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Non-structural proteins of arthropod-borne bunyaviruses: roles and functions.

Eifan S, Schnettler E, Dietrich I, Kohl A, Blomström AL - Viruses (2013)

Bottom Line: Many bunyaviruses are arthropod-borne, so-called arboviruses.Depending on the genus, bunyaviruses encode, in addition to the RNA-dependent RNA polymerase and the different structural proteins, one or several non-structural proteins.In this review, we will summarize current knowledge and understanding of insect-borne bunyavirus non-structural protein function(s) in vertebrate, plant and arthropod.

View Article: PubMed Central - PubMed

Affiliation: Department of Botany and Microbiology, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia. anne-lie.blomstrom@slu.se.

ABSTRACT
Viruses within the Bunyaviridae family are tri-segmented, negative-stranded RNA viruses. The family includes several emerging and re-emerging viruses of humans, animals and plants, such as Rift Valley fever virus, Crimean-Congo hemorrhagic fever virus, La Crosse virus, Schmallenberg virus and tomato spotted wilt virus. Many bunyaviruses are arthropod-borne, so-called arboviruses. Depending on the genus, bunyaviruses encode, in addition to the RNA-dependent RNA polymerase and the different structural proteins, one or several non-structural proteins. These non-structural proteins are not always essential for virus growth and replication but can play an important role in viral pathogenesis through their interaction with the host innate immune system. In this review, we will summarize current knowledge and understanding of insect-borne bunyavirus non-structural protein function(s) in vertebrate, plant and arthropod.

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Related in: MedlinePlus

Tospovirus NSs interaction with the RNAi pathway in plants. Upon infection of tospovirus in plants siRNA/viRNA pathways are activated as a response to the viral dsRNA. This pathway activation leads to specific cleavage of viral RNA. The miRNA pathway is activated by expression of endogenous primary miRNA transcripts and can lead to translational inhibition and cleavage of host mRNA. This figure illustrates where the NSs of different tospoviruses act in order to interfere with these small RNA pathways of the host.
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viruses-05-02447-f004: Tospovirus NSs interaction with the RNAi pathway in plants. Upon infection of tospovirus in plants siRNA/viRNA pathways are activated as a response to the viral dsRNA. This pathway activation leads to specific cleavage of viral RNA. The miRNA pathway is activated by expression of endogenous primary miRNA transcripts and can lead to translational inhibition and cleavage of host mRNA. This figure illustrates where the NSs of different tospoviruses act in order to interfere with these small RNA pathways of the host.

Mentions: NSs proteins of some tospoviruses have been shown to interfere with the antiviral RNAi or RNA silencing response in plants (TSWV, tomato yellow ring virus [TYRV]) [94,95,96] and different arthropod cells (TSWV in drosophila, tick and mosquito) [27,95,97]. Similar results have been reported for the NS3 proteins of the tenuiviruses, rice hoja blanca virus and rice stripe virus, which share high phylogenetic similarities with tospoviruses and encode the NS3 ORF at an analogous position in the viral genome [94,98,99,100,101]. The RNAi response is a sequence specific breakdown mechanism, which can be divided into different pathways dependent on the small RNA molecules involved. The small interfering (si)RNA pathway is known to act antivirally in plants and arthropods [102,103]. It is induced by exogenous long dsRNA molecules that are recognized and cleaved into siRNA molecules. The siRNAs (or viRNAs) are taken up by a multi-protein complex that uses one strand of the siRNA as a guide to find complementary single stranded RNA, which is cleaved and degraded after recognition (Figure 4). In contrast, the micro (mi)RNA pathway is induced by exogenous single stranded RNAs that fold back to form a stem loop structure, and upon cleavage result in miRNA duplexes. One strand of these duplexes is used as a guide to find (partially) complementary sequences, resulting in target cleavage or translational inhibition (Figure 4). The miRNA pathway is present in a variety of organisms and used to regulate gene expression, mainly during development. The antiviral potential of the siRNA pathway is well established in plants and arthropods and, with regards to arbovirus vectors, in particular mosquitoes [104].


