scholarly journals Dissection of Double-Stranded RNA Binding Protein B2 from Betanodavirus

2007 ◽  
Vol 81 (11) ◽  
pp. 5449-5459 ◽  
Author(s):  
Beau J. Fenner ◽  
Winnie Goh ◽  
Jimmy Kwang
Keyword(s):  
Rna Silencing ◽  
Rna Binding ◽  
Amino Acid Residues ◽  
Alanine Scanning Mutagenesis ◽  
Marine Aquaculture ◽  
Double Stranded Rna ◽  
Dsrna Binding ◽  
Fish Cells ◽  
Interfering Rna

ABSTRACT Betanodaviruses are small RNA viruses that infect teleost fish and pose a considerable threat to marine aquaculture production. These viruses possess a small protein, termed B2, which binds to and protects double-stranded RNA. This prevents cleavage of virus-derived double-stranded RNAs (dsRNAs) by Dicer and subsequent production of small interfering RNA (siRNA), which would otherwise induce an RNA-silencing response against the virus. In this work, we have performed charged-to-alanine scanning mutagenesis of the B2 protein in order to identify residues required for dsRNA binding and protection. While the majority of the 19 mutated B2 residues were required for maximal dsRNA binding and protection in vitro, residues R53 and R60 were essential for both activities. Subsequent experiments in fish cells confirmed these findings by showing that mutations in these residues abolished accumulation of both the RNA1 and RNA2 components of the viral genome, in addition to preventing any significant induction of the host interferon gene, Mx. Moreover, an obvious positive correlation was found between dsRNA binding and protection in vitro and RNA1, RNA2, and Mx accumulation in fish cells, further validating the importance of the selected amino acid residues. The same trend was also demonstrated using an RNA silencing system in HeLa cells, with residues R53 and R60 being essential for suppression of RNA silencing. Importantly, we found that siRNA-mediated knockdown of Dicer dramatically enhanced the accumulation of a B2 mutant. In addition, we found that B2 is able to induce apoptosis in fish cells but that this was not the result of dsRNA binding.

scholarly journals Structure, dynamics and roX2-lncRNA binding of tandem double-stranded RNA binding domains dsRBD1,2 of Drosophila helicase Maleless

2018 ◽  
Author(s):  
Pravin Kumar Ankush Jagtap ◽  
Marisa Müller ◽  
Pawel Masiewicz ◽  
Sören von Bülow ◽  
Nele Merret Hollmann ◽  
...  
Keyword(s):  
Rna Binding ◽  
Binding Motifs ◽  
Double Stranded Rna ◽  
Binding Domains ◽  
Dsrna Binding ◽  
Rna Binding Domains ◽  
Human Orthologue ◽  
Rox Rna

ABSTRACTMaleless (MLE) is an evolutionary conserved member of the DExH family of helicases in Drosophila. Besides its function in RNA editing and presumably siRNA processing, MLE is best known for its role in remodelling non-coding roX RNA in the context of X chromosome dosage compensation in male flies. MLE and its human orthologue, DHX9 contain two tandem double-stranded RNA binding domains (dsRBDs) located at the N-terminal region. The two dsRBDs are essential for localization of MLE at the X-territory and it is presumed that this involves binding roX secondary structures. However, for dsRBD1 roX RNA binding has so far not been described. Here, we determined the solution NMR structure of dsRBD1 and dsRBD2 of MLE in tandem and investigated its role in double-stranded RNA (dsRNA) binding. Our NMR data show that both dsRBDs act as independent structural modules in solution and are canonical, non-sequence-specific dsRBDs featuring non-canonical KKxAK RNA binding motifs. NMR titrations combined with filter binding experiments document the contribution of dsRBD1 to dsRNA binding in vitro. Curiously, dsRBD1 mutants in which dsRNA binding in vitro is strongly compromised do not affect roX2 RNA binding and MLE localization in cells. These data suggest alternative functions for dsRBD1 in vivo.

scholarly journals Trafficking of siRNA precursors by the dsRBD protein Blanks in Drosophila

