CCAAT/enhancer binding proteins α and β regulate the tumor necrosis factor receptor 1 gene promoter

CCAAT/enhancer binding protein (C/EBP) transcription factors play essential roles in regulating an array of cellular processes, including differentiation, energy metabolism, and inflammation. In this report we demonstrate that both C/EBPα and C/EBPβ activate the promoter driving transcription of the tumor necrosis factor receptor 1 (TNFR1). TNFR1 is the major receptor for tumor necrosis factor (TNF), a critical cytokine mediator of the inflammatory response. Although the TNFR1 protein has been shown to be regulated through post-translational modifications, very little is known about the transcriptional regulation of the TNFR1 gene. Here we have identified a specific C/EBP binding site within the TNFR1 promoter, and shown that this site is required for both C/EBPα and C/EBPβ activation of the promoter in reporter gene assays. Furthermore, we show that both C/EBPα and C/EBPβ are bound to the TNFR1 promoter in cells using chromatin immunoprecipitation assays. Finally, we demonstrate that reducing the level of C/EBPα and C/EBPβ expression in cells using siRNA technology leads to decreased expression of the TNFR1 protein. These results suggest that the C/EBPα and C/EBPβ transcription factors enhance expression of the TNFR1 protein in cells. Given that TNF and C/EBPβ are known to activate each other's expression, C/EBPβ may greatly amplify the initial TNF signal through a positive auto-regulatory mechanism.