RESUMO
Intracellular adhesion molecule 1 (ICAM-1) is one of the most extensively studied inducible cell adhesion molecules which is responsible for several immune functions like T cell activation, extravasation, inflammation, etc. The molecule is constitutively expressed over the cell surface and is regulated up / down in response to inflammatory mediators like cellular stress, proinflammatory cytokines, viral infection. These stimuli modulate the expression of ICAM-1 primarily through regulating the ICAM-1 gene transcription. On account of the presence of various binding sites for NF-κB, AP-1, SP-1, and many other transcription factors, the architecture of the ICAM-1 promoter become complex. Transcription factors in union with other transcription factors, coactivators, and suppressors promote their assembly in a stereospecific manner on ICAM-1 promoter which mediates ICAM-1 regulation in response to different stimuli. Along with transcriptional regulation, epigenetic modifications also play a pivotal role in controlling ICAM-1 expression on different cell types. In this review, we summarize the regulation of ICAM-1 expression both at the transcriptional as well as post-transcriptional level with an emphasis on transcription factors and signaling pathways involved.
Assuntos
Regulação da Expressão Gênica/imunologia , Molécula 1 de Adesão Intercelular/imunologia , Ativação Linfocitária , Transdução de Sinais/imunologia , Linfócitos T/imunologia , Transcrição Gênica/imunologia , Humanos , Elementos de Resposta/imunologia , Fatores de Transcrição/imunologiaRESUMO
We previously identified a subset of interferon-stimulated genes (ISGs) upregulated by West Nile virus (WNV) infection in wild-type mouse embryo fibroblasts (MEFs) after viral proteins had inhibited type I interferon (IFN)-mediated JAK-STAT signaling and also in WNV-infected RIG-I-/-, MDA5-/-, STAT1-/-, STAT2-/-, IFNAR-/-, IRF3-/-, IRF7-/-, and IRF3/7-/- MEFs. In this study, ISG upregulation by WNV infection in IFNAR-/- MEFs was confirmed by transcriptome sequencing (RNA-seq). ISG upregulation by WNV infection was inhibited in RIG-I/MDA5-/- MEFs. ISGs were upregulated in IRF1-/- and IRF5-/- MEFs but only minimally upregulated in IRF3/5/7-/- MEFs, suggesting redundant IRF involvement. We previously showed that a single proximal interferon-stimulated response element (ISRE) in the Oas1a and Oas1b promoters bound the ISGF3 complex after type I IFN treatment. In this study, we used wild-type and mutant promoter luciferase reporter constructs to identify critical regions in the Oas1b and Ifit1 promoters for gene activation in infected IFNAR-/- MEFs. Two ISREs were required in both promoters. Mutation of these ISREs in an Ifit1 promoter DNA probe reduced in vitro complex formation with infected nuclear extracts. An NF-κB inhibitor decreased Ifit1 promoter activity in cells and in vitro complex formation. IRF3 and p50 promoter binding was detected by chromatin immunoprecipitation (ChIP) for upregulated ISGs with two proximal ISREs. The data indicate that ISREs function cooperatively to upregulate the expression of some ISGs when type I IFN signaling is absent, with the binding complex consisting of IRF3, IRF5, and/or IRF7 and an NF-κB component(s) as well as other, as-yet-unknown factors. IMPORTANCE Type I IFN signaling in mammalian cells induces formation of the ISGF3 transcription factor complex, which binds to interferon stimulated response elements (ISREs) in the promoters of interferon-stimulated genes (ISGs) in the cell nucleus. Flavivirus proteins counteract type I IFN signaling by preventing either the formation or nuclear localization of ISGF3. A subset of ISRE-regulated ISGs was still induced in West Nile virus (WNV)-infected mouse embryo fibroblasts (MEFs), indicating that cells have an alternative mechanism for activating these ISGs. In this study, cellular components involved in this ISG upregulation mechanism were identified using gene knockout MEFs and ChIP, and critical promoter regions for gene activation were mapped using reporter assays. The data indicate a cooperative function between two ISREs and required binding of IRF3, IRF5, and/or IRF7 and an NF-κB component(s). Moreover, type I IFN signaling-independent ISG activation requires different additional promoter activation regions than type I IFN-dependent activation.
