The PRMT5/WDR77 complex restricts hepatitis E virus replication.

Hepatitis E virus (HEV) is one of the main pathogenic agents of acute hepatitis in the world. The mechanism of HEV replication, especially host factors governing HEV replication is still not clear. Here, using HEV ORF1 trans-complementation cell culture system and HEV replicon system, combining with stable isotope labelling with amino acids in cell culture (SILAC) and mass spectrometry (MS), we aimed to identify the host factors regulating HEV replication. We identified a diversity of host factors associated with HEV ORF1 protein, which were putatively responsible for viral genomic RNA replication, in these two cell culture models. Of note, the protein arginine methyltransferase 5 (PRMT5)/WDR77 complex was identified in both cell culture models as the top hit. Furthermore, we demonstrated that PRMT5 and WDR77 can specifically inhibit HEV replication, but not other viruses such as HCV or SARS-CoV-2, and this inhibition is conserved among different HEV strains and genotypes. Mechanistically, PRMT5/WDR77 can catalyse methylation of ORF1 on its R458, impairing its replicase activity, and virus bearing R458K mutation in ORF1 relieves the restriction of PRMT5/WDR77 accordingly. Taken together, our study promotes more comprehensive understanding of viral infections but also provides therapeutic targets for intervention.

FBXO11 amplifies type I interferon signaling to exert antiviral effects by facilitating the assemble of TRAF3-TBK1-IRF3 complex.

As the key component of host innate antiviral immunity, type I interferons (IFN-Is) exert multiple antiviral effects by inducing hundreds of IFN-stimulated genes. However, the precise mechanism involved in host sensing of IFN-I signaling priming is particularly complex and remains incompletely resolved. This research identified F-box protein 11 (FBXO11), a component of the E3-ubiquitin ligase SKP/Cullin/F-box complex, acted as an important regulator of IFN-I signaling priming and antiviral process against several RNA/DNA viruses. FBXO11 functioned as an essential enhancer of IFN-I signaling by promoting the phosphorylation of TBK1 and IRF3. Mechanistically, FBXO11 facilitated the assembly of TRAF3-TBK1-IRF3 complex by mediating the K63 ubiquitination of TRAF3 in a NEDD8-dependent manner to amplify the activation of IFN-I signaling. Consistently, the NEDD8-activating enzyme inhibitor MLN4921 could act as a blocker for FBXO11-TRAF3-IFN-I axis of signaling. More significantly, examination of clinical samples of chronic hepatitis B virus (HBV) infection and public transcriptome database of severe acute respiratory syndrome coronavirus-2-, HBV-, and hepatitis C virus-infected human samples revealed that FBXO11 expression was positively correlated with the stage of disease course. Taken together, these findings suggest that FBXO11 is an amplifier of antiviral immune responses and might serve as a potential therapeutic target for a number of different viral diseases.

Transcriptome Analysis of Peripheral Blood Mononuclear Cells Response in Patients with Severe COVID-19 Reveals Crucial Genes Regulating Protein Ubiquitination.

BACKGROUND We sought to further our understanding of the biological characteristics underlying severe COVID-19. MATERIAL AND METHODS RNA sequencing (RNA-Seq) analysis was used to evaluate peripheral blood mononuclear cells from 4 patients with severe COVID-19 and 4 healthy controls. We performed gene expression analyses to detect differentially expressed genes (DEGs). Enrichment analyses were performed to identify their molecular processes and signaling pathways, and the protein-protein interaction network was constructed to extract the core gene cluster. The investigation of protein-chemical interactions and regulatory signatures for specific regulatory checkpoints and powerful chemical agents was then conducted for these essential genes. Finally, we used single-cell RNA-Seq analysis from an online platform to show how these genes were expressed differently, depending on the kind of cell. RESULTS A total of 268 DEGs were found. The biological process of protein ubiquitination was later discovered to be highly influenced by the core gene cluster (ITCH, TRIM21, RNF130, FBXO11, UBE2J1, and ASB16) at the transcriptome level. Six transcription factors, FNIC, FOXA1, YY1, GATA2, MET2A, and FOXC1, as well as miRNAs hsa-miR-1-3p and hsa-miR-27a-3p were identified. We found a potent chemical agent, copper sulfate, may regulate protein ubiquitination genes cooperatively, and the genes regulating protein ubiquitination could be expressed highly on the macrophages. CONCLUSIONS Taken together, we suggest that protein ubiquitination is a crucial functional process in patients with severe COVID-19. This study will give a deeper insight into biological characteristics and progression of COVID-19 and facilitate development of novel therapeutics, leading to significant advancements in the COVID-19 pandemic.

PRMT5 epigenetically regulates the E3 ubiquitin ligase ITCH to influence lipid accumulation during mycobacterial infection.

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), triggers enhanced accumulation of lipids to generate foamy macrophages (FMs). This process has been often attributed to the surge in the expression of lipid influx genes with a concomitant decrease in those involved in lipid efflux. Here, we define an Mtb-orchestrated modulation of the ubiquitination of lipid accumulation markers to enhance lipid accretion during infection. We find that Mtb infection represses the expression of the E3 ubiquitin ligase, ITCH, resulting in the sustenance of key lipid accrual molecules viz. ADRP and CD36, that are otherwise targeted by ITCH for proteasomal degradation. In line, overexpressing ITCH in Mtb-infected cells was found to suppress Mtb-induced lipid accumulation. Molecular analyses including loss-of-function and ChIP assays demonstrated a role for the concerted action of the transcription factor YY1 and the arginine methyl transferase PRMT5 in restricting the expression of Itch gene by conferring repressive symmetrical H4R3me2 marks on its promoter. Consequently, siRNA-mediated depletion of YY1 or PRMT5 rescued ITCH expression, thereby compromising the levels of Mtb-induced ADRP and CD36 and limiting FM formation during infection. Accumulation of lipids within the host has been implicated as a pro-mycobacterial process that aids in pathogen persistence and dormancy. In line, we found that perturbation of PRMT5 enzyme activity resulted in compromised lipid levels and reduced mycobacterial survival in mouse peritoneal macrophages (ex vivo) and in a therapeutic mouse model of TB infection (in vivo). These findings provide new insights into the role of PRMT5 and YY1 in augmenting mycobacterial pathogenesis. Thus, we posit that our observations could help design novel adjunct therapies and combinatorial drug regimen for effective anti-TB strategies.