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Ortolá B, Daròs JA. RNA Interference in Insects: From a Natural Mechanism of Gene Expression Regulation to a Biotechnological Crop Protection Promise. BIOLOGY 2024; 13:137. [PMID: 38534407 DOI: 10.3390/biology13030137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 02/14/2024] [Accepted: 02/19/2024] [Indexed: 03/28/2024]
Abstract
Insect pests rank among the major limiting factors in agricultural production worldwide. In addition to direct effect on crops, some phytophagous insects are efficient vectors for plant disease transmission. Large amounts of conventional insecticides are required to secure food production worldwide, with a high impact on the economy and environment, particularly when beneficial insects are also affected by chemicals that frequently lack the desired specificity. RNA interference (RNAi) is a natural mechanism gene expression regulation and protection against exogenous and endogenous genetic elements present in most eukaryotes, including insects. Molecules of double-stranded RNA (dsRNA) or highly structured RNA are the substrates of cellular enzymes to produce several types of small RNAs (sRNAs), which play a crucial role in targeting sequences for transcriptional or post-transcriptional gene silencing. The relatively simple rules that underlie RNAi regulation, mainly based in Watson-Crick complementarity, have facilitated biotechnological applications based on these cellular mechanisms. This includes the promise of using engineered dsRNA molecules, either endogenously produced in crop plants or exogenously synthesized and applied onto crops, as a new generation of highly specific, sustainable, and environmentally friendly insecticides. Fueled on this expectation, this article reviews current knowledge about the RNAi pathways in insects, and some other applied questions such as production and delivery of recombinant RNA, which are critical to establish RNAi as a reliable technology for insect control in crop plants.
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Affiliation(s)
- Beltrán Ortolá
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universitat Politècnica de València, 46022 Valencia, Spain
| | - José-Antonio Daròs
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universitat Politècnica de València, 46022 Valencia, Spain
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2
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Estevez-Castro CF, Rodrigues MF, Babarit A, Ferreira FV, de Andrade EG, Marois E, Cogni R, Aguiar ERGR, Marques JT, Olmo RP. Neofunctionalization driven by positive selection led to the retention of the loqs2 gene encoding an Aedes specific dsRNA binding protein. BMC Biol 2024; 22:14. [PMID: 38273313 PMCID: PMC10809485 DOI: 10.1186/s12915-024-01821-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 01/10/2024] [Indexed: 01/27/2024] Open
Abstract
BACKGROUND Mosquito borne viruses, such as dengue, Zika, yellow fever and Chikungunya, cause millions of infections every year. These viruses are mostly transmitted by two urban-adapted mosquito species, Aedes aegypti and Aedes albopictus. Although mechanistic understanding remains largely unknown, Aedes mosquitoes may have unique adaptations that lower the impact of viral infection. Recently, we reported the identification of an Aedes specific double-stranded RNA binding protein (dsRBP), named Loqs2, that is involved in the control of infection by dengue and Zika viruses in mosquitoes. Preliminary analyses suggested that the loqs2 gene is a paralog of loquacious (loqs) and r2d2, two co-factors of the RNA interference (RNAi) pathway, a major antiviral mechanism in insects. RESULTS Here we analyzed the origin and evolution of loqs2. Our data suggest that loqs2 originated from two independent duplications of the first double-stranded RNA binding domain of loqs that occurred before the origin of the Aedes Stegomyia subgenus, around 31 million years ago. We show that the loqs2 gene is evolving under relaxed purifying selection at a faster pace than loqs, with evidence of neofunctionalization driven by positive selection. Accordingly, we observed that Loqs2 is localized mainly in the nucleus, different from R2D2 and both isoforms of Loqs that are cytoplasmic. In contrast to r2d2 and loqs, loqs2 expression is stage- and tissue-specific, restricted mostly to reproductive tissues in adult Ae. aegypti and Ae. albopictus. Transgenic mosquitoes engineered to express loqs2 ubiquitously undergo developmental arrest at larval stages that correlates with massive dysregulation of gene expression without major effects on microRNAs or other endogenous small RNAs, classically associated with RNA interference. CONCLUSIONS Our results uncover the peculiar origin and neofunctionalization of loqs2 driven by positive selection. This study shows an example of unique adaptations in Aedes mosquitoes that could ultimately help explain their effectiveness as virus vectors.
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Affiliation(s)
- Carlos F Estevez-Castro
- Department of Biochemistry and Immunology, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, 31270-901, Brazil
- CNRS UPR9022, Inserm U1257, Université de Strasbourg, 67084, Strasbourg, France
| | - Murillo F Rodrigues
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR, 97403-5289, USA
| | - Antinéa Babarit
- CNRS UPR9022, Inserm U1257, Université de Strasbourg, 67084, Strasbourg, France
| | - Flávia V Ferreira
- Department of Biochemistry and Immunology, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, 31270-901, Brazil
| | - Elisa G de Andrade
- Department of Biochemistry and Immunology, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, 31270-901, Brazil
- CNRS UPR9022, Inserm U1257, Université de Strasbourg, 67084, Strasbourg, France
| | - Eric Marois
- CNRS UPR9022, Inserm U1257, Université de Strasbourg, 67084, Strasbourg, France
| | - Rodrigo Cogni
- Department of Ecology, Institute of Biosciences, University of São Paulo, São Paulo, 05508-090, Brazil
| | - Eric R G R Aguiar
- Department of Biological Science, Center of Biotechnology and Genetics, State University of Santa Cruz, Ilhéus, 45662-900, Brazil
| | - João T Marques
- Department of Biochemistry and Immunology, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, 31270-901, Brazil.
