1
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Knudsen-Palmer DR, Raman P, Ettefa F, De Ravin L, Jose AM. Target-specific requirements for RNA interference can arise through restricted RNA amplification despite the lack of specialized pathways. eLife 2024; 13:RP97487. [PMID: 39161220 PMCID: PMC11335349 DOI: 10.7554/elife.97487] [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] [Indexed: 08/21/2024] Open
Abstract
Since double-stranded RNA (dsRNA) is effective for silencing a wide variety of genes, all genes are typically considered equivalent targets for such RNA interference (RNAi). Yet, loss of some regulators of RNAi in the nematode Caenorhabditis elegans can selectively impair the silencing of some genes. Here, we show that such selective requirements can be explained by an intersecting network of regulators acting on genes with differences in their RNA metabolism. In this network, the Maelstrom domain-containing protein RDE-10, the intrinsically disordered protein MUT-16, and the Argonaute protein NRDE-3 work together so that any two are required for silencing one somatic gene, but each is singly required for silencing another somatic gene, where only the requirement for NRDE-3 can be overcome by enhanced dsRNA processing. Quantitative models and their exploratory simulations led us to find that (1) changing cis-regulatory elements of the target gene can reduce the dependence on NRDE-3, (2) animals can recover from silencing in non-dividing cells, and (3) cleavage and tailing of mRNAs with UG dinucleotides, which makes them templates for amplifying small RNAs, are enriched within 'pUG zones' matching the dsRNA. Similar crosstalk between pathways and restricted amplification could result in apparently selective silencing by endogenous RNAs.
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Affiliation(s)
- Daphne R Knudsen-Palmer
- Department of Cell Biology and Molecular Genetics, Biological Sciences Graduate Program, University of MarylandCollege ParkUnited States
| | - Pravrutha Raman
- Department of Cell Biology and Molecular Genetics, Biological Sciences Graduate Program, University of MarylandCollege ParkUnited States
| | - Farida Ettefa
- Department of Cell Biology and Molecular Genetics, Biological Sciences Graduate Program, University of MarylandCollege ParkUnited States
| | - Laura De Ravin
- Department of Cell Biology and Molecular Genetics, Biological Sciences Graduate Program, University of MarylandCollege ParkUnited States
| | - Antony M Jose
- Department of Cell Biology and Molecular Genetics, Biological Sciences Graduate Program, University of MarylandCollege ParkUnited States
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2
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Phan P, Fogarty CE, Eamens AL, Duke MG, McManus DP, Wang T, Cummins SF. ARGONAUTE2 Localizes to Sites of Sporocysts in the Schistosome-Infected Snail, Biomphalaria glabrata. Genes (Basel) 2024; 15:1023. [PMID: 39202383 PMCID: PMC11353429 DOI: 10.3390/genes15081023] [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: 06/24/2024] [Revised: 07/30/2024] [Accepted: 08/01/2024] [Indexed: 09/03/2024] Open
Abstract
MicroRNAs (miRNAs) are a class of small regulatory RNA that are generated via core protein machinery. The miRNAs direct gene-silencing mechanisms to mediate an essential role in gene expression regulation. In mollusks, miRNAs have been demonstrated to be required to regulate gene expression in various biological processes, including normal development, immune responses, reproduction, and stress adaptation. In this study, we aimed to establishment the requirement of the miRNA pathway as part of the molecular response of exposure of Biomphalaria glabrata (snail host) to Schistosoma mansoni (trematode parasite). Initially, the core pieces of miRNA pathway protein machinery, i.e., Drosha, DGCR8, Exportin-5, Ran, and Dicer, together with the central RNA-induced silencing complex (RISC) effector protein Argonaute2 (Ago2) were elucidated from the B. glabrata genome. Following exposure of B. glabrata to S. mansoni miracidia, we identified significant expression up-regulation of all identified pieces of miRNA pathway protein machinery, except for Exportin-5, at 16 h post exposure. For Ago2, we went on to show that the Bgl-Ago2 protein was localized to regions surrounding the sporocysts in the digestive gland of infected snails 20 days post parasite exposure. In addition to documenting elevated miRNA pathway protein machinery expression at the early post-exposure time point, a total of 13 known B. glabrata miRNAs were significantly differentially expressed. Of these thirteen B. glabrata miRNAs responsive to S. mansoni miracidia exposure, five were significantly reduced in their abundance, and correspondingly, these five miRNAs were determined to putatively target six genes with significantly elevated expression and that have been previously associated with immune responses in other animal species, including humans. In conclusion, this study demonstrates the central importance of a functional miRNA pathway in snails, which potentially forms a critical component of the immune response of snails to parasite exposure. Further, the data reported in this study provide additional evidence of the complexity of the molecular response of B. glabrata to S. mansoni infection: a molecular response that could be targeted in the future to overcome parasite infection and, in turn, human schistosomiasis.
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Affiliation(s)
- Phong Phan
- Centre for Bioinnovation, University of the Sunshine Coast, Maroochydore, QLD 4558, Australia; (P.P.); (C.E.F.); (T.W.)
- School of Science, Technology and Engineering, University of the Sunshine Coast, Maroochydore, QLD 4558, Australia
| | - Conor E. Fogarty
- Centre for Bioinnovation, University of the Sunshine Coast, Maroochydore, QLD 4558, Australia; (P.P.); (C.E.F.); (T.W.)
- School of Science, Technology and Engineering, University of the Sunshine Coast, Maroochydore, QLD 4558, Australia
| | - Andrew L. Eamens
- School of Health, University of the Sunshine Coast, Maroochydore, QLD 4558, Australia;
| | - Mary G. Duke
- Molecular Parasitology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, QLD 4006, Australia;
| | - Donald P. McManus
- Molecular Parasitology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, QLD 4006, Australia;
| | - Tianfang Wang
- Centre for Bioinnovation, University of the Sunshine Coast, Maroochydore, QLD 4558, Australia; (P.P.); (C.E.F.); (T.W.)
- School of Science, Technology and Engineering, University of the Sunshine Coast, Maroochydore, QLD 4558, Australia
| | - Scott F. Cummins
- Centre for Bioinnovation, University of the Sunshine Coast, Maroochydore, QLD 4558, Australia; (P.P.); (C.E.F.); (T.W.)
- School of Science, Technology and Engineering, University of the Sunshine Coast, Maroochydore, QLD 4558, Australia
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3
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Knudsen-Palmer DR, Raman P, Ettefa F, De Ravin L, Jose AM. Target-specific requirements for RNA interference can arise through restricted RNA amplification despite the lack of specialized pathways. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.02.07.527351. [PMID: 36798330 PMCID: PMC9934570 DOI: 10.1101/2023.02.07.527351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Since double-stranded RNA (dsRNA) is effective for silencing a wide variety of genes, all genes are typically considered equivalent targets for such RNA interference (RNAi). Yet, loss of some regulators of RNAi in the nematode C. elegans can selectively impair the silencing of some genes. Here we show that such selective requirements can be explained by an intersecting network of regulators acting on genes with differences in their RNA metabolism. In this network, the Maelstrom domain-containing protein RDE-10, the intrinsically disordered protein MUT-16, and the Argonaute protein NRDE-3 work together so that any two are required for silencing one somatic gene, but each is singly required for silencing another somatic gene, where only the requirement for NRDE-3 can be overcome by enhanced dsRNA processing. Quantitative models and their exploratory simulations led us to find that (1) changing cis-regulatory elements of the target gene can reduce the dependence on NRDE-3, (2) animals can recover from silencing in non-dividing cells and (3) cleavage and tailing of mRNAs with UG dinucleotides, which makes them templates for amplifying small RNAs, is enriched within 'pUG zones' matching the dsRNA. Similar crosstalk between pathways and restricted amplification could result in apparently selective silencing by endogenous RNAs.
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Affiliation(s)
- Daphne R. Knudsen-Palmer
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, USA. Biological Sciences Graduate Program, University of Maryland, College Park, USA
| | - Pravrutha Raman
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, USA. Biological Sciences Graduate Program, University of Maryland, College Park, USA
- Current address: Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Farida Ettefa
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, USA. Biological Sciences Graduate Program, University of Maryland, College Park, USA
- Current address: Institute for Systems Genetics, New York University School of Medicine, New York, NY, USA
| | - Laura De Ravin
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, USA. Biological Sciences Graduate Program, University of Maryland, College Park, USA
| | - Antony M. Jose
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, USA. Biological Sciences Graduate Program, University of Maryland, College Park, USA
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4
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Consalvo CD, Aderounmu AM, Donelick HM, Aruscavage PJ, Eckert DM, Shen PS, Bass BL. Caenorhabditis elegans Dicer acts with the RIG-I-like helicase DRH-1 and RDE-4 to cleave dsRNA. eLife 2024; 13:RP93979. [PMID: 38747717 PMCID: PMC11095941 DOI: 10.7554/elife.93979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2024] Open
Abstract
Invertebrates use the endoribonuclease Dicer to cleave viral dsRNA during antiviral defense, while vertebrates use RIG-I-like Receptors (RLRs), which bind viral dsRNA to trigger an interferon response. While some invertebrate Dicers act alone during antiviral defense, Caenorhabditis elegans Dicer acts in a complex with a dsRNA binding protein called RDE-4, and an RLR ortholog called DRH-1. We used biochemical and structural techniques to provide mechanistic insight into how these proteins function together. We found RDE-4 is important for ATP-independent and ATP-dependent cleavage reactions, while helicase domains of both DCR-1 and DRH-1 contribute to ATP-dependent cleavage. DRH-1 plays the dominant role in ATP hydrolysis, and like mammalian RLRs, has an N-terminal domain that functions in autoinhibition. A cryo-EM structure indicates DRH-1 interacts with DCR-1's helicase domain, suggesting this interaction relieves autoinhibition. Our study unravels the mechanistic basis of the collaboration between two helicases from typically distinct innate immune defense pathways.
