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IRF-7 mediates robust production of type I IFN via MyD88 of the TLR9 pathway in plasmacytoid dendritic cells (pDCs). Previous in vitro studies using bone marrow-derived dendritic cells lacking either Irf7 or Irf3 have demonstrated that only IRF-3 is required for IFN-β production in the TLR4 pathway. Here, we show that IRF-7 is essential for both type I IFN induction and IL-1β responses via TLR4 in mice. Mice lacking Irf7 were defective in production of both IFN-β and IL-1β, an IFN-β-induced pro-inflammatory cytokine, after LPS challenge. IFN-β production in response to LPS was impaired in IRF-7-deficient macrophages, but not dendritic cells. Unlike pDCs, IRF-7 is activated by the TRIF-, but not MyD88-, dependent pathway via TBK-1 in macrophages after LPS stimulation. Like pDCs, resting macrophages constitutively expressed IRF-7 protein. This basal IRF-7 protein was completely abolished in either Ifnar1−/− or Stat1−/− macrophages, which corresponded with the loss of LPS-stimulated IFN-β induction in these macrophages. These findings demonstrate that macrophage IRF-7 is critical for LPS-induced type I IFN responses, which in turn facilitate IL-1β production in mice.

Prolonged NOD2 ligand engagement induces tolerance and attenuated NOD2 signalling, but the molecular mechanisms leading to this tolerance induction are unclear. Here the authors show that the degradation of a NOD2 adaptor, RIP2, by the E3 ligase ZNRF4 is essential for the down-regulation of NOD2 signalling.

Nature Communications 8 Article number: 15865 (2017); Published: 28 June 2017; Updated: 18 August 2017 The previously published version of this Article contained a line number in the Abstract within the sentence ‘A fraction of RIP2 localizes to the endoplasmic reticulum (ER), where it interacts withZNRF4 under either unstimulated and muramyl dipeptide-stimulated conditions’.

Tight regulation of p53 is essential for maintaining normal cell growth. Here we report that BLIMP1 acts in an autoregulatory feedback loop that controls p53 activity through repression of p53 transcription, p53 binds to and positively regulates BLIMP1, which encodes for a known B cell transcriptional repressor. Knockdown of BLIMP1 by siRNA results in both apoptosis and growth arrest in human colon cancer cells and cell-cycle arrest in primary human fibroblasts. Interestingly, the levels of both p53 mRNA and protein are substantially increased after BLIMP1 depletion, which is accompanied by the induction of p53 target genes. Importantly, the apoptosis induced by BLIMP1 depletion in HCT116 cells is largely abrogated in cells lacking p53 or in cells depleted in p53 by siRNA. We further demonstrate that BLIMP1 binds to the p53 promoter and represses p53 transcription, and this provides a mechanistic explanation for the induction of p53 response in cells depleted of BLIMP1. Hence, suppression of p53 transcription is a crucial function of endogenous BLIMP1 and is essential for normal cell growth. [ABSTRACT FROM AUTHOR]

Type I IFNs induce the expression of IFN-stimulated gene 15 (ISG15) and its conjugation to cellular targets. ISGylation is a multistep process involving IFN-inducible Ube1L, UbcH8, and a yet-to-be identified E3 ligase. Here we report the identification of an IFN-induced HECT-type E3 protein ligase, HERC5/Ceb1, which mediates ISGylation. We also defined a number of proteins modified by ISG15 after IFN triggering or HERC5 overexpression. A reduction in endogenous HERC5 by small interfering RNA inhibition blocks the IFN-induced ISG15 conjugation. Conversely, HERC5 coexpression with Ube1L and UbcH8 induces the ISG15 conjugation in vivo independent of IFN stimulation. A targeted substitution of Cys-994 to Ala in the HECT domain of HERC5 completely abrogates its E3 protein ligase activity. Therefore, this study demonstrates that HERC5/Ceb1 is involved in the conjugation of ISG15 to cellular proteins. [ABSTRACT FROM AUTHOR]

Describes the role of IFN-inducible antiviral protein directly induced by human cytomegalovirus (HCMV). Identification of cytoplasmic antiviral protein; Regulation of the HCMV structural proteins; Mechanism of HCMV to evade the antiviral function.

Presents a report showing that Class II transactivator (CIITA) binds guanosine triphosphate (GTP), and mutations in these motifs decrease its GTP-binding and transactivation activity. Methods; Results; Conclusions.

BACKGROUND: Despite the seriousness of dengue-related disease, with an estimated 50-100 million cases of dengue fever and 250,000-500,000 cases of dengue hemorrhagic fever/dengue shock syndrome each year, a clear understanding of dengue pathogenesis remains elusive. Because of the lack of a disease model in animals and the complex immune interaction in dengue infection, the study of host response and immunopathogenesis is difficult. The development of genomics technology, microarray and high throughput quantitative PCR have allowed researchers to study gene expression changes on a much broader scale. We therefore used this approach to investigate the host response in dengue virus-infected cell lines and in patients developing dengue fever. METHODOLOGY/PRINCIPAL FINDINGS: Using microarray and high throughput quantitative PCR method to monitor the host response to dengue viral replication in cell line infection models and in dengue patient blood samples, we identified differentially expressed genes along three major pathways; NF-kappaB initiated immune responses, type I interferon (IFN) and the ubiquitin proteasome pathway. Among the most highly upregulated genes were the chemokines IP-10 and I-TAC, both ligands of the CXCR3 receptor. Increased expression of IP-10 and I-TAC in the peripheral blood of ten patients at the early onset of fever was confirmed by ELISA. A highly upregulated gene in the IFN pathway, viperin, was overexpressed in A549 cells resulting in a significant reduction in viral replication. The upregulation of genes in the ubiquitin-proteasome pathway prompted the testing of proteasome inhibitors MG-132 and ALLN, both of which reduced viral replication. CONCLUSION/SIGNIFICANCE: Unbiased gene expression analysis has identified new host genes associated with dengue infection, which we have validated in functional studies. We showed that some parts of the host response can be used as potential biomarkers for the disease while others can be used to control dengue viral replication, thus representing viable targets for drug therapy.

Transcriptional elongation by RNA polymerase II (Pol II) is regulated by positive transcription elongation factor b (P-TEFb) in association with bromodomain-containing protein 4 (BRD4). We used genome-wide chromatin immunoprecipitation sequencing in primary human CD4+ T cells to reveal that BRD4 co-localizes with Ser-2-phosphorylated Pol II (Pol II Ser-2) at both enhancers and promoters of active genes. Disruption of bromodomain-histone acetylation interactions by JQ1, a smallmolecule bromodomain inhibitor, resulted in decreased BRD4 binding, reduced Pol II Ser-2, and reduced expression of lineage- specific genes in primary human CD4+ T cells. A large number of JQ1-disrupted BRD4 binding regions exhibited diacetylated H4 (lysine 5 and -8) and H3K27 acetylation (H3K27ac), which correlated with the presence of histone acetyltransferases and deacetylases. Genes associated with BRD4/H3K27ac co-occupancy exhibited significantly higher activity than those associated with H3K27ac or BRD4 binding alone. Comparison of BRD4 binding in T cells and in human embryonic stem cells revealed that enhancerBRD4binding sites were predominantly lineage-specific. Our findings suggest that BRD4-driven Pol II phosphorylation at serine 2 plays an important role in regulating lineage-specific gene transcription in human CD4+ T cells [ABSTRACT FROM AUTHOR]