scholarly journals Strawberry Mottle Virus (Family Secoviridae, Order Picornavirales) Encodes a Novel Glutamic Protease To Process the RNA2 Polyprotein at Two Cleavage Sites

2018 ◽  
Vol 93 (5) ◽  
Author(s):  
Krin S. Mann ◽  
Joan Chisholm ◽  
Hélène Sanfaçon
Keyword(s):  
Cysteine Proteases ◽  
Terminal Region ◽  
Mottle Virus ◽  
Cleavage Sites ◽  
Virus Family ◽  
Positive Strand ◽  
Viral Proteases ◽  
Bipartite Genome ◽  
The Family ◽  
Positive Strand Rna

ABSTRACT Strawberry mottle virus (SMoV) belongs to the family Secoviridae (order Picornavirales) and has a bipartite genome with each RNA encoding one polyprotein. All characterized secovirids encode a single protease related to the picornavirus 3C protease. The SMoV 3C-like protease was previously shown to cut the RNA2 polyprotein (P2) at a single site between the predicted movement protein and coat protein (CP) domains. However, the SMoV P2 polyprotein includes an extended C-terminal region with a coding capacity of up to 70 kDa downstream of the presumed CP domain, an unusual characteristic for this family. In this study, we identified a novel cleavage event at a P↓AFP sequence immediately downstream of the CP domain. Following deletion of the PAFP sequence, the polyprotein was processed at or near a related PKFP sequence 40 kDa further downstream, defining two protein domains in the C-terminal region of the P2 polyprotein. Both processing events were dependent on a novel protease domain located between the two cleavage sites. Mutagenesis of amino acids that are conserved among isolates of SMoV and of the related Black raspberry necrosis virus did not identify essential cysteine, serine, or histidine residues, suggesting that the RNA2-encoded SMoV protease is not related to serine or cysteine proteases of other picorna-like viruses. Rather, two highly conserved glutamic acid residues spaced by 82 residues were found to be strictly required for protease activity. We conclude that the processing of SMoV polyproteins requires two viral proteases, the RNA1-encoded 3C-like protease and a novel glutamic protease encoded by RNA2. IMPORTANCE Many viruses encode proteases to release mature proteins and intermediate polyproteins from viral polyproteins. Polyprotein processing allows regulation of the accumulation and activity of viral proteins. Many viral proteases also cleave host factors to facilitate virus infection. Thus, viral proteases are key virulence factors. To date, viruses with a positive-strand RNA genome are only known to encode cysteine or serine proteases, most of which are related to the cellular papain, trypsin, or chymotrypsin proteases. Here, we characterize the first glutamic protease encoded by a plant virus or by a positive-strand RNA virus. The novel glutamic protease is unique to a few members of the family Secoviridae, suggesting that it is a recent acquisition in the evolution of this family. The protease does not resemble known cellular proteases. Rather, it is predicted to share structural similarities with a family of fungal and bacterial glutamic proteases that adopt a lectin fold.

scholarly journals A Newly Identified Virus in the Family Potyviridae Encodes Two Leader Cysteine Proteases in Tandem That Evolved Contrasting RNA Silencing Suppression Functions

2020 ◽  
Vol 95 (1) ◽  
Author(s):  
Li Qin ◽  
Wentao Shen ◽  
Zhongfa Tang ◽  
Weiyao Hu ◽  
Lingna Shangguan ◽  
...  
Keyword(s):  
Rna Silencing ◽  
Rna Viruses ◽  
Evolutionary Relationship ◽  
Cysteine Proteases ◽  
Terminal Region ◽  
Crop Damage ◽  
Virus Species ◽  
Protease Domain ◽  
The Family ◽  
Silencing Suppression