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Affiliation(s)
- Claudia D Consalvo
- Department of Biochemistry, University of UtahSalt Lake CityUnited States
| | | | - Helen M Donelick
- Department of Biochemistry, University of UtahSalt Lake CityUnited States
| | | | - Debra M Eckert
- Department of Biochemistry, University of UtahSalt Lake CityUnited States
| | - Peter S Shen
- Department of Biochemistry, University of UtahSalt Lake CityUnited States
| | - Brenda L Bass
- Department of Biochemistry, University of UtahSalt Lake CityUnited States
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5
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Bass BL. Adenosine deaminases that act on RNA, then and now. RNA (NEW YORK, N.Y.) 2024; 30:521-529. [PMID: 38531651 PMCID: PMC11019741 DOI: 10.1261/rna.079990.124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2024] [Accepted: 02/11/2024] [Indexed: 03/28/2024]
Abstract
In this article, I recount my memories of key experiments that led to my entry into the RNA editing/modification field. I highlight initial observations made by the pioneers in the ADAR field, and how they fit into our current understanding of this family of enzymes. I discuss early mysteries that have now been solved, as well as those that still linger. Finally, I discuss important, outstanding questions and acknowledge my hope for the future of the RNA editing/modification field.
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Affiliation(s)
- Brenda L Bass
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112, USA
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6
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Consalvo CD, Aderounmu AM, Donelick HM, Aruscavage PJ, Eckert DM, Shen PS, Bass BL. C. elegans Dicer acts with the RIG-I-like helicase DRH-1 and RDE-4 to cleave dsRNA. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.09.21.558868. [PMID: 37790392 PMCID: PMC10542151 DOI: 10.1101/2023.09.21.558868] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
Invertebrates use the endoribonuclease Dicer to cleave viral dsRNA during antiviral defense, while vertebrates use RIG-I-like Receptors (RLRs), which bind viral dsRNA to trigger an interferon response. While some invertebrate Dicers act alone during antiviral defense, C. elegans Dicer acts in a complex with a dsRNA binding protein called RDE-4, and an RLR ortholog called DRH-1. We used biochemical and structural techniques to provide mechanistic insight into how these proteins function together. We found RDE-4 is important for ATP-independent and ATP-dependent cleavage reactions, while helicase domains of both DCR-1 and DRH-1 contribute to ATP-dependent cleavage. DRH-1 plays the dominant role in ATP hydrolysis, and like mammalian RLRs, has an N-terminal domain that functions in autoinhibition. A cryo-EM structure indicates DRH-1 interacts with DCR-1's helicase domain, suggesting this interaction relieves autoinhibition. Our study unravels the mechanistic basis of the collaboration between two helicases from typically distinct innate immune defense pathways.
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Affiliation(s)
| | - Adedeji M. Aderounmu
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112
- These authors contributed equally
| | - Helen M. Donelick
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112
- These authors contributed equally
| | - P. Joe Aruscavage
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112
| | - Debra M. Eckert
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112
| | - Peter S. Shen
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112
| | - Brenda L. Bass
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112
- Lead Contact
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7
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Bayraktar E, Bayraktar R, Oztatlici H, Lopez-Berestein G, Amero P, Rodriguez-Aguayo C. Targeting miRNAs and Other Non-Coding RNAs as a Therapeutic Approach: An Update. Noncoding RNA 2023; 9:27. [PMID: 37104009 PMCID: PMC10145226 DOI: 10.3390/ncrna9020027] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 03/29/2023] [Accepted: 04/07/2023] [Indexed: 04/28/2023] Open
Abstract
Since the discovery of the first microRNAs (miRNAs, miRs), the understanding of miRNA biology has expanded substantially. miRNAs are involved and described as master regulators of the major hallmarks of cancer, including cell differentiation, proliferation, survival, the cell cycle, invasion, and metastasis. Experimental data indicate that cancer phenotypes can be modified by targeting miRNA expression, and because miRNAs act as tumor suppressors or oncogenes (oncomiRs), they have emerged as attractive tools and, more importantly, as a new class of targets for drug development in cancer therapeutics. With the use of miRNA mimics or molecules targeting miRNAs (i.e., small-molecule inhibitors such as anti-miRS), these therapeutics have shown promise in preclinical settings. Some miRNA-targeted therapeutics have been extended to clinical development, such as the mimic of miRNA-34 for treating cancer. Here, we discuss insights into the role of miRNAs and other non-coding RNAs in tumorigenesis and resistance and summarize some recent successful systemic delivery approaches and recent developments in miRNAs as targets for anticancer drug development. Furthermore, we provide a comprehensive overview of mimics and inhibitors that are in clinical trials and finally a list of clinical trials based on miRNAs.
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Affiliation(s)
- Emine Bayraktar
- Department of Gynecologic Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- UTHealth Houston Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Recep Bayraktar
- UTHealth Houston Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Hulya Oztatlici
- Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- Department of Histology and Embryology, Gaziantep University, Gaziantep 27310, Turkey
| | - Gabriel Lopez-Berestein
- Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Paola Amero
- Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Cristian Rodriguez-Aguayo
- Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- Center for RNA Interference and Non-Coding RNA, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
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8
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Liontis T, Verma K, Grishok A. DOT-1.1 (DOT1L) deficiency in C. elegans leads to small RNA-dependent gene activation. BBA ADVANCES 2023; 3:100080. [PMID: 37082252 PMCID: PMC10074844 DOI: 10.1016/j.bbadva.2023.100080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/27/2023] [Accepted: 01/30/2023] [Indexed: 02/04/2023] Open
Abstract
Methylation of histone H3 at lysine 79 (H3K79) is conserved from yeast to humans and is accomplished by Dot1 (disruptor of telomeric silencing-1) methyltransferases. The C. elegans enzyme DOT-1.1 and its interacting partners are similar to the mammalian DOT1L (Dot1-like) complex. The C. elegans DOT-1.1 complex has been functionally connected to RNA interference. Specifically, we have previously shown that embryonic and larval lethality of dot-1.1 mutant worms deficient in H3K79 methylation was suppressed by mutations in the RNAi pathway genes responsible for generation (rde-4) and function (rde-1) of primary small interfering RNAs (siRNAs). This suggests that dot-1.1 mutant lethality is dependent on the enhanced production of some siRNAs. We have also found that this lethality is suppressed by a loss-of-function of CED-3, a conserved apoptotic protease. Here, we describe a comparison of gene expression and primary siRNA production changes between control and dot-1.1 deletion mutant embryos. We found that elevated antisense siRNA production occurred more often at upregulated than downregulated genes. Importantly, gene expression changes were dependent on RDE-4 in both instances. Moreover, the upregulated group, which is potentially activated by ectopic siRNAs, was enriched in protease-coding genes. Our findings are consistent with a model where in the absence of H3K79 methylation there is a small RNA-dependent activation of protease genes, which leads to embryonic and larval lethality. DOT1 enzymes' conservation suggests that the interplay between H3K79 methylation and small RNA pathways may exist in higher organisms.
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9
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Carro MDLM, Grimson A, Cohen PE. Small RNAs and their protein partners in animal meiosis. Curr Top Dev Biol 2022; 151:245-279. [PMID: 36681472 DOI: 10.1016/bs.ctdb.2022.06.001] [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] [Indexed: 01/25/2023]
Abstract
Meiosis is characterized by highly regulated transitions in gene expression that require diverse mechanisms of gene regulation. For example, in male mammals, transcription undergoes a global shut-down in early prophase I of meiosis, followed by increasing transcriptional activity into pachynema. Later, as spermiogenesis proceeds, the histones bound to DNA are replaced with transition proteins, which are themselves replaced with protamines, resulting in a highly condensed nucleus with repressed transcriptional activity. In addition, two specialized gene silencing events take place during prophase I: meiotic silencing of unsynapsed chromatin (MSUC), and the sex chromatin specific mechanism, meiotic sex chromosome inactivation (MSCI). Notably, conserved roles for the RNA binding protein (RBP) machinery that functions with small non-coding RNAs have been described as participating in these meiosis-specific mechanisms, suggesting that RNA-mediated gene regulation is critical for fertility in many species. Here, we review roles of small RNAs and their associated RBPs in meiosis-related processes such as centromere function, silencing of unpaired chromatin and meiotic recombination. We will discuss the emerging evidence of non-canonical functions of these components in meiosis.
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Affiliation(s)
- María de Las Mercedes Carro
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, United States; Cornell Reproductive Sciences Center (CoRe), Cornell University, Ithaca, NY, United States
| | - Andrew Grimson
- Cornell Reproductive Sciences Center (CoRe), Cornell University, Ithaca, NY, United States; Department of Molecular Biology & Genetics, Cornell University, Ithaca, NY, United States.
| | - Paula E Cohen
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, United States; Cornell Reproductive Sciences Center (CoRe), Cornell University, Ithaca, NY, United States.
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10
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Abstract
One of the first layers of protection that metazoans put in place to defend themselves against viruses rely on the use of proteins containing DExD/H-box helicase domains. These members of the duplex RNA–activated ATPase (DRA) family act as sensors of double-stranded RNA (dsRNA) molecules, a universal marker of viral infections. DRAs can be classified into 2 subgroups based on their mode of action: They can either act directly on the dsRNA, or they can trigger a signaling cascade. In the first group, the type III ribonuclease Dicer plays a key role to activate the antiviral RNA interference (RNAi) pathway by cleaving the viral dsRNA into small interfering RNAs (siRNAs). This represents the main innate antiviral immune mechanism in arthropods and nematodes. Even though Dicer is present and functional in mammals, the second group of DRAs, containing the RIG-I-like RNA helicases, appears to have functionally replaced RNAi and activate type I interferon (IFN) response upon dsRNA sensing. However, recent findings tend to blur the frontier between these 2 mechanisms, thereby highlighting the crucial and diverse roles played by RNA helicases in antiviral innate immunity. Here, we will review our current knowledge of the importance of these key proteins in viral infection, with a special focus on the interplay between the 2 main types of response that are activated by dsRNA.
