Critical Role for Transcription Factor C/EBP-β in Regulating the Expression of Death-Associated Protein Kinase 1
Sanjit K. Roy,
Shreeram C. Nallar
Dhananjaya V. Kalvakolanu
Molecular and Cellular Biology,
2008, 28(8), 2528-2548. DOI: 10.1128/MCB.00784-07
Transcription factor C/EBP-β regulates a number of physiological responses. During an investigation of the growth-suppressive effects of interferons (IFNs), we noticed that cebpb–/– cells fail to undergo apoptosis upon gamma IFN (IFN-γ) treatment, compared to wild-type controls. To examine the basis for this response, we have performed gene expression profiling of isogenic wild-type and cebpb–/– bone marrow macrophages and identified a number of IFN-γ-regulated genes that are dependent on C/EBP-β for their expression. These genes are distinct from those regulated by the JAK-STAT pathways. Genes identified in this screen appear to participate in various cellular pathways. Thus, we identify a new pathway through which the IFNs exert their effects on cellular genes through C/EBP-β. One of these genes is death-associated protein kinase 1 (dapk1). DAPK1 is critical for regulating the cell cycle, apoptosis, and metastasis. Using site-directed mutagenesis, RNA interference, and chromatin immunoprecipitation assays, we show that C/EBP-β binds to the promoter of dapk1 and is required for the regulation of dapk1. Both mouse dapk1 and human dapk1 exhibited similar dependences on C/EBP-β for their expression. The expression of the other members of the DAPK family occurred independently of C/EBP-β. Members of the C/EBP family of transcription factors other than C/EBP-β did not significantly affect dapk1 expression. We identified two elements in this promoter that respond to C/EBP-β. One of these is a consensus C/EBP-β-binding site that constitutively binds to C/EBP-β. The other element exhibits homology to the cyclic AMP response element/activating transcription factor binding sites. C/EBP-β binds to this site in an IFN-γ-dependent manner. Inhibition of ERK1/2 or mutation of an ERK1/2 site in the C/EBP-β protein suppressed the IFN-γ-induced response of this promoter. Together, our data show a critical role for C/EBP-β in a novel IFN-induced cell growth-suppressive pathway via DAPK1.