ABSTRACT Potyviridae is the largest family of plant-infecting RNA viruses and includes many agriculturally and economically important viral pathogens. The viruses in the family, known as potyvirids, possess single-stranded, positive-sense RNA genomes with polyprotein processing as a gene expression strategy. The N-terminal regions of potyvirid polyproteins vary greatly in sequence. Previously, we identified a novel virus species within the family, Areca palm necrotic spindle-spot virus (ANSSV), which was predicted to encode two cysteine proteases, HCPro1 and HCPro2, in tandem at the N-terminal region. Here, we present evidence showing self-cleavage activity of these two proteins and define their cis-cleavage sites. We demonstrate that HCPro2 is a viral suppressor of RNA silencing (VSR), and both the variable N-terminal and conserved C-terminal (protease domain) moieties have antisilencing activity. Intriguingly, the N-terminal region of HCPro1 also has RNA silencing suppression activity, which is, however, suppressed by its C-terminal protease domain, leading to the functional divergence of HCPro1 and HCPro2 in RNA silencing suppression. Moreover, the deletion of HCPro1 or HCPro2 in a newly created infectious clone abolishes viral infection, and the deletion mutants cannot be rescued by addition of corresponding counterparts of a potyvirus. Altogether, these data suggest that the two closely related leader proteases of ANSSV have evolved differential and essential functions to concertedly maintain viral viability. IMPORTANCE The Potyviridae represent the largest group of known plant RNA viruses and account for more than half of the viral crop damage worldwide. The leader proteases of viruses within the family vary greatly in size and arrangement and play key roles during the infection. Here, we experimentally demonstrate the presence of a distinct pattern of leader proteases, HCPro1 and HCPro2 in tandem, in a newly identified member within the family. Moreover, HCPro1 and HCPro2, which are closely related and typically characterized with a short size, have evolved contrasting RNA silencing suppression activity and seem to function in a coordinated manner to maintain viral infectivity. Altogether, the new knowledge fills a missing piece in the evolutionary relationship history of potyvirids and improves our understanding of the diversification of potyvirid genomes.

scholarly journals Cysteine proteases of positive strand RNA viruses and chymotrypsin-like serine proteases

FEBS Letters ◽  
1989 ◽  
Vol 243 (2) ◽  
pp. 103-114 ◽  
Author(s):  
Alexander E. Gorbalenya ◽  
Alexei P. Donchenko ◽  
Vladimir M. Blinov ◽  
Eugene V. Koonin
Keyword(s):  
Serine Proteases ◽  
Rna Viruses ◽  
Cysteine Proteases ◽  
Positive Strand ◽  
Positive Strand Rna

scholarly journals The Small-Compound Inhibitor K22 Displays Broad Antiviral Activity against Different Members of the Family Flaviviridae and Offers Potential as a Panviral Inhibitor

2018 ◽  
Vol 62 (11) ◽  
Author(s):  
Obdulio García-Nicolás ◽  
Philip V'kovski ◽  
Nathalie J. Vielle ◽  
Nadine Ebert ◽  
Roland Züst ◽  
...  
Keyword(s):  
Antiviral Activity ◽  
Host Cell ◽  
Rna Viruses ◽  
Close Association ◽  
Viral Inhibition ◽  
Virus Family ◽  
Positive Strand ◽  
Content Type ◽  
Small Compound ◽  
Positive Strand Rna

ABSTRACT The virus family Flaviviridae encompasses several viruses, including (re)emerging viruses which cause widespread morbidity and mortality throughout the world. Members of this virus family are positive-strand RNA viruses and replicate their genome in close association with reorganized intracellular host cell membrane compartments. This evolutionarily conserved strategy facilitates efficient viral genome replication and contributes to evasion from host cell cytosolic defense mechanisms. We have previously described the identification of a small-compound inhibitor, K22, which exerts a potent antiviral activity against a broad range of coronaviruses by targeting membrane-bound viral RNA replication. To analyze the antiviral spectrum of this inhibitor, we assessed the inhibitory potential of K22 against several members of the Flaviviridae family, including the reemerging Zika virus (ZIKV). We show that ZIKV is strongly affected by K22. Time-of-addition experiments revealed that K22 acts during a postentry phase of the ZIKV life cycle, and combination regimens of K22 together with ribavirin (RBV) or interferon alpha (IFN-α) further increased the extent of viral inhibition. Ultrastructural electron microscopy studies revealed severe alterations of ZIKV-induced intracellular replication compartments upon infection of K22-treated cells. Importantly, the antiviral activity of K22 was demonstrated against several other members of the Flaviviridae family. It is tempting to speculate that K22 exerts its broad antiviral activity against several positive-strand RNA viruses via a similar mechanism and thereby represents an attractive candidate for development as a panviral inhibitor.

