Project description:In Hawaii, a rapidly-evolving mutation in the field cricket Teleogryllus oceanicus silences males by interfering with the development of sound-producing structures on their forewings. The mutation is called flatwing (fw), and it persists because of natural selection imposed by an acoustically-orienting parasitoid. We examined gene expression differences between wild-type and mutant crickets, focusing on juvenile wing buds. We profiled mRNA expression levels using RNA-seq, and characterized the wing bud proteome using quantitative mass spectrometry. Accessing protein expression profiles under the same experimental conditions enabled us to test correspondence between the two ‘omic levels.
Project description:In Hawaii, a rapidly-evolving mutation in the field cricket Teleogryllus oceanicus silences males by interfering with the development of sound-producing structures on their forewings. The mutation is called flatwing (fw), and it persists because of natural selection imposed by an acoustically-orienting parasitoid. We examined gene expression differences between wild-type and mutant crickets, focusing on juvenile wing buds. We profiled mRNA expression levels using RNA-seq, and characterized the wing bud proteome using quantitative mass spectrometry.
Project description:The dicistrovirus is a positive-strand single-stranded RNA virus that possesses two internal ribosome entry sites (IRES) that direct translation of distinct open reading frames encoding the viral structural and nonstructural proteins. Through an unusual mechanism, the intergenic region (IGR) IRES responsible for viral structural protein expression mimics a tRNA to directly recruit the ribosome and set the ribosome into translational elongation. In this study, we explored the mechanism of host translational shutoff in Drosophila S2 cells infected by the dicistrovirus, cricket paralysis virus (CrPV). CrPV infection of S2 cells results in host translational shutoff concomitant with an increase in viral protein synthesis. CrPV infection resulted in the dissociation of eukaryotic translation initiation factor 4G (eIF4G) and eIF4E early in infection and the induction of deIF2alpha phosphorylation at 3 h postinfection, which lags after the initial inhibition of host translation. Forced dephosphorylation of deIF2alpha by overexpression of dGADD34, which activates protein phosphatase I, did not prevent translational shutoff nor alter virus production, demonstrating that deIF2alpha phosphorylation is dispensable for host translational shutoff. However, premature induction of deIF2alpha phosphorylation by thapsigargin treatment early in infection reduced viral protein synthesis and replication. Finally, translation mediated by the 5' untranslated region (5'UTR) and the IGR IRES were resistant to impairment of eIF4F or eIF2 in translation extracts. These results support a model by which the alteration of the deIF4F complex contribute to the shutoff of host translation during CrPV infection, thereby promoting viral protein synthesis via the CrPV 5'UTR and IGR IRES.
Project description:Insect viruses have evolved strategies to control the host RNAi antiviral defense mechanism. In nature, Drosophila melanogaster C virus (DCV) infection causes low mortality and persistent infection, whereas the closely related cricket paralysis virus (CrPV) causes a lethal infection. We show that these viruses use different strategies to modulate the host RNAi defense machinery. The DCV RNAi suppressor (DCV-1A) binds to long double-stranded RNA and prevents processing by Dicer2. In contrast, the CrPV suppressor (CrPV-1A) interacts with the endonuclease Argonaute 2 (Ago2) and inhibits its activity without affecting the microRNA (miRNA)-Ago1-mediated silencing. We examined the link between viral RNAi suppressors and the outcome of infection using recombinant Sindbis viruses encoding either CrPV-1A or DCV-1A. Flies infected with Sindbis virus expressing CrPV-1A showed a marked increase in virus production, spread and mortality. In contrast, Sindbis pathogenesis was only modestly increased by expression of DCV- 1A. We conclude that RNAi suppressors function as virulence factors in insects and can target the Drosophila RNAi pathway at different points.
Project description:RNA interference (RNAi) functions as the major host antiviral defense in insects, while less is understood about how to utilize antiviral RNAi in controlling viral infection in insects. Enoxacin belongs to the family of synthetic antibacterial compounds based on a fluoroquinolone skeleton that has been previously found to enhance RNAi in mammalian cells. In this study, we showed that enoxacin efficiently inhibited viral replication of Drosophila C virus (DCV) and Cricket paralysis virus (CrPV) in cultured Drosophila cells. Enoxacin promoted the loading of Dicer-2-processed virus-derived siRNA into the RNA-induced silencing complex, thereby enhancing antiviral RNAi response in infected cells. Moreover, enoxacin treatment elicited an RNAi-dependent in vivo protective efficacy against DCV or CrPV challenge in adult fruit flies. In addition, enoxacin also inhibited replication of flaviviruses, including Dengue virus and Zika virus, in Aedes mosquito cells in an RNAi-dependent manner. Together, our findings demonstrated that enoxacin can enhance RNAi in insects, and enhancing RNAi by enoxacin is an effective antiviral strategy against diverse viruses in insects, which may be exploited as a broad-spectrum antiviral agent to control vector transmission of arboviruses or viral diseases in insect farming.
