Biology subjects

Bonner, J.

Publications and source records attributed to Bonner, J..

3 recordsLinked to original sources

bioRxiv2025

Nonsense-mediated decay controls a negative feedback loop in innate immune sensing

Nonsense-mediated decay (NMD) is an mRNA decay pathway which degrades potential harmful transcripts that contain premature termination codons. However, NMDs importance also extends to the control of isoform abundance under physiological conditions. During viral infection, NMD is inhibited through numerous mechanisms; however, NMD has been shown to have both antiviral as well as proviral activities, raising further questions into the role and control of NMD during viral infection. These observations have led us to investigate the potential involvement of NMD in dsRNA sensing as a mechanism that might explain these discrepancies. Using EIF4A2 exon 10B inclusion as an example of AS-NMD isoform accumulating during viral infection, we show that dsRNA sensing inhibits NMD. This effect is correlated with translational blockade and is driven primarily by RNaseL activation, and by PKR in the absence of RNaseL activation. Surprisingly, NMD inhibition limits the induction of IFN-{beta} as well as interferon-stimulated genes, and this effect is upstream of IRF3 phosphorylation and translocation to the nucleus. NMD inhibition also decreases PKR and RNaseL activation as well as PIC-mediated cell death by decreasing the dsRNA content, suggesting NMD directly controls dsRNA sensing by controlling the dsRNA load. Therefore, inhibition of NMD upon dsRNA sensing provides a negative feedback loop that contributes to shaping the innate immune sensing pathways. SIGNIFICANCENonsense-mediated decay (NMD) is a translation-dependent mRNA decay pathway that plays an important role in shaping the transcriptome. In this manuscript, we show that dsRNA sensing, as is typical during viral infection, inhibits NMD mainly through the translational inhibition caused by RNaseL activation. This NMD inhibition forms a negative-feedback loop that limits dsRNA sensing, thus preventing overactivation of dsRNA-mediated pathways. These findings contribute to a better understanding of the molecular mechanisms that limit antiviral responses as well as inflammation and inform the critical role that mRNA processes plays in innate immunity.

immunology↗

bioRxiv2024

Divergence in poxvirus-encoded E3-like proteins can dictate poxvirus activation of cellular necroptosis

Poxviruses encode a plethora of proteins to modulate diverse cellular responses against viruses. Poxvirus-encoded E3-like proteins are multifunctional, regulating diverse cellular antiviral responses. The canonical Vaccinia E3-like proteins have two domains: an N-terminal Z-form nucleic acid binding domain (Z-BD) and a C-terminal double-stranded RNA binding domain (dsRNA-BD)-.Using protein sequence and structural homology modeling, we identified the presence of dsRNA- BD-containing proteins in all the poxviruses except Avipoxviruses, Salmon poxvirus and Entemopoxviruses. However, the acquisition of these proteins likely happened under three distinct events. Using structural homology modeling and FATCAT score, we can classify E3-like proteins in three distinct categories: i) the E3-like proteins with highly conserved dsRNA-BD but with or without the N-terminal domain, present in most poxviruses; ii) unconventional E3-like proteins with highly diverged dsRNA-BD, present in Macropoxvirus and Molluscipoxvirus and iii) E3-like protein with dsRNA-BD that may have different origin present in Crocodilepoxvirus.12-52-6 Members of Leporipoxvirus, Waddenpoxvirus, Cetaceanpoxvirus, and selected members of Orthopoxvirus contain E3-like proteins missing the N-terminal Z-BD required for necroptosis inhibition. Additionally, using Alphafold, we show that the Z-BD of Chordopoxviruses E3-like proteins is structurally more variable than the ds-RNA binding domain. Compared to members of Orthopoxviruses-Vaccinia virus (VACV) and Cowpox virus (CPXV) that have been shown to inhibit necroptosis and contain an N-terminus Z-BD of the canonical E3 protein, our results show that members of leporipoxviruses induce necroptosis in human and mouse necroptosis competent cell lines. Furthermore, myxoma virus (MYXV) infection activates RIP1 and RIP3-mediated necroptosis in both human and mouse necroptosis-competent cells. These data suggest that Leporipoxviruses lack countermeasures to necroptosis compared to Orthopoxviruses that encode multiple key regulators of necroptosis, possibly due to a lack of selective pressure within the viral host species (Lagomorphs). Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/627069v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@132ce9borg.highwire.dtl.DTLVardef@9a459borg.highwire.dtl.DTLVardef@4fc88dorg.highwire.dtl.DTLVardef@1f7ac6c_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2024

Regulation of Necroptosis and the Type Interferon Response by Monkeypox/mpox Virus.

Monkeypox/mpox virus (MPXV) has re-emerged as the most important orthopoxvirus infection of humans. Despite being pathogenic, it contains a natural truncation at the N-terminus of its homologue of the vaccinia virus (VACV) innate immune evasion protein, E3, leading to the loss of the first 37 amino acids. Our previous data have shown that VACV E3 protein is required for interferon-resistance of VACV. The N-terminal Z-nucleic acid binding domain is necessary to inhibit induction of necroptosis, as VACV containing an N-terminal deletion (VACV-E3L{Delta}37N) undergoes rapid ZBP1-dependent necroptotic cell death, through activation of RIPK3, and subsequent phosphorylation and trimerization of the executioner of necroptosis, MLKL. Despite lacking parts of the N-terminus, MPXV has evolved ways in circumventing necroptotic cell death in mouse L929 cells. Our data shows that MPXV infection inhibits phosphorylation of MLKL and does not lead to MLKL trimerization, nor cell death. We show that MPXV inhibits necroptosis in two steps: by degrading RIPK3 through either a caspase-dependent pathway or through the "viral inducer of RIPK3 degradation" (vIRD) and by inhibiting MLKL aggregation. Additionally, MPXV shows interferon sensitivity that is fully ZBP1- and RIPK3- and MLKL-dependent, but independent of necroptosis. Addition of a pancaspase inhibitor (zVAD), or a proteasome inhibitor (MLN4924) does not increase cell death but leads to an increase in interferon sensitivity comparable to VACV-E3L{Delta}37N. Thus, treatment with an interferon inducer along with a pancaspase or proteasome inhibitor could potentially be a beneficial treatment against MPXV infections.

molecular biology↗