- CNRS UPR9022, Inserm U1257, Université de Strasbourg, 67084, Strasbourg, France.
| | - Roenick P Olmo
- Department of Biochemistry and Immunology, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, 31270-901, Brazil.
- CNRS UPR9022, Inserm U1257, Université de Strasbourg, 67084, Strasbourg, France.
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Deng T, Su S, Yuan X, He J, Huang Y, Ma J, Wang J. Structural mechanism of R2D2 and Loqs-PD synergistic modulation on DmDcr-2 oligomers. Nat Commun 2023; 14:5228. [PMID: 37633971 PMCID: PMC10460399 DOI: 10.1038/s41467-023-40919-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Accepted: 08/16/2023] [Indexed: 08/28/2023] Open
Abstract
Small interference RNAs are the key components of RNA interference, a conserved RNA silencing or viral defense mechanism in many eukaryotes. In Drosophila melanogaster, Dicer-2 (DmDcr-2)-mediated RNAi pathway plays important roles in defending against viral infections and protecting genome integrity. During the maturation of siRNAs, two cofactors can regulate DmDcr-2's functions: Loqs-PD that is required for dsRNA processing, and R2D2 that is essential for the subsequent loading of siRNAs into effector Ago2 to form RISC complexes. However, due to the lack of structural information, it is still unclear whether R2D2 and Loqs-PD affect the functions of DmDcr-2 simultaneously. Here we present several cryo-EM structures of DmDcr-2/R2D2/Loqs-PD complex bound to dsRNAs with various lengths by the Helicase domain. These structures revealed that R2D2 and Loqs-PD can bind to different regions of DmDcr-2 without interfering with each other. Furthermore, the cryo-EM results demonstrate that these complexes can form large oligomers and assemble into fibers. The formation and depolymerization of these oligomers are associated with ATP hydrolysis. These findings provide insights into the structural mechanism of DmDcr-2 and its cofactors during siRNA processing.
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Affiliation(s)
- Ting Deng
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Centre of Genetics and Development, Department of Biochemistry and Biophysics, Institute of Plant Biology, School of Life Sciences, Fudan University, 200438, Shanghai, China
| | - Shichen Su
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Centre of Genetics and Development, Department of Biochemistry and Biophysics, Institute of Plant Biology, School of Life Sciences, Fudan University, 200438, Shanghai, China
| | - Xun Yuan
- Shanghai Key Laboratory of Biliary Tract Disease Research, Shanghai Research Center of Biliary Tract Disease, Department of General Surgery, Xinhua Hospital, Affiliated with Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jinqiu He
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Centre of Genetics and Development, Department of Biochemistry and Biophysics, Institute of Plant Biology, School of Life Sciences, Fudan University, 200438, Shanghai, China
| | - Ying Huang
- Shanghai Key Laboratory of Biliary Tract Disease Research, Shanghai Research Center of Biliary Tract Disease, Department of General Surgery, Xinhua Hospital, Affiliated with Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jinbiao Ma
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Centre of Genetics and Development, Department of Biochemistry and Biophysics, Institute of Plant Biology, School of Life Sciences, Fudan University, 200438, Shanghai, China.
| | - Jia Wang
- Ministry of Education Key Laboratory of Protein Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center of Biological Structures, School of Life Sciences, Tsinghua University, Beijing, China.
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Torrez RM, Ohi MD, Garner AL. Structural Insights into the Advances and Mechanistic Understanding of Human Dicer. Biochemistry 2023; 62:1-16. [PMID: 36534787 DOI: 10.1021/acs.biochem.2c00570] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The RNase III endoribonuclease Dicer was discovered to be associated with cleavage of double-stranded RNA in 2001. Since then, many advances in our understanding of Dicer function have revealed that the enzyme plays a major role not only in microRNA biology but also in multiple RNA interference-related pathways. Yet, there is still much to be learned regarding Dicer structure-function in relation to how Dicer and Dicer-like enzymes initiate their cleavage reaction and release the desired RNA product. This Perspective describes the latest advances in Dicer structural studies, expands on what we have learned from this data, and outlines key gaps in knowledge that remain to be addressed. More specifically, we focus on human Dicer and highlight the intermediate processing steps where there is a lack of structural data to understand how the enzyme traverses from pre-cleavage to cleavage-competent states. Understanding these details is necessary to model Dicer's function as well as develop more specific microRNA-targeted therapeutics for the treatment of human diseases.