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Affiliation(s)
- Morgane Baldaccini
- Université de Strasbourg, Architecture et Réactivité de l’ARN, Institut de Biologie Moléculaire et Cellulaire du CNRS, Strasbourg, France
| | - Sébastien Pfeffer
- Université de Strasbourg, Architecture et Réactivité de l’ARN, Institut de Biologie Moléculaire et Cellulaire du CNRS, Strasbourg, France
- * E-mail:
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11
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Cecere G. Small RNAs in epigenetic inheritance: from mechanisms to trait transmission. FEBS Lett 2021; 595:2953-2977. [PMID: 34671979 PMCID: PMC9298081 DOI: 10.1002/1873-3468.14210] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 10/08/2021] [Accepted: 10/18/2021] [Indexed: 01/02/2023]
Abstract
Inherited information is transmitted to progeny primarily by the genome through the gametes. However, in recent years, epigenetic inheritance has been demonstrated in several organisms, including animals. Although it is clear that certain post‐translational histone modifications, DNA methylation, and noncoding RNAs regulate epigenetic inheritance, the molecular mechanisms responsible for epigenetic inheritance are incompletely understood. This review focuses on the role of small RNAs in transmitting epigenetic information across generations in animals. Examples of documented cases of transgenerational epigenetic inheritance are discussed, from the silencing of transgenes to the inheritance of complex traits, such as fertility, stress responses, infections, and behavior. Experimental evidence supporting the idea that small RNAs are epigenetic molecules capable of transmitting traits across generations is highlighted, focusing on the mechanisms by which small RNAs achieve such a function. Just as the role of small RNAs in epigenetic processes is redefining the concept of inheritance, so too our understanding of the molecular pathways and mechanisms that govern epigenetic inheritance in animals is radically changing.
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Affiliation(s)
- Germano Cecere
- Mechanisms of Epigenetic Inheritance, Department of Developmental and Stem Cell Biology, Institut Pasteur, UMR3738, CNRS, Paris, France
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12
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Paturi S, Deshmukh MV. A Glimpse of "Dicer Biology" Through the Structural and Functional Perspective. Front Mol Biosci 2021; 8:643657. [PMID: 34026825 PMCID: PMC8138440 DOI: 10.3389/fmolb.2021.643657] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 04/07/2021] [Indexed: 01/05/2023] Open
Abstract
The RNA interference pathway (RNAi) is executed by two core enzymes, Dicer and Argonaute, for accomplishing a tailored transcriptional and post-transcriptional gene regulation. Dicer, an RNase III enzyme, initiates the RNAi pathway, plays a pivotal role in fighting infection against pathogens, and acts as a housekeeping enzyme for cellular homeostasis. Here, we review structure-based functional insights of Dicer and its domains present in a diverse group of organisms. Although Dicer and its domains are evolutionarily conserved from microsporidian parasites to humans, recent cryo-electron microscopy structures of Homo sapiens Dicer and Drosophila melanogaster Dicer-2 suggest characteristic variations in the mechanism of the dsRNA substrate recognition. Interestingly, the necessity for more than one functionally distinct Dicer paralogs in insects and plants compared with a single Dicer in other eukaryotic life forms implies Dicer’s role in the interplay of RNAi and other defense mechanisms. Based on the structural and mechanistic information obtained during the last decade, we aim to highlight the significance of key Dicer domains that are crucial to Dicer specific recognition and precise cleavage of dsRNA substrates. Further, the role of Dicer in the formation of Argonaute-based RNA-induced silencing complex (RISC) assembly formation, Dicer’s ability to regulate a complex protein interaction network, and its role in other cellular processes, as well as its therapeutic potentials, are emphasized.
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Affiliation(s)
- Sneha Paturi
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Hyderabad, India
| | - Mandar V Deshmukh
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Hyderabad, India
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13
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Houri-Zeevi L, Teichman G, Gingold H, Rechavi O. Stress resets ancestral heritable small RNA responses. eLife 2021; 10:e65797. [PMID: 33729152 PMCID: PMC8021399 DOI: 10.7554/elife.65797] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 03/15/2021] [Indexed: 12/15/2022] Open
Abstract
Transgenerational inheritance of small RNAs challenges basic concepts of heredity. In Caenorhabditis elegans nematodes, small RNAs are transmitted across generations to establish a transgenerational memory trace of ancestral environments and distinguish self-genes from non-self-elements. Carryover of aberrant heritable small RNA responses was shown to be maladaptive and to lead to sterility. Here, we show that various types of stress (starvation, high temperatures, and high osmolarity) induce resetting of ancestral small RNA responses and a genome-wide reduction in heritable small RNA levels. We found that mutants that are defective in various stress pathways exhibit irregular RNAi inheritance dynamics even in the absence of stress. Moreover, we discovered that resetting of ancestral RNAi responses is specifically orchestrated by factors that function in the p38 MAPK pathway and the transcription factor SKN-1/Nrf2. Stress-dependent termination of small RNA inheritance could protect from run-on of environment-irrelevant heritable gene regulation.
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Affiliation(s)
- Leah Houri-Zeevi
- Department of Neurobiology, Wise Faculty of Life Sciences & Sagol School of Neuroscience, Tel Aviv UniversityTel AvivIsrael
| | - Guy Teichman
- Department of Neurobiology, Wise Faculty of Life Sciences & Sagol School of Neuroscience, Tel Aviv UniversityTel AvivIsrael
| | - Hila Gingold
- Department of Neurobiology, Wise Faculty of Life Sciences & Sagol School of Neuroscience, Tel Aviv UniversityTel AvivIsrael
| | - Oded Rechavi
- Department of Neurobiology, Wise Faculty of Life Sciences & Sagol School of Neuroscience, Tel Aviv UniversityTel AvivIsrael
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14
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Abstract
RNA interference is a powerful tool for dissecting gene function. In Caenorhabditis elegans, ingestion of double stranded RNA causes strong, systemic knockdown of target genes. Further insight into gene function can be revealed by tissue-specific RNAi techniques. Currently available tissue-specific C. elegans strains rely on rescue of RNAi function in a desired tissue or cell in an otherwise RNAi deficient genetic background. We attempted to assess the contribution of specific tissues to polyunsaturated fatty acid (PUFA) synthesis using currently available tissue-specific RNAi strains. We discovered that rde-1 (ne219), a commonly used RNAi-resistant mutant strain, retains considerable RNAi capacity against RNAi directed at PUFA synthesis genes. By measuring changes in the fatty acid products of the desaturase enzymes that synthesize PUFAs, we found that the before mentioned strain, rde-1 (ne219) and the reported germline only RNAi strain, rrf-1 (pk1417) are not appropriate genetic backgrounds for tissue-specific RNAi experiments. However, the knockout mutant rde-1 (ne300) was strongly resistant to dsRNA induced RNAi, and thus is more appropriate for construction of a robust tissue-specific RNAi strains. Using newly constructed strains in the rde-1(null) background, we found considerable desaturase activity in intestinal, epidermal, and germline tissues, but not in muscle. The RNAi-specific strains reported in this study will be useful tools for C. elegans researchers studying a variety of biological processes.
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15
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Ravikumar S, Devanapally S, Jose AM. Gene silencing by double-stranded RNA from C. elegans neurons reveals functional mosaicism of RNA interference. Nucleic Acids Res 2019; 47:10059-10071. [PMID: 31501873 PMCID: PMC6821342 DOI: 10.1093/nar/gkz748] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 08/12/2019] [Accepted: 08/20/2019] [Indexed: 12/12/2022] Open
Abstract
Delivery of double-stranded RNA (dsRNA) into animals can silence genes of matching sequence in diverse cell types through mechanisms that have been collectively called RNA interference. In the nematode Caenorhabditis elegans, dsRNA from multiple sources can trigger the amplification of silencing signals. Amplification occurs through the production of small RNAs by two RNA-dependent RNA polymerases (RdRPs) that are thought to be tissue-specific - EGO-1 in the germline and RRF-1 in somatic cells. Here we demonstrate that EGO-1 can compensate for the lack of RRF-1 when dsRNA from neurons is used to silence genes in intestinal cells. However, the lineal origins of cells that can use EGO-1 varies. This variability could be because random sets of cells can either receive different amounts of dsRNA from the same source or use different RdRPs to perform the same function. Variability is masked in wild-type animals, which show extensive silencing by neuronal dsRNA. As a result, cells appear similarly functional despite underlying differences that vary from animal to animal. This functional mosaicism cautions against inferring uniformity of mechanism based on uniformity of outcome. We speculate that functional mosaicism could contribute to escape from targeted therapies and could allow developmental systems to drift over evolutionary time.
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Affiliation(s)
- Snusha Ravikumar
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Sindhuja Devanapally
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Antony M Jose
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
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16
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Esse R, Gushchanskaia ES, Lord A, Grishok A. DOT1L complex suppresses transcription from enhancer elements and ectopic RNAi in Caenorhabditis elegans. RNA (NEW YORK, N.Y.) 2019; 25:1259-1273. [PMID: 31300558 PMCID: PMC6800474 DOI: 10.1261/rna.070292.119] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 07/10/2019] [Indexed: 05/14/2023]
Abstract
Methylation of histone H3 on lysine 79 (H3K79) by DOT1L is associated with actively transcribed genes. Earlier, we described that DOT-1.1, the Caenorhabditis elegans homolog of mammalian DOT1L, cooperates with the chromatin-binding protein ZFP-1 (AF10 homolog) to negatively modulate transcription of highly and widely expressed target genes. Also, the reduction of ZFP-1 levels has consistently been associated with lower efficiency of RNA interference (RNAi) triggered by exogenous double-stranded RNA (dsRNA), but the reason for this is not clear. Here, we demonstrate that the DOT1L complex suppresses transcription originating from enhancer elements and antisense transcription, thus potentiating the expression of enhancer-regulated genes. We also show that worms lacking H3K79 methylation do not survive, and this lethality is suppressed by a loss of caspase-3 or Dicer complex components that initiate gene silencing response to exogenous dsRNA. Our results suggest that ectopic elevation of endogenous dsRNA directly or indirectly resulting from global misregulation of transcription in DOT1L complex mutants may engage the Dicer complex and, therefore, limit the efficiency of exogenous RNAi.
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Affiliation(s)
- Ruben Esse
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA
| | | | - Avery Lord
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA
| | - Alla Grishok
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA
- Genome Science Institute, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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17
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Melnick M, Gonzales P, Cabral J, Allen MA, Dowell RD, Link CD. Heat shock in C. elegans induces downstream of gene transcription and accumulation of double-stranded RNA. PLoS One 2019; 14:e0206715. [PMID: 30958820 PMCID: PMC6453478 DOI: 10.1371/journal.pone.0206715] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 03/25/2019] [Indexed: 12/14/2022] Open
Abstract
We observed that heat shock of Caenorhabditis elegans leads to the formation of nuclear double-stranded RNA (dsRNA) foci, detectable with a dsRNA-specific monoclonal antibody. These foci significantly overlap with nuclear HSF-1 granules. To investigate the molecular mechanism(s) underlying dsRNA foci formation, we used RNA-seq to globally characterize total RNA and immunoprecipitated dsRNA from control and heat shocked worms. We find a subset of both sense and antisense transcripts enriched in the dsRNA pool by heat shock overlap with dsRNA transcripts enriched by deletion of tdp-1, which encodes the C. elegans ortholog of TDP-43. Interestingly, transcripts involved in translation are over-represented in the dsRNAs induced by either heat shock or deletion of tdp-1. Also enriched in the dsRNA transcripts are sequences downstream of annotated genes (DoGs), which we globally quantified with a new algorithm. To validate these observations, we used fluorescence in situ hybridization (FISH) to confirm both antisense and downstream of gene transcription for eif-3.B, one of the affected loci we identified.
