scholarly journals Viral suppressors from members of the family Closteroviridae combating antiviral RNA silencing: a tale of a sophisticated arms race in host-pathogen interactions

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Muhammad Dilshad Hussain ◽  
Tahir Farooq ◽  
Xi Chen ◽  
Muhammad Tariqjaveed ◽  
Tong Jiang ◽  
...  
Keyword(s):  
Rna Silencing ◽  
Protein S ◽  
Specific Protein ◽  
Small Interfering Rnas ◽  
Virus Infections ◽  
Antiviral Responses ◽  
The Family ◽  
Inactivation Mechanism ◽  
Recent Developments ◽  
Viral Suppressors

AbstractRNA silencing is an evolutionarily homology-based gene inactivation mechanism and plays critical roles in plant immune responses to acute or chronic virus infections, which often pose serious threats to agricultural productions. Plant antiviral immunity is triggered by virus-derived small interfering RNAs (vsiRNAs) and functions to suppress virus further replication via a sequence-specific degradation manner. Through plant-virus arms races, many viruses have evolved specific protein(s), known as viral suppressors of RNA silencing (VSRs), to combat plant antiviral responses. Numerous reports have shown that VSRs can efficiently curb plant antiviral defense response via interaction with specific component(s) involved in the plant RNA silencing machinery. Members in the family Closteroviridae (closterovirids) are also known to encode VSRs to ensure their infections in plants. In this review, we will focus on the plant antiviral RNA silencing strategies, and the most recent developments on the multifunctional VSRs encoded by closterovirids. Additionally, we will highlight the molecular characters of phylogenetically-associated closterovirids, the interactions of these viruses with their host plants and transmission vectors, and epidemiology.

scholarly journals Inhibition of RNA silencing by the coat protein of Pelargonium flower break virus: distinctions from closely related suppressors

2009 ◽  
Vol 90 (2) ◽  
pp. 519-525 ◽  
Author(s):  
Sandra Martínez-Turiño ◽  
Carmen Hernández
Keyword(s):  
Coat Protein ◽  
Potato Virus ◽  
Rna Silencing ◽  
Potato Virus X ◽  
Plant Viruses ◽  
Small Interfering Rnas ◽  
Silencing Suppression ◽  
Viral Suppressors

Viral-derived double-stranded RNAs (dsRNAs) activate RNA silencing, generating small interfering RNAs (siRNAs) which are incorporated into an RNA-induced silencing complex (RISC) that promotes homology-dependent degradation of cognate RNAs. To counteract this, plant viruses express RNA silencing suppressors. Here, we show that the coat protein (CP) of Pelargonium flower break virus (PFBV), a member of the genus Carmovirus, is able to efficiently inhibit RNA silencing. Interestingly, PFBV CP blocked both sense RNA- and dsRNA-triggered RNA silencing and did not preclude generation of siRNAs, which is in contrast with the abilities that have been reported for other carmoviral CPs. We have also found that PFBV CP can bind siRNAs and that this ability correlates with silencing suppression activity and enhancement of potato virus X pathogenicity. Collectively, the results indicate that PFBV CP inhibits RNA silencing by sequestering siRNAs and preventing their incorporation into a RISC, thus behaving similarly to unrelated viral suppressors but dissimilarly to orthologous ones.

scholarly journals The 3A protein of coxsackievirus B3 acts as a viral suppressor of RNA interference

2020 ◽  
Vol 101 (10) ◽  
pp. 1069-1078
Author(s):  
Jingfang Mu ◽  
Haobo Zhang ◽  
Tao Li ◽  
Ting Shu ◽  
Yang Qiu ◽  
...  
Keyword(s):  
Rna Interference ◽  
Mammalian Cells ◽  
Mutational Analysis ◽  
Nonstructural Protein ◽  
Viral Myocarditis ◽  
Coxsackievirus B3 ◽  
Small Interfering Rnas ◽  
The Family ◽  
Viral Suppressors