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Affiliation(s)
- Rachel M Torrez
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, 428 Church Street, Ann Arbor, Michigan 48109, United States.,Life Sciences Institute, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, Michigan 48109, United States
| | - Melanie D Ohi
- Life Sciences Institute, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, Michigan 48109, United States.,Department of Cell and Developmental Biology, University of Michigan Medical School, 109 Zina Pitcher Place, Ann Arbor, Michigan 48109, United States
| | - Amanda L Garner
- Department of Medicinal Chemistry, College of Pharmacy, University of Michigan, 428 Church Street, Ann Arbor, Michigan 48109, United States
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5
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Gao L, Wang Y, Abbas M, Zhang T, Ma E, Merzendorfer H, Zhu KY, Zhang J. Both LmDicer-1 and two LmDicer-2s participate in siRNA-mediated RNAi pathway and contribute to high gene silencing efficiency in Locusta migratoria. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2022; 151:103865. [PMID: 36336194 DOI: 10.1016/j.ibmb.2022.103865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 10/29/2022] [Accepted: 10/29/2022] [Indexed: 06/16/2023]
Abstract
Dicers belong to a class of large RNase III multidomain ribonucleases and are central components of the RNA interference (RNAi) pathways. In insects, Dicer-2 has been known to cleave long double-stranded RNA (dsRNA) in small interfering RNA (siRNA)-mediated-RNAi pathway. However, Dicer-1 is responsible for cleaving precursor microRNAs (pre28 miRNAs) in miRNA-mediated RNAi pathway. In this study, we identified one LmDicer-1 and two LmDicer-2 (LmDicer-2a and LmDicer-2b) genes in Locusta migratoria. The RNAi of RNAi assay showed that knockdown of each of the Dicer genes reduced RNAi efficiency against a target gene (Lmβ-Tubulin), suggesting that all these genes participated in the siRNA-mediated RNAi pathway. Sequence analyses of the siRNAs generated from dsLmβ-Tubulin after silencing each LmDicer gene showed no significant difference in the pattern of siRNAs mapped to dsLmβ-Tubulin. This result indicated that all the three LmDicers are capable of generating siRNAs from the dsRNA. We then generated recombinant proteins consisting of different domains using Escherichia coli expression system and incubated each recombinant protein with dsLmβ-Tubulin. We found that the recombinant Dicer proteins successfully cleaved dsLmβ-Tubulin. However, LmDicer-2a-R lacking dsRBD domain lost activity, suggesting that dsRBD domain is critical for Dicer function. Furthermore, overexpression of these proteins in Drosophila S2 cells improved RNAi efficiency. Our siRNA affinity chromatography and LC-MS/MS analysis identified LmDicer-2a, LmDicer-2b, LmR2D2, LmAgo2a, LmAgo1, LmStaufen and LmTARBP2 as constituents of RNA-induced silencing complex. Taken together, these data show that both LmDicer-1 and two LmDicer-2s all participate in siRNA-mediated RNAi pathway and likely contribute to high RNAi efficiency in L. migratoria.
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Affiliation(s)
- Lu Gao
- Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi, 030006, China; College of Life Science, Shanxi University, Taiyuan, China
| | - Yanli Wang
- Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi, 030006, China
| | - Mureed Abbas
- Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi, 030006, China
| | - Tingting Zhang
- Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi, 030006, China
| | - Enbo Ma
- Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi, 030006, China
| | | | - Kun Yan Zhu
- Department of Entomology, 123 Waters Hall, Kansas State University, Manhattan, KS, 66506, USA.
| | - Jianzhen Zhang
- Institute of Applied Biology, Shanxi University, Taiyuan, Shanxi, 030006, China.
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He L, Huang Y, Tang X. RNAi-based pest control: Production, application and the fate of dsRNA. Front Bioeng Biotechnol 2022; 10:1080576. [PMID: 36524052 PMCID: PMC9744970 DOI: 10.3389/fbioe.2022.1080576] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 11/17/2022] [Indexed: 10/21/2023] Open
Abstract
The limitations of conventional pesticides have raised the demand for innovative and sustainable solutions for plant protection. RNA Interference (RNAi) triggered by dsRNA has evolved as a promising strategy to control insects in a species-specific manner. In this context, we review the methods for mass production of dsRNA, the approaches of exogenous application of dsRNA in the field, and the fate of dsRNA after application. Additionally, we describe the opportunities and challenges of using nanoparticles as dsRNA carriers to control insects. Furthermore, we provide future directions to improve pest management efficiency by utilizing the synergistic effects of multiple target genes. Meanwhile, the establishment of a standardized framework for assessment and regulatory consensus is critical to the commercialization of RNA pesticides.
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Affiliation(s)
- Li He
- School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China
- Key Laboratory of Urban Agriculture, Ministry of Agriculture and Rural Affairs, Shanghai, China
- Shanghai Yangtze River Delta Eco-Environmental Change and Management Observation and Research Station, Ministry of Science and Technology, Ministry of Education, Shanghai, China
| | - Yanna Huang
- School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China
- Key Laboratory of Urban Agriculture, Ministry of Agriculture and Rural Affairs, Shanghai, China
- Shanghai Yangtze River Delta Eco-Environmental Change and Management Observation and Research Station, Ministry of Science and Technology, Ministry of Education, Shanghai, China
| | - Xueming Tang
- School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China
- Key Laboratory of Urban Agriculture, Ministry of Agriculture and Rural Affairs, Shanghai, China
- Shanghai Yangtze River Delta Eco-Environmental Change and Management Observation and Research Station, Ministry of Science and Technology, Ministry of Education, Shanghai, China
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7
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Su S, Wang J, Deng T, Yuan X, He J, Liu N, Li X, Huang Y, Wang HW, Ma J. Structural insights into dsRNA processing by Drosophila Dicer-2-Loqs-PD. Nature 2022; 607:399-406. [PMID: 35768513 PMCID: PMC9279154 DOI: 10.1038/s41586-022-04911-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 05/25/2022] [Indexed: 12/21/2022]
Abstract
Small interfering RNAs (siRNAs) are the key components for RNA interference (RNAi), a conserved RNA-silencing mechanism in many eukaryotes1,2. In Drosophila, an RNase III enzyme Dicer-2 (Dcr-2), aided by its cofactor Loquacious-PD (Loqs-PD), has an important role in generating 21 bp siRNA duplexes from long double-stranded RNAs (dsRNAs)3,4. ATP hydrolysis by the helicase domain of Dcr-2 is critical to the successful processing of a long dsRNA into consecutive siRNA duplexes5,6. Here we report the cryo-electron microscopy structures of Dcr-2-Loqs-PD in the apo state and in multiple states in which it is processing a 50 bp dsRNA substrate. The structures elucidated interactions between Dcr-2 and Loqs-PD, and substantial conformational changes of Dcr-2 during a dsRNA-processing cycle. The N-terminal helicase and domain of unknown function 283 (DUF283) domains undergo conformational changes after initial dsRNA binding, forming an ATP-binding pocket and a 5'-phosphate-binding pocket. The overall conformation of Dcr-2-Loqs-PD is relatively rigid during translocating along the dsRNA in the presence of ATP, whereas the interactions between the DUF283 and RIIIDb domains prevent non-specific cleavage during translocation by blocking the access of dsRNA to the RNase active centre. Additional ATP-dependent conformational changes are required to form an active dicing state and precisely cleave the dsRNA into a 21 bp siRNA duplex as confirmed by the structure in the post-dicing state. Collectively, this study revealed the molecular mechanism for the full cycle of ATP-dependent dsRNA processing by Dcr-2-Loqs-PD.