Assuntos
Fibroblastos , Regulação da Expressão Gênica/imunologia , Interferon Tipo I/imunologia , Febre do Nilo Ocidental/imunologia , Vírus do Nilo Ocidental/imunologia , Animais , Fibroblastos/imunologia , Fibroblastos/virologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Elementos de Resposta/imunologiaRESUMO
Alphaherpesviruses are large dsDNA viruses with an ability to establish persistent infection in hosts, which rely partly on their ability to evade host innate immune responses, notably the type I IFN response. However, the relevant molecular mechanisms are not well understood. In this study, we report the UL42 proteins of alphaherpesvirus pseudorabies virus (PRV) and HSV type 1 (HSV1) as a potent antagonist of the IFN-I-induced JAK-STAT signaling pathway. We found that ectopic expression of UL42 in porcine macrophage CRL and human HeLa cells significantly suppresses IFN-α-mediated activation of the IFN-stimulated response element (ISRE), leading to a decreased transcription and expression of IFN-stimulated genes (ISGs). Mechanistically, UL42 directly interacts with ISRE and interferes with ISG factor 3 (ISGF3) from binding to ISRE for efficient gene transcription, and four conserved DNA-binding sites of UL42 are required for this interaction. The substitution of these DNA-binding sites with alanines results in reduced ISRE-binding ability of UL42 and impairs for PRV to evade the IFN response. Knockdown of UL42 in PRV remarkably attenuates the antagonism of virus to IFN in porcine kidney PK15 cells. Our results indicate that the UL42 protein of alphaherpesviruses possesses the ability to suppress IFN-I signaling by preventing the association of ISGF3 and ISRE, thereby contributing to immune evasion. This finding reveals UL42 as a potential antiviral target.
Assuntos
DNA Polimerase Dirigida por DNA/imunologia , Exodesoxirribonucleases/imunologia , Herpesvirus Suídeo 1/imunologia , Interferon Tipo I/imunologia , Fator Gênico 3 Estimulado por Interferon, Subunidade gama/imunologia , Proteínas Virais/imunologia , Animais , Linhagem Celular , Linhagem Celular Tumoral , Células HEK293 , Células HeLa , Herpesvirus Humano 1/imunologia , Humanos , Evasão da Resposta Imune/imunologia , Imunidade Inata/imunologia , Pseudorraiva/imunologia , Elementos de Resposta/imunologia , Transdução de Sinais/imunologia , Suínos , Transcrição Gênica/imunologiaRESUMO
IL-13 plays a critical role in mediating many biological processes responsible for allergic inflammation. Mast cells express Il13 mRNA and produce IL-13 protein in response to antigenic stimulation. Enhancers are essential in promoting gene transcription and are thought to activate transcription by delivering essential accessory cofactors to the promoter to potentiate gene transcription. However, enhancers mediating Il13 have not been identified. Furthermore, which Il13 enhancers detect signals triggered by antigenic stimulation have not yet been defined. In this study, we identified potential mouse Il13 enhancers using histone modification monomethylation at lysine residue 4 on histone 3 (H3K4me1) chromatin immunoprecipitation sequencing and acetylation at lysine residue 27 on histone 3 (H3K27ac) chromatin immunoprecipitation sequencing. We used Omni-assay for transposase-accessible chromatin sequencing to determine which accessible regions within the potential Il13 enhancers that responded to IgE receptor crosslinking. We also demonstrated that the transcription factor cluster consisting of the NFATC2, STAT5, GATA2, AP1, and RUNX1 binding sites at the proximal Il13 enhancer and the transcription factor cluster consisting of the EGR2 binding site at the distal Il13 E+6.5 enhancer are critical in sensing the signals triggered by antigenic stimulation. Those enhancers, which are responsive to antigenic stimulation and are constitutively active, cooperate to generate greater transcriptional outputs. Our study reveals a novel mechanism underlying how antigenic stimulation induces robust Il13 mRNA expression in mouse mast cells.
Assuntos
Antígenos/imunologia , Subunidade alfa 2 de Fator de Ligação ao Core/imunologia , Proteína 2 de Resposta de Crescimento Precoce/imunologia , Fator de Transcrição GATA2/imunologia , Interleucina-13/imunologia , Mastócitos/imunologia , Fatores de Transcrição NFATC/imunologia , Elementos de Resposta/imunologia , Fator de Transcrição STAT5/imunologia , Fator de Transcrição AP-1/imunologia , Transcrição Gênica/imunologia , Animais , Linhagem Celular , Mastócitos/citologia , CamundongosRESUMO
The Toll-like receptor 8 (TLR8) has an important role in innate immune responses to RNA viral infections, including respiratory syncytial virus (RSV). We previously reported that TLR8 expression was increased directly by the tumor suppressor and transcription factor p53 via a single nucleotide polymorphism (SNP) (rs3761624) in the TLR8 promoter, thereby placing TLR8 in the p53/immune axis. Because this SNP is in linkage disequilibrium with other SNPs associated with several infectious diseases, we addressed the combined influence of p53 and the SNP on downstream inflammatory signaling in response to a TLR8 cognate ssRNA ligand. Using human primary lymphocytes, p53 induction by chemotherapeutic agents such as ionizing radiation caused SNP-dependent synergistic increases in IL-6 following incubation with an ssRNA ligand, as well as TLR8 RNA and protein expression along with p53 binding at the TLR-p53 SNP site. Because TLR8 is X-linked, the increases were generally reduced in heterozygous females. We found a corresponding association of the p53-responsive allele with RSV disease severity in infants hospitalized with RSV infection. We conclude that p53 can strongly influence TLR8-mediated immune responses and that knowledge of the p53-responsive SNP can inform diagnosis and prognosis of RSV disease and other diseases that might have a TLR8 component, including cancer.