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Affiliation(s)
- Marko Melnick
- Integrative Physiology, University of Colorado, Boulder, Colorado, United States of America
| | - Patrick Gonzales
- Integrative Physiology, University of Colorado, Boulder, Colorado, United States of America
| | - Joseph Cabral
- Integrative Physiology, University of Colorado, Boulder, Colorado, United States of America
| | - Mary A. Allen
- BioFrontiers Institute, University of Colorado, Boulder, Colorado, United States of America
| | - Robin D. Dowell
- BioFrontiers Institute and Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America
| | - Christopher D. Link
- Integrative Physiology, University of Colorado, Boulder, Colorado, United States of America
- Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado, United States of America
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18
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Bezler A, Braukmann F, West SM, Duplan A, Conconi R, Schütz F, Gönczy P, Piano F, Gunsalus K, Miska EA, Keller L. Tissue- and sex-specific small RNAomes reveal sex differences in response to the environment. PLoS Genet 2019; 15:e1007905. [PMID: 30735500 PMCID: PMC6383947 DOI: 10.1371/journal.pgen.1007905] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 02/21/2019] [Accepted: 12/17/2018] [Indexed: 11/19/2022] Open
Abstract
RNA interference (RNAi) related pathways are essential for germline development and fertility in metazoa and can contribute to inter- and trans-generational inheritance. In the nematode Caenorhabditis elegans, environmental double-stranded RNA provided by feeding can lead to heritable changes in phenotype and gene expression. Notably, transmission efficiency differs between the male and female germline, yet the underlying mechanisms remain elusive. Here we use high-throughput sequencing of dissected gonads to quantify sex-specific endogenous piRNAs, miRNAs and siRNAs in the C. elegans germline and the somatic gonad. We identify genes with exceptionally high levels of secondary 22G RNAs that are associated with low mRNA expression, a signature compatible with silencing. We further demonstrate that contrary to the hermaphrodite germline, the male germline, but not male soma, is resistant to environmental RNAi triggers provided by feeding, in line with previous work. This sex-difference in silencing efficacy is associated with lower levels of gonadal RNAi amplification products. Moreover, this tissue- and sex-specific RNAi resistance is regulated by the germline, since mutant males with a feminized germline are RNAi sensitive. This study provides important sex- and tissue-specific expression data of miRNA, piRNA and siRNA as well as mechanistic insights into sex-differences of gene regulation in response to environmental cues.
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Affiliation(s)
- Alexandra Bezler
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Fabian Braukmann
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, United Kingdom
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
- Wellcome Sanger Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom
| | - Sean M. West
- Center for Genomics & Systems Biology, New York University, New York, New York, United States of America
| | - Arthur Duplan
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Raffaella Conconi
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Frédéric Schütz
- Bioinformatics Core Facility; SIB Swiss Institute of Bioinformatics and Centre for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Pierre Gönczy
- Swiss Institute for Experimental Cancer Research (ISREC), Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland
| | - Fabio Piano
- Center for Genomics & Systems Biology, New York University, New York, New York, United States of America
- Center for Genomics & Systems Biology, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Kristin Gunsalus
- Center for Genomics & Systems Biology, New York University, New York, New York, United States of America
- Center for Genomics & Systems Biology, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Eric A. Miska
- Wellcome Trust/Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, United Kingdom
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
- Wellcome Sanger Institute, Wellcome Trust Genome Campus, Cambridge, United Kingdom
| | - Laurent Keller
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
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19
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Regulating gene expression in animals through RNA endonucleolytic cleavage. Heliyon 2018; 4:e00908. [PMID: 30426105 PMCID: PMC6223193 DOI: 10.1016/j.heliyon.2018.e00908] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 10/28/2018] [Accepted: 10/29/2018] [Indexed: 12/22/2022] Open
Abstract
The expression of any gene must be precisely controlled for appropriate function. This expression can be controlled at various levels. This includes epigenetic regulation through DNA methylation or histone modifications. At the posttranscriptional level, regulation can be via alternative splicing or controlling messenger RNA (mRNA) stability. RNA cleavage is one way to control mRNA stability. For example, microRNA (miRNA)-induced mRNA cleavage has long been recognised in plants. RNA cleavage also appears to be widespread in other kingdoms of life, and it is now clear that mRNA cleavage plays critical functions in animals. Although miRNA-induced mRNA cleavage can occur in animals, it is not a widespread mechanism. Instead, mRNA cleavage can be induced by a range of other mechanisms, including by endogenous short inhibitory RNAs (endo-siRNAs), as well as the Ribonuclease III (RNase III) enzymes Drosha and Dicer. In addition, RNA cleavage induced by endo-siRNAs and PIWI-interacting RNAs (piRNAs) is important for genome defence against transposons. Moreover, several RNase has been identified as important antiviral mediators. In this review, we will discuss these various RNA endonucleolytic cleavage mechanisms utilised by animals to regulate the expression of genes and as a defence against retrotransposons and viral infection.
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20
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Pinto S, Sato VN, De-Souza EA, Ferraz RC, Camara H, Pinca APF, Mazzotti DR, Lovci MT, Tonon G, Lopes-Ramos CM, Parmigiani RB, Wurtele M, Massirer KB, Mori MA. Enoxacin extends lifespan of C. elegans by inhibiting miR-34-5p and promoting mitohormesis. Redox Biol 2018; 18:84-92. [PMID: 29986212 PMCID: PMC6037660 DOI: 10.1016/j.redox.2018.06.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 06/17/2018] [Indexed: 11/29/2022] Open
Abstract
Alterations in microRNA (miRNA) processing have been previously linked to aging. Here we used the small molecule enoxacin to pharmacologically interfere with miRNA biogenesis and study how it affects aging in C. elegans. Enoxacin extended worm lifespan and promoted survival under normal and oxidative stress conditions. Enoxacin-induced longevity required the transcription factor SKN-1/Nrf2 and was blunted by the antioxidant N-acetyl-cysteine, suggesting a prooxidant-mediated mitohormetic response. The longevity effects of enoxacin were also dependent on the miRNA pathway, consistent with changes in miRNA expression elicited by the drug. Among these differentially expressed miRNAs, the widely conserved miR-34-5p was found to play an important role in enoxacin-mediated longevity. Enoxacin treatment down-regulated miR-34-5p and did not further extend lifespan of long-lived mir-34 mutants. Moreover, N-acetyl-cysteine abrogated mir-34(gk437)-induced longevity. Evidence also points to double-stranded RNA-specific adenosine deaminases (ADARs) as new targets of enoxacin since ADAR loss-of-function abrogates enoxacin-induced lifespan extension. Thus, enoxacin increases lifespan by reducing miR-34-5p levels, interfering with the redox balance and promoting healthspan.
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Affiliation(s)
- Silas Pinto
- Department of Biophysics, Program in Molecular Biology, São Paulo School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil; Laboratory of Aging Biology (LaBE), Department of Biochemistry and Tissue Biology, Program in Genetics and Molecular Biology, Institute of Biology, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Vitor N Sato
- Department of Biophysics, Program in Molecular Biology, São Paulo School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Evandro A De-Souza
- Department of Biophysics, Program in Molecular Biology, São Paulo School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil; Laboratory of Aging Biology (LaBE), Department of Biochemistry and Tissue Biology, Program in Genetics and Molecular Biology, Institute of Biology, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Rafael C Ferraz
- Department of Biophysics, Program in Molecular Biology, São Paulo School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Henrique Camara
- Department of Biophysics, Program in Molecular Biology, São Paulo School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil; Laboratory of Aging Biology (LaBE), Department of Biochemistry and Tissue Biology, Program in Genetics and Molecular Biology, Institute of Biology, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Ana Paula F Pinca
- Department of Biophysics, Program in Molecular Biology, São Paulo School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil; Laboratory of Aging Biology (LaBE), Department of Biochemistry and Tissue Biology, Program in Genetics and Molecular Biology, Institute of Biology, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Diego R Mazzotti
- Department of Psychobiology. São Paulo School of Medicine. Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Michael T Lovci
- Center for Molecular Biology and Genetic Engineering (CBMEG), University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Guilherme Tonon
- Laboratory of Aging Biology (LaBE), Department of Biochemistry and Tissue Biology, Program in Genetics and Molecular Biology, Institute of Biology, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | | | | | - Martin Wurtele
- Institute of Science and Technology, Federal University of Sao Paulo (UNIFESP), São Paulo, SP, Brazil
| | - Katlin B Massirer
- Center for Molecular Biology and Genetic Engineering (CBMEG), University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Marcelo A Mori
- Department of Biophysics, Program in Molecular Biology, São Paulo School of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, SP, Brazil; Laboratory of Aging Biology (LaBE), Department of Biochemistry and Tissue Biology, Program in Genetics and Molecular Biology, Institute of Biology, University of Campinas (UNICAMP), Campinas, SP, Brazil.
