Critical role for transcription factor C/EBP-beta in regulating the expression of death-associated protein kinase 1

Authors:
Gade P, Roy SK, Li H, Nallar SC, Kalvakolanu DV
In:
Source: Mol Cell Biol
Publication Date: (2008)
Issue: 28(8): 2528-48
Research Area:
Immunotherapy / Hematology
Cells used in publication:
Macrophage, mouse - C57BL/6
Species: mouse
Tissue Origin: bone marrow
Platform:
Nucleofector® I/II/2b
Abstract
Transcription factor C/EBP-beta regulates a number of physiologic responses. During an investigation of the growth-suppressive effects of IFNs, we noticed that cebpb (-/-) cells fail to undergo apoptosis upon IFN-gamma treatment compared to the wild-type controls. To examine the basis for this response, we have performed a gene expression profiling of the isogenic wild-type and cebpb (-/-) bone marrow macrophages and identified a number of IFN-gamma regulated genes that are dependent on C/EBP-beta 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-beta. One of these genes is the death-associated protein kinase 1 (dapk1). DAPK1 is critical for regulating cell cycle, apoptosis and metastasis. Using site-directed mutagenesis, RNAi and ChIP assays, we show that C/EBP-beta binds to the promoter of dapk1 and is required for the regulation of dapk1. Both mouse and human dapk1 exhibited similar dependence on C/EBP-beta for their expression. The expression of the other members of DAPK family occurred independently of C/EBP-beta. Members of the C/EBP family of transcription factors, other than C/EBP-beta did not significantly affect dapk1 expression. We identified two elements in this promoter that respond to C/EBP-beta. One of these is a consensus CBS that constitutively binds to C/EBP-beta. The other element exhibits homology to the cAMP-response element/activating transcription factor binding sites. C/EBP-beta binds to this site in an IFN-gamma-dependent manner. Inhibition of ERK1/2 or mutation of an ERK1/2 site in the C/EBP-beta protein suppressed the IFN-gamma-induced response of this promoter. Together our data show a critical role for C/EBP-beta in a novel IFN-induced cell growth-suppressive pathway via DAPK1.