ABSTRACT: Endogenous retroviruses (ERVs) are transposable elements that cause host genome instability and usually play deleterious roles such as tumorigenesis. Recent advances also suggest that this 'enemy within' may encode viral mimic to induce antiviral immune responses through viral sensors. Here, through whole genome RNA-seq we discovered a full-length ERV-derived long non-coding RNA (lncRNA), designated lnc-EPAV (ERV-derived lncRNA positively regulates antiviral responses), as a positive regulator of NF-κB signaling. Lnc-EPAV expression was rapidly up-regulated by viral RNA mimic or RNA viruses to facilitate the expression of RELA, an NF-κB subunit that plays a critical role in antiviral responses. In turn, RELA promoted the transcription of lnc-EPAV to form a positive feedback loop. Transcriptome analysis of lnc-EPAV-silenced macrophages, combined with gain- and loss-of-function experiments, showed that lnc-EPAV was critical for induction of type I interferon (IFN) and inflammatory cytokine expression by RNA viruses. Consistently, lnc-EPAV-deficient mice exhibited reduced expression of type I IFNs, and consequently increased viral loads and mortality following lethal RNA virus infection. Mechanistically, lnc-EPAV promoted expression of RELA by competitively binding to and displacing SFPQ, a transcriptional repressor of RELA. The binding between ERV-derived RNAs and SFPQ also existed in human cells. Altogether, our work demonstrates an alternative mechanism by which ERVs regulate antiviral immune responses.
Project description:Pseudogenes are thought to be inactive gene sequences, but recent evidence of extensive pseudogene transcription raised the question of potential function. Here we discover and characterize the sets of lncRNAs induced by inflammatory signaling via TNFα. TNFα regulates hundreds of lncRNAs, including 54 pseudogene lncRNAs, several of which show exquisitely selective expression in response to specific cytokines and microbial components in a NF-κB-dependent manner. Lethe, a pseudogene lncRNA, is selectively induced by proinflammatory cytokines via NF-κB or glucocorticoid receptor agonist, and functions in negative feedback signaling to NF-κB. Lethe interacts with NF-κB subunit RelA to inhibit RelA DNA binding and target gene activation. Lethe level decreases with organismal age, a physiological state associated with increased NF-κB activity. These findings suggest that expression of pseudogenes lncRNAs are actively regulated and constitute functional regulators of inflammatory signaling. RNA profiles of wild type (WT) MEFs treated with TNF-alpha were generated by deep sequencing using Illumina GAIIx. Examination of H3K4me3 histome modification in MEF.
Project description:Background: Lymphotoxin signaling via the lymphotoxin-β receptor (LTβR) has been implicated in several biological processes, ranging from development of secondary lymphoid organs, maintenance of splenic tissue, host defense against pathogens, autoimmunity, and lipid homeostasis. The major transcription factor that is activated by LTβR crosslinking is NF-κB. Two signaling pathways have been described that result in the activation of classical p50-RelA and alternative p52-RelB NF-κB heterodimers. Results: Using microarray analysis, we investigated the transcriptional response downstream of the LTβR in mouse embryoni fibroblasts (MEF) and its regulation by the RelA and RelB subunits of NF-κB. We describe novel LTβR-responsive genes that are regulated by RelA and/or RelB. Interestingly, we found that the majority of LTβR-regulated genes require the presence of both RelA and RelB, suggesting significant crosstalk between the two NF-κB activation pathways. Gene Ontology (GO) analysis confirmed that LTβR-NF-κB target genes are predominantly involved in the regulation of immune responses. However, other biological processes, such as apoptosis/cell death, cell cycle, angiogenesis, and taxis were also regulated by LTβR signaling. Moreover, we show that activation of the LTβR inhibits the expression of a key adipogenic transcription factor, peroxisome proliferator activated receptor-γ (pparg), suggesting that LTβR signaling may interfere with adipogenic differentiation. Conclusions: Thus, microarray analysis of LTβR-stimulated fibroblasts revealed further insight into the transcriptional response of LTβR signaling and its regulation by the NF-κB family members RelA and RelB. Keywords: cell type comparison (wt vs relA-/- vs relB-/-) after genetic modification using a time course for each cell type (wt, relA-/-, relB-/-) two time points were analysed (0h as control and 10h) using 3 technical replicates resulting in 18 samples in total