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21
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Transgene-Assisted Genetic Screen Identifies rsd-6 and Novel Genes as Key Components of Antiviral RNA Interference in Caenorhabditis elegans. J Virol 2018; 92:JVI.00416-18. [PMID: 29950414 PMCID: PMC6096818 DOI: 10.1128/jvi.00416-18] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 06/16/2018] [Indexed: 12/21/2022] Open
Abstract
RNA interference (RNAi) is a widespread antiviral mechanism triggered by virus-produced double-stranded RNAs (dsRNAs). In Caenorhabditis elegans, antiviral RNAi involves a RIG-I-like RNA helicase, termed DRH-1 (dicer related RNA helicase 1), that is not required for classical RNAi triggered by artificial dsRNA. Currently, whether antiviral RNAi in C. elegans involves novel factors that are dispensable for classical RNAi remains an open question. To address this question, we designed and carried out a genetic screen that aims to identify novel genes involved in worm antiviral RNAi. By introducing extra copies of known antiviral RNAi genes into the reporter worms, we managed to reject alleles derived from 4 known antiviral RNAi genes, including the DRH-1 coding gene, during the screen. Our genetic screen altogether identified 25 alleles, which were assigned to 11 candidate genes and 2 known antiviral RNAi genes through genetic complementation tests. Using a mapping-by-sequencing strategy, we identified one of the candidate genes as rsd-6, a gene that helps maintain genome integrity through an endogenous gene-silencing pathway but was not known to be required for antiviral RNAi. More importantly, we found that two of the candidate genes are required for antiviral RNAi targeting Orsay virus, a natural viral pathogen of C. elegans, but dispensable for classical RNAi. Since drh-1 is so far the only antiviral RNAi gene not required for classical RNAi, we believe that our genetic screen led to identification of novel worm genes that may target virus-specific features to function in RNAi.IMPORTANCE In nematode worms, drh-1 detects virus-produced double-stranded RNA (dsRNA), thereby specifically contributing to antiviral RNA silencing. To identify drh-1-like genes with dedicated function in antiviral RNAi, we recently carried out a genetic screen that was designed to automatically reject all alleles derived from 4 known antiviral silencing genes, including drh-1 Of the 11 candidate genes identified, we found two of them to be required for antiviral silencing targeting a natural viral pathogen of C. elegans but not for classical RNA silencing triggered by artificial dsRNA. We believe that these two genes are novel components of worm antiviral RNAi, considering the fact that drh-1 is the only known antiviral RNAi gene that is dispensable for classical RNAi. This genetic screen also identified rsd-6, a gene that maintains genome integrity under unfavorable conditions, as a key regulator of worm antiviral silencing, demonstrating an interplay between antiviral immunity and genome integrity maintenance.
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22
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Raman P, Zaghab SM, Traver EC, Jose AM. The double-stranded RNA binding protein RDE-4 can act cell autonomously during feeding RNAi in C. elegans. Nucleic Acids Res 2017; 45:8463-8473. [PMID: 28541563 PMCID: PMC5737277 DOI: 10.1093/nar/gkx484] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 05/17/2017] [Indexed: 02/07/2023] Open
Abstract
Long double-stranded RNA (dsRNA) can silence genes of matching sequence upon ingestion in many invertebrates and is therefore being developed as a pesticide. Such feeding RNA interference (RNAi) is best understood in the worm Caenorhabditis elegans, where the dsRNA-binding protein RDE-4 initiates silencing by recruiting an endonuclease to process long dsRNA into short dsRNA. These short dsRNAs are thought to move between cells because muscle-specific rescue of rde-4 using repetitive transgenes enables silencing in other tissues. Here, we extend this observation using additional promoters, report an inhibitory effect of repetitive transgenes, and discover conditions for cell-autonomous silencing in animals with tissue-specific rescue of rde-4. While expression of rde-4(+) in intestine, hypodermis, or neurons using a repetitive transgene can enable silencing also in unrescued tissues, silencing can be inhibited wihin tissues that express a repetitive transgene. Single-copy transgenes that express rde-4(+) in body-wall muscles or hypodermis, however, enable silencing selectively in the rescued tissue but not in other tissues. These results suggest that silencing by the movement of short dsRNA between cells is not an obligatory feature of feeding RNAi in C. elegans. We speculate that similar control of dsRNA movement could modulate tissue-specific silencing by feeding RNAi in other invertebrates.
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Affiliation(s)
- Pravrutha Raman
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Soriayah M Zaghab
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Edward C Traver
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Antony M Jose
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
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23
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Trettin KD, Sinha NK, Eckert DM, Apple SE, Bass BL. Loquacious-PD facilitates Drosophila Dicer-2 cleavage through interactions with the helicase domain and dsRNA. Proc Natl Acad Sci U S A 2017; 114:E7939-E7948. [PMID: 28874570 PMCID: PMC5617286 DOI: 10.1073/pnas.1707063114] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Loquacious-PD (Loqs-PD) is required for biogenesis of many endogenous siRNAs in Drosophila In vitro, Loqs-PD enhances the rate of dsRNA cleavage by Dicer-2 and also enables processing of substrates normally refractory to cleavage. Using purified components, and Loqs-PD truncations, we provide a mechanistic basis for Loqs-PD functions. Our studies indicate that the 22 amino acids at the C terminus of Loqs-PD, including an FDF-like motif, directly interact with the Hel2 subdomain of Dicer-2's helicase domain. This interaction is RNA-independent, but we find that modulation of Dicer-2 cleavage also requires dsRNA binding by Loqs-PD. Furthermore, while the first dsRNA-binding motif of Loqs-PD is dispensable for enhancing cleavage of optimal substrates, it is essential for enhancing cleavage of suboptimal substrates. Finally, our studies define a previously unrecognized Dicer interaction interface and suggest that Loqs-PD is well positioned to recruit substrates into the helicase domain of Dicer-2.
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Affiliation(s)
- Kyle D Trettin
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112
| | - Niladri K Sinha
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112
| | - Debra M Eckert
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112
| | - Sarah E Apple
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112
| | - Brenda L Bass
- Department of Biochemistry, University of Utah, Salt Lake City, UT 84112
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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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25
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Paces J, Nic M, Novotny T, Svoboda P. Literature review of baseline information to support the risk assessment of RNAi‐based GM plants. ACTA ACUST UNITED AC 2017. [PMCID: PMC7163844 DOI: 10.2903/sp.efsa.2017.en-1246] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Jan Paces
- Institute of Molecular Genetics of the Academy of Sciences of the Czech Republic (IMG)
| | | | | | - Petr Svoboda
- Institute of Molecular Genetics of the Academy of Sciences of the Czech Republic (IMG)
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26
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Braukmann F, Jordan D, Miska E. Artificial and natural RNA interactions between bacteria and C. elegans. RNA Biol 2017; 14:415-420. [PMID: 28332918 DOI: 10.1080/15476286.2017.1297912] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Nineteen years after Lisa Timmons and Andy Fire first described RNA transfer from bacteria to C. elegans in an experimental setting 48 the biologic role of this trans-kingdom RNA-based communication remains unknown. Here we summarize our current understanding on the mechanism and potential role of such social RNA.
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Affiliation(s)
- Fabian Braukmann
- a Gurdon Institute, University of Cambridge , Cambridge , UK.,b Department of Genetics , University of Cambridge , Cambridge , UK
| | - David Jordan
- a Gurdon Institute, University of Cambridge , Cambridge , UK.,b Department of Genetics , University of Cambridge , Cambridge , UK
| | - Eric Miska
- a Gurdon Institute, University of Cambridge , Cambridge , UK.,b Department of Genetics , University of Cambridge , Cambridge , UK.,c Wellcome Trust Sanger Institute , Wellcome Trust Genome Campus, Cambridge , UK
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27
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Fukudome A, Fukuhara T. Plant dicer-like proteins: double-stranded RNA-cleaving enzymes for small RNA biogenesis. JOURNAL OF PLANT RESEARCH 2017; 130:33-44. [PMID: 27885504 DOI: 10.1007/s10265-016-0877-1] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 10/08/2016] [Indexed: 05/20/2023]
Abstract
Dicer, a double-stranded RNA (dsRNA)-specific endoribonuclease, plays an essential role in triggering both transcriptional and post-transcriptional gene silencing in eukaryotes by cleaving dsRNAs or single-stranded RNAs bearing stem-loop structures such as microRNA precursor transcripts into 21- to 24-nt small RNAs. Unlike animals, plants have evolved to utilize at least four Dicer-like (DCL) proteins. Extensive genetic studies have revealed that each DCL protein participates in a specific gene silencing pathway, with some redundancy. However, a mechanistic understanding of how the specific action of each DCL protein is regulated in its respective pathway is still in its infancy due to the limited number of biochemical studies on plant DCL proteins. In this review, we summarize and discuss the biochemical properties of plant DCL proteins revealed by studies using highly purified recombinant proteins, crude extracts, and immunoprecipitates. With help from co-factor proteins and an ATPase/DExH-box RNA-helicase domain, the microRNA-producing enzyme DCL1 recognizes bulges and terminal loop structures in its substrate transcripts to ensure accurate and efficient processing. DCL4 prefers long dsRNA substrates and requires the dsRNA-binding protein DRB4 for its activity. The short-dsRNA preference of DCL3 is well suited for short-RNA transcription and subsequent dsRNA formation by coupling between a plant-specific DNA-dependent RNA-polymerase IV and RNA-dependent RNA-polymerase 2 in the transcriptional gene silencing pathway. Inorganic phosphate also seems to play a role in differential regulation of DCL3 and DCL4 activities. Further development of biochemical approaches will be necessary for better understanding of how plant DCL proteins are fine-tuned in each small RNA biogenesis pathway under various physiological conditions.
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Affiliation(s)
- Akihito Fukudome
- Molecular and Environmental Plant Sciences, Department of Horticultural Sciences, Vegetable and Fruit Improvement Center, Texas A&M University, College Station, TX, 77843, USA
| | - Toshiyuki Fukuhara
- Department of Applied Biological Sciences and Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, 3-5-8 Saiwaicho, Fuchu, Tokyo, 183-8509, Japan.
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Svobodova E, Kubikova J, Svoboda P. Production of small RNAs by mammalian Dicer. Pflugers Arch 2016; 468:1089-102. [PMID: 27048428 PMCID: PMC4893058 DOI: 10.1007/s00424-016-1817-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Revised: 03/20/2016] [Accepted: 03/24/2016] [Indexed: 01/16/2023]
Abstract
MicroRNA (miRNA) and RNA interference (RNAi) pathways employ RNase III Dicer for the biogenesis of small RNAs guiding post-transcriptional repression. Requirements for Dicer activity differ in the two pathways. The biogenesis of miRNAs requires a single Dicer cleavage of a short hairpin precursor to produce a small RNA with a precisely defined sequence, while small RNAs in RNAi come from a processive cleavage of a long double-stranded RNA (dsRNA) into a pool of small RNAs with different sequences. While Dicer is generally conserved among eukaryotes, its substrate recognition, cleavage, and biological roles differ. In Metazoa, a single Dicer can function as a universal factor for RNAi and miRNA pathways or as a factor adapted specifically for one of the pathways. In this review, we focus on the structure, function, and evolution of mammalian Dicer. We discuss key structural features of Dicer and other factors defining Dicer substrate repertoire and biological functions in mammals in comparison with invertebrate models. The key for adaptation of Dicer for miRNA or RNAi pathways is the N-terminal helicase, a dynamically evolving Dicer domain. Its functionality differs between mammals and invertebrates: the mammalian Dicer is well adapted to produce miRNAs while its ability to support RNAi is limited.
