Enterovirus 71 (EV71) is a human pathogen that induces hand, foot, and mouth disease and fatal neurological diseases. Immature or impaired immunity is thought to associate with increased morbidity and mortality. In a murine model, EV71 does not facilitate the production of type I interferon (IFN) that plays a critical role in the first-line defense against viral infection. Administration of a neutralizing antibody to IFN-␣/␤ exacerbates the virus-induced disease. However, the molecular events governing this process remain elusive. Here, we report that EV71 suppresses the induction of antiviral immunity by targeting the cytosolic receptor retinoid acid-inducible gene I (RIG-I). In infected cells, EV71 inhibits the expression of IFN-␤, IFN-stimulated gene 54 (ISG54), ISG56, and tumor necrosis factor alpha. Among structural and nonstructural proteins encoded by EV71, the 3C protein is capable of inhibiting IFN-␤ activation by virus and RIG-I. Nevertheless, EV71 3C exhibits no inhibitory activity on MDA5. Remarkably, when expressed in mammalian cells, EV71 3C associates with RIG-I via the caspase recruitment domain. This precludes the recruitment of an adaptor IPS-1 by RIG-I and subsequent nuclear translocation of interferon regulatory factor 3. An R84Q or V154S substitution in the RNA binding motifs has no effect. An H40D substitution is detrimental, but the protease activity associated with 3C is dispensable. Together, these results suggest that inhibition of RIG-I-mediated type I IFN responses by the 3C protein may contribute to the pathogenesis of EV71 infection.

Summary Epstein-Barr virus (EBV) causes Burkitt, Hodgkin, and post-transplant B cell lymphomas. How EBV remodels metabolic pathways to support rapid B cell outgrowth remains largely unknown. To gain insights, primary human B cells were profiled by tandem-mass-tag-based proteomics at rest and at nine time points after infection; >8,000 host and 29 viral proteins were quantified, revealing mitochondrial remodeling and induction of one-carbon (1C) metabolism. EBV-encoded EBNA2 and its target MYC were required for upregulation of the central mitochondrial 1C enzyme MTHFD2, which played key roles in EBV-driven B cell growth and survival. MTHFD2 was critical for maintaining elevated NADPH levels in infected cells, and oxidation of mitochondrial NADPH diminished B cell proliferation. Tracing studies underscored contributions of 1C to nucleotide synthesis, NADPH production, and redox defense. EBV upregulated import and synthesis of serine to augment 1C flux. Our results highlight EBV-induced 1C as a potential therapeutic target and provide a new paradigm for viral onco-metabolism.

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Epstein-Barr virus (EBV) causes endemic Burkitt lymphoma (BL) and immunosuppression-related lymphomas. These B cell malignancies arise by distinct transformation pathways and have divergent viral and host expression programs. To identify host dependency factors resulting from these EBV+, B cell-transformed cell states, we performed parallel genome-wide CRISPR/Cas9 loss-of-function screens in BL and lymphoblastoid cell lines (LCLs). These highlighted 57 BL and 87 LCL genes uniquely important for their growth and survival. LCL hits were enriched for EBV-induced genes, including viral super-enhancer targets. Our systematic approach uncovered key mechanisms by which EBV oncoproteins activate the PI3K/AKT pathway and evade tumor suppressor responses. LMP1-induced cFLIP was found to be critical for LCL defense against TNFα-mediated programmed cell death, whereas EBV-induced BATF/IRF4 were critical for BIM suppression and MYC induction in LCLs. Finally, EBV super-enhancer-targeted IRF2 protected LCLs against Blimp1-mediated tumor suppression. Our results identify viral transformation-driven synthetic lethal targets for therapeutic intervention.

Summary Epstein-Barr Virus (EBV) transforms B cells to continuously proliferating lymphoblastoid cell lines (LCLs), which represent an experimental model for EBV-associated cancers. EBNAs and LMP1 are EBV transcriptional regulators that are essential for LCL establishment, proliferation, and survival. Starting with the 3D genome organization map of LCL, we constructed a comprehensive EBV regulome encompassing 1992 viral/cellular genes and enhancers. ~30% of genes essential for LCL growth were linked to EBV enhancers. Deleting EBNA2 sites significantly reduced their target gene expression. Additional EBV super-enhancer (ESE) targets included MCL1, IRF4, and EBF. MYC ESE looping to the transcriptional stat site of MYC was dependent on EBNAs. Deleting MYC ESEs greatly reduced MYC expression and LCL growth. EBNA3A/3C altered CDKN2A/B spatial organization to suppress senescence. EZH2 inhibition decreased the looping at the CDKN2A/B loci and reduced LCL growth. This study provides a comprehensive view of the spatial organization of chromatin during EBV-driven cellular transformation.