2020 ◽  
Vol 48 (7) ◽  
pp. 3906-3921 ◽  
Author(s):  
Volker Nitschko ◽  
Stefan Kunzelmann ◽  
Thomas Fröhlich ◽  
Georg J Arnold ◽  
Klaus Förstemann
Keyword(s):  
Small Rnas ◽  
Rna Binding ◽  
Small Interfering Rnas ◽  
Double Stranded Rna ◽  
Binding Domains ◽  
Convergent Transcription ◽  
Dsrna Binding ◽  
Functional Screens

Abstract RNA interference targets aberrant transcripts with cognate small interfering RNAs, which derive from double-stranded RNA precursors. Several functional screens have identified Drosophila blanks/lump (CG10630) as a facilitator of RNAi, yet its molecular function has remained unknown. The protein carries two dsRNA binding domains (dsRBD) and blanks mutant males have a spermatogenesis defect. We demonstrate that blanks selectively boosts RNAi triggered by dsRNA of nuclear origin. Blanks binds dsRNA via its second dsRBD in vitro, shuttles between nucleus and cytoplasm and the abundance of siRNAs arising at many sites of convergent transcription is reduced in blanks mutants. Since features of nascent RNAs - such as introns and transcription beyond the polyA site – contribute to the small RNA pool, we propose that Blanks binds dsRNA formed by cognate nascent RNAs in the nucleus and fosters its export to the cytoplasm for dicing. We refer to the resulting small RNAs as blanks exported siRNAs (bepsiRNAs). While bepsiRNAs were fully dependent on RNA binding to the second dsRBD of blanks in transgenic flies, male fertility was not. This is consistent with a previous report that linked fertility to the first dsRBD of Blanks. The role of blanks in spermatogenesis appears thus unrelated to its role in dsRNA export.

scholarly journals Sequestration and Protection of Double-Stranded RNA by the Betanodavirus B2 Protein

2006 ◽  
Vol 80 (14) ◽  
pp. 6822-6833 ◽  
Author(s):  
Beau J. Fenner ◽  
Winnie Goh ◽  
Jimmy Kwang
Keyword(s):  
Rna Interference ◽  
Rna Virus ◽  
Interferon Response ◽  
Wild Type ◽  
Virus Family ◽  
Double Stranded Rna ◽  
Dsrna Binding ◽  
Sense Strand ◽  
Fish Cells

ABSTRACT Betanodavirus B2 belongs to a group of functionally related proteins from the sense-strand RNA virus family Nodaviridae that suppress cellular RNA interference. The B2 proteins of insect alphanodaviruses block RNA interference by binding to double-stranded RNA (dsRNA), thus preventing Dicer-mediated cleavage and the subsequent generation of short interfering RNAs. We show here that the fish betanodavirus B2 protein also binds dsRNA. Binding is sequence independent, and maximal binding occurs with dsRNA substrates greater than 20 bp in length. The binding of B2 to long dsRNA is sufficient to completely block Dicer cleavage of dsRNA in vitro. Protein-protein interaction studies indicated that B2 interacts with itself and with other dsRNA binding proteins, the interaction occurring through binding to shared dsRNA substrates. Induction of the dsRNA-dependent interferon response was not antagonized by B2, as the interferon-responsive Mx gene of permissive fish cells was induced by wild-type viral RNA1 but not by a B2 mutant. The induction of Mx instead relied solely on viral RNA1 accumulation, which is impaired in the B2 mutant. Hyperediting of virus dsRNA and site-specific editing of 5-HT2C mRNA were both antagonized by B2. RNA editing was not, however, observed in transfected wild-type or B2 mutant RNA1, suggesting that this pathway does not contribute to the RNA1 accumulation defect of the B2 mutant. We thus conclude that betanodavirus B2 is a dsRNA binding protein that sequesters and protects both long and short dsRNAs to protect betanodavirus from cellular RNA interference.

scholarly journals Double-Stranded RNA Binding May Be a General Plant RNA Viral Strategy To Suppress RNA Silencing

