scholarly journals Adding Genes to the RNA Genome of Vesicular Stomatitis Virus: Positional Effects on Stability of Expression

2002 ◽  
Vol 76 (15) ◽  
pp. 7642-7650 ◽  
Author(s):  
Gail W. Wertz ◽  
Robin Moudy ◽  
L. Andrew Ball

ABSTRACT Gene expression of the nonsegmented negative strand (NNS) RNA viruses is controlled primarily at the level of transcription by the position of the genes relative to the single transcriptional promoter. We tested this principle by generating engineered variants of vesicular stomatitis virus in which an additional, identical, transcriptional unit was added to the genome at each of the viral gene junctions. Analysis of transcripts confirmed that the level of transcription was determined by the position of the gene relative to the promoter. However, the position at which a gene was inserted affected the replication potential of the viruses. Adding a gene between the first two genes, N and P, reduced replication by over an order of magnitude, whereas addition of a gene at the other gene junctions had no effect on replication levels. All genes downstream of the inserted gene had decreased levels of expression, since transcription of the extra gene introduced an additional transcriptional attenuation event. The added gene was stably maintained in the genome upon repeated passage in all cases. However, expression of the added gene was stable at only three of the four positions. In the case of insertion between the N and P genes, a virus population arose within two passages that had restored replication to wild-type levels. In this population, expression of the additional gene as a monocistronic mRNA was suppressed by mutations at the end of the upstream (N) gene that abolished transcriptional termination. Because transcription is obligatorily sequential, this prevented transcription of the inserted downstream gene as a monocistronic mRNA and resulted instead in polymerase reading through the gene junction to produce a bicistronic mRNA. This eliminated the additional attenuation step and restored expression of all downstream genes and viral replication to wild-type levels. These data show that transcriptional termination is a key element in control of gene expression of the negative strand RNA viruses and a means by which expression of individual genes may be regulated within the framework of a single transcriptional promoter. Further, these results are directly relevant to the use of NNS viruses as vectors and vaccine delivery agents, as they show that the level of expression of an added gene can be controlled by its insertion position but that not all positions of insertion yield stable expression of the added gene.

2020 ◽  
Vol 94 (13) ◽  
Author(s):  
Louis-Marie Bloyet ◽  
Benjamin Morin ◽  
Vesna Brusic ◽  
Erica Gardner ◽  
Robin A. Ross ◽  
...  

ABSTRACT Nonsegmented negative-strand (NNS) RNA viruses possess a ribonucleoprotein template in which the genomic RNA is sequestered within a homopolymer of nucleocapsid protein (N). The viral RNA-dependent RNA polymerase (RdRP) resides within an approximately 250-kDa large protein (L), along with unconventional mRNA capping enzymes: a GDP:polyribonucleotidyltransferase (PRNT) and a dual-specificity mRNA cap methylase (MT). To gain access to the N-RNA template and orchestrate the LRdRP, LPRNT, and LMT, an oligomeric phosphoprotein (P) is required. Vesicular stomatitis virus (VSV) P is dimeric with an oligomerization domain (OD) separating two largely disordered regions followed by a globular C-terminal domain that binds the template. P is also responsible for bringing new N protomers onto the nascent RNA during genome replication. We show VSV P lacking the OD (PΔOD) is monomeric but is indistinguishable from wild-type P in supporting mRNA transcription in vitro. Recombinant virus VSV-PΔOD exhibits a pronounced kinetic delay in progeny virus production. Fluorescence recovery after photobleaching demonstrates that PΔOD diffuses 6-fold more rapidly than the wild type within viral replication compartments. A well-characterized defective interfering particle of VSV (DI-T) that is only competent for RNA replication requires significantly higher levels of N to drive RNA replication in the presence of PΔOD. We conclude P oligomerization is not required for mRNA synthesis but enhances genome replication by facilitating RNA encapsidation. IMPORTANCE All NNS RNA viruses, including the human pathogens rabies, measles, respiratory syncytial virus, Nipah, and Ebola, possess an essential L-protein cofactor, required to access the N-RNA template and coordinate the various enzymatic activities of L. The polymerase cofactors share a similar modular organization of a soluble N-binding domain and a template-binding domain separated by a central oligomerization domain. Using a prototype of NNS RNA virus gene expression, vesicular stomatitis virus (VSV), we determined the importance of P oligomerization. We find that oligomerization of VSV P is not required for any step of viral mRNA synthesis but is required for efficient RNA replication. We present evidence that this likely occurs through the stage of loading soluble N onto the nascent RNA strand as it exits the polymerase during RNA replication. Interfering with the oligomerization of P may represent a general strategy to interfere with NNS RNA virus replication.


2018 ◽  
Vol 92 (8) ◽  
pp. e00146-18 ◽  
Author(s):  
Ryan H. Gumpper ◽  
Weike Li ◽  
Carlos H. Castañeda ◽  
M. José Scuderi ◽  
James K. Bashkin ◽  
...  