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Affiliation(s)
- Shichen Su
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Biochemistry and Biophysics, School of Life Sciences, Fudan University, Shanghai, China
| | - Jia Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center of Biological Structures, School of Life Sciences, Tsinghua University, Beijing, China
| | - Ting Deng
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Biochemistry and Biophysics, School of Life Sciences, Fudan University, Shanghai, China
| | - Xun Yuan
- Shanghai Key Laboratory of Biliary Tract Disease Research, Shanghai Research Center of Biliary Tract Disease, Department of General Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jinqiu He
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Biochemistry and Biophysics, School of Life Sciences, Fudan University, Shanghai, China
| | - Nan Liu
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center of Biological Structures, School of Life Sciences, Tsinghua University, Beijing, China
| | - Xiaomin Li
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center of Biological Structures, School of Life Sciences, Tsinghua University, Beijing, China
| | - Ying Huang
- Shanghai Key Laboratory of Biliary Tract Disease Research, Shanghai Research Center of Biliary Tract Disease, Department of General Surgery, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Hong-Wei Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center of Biological Structures, School of Life Sciences, Tsinghua University, Beijing, China.
| | - Jinbiao Ma
- State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Biochemistry and Biophysics, School of Life Sciences, Fudan University, Shanghai, China.
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Gestuveo RJ, Parry R, Dickson LB, Lequime S, Sreenu VB, Arnold MJ, Khromykh AA, Schnettler E, Lambrechts L, Varjak M, Kohl A. Mutational analysis of Aedes aegypti Dicer 2 provides insights into the biogenesis of antiviral exogenous small interfering RNAs. PLoS Pathog 2022; 18:e1010202. [PMID: 34990484 PMCID: PMC8769306 DOI: 10.1371/journal.ppat.1010202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 01/19/2022] [Accepted: 12/15/2021] [Indexed: 12/13/2022] Open
Abstract
The exogenous small interfering RNA (exo-siRNA) pathway is a key antiviral mechanism in the Aedes aegypti mosquito, a widely distributed vector of human-pathogenic arboviruses. This pathway is induced by virus-derived double-stranded RNAs (dsRNA) that are cleaved by the ribonuclease Dicer 2 (Dcr2) into predominantly 21 nucleotide (nt) virus-derived small interfering RNAs (vsiRNAs). These vsiRNAs are used by the effector protein Argonaute 2 within the RNA-induced silencing complex to cleave target viral RNA. Dcr2 contains several domains crucial for its activities, including helicase and RNase III domains. In Drosophila melanogaster Dcr2, the helicase domain has been associated with binding to dsRNA with blunt-ended termini and a processive siRNA production mechanism, while the platform-PAZ domains bind dsRNA with 3’ overhangs and subsequent distributive siRNA production. Here we analyzed the contributions of the helicase and RNase III domains in Ae. aegypti Dcr2 to antiviral activity and to the exo-siRNA pathway. Conserved amino acids in the helicase and RNase III domains were identified to investigate Dcr2 antiviral activity in an Ae. aegypti-derived Dcr2 knockout cell line by reporter assays and infection with mosquito-borne Semliki Forest virus (Togaviridae, Alphavirus). Functionally relevant amino acids were found to be conserved in haplotype Dcr2 sequences from field-derived Ae. aegypti across different continents. The helicase and RNase III domains were critical for silencing activity and 21 nt vsiRNA production, with RNase III domain activity alone determined to be insufficient for antiviral activity. Analysis of 21 nt vsiRNA sequences (produced by functional Dcr2) to assess the distribution and phasing along the viral genome revealed diverse yet highly consistent vsiRNA pools, with predominantly short or long sequence overlaps including 19 nt overlaps (the latter representing most likely true Dcr2 cleavage products). Combined with the importance of the Dcr2 helicase domain, this suggests that the majority of 21 nt vsiRNAs originate by processive cleavage. This study sheds new light on Ae. aegypti Dcr2 functions and properties in this important arbovirus vector species. Aedes aegypti mosquitoes that transmit human-pathogenic viruses rely on the exogenous small interfering RNA (exo-siRNA) pathway as part of antiviral responses. This pathway is triggered by virus-derived double-stranded RNA (dsRNA) produced during viral replication that is then cleaved by Dicer 2 (Dcr2) into virus-derived small interfering RNAs (vsiRNAs). These vsiRNAs target viral RNA, leading to suppression of viral replication. The importance of Dcr2 in this pathway has been intensely studied in the Drosophila melanogaster model but is largely lacking in mosquitoes. Here, we have identified conserved and functionally relevant amino acids in the helicase and RNase III domains of Ae. aegypti Dcr2 that are important in its silencing activity and antiviral responses against Semliki Forest virus (SFV). Small RNA sequencing of SFV-infected mosquito cells with functional or mutated Dcr2 gave new insights into the nature and origin of vsiRNAs. The findings of this study, together with the different molecular tools we have previously developed to investigate the exo-siRNA pathway of mosquito cells, have started to uncover important properties of Dcr2 that could be valuable in understanding mosquito-arbovirus interactions and potentially in developing or assisting vector control strategies.
