Regulation of c-Fos Gene Expression by NF-[kappa]B: A p65 Homodimer Binding Site in Mouse Embryonic Fibroblasts but Not Human HEK293 Cells

• Published in: PloS one Vol. 8; no. 12; p. e84062
• Main Authors: Tu, Yu-Cheng, Huang, Duen-Yi, Shiah, Shine-Gwo, Wang, Jang-Shiun, Lin, Wan-Wan
• Format: Journal Article
• Language: English
• Published: Public Library of Science 30.12.2013
• Subjects: Cells (Biology); Gene expression; Genes; Protein binding; Tumor necrosis factor
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0084062

The immediate early gene c-Fos is reported to be regulated by Elk-1 and cAMP response element-binding protein (CREB), but whether nuclear factor (NF)-[kappa]B is also required for controlling c-Fos expression is unclear. In this study, we determined how NF-[kappa]B's coordination with Elk/serum response factor (SRF) regulates c-fos transcription. We report that PMA strongly induced c-Fos expression, but tumor necrosis factor (TNF)-[alpha] did not. In mouse embryonic fibroblasts, the PMA induction of c-Fos was suppressed by a deficiency in IKK[alpha], IKK[beta], IKK[gamma], or p65. By contrast, in human embryonic kidney 293 cells, PMA induced c-Fos independently of p65. In accordance with these results, we identified an NF-[kappa]B binding site in the mouse but not human c-fos promoter. Under PMA stimulation, IKK[alpha]/[beta] mediated p65 phosphorylation and the binding of the p65 homodimer to the NF-[kappa]B site in the mouse c-fos promoter. Furthermore, our studies demonstrated independent but coordinated functions of the IKK[alpha]/[beta]-p65 and extracellular signal-regulated kinase (ERK)-Elk-1 pathways in the PMA induction of c-Fos. Collectively, these results reveal the distinct requirement of NF-[kappa]B for mouse and human c-fos regulation. Binding of the p65 homodimer to the [kappa]B site was indispensable for mouse c-fos expression, whereas the [kappa]B binding site was not present in the human c-fos promoter. Because of an inability to evoke sufficient ERK activation and Elk-1 phosphorylation, TNF-[alpha] induces c-Fos more weakly than PMA does in both mouse and human cells.