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Affiliation(s)
- Eliska Svobodova
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnska 1083, Prague 4, 142 20, Czech Republic
| | - Jana Kubikova
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnska 1083, Prague 4, 142 20, Czech Republic
| | - Petr Svoboda
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Videnska 1083, Prague 4, 142 20, Czech Republic.
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A Single RNaseIII Domain Protein from Entamoeba histolytica Has dsRNA Cleavage Activity and Can Help Mediate RNAi Gene Silencing in a Heterologous System. PLoS One 2015; 10:e0133740. [PMID: 26230096 PMCID: PMC4521922 DOI: 10.1371/journal.pone.0133740] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 06/30/2015] [Indexed: 11/25/2022] Open
Abstract
Dicer enzymes process double-stranded RNA (dsRNA) into small RNAs that target gene silencing through the RNA interference (RNAi) pathway. Dicer enzymes are complex, multi-domain RNaseIII proteins, however structural minimalism of this protein has recently emerged in parasitic and fungal systems. The most minimal Dicer, Saccharomyces castellii Dicer1, has a single RNaseIII domain and two double stranded RNA binding domains. In the protozoan parasite Entamoeba histolytica 27nt small RNAs are abundant and mediate silencing, yet no canonical Dicer enzyme has been identified. Although EhRNaseIII does not exhibit robust dsRNA cleavage in vitro, it can process dsRNA in the RNAi-negative background of Saccharomyces cerevisiae, and in conjunction with S. castellii Argonaute1 can partially reconstitute the RNAi pathway. Thus, although EhRNaseIII lacks the domain architecture of canonical or minimal Dicer enzymes, it has dsRNA processing activity that contributes to gene silencing via RNAi. Our data advance the understanding of small RNA biogenesis in Entamoeba as well as broaden the spectrum of non-canonical Dicer enzymes that contribute to the RNAi pathway.
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30
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Jose AM. Movement of regulatory RNA between animal cells. Genesis 2015; 53:395-416. [PMID: 26138457 PMCID: PMC4915348 DOI: 10.1002/dvg.22871] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Revised: 06/28/2015] [Accepted: 06/29/2015] [Indexed: 12/12/2022]
Abstract
Recent studies suggest that RNA can move from one cell to another and regulate genes through specific base-pairing. Mechanisms that modify or select RNA for secretion from a cell are unclear. Secreted RNA can be stable enough to be detected in the extracellular environment and can enter the cytosol of distant cells to regulate genes. Mechanisms that import RNA into the cytosol of an animal cell can enable uptake of RNA from many sources including other organisms. This role of RNA is akin to that of steroid hormones, which cross cell membranes to regulate genes. The potential diagnostic use of RNA in human extracellular fluids has ignited interest in understanding mechanisms that enable the movement of RNA between animal cells. Genetic model systems will be essential to gain more confidence in proposed mechanisms of RNA transport and to connect an extracellular RNA with a specific biological function. Studies in the worm C. elegans and in other animals have begun to reveal parts of this novel mechanism of cell-to-cell communication. Here, I summarize the current state of this nascent field, highlight the many unknowns, and suggest future directions.
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Affiliation(s)
- Antony M Jose
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland
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31
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Heyam A, Lagos D, Plevin M. Dissecting the roles of TRBP and PACT in double-stranded RNA recognition and processing of noncoding RNAs. WILEY INTERDISCIPLINARY REVIEWS. RNA 2015; 6:271-89. [PMID: 25630541 PMCID: PMC7169789 DOI: 10.1002/wrna.1272] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 10/08/2014] [Accepted: 10/09/2014] [Indexed: 12/27/2022]
Abstract
HIV TAR RNA-binding protein (TRBP) and Protein Activator of PKR (PACT) are double-stranded (ds) RNA-binding proteins that participate in both small regulatory RNA biogenesis and the response to viral dsRNA. Despite considerable progress toward understanding the structure-function relationship of TRBP and PACT, their specific roles in these seemingly distinct cellular pathways remain unclear. Both proteins are composed of three copies of the double-stranded RNA-binding domain, two of which interact with dsRNA, while the C-terminal copy mediates protein-protein interactions. PACT and TRBP are found in a complex with the endonuclease Dicer and facilitate processing of immature microRNAs. Their precise contribution to the Dicing step has not yet been defined: possibilities include precursor recruitment, rearrangement of dsRNA within the complex, loading the processed microRNA into the RNA-induced silencing complex, and distinguishing different classes of small dsRNA. TRBP and PACT also interact with the viral dsRNA sensors retinoic acid-inducible gene I (RIG-I) and double-stranded RNA-activated protein kinase (PKR). Current models suggest that PACT enables RIG-I to detect a wider range of viral dsRNAs, while TRBP and PACT exert opposing regulatory effects on PKR. Here, the evidence that implicates TRBP and PACT in regulatory RNA processing and viral dsRNA sensing is reviewed and discussed in the context of their molecular structure. The broader implications of a link between microRNA biogenesis and the innate antiviral response pathway are also considered.
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MESH Headings
- Amino Acid Sequence
- Carboxypeptidases/chemistry
- Carboxypeptidases/metabolism
- Carboxypeptidases/physiology
- Models, Genetic
- Models, Molecular
- Molecular Sequence Data
- Protein Structure, Tertiary
- RNA, Double-Stranded/chemistry
- RNA, Double-Stranded/immunology
- RNA, Double-Stranded/metabolism
- RNA, Untranslated/metabolism
- RNA, Viral/chemistry
- RNA, Viral/immunology
- RNA, Viral/metabolism
- RNA-Binding Proteins/chemistry
- RNA-Binding Proteins/metabolism
- RNA-Binding Proteins/physiology
- Ribonuclease III/chemistry
- Ribonuclease III/metabolism
- Ribonuclease III/physiology
- Structure-Activity Relationship
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Affiliation(s)
- Alex Heyam
- Department of Biology, University of York, York, UK
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Whipple JM, Youssef OA, Aruscavage PJ, Nix DA, Hong C, Johnson WE, Bass BL. Genome-wide profiling of the C. elegans dsRNAome. RNA (NEW YORK, N.Y.) 2015; 21:786-800. [PMID: 25805852 PMCID: PMC4408787 DOI: 10.1261/rna.048801.114] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Accepted: 12/23/2014] [Indexed: 06/01/2023]
Abstract
Recent studies hint that endogenous dsRNA plays an unexpected role in cellular signaling. However, a complete understanding of endogenous dsRNA signaling is hindered by an incomplete annotation of dsRNA-producing genes. To identify dsRNAs expressed in Caenorhabditis elegans, we developed a bioinformatics pipeline that identifies dsRNA by detecting clustered RNA editing sites, which are strictly limited to long dsRNA substrates of Adenosine Deaminases that act on RNA (ADAR). We compared two alignment algorithms for mapping both unique and repetitive reads and detected as many as 664 editing-enriched regions (EERs) indicative of dsRNA loci. EERs are visually enriched on the distal arms of autosomes and are predicted to possess strong internal secondary structures as well as sequence complementarity with other EERs, indicative of both intramolecular and intermolecular duplexes. Most EERs were associated with protein-coding genes, with ∼1.7% of all C. elegans mRNAs containing an EER, located primarily in very long introns and in annotated, as well as unannotated, 3' UTRs. In addition to numerous EERs associated with coding genes, we identified a population of prospective noncoding EERs that were distant from protein-coding genes and that had little or no coding potential. Finally, subsets of EERs are differentially expressed during development as well as during starvation and infection with bacterial or fungal pathogens. By combining RNA-seq with freely available bioinformatics tools, our workflow provides an easily accessible approach for the identification of dsRNAs, and more importantly, a catalog of the C. elegans dsRNAome.
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Affiliation(s)
- Joseph M Whipple
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112-5650, USA
| | - Osama A Youssef
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112-5650, USA
| | - P Joseph Aruscavage
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112-5650, USA
| | - David A Nix
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah School of Medicine, Salt Lake City, Utah 84112-5775, USA
| | - Changjin Hong
- Division of Computational Biomedicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA
| | - W Evan Johnson
- Division of Computational Biomedicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA
| | - Brenda L Bass
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112-5650, USA
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33
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E. coli OxyS non-coding RNA does not trigger RNAi in C. elegans. Sci Rep 2015; 5:9597. [PMID: 25873159 PMCID: PMC4397834 DOI: 10.1038/srep09597] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 03/09/2015] [Indexed: 02/01/2023] Open
Abstract
The discovery of RNA interference (RNAi) in C. elegans has had a major impact on scientific research, led to the rapid development of RNAi tools and has inspired RNA-based therapeutics. Astonishingly, nematodes, planaria and many insects take up double-stranded RNA (dsRNA) from their environment to elicit RNAi; the biological function of this mechanism is unclear. Recently, the E. coli OxyS non-coding RNA was shown to regulate gene expression in C. elegans when E. coli is offered as food. This was surprising given that C. elegans is unlikely to encounter E. coli in nature. To directly test the hypothesis that the E. coli OxyS non-coding RNA triggers the C. elegans RNAi pathway, we sequenced small RNAs from C. elegans after feeding with bacteria. We clearly demonstrate that the OxyS non-coding RNA does not trigger an RNAi response in C. elegans. We conclude that the biology of environmental RNAi remains to be discovered.
