Project description:The inflammatory response mediated by NF-κB signaling is essential for host defense against pathogens. Although the components and regulatory mechanism of NF-κB signaling have been well-studied, molecular basis for the epigenetic regulation of the inflammatory response is poorly understood. Here, we identify a new signaling axis of PKCα- LSD1-NF-κB p65 which is critical for activation and amplification of the inflammatory response and triggering systemic inflammatory diseases. In response to excessive inflammatory stimuli, PKCα translocates to the nucleus and phosphorylates LSD1. Phosphorylation of LSD1 is required for its interaction with p65 and facilitates demethylation of p65 leading to enhanced protein stability. Genome-wide analysis reveals a critical role of LPS-induced LSD1 phosphorylation in the transcriptional activation of NF-κB target genes. Together, we demonstrate that PKCα-LSD1-NF-κB signaling cascade is crucial for epigenetic control of the inflammatory response.
Project description:The inflammatory response mediated by NF-κB signaling is essential for host defense against pathogens. Although the components and regulatory mechanism of NF-κB signaling have been well-studied, molecular basis for the epigenetic regulation of the inflammatory response is poorly understood. Here, we identify a new signaling axis of PKCα- LSD1-NF-κB p65 which is critical for activation and amplification of the inflammatory response and triggering systemic inflammatory diseases. In response to excessive inflammatory stimuli, PKCα translocates to the nucleus and phosphorylates LSD1. Phosphorylation of LSD1 is required for its interaction with p65 and facilitates demethylation of p65 leading to enhanced protein stability. Genome-wide analysis reveals a critical role of LPS-induced LSD1 phosphorylation in the transcriptional activation of NF-κB target genes. Together, we demonstrate that PKCα-LSD1-NF-κB signaling cascade is crucial for epigenetic control of the inflammatory response.
Project description:A20 is a negative regulator of NF-κB signaling, crucial to control inflammatory responses and ensure tissue homeostasis. A20 is thought to restrict NF-κB activation both by its ubiquitin-editing activity as by non-enzymatic activities. Besides its role in NF-κB signaling, A20 also acts as a protective factor inhibiting apoptosis and necroptosis. Because of the ability of A20 to both ubiquitinate and deubiquitinate substrates and its involvement in many cellular processes, we hypothesized that deletion of A20 might generally impact on protein levels, thereby disrupting cellular processes. We performed a differential proteomics study of bone marrow derived macrophages (BMDMs) from control and myeloid-specific A20 knockout mice, both in untreated conditions and after LPS and TNF treatment, and demonstrate proteome-wide changes in protein expression upon A20 deletion. Several inflammatory proteins are up-regulated in the absence of A20, even without an inflammatory stimulus. Depending on the treatment and the time, more proteins are regulated. Together these changes may affect multiple signaling pathways disturbing tissue homeostasis and inducing (autoimmune) inflammation, as suggested by genetic studies in patients.
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:TNFα has an evolutionary conserved role in mediating inflammation via activation of the transcription factor NF-κB. The functions of individual NF-κB binding sites are not well understood. To identify conserved and functionally important NF-κB binding sites in mammals, we performed ChIP-seq to map the genome-wide binding of RELA and select histone modifications in primary vascular endothelial cells (ECs) isolated from the aortas of human (HAEC), mouse (MAEC) and cow (BAEC), before and after TNFα. The conserved RELA binding sites show strong epigenetic changes in response to TNFα and enrich near genes controlling vascular development and pro-inflammatory responses. Our method identifies novel modes of RELA-chromatin interactions that are conserved in mammals and shared between multiple cell-types. Particularly, genomic regions bound by RELA prior to stimulation are important responders during TNFα stimulation. We use CRISPR/Cas9 genome editing to validate the roles of the conserved RELA pre-bound sites near pro-inflammatory genes such as CCL2 and PLK2. Our evolutionary approach describes new aspects of mammalian NF-κB biology including its role within super-enhancers and relevance in inflammatory disorders.
Project description:Following partial hepatectomy, a coordinated series of molecular events occurs to regulate hepatocyte entry into the cell cycle to recover lost mass. In rats during the first six hours following resection, hepatocytes are primed by a tightly controlled cytokine response to prepare hepatocytes to begin replication. Although it appears to be a critical element driving regeneration, the cytokine response to resection has not yet been fully characterized. Specifically, the role of one of the key response elements to cytokine signaling (NF-κB) remains incompletely characterized. In this study, we present a novel, genome-wide, pattern-based analysis characterizing NF-κB binding during the priming phase of liver regeneration. We interrogated the dynamic regulation of priming by NF-κB through categorizing NF-κB binding in different temporal profiles: immediate sustained response, early transient response, and delayed response to partial hepatectomy. We then identified functional regulation of NF-κB binding by relating the temporal response profile to differential gene expression. We found that NF-κB bound genes govern negative regulation of cell growth and inflammatory response immediately following hepatectomy. NF-κB also transiently regulates genes responsible for lipid biosynthesis and transport as well as induction of apoptosis following hepatectomy. By the end of the priming phase, NF-κB regulation of genes involved in inflammatory response, negative regulation of cell death, and extracellular structure organization became prominent. These results suggest that the immediate, transient, and delayed NF-κB signaling serve different functional transitions that drive the onset of regeneration.
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.
Project description:The non-canonical NF-κB signaling cascade is essential for lymphoid organogenesis, B-cell maturation, osteoclast differentiation, and inflammation in mammals, whereas dysfunction of this system is associated with human diseases, including immunological disorders and cancer. While controlled expression of NF-κB Inducing Kinase (NIK) is the rate-limiting step in non-canonical NF-κB activation, mechanisms of inhibition remain largely unknown. Here, we report the identification of the sine oculis homeobox homolog family transcription factors SIX1 and SIX2 as essential inhibitory components of the non-canonical NF-κB signaling pathway. The developmentally silenced SIX-proteins are reactivated in differentiated macrophages by NIK-mediated suppression of the ubiquitin proteasome pathway. Consequently, SIX1 and SIX2 target a subset of inflammatory gene promoters and directly inhibit RelA and RelB trans-activation function in a negative feedback circuit. In support of a physiologically pivotal role for SIX-proteins in host immunity, human SIX1 transgene suppressed inflammation and promoted the recovery of mice from endotoxic shock. In addition, SIX1 and SIX2 protected RAS/p53-driven lung adenocarcinoma cells from inflammatory cell death induced by SMAC-mimetic chemotherapeutic agents, small-molecule activators of the non-canonical NF-κB pathway. Collectively, our study reveals a NIK-SIX signaling axis that fine-tunes inflammatory gene expression programs under both physiological and pathological conditions.