Non-structural proteins of arthropod-borne bunyaviruses: roles and functions.

Eifan S, Schnettler E, Dietrich I, Kohl A, Blomström AL - Viruses (2013)

Tospovirus NSs interaction with the RNAi pathway in plants. Upon infection of tospovirus in plants siRNA/viRNA pathways are activated as a response to the viral dsRNA. This pathway activation leads to specific cleavage of viral RNA. The miRNA pathway is activated by expression of endogenous primary miRNA transcripts and can lead to translational inhibition and cleavage of host mRNA. This figure illustrates where the NSs of different tospoviruses act in order to interfere with these small RNA pathways of the host.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3814597&req=5

viruses-05-02447-f004: Tospovirus NSs interaction with the RNAi pathway in plants. Upon infection of tospovirus in plants siRNA/viRNA pathways are activated as a response to the viral dsRNA. This pathway activation leads to specific cleavage of viral RNA. The miRNA pathway is activated by expression of endogenous primary miRNA transcripts and can lead to translational inhibition and cleavage of host mRNA. This figure illustrates where the NSs of different tospoviruses act in order to interfere with these small RNA pathways of the host.
Mentions: NSs proteins of some tospoviruses have been shown to interfere with the antiviral RNAi or RNA silencing response in plants (TSWV, tomato yellow ring virus [TYRV]) [94,95,96] and different arthropod cells (TSWV in drosophila, tick and mosquito) [27,95,97]. Similar results have been reported for the NS3 proteins of the tenuiviruses, rice hoja blanca virus and rice stripe virus, which share high phylogenetic similarities with tospoviruses and encode the NS3 ORF at an analogous position in the viral genome [94,98,99,100,101]. The RNAi response is a sequence specific breakdown mechanism, which can be divided into different pathways dependent on the small RNA molecules involved. The small interfering (si)RNA pathway is known to act antivirally in plants and arthropods [102,103]. It is induced by exogenous long dsRNA molecules that are recognized and cleaved into siRNA molecules. The siRNAs (or viRNAs) are taken up by a multi-protein complex that uses one strand of the siRNA as a guide to find complementary single stranded RNA, which is cleaved and degraded after recognition (Figure 4). In contrast, the micro (mi)RNA pathway is induced by exogenous single stranded RNAs that fold back to form a stem loop structure, and upon cleavage result in miRNA duplexes. One strand of these duplexes is used as a guide to find (partially) complementary sequences, resulting in target cleavage or translational inhibition (Figure 4). The miRNA pathway is present in a variety of organisms and used to regulate gene expression, mainly during development. The antiviral potential of the siRNA pathway is well established in plants and arthropods and, with regards to arbovirus vectors, in particular mosquitoes [104].

Bottom Line: Many bunyaviruses are arthropod-borne, so-called arboviruses.Depending on the genus, bunyaviruses encode, in addition to the RNA-dependent RNA polymerase and the different structural proteins, one or several non-structural proteins.In this review, we will summarize current knowledge and understanding of insect-borne bunyavirus non-structural protein function(s) in vertebrate, plant and arthropod.

View Article: PubMed Central - PubMed

Affiliation: Department of Botany and Microbiology, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia. anne-lie.blomstrom@slu.se.

ABSTRACT
Viruses within the Bunyaviridae family are tri-segmented, negative-stranded RNA viruses. The family includes several emerging and re-emerging viruses of humans, animals and plants, such as Rift Valley fever virus, Crimean-Congo hemorrhagic fever virus, La Crosse virus, Schmallenberg virus and tomato spotted wilt virus. Many bunyaviruses are arthropod-borne, so-called arboviruses. Depending on the genus, bunyaviruses encode, in addition to the RNA-dependent RNA polymerase and the different structural proteins, one or several non-structural proteins. These non-structural proteins are not always essential for virus growth and replication but can play an important role in viral pathogenesis through their interaction with the host innate immune system. In this review, we will summarize current knowledge and understanding of insect-borne bunyavirus non-structural protein function(s) in vertebrate, plant and arthropod.

Show MeSH
Related in: MedlinePlus