Early growth response 2 (Egr-2) expression is triggered by NF-κB activation

Transcription factors are known to play multiple roles in cellular function. Investigators report that factors such as early growth response (Egr) protein and nuclear factor kappa B (NF-κB) are activated in the brain during cancer, brain injury, inflammation, and/or memory. To explore NF-κB activity further, we investigated the transcriptomes of hippocampal slices following electrical stimulation of NF-κB p50 subunit knockout mice (p50^-/-) versus their controls (p50^+/+). We found that the early growth response gene Egr-2 was upregulated by NF-κB activation, but only in p50^+/+ hippocampal slices. We then stimulated HeLa cells and primary cortical neurons with tumor necrosis factor alpha (TNFα) to activate NF-κB and increase the expression of Egr-2. The Egr-2 promoter sequence was analyzed for NF-κB binding sites and chromatin immunoprecipitation (ChIP) assays were performed to confirm promoter occupancy in vivo. We discovered that NF-κB specifically binds to an NF-κB consensus binding site within the proximal promoter region of Egr-2. Luciferase assay demonstrated that p50 was able to transactivate the Egr-2 promoter in vitro. Small interfering RNA (siRNA)-mediated p50 knockdown corroborated other Egr-2 expression studies. We show for the first time a novel link between NF-κB activation and Egr-2 expression with Egr-2 expression directly controlled by the transcriptional activity of NF-κB.