NF-κB interacts with SP3 to limit SP1-mediated FGF-10 expression in the developing fetal lung

Abstract

Arrested lung development in preterm infants leads to bronchopulmonary dysplasia (BPD). Inflammation and NF-κB activation in the fetal lung inhibit airway morphogenesis and contribute to BPD. The mesenchymal growth factor FGF-10 is crucial for normal airway branching and is decreased in lungs of patients with BPD. I therefore hypothesized that when activated, NF-κB disrupts normal FGF-10 transcription. I discovered that FGF-10 is in fact downregulated by NF-κB activation, but in an indirect manner. Further analysis of the FGF-10 promoter revealed many sites consistent with regulation by Sp proteins. Experiments revealed that Sp1 and Sp3 also regulate FGF-10; Sp1 activates transcription, while Sp3 downregulates Sp1-mediated expression. I further discovered that Sp3 and the NF-κB dimer interact during FGF-10 suppression, suggesting that NF-κB recruits Sp3 to the FGF-10 promoter. This is a novel mechanism of gene regulation in the developing lung.