ROLE FOR NF-KAPPA-B IN THE REGULATION OF FERRITIN-H BY TUMOR-NECROSIS-FACTOR-ALPHA

Ferritin is a ubiquitously distributed iron-binding protein that plays a key role in cellular iron homeostasis. It is composed of two subuni ts, termed H (heavy or heart) and L (light or liver), In fibroblasts a nd other cells, the cytokine tumor necrosis factor-alpha (TNF) specifi cally induces synthesis of the ferritin H subunit. Using nuclear run-o ff assays, we demonstrate that this TNF-dependent increase in ferritin H is mediated by a selective increase in ferritin H transcription. Tr ansfection of murine fibroblasts with chimeric genes containing the 5' -flanking region of murine ferritin H fused to the human growth hormon e reporter gene reveals that the cia-acting element that mediates this response is located similar to 4.8 kilobases distal to the start site of transcription. Deletion analyses delimit the TNF-responsive region to a 40-nucleotide sequence located between nucleotides -4776 and -47 36, which we term FER-2. Electrophoretic mobility shift assays and sit e-specific mutations indicate that this region contains two independen t elements: one contains a sequence that binds a member of the NF-kapp a B family of transcription factors, and a second contains a novel seq uence that partially conforms to the NF-kappa B consensus sequence and may bind a different member of the NF-kappa B/Rel transcription facto r family, Thus, effects of an inflammatory cytokine on ferritin are me diated by a family of transcription factors responsive to oxidative st ress.