2006 ◽  
Vol 80 (12) ◽  
pp. 5747-5756 ◽  
Author(s):  
Zsuzsanna Mérai ◽  
Zoltán Kerényi ◽  
Sándor Kertész ◽  
Melinda Magna ◽  
Lóránt Lakatos ◽  
...  
Keyword(s):  
Rna Silencing ◽  
Rna Binding ◽  
Binding Protein ◽  
Turnip Crinkle Virus ◽  
Double Stranded Rna ◽  
Dsrna Binding ◽  
Beet Yellows Virus ◽  
Dsrna Binding Protein ◽  
Silencing Suppression ◽  
Suppression Strategy

ABSTRACT In plants, RNA silencing (RNA interference) is an efficient antiviral system, and therefore successful virus infection requires suppression of silencing. Although many viral silencing suppressors have been identified, the molecular basis of silencing suppression is poorly understood. It is proposed that various suppressors inhibit RNA silencing by targeting different steps. However, as double-stranded RNAs (dsRNAs) play key roles in silencing, it was speculated that dsRNA binding might be a general silencing suppression strategy. Indeed, it was shown that the related aureusvirus P14 and tombusvirus P19 suppressors are dsRNA-binding proteins. Interestingly, P14 is a size-independent dsRNA-binding protein, while P19 binds only 21-nucleotide ds-sRNAs (small dsRNAs having 2-nucleotide 3′ overhangs), the specificity determinant of the silencing system. Much evidence supports the idea that P19 inhibits silencing by sequestering silencing-generated viral ds-sRNAs. In this study we wanted to test the hypothesis that dsRNA binding is a general silencing suppression strategy. Here we show that many plant viral silencing suppressors bind dsRNAs. Beet yellows virus Peanut P21, clump virus P15, Barley stripe mosaic virus γB, and Tobacco etch virus HC-Pro, like P19, bind ds-sRNAs size-selectively, while Turnip crinkle virus CP is a size-independent dsRNA-binding protein, which binds long dsRNAs as well as ds-sRNAs. We propose that size-selective ds-sRNA-binding suppressors inhibit silencing by sequestering viral ds-sRNAs, whereas size-independent dsRNA-binding suppressors inactivate silencing by sequestering long dsRNA precursors of viral sRNAs and/or by binding ds-sRNAs. The findings that many unrelated silencing suppressors bind dsRNA suggest that dsRNA binding is a general silencing suppression strategy which has evolved independently many times.

scholarly journals RNA Helicase A Regulates the Replication of RNA Viruses

Viruses ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 361
Author(s):  
Rui-Zhu Shi ◽  
Yuan-Qing Pan ◽  
Li Xing
Keyword(s):  
Virus Replication ◽  
Rna Binding ◽  
Rna Viruses ◽  
Rna Helicase ◽  
Rna Helicase A ◽  
Double Stranded Rna ◽  
Binding Domains ◽  
N Terminus

The RNA helicase A (RHA) is a member of DExH-box helicases and characterized by two double-stranded RNA binding domains at the N-terminus. RHA unwinds double-stranded RNA in vitro and is involved in RNA metabolisms in the cell. RHA is also hijacked by a variety of RNA viruses to facilitate virus replication. Herein, this review will provide an overview of the role of RHA in the replication of RNA viruses.

scholarly journals Requirement of PKR Dimerization Mediated by Specific Hydrophobic Residues for Its Activation by Double-Stranded RNA and Its Antigrowth Effects in Yeast

1998 ◽  
Vol 18 (12) ◽  
pp. 7009-7019 ◽  
Author(s):  
Rekha C. Patel ◽  
Ganes C. Sen
Keyword(s):  
Helical Structure ◽  
Wild Type ◽  
Dimerization Domain ◽  
Double Stranded Rna ◽  
Mutant Proteins ◽  
Hydrophobic Residues ◽  
Dsrna Binding ◽  
Dependent Protein ◽  
Substitution Mutations

