are specifically adapted to associate with methylated small RNAs in C. elegans.
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Affiliation(s)
| | | | | | | | | | | | - Gary Ruvkun
- Department of Molecular Biology, Massachusetts General Hospital, Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
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