Article

Differential roles of C/EBP beta regulatory domains in specifying MCP-1 and IL-6 transcription.

Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.
Molecular Immunology (Impact Factor: 2.65). 03/2007; 44(6):1384-92. DOI: 10.1016/j.molimm.2006.05.004
Source: PubMed

ABSTRACT C/EBPbeta is a member of the CCAAT/enhancer binding protein family of transcription factors and has been shown to be a critical transcriptional regulator of various proinflammatory genes, including IL-6 and MCP-1. To examine the roles of the C/EBPbeta transactivation and regulatory domains in LPS-induced MCP-1 and IL-6 expression, we expressed various N-terminal truncations and deletions of C/EBPbeta in P388 murine B lymphoblasts, which lack endogenous C/EBPbeta expression and are normally unresponsive to LPS for expression of IL-6 and MCP-1. Unexpectedly, a region between amino acids 105 and 212 of C/EBPbeta that includes regulatory domains 1 and 2 facilitates C/EBPbeta activation of IL-6 expression, while having an inhibitory effect on MCP-1 expression. Thus, this region can mediate promoter-specific effects on cytokine and chemokine gene transcription. LIP, the naturally occurring truncated form of C/EBPbeta, largely retains these regulatory domains and stimulates IL-6 but not MCP-1 transcription.

0 Bookmarks
 · 
80 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: OBJECTIVE: Persistent inflammation and impaired adipogenesis are frequent features of obesity and underlie the development of its complications. However, the factors behind adipose tissue dysfunction are not completely understood. We have previously shown that histone demethylase KDM1A is required for adipogenesis. DESIGN AND METHODS: Kdm1a expression was knocked down in 3T3-L1 preadipocytes by siRNA transfection and whole-genome expression profiling was performed by microarray hybridization. The role of NF-κβ and C/EBPβ was analyzed by incubation with the inhibitor parthenolide and by cebpb knockdown, respectively. RESULTS: Knockdown of kdm1a or rcor2 in 3T3-L1 preadipocytes results in impaired differentiation and induction of inflammatory gene expression. Enhanced expression of il6 in kdm1a knocked down preadipocytes is associated with increased recruitment of C/EBPβ and the NF-β subunit RelA to the il6 promoter. Cebpb knockdown attenuates the induction of il6 expression in kdm1a knocked down cells, whereas simultaneous cebpb knockdown and NF-β inhibition abrogates it. Dietary-induced and genetic mouse models of obesity display decreased KDM1A in adipose tissue, and this correlates with increased expression of proinflammatory genes and C/EBPβ. CONCLUSION: KDM1A represses the expression of inflammatory genes in preadipocytes. Dysregulated kdm1a expression in preadipocytes may thus participate in the development of obesity-associated inflammation.
    Obesity 04/2013; · 3.92 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: There is an emerging consensus that gene regulation evolves through changes in cis-regulatory elements and transcription factors. Although it is clear how nucleotide substitutions in cis-regulatory elements affect gene expression, it is not clear how amino-acid substitutions in transcription factors influence gene regulation. Here we show that amino-acid changes in the transcription factor CCAAT/enhancer binding protein-β (CEBPB, also known as C/EBP-β) in the stem-lineage of placental mammals changed the way it responds to cyclic AMP/protein kinase A (cAMP/PKA) signalling. By functionally analysing resurrected ancestral proteins, we identify three amino-acid substitutions in an internal regulatory domain of CEBPB that are responsible for the novel function. These amino-acid substitutions reorganize the location of key phosphorylation sites, introducing a new site and removing two ancestral sites, reversing the response of CEBPB to GSK-3β-mediated phosphorylation from repression to activation. We conclude that changing the response of transcription factors to signalling pathways can be an important mechanism of gene regulatory evolution.
    Nature 11/2011; 480(7377):383-6. · 38.60 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: CCAAT/enhancer binding protein (C/EBP)β, and C/EBP binding sites in the HIV/SIV- long terminal repeat (LTR) are crucial for regulating transcription and for IFNβ-mediated suppression of virus replication in macrophages, the predominant source of productive virus replication in the brain. We investigated sequence variation within the SIV-LTR C/EBP sites that may be under selective pressure in vivo and therefore associated with disease progression. Using the SIV-macaque model, we examined viral LTR sequences derived from the spleen, a site of macrophage and lymphocyte infection, and the brain from macaques euthanized at 10, 21, 42, 48 and 84 days postinoculation (p.i.). A dominant variant, DS1C/A, containing an adenine-to-guanine substitution and a linked cytosine-to-adenine substitution in the downstream (DS1) C/EBP site, was detected in the spleen at 10 days p.i. The DS1C/A genotype was not detected in the brain until 42 days p.i., after which it was the predominant replicating genotype in both brain and spleen. Functional characterization of the DS1C/A containing SIV showed increased infectivity with or without IFNβ treatment over the wild-type virus, SIV/17E-Fr. The DS1C/A C/EBP site had higher affinity for both protein isoforms of C/EBPβ compared to the wild-type DS1 C/EBP site. Cytokine expression in spleen compared to brain implicated IFNβ and IL-6 responses as part of the selective pressures contributing to emergence of the DS1C/A genotype in vivo. These studies demonstrate selective replication of virus containing the DS1C/A genotype that either emerges very early in spleen and spreads to the brain, or evolves independently in the brain when IFNβ and IL-6 levels are similar to that found in spleen earlier in infection.
    PLoS ONE 01/2012; 7(8):e42801. · 3.53 Impact Factor