ABSTRACT The roles of protein dimerization and double-stranded RNA (dsRNA) binding in the biochemical and cellular activities of PKR, the dsRNA-dependent protein kinase, were investigated. We have previously shown that both properties of the protein are mediated by the same domain. Here we show that dimerization is mediated by hydrophobic residues present on one side of an amphipathic α-helical structure within this domain. Appropriate substitution mutations of residues on that side produced mutants with increased or decreased dimerization activities. Using these mutants, we demonstrated that dimerization is not essential for dsRNA binding. However, enhancing dimerization artificially, by providing an extraneous dimerization domain, increased dsRNA binding of both wild-type and mutant proteins. In vitro, the dimerization-defective mutants could not be activated by dsRNA but were activated normally by heparin. In Saccharomyces cerevisiae, unlike wild-type PKR, these mutants could not inhibit cell growth and the dsRNA-binding domain of the dimerization-defective mutants could not prevent the antigrowth effect of wild-type PKR. These results demonstrate the biological importance of the dimerization properties of PKR.

scholarly journals CryoEM structures of MDA5-dsRNA filaments at different stages of ATP hydrolysis

2018 ◽  
Author(s):  
Qin Yu ◽  
Kun Qu ◽  
Yorgo Modis
Keyword(s):  
Rna Binding ◽  
Atp Hydrolysis ◽  
Type I ◽  
List Type ◽  
Base Pairs ◽  
Nucleotide Analogs ◽  
Double Stranded Rna ◽  
Transition State Analogs ◽  
Helical Twist ◽  
Dsrna Binding

SummaryDouble-stranded RNA (dsRNA) is a potent proinflammatory signature of viral infection. Long cytosolic dsRNA is recognized by MDA5. The cooperative assembly of MDA5 into helical filaments on dsRNA nucleates the assembly of a multiprotein type-I-interferon signaling platform. Here, we determined cryoEM structures of MDA5-dsRNA filaments with different helical twists and bound nucleotide analogs, at resolutions sufficient to build and refine atomic models. The structures identify the filament forming interfaces, which encode the dsRNA binding cooperativity and length specificity of MDA5. The predominantly hydrophobic interface contacts confer flexibility, reflected in the variable helical twist within filaments. Mutation of filament-forming residues can result in loss or gain of signaling activity. Each MDA5 molecule spans 14 or 15 RNA base pairs, depending on the twist. Variations in twist also correlate with variations in the occupancy and type of nucleotide in the active site, providing insights on how ATP hydrolysis contributes to MDA5-dsRNA recognition.eTOCStructures of MDA5 bound to double-stranded RNA reveal a flexible, predominantly hydrophobic filament forming interface. The filaments have variable helical twist. Structures determined with ATP and transition state analogs show how the ATPase cycle is coupled to changes in helical twist, the mode of RNA binding and the length of the RNA footprint of MDA5.HighlightsCryoEM structures of MDA5-dsRNA filaments determined for three catalytic statesFilament forming interfaces are flexible and predominantly hydrophobicMutation of filament-forming residues can cause loss or gain of IFN-β signalingATPase cycle is coupled to changes in filament twist and size of the RNA footprint

scholarly journals Double-stranded RNA drives SARS-CoV-2 nucleocapsid protein to undergo phase separation at specific temperatures

2021 ◽  
Author(s):  
Christine Roden ◽  
Yifan Dai ◽  
Ian Seim ◽  
Myungwoon Lee ◽  
Rachel Sealfon ◽  
...  
Keyword(s):  
Phase Separation ◽  
Rna Structure ◽  
Nucleocapsid Protein ◽  
Rna Binding ◽  
Genome Packaging ◽  
Rna Motifs ◽  
Double Stranded Rna ◽  
N Protein ◽  
Binding Domains

Betacoronavirus SARS-CoV-2 infections caused the global Covid-19 pandemic. The nucleocapsid protein (N-protein) is required for multiple steps in the betacoronavirus replication cycle. SARS-CoV-2-N-protein is known to undergo liquid-liquid phase separation (LLPS) with specific RNAs at particular temperatures to form condensates. We show that N-protein recognizes at least two separate and distinct RNA motifs, both of which require double-stranded RNA (dsRNA) for LLPS. These motifs are separately recognized by N-protein's two RNA binding domains (RBDs). Addition of dsRNA accelerates and modifies N-protein LLPS in vitro and in cells and controls the temperature condensates form. The abundance of dsRNA tunes N-protein-mediated translational repression and may confer a switch from translation to genome packaging. Thus, N-protein's two RBDs interact with separate dsRNA motifs, and these interactions impart distinct droplet properties that can support multiple viral functions. These experiments demonstrate a paradigm of how RNA structure can control the properties of biomolecular condensates.