Project description:Pro-inflammatory cytokines were shown to promote growth and survival of cancerous cells. TNF induced RelA:p50 NF-κB dimer via the canonical pathway is thought to link inflammation with cancer. Integrating biochemical and computational studies we identify that deficiency of non-canonical signal transducer p100 triggers a positive autoregulatory loop, which instead perpetuates an alternate RelB:p50 containing NF-κB activity upon TNF treatment. TNF stimulated RelB:p50 dimer is sufficient for mediating NF-κB target gene-expressions and suppressing apoptotic cellular death independent of principal NF-κB subunit RelA. We further demonstrate that activating mutations in non-canonical NF-κB module deplete multiple myeloma cells of p100, thereby, provoking autoregulatory RelB:p50 activation. Finally, autoregulatory control reinforces protracted pro-survival NF-κB response, albeit comprising of RelB:p50, upon TNF priming that protects myeloma cells with dysfunctional p100 from subsequent apoptotic insults. In sum, we present evidence for positive autoregulation mediated through the NF-κB system and its potential involvement in human neoplasm. Overall design: Total RNA isolated from biological replicate samples comprising of untreated and 6h TNF (10ng/ml) treated WT, Rela-/-Nfkb2-/- and Rela-/-Relb-/-Rel-/- MEFs were analyzed for global gene expression levels
Project description:The NF-κB transcription factors are activated via diverse molecular mechanisms in response to various types of stimuli. A plethora of functions associated with specific sets of target genes could be regulated differentially by this factor, affecting cellular response to stress including an anticancer treatment. Here we aimed to compare subsets of NF-κB-dependent genes induced in cells stimulated with a pro-inflammatory cytokine and in cells damaged by a high dose of ionizing radiation (4 and 10 Gy). The RelA-containing NF-κB species were activated by the canonical TNFα-induced and the atypical radiation-induced pathways in human osteosarcoma cells. NF-κB-dependent genes were identified using the gene expression profiling (by RNA-Seq) in cells with downregulated RELA combined with the global profiling of RelA binding sites (by ChIP-Seq), with subsequent validation of selected candidates by quantitative PCR. There were 37 NF-κB-dependent protein-coding genes identified: in all cases RelA bound in their regulatory regions upon activation while downregulation of RELA suppressed their stimulus-induced upregulation, which apparently indicated the positive regulation mode. This set of genes included a few “novel” NF-κB-dependent species. Moreover, the evidence for possible negative regulation of ATF3 gene by NF-κB was collected. The kinetics of the NF-κB activation was slower in cells exposed to radiation than in cytokine-stimulated ones. However, subsets of NF-κB-dependent genes upregulated by both types of stimuli were essentially the same. Hence, one should expect that similar cellular processes resulting from activation of the NF-κB pathway could be induced in cells responding to pro-inflammatory cytokines and in cells where so-called “damage-induced inflammation” response was initiated by ionizing radiation Overall design: We sequenced mRNA from wild type U2OS cells and cells transiently transfected using siRNA specific for RELA gene or control siRNA. Cells were untreated (control) or stimulated using TNFalpha cytokine for specific time or subjected to ionizing radiation with subsequent recovery. Three biological replicates were performed and sequenced.
Project description:Cellular response to ionizing radiation involves activation of the p53-dependent pathways and activation of the atypical NF-κB pathway. Mechanisms of the crosstalk between these two transcriptional networks include (co)regulation of common gene targets. Novel genes potentially (co)regulated by p53 and NF-κB were found using high-throughput genomics screening in human osteosarcoma U2-OS cells irradiated with a high dose (4 and 10 Gy). Radiation-induced expression in cells with silenced TP53 or RELA (coding the p65 NF-κB subunit) genes was analyzed by RNA-Seq while radiation-induced binding of p53 and RelA (p65) in putative regulatory regions was analyzed by ChIP-Seq, then selected candidates were validated by qPCR. A subset of radiation-modulated genes whose expression was affected by silencing of both TP53 and RELA, and a subset of radiation-upregulated genes where radiation stimulated binding of both p53 and RelA were identified. Competition for the same transcriptional coactivators of p53 and NF-κB was the most probable mechanism of a frequent antagonistic effect of the TP53 and RELA silencing. However, this mode of regulation was noted for 3 genes where radiation-induced binding of both p53 and RelA was observed, namely IL4I1, SERPINE1, and CDKN1A. This suggested a possibility of a direct antagonistic (co)regulation by both factors: activation by NF-κB and inhibition by p53 of IL4I1, and activation by p53 and inhibition by NF-κB of CDKN1A and SERPINE1. On the other hand, radiation-induced binding of both p53 and RelA was observed in a putative regulatory region of RRAD gene whose expression was downregulated both by TP53 and RELA silencing, which suggested a possibility of direct (co)activation by both factors. Overall design: We sequenced DNA immunoprecipitated from wild type U2OS cells using rabbit polyclonal anti-p65 antibodies or rabbit polyclonal anti-p53 antibody. Cells were untreated (control) or subjected to ionizing radiation with subsequent recovery. Six ChIP replicates were collected and pooled per each sequenced sample. Input samples were included as negative control (no DNA enrichment was observed in mock-IP samples).