Project description:There were important gaps in our knowledge of Israeli acute paralysis virus (IAPV), when IAPV was tightly linked to bee Colony Collapse Disorder (CCD), the mysterious disease that, starting in 2006-2007, has been wiping out honey bees in the US. To fill in these gaps we studied the molecular basis of transmission, pathogenesis, and genetic diversity of IAPV infection in honey bees. We investigated the impact of IAPV infection on colony losses and host transcriptional response to IAPV infections, and exploited the potential of RNAi-based strategies for treating viral diseases in honey bees. Our study clearly shows that IAPV has become established as a persistent infection and is highly prevalent in the honey bee population. The existence of both horizontal and vertical transmission pathways of the virus likely accounts for the high prevalence of IAPV in bees. While IAPV is probably not the only culprit responsible for CCD, its ability to cause increased mortality in honey bees is firmly demonstrated. The phenotypic differences in pathology among different strains of IAPV may be due to their high level of standing genetic variation. The JAK-STAT pathway, along with other signaling events such as mTOR and MAPK pathways, likely involves honey bees’ antiviral immune responses to the IAPV infection. The identification of IAPV-encoded putative suppressor of RNAi and evidence that silencing the RNAi suppressor led to a significant reduction in IAPV replication in infected bees illustrates the therapeutic potential of targeting viral suppressor protein to reduce virus replication. Our study gives direction for developing strategies to reduce colony losses due to viral diseases. Adult worker bees and brood were collected from colonies that were declining and identified with IAPV infections and its control with 6 replications per group.
Project description:Stress granules (SGs) are cytosolic ribonucleoprotein aggregates that are induced during cellular stress. Several viruses modulate SG formation, suggesting that SGs have an impact on virus infection. However, the mechanisms and impact of modulating SG assembly in infected cells are not completely understood. In this study, we identify the dicistrovirus cricket paralysis virus 1A (CrPV-1A) protein that functions to inhibit SG assembly during infection. Moreover, besides inhibiting RNA interference, CrPV-1A also inhibits host transcription, which indirectly modulates SG assembly. Thus, CrPV-1A is a multifunctional protein. We identify a key R146A residue that is responsible for these effects, and mutant CrPV(R146A) virus infection is attenuated in Drosophila melanogaster S2 cells and adult fruit flies and results in increased SG formation. Treatment of CrPV(R146A)-infected cells with actinomycin D, which represses transcription, restores SG assembly suppression and viral yield. In summary, CrPV-1A modulates several cellular processes to generate a cellular environment that promotes viral translation and replication.IMPORTANCE RNA viruses encode a limited set of viral proteins to modulate an array of cellular processes in order to facilitate viral replication and inhibit antiviral defenses. In this study, we identified a viral protein, called CrPV-1A, within the dicistrovirus cricket paralysis virus that can inhibit host transcription, modulate viral translation, and block a cellular process called stress granule assembly. We also identified a specific amino acid within CrPV-1A that is important for these cellular processes and that mutant viruses containing mutations of CrPV-1A attenuate virus infection. We also demonstrate that the CrPV-1A protein can also modulate cellular processes in human cells, suggesting that the mode of action of CrPV-1A is conserved. We propose that CrPV-1A is a multifunctional, versatile protein that creates a cellular environment in virus-infected cells that permits productive virus infection.
Project description:The cricket paralysis virus internal ribosome entry site (CrPV-IRES) is a folded structure in a viral mRNA that allows initiation of translation in the absence of any host initiation factors. By using recent advances in single-particle electron cryomicroscopy, we have solved the structure of CrPV-IRES bound to the ribosome of the yeast Kluyveromyces lactis in both the canonical and rotated states at overall resolutions of 3.7 and 3.8 Å, respectively. In both states, the pseudoknot PKI of the CrPV-IRES mimics a tRNA/mRNA interaction in the decoding center of the A site of the 40S ribosomal subunit. The structure and accompanying factor-binding data show that CrPV-IRES binding mimics a pretranslocation rather than initiation state of the ribosome. Translocation of the IRES by elongation factor 2 (eEF2) is required to bring the first codon of the mRNA into the A site and to allow the start of translation.
Project description:Viruses are classically characterized as being either enveloped or nonenveloped depending on the presence or absence of a lipid bi-layer surrounding their proteinaceous capsid. In recent years, many studies have challenged this view by demonstrating that some nonenveloped viruses (e.g. hepatitis A virus) can acquire an envelope during infection by hijacking host cellular pathways. In this study, we examined the role of exosome-like vesicles (ELVs) during infection of Drosophilia melanogaster S2 cells by Cricket paralysis virus (CrPV). Utilizing quantitative proteomics, we demonstrated that ELVs can be isolated from both mock- and CrPV-infected S2 cells that contain distinct set of proteins compared to the cellular proteome. Moreover, 40 proteins increased in abundance in ELVs derived from CrPV-infected cells compared to mock, suggesting specific factors associate with ELVs during infection. Interestingly, peptides from CrPV capsid proteins (ORF2) and viral RNA were detected in ELVs from infected cells. Finally, ELVs from CrPV-infected cells are infectious suggesting that CrPV may hijack ELVs to acquire an envelope during infection of S2 cells. This study further demonstrates the diverse strategies of nonenveloped viruses from invertebrates to vertebrates to acquire an envelope in order to evade the host response or facilitate transmission.