scholarly journals A novel RNA mycovirus in a hypovirulent isolate of the plant pathogen Diaporthe ambigua

2000 ◽  
Vol 81 (12) ◽  
pp. 3107-3114 ◽  
Author(s):  
O. Preisig ◽  
N. Moleleki ◽  
W. A. Smit ◽  
B. D. Wingfield ◽  
M. J. Wingfield
Keyword(s):  
Genome Organization ◽  
Rna Virus ◽  
Plant Viruses ◽  
Translation Product ◽  
Terminal Part ◽  
Virus Family ◽  
Positive Strand ◽  
Positive Strand Rna Virus ◽  
Positive Strand Rna ◽  
Diaporthe Ambigua

Hypovirulent isolates of the fruit tree fungal pathogen Diaporthe ambigua have previously been shown to harbour a double-stranded (ds)RNA genetic element of about 4 kb. In this study, we established the complete cDNA sequence of this dsRNA, which represents a replicative form of a positive-strand RNA virus that we have named D. ambigua RNA virus (DaRV). The nucleotide sequence of the genome is 4113 bp and has a GC content of 53%. Two large ORFs are present in the same reading frame. They are most probably translated by readthrough of a UAG stop codon in the central part of the genome. The longest possible translation product (p125) has a predicted molecular mass of about 125 kDa. A significant homology can be found to the non-structural proteins of carmoviruses of the positive-strand RNA virus family Tombusviridae. These proteins also include the conserved RNA-dependent RNA polymerase (RDRP) domain. In contrast to the genome organization of these plant viruses, no ORF is present at the 3′ end of the DaRV genome that encodes a coat protein. Therefore, it is proposed that DaRV is not encapsidated but that it occurs as RNA–RDRP complexes and/or that it might be associated with cell membranes. Interestingly, six putative transmembrane helices are predicted in the N-terminal part of p56 (translation product of the first ORF, N-terminal part of p125), which might direct and anchor the viral complex to membranes. DaRV is a mycovirus with a unique genome organization and has a distant relationship to the plant virus family Tombusviridae.

Rapid pre-symptomatic recognition of tristeza viral RNA by a novel fluorescent self-dimerized DNA–silver nanocluster probe

RSC Advances ◽  
2016 ◽  
Vol 6 (101) ◽  
pp. 99437-99443 ◽  
Author(s):  
Ehsan Shokri ◽  
Morteza Hosseini ◽  
Farnoush Faridbod ◽  
Mahdi Rahaie
Keyword(s):  
Citrus Tristeza Virus ◽  
Rna Virus ◽  
Viral Rna ◽  
Positive Strand ◽  
Silver Nanocluster ◽  
The Family ◽  
Positive Strand Rna Virus ◽  
Positive Strand Rna ◽  
Tristeza Virus ◽  
Citrus Tristeza

Citrus tristeza virus (CTV), a positive-strand RNA virus within the family of Closteroviridae, is distributed worldwide and causes one of the most economically important diseases of citrus.

scholarly journals The RNA of maize chlorotic mottle virus - the essential virus in maize lethal necrosis disease - is translated via a panicum mosaic virus-like cap-independent translation element

2020 ◽  
Author(s):  
Elizabeth Carino ◽  
Kay Scheets ◽  
W. Allen Miller
Keyword(s):  
Translation Initiation ◽  
Rna Viruses ◽  
Viral Rna ◽  
Mottle Virus ◽  
Positive Strand ◽  
Chlorotic Mottle Virus ◽  
Maize Chlorotic Mottle Virus ◽  
Chlorotic Mottle ◽  
Positive Strand Rna ◽  
Independent Translation