Assuntos
Imunidade Inata/genética , Polimorfismo de Nucleotídeo Único , Infecções por Vírus Respiratório Sincicial , Vírus Sinciciais Respiratórios/imunologia , Receptor 8 Toll-Like , Proteína Supressora de Tumor p53 , Adulto , Idoso , Feminino , Humanos , Interleucina-6/genética , Interleucina-6/imunologia , Desequilíbrio de Ligação/imunologia , Masculino , Pessoa de Meia-Idade , Infecções por Vírus Respiratório Sincicial/genética , Infecções por Vírus Respiratório Sincicial/imunologia , Elementos de Resposta/imunologia , Receptor 8 Toll-Like/genética , Receptor 8 Toll-Like/imunologia , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/imunologiaRESUMO
The NF-κB transcription regulation system governs a diverse set of responses to various cytokine stimuli. With tools from in vitro biochemical characterizations, to omics-based whole genome investigations, great strides have been made in understanding how NF-κB transcription factors control the expression of specific sets of genes. Nonetheless, these efforts have also revealed a very large number of potential binding sites for NF-κB in the human genome, and a puzzle emerges when trying to explain how NF-κB selects from these many binding sites to direct cell-type- and stimulus-specific gene expression patterns. In this review, we surmise that target gene transcription can broadly be thought of as a function of the nuclear abundance of the various NF-κB dimers, the affinity of NF-κB dimers for the regulatory sequence and the availability of this regulatory site. We use this framework to place quantitative information that has been gathered about the NF-κB transcription regulation system into context and thus consider questions it answers, and questions it raises. We end with a brief discussion of some of the future prospects that new approaches could bring to our understanding of how NF-κB transcription factors orchestrate diverse responses in different biological contexts.
Assuntos
Regulação da Expressão Gênica/imunologia , NF-kappa B/imunologia , Elementos de Resposta/imunologia , Transcrição Gênica/imunologia , Animais , HumanosRESUMO
Benign neutropenia, observed in different ethnic groups, is the most common form of neutropenia worldwide. A specific single nucleotide polymorphism, rs2814778, located at the promoter of the ACKR1 (previously termed DARC) gene, which disrupts a binding site for the GATA1 erythroid transcription factor, resulting in a ACKR1-null phenotype, was found to serve as a predictor of low white blood cell and neutrophil counts in African-Americans and Yemenite Jews. Individuals with benign neutropenia due to the ACKR1-null allele have been found to have an increased susceptibility to human immunodeficiency virus infection and, on the other hand, a protective effect against malaria. The associated protective effect may explain the spread of the ACKR1-null allele by natural selection. The reviewed relationships between ACKR1 polymorphism and various pathological states may have important clinical implications to individuals with and without benign neutropenia. Potential mechanisms for ACKR1 (previously termed DARC) modulation during neutrophil recruitment to inflammation, and chemokine bioavailability in the circulation and in local tissue are reviewed and discussed.
Assuntos
Sistema do Grupo Sanguíneo Duffy , Fator de Transcrição GATA1 , Neutropenia , Polimorfismo de Nucleotídeo Único , Receptores de Superfície Celular , Elementos de Resposta/imunologia , Sistema do Grupo Sanguíneo Duffy/genética , Sistema do Grupo Sanguíneo Duffy/imunologia , Fator de Transcrição GATA1/genética , Fator de Transcrição GATA1/imunologia , Predisposição Genética para Doença , Infecções por HIV/genética , Infecções por HIV/imunologia , Infecções por HIV/patologia , HIV-1/imunologia , Humanos , Malária/genética , Malária/imunologia , Malária/patologia , Neutropenia/genética , Neutropenia/imunologia , Neutropenia/patologia , Neutrófilos/imunologia , Neutrófilos/patologia , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/imunologiaRESUMO
Nuclear hormone receptors including the estrogen receptor (ERα) and the retinoic acid receptor regulate a plethora of biological functions including reproduction, circulation and immunity. To understand how estrogen and other nuclear hormones influence antibody production, we characterized total serum antibody isotypes in female and male mice of C57BL/6J, BALB/cJ and C3H/HeJ mouse strains. Antibody levels were higher in females compared to males in all strains and there was a female preference for IgG2b production. Sex-biased patterns were influenced by vitamin levels, and by antigen specificity toward influenza virus or pneumococcus antigens. To help explain sex biases, we examined the direct effects of estrogen on immunoglobulin heavy chain sterile transcript production among purified, lipopolysaccharide-stimulated B cells. Supplemental estrogen in B-cell cultures significantly increased immunoglobulin heavy chain sterile transcripts. Chromatin immunoprecipitation analyses of activated B cells identified significant ERα binding to estrogen response elements (EREs) centered within enhancer elements of the immunoglobulin heavy chain locus, including the Eµ enhancer and hypersensitive site 1,2 (HS1,2) in the 3' regulatory region. The ERE in HS1,2 was conserved across animal species, and in humans marked a site of polymorphism associated with the estrogen-augmented autoimmune disease, lupus. Taken together, the results highlight: (i) the important targets of ERα in regulatory regions of the immunoglobulin heavy chain locus that influence antibody production, and (ii) the complexity of mechanisms by which estrogen instructs sex-biased antibody production profiles.