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Affiliation(s)
- Rommel J. Gestuveo
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
- Division of Biological Sciences, University of the Philippines Visayas, Miagao, Iloilo, Philippines
- * E-mail: (R.J.G.); (M.V.); (A.K.)
| | - Rhys Parry
- School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Australia
| | - Laura B. Dickson
- Insect-Virus Interactions Unit, Institut Pasteur, UMR2000, CNRS, Paris, France
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Sebastian Lequime
- Insect-Virus Interactions Unit, Institut Pasteur, UMR2000, CNRS, Paris, France
- Cluster of Microbial Ecology, Groningen Institute for Evolutionary Life Sciences, Groningen, The Netherlands
| | | | - Matthew J. Arnold
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Alexander A. Khromykh
- School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Australia
- Australian Infectious Diseases Research Centre, Global Virus Network Centre of Excellence, Brisbane, Queensland, Australia
| | - Esther Schnettler
- Bernhard-Nocht-Institute for Tropical Medicine, Hamburg, Germany
- German Centre for Infection Research (DZIF), Partner Site Hamburg-Luebeck-Borstel-Riems, Hamburg, Germany
- Faculty of Mathematics, Informatics and Natural Sciences, University Hamburg, Hamburg, Germany
| | - Louis Lambrechts
- Insect-Virus Interactions Unit, Institut Pasteur, UMR2000, CNRS, Paris, France
| | - Margus Varjak
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
- Institute of Technology, University of Tartu, Tartu, Estonia
- * E-mail: (R.J.G.); (M.V.); (A.K.)
| | - Alain Kohl
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
- * E-mail: (R.J.G.); (M.V.); (A.K.)
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9
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Jonely M, Singh RK, Donelick HM, Bass BL, Noriega R. Loquacious-PD regulates the terminus-dependent molecular recognition of Dicer-2 toward double-stranded RNA. Chem Commun (Camb) 2021; 57:10879-10882. [PMID: 34590626 DOI: 10.1039/d1cc03843e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Dicer-2 cleaves double-stranded RNA into siRNAs in a terminus-dependent manner as part of D. melanogaster's RNA interference pathway. Using ultrafast fluorescence, we probe the local environment of chromophores at the dsRNA terminus upon binding by Dicer-2 and interrogate the effects of Loquacious-PD, an accessory protein. We find substrate-selective modes of molecular recognition that distinguish between blunt and 3'overhang termini, but whose differences are greatly reduced by Loquacious-PD. These results connect the molecular recognition properties of Dicer-2 to its selective processing of dsRNAs with different termini and to its need for Loquacious-PD to efficiently produce endogenous siRNAs.
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Affiliation(s)
- McKenzie Jonely
- University of Utah, Department of Chemistry, Salt Lake City, UT 84112, USA.
| | - Raushan K Singh
- University of Utah, Department of Biochemistry, Salt Lake City, UT 84112, USA
| | - Helen M Donelick
- University of Utah, Department of Biochemistry, Salt Lake City, UT 84112, USA
| | - Brenda L Bass
- University of Utah, Department of Biochemistry, Salt Lake City, UT 84112, USA
| | - Rodrigo Noriega
- University of Utah, Department of Chemistry, Salt Lake City, UT 84112, USA.
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10
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Kim K, Koo J, Yoon JS, Reddy Palli S. Coleopteran-specific StaufenC functions like Drosophila melanogaster Loquacious-PD in dsRNA processing. RNA Biol 2021; 18:467-477. [PMID: 34376105 DOI: 10.1080/15476286.2021.1960687] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
In Drosophila melanogaster, PD isoform of the double-stranded RNA binding protein (dsRBP) Loquacious (Loqs-PD) facilitates dsRNA cleavage to siRNA by Dicer-2. StaufenC (StauC) was discovered as a coleopteran-specific dsRBP required for dsRNA processing in coleopteran insects. Here, we show that StauC is essential for the high RNAi efficiency observed in coleopterans. Knockdown of StauC but not the homologs of Loqs-PD and R2D2 evoked a long-lasting insensitivity to RNAi in the coleopteran cell line, Ledp-SL1. The dsRNA insensitivity induced by StauC knockdown could not be overcome merely by an increase in dose or time of exposure to dsRNA or expression of Loquacious or R2D2. Furthermore, StauC but not Loqs and R2D2 are required for processing of dsRNA into siRNA. StauC overexpression also partly restored the impaired RNAi caused by the knockdown of Loqs-PD in D. melanogaster Kc cells. However, StauC was unable to compensate for the loss-of-the function of Dcr-2 or R2D2. Overall, these data suggest that StauC functions like Lops-PD in processing dsRNA to siRNA.
