The CCAAT/enhancer (C/EBP) family of basic-leucine zipper (bZIP) transcription factors is a multifaceted highly-regulated system for gene regulation.
ABSTRACT The C/EBP family of proteins represents an important group of bZIP transcription factors that are key to the regulation of essential functions such as cell cycle, hematopoiesis, skeletal development, and host immune responses. They are also intimately associated with tumorigenesis and viral disease. These proteins are regulated at multiple levels, including gene induction, alternative translational initiation, post-translational modification, and protein-protein interaction. This review attempts to integrate recent reports with more than 20 years of previous effort focused on this fascinating collection of regulators.
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ABSTRACT: Long-range enhancers of transcription are a key component of the genomic regulatory architecture. Recent studies have identified bi-directionally transcribed RNAs emanating from these enhancers known as eRNAs. However, it remains unclear how tightly coupled eRNA production is with enhancer activity. Through our systematic search for long-range elements that interact with the interferon-β gene, a model system for studying inducible transcription, we have identified a novel enhancer, which we have named L2 that regulates the expression of interferon-β. We have demonstrated its virus-inducible enhancer activity by analyzing epigenomic profiles, transcription factor association, nascent RNA production and activity in reporter assays. This enhancer exhibits intimately linked virus-inducible enhancer and bidirectional promoter activity that is largely dependent on a conserved Interferon Stimulated Response Element and robustly generates virus inducible eRNAs. Notably, its enhancer and promoter activities are fully retained in reporter assays even upon a complete elimination of its associated eRNA sequences. Finally, we show that L2 regulates IFNB1 expression by siRNA knockdown of eRNAs, and the deletion of L2 in a BAC transfection assay. Thus, L2 is a novel enhancer that regulates IFNB1 and whose eRNAs exert significant activity in vivo that is distinct from those activities recapitulated in the luciferase reporter assays.Nucleic Acids Research 10/2014; · 8.81 Impact Factor
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ABSTRACT: It has recently been found that both nuclear epithelial-expressed histone deacetylases Hdac1 and Hdac2 are important to insure intestinal homeostasis and control the mucosal inflammatory response in vivo. In addition, HDAC inhibitors modulate epithelial cell inflammatory responses in cancer cells. However, little is known of the specific role of different HDAC, notably Hdac1, in the regulation of inflammatory gene expression in intestinal epithelial cells (IEC). We investigated the role of Hdac1 in non-transformed IEC-6 rat cells infected with lentiviral vectors expressing specific Hdac1 shRNAs, to suppress Hdac1 expression. Proliferation was assessed by cell counting. Deacetylase activity was measured with a colorimetric HDAC assay. Cells were treated with IL-1β and/or the JQ1 bromodomain acetyl-binding inhibitor. Nuclear protein levels of Hdac1, Hdac2, phosphorylated or unphosphorylated NF-κB p65 or C/EBPβ, and NF-κB p50 and actin were determined by Western blot. Chemokine and acute phase protein expression was assessed by semi-quantitative RT-PCR analysis. Secreted cytokine and chemokine levels were assessed with a protein array. Chromatin immunoprecipitation experiments were done to assess RNA polymerase II recruitment. Reduced Hdac1 protein levels led to Hdac2 protein increases and decreased cell proliferation. Hdac1 depletion prolonged nuclear IL-1β-induced phosphorylation of NF-κB p65 protein on Ser536 as opposed to total p65, and of C/EBPβ on Ser105. In addition, semi-quantitative RT-PCR analysis revealed three patterns of expression caused by Hdac1 depletion, namely increased basal and IL-1β-stimulated levels (Hp, Kng1), increased IL-1β-stimulated levels (Cxcl2) and decreased basal levels with normal IL-1β induction levels (Ccl2, Ccl5, Cxcl1, C3). Secreted cytokine and chemokine measurements confirmed that Hdac1 played roles both as an IL-1β signalling repressor and activator. Hdac1 depletion did not alter the JQ1 dependent inhibition of basal and IL-1β-induced inflammatory gene expression. Hdac1 depletion led to decreased basal levels of RNA polymerase II enrichment on the Ccl2 promoter, as opposed to the Gapdh promoter, correlating with decreased Ccl2 basal mRNA expression. Hdac1 is a major nuclear HDAC controlling IL-1β-dependent inflammatory response in IEC, notably by regulating gene-specific transcriptional responses. Hdac1 may be important in restricting basal and inflammatory-induced gene levels to defined ranges of expression.Journal of inflammation (London, England). 01/2014; 11(1):43.
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ABSTRACT: Activation of the ATP-dependent P2X7 receptor modulates glucose transport in intestinal epithelial cells through the downregulation of glucose transporter GLUT2. In the present study, we show that an increase in glucose concentration stimulates P2X7 receptor transcription via modulation of CCAAT/enhancer binding proteins (C/EBPs) α and β expression. The described human P2X7 receptor promoter region (GenBank Y12851) was cloned upstream of a luciferase reporter gene in pGL4.10 plasmid and used to determine whether C/EBPs, namely C/EBPα and C/EBPβ, are able to stimulate the transcription of P2X7 receptor. Results show that C/EBPβ was the main regulator of P2X7 receptor expression in response to a glucose challenge. Chromatin immunoprecipitation (ChIP) assays further revealed that C/EBPβ occupied the -213 to +6 nt P2X7 promoter region. Surprisingly, C/EBPα was also able to bind this region as revealed by ChIP assays, but without inducing receptor transcription. In fact, C/EBPα and the C/EBPβ-LIP isoform blocked the C/EBPβ-dependent regulation of P2X7 receptor transcription. These findings suggest that glucose is not only the major source of energy for cell function but may also act as a signaling molecule to stimulate the expression of regulatory proteins.Biochemistry and Cell Biology 09/2014; · 2.35 Impact Factor