AbstractMaize chlorotic mottle virus (MCMV) combines with a potyvirus in maize lethal necrosis disease (MLND), an emerging disease worldwide that often causes catastrophic yield loss. To inform resistance strategies, we characterized the translation initiation mechanism of MCMV. We report that, like other tombusvirids, MCMV RNA contains a cap-independent translation element (CITE) in its 3’ untranslated region (UTR). The MCMV 3’ CITE (MTE) was mapped to nucleotides 4164-4333 in the genomic RNA. SHAPE probing revealed that the MTE is a variant of the panicum mosaic virus-like 3’ CITE (PTE). Like the PTE, electrophoretic mobility shift assays (EMSAs) indicated that eukaryotic translation initiation factor 4E (eIF4E) binds the MTE despite the absence of a m7GpppN cap structure, which is normally required for eIF4E to bind RNA. The MTE interaction with eIF4E suggests eIF4E may be a soft target for engineered resistance to MCMV. Using a luciferase reporter system, mutagenesis to disrupt and restore base pairing revealed that the MTE interacts with the 5’ UTRs of both genomic RNA and the 3’-coterminal subgenomic RNA1 via long-distance kissing stem-loop base pairing to facilitate translation in wheat germ extract and in protoplasts. However, the MTE is a relatively weak stimulator of translation and has a weak, if any, pseudoknot, which is present in the most active PTEs. Most mutations designed to form a pseudoknot decreased translation activity. Mutations in the viral genome that reduced or restored translation prevented and restored virus replication, respectively, in maize protoplasts and in plants. We propose that MCMV, and some other positive strand RNA viruses, favors a weak translation element to allow highly efficient viral RNA synthesis.Author SummaryIn recent years, maize lethal necrosis disease has caused massive crop losses in East Africa and Ecuador. It has also emerged in East Asia. Maize chlorotic mottle virus (MCMV) infection is required for this disease. While some tolerant maize lines have been identified, there are no known resistance genes that confer full immunity to MCMV. In order to design better resistance strategies against MCMV, we focused on how the MCMV genome is translated, the first step of gene expression required for infection by all positive strand RNA viruses. We identified a structure (cap-independent translation element) in the 3’ untranslated region of the viral RNA genome that allows the virus to usurp a host translation initiation factor in a way that differs from host mRNA interactions with the translational machinery. This difference may guide engineering of – or breeding for – resistance to MCMV. Moreover, this work adds to the diversity of known eukaryotic translation initiation mechanisms, as it provides more information on mRNA structural features that permit noncanonical interaction with a translation factor. Finally, owing to the conflict between ribosomes translating and viral replicase copying viral RNA, we propose that MCMV has evolved a relatively weak translation element in order to permit highly efficient RNA synthesis, and that this replication-translation trade-off may apply to other positive strand RNA viruses.

Coronavirus: history, genome structure and pathogenesis

Coronaviruses ◽  
2020 ◽  
Vol 01 ◽  
Author(s):  
Poonam B ◽  
Prabhjot Kaur Gill
Keyword(s):  
Genome Structure ◽  
Public Health Research ◽  
Replication Process ◽  
Virus Family ◽  
Enveloped Virus ◽  
Target Organs ◽  
Transcription Process ◽  
Recent Emergence ◽  
The Family ◽  
Discontinuous Transcription

Background: The positive sense and inordinate large RNA genome are enclosed by helical nuceocapsids along with an outermost layer belongs to the family Coronaviridae. The phylogenetic tree of this family has been quartered into Class1 as alpha, Class 2 as beta, Class 3 as gamma and Class 4 as delta CoV. The mammalian respiratory and gastrointestinal tracts are the main target organs of this enveloped virus with misperceived mechanisms. The relevance of this virus family has considerably increased by the dint of recent emergence of the Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS), which are caused by viruses belonging to the beta-CoV group. Aim: Aforesaid illustrations of emergence of coronavirus diseases over the past two decades, SARS (2002 and 2003) and MERS (2012 to present) - the ongoing COVID-19 outbreak has pressurized the WHO to take innovative measures for public health, research and medical communities. The aim of the present review is to have proficiency in coronavirus replication and transcription process which is still in its infancy. Conclusion: An outcome of epidemics, it is being recognized as one of the most advancing viruses by the virtue of high genomic nucleotide substitution rates and recombination. The hallmark of coronavirus replication is discontinuous transcription resulting in the production of multiple subgenomic mRNAs having sequences complementary to both ends of the genome. Therefore, complete genome sequence of coronavirus will be used as frame of reference for knowing this classical phenomenon of RNA replication process. Finally, research on the pathogenesis of coronaviruses and the host immunopathological response will aid in designing vaccines and minimizing mortality rate.

Sign in / Sign up

Export Citation Format

Share Document