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Affiliation(s)
- Kyungbo Kim
- Department of Entomology, College of Agriculture, Food and Environment, University of Kentucky, Kentucky, USA
| | - Jinmo Koo
- Department of Entomology, College of Agriculture, Food and Environment, University of Kentucky, Kentucky, USA
| | - June-Sun Yoon
- Department of Entomology, College of Agriculture, Food and Environment, University of Kentucky, Kentucky, USA.,Department of Agricultural Convergence Technology, Jeonbuk National University, Jeonju, Republic of Korea
| | - Subba Reddy Palli
- Department of Entomology, College of Agriculture, Food and Environment, University of Kentucky, Kentucky, USA
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11
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Naganuma M, Tadakuma H, Tomari Y. Single-molecule analysis of processive double-stranded RNA cleavage by Drosophila Dicer-2. Nat Commun 2021; 12:4268. [PMID: 34257295 PMCID: PMC8277814 DOI: 10.1038/s41467-021-24555-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 06/23/2021] [Indexed: 11/09/2022] Open
Abstract
Drosophila Dicer-2 (Dcr-2) produces small interfering RNAs from long double-stranded RNAs (dsRNAs), playing an essential role in antiviral RNA interference. The dicing reaction by Dcr-2 is enhanced by Loquacious-PD (Loqs-PD), a dsRNA-binding protein that partners with Dcr-2. Previous biochemical analyses have proposed that Dcr-2 uses two distinct—processive or distributive—modes of cleavage by distinguishing the terminal structures of dsRNAs and that Loqs-PD alters the terminal dependence of Dcr-2. However, the direct evidence for this model is lacking, as the dynamic movement of Dcr-2 along dsRNAs has not been traced. Here, by utilizing single-molecule imaging, we show that the terminal structures of long dsRNAs and the presence or absence of Loqs-PD do not essentially change Dcr-2’s cleavage mode between processive and distributive, but rather simply affect the probability for Dcr-2 to undergo the cleavage reaction. Our results provide a refined model for how the dicing reaction by Dcr-2 is regulated. Fly Dicer-2 is thought to use two distinct – processive or distributive – modes of cleavage by distinguishing the terminal structures of double-stranded RNA (dsRNA) substrates with the help of its cofactor LoquaciousPD (Loqs-PD). Here the authors show by single-molecule imaging that dsRNA terminal structures and Loqs-PD change the probability for Dicer to initiate processive cleavage but not the mode of cleavage action per se.
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Affiliation(s)
- Masahiro Naganuma
- Laboratory of RNA Function, Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.,RIKEN Center for Biosystems Dynamics Research, Yokohama, Japan
| | - Hisashi Tadakuma
- Laboratory of RNA Function, Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan. .,School of Life Science and Technology, ShanghaiTech University, Shanghai, People's Republic of China.
| | - Yukihide Tomari
- Laboratory of RNA Function, Institute for Quantitative Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan. .,Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
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12
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Rosendo Machado S, van der Most T, Miesen P. Genetic determinants of antiviral immunity in dipteran insects - Compiling the experimental evidence. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2021; 119:104010. [PMID: 33476667 DOI: 10.1016/j.dci.2021.104010] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 01/08/2021] [Accepted: 01/09/2021] [Indexed: 06/12/2023]
Abstract
The genetic basis of antiviral immunity in dipteran insects is extensively studied in Drosophila melanogaster and advanced technologies for genetic manipulation allow a better characterization of immune responses also in non-model insect species. Especially, immunity in vector mosquitoes is recently in the spotlight, due to the medical impact that these insects have by transmitting viruses and other pathogens. Here, we review the current state of experimental evidence that supports antiviral functions for immune genes acting in different cellular pathways. We discuss the well-characterized RNA interference mechanism along with the less well-defined JAK-STAT, Toll, and IMD signaling pathways. Furthermore, we highlight the initial evidence for antiviral activity observed for the autophagy pathway, transcriptional pausing, as well as piRNA production from endogenous viral elements. We focus our review on studies from Drosophila and mosquito species from the lineages Aedes, Culex, and Anopheles, which contain major vector species responsible for virus transmission.
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Affiliation(s)
- Samara Rosendo Machado
- Department of Medical Microbiology, Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, the Netherlands
| | - Tom van der Most
- Department of Medical Microbiology, Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, the Netherlands
| | - Pascal Miesen
- Department of Medical Microbiology, Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen Medical Center, P.O. Box 9101, 6500 HB, Nijmegen, the Netherlands.
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13
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Schneider J, Imler JL. Sensing and signalling viral infection in drosophila. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2021; 117:103985. [PMID: 33358662 DOI: 10.1016/j.dci.2020.103985] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 12/16/2020] [Accepted: 12/17/2020] [Indexed: 06/12/2023]
Abstract
The fruitfly Drosophila melanogaster is a valuable model to unravel mechanisms of innate immunity, in particular in the context of viral infections. RNA interference, and more specifically the small interfering RNA pathway, is a major component of antiviral immunity in drosophila. In addition, the contribution of inducible transcriptional responses to the control of viruses in drosophila and other invertebrates is increasingly recognized. In particular, the recent discovery of a STING-IKKβ-Relish signalling cassette in drosophila has confirmed that NF-κB transcription factors play an important role in the control of viral infections, in addition to bacterial and fungal infections. Here, we review recent developments in the field, which begin to shed light on the mechanisms involved in sensing of viral infections and in signalling leading to production of antiviral effectors.
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Affiliation(s)
- Juliette Schneider
- Université de Strasbourg, CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, Strasbourg, France
| | - Jean-Luc Imler
- Université de Strasbourg, CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, Strasbourg, France; Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou 511436, China.