ABSTRACTPolyamides have been shown to bind double-stranded DNA by complementing the curvature of the minor groove and forming various hydrogen bonds with DNA. Several polyamide molecules have been found to have potent antiviral activities against papillomavirus, a double-stranded DNA virus. By analogy, we reason that polyamides may also interact with the structured RNA bound in the nucleocapsid of a negative-strand RNA virus. Vesicular stomatitis virus (VSV) was selected as a prototype virus to test this possibility since its genomic RNA encapsidated in the nucleocapsid forms a structure resembling one strand of an A-form RNA duplex. One polyamide molecule, UMSL1011, was found to inhibit infection of VSV. To confirm that the polyamide targeted the nucleocapsid, a nucleocapsid-like particle (NLP) was incubated with UMSL1011. The encapsidated RNA in the polyamide-treated NLP was protected from thermo-release and digestion by RNase A. UMSL1011 also inhibits viral RNA synthesis in the intracellular activity assay for the viral RNA-dependent RNA polymerase. The crystal structure revealed that UMSL1011 binds the structured RNA in the nucleocapsid. The conclusion of our studies is that the RNA in the nucleocapsid is a viable antiviral target of polyamides. Since the RNA structure in the nucleocapsid is similar in all negative-strand RNA viruses, polyamides may be optimized to target the specific RNA genome of a negative-strand RNA virus, such as respiratory syncytial virus and Ebola virus.IMPORTANCENegative-strand RNA viruses (NSVs) include several life-threatening pathogens, such as rabies virus, respiratory syncytial virus, and Ebola virus. There are no effective antiviral drugs against these viruses. Polyamides offer an exceptional opportunity because they may be optimized to target each NSV. Our studies on vesicular stomatitis virus, an NSV, demonstrated that a polyamide molecule could specifically target the viral RNA in the nucleocapsid and inhibit viral growth. The target specificity of the polyamide molecule was proved by its inhibition of thermo-release and RNA nuclease digestion of the RNA bound in a model nucleocapsid, and a crystal structure of the polyamide inside the nucleocapsid. This encouraging observation provided the proof-of-concept rationale for designing polyamides as antiviral drugs against NSVs.


2020 ◽  
Author(s):  
Kunzhang Lin ◽  
Xin Zhong ◽  
Min Ying ◽  
Lei Li ◽  
Sijue Tao ◽  
...  

Abstract Understanding the connecting structure of brain network is the basis to reveal the principle of the brain function and elucidate the mechanism of brain diseases. Trans-synaptic tracing with neurotropic viruses has become one of the most effective technologies to dissect the neural circuits. Although the retrograde trans-synaptic tracing for analyzing the input neural networks with recombinant rabies and pseudorabies virus has been broadly applied in neuroscience, viral tools for analyzing the output neural networks are still lacking. The recombinant vesicular stomatitis virus (VSV) has been used for the mapping of synaptic outputs. However, several drawbacks, including high neurotoxicity and rapid lethality in experimental animals, hinder its application in long-term studies of the structure and function of neural networks. To overcome these limitations, we generated a recombinant VSV with replication-related N gene mutation, VSV-NR7A, and examined its cytotoxicity and efficiency of trans-synaptic spreading. We found that by comparison with the wild-type tracer of VSV, the NR7A mutation endowed the virus lower rate of propagation and cytotoxicity in vitro, as well as significantly reduced neural inflammatory responses in vivo and much longer animal survival when it was injected into the nucleus of the mice brain. Besides, the spreading of the attenuated VSV was delayed when injected into the VTA. Importantly, with the reduced toxicity and extended animal survival, the number of brain regions that was trans-synaptically labeled by the mutant VSV was more than that of the wild-type VSV. These results indicated that the VSV-NR7A, could be a promising anterograde tracer that enables researchers to explore more downstream connections of a given brain region, and observe the anatomical structure and the function of the downstream circuits over a longer time window. Our work could provide an improved tool for structural and functional studies of neurocircuit.


2015 ◽  
Vol 90 (2) ◽  
pp. 715-724 ◽  
Author(s):  
Shihong Qiu ◽  
Minako Ogino ◽  
Ming Luo ◽  
Tomoaki Ogino ◽  
Todd J. Green

