RESUMO
The expression of interferon-ß (IFN-ß) in virus-infected HeLa cells established a paradigm of multifactorial gene regulation, in which cooperative assembly of transcription factors (TFs) at the composite DNA element (enhanceosome), is central for amplification of weak activating signals provided by individual TFs. However, whether the same TFs and the same DNA element are essential for IFN-ß induction in response to bacterial stimuli are less well understood. Here we report that rapid and transient transcription of IFN-ß in response to TLR4 stimulation with bacterial lipopolysaccharide (LPS) follows nuclear factor-κB (NF-κB) RelA activation and recruitment to the IFN-ß genomic locus at multiple spatially separated regulatory regions. We demonstrate that the IFN-ß enhanceosome region is not sufficient for maximal gene induction in response to LPS and identify an essential cluster of homotypic κB sites in the 3' downstream of the gene. The cluster is characterized by elevated levels of histone 3 lysine 4 mono-methylation, a chromatin signature of enhancers, and efficiently binds RelA-containing NF-κB complexes in vitro and in vivo. These findings demonstrate that IFN-ß gene activation via multifactorial enhanceosome assembly is potentiated in LPS-stimulated cells by NF-κB interactions with all functional κB sites in the locus.
Assuntos
Elementos Facilitadores Genéticos , Regulação da Expressão Gênica , Interferon beta/genética , Lipopolissacarídeos/farmacologia , NF-kappa B/metabolismo , Elementos Reguladores de Transcrição , Ativação Transcricional/efeitos dos fármacos , Western Blotting , Núcleo Celular/fisiologia , Células Cultivadas , Imunoprecipitação da Cromatina , DNA Polimerase II/metabolismo , Ensaio de Desvio de Mobilidade Eletroforética , Humanos , Interferon beta/metabolismo , Rim/citologia , Rim/efeitos dos fármacos , Rim/metabolismo , Luciferases/metabolismo , NF-kappa B/genética , Regiões Promotoras Genéticas/genética , RNA Mensageiro/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Receptor 4 Toll-Like/genética , Receptor 4 Toll-Like/metabolismo , Sítio de Iniciação de Transcrição , Transcrição GênicaRESUMO
Our immune system is designed to protect us from danger. Upon pathogen invasion and tissue injury, activation of both innate and adaptive immunity enables us to combat infection and to repair tissue damage. Tenascin-C is a large, extracellular matrix glycoprotein that has a very tightly controlled pattern of expression. Little or no tenascin-C is expressed in most healthy adult tissues; however, it is rapidly and transiently induced at sites of tissue injury and infection. Persistent tenascin-C expression is associated with pathologies such as chronic, non-healing wounds, autoimmune diseases, cancer, and fibrotic diseases. We discuss the myriad roles that this multifunctional molecule plays during the immune response, with a focus on how tissue levels of tenascin-C are regulated and the consequences of misregulated tenascin-C expression in immune regulated disease pathogenesis.
Assuntos
Regulação da Expressão Gênica no Desenvolvimento , Infecções/imunologia , Tenascina/imunologia , Imunidade Adaptativa , Animais , Regulação da Expressão Gênica no Desenvolvimento/imunologia , Humanos , Imunidade Inata , CicatrizaçãoRESUMO
IFNs lambda1, lambda2, and lambda3, or type III IFNs, are recently identified cytokines distantly related to type I IFNs. Despite an early evolutionary divergence, the 2 types of IFNs display similar antiviral activities, and both are produced primarily in dendritic cells. Although virus induction of the type I IFN-beta gene had served as a paradigm of gene regulation, relatively little is known about the regulation of IFN-lambda gene expression. Studies of virus induction of IFN-lambda1 identified an essential role of IFN regulatory factors (IRF) 3 and 7, which bind to a regulatory DNA sequence near the start site of transcription. Here, we report that the proximal promoter region of the IFN-lambda1 regulatory region is not sufficient for maximal gene induction in response to bacterial LPS, and we identify an essential cluster of homotypic NF-kappaB binding sites. Remarkably, these sites, which bind efficiently to NF-kappaB and function independently of the IRF3/7 binding sites, originate as transposable elements of the Alu and LTR families. We also show that depletion of the NF-kappaB RelA protein significantly reduces the level of the IFN-lambda1 gene expression. We conclude that IFN-lambda1 gene expression requires NF-kappaB, and we propose a model for IFN-lambda1 gene regulation, in which IRF and NF-kappaB activate gene expression independently via spatially separated promoter elements. These observations provide insights into the independent evolution of the IFN-lambda1 and IFN-beta promoters and directly implicate transposable elements in the regulation of the IFN-lambda1 gene by NF-kappaB.