Project description:ChIP sequencing performed on A549 cells following either Mock infection, infection with WT SARS-CoV-02, or infection with SARS-CoV-02 with Orf8 deletion
Project description:ChIP sequencing performed on A549 cells following either Mock infection, infection with WT SARS-CoV-02, or infection with SARS-CoV-02 with Orf8 or ARKSAP deletion
Project description:SARS-CoV-2 infection triggers cytokine-mediated inflammation, leading to a myriad of clinical presentations in COVID19. The SARS-CoV-2 ORF8 is a secreted and rapidly evolving glycoprotein. Patients infected with SARS-CoV-2 ORF8-deleted variants are associated with mild disease outcomes, but the molecular mechanism this behind is unknown. Here, we report that SARS-CoV-2 ORF8 is a viral cytokine that is similar but distinct from interleukin 17A (IL-17A) as it induces stronger and broader human IL-17 receptor (hIL-17R) signaling than IL-17A. ORF8 primarily targeted blood monocytes and induced the heterodimerization of hIL-17RA and hIL-17RC, triggering robust inflammatory response. Transcriptome analysis revealed that besides its activation of the hIL-17R pathway, ORF8 upregulated gene expressions for fibrosis signaling and coagulation dysregulation. A naturally occurring ORF8 L84S variant that highly associated with mild COVID-19 showed reduced hIL-17RA binding and attenuated inflammatory responses. This study discovers SARS-CoV-2 ORF8 as a viral mimicry of IL-17 cytokine to contribute COVID-19 severe inflammation.
Project description:SARS-CoV-2 emerged in China at the end of 2019 and caused the global pandemic of COVID-19, a disease with high morbidity and mortality. While our understanding of this new virus is rapidly increasing, gaps remain in our understanding of how SARS-CoV-2 can effectively suppress host cell antiviral responses. Recent work on other viruses has demonstrated a novel mechanism through which viral proteins can mimic critical regions of human histone proteins. Histone proteins are responsible for governing genome accessibility and their precise regulation is critical for a cell’s ability to control transcription and respond to viral threats. Here, we show that the protein encoded by ORF8 (Orf8) in SARS-CoV-2 functions as a histone mimic of the ARKS motif in histone 3. Orf8 is associated with chromatin, binds to numerous histone-associated proteins, and is itself acetylated within the histone mimic site. Orf8 expression in cells disrupts multiple critical histone post-translational modifications (PTMs) including H3K9ac, H3K9me3, and H3K27me3 and promotes chromatin compaction while Orf8 lacking the histone mimic motif does not. Further, SARS-CoV-2 infection in human cell lines and postmortem patient lung tissue cause these same disruptions to chromatin. However, deletion of the Orf8 gene from SARS-CoV-2 largely blocks its ability to disrupt host-cell chromatin indicating that Orf8 is responsible for these effects. Finally, deletion of the ORF8 gene affects the host-cell transcriptional response to SARS-CoV-2 infection in multiple cell types and decreases the replication of SARS-CoV-2 in human induced pluripotent stem cell-derived lung alveolar type 2 (iAT2) pulmonary cells. These findings demonstrate a novel function for the poorly understood ORF8-encoded protein and a mechanism through which SARS-CoV-2 disrupts host cell epigenetic regulation. Finally, this work provides a molecular basis for the finding that SARS-CoV-2 lacking ORF8 is associated with decreased severity of COVID-19.
Project description:The replication machinery of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is closely associated with the endoplasmic reticulum (ER) in host cells. Activation of the unfolded protein response (UPR) is a strategy hijacked by coronavirus to facilitate its replication and suppress host innate immunity. Here, we identified that many protein disulfide isomerase family members are enriched in the ORF8 interactome, and found that ORF8 protein accumulates in the ER and escapes the degradation system by forming mixed disulfide complexes with ER oxidoreductases. ORF8 induces the activation of three UPR pathways through targeting key UPR components, remodels ER morphology and accelerates protein trafficking.