Assuntos
Formação de Anticorpos/genética , Elementos Facilitadores Genéticos , Cadeias Pesadas de Imunoglobulinas/genética , Receptores de Estrogênio/metabolismo , Elementos de Resposta/genética , Caracteres Sexuais , Animais , Formação de Anticorpos/imunologia , Sítios de Ligação , Cadeias Pesadas de Imunoglobulinas/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C3H , Camundongos Endogâmicos C57BL , Elementos de Resposta/imunologiaRESUMO
RAR-related orphan receptor γ (RORγ) is a nuclear receptor that plays an essential role in the development of T helper 17 (Th17) cells of the adaptive immune system. The NLRP3 inflammasome is a component of the innate immune system that processes interleukin (IL)-1ß into a mature cytokine. Elevated activity of the NLRP3 inflammasome contributes to the progression of an array of inflammatory diseases. Bone marrow-derived macrophages (BMDMs) isolated from RORγ-null mice displayed reduced capacity to secrete IL-1ß, and they also displayed a reduction in Nlrp3 and Il1b gene expression. Examination of the promoters of the Il1b and Nlrp3 genes revealed multiple putative ROR response elements (ROREs) that were occupied by RORγ. RORγ inverse agonists were effective inhibitors of the inflammasome. RORγ inverse agonists suppressed lipopolysaccharide (LPS)/ATP-stimulated IL-1ß secretion and expression of Il1b and Nlrp3 in BMDMs. Additionally, the ability of the RORγ inverse agonists to suppress IL-1ß secretion was lost in Nlrp3-null macrophages. The potential for targeting the NLRP3 inflammasome in vivo using RORγ inverse agonists was examined in two models: LPS-induced sepsis and fulminant hepatitis. Pharmacological inhibition of RORγ activity reduced plasma IL-1ß as well as IL-1ß production by peritoneal macrophages in a model of LPS-induced sepsis. Additionally, RORγ inverse agonists reduced mortality in an LPS/d-galactosamine-induced fulminant hepatitis mouse model. These results illustrate a major role for RORγ in regulation of innate immunity via modulation of NLRP3 inflammasome activity. Furthermore, these data suggest that inhibiting the NLRP3 inflammasome with RORγ inverse agonists may be an effective method to treat NLRP3-associated diseases.
Assuntos
Imunidade Inata , Inflamassomos/imunologia , Macrófagos/imunologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/imunologia , Membro 3 do Grupo F da Subfamília 1 de Receptores Nucleares/imunologia , Células Th17/imunologia , Animais , Galactosamina/toxicidade , Inflamassomos/genética , Interleucina-1beta/genética , Interleucina-1beta/imunologia , Lipopolissacarídeos/toxicidade , Falência Hepática Aguda/induzido quimicamente , Falência Hepática Aguda/genética , Falência Hepática Aguda/imunologia , Falência Hepática Aguda/patologia , Macrófagos/patologia , Camundongos , Camundongos Knockout , Proteína 3 que Contém Domínio de Pirina da Família NLR/genética , Membro 3 do Grupo F da Subfamília 1 de Receptores Nucleares/genética , Elementos de Resposta/imunologia , Sepse/induzido quimicamente , Sepse/genética , Sepse/imunologia , Sepse/patologia , Células Th17/patologiaRESUMO
Igκ locus contraction and Vκ gene usage are controlled by Cer, a cis-acting sequence in the Vκ-Jκ intervening region. This effect is attributed to two CTCF-binding sites within Cer that are oriented toward the Vκ gene region. However, the importance of Cer CTCF orientation in regulating VκJκ rearrangement is unknown. We used CRISPR/Cas9 editing to delete and invert Cer in murine Abl pro-B cell lines. This revealed that Cer orientation is critical because clones with either an inverted or deleted Cer element show skewing toward Jκ-proximal Vκ gene usage. However, only Cer deletion increased Jκ-proximal Vκ germline transcription, suggesting an insulating function of Cer. Lastly, circularized chromosome conformation capture interaction data show that Cer CTCF orientation regulates long-range interactions with inversion clones displaying fewer interactions with regions in the middle and distal parts of the Vκ locus and more interactions to downstream regions compared with wild-type or deletion clones.