ABSTRACTViruses have various mechanisms to duplicate their genomes and produce virus-specific mRNAs. Negative-strand RNA viruses encode their own polymerases to perform each of these processes. For the nonsegmented negative-strand RNA viruses, the polymerase is comprised of the large polymerase subunit (L) and the phosphoprotein (P). L proteins from members of theRhabdoviridae,Paramyxoviridae, andFiloviridaeshare sequence and predicted secondary structure homology. Here, we present the structure of the N-terminal domain (conserved region I) of the L protein from a rhabdovirus, vesicular stomatitis virus, at 1.8-Å resolution. The strictly and strongly conserved residues in this domain cluster in a single area of the protein. Serial mutation of these residues shows that many of the amino acids are essential for viral transcription but not for mRNA capping. Three-dimensional alignments show that this domain shares structural homology with polymerases from other viral families, including segmented negative-strand RNA and double-stranded RNA (dsRNA) viruses.IMPORTANCENegative-strand RNA viruses include a diverse set of viral families that infect animals and plants, causing serious illness and economic impact. The members of this group of viruses share a set of functionally conserved proteins that are essential to their replication cycle. Among this set of proteins is the viral polymerase, which performs a unique set of reactions to produce genome- and subgenome-length RNA transcripts. In this article, we study the polymerase of vesicular stomatitis virus, a member of the rhabdoviruses, which has served in the past as a model to study negative-strand RNA virus replication. We have identified a site in the N-terminal domain of the polymerase that is essential to viral transcription and that shares sequence homology with members of the paramyxoviruses and the filoviruses. Newly identified sites such as that described here could prove to be useful targets in the design of new therapeutics against negative-strand RNA viruses.


2007 ◽  
Vol 81 (8) ◽  
pp. 4104-4115 ◽  
Author(s):  
Jianrong Li ◽  
John S. Chorba ◽  
Sean P. J. Whelan

ABSTRACT Sinefungin (SIN), a natural S-adenosyl-l-methionine analog produced by Streptomyces griseolus, is a potent inhibitor of methyltransferases. We evaluated the effect of SIN on replication of vesicular stomatitis virus (VSV), a prototype of the nonsegmented negative-strand RNA viruses. The 241-kDa large polymerase (L) protein of VSV methylates viral mRNA cap structures at the guanine-N-7 (G-N-7) and ribose-2′-O (2′-O) positions. By performing transcription reactions in vitro, we show that both methylations are inhibited by SIN and that methylation was more sensitive at the G-N-7 than at 2′-O position. We further show that SIN inhibited growth of VSV in cell culture, reducing viral yield by 50-fold and diminishing plaque size. We isolated eight mutants that were resistant to SIN as judged by their growth characteristics. The SIN-resistant (SINR) viruses contained mutations in the L gene, the promoter for L gene expression provided by the conserved sequence elements of the G-L gene junction and the M gene. Five mutations resulted in amino acid substitutions to conserved regions II/III and VI of the L protein. For each mutant, we examined viral gene expression in cells and cap methylation in vitro. SINR mutants upregulated RNA synthesis in the presence of SIN, which may be responsible for their resistance. We also found that some SINR viruses with L gene mutations were defective in cap methylation in vitro, yet their methylases were less sensitive to SIN inhibition than those of the wild-type parent. These studies show that the VSV methylases are inhibited by SIN, and they define new regions of L protein that affect cap methylation. These studies also provide experimental evidence that inhibition of cap methylases is a potential strategy for development of antiviral therapeutics against nonsegmented negative-strand RNA viruses.


2000 ◽  
Vol 74 (17) ◽  
pp. 7895-7902 ◽  
Author(s):  
E. Brian Flanagan ◽  
L. Andrew Ball ◽  
Gail W. Wertz

ABSTRACT Vesicular stomatitis virus (VSV) is the prototype of the Rhabdoviridae and contains nonsegmented negative-sense RNA as its genome. The 11-kb genome encodes five genes in the order 3′-N-P-M-G-L-5′, and transcription is obligatorily sequential from the single 3′ promoter. As a result, genes at promoter-proximal positions are transcribed at higher levels than those at promoter-distal positions. Previous work demonstrated that moving the gene encoding the nucleocapsid protein N to successively more promoter-distal positions resulted in stepwise attenuation of replication and lethality for mice. In the present study we investigated whether moving the gene for the attachment glycoprotein G, which encodes the major neutralizing epitopes, from its fourth position up to first in the gene order would increase G protein expression in cells and alter the immune response in inoculated animals. In addition to moving the G gene alone, we also constructed viruses having both the G and N genes rearranged. This produced three variant viruses having the orders 3′-G-N-P-M-L-5′ (G1N2), 3′-P-M-G-N-L-5′ (G3N4), and 3′-G-P-M-N-L-5′ (G1N4), respectively. These viruses differed from one another and from wild-type virus in their levels of gene expression and replication in cell culture. The viruses also differed in their pathogenesis, immunogenicity, and level of protection of mice against challenge with wild-type VSV. Translocation of the G gene altered the kinetics and level of the antibody response in mice, and simultaneous reduction of N protein expression reduced replication and lethality for animals. These studies demonstrate that gene rearrangement can be exploited to design nonsegmented negative-sense RNA viruses that have characteristics desirable in candidates for live attenuated vaccines.


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