Elimination of antiviral defense by viral RNase III

Cuellar, Wilmer J.; Kreuze, Jan; Rajamäki, Minna-Liisa; Cruzado, Karin R.; Untiveros, Milton; Valkonen, Jari P. T.

doi:10.1073/pnas.0806042106

Cited by 134 publications

(166 citation statements)

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“…It was earlier found that SPCSV RNase III enhances RNA interference (RNAi) suppression induced by another virus-encoded protein (p22) (20). Recently, the same protein was reported to mediate synergism with other unrelated viruses to break down antiviral resistance in plants (see the Discussion) (12).…”

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confidence: 99%

An Ascovirus-Encoded RNase III Autoregulates Its Expression and Suppresses RNA Interference-Mediated Gene Silencing

Hussain

Abraham

Asgari

2010

J Virol

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RNase III proteins play vital roles in processing of several types of RNA molecules and gene silencing. Recently, it has been discovered that some plant and animal viruses encode RNase III-like proteins as well. Genome sequencing of four virus species belonging to the Ascoviridae family has revealed sequence conservation of an RNase III open reading frame among the viruses. These have not been explored in ascoviruses, and therefore their role in host-virus interaction is unknown. Here, we confirmed expression of Heliothis virescens ascovirus (HvAV-3e) open reading frame 27 (orf27) that encodes an RNase III-like protein after infection and demonstrated dsRNA specific endoribonuclease activity of the encoded protein. Analysis of the expression patterns of orf27 in virus-infected insect cells and a bacterial expression system revealed autoregulation of this protein over time. Moreover, HvAV-3e RNase III was found essential for virus DNA replication and infection using RNA interference (RNAi)-mediated gene silencing. In addition, using green fluorescent protein gene as a marker, we provide evidence that RNase III is involved in the suppression of gene silencing. To our knowledge, this is the first insect virus-encoded RNase III described and shown to suppress host cell RNAi defense mechanism.

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confidence: 99%

An Ascovirus-Encoded RNase III Autoregulates Its Expression and Suppresses RNA Interference-Mediated Gene Silencing

Hussain

Abraham

Asgari

2010

J Virol

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“…It was shown that Sweet potato chlorotic stunt crinivirus (SPCSV) suppressor RNase3 cleaves the 21-24 nt vsiRNAs into 14 bp products rendering them inactive (Cuellar et al 2009;Kreuze et al 2005). Although this is a completely different strategy to siRNA-binding, it has a very similar outcome: vsiRNAs are unavailable for AGO-loading.…”

Section: Vsirna Sequestrationmentioning

confidence: 99%

Antiviral Silencing and Suppression of Gene Silencing in Plants

Csorba

Burgyán

2016

Current Research Topics in Plant Virology

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RNA silencing is an evolutionary conserved sequence-specific gene inactivation mechanism that contributes to the control of development, maintains heterochromatin, acts in stress responses, DNA repair and defends against invading nucleic acids like transposons and viruses. In plants RNA silencing functions as one of the main immune systems. RNA silencing process involves the small RNAs and trans factor components like Dicers, Argonautes and RNA-dependent RNA polymerases. To deal with host antiviral silencing responses viruses evolved mechanisms to avoid or counteract this, most notably through expression of viral suppressors of RNA silencing. Due to the overlap between endogenous and antiviral silencing pathways while blocking antiviral pathways viruses also impact endogenous silencing processes. Here we provide an overview of antiviral silencing pathway, host factors implicated in it and the crosstalk between antiviral and endogenous branches of silencing. We summarize the current status of knowledge about the viral counter-defense strategies acting at various steps during virus infection in plants with the focus on representative, well studied silencing suppressor proteins. Finally we discuss future challenges of the antiviral silencing and counter-defense research field.

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“…Viruses encode a variety of proteins named Viral Suppressors of RNA Silencing (VSRs) to block the host's RNAi system [47]. In plants, a class 1 RNase III VSR from sweet potato chlorotic stunt virus inhibits anti-viral RNAi by disabling siRNA amplification by the RdRP RDR6 [48]. Similarly, the Tomato yellow leaf curl virus VSR V2 outcompetes the SUPPRESSOR OF GENE SILENCING 3 (SGS3) protein for binding to the 5' overhang of dsRNAs, thus preventing its interaction which is required for initiating RdRP-mediated amplification of anti-viral viRNAs [49].…”

Section: Manipulation Of Transgenerational Immunitymentioning

confidence: 99%

Guest list or black list: heritable small RNAs as immunogenic memories

Rechavi

2014

Trends in Cell Biology

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Small RNA-mediated gene silencing plays a pivotal role in genome immunity by recognizing and eliminating viruses and transposons which otherwise may colonize the genome. However, this can be challenging since individual genomic parasites are highly diverse, and employ multiple immune evasion techniques. In this review, I discuss a new theory proposing that the integrity of the germline is maintained by transgenerationally-transmitted RNA "memories" that record ancestral gene expression patterns, and delineate "Self" from "Foreign" sequences. To maintain such recollection two tactics are employed in parallel: "black listing" of invading nucleic acids, and "guest listing" of endogenous genes. Studies in a number of organisms have shown that this memorization is used by the next generation small RNAs to act as "Inherited Vaccines" that ambush invading elements, or as "Inherited Licenses" that grant the transcription of autogenous sequences. KeywordsSmall RNA; Transgenerational Inheritance; Inherited Immunity; Self Vs. Non-Self; "Inherited Vaccines" Overview of transgenerational inheritanceEvolution progresses through an interplay between two major forces, selection and variation. Since the formulation of the Modern Synthesis the theory holds that the environment is limited in its contribution to the evolutionary course of action -it affects selection, but not the degree of variation [1,2]. However, recent discoveries in epigenetics suggest that the environment may influence variability as well [1]. If the parental environment is predictive of the conditions that the progeny will face (often for sessile or short-lived organisms), epigenetic responses can change the output of the encoded genetic information in an adaptive manner [3]. For example, the water flea Daphnia changes its normal developmental course and develops a "helmet" that protects it from predators, if it is born to a mother that survived a similar attack [4].Correspondence to: odedrechavi@gmail.com. Over the years, controversy surrounded the study of environmentally affected transgenerational inheritance. Today, an improved understanding of epigenetic mechanisms at the molecular level has provided a logical background to explain how, heretically, an adaptive acquired trait could become heritable [5]. Several epigenetic mechanisms could regulate the expression of relevant genes during transgenerational inheritance including DNA methylation, histone modification, and transmission of regulatory RNAs. Moreover, in many organisms, these pathways appear to be interconnected [5][6][7][8]. Europe PMC Funders GroupThis review will concentrate on recent discoveries that establish a role for small RNAs in transgenerational transmission of acquired defense. Furthermore, exciting examples of RNA-mediated non-Mendelian genetic effects will be discussed, along with their possible implications for the study of evolution and immunology. RNA-mediated gene silencing and inheritanceSince the original discovery that small RNAs derived from exogenously-provided dou...

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Elimination of antiviral defense by viral RNase III

Cited by 134 publications

References 40 publications

An Ascovirus-Encoded RNase III Autoregulates Its Expression and Suppresses RNA Interference-Mediated Gene Silencing

An Ascovirus-Encoded RNase III Autoregulates Its Expression and Suppresses RNA Interference-Mediated Gene Silencing

Antiviral Silencing and Suppression of Gene Silencing in Plants

Guest list or black list: heritable small RNAs as immunogenic memories

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