Assuntos
Linfócitos B/imunologia , Fator de Ligação a CCCTC , Região de Junção de Imunoglobulinas , Cadeias kappa de Imunoglobulina , Elementos de Resposta/imunologia , Transcrição Gênica/imunologia , Animais , Fator de Ligação a CCCTC/genética , Fator de Ligação a CCCTC/imunologia , Região de Junção de Imunoglobulinas/genética , Região de Junção de Imunoglobulinas/imunologia , Cadeias kappa de Imunoglobulina/genética , Cadeias kappa de Imunoglobulina/imunologia , Camundongos , Camundongos KnockoutRESUMO
Airway epithelial cells (AECs) orchestrate inflammatory responses to airborne irritants that enter the respiratory system. A viscous mucus layer produced by goblet cells in the airway epithelium also contributes to a physiological defense mechanism through the physical and chemical barriers it provides. Dysregulation or impairment in these functions has been implicated as a cause of the chronic inflammation and tissue remodeling that constitute major pathological features of asthma. In particular, mucus hypersecretion leading to airway obstruction and impaired pulmonary function is associated with morbidity and mortality in asthma patients. Peroxisome proliferator-activated receptor γ (PPARγ) is a ligand-activated transcription factor involved in a variety of cellular processes. Accumulating evidence indicates that PPARγ agonists antagonize exaggerated inflammatory responses, yet PPARγ's precise role in airway remodeling/mucus hypersecretion has yet to be defined. In this study, we created an AEC-specific PPARγ (AEC-PPARγ) deletion to investigate PPARγ's functions in a murine model of allergic airway disease. AEC-PPARγ deficiency exaggerated airway hyperresponsiveness, inflammation, cytokine expression, and tissue remodeling. We also found that PPARγ directly bound to a PPAR response element found in MUC5AC and repressed gene expression. Likewise, PPARγ regulated mucin and inflammatory factors in primary human bronchial epithelial cells. In light of the current standard therapies' limited and inadequate direct effect on airway mucus hypersecretion, our study showing AEC-PPARγ's role as a transcriptional repressor of MUC5AC highlights this receptor's potential as a pharmacological target for asthma.
Assuntos
Asma/imunologia , Células Epiteliais/imunologia , Regulação da Expressão Gênica/imunologia , Mucina-5AC/imunologia , PPAR gama/imunologia , Mucosa Respiratória/imunologia , Animais , Asma/genética , Asma/patologia , Células Cultivadas , Células Epiteliais/patologia , Feminino , Humanos , Inflamação/genética , Inflamação/imunologia , Inflamação/patologia , Masculino , Camundongos , Camundongos Knockout , Mucina-5AC/genética , PPAR gama/genética , Mucosa Respiratória/patologia , Elementos de Resposta/imunologiaRESUMO
Active participation of endogenous retroviruses (ERVs) in disease processes has been exemplified by the finding that the HERV (human ERV)-W envelope protein is involved in the pathogenesis of multiple sclerosis, an autoimmune disease. We also demonstrated that injury-elicited stressors alter the expression of murine ERVs (MuERVs), both murine leukemia virus-type and mouse mammary tumor virus (MMTV)-type (MMTV-MuERV). In this study, to evaluate MMTV-MuERVs' responses to stress (e.g., injury, infection)-elicited systemic glucocorticoid (GC) levels, we examined the GC-stress response of 64 MMTV-MuERV promoters isolated from the genomes of 23 mouse strains. All 64 promoters responded to treatment with a synthetic GC, dexamethasone (DEX), at a wide range from a 0.6- to 85.7-fold increase in reporter activity compared to no treatment. An analysis of the 10 lowest and 10 highest DEX responders revealed specific promoter elements exclusively present in either the three lowest or the two highest responders. Each promoter had a unique profile of transcription regulatory elements and the glucocorticoid response element (GRE) was identified in all promoters with the number of GREs ranging from 2 to 7. The three lowest DEX responders were the only promoters with two GREs. The findings from this study suggest that certain MMTV-MuERVs are more responsive to stress-elicited systemic GC elevation compared to the others. The mouse strain-specific genomic MMTV-MuERV profiles and individual MMTV-MuERVs' differential responses to GC-stress might explain, at least in part, the variable inflammatory responses to injury and/or infection, often observed among different mouse strains. This article is part of a Special Issue entitled: Immune and Metabolic Alterations in Trauma and Sepsis edited by Dr. Raghavan Raju.