RNA interference (RNAi) is a potent antiviral defence mechanism in eukaryotes, and numerous viruses have been found to encode viral suppressors of RNAi (VSRs). Coxsackievirus B3 (CVB3) belongs to the genus Enterovirus in the family Picornaviridae, and has been reported to be a major causative pathogen for viral myocarditis. Despite the importance of CVB3, it is unclear whether CVB3 can also encode proteins that suppress RNAi. Here, we showed that the CVB3 nonstructural protein 3A suppressed RNAi triggered by either small hairpin RNAs (shRNAs) or small interfering RNAs (siRNAs) in mammalian cells. We further uncovered that CVB3 3A interacted directly with double-stranded RNAs (dsRNAs) and siRNAs in vitro. Through mutational analysis, we found that the VSR activity of CVB3 3A was significantly reduced by mutations of D24A/L25A/L26A, Y37A/C38A and R60A in conserved residues. In addition, the 3A protein encoded by coxsackievirus B5 (CVB5), another member of Enterovirus, also showed VSR activity. Taken together, our findings showed that CVB3 3A has in vitro VSR activity, thereby providing insights into the pathogenesis of CVB3 and other enteroviruses.

scholarly journals Optimal viral strategies for bypassing RNA silencing

2010 ◽  
Vol 8 (55) ◽  
pp. 257-268 ◽  
Author(s):  
Guillermo Rodrigo ◽  
Javier Carrera ◽  
Alfonso Jaramillo ◽  
Santiago F. Elena
Keyword(s):  
Rna Silencing ◽  
Small Interfering Rnas ◽  
Defence Mechanism ◽  
Model Driven ◽  
Transcriptional Suppression ◽  
Specific Manner ◽  
Forward Engineering ◽  
Working Principle ◽  
Viral Suppressors ◽  
Shed Light

The RNA silencing pathway constitutes a defence mechanism highly conserved in eukaryotes, especially in plants, where the underlying working principle relies on the repressive action triggered by the intracellular presence of double-stranded RNAs. This immune system performs a post-transcriptional suppression of aberrant mRNAs or viral RNAs by small interfering RNAs (siRNAs) that are directed towards their target in a sequence-specific manner. However, viruses have evolved strategies to escape from silencing surveillance while promoting their own replication. Several viruses encode suppressor proteins that interact with different elements of the RNA silencing pathway and block it. The different suppressors are not phylogenetically nor structurally related and also differ in their mechanism of action. Here, we adopt a model-driven forward-engineering approach to understand the evolution of suppressor proteins and, in particular, why viral suppressors preferentially target some components of the silencing pathway. We analysed three strategies characterized by different design principles: replication in the absence of a suppressor, suppressors targeting the first protein component of the pathway and suppressors targeting the siRNAs. Our results shed light on the question of whether a virus must opt for devoting more time into transcription or into translation and on which would be the optimal step of the silencing pathway to be targeted by suppressors. In addition, we discussed the evolutionary implications of such designing principles.

A Mutation in the Protein S Pseudogene Is Linked to Protein S Deficiency in a Thrombophilic Family

1989 ◽  
Vol 62 (03) ◽  
pp. 897-901 ◽  
Author(s):  
Hans K Ploos van Amstel ◽  
Pieter H Reitsma ◽  
Karly Hamulyák ◽  
Christine E M de Die-Smulders ◽  
Pier M Mannucci ◽  
...  
Keyword(s):  
Total Protein ◽  
Protein S ◽  
Southern Analysis ◽  
Type I ◽  
Protein S Deficiency ◽  
S Deficiency ◽  
The Family ◽  
Dna Pattern ◽  
Deficiency Type ◽  
S Genes