Innate immunity provides the first line of host defense against invading microbial pathogens. This defense involves retinoic acidinducible gene-I-like receptors that detect viral RNA and activate the mitochondrial antiviral-signaling (MAVS) protein, an adaptor protein, leading to activation of the innate antiviral immune response. The mechanisms by which the MAVS signalosome assembles on mitochondria are only partially understood. Here, we identify tripartite motif 14 (TRIM14) as a mediator in the immune response against viral infection. TRIM14 localizes to the outer membrane of mitochondria and interacts with MAVS. Upon viral infection, TRIM14 undergoes Lys-63-linked polyubiquitination at Lys-365 and recruits NF-κB essential modulator to the MAVS signalosome, leading to the activation of both the IFN regulatory factor 3 and NF-κB pathways. Knockdown of TRIM14 disrupts the association between NF-κB essential modulator and MAVS and attenuates the antiviral response. Our results indicate that TRIM14 is a component of the mitochondrial antiviral immunity that facilitates the immune response mediated by retinoic acidinducible gene-I-like receptors.A ctivation of the innate immune response involves the detection of pathogen-associated molecular patterns (PAMPs), such as microbial nucleic acids, proteins, lipids, and carbohydrates. PAMPs are recognized by cellular pattern recognition receptors (PRRs), including Toll-like receptors, retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), NOD-like receptors, and C-type lectin receptors. Upon recognition, PRRs trigger a series of signaling events that lead to the induction of type I IFNs and proinflammatory cytokines (1).RLRs such as RIG-I and melanoma differentiation-associated antigen 5 (MDA5) recognize cytosolic viral RNA (2). Upon binding of RNA to the helicase domain, RIG-I or MDA5 undergoes a conformational change (3) and is recruited to the mitochondrial antiviral signaling (MAVS) adaptor. After binding of RIG-1 or MAD5, MAVS recruits various downstream molecules and further activates two kinase complexes: the noncanonical IκB kinases (IKKs) [TANK-binding kinase 1 (TBK1)/IKKi] and the canonical IKK complexes comprised of IKKα, IKK-β, and NF-κB essential modulator (NEMO) (4, 5). The TBK1/IKKi kinases phosphorylate IFN regulatory factor 3/7 (IRF3/7), which translocates to the nucleus and drives the transcription of IFNs (6). The canonical IKKs phosphorylate IκBα, resulting in the ubiquitination and proteasomal degradation of IκBα. NF-κB then is released to the nucleus and stimulates the expression of proinflammatory genes (7).MAVS-deficient mice show abolished virus-triggered induction of IFNs and increased susceptibility to viral infection (8), indicating that MAVS is essential for the innate immune response. MAVS consists of an N-terminal caspase activation and recruitment domain, a proline-rich domain, and a C-terminal transmembrane domain that targets it to the mitochondrial outer membrane (9). It has been suggested that the mitochondrial outer membrane pr...

Metastasis is the main event leading to death in cancer patients. Over the past decade, high-throughput technologies have provided genome-wide view of transcriptomic changes associated with cancer metastases. Many microarray and RNA sequencing studies have addressed metastases-related expression patterns in various types of cancer, and the number of relevant works continues to increase rapidly. These works have characterized genes that orchestrate the metastatic phenotype of cancer cells. However, these expression data have been deposited in various repositories, and efficiently analyzing these data is still difficult because of the lack of an integrated data mining platform. To facilitate the in-depth analyses of transcriptome data on metastasis, it is quite important to make a comprehensive integration of these metastases-related expression data. Here, we presented a database, HCMDB (the human cancer metastasis database, http://hcmdb.i-sanger.com/index), which is freely accessible to the research community query cross-platform transcriptome data on metastases. HCMDB is developed and maintained as a useful resource for building the systems-biology understanding of metastasis.

The ICP34.5 protein of herpes simplex virus type 1 is a neurovirulence factor that plays critical roles in viral replication and anti-host responses. One of its functions is to recruit protein phosphatase 1 (PP1) that leads to the dephosphorylation of the ␣ subunit of translation initiation factor eIF2 (eIF2␣), which is inactivated by infection-induced phosphorylation. As PP1 is a protein phosphatase with a wide range of substrates, the question remains to be answered how ICP34.5 directs PP1 to specifically dephosphorylate eIF2␣. Here we report that ICP34.5 not only binds PP1 but also associates with eIF2␣ by in vitro and in vivo assays. The binding site of eIF2␣ is identified at amino acids 233-248 of ICP34.5, which falls in the highly homologous region with human gene growth arrest and DNA damage 34. The interaction between ICP34.5 and eIF2␣ is independent of the phosphorylation status of eIF2␣ at serine 51. Deletion mutation of this region results in the failure of dephosphorylation of eIF2␣ by PP1 and, consequently, interrupts viral protein synthesis and replication. Our data illustrated that the binding between viral protein ICP34.5 and the host eIF2␣ is crucial for the specific dephosphorylation of eIF2␣ by PP1. We propose that herpes simplex virus protein ICP34.5 bridges PP1 and eIF2␣ via their binding motifs and thereby facilitates the protein synthesis and viral replication.Viral infection can activate a series of host immune responses. One of the essential responses is the interruption of the viral protein synthesis, which is executed by doublestranded RNA-dependent protein kinase (PKR) (1). PKR is induced and activated upon viral infection and leads to the phosphorylation of the ␣ subunit of translation initiation factor eIF2 (eIF2␣) 2 at serine 51 (2). The phosphorylation of eIF2␣ globally inhibits the synthesis of viral proteins and cellular proteins (3), thus halting the viral replication.Many viruses have evolved strategies to counteract the antiviral response of PKR (4). For example, PKR activity can be inhibited by HIV-encoded Tar (5), hepatitis C virus NS5A (6), influenza virus NS1 (7), and so forth. In addition to affecting PKR activation as mentioned above, HSV-1 adopted mechanisms not only inhibiting PKR by Us11 (8) but also reversing the biochemical reaction catalyzed by PKR with its neurovirulent factor ICP34.5 (9).ICP34.5 is encoded by the ␥ 1 34.5 gene of HSV-1 and HSV-2. The HSV-1(F) ICP34.5 consists of 263 amino acids and can be divided into three domains: an amino-terminal domain, a linker region of ATP (Ala-Thr-Pro) repeats, and a carboxyl-terminal domain (9, 10). The function of the amino-terminal domain is implicated in the control of TBK1-mediated signaling (11) and also related to autophagy (12). The linker region, with a varying number of the Ala-Thr-Pro repeats, may affect the protein localization (13). The carboxyl-terminal domain is a stretch of 84 amino acids containing a consensus binding motif (R/KVXF) for protein phosphatase 1 (PP1) followed by an Ala-Arg-rich motif and i...