Assuntos
Dexametasona/farmacologia , Retrovirus Endógenos/imunologia , Glucocorticoides/farmacologia , Vírus da Leucemia Murina/imunologia , Vírus do Tumor Mamário do Camundongo/imunologia , Estresse Fisiológico , Animais , Retrovirus Endógenos/genética , Vírus da Leucemia Murina/genética , Vírus do Tumor Mamário do Camundongo/genética , Camundongos , Elementos de Resposta/imunologia , Especificidade da Espécie , Estresse Fisiológico/efeitos dos fármacos , Estresse Fisiológico/imunologiaRESUMO
Females and males differ in antibody isotype expression patterns and in immune responses to foreign- and self-antigens. For example, systemic lupus erythematosus is a condition that associates with the production of isotype-skewed anti-self antibodies, and exhibits a 9:1 female:male disease ratio. To explain differences between B cell responses in males and females, we sought to identify direct interactions of the estrogen receptor (ER) with the immunoglobulin heavy chain locus. This effort was encouraged by our previous identification of estrogen response elements (ERE) in heavy chain switch (S) regions. We conducted a full-genome chromatin immunoprecipitation analysis (ChIP-seq) using DNA from LPS-activated B cells and an ERα-specific antibody. Results revealed ER binding to a wide region of DNA, spanning sequences from the JH cluster to Cδ, with peaks in Eµ and Sµ sites. Additional peaks of ERα binding were coincident with hs1,2 and hs4 sites in the 3' regulatory region (3'RR) of the heavy chain locus. This first demonstration of direct binding of ER to key regulatory elements in the immunoglobulin locus supports our hypothesis that estrogen and other nuclear hormone receptors and ligands may directly influence antibody expression and class switch recombination (CSR). Our hypothesis encourages the conduct of new experiments to evaluate the consequences of ER binding. A better understanding of ER:DNA interactions in the immunoglobulin heavy chain locus, and respective mechanisms, may ultimately translate to better control of antibody expression, better protection against pathogens, and prevention of pathologies caused by auto-immune disease.
Assuntos
Linfócitos B/imunologia , Regulação da Expressão Gênica/imunologia , Cadeias Pesadas de Imunoglobulinas/imunologia , Região de Troca de Imunoglobulinas/imunologia , Receptores de Estrogênio/imunologia , Elementos de Resposta/imunologia , Animais , Formação de Anticorpos/genética , Formação de Anticorpos/imunologia , Imunoprecipitação da Cromatina , Feminino , Humanos , Ativação Linfocitária/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Reação em Cadeia da Polimerase , Receptores de Estrogênio/metabolismoRESUMO
Activation-induced cytidine deaminase (AID), the enzyme responsible for induction of sequence variation in immunoglobulins (Igs) during the process of somatic hypermutation (SHM) and also Ig class switching, can have a potent mutator phenotype in the development of lymphoma. Using various Epstein-Barr virus (EBV) recombinants, we provide definitive evidence that the viral nuclear protein EBNA3C is essential in EBV-infected primary B cells for the induction of AID mRNA and protein. Using lymphoblastoid cell lines (LCLs) established with EBV recombinants conditional for EBNA3C function, this was confirmed, and it was shown that transactivation of the AID gene (AICDA) is associated with EBNA3C binding to highly conserved regulatory elements located proximal to and upstream of the AICDA transcription start site. EBNA3C binding initiated epigenetic changes to chromatin at specific sites across the AICDA locus. Deep sequencing of cDNA corresponding to the IgH V-D-J region from the conditional LCL was used to formally show that SHM is activated by functional EBNA3C and induction of AID. These data, showing the direct targeting and induction of functional AID by EBNA3C, suggest a novel role for EBV in the etiology of B cell cancers, including endemic Burkitt lymphoma.
Assuntos
Linfoma de Burkitt/imunologia , Citidina Desaminase/imunologia , Antígenos Nucleares do Vírus Epstein-Barr/imunologia , Regulação Enzimológica da Expressão Gênica/imunologia , Regulação Neoplásica da Expressão Gênica/imunologia , Rearranjo Gênico do Linfócito B/imunologia , Herpesvirus Humano 4/imunologia , Proteínas de Neoplasias/imunologia , Hipermutação Somática de Imunoglobulina/imunologia , Linfoma de Burkitt/genética , Linhagem Celular , Citidina Desaminase/genética , Antígenos Nucleares do Vírus Epstein-Barr/genética , Feminino , Regulação Neoplásica da Expressão Gênica/genética , Rearranjo Gênico do Linfócito B/genética , Herpesvirus Humano 4/genética , Humanos , Masculino , Proteínas de Neoplasias/genética , Elementos de Resposta/imunologia , Hipermutação Somática de Imunoglobulina/genéticaRESUMO
In the canonical pathway of IFN-I-mediated signaling, phosphorylation of STAT1 and STAT2 leads to heterodimerization and interaction with IRF9. This complex, also known as IFN-stimulated gene factor 3 (ISGF3), then translocates into the nucleus and binds the IFN-I-stimulated response element (ISRE) leading to the activation of transcription of over 300 interferon stimulated genes (ISGs). In addition, STAT1 homodimers [known as γ-activated factor (GAF)] are formed and translocate to the nucleus, where they target genes containing the γ-activated sequence (GAS). The primary function of ISGF3 is to mediate a rapid and robust IFN-I activated response by regulating transient transcription of antiviral ISGs. This requires the quick assembly of ISGF3 from its pre-existing components STAT1, STAT2 and IRF9 and transport to the nucleus to bind ISRE-containing ISGs. The exact events that take place in formation, nuclear translocation and DNA-binding of active ISGF3 are still not clear. Over the years many studies have provided evidence for the existence of a multitude of alternative STAT2-containing (ISRE or GAS-binding) complexes involved in IFN-I signaling, emphasizing the importance of STAT2 in the regulation of specific IFN-I-induced transcriptional programs, independent of its involvement in the classical ISGF3 complex. This review describes the unique role of STAT2 in differential complex formation of unphosphorylated and phosphorylated ISGF3 components that direct constitutive and IFN-I-stimulated transcriptional responses. In addition, we highlight the existence of a STAT1-independent IFN-I signaling pathway, where STAT2/IRF9 can potentially substitute for the role of ISGF3 and offer a back-up response against viral infection.