SummaryProbands from 15 unrelated families with hereditary protein S deficiency type I, that is having a plasma total protein S concentration fifty percent of normal, were screened for abnormalities in their protein S genes by Southern analysis. Two probands were found to have a deviating DNA pattern with the restriction enzyme Mspl. In the two patients the alteration concerned the disappearance of a Mspl restriction site, CCGG, giving rise to an additional hybridizing Mspl fragment.Analysis of relatives of both probands showed that in one family the mutation does not co-segregate with the phenotype of reduced plasma protein S. In the family of the other proband, however, complete linkage between the mutated gene pattern and the reduced total protein S concentration was found: 12 heterozygous relatives showed the additional Mspl fragment but none of the investigated 26 normal members of the family. The mutation is shown to reside in the PSβ gene, the inactive protein S gene. The cause of type I protein S deficiency, a defect PSα gene has escaped detection by Southern analysis. No recombination has occurred between the PSα gene and the PSβ gene in 23 informative meioses. This suggests that the two protein S genes, located near the centromere of chromosome 3, are within 4 centiMorgan of each other.

scholarly journals RNA Silencing Suppression by a Second Copy of the P1 Serine Protease of Cucumber Vein Yellowing Ipomovirus, a Member of the Family Potyviridae That Lacks the Cysteine Protease HCPro

2006 ◽  
Vol 80 (20) ◽  
pp. 10055-10063 ◽  
Author(s):  
Adrian Valli ◽  
Ana Montserrat Martín-Hernández ◽  
Juan José López-Moya ◽  
Juan Antonio García
Keyword(s):  
Rna Silencing ◽  
Fluorescent Protein ◽  
Serine Proteinase ◽  
Plum Pox Virus ◽  
Coding Region ◽  
Long Distance ◽  
Systemic Spread ◽  
The Family ◽  
Silencing Suppression ◽  
Green Fluorescent

ABSTRACT The P1 protein of viruses of the family Potyviridae is a serine proteinase, which is highly variable in length and sequence, and its role in the virus infection cycle is not clear. One of the proposed activities of P1 is to assist HCPro, the product that viruses of the genus Potyvirus use to counteract antiviral defense mediated by RNA silencing. Indeed, an HCPro-coding region is present in all the genomes of members of the genera Potyvirus, Rymovirus, and Tritimovirus that have been sequenced. However, it was recently reported that a sequence coding for HCPro is lacking in the genome of Cucumber vein yellowing virus (CVYV), a member of the genus Ipomovirus, the fourth monopartite genus of the family. In this study, we provide further evidence that P1 enhances the activity of HCPro in members of the genus Potyvirus and show that it is duplicated in the ipomovirus CVYV. The two CVYV P1 copies are arranged in tandem, and the second copy (P1b) has RNA silencing suppression activity. CVYV P1b suppressed RNA silencing induced either by sense green fluorescent protein (GFP) mRNA or by a GFP inverted repeat RNA, indicating that CVYV P1b acts downstream of the formation of double-stranded RNA. CVYV P1b also suppressed local silencing in agroinfiltrated patches of transgenic Nicotiana benthamiana line 16c and delayed its propagation to the neighboring cells. However, neither the short-distance nor long-distance systemic spread of silencing of the GFP transgene was completely blocked by CVYV P1b. CVYV P1b and P1-HCPro from the potyvirus Plum pox virus showed very similar behaviors in all the assays carried out, suggesting that evolution has found a way to counteract RNA silencing by similar mechanisms using very different proteins in viruses of the same family.

scholarly journals Vitamin K-dependent protein S is similar to rat androgen-binding protein

1987 ◽  
Vol 243 (1) ◽  
pp. 293-296 ◽  
Author(s):  
M E Baker ◽  
F S French ◽  
D R Joseph
Keyword(s):  
Vitamin K ◽  
Binding Protein ◽  
Protein A ◽  
Serine Proteinase ◽  
Protein S ◽  
Clotting Factors ◽  
The Family ◽  
Androgen Binding Protein ◽  
Dependent Protein ◽  
Androgen Binding

Vitamin K-dependent protein S belongs to the family of clotting factors (e.g. Factors IX and X, and protein C). Unlike the other clotting factors, the C-terminal half (residues 250-634) of protein S is not a serine proteinase. In fact, the function of residues 250-634 of protein S is unknown. By using computer programs designed to detect evolutionary relationships between proteins, we find that this part of protein S is similar to rat androgen-binding protein, a protein produced and secreted by testicular Sertoli cells. The homology between protein S and androgen-binding protein suggests new approaches for elucidating their functions.