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Soares ZG, Gonçalves ANA, de Oliveira KPV, Marques JT. Viral RNA recognition by the Drosophila small interfering RNA pathway. Microbes Infect 2014; 16:1013-21. [DOI: 10.1016/j.micinf.2014.09.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Revised: 08/31/2014] [Accepted: 09/01/2014] [Indexed: 12/24/2022]
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35
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Structure of RDE-4 dsRBDs and mutational studies provide insights into dsRNA recognition in the Caenorhabditis elegans RNAi pathway. Biochem J 2014; 458:119-30. [PMID: 24256178 DOI: 10.1042/bj20131347] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The association of RDE-4 (RNAi defective 4), a protein containing two dsRBDs (dsRNA-binding domains), with long dsRNA and Dcr-1 (Dicer1 homologue) initiates the siRNA pathway in Caenorhabditis elegans. Unlike its homologues in higher eukaryotes, RDE-4 dsRBDs possess weak (micromolar) affinity for short dsRNA. With increasing length of dsRNA, RDE-4 exhibits enhanced affinity due to co-operativity. The linker and dsRBD2 are indispensable for RDE-4's simultaneous interaction with dsRNA and Dcr-1. In the present study, we have determined the solution structures of RDE-4 constructs that contain both dsRBDs and the linker region. In addition to the canonical dsRBD fold, both dsRBDs of RDE-4 show modified structural features such as truncation in the β1-β2 loop that rationalize RDE-4's relatively weak dsRNA affinity. Structure and binding studies demonstrate that dsRBD2 plays a decisive role in the RDE-4-dsRNA interaction; however, in contrast with previous findings, we found ephemeral interaction of RDE-4 dsRBD1 with dsRNA. More importantly, mutations in two tandem lysine residues (Lys217 and Lys218) in dsRBD2 impair RDE-4's dsRNA-binding ability and could obliterate RNAi initiation in C. elegans. Additionally, we postulate a structural basis for the minimal requirement of linker and dsRBD2 for RDE-4's association with dsRNA and Dcr-1.
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36
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de Faria IJDS, Olmo RP, Silva EG, Marques JT. dsRNA sensing during viral infection: lessons from plants, worms, insects, and mammals. J Interferon Cytokine Res 2013; 33:239-53. [PMID: 23656598 DOI: 10.1089/jir.2013.0026] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Host defense systems often rely on direct and indirect pattern recognition to sense the presence of invading pathogens. Patterns can be molecules directly produced by the pathogen or indirectly generated by changes in host parameters as a consequence of infection. Viruses are intracellular pathogens that hijack the cellular machinery to synthesize their own molecules making direct recognition of viral molecules a great challenge. Antiviral systems in prokaryotes and eukaryotes commonly exploit aberrant nucleic acid sensing to recognize virus infection as host and viral nucleic acid metabolism can greatly differ. Indeed, the generation of dsRNA is often associated with viral infection. In this review, we discuss current knowledge on the mechanisms of viral dsRNA sensing utilized by 2 important antiviral defense systems, RNA interference (RNAi) and the vertebrate immune system. The major viral sensors of the vertebrate immune systems are RIG-like receptors, while RNAi pathways depend on Dicer proteins. These 2 families of sensors share a similar helicase domain with high specificity for dsRNA, which is necessary, but not sufficient for efficient recognition by these receptors. Additional intrinsic features to the dsRNA molecule are also necessary for activation of antiviral systems. Studies utilizing synthetic ligands, in vitro biochemistry and reporter systems have greatly helped increase our knowledge on intrinsic features of dsRNA recognition. However, characteristics such as subcellular localization are extrinsic to the dsRNA itself, but certainly influence the recognition in vivo. Thus, mechanisms of viral dsRNA recognition must address how cellular sensors are recruited to nucleic acids or vice versa. Accessory proteins are likely important for in vivo recognition of extrinsic features of viral RNA, but have mostly remained undiscovered due to the limitations of previous strategies. Hence, the identification of novel components of antiviral systems must take into account the complexities involved in viral recognition in vivo.
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Roth BM, Ishimaru D, Hennig M. The core microprocessor component DiGeorge syndrome critical region 8 (DGCR8) is a nonspecific RNA-binding protein. J Biol Chem 2013; 288:26785-99. [PMID: 23893406 DOI: 10.1074/jbc.m112.446880] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MicroRNA (miRNA) biogenesis follows a conserved succession of processing steps, beginning with the recognition and liberation of an miRNA-containing precursor miRNA hairpin from a large primary miRNA transcript (pri-miRNA) by the Microprocessor, which consists of the nuclear RNase III Drosha and the double-stranded RNA-binding domain protein DGCR8 (DiGeorge syndrome critical region protein 8). Current models suggest that specific recognition is driven by DGCR8 detection of single-stranded elements of the pri-miRNA stem-loop followed by Drosha recruitment and pri-miRNA cleavage. Because countless RNA transcripts feature single-stranded-dsRNA junctions and DGCR8 can bind hundreds of mRNAs, we explored correlations between RNA binding properties of DGCR8 and specific pri-miRNA substrate processing. We found that DGCR8 bound single-stranded, double-stranded, and random hairpin transcripts with similar affinity. Further investigation of DGCR8/pri-mir-16 interactions by NMR detected intermediate exchange regimes over a wide range of stoichiometric ratios. Diffusion analysis of DGCR8/pri-mir-16 interactions by pulsed field gradient NMR lent further support to dynamic complex formation involving free components in exchange with complexes of varying stoichiometry, although in vitro processing assays showed exclusive cleavage of pri-mir-16 variants bearing single-stranded flanking regions. Our results indicate that DGCR8 binds RNA nonspecifically. Therefore, a sequential model of DGCR8 recognition followed by Drosha recruitment is unlikely. Known RNA substrate requirements are broad and include 70-nucleotide hairpins with unpaired flanking regions. Thus, specific RNA processing is likely facilitated by preformed DGCR8-Drosha heterodimers that can discriminate between authentic substrates and other hairpins.
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Affiliation(s)
- Braden M Roth
- From the Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425
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38
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RNAi pathways in the recognition of foreign RNA: antiviral responses and host–parasite interactions in nematodes. Biochem Soc Trans 2013; 41:876-80. [DOI: 10.1042/bst20130021] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The nematode Caenorhabditis elegans was the first animal for which RNAi (RNA interference) in response to exogenous triggers was shown experimentally and subsequently the molecular components of the RNAi pathway have been characterized in some detail. However, the function of RNAi in the life cycle of nematodes in the wild is still unclear. In the present article, we argue that RNAi could be used in nematodes as a mechanism to sense and respond to foreign RNA that the animal might be exposed to either through viral infection or through ingestion of food sources. This could be of potential importance to the life cycle of parasitic nematodes as they ingest RNA from different hosts at different points during their life cycle. We postulate that RNA ingested from the host could be used by the parasite to regulate its own genes, through the amplification mechanism intrinsic to the nematode RNAi pathway.
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39
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Lee HY, Zhou K, Smith AM, Noland CL, Doudna JA. Differential roles of human Dicer-binding proteins TRBP and PACT in small RNA processing. Nucleic Acids Res 2013; 41:6568-76. [PMID: 23661684 PMCID: PMC3711433 DOI: 10.1093/nar/gkt361] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
During RNA interference and related gene regulatory pathways, the endonuclease Dicer cleaves precursor RNA molecules to produce microRNAs (miRNAs) and short interfering RNAs (siRNAs). Human cells encode a single Dicer enzyme that can associate with two different double-stranded RNA (dsRNA)-binding proteins, protein activator of PKR (PACT) and trans-activation response RNA-binding protein (TRBP). However, the functional redundancy or differentiation of PACT and TRBP in miRNA and siRNA biogenesis is not well understood. Using a reconstituted system, we show here that PACT and TRBP have distinct effects on Dicer-mediated dsRNA processing. In particular, we found that PACT in complex with Dicer inhibits the processing of pre-siRNA substrates when compared with Dicer and a Dicer–TRBP complex. In addition, PACT and TRBP show non-redundant effects on the production of different-sized miRNAs (isomiRs), which in turn alter target-binding specificities. Experiments using chimeric versions of PACT and TRBP suggest that the two N-terminal RNA-binding domains of each protein confer the observed differences in dsRNA substrate recognition and processing behavior of Dicer–dsRNA-binding protein complexes. These results support the conclusion that in humans, Dicer-associated dsRNA-binding proteins are important regulatory factors that contribute both substrate and cleavage specificity during miRNA and siRNA production.
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Affiliation(s)
- Ho Young Lee
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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40
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Rogers K, Chen X. microRNA biogenesis and turnover in plants. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2013; 77:183-94. [PMID: 23439913 DOI: 10.1101/sqb.2013.77.014530] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
microRNAs (miRNAs) are short RNAs that regulate gene expression in eukaryotes. The biogenesis and turnover of miRNAs determine their spatiotemporal accumulation within tissues. miRNA biogenesis is a multistep process that entails transcription, processing, nuclear export, and formation of the miRNA-ARGONAUTE complex. Factors that perform each of these steps have been identified. Generation of mature miRNAs from primary transcripts, i.e., miRNA processing, is a key step in miRNA biogenesis. Our understanding of miRNA processing has expanded beyond the enzyme that performs the reactions, as more and more additional factors that impact the efficiency and accuracy of miRNA processing are uncovered. In contrast to miRNA biogenesis, miRNA turnover is an important but poorly understood process that contributes to the steady-state levels of miRNAs. Enzymes responsible for miRNA degradation have only recently been identified. This review describes the processes of miRNA maturation and degradation in plants.
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Affiliation(s)
- K Rogers
- Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, California 92521, USA
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41
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Ageing and the small, non-coding RNA world. Ageing Res Rev 2013; 12:429-35. [PMID: 22504407 DOI: 10.1016/j.arr.2012.03.012] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 03/12/2012] [Accepted: 03/29/2012] [Indexed: 01/09/2023]
Abstract
MicroRNAs, a class of small, non-coding RNAs, are now widely known for their importance in many aspects of biology. These small regulatory RNAs have critical functions in diverse biological events, including development and disease. Recent findings show that microRNAs are essential for lifespan determination in the model organisms, Caenorhabditis elegans and Drosophila, suggesting that microRNAs are also involved in the complex process of ageing. Further, short RNA fragments derived from longer parental RNAs, such as transfer RNA cleavage fragments, have now emerged as a novel class of regulatory RNAs that inhibit translation in response to stress. In addition, the RNA editing pathway is likely to act in the double-stranded RNA-mediated silencing machinery to suppress unfavorable RNA interference activity in the ageing process. These multiple, redundant layers in gene regulatory networks may make it possible to both stably and flexibly regulate genetic pathways in ensuring robustness of developmental and ageing processes.