Assuntos
Interferon Tipo I/imunologia , Fator de Transcrição STAT2/imunologia , Transdução de Sinais/imunologia , Transcrição Gênica/imunologia , Viroses/imunologia , Animais , Humanos , Fator Gênico 3 Estimulado por Interferon, Subunidade gama/imunologia , Elementos de Resposta/imunologiaRESUMO
Oxidative stress status has a key role in hepatocellular carcinoma (HCC) development and progression. Normally, reactive oxygen species (ROS) levels are tightly controlled by an inducible antioxidant program that responds to cellular stressors. How HCC cells respond to excessive oxidative stress remains elusive. Here, we identified a feedback loop between gankyrin, an oncoprotein overexpressed in human HCC, and Nrf2 maintaining the homeostasis in HCC cells. Mechanistically, gankyrin was found to interact with the Kelch domain of Keap1 and effectively competed with Nrf2 for Keap1 binding. Increased expression of gankyrin in HCC cells blocked the binding between Nrf2 and Keap1, inhibiting the degradation of Nrf2 by proteasome. Interestingly, accumulation and translocation of Nrf2 increased the transcription of gankyrin through binding to the ARE elements in the promoter of gankyrin. The positive feedback regulation involving gankyrin and Nrf2 modulates a series of antioxidant enzymes, thereby lowering intracellular ROS and conferring a steadier intracellular environment, which prevents mitochondrial damage and cell death induced by excessive oxidative stress. Our results indicate that gankyrin is a regulator of cellular redox homeostasis and provide a link between oxidative stress and the development of HCC.
Assuntos
Carcinoma Hepatocelular/imunologia , Neoplasias Hepáticas/imunologia , Fator 2 Relacionado a NF-E2/imunologia , Complexo de Endopeptidases do Proteassoma/imunologia , Proteólise , Proteínas Proto-Oncogênicas/imunologia , Transdução de Sinais/imunologia , Carcinoma Hepatocelular/genética , Linhagem Celular Tumoral , Humanos , Proteína 1 Associada a ECH Semelhante a Kelch/genética , Proteína 1 Associada a ECH Semelhante a Kelch/imunologia , Neoplasias Hepáticas/genética , Fator 2 Relacionado a NF-E2/genética , Estresse Oxidativo/genética , Estresse Oxidativo/imunologia , Complexo de Endopeptidases do Proteassoma/genética , Proteínas Proto-Oncogênicas/genética , Espécies Reativas de Oxigênio/imunologia , Elementos de Resposta/imunologia , Transdução de Sinais/genéticaRESUMO
B-cell fate is orchestrated by a series of well-characterized developmental regulators. Here, we found that the onset of B-cell development was accompanied by large-scale changes in DNA cytosine modifications associated with promoters, enhancers, and anchors. These changes were tightly linked to alterations in transcription factor occupancy and nascent RNA (eRNA) transcription. We found that the prepro-B to the pro-B-cell transition was associated with a global exchange of DNA cytosine modifications for polycomb-mediated repression at CpG islands. Hypomethylated regions were found exclusively in the active/permissive compartment of the nucleus and were predominantly associated with regulatory elements or anchors that orchestrate the folding patterns of the genome. We identified superanchors, characterized by clusters of hypomethylated CCCTC-binding factor (CTCF)-bound elements, which were predominantly located at boundaries that define topological associated domains. A particularly prominent hypomethylated superanchor was positioned down-stream of the Ig heavy chain (Igh) locus. Analysis of global formaldehyde-cross-linking studies indicated that the Igh locus superanchor interacts with the VH region repertoire across vast genomic distances. We propose that the Igh locus superanchor sequesters the VH and DHJH regions into a spatial confined geometric environment to promote rapid first-passage times. Collectively, these studies demonstrate how, in developing B cells, DNA cytosine modifications associated with regulatory and architectural elements affect patterns of gene expression, folding patterns of the genome, and antigen receptor assembly.