Project description:Post-translational modification of NF-κB subunits provides a mechanism to differentially regulate their activity in response to the many stimuli that can induce this pathway. However, the physiological significance of these modifications is largely unknown and it remains unclear if these have a critical role in the normal and pathological functions of NF-κB in vivo. Among these, phosphorylation of the RelA(p65) Thr505 residue has been described as an important regulator of NF-κB activity in cell lines but its physiological significance was not known. Therefore, to learn more about the role of this pathway in vivo, we generated a knockin mouse with a RelA T505A mutation. Unlike RelA knockout mice, the RelA T505A mice develop normally but exhibit aberrant hepatocyte proliferation following liver partial hepatectomy or damage resulting from carbon tetrachloride treatment. Consistent with these effects, RelA T505A mice exhibit earlier onset of cancer in the N-nitrosodiethylamine (DEN) model of hepatocellular carcinoma. This data reveals a critical pathway controlling NF-κB function in the liver that acts to suppress tumour-promoting activities of RelA.
Project description:Long noncoding RNAs (lncRNAs) have emerged as important components of gene regulatory network in embryonic stem cells (ESCs). However, the function and molecular mechanism of lncRNAs are still largely unknown. Here we identified Trincr1 (TRIM71 interacting long noncoding RNA 1) lncRNA that regulates the FGF/ERK signaling and self-renewal of ESCs. Trincr1 is exported by THOC complex to cytoplasm where it binds and represses TRIM71, leading to the downregulation of SHCBP1 protein. Knocking out Trincr1 leads to the upregulation of phosphorylated ERK and ERK pathway target genes and the decrease of ESC self-renewal, while knocking down Trim71 completely rescues the defects of Trincr1 knockout. Furthermore, ectopic expression of Trincr1 represses FGF/ERK signaling and the self-renewal of neural progenitor cells. Together, this study reveals more regulators in FGF/ERK signaling pathway and highlights lncRNA as an important player in cell signaling network to coordinate cell fate specification.
Project description:In vertebrates, the presence of viral RNA in the cytosol is sensed by members of the RIG-I like receptor (RLR) family , which signal to induce production of type I interferons (IFN). These key anti-viral cytokines act in a paracrine and autocrine manner to induce hundreds of interferon-stimulated genes (ISGs), whose protein products restrict viral entry, replication and budding. ISGs include the RLRs themselves: RIG-I, MDA5 and the least-studied family member, LGP2. In contrast, the IFN system is absent in plants and invertebrates, which defend themselves from viral intruders using RNA interference (RNAi). In RNAi, the endoribonuclease Dicer cleaves virus-derived double stranded RNA (dsRNA) into small interfering RNAs (siRNAs) that target complementary viral RNA for cleavage. Interestingly, the RNAi machinery is conserved in mammals and we have recently demonstrated that it is able to participate in mammalian antiviral defence in conditions in which the IFN system is suppressed. In contrast, when the IFN system is active, one or more ISGs act to mask or suppress antiviral RNAi. Here, we demonstrate that LGP2 constitutes one of the ISGs that can inhibit antiviral RNAi in mammals. We identify Dicer as an LGP2-associated protein and show that LGP2 inhibits Dicer cleavage of dsRNA into siRNAs both in vitro and in vivo. Further, we show that in cells lacking an IFN response, ectopic expression of LGP2 interferes with RNAi-dependent suppression of gene expression. Thus, the inefficiency of RNAi as a mechanism of antiviral defence in mammalian somatic cells can be in part attributed to Dicer inhibition by LGP2 induced by type I IFNs.
Project description:Malignant Hodgkin's lymphoma (HL) cells are characterized by constitutive activation of the canonical as well as the non-canonical NF-κB signaling cascades. We depleted subunit combinations corresponding to either canonical (p50/RelA) or non-canonical (p52/RelB) dimers in the HL cell line L-1236 and performed Affymetrix microarray analysis. Knockdown of p52/RelB affected the expression of a significantly higher number of genes than the knockdown of p50/RelA. The two sets of target genes presented a partial overlap, however they also revealed specific genes that are involved in distinct aspects of tumor biology. The knockdown of subunit combinations corresponding to either canonical (p50/RelA, experimental group 1) or non-canonical (p52/RelB, experimental group 2) NF-κB heterodimers were carried out in L-1236 cells. Two distinct siRNA sequences for every NF-κB subunit and two non-targeting siRNA sequences (control) were used for each experimental group. Experiments were performed in biological triplicates.
Project description:Splicing factor proline and glutamine rich (SFPQ), DNA- and RNA binding protein, is crucial in various nuclear processes, including paraspeckle formation, miRNA synthesis and specially in transcription regulation. In addition, SFPQ play a role in the innate immune response to viruses, including DNA and RNA viruses. However, the connections between SFPQ and EMCV infection remain unclear. Here we report that the SFPQ is essential for EMCV replication. Depletion of SFPQ impairs EMCV production, while forced expression of SFPQ could promote viral replication. Mechanistically, EMCV inhibited viral RNA-mediated type I IFN and IL6 production to eliminate host antiviral immune responses. Cellular SFPQ was cleaved by the EMCV proteinase then entered the cytoplasm and interacted with other ribosomal proteins to facilitate its internal ribosome entry site (IRES)-dependent translation. Moreover, loss of SFPQ may impress host translation related gene expression and thus facilitate the EMCV replication. Altogether, our work provides a possible target for resisting EMCV or EMCV-like virus’s infection.