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14
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Arraes FBM, Martins-de-Sa D, Noriega Vasquez DD, Melo BP, Faheem M, de Macedo LLP, Morgante CV, Barbosa JARG, Togawa RC, Moreira VJV, Danchin EGJ, Grossi-de-Sa MF. Dissecting protein domain variability in the core RNA interference machinery of five insect orders. RNA Biol 2020; 18:1653-1681. [PMID: 33302789 DOI: 10.1080/15476286.2020.1861816] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
RNA interference (RNAi)-mediated gene silencing can be used to control specific insect pest populations. Unfortunately, the variable efficiency in the knockdown levels of target genes has narrowed the applicability of this technology to a few species. Here, we examine the current state of knowledge regarding the miRNA (micro RNA) and siRNA (small interfering RNA) pathways in insects and investigate the structural variability at key protein domains of the RNAi machinery. Our goal was to correlate domain variability with mechanisms affecting the gene silencing efficiency. To this end, the protein domains of 168 insect species, encompassing the orders Coleoptera, Diptera, Hemiptera, Hymenoptera, and Lepidoptera, were analysed using our pipeline, which takes advantage of meticulous structure-based sequence alignments. We used phylogenetic inference and the evolutionary rate coefficient (K) to outline the variability across domain regions and surfaces. Our results show that four domains, namely dsrm, Helicase, PAZ and Ribonuclease III, are the main contributors of protein variability in the RNAi machinery across different insect orders. We discuss the potential roles of these domains in regulating RNAi-mediated gene silencing and the role of loop regions in fine-tuning RNAi efficiency. Additionally, we identified several order-specific singularities which indicate that lepidopterans have evolved differently from other insect orders, possibly due to constant coevolution with plants and viruses. In conclusion, our results highlight several variability hotspots that deserve further investigation in order to improve the application of RNAi technology in the control of insect pests.
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Affiliation(s)
| | - Diogo Martins-de-Sa
- Departamento De Biologia Celular, Universidade De Brasília, Brasília-DF, Brazil
| | - Daniel D Noriega Vasquez
- Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil.,Catholic University of Brasília, Brasília-DF, Brazil
| | - Bruno Paes Melo
- Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil.,Viçosa University, UFV, Viçosa-MG, Brazil
| | - Muhammad Faheem
- Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil.,Department of Biological Sciences, National University of Medical Sciences, Punjab, Pakistan
| | | | - Carolina Vianna Morgante
- Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil.,Embrapa Semiarid, Petrolina-PE, Brazil.,National Institute of Science and Technology, Jakarta Embrapa-Brazil
| | | | - Roberto Coiti Togawa
- Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil
| | - Valdeir Junio Vaz Moreira
- Biotechnology Center, Brazil.,Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil.,Departamento De Biologia Celular, Universidade De Brasília, Brasília-DF, Brazil
| | - Etienne G J Danchin
- National Institute of Science and Technology, Jakarta Embrapa-Brazil.,INRAE, Université Côte d'Azur, CNRS, Institut Sophia Agrobiotech, Sophia-Antipolis, France
| | - Maria Fatima Grossi-de-Sa
- Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil.,Catholic University of Brasília, Brasília-DF, Brazil.,National Institute of Science and Technology, Jakarta Embrapa-Brazil
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15
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Donelick HM, Talide L, Bellet M, Aruscavage PJ, Lauret E, Aguiar ERGR, Marques JT, Meignin C, Bass BL. In vitro studies provide insight into effects of Dicer-2 helicase mutations in Drosophila melanogaster. RNA (NEW YORK, N.Y.) 2020; 26:1847-1861. [PMID: 32843367 PMCID: PMC7668257 DOI: 10.1261/rna.077289.120] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 08/20/2020] [Indexed: 05/03/2023]
Abstract
In vitro, Drosophila melanogaster Dicer-2 (Dcr-2) uses its helicase domain to initiate processing of dsRNA with blunt (BLT) termini, and its Platform•PAZ domain to initiate processing of dsRNA with 3' overhangs (ovrs). To understand the relationship of these in vitro observations to roles of Dcr-2 in vivo, we compared in vitro effects of two helicase mutations to their impact on production of endogenous and viral siRNAs in flies. Consistent with the importance of the helicase domain in processing BLT dsRNA, both point mutations eliminated processing of BLT, but not 3'ovr, dsRNA in vitro. However, the mutations had different effects in vivo. A point mutation in the Walker A motif of the Hel1 subdomain, G31R, largely eliminated production of siRNAs in vivo, while F225G, located in the Hel2 subdomain, showed reduced levels of endogenous siRNAs, but did not significantly affect virus-derived siRNAs. In vitro assays monitoring dsRNA cleavage, dsRNA binding, ATP hydrolysis, and binding of the accessory factor Loquacious-PD provided insight into the different effects of the mutations on processing of different sources of dsRNA in flies. Our in vitro studies suggest effects of the mutations in vivo relate to their effects on ATPase activity, dsRNA binding, and interactions with Loquacious-PD. Our studies emphasize the importance of future studies to characterize dsRNA termini as they exist in Drosophila and other animals.