Assuntos
Ilhas de CpG/imunologia , Citosina/imunologia , Metilação de DNA/imunologia , Regulação da Expressão Gênica/imunologia , Células Precursoras de Linfócitos B/imunologia , RNA/imunologia , Elementos de Resposta/imunologia , Animais , Sequência de Bases , Ilhas de CpG/genética , Metilação de DNA/genética , Regulação da Expressão Gênica/genética , Camundongos , Dados de Sequência Molecular , Células Precursoras de Linfócitos B/citologia , RNA/genéticaRESUMO
Rag1 and Rag2 gene expression in CD4(+)CD8(+) double-positive (DP) thymocytes depends on the activity of a distant anti-silencer element (ASE) that counteracts the activity of an intergenic silencer. However, the mechanistic basis for ASE activity is unknown. Here, we show that the ASE physically interacts with the distant Rag1 and Rag2 gene promoters in DP thymocytes, bringing the two promoters together to form an active chromatin hub. Moreover, we show that the ASE functions as a classical enhancer that can potently activate these promoters in the absence of the silencer or other locus elements. In thymocytes lacking the chromatin organizer SATB1, we identified a partial defect in Tcra gene rearrangement that was associated with reduced expression of Rag1 and Rag2 at the DP stage. SATB1 binds to the ASE and Rag promoters, facilitating inclusion of Rag2 in the chromatin hub and the loading of RNA polymerase II to both the Rag1 and Rag2 promoters. Our results provide a novel framework for understanding ASE function and demonstrate a novel role for SATB1 as a regulator of Rag locus organization and gene expression in DP thymocytes.
Assuntos
Diferenciação Celular/imunologia , Cromatina/imunologia , Proteínas de Ligação a DNA/imunologia , Proteínas de Homeodomínio/imunologia , Proteínas de Ligação à Região de Interação com a Matriz/imunologia , Elementos de Resposta/imunologia , Timócitos/imunologia , Animais , Diferenciação Celular/genética , Cromatina/genética , Proteínas de Ligação a DNA/genética , Regulação da Expressão Gênica/genética , Proteínas de Homeodomínio/genética , Proteínas de Ligação à Região de Interação com a Matriz/genética , Camundongos , Camundongos Knockout , Timócitos/citologiaRESUMO
T cell activation causes the translocation of NF-κB dimers from the cytoplasm into the nucleus where NF-κB regulates inflammatory and immune response genes. Cbl-b is a negative regulator of T cell activation. However, the correlation between NF-κB activity and Cbl-b expression remains unclear. We showed that IκBαΔN-Tg T cells exhibited less NF-κB activity but higher levels of Cbl-b when compared with wild-type T cells. Furthermore, ursolic acid suppressed NF-κB activation and inhibited the downregulation of Cbl-b in wild-type T cells. NF-κBp65 specifically bound to an 11-bp NF-κB consensus sequence (gcaggaagtcc) in the Cbl-b promoter. Binding of NF-κB to this sequence suppressed Cbl-b transcription, thereby resulting in the negative regulation of Cbl-b expression. In addition, Cbl-b knockout led to the loss of cardiac allograft tolerance in IκBαΔN-Tg mice. These results indicated that NF-κB downregulated Cbl-b by binding and suppressing Cbl-b promoter in T cell activation. Our findings provide a novel role for NF-κB signaling in T cell activation.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/imunologia , Transplante de Coração , Ativação Linfocitária , Proteínas Proto-Oncogênicas c-cbl/imunologia , Elementos de Resposta/imunologia , Linfócitos T/imunologia , Fator de Transcrição RelA/imunologia , Proteínas Adaptadoras de Transdução de Sinal/genética , Aloenxertos , Animais , Técnicas de Silenciamento de Genes , Proteínas I-kappa B/genética , Proteínas I-kappa B/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Transgênicos , Inibidor de NF-kappaB alfa , Proteínas Proto-Oncogênicas c-cbl/genética , Elementos de Resposta/genética , Fator de Transcrição RelA/genética , Tolerância ao TransplanteRESUMO
Macrophages form a heterogeneous population of immune cells, which is critical for both the initiation and resolution of inflammation. They can be skewed to a proinflammatory subtype by the Th1 cytokine IFN-γ and further activated with TLR triggers, such as LPS. In this work, we investigated the effects of IFN-γ priming on LPS-induced gene expression in primary mouse macrophages. Surprisingly, we found that IFN-γ priming represses a subset of LPS-induced genes, particularly genes involved in cellular movement and leukocyte recruitment. We found STAT1-binding motifs enriched in the promoters of these repressed genes. Furthermore, in the absence of STAT1, affected genes are derepressed. We also observed epigenetic remodeling by IFN-γ priming on enhancer or promoter sites of repressed genes, which resulted in less NF-κB p65 recruitment to these sites without effects on global NF-κB activation. Finally, the epigenetic and transcriptional changes induced by IFN-γ priming reduce neutrophil recruitment in vitro and in vivo. Our data show that IFN-γ priming changes the inflammatory repertoire of macrophages, leading to a change in neutrophil recruitment to inflammatory sites.