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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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43
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Chiliveri SC, Kumar S, Marelli UK, Deshmukh MV. Backbone and sidechain methyl Ile (δ1), Leu and Val chemical shift assignments of RDE-4 (1-243), an RNA interference initiation protein in C. elegans. BIOMOLECULAR NMR ASSIGNMENTS 2012; 6:143-146. [PMID: 22002349 DOI: 10.1007/s12104-011-9343-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 09/27/2011] [Indexed: 05/31/2023]
Abstract
The RNAi pathway of several organisms requires presence of double stranded RNA binding proteins for functioning of Dicer in gene regulation. In C. elegans, a double stranded RNA binding protein, RDE-4 (385 aa, 44 kDa) recognizes long exogenous dsRNA and initiates the RNAi pathway. We have achieved complete backbone and stereospecific methyl sidechain Ile (δ1), Leu and Val chemical shifts of first 243 amino acids of RDE-4, namely RDE-4ΔC.
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Affiliation(s)
- Sai Chaitanya Chiliveri
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500007, India
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44
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Silencing of host genes directed by virus-derived short interfering RNAs in Caenorhabditis elegans. J Virol 2012; 86:11645-53. [PMID: 22896621 DOI: 10.1128/jvi.01501-12] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Small interfering RNAs (siRNAs) processed from viral replication intermediates by RNase III-like enzyme Dicer guide sequence-specific antiviral silencing in fungi, plants, and invertebrates. In plants, virus-derived siRNAs (viRNAs) can target and silence cellular transcripts and, in some cases, are responsible for the induction of plant diseases. Currently it remains unclear whether viRNAs are also capable of modulating the expression of cellular genes in the animal kingdom, although animal virus-encoded microRNAs (miRNAs) are known to guide efficient silencing of host genes, thereby facilitating virus replication. In this report, we showed that viRNAs derived from a modified nodavirus triggered potent silencing of homologous cellular transcripts produced by the endogenous gene or transgene in the nematode worm Caenorhabditis elegans. Like that found in plants, virus-induced gene silencing (VIGS) in C. elegans also involves RRF-1, a worm RNA-dependent RNA polymerase (RdRP) that is known to produce single-stranded secondary siRNAs in a Dicer-independent manner. We further demonstrated that VIGS in C. elegans is inheritable, suggesting that VIGS has the potential to generate profound epigenetic consequences in future generations. Altogether, these findings, for the first time, confirmed that viRNAs have the potential to modulate host gene expression in the animal kingdom. Most importantly, the success in uncoupling the trigger and the target of the antiviral silencing would allow for the exploration of novel features of virus-host interactions mediated by viRNAs in the animal kingdom.
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Guo S, Xu D, Xu HX, Wang T, Li JL, Lu LQ. Suppression of RNA interference pathway in vitro by Grass carp reovirus. Virol Sin 2012; 27:109-19. [PMID: 22492002 DOI: 10.1007/s12250-012-3230-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 02/13/2012] [Indexed: 12/25/2022] Open
Abstract
The means of survival of genomic dsRNA of reoviruses from dsRNA-triggered and Dicer-initiated RNAi pathway remains to be defined. The present study aimed to investigate the effect of Grass carp reovirus (GCRV) replication on the RNAi pathway of grass carp kidney cells (CIK). The dsRNA-triggered RNAi pathway was demonstrated unimpaired in CIK cells through RNAi assay. GCRV-specific siRNA was generated in CIK cells transfected with purified GCRV genomic dsRNA in Northern blot analysis; while in GCRV-infected CIK cells, no GCRV-specific siRNA could be detected. Infection and transfection experiments further indicated that replication of GCRV correlated with the increased transcription level of the Dicer gene and functional inhibition of in vitro synthesized egfp-siRNA in silencing the EGFP reporter gene. These data demonstrated that although only the genomic dsRNA of GCRV was sensitive to the cellular RNAi pathway, unidentified RNAi suppressor protein(s) might contribute to the survival of the viral genome and efficient viral replication.
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Affiliation(s)
- Shuai Guo
- Key Laboratory of Aquatic Genetic Resources and Utilization /Ministry of Agriculture, Shanghai Ocean University, Shanghai 201306, China
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Wang S, Chen AJ, Shi LJ, Zhao XF, Wang JX. TRBP and eIF6 homologue in Marsupenaeus japonicus play crucial roles in antiviral response. PLoS One 2012; 7:e30057. [PMID: 22279564 PMCID: PMC3261181 DOI: 10.1371/journal.pone.0030057] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Accepted: 12/09/2011] [Indexed: 11/30/2022] Open
Abstract
Plants and invertebrates can suppress viral infection through RNA silencing, mediated by RNA-induced silencing complex (RISC). Trans-activation response RNA-binding protein (TRBP), consisting of three double-stranded RNA-binding domains, is a component of the RISC. In our previous paper, a TRBP homologue in Fenneropenaeus chinensis (Fc-TRBP) was reported to directly bind to eukaryotic initiation factor 6 (Fc-eIF6). In this study, we further characterized the function of TRBP and the involvement of TRBP and eIF6 in antiviral RNA interference (RNAi) pathway of shrimp. The double-stranded RNA binding domains (dsRBDs) B and C of the TRBP from Marsupenaeus japonicus (Mj-TRBP) were found to mediate the interaction of TRBP and eIF6. Gel-shift assays revealed that the N-terminal of Mj-TRBP dsRBD strongly binds to double-stranded RNA (dsRNA) and that the homodimer of the TRBP mediated by the C-terminal dsRBD increases the affinity to dsRNA. RNAi against either Mj-TRBP or Mj-eIF6 impairs the dsRNA-induced sequence-specific RNAi pathway and facilitates the proliferation of white spot syndrome virus (WSSV). These results further proved the important roles of TRBP and eIF6 in the antiviral response of shrimp.
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Affiliation(s)
- Shuai Wang
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation of Ministry of Education, School of Life Sciences, Shandong University, Jinan, Shandong, People's Republic of China
- Wuhan Institute of Virology, Chinese Academy of Science, Wuchang, Hubei, People's Republic of China
| | - An-Jing Chen
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation of Ministry of Education, School of Life Sciences, Shandong University, Jinan, Shandong, People's Republic of China
| | - Li-Jie Shi
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation of Ministry of Education, School of Life Sciences, Shandong University, Jinan, Shandong, People's Republic of China
| | - Xiao-Fan Zhao
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation of Ministry of Education, School of Life Sciences, Shandong University, Jinan, Shandong, People's Republic of China
| | - Jin-Xing Wang
- The Key Laboratory of Plant Cell Engineering and Germplasm Innovation of Ministry of Education, School of Life Sciences, Shandong University, Jinan, Shandong, People's Republic of China
- * E-mail:
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Dicer Proteins and Their Role in Gene Silencing Pathways. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/b978-0-12-404741-9.00001-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/15/2023]
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Jose AM, Garcia GA, Hunter CP. Two classes of silencing RNAs move between Caenorhabditis elegans tissues. Nat Struct Mol Biol 2011; 18:1184-8. [PMID: 21984186 PMCID: PMC3210371 DOI: 10.1038/nsmb.2134] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Accepted: 08/09/2011] [Indexed: 12/27/2022]
Abstract
Organism-wide RNA interference (RNAi) is due to the transport of mobile silencing RNA throughout the organism but the identities of these mobile RNA species in animals are unknown. Here we present genetic evidence that both the initial double-stranded RNA (dsRNA), which triggers RNAi, and at least one dsRNA intermediate produced during RNAi can act as or generate mobile silencing RNA in Caenorhabditis elegans. This dsRNA intermediate requires the long dsRNA-binding protein RDE-4, the endonuclease DCR-1, which cleaves long dsRNA into double-stranded short-interfering RNA (ds-siRNA), and the putative nucleotidyltransferase MUT-2 (RDE-3). However, single-stranded siRNA and downstream secondary siRNA produced upon amplification by the RNA-dependent RNA Polymerase RRF-1 do not generate mobile silencing RNA. Restricting inter-tissue transport to long dsRNA and directly processed siRNA intermediates rather than amplified siRNA may serve to modulate the extent of systemic silencing in proportion to available dsRNA.
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Affiliation(s)
- Antony M Jose
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA
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Wu D, Lamm AT, Fire AZ. Competition between ADAR and RNAi pathways for an extensive class of RNA targets. Nat Struct Mol Biol 2011; 18:1094-101. [PMID: 21909095 PMCID: PMC3190075 DOI: 10.1038/nsmb.2129] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Accepted: 07/28/2011] [Indexed: 12/22/2022]
Abstract
Adenosine deaminases that act on RNAs (ADARs) interact with double-stranded RNAs, deaminating adenosines to inosines. Previous studies of Caenorhabditis elegans suggested an antagonistic interaction between ADAR and RNAi machineries, with ADAR defects suppressed upon additional knockout of RNAi. These results suggest a pool of common RNA substrates capable of engaging both pathways. To define and characterize such substrates, we examined small RNA and mRNA populations of ADAR mutants and identified a distinct set of loci from which RNAi-dependent short RNAs are dramatically upregulated. At these same loci, we observe populations of multiply edited transcripts, supporting a specific role for ADARs in preventing access to the RNAi pathway for an extensive population of dsRNAs. Characterization of these loci reveal an extensive overlap with non-coding and intergenic regions, suggesting that the landscape of ADAR targets may extend beyond previously annotated classes of transcripts.
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Affiliation(s)
- Diane Wu
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
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The role of the precursor structure in the biogenesis of microRNA. Cell Mol Life Sci 2011; 68:2859-71. [PMID: 21607569 PMCID: PMC3155042 DOI: 10.1007/s00018-011-0726-2] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 04/20/2011] [Accepted: 05/03/2011] [Indexed: 12/18/2022]
Abstract
The human genome contains more than 1,000 microRNA (miRNA) genes, which are transcribed mainly by RNA polymerase II. The canonical pathway of miRNA biogenesis includes the nuclear processing of primary transcripts (pri-miRNAs) by the ribonuclease Drosha and further cytoplasmic processing of pre-miRNAs by the ribonuclease Dicer. This review discusses the issue of miRNA end heterogeneity generated primarily by Drosha and Dicer cleavage and focuses on the structural aspects of the Dicer step of miRNA biogenesis. We examine the structures of miRNA precursors, both predicted and experimentally determined, as well as the influence of various motifs that disturb the regularity of pre-miRNA structure on Dicer cleavage specificity. We evaluate the structural determinants of the length diversity of miRNA generated by Dicer from different precursors and highlight the importance of asymmetrical motifs. Finally, we discuss the impact of Dicer protein partners on cleavage efficiency and specificity and propose the contribution of pre-miRNA structural plasticity to the dynamics of the dicing complex.
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