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Mechanistic Insight into the Host Transcription Inhibition Function of Rift Valley Fever Virus NSs and Its Importance in Virulence
- Source :
- PLoS Neglected Tropical Diseases, Vol 10, Iss 10, p e0005047 (2016), PLOS Neglected Tropical Diseases, PLoS Neglected Tropical Diseases
- Publication Year :
- 2016
- Publisher :
- Public Library of Science (PLoS), 2016.
-
Abstract
- Rift Valley fever virus (RVFV), a member of the genus Phlebovirus within the family Bunyaviridae, causes periodic outbreaks in livestocks and humans in countries of the African continent and Middle East. RVFV NSs protein, a nonstructural protein, is a major virulence factor that exhibits several important biological properties. These include suppression of general transcription, inhibition of IFN-β promoter induction and degradation of double-stranded RNA-dependent protein kinase R. Although each of these biological functions of NSs are considered important for countering the antiviral response in the host, the individual contributions of these functions towards RVFV virulence remains unclear. To examine this, we generated two RVFV MP-12 strain-derived mutant viruses. Each carried mutations in NSs that specifically targeted its general transcription inhibition function without affecting its ability to degrade PKR and inhibit IFN-β promoter induction, through its interaction with Sin3-associated protein 30, a part of the repressor complex at the IFN-β promoter. Using these mutant viruses, we have dissected the transcription inhibition function of NSs and examined its importance in RVFV virulence. Both NSs mutant viruses exhibited a differentially impaired ability to inhibit host transcription when compared with MP-12. It has been reported that NSs suppresses general transcription by interfering with the formation of the transcription factor IIH complex, through the degradation of the p62 subunit and sequestration of the p44 subunit. Our study results lead us to suggest that the ability of NSs to induce p62 degradation is the major contributor to its general transcription inhibition property, whereas its interaction with p44 may not play a significant role in this function. Importantly, RVFV MP-12-NSs mutant viruses with an impaired general transcription inhibition function showed a reduced cytotoxicity in cell culture and attenuated virulence in young mice, compared with its parental virus MP-12, highlighting the contribution of NSs-mediated general transcription inhibition towards RVFV virulence.<br />Author Summary Rift Valley fever virus (RVFV) has a significant impact on the livestock industry because of its high mortality rate in young ruminants and causation of a high abortion rate in pregnant animals. Human RVFV infections generally manifest as self-limiting and non-fatal illnesses. However, a small percentage of patients develop encephalitis, vision loss and hemorrhagic fever with a high mortality rate. Currently, there is no commercially available vaccine for human use or effective antiviral drug for RVFV treatment. The non-structural protein NSs is a major virulence factor of RVFV, which mediates suppression of host general transcription, inhibition of IFN-β transcription and degradation of PKR, to block host antiviral responses. To examine the contribution of host transcription inhibition to RVFV virulence, we generated RVFV MP-12 strain-derived mutants that have attenuated inhibitory activity on host transcription due to amino acid mutations in NSs. The mutant viruses showed attenuated cytotoxicity in cell culture and attenuated virulence in young mice, demonstrating the contribution of NSs-mediated host transcription inhibition to the virulence of RVFV.
- Subjects :
- RNA viruses
0301 basic medicine
Rift Valley Fever
Transcription, Genetic
Physiology
Viral Nonstructural Proteins
Biochemistry
Virulence factor
Mice
Transcription (biology)
Immune Physiology
Chlorocebus aethiops
Bunyaviruses
Promoter Regions, Genetic
Pathology and laboratory medicine
2. Zero hunger
Genetics
Immune System Proteins
Messenger RNA
lcsh:Public aspects of medicine
Microbial Mutation
Animal Models
Medical microbiology
Precipitation Techniques
3. Good health
Nucleic acids
Infectious Diseases
Host-Pathogen Interactions
Viruses
Pathogens
Research Article
lcsh:Arctic medicine. Tropical medicine
Virulence Factors
lcsh:RC955-962
DNA transcription
Immunology
Repressor
Virulence
Mouse Models
Biology
Research and Analysis Methods
Microbiology
Antibodies
03 medical and health sciences
Model Organisms
Virology
Animals
Humans
Immunoprecipitation
Vero Cells
Transcription factor
Medicine and health sciences
Biology and life sciences
Organisms
Viral pathogens
Public Health, Environmental and Occupational Health
Proteins
lcsh:RA1-1270
Interferon-beta
Rift Valley fever virus
Protein kinase R
Viral Replication
Microbial pathogens
030104 developmental biology
Transcription Factor TFIIH
Viral replication
Mutation
RNA
Gene expression
Transcription Factors
Subjects
Details
- Language :
- English
- ISSN :
- 19352735 and 19352727
- Volume :
- 10
- Issue :
- 10
- Database :
- OpenAIRE
- Journal :
- PLoS Neglected Tropical Diseases
- Accession number :
- edsair.doi.dedup.....28ca8f2867431032de170bcf13d98436