scholarly journals Targeted Deletion of the Murine apobec-1 Complementation Factor (acf) Gene Results in Embryonic Lethality

2005 ◽  
Vol 25 (16) ◽  
pp. 7260-7269 ◽  
Author(s):  
Valerie Blanc ◽  
Jeffrey O. Henderson ◽  
Elizabeth P. Newberry ◽  
Susan Kennedy ◽  
Jianyang Luo ◽  
...  
Keyword(s):  
Rna Binding ◽  
Cytidine Deaminase ◽  
Mrna Editing ◽  
Targeted Deletion ◽  
Apob Mrna ◽  
Rna Knockdown ◽  
Interfering Rna ◽  
Binding Subunit ◽  
Apparently Healthy

ABSTRACT apobec-1 complementation factor (ACF) is an hnRNP family member which functions as the obligate RNA binding subunit of the core enzyme mediating C-to-U editing of the nuclear apolipoprotein B (apoB) transcript. ACF binds to both apoB RNA and apobec-1, the catalytic cytidine deaminase, which then results in site-specific posttranscriptional editing of apoB mRNA. Targeted deletion of apobec1 eliminates C-to-U editing of apoB mRNA but is otherwise well tolerated. However, the functions and potential targets of ACF beyond apoB mRNA editing are unknown. Here we report the results of generating acf knockout mice using homologous recombination. While heterozygous acf +/ − mice were apparently healthy and fertile, no viable acf − / − mice were identified. Mutant acf − / − embryos were detectable only until the blastocyst (embryonic day 3.5 [E3.5]) stage. No acf − / − blastocysts were detectable following implantation at E4.5, and isolated acf − / − blastocysts failed to proliferate in vitro. Small interfering RNA knockdown of ACF in either rat (apobec-1-expressing) or human (apobec-1-deficient) hepatoma cells decreased ACF protein expression and induced a commensurate increase in apoptosis. Taken together, these data suggest that ACF plays a crucial role, which is independent of apobec-1 expression, in cell survival, particularly during early embryonic development.

scholarly journals RNA-Regulated Interaction of Transportin-1 and Exportin-5 with the Double-Stranded RNA-Binding Domain Regulates Nucleocytoplasmic Shuttling of ADAR1

2009 ◽  
Vol 29 (6) ◽  
pp. 1487-1497 ◽  
Author(s):  
Jutta Fritz ◽  
Alexander Strehblow ◽  
Andreas Taschner ◽  
Sandy Schopoff ◽  
Pawel Pasierbek ◽  
...  
Keyword(s):  
Nuclear Export ◽  
Rna Binding ◽  
Nuclear Export Signal ◽  
Nucleocytoplasmic Transport ◽  
Nucleocytoplasmic Shuttling ◽  
Double Stranded Rna ◽  
Binding Domains ◽  
Dsrna Binding ◽  
Localization Signal ◽  
Editing Enzyme

ABSTRACT Double-stranded RNA (dsRNA)-binding proteins interact with substrate RNAs via dsRNA-binding domains (dsRBDs). Several proteins harboring these domains exhibit nucleocytoplasmic shuttling and possibly remain associated with their substrate RNAs bound in the nucleus during nuclear export. In the human RNA-editing enzyme ADAR1-c, the nuclear localization signal overlaps the third dsRBD, while the corresponding import factor is unknown. The protein also lacks a clear nuclear export signal but shuttles between the nucleus and the cytoplasm. Here we identify transportin-1 as the import receptor for ADAR1. Interestingly, dsRNA binding interferes with transportin-1 binding. At the same time, each of the dsRBDs in ADAR1 interacts with the export factor exportin-5. RNA binding stimulates this interaction but is not a prerequisite. Thus, our data demonstrate a role for some dsRBDs as RNA-sensitive nucleocytoplasmic transport signals. dsRBD3 in ADAR1 can mediate nuclear import, while interaction of all dsRBDs might control nuclear export. This finding may have implications for other proteins containing dsRBDs and suggests a selective nuclear export mechanism for substrates interacting with these proteins.

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