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Affiliation(s)
- Helen M Donelick
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112, USA
| | - Loïc Talide
- Université de Strasbourg, CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
| | - Matthieu Bellet
- Université de Strasbourg, CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
| | - P Joseph Aruscavage
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112, USA
| | - Emilie Lauret
- Université de Strasbourg, CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
| | - Eric R G R Aguiar
- Centro de Biotecnologia e Genética, Universidade Estadual de Santa Cruz, Ilhéus 45662-900, Bahia, Brazil
| | - Joao T Marques
- Université de Strasbourg, CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
- Department of Biochemistry and Immunology, Universidade Federal de Minas Gerais, Belo Horizonte, CEP 31270-901, Brazil
| | - Carine Meignin
- Université de Strasbourg, CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, 67084 Strasbourg, France
| | - Brenda L Bass
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112, USA
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16
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aBravo Is a Novel Aedes aegypti Antiviral Protein that Interacts with, but Acts Independently of, the Exogenous siRNA Pathway Effector Dicer 2. Viruses 2020; 12:v12070748. [PMID: 32664591 PMCID: PMC7411624 DOI: 10.3390/v12070748] [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: 06/10/2020] [Revised: 07/03/2020] [Accepted: 07/08/2020] [Indexed: 12/12/2022] Open
Abstract
Mosquitoes, such as Aedes aegypti, can transmit arboviruses to humans. The exogenous short interfering RNA (exo-siRNA) pathway plays a major antiviral role in controlling virus infection in mosquito cells. The Dicer 2 (Dcr2) nuclease is a key effector protein in this pathway, which cleaves viral double-stranded RNA into virus-derived siRNAs that are further loaded onto an effector called Argonaute 2 (Ago2), which as part of the multiprotein RNA-induced silencing complex (RISC) targets and cleaves viral RNA. In order to better understand the effector protein Dcr2, proteomics experiments were conducted to identify interacting cellular partners. We identified several known interacting partners including Ago2, as well as two novel and previously uncharacterized Ae. aegypti proteins. The role of these two proteins was further investigated, and their interactions with Dcr2 verified by co-immunoprecipitation. Interestingly, despite their ability to interact with Ago2 and Piwi4, neither of these proteins was found to affect exo-siRNA silencing in a reporter assay. However, one of these proteins, Q0IFK9, subsequently called aBravo (aedine broadly active antiviral protein), was found to mediate antiviral activity against positive strand RNA arboviruses. Intriguingly the presence of Dcr2 was not necessary for this effect, suggesting that this interacting antiviral effector may act as part of protein complexes with potentially separate antiviral activities.
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17
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Hansen SR, Aderounmu AM, Donelick HM, Bass BL. Dicer's Helicase Domain: A Meeting Place for Regulatory Proteins. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2020; 84:185-193. [PMID: 32179591 PMCID: PMC7384945 DOI: 10.1101/sqb.2019.84.039750] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The function of Dicer’s helicase domain has been enigmatic since its discovery. Why do only some Dicers require ATP, despite a high degree of sequence conservation in their helicase domains? We discuss evolutionary considerations based on differences between vertebrate and invertebrate antiviral defense, and how the helicase domain has been co-opted in extant organisms as the binding site for accessory proteins. Many accessory proteins are double-stranded RNA binding proteins, and we propose models for how they modulate Dicer function and catalysis.
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Affiliation(s)
- Sarah R Hansen
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112-5650, USA
| | - Adedeji M Aderounmu
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112-5650, USA
| | - Helen M Donelick
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112-5650, USA
| | - Brenda L Bass
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112-5650, USA
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18
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Fukunaga R. Loquacious-PD removes phosphate inhibition of Dicer-2 processing of hairpin RNAs into siRNAs. Biochem Biophys Res Commun 2018; 498:1022-1027. [PMID: 29550490 DOI: 10.1016/j.bbrc.2018.03.108] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 03/13/2018] [Indexed: 01/20/2023]
Abstract
Drosophila Dicer-2 processes RNA substrates into short interfering RNAs (siRNAs). Loquacious-PD (Loqs-PD), a dsRNA-binding protein that associates with Dicer-2, is required for processing of a subset of RNA substrates including hairpin RNAs into siRNAs. Inorganic phosphate-a small molecule present in all cell types-inhibits Dicer-2 from processing precursor of microRNAs (pre-miRNAs), which are processed by Dicer-1. Whether or how Loqs-PD modulates the inhibitory effect of inorganic phosphate on Dicer-2 processing of RNA substrates is unknown. To address this question, I performed in vitro hairpin RNA processing assay with Dicer-2 in the presence or absence of Loqs-PD and/or inorganic phosphate. I found that inorganic phosphate inhibits Dicer-2 alone, but not Dicer-2 + Loqs-PD, from processing blunt-end hairpin RNAs into siRNAs. Thus, Loqs-PD removes the inhibitory effect of inorganic phosphate on Dicer-2 processing of blunt-end hairpin RNAs, allowing siRNA production in the presence of inorganic phosphate.
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Affiliation(s)
- Ryuya Fukunaga
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe Street, 521A Physiology Building, Baltimore, MD, 21205, USA.
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19
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Sinha NK, Iwasa J, Shen PS, Bass BL. Dicer uses distinct modules for recognizing dsRNA termini. Science 2018; 359:329-334. [PMID: 29269422 PMCID: PMC6154394 DOI: 10.1126/science.aaq0921] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 12/11/2017] [Indexed: 12/19/2022]
Abstract
Invertebrates rely on Dicer to cleave viral double-stranded RNA (dsRNA), and Drosophila Dicer-2 distinguishes dsRNA substrates by their termini. Blunt termini promote processive cleavage, while 3' overhanging termini are cleaved distributively. To understand this discrimination, we used cryo-electron microscopy to solve structures of Drosophila Dicer-2 alone and in complex with blunt dsRNA. Whereas the Platform-PAZ domains have been considered the only Dicer domains that bind dsRNA termini, unexpectedly, we found that the helicase domain is required for binding blunt, but not 3' overhanging, termini. We further showed that blunt dsRNA is locally unwound and threaded through the helicase domain in an adenosine triphosphate-dependent manner. Our studies reveal a previously unrecognized mechanism for optimizing antiviral defense and set the stage for the discovery of helicase-dependent functions in other Dicers.
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Affiliation(s)
- Niladri K. Sinha
- Department of Biochemistry, University of Utah, Salt Lake City, UT, 84112, USA
| | - Janet Iwasa
- Department of Biochemistry, University of Utah, Salt Lake City, UT, 84112, USA
| | - Peter S. Shen
- Department of Biochemistry, University of Utah, Salt Lake City, UT, 84112, USA
| | - Brenda L. Bass
- Department of Biochemistry, University of Utah, Salt Lake City, UT, 84112, USA
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