Project description:The importance of unanchored Ub in innate immunity has been shown only for a limited number of unanchored Ub-interactors. We investigated what additional cellular factors interact with unanchored Ub and whether unanchored Ub plays a broader role in innate immunity. To identify unanchored Ub-interacting factors from murine lungs, we used His-tagged recombinant poly-Ub chains as bait. These chains were mixed with lung tissue lysates and protein complexes were isolated with Ni-NTA beads. Sample elutions were subjected to mass spectrometry (LC-MSMS) analysis.
Project description:Host innate immune defences play a critical role in restricting the intracellular propagation and pathogenesis of invading viral pathogens. Here we show that the histone H3.3 chaperone HIRA (histone cell cycle regulator) associates with promyelocytic leukaemia nuclear bodies (PML-NBs) to stimulate the induction of innate immune defences against herpes simplex virus 1 (HSV-1) infection. Following the activation of innate immune signalling, HIRA localized at PML-NBs in a Janus-Associated Kinase (JAK), Cyclin Dependent Kinase (CDK), and Sp100-dependent manner. RNA-seq analysis revealed that HIRA promoted the transcriptional upregulation of a broad repertoire of host genes that regulate innate immunity to HSV-1 infection, including those involved in MHC-I antigen presentation, cytokine signalling, and interferon stimulated gene (ISG) expression. ChIP-seq analysis revealed that PML, the principle scaffolding protein of PML-NBs, was required for the enrichment of HIRA onto ISGs, identifying a role for PML in the HIRA-dependent regulation of innate immunity to virus infection. Our data identifies independent roles for HIRA in the intrinsic silencing of viral gene expression and the induction of innate immune defences to restrict the initiation and propagation of HSV-1 infection, respectively. These intracellular host defences are antagonized by the HSV-1 ubiquitin ligase ICP0, which disrupts the stable recruitment of HIRA to infecting viral genomes and PML-NBs at spatiotemporally distinct phases of infection. Our study highlights the importance of histone chaperones to regulate multiple phases of intracellular immunity to virus infection, findings that are likely to be highly pertinent in the cellular restriction of many clinically important viral pathogens.
Project description:Innate immunity is a highly reactive response aiming at clearing pathogens. Abnormal induction of innate immune genes can lead to deleterious consequences to the host. However, little is known about the intrinsic signaling pathway that prohibits constitutive activation of innate immunity. Here using fruit flies, we profile the microRNA targetomes in young and aged animals. We demonstrate FoxO, and miR-252 inhibit spontaneous induction of innate immunity by repressing Daw. We further determine the signaling cascade by which Daw causes the reduction of Atg8a-mediated selective autophagy on kenny protein, which in turn activates Relish protein and consequential upregulation of innate immune genes. Finally, while aging leads to a decline in FOXO signaling activity concomitant with a progressive induction of innate immune genes, transgenic increase of FoxO, miR-252, and Atg8a in wild-type Drosophila promotes longevity and mitigates the expression of age-onset innate immune genes. Together, we propose that FoxO and miR-252 define a pro-survival mechanism by inhibiting constitutive innate immunity.
Project description:Hepatitis C virus (HCV) infection is a major cause of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. HCV can be sensed by host innate immunity to induce expression of interferons (IFNs) and a number of antiviral effectors. HCV-encoded NS3/4 serine protease can subvert host innate immune responses by cleaving MAVS, a critical adaptor protein in the RLR-mediated IFN signaling. To study innate immunity in the context of HCV infection, we constructed Huh7-MAVSR cells which express a mutant MAVS resistant to NS3/4A cleavage. HCV infection induces robust IFN response in Huh7-MAVSR cells, providing a cellular system to study antiviral innate immune response against HCV infection. To analyze host innate antiviral effectors against HCV infection, we performed an mRNA microarray analysis in the HCV-infected Huh7-MAVSR cells.