The yeast UME5 gene regulates the stability of meiotic mRNAs in response to glucose

1994 ◽  
Vol 14 (5) ◽  
pp. 3446-3458
Author(s):  
R T Surosky ◽  
R Strich ◽  
R E Esposito
Keyword(s):  
Vegetative Growth ◽  
Signal Transduction Pathway ◽  
Kinase Domain ◽  
Specific Protein ◽  
Transcript Stability ◽  
The Family ◽  
Two Factors ◽  
Genetic Epistasis ◽  
The Stability ◽  
Acetate Medium

We reported previously that early meiotic transcripts are highly unstable. These mRNAs exhibit half-lives of approximately 3 min when expressed during vegetative growth in glucose medium and are stabilized twofold during sporulation in acetate medium. Two genes, UME2 and UME5, that regulate the stability of meiosis-specific transcripts have been identified. The wild-type UME5 gene, which has been analyzed in detail, decreases the stability of all meiotic mRNAs tested approximately twofold when expressed during vegetative growth but has no effect on the half-lives of a number of vegetative mRNAs examined. The UME5 gene is dispensable for mitotic and meiotic development. Cells in which the entire UME5 gene has been deleted are viable, although the generation time is slightly longer and sporulation is less efficient. The UME5 transcript is constitutively expressed, and its stability is not autoregulated. The UME5 gene encodes a predicted 63-kDa protein with homology to the family of CDC28 serine/threonine-specific protein kinases. The kinase activity appears to be central to the function of the UME5 protein, since alteration of a highly conserved amino acid in the kinase domain results in a phenotype identical to that of a ume5 deletion. Genetic epistasis studies suggest that the UME2 and UME5 gene products act in the same pathway to regulate meiotic transcript stability. This pathway is independent of deadenylation and translation, two factors known to be important in regulating mRNA turnover. Significantly, the UME5-mediated destabilization of meiotic mRNAs occurs in glucose- but not in acetate-containing medium. Thus, the UME5 gene appears to participate in a glucose signal transduction pathway governing message stability.

scholarly journals Phytophthora effector targets a novel component of small RNA pathway in plants to promote infection

2015 ◽  
Vol 112 (18) ◽  
pp. 5850-5855 ◽  
Author(s):  
Yongli Qiao ◽  
Jinxia Shi ◽  
Yi Zhai ◽  
Yingnan Hou ◽  
Wenbo Ma
Keyword(s):  
Small Rna ◽  
Rna Silencing ◽  
Effector Proteins ◽  
Helicase Domain ◽  
Small Interfering Rnas ◽  
Developmental Defects ◽  
Interacting Protein ◽  
Homologous Genes ◽  
Unidentified Component ◽  
Virulence Target

A broad range of parasites rely on the functions of effector proteins to subvert host immune response and facilitate disease development. The notorious Phytophthora pathogens evolved effectors with RNA silencing suppression activity to promote infection in plant hosts. Here we report that the Phytophthora Suppressor of RNA Silencing 1 (PSR1) can bind to an evolutionarily conserved nuclear protein containing the aspartate–glutamate–alanine–histidine-box RNA helicase domain in plants. This protein, designated PSR1-Interacting Protein 1 (PINP1), regulates the accumulation of both microRNAs and endogenous small interfering RNAs in Arabidopsis. A null mutation of PINP1 causes embryonic lethality, and silencing of PINP1 leads to developmental defects and hypersusceptibility to Phytophthora infection. These phenotypes are reminiscent of transgenic plants expressing PSR1, supporting PINP1 as a direct virulence target of PSR1. We further demonstrate that the localization of the Dicer-like 1 protein complex is impaired in the nucleus of PINP1-silenced or PSR1-expressing cells, indicating that PINP1 may facilitate small RNA processing by affecting the assembly of dicing complexes. A similar function of PINP1 homologous genes in development and immunity was also observed in Nicotiana benthamiana. These findings highlight PINP1 as a previously unidentified component of RNA silencing that regulates distinct classes of small RNAs in plants. Importantly, Phytophthora has evolved effectors